Monsoonal influences on evapotranspiration of savanna vegetation of northern Australia
Monsoonal influences on evapotranspiration of savanna vegetation of northern Australia
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DOI：
10.1007/s004420000539
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发表时间：
2001-02
期刊：
影响因子：
2.7
通讯作者：
L. Hutley;Anthony P. O'Grady;D. Eamus
中科院分区：
文献类型：
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作者：
L. Hutley;Anthony P. O'Grady;D. Eamus
本文提供了澳大利亚北部热带草原的净辐射、潜热和感热、生态系统表面电导（Gs）和立地水利用的数据，覆盖纬度范围为5°或700 km。测量是在距离北部海岸线越来越远的三个地点进行的，分别代表高（1750毫米）、中（890毫米）和低（520毫米）降雨量地点。这种降雨梯度是由于季风影响随着内陆距离的增加而减弱。数据与树木和下层的叶面积指数（LAI）的季节性估计值相耦合。所有参数均在湿季和干季的极端季节进行测量。在雨季，日蒸散速率为3.1 ~ 3.6 mm day - 1，沿降雨梯度各站点的日蒸散速率相似，不反映年降雨量的站点差异。干季的蒸散量比湿季低2 ~ 18倍，随距离海岸的远近和年降雨量的减少，季节差异增大。由于上层LAI较低，80%以上的水汽通量来自下层。蒸散量的季节差异主要是由于干季林下叶面积的减少。单株树木的水分利用在干湿季节之间没有差异，立地水利用是树木密度的简单函数。在旱季，所有样地的gs均显著下降，因此我们认为稀树草原的水（碳）平衡主要由gs及其对大气和土壤含水量的响应以及冠层叶面积的季节性调整决定。
Data from savannas of northern Australia are presented for net radiation, latent and sensible heat, ecosystem surface conductance (Gs) and stand water use for sites covering a latitudinal range of 5° or 700 km. Measurements were made at three locations of increasing distance from the northern coastline and represent high- (1,750 mm), medium- (890 mm) and low- (520 mm) rainfall sites. This rainfall gradient arises from the weakened monsoonal influence with distance inland. Data were coupled to seasonal estimates of leaf area index (LAI) for the tree and understorey strata. All parameters were measured at the seasonal extremes of late wet and dry seasons. During the wet season, daily rates of evapotranspiration were 3.1–3.6 mm day–1and were similar for all sites along the rainfall gradient and did not reflect site differences in annual rainfall. During the dry season, site differences were very apparent with evapotranspiration 2–18 times lower than wet season rates, the seasonal differences increasing with distance from coast and reduced annual rainfall. Due to low overstorey LAI, more than 80% of water vapour flux was attributed to the understorey. Seasonal differences in evapotranspiration were mostly due to reductions in understorey leaf area during the dry season. Water use of individual trees did not differ between the wet and dry seasons at any of the sites and stand water use was a simple function of tree density.Gsdeclined markedly during the dry season at all sites, and we conclude that the savanna water (and carbon) balance is largely determined byGsand its response to atmospheric and soil water content and by seasonal adjustments to canopy leaf area.