TROPICS Vol. 18 (2) Issued June 30, 2009 ?Mini Review? Review of Soils on the 52 ha Long Term Ecological Research Plot in Mixed Dipterocarp Forest at Lambir, Sarawak, Malaysian Borneo Sylvester TAN1, Takuo YAMAKURA2, Masako TANI2, Peter PALMIOTTO3, James Dawos MAMIT4, Chin Siew PIN5, Stuart DAVIES6, Peter ASHTON6 and Ian BAILLIE7,? 1Forest Department, 93660, Kuching, Sarawak, Malaysia. 2Department of Biology, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan. 3Antioch New England Graduate School, 40 Avon Street, Keene, NH 03431-3516, U.S.A. 4Yang Berhormat, Federal Parliament of Malaysia, Parliament Building, 50680 Kuala Lumpur, Malaysia. 5Agriculture Research Centre, Semongok, P O Box 977, 93720 Kuching, Sarawak, Malaysia. 6Arnold Arboretum, Harvard University, 22 Divinity Avenue, Cambridge, M 02138, U.S.A. 7Harvard Forest, PO Box 68,Petersham, MA 01366, U.S.A. and Arnold Arboretum, Harvard University, 22 Divinity Avenue, Cambridge, MA 02138, U.S.A. ?Corresponding author: National Soil Resources Institute, Cran?eld University, MK43 0AL, UK. E-mail: i.baillie@tiscali.co.uk. ABSTRACT??Much of the structural, ?oristic and dynamic variation in the hyperdiverse dipterocarp forest on the 52 ha long term ecological research plot at Lambir, Sarawak, is associated with soil dif ferences, as indicated by topography, labile topsoil nutrients, and humus. This review expands the edaphic characterisation of the plot by collation of published and unpublished data on soil morphology, physical properties and non-labile nutrients. Topographically the plot consists of two dipslopes at dif ferent elevations with a steep and unstable intervening scarp. Sandstone underlies the main upper dipslope and shale the lower, and the scarp has mixed clastic sedimentary lithology. Most of the dipslope soils are moderately developed Red Yellow Podzolics (Acrisols/Udults). They are of medium depth, with thin topsoils and reddish yellow blocky subsoils that become redder, finer textured, ?rmer and blockier with depth. Textures vary with lithology, and range from loamy sand over sandy loam on sandstone to silty clay over clay on shale. The scarp has shallower, stonier and less horizonated Skeletal soils (Cambisols/Inceptisols). All of the soils are very acid, and have low contents of all labile nutrients. Contents of non-labile forms of P are low and those of Ca extremely low, but K and Mg are moderate. All nutrients are signi?cantly lower in sandstone soils than on shale. The dif ferences are more pronounced for non-labile than labile forms and in subsoils than topsoils. Ratios of mineral nutrient are stoichiometrically typical for Red Yellow Podzolics on clastic sediments, and differ from morphologically similar soils on other parent materials. The ecologically significant reserves of K and Mg are attributed to small but sustained replenishments by mica weathering. Key words: dipterocarp forest, soils, stoichiometery, topography, Borneo INTRODUCTION The Mixed Dipterocarp Forest (MDF) on the long-term ecological research (LTER) plot at Lambir, northern Sarawak (Fig. 1), is located in the Bornean heartland of dipterocarp diversity (Ashton, 1989 and 1995), and was sited to include a range of forest and soil types (Ashton, 1978). The forest has the highest tree species richness so far documented in the paleotropics (Lee et al. 2002a). Much of the variation in forest floristics, structure and dynamics on the plot has been associated with an edaphic gradient from very dystrophic soils on sandstone to less dystrophic clays on shale (Davies, 2001; Davies et al. 1998 and 2005; Debski et al. 2002; Harrison et al. 2003; Itoh, 1997; Itoh et al. 2003; Lee et al. 2002a; Palmiotto, 1998; Palmiotto et al. 2004; Potts et al. 2004; Russo et al. 2005; Yamada et al. 1997 and 2000; Yamakura et al. 1996). This parallels associations between MDF and soils elsewhere in the Lambir area (Hirai et al. 1997; Ishizuka et al. 2001; Itoh, 1995; Itoh et al. 1995; Iwasaki et al. 1997; Nagamasu and Momose, 1997; Putz and Chai, 1987). Associations of MDF floristics and structure with soil lithology and reserve nutrients, especially those of P and Mg, have 62 Sylvester TAN, Takuo YAMAKURA, Masako TANI, Peter PALMIOTTO, James Dawos MAMIT, Chin Siew PIN, Stuart DAVIES, Peter ASHTON, Ian BAILLIE been found on a range of rock types in other parts of Sarawak, (Ashton, 1973; Ashton and Hall, 1992; Baillie et al. 1987; Potts et al. 2002), and elsewhere in Borneo (Austin et al. 1972; Baltzer et al. 2005; McKinnon et al. 1997; Ohta et al. 1992; Webb and Pear t, 2000). Soil dif ferences are considered important enough to have been integrated into logging protocols for dipterocarp forests in Sabah (Glauner et al. 2003). Because of the apparent importance of site-forest associations in Bornean MDF, the soils of the LTER plot at Lambir have been investigated in some detail, but many of the data are unpublished and inaccessible. We collate them here with published ?ndings in order to: 1) Clarify soil spatial patterns, especially the nature and intensity of the edaphic gradient; 2) Compare the soils of the plot with those of other tropical forests; 3) Avoid unnecessary soil sampling and analyses in the future We concentrate on the plot?s physiography and on the mineral and inorganic attributes of the soils, as Baillie et al. (2006) have already examined the morphology, dynamics and edaphic implications of the litter and humus. We use ?labile? to refer to nutrients extracted by mild reagents, and include exchangeable cations leached by 1M NH4OOCH3 , extractable cations leached by 1M KCl and 1M NH4Cl, and available P extracted with the Bray 2 reagent. Non-labile nutrients include reserves extracted with concentrated HCl and totals extracted with concentrated H2 SO4 or HClO4. THE STUDY SITE Location and access The Lambir LTER plot was established in 1991 as part of the pantropical network of similar plots coordinated by the Center for Tropical Forest Science (CTFS) and, for Asia, the Arnold Arboretum of Harvard University. The plot is at 4o 11? N, 114o 01? E in Taman Negara Bukit Lambir (Lambir Hills National Park), Northern Sarawak, Malaysian Borneo (Fig.1). It measures 0.5? 1.04 km, corrected for slope (Yamakura et al. 1995). There is a good path along the major axis, and the plot is accessible from the Miri-Sibu highway. Navigation within the plot is Fig. 1. Location of Lambir Hills National Park 63Review of Soils on the 52 ha Long Term Ecological Research Plot in Mixed Dipterocarp Forest at Lambir, Sarawak, Malaysian Borneo facilitated by pegs at the corners of the 1300 slope- corrected 20?20 m quadrats, and by the inclusion of quadrat numbers on the permanent metal tags on all monitored trees and saplings (Lee et al. 2002a; Yamakura et al. 1995) Forest The plot contains approximately 350 000 free-standing trees and saplings of > 1 cm diameter at reference height. These were inventoried in1992-3 for species, size and form, and permanently tagged according to standard CTFS procedures (Condit, 1998; Lee et al. 2002a), and re- measured in 1998-9 and 2002-3, with another recensus currently under way in 2007-8. The forest is structurally typical of Bornean MDF, with tall, slim-boled and high- buttressed trees, a dense irregular canopy at 40-50 m, with a few emergents exceeding 60 m. Basal areas are moderate, at 35-45 m2.ha? 1, but the tall trees give a substantial above-ground biomass, estimated to average over 500 t. ha?1 (Lee et al. 2002a; Yamakura et al. 1986). The plot contains almost 1200 species of trees and saplings (Potts et al. 2004), with dipterocarps of eight genera and 87 species dominating the canopy and larger size classes (Lee et al. 2002b). Climate The climate is equatorial aseasonal. Monthly mean temperatures vary little, ranging from 26 to 28 oC, and diurnal ranges are 8-10 oC. The mean annual rainfall of 2500 ? 