科尔沁沙地差巴嘎蒿种群生态位适宜度分析

 以生长在科尔沁沙地的差巴嘎蒿(Artemisia halodendron)为研究对象，对其在不同类型沙地上的综合活力指数和生态位适宜度进行计算，主要结论如下：1)在生长旺季，差巴嘎蒿种群综合活力指数随着沙地的固定显著下降。2)在同一生长季内，综合生态位适宜度表现为半固定沙地>固定沙地和流动沙地；水分生态位适宜度表现为流动沙地>半固定沙地>固定沙地。随着土壤含水量的变化，土壤水分的限制土层深度也有所不同：7月各类型沙地均为15～30 cm土层；8月随着雨水的下渗，限制土层也有所加深，为45～60 cm土层；9月除流动沙地为15～30 cm外，半固定沙地和固定沙地均为30～45 cm。3)在同一生长季内的不同生境上种群的限制因子(NFmin)不同：在流动沙地上为土壤有机质，而在半固定沙地和固定沙地上为土壤含水量，且土壤有机质和土壤水分的配置关系直接影响综合生态位适宜度值的高低。在一定范围内，二者的比值可直接反映有机质对植物细根的有效性，同时种群通过调节细根生长状况来适应限制因子间的配置关系。

ANALYSIS OF NICHE FITNESS OF ARTEMISIA HALONDENDRON POPULATION ON HORQIN SANDY LAND

Background and Aims Niche fitness of Artemisia halondendron population, that fixes shifting and semi-fixed sandy soils in Horqin sandy land, rarely has been explored. This study addresses 1) spatial and temporal differences in niche fitness and composite vigor and 2) limiting factors of niche fitness in different habitats. Methods Mathematical models were adapted to calculate composite vigor index (CVI) and niche fitness values of a population of A. halondendron inhabiting shifting, semi-fixed, and fixed sandy lands. Data on CVI and niche fitness were collected by measuring height, size of canopy, branches, and biomass of individuals, as well as soil moisture content, nutrient content, and bulk density. Key Results CVI was remarkably low on fixed sandy land, indicating that the ecological function of the population was weakened. Composite niche fitness values for different soils during the growing season ranked: semi-fixed > fixed > shifting sandy land. Moisture fitness values ranked: shifting > semi-fixed > fixed sandy land. As the soil moisture content changed, the limiting layer also changed. It was 15-30 cm in the different sandy lands in July, but with the infiltration of rain water, the layer deepened to 45-60 cm in August. In September, it was 30-45 cm in semi-fixed and fixed sandy lands, but remained 15-30 cm in shifting sandy land. The limiting factors in different habitats were different: soil organic matter content was limiting on shifting sandy land and soil moisture content was limiting on semi-fixed and fixed sandy lands. Conclusions This study indicated that soil moisture content and nutrient content affected composite niche fitness. The relationship of soil moisture content and nutrient content directly influences composite niche fitness. Their ratio could reflect the importance of organic matter to fine roots, and the population could adapt to the ratio by adjusting the growth of fine roots.