广西不同石漠化程度下典型植物水分来源分析

以广西岩溶地区不同石漠化程度下的典型优势灌木为研究对象，利用氢氧和碳稳定同位素技术，结合叶片水势和土壤水势等，分析广西石漠化地区典型植物的水分利用来源。实验结果表明：随着石漠化的加剧，植物叶片水势和d¹³C值呈降低的趋势，但并没有呈直线下降，且不同石漠化程度下植物的水势和碳同位素差异性均不显著。在轻度和中度石漠化环境下，灌木主要以吸收土壤水（＞70%）为主；重度石漠化环境下，黄荆以夏季早期降雨储存在裂隙孔隙中的水（71.1%）为主要水源，而红背山麻杆则主要吸收土壤水（57.6%）和夏季早期降雨储存在裂隙孔隙中的水（42.4%）。土壤水是石漠化地区植物水分利用的重要来源，在重度石漠化环境下，植物对岩溶裂隙水的利用比例增大。为适应石漠化地区水分不足的现象，植物具有相似的水分利用策略：保持比较低的水势，较高的水分利用效率。植物对不同水源的利用存在转移以适应石漠化环境的加剧。

Water Sources of Typical Plants in Different Rocky Desertification Grades in Guangxi

Using the stable isotope technique and water potentials, we research the water sources of typical plants in Guangxi and their respond to rocky desertification in three different rocky desertification grades. Results show that: Plant water potential and carbon isotope reduce with the increase of rocky desertification. No significant difference is found between the two dominant species both in water potential and carbon isotope in different rocky desertification areas. In slight and moderate rocky desertification area, an average of >70% of water for the two species comes from soil water, where soil is scattered only in rock fractures and is underlain by rigid carbonate rock. In intense rocky desertification area, V. negundo mainly uses rainwater which stored in fissures, and A. trewioides relies on a mixture of soil water and rainwater, which account for 57.6% and 42.4% of the total, respectively. These two deciduous shrub species use more previous rainwater (>40%) and little recent rainwater in intense rocky desertification area. Soil water is the important water sources for plant growth in rocky desertification area. Water quantity that plant uptake from shollow fractured rock zone is increased gradually in intense rocky desertification area. Plants have the same water use strategy against rocky desertification, such as low water potential and photosynthetic rate, high water use efficiency, and change of water sources.