3000 mm is distributed throughout the year, although heavier during the landas (nor th-eastern monsoon) in November-Februar y (Watson, 1985). Because the plot is sited in a freestanding peri-coastal range of hills, it receives localised orographic rainfall, which may add 100?200 mm p.a. to the regional mean (Palmiotto, 1998; Sakai, et al. 1997). Soil reserves of available moisture are suf?cient to permit uninterrupted transpiration though the drier months in most years (Hirai, et al. 1997; Kumagai, et al. 2004a, 2005) but ecologically significant droughts occur in ENSO years (Harrison, 2000; Ichie et al. 2004; Itioka and Yamanti, 2004; Nakagawa, 2000; Potts, 2003). Run-of-wind totals are low but brief and narrow-fronted squalls precede many rainfall events. However, Borneo is too near the equator for typhoons, except extremely rarely (Proctor et al. 2001). Geology The predominantly clastic sedimentary rocks of the Lambir Formation underlying the plot were deposited in deltaic and coastal environments during the Mio-Pliocene (Morley et al. 2003). They are underlain at depth by the continental basement of the Luconia block, a micro- terrane that moved southwards from South China in the early Tertiary (Hutchison, 1988). The main rock type is light grey, yellowish and pinkish yellow sandstone. It is mostly medium- and fine-grained but there are some coarser beds (Wilford, 1961). The sand grains are predominantly quartz, with subordinate fragments of mudstone and chert, set in a matrix of silt- and clay-sized quar tz and subordinate ferruginous sesquioxides (Rubiah, 1994). The generally siliceous nature of the Lambir sandstone limits the quantities of clays and cationic nutrients generated by weathering (Hill et al. 1992). The Lambir formation includes subordinate dark grey, weakly consolidated shales, which occur both as thin partings and thick beds. The thick beds are more frequent towards the base of the formation and in the south and east of the plot. The main shale minerals are micas, with subordinate ?ne-grained quartz and pyrites. Some of the shales are carbonaceous and almost black when fresh. Thin coal seams are reported in the lower parts of the formation (Noryati, 1995), although none were seen on the plot. There are also thin calcareous beds near the base (Wilford, 1961; Rubiah, 1994) but none were seen on the plot. Some of the shales are fer r uginised, with indurated orange-r ust brown interlayers of concentrated ferric sesquioxides up to 10 cm thick. These formed during sedimentation rather than after exhumation (Lim and Leman, 1994). The Lambir formation is about 1 km thick and has been uplifted by at least half a kilometre since deposition (Banda, 1998). Satellite imagery shows linear breaks of slope at the base of the range, suggesting that it is a fault- defined horst (Caline and Huong, 1992). The uplift occur red spasmodically during the Pliocene and Pleistocene (Wilford, 1961; Wall, 1964), and concurrent tilting gave the beds their current 15-35 degrees dip down to the N-NW. The tectonic movements caused normal, reverse and transverse faults (Yasin, 1990). There is no current volcanic activity but limited seismicity indicates that, tectonically, the area is not completely inert. Topography and hydrology The plot is located on the southern slopes of the Lambir Hills, a low free-standing range rising out of the North Sarawak coastal lowlands. The range consists of cuestas (dip-controlled asymmetrical ridges) and steep hills. The cuestas dip NW, and dipslopes are best seen on the 64 Sylvester TAN, Takuo YAMAKURA, Masako TANI, Peter PALMIOTTO, James Dawos MAMIT, Chin Siew PIN, Stuart DAVIES, Peter ASHTON, Ian BAILLIE northern slopes (Wall, 1964; Watson, 1985). The plot is located in the more broken terrain on the southern side. Yamakura et al. (1995) derived a contour map for the plot (Fig. 2) and estimated slope gradients and indices of ver tical convexity/concavity from detailed levelling surveys. I.C. Baillie and S. Tan (unpublished data, 2003) assessed site drainage, microrelief and plan convergence/ divergence on 245 quadrats. Although at low altitude (< 250 m a.s.l.), the terrain is rugged, and the plot has internal relief of 140 m and many slopes steeper than 50% (Yamakura et al. 1995). The main topographic elements are an extensive elevated NW- sloping cuesta dipslope on sandstone, a cuesta scarp complex of steep slopes and streambeds on mixed lithology, and a smaller and lower NW-dipping cuesta on shale (Figs 2 and 3). The asymmetry of the cuestas is attributed to the shallow dip of the beds and relatively higher competence of the sandstones. Westward-flowing headwaters of Sungai Liam have incised two shallow asymmetrical valleys in the upper main sandstone dipslope. Within these valleys, the south- bank streams have cut through the sandstone and their shallow channels run over smooth, ferruginised, case- hardened, shallow dipping shale beds. The north bank streams have narrower, steeper and less regular beds, with alternating small cascades over sandstone bands and pools hollowed out in the shales. The dip-aligned interfluve slopes on the south banks are moderately Fig. 2. Landforms of Lambir LTER Plot Contours after Yamakura et al. 1995; soil types based on I.C. Baillie, J.D. Mamit and S. Tan unpublished data, 1971 - 2003. Fig. 3. Topographic sections of Lambir LTER Plot ???? Based on I.C. Baillie, J.D. Mamit, M. Tani, T Yamakura and S. Tan unpublished data, 1971 - 2003; and Yamakura et al. (1995). 65Review of Soils on the 52 ha Long Term Ecological Research Plot in Mixed Dipterocarp Forest at Lambir, Sarawak, Malaysian Borneo graded and rectilinear, whilst north bank slopes are steep and stepped meso-scarps with minor sandstone bluffs (Section A-B in Figs 2 and 3). The main scarp is a complex of steep, irregular, unstable slopes and streambeds. The upper slopes are steeply convex, with discontinuous transverse sandstone bluf fs. The lower slopes are steep and irregularly c onca ve , a nd man t l ed w i t h d eb r i s , wh i ch i s unconsolidated and unvegetated when fresh, and vulnerable to surface wash and gullying (Dyke, 1996). There are some wide landslip scars, which were probably initiated by the exceptional rains of 1963 (Watson, 1985), but have since been patchily reactivated. Other slips have narrow tracks, with run-out deposits confined between steep spurs. The scarp complex is interrupted in the southeast by a substantial sandstone spur with an irregular plunging crest and symmetrical, steep side slopes. The smaller and lower cuesta on shale in the south of the plot has a more or less undissected NW low angle dipslope (Sect ion C-D in Figs 2 and 3) , and an insigni?cant scarp on its eastern edge The plot is drained to the east and west by low order streams. In the landas of late 2003, surface wash scoured fresh runnels into thick forest litter and exposed well- established shallow root mats. Surface runoff appears be infrquent, and infiltration adsorbs most throughfall and stem?ow. Root and microbial uptakes of soil moisture are substantial (Kumagai, et al. 2004b), but there is suf?cient remaining to give runoff and steam ?ow throughout the year (Kumagai et al. 2005). On shales a high proportion of the outflow from the soils is diver ted laterally as shallow throughflow and contributes to stream storm- and quick?ows, whilst on sandstone a higher proportion leaches deeply and feeds baseflows (Baillie, 1975 and1996; Pullen et al. 2004). Regolith The saprolites on the dipslopes are stable, and the soils are formed in residua and colluvia. Soil pits dug in 1971 show the stability of the dipslope regolith, as 57 out of 60 were still visible in 2003, and 45 were still moderately deep, with extant free faces of 80-100 cm. In?ll has been mainly by spalling from friable upper subsoils, leaving the more competent, root-bound topsoils as slight overhangs (Baillie, Mamit and Tan, unpublished data, 1971-2003; Baillie, 1978). The regoliths on the scarp are unstable. They tend to be truncated, and shallow on the upper slopes. The overnight collapse of an upper scarp trench intended for throughflow monitoring in the landas of late 2003 highlighted the instability. Throughflow was the main destabilising process in this instance, with the friable upper subsoil caving in and retreating upslope by about 25 cm after 18 hours of heavy rain, leaving a 15 cm overhang of more stable, well-rooted topsoil. The lower scarp regoliths are deep mixtures of allochthonous colluvium, landslip debris and gully wash. SOIL DATA COLLECTION The earliest known soils work on the plot was by P.S. Ashton during the setting up of a network of 105?0.6 ha ecological research plots in Sarawak MDF during the 1960?s (Ashton, 1973). He established six plots at Lambir, of which four were permanent forest dynamics plots. These were re-measured at intervals until about 1990 (Ashton and Hall, 1992) and then incorporated into the 52 ha LTER plot in 1991. All four