Effects Of The Three Northern Regions (Northeastern,Northwestern And Northern China) Shelter Forest Program On Plant Biodiversity And Community Function In The North Of Shaanxi Province

The construction of The Three-Northern Regions(northeastern,northwestern and northern China)Shelter Forest Program in the northern part of Shaanxi Province has been going on for nearly 40 years.At present,most of the researches focus merely on the surface evaluation of the Three-North Shelter Forest Program and the remote sensing of vegetation coverage,and there is no deep study into the Three-North Shelter Forest Program plant communities.Under this circumstance,this study takes the Three-North Shelter Forest Program in Yulin City,Shaanxi Province as the research object.Through wide and deep investigations on the restoration status of plant communities in the wind-fixing and sand-fixing area(sand area)and the water erosion control area(loess area).We get to understand how the construction of Three-North Shelter Forest Program influences the biodiversity and function of the plant communities,so that a reference for the future ecological environment management in Shaanxi Province could be provided.The main conclusions are as follows:(1)In this study,59 species belonging to 44 genera out of 19 families are found from both treated and untreated areas in the windbreak and sand fixing zones.38 species belonging to 30 genera out of 13 families are involved in the first period of the program.16 species belonging to 7 families and 15 genera are discovered in the second period.22 species belonging to 9 families and 20 genera are consisted in the third period.28 species belonging to 9 families and 24 genera are found in the forest in the fourth period.15 species belonging to 7 families and 13 genera are found in the fifth period.A total of 59 species belonging to 48 families and 48 genera are found in the water erosion control area.The first period involved17 species,belonging to 7 families and 13 genera;the second period involved 9 species,belonging to 5 families and 9 genera,and 23 plants in the third period.It belongs to 11 families and 19 genera;there are 20 species in the fourth phase of the project,belonging to 9families,16 genera,and 5 species of distributed species,belonging to 10 families and 15 genera.(2)Through the calculation of the species diversity index of each vegetation restoration community in different program areas,it is found that the introduction of plantation in windbreak and sand fixing zones significantly increased the species diversity of plant communities,and the species diversity index of shrub land was lower than that of trees.The species diversity among the plant communities in water erosion control area bears less difference.The plant community in the forestland transformed from farmland without theintroduction of plantation has a higher species diversity index.The introduction of plantation in water erosion control regions has no significant impact on species diversity of the plant communities.(3)The water content in soil in water erosion control regions is higher than that in windbreak and sand fixing zones.The plant community in windbreak and sand fixing zones has a larger leaf tissue density and a larger specific root length,wherease the plants in water erosion control regions have larger specific leaf area and higher leaf and root nitrogen content.The introduction of plantation in windbreak and sand fixing zones significantly increase the functional diversity of the plant communities compared with the untreated area.On the contrary,the introduction of plantation in the water-erosion regions did not help to increase the functional diversity of the plant community,and instead may decrease the functional diversity of the plant community in some regions.(4)The species in windbreak and sand-fixing zones and water-erosion regions are divided into different functional types based on plant functional traits.According to the CRS plant survival strategy model,the species belonging to the sandy soil functional type 1(PFT1)and the loess regional functional type III(PFT III)usually have larger specific leaf area and longer roots,and own a strong competitive advantage over resources.They thus are classified the “competitive type” in CSR models.The species in functional area 2(PFT2)and functional type I(PFT I)in loess area have large leaf and root tissue density,small and thick leaves,and the plant growth is conservative,and it has strong resistance to the external environment.They belong to the “stress tolerance type” in the CSR model.The species in the sandy soil function type 3(PFT3)and loess area functional type II(PFT II)have higher leaf and root nitrogen content,and the plant body is richer in nutrients.The specific leaf area is between “stress tolerance type” and “competitive type”,and the survival strategy is in between.They are more like "interference type" in the CSR model.