1996-2015年滇西北香格里拉植被净初级生产力变化

Abstract

地处青藏高原东南缘的滇西北香格里拉，其植被NPP的时空格局变化，对于深入了解青藏高原区域植被对气候变化的响应具有重要的科学意义。基于地面气象数据和MODIS-NDVI等遥感数据，运用改进的CASA模型，估算了1996-2015年香格里拉区域不同植被类型NPP，分析探讨了区域植被NPP的演变特征及其对气候变化的响应规律。研究显示：1）1995-2015年间，香格里拉区域6-8月平均气温总体呈上升趋势，增速为0.037℃/a；6-8月总降水量为373.1 mm，呈微弱下降趋势；20年间辐射量基本维持波动稳定状态；2）1996-2015年，香格里拉区域6-8月最大月植被NPP平均值为176.9 gC/m²，不同植被类型的变化范围为128.9-286.9 gC/m²；空间格局上，表现为"从西北、东南及金沙江沿岸向中部递减"的特征；3）香格里拉区域植被NPP显著地受到气温变化的调控（P<0.05），20年间随着气温的持续升高，区域NPP总体呈增加趋势；4）区域植被NPP未表现出受降水变化的显著影响（P>0.05），水分条件对区域植被NPP未形成限制性的影响作用。区域内植被NPP在2005年前后的变化特征，一定程度上也表明了人类活动干扰及生态保护修复等政策措施的影响。;Studying on the spatial and temporal variation pattern of net primary productivity (NPP) in Shangri-La region in northwest Yunnan Province, which lies on the edge of southeast Qinghai-Tibet Plateau, is of scientific significance for exploring the response of vegetation to climate change. In this study, the NPPs of different vegetation types were estimated through using the improved CASA model based on surface meteorological data and remote sensing data including MODIS-NDVI and Landsat 5 TM image in Shangri-La region from 1996 to 2015. The spatial and temporal patterns of the NPP were analyzed and the responses of the NPP to major climate factors were revealed based on correlation analysis method. The results showed that:1) from 1996 to 2015, the annually average temperature from June to August in Shangri-La area indicated an overall trend of increase, with an increase rate of 0.037℃/a; the annually average precipitation of June-August was 373.1 mm, showing a slight downward trend; the annually total solar radiation basically maintained the fluctuation stable state during the period of 20 years; 2) From 1996 to 2015, the annually average NPP of vegetation in the Shangri-La area in June-August was 176.9 gC/m^2, and the variation range of different vegetation types was from 128.9-286.9 gC/m². Among them, the NPP of broad-leaved forest was significantly higher than that of other vegetation types, followed by cultivated land, grassland, shrub, and the NPP of coniferous forest was the lowest. The maximum monthly NPP of each vegetation type increased from 171.6 gC/m² to 182.3 gC/m² from the first 10 years to the second 10 years, increasing by 6.2%. In addition, the pattern of spatial distribution presented a trend of decrease from the northwest and southeast to middle of the zone; 3) The NPP of vegetation in Shangri-La region was significantly affected by annual temperature change (P<0.05), and presented an increasing trend generally with the continuous rise of temperature over 20 years; 4) The NPP of vegetation in this region was not significantly affected by precipitation change (P>0.05) which showed an nonrestrictive effect of water conditions to the NPP of vegetation. During the period from 1996 to 2005, the spatial distribution of NPP in Shangri-La was generally declining, and was obviously increasing during the period from 2005 to 2015. This change trend of NPP in the zone before and after 2005 also presented to some extent the influence of human activity disturbance and policy measures such as ecological protection and restoration on the NPP of regional vegetation.