permanent plots were sited on dipslopes, three on sandstone and one on shale. The pro?les of three soil pits on each plot were described for Munsell hue and texture, sampled at 0-22 cm and 22-75 cm, and the samples bulked to give one topsoil and one subsoil composite per plot. These were analysed at the Sarawak Agricultural Research Centre, Semongok for disturbed bulk density, granulometry, pH, and total nitrogen. Reser ve nutrients and non-cr ystall ine sesquioxides of Fe and Al were extracted by digestion with concentrated HCl and assayed by flame emission spectrophotometery for K and Na, and by titration for Ca, Mg, Fe and Mg. Reserve nutrients were preferred to more labile forms, because they correlate better with fertiliser responses in Sarawak, especially for tree crops (Bailey, 1964 and 1967). In 1971 Baillie and Mamit edaphically characterised Ashton?s four permanent plots in more detail, with 15 profile pits per plot After description and topsoil and subsoil sampling, the pit faces were cut back in layers to give horizontal surfaces for triplicate determinations of topsoil and subsoil undisturbed bulk density by sand pouring. Topsoil bulk densities were determined and samples collected at four additional points around each pit. The coef ficient of linear expansion (COLE) was determined in s i l i cone -coated copper t roughs (Dumbleton, 1975) for the soil excavated for each bulk density determination. Par ticle specific gravity was determined by pycnometer. The 75 topsoil and 15 subsoil samples from each plot were bulked to give three composites for each depth (Baillie, 1978). These were analysed at Semongok for pH, organic carbon, total 66 Sylvester TAN, Takuo YAMAKURA, Masako TANI, Peter PALMIOTTO, James Dawos MAMIT, Chin Siew PIN, Stuart DAVIES, Peter ASHTON, Ian BAILLIE nitrogen, reserve nutrients and Fe and Al non-crystalline sesquioxides, using the same methods as above. P.A. Palmiotto measured the thickness of surface litter and depth of rooting and determined ?eld textures at 5-15 cm in all quadrats in 1994-5 (Palmiotto, 1995 and 1998; Palmiotto et al. 2004). He bulked ten subsamples from the top- and sub-soils at each of six sites on sandstone within the plot and three on shale, and the composites were analysed at Yale University for organic carbon, total nitrogen, and particle size, and extracted with NH4Cl for extractable cations, Bray 2 solution for available P, and concentrated H2SO4 for total nutrients. All extracts were assayed by inductively coupled plasma (ICP) spectrophotometery. S . Tan co l l ec ted 501 s am p l e s a t 5 - 1 5 c m t o characterise soil nutrients and their spatial variation on the plot in 2001 . The samples were analysed at Semongok b y e x t r a c t i o n w i t h 1M NH4OOCH3 for exchangeable cations, Bray 2 for available P, and HClO 4 for total P. Al l extracts were assayed by ICP (Chin, 2002). In 2003 I.C. Baillie and S. Tan described the soils on 245 quadrats by augering to one metre. Topsoil (A1 horizon, 0 -10 cm) and subsoi l (B t horizon, 45-55 cm) samples f r om 60 auger ings were analysed at Semongok by extraction with NH4OOCH3 for exchangeable cations, Bray 2 for available P, and digestion with concentrated HCl for reserve nutrients. All extracts were assayed by ICP (Chin, 2002). Collation of soils data from various laboratories over long periods is complicated by methodological dif ferences and drift. Fortunately, most of the soil data reviewed here come from the Semongok laborator y, which has ISO accreditation and participates in national and international inter-laboratory quality control programmes (Chin, 1996; Chin and Sim, 1990). All statistical analyses used SPSS version 12.0. Significances of dif ferences between means were estimated by t-tests and Tukey HSD analyses of variance. The spatial correspondence between Mantel habitats derived from the 2001 topsoil data and the 2003 soil series and (Fig 4 and Table 11) was tested with chi2. In order to identify underlying trends within the data, principal components were extracted from the 2003 data. Fig. 4. Soil series and Mantel Habitats of Lambir LTER plot ???? (A) Soil series ???? Sandstone series: B, Bekenu; N Nyalau; P, Peninjau. Shale series: M, Merit. Scarp and stream complex: K, Kapit family; L, landslip; S, streambed. ???? Based on I.C. Baillie, J.D. Mamit and S. Tan unpublished data, 1971 - 2003. ???? (B) Habitats. Defined by Mantel analysis of 2001 topsoil data (after Potts et al. 2004) 67Review of Soils on the 52 ha Long Term Ecological Research Plot in Mixed Dipterocarp Forest at Lambir, Sarawak, Malaysian Borneo RESULTS: SOILS OF THE LAMBIR 52 HA LTER PLOT Although each of the soil data sets for the plot (Table 1) has limitations, collectively they give a clear general overview, which is amplified by the findings from soil surveys of nearby areas (Baillie, 1970, 1971; Baillie and Ahmed, 1984; Danida/SWMPI, 2003; Ishizuka et al. 1998, 2001; Lim, 1970a, 1970b; Lim and Rosli, 1971; Sakurai, 1999; Soepadmo et al. 1984; Wall, 1962, 1964, 1965). Soil classification and mapping We considered using the one or both of the international systems, i.e. World Reference Base (WRB) for Soil Resources (FAO, 2006) and Soil Taxonomy (ST) of the USDA (Soil Survey Staff, 1999 and 2006), for the primary classi?cation of the plot?s soils. However, we aopted the Sarawak system (Teng, 1996) because it uses locally appropriate criteria and its taxa can be related to Sarawak agronomic results. Also its taxa are relatively stable, whereas new data can lead to substantial reclassi?cation in the international systems (Schwendenmann et al. 2003;). Furthermore, WRB is explicitly intended for use in conjunction with, not instead of, local classifications (Deckers et al. 2005). The Sarawak Soil Classification (Table 2) is a hierarchical divisive system, the main levels of which are soil group, family and series. The taxa are de?ned on non- Table 1. Soil data sets for Lambir LTER plot and National Park Data collected by: Type of study Area Sites with topographic and soil morphological data Number of analysed soil samples Analyses Reference 52 ha LTER plot Ashton Edaphic characterisation of Sarawak MDF permanent ecological plots 4?0.6 ha 11? pit descriptions (+ 1 just outside) 11?topsoil and subsoil (+ 1 just outside) pH, HCl extractable reserve P, Ca, Mg, K, and Fe + Al sesquioxides Ashton, 1973 Baillie and Mamit More detailed characterisation of Ashton?s plots Same 4? 0.6 ha 57?full pro?le descriptions; and 456 ?in situ bulk density and porosity (+ 3 and 24 just outside) 11?bulked topsoil + subsoil (+ 1 just outside) Particle speci?c gravity, COLE,, pH,, HCl extractable reserve P, Ca, Mg, K, and Fe + Al sesquioxides Baillie, 1978 Palmiotto Soil characterisation as background for nutrient cycling and experimental studies 52 ha 1278?surface organic matter and shallow auger descriptions 9?bulked topsoil + shallow subsoil (+ 6 outside) NH4Cl extractable bases, Bray 2 available P, H2SO4 extractable total bases, Fe, Mn, Al and P Palmiotto, 1995 and 1998; Palmiotto et al. 2004 Tan and Chin Topsoil available nutrient fertility survey 52 ha - 501 topsoil pH, NH4COOH3 exchangeable Ca, Mg, K, CEC; available (Bray 2) and total (HClO4 )P Potts et al. 2004 Baillie, Tan and Chin Soil mapping and nutrient study 52 ha 242?descriptions of site, surface organic matter and augerings. 60?topsoil + subsoil pH, NH4COOH3 exchangeable Ca, Mg, K; Available (Bray 2) P, , HCl extractable reserve Ca, Mg, K and P This study Elsewhere in Bukit Lambir National Park Hirai et al. Soil and site associations with distributions of Dryobalanops spp 8 NH4COOH3 exchangeable cations, 1M KCl extractable Al and H; hydraulic conductivity and available moisture capacity, tensiometers at 10 and 30 cm depths Hirai et al . 