基于CASA模型探究泾河流域植被NPP时空动态及其对气候变化的响应

植被NPP是判定生态系统碳源/碳汇及调节生态过程的主要因子,基于CASA模型估算NPP,探究时空尺度NPP的变化及其对气候变化的响应状况,可了解泾河流域植被恢复状况并为流域生态环境改善提供科学参考及建议。以泾河流域为研究区域,基于2000年、2009年、2018年MODIS NDVI数据、气象数据与植被分布数据等,运用CASA模型(Carnegie-Ames-Stanford approach,CASA)对2000年、2009年及2018年流域NPP进行了估算,探究流域内NPP时空动态及其对气候变化的响应,并分析了各植被类型下NPP分布规律。结果表明:(1)时间尺度上,2000年、2009年及2018年泾河流域NPP均值分别为521.81 gC/(m²·a),664.77 gC/(m²·a),719.78 gC/(m²·a),年际变化呈增长趋势; 月际变化曲线呈单峰型,4—8月呈较强上升趋势,8月后逐渐下降; 各季节的NPP均值由高到低依次为夏季>秋季>春季>冬季。(2)空间尺度上,NPP分布存在一定的地域差异性,水平方向呈“南高北低”的特点; 垂直方向上,NPP值随海拔高度的升高呈先下降后上升的趋势。(3)不同植被类型下NPP均值存在明显差异,其中常绿阔叶林年均NPP值最高,为1 544.50 gC/(m²·a)。(4)气候变化背景下,NPP主要受气温与降水的影响,且降水为主导因素。研究结果表明泾河流域NPP呈增加趋势,即植被覆盖情况在逐步改善; 流域北部植被覆盖状况仍有待改善,建议加大退耕还林政策实施力度,加大果树、茶树等防护型林地的种植; 且该流域NPP对降水的响应强于气温,故可加大植树造林恢复植被的力度,也可修建水库和水利工程,退田还湖,并加大湿地保护,从而保证空气湿度,增加降水,改善植被覆盖,实现人与自然和谐共生。

Spatiotemporal Change of NPP Based on CASA Model and Its Response to Climate Change in Jing River Basin

NPP is the main factor to judge the carbon source/sink of ecosystem and regulate the ecological process.Therefore,we estimated NPP based on CASA model,and explored the change of NPP in temporal and spatial scale and its response to climate change,which can present the vegetation restoration status of Jinghe River Basin,and provide scientific reference and suggestions for the improvement of ecological environment of this basin.Based on MODIS NDVI data in 2000,2009,2018,meteorological data and vegetation distribution data,etc.,we used Carnegie-Ames-Stanford approach(CASA)model to estimate NPP of the basin vegetation in 2000,2009 and 2018,explored the NPP in the basin and its response to climate change,and analyzed the distribution rule of NPP under various vegetation types.The results showed that:(1)on the time scale,the mean values of NPP in the Jing River Basin in 2000,2009 and 2018 were 521.81,664.77 and 719.78 gC/(m²·a),respectively,showing an increasing trend in the inter-annual variation;the intermonthly change curve showed a single peak type,showing the strong upward trend from April to August,and gradually decreased after August;the mean value of NPP in each season decreased in the order:summer>autumn>spring>winter;(2)on the spatial scale,there was certain spatial differences in the distribution of NPP:the horizontal direction showed the characteristics of high in the south and low in the north;in the vertical direction,the value of NPP decreased first and then increased with the increase of altitude;(3)the mean values of NPP of different vegetation types were significantly different,among which the average annual value of NPP1544 gC/(m²·a)]of evergreen broad-leaved forest landscape was higher than those of the others;(4)under the background of climate change,NPP was mainly affected by temperature and precipitation,and precipitation was the dominant factor.These results show that the NPP in Jinghe River Basin is increasing,that is,the vegetation coverage is gradually improving;the vegetation coverage in the north of the basin still needs to be improved.It is suggested to strengthen the implementation of the policy of returning farmland to forest and increase the planting of protective forest lands such as fruit trees and tea trees;moreover,the response of NPP in the basin to precipitation is stronger than that of temperature,therefore,increasing the intensity of afforestation and vegetation restoration,building reservoirs and water conservancy projects,returning farmland to lake,and enhancing wetland protection were suggessted,so as to ensure air humidity,increase precipitation,improve vegetation coverage,and realize the harmonious coexistence between human and nature.