In this study, the eff ects of soil moisture on sand saltation and dust emission over the Horqin Sandy Land area are investigated, based on observations of three dust events in 2010. The minimum friction velocity init...In this study, the eff ects of soil moisture on sand saltation and dust emission over the Horqin Sandy Land area are investigated, based on observations of three dust events in 2010. The minimum friction velocity initiating the motion of surface particles, namely, the threshold friction velocity, is estimated to be 0.34, 0.40, and 0.50 m s？1 under the very dry, dry, and wet soil conditions, respectively. In comparison with the observations during the dust events under the very dry and dry soil conditions, the dust emission fl ux during the wet event is smaller, but the saltation activities of sand particles （d≧50 μm） are stronger. The size distributions of airborne dust particles （0.1≦d≦20 μm） show that concentrations of the fi ner dust particles （0.1≦d≦0.3 μm） have a secondary peak under dry soil conditions, while they are absent under wet soil conditions. This suggests that the surface soil particle size distribution can be changed by soil moisture. Under wet soil conditions, the particles appear to have a larger size, and hence more potential saltating particles are available. This explains the occurrence of stronger saltation processes observed under wet soil conditions.展开更多
Slash Pine(Pinus elliottii) is an introduced tree species that can adapt different site types. Since 1970s, in order to enrich the tree species resource, Slash Pine was planted on the cut_over area of Casuarina equise...Slash Pine(Pinus elliottii) is an introduced tree species that can adapt different site types. Since 1970s, in order to enrich the tree species resource, Slash Pine was planted on the cut_over area of Casuarina equisetifolia protection forest in Chishan Protection Forest Farm of Dongshan County, Fujian Province. It could prevent soil fertility from degeneration, improve forest productivity and provide fundamental data for soil ecological management to study the soil nutrient content and enzyme activities of different age stands of Slash Pine. The effect of Slash Pine on fertility of coastal sandy land was studied in this paper. The results showed that it would make the soil acid to plant Slash Pine on the cut_over area of C.equisetifolia protection forest Compared, because the pH value was declined as the growth of Slash Pine stand, and it declined to 3.96(0～20*!cm) and 3.87(20～40*!cm) when Slash Pine stand was 26*!a; Compared with the second generation coastal protection forest of C.equisetifolia the nutrients content in the soil of 26*!a Slash Pine stand were lower than that in the soil of the second generation forest, especially for available P, available K, and total N. The CEC in soil layer of 0～20*!cm was obviously effected by Slash Pine. In this soil layer, the CEC was increased as the growth of Slash Pine stands, and it was as 1.22 times as the content in the soil of the second generation forest. There was no obvious effect on urease activity, but the activities of phosphataese, polyphenol oxidase, and peroxidase were declined by planted Shash Pine on the cut_over area of Casuarina protection forest.展开更多
基金Supported by the National(Key)Basic Research and Development(973)Program of China(2010CB428501)China Meteorological Administration Special Public Welfare Research Fund(GYHY201006014)+1 种基金National Natural Science Foundation of China(41075005)Research Fund for Doctoral Program of Higher Education of China(20110001130010)
文摘In this study, the eff ects of soil moisture on sand saltation and dust emission over the Horqin Sandy Land area are investigated, based on observations of three dust events in 2010. The minimum friction velocity initiating the motion of surface particles, namely, the threshold friction velocity, is estimated to be 0.34, 0.40, and 0.50 m s？1 under the very dry, dry, and wet soil conditions, respectively. In comparison with the observations during the dust events under the very dry and dry soil conditions, the dust emission fl ux during the wet event is smaller, but the saltation activities of sand particles （d≧50 μm） are stronger. The size distributions of airborne dust particles （0.1≦d≦20 μm） show that concentrations of the fi ner dust particles （0.1≦d≦0.3 μm） have a secondary peak under dry soil conditions, while they are absent under wet soil conditions. This suggests that the surface soil particle size distribution can be changed by soil moisture. Under wet soil conditions, the particles appear to have a larger size, and hence more potential saltating particles are available. This explains the occurrence of stronger saltation processes observed under wet soil conditions.
文摘Slash Pine(Pinus elliottii) is an introduced tree species that can adapt different site types. Since 1970s, in order to enrich the tree species resource, Slash Pine was planted on the cut_over area of Casuarina equisetifolia protection forest in Chishan Protection Forest Farm of Dongshan County, Fujian Province. It could prevent soil fertility from degeneration, improve forest productivity and provide fundamental data for soil ecological management to study the soil nutrient content and enzyme activities of different age stands of Slash Pine. The effect of Slash Pine on fertility of coastal sandy land was studied in this paper. The results showed that it would make the soil acid to plant Slash Pine on the cut_over area of C.equisetifolia protection forest Compared, because the pH value was declined as the growth of Slash Pine stand, and it declined to 3.96(0～20*!cm) and 3.87(20～40*!cm) when Slash Pine stand was 26*!a; Compared with the second generation coastal protection forest of C.equisetifolia the nutrients content in the soil of 26*!a Slash Pine stand were lower than that in the soil of the second generation forest, especially for available P, available K, and total N. The CEC in soil layer of 0～20*!cm was obviously effected by Slash Pine. In this soil layer, the CEC was increased as the growth of Slash Pine stands, and it was as 1.22 times as the content in the soil of the second generation forest. There was no obvious effect on urease activity, but the activities of phosphataese, polyphenol oxidase, and peroxidase were declined by planted Shash Pine on the cut_over area of Casuarina protection forest.
