Characteristics And Functions Of Vegetation On Down-reach Floodplain Of Yellow River In He' Nan

Floodplain is a seasonally inundated micro-geography on plain riverbed. With exerllent site condition, floodplains are historically exploited for agricultural purposes, which efficiently relieves the man-land crisis, playing an important role in the food and byproduct supply in China. But improper use of floodplains has arised environmental and ecological hazards, which are eager to solve. Foreign studies involving floodplain concentrated on riparian zones, marked with vegetations. The results enlightened the riparian zone (or floodplain vegetation) with complete ecosystem functions on one hand and on the other hand, revealed this ecosystem as fragile. Its functions can be easily degraded by riparian situations, vegetation attributes and disturbances, and fail to meet the need of social development. Functional study of floodplain vegetation on a community scale will enrich the theories on riparian study and restoration ecology, and will guide ecosystem health management and integrated exploitation of floodplain. Community-scale study is of great applying value, as it embodies the overall situation of micro-scale ecosystem and conveys information of large-scale ecosystems. This dissertation systemically documents the domestic and abroad studies on riparian vegetations, and conveys an integrated, systematical and profound study on the characteristics and functions of original vegetation and typical artificial vegetation localized on the down-reach floodplain of Yellow River in He'nan, for the first time. The study was carried out according to on-the-spot situation of the floodplain area, with sandy and windy environmental condition and with frequently occurring Locusta migratoria manilersis (Meyen) disasters. The thorough study on the exploitation political tendency and scientific achievements in forest silviculture, vegetation ecology, restoration ecology, riparian vegetation, together with the ecosystem health management theories, etc entitles the study to the priority in this academic field. Besides, the research also learned a lot from the Chinese forest eco-network system "line"research and demonstrative program, and "aforestation for snail (Oncomelania) control and Chistosomias prevention"study on middle and down-reach floodplains of Yangtze River. The dissertation study concentrates on the following 3 aspects:â… , vegetation characteristics of down-reach floodplain of Yellow River. Concerning flora study, spatial structure of communities, and inter-specific relationships. â…¡, ecosystem functions of floodplain vegetation on He'nan reach of Yellow River. These functions include production, biodiversity conservation, microclimate effects, protecting and enriching soil, non-point source pollution control and Locusta migratoria manilersis (Meyen) control. â…¢, Study the important role of vegetation in down-reach floodplain exploitation, and propose the "forest dominating "integrative exploitation and corresponding key problems. The main conclusions are as follows: 1. The floodplain flora of Yellow river in He'nan has an obvious temperate origin, and a relatively old resource. Its composition is simple, with herbaceous plants dominating the community. An obvious connection of this flora is found in longitudinal direction with its upper and down reach flora and a transverse direction connection with that of Huang Huai plain is found as well, which reveals the continuity and integrity of Yellow River flora. 2. Structural characteristics or floodplain forest (plantation or mix forest) are successfully analyzed with typical community survey method integrated with modern forest management method. By studying the size differentiation and spatial distributive pattern of the forests, we find that floodplain forests structures may differ from tree species, forest sources, forest types, allocation patterns, development status and management treatments From simple structure to the complex, there appears in turn Swallow forest, Poplar forest; natural forest and poor managed forest, agriforest; old forest, young forest. Size differentiation in crown is higher than that of DBH and tree height. In agriforests of 3 to 4 years old, there are some extent size differentiations, which is higher in crown than that in DBH and tree height. The effects of crown mainly occur between individuals in the same row. 3. Vegetation's function differs significantly between 5 different types. Forests possess the highest comprehensive function, composed of highest productivity function, microclimate effect, Locusta migratoria manilersis (Meyen) control function, soil protecting and enriching function and non-point resources pollution control function as well as relatively high and stable biodiversity conservation function. Tamarix-Swillow forests on the floodplain have a relatively high integrated function, consist of the highest biodiversity and relative high productivity function, microclimate effect, Locusta migratoria manilersis (Meyen) control function, soil protecting and enriching function and non-point resources pollution control function. Cropland ecosystem has a relatively low overall function, except its high productivity, cropland ecosystem has a low biodiversity and Locusta migratoria manilersis(Meyen) control ability. The integrative function of artificial grassland in the low, with poor productivity and low biodiversity conservation capacity, slight microclimate effect, moderate soil protection ability, non-point source pollution control ability, and even Locusta migratoria manilersis (Meyen) acceleration. Bare lands have the lowest function. 4. Based on the floodplain exploitation situation, this dissertation proposes a "forest dominating exploitation"on the down-reach flood plain of Yellow River. It is feasible as it abides by ecological principles and meets the global ecological construction and Globalization of the Economy. So that "forest dominating exploitation"on the down-reach flood plain of Yellow River is expected to promote sustainable development in floodplain area, with full use of environment resources of floodplain, and precious chance during Xiaolangdi reservoir operation. Successful experiences in floodplain exploitation on mid and down-reach Yangtze River provide guidance in "forest dominating exploitation"on the down-reach flood plain of Yellow River. Issues need to be emphasized are: to incorporate the floodplain exploitation to the entire river ecosystem management, with scientific planning, fulfilling and sound management; to highlight "forest dominance"and "ecology priority "; to strengthen scientific study, multidiscipline cooperation, social participation; to promote the floodplain exploitation on a scientific base, with research, improvement and extension.