丛生竹种不同年龄茎秆的水分利用特征研究

Bamboos are considered non-timber tree growth forms and represent renewable forest resources and important landscape plants. Bamboos are increasingly becoming significant in our economic development and some products made from bamboos are employed in our daily life, especially in South China regions where bamboo resource reaches its abundant in both species diversity and ethnobotany diversity. However, the rapid expansion of bamboo forests might change local water cycle and even the structure of forest ecosystems. Unlike most trees, bamboo species not only have central hollow of culms, randomly scatted vascular bundles across culm wall, but also lack secondary growth, which results in the fact that xylem vessels cannot renew or regenerate after their initial establishment. Therefore, the effects of culm ages on water use process become significant to consider. However, little is known about water use characteristics of bamboos with different culm ages and water consumption rules of bamboo forests. In the present study, six common clumping bamboo species with important ecological and economical values will be selected and studied in Yunnan Province. The sap flux density, micro-variation of culm circumference, transpiration rate, and root pressure will be monitored in four different age groups of bamboo culms. The comparison of water transport, storage, consumption and redistribution of clumping bamboos with four age classes, combined with their morphological and anatomical structure of bamboo culms, will also be investigated. The knowledge that will generate from this study based on our experiments represents an important step toward accurate estimate of water use in bamboo forests and helps to elucidate local water resource use. This investigation on water use characteristics of culms with different ages will not only provide a basis for the scientific knowledge but also assist the management and sustainable utilization of clumping bamboo species in gardens and forests.

作为非木材的可再生林业资源和重要的园林绿化植物，竹子在人们日常经济生活中的重要性日益突显，尤其是在竹类资源较为丰富的我国南方地区。然而，竹林的快速扩张可能会对当地的水分循环和森林生态系统的结构产生深远影响。有别于大多数树木，竹子茎秆中央中空、竹壁内维管束分布不均匀且因缺乏次生生长而导致木质部无法更新，故其水分利用过程可能受年龄影响的程度明显，但目前人们对竹子水分利用特征及竹林耗水规律的认识还非常有限。本项目以6种常见的且具有重要经济和生态价值的丛生竹种为研究对象，通过测定茎秆液流、直径微变化、蒸腾速率及根压等，比较丛生竹种不同年龄茎秆中水分的运输、储存、消耗及再分配情况，结合其茎秆的形态及解剖结构，从而全面地揭示丛生竹种不同年龄茎秆的水分利用特征。本项目将对准确估算竹林的水分消耗及合理高效利用当地水资源具有重要意义，同时也可为丛生竹种的科学经营管理及可持续开发利用提供重要理论依据。

有别于大多数常见树木，竹子因缺乏次生生长而导致茎秆木质部无法更新，故其水分利用过程可能受年龄影响的程度明显，但目前人们对竹子水分利用特征及竹林耗水规律的认识还非常有限。作为终生以一套固定的水力系统来维持生长的植物，竹子水分利用特征可能会因不同物候期（如发笋、长叶等）、不同年龄茎秆对水分需求不同而表现出差异。本项目以麻竹为实验材料，通过使用热消散探针的方法，原位监测了其茎秆的液流，并同步监测了根压、茎秆周长及叶片冠层气体交换的动态变化。我们的主要研究结果是：(1)驱动茎干液流的主要影响因素是叶片蒸腾，而物候差异会影响叶片蒸腾，故物候（长叶前后）是导致不同年龄麻竹茎秆液流及日间水分消耗差异的原因之一。(2)不同物候及年龄都会影响麻竹的茎秆液流对 PAR 和 VPD 的敏感性，但麻竹茎秆液流对 VPD 的响应更强烈。不同年龄麻竹茎秆日间最大液流密度与 PAR 和 VPD 的峰值之间存在明显时滞现象。(3)麻竹茎秆水力特性与其冠层叶片水势、叶片水力导度、净光合作用、气孔导度之间有一定关联。冠层叶片生理与茎秆水力特性之间的协调关系共同决定着不同物候期不同年龄麻竹整株水分的利用特征。本项目揭示了不同年龄麻竹不同物候期茎秆液流的变化规律、耗水特性及茎秆液流对主要环境因子的响应；阐明了不同物候期不同年龄麻竹的茎秆水力特性与冠层叶片生理之间的协调关系；明确了不同物候期不同年龄麻竹的水分利用特征。本研究有助于我们更好地了解麻竹（丛生竹）的水分生理生态适应性，为麻竹等丛生竹栽培及其竹林的科学管理等提供理论基础和参考依据。

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