关键词: 高寒沙地, 沙堆形态, 堆积强度, 沙堆断面, 方位差异, 固沙效益, 青海

Abstract: Morphology of plant sandpiles is an important reflection of ecological suitability and sand-fixing benefits of different artificial plants.Based on the explorations of the features and formation causes of sandpiles,the erosion and deposition of plant sandpiles can be instinctively compared to provide some basic reasons for selecting the sand-fixing plant species.It is also vital to reveal the relationship between alpine vegetation growth and wind-blown sand activities.The main sandpiles where five typical sand-fixing plant species were afforested in the Ketu sand land on the eastern shore of Qinghai Lake were focused on.Based on the methods of morphological fitting and sand-deposition monitoring,three-dimensional morphology of vegetation sandpiles was simulated and analyzed with the vegetation investigations and wind-blown sand observations during the period of 2015-2016.Based on the statistic results of the total and sectional deposition depths,intensity and affecting factors of wind-blown sand,we found that: ① The sandpiles with conical,hemispherical or linear shapes could form if Hippophae rhamnoides,Salix cheilophila,Pinus sylvestris,Simon poplar and Artemisia desertorum were afforested.Deep and strong sand deposition could occur on the H.rhamnoides and A.desertorum sandpiles,and the projected area and three-dimensional volume of these sandpiles were larger than those of other three light-erosive or light-depositional plant sandpiles; ② Among the eight directional sections of the sandpiles,sand deposition occurred mainly along the northeast-east-southeast directions.In consequence of significant negative correlations between depositional intensity and sediment transport rate along the same directions,the depositional intensity and direction over all the vegetation sandpiles were quite different,especially over the S.cheilophila,S.poplar and A.desertorum sandpiles.In addition,the deposition depth and intensity changed significantly along the directions of northwest,east and southeast; ③ The morphologic differences of plant sandpiles were mainly affected by vegetation growth,the sand depositional depth of H.rhamnoides and S.poplar sandpiles increased with the increase of plant height and canopy and soil crust,especially with their coupling effects.P.sylvestris and S.poplar sandpiles were strongly affected by the basal diameter and clear bole length.Furthermore,the strong west-northwest-north winter wind affected the sandpile erosion,it was also verified by the significantly negative correlations between the directional sand accumulated depth and sand transport intensity,especially for the S.cheilophila and A.desertorum.Calculated by the sand-fixing intensity and surface sediment transport intensity,we could predict the sand accumulation modulus of the five forest dunes,the H.rhamnoides and S.cheilophila forests prevented the sand most with the amount of 400-1 100 t·hm^-2 because of their high afforesting density and surviving rates.In general,H.rhamnoides,S.cheilophila and A.desertorum could be chosen as the adaptive and efficient sand-fixing vegetation species with sand-fixing benefits of 40.45%,15.53% and 62.72% respectively,while the other artificial plant species demand afforesting conservation and structure optimization for their low sand-prevention effects lower than 5%.

Key words: alpine sand land, morphologic feature, depositional intensity, sandpile section, direction difference, sand-fixing benefit, Qinghai