RESUMEN
Given the facts that urban land is extremely limited and ecological environment protection is confronted with severe challenges, it is of great importance to effectively construct green infrastructure (GI) network and identify relatively important landscape ecological components. We identified and prioritized GI network centers in Fuzhou downtown area using the MSPA and the landscape connectivity evaluation. The least cost path method and gravity model were used to construct the potential corridors at multiple levels. The density analysis and blind area analysis were used to extract and prioritize the GI nodes and to obtain the optimized GI network. The results showed that the first-level GI network centers were mainly distributed in the north and south of Fuzhou downtown, while those in the central region were small and scattered. The comprehensive resistance of landscape was low in the periphery but high in the middle, with poor integral connectivity. The GI corridor system with existing corridors and potential corridors was employed to enhance the connectivity among network centers. Furthermore, the GI nodes were extracted to provide a "transfer station" for material circulation and energy flow, which could partly solve the problems including excessive substrate resistance and the long connection corridor in some areas. The spatial prioritization of GI elements could make the construction of GI network more scientific and also provide reference for the future planning period and construction timing of GI network in Fuzhou.
Asunto(s)
Conservación de los Recursos Naturales , Ecosistema , ChinaRESUMEN
We employed a comparative study to examine the effects of tree species transition on soil microbial biomass, community composition and enzymes activities under Cunninghamia lanceolata (Lamb.) Hook, Eucalyptus grandis and a N-fixing species, Acacia melanoxylon in subtropical China. Results showed that the effect of tree species on soil microbial community and enzymes activities was significant only in the 0-10 cm soil layer. Reforestation with N-fixing species A. melanoxylon on the C. lanceolata harvest site significantly increased the total phospholipid fatty acid (PLFA), fungal PLFAs, Gram-positive bacterial PLFAs, Gram-negative bacterial PLFAs and actinomycetes biomasses in the 0-10 cm soil layer. The principal component analysis (PCA) showed that the soil microbial community composition in A. melanoxylon soil differed significantly from that in C. lanceolata and E. grandis soils. N-fixing species (A. melanoxylon) significantly enhanced the percent abundance of Gram-positive bacteria, Gram-negative bacteria and actinomycetes. Activities of cellobiohydrolase, N-acetyl-ß-d-glucosaminidase and acid phosphatase were significantly higher under A. melanoxylon than under C. lanceolata and E. grandis plantations. Our results suggested that reforestation with N-fixing species, A. melanoxylon on C. lanceolata harvest site could increase soil microbial biomass, enzyme activities and soil organic matter content.