热带岩溶植物生理生态适应性对于南方石漠化土地生态重建的启示

Implications of the Ecophysiological Adaptation of Plants on Tropical Karst Habitats for the Ecological Restoration of Desertified Rocky Lands in Southern China

岩溶地质在我国分布广泛,特别是西南地区连片分布着世界上面积最大的岩溶地貌.由于长期人为活动的影响,目前我国南方地区岩溶石漠化土地面积已达1.2×105 km2,导致当地生态条件恶化,经济、社会发展面临严重困难.南方岩溶山地土层薄,养分贫瘠,保水性能差.对热带岩溶森林开展了一系列生理生态研究,研究结果对南方岩溶石漠化山地生态重建有启发意义.研究结果暗示,岩溶生境常绿、落叶木本植物和木质藤本植物共存对于维持生态系统水分平衡有重要意义.常绿植物枝条木质部耐气穴化能力强,叶片耐失水性能强.落叶植物采取避旱策略,通过落叶减少旱季蒸腾和水分消耗.岩溶山地大部分植物具有很深的根系,藤本植物根系更深,旱季能利用地下深层岩石下和缝隙水.有些植物如木棉、董棕利用树干储存水保持旱季必要的生理代谢.岩溶山地木本植物叶片和枝条木质部结构和生理功能的密切关联对于适应水分胁迫起重要作用.热带岩溶植物可能普遍缺乏锌、钾元素,这方面问题需引起重视和研究.藤蔓植物可以利用石漠化岩溶山地局部水土资源和丰富的生长空间和光照资源,并且大多数藤蔓植物气孔调节能力强,对强光的适应和利用能力强,是石漠化山地生态重建的理想植物材料.目前中国科学院西双版纳植物园正在推广的一种珍贵的油料植物—星油藤,可以作为南方热区石漠化山地生态重建的理想植物材料.石漠化土地的重建要合理利用不同功能类群植物,特别是岩溶生境的乡土植物,最好构建多层复合群落.

Karst lands are widely spread in China, particularly in Southwest China, which cover the largest continuous karst area with a unique landscape. Due to the human interference for a long time and the special substrate and hot and humid climate, the karst lands in this region have been severely degraded, the desertified rocky karst lands now totally cover the area of 1.2x105 km2 in southern China. This results in environmental deterioration and difficulty for the social and economical development. Karst lands in southern China are characterized with thin or little soil, low soil nutrients and low water holding capacity. We have done a series of research on the ecophysiological adaption of plants on a tropical karst mountain. In this article, we briefly synthesize our research and the key findings, and also some other research in order to provide reference information for the ecological restoration of desertified karst lands. Our studies have indicated that the co-existence of evergreen and deciduous trees and lianas is helpful for the maintenance of water balance of karst ecosystems. The evergreen trees are tolerant to water deficit and xylem cavitation, while deciduous trees shed leaves to reduce water use in the dry season. Most of karst woody plants have deep roots, while the lianas have the deepest roots in order to reach deeper water source belowground in dry season. Some plants such as Bombax ceiba Linn. and Caryota urens Linn. store water in their stems to support the necessary physiological processes in dry season. Most of the tropical karst plants are short of Zn and K nutrients according to the foliar nutrient analysis, this should be taken into account during the ecological restoration and agricultural practices. Lianas are able to use the localized water and nutrients and employ the abundant light source and spaces of desertified karst lands by means of their climbing stems. They often have high photosynthesis and strong regulation of water use, and are useful plant materials for the restoration of the desertified karst lands. An important oil liana, Plukenetia volubilis L, is now recommended for plantation by the Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, which is an ideal plant for the restoration of desertified karst lands. The ecological restoration of desertified karst lands could consider using different function groups of plants to construct a multiole-storev community.