| Element migration process,as the basic process of the ecological system,is also one of the key contents in research of ecological system,precipitation is the element transfer of the important driving force in forest composition units in forest.Current some researches focus on forest ecosystem about the precipitation in the nonmetallic element,such as carbon,nitrogen and phosphorus source pattern,and ignore the equally important in forest vegetation communities metal elements(such as Ca,K,Na and Mg)and its transfer process.The apline forest of Western Sichuan,as the main body in southwest of forest ecological system,is an important water conservation area of the Yangtze river upstream,at the same time,which plays an important role in the regional climate regulation,water conservation,purifying water quality and maintenance of biological diversity.As a consequens,the apline forest in the process of hydrological Ca,K,Na and Mginterception and redistribution of metal elements is of great significance.But so far,what about the apline forest on distribution of atmospheric precipitation and precipitation of Ca,K,Na and Mgand redistribution of the metal elements,we lack the necessary attention.Hence,this study selected alpine forest in western of Sichuan province as the research object,based on positioning monitoring and statistical techniques from August in 2015 to July in 2016.Ca,K,Na and Mgconcentrations in bulk precipitation,throughfall,stemflow and soil percolating water were measured in forest gap,forest edge and under-forest,so as to provide basic data and scientific basis for the interception efficiencies of canopy for carbon and nitrogen in alpine forest.Experimental results showed that:All observation period,the amount of precipitation was 802.08 mm,of which 10?P<25 mm rainfall in the majority.First distribution of precipitation through canopy layer,which mainly includes throughfall,stemflow and canopy interception.During the period of observation,throughfall under the conditions of different canopy was forest gap(738.33 mm)>forest edge(658.61 mm)>underforest(541.06 mm),respectively.Stemflow is in the process of rainfall distribution proportion was very small,about 8.49%of annual precipitation.The study found that soil infiltration collection of 28 times,non forest,forest gap and forest edge and under forest was 495.72 mm and 395.79 mm,477.24 mm and 529.44 mm.The canopy interception was under forest(202.18 mm)>forest edge(143.46 mm)>forest gap(63.75 mm),forest gap of the strongest ability to intercept,next was the forest edge,under forest of interception ability was the weakest.After the first allocation of forest canopy,the difference of Ca,K,Mg and Na in throughfall and stemflow was obtained.During observation period,K,Mg and Na of throughfall content,which compared with the atmospheric precipitation,was shown to increase in different times,as a result of the reason why the vegetation canopy on K,Mg and Na adsorption,enrichment and transfer,and easy stripping,strong mobility in K increased in all nutrient elements the biggest.But Ca of water through the forest canopy,compared to the precipitation decreased by 0.10-0.47 mg·L-1,indicating that the forest canopy on rainfall in Ca had a certain absorption and interception of part Ca.In stemflow,the content of Ca nutrient content in the highest,the weighted average value of 7.79mg·L-1,about 2.09 times the atmospheric precipitation.The forest surface soil again after the distribution of precipitation in K and Mg was increased,compared with the precipitation,while Ca and Na was decreased,and the throughfall,stemflow and soil infiltration in Ca,K,Na and Mg showed that:under forest>forest edge>forest gap.The observation period,Ca,K,Mg and Na of precipitation input was 30.39 kg·hm-2·a-1,10.74 kg·hm-2·a-1,2.37 kg·hm-2·a-1 and 12.70 kg·hm-2·a-1.The effect of forest canopy on rainfall redistribution and nutrient elements,which showed transfer characteristics different,compared to atmospheric precipitation,Ca and Na of throughfall input was decreased,and K and Mg of throughfall showed an increasing trend.Stemflow in Ca,K,Mg and Na the relative amount of precipitation was the least,the nutrient input was 1.39kg·hm-2·a-1,2.93 kg·hm-2·a-1,0.30 kg·hm-2·a-1 and 0.82 kg·hm-2·a-1,but which can not be ignored,directly used the vegetation root.Ca,K,Mg and Na through the soil infiltration of output,to complete the metal elements in the atmosphere,vegetation and soil elements between sequestration,retention and transfer.The amount of Ca,K,Na and Mg in the under forest was highest,respectively15.21 kg·hm-2·a-1,21.63 kg·hm-2·a-1,6.66 kg·hm-2·a-1 and 4.87 kg·hm-2·a-1.In the redistribution effects of canopy precipitation on the whole process and the elements of the transfer,no forest,forest gap,forest edge and under forest of Ca and Na mainly showed a net input function,through,all forest canopy of Mg showed a net output function,besides the under forest,no forest,forest gap and forest edge on K showed a net input.While Ca,K,Mg and Na interception capacity of forest vegetation in the canopy and soil layer was different,no forest Ca interception ability is the strongest,the strongest interception capacity of forest gaps on K,Na and Mg.From the above,The contents of Ca,K,Na and Mg contents in precipitation,throughfall,stemflow and soil infiltration was studied by comparing the effects of different forest canopy on the interception effect of different forest canopy conditions,and comparing the contents of redistribution characteristics,We concluded that Ca,K,Na and Mg content of forest gap,forest edge and under forest of forest canopy and soil layer showed distributional effects.These experimental results provide basic data support for deep understanding of the mechanism of atmospheric humidification and its important role in the cycle of matter in forest ecosystems,and at the same time,in order to strengthen the conservation of forest vegetation and sustainable green economy to a certain extent,which give the theoretical basis. |
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