塔克拉玛干沙漠北缘柽柳灌丛沙堆对甲虫的庇护作用

以塔克拉玛干沙漠北缘典型荒漠区柽柳灌丛沙堆-柽柳包为研究对象,在2005—2006年期间调查了柽柳包及相邻沙漠裸地地表甲虫多样性。结果表明:2005年和2006年柳包上地表甲虫个体数量和物种数均高于沙漠裸地,柽柳包上的地表甲虫物种数分别为21种和16种,沙漠裸地中分别为10种和12种,柽柳包上物种丰富度明显高于沙漠裸地。选取优势种髋胫小土甲(Penthicicus koltzei Reitter)进行相对种群密度的估算,髋胫小土甲在柽柳包上分布数量较多,密度可达到每平方米在13头以上;但沙漠裸地仅有6头左右。柽柳包对甲虫多样性有明显的庇护所的作用,有利于维持甲虫物种多样性。2种不同生境条件下地表甲虫的数量存在明显的季节变动,其数量高峰分别出现在2005年6月和2006年7月,可能与不同季节环境的极端性(如气温峰值和洪水早晚)导致的食物丰富程度有关。

The shelter belt effect: beetles in the litter-layer of Tamarix nebkha in the north rim of Taklamakan

Tamarix nebkhas (nebkhas) has been widely planted to stabilize sand movement and develop soils along desert margins. The influence of this man made localized landscape on insect diversity is not well known. Some groups of beetles are well adapted to life in the arid and thermally stressing environments found in desert regions. In 2005 and 2006, we investigated the species diversity and abundance of beetles in the litter-layer in areas planted with T. nebkhas and bare patches between these in the northern edge of Taklamakan desert, the biggest sand dune area in China, and second in the world in terms of sand dune movement. Six nebkhas areas and contiguous bare patches were monitored from June to August in both years by pitfall traps. Beetle in each trap were collected at half-month intervals, and kept in alcohol for later identification. A mark-recapture method was employed to estimate the density of beetles and the probability of movement between nebkhas. The community of litter-layer beetles in the T. nebkhas was higher and stabilized than in bare patches. In 2005 and 2006 the total number of beetles collected in the T. nebkhas, 360 and 209 in each year, was greater than in bare patches,209 and 158. Some 21 species of litter-layer beetles were observed in the T. nebkhas and 10 species in bare patches in 2005, with 16 species and 12 species trapped in each patch type in 2006. Species richness, Shanon-Weiner index and Evenness 21 species of litter-layer beetles were observed in the T. nebkhas and 10 species in bare patches in 2005, with 16 species and 12 species trapped in each patch type in 2006. Species richness, Shanon-Weiner index and Evenness index were higher at the T. nebkhas areas than in bare patches, and Simpson Index was greatest in bare patches in 2005.Based on mark-recapture the density of Penthicicus koltzei Reitter was higher in T. nebkhas areas (13/m²) compared to bare patches (6/m²). Areas planted with T. nebkha act as a refuge for conserving P. koltzei and other beetles in desert areas. Movement of beetles was very localized. Only one beetle was recorded as moving from on nebkhas to another, a distance of 30 m. This implied that beetle in nebkhas might be independent, and refuges are highly localised. There was high seasonal variability in the litter-layer beetles species abundance and biodiversity in the two types of patchy: the beetle density in both areas peaked in the June, 2005 and July, 2007. This may be attributed to the abundance of food for beetle in different season and the effect of microhabitat, particularly moisture effects in harsh desert areas. The nebkhas alongside deserts offer a refuge, sustaining the diversity of beetle. Expanding the creation of the distinctive landscape composed of nebhkhas and its biodiversity, provides a buffer between desert and agriculture reclamation should be a priority.