成熟刺槐林下植被对土壤干层发育影响的试验研究

A dried soil layer (DSL) is generally formed in the soil profile in an artificial black locust (Robinia pseudoacacia L.) plantation in the Loess Plateau. The R. pseudoacacia would gradually decay with increasing ages due to the lack of water at deeper depths, which would decrease the forest canopy closure, the net primary productivity, and the transpiration rate, while the understory shrubs and grass develop actively. The water-consume and rainfall-interception by understory canopy may have important effect on the development of the DSL in decayed R. pseudoacacia plantations. Few reports, however, have addressed the possible effects of understory on the DSL. This project will be conducted in Ziwuling Mountain in the middle of the Loess Plateau. Field monitoring and isotope techniques will be combined. We aim (1) to study the controlling processes of understory on the transition of precipitation to soil water in mature R. pseudoacacia plantings; (2) to analyze the dynamic relationships between the DSL and water-absorption processes by understory; (3) to ascertain the water sources in different soil layers for the typical understory plants and their utilization ratio as well as seasonal dynamics; and (4) to reveal the affecting intensity and the key process of understory on the DSL. This research will be conductive to understand the DSL’s formation and evolution mechanism in the construction of artificial vegetation. This research will also provide new idea to produce sustainable ecological function of the secondary forest in the Loess Plateau.

黄土高原刺槐人工林下伏土壤干层。成熟刺槐林随林龄增加，林木逐渐衰败，郁闭度下降，初级生产力减小，蒸腾降低，林下灌、草植被发育活跃。林下植被耗水、截持降雨作用可能对衰退刺槐林地土壤干层发育产生重要影响，但其影响大小和作用途径鲜有报道。为此，项目选择黄土区中部子午岭林区为研究对象，通过野外定位观测，结合同位素技术，研究成熟刺槐林下植被对降水补给土壤水分的影响过程，分析林下植被耗水与土壤干层的动态关系，查明典型林下灌、草植物对深剖面不同层次土壤水分的吸收利用比例及季节变化，探究林下植被对土壤干层发育的作用强度及关键作用途径。研究结果一方面有助于深化认识人工植被建设中土壤干层形成和演变机制，另一方面可为黄土高原次生林生态功能的充分发挥提供借鉴。

林下植被对人工林土壤水循环过程具有重要影响。本项目按照项目计划书开展相关研究工作，以半湿润黄土区成熟刺槐林为研究对象，在样地尺度，通过田间观测和室内分析，获得了人工刺槐林大量土壤水分、植被耗水相关数据和资料，明确了人工刺槐林下植被对土壤理化性质的影响，阐明了林下植被耗水过程与土壤水分间的动态关系，明确了上层林木和林下植被对土壤水的利用数量及差异，揭示了林下植被对人工刺槐林土壤水文过程的影响机制。研究结果对深入认识人工林土壤水循环特征具有重要意义，为黄土高原人工林管理提供了依据。在该项目的支持下，目前发表科研论文19篇，其中SCI刊物收录12篇（第一标注SCI论文3篇），中文核心期刊论文6篇（EI收录论文3篇），其他刊物1篇。发表的1篇第一作者SCI论文入选美国ESI数据库Engineering学术领域1%高被引论文。协助培养博士研究生2名。在项目资助下，项目负责人获得2017年第十二届中国土壤学会科学技术一等奖、2017年中国科学院教育教学成果二等奖和2018年第六届中国土壤学会优秀青年学者奖，2017年成为中国科学院青年创新促进会会员。