1997 Ishizuka et al. Characterisation of soil texture and consistence 2 Ishizuka et al. 1998 Sakurai Characterisation of soils for Dryobalanops habitats Includes oxalate and dithionite extractable Si and Fe, Al sesquioxides Sakurai, 1999 68 Sylvester TAN, Takuo YAMAKURA, Masako TANI, Peter PALMIOTTO, James Dawos MAMIT, Chin Siew PIN, Stuart DAVIES, Peter ASHTON, Ian BAILLIE ephemeral morphological and physical features, especially texture, depth and drainage (Teng, 1996; Tie, 1982). For the more mature soils on the dipslopes we differentiate soil series, but in some scarp areas with very heterogeneous soils we generalise at family and group levels. Although chemical attributes are not definitive, mineral nutrients are affected by parent material lithology and reflected in soil textures, and Sarawak soil series differ somewhat with respect to nutrient fertility. The dipslope soil mapping units (Fig.4a) are consociations, with one series predominant and others as minor inclusions. The spatial variability of the scarp and streambeds necessitates mapping of soil complexes, with several taxa co-dominant. Soil morphology Most of the dipslope soils are well-drained mature soils of the Red Yellow Podzolic (RYP) group in the Sarawak system (= Acrisols in WRB and Udults in ST). The coarsest textured soils are morphologically similar but Table 2. Morphology, classi?cation and mapping, of the soils of the LTER plot, Lambir Map unit symbol (Fig. 4a) Topography Position Sarawak soil classi?cation* Main morphological features Depth Textural pro?le Surface organic matter Group Family Series P Sandstone dipslope Knolls on main ridge Arenaceous Peninjau Peninjau Deep, yellow (10YR), sandy, very friable and permeable subsoil > 100 cm to weathered sandstone, mostly > 150 cm Loamy sand / sandy loam to > 100 cm Thick litter and continuous rooted humus mat N Main ridge and spurs Red Yellow Podzolic Nyalau Nyalau Yellowish (10YR) coarse topsoil over redder (7.5YR) loam subsoil, moderately friable subsoil > 50 cm to weathered sandstone, mostly > 100 cm Sandy loam, over sandy clay loam within 100 cm B Slopes of N and W valleys Bekenu Bekenu Yellowish (10YR) loam topsoil over redder (7.5YR) and ?ne loam subsoil, moderately friable subsoil > 50 cm to weathered sandstone/ shale, mostly > 100 cm Sandy loam / sandy clay loam, over sandy clay within 100 cm Moderate litter and patchy rooted humus mat M Shale cuesta Undissected dipslope Merit Merit Yellowish (10YR) ?ne loam topsoil over redder (7.5YR) ?rm clay subsoil > 50 cm to weathered shale Clay loam / silty clay loam, over clay / silty clay within 100 cm Thin and patchy litter. Occasional non- humic root mat K Upper scarp slope Cliffs and rock bands Skeletal Meluan Meluan #1 Bare rock, +/- thin soil cover < 25 cm to hard rock Variable over rock Variable litter, with patchy humus root mat Convex steep upper slopes Kapit Kapit Yellowish (10YR) stony loam topsoil over thin (7.5YR) stony ?ne loam subsoil, over shallow saprolite < 50 cm to weathered rock Variable over weathered rock Variable litter, with patchy humus root mat L Concave lower scarp Irregular runout deposits Tutoh Tutoh Patchy thin topsoil over deep, mixed 10YR and 7.5YR stony loam subsoil < 50 cm to > 50% stones Variable over stony Variable litter, but no humus root mat S Streams Streambeds and toe slopes Gley Semadoh Tumau Dark mucky topsoil over grey mixed texture and, +/- mottles and stones Variable Variable No litter or humus root mat Based on Baillie, Mamit and Tan, unpublished data, 1971 ? 2003, Palmiotto (1998) and Baillie et al. (2006) * Adapted from Teng (1996). 69Review of Soils on the 52 ha Long Term Ecological Research Plot in Mixed Dipterocarp Forest at Lambir, Sarawak, Malaysian Borneo are separated in the Arenaceous group (Teng, 1996). The mineral topsoils of these soils are thin, moderately darkened, and have friable, porous crumb structures. By 10-15 cm they grade to reddish yellow and moderately porous blocky subsoils, which become redder and ?ner textured with depth. Subsoil consistence is ?rm, and Ishizuka et al. (1998) found drop cone penetrometer resistance to be moderate. The subsoils overlie patchy red, white and yellow soft weathered rock (saprolite) at depths of 0.5-2.5 m, and there are variable contents of saprolitic fragments above the main paralithic contact. The RYP/Arenaceous soils on the plot form a textural gradient from Peninjau series (Arenosol/Paleudult, sandy), through Nyalau (Acrisol/Paleudult, coarse loamy), Bekenu (Acrisol/Hapludult, ?ne loamy) to Merit series (Acrisol/Hapludult, clay) (Table 2). The coarse textured Peninjau and Nyalau series occur on sandstone-dominated regoliths on the ridge and upper slopes of the main dipslope. They are the deepest and most weathered soils on the plot, with sola often more than 2 m deep. Relatively deep RYP are common on sandstone ridges elsewhere in Sarawak (Wall, 1964; Baillie et al. 1987), but not at Belalong in adjacent Brunei, where the sandstone ridge soils are shallow and stony (Ross and Dyke, 1996). The subsoils of Peninjau series are porous, friable and no finer than sandy loam within the top metre, whereas subsoils in Nyalau series grade to slightly firm sandy clay loam. Although clay contents increase with depth, subsoil contents are still low and clayskins are absent or weak. These soils have almost continuous mats of dark reddish brown humus, which are mostly less than 10 cm thick but are densely rooted and can be lifted off the surface like a carpet (Baillie et al. 2006). The humus is mor or dysmoder (Ponge et al. 2002), with little faunal mixing into the underlying mineral soil. The soils of Bekenu series are the most extensive on the plot and cover much of the main dipslope (Fig. 4a). They are of intermediate texture and depth, and form on sandstone with some shale. Some of the soils of Bekenu series have thin and discontinuous humus root mats. Clay content increases in with depth, from sandy loam topsoil Table 3. Physical data for soils of Lambir LTER Plot Data reference Soil series Depth n Stones Sand Silt Clay Bulk density Total Pores COLE cm % g.ml-1 % Ashton (1973) Nyalau (12 of 15 quadrats of Plot L4) 0-22 1 nd 58 20 22 1.54 nd 22-75 1 63 14 23 1.82 Baillie and Mamit (Baillie, 1978) 0-15 2 0 (n=60) 62 17 19 0.9 (n=60) 66 (n=60) 6.5 (n=60) Bt 2 5 (n=36) 57 16 27 1.6 (n=36) 41 (n=36) 13.7 (n=36) Ashton (1973) Bekenu (Plots L3 and L5)) 0-22 2 nd 60 19 21 1.52 nd 22-75 2 65 16 19 1.8 Baillie and Mamit (Baillie, 1978) 0-15 6 0 (n=150) 69 14 17 1.00 (n=150) 62 (n=150) 6.6 (n=150) Bt 6 5 (n=90) 64 14 22 1.5 (n=90) 41 (n=90) 9.5 (n=90) Ashton (1973) Merit, (Plot L2) 0-22 1 nd 27 43 30 1.6 nd 22-75 1 14 44 42 1.66 Baillie and Mamit (Baillie, 1978) 0-15 3 0 (n=75) 47 28 24 1.04 (n=75) 61 (n=75) 9.0 (n=75) Bt 3 7 (n=45) 36 28 35 1.43 (n=45) 46 (n=45) 13.0 (n=45) Palmiotto (1998) ?Humult? (=sandstone soils) 0-15 6 nd 69 17 13 0.8 nd 15-30 6 66 14 17 nd ?Udult? (=Merit series) 0-15 3 43 35 22 1.0 15-30 3 36 33 31 nd Based on Ashton, Baillie, Mamit, and Palmiotto, unpublished data, 1966 ? 2003; Palmiotto, 1998 70 Sylvester TAN, Takuo YAMAKURA, Masako TANI, Peter PALMIOTTO, James Dawos MAMIT, Chin Siew PIN, Stuart DAVIES, Peter ASHTON, Ian BAILLIE to sandy clay within the top metre. The bright reddish yellow and slightly mottled subsoils have firm, blocky structures with low porosities and moderate clayskins. Soils of Bekenu series are moderately deep, mostly 1-1.5 m to the paralithic contact. Merit series are the ?nest textured RYP?s on the plot. They develop on shales, especially on the dipslope of the lower southern cuesta. Small areas also occur on the main dipslope, where dissection has cut through the capping sandstone into subjacent shale. These soils are well horizonated and apparently mature, but are shallower than the coarser-textured RYP series, with the paralithic contact often about 1 m. The litter normally lies directly on the mineral topsoil, with no humus mat (Baillie et al. 2006). Textures are (silty) clay loam in the topsoils, over (silty) clay subsoils. The bright reddish yellow and moderately mottled subsoils have moderate blocky structures, continuous clayskins, firm consistence, and few visible pores. Most soils on the convex upper scarp are less than 1 m deep to hard rock or saprolite. Many are weakly developed versions of the RYP series, with reddish yellow subsoils and increased reddening and clay content with depth. Soils less than 50 cm deep to the lithic/paralithic contact or very stony layers qualify for the Skeletal group in the Sarawak system (Teng, 1996). Those over saprolite belong to Kapit family (Skeletic Cambisol/ Typic Dystrudept) and those over hard rock to Meluan family (Leptic Cambisol/ Lithic Dystrudept). The deep, stony, and erratically textured soils on fresh or recent wash and slip deposits downslope are in Tutoh family (Skeletic Regosol/ Typic Udorthent). Many of the stream are steep and bare rocky beds, but there are intermittent nar row stretches with gullywash and alluvium. Some of the shallow and stony soils