| Qilian Mountains is located in the center of the Eurasian continent, is one of China’s high mountain, unique environment, ecological system is fragile,is China’s key areas and natural protection object.The water conservation forests in Qilian Mountains plays a decisive role in the health and stability of the whole Hexi Corridor social-economic-ecological composite system,and the stability of runoff volume in the inland river and the Qilian Mountains.In the forest stand structure of water conservation forests,all kinds of the same or different structure are interrelated,interdependent,decided the playing of the forest function.If the forest structure is bad or insufficient resources, it can not play a good function, which seriously restricts the supply and demand of water resources in the region,then have an adverse effect on the development of social economy.In this paper, based on the research and public service industry, a special of the State Forestry Administration "Researcher on typical forest ecosystem monitoring and management technology (200904022)"and "Study on the typical forest vegetation formation process regulation of water resources (201104005)"and "Researcher on northwest typical area based on water management on the forest vegetation carrying capacity (200904056)"etc.Research on forest structure and function of water conservation in Xishui forests area of Qilian Mountains to develop and perfect the technical system of the relationship between water conservation forest structure and ecological function,in order to provide scientific basis for the conservation of Qilian mountain forest construction and ecological environment sustainable development.The research is include the community structure, population structure, spatial structure in Xishui forests area of Qilian Mountains and soil conservation and water conservation function of Picea crassifolia,the main research results are as follows:The layer structure difference is obvious for the P. crassifolia community,and it can be divided into tree layer,shrub layer,herb layer and bryophyta layer.The tree layer is the main layer of the community,and its vertical structure is more complex than the shrub layer and herb layer,and the bryophyta layer is also well developed.DBH size class frequency distribution of Picea crassifolia population is "pour J" type,DBH size classweth the change of individual level is quite fit for the logarithmic equation y=219.32In(x)+482.67(R2=0.9638, P<0.01),differentiation index of DBH is0.48,the differences of DBH in the population for each individual is obvious;The height structure of the P. crassifolia indiciduals with DBH greater than lcm is single-peak form,and the height of the main individuals is less than6m,which account for more than60.00%of the total individuals.So the height of the P. Crassifolia individuals is relatively low,and young trees are much,nid terrs hold a certain proportion,and big trees are little.Frequency distribution of the tree height is "intermittent" type,Tree height size class and individual level can be explained by quadratic equation y=0.975x2-31.23x+285.1(R2=0.603, P<0.01),differentiation index of tree height is0.55,tree height difference is evident;The logarithmic equation y=5.912In(x)4.2493(R2=0.603, P<0.01) can be used to show the relation between tree height and DBH;Crown breadth size class and individual are accorded with equation y=5.3176x3-91.759x2+408.88x-173.87(R2=0.8355, P0.01),differentiation index of crown breadth is0.53,the differentiation crown breadth of population individual is apparent. In general,Picea crassifolia seedlings is relatively rich,natural regeneration ability is strong,at present the performance of Picea crassifolia population is the mature stable populations.The diameter distribution of Picea crassifolia stands indicated that it is typical uneven aged diameter structure;Picea crassifolia was climax community and single gathered stands, space isolation degree is zero nitrogen fixation;Mean value of diameter neighborhood comparison and height neighborhood comparison of Picea crassifolia were0.49, its growth was in moderation state, and size differentiation degree was general;Uniform angle index of Picea crassifolia was normal distribution and average of it is0.526, and distribution of Picea crassifolia is round state from the stand level distribution pattern;Open degree of Picea crassifoliawas1.667, for the growth space was very sufficient.The study on the soil conservation function of Picea crassifolia show that:The mean values of soil bulk density were above0.74g/cm3,the coefficient of variation in39.02%～14.46%from the surface layer to the bottom layer.The vegetation have a big influence on soil bulk density of the surface layer.The average values of soil total porosity, capillary porosity and non-capillary porosity were63.86%,49.02%and13.72%,identify that the Picea crassifolia in Xishui forests areas has good water permeability;The sequence of soil total porosity is:Shrub-Picea crassifolia> moss-Picea crassifolia> grass-Picea crassifolia> renewal forests of Picea crassifolia> bare land;In the elevation gradient, soil organic matter, total nitrogen and total phosphorus average content of the0-40cm soil layer at higher elevations higher than low altitude, average content at high altitude and low altitude significant difference (P<0.05); Soil total potassium and rapidly-available potassium content at high altitude is lower than low altitude, difference also significantly (P<0.05); Available phosphorus with the elevations rise without a significant change laws, and the differences between the elevation are not significant (P>0.05); Soil PH value with the elevations rise continuously the size is reduced, but the differences between the elevation are also not significant (P>0.05).(2) In different soil depth, soil organic matter, total nitrogen, total phosphorus, available phosphorus and rapidly-available potassium content at0-10cm soil layer are more than10-20cm and20-40cm soil layer content, and0-10cm soil significant higher than content20-40cm soil layer content (P0.05); Soil PH value size and total potassium content is increased with soil depth, and its numerical is on the increase, PH value in0-10cm soil layer and20-40cm significant difference (P<0.05), but total potassium content in different soil layer are not significant difference (P>0.05).Different soil nutrient and PH value correlation analysis showed that:In the cycling of carbon, nitrogen, phosphorus, potassium nutrient, soil pH value and soil organic matter may as the primary limiting factor to influence the nutrient supply of Pice a crassifolia.The canopy inter ception,stem-flow, thro ughfall are139.1mm,1.96mm and237.8mm,which account for35.28%,0.49%and60.33%,respectively.When precipitation over0.8mm and12.6mm,throughfall and stem-flow could be recorded respectively.The biomass of litter layer in different forest types show that:Picea crassifolia is33.12T/hm2, which moss-Picea crassifolia for a maximum of45.68T·hm-2·a-1,renewal forests of Picea crassifolia for a minimum of22.04hm-2·a-1,Shrub-Picea crassifolia and gxass-Picea crassifolia was34.19T·hm-2·a-1and30.57T·hm-2·a-1,respectively.In the forest land of Picea crassifolia, volume, maximum water holding capacity (saturation water holding rate) and the maximum water holding capacity of shrub-spruce forest was the highest, are34.19t/hm2,49.52%t/hm2,119.50t/hm2(equivalent to11.95mm depth) respectively; the forest land was higher than that of bare land.Under the conditions of precipitation, the interception of litter layer is divided into saturated with water interception, infiltration stage stage and saturation stage;The mean value of saturated water content distribution is65.67%～149.12%in each layer of Picea crassifolia,The mean value of non capillary water capacity is10.64%～18.43%.The sequence of soil non-capillary water-holding capacity is:moss-Picea crassifolia> shrub-Picea crassifolia> grass-Picea crassifolia renewal forests of Picea crassifolia> bare land;The soil permeability rate in forest region is significantly higher than that in non-stocked land. The minimum value permeability coefficient (K10) of bare land is0.68mm/min,The order of soil permeability coeficient in the forests (K10)is shrub-Picea crassifolia> moss-Picea crassifolia> grass-Picea crassifolia> renewal forests of Picea crassifolia> bare land,The permeability coefficient (K10) higher than bare land (38.85times,33.07times,7.29times,4.79times,1.85times, respectively).Both in the dry season or rainy season,The soil moisture content of forest land were significantly higher than bare land, The sequence of mean soil moisture content are as follows:shrub-Picea crassifolia> moss-Picea crassifolia> grass-Picea crassifolia> renewal forests of Picea crassifolia> bare land.. |
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