基于SPOT NDVI的2010-2018年青海省草地资源动态监测研究

Monitoring grassland resource dynamics in Qinghai Province from 2010 to 2018 based on SPOT NDVI

摘要:

【目的】动态监测草地资源对草地资源的合理利用及生态建设具有重要意义，可实现对青海省草地资源的动态监测，为草原管理提供决策依据。【方法】选择植被覆盖度和地上生物量作为研究指标，利用 2010-2018 年青海省 8 月 NDVI、年降水量、年均气温和 2015-2017 年实测地上生物量数据， 反演植被覆盖度（FVC）时空变化趋势，分析植被覆盖度与气候因子的相关性，获得地上生物量反演模型并分析其时空变化趋势。【结果】1）近 9 a 青海省平均 FVC 呈极显著下降趋势（P＜0. 05），平均地上生物量呈增长趋势；2）近 9 a 青海省 16. 90% 区域的 FVC 呈极显著降低（P＜0. 01），15. 42% 区域显著降低（P＜0. 05）；极显著好转（P＜0. 01）面积占 0. 94%，显著好转（P＜0. 05）面积占 1. 43%；3）年降水量和年均气温在近 9 a均呈起伏上升趋势，年际间呈负协同现象；4） FVC 与年降水量、年均气温呈弱显著相关区域占 20% 左右（P＜0. 1）；5）指数模型 y=496. 21e^{2. 4497x} 为青海省地上生物量反演的最优模型 （R² =0. 42，P＜0. 01）。6）地上生物量减少趋势最大为 276. 71 kg/hm² ，增加趋势最大为 544. 68 kg/hm² ， 占比为 69. 18%、30. 82%。【结论】青海省草地资源在逐步恢复，且其变化与人类活动有重要关系。

Abstract:

Monitoring grassland resource dynamics is of great significance for its rational utilization and ecologi- cal construction. This study selected fractional vegetation cover and above-ground biomass of grassland in Qinghai province as indicators. NDVI，annual precipitation，average annual temperature from August 2010 to 2018，and the above-ground biomass data measured 2015 and 2017 were used to simulate the trend of the spatial and temporal varia- tion of fractional vegetation cover. The correlation between fractional vegetation coverage and climatic factors was analysed to find a inversion model to simulate its spatial and temporal variation trend. The results showed that：（1） In the recent 9 years，the average fractional vegetation cover of Qinghai province showed an extremely significant downward trend （P＜0. 05），and the average above -ground biomass showed an increasing trend.（2） The fractional vegetation cover in 16. 90% regions of Qinghai province decreased very significantly （P＜0. 01） and 15. 42% regions decreased significantly （P＜0. 05）. By contrastonly 0. 94% regions increased very significantly （P＜0. 01） and1. 43% regions increased significantly （P＜0. 05）.（3） The annual precipitation and the average annual tempera- ture showed a fluctuating upward trend in the past 9 years with a negative synergy between years.（4） About 20% re- gions of Qinghai province showed weak correlation between average fractional vegetation and annual precipitation or annual temperature （P＜0. 1）.（5） The exponential model y=496. 21e^{2. 4497x} was the optimal model for above-ground biomass inversion in Qinghai province （R² =0. 42，P＜0. 01）.（6） The maximum decreasing trend of above -ground biomass was 276. 71 kg/hm² ，and the maximum increasing trend was 544. 68 kg/hm² ，the proportions were 69. 18% and 30. 82% respectively. It was concluded that grassland resources in Qinghai province were gradually recovering， and its change was closely related to human activities.