Research On The Hydrological Effects Of Typical Forest Types In Miaoshanwu Nature Reserve

The precipitation partition of two subtropical typical forests (natural secondary forest and artificial bamboo forest) in Miaoshanwu Nature Reserve in Zhejiang was studied. The rainfall interception of varied layers of the tree canopy, shrub and litter was measured, with the function of soil and water conservation, and the effects of different components of the forest ecosystem on water quality discussed. The equations were established to simulate the relationship between the precipitation partitioning and the atmosphere precipitation. This study is of great theoretical and practical significance, as it provides the basic data for the objective evaluations on the function of water resources conservancy, as well as soil and water conservation of different forest types, and also it provides a theoretical foundation for sustainable management and improvement of natural forests and plantations. The results are as follows:(1) The forests are effective on precipitation partitioning, with the forest vegetation canopy, understory shrub layer and litter layer intercepting rainfall to a varied extent. The artificial bamboo forest canopy interception rate is 14.5%, and the litter maximum water-holding capacity is 0.98 mm; while the natural secondary forest canopy interception rate is 33.8%, understory shrub layer interception rate is 7.0%, with the total interception rate reaching 40.8%, and the litter maximum water-holding capacity is 1.58 mm. It can be seen that the canopy interception and the litter water-holding capacity of natural secondary forest are better than that of artificial bamboo forest.(2) The surface runoff and erosion sediment of forest ecosystems are very low, implying that the function of soil and water conservation is pretty good. The runoff coefficients of natural secondary forest and artificial bamboo forest are only 0.10% and 0.20%, and the minimum precipitation generating the surface runoff are 10.1 mm and 7.0 mm respectively. The erosion sediment of natural secondary forest and artificial bamboo forest are as low as 0.262 kg/(hm²Â·mm) and 1.034 kg/(hm²Â·mm) respectively. The function of soil and water conservation of natural secondary forest is better than that of artificial bamboo forest.(3) The relationship can be perfectly simulated by mathematical equations between the precipitation partitioning and the atmosphere precipitation either for natural secondary forest or artificial bamboo forest with a high relevance and significance level. The linear equation is the best to simulate the relationship between the throughfall, stem flow as well as surface runoff and the atmosphere precipitation, while the throughfall ratio, stem flow ratio and runoff coefficient with the atmosphere precipitation are best fit by logarithmic equation. A power regression exist between the canopy interception/ratio and precipitation; the stemflow is positively correlated with tree diameter at breast height.(4) Vegetation canopy, litter layer, soil and rock in forest ecosystems have changed the chemical composition of precipitation and certainly improved water quality. All Indexes for water quality tend to increase from the atmosphere precipitation to the surface runoff except pH value, which mainly reflect the leaching of precipitation on the forest canopy and litter layer. NO₃^-, NH₄⁺, K⁺, and Na⁺ significantly decrease, indicating that forest soil has "Storage tank" role in maintaining NO₃^-, NH₄⁺, K⁺, and Na⁺, while Ca²⁺ and Mg²⁺ content in outlet flow increase due to the dissolution of Ca and Mg in soil and rock.In conlcusion, natural secondary forest and artificial bamboo forest play an important role in precipitation interception, waer resources conservancy, soil and water conservation, and water quality improvment. The hydrological effect of natural secondary forest is better than that of artificial bamboo forest, and the function of soil and water conservation of natural secondary forest is also more powerful.