科尔沁沙质草地生物量积累过程对降水变化的响应模拟

Simulating the response of biomass accumulation process in semi-arid grassland to changes in precipitation

科尔沁沙地是中国北方严重的沙漠化区域之一,理解其沙质草地生物量积累对降水变化的响应有利于该区域的生态恢复和后续经营管理。在植被-土壤水分耦合模型的基础上结合植被阈值-迟滞响应模式(T-D),在点尺度上模拟科尔沁沙质草地生长季植被生物量积累过程对降水变化的响应。结果表明(1)植被生物量积累对降水量变化表现出明显的非线性响应。降水量增加,促进植被生物量积累,反之则抑制生物量积累,但在同等程度的降水量变化下生物量积累对降水增加的响应远大于对降水量减少的响应。(2)生物量积累对降水频率变化的响应与单次有效降水量变化在干旱年和湿润年都显著正相关,但与累计有效降水量相关性微弱,而与有效降水间隔变化只在干旱年显著相关,表明在不同年份间降水频率变化实际上通过改变单次有效降水量和有效降水间隔来影响生物量的积累。(3)生物量积累过程对降水频率变化存在明显的响应阈值,但该阈值在不同的降水量和降水特征下并不相同。科尔沁沙质草地植被生物量积累过程对降水变化有明显的响应,植被-土壤水分耦合模拟与T-D模型的结合能有效地在日尺度上识别这种响应,这为探究植被和降水关系提供了新工具。

Horqin Sandy Land is one of the serious desertification areas in north China. Understanding the response of the sandy grassland biomass accumulation to precipitation changes is beneficial to the ecological restoration and ecosystem management for this area. In our study, we simulated the response of vegetation biomass accumulation process to precipitation change in the growing season of Horqin sandy grassland on point scale by combining the vegetation-soil water coupling model and the vegetation Threshold-Delay response model(T-D). The results revealed that(1) the accumulation of vegetation biomass was improved with the increase of precipitation, and otherwise inhibited with the decrease of precipitation. However, under the same degree of change in precipitation, the response of biomass accumulation to the increase of precipitation was far greater than the response to the decrease of precipitation, which revealed that there was a significant nonlinear responding relationship between the accumulation of vegetation biomass and the change in precipitation.(2) The response of biomass accumulation to change in precipitation frequency was significantly positively correlated with the change of single effective precipitation in both dry year and wet year, weakly correlated with the change of cumulative effective precipitation, and significantly correlated with change in effective precipitation interval only in dry years. This result showed that the change of precipitation frequency in different precipitation years actually affects the accumulation of biomass by changing the single effective precipitation and effective precipitation interval.(3) Vegetation biomass accumulation process had obvious response threshold to precipitation frequency change, and this response thresholds were different under different precipitation amount and precipitation characteristics. In all, there was obvious response of biomass accumulation to precipitation change, and the combination of vegetation-soil moisture coupling process model and T-D model can effectively identify this response on daily scale, which provided a new tool for exploring the relationship between vegetation and precipitation.