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利用稳定性氢氧及碳同位素技术,与邻近乡土植物枫香比较,对喀斯特坡地尾巨桉水分来源与水分利用效率的季节性差异进行研究,分析喀斯特地区桉树人工林建设的干旱胁迫风险.结果表明:浅层(0~50 cm)土壤水同位素值渐变特征明显且与近期雨水同位素值相近,而深层(50~100 cm)土壤水同位素值整体较稳定且明显区别于浅层.土壤含水量整体呈现雨季(5、9月)高于旱季(10月),且上坡高于下坡的基本特征.枫香不受旱、雨季土壤含水率差异的影响,始终以浅层土壤水为主要水源,水分利用效率持续较高.尾巨桉水分来源受不同季节、坡位土壤含水率差异的影响:雨季上坡以浅层土壤水为主,雨季下坡对深层土壤水利用比例明显增加;旱季上坡主要利用较深层水分,旱季下坡依赖浅层土壤水.桉树水分利用效率始终低于枫香,但旱季时显著升高.尾巨桉水分来源灵活多变,但干旱条件下水分利用效率显著升高,表明其并未能获得充足的水分供应,预示着生长速率及经济收益遭受负面影响,干旱致死的风险较高.
Using the technology of stable oxygen and carbon isotopes, compared with the sweetpotentials of the neighboring native plants, the seasonal differences of water sources and water use efficiency of Eucalyptus grandis in karst slopes were studied, and the risk of drought stress in eucalypt plantation construction in karst areas was analyzed.Results The results show that the apparent water isotopic gradients of shallow soil (0-50 cm) are obviously changed and similar to the recent rainfall isotope values, while the values of water isotopes in the depths of 50-100 cm are stable and distinctly different from the shallow ones. Overall, the rainy season (May-September) is higher than the dry season (October), and the uphill is higher than the downhill.The sweet-scented ash is not affected by the difference of the soil moisture in rainy season and rainy season, and always takes the shallow soil water as the main Water source and water use efficiency continued to be higher.The water source of E. urophylla was affected by the difference of soil moisture content in different seasons and slope positions: shallow soil water was the main slope in the rainy season, The uphill slope in the dry season mainly used deeper water, and the descending slope in the dry season relied on shallow soil water. The water use efficiency of Eucalyptus was always lower than that of Liquidambar formosana, but significantly increased in the dry season. Under water use efficiency increased significantly, indicating that it failed to get adequate water supply, indicating that economic growth rate and earnings suffer, and droughts higher risk of death.