滇中岩溶高原滇青冈原生林植物水分利用来源的稳定同位素分析

Soil-water utilization levels in a Cyclobalanopsis glaucoides virgin forest on the Central Yunnan Karst Plateau

为阐明滇中岩溶高原滇青冈Cyclobalanopsis glaucoides原生林植物水分利用机理及其对岩溶干旱生境的适应策略，运用氧稳定同位素技术，分析了滇青冈，云南木樨揽Olea yue nnanensis，清香木Pistacia weinmannifolia等3种不同年龄阶段常见优势木琴植物小枝木质部水分及土壤水、表层岩溶带水氧同位素值的相关性，确定植物水分来源，并通过IsoSource模型计算不同潜在水源对滇青冈原生林的贡献。结果表明：滇青冈及其伴生的乔木水分利用层位及利用比例呈现时空差异，并形成明显的水分竞争关系。旱季，滇青冈、成熟云南木樨揽、幼龄清香木主要利用55～115 cm深层土壤水，成熟的滇青冈和清香木对表层岩溶带水利用比例增加。雨季，成熟的滇青冈、云南木樨揽、清香木和幼龄清香木因大气降水对浅表层土壤的补给主要利用20-55cm土壤水，利用比例分别为100％，33．3％，66．0％，37．4％，幼龄植株对表层岩溶带水的利用比例大于成熟植株。

To explain the water utilization mechanism of a Cyclobalanopsis glaucoides virgin forest on the Cen- tral Yunnan Karst Plateau in southwest China, and its adaptive strategies in an arid karst habitat, a stable iso- tope technique was featured to determine soil-water levels utilized By plants. Several dominant plant species （C. glaucoides, Olea yuennanensis, and Pistaeia weinmannifolia） were selected and tested with oxygen iso- topes of water on stems and soils from the virgin forest. Using IsoSource model calculations the contribution of different water samples was determined. Results revealed that water utilization positions and proportions for C. glaucoides in the primeval forest and its accompanying trees varied in time and space, and were competitors for water. During dry seasons, C. gtaucoides, mature O. yuennanensis, and young P. weinmannifolia used soil water from depths of 55-115 cm with more groundwater used for mature C. glaucoides and mature P. weinmannifolia. In rainy seasons, because of the precipitation, 100% of the mature C. glaucoides, 33.3% of the O. yuennanensis, 66.0% of the P. weinnmanifolia, and 37.4% of the young P. weinmannifolia used the 20-55 cm soil-water level. [Ch, 2 fig. 23 ref.]