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.