荒漠生态系统对大气CO2浓度升高响应的干湿年差异

Difference of Desert Ecosystem Responses to Elevated Atmospheric CO2 Concentration between Dry and Wet Years

摘要:

利用一个基于详细生理学过程的生态系统模型PALS-FT,通过模拟实验分析了美国亚利桑那州（Arizona）首府凤凰城（Phoenix）市西郊的Larrea tridentata荒漠生态系统在干湿年份（1988-2002年）对大气CO₂浓度升高响应的差别.结果表明,生态系统地上净初级生产力（ANPP）和土壤有机质年累积速率（SOM）均随大气CO2浓度升高而呈非线性（湿年）或线性（正常年和干年）增加;所有年份的土壤N含量（N_soil）则呈非线性显著下降.ANPP与SOM的绝对变化量总是湿年大于正常年和干年,相对变化量则与所分析的CO₂处理水平有关;N_soil的绝对变化量和相对变化量均为湿年大于正常年和干年.不同功能型的植物ANPP对大气CO₂浓度升高的绝对变化量均为湿年大于正常年和干年;相对变化量则因具体植物功能型而异,灌木和亚灌木为干年大于正常年和湿年,一年生C₃和C₄草本均为湿年大于正常年和干年.因此,无论是生态系统水平还是植物功能型（或物种）水平,荒漠生态系统对未来大气CO₂浓度升高的响应都将受降水格局的显著影响.

Abstract:

Simulation experiments were undertaken to analyze the difference ofLarrea tridentata desert ecosystem in Phoenix, USA responses to elevated atmospheric CO₂ concentration between dry and wet years. A physiologicalbased ecosystem model, PALS-FT was used in the simulation analysis. Aboveground net primary productivity （ANPP） and annual accumulation rate of soil organic matter （SOM） increased nonlinearly with increasing [CO₂] in wet years, but linearly in normal and dry years, while N content in soil （N_soil） decreased nonlinearly with increasing [CO₂] in all types of years. The absolute changes of ANPP and SOM were always larger in wet years than in normal and dry years, and the relative changes of them were dependent greater on the [CO₂] level of interest rather than on year types （i.e., wet, normal, and dry years）. However, both the absolute and relative changes of Nsoil were always larger in wet years than in normal and dry years. The absolute changes of ANPP in different plant functional types （PFTs） responding to elevated [CO₂] were larger in wet years than in normal and dry years, but the relative changes varied also PFT-specifically. Shrub and subshrub FTs showed larger responses in dry years, whereas C₃ and C₄ annuals showed larger responses in wet years. Therefore, responses of desert ecosystems to a future elevated CO₂ would be markedly influenced by precipitation patterns.