Surface characteristics of grasslands in Inner Mongolia as detected by micrometeorological measurements
Surface characteristics of grasslands in Inner Mongolia as detected by micrometeorological measurements
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DOI：
10.1007/s00484-008-0148-5
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发表时间：
2008-04
影响因子：
3.2
通讯作者：
B. Ketzer;Huizhi Liu;C. Bernhofer
中科院分区：
文献类型：
--
作者：
B. Ketzer;Huizhi Liu;C. Bernhofer
以内蒙古某半干旱草原为研究对象，采用流动塔的概念，对1979年封育后未放牧的半干旱草原生态系统与不同放牧方式的半干旱草原生态系统进行比较。这项研究是在连续三年进行的，其特点是降水对比。不同的放牧强度包括连续和中度放牧（CG）、冬季放牧（WG）和重度放牧（HG）。在这里，我们比较了不同管理地块的能量通量和表面参数。主要关注感热通量(H)、有效能（AE）、地表温度（Ts）和地表反照率（α）。通过仪器的侧对侧相互比较排除了系统误差，并且通过固定涡动相关塔与流动涡动相关塔之间的近距离将系统气候差异最小化。在统计上，在两个同时测量的放牧强度之间，aev和tsv总是显著差异。所有年份在UG79的温度都较高（平均差值约为19Wm−2），而在UG79的温度通常较低（平均差值为0.4°C至约2°C）。唯一的例外是2004年植被期结束时，UG79的温度比CG高0.6°C。UG79 α显著降低，h显著升高。因此，潜热通量（作为能量平衡剩余量和直接测量值）在不同放牧强度之间没有太大差异。结果表明：(1)粗线塔概念能够检测出放牧引起的差异；(2)不同站点之间的差异可归因于真实的地表差异；(3)放牧强度引起的差异与地表通量的年际差异相比较小。
A roving tower concept was used to compare a semi-arid grassland site in Inner Mongolia (China), which was fenced in 1979 and ungrazed thereafter (UG79) with differently grazed semi-arid steppe ecosystems. The study was conducted during three consecutive years characterised by contrasting precipitation. The different grazing intensities included continuously and moderately grazed (CG), winter grazed (WG), and heavily grazed (HG). Here, we compare the energy fluxes and surface parameters that characterise the differently managed plots. The main focus is on sensible heat flux (H), available energy (AE), surface temperature (Ts), and surface albedo (α). Systematic errors were excluded by a side-to-side intercomparison of the instruments, and systematic climatic differences were minimised by the close distance between the fixed and the roving eddy covariance tower. Statistically,AEandTswere always significantly different between two simultaneously measured grazing intensities. WhereasAEwas higher at UG79 in all years (mean difference of about 19Wm−2),Tswas typically lower at UG79 (mean differences of 0.4°C to about 2°C). The exception was the end of the vegetation period in 2004 whenTswas 0.6°C higher at UG79 compared to CG. At UG79 α was typically significantly lower, andHwas typically significantly higher. Consequently, latent heat fluxes (both as energy balance residual and directly measured) do not differ much between the different grazing intensities. It is concluded, that (1) the roving tower concept is able to detect differences due to grazing, (2) differences between the sites can be attributed to real surface differences, and (3) differences due to grazing intensities are small compared to interannual differences in surface fluxes.