摘要:
在全球气候变化背景下研究陆地植被的时空变化规律,探讨气候因素的驱动作用,对于预测未来气候变化对生态系统的可能影响、制定合适的生态环境保护策略具有重要意义。利用2000—2009年MODIS归一化差值植被指数( normalized difference vegetation index,NDVI)时间序列数据和地面气象站点的气温、降水量数据,从遥感角度分析环渤海地区植被的时空变化,并研究变化与气温、降水的相关关系,探讨区域植被年内和年际变化的驱动因素。结果表明,2000—2009年环渤海地区植被覆盖总体呈增加的趋势,但存在一定的空间异质性,局部有减少的倾向;区域植被的生长受温度和降水的双重驱动,对降水和温度的响应存在明显的滞后,滞后期大约为1个合成期;年际的变化主要受降水和人类活动的影响,降水增加可使区域NDVI提高;不同的人类活动会导致NDVI向相反的方向发展。
Abstract:
Vegetation is one of the most important components of terrestrial ecosystem. The dynamics of vegetation is affected by climate factors and human activities. Generally, natural vegetation is mainly affected by climate factors, especially temperature and precipitation. Presently, global climate change has occurred. To predict the influence of global climate change on vegetation, reduce the unfavorable or adverse effect and protect the ecosystem environment, it is necessary to study the correlation between vegetation and climate factors. Normalized difference vegetation index ( NDVI) is generally regarded as a good indicator of terrestrial vegetation. In this study, ten-year MODIS NDVI time-series data and temperature, precipitation data from 2000 to 2009 in Circum-Bohai Sea area were used. A modified SPLINE method was adopted to remove the effect of noise and to reconstruct NDVI time series. On the basis of these data, the temporal and spatial dynamics of NDVI were analyzed through least-square regression. The correlation and lagged correlation coefficients between NDVI and temperature, precipitation were calculated. The results showed that an increasing trend in NDVI was found in the study area, but there was an obvious heterogeneity. The areas with significant increase and decrease in NDVI were small. In the Circum-Bohai Sea area, the development of vegetation was driven by temperature and precipitation, and the correlation coefficients between vegetation NDVI and temperature were greater than those between vegetation NDVI and precipitation in the same period. The response of vegetation to temperature and precipitation lagged and the lag period was about 16 days. Inter-annual NDVI change in the Circum-Bohai Sea area was mainly influenced by precipitation and human activities, and a positive correlation between precipitation and annual NDVI was found. Human activities influenced vegetation dynamics through changing land use. Urban sprawl led to decrease in NDVI, but the effort to return farmland to forest increased NDVI.
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