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China University (2010)

Study On The Plant Ecological Adaptation Strategy Of Degraded Seriphidium Transiliense Desert Grassland

Jin G L

Titre : Study On The Plant Ecological Adaptation Strategy Of Degraded Seriphidium Transiliense Desert Grassland

Auteur : Jin G L

Grade : Doctoral Dissertation 2010

Université : China University

Résumé partiel
Seriphidium transiliense desert grassland belongs to the climatic type desert of Central Asia, and distributed only in Xinjiang, the western region of China. This grassland ecosystem is too vulnerable, but still suffering heavy grazing pressure, furthermore, frequent anthropogenic destruction and lack of the public protection awareness which resulting the grassland severely degraded at large. These are seriously threatening the grassland biodiversity, livestock production and oasis ecological security. In this study, the approach for subdivision of degradation succession was explored by using the methodology of spatial sequence instead of temporal sequence, the organizational coordination capacity in terms of plant community, soil seed bank, nutrients, and physiological function during the process of grassland degradation was studied for clarifying its ecological adaptation strategy, assessing the ecosystem risk, and providing theoretical and practical basis on comprehensively understanding the mechanism of grassland degradation, timely conducting ecosystem restoration and sustainable utilization programs. The main results are as follows :(1) The Approach for Subdivision of the Degradation SuccessionBy TWINSPAN, DCA and DCCA, the S. transiliense desert grassland of the study area was subdivided into five successional stages, non-degraded stage (I), medium-degraded stage (II), heavy-degraded stage (III), over-degraded stage (IV), and system-collapse stage (V). The outputs of DCA provided interpretation on the degradation successional sequence from stress injury rate and resistibility, whereas the outputs of DCCA served as an environmental interpretation on degradation successional sequence from the soil physical and chemical properties.(2) The Ecological Adaptation Strategy of the Plant CommunityWith the intensity of grassland degradation, at individual level, the plant autoecology of main species, S. transiliense, Petrosimonia sibirica, Ceratocarpus arenarius, Trigonella arcuata, Tulipa iliensis, Gagea bulbifera, and Geranium transversale, tended to miniaturize for avoidance strategy. At the population level, the plant populations format their individual ecological adaptation strategy in different degraded stages, mainly through adjusting reproductive strategy to adapt the stress. At the community level, community adopts the ecological adaptation strategy of increasing the species number to enhance the competitiveness to filter the dominant species for adapting grazing stress, which possesses high reproductive capacity, grazing tolerance and resistance, but this often leads to main plant species changed and loss of the original vegetation. The plant community had experienced the ecological adaptation process from quantitative to qualitative change.(3) The Ecological Adaptation Strategy of the Soil Seed BankThe soil seed bank had the ecological adaptation strategy by taking advantage of rainfall conditions to germinate rapidly,and had an ecological insurance mechanism of retaining some seeds to resist external interference. The assessment of soil seed bank species diversity showed that its changes were in accordance with"medium disturbance theory", the species diversity of transient seedbank was greater than that of persistent seedbank and with greater fluctuation. The substitution speed of plant species was higher in early and late stages of degradation process, thus accelerated the changes both from non-degraded stage to degraded stages and from degraded stages to system-collapse stage. The similarities of soil seed bank species diversity in different degraded stages were low from 0.22 0.34 respectively, indicating that all the seedbanks were unstable caused by the degraded aboveground vegetation.

Mots clés : Seriphidium transiliense desert grassland, Degradion succession, Ecological adaptation strategy, Soil seed bank, Plant nutrition, Plant physiological resistance, Ecological risk assessment

Présentation (Globethesis)

Page publiée le 8 mai 2013, mise à jour le 4 mai 2018