are freely or imperfectly drained, but mnay have greyish matrix colours and bright orange and rust brown mottles, indicating persistently impeded drainage. Soil physical properties The limited granulometric data differentiate Merit series from the other RYP?s, but not between the sandstone series (Table 3), possibly because of clay dispersion problems. Undisturbed bulk density in topsoils increases with clay content from 0.85-0.9 in Nyalau series to 1.0-1.05 in Merit (I.C Baillie and J.D. Mamit, unpublished data, 1971). Subsoil bulk densities are about 1.6 in Nyalau series and 1.4 in Merit. The bulk density contrast between top- and subsoils decreases with clay content, being almost double in Nyalau series but increasing by only one third in Merit. Ashton ?s bulk density data are for disturbed samples but show similar trends. The pattern for total porosity complements that of bulk density, with Nyalau series having the highest topsoil and lowest subsoil values, and sharpest decrease with depth. Ishizuka et al. (1998) found total porosities of 60-70% in a Nyalau series topsoil on an upper slope elsewhere at Lambir, compared to 50% in a lower slope soil of Peninjau series, but the subsoils were similar, with total porosities of 40-45%. Particle speci?c gravity values are not tabulated because they vary over such a narrow range, from 2.5 to 2.65. They are consistent with a predominantly quartz and mica mineralogy. Coef ficients of l inear expansion (COLE) are moderate. They accord with the presence of some expansible clay minerals, such as illites and hydrated inter-layered vermiculites, but not smectites, reported elsewhere at Lambir (Ishizuka et al. 1998). COLE?s vary between series but do not show the expected systematic increase with clay content. Total porosity values (Table 3) do not indicate the proportions of different sized pores, the balance of which is crucial for drainage, aeration and the bio-availability of soil water. Subsoil matrix Munsell hues of 10YR or redder, and chromas and values of 5 or higher indicate that most soils are freely drained and have effective macro- and meso-pore systems. There are varicoloured mottles in some subsoils in Bekenu series and many in Merit series, but few are grey or ochreous and they look as much like incomplete weathering as hydromorphism. The pale patches in the saprolites are also mostly attributed to incomplete weathering. Some sandstone soils had very wet but bright and almost unmottled reddish yellow subsoils when augered in the 2003 landas (NE monsoon). The wetness was diffuse in a few soils but concentrated as a distinct layer in most, with drier soil beneath as well as above. Moisture tensions have been traced in coarse textured soils elsewhere at Lambir (Ishizuka et al. 1998). In the drier par t of the year topsoil tensions were measured as high as pF 4.0 (1 MPa) in a soil of Nyalau series on an upper slope, but only up to pF 3.2 (0.15 MPa) in a coarser textured soil of Peninjau series downslope, perhaps because of lateral recharge by throughflow. However, both soils dried to permanent wilting and no measurements were possible for about one month during a severe drought. Although the sandstone soils are drier than those on shale (S. E. Russo, unpublished data, 2005), Kumaga i e t a l . (2005 ) conc luded tha t f o r e s t evapotranspiration in non-ENSO years at Lambir is 71Review of Soils on the 52 ha Long Term Ecological Research Plot in Mixed Dipterocarp Forest at Lambir, Sarawak, Malaysian Borneo determined more by radiation than soil moisture de?cits. Soil chemical properties The analyses of samples collected in the 1960?s and 1970?s indicated that HCl-extractable reserves in the mature RYP soils on the plot are moderate for K and Mg, low for P, very low for Ca, and increase with clay content for all nutrients. Similar trends are apparent in the 1990?s data for H2SO4-extractable totals (Table 4) The RYP?s on the plot are intensively leached, very Table 4. Pre-2000 data for non-labile nutrients in soils of Lambir LTER plot Data reference Soil series Depth n P Ca Mg K Group III oxides cm mg.kg-1 % Reserve (conc. HCl) Ashton 1966 Nyalau (Plot L4) 0-22 1 70 213 575 1613 4.6 22-75 1 69 Tr 317 1178 8.0 Baillie and Mamit 1971 0-15 2 72 95 636 1495 nd Bt 2 61 152 1116 1968 Ashton 1966 Bekenu (Plots L3 and L5) 0-22 2 60 159 507 2088 3.9 22-75 2 85 136 782 2574 9.0 Baillie and Mamit 1971 0-15 6 71 87 549 1516 nd Bt 6 57 99 821 2247 Ashton 1966 Merit (Plot L2) 0-22 1 133 111 1272 4226 7.9 22-75 1 116 Tr 1842 5530 10.3 Baillie and Mamit 1971 0-15 3 136 187 1141 2511 nd Bt 3 98 192 1876 3718 Total (conc. H2SO4) Palmiotto (1998) P Ca Mg K Mn Al Fe mg.kg-1 % ?Humult? (=sandstone soils) 0-15 9 75b 19b 538b 2404b 4b 1.46b 0.65b 15-30 9 63b 15b 435b 2732b 2b 1.27b 0.59b ?Udult? (=Merit series) 0-15 6 131a 106a 1574a 7180a 123a 2.69a 1.45a 15-30 6 121a 38ab 1735a 9328a 45a 3.03a 1.52a Based on Ashton Baillie and Mamit, unpublished data, 1966 ? 1971; Baillie, 1978 Different letter superscripts indicate differences are signi?cant (p < 0.05) Table 5. NH4Cl-extractable nutrients in soils of Lambir LTER plot Soil series Depth(cm) Org.C Total N C:N ratio Extractable (NH4Cl) P Ca Mg K Mn Al Fe % mg.kg?1 cmol+.kg?1 ?Humult? (= sandstone soils) 0-15 1.9 b 0.14 a 14 a 3a 0.06 b 0.18 a 0.10 a 0.01 b 3.83 a 0.31 a 15-30 0.61 c 0.07 c 10 b 1 b 0.01 c 0.07 a 0.07 a tr d 2.36 a 0.10 b Udult (= Merit series) 0-15 1.4 a 0.12 a 12 b 2 a 0.35 a 0.59 a 0.11 a 0.21 a 3.26 a 0.19 ab 15-30 0.56 c 0.09 b 7 c tr b 0.07 b 0.46 a 0.08 a 0.06 b 3.72 a 0.10 b Based on Palmiotto, 1998 Different letter superscripts indicate differences are signi?cant (Tukey HSD, < 0.05). *Converted from mg.kg-1, assuming valencies of Mn4+ and Fe3+ in freely drained soils 72 Sylvester TAN, Takuo YAMAKURA, Masako TANI, Peter PALMIOTTO, James Dawos MAMIT, Chin Siew PIN, Stuart DAVIES, Peter ASHTON, Ian BAILLIE Table 6. Means of 2001 data for topsoil nutrients in soils of Lambir LTER plot 2003 Soil Map Unit (see Figure 4a) Depth n pH (H2O) Org C Total N C:N Total P Avail. P Exchangeable (neutral NH4OOCCH3) Ca Mg K Na TEB CEC BS % mg.kg-1 cmolc.kg ?1 (= me%) % P Top 6 4.8a 1.2a 0.09 13 c 27 a 2 0.23 ab 0.12 ab 0.08 a 0.13 0.55 ab 5.72 a 10 ab N 61 4.6abc 1.1ab 0.10 11 b 57 bc 1 0.20 a 0.11 a 0.11 ab 0.06 0.48 a 7.28 b 6 a B 113 4.6ab 1.0ab 0.10 10 ab 46 ab 1 0.23 ab 0.14 ab 0.12 ab 0.06 0.55 ab 7.64 b 8 ab M 51 4.4cde 1.0b 0.10 10 ab 108 d 1 0.36 c 0.26 c 0.14 b 0.08 0.83 c 7.21 ab 12 b K 120 4.4de 0.9b 0.10 10 ab 64 bc 2 0.25 ab 0.15 ab 0.13 b 0.08 0.61 abc 6.96 ab 9 ab L 121 4.3e 0.9b 0.10 9 a 78 c 2 0.30 bc 0.26 c 0.14 b 0.08 0.77 bc 6.82 ab 12 b S 28 4.3bcd 0.9b 0.10 9 a 73 c 2 0.28abc 0.21bc 0.13 b 0.08 0.71abc 7.53 b 13 b Overall mean 487 -500 4.46 1.0 0.10 9.65 67 1.6 0.26 0.18 0.13 0.07 0.65 7.23 8.9 p of ANOVA F ratio for SMU means 0.00 0.00 0.05 (ns) 0.00 0.00 0.02 (ns) 0.00 0.00 0.00 0.34 (ns) 0.00 0.00 0.00 Based on Tan and Chin, unpublished data, 2001 Different letter superscripts for signi?cantly different means (Tukey HSD, < 0.05) Table 7. Means of 2003 data for labile nutrients in soils of Lambir LTER plot Soil map unit (see Fig. 4a) Depth n pH Org. Total N C:N Avail P Exchangeable (H2O) C (neutral NH4OOCCH3) Ca Mg K Na TEB cm % ppm cmolc.kg ?1 (=me%) Topsoil P 0 - 10 3 4.4 2.4 0.15 16a 5 0.36 0.12 0.14 0.08 0.7 N 15 4.5 2 0.13 14ab 5 0.43 0.21 0.15 0.1 0.89 B 20 4.5 1.8 0.14 13ab 4 0.46 0.25 0.15 0.11 0.97 M 8 4.5 1.2 0.12 10b 4 0.6 0.62 0.19 0.15 1.56 K 11 4.3 1.6 0.13 12ab 5 0.53 0.3 0.15 0.08 1.07 L + S 3 4.2 1.3 0.13 10b 5 0.34 0.18 0.16 0.08 0.76 Overall 60 4.42 1.74 0.132 12.7 4.5 0.47 0.29 0.16 0.1 1.02 mean p of F ratio 0.33 0.16 0.06 0.002 0.62 0.53 0.1 0.82 0.16 0.09 ? (ns) (ns) (ns) (ns) (ns) (ns) (ns) (ns) (ns) Subsoil P 45 - 55 3 4.8a nd nd nd 4 0.18 0.06 0.08 0.05 0.37 a N 15 4.7ab 2 0.17 0.13 0.09 0.08 0.47 a B 20 4.6 ab 3 0.24 0.18 0.12 0.13 0.66 ab M 8 4.7 ab 3 0.27 0.71 0.16 0.18 1.33 b K 11 4.3b 4 0.18 0.16 0.1 0.08 0.52 a L + S 3 4.7 ab 3 0.24 0.22 0.1 0.19 0.75 ab Overall mean 60 4.6 3 0.21 0.23 0.11 0.11 0.67 p of F ratio 0.005 0.34 (ns) 0.28 (ns) 0.02 (ns) 0.07 (ns) 0.07 (ns) 0.001 Based on Baillie, Tan and Chin, unpublished data for 60 auger pro?les, 2003. Different letter superscripts indicate means are signi?cantly different (Tukey HSD, < 0.05). 