| Tianlaochi catchment is located in the upper reach of the Heihe River in Qilian mountains, in which studying the plant interception of rainfall has a vital significance to the hydrological cycle and water balance. We took Picea crassifolia and Sabina przewalskii forests as this study’s objects, which are two only arbor forests in Tianlaochi catchment. A sample plot was set to measure the forest canopy interception of rainfall in two kinds of forest respectively. By analyzing rainfall interception laws, precipitation and leaf area index were selected to establish an empirical model to calculate the canopy interception. Then we spatialize the forest canopy interception with the parameter spatial distribution in the study area. What’s more, the land under Picea crassifolia forest is widely covered by bryophytes. In this study, after researching how bryophytes biomass distribute, establishing a relationship between biomass and their maximum rainfall storage capacity, then we simulated the spatial distribution of the maximum rainfall storage capacity of bryophytes. At last with the spatial distribution of the maximum rainfall storage capacity of Picea crassifolia forest canopy, we simulated the bryophyte-spruce forest system’s spatial distribution of the maximum rainfall storage capacity. The main research results of this paper are as follows:(1) The results of sample observation in 2015 shows that Picea crassifolia forest throughfall rates were between 35.95% and 88.24%, and the average value was 65.78%; Sabina przewalskii forest throughfall rates were between 58.98% and 88.54%, and the average was 74.75%.The stem flow rates of Picea crassifolia forest were between 0.012% and 0.199%, the average value was 0.054%, while the stem flow rates of Sabina przewalskii forest were between 0.001%and 0.133%, whose average value was 0.042%. Picea crassifolia and Sabina przewalskii forests stem flow were very low, this is possible because that the bark of the trees are so cracked and rough that rainfall is not easy pass through the stem to the ground. The accumulation of Picea crassifolia and Sabina przewalskii forest interception were 68.00mm and 53.50mm, accounted for 26.91% and 20.43% of the rainfall respectively during the observation period. The interception rates of Picea crassifolia forest canopy were between 11.57% and 64.02%, whose average value was 34.16%. While the interception rates of Sabina przewalskii forest canopy were between 11.36% and 41.00%, and the average value was 25.18%. Basically Picea crassifolia forest canopy interception was higher than that of Sabinaprzewalskii forest.(2) After regression analysis, we established a leaf area index(LAI) inversion model based on airborne LiDAR data, with which we gained the spatial distribution of the arbor forests in Tianlaochi catchment. The results showed that Picea crassifolia forest LAI was between 0 and 5.44, and the average value is 1.38.And Sabina przewalskii forest LAI was between 0 and 5.82, whose average value was 1.12. The spatial interpolation of rainfall in the watershed was carried out by Kriging model, and the results showed that rainfall was between 300 and 434.0mm in the watershed in 2014. Effects of rainfall redistribution of Arbor forest canopy is great that can not be ignored in the estimation of the regional water balance. In 2014, Picea crassifolia forest canopy interception amount were in the range of 0-226.2 mm and the average was 118.6 mm, the total interception amount was 3.85 × 105 m3. While Sabina przewalskii forest canopy interception amount were in the range of 0-276.7 mm and the average was 104.4mm, the total interception was 1.78 × 105 m3. The total interception of Picea crassifolia forest is 2.16 times than Sabina przewalskii forest. Picea crassifolia forest plays a more important role in water conservation.(3) We selected elevation, aspect, slope and LAI of forest canopy to establish a model to simulate the spatial distribution of bryophytes biomass. The results showed that bryophytes biomass amount ranged from 0 to 34.88 t/hm2 and the average value was 16.40 t/hm2. Our study area is in deep mountains, in which precipitation is always huge during the growing season and Picea crassifolia forest covers a large area. This is the reason why the bryophyte biomass is much larger. The maximum storage capacity of the bryophytes were in the range of 0-14.33 mm, the average value was 6.74 mm. The maximum storage capacity of the bryophytes is in direction proportion to their biomass. Picea crassifolia forest canopy storage capacity amount were between 0 and 3.90 mm, with an average of 0.99 mm. The maximum storage capacity amount of bryophyte-spruce system were in the range of 0-16.17 mm and the average was 7.83 mm. The maximum storage capacity of the moss layer was significantly greater than that of Picea crassifolia forest, while the moss layer was short, but there are a large amount of capillary pores inside them, so the water absorption capacity was very high. In this research area, the amount of moss is larger, and the water absorption of moss is larger too, so the bryophytes play an important role in the water conservation in the basin. |
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