Comprehensive Research Base of Utilization and Innovation of Germplasm Resources in Shigatse City
沿环境梯度揭示植物群落特征及其环境影响因子的研究是生态学研究的重点内容之一。雅鲁藏布江作为世界海拔最高的河流之一,目前尚未开展流域内白草(Pennisetum centrasiaticum)主要分布区植物群落研究。从雅鲁藏布江上游源头区仲巴县帕羊镇至中游米林县派镇白草主要分布区设置26个样地对植物群落特征进行调查。研究结果表明:(1)雅鲁藏布江中上游白草主要分布区有119个植物物种,属35科96属,主要有禾本科、菊科和豆科。各样点优势种有白草、砂生槐(Sophora moorcroftiana)、藏沙蒿(Artemisia wellbyi)、白莲蒿(Artemisia sacrorum)、固沙草(Orinus thoroldii),白草群落物种丰富度最大的是江孜县(S=37),最小的是桑日县(S=12),白草重要值最大的是拉孜县(67.52%),最小的是桑日县(11.88%);(2)26个样点的平均地下生物量为3374.23 g/m2,各白草主要分布区群落在0-10 cm、10-20 cm和20-30 cm土层的地下生物量占比分别为60.38%,26.36%和13.26%;(3)相关分析结果表明,白草高度与海拔(r=-0.60),白草高度与土壤pH(r=-0.53),白草生物量与土壤pH(r=-0.55)呈极显著负相关(P<0.01);(4)RDA分析表明:轴1和轴2共解释全部方差的40.60%,在环境-群落的解释中起主导作用。(5)通过聚类分析,将雅鲁藏布江中上游白草主要分布区划分为梯度Ⅰ(平均3008.67 m)、梯度Ⅱ(平均3824.75 m)和梯度Ⅲ(平均4419.29 m),禾本科功能群在不同海拔梯度均有最大的高度、盖度和重要值,4个功能群(禾本科、豆科、菊科和杂类草)的高度随海拔上升而下降,群落物种丰富度和群落地下生物量占比随海拔上升而增加。上述结果表明白草是雅鲁藏布江中上游广泛分布的乡土草种,其群落特征多样,与环境因子有较强的相关性。
The study on characteristics of plant communities and their environmental factors along the environmental gradient remains an important topic in ecological research. The Yarlung Zangbo River is one of the highest rivers on earth, and the most important river in Tibet. There was no systematic study on the plant community of P. centrasiaticum in its basin. In this study, 26 sampling sites were set up in the main distribution area of P. centrasiaticum from Payang Town, Zhongba County, the source area of the Yarlung Zangbo River, to Pai Town, Milin County, the middle reaches of the Yarlung Zangbo River to investigate the characteristics of P. centrasiaticum communities. The results showed that (1) a total of 119 plant species belonging to 35 families and 96 genera in the distribution area of P. centrasiaticum mainly included Compositae, Gramineae and Leguminosae. The dominant species in these sample sites were P. centrasiaticum, Sophora moorcroftiana, Artemisia wellbyi, Artemisia sacrorum and Orinus thoroldii. The average richness in P. centrasiaticum communities was 22.04, ranging from 12 (Sangri county) to 37 (Gyantse county), and the average importance value of P. centrasiaticum was 39.38%, ranging from 11.88% (Sangri county) to 67.52% (Lhatse county). (2) The average underground biomass of 26 P. centrasiaticum communities was 3374.23 g/m2, and the percentage of the underground biomass in the 0-10 cm, 10-20 cm and 20-30 cm soil layers of P. centrasiaticum communities were 60.38%, 26.36% and 13.26%, respectively. (3) The significantly negative correlations (P<0.01) were detected between altitude and height of P. centrasiaticum (r=-0.60), soil pH and height of P. centrasiaticum (r=-0.53), soil pH and biomass of P. centrasiaticum (r=-0.55). (4) Redundancy analysis (RDA) showed that axis 1 and axis 2 explained 40.60% of the total variance, and played a leading role in the explanation of environment-P. centrasiaticum communities. Among them, the RDA1 axis showed a strong relationship with soil pH, precipitation, soil total nitrogen content (TNC), soil alkaline nitrogen content (ANC), soil available phosphorus content (APC), soil organic carbon content (SOC), and soil moisture, which explained 23.30% of the variance. It also revealed that soil nutrient factors and precipitation influenced the structure of the P. centrasiaticum communities. The RDA2 axis showed a strong correlation with temperature and total phosphorus content, which explained 17.3% of the variation. (5) Cluster analysis of altitude data in distribution area of P. centrasiaticum was conducted, and the sample sites in the upper and middle reaches of the Yarlung Zangbo River could be divided into altitude gradient Ⅰ (3008.67 m), altitude gradient Ⅱ (3824.75 m), and altitude gradient Ⅲ (4419.29 m). In the three altitude gradients, the height of 4 functional groups (Gramineae, Leguminosae, Compositae and Weeds) were decreased with altitude, the Gramineae functional group possessed the largest height, coverage and importance values in different altitude gradients. The species richness and percentage of underground biomass increased with altitude. The results showed that P. centrasiaticum was widely distributed in the upper and middle reaches of Yarlung Zangbo River Basin, and the characteristics of P. centrasiaticum communities showed strong correlation with environmental factors.