73Review of Soils on the 52 ha Long Term Ecological Research Plot in Mixed Dipterocarp Forest at Lambir, Sarawak, Malaysian Borneo acid, and de?cient in NH4Cl-extractable P and bases, and Al is the dominant labile cation (Table 5). Labile forms of all of the main mineral nutrients increase from coarse to ?ne textured soils, but levels are still low. The 2001 data (S. Tan, unpublished) con?rm that topsoils are very acid, and show that they all have low contents of NH4OOCH3- exchangeable cations (Table 6), with few significant differences between Peninjau, Nyalau and Bekenu series, but the clays of Merit series have significantly better exchangeable base status. Bray 2 available P contents are low throughout and vary little between series, but HClO4- extracted total P increases signi?cantly with clay content. The 2003 data (I.C. Baillie and S. Tan, unpublished) also indicate that subsoils are very acid and have low contents of exchangeable cations and Bray 2 available P (Table 7). Series means increase with clay content, but not significantly. When individual sites are grouped by ?eld texture, most labile nutrients increase systematically from sand to clay. However, the increases in topsoils are signi?cant (p < 0.05) only for C:N, exchangeable Mg, and total exchangeable bases (TEB). Significance levels are higher in subsoils than topsoils but are very signi?cant (p < 0.01) only for subsoil exchangeable K, Mg and TEB. The 2003 data con?rm that HCl-extractable reserves are moderate for K and Mg, low for P, and very low for Ca (Table 8). The differences between series are clearer for Table 8. Means of 2003 data for reserve (HCl) nutrients in soils of Lambir LTER plot Soil Map Unit (see Fig 4a) Depth n Reserve (conc.HCl) cm P K Ca Mg Mn Cu Zn B Fe mg.kg-1 % Topsoil P 0 - 10 3 102 1864a 94 574 a 1 1 15 ab 19a 0.88 a N 15 91 2228 a 141 685 a 4 1 10 a 17 a 0.79 a B 20 88 2526ab 133 792 ab 6 2 10 a 19 a 0.76 a M 8 129 4231b 170 1421 b 88 3 23 b 33 b 1.46 b K 11 100 3276ab 158 874 ab 9 2 12 a 23 ab 0.99 a L + S 3 121 3291ab 124 967 ab 11 1 12 a 20 ab 0.84 a Overall mean 60 99 2822 142 862 17 2 12 21 0.91 p of F ratio 0.10 (ns) 0.008 0.38 (ns) 0.000 0.05 (ns) 0.02 (ns) 0.000 0.001 0.000 Subsoil P 45 - 55 3 78 1782 a 111 579 a 1 1 7a 21a 0.96a N 15 78 2499ab 129 796 a 2 2 12 21a 0.94a B 20 78 3078abc 139 967ab 3 2 12a 23a 1.04 a M 8 123 4630 c 127 1667b 68 3 25b 38b 1.60 b K 11 88 3867bc 124 997ab 5 3 13a 28ab 1.18ab L + S 3 102 3423bc 117 1188ab 4 3 14a 26ab 1.10ab Overall mean 60 87 3237 130 1014 12 2 14 25 1.11 p of F ratio 0.03 (ns) 0.001 0.32 (ns) 0.001 0.05 (ns) 0.08 (ns) 0.000 0.000 0.001 Based on Baillie, Tan and Chin, unpublished data, 2003. Different letter superscripts indicate means are signi?cantly different (Tukey HSD, < 0.05) Table 9(a). Principal Components in data for auger pro?les (n = 60) Principal Component 1 2 3 4 Eigenvalue 12.94 3.83 2.82 2.44 % Total variance 37 11 8 7 Based on Baillie, Tan and Chin, unpublished data, 2003. 74 Sylvester TAN, Takuo YAMAKURA, Masako TANI, Peter PALMIOTTO, James Dawos MAMIT, Chin Siew PIN, Stuart DAVIES, Peter ASHTON, Ian BAILLIE Table 9(b). Main loadings on Principal Components 1 - 4 Principal Component Variable groups Individual variables 1 2 3 4 Communality Highest loading Whole solum Texture class 0.50 0.56 Depth 0.37 0.44 Organic matter Humus thickness 0.32 0.42 Org C 0.79 0.83 C:N 0.73 0.62 Topsoil labile nutrients pH 0.60 0.71 Exch Ca 0.43 0.53 Exch Mg 0.78 0.78 Exch K 0.65 0.65 Exch Na 0.41 0.56 Available P 0.75 0.81 Topsoil reserve nutrients P 0.83 0.83 K 0.80 0.84 Mg 0.86 0.92 Ca 0.56 0.45 Fe 0.70 0.78 Mn 0.80 0.66 Cu 0.50 0.49 Zn 0.78 0.86 B 0.69 0.77 Subsoil labile nutrients pH 0.60 0.77 Exch Ca 0.18 0.39 Exch Mg 0.82 0.77 Exch K 0.58 0.57 Exch Na 0.28 0.44 Available P 0.46 0.38 Subsoil reserve nutrients P 0.81 0.84 K 0.80 0.86 Mg 0.87 0.93 Ca 0.11 0.28 Fe 0.59 0.73 Mn 0.71 0.63 Cu 0.60 0.61 Zn 0.72 0.82 B 0.65 0.78 Component interpretation and designation Mica Ca Organic matter Non-mica minerals 75Review of Soils on the 52 ha Long Term Ecological Research Plot in Mixed Dipterocarp Forest at Lambir, Sarawak, Malaysian Borneo reserves than for labile forms of the same nutrients. Series means of reserves differ significantly for K, Mg, Fe, Zn and B at both depths. Series dif ferences for reserve Mn are not statistically signi?cant although the series means span an order of magnitude. Merit series has the highest means for 14 of the 18 reserve nutrient variables, and Peninjau series the lowest for ten. In the sandstone RYP?s 12 of the reserve nutrient variables increase with clay content from Peninjau series through Nyalau to Bekenu. Significance levels of inter-series differences in reserve nutrients are similar for topsoils and subsoils. As with more labile forms (exchangeable, extractable and available), the trends for reserve nutrients are clearer when individual sites are grouped by ?eld texture. Clays have the highest means in 16 of the 18 reserve nutrient variables; differences for reserve Mn become statistically significant; and dif ferences are more pronounced in subsoils than topsoils. Principal component analysis (PCA) Pedological and ecological interpretations of multivariate soil data are complicated by correlations between attributes. Apparently influential variables may not be important themselves but correlated with genuinely signi?cant attributes. Alternatively, none of the correlated variables may themselves be causally important but may be indicators of underlying unmeasured trends. In order to identify the main trends in the Lambir soils, principal components (PC) were extracted from the 2003 data of 35 variables covering humus thickness, soil depth, textural class and nutrients for 60 sites (I. C. Baillie, S. Tan, and S.P Chin, unpublished). Total N and TEB were omitted from the initial data because of their linear dependence on other variables. A preliminary scree test indicated a break of slope at four components. Varimax rotation made little difference to an already interpretable structure, so the orthogonal PCA was retained. The first four unrotated principal components incorporate almost two thirds of the total variance(Table 9a). Elision of the minor loadings highlights the main features of the component structures (Table 9b). The ?rst three components are similar to those extracted for MDF soils on clastic sedimentary rocks in Central Sarawak (Baillie et al. 1987). The main component (PC1) incorporates 37 % of total variance and is heavily loaded with clay and reserve nutrients, especially Mg and K. It parallels the proportions of shale and sandstone in the soil parent materials, and is interpreted as re?ecting the in?uence of micaceous minerals. Component PC2 (11%) is loaded by pH and Ca variables, although the Ca subsoil variables have low communalities, i.e. much error variance, with only a small fraction contributing to the PCA. The loading of Ca onto a separate component highlights the dif ferences between it and the other cationic nutrients in these soils. The main loadings on component PC3 (8%) are for organic matter and topsoil available P. The loadings for subsoil exchangeable K and Na suggest that component PC 4 (7%) may reflect the effect of non-micaceous minerals in the parent material, such as feldspars and halites. DISCUSSION International soil correlations The use of the Sarawak system for the classification of the soils of the plot parallels applications of local soil taxonomies to edaphic characterisation of other forest ecological research sites (Baillie et al. 2007a; Clark et al. 1999; Johnston, 1987; Sollins et. al., 1994; Yamashita et al. 2003). However, local taxa are meaningful only in their home territories and it is necessary to correlate them with international systems such as WRB and/or ST for wider communication and comparisons. Most of the mature RYP soils on the plot correlate with Acrisols in WRB, with the required increases in clay with depth, low base saturations, and low activity clays (< CEC 24 cmolc kg ?1 clay) (Table 10). Most of them are sufficiently base-depleted to be Hyperdystric, with the remainder mainly Haplic. There are a few soils in Bekenu and Merit series with more active clays, on which Al is the dominant labile cation, and these qualify as Alisols. Like the Sarawak system, WRB separates ver y coarse textured soils at high level, and those soils in Peninjau series with loamy sand textures to below 1 m correlate as WRB Arenosols. The weak clayskins, high friability and porosity in some