Publication Date:
2016-12-28
Description:
Accurate predictions of net ecosystem productivity (NEP c ) of forest ecosystems are essential for climate change decisions and requirements in the context of national forest growth and greenhouse gas inventories. However, drivers and underlying mechanisms determining NEP c (e.g. climate, nutrients) are not entirely understood yet, particularly when considering the influence of past periods. Here we explored the explanatory power of the compensation day (cDOY) —defined as the day of year when winter net carbon losses are compensated by spring assimilation— for NEP c in 26 forests in Europe, North America, and Australia, using different NEP c integration methods. We found cDOY to be a particularly powerful predictor for NEP c of temperate evergreen needle-leaf forests (R 2 = 0.58) and deciduous broadleaf forests (R 2 = 0.68). In general, the latest cDOY correlated with the lowest NEP c . The explanatory power of cDOY depended on the integration method for NEP c , forest type, and whether the site had a distinct winter net respiratory carbon loss or not. The integration methods starting in autumn led to better predictions of NEP c from cDOY then the classical calendar method starting at January 1. Limited explanatory power of cDOY for NEP c was found for warmer sites with no distinct winter respiratory loss period. Our findings highlight the importance of the influence of winter processes and the delayed responses of previous seasons’ climatic conditions on current year's NEP c . Such carry-over effects may contain information from climatic conditions, carbon storage levels and hydraulic traits of several years back in time.
Print ISSN:
0148-0227
Topics:
Biology
,
Geosciences
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