Growing season extension and its impact on terrestrial carbon cycle in the Northern Hemisphere over the past 2 decades
Growing season extension and its impact on terrestrial carbon cycle in the Northern Hemisphere over the past 2 decades
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DOI：
10.1029/2006gb002888
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发表时间：
2007-09-25
影响因子：
5.2
通讯作者：
Demarty, Jerome
中科院分区：
文献类型：
--
作者：
Piao, Shilong;Friedlingstein, Pierre;Demarty, Jerome
许多研究表明，在过去几十年中，生长季节的持续时间显著延长，但物候变异性与陆地碳(C)循环之间的联系还远不清楚。本文采用基于“动态生态系统中组织碳和水文”（ORCHIDEE）过程的生态系统模型，结合气候观测资料，研究了1980—2002年北半球（bb0 25°N）物候时空变化及其对碳通量的影响。结果表明，由于春季较早开始（0.16 d /年（-1）），秋季较晚结束（0.14 d /年（-1）），生长季长（GSL）增加了0.30 d /年（-1）（R-2 = 0.27, P = 0.010）。然而，GSL的趋势在各地区之间差异很大。研究期间，欧亚大陆地区植被变绿时间提前0.28 d /年（-1）（R-2 = 0.32, P = 0.005），北美地区植被变绿时间明显推迟0.28 d /年（-1）（R-2 = 0.26, P = 0.013）。GSL与年总初级生产力（GPP）和净初级生产力（NPP）有较强的相关性，表明较长的生长季节可能最终促进植被的生长。GSL延长1天导致年GPP增加5.8 gC m(-2) yr(-1)（或每天0.6%），NPP增加2.8 gC m(-2) yr(-1) /天。然而，由于土壤碳分解随GPP的增加而增强，GSL的变化与年净生态系统生产力（NEP）的变化相关性较差。
A number of studies have suggested that the growing season duration has significantly lengthened during the past decades, but the connections between phenology variability and the terrestrial carbon (C) cycle are far from clear. In this study, we used the "ORganizing Carbon and Hydrology In Dynamic Ecosystems" (ORCHIDEE) process based ecosystem model together with observed climate data to investigate spatiotemporal changes in phenology and their impacts on carbon fluxes in the Northern Hemisphere (> 25 degrees N) during 1980-2002. We found that the growing season length (GSL) has increased by 0.30 days yr(-1) (R-2 = 0.27, P = 0.010), owing to the combination of an earlier onset in spring (0.16 days yr(-1)) and a later termination in autumn (0.14 days yr(-1)). Trends in the GSL are however highly variable across the regions. In Eurasia, there is a significant trend toward earlier vegetation green-up with an overall advancement rate of 0.28 days yr(-1) (R-2 = 0.32, P = 0.005), while in North America there is a significantly delayed vegetation senescence by 0.28 days yr(-1) (R-2 = 0.26, P = 0.013) during the study period. Our results also suggested that the GSL strongly correlates with annual gross primary productivity (GPP) and net primary productivity (NPP), indicating that longer growing seasons may eventually enhance vegetation growth. A 1-day extension in GSL leads to an increase in annual GPP of 5.8 gC m(-2) yr(-1) (or 0.6% per day), and an increase in NPP of 2.8 gC m(-2) yr(-1) per day. However, owing to enhanced soil carbon decomposition accompanying the GPP increase, a change in GSL correlates only poorly with a change in annual net ecosystem productivity (NEP).