中国南方亚热带丘陵地区草地植被重建

A Study on the Grassland Reconstruction in the Subtropical Hilly Regions of Southern ChinaCandidate:

Measures taken according to experimental ecology and ecological engineering to modify environment of the subtropical hilly regions of southern China, cultivated grasslands of Chinese lespedeza (Lespedeza cuneata) and broadleaf paspalum (Paspalum wettsteinii) were raised. The sown pastures replaced the degraded grasslands of shrub-herb and herb growths of low-productivity in order to improve the degenerated ecosystem of the region. Some early stage ecological restoration measures and processes to ensure the grassland reconstruction were adopted.Results show that the soil productivity could be raised to provide yield of Chinese lespedeza to 12160 kg/hm^2 and of broadleaf paspalum to 17690 kg/hm^2 in the first year of cultivation, and to 13400 kg/hm^2 of the former, 20750 kg/hm^2 of the latter in the second year, an increase of 2.61~5.16 times of the yield of the previous degraded pastures. The solar energy utilization efficiency increased from 0.14% to 0.64% with the Chinese lespedeza grassland and to 0.93% with the broadleaf paspalum in the first year, then to 0.68% with the former and 1.01% with the latter in the second year. The output of energy, nitrogen and phosphorus were manifold of those of the degraded grassland. Effects in the second year were still better. The cultivated grassland prevented soil erosion efficiently by restoring vegetation, thickening the vegetation coverage, and establishing better above- and under-ground vegetation construction. The amount of soil erosion in the first year was deducted by about three quarters of that of the previous half-barren grassland. Soil erosion in the second year was cut by 51.77% in the Chinese lespedeza plot and 61.47% in the broadleaf paspalum grassland compared to the extent of soil erosion in the previous year.Compared to the former grassland, the newly cultivated pastures boasted higher soil pH value, richer amount of organic matter, total N, total P and available nutrients of the soil, as well as increased activities of catalase, acid phosphatase and urease, though the soil total K content and the activity of polyphenol oxidase were not regularly effected. Intensive cultivation and management ensures the soil qualities of the grassland. More organic carbon was fixed in the pasture with the increased vegetative cover. The soil organic carbon increased by 23% in the Chinese lespedeza pasture and 27% in the broadleaf paspalum one due to more organic matter input into the soil and the friendly environment conditions.Much more economic benefits have been gained in the reconstructed pasture. There is a payoff of RMB 5015.73 yuan/hm^2 with the Chinese lespedeza grassland and 5755.80 yuan/hm^2 with the broadleaf paspalum one in the first year, and RMB 8940.07 yuan/hm^2 of the former, and 9330.36 yuan/hm^2 of the latter in the second year. The input/output is 2.09 and 2.60 in the first year, and 7.15 and 7.39 in the second year, respectively.

Measures taken according to experimental ecology and ecological engineering to modify environment of the subtropical hilly regions of southern China, cultivated grasslands of Chinese lespedeza （Lespedeza cuneata） and broadleaf paspalum （Paspalum wettsteinii） were raised. The sown pastures replaced the degraded grasslands of shrub-herb and herb growths of low-productivity in order to improve the degenerated ecosystem of the region. Some early stage ecological restoration measures and processes to ensure the grassland reconstruction were adopted.