subsoils in Peninjau and Nyalau series are ferralic attributes, and these soils qualify as Ferralsols or Ferralic Arenosols. In ST all of the Lambir RYP?s are Udults. They are subdivided on the depth profiles of their clay contents. Most of the Lambir RYP?s show no systematic decrease below the clay-increase argillic horizon, and the textural profiles are ?stepped ? rather than ?bulging ?. Many therefore appear to be Paleudults. However, as its name indicates, this group is intended for old, well developed soils and is defined as having the paralithic contact at least 1.5 m deep. At Lambir most soils in Peninjau and Nyalau series and some in Bekenu are suf?ciently deep, but most of the clays in Merit series are too shallow. They 76 Sylvester TAN, Takuo YAMAKURA, Masako TANI, Peter PALMIOTTO, James Dawos MAMIT, Chin Siew PIN, Stuart DAVIES, Peter ASHTON, Ian BAILLIE therefore correlate as Hapludults (Typic or Inceptic). Transitional oxic subsoils mean that some profiles of Peninjau and Nyalau series qualify for the Hapludox group or the Hapludoxic subgroups of the Paleudults. A few soils in Peninjau series are coarse textured enough to be Psammic, but most of the non-oxic Paleudults have loam or ?ner textures, and so qualify for Typic subgroup. Like WRB, ST dif ferentiates on clay activity but, unfortunately, it does not use the same criterion. Many Lambir RYP subsoils have CEC values below the ST limit for low activity clays (16 cmolc.kg?1 clay), and qualify as kandic horizons. The deep sandstone soils are therefore mostly kandic equivalents of the Paleudults and qualify as Hapludoxic or Typic Kandiudults. Similarly, some of the clays of Merit series are Typic Kanhapudults. The shallow scarp soils of Kapit and Meluan series are Leptic and Haplic Cambisols in WRB and Dystrudepts in ST. The deeper debris soils of Tutoh series are Colluvic Regosols in WRB and Typic Udorthents in ST. Humus mats and the absence of Humults Despite its limitations (Baillie, 1996, and 2001), ST has been used in previous ecological studies at Lambir and elsewhere in Bornean MDF. Non-humic soils at Lambir were correctly classi?ed as Udults, but those with humic mats were designated as Humults (Ashton, and Hall, 1992; Cranbrook and Edwards, 1995; Davies, et al. 1998; Nagamasu and Momose, 1997; Palmiotto et al. 2004; Potts et al. 2004; Yamada et al. 1997). This was based on the reasonable assumption that a feature as ecologically signi?cant as a humus mat would warrant pedotaxonomic recognition. However, most soil classification systems have agricultural, rather than ecological, orientations and differentiate soils on features that survive changes in land use and persist in agricultural soils. As thin sur face humus disappears when forest is cleared and soil surfaces are exposed to direct rainfall, fire, cultivation, sunlight, high temperatures and desiccation, humus layers less than 10 cm thick are considered ephemeral and are ignored as pedotaxonomic criteria in the tropics. Furthermore, the ST Humult suborder is de?ned as having organic matter extending well into the subsoil, with organic carbon contents >0.9% down to at least 15 cm into the argillic horizon, and is intended for soils with active mixing of organic and mineral matter. Humults mostly develop on volcanic parent materials, as in Jaguar and Matabuey series at La Selva (Sollins et al. 1994). As humus at Lambir occurs as discrete, unmixed surface layers, none of the RYP?s quali?es as Humults. Although understandable, this discounting of thin surface humus layers is ecologically regrettable, as it means that the conventional soil classi?cations ignore an Table 10. International correlations of soils of Lambir LTER plot Sarawak soil taxon World Reference Base (FAO, 2006) Soil Taxonomy (Soil Survey Staff, 1999 and 2006) Subgroup Particle size and mineralogy families Peninjau series Hyperdystric, Haplic or Ferralic Arenosol; or Arenic Acrisol; or Areni-Acric Ferralsol Psammic, Hapludoxic or Typic Paleudult or Kandiudult; Psammic Hapludox Sandy and coarse- loamy; kaolinitic and mixed Nyalau series Hyperdystric or Haplic Acrisol; or Acric Ferralsol Hapludoxic and Typic Paleudult and Kandiudult Coarse-loamy; kaolinitic and mixed Bekenu series Haplic or Hyperdystric Acrisol or Alisol Typic Hapludult, Paleudult, Kanhapludult and Kandiudult Fine-loamy; mixed Merit series Haplic Acrisol or Alisol Typic Hapludult or Kanhapludult Clayey; mixed Kapit series Skeleti-Dystric Cambisol Lithic Dystrudept Loamy- skeletal; mixed Meluan series Dystric Leptosol or Skeleti-Dystric Cambisol Lithic Dystrudept Loamy- skeletal; mixed Tutoh series Skeleti-Dystric Regosol Typic Udorthent Semadoh family Lepti-Dystric Gleysol Lithic and Typic Endoaquent Based on Tie (1982); Teng, (1996); I C Baillie, J. D. Mamit and S. Tan, unpublished data, 1971-2003 77Review of Soils on the 52 ha Long Term Ecological Research Plot in Mixed Dipterocarp Forest at Lambir, Sarawak, Malaysian Borneo important attribute in soils that remain under forest. If the Lambir RYP?s are separated at phase (i.e. sub-series) level on the presence/absence of humus mats > 5 cm thick, there are clear differences between the soil series. 88% of the 2003 augerings in Peninjau series would qualify for the epihumic phase, 59% in Nyalau and 56% in Bekenu, but only 12% in Merit and 13% in Kapit (I.C. Baillie and S. Tan, unpublished data). Edaphecological habitat characterisation This review was undertaken in order to provide the fullest possible data for the consideration of edaphic effects in the ecology of MDF at Lambir. Early studies of site-forest association at Lambir were limited by the lack of systematic data on soil nutrients, and the differentiations of edaphic habitats were mainly based on altitude and slope gradients, and humic and non-humic sur faces (Davies, et al. 1998; Nagamasu and Momose, 1997; Palmiotto et al. 2004; Potts et al. 2004; Yamada et al. 1997 and 2000). The application of Mantel analysis to the 2001 topsoil labile nutrient data was a considerable advance (Potts et al. 2004), and enabled convincing con?rmation of the existence of strong soil-forest associations (Davies, et al. 2005; Russo et al. 2005). Figure 4 compares our soil series, which are mainly defined on field-observable morphological attributes, with the nutrient-defined Mantel habitats. The correspondence is striking, and our mo r pho l o g i c a l l y - b a s e d s o i l m a p d e l i n e a t e s edaphecologically distinct areas (Fig. 4b and Table 11). The distributions of edaphic specialist tree species (Davies et al. 2005) correspond well with the soil map, as do differences in forest dynamics (Russo et al. 2005). Comparison with other tropical forest soils RYP and associated shallow soils are the most extensive soils in Sarawak (Andriesse, 1972; Teng, 1996), and are the main lowland soils on clastic sedimentary parent materials in Borneo and aseasonal Southeast Asia (Dudal and Moormann, 1964; Soepraptohardtjo and Ismangun, 1980). Morphologically similar Acrisols are extensive on clastic sedimentary parent materials elsewhere in the humid tropics (Driessen and Dudal, 1991; Duivenvoorden and Lips, 1995; Johnston, 1987; Wright et al. 1959) They form a distinct subgroup within the soils of tropical forests. Their physical distinction results from the substantial contents of 2:1 and 2:1:1 clay minerals, which give their subsoils moderate bulk density, porosity and firm consistence. This makes the subsoils less Table 11. Correspondence between Mantel edaphic habitats and Sarawak soil taxa, Lambir LTER plot Mantel habitat (after Potts et al. 2004) Predominant lithology Topographic position Main Sarawak soil taxa Ranking of edaphic constraints 1 Sandstone Main dipslope Peninjau, Nyalau and Bekenu series Low nutrients > moisture stress > site instability 2 Shale Lesser dipslope Meritseries Occasional anoxia and moderately low nutrients > site instability 3 Sandstone + some shale Steep convex upper scarp Kapit and Tutoh series Site instability > moisture stress > low nutrients 4 Shale + some sandstone Steep concave lower scarp Semadoh and Meluan families Site instability >> patchy moisture stress and occasional anoxia and moderately low nutrients > More important than ?