Time lag and negative responses of forest greenness and tree growth to warming over circumboreal forests
Time lag and negative responses of forest greenness and tree growth to warming over circumboreal forests
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DOI：
10.1111/gcb.14135
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发表时间：
2018-03
影响因子：
11.6
通讯作者：
S. Tei;A. Sugimoto
中科院分区：
文献类型：
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作者：
S. Tei;A. Sugimoto
几十年来，北方高纬度地区的陆地森林生态系统一直在经历显着的变暖速度。这些森林被认为对气候系统和全球碳循环至关重要，特别容易受到气候变化的影响。为了获得对植被活动响应的更好估计，例如，森林绿度和树木生长，气候变化，我们调查了时空变化的两个独立的数据集包含树木生态信息，该地区在过去的30年。这些指数是归一化差异植被指数（NDVI3g）和树轮宽度指数（RWI），两者都显示了过去趋势和对气候变化的响应的显著空间变异性。这些趋势和对气候变化的响应在环北极（纬度高于67°N）和环北方森林（纬度分别高于和低于50°N和67°N）的生态系统中存在显著差异，但它们在NDVI3g和RWI中的差异方式相对相似。在环北极生态系统中，当年夏季的气候变量是对温度升高的积极响应的主要气候驱动因素，这两个指数都显示了NDVI3g和RWI。另一方面，在环寒带森林生态系统中，前一年（从夏季到冬季）的气候变量也是NDVI3g和RWI的重要气候驱动因子。重要的是，这两个指数都表明，前一年的温度对生态系统产生了负面影响。虽然这种对变暖的负面反应并不一定会导致过去的负线性趋势，在过去的30年中，在NDVI3g和RWI，未来的气候变暖可能会导致严重减少森林绿化和树木生长在环北方森林生态系统。
The terrestrial forest ecosystems in the northern high latitude region have been experiencing significant warming rates over several decades. These forests are considered crucial to the climate system and global carbon cycle and are particularly vulnerable to climate change. To obtain an improved estimate of the response of vegetation activity, e.g., forest greenness and tree growth, to climate change, we investigated spatiotemporal variations in two independent data sets containing the dendroecological information for this region over the past 30 years. These indices are the normalized difference vegetation index (NDVI3g) and the tree‐ring width index (RWI), both of which showed significant spatial variability in past trends and responses to climate changes. These trends and responses to climate change differed significantly in the ecosystems of the circumarctic (latitude higher than 67°N) and the circumboreal forests (latitude higher and lower than 50°N and 67°N, respectively), but the way in which they differed was relatively similar in the NDVI3g and the RWI. In the circumarctic ecosystem, the climate variables of the current summer were the main climatic drivers for the positive response to the increase in temperatures showed by both the NDVI3g and the RWI indices. On the other hand, in the circumboreal forest ecosystem, the climate variables of the previous year (from summer to winter) were also important climatic drivers for both the NDVI3g and the RWI. Importantly, both indices showed that the temperatures in the previous year negatively affected the ecosystem. Although such negative responses to warming did not necessarily lead to a past negative linear trend in the NDVI3g and the RWI over the past 30 years, future climate warming could potentially cause severe reduction in forest greenness and tree growth in the circumboreal forest ecosystem.