Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Doctorat → Chine → 2010 → Response Mechanism of Desert Plant Allometric Exponents and Spatial Patterns to a Precipitation Gradient

Lanzhou University (2010)

Response Mechanism of Desert Plant Allometric Exponents and Spatial Patterns to a Precipitation Gradient

李涛;Li Tao

Titre : Response Mechanism of Desert Plant Allometric Exponents and Spatial Patterns to a Precipitation Gradient

Auteur : 李涛;Li Tao

Grade : Doctoral Dissertation 2010

Université : Lanzhou University

Résumé partiel
Plant allometry is the quantitiative relationship between growth and allocation. In response to numerous selection pressures and constraints, plants evolve many allometric patterns, which can in turn help explain many behaviors of plant individuals and poulations, such as interactions between neighboring plants. The spatial pattern of plant individuals observed in a plant community at any point in time is the product of many processes in its past, both biotic and abiotic. Plant spatial patterns determine the direction and strength of plant interactions, and consequently influence the allometric relationships at different scales. Therefore, the analysis of allometric growth patterns and spatial patterns of plant individuals would facilitate the comprehension of the role of both biotic interactoins and abiotic variables influencing the dynamics and structure of plant communities. Howevere, allometric growth patterns and spatial patterns of plant individuals in the desert plant communities have yet to be explicitly investigated, in particular their response to the environmental gradient.To this end, the present study analyzes the allometric growth patterns and spatial patterns of plant individuals in differnt desert plant communities along a precipitation gradient (i.e., Jingtai, Zhangye, Jiuquan, Jiayuguan, Guazhou and Dunhuang), in an attempt to explore how plant allometric relationships and plant spatial patterns respond to the precipitation gradient. The study results will guide us to better manage the natural resources of the desert region of northwest China, to restore the degraded vegetation and to acheive a sustainabel use of natural resources. The main resulsts and conclusions obtained in the present study run as follows :(1) The scaling exponent of the relationship between plant height (H) and basal stem diameter (D) approximates 1.0 for each of the three desert herbaceous species, as predicted by the geometric self-similarity model. While the H-D scaling exponents do not differ significantly among the five desert shrub species (ranging from 0.55 to 0.79), they do not exclusively follow any of the three models (i.e., geometric, elastic and stress self-simiarity model). Nevertheless, the observed scaling exponents for the five shrub species are closer to the predicted value by the elastic self-similarity model, compared to the other two models. The higher scaling exponent for herbaceous species than shrub species may be attributed to the differnce among them in stem anatomy and physical properties. In addition, the intercepts of the H-D scaling relationship are found to decrease with decreasing precipitation, suggesting that as plants are subjected to a more severe water stress, plants are confronted with higher mechanical and physiological constraints, resulting in a lower growth rate in height relative to the horizontal expasion of the stem and crown.(2) For Reaumuria soongorica growing in Zhangye, standing leaf biomass (ML) is found to scale as the 0.86 power of standing stem biomass (Ms) and as the 0.80 power of standing root biomass(MR), and standing MS is found to scale as the 0.93 power of standing MR, i.e. ML∝MS0.86, ML∝MR0.80 and MS∝MR0.93, respectively. Furthermore, standing aboveground biomass (which equils the sum of ML and MS) scales nearly isometrically with respect to standing belowground biomass (i.e. root biomass MR) for all three shrub species from differnt field samplin sites, i.e., R. soongorica in Zhangye, Ajania fruticulosa in Jiayuguan and Salsola passerina in Jiayuguan (scaling exponents are 0.87,1.14 and 0.90, respectively).

Mots clés : allometric growth; allometric theory; biomass partitioning and allocation; individual size class frequency distribution; spatial point pattern; spatial correlation; interactions between neighboring plants; desert;

Présentation (CNKI)

Page publiée le 2 mai 2013, mise à jour le 2 mai 2018