[Capacity of Caragana microphylla shrub on counteracting snow movement and its influence on snow morphology in the Xilinhot Steppe, China.] / é”¡æž—æµ©ç‰¹è‰åŽŸå°å¶é”¦é¸¡å„¿çŒä¸›çš„é˜»é›ªèƒ½åŠ›åŠå ¶å¯¹ç§¯é›ªå½¢æ€çš„å½±å“.

The aim of this study was to examine the impacts of characteristics of the shrub (shrub height, shrub width on the windward side, shrub length on the downwind side) on the snow morphology (snow height, snow width, and snow tail length) in the typical steppe of Xilinhot, China. The relationship between shrub height and parameters of snow morphology showed significant quadratic polynomial regression. The relationship between shrub width on the windward side, length on the downwind side and parameters of snow morphology showed significant power function (exponent was less than 1). The morphology and development characteristics of shrub snow were affected by the shrub characteristic parameters. Shrub height had the greatest influence on snow height. Shrub width at the windward side had the greatest influence on snow width and snow tail length. The snow morphology developed faster when the shrub was small, and then tended to be stable. The two-dimensional snow retention range model of shrub directly reflected the disturbance range of shrub to wind and the potential range of snow, indirectly reflected the capacity of shrub to retard snow movement. The three-dimensional snow blocking volume model of shrub snow directly reflected the snow resistance capacity of shrub under certain snow sources and wind conditions. Both models established here would provide a theoretical basis for estimating snow resources and preventing snow disaster in the wind blown snow area of typical steppe.

[Spatial structure of Quercus mongolica forest in Beijing Songshan Mountain Nature Reserve].

Based on the survey data of a 0.6 hm2 plot in Songshan Mountain Nature Reserve, and by using the uniform angle index, neighborhood comparison and mingling degree, this paper analyzed the spatial structural characteristics of Quercus mongolica forest in the Reserve. There were 10 populations in the tree layer of the forest, among which, Q. mongolica had the obvious advantage in population density and basal area, being the dominant and constructive species of the tree layer. The average mingling degree of the forest was 0.299, suggesting the low mingling degree of stands. The dominant species was mainly none- or less-mixed, while the accompanying species were generally well-mixed. In the spatial structural units, Q. mongolica and Pinus tabulaeformis populations were mainly of dominant, sub-dominant, and intermediate trees, accounting for 68% and 58% of the total plants of the populations, respectively, while the advantages of other populations were not obvious, being mostly of suppressed trees. The spatial pattern of the stands was of aggregative distribution, but the aggregation degree was not high and the aggregation scale was not large.