Effects of elevated UV-B radiation and N deposition on the decomposition

Increases in nitrogen (N) deposition and ultraviolet-B (UV-B) radiation play an important role in global climate.change. Because coarse woody debris (CWD) represents a sizeable proportion of total carbon (C) pool in forest.ecosystems, understanding the response of CWD decomposition to increased UV-B and N deposition become.necessary for evaluating forest C storage under global climate change. In this study, we investigated the respiration.of CWD (RCWD) in response to increased UV-B and N deposition over a two-year period for two tree species.in subtropical Chinese forests: Cunninghamia lanceolata (Lamb.)Hook. (CL) and Cinnamomumcamphora (L.) Presl.(CC).We found thatN and UV-B treatment, alone or in combination, significantly promoted RCWD, whichwas further.magnified by increased temperature.Moreover, the combined treatment (UV-B+N) far exceeded the sum.of the individual effects of N and UV-B treatments. Our results indicated that the three components of global climate.change (increased UV-B, N deposition, and warming) worked interactively to accelerate CWD decomposition.in forest ecosystems, suggesting that the biogeochemical cycling of subtropical forests could be altered.greatly in the future, and this alteration must be considered in modelling the effects of global climate change.

氮（N）沉降和紫外线-B（UV - B）辐射的增加在全球气候变化中起着重要作用。由于粗木质残体（CWD）在森林生态系统的总碳（C）库中占相当大的比例，了解CWD分解对UV - B增加和N沉降的响应对于评估全球气候变化下的森林碳储量是必要的。在本研究中，我们对中国亚热带森林中的两种树木——杉木[Cunninghamia lanceolata (Lamb.) Hook.]（CL）和樟树[Cinnamomum camphora (L.) Presl.]（CC），进行了为期两年的研究，调查了CWD呼吸作用（RCWD）对UV - B增加和N沉降的响应。我们发现，N和UV - B处理，无论是单独处理还是联合处理，都显著促进了RCWD，并且温度升高进一步加剧了这种促进作用。此外，联合处理（UV - B + N）的效果远远超过了N处理和UV - B处理单独作用效果之和。我们的研究结果表明，全球气候变化的三个组成部分（UV - B增加、N沉降和气候变暖）相互作用，加速了森林生态系统中CWD的分解，这表明亚热带森林的生物地球化学循环在未来可能会发生很大变化，在模拟全球气候变化的影响时必须考虑到这种变化。