安徽省植被净初级生产力估算--基于改进的CASA模型

Estimation of net primary productivity of vegetation in Anhui Province based on improved CASA Model

定量估算植被净初级生产力(NPP)对预测陆地碳循环趋势具有重要意义,目前广泛应用于NPP估算的CASA模型其精度仍有待提高。在已有CASA模型优化的基础上,考虑最大光能利用率(LUEmax)的动态变化来改进CASA模型,对改进前后的模拟结果进行比较,并利用改进后的模型估算2001-2020年安徽省植被NPP。结论如下:(1)改进的CASA模型可应用于研究区的植被NPP估算,NPP模拟值与实测值之间的相关性达到显著水平(R^(2)=0.736,P<0.01)。(2)改进后模拟的安徽省植被NPP在空间表达上能够呈现更多细节,时间上较改进前在生长季NPP值更高,非生长季值更低,拉大了NPP的年内变化。(3)2001-2020年安徽省植被NPP整体呈波动上升趋势,多年平均值为547.61 gC m^(-2)a^(-1),年均增长量达2.18 gC m^(-2)a^(-1),2016-2020年间NPP增长最快。年内NPP具有明显的季节差异,表现为夏季>秋季>春季>冬季。(4)安徽省植被NPP具有较强的空间分异性,呈南北多、中间少的分布格局,高值区主要分布在皖南山区,皖西大别山区及部分淮北平原农作物区,低值区多分布在巢湖、长江沿线和淮河流域等植被覆盖密度较低区域。2001-2020年间安徽省植被NPP呈明显的上升趋势,上升面积占总面积的74.04%,大部分分布在地势平坦的淮北平原。

The quantitative estimation of vegetation net primary productivity(NPP)is important for predicting the trend of terrestrial carbon cycle,and the accuracy of the CASA model,which is widely used for NPP estimation,still needs to be improved.Based on the optimization of existing CASA model,we improved the CASA model by considering the dynamic changes of the maximal light use efficiency(LUEmax),compared the simulation results before and after the improvement,and estimated the vegetation NPP in Anhui Province from 2001 to 2020 using the improved CASA model.Results are as follows:(1)the improved CASA model can be applied to the estimation of vegetation NPP in the study area,with significant correlation between simulated NPP and observed date(R^(2)=0.736,P<0.01).(2)The improved CASA model simulated vegetation NPP in Anhui Province was able to present more details in spatial expression and the temporal NPP values were higher in the growing season and lower in the non-growing season than those in the pre-improvement period,which widened the intra-annual variation of NPP.(3)From 2001 to 2020,the overall NPP of vegetation in Anhui Province showed a fluctuating upward trend,with a multi-year average value of 547.61 gC m^(-2)a^(-1),and the average annual growth amounted to 2.18 gC m^(-2)a^(-1),with the fastest growth of NPP was observed between 2016 and 2020.The intra-annual NPP had obviously seasonal differences,which showed that summer>autumn>spring>winter.(4)The vegetation NPP in Anhui Province had strongly spatial differentiation,with a distribution pattern of more in the north and south while less in the middle,with high value areas mainly distributed in the mountainous areas of southern Anhui,the Ta-pieh Mountains area in western Anhui and part of the Huaibei Plain crop areas,and low value areas mostly distributed in the areas with lower vegetation cover density such as Chaohu lake,along the Yangtze River and the Huaihe river basin.During the period of 2001—2020,the vegetation NPP in Anhui Province showed an obviously rising trend,the rising area accounted for 74.04%of the total area,mostly distributed in the flat terrain of the Huaibei Plain.