不同造林模式红树林的促淤固滩作用对比

With the decline of the covered area of natural mangrove forests, plantation of mangrove forests has become an important method to protect shoreline. Although monoculture and mixed mangrove plantations were widely adopted within mangrove reforestation, two major questions of mangrove plantation are what are the effect of root systems of monoculture and mixed plantation on the process of sediment trapping and erosion prevention, and what are the characteristic of sediment trapping and erosion prevention of monoculture mangrove plantation and mixed mangrove plantation. The research will carry out experiments on the sites of monculture and mixed mangrove plantations in Beibu Gulf, and the barren and natural forest sites were treated as controls. This research will also observed the relations between Aerial roots (and stem) and sediment trapping, as well as the relations between below-ground roots and soil erosion among seasons, years and plantation years. By the relationship between density, height, diameter of above-ground systems and relating accretion rate , grain size of bed sediment, this research will analyze above-ground root systems how to regulate bed sediment. Analyzing the influence of below-ground root layer, diameter and length on the soil stability index and soil aggregate stability,and then reveal the relationship between underground root and soil stability. Combining with the erosion processes and their period of occurrence in the study area, we will also analyze the characteristices for sediment trapping and erosion prevention of monoculture and mixed mangrove reforestation. The research aims in (1) further understanding the role of mangroves in sediment trapping and erosion prevention;(2)providing a theoretical basis for mangrove reforestation.

人工营造红树林是减缓海岸侵蚀保护海岸线的重要途径。目前（单）纯林和混交林的造林模式虽已被普遍采用，但由于“纯林和混交林根系促淤固滩作用”问题认识的尚不深入，一直都难以对比回答“纯林和混交林促淤固滩效果”这一造林中的现实问题。拟开展的研究以北部湾典型红树林人工纯林和混交林为对象，设置天然林或光滩作为对照，在季节、年际、林龄时间尺度下，观测地表根系（和茎干）的促淤作用和地下根系的固滩作用。通过地表根系（和茎干）密度、高度、表面积等与沉积物淤积厚度、粒度的关系，理解纯林和混交林对促淤的影响；通过地下根系分布层次、径级、密度等对土壤团聚体稳定性和水稳性指数的影响，探讨纯林和混交林对固滩的作用。然后，结合研究地淤侵季节变化规律及潮滩侵蚀过程，比较阐明北部湾典型红树林人工纯林和混交林固滩促淤效果。研究不仅能加深理解红树林促淤保滩功能，同时也能为科学营造红树林提供理论依据。

人工营造红树林是减缓海岸侵蚀保护海岸线的重要途径。目前纯林和混交林的造林模式虽已被普遍采用，但对“纯林和混交林根系促淤固滩作用”的认识仍不深入。研究以10龄和6龄无瓣海桑纯林（简称无瓣纯林）、无瓣海桑-白骨壤混交林（无-白混交）； 14龄和8龄无瓣海桑纯林、桐花树纯林、无瓣海桑-桐花树混交林（无-桐混交）为对象，通过对滩面沉积物淤积厚度（A）、平均粒度（M）、地表障碍物（地表根系、幼苗）体积（Vm）、地下根系根长密度（RLD）、土壤水稳性指数（S）的监测，发现：.1）无瓣纯林和无-白混交下A和Vm、RLD和S均随林龄增大而增大。A和Vm、0-20cm深度的RLD和S在低龄纯林和混交林间存在显著差异（P<0.05），在高龄纯林和混交林间无显著差异。具体如：A和Vm在6龄无-白混交下均显著性的高于6龄无瓣纯林，但在10龄无-白混交与10龄无瓣纯林间无显著性差异；M在不同林龄和造林处理间不存在显著性差异。在0-20cm土壤深度，RLD和S在6龄无-白混交下均显著性的高于6龄无瓣纯林，但在10龄无-白混交与10龄无瓣纯林间无显著性差异；在20-60cm层次，RLD和S在6龄与10龄纯林和混交林间均不存在显著性差异；.2）无瓣纯林、桐花树纯林、无-桐混交下A和Vm、RLD和S均随林龄增大而增大。A和Vm、0-20cm深度的RLD和S在低龄纯林和混交林间存在显著差异（P<0.05），在高龄纯林和混交林间无显著差异。具体为：A和Vm在8龄无-桐混交下均显著高于8龄桐花树纯林和无瓣纯林；14龄无-桐混交下A和Vm与14龄无瓣纯林间无显著性差异，但它们二者均显著高于14龄桐花树纯林；M在不同林龄和造林处理间不存在显著性差异。在0-20cm层次，RLD和S在8龄无-桐混交下均显著的高于8龄无瓣纯林和8龄桐花树纯林，但在14龄无-桐混交与14龄无瓣纯林间不存在显著差异；在20-60cm层次，RLD和S在所有林龄和造林处理间均不存在显著差异。.研究表明，无瓣海桑与白骨壤或桐花树混交，在低龄期能比纯林种植更能促进淤积和潮滩稳定，但随林龄增加，淤积和稳定优势消失。