Hydrometeorology of tropical montane cloud forests: emerging patterns
Hydrometeorology of tropical montane cloud forests: emerging patterns
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DOI：
10.1002/hyp.7974
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发表时间：
2011-01-30
影响因子：
3.2
通讯作者：
Scatena, Frederick N.
中科院分区：
文献类型：
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作者：
Bruijnzeel, L. A.;Mulligan, Mark;Scatena, Frederick N.
热带山地云雾林（TMCF）通常会经历频繁持续的雾。根据TMCF通常发生的海拔界限（800-3500 m.a.s.l.），取决于山脉的大小和到海岸的距离），它们目前的分布范围估计约为215 000公里（2），占所有山地热带森林的6.6%。或者，根据遥感云出现的频率，受雾影响的森林可能占据多达2.21 Mkm（2）。山地森林可分为4种类型，即云带下的低山雨林（LMRF）、高大的低山云雾林（LMCF）、中等高度的高山云雾林（UMCF）和发育不良的亚高山云雾林（SACF）和“矮化”云雾林（ECF）。平均穿透雨与降水的比率从LMRF（n = 15）的0.72 +/- 0.07增加到LMCF（n = 23）的0.81 +/- 0.11，UMCF和SACF-ECF分别增加到1.0 +/- 0.27（n = 18）和1.04 +/- 0.25（n = 8）。从LMRF到UMCF和ECF，茎流平均组分逐渐增加，而叶面积指数（LAI）和年蒸散量（ET）沿着降低。尽管UMCF（n = 3）和ECF（n = 2）的数据集非常有限，但UMCF（783 +/- 112 mm）和ECF（547 +/- 25 mm）的ET明显低于LMCF（1188 +/- 239 mm，n = 9）和LMRF（1280 +/- 72 mm; n = 7）。实地测量的年度“云水”拦截（CWI）与湿冠层水收支法（WCWB）确定的总量变化很大，位置和范围之间的22和1990毫米（n = 15）。实地测量值也往往比模拟的雾截获量大得多，特别是在暴露的网站。这被认为反映了潜在的模型局限性，模型应用的尺度（1x 1公里）和测量尺度（小地块）之间的不匹配，以及在WCWB的CWI估计中包含近水平的风驱动降水。区域地图的模拟量的雾拦截整个热带地区，显示主要的空间变异。CWI的模拟贡献在潮湿地区占总降水量的5%以下，在低降雨地区占75%以上。集水产量通常从LMRF增加到UMCF和SACF-ECF，反映了入射降水的同时增加和蒸发损失的减少。将LMCF（或LMRF）转化为牧草可能会导致产水量大幅增加。UMCF转换后的产水量变化可能是适度的，由于ET和CWI的同时变化之间的权衡。大气环流模型（GCM）-预计到2050年SRES温室气体情景下的气候干燥率被认为对TMCF水文功能和生态有深远的影响，尽管不同的GCM产生不同的，有时相反的结果。虽然我们对TMCF中运行的水文过程的理解有了实质性的增加，但还需要进行更多的研究，以提高隐性降水输入（CWI和风驱动降水）的量化，并更好地了解气候和土地利用变化的水文影响。版权所有（C）2010约翰威利父子有限公司
Tropical montane cloud forests (TMCF) typically experience conditions of frequent to persistent fog. On the basis of the altitudinal limits between which TMCF generally occur (800-3500 m.a.s.l. depending on mountain size and distance to coast) their current areal extent is estimated at similar to 215 000 km(2) or 6.6% of all montane tropical forests. Alternatively, on the basis of remotely sensed frequencies of cloud occurrence, fog-affected forest may occupy as much as 2.21 Mkm(2). Four hydrologically distinct montane forest types may be distinguished, viz. lower montane rain forest below the cloud belt (LMRF), tall lower montane cloud forest (LMCF), upper montane cloud forest (UMCF) of intermediate stature and a group that combines stunted sub-alpine cloud forest (SACF) and 'elfin' cloud forest (ECF). Average throughfall to precipitation ratios increase from 0.72 +/- 0.07 in LMRF (n = 15) to 0.81 +/- 0.11 in LMCF (n = 23), to 1.0 +/- 0.27 (n = 18) and 1.04 +/- 0.25 (n = 8) in UMCF and SACF-ECF, respectively. Average stemflow fractions increase from LMRF to UMCF and ECF, whereas leaf area index (LAI) and annual evapotranspiration (ET) decrease along the same sequence. Although the data sets for UMCF (n = 3) and ECF (n = 2) are very limited, the ET from UMCF (783 +/- 112 mm) and ECF (547 +/- 25 mm) is distinctly lower than that from LMCF (1188 +/- 239 mm, n = 9) and LMRF (1280 +/- 72 mm; n = 7). Field-measured annual 'cloud-water' interception (CWI) totals determined with the wet-canopy water budget method (WCWB) vary widely between locations and range between 22 and 1990 mm (n = 15). Field measured values also tend to be much larger than modelled amounts of fog interception, particularly at exposed sites. This is thought to reflect a combination of potential model limitations, a mismatch between the scale at which the model was applied (1 x 1 km) and the scale of the measurements (small plots), as well as the inclusion of near-horizontal wind-driven precipitation in the WCWB-based estimate of CWI. Regional maps of modelled amounts of fog interception across the tropics are presented, showing major spatial variability. Modelled contributions by CWI make up less than 5% of total precipitation in wet areas to more than 75% in low-rainfall areas. Catchment water yields typically increase from LMRF to UMCF and SACF-ECF reflecting concurrent increases in incident precipitation and decreases in evaporative losses. The conversion of LMCF (or LMRF) to pasture likely results in substantial increases in water yield. Changes in water yield after UMCF conversion are probably modest due to trade-offs between concurrent changes in ET and CWI. General circulation model (GCM)-projected rates of climatic drying under SRES greenhouse gas scenarios to the year 2050 are considered to have a profound effect on TMCF hydrological functioning and ecology, although different GCMs produce different and sometimes opposing results. Whilst there have been substantial increases in our understanding of the hydrological processes operating in TMCF, additional research is needed to improve the quantification of occult precipitation inputs (CWI and wind-driven precipitation), and to better understand the hydrological impacts of climate-and land-use change. Copyright (C) 2010 John Wiley & Sons, Ltd.