陕北沙漠化逆转过程中土壤-植物反馈机制及植被演替效应研究

Succession and internal interactions of plant-soil system are important fields ofthe geographical-ecological process research. Due to the complicated factors ofplant-soil system, current studies mainly focus on the corrections betweenabiotic, biotic soil properties and ecological, physiological plantcharacteristics, phenomenological models have demonstrated the important role ofplant-soil system on maintaining plant communities diversity, plant coexistenceand ecosystem stability, but there is little mechanistic studies withconsideration of the synthetical viewpoint. Northern Shaanxi, China, where thedesertification is reversing, is taken as the study area. The desertificationreversion process is divided into three stages, the early successional stage, themiddle successional stage and the later successional stage. The plant-soilfeedback mechanism in natural fields is researched in this study, based on theLotka-Volterra competition model and the individual-based competition model,propose the plant-soil feedback models of different plant species and the plantsuccessional models under feedbacks. To parameterize our models, we will conductedfield experiments using three constructive species and some other dominant speciesin every successional stages. Parameterized plant-soil feedback models ofdifferent plant species could quantity the intensity of feedbacks, confirm thedirection of feedbacks and explain the mechanism of plant-soil feedbacks inmaintaining plant coexistence and community stability, and predict thetrajectories of stable and oscillating of different species coexistence. The plantsuccessional models, which will be conducted on GIS platform written by the CAmodels, will simulate the spatial and temporal evolutions of different species,show the effects of feedbacks on community dynamics and successional dynamics andrealize the space expression of succession under plant-soil feedbacks. Analysisand discussion of this scientific proposition, expect to thoroughly understand theecological process of desertification reverse, deepen the theoretical basis ofdesertification research, provide basis and reference for maintaining thestability of ecosystems in desertification area and realizing sustainabledevelopment in resources-based ecological fragile area.NSFC2014

土壤-植物系统演变及其内在作用规律是地理-生态过程研究的核心议题。当前，该领域的研究大多是从土壤、植物特性相关性这一单一视角展开，对综合效应的研究尚不多见。项目以陕北毛乌素沙地东南缘沙漠化逆转明显区域为研究区，综合分析不同物种组合下土壤、植物内部作用关系，构建土壤-植物反馈概念模型和基于反馈的植被演替模型，并借助连续三年的野外实验数据对模型参数化，在Matlab软件平台下运用土壤-植物反馈模型预测不同物种组合状态下土壤-植物反馈的方向、强度和动态轨迹，运用GIS软件平台构建CA模型模拟不同群落演替的时空序列，揭示土壤-植物反馈在维持物种共存和群落稳定性中的作用机理，明确反馈作用下植被的演替效应，实现演替过程的时空表达。理论上揭示反馈作用下沙漠化逆转的生态驱动机制，并探讨土壤-植物反馈的生态效应；实践上为解决沙漠化地区生态修复和重建提供科学依据，对资源型生态脆弱区实现可持续发展具有重要意义。

项目将土壤-植物反馈视为维持土壤-植被系统平衡的内在作用机制，以陕北毛乌素沙地东南缘为研究区，对沙漠化逆转过程中土壤-植被的反馈机制及植被的演替效应进行研究。重点内容：土壤-植被反馈模型的构建、土壤-植被反馈关系及反馈机制研究和植被演替效应研究。重要结果：（1）基于土壤-植被反馈模型对本氏针茅和糙隐子草的反馈关系进行分析，结果显示本氏针茅的竞争系数和反馈系数阈值区间均大于糙隐子草，表明其在土壤-植被反馈关系中竞争优势更为明显；（2）对五种沙漠化共有种植物在沙漠化逆转过程中土壤-植被反馈关系进行分析，结果显示，五种共有种植物表现出对沙漠化土壤环境不同的反馈适应性，油蒿和牛心朴子的适应性较强，对沙漠化逆转演替发挥着积极的作用，相较而言，本氏针茅和糙隐子草更适宜生长在沙漠化逆转演替的高级阶段；对研究区四种典型草本的土壤性质进行分析，结果显示四种草本在对土壤的适应过程中呈现出从牛心朴子到阿尔泰狗娃花到本氏针茅到糙隐子草的逆转演替序列；对六种灌木的分析结果显示，臭柏和沙蒿群落下土壤肥力最差，表明二者对沙漠化的适应能力较强，柠条和羊柴群落下土壤肥力最好，长梗扁桃和沙柳次之，其综合反映了土壤—植被反馈作用的结果；（3）对沙漠化逆转演替过程中土壤-植被系统稳定性进行定量评价，结果显示沙漠化逆转过程伴随着土壤-植被系统稳定性指数的不断提升；时空演替分析结果显示，研究区沙漠化程度整体上呈现波动性逆转趋势，且北部的沙漠化恢复状态比南部好；驱动力分析结果显示，降水是该区域植被生长的限制因子，对植被变化过程起到主导作用。科学意义：（1）对沙漠化逆转过程中土壤-植被反馈关系的研究揭示了沙漠化逆转的内在作用机理；（2）微观尺度和宏观尺度分析的结合更深入的探究了研究区土壤-植被反馈的方向和轨迹；（3）人为要素在研究区沙漠化逆转过程中同样影响重大，在后续研究中应予以考虑。