Subalpine meadow is extremely sensitive to climate change. Few studies, however, focused on the responses of subalpine meadow to climatic factors in subtropical regions. It is still a challenge to extract the biophysical parameters from optical remote sensing imagery during the growing season. Based on the normalized difference vegetation index (NDVI) time series dataset from the MOD13Q1 vegetation index products and meteorological data, we analyzed the changes of vegetation growth of subalpine meadow at Huanggang Mountain in the top of Wuyishan National Park from 2000 to 2019, its responses to climate factors and the time lag effects. The results showed that NDVI in summer increased insignificantly during 2000-2019, and that NDVI in the growing season, spring, and autumn increased significantly. The enhancement of NDVI was mainly contributed by the increasing temperature (0.026 ℃·a-1) from 2000 to 2019. The increasing temperature in spring and autumn influenced meadow growth more than that in summer and growing season. NDVI of the growing season in subalpine meadow was sensitive to precipitation,indicating that the growth of subalpine meadow was strongly affected by precipitation even in the subtropical region with sufficient precipitation. Temperature and precipitation in different growth periods had different time lag effects on the NDVI of subalpine meadowo. The time lag effects of temperature on subalpine meadow were 0-1 month, and that of precipitation were 2-3 month.
亚高山草甸对气候变化十分敏感,但目前缺少气候因子对亚热带地区亚高山草甸影响的相关研究,且光学遥感数据对该地区草地信息的提取仍存在一定的挑战。本研究基于MOD13Q1植被指数产品中的归一化植被指数(NDVI)数据集,并结合气象数据,分析2000—2019年间武夷山国家公园黄岗山顶的亚高山草甸的生长变化及其对气候因子的响应和时滞效应。结果表明: 2000—2019年,夏季NDVI呈不显著增加趋势,整个生长季、春季和秋季NDVI均呈极显著增加趋势。NDVI的增加主要受温度增加(0.026 ℃·a-1)的影响,其中春、秋季温度的增加对草地生长的影响显著高于夏季和整个生长季。生长季NDVI对降水的变化十分敏感,说明即使在降水充沛的亚热带地区,亚高山草甸的生长仍然受到降水的较大影响。不同生长时段温度和降水对草甸NDVI的滞后影响程度不同,温度对亚高山草甸生长的滞后影响为0～1个月,降水对草甸生长的滞后性影响为2～3个月。.
Keywords: MODIS; NDVI; climate factor; subalpine meadow; time lag effect.