>> Much more important than 78 Sylvester TAN, Takuo YAMAKURA, Masako TANI, Peter PALMIOTTO, James Dawos MAMIT, Chin Siew PIN, Stuart DAVIES, Peter ASHTON, Ian BAILLIE Fig. 5. Stoichiometric roses of topsoil mineral nutrients of Lambir LTER Plot and other Borneo RYP on Tertiary sedimentary parent materials ???? Lambir roses based on Baillie, Mamit and Tan unpublished data, 1971 - 2003; Central Sarawak data from Baillie (1978) ; Danum data from Burghouts et al. (1998) 79Review of Soils on the 52 ha Long Term Ecological Research Plot in Mixed Dipterocarp Forest at Lambir, Sarawak, Malaysian Borneo Fig. 6. Stoichiometric roses of topsoil mineral nutrients of tropical forest soils on crystalline parent materials ???? Sarawak profiles (a and b) based on data of Andriesse (1972); Sinharaja profile (c) after Baillie et al. (2007b); Huai Kha Khaeng profile (d) based on S. Bunyavejchewin, unpublished data, 2007 80 Sylvester TAN, Takuo YAMAKURA, Masako TANI, Peter PALMIOTTO, James Dawos MAMIT, Chin Siew PIN, Stuart DAVIES, Peter ASHTON, Ian BAILLIE permeable than the topsoils, so that much soil water movement occurs as shallow lateral through?ow (Wenzel et al. 1998). The discrete wet layers seen in some Lambir sandstone dipslope subsoils in 2003 are attributed to concentrated throughflow. The throughflow in this instance is apparently too infrequent and short lived to affect drainage, aeration and colours. However, the lack of gleying and mottles may be also par tly due to a deficiency of carbonaceous energy sources for the endothermic microbial reduction of iron (Stemmler and Ber thelin, 2003). The prevalence of throughflow dif ferentiates the RYP ?s hydrologically from more permeable modal kaolisols (Ferralsols/Oxisols), in which drainage is predominantly vertical (Baillie, 1996). The RYP/Acrisols on clastic sedimentary rocks are also chemically distinct. The low pH and low contents of available nutrients are common to many tropical forest soils. However, their combination with moderate reserves/totals of K and Mg and low reserves of P and Ca results in distinctive stoichiometric pro?les for these soils. These can be depicted as stoichiometric roses (Fig. 5), as devised for Amazonian soils by Alvim (1978) and also used for the nutrient characterisation of tropical forest soils in Sri Lanka and Panama (Baillie et al. 2007a and b). The larger rose for Merit series (Fig 5a) indicates that its contents of all nutrients are higher than those of the sandstone soils (Fig. 5b). The congruent shapes mean that the nutrient ratios are similar, so that the Lambir RYP?s can be arrayed along a single mineral nutrient fer tility axis. The roses of other RYP?s on Ter tiar y clastic sedimentar y rocks in Sarawak and Borneo are also more or less congruent with those on the plot (Figs. 5c and 5d), reflecting similarly micaceous source rocks. However, the roses of Sarawak RYP?s on felsic crystalline rocks and of ferralic/oxic clays and loams on ma?c rocks (Fig.6) are incongruent, indicating substantially different nutrient ratios. Edaphic effects of mineral weathering The distinctive hydrology and stoichiometery of the RYP/Acrisols are attributed to the lithology of the clastic sedimentary materials and their weathering products, especially the primary micas and secondary 2:1 and 2:1:1 clay minerals. The persistence of some moderately active clay minerals, combined with moderate solum depths and fragments of saprolite, indicate that weathering is not terminal in these soils, despite the high leaching potential of the climate (Islam et al. 2002; Selvaraj and Chen, 2005). On the plot, these slightly immature features are more pronounced in the Merit clays than in the sandstone soils. The less intense weathering in the clays is partly due to their high proportion of throughflow. This limits deep vertical leaching and the amount of water available for weathering lower subsoils and saprolites. More moisture leaches vertically in the sandstone soils and their subsoils weather more rapidly. The creation of shear planes in anisotropically wetted layers is another mechanism by which throughflow contributes to the persistence of moderately shallow soils. Failures along such planes can cause soil pro?le truncation (Furian et al. 1999; Jackson, 1966), and facilitate the uprooting of trees (Blancaneaux, 1973), thus exhuming fresh minerals and resetting weathering. The reser ves of Mg and K and the dist inct stoichiometric pro?le of these soils also derive from the micaceous, 2:1 and 2:1:1 minerals. Although not rapidly labile, these nutrient reserves appear to be partially accessible to, and to ?gure in the budgets of, long-lived organisms such as mature trees. Reserve nutrients are ecologically important in Bornean MDF and are more closely associated than more labile forms with the dynamics of litter decomposition at Lambir (Baillie et al. 2006), and the distribution of tree species in MDF in Central Sarawak (Baillie et al. 1987). Th e i r e f f e c t i s a t t r i b u t e d t o s i g n i f i c a n t replenishments of forest nutrient cycles by micaceous weathering. Such replenishments may be slight but they allow for partially open cycling of mica-sourced Mg and K in shale-derived Merit soils. The lower mica and illite contents and replenishment capacities of the sandstone soils constrain their forests towards more closed nutrient cycles, shown by the greater sequestration of nutrients in recalcitrant humus mats (Baillie et al. 2006), and by the slow growth and low mor tality rates of sandstone specialist tree species (Russo et al. 2005). Such replenishment of mineral nutrients requires that weathering occur within rooting depth. This is more l ikely in landscapes where tectonic activity and topographic dissection tend to keep sola shallow (Taylor and Howard, 1999; Vitousek et al. 2003). It is also favoured by deep rooting (Schenk and Jackson, 2002), as in MDF in Central Sarawak, where roots penetrate several metres down into saprolite and along cracks in slightly weathered shale (Baillie and Mamit, 1983). In some tropical forests, however, deep roots appear to tap the saprolite moisture reserves, but not nutrients (Poszwa et al. 2002). Ecologically signi?cant replenishment also requires that the weathering minerals contain the essential nutrients in significant quantities. At Lambir, mineral 81Review of Soils on the 52 ha Long Term Ecological Research Plot in Mixed Dipterocarp Forest at Lambir, Sarawak, Malaysian Borneo reserves of Ca are low, and weathering replenishment appears to be an unimportant. Ca may be mainly topped up by atmospheric inputs, similar to the aeolian contributions to the K nutrition of Hawaiian forests on old geomorphic surfaces with deeply weathered K-de?cient ma?c regoliths (Chadwick et al. 1999; Juang and Uehara, 1968; Vitousek, 2004). CONCLUSION The collation of multiple soil data sets shows that pedo log i ca l t axa and so i l maps d i f f e r en t i a t e edaphecological habitats on the Lambir 52 ha LTER plot. The combination of soil series with physiographic factors enables edaphic characterisation to extend beyond labile nutrients and to encompass the other important facets of tropical forest soil fertility, i.e. moisture, root aeration, site stability and non-labile mineral nutrients (Table 11). ACKNOWLEDGEMENTS??We are grateful to: the Director of Forestry for permission to use data of the Government of Sarawak; our colleagues in the Sarawak Forestry Department for facilitation of the work; Mr Augustine Lai, Warden and other staff of Taman Negara Bukit Lambir for logistic assistance; Mrs Margaret Abat and past and current staff of the Soils Laboratory of the Agricultural Research Centre, Semongok for numerous soil analyses between 1966 to 2004; Dr S.E. Russo for unpublished data on soil moisture contents on the plot; Dr S. Bunyavejchewin for data from the Huai Kha Khaeng LTER plot, Thailand; Professor I.A.U.N. Gunatilleke for data from the Sinharaja LTER plot , Sri Lanka; and Mr Lim Chin Pang for advice on the soils of North Sarawak. The Lambir LTER plot was established by the Sarawak Forest Department, the Arnold Arboretum-CTFS Asia Program, the Smithsonian Tropical Research Institute and Osaka City University, with financial contributions from the Governments of Malaysia and the State of Sarawak, the National Science Foundation (USA), the Mobusho Grants (Japan), and the Rockefeller, Merck, and John D. and Catherine T. MacArthur Foundations. Drs Kristiina and Daniel Vogt gave academic and ?nancial support to PAP during his work. 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