Ongoing climate change and human conversion of forests to other land uses alter regional evapotranspiration dynamics and, consequently, impact associated hydrological systems in Amazonia. We studied the effects of drought and fragmentation on forest evapotranspiration using the surface energy balance-based model METRIC (Mapping Evapotranspiration at high Resolution with Internalized Calibration) for a fragmented forest landscape in Brazil's Amazonian state of Rondônia.

Dry season (June-August) forest evapotranspiration estimates were produced for the 2009-2011 period that encompassed the 2010 drought event, one of the extreme droughts in the Amazon. METRIC evapotranspiration data were analyzed in relation to climate (monthly precipitation and cumulative water deficit) and forest fragmentation (edge distance from 100m to 1000m from forest edge and edge density). During the dry season of 2009, pre-drought, forest evapotranspiration did not fall below 110mm/month. However, the 2010 drought year showed a drastic decline in evapotranspiration by 32%, to 75mm/month, from July to August. In 2011, evapotranspiration rates were still depressed with August rates dropping as low as 85mm/month. Forest evapotranspiration dynamics were driven mainly by precipitation and corresponding water deficits in the drier years (2010 and 2011), although evapotranspiration deficits along the edges of forest fragments were locally significant, at the landscape scale. The forests near edges (to 100m) had progressively lower evapotranspiration levels than interior forests as dry seasons progressed and these differences were greatest in the 2010 drought year, reaching almost 5%.

Our results suggest that during the driest months, fragmentation exacerbated both the rate and extent of evapotranspiration reductions over forest areas up to 100m from edges, equivalent to ~20% of the forested landscape in our study area.

持续的气候变化和森林向其他土地的人类转化改变了区域蒸散量的动态，因此影响了亚马逊地区相关的水文系统。我们使用基于表面能平衡的模型METRIC（通过内部校准对高分辨率的蒸散进行映射）对巴西亚马逊州Rondônia的零散森林景观研究了干旱和破碎对森林蒸散的影响。

对2009年至2011年期间的旱季（6月至8月）森林蒸散量进行了估算，其中包括2010年干旱事件，这是亚马逊地区的极端干旱之一。根据气候（月降水量和累积水分亏缺）和森林破碎（森林边缘和边缘密度从100m到1000m的边缘距离）对METRIC蒸散数据进行了分析。在2009年的干旱季节，干旱前的森林蒸散量不低于110毫米/月。但是，2010年的干旱年显示，从7月到8月，蒸散量急剧下降了32％，降至每月75mm /月。2011年，蒸散量仍然很低，8月份的蒸散量降至每月85mm /月。尽管在景观尺度上沿森林碎片边缘的蒸散量在局部上是显着的，但在较干燥的年份（2010年和2011年），森林的蒸散量主要由降水和相应的水分亏缺驱动。随着干旱季节的发展，边缘（至100m）附近的森林的蒸散量逐渐低于室内森林，这些差异在2010年干旱年最大，达到近5％。

我们的研究结果表明，在最干燥的月份中，碎片化加剧了距边缘100m以内的森林区域蒸散量减少的速度和程度，相当于我们研究区域森林景观的约20％。