Suri Sehgal Centre for Biodiversity and Conservation, Ashoka Trust for Research in Ecology and the Environment, Jakkur Post, Royal Enclave, Sriramapura, Bangalore, 560064, India.
Glob Chang Biol. 2014 Jan;20(1):203-15. doi: 10.1111/gcb.12362. Epub 2013 Nov 17.
Global climate change has emerged as a major driver of ecosystem change. Here, we present evidence for globally consistent responses in vegetation dynamics to recent climate change in the world's mountain ecosystems located in the pan-tropical belt (30°N-30°S). We analyzed decadal-scale trends and seasonal cycles of vegetation greenness using monthly time series of satellite greenness (Normalized Difference Vegetation Index) and climate data for the period 1982-2006 for 47 mountain protected areas in five biodiversity hotspots. The time series of annual maximum NDVI for each of five continental regions shows mild greening trends followed by reversal to stronger browning trends around the mid-1990s. During the same period we found increasing trends in temperature but only marginal change in precipitation. The amplitude of the annual greenness cycle increased with time, and was strongly associated with the observed increase in temperature amplitude. We applied dynamic models with time-dependent regression parameters to study the time evolution of NDVI-climate relationships. We found that the relationship between vegetation greenness and temperature weakened over time or was negative. Such loss of positive temperature sensitivity has been documented in other regions as a response to temperature-induced moisture stress. We also used dynamic models to extract the trends in vegetation greenness that remain after accounting for the effects of temperature and precipitation. We found residual browning and greening trends in all regions, which indicate that factors other than temperature and precipitation also influence vegetation dynamics. Browning rates became progressively weaker with increase in elevation as indicated by quantile regression models. Tropical mountain vegetation is considered sensitive to climatic changes, so these consistent vegetation responses across widespread regions indicate persistent global-scale effects of climate warming and associated moisture stresses.
全球气候变化已成为生态系统变化的主要驱动因素。在这里，我们提供了证据表明，在位于泛热带带（30°N-30°S）的世界山地生态系统中，植被动态对最近的气候变化存在全球一致的响应。我们分析了植被绿色度的十年尺度趋势和季节周期，使用了 1982-2006 年期间卫星绿色度（归一化差异植被指数）和气候数据的月度时间序列，为五个生物多样性热点地区的 47 个山区保护区进行了分析。五个大陆地区的年最大 NDVI 的时间序列显示，轻度绿化趋势随后在 20 世纪 90 年代中期左右逆转，出现更强的褐变趋势。在此期间，我们发现气温呈上升趋势，而降水量仅略有变化。年绿色度周期的振幅随时间增加，与观察到的温度振幅增加密切相关。我们应用具有时变回归参数的动态模型来研究 NDVI-气候关系的时间演变。我们发现，植被绿色度与温度之间的关系随着时间的推移而减弱或呈负相关。这种对温度敏感性的丧失在其他地区也有记录，是对温度引起的水分胁迫的响应。我们还使用动态模型提取了在考虑温度和降水影响后仍然存在的植被绿色度趋势。我们发现所有地区都存在残余的褐变和绿化趋势，这表明除了温度和降水之外，其他因素也会影响植被动态。分位数回归模型表明，随着海拔的升高，褐变速度逐渐减弱。热带山地植被被认为对气候变化敏感，因此这些广泛分布地区的一致植被响应表明，气候变暖及其相关水分胁迫的全球范围影响持续存在。
