| The relationship between forest and water is more and more important in the study of forest hydrology. Especially with the development of society and economy, water pollution and extremly lack of water resources, which caused by these development at the cost of environment, has become more and more serious, which is constantly concerned by people of the importance of water and forest. Heiquan reservoir as a seventh water source provides 60% of the water supply for Xining City, the provincial capital of Qinghai,and plays an important role in the security of the industrial and agricultural water use as well as life and ecological use of water,so the study area,Baoku river basin,is more important as a water source of Heiquan reservoir.Therefore, the research on the systemconstruction of water conservation forest in this area should be a priority. As the object of study,seven main tree species were chosen including Picea crassifolia, Betula platyphylla Suk., Hippophae rhamnoides,Populus cathayana, Larix principis-rupprech Mayri, Picea crassifolia and Larix principis-rupprechi mixed forest, Picea crassifolia and Betula platyphylla mixed forest to measure and analyse the water distribution of canopy interception process and nutrient elements content with the method of field investigation and laboratory experiment combination and using variance analysis, correlation analysis and principal component analysis.Based on the different response of different vegetation types,the appropriate vegetation types of best quantity and quality regulating function of water are chosed through comparing,and provides a theoretical basis for the construction of the local water conservation forest system.The results are as follows.(1)The order of canopy interception capacity of 7 forest stands is:Picea crassifolia and Larix principis-rupprechi mixed forest (43.18%)> Picea crassifolia and Betula platyphylla mixed forest (40.94%)> Larix principis-rupprech Mayri. (37.8%)> Betula platyphylla Suk. (34.5%)> Picea crassifolia (30.49%)> Populus cathayana (30.49%)> Hippophae rhamnoides (30.33%), as we can see that coniferous and broad-leaved mixed forest and coniferous forest show a strong interception capacity. It shows an exponential function relation between canopy interception and precipitation,on the contrary, between interception rate and precipitation presents a logarithmic function relation. Such as Picea crassifolia,the relation is:y= 0.7709x0.5583, R2= 0.533, P<0.01; y=-13.361n(x)+64.87, R2= 0.5166, P<0.01.(2)The sequence of stemflow is:Populus cathayana (0.551mm)> Picea crassifolia (0.459mm)> Hippophae rhamnoides (0.375mm)> Picea crassifolia and Betula platyphylla mixed forest(0.313mm)> Picea crassifolia and Larix principis-rupprechi mixed forest (0.119mm)> Betula platyphylla Suk. (0.033mm)> Larix principis-rupprech Mayri. (0.026mm).The tree structure,recipitation,rainfall intensity and so on are becoming main influence factor for stemflow,besides,rainfall shows a monthly distribution pattern which give rise to a monthly distribution in stemflow.The correlation is significant between stemflow and precipitation (P< 0.01),but the stemflow may not like this. It shows a linear relationship between stemflow and rainfall,such as Picea crassifolia:y= 0.0478x-0.1544, R2= 0.9692.The stemflow has a negative correlation with DBH.Regression equation of Picea crassifolia, Betula platyphylla Suk., Larix principis-rupprech Mayri., Picea crassifolia and Be tula platyphylla mixed forest,Picea crassifolia and Larix principis-rupprechi mixed forest is logarithmic relationship between DHB and stemflow,but exponent relation is showed in Populus cathayana and Hippophae rhamnoides.(3) The sequence of mean throughfall is:Larix principis-rupprech Mayri.> Hippophae rhamnoides> Betula platyphylla Suk.> Picea crassifolia and Larix principis-rupprechi mixed forest> Picea crassifolia> Picea crassifolia and Betula platyphylla mixed forest> Populus cathayana,and this caused by canopy structure and surface properties of branches and leaves.Most water conservation forests show a significant linear correlation between throughfall and rainfall (P< 0.01),for instant, Picea crassifolia is:y= 0.779x-0.9824, R2=0.9895.(4)The sequence of the content of nutrient elements in atmospheric precipitation is:Ca>N>K>S > Na> Mg> P> Zn> Fe> Mn> Cu,and most of the elements content show higher in September, lower in June.There is a linear relationship correlation between elements content and rainfall.P, Ca, K, Mg, Mn, S, Zn contribute most which mainly come from weathered material of soil and mineral as well as human activities.The sequence of chemical element input is:Ca>K>N>S>Na >Mg>Mn>P>Zn>Fe>Cu.(5)Throughfall has the highest content of element Ca in 7 forest stand and canopy shows a adsorption of element Mn and Zn.7 different stands has the same variation trend and chemical element contents increase through canopy.It is considered relatively large in concentration,leaching amount,inputs and contribution of nutrient elements of coniferous trees and coniferous and broad-leaved mixed forest.Same elements have differences among different species,but correlation shows in different elements of the same tree species.There is also exponential relationship between concentration and througfall.For exsample, Hippophae rhamnoides is:y= 84.801x-0.373,R2= 0.8418,P<0.01.(6)Changes in the content of nutrient elements of different tree species’s stemflow have the same trend which also get the highest concent of element Ca. Through principal component analysis,the sequence of nutrient elements supply is:Larix principis-rupprech Mayri.> Populus cathayana> Hippophae rhamnoides> Betula platyphylla Suk.> Picea crassifolia.Nutrient input is less than precipitation and Zn shows a negative leaching in Hippophae rhamnoides, Populus cathayana and Picea crassifolia.Through variance analysis differences show in different trees while it has correlation in different elements by correlation analysis.We can see a negative linear relationship between concentration and precipitation,such as content of element Ca in Betula platyphylla Suk.:y=-0.756x+ 64.826,R2=0.7724,P<0.01. |
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