基于CASA模型的陕西省植被净初级生产力时空分析

Spatial-temporal Analysis of Vegetation Net Primary Productivity in Shaanxi Province Based on CASA Model

[目的]探明陕西省近年来植被净初级生产力(net primary productivity,NPP)的变化及评估植被的生长条件。[方法]基于CASA(Carnegie Ames Stanford Approach)模型估算陕西省2003—2012年逐月NPP,并分析其年际、年内的时空变化特征及趋势。[结果](1)陕西省2003—2012年植被NPP总体呈增长趋势(p<0.01),年均增量为3.940 6g/(m^2·a)(以C含量计);年总NPP从2003年的84.44Tg(1Tg=1012g)增加到2012年的91.98Tg。(2)NPP年内变化明显,夏季NPP占年总量的比例最高,达到52.43%,7,8两月占比最高,分别为18.52%和18.41%。只有3和8月NPP增长趋势显著或极显著,其他月份NPP变化不显著。(3)不同植被NPP的年际变化比较平稳,除永久湿地外,其他植被类型的NPP呈增长趋势,耕地的NPP增长最快(p<0.01),年均增量为5.89g/(m2·a)。(4)NPP整体呈南高北低、高低相间的分布特征,全省78.53%的区域NPP呈增长趋势,24.47%的区域增长显著或极显著;NPP降低显著/极显著的面积仅占2.27%,主要分布在陕西中部和西安周边地区。[结论]陕西植被生长条件总体在改善,但局部在恶化。

[Objective]This study aims to verify variation of vegetation net primary productivity（NPP）in Shaanxi Province in recent years in order to evaluate vegetation growing conditions.[Methods]Based on the Carnegie Ames Stanford approach（CASA）model,this study estimated the monthly NPP from 2003 to 2012in Shaanxi Province.The annual and inter-annual variation of NPP were analyzed at both spatial and temporal scale.[Results]（1）The NPP in Shaanxi Province showed an increasing trend and increased（p〈0.01）at a rate of 3.940 6g/（m^2·a）.The total annual NPP increased from 84.44Tg（1Tg=1 012g）in 2003to91.98 Tg in 2012（in terms of carbon content）.（2）The NPP varied greatly in different seasons.The highest NPP occurred in summer,which accounted for 52.43% of the total NPP,and NPP in July,August accounted for 18.52%,18.41%respectively.NPP in March or August increased significantly or extremely significantly,while no significant change of NPP was found in the other months.（3）Annual variation of NPP for different vegetation types was comparatively stable,and showed an increasing tendency except the permanent wetlands.The fastest increase of NPP was crop land（p〈0.01）,with an average annual increment rate of5.89g/（m^2·a）.（4）The NPP in Southern Shaanxi was higher than the northern,78.53% of the area showed a growing trend in NPP,and 24.47% of the area increased significant or extremely significant.Only2.27% of the area showed a significantly or extremely significantly decreasing trend in NPP,those areas were mainly distributed in the central Shaanxi Province and surrounding area of Xi＇an City.[Conclusion]The vegetation growing conditions in Shaanxi Province was generally improved,but the local region were deteriorating.