The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature
The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature
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DOI：
10.1088/1748-9326/6/3/035502
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发表时间：
2011-07-01
影响因子：
6.7
通讯作者：
Berendse, Frank
中科院分区：
文献类型：
--
作者：
Blok, Daan;Schaepman-Strub, Gabriela;Berendse, Frank
最近从归一化植被指数（NDVI）数据中观察到的北极绿化趋势表明，灌木的生长正在增加，以应对夏季温度的上升。灌木覆盖的增加预计会减少夏季的降雨量，从而对气候变暖产生积极的反馈。然而，它是未知的，植被和植被指数是如何影响灌木覆盖和年际变化在夏季气候。在这里，我们研究落叶灌木覆盖率，植被指数和植被覆盖度之间的关系，使用在西伯利亚东北部的苔原网站收集的实地数据。结果表明，随着落叶灌木覆盖度的增加，植被指数呈上升趋势，植被指数呈下降趋势。然后，我们选择了四个北极苔原研究领域，编制年度生长季节最大的NDVI和最小的植被覆盖度地图，从MODIS卫星数据（2000-10）和相关的这些卫星产品苔原植被类型（灌木，禾本科，贫瘠和湿地苔原）和区域夏季温度。我们观察到，最大的植被指数是最大的灌木苔原和年际变化是负相关的夏季最低气温，但没有表现出一致的关系，夏季温度。在所有四个研究区域中，灌丛冻原的植被覆盖度均高于湿地和贫瘠冻原。这些结果表明，北移的灌木苔原可能不会导致减少夏季最低气温在无雪季节时，取代湿地苔原。然而，需要进行一项全面的综合研究，将卫星数据的结果与整个北极的实地观测结果联系起来，以测试增加灌木覆盖对不同苔原植被类型夏季植被的影响。
Recently observed Arctic greening trends from normalized difference vegetation index (NDVI) data suggest that shrub growth is increasing in response to increasing summer temperature. An increase in shrub cover is expected to decrease summer albedo and thus positively feed back to climate warming. However, it is unknown how albedo and NDVI are affected by shrub cover and inter-annual variations in the summer climate. Here, we examine the relationship between deciduous shrub fractional cover, NDVI and albedo using field data collected at a tundra site in NE Siberia. Field data showed that NDVI increased and albedo decreased with increasing deciduous shrub cover. We then selected four Arctic tundra study areas and compiled annual growing season maximum NDVI and minimum albedo maps from MODIS satellite data (2000-10) and related these satellite products to tundra vegetation types (shrub, graminoid, barren and wetland tundra) and regional summer temperature. We observed that maximum NDVI was greatest in shrub tundra and that inter-annual variation was negatively related to summer minimum albedo but showed no consistent relationship with summer temperature. Shrub tundra showed higher albedo than wetland and barren tundra in all four study areas. These results suggest that a northwards shift of shrub tundra might not lead to a decrease in summer minimum albedo during the snow-free season when replacing wetland tundra. A fully integrative study is however needed to link results from satellite data with in situ observations across the Arctic to test the effect of increasing shrub cover on summer albedo in different tundra vegetation types.