太行山地区荆条灌木"肥岛"对外源氮响应机制及保育作用研究

Creating forest surroundings is one of the the ultimate goals in Taihang Mountain.For efficient and convenient recovering forest cover in tough circumstances, making good use of protective effect of shrub could be applied to speed up the succession of community. Fertile island effect of shrub was a common phenomenon in arid and semi-arid region. This effect could be increased and enhanced by applying artificial nitrogen source. It was positive to reasonably use shrub fertile island for forestation and vegetation restoration in arid region. The research took shrubs communities of Vitex negundo var. heterophylla for example, studying the spatial framework of the fertile island effect, discussing the characteristic changes of this effect in condition of artificial nitrogen source, finding out sensitive ecological factors to applying artificial nitrogen source and learning the function of this effect to forest seedling conservation. The main contents were as follows: (1) From the analysis about soil physical and chemical properties and soil microorganism, this article analyzed the response of shrub fertile island under the conditions of artificial nitrogen source and the features of changes in space; (2) According to the growth indicators of aboveground vegetation、making microclimate observation and analysis of underground soil nutrient, probe into the result of the fertile island effect to forest seedling conservation

【意义】干旱半干旱地区，合理利用灌木的保护效应能加快群落的演替速度，是困难条件下森林植被恢复的有效和便捷的途径之一。灌木"肥岛"效应是一种普遍现象，合理利用灌木"肥岛"的保育作用对干旱地区造林和植被恢复具有积极意义。【问题】但其空间分布格局不清；"肥岛"效应可以通过人工外加氮源得到提升和加强，但它对外源氮如何响应不明确。【研究内容】本项目以太行山地区主要灌木荆条为对象（1）从土壤理化性质和土壤微生物分析入手，分析灌木"肥岛"效应对外加氮源的响应及其空间变化特征；（2）根据地上的植物生长指标、小气候观测和地下土壤养分分析，探讨灌木的"肥岛"效应对林木幼苗保育效果。【预期结果】得到"肥岛"效应的空间格局和外加源氮下"肥岛"效应的变化特征；找出对施氮响应的敏感生态因子；最优化发挥灌木"肥岛"效应对林木幼苗保育作用的营养形成机制。

灌木下的土壤具有“肥岛”现象，这为土壤的动物和微生物提供良好的生境，也对林木种子萌发和幼苗生长具有较好保育作用。本项目为揭示太行山半干旱地区的荆条灌木下土壤中“肥岛”的形成机制，采用样地法，在生境要素调查的基础上，分析了荆条灌木下土壤养分元素的空间结构；通过设置控制试验，研究了外源氮在灌木土壤“肥岛”形成和发展过程中的作用；利用分子生物学等手段，探讨了荆条灌木土壤微生物分布格局和根际土壤微生物的多样性；还初步研究了土壤“肥岛”效应对林木幼苗（侧柏）生长的促进作用。研究取得以下成果：.1、太行山地区荆条灌木下的土壤存在显著的“肥岛”效应；荆条灌丛对其周围土壤养分在水平和垂直空间结构上能够产生“聚集效应”。土壤养分具有冠幅内高于冠幅外，表层大于深层的规律。构建了太行山地区荆条灌丛的土壤“肥岛”的空间结构模型；.2、揭示了外源氮添加后，土壤全氮、速效磷和有机质空间变化规律。大气氮沉降加能够加剧灌木的“肥岛”效应提高；发现了荆条灌丛土壤微生物呈现岛状分布；冠下土壤的菌根真菌拥有较高的物种丰度和均匀度。根际土壤菌根真菌以球囊霉属、拟枝瑚菌属、珊瑚菌属等为主；.3、初步研究了荆条土壤“肥岛”对林木幼苗期生长的保护作用。