宁夏沙湖4种干旱区群落中主要植物种间关系的格局分析

格局分析是研究群落结构、种群特征、种内种间关系以及生物与环境间相互作用的重要手段。应用Ripley’s K函数的双变量点格局分析技术, 对宁夏沙湖4种干旱区群落中主要植物种间的空间关联关系进行了研究; 同时, 根据关联物种间相对位置的规则性, 基于Ripley’s K函数, 提出一种用于检测种间格局控制关系的技术方法。研究结果表明: 1) 沙枣(Elaeagnus angustifolia)-芨芨草(Achnatherum splendens)、芨芨草-苦豆子(Sophora alopecuroides)、白刺(Nitraria tangutorum)-芨芨草3个群落中, 主要物种间在个体大小、根系特点和生态习性等方面存在较大的差异, 并分别在一定的尺度范围内存在正关联关系; 而在物种生态需求和形态大小等方面相对一致的红砂(Reaumuria soongorica)-盐爪爪(Kalidium foliatum)群落中, 红砂和盐爪爪之间在整个观测尺度内(0~15 m)存在负关联关系。2) 格局控制分析表明, 在主要物种间存在空间正关联关系的3个群落中, 均检测出主要物种间在一定尺度范围内存在格局控制关系, 其中格局控制种一般个体较大、生境改造能力较强; 而在主要物种生活型相似的红砂-盐爪爪群落中, 未检测到主要物种间的格局控制关系。

PATTERN ANALYSIS OF INTER-SPECIFIC RELATIONSHIPS IN FOUR ARID COMMUNITIES IN SAND LAKE, NINGXIA HUI AUTONOMOUS REGION, CHINA

Aims Inter-specific interactions in plant communities can be characterized by their spatial relationships. Because these interactions are usually asymmetrical, i.e., one species exerts more influences on the other, asymmetric spatial patterns should be expected. Our objective was to study how species spatially adapt to arid conditions in four typical arid communities that differed in growth-form composition (tree-grass, shrub-grass, shrub-semishrub and forb-grass). Methods We selected four representative arid plant communities near Sand Lake in Xidatan, Pingluo County, Ningxia Hui Autonomous Region and measured the position, height and crown diameter of each individual in a 30 m × 30 m plot in each community. We applied the bivariate Ripley’s K function in spatial association analysis and developed a new method named pattern control analysis (PCA) for investigating asymmetric spatial relationships. PCA was derived from the assumption that the controlled species should be distributed around the controlling species regularly at a specific scale. Two simulated community patterns were used to test the new method. Important findings In communities of Elaeagnus angustifolia-Achnatherum splendens (EA), Nitraria tangutorum-A. splendens (NA) and A. splendens-Sophora alopecuroides (AS), significant positive spatial associations were detected between the dominant species (at scales of 0–15 m, 0–7.5 m and 0–7 m, respectively), and species pairs with positive spatial association significantly differed with each other in growth form. In the community of Reaumuria soongorica-Kalidium foliatum (RK), negative spatial association was detected (at the scale of <15 m) between the two dominant species, which are similar in growth form. Pattern control analysis showed a relationship between the dominant species in the three communities with positive spatial associations at scales of 0–6.5 m, 0–0.65 m and 0–1.5 m in EA, NA and AS, respectively. The pattern-controlling species in each community are larger in size and produced better developed microhabitats. However, no such relationship was detected between the dominant species of similar growth form and comparable microhabitats in RK. Results indicate that certain spatial relationships, especially pattern-controlling relationships, might be mechanisms for adaptation within plant communities. This might help in understanding inter-specific interactions within plant communities.