西双版纳地区不同胶农(林)复合系统的植物水分利用效率比较

Comparing the water use efficiency of plants in different types of rubber-based agroforestry ecosystem in Xishuangbanna,Southwest China

当前,西双版纳地区大面积橡胶单一种植林已引发了诸多的生态环境问题,为解决这些问题同时协调当地的经济发展,农林复合系统被生态学者们认为是最好的解决办法。然而目前关于不同间作模式下橡胶树水分利用效率研究还很少。因此,于2013-2014年的雨季中期(8月)和末期(11月)、雾凉季(1月)、干热季(3月),分别测定了中国科学院西双版纳热带植物园内四种不同胶农(林)复合系统(橡胶—叶茶、橡胶—咖啡、橡胶—大叶千斤拔、橡胶—可可复合系统)及单层橡胶林的土壤含水量、橡胶树及其林下间作植物的枝条凌晨水势和正午水势,以及它们植物叶片的δ^(13)C值,分析了各胶农(林)复合系统内橡胶树的水分利用效率,以期遴选出水分关系配置合理的复合橡胶林栽培模式,为环境友好型橡胶种植林的建设和推广提供相关的参考依据和理论支持。结果表明:除橡胶—可可复合系统以外,其余胶农(林)复合系统内的橡胶树水分利用效率值均高于单层橡胶林;橡胶—大叶千斤拔复合系统的土壤含水量显著高于其它复合系统;橡胶—叶茶复合系统的土壤含水量虽然低于橡胶—大叶千斤拔复合系统,但其最为稳定、季节变化小;橡胶—咖啡复合系统的水分利用效率最高最稳定,即使受到寒害也没有引起明显变化;而橡胶—可可复合系统的作用不明显,所有特征都与单层橡胶林相似。这表明除了橡胶—可可复合系统外,其他3种胶农(林)复合系统都显著地缓解了橡胶树在旱季所遭受的水分胁迫,同时也能有效地抵御突发性天气灾害。

A huge area of rubber（ Hevea brasiliensis） monoculture in Xishuangbanna,Southwest of China have caused many ecological and environmental problems now. In order to coordinate these problems and local economicdevelopment,agroforestry ecosystem as ecologists＇ common advise has been considered the best way to solve above problems. However,little information about rubber＇s water use efficiency is known in different agroforestry ecosysterns. For this reason,we measured soil water content,the shoot predawn and middy water potential,and the leaf δ13C of Hevea brasiliensis as well as its interplant in four rubber-based agroforestry ecosystems（ Hevea brasiliensis—Theobroma cacao agroforestry ecosystem,Hevea brasiliensis—Camellia sinensis agroforestry ecosystem,Hevea brasiliensis—Coffea arabica agroforestry ecosystem,Hevea brasiliensis—Flemingia macrophylla agroforestry ecosystem） and one rubber monoculture which was locatd at Xishuangbanna Tropical Botanical Garden in Southwest Yunnan Province,China in August 2013（ rainy season）,November（ conversion of the rainy and dry seasons） 2013,January 2014（ foggy season） and March2014（ pronounced dry season）. We aimed to apply stable carbon isotopes techniques in the study of the water use efficiency of Hevea brasiliensis in those rubber-based agroforestry ecosystems,and thus to select optimal agroforestry ecosystems which can use water reasonably and effectively. Depending on the multivariate statistical analysis,the results were as follows：（ 1） The average leaf δ13C of Hevea brasiliensis in those agroforestry ecosystems（ except for Hevea brasiliensis—Coffea arabica agroforestry ecosystem） were higher than that in rubber monoculture;（ 2） The soil water content in Hevea brasiliensis—Flemingia macrophylla agroforestry ecosystem was always higher than others during the research period（ P〈0.01）;（ 3） Despite the soil water content of Hevea brasiliensis—Camellia sinensis agroforestry ecosystem was the second highest,but it was the most stable one which change small with season;（ 4） The water use efficiency of Hevea brasiliensis—Coffea arabica agroforestry ecosystem was the most stable,and it was the highest one in despite of the chilling injury at the end of 2014;（ 5） As well as the rubber monoculture,Hevea brasiliensis—Theobroma cacao agroforestry ecosystem did not play a significant role during the whole period,and it expressed many characteristics like the rubber monoculture. All above results indicated that the agroforestry ecosystem（ except Hevea brasiliensis—Coffea arabica agroforestry ecosystem） could alleviate the water stress suffered by Hevea brasiliensis in the pronounced dry season. Not only could they keep higher growth and yield than rubber monoculture,but they also could make sure that the Hevea brasiliensis can resist the burst weather disaster at the same time. The results provides the relative theory and reference to support and guide the construction of environmentally-friendly rubber plantation.