Macropores Properties Of Forest Soil And Its Influence On Water Infiltration In The Upper Reaches Of Minjiang River

Based on the fractal theory and brilliant blue dye tracer method,the soil macropore properties of the 5 major forest vegetation types in Wolong area of Sichuang province was systematically studied.The water infiltration capacity was measured by using ring sword methods.The relationship between the soil macropore,the water infiltration and the root system was analyzed.The main results were as follows:1. The result of colouration experiment which was conducted successfully in 4 forest vegetation types except Fargesia nitida forest,showed that there existed obvious preferential flow in soil profiles.But there existed obvious differentiation in the 4 kinds of plant communities.The soil prefenrential flow was much more active in Quercus aquifolioides and Abies faxoniana forest soils;2. Soil initial and steady infiltration rate varied significantly in different forests.The sequence of the average initial infiltration rate of soils was Quercus aquifolioides forest (18.40mm/min)>Fargesia nitida forest (17.53mm/min)>broad -leaved forest (15.03mm/min)> Abies faxoniana forest(13.45mm/min)>subalpine meadows (7.72mm/min);and the steady infiltration rate was as follows:Fargesia nitida forest(13.79mm/min)>Quercus aquifolioides forest(13.60mm/min)>broad -leaved forest(11.80mm/min)>Abies faxoniana forest(10.97mm/min)>subalpine meadows (4.86mm/min).The steady infiltration rate of soils in shady slope was higher than that in sunny slope.It was concluded that the water infiltration capacity in shady slope was higher than that in sunny slope,reducing more effectively the surface runoff and preventing water and soil loss.3. The result of the simulation of water infiltration processes of 5 forest vegetation types with Kostiakov model,Horton model,Philip model and Fang zhengsan infiltration model used,indicated that it was more accurate to simulate the infiltration process of the 5 different soil types by using Fang zhengsan infiltration model,and it is recommended to apply this model to the simulation of water infiltration process in Wolong area; 4. The soil macropore properties of the 5 major forest vegetation types were calculated based on the fractal theory, the sequence of the average soil macropore radius of 5 forest vegetation types is: Abies faxoniana forest(1.200mm)>Quercus aquifolioides forest(1.190mm)>Fargesia nitida forest (1.120mm)>broad-leaved forest(1.050mm)>subalpine meadows(0.910mm);and the number was:Abies faxoniana forest(4879/m3)>Quercus aquifolioides forest(4334m3)>Fargesia nitida forest(3932m3)>subalpine meadows (3566m3)> broad-leaved forest(1395m3).5. The result of correlation analysis showed that there exited a positive correlation between root biomass and the steady infiltration rate,the number of macropore,macroporosity.The root system played a major role in improving water infiltration capacity through increasing macroporosity.