| Guizhou is one of the most karst rocky desertification provinces in China. In the most of areas, there is the distribution of carbonate rocks. The development of Karst is fully that forms Karst plateau, mountain and hills all over the province.The environment of Karst plateau is extremely special, it has the high rate of exposed rock, shallow soil and discontinuous scattered in the crevice with small soil water retention capacity, and high content of calcium and magnesium,and the ecosystem is fragile, etc.There is an obvious difference between the Karst plant community development in these special habitats on it and non-zonal plant communities in Karst.The vegetation in the Karst have species richness and shape differences. On the one hand,the plants absorb nutrients from the soil. On the other hand, they are also affected by the nutrient element content in soil environment.This study choose the typical karst plateau secondary forest as the research object. Based on the investigation and sampling analysis of the secondary forest ecosystem’s biomass, species composition, element content and accumulation as well as the physical and chemical properties of soil. The main results showed as follows:1) In this secondary forest, spatial heterogeneity of soil is very large. regional soil thickness can be distributed in 10-70 cm, distribution is extremely uneven, but the average soil thickness is only 37.5 cm;Soil bulk density changes in the range of 0.79-0.79 g·cm-3, the average density is0.98 g·cm-3, the water content is 21.22%- 37.38%; The average organic matter content is 79.89g·kg-1, the total nitrogen in soil is 0.55g·kg-1, available N is 55.20 mg·kg-1, the total phosphorus content is 0.08g·kg-1, available P is 11.49mg·kg-1, the total potassium content is 12.62g·kg-1,available K is 369.83mg·kg-1. The soil of Secondary forest is shallow, moist, and have abundant organic matter, but low nitrogen and phosphorus and rich in potassium.2)In the secondary forest ecosystem, carbon, nitrogen, phosphorus and potassium in the total reserves respectively were 815.41t·hm-2, 12.04t·hm-2, 1.68t·hm-2, 271.49t·hm-2, in which theorganic carbon storage is 5.11t·hm-2. Nitrogen reserves is 4.61t·hm-2; Phosphorus reserves are 1.56t·hm-2; Potassium reserves is 63.36 t·hm-2;accounted for 0.62%, 0.03%, 0.07%, 0.02% of the whole ecosystem nutrient elements. Phosphorus reserves at least in the plant, but the proportion in the whole ecosystem is higher than the nitrogen and potassium, indicating in plant life activities,the absorption of phosphorus removal efficiency higher than that of nitrogen and potassium.3)In the tree layer, nitrogen and potassium content of trunks have significant correlation(P <0.01), between nitrogen, phosphorus and potassium content in the branches and leaves are very significant correlation(P<0.01). The shrub layer, phosphorus and potassium content significantly correlated in the plant trunks(P<0.01); nitrogen and phosphorus content of branches has significant correlation(P<0.05), phosphorus and potassium significantly correlated(P<0.01).Nitrogen, phosphorus and potassium content in leaf were extremely significant correlation between each other(P<0.01). Herbaceous plants on the whole nitrogen and phosphorus,nitrogen and potassium, phosphorus and potassium element content into extremely significant correlation(P < 0.01).While plant organic carbon content and nitrogen, phosphorus and potassium have no obvious correlation between three elements.4)In the secondary forest,the soil organic carbon, total nitrogen, total phosphorus, total potassium, available nitrogen, available potassium were significantly related to each other,including total potassium and organic carbon, total nitrogen, total phosphorus, available nitrogen,available potassium was significantly negative correlation, available p and organic carbon, total nitrogen, total phosphorus, total potassium, available nitrogen, available potassium were not significantly correlated.The contention of the organic matter in the soil is in high latitude in comparison with others in the same zonal expect nitrogen and phosphorus. It has a seriously lack of s nitrogen and the phosphorus is less, too. But the contention of potassium is rich. The plant on the growth in the soil is restricted by the conditions of nitrogen obviously.5)The area of soil nutrients have all been absorbed by the plant, which is equivalent secondary forest growth under ideal conditions nearly 600 years of nutrient reserves. Soil available nutrient content sufficient to fully meet the needs of plant nutrients per year, but in the effective state nutrient content in certain circumstances, the plant will be in 100 years by the lack of effective state phosphorus restrictions. |
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