塔克拉玛干沙漠头状沙拐枣光合器官生长对风蚀的 响应与适应策略分析

风蚀是沙区生态建设工程的重要危害形式。分析不同植物种生长对风蚀的响应和适应策略,确定其耐风蚀阈值,是优良耐风蚀生态建设植物种筛选的重要理论基础。本文以塔克拉玛干沙漠腹地纵向复合沙垄上栽植的头状沙拐枣人工林为研究对象,对不同风蚀深度植株的部分枝条节上和全株光合器官生长状况进行了观测和分析。结果表明,随风蚀强度增加,头状沙拐枣植株光合器官的单节同化枝数量、单节同化枝总长度和单根同化枝平均长度、单根同化枝平均重量、单株光合器官鲜重、单株同化枝表面积呈降低趋势,光合器官生长均与风蚀深度呈线性负相关。当风蚀深度小于40 cm时,头状沙拐枣的单节同化枝数量、单根同化枝长度、单节同化枝总长度降低幅度较小,但当风蚀深度大于40 cm后,单节同化枝数量、单根同化枝长度、单节同化枝总长度都大幅降低,全株光合器官的重量和表面积也大幅下降,而过强的风蚀可使植株死亡。头状沙拐枣光合器官对风蚀的适应方式是数量和形态变化,同化枝数量、长度、直径、表面积降低。对风蚀的适应策略是有限资源重点配置,即植株把能量主要分配在有限的节上,节上保持一定数量的光合器官生长,以维持植株存活。研究结果可为沙区生态建设适宜植物种筛选提供参考。

Response and adaptive strategy of photosynthetic organ growth of Calligonum caput-medusae Schrenk to wind erosion in the Central Taklimakan Desert

Wind erosion, especially via blown sands, is hazardous to fragile ecosystems in desert regions. It is critical for ecological constructions in desert regions to determine the resistance thresholds of different plant species to wind erosion. In this study, the Tazhong Si Oilfield shelter forest of Calligonum caput-medusae Schrenk in the hinterland of Taklimakan Desert was investigated. The C. caput-medusae plants with different wind erosion depths (range of 1~82 cm) were set as treatments and other plants not affected by wind erosion as the control. The study was conducted in 2007 on a secondary dune that was in the leeward slope of a complex sand-ridge. In the study, the number and length of photosynthetic organs per joint and whole plant were recorded. Photosynthetic organ samples of whole plants that settled in the 40 cm erosion depth were collected along with the control. Conclusion drawn from the analyses were as follows: The number and total length of assimilative branches per joint, average length and weight of single assimilative branch, and fresh weight and surface area of photosynthetic organ per whole plant decreased with increasing wind erosion depth. Photosynthetic organ growth was negatively correlated with wind erosion depth. When wind erosion depth was less than 40 cm, photosynthetic organ growth decreased slightly. However, when wind erosion depth was more than 40 cm, photosynthetic organ growth declined significantly. Then when wind erosion depth exceeded 80 cm, plants withered and finally died. The number, length, diameter of assimilative branches and the surface area of photosynthetic organs reduced in order to adapt to the conditions of wind erosion. The numerical and morphological readjustments constituted an important form of adaption of photosynthetic organs of C. caput-medusae to wind erosion. The number of joints with photosynthetic organs and length and diameter of assimilative branches on plants reduced due to wind erosion to reduce transpirative water consumption. Despite the fewer photosynthetic organs per joint, some amount of photosynthetic organs grew at plant joints to sustain the plants alive. The adaptive strategy was that limited resources were configured at key locations on the plant to enhance plant survival. This research result was significant for theoretical guidance in ecological construction in desert regions.