1954-2010年西南高山地区土壤碳储量时空动态及对气候变化的响应

西南高山地区生态系统类型丰富、地形复杂, 是响应全球气候变化的重点区域,对全球气候变化具有重要的指示作用。研究应用生态系统模型CEVSA(Carbon Exchange betweenVegetation, Soil, and the Atmosphere)估算了1954-2010 年西南高山地区土壤有机碳(Soil Organic Carbon, SOC)的时空变化,分析了其对气候变化的响应。结果表明:①西南高山地区1954-2010 年平均土壤有机碳密度为14.16 kg C·m^-2,在空间分布上,SOC密度自东南向西北递增,与温度显著负相关(r=-0.447,P<0.01),而与降水量相关性不显著;②西南高山地区1954-2010 年SOC 总量变动范围为6.95~7.64 Pg C,增加趋势显著(P<0.05),平均每年增加0.013 Pg C,土壤有机碳密度平均增加26.94 g C·m^-2;③常绿针叶林、常绿阔叶林和草地SOC密度增加趋势均显著,除常绿阔叶林SOC密度与温度相关性不显著外,其他两种植被类型SOC都与年平均温度显著正相关(草地:r=0.527, P<0.01; 常绿针叶林:r=0.501, P<0.01),且3 种植被类型SOC与年降水量均相关性不显著;④由于作为土壤有机碳输入的凋落物产生量对温度不如异养呼吸敏感,所以未来升温条件下,土壤有机碳储量的增速减缓或者呈下降趋势。

Temporal-spatial Variations of Soil Organic Carbon and Their Responses to Climate Change in Alpine Area of Southwest China during 1954-2010

There are various types of ecosystems and complex landform in alpine area of southwest China, which make it an ideal place to research regional response to global changes in climate. A process-based biogeochemical model CEVSA (Carbon Exchange between Vegetation, Soil, and the Atmosphere) was used to estimate temporal and spatial variations of soil organic carbon (SOC) in alpine area of southwest China during 1954-2010. The results showed: 1) The mean values of SOC density were 14.16 kg C·m^-2 during1954-2010 in alpine area of southwest China. In spatial distribution, SOC density increased from southeast to northwest and was significantly negatively correlated with annual mean temperature(r=-0.447, P<0.01), but had no significant correlation with annual total precipitation. 2) Total SOC storage ranged from 6.95 to 7.64 Pg C and showed a statistically significant increasing trend with a growth rate of 0.013 Pg C (P<0.05) during 1954-2010. 3) The increasing trend of SOC density was highly significant (P<0.01) in herbaceous cover (closed-open), evergreen needle-leaved tree cover and evergreen broad-leaved tree cover which was the three main vegetation types. SOC density of herbaceous cover (closed- open) and evergreen needle- leaved tree cover in the study area were both correlated positively with annual mean temperature (r=0.527, P<0.01; r=0.501, P<0.01) but SOC density of evergreen broad-leaved tree cover had no correlation with annual mean temperature. There were no significant correlation between SOC density and annual total precipitation in all of the three vegetation types. 4) The growth of soil organic carbon (SOC) storage may slow down or reverse by ongoing climate change, for that HR was more sensitive to temperature than LT which acted as the carbon input of soil ecosystem.