科尔沁沙地不同沙地景观区植被指数对水热因素响应

在全球气候变化背景下,不同尺度下植物对环境条件的响应机制是生态学研究的核心。为了更好理解不同沙地景观区域植被指数(NDVI)对气象水热环境因子的响应机制,以2000-2013年7-9月MODIS遥感影像为数据源,采用3S空间分析技术和通径分析方法,对科尔沁沙地围封保护区、人工造林固沙区和流动沙丘区等3种景观类型区NDVI的变化趋势和影响其变化的同期气象水热因子年降水、关键期降水、关键期最大一次性降水、重要期降水、年均温、关键期均温、关键期最高气温、关键期最低气温等8个因素进行了分析。结果表明:不同景观类型区NDVI整体上呈现增长的态势。降水的影响明显高于气温,且降水主要起正相关作用,气温主要起负相关作用。促进沙地围封保护景观区NDVI增长的气象因子是关键期降水,决策系数最大且为正(0.445);人工造林固沙景观区受到人工造林更新和农业开垦的影响,削弱了水热条件对NDVI的影响,相比较而言,重要期降水影响较大;流动沙丘景观类型区主要受到关键期气温极值的影响,其他因子影响不显著。

Responses of NDVI Changes to Air Temperature and Precipitation of Different Sandy Landscape Areas in the Horqin Sandy Land

It is a keystone to recognize relationship between plant and environmental factors in different ecological scales under global climate change situation. For best understanding the meterological factor change impact on vegetation productivity(appr. NDVI) in different sandy landscape areas that include sandy landscape of fenced sandy protective area, artificial afforestation and sand-fixation area, and mobile sand dune area, we employed "3S" technology and path analysis methods to analyze change trends of the NDVI and the meterological factor and relation between them that MODIS NDVI is used as an indicator of vegetation productivity and the meterological factor include precipitation(year, critical period, maximum daily in critical period, important period) and air temperature(yearly mean, critical period mean, maximum daily mean in critical period, minimum daily mean in critical period), respectively. Results indicated that the NDVI change trends increased and the precipitation effect was more significantly than the temperature at overall level in different sandy landscape types. More research details also illustrated that precipitation was apparent positive correlation effect and the temperature was versa. Critical period precipitation was the direct factor to influence the sandy landscape of fenced protective area, the decision coefficient was maximum and positive, and it reached 0.455. Nevertheless, the agriculture reclaiming and woodland renewing reduced the effect of hydrothermal conditions to NDVI in the artificial afforestation and sand-fixation area, but it was still remarkable to the important period precipitation had a greatest impact among the factors by comparative identification. Beside the effect of extreme temperature in the critical period, rest factors were not obvious in the sandy landscape of mobile sand dune area.