Ecological Wood Anatomy of Tropical trees

在生长在泰国热带季节性森林的双龙科物种中，落叶物种往往比常绿物种具有更窄的容器。尤其在干二龙果林中，狭窄导管数量较多，导管管腔大小呈二态分布（导管二态）。这些品种的较窄的血管将减少在旱季栓塞的风险。热带季节森林中许多双龙科植物的管腔随茎高的增加而变窄，而管腔密度随茎高的增加而增大。基于氢同位素分析、树流测量和木材解剖调查，揭示了落叶龙脑林树种具有不同的水力状态。它们通过深根、低蒸腾、窄管和连续落叶建立了对土壤水分的有效利用，并在雨季到来之前开始冲叶和开花。我们比较了巴恩斯的基纳巴卢山上两种截然不同的山地森林。建立在超基性岩养分贫乏土壤上的森林中有7种树高较低，叶厚较厚，而建立在沉积岩上的森林中有6种树高较低。两种林分的木材密度、导管管腔面积和导管密度总体上无显著差异。但在同一属的种间比较，超基性岩上的种比沉积岩上的种具有更高的木材密度和更窄的容器。压力-体积分析数据还表明，超基性岩的种类暴露于生理性干旱，这可能是由于土壤养分含量低造成的。生长在基纳巴卢山山地森林中的树种根据其最大高度有不同的木材密度和管腔大小。旱季严重干旱的冠层物种通过调节叶片渗透压等多种机制来避免干旱。

In Dipterocarpaceae species growing in a tropical seasonal forest of Thailand, deciduous species tend to have narrower vessels than evergreen species. Especially the species in dry dipterocarp forests have more number of narrow vessels, and the distribution of vessel lumen size showed a dimorphic pattern (vessel dimorphism). Narrower vessels of such species will reduce the risk of embolism during the dry season. Vessel lumen size of many Dipterocarpaceae species in tropical seasonal forests became narrow with increasing the stem height, whereas vessel density became higher. Tree species in deciduous dipterocarp forests were appeared to have various hydraulic regimes, based on hydrogen isotope analysis, sapflow measurement and wood anatomical survey. They have established effective use of soil moisture by deep rooting, low transpiration, narrow vessels and successive leaf-falling, and have started leaf flush and flowering before the onset of the rainy season.We compared two remarkably different montane forests on Mt. Kinabalu, Barnes. Seven species in the forest established on a nutrient poor soil derived from ultrabasic rock have low tree height and thicker leaves than 6 species in the forest on sedimentary rock. Wood density, vessel lumen area and vessel density showed no significant differences as a whole between the two forests. However, when compared the species of same genus, the species on ultrabasic rock have higher wood density and narrower vessels than those on sedimentary rock. The data obtained by pressure-volume analysis also indicated that the species of ultrabasic rock are exposed to physiological draught, probably caused by low nutrient content of the soil. Tree species growing in the montane forests of Mt. Kinabalu have different wood density and vessel lumen size according to their maximum heights. Canopy species experiencing sever drought during the dry season avoid the stress by various mechanism such as the regulation of leaf osmotic pressure.