退耕还林地结构与生态功能的耦合关系

退耕还林的林地结构与生态功能效益是退耕还林工程的关键性问题。基于典型黄土高原丘陵沟壑地7种代表性的退耕还林模式的野外调查和取样分析结果,选取14个林地结构因子和2个代表性生态功能因子,对林地结构进行因子分析,并构建了林地结构与生态功能的灰色关联度模型和耦合协调度模型。用建立的模型分析吴起县退耕还林地7种模式的林地结构、土壤侵蚀及地表径流数据,结果表明,不同林地结构因子间相关度不同,经过主成分分析降维为4个主成分因子,分别反映了林分的乔木层结构指标、上层结构生物量指标、土壤层指标及其它指标;不同林地结构因子与生态功能的关联度系数不同,林地结构因子对地表径流的影响明显高于对土壤侵蚀率的影响,其中林分组成对径流的影响最明显,土壤因子影响最不明显;草本层生物量、枯落物生物量等近地表的相关结构对土壤侵蚀的作用明显。不同退耕还林模式的林地结构与生态功能的耦合协调度状况都不良好,仍需要进行调整和改善。

Modeling the degree of coupling and interaction between forest structure and ecological function in a grain for green project, Shanxi, China

Forest structure and ecological function serve important roles in China's Grain for Green project. This paper analyzes seven grain for green patterns in the Loess Plateau Gully and Hill Region using data analysis and modeling. Fourteen forest structure factors and two ecological function factors were selected for analysis; these factors were reduced dimensionally using factor analysis, and models of the degree of coupling and interaction between forest structure and ecological function were constructed. Based on the model, analysis of data related to forest structure, soil erosion and runoff was completed for the Grain for Green project in WuQi County, Shanxi Province, China. The results reveal various relationships exist between the different forest structural factors analyzed here. All the factors can be reduced dimensionally into four main factors identified here as F1, F2, F3, and F4. These four factors represent the tree layer, upper canopy layer mass, soils and an alternative factor, respectively. A component score coefficient matrix in the Grain for Green patterns was obtained by multiplying the factor coefficient and the corresponding basic data, and then combining the scores to calculate a component score. Each forest structural feature was expressed using the component score coefficient matrix, which shows that two types of forests, pure Robinia pseudoacacia and mixed Robinia pseudoacacia/Fructus Hippophae had the highest F1 score; pure Caragana intermedia forest had the highest F2 score; and pure Fructus Hippophae forest had the highest F3 score. The coupling degree of the Grain for Green patterns differed between different models, and the integrative indices of forest structure did not correlate well with those of ecological function. The integrated index measuring the relationship between ecological function and surface runoff is larger than the index measuring the relationship between ecological function and soil erosion. Forest component factors have the most obvious effect on ecological function, and the effect of the soil factor is the least obvious. The mass of herb layer, litter layer and some other structures near the ground play the main role in the ecological function of controlling soil erosion. The relationships of forest structure and ecological function in the grain for green project differ in the various patterns. Forest structure and ecological function were most closely related in areas with pure Fructus Hippophae, while index score belongs to the middle coupling coordinative level. Pinus tabulaeformis had the least interaction between forest structure and ecological function. Calculating the score for all types of models discussed above shows a measure of the degree of interaction between the forest structure and ecological functions can be measured with a score of 0.6, which is considered to indicate a weak interaction. Therefore, forest structure and ecological function should be improved during the application of any Grain for Green project in the Loess Plateau Gully and Hill Region.