黄土高原草地和农田系统碳动态对降雨、温度和CO2浓度变化响应的模拟

全球气候变化通常是多种环境条件同时连续地发生变化,而多因子的控制实验并不能完全模拟环境的变化且其通常需要耗费很高的成本。应用模型可以加深理解全球气候变化对生态系统结构和功能的影响。应用陆地生态系统(TECO)模型模拟黄土高原草地和农田生态系统在CO₂浓度、温度和降水改变情况下生态系统碳动态,探讨黄土高原草地和农田生态系统碳动态对未来气候变化响应。研究结果表明,随着温度升高,草地和农田生态系统净初级生产力(NPP)和异养呼吸(Rh)都呈现先增加后减少的趋势,生态系统碳净交换(NEE)表现出先减少后增加趋势,除农田系统的Rh对温度响应的拐点在当前温度,其余对温度响应拐点在增温4 ℃,此时系统固碳能力最高。降水和CO₂浓度增加改变生态系统NPP,Rh和NEE对温度变化的响应。随着降水增加,生态系统对温度响应更敏感;草地生态系统NPP,Rh和NEE对温度变化响应拐点发生改变,而农田系统无变化。CO₂浓度升高使农田生态系统NPP,Rh和NEE在增加4 ℃情景下,对温度变化响应不敏感。增加降水和增温对草地和农田生态系统NPP、Rh和NEE交互作用相对强度最大,分别为51.0%和30.0%、51.3%和16.6%以及-46.1%和-28.9%;增雨和增加CO₂浓度对草地和农田生态系统NPP、Rh和NEE交互作用相对强度最小,分别为2.4%和7.5%、3.7%和3.4%以及8.1%和-9.0%。三因子交互作用对生态系统NPP,Rh和NEE没有明显促进作用。与农田相比,草地生态系统碳动态对气候变化交互作用响应更显著。

Modeled effects of precipitation,temperature, and CO2 changes on carbon dynamics in grassland and cropland on the Loess Plateau

Global climate change usually involves simultaneous and continuous changes under different environmental conditions.However,it is very difficult and expensive to explore those climate change in manipulative experiments.Applying models can help us to understand the responses of ecosystem structure and function to global climate change.To explore the effects of climate change on carbon processes in grassland and cropland on the Loess Plateau,the Terrestrial Ecosystem (TECO) model was applied to identify patterns of ecosystem carbon processes in response to changes in CO2 concentration,temperature,and precipitation.The results showed that net primary production (NPP) and heterotrophic respiration (Rh) increased with temperature up to +4 ℃ and then declined,except that the highest Rh in cropland ecosystem was at 0 ℃ (ambient conditions).Net ecosystem exchange (NEE) showed the opposite trend with the lowest value at +4 ℃,and the highest C sequestration was at +4 ℃ in both systems.Changes in precipitation and CO2 concentration affected the responses of NPP,Rh,and NEE to temperature change.The NPP,Rh,and NEE became more sensitive to temperature change with increased precipitation.Changes in precipitation affected the turning points of temperature responses for NPP,Rh,and NEE in the grassland ecosystem,but not in the cropland ecosystem.With increased CO2 concentration,the patterns of NPP,Rh,and NEE became flatter when temperature change was greater than +4 ℃.The interaction between increased precipitation and warming had the highest relative strength in terms of effects on NPP,Rh,and NEE,with values of 51.0％ and 30.0％,51.3％ and 16.6％,and-46.1％ and-28.9％ in the grassland and cropland ecosystem,respectively.The interaction between increased precipitation and increased CO2 concentration had the smallest relative strength in terms of effects on NPP,Rh,and NEE,with values of 2.4％ and 7.5％,3.7％ and 3.4％,and 8.1％ and-9.0％,in the grassland and cropland ecosystems,respectively.Three-factor interactions were not significant for these ecosystems.Our results suggest that carbon dynamics are less sensitive in the cropland ecosystem than in the grassland ecosystem to interactions among climatic factors under climate change.