Variability in radial sap flux density patterns and sapwood area among seven co-occurring temperate broad-leaved tree species
Variability in radial sap flux density patterns and sapwood area among seven co-occurring temperate broad-leaved tree species
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DOI：
10.1093/treephys/28.12.1821
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发表时间：
2008-12-01
期刊：
影响因子：
4
通讯作者：
Leuschner, Christoph
中科院分区：
文献类型：
--
作者：
Gebauer, Tobias;Horna, Viviana;Leuschner, Christoph
森林蒸腾量的估算通常是基于水分活跃的树干边材外部木质部液流的测量。我们使用Granier的恒定加热技术与加热探头在不同的木质部深度分析径向模式的树干液流密度在7个阔叶树种的边材不同的木材密度和木质部结构。研究目的是（1）比较散孔和环孔树木的径向液流密度分布和（2）分析水活性边材面积与茎直径之间的关系。在所有调查的物种中，除了散孔山毛榉（Fagus sylvatica L.）和环孔白蜡（Fraxinus excelsior L.），液流密度在形成层下1 ~ 4cm处达到峰值，呈驼峰状曲线，具有种特异性斜率。山毛榉和白蜡树在最年轻的年轮中形成层下方的液流密度达到最大。染料试验表明，散孔树种成熟木的水活性边材占树干横截面积的70 ~ 90%，而环孔树种的水活性边材仅占树干横截面积的21%。年轮学分析表明，旧边材的船只可能会保持功能为100年或更长的时间在弥漫多孔的物种和长达27年的环孔灰。我们的结论是径向液流密度模式在很大程度上取决于树种，这可能会引入严重的偏见，在树液流量导出的森林蒸腾估计，如果非特定的液流配置文件假设。
Forest transpiration estimates are frequently based on xylem sap flux measurements in the outer sections of the hydro-active stem sapwood. We used Granier's constant-heating technique with heating probes at various xylem depths to analyze radial patterns of sap flux density in the sapwood of seven broad-leaved tree species differing in wood density and xylem structure. Study aims were to (1) compare radial sap flux density profiles between diffuse- and ring-porous trees and (2) analyze the relationship between hydro-active sapwood area and stem diameter. In all investigated species except the diffuse-porous beech (Fagus sylvatica L.) and ring-porous ash (Fraxinus excelsior L.), sap flux density peaked at a depth of I to 4 cm beneath the cambium, revealing a hump-shaped curve with species-specific slopes. Beech and ash reached maximum sap flux densities immediately beneath the cambium in the Youngest annual growth rings. Experiments with dyes showed that the hydro-active sapwood occupied 70 to 90% of the stein cross-sectional area in mature trees of diffuse-porous species, whereas it Occupied only about 21% in ring-porous ash. Dendrochronological analyses indicated that vessels in the older sapwood may remain functional for 100 years or more in diffuse-porous species and for up to 27 years in ring-porous ash. We conclude that radial sap flux density patterns are largely dependent on tree species, which may introduce serious bias in sap-flux-derived forest transpiration estimates, if non-specific sap flux profiles are assumed.