干旱沙区生物土壤结皮发育对红砂形态及干物质积累的影响

为了探讨干旱沙区生物土壤结皮发育对红砂形态及干物质积累的影响，以巴丹吉林沙漠南缘已发育不同类型生物土壤结皮并有红砂种群成功定居的区域为研究场所，通过野外监测与室内测定的方法对藻类-地衣、地衣、地衣-藓类结皮上的红砂（当年生、幼株、成株）形态特征及生物量进行了调查研究。结果表明：（1）藻类-地衣结皮演替到地衣-藓类结皮的过程中，当年生红砂形态差异不显著，但5 a以上植株基部分枝长、树冠/侧冠投影面积、主根长均显著减小；同时，地衣-藓类结皮的3-5 a植株基部分枝数明显减少，且5 a以上植株明显矮化。（2）生物土壤结皮发育不仅降低了红砂幼株或成株生物量积累能力，还减小了植株根冠比，且降低/减小程度随结皮演替或株龄的增大逐渐增大。（3）红砂形态、生物量指标与物理或藻类结皮面积百分比呈极显著正相关关系，与藓类结皮面积百分比呈极显著的负相关关系。因此认为，生物土壤结皮的演替导致土壤关键生态因子（如土壤水分）发生变化，进而影响红砂植株生长发育能力，从而使得不同发育阶段结皮上的同龄红砂形态特征及生物量存在差异性。

Effects of biological soil crusts development on morphology and dry matter accumulation of Reaumuria soongorica in arid desert area

In order to explore whether the development of biological soil crusts (formed by cryptogamous plants, microorganisms and other related organisms cementing soil surface particles with secretions, mycelium and pseudoroots) could influence morphology and matter accumulation of Reaumuria soongorica (a salt-secreting xerophytic shrub) in arid desert area, the morphological characteristics and biomasses of plants in different age groups (seedlings, young plants and adult plants), separately growing in three types transect regions at the southern edge of Badain Jaran Desert covered by algae-lichen, lichen and lichen-moss, were investigated and studied. The results showed that:(1) with succession from the algae-lichen crusts to lichen-moss crusts, the morphological differences in current year plants of R. soongorica were no observed. However, the length of basal branches, projection area of transverse/longitudinal crown, and root length of plants older than five years were significantly reduced, respectively. At the same time, the number of basal branches of plants in 3-5 years growing in lichen-moss crusts obviously decreased compared with those growing in algae-lichen crusts, and the plants older than five years were dwarfed distinctly. (2) The development of biological soil crusts not only reduced the capacity of biomass accumulation in young or adult plants, but also diminished their root-shoot ratio. Moreover, the increase or decrease degrees of biomass accumulation in unit time were enlarged gradually with the prolonging of biological soil crust succession or increasing of plant age. (3) The indexes of morphology and biomass in R. soongorica plants had an extremely significantly positive correlation with the area percentage of physical crusts or algal crusts, while a very conspicuous negative correlation with that of moss crusts. Therefore, it is considered that the succession of biological soil crusts results in changing of area percentages of soil crusts, which causes the alteration of key ecological factors (such as soil moisture). As a result, the significant differences were induced in morphological characteristics and biomasses of R. soongorica plants possessing same plant age and growing in different types of soil crusts. Based on the above results, it suggests that the population construction of R. soongorica can be carried out by methods of planting seedlings and supplying seeds in the oasis desert transitional zone of arid sand area where soil crusts are developing from no crusts to lichen crusts stage, and of which the planting seedlings should mainly been taken in the succession of no crusts to algae-lichen crusts stage while the supplying seeds to lichen crusts stage.