Growing season moisture drives interannual variation in woody productivity of a temperate deciduous forest

Abstract

1.The climate sensitivity of forest ecosystem woody productivity (ANPPstem ) influences carbon cycle responses to climate change. For the first time, we combine long-term annual growth and forest census data of a diverse temperate broadleaf deciduous forest, seeking to resolve whether ANPPstem is primarily moisture- or energy-limited and whether climate sensitivity has changed in recent decades characterized by more mesic conditions and elevated CO2 . 2.We analyzed tree-ring chronologies across 109 years of monthly climatic variation (1901-2009) for 14 species representing 97% of ANPPstem in a 25.6-ha plot in northern Virginia, USA. 3.Radial growth of most species and ecosystem-level ANPPstem responded positively to cool, moist growing season conditions, but the same conditions in the previous May-July were associated with reduced growth. In recent decades (1980-2009), responses were more variable and on average, weaker. 4.Our results indicate that woody productivity is primarily limited by current growing season moisture, as opposed to temperature or sunlight, but additional complexity in climate sensitivity may reflect the use of stored carbohydrate reserves. Overall, while such forests currently display limited moisture sensitivity, their woody productivity is likely to decline under projected hotter and potentially drier growing season conditions. This article is protected by copyright. All rights reserved.