Soil Water Physical Properties Of Platycladus Orientalis Plantation In Northern Mountain Of Lanzhou

The artificial forest plays an important role in wood production, environmental protection and landscape design, and will become more and more important in forest ecosystems. Ar- tificial forest ecosystem of Lanhzou South-north Hills is an important component of Lanzhou urban ecosystem,it has decisive influence on Lanzhou urban ecological environment.Study on soil water physical properties of the artificial forest, which can reveal interaction mech- anism between forest and soil ,can clarify forest protective function to environment, so it has essentially theoretical and practical value. Based on the systematic research on forest stan- ds characteristics and the space distribution of soil hydro-physical property, soil infiltration characteristics,the main results are as follows:(1)Soil water vertical variation tendency of five site types was basically identical at the same period and showed an unstable tendency from top to bottom. Except liang, mao and tai, the variation coefficient of other site types basically showed a tendency to reduce from top to bottom. The variation coefficient was as the following: semi-shady slope>liang and mao and tai> semi-sunny slope> shady slope> sunny slope.(2)The maximum moisture capacity of Platycladus orientalis forestland had no distinctive difference in different stand ages,but the water conservation content varied significantly.The water conservation content of 4 different afforestation ages (4-year-old,7-year-old,10-year- old and 13-year-old) had been increased 201,268,251 and 208t·hm-2 than that of slope wasteland separately. It showed that Platycladus orientalis plantations have the high fun- ction of conservation water.(3)The maximal holding of water in soil, capillary water capacity, field capacity and optimum water rate increased with tree ages. In these indexes,those of 13-year-stand age were the most and those of wasteland were the least; soil water availability of forestland(0～30cm) was moderate 4a,and was irreadly available for other forestland; Compared with wasted land, soil moisture content of different young plantation stages increased to some degree. These findings showed that Platycladus orientalis plantations could improve soil surface water condition.(4)The soil bulk density of the Platycladus orientals plantation of different ages were decreased with tree ages, but it increased with the depth of soil layer incresed. However, the no-capillary and total porosity increased as tree ages, and decreased with the depth of soil layer increased. The total porosity of forestland was higher than the wasted land. The results showed that the structures and physical characters of forestland better than that of the wasted land.(5)There were obvious permeability differences in different planting forestland. It displayed as: the better the soil percolation capacity, the longer the forest was planted. Soil permeability process of forest land followed Horton equation f= f 0+﹙f c- f 0﹚×e- kt, correlation coefficient 0.64～0.95.(6) Congress equation of the infiltration coefficient and soil bulk density of Chinese pine stand was: y1=1.381-0.609x1,R=-0.790;Congress equation of the infiltration coefficient and no-capillary of Chinese pine stand was : y2=3.664+5.096x2,R= 0.68.(7) There were obvious permeability differences in different irrigation patterns, and the soil percolation capacity of the upper soil layer(0～20㎝)was better than the under layer(20～40㎝). The soil percolation capacity in different irrigation patterns was as following: Sprinkler Irrigation﹥flood irrigation﹥abandoned irrigation﹥bare-slope. Soil permeability process conformed to logarithm function law. It was proved by equation which the simulation calculation result was basically same as that obtained by actual measuring.(8)There were differences in soil permeability characteristics of different planting forestland, but soil permeability characteristics of forestland were better than bare-slope. For example, the final infiltration rate of forestland(0.43mm·min-1)﹥bare-slope(0.09mm·min-1), the average rate of forestland(0.53 mm·min-1)﹥(0.19 mm·min-1).