A study on the changes of soil water infiltration in alpine meadow of permafrost regions in the Tibetan Plateau
A typical slope of the permafrost regions was divided into three slope positions:the low ( L) , middle ( M) and high ( H) parts. The vegetation coverage of 92％, 60％ and 30％ for each slope position were selected as study objects to determine the soil water infiltration process by double ring infiltration apparatus. The environ-mental factors,which impact the process of soil infiltration, were analyzed and model simulation had done based on soil physical properties and soil water. The results showed that the soil water infiltration of different vegetation coverage in the study area had obvious difference during the freezing and thawing process of the active layer, and the initial soil water content had a good negative correlation with the initial infiltration rate. The stable infiltration rate was:vegetation coverage of 92％ (0. 61 mm·min-1 ) > vegetation coverage of 60％ (0. 50 mm·min-1 )> vegetation coverage of 30％ (0. 29 mm·min-1 ) during the period of active layer thawing, and vegetation coverage of 60％ (0. 56 mm·min -1 ) > vegetation coverage of 30％ (0. 39 mm·min-1 ) > vegetation cov-erage of 92％ (0. 26 mm·min-1 ) during the beginning period of active layer freezing. The soil water infiltra-tion rate had a significant difference among slope positions and was closely related to the freezing-thaw cycle, mainly reflected in that the infiltration rate decreased with the slope position downwards;the infiltration rate dur-ing the beginning period of freezing was less than that during the thawing period on the same slope position. Dur-ing the whole infiltration stage, the cumulative infiltration at the slope top was the maximum, showing a better infiltration performance. The environmental factors influencing the infiltration of alpine meadow soil were bulk density, organic matter content and particle size. It was concluded that in the source regions of the Yangtze River the general empirical model f( t) = a +bt-n is more suitable for the period of active layer thawing to study soil water infiltration in alpine meadow in the study area, while the Horton model f(t) = ic + (i0 - ic)e-kt is more suitable for the beginning period of active layer freezing.
Tibetan Plateaupermafrost regionssoil infiltrationfreezing-thawing process
NETL
NSTL
万方数据
维普
