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Nanjing University (2011)

Plant Interactions In Two Arid Communities : Implications From Spatial Patterns

张明娟;Zhang Ming Juan

Titre : Plant Interactions in Two Arid Communities : Implications from Spatial Patterns

Auteur : 张明娟;Zhang Ming Juan

Grade : Doctoral Dissertation 2011

Université : Nanjing University

Résumé partiel
Plant interactions are intrinsically spatial : since plant individuals can react only to their local environment, the spatial distributions of plant individuals have great importance for the attribute and strength of plant interactions ; a relative stable spatial pattern is the result of plant interactions in the past. Clarifying the linkage between spatial patterns and plant interactions would be helpful for understanding the species coexistence mechanism and adaption strategies. The aboveground and underground patterns of a shrub-herb community (Nitraria tangutorum-Achnatherum splendens community) and a tree-grass community (Elaeagnus angustifolia-Achnatherum splendens) in northwest China investigated to analyze the inter/intra specific interactions between plants and the adaptation strategy of species to draught stress.(1) For the intra-specific interactions and aboveground structure of community, the spatial association analysis was applied to test the hypothesis that the species could be more beneficial in association with two-nurse species than with single-nurse species in the N. tangutorum-A. splendens community. The performance (frequency, abundance, and size) of the two associate species in neighbored patches (patches formed by a dominant species which were closely adjacent to the patches formed by the other dominant species), isolated patches (patches formed by one dominant species with no neighbor) and open areas was compared to analyze the individual and combined effects of the two dominant species. A. splendens and N. tangutorum appeared to have reciprocal facilitation effects when growing adjacent to one another, as evidenced by the increased size of neighbored patches over isolated ones. The individual effects of A. splendens on the associate species should be generally neutral, while the individual effects of N. tangutorum were positive to the associate species R. soongorica. In comparison to the isolated patches, there were significantly higher frequency and abundance (p<0.05), larger sizes (p<0.05), and higher co-occurrence frequency (p<0.05) of the two associate species in neighbored N. tangutorum patches. Since the neighbored patches could be influenced by both dominant species, the combined effects of A. splendens and N. tangutorum were identified as positive and over-additive.(2) For the intra-specific interactions and aboveground structure, K2 point pattern function, which could avoid the effects of environmental heterogeneity, was applied to analyze the spatial pattern and intra-specific interactions of A. splendens within a small scale (within 0.5m) in the Elaeagnus angustifolia-Achnatherum splendens community. Sixty-three A. splendens quadrats were established and studied in an arid community dominated by E. angustifolia and A. splendens in the northwest China. The quadrats were established at three density levels in three microenvironmental types and with seven replicates of each. The different responses of A. splendens were compared based on the three spatial density patterns, low, medium, and high, and three microenvironmental types, subcanopy, transitional, and open areas. The soil physicochemical properties of electricity conductance, soil organic matter, and soil bulk density, were measured in the three microenvironments to quantify the environmental stresses. The results show soil physicochemical stress increased along the subcanopy to transitional area to open area gradient.

Mots clés : Spatial Pattern; Tree Canopy; K2 Point Pattern Analysis; Rooting; Pattern; Size Inequality; Facilitation; Competition;

Présentation (CNKI)

Page publiée le 19 avril 2013, mise à jour le 4 mai 2018