Department of Environmental Sciences, University of Puerto Rico, Rio Piedras, San Juan, PR 00936, USA.
Duke University, Durham, NC 27705, USA.
Sci Rep. 2017 Jan 25;7:41256. doi: 10.1038/srep41256.
Tropical forests have essential functions in global C dynamics but vulnerable to changes in land cover land use (LCLUC) and climate. The tropics of Caribbean are experiencing warming and drying climate and diverse LCLUC. However, large-scale studies to detect long-term trends of C and mechanisms behind are still rare. Using MODIS Enhanced Vegetation Index (EVI), we investigated greenness trend in the Greater Antilles Caribbean during 2000-2015, and analyzed trend of vegetation patches without LCLUC to give prominence to climate impacts. We hypothesized that night warming and heavy cloudiness would reduce EVI in this mountainous tropical region. Over the 15 years, EVI decreased significantly in Jamaica, Haiti, Dominican Republic, and Puerto Rico, but increased in Cuba partly due to its strong reforestation. Haiti had the largest decreasing trend because of continuous deforestation for charcoals. After LCLUC was excluded, EVI trend still varied greatly, decreasing in the windward but increasing in the leeward of Puerto Rico. Nighttime warming reinforced by spatially heterogeneous cloudiness was found to significantly and negatively correlate with EVI trend, and explained the spatial pattern of the latter. Although cooled daytime and increased rainfall might enhance EVI, nighttime warming dominated the climate impacts and differentiated the EVI trend.
热带森林在全球碳动态中具有重要功能，但易受到土地覆盖和土地利用变化（LCLU）以及气候变化的影响。加勒比的热带地区正经历着气候变暖、干燥以及多样化的 LCLU。然而，检测碳的长期趋势及其背后机制的大规模研究仍然很少。本研究利用 MODIS 增强植被指数（EVI），调查了 2000-2015 年期间大安的列斯群岛加勒比地区的绿化趋势，并分析了无 LCLU 的植被斑块的趋势，以突出气候的影响。我们假设夜间增温和多云会减少这个多山的热带地区的 EVI。在过去的 15 年里，牙买加、海地、多米尼加共和国和波多黎各的 EVI 显著下降，但古巴的 EVI 部分增加，这主要是由于其强烈的重新造林。海地的 EVI 下降趋势最大，因为持续的木炭砍伐导致森林减少。排除 LCLU 后，EVI 趋势仍有很大差异，在波多黎各的迎风面减少，而在背风面增加。发现空间异质云对夜间增温的增强与 EVI 趋势呈显著负相关，并解释了后者的空间格局。尽管白天降温、降雨增加可能会提高 EVI，但夜间增温主导了气候的影响，从而使 EVI 趋势出现差异。
