Canopy Conductance of Coniferous Forests Related to Climate
Canopy Conductance of Coniferous Forests Related to Climate
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与气候相关的针叶林冠层导度
DOI：
10.1029/wr021i003p00297
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发表时间：
1985
影响因子：
5.4
通讯作者：
A. Lindroth
中科院分区：
文献类型：
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作者：
A. Lindroth
冠层电导率，G，和特定的冠层电导率，克，估计从波文比测量以上稀疏苏格兰松林。这两个电导随着太阳辐射的增加而增加，Rg，在低Rg范围内的最高灵敏度。在400-500 W m−2以上，它们相对于Rg几乎是恒定的。在典型的白天情况下，电导主要取决于蒸汽压赤字，VPD。当Rg大于500 W m−2时，g从VPD为300 Pa时的11 mm s−1下降到800 Pa时的5.5 mm s−1，然后更缓慢地下降到2000 Pa时的3 mm s−1。g的日变化特征是在早上快速增加到约6 mm s-1，然后缓慢下降到中午，下午有所恢复，晚上再次下降到约2.5 mm s-1。从5月到8月，预计针叶面积指数从2.0到2.6不等，而总冠层导度增加了100%，由于气候（50%），针叶面积（30%），气孔效率（20%）的变化。三个森林之间的比较表明，这是更重要的是要了解的机制背后的季节性变化的G比评估森林之间的差异G，这些后者的差异非常小。
Canopy conductance, G, and specific canopy conductance, g, were estimated from Bowen ratio measurements above a sparse Scots pine forest. Both conductances increased with increasing solar radiation, Rg, with the highest sensitivity in the low Rg range. Above 400–500 W m−2 they were practically constant with respect to Rg. During typical daytime situations the conductances depended primarily on vapor pressure deficit, VPD. For Rg above 500 W m−2, g decreased from 11 mm s−1 at a VPD of 300 Pa down to 5.5 mm s−1 at 800 Pa, then more slowly down to 3 mm s−1 at 2000 Pa. The diurnal variation of g was characterized by a rapid increase in the morning up to about 6 mm s−1, then g slowly decreased until noon and recovered somewhat in the afternoon to decrease again down to about 2.5 mm s−1 in the evening. From May to August the projected needle area index varied from 2.0 to 2.6, whereas total canopy conductance increased by 100% due to variations in climate (50%), needle area (30%), and stomatal efficiency (20%). Comparison between three forests indicated that it was more important to understand the mechanisms behind the seasonal variation of G than to assess differences in G between forests, these latter differences being remarkably small.