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Accueil du site → Doctorat → Chine → 2008 → The Individual Characteristics of Nitraria Tangutorum Sand Mounds and Their Spatial Distribution Patterns in Desert-Riverside Ecotone

Chinese Academy of Forestry (2008)

The Individual Characteristics of Nitraria Tangutorum Sand Mounds and Their Spatial Distribution Patterns in Desert-Riverside Ecotone

Liang Ji Ye

Titre : The Individual Characteristics of Nitraria Tangutorum Sand Mounds and Their Spatial Distribution Patterns in Desert-Riverside Ecotone

Auteur : Liang Ji Ye

Grade : Doctoral Dissertation 2008

Université : Chinese Academy of Forestry

Résumé
Generally, arid ecosystems are some kinds of dynamic balance systems which have beenthe long—term development, although these systems are undulation, but still could maintaintheir structure and function in some certain space and time. However under the change ofnatural conditions and some unreasonable artificial disturbances, these systems will change thestructure and function, then initiate a series of changes, if these disturbances surpasses thethreshold value, which are keeping the system dynamic balance, It will cause the overallsystem change, some intense disturbances finally cause desertification. The arid and semiariddesert—river ecotone is such kind of latent desertification region. The native plant resourcesplay an essential role to maintain the ecosystem normal operation in these regions. Thereforetheir existence and the reasonable disposition can not be substituted for the stabilization andsustainable development of regional frail ecosystem.The Tangut Nitraria broadly spread not only between Kubqi desert and Yellow river innorth edge Ordos plateau, But also in more than ten provinces of China, because they can bearAlkalized-Stalinized condition and be tolerant to sand buried. Such kinds of plants are veryimportant to the combating desertification and keeping stability of ecosystem in some regions.Therefore I hoped the research on the individual characteristics and special distribution patternsof Tangut Nitraria sand mounds, can provide the theory support for the desertificationcombating in north edge Ordos, and also can provide the reference about use and protect theseplants for other people.In this research I except used some conventional methods to analysis the characteristics onthe structure, soil, animals, plants as well as carbon of the individual Tangut Nitraria sandmounds, but also attempted some methods to analysis their spatial distribution patterns. Suchas geostatistics and the pattern analysis, and used software such as Arcgis, GS+ and Surfer tosimulating the spatial distribute on of the sand mounds, analyzed their influences on the otherplants. The finally results show that (1)The fine grain matters have the trend of escalation from the crown to ground in the sand mounds ; The soil moisture and soil nutrient have the obviousincrease from surface to ground in the mounds, and they are most remarkable in the 0—10cmbelow ground ; This layer of soil on the surface of the ground is very important to plant growth ;The particle size and nutrient of soil have the obvious difference between the sand mounds andthe intersand mounds spaces, the soil is mainly the fine sand which is between 0.05 to 0.25 mmin the sand mounds, but they are mainly the fine sand and coarse grains which are between0.05 to 0.25 mm and 0.01 to 0.05mm in the intersand mounds spaces, the soil’s fine grainscontent of sand mounds, are between 0.001 to 0.005 mm, are increased more significantly thanthe same level of intersand mounds spaces., it show sand mounds are helpful to improve thestructure of soil ; The animals and plants on the sand mounds are more than the intersandmounds spaces ; The thin roots in the 0—30cm of sand mounds are more dense, they have thepositive roles to absorb the nutrient sand moisture as well as pool sand ; The Tangut Nitrariaand their sand mounds can pool about 356.134t carbon in the 1.33km2 area by the preliminaryestimate. The research on individual sand mounds confirmed their gathering function about soil,moisture, animals, plants and carbon (2)The sand mounds show randomly distribution inhorizon with the analysis of L and g function ; and different sand mounds appear certaincompetition when their distances are short than the mean distance 6.40m, This shows that theindividual Tangut Nitraria have been the process of self—thinning, and they are relative to bedevelopment of an independent, Such independence is based on the formation of the sandmounds ; Moran’s I was used to calculated the spatial autocorrelation on the height of sandmounds, the result shows that the similar height (growth stages) sand mounds are unevendistribution in all directions, and appear the random distribution ; The calculation results showthat Bassia dasyphylla are gathering distribution when their distance approach the meandiameter 5.54m of sand mounds, and randomly distribute when their distance surpass the scope,It can explain their gathering on the sand mounds and they have the close relation with the sandmounds. These results can prove Tangut Nitraria sand mounds have the function ofheterogeneity and the biodiversity contribution in the community. (3) The surface soil nutrienton these sand mounds appears to be the plots shape of "island" in horizon. If analyze with the conclusion on the individual sand mounds, It shows Tangut Nitraria are the driving force to theresources heterogeneity and the community structure of community ; these sand mounds’characteristics have some differences with the traditional concept of "resource islands",Therefore we can not simply use its theory to explain the formation of Tangut Nitraria sandmounds. The distinctions are mainly in these aspects. Firstly, Tangut Nitraria sand moundsgathered majority of resources are from the external community system ; Secondly, they capturethe resources, such as soil, its unit nutrient content is not higher than the intersand moundsspaces ; Thirdly, as the driving factor of building system’s heterogeneity structure, TangutNitraria could maintain the structure and function after the formation of sand mounds, but notaccelerate system unstable with the increase of proportion heterogeneity plots, So the TangutNitraria sand mounds are other types of resource pool.In short, Tangut Nitraria and their sand mounds have an important role to the regionalecosystem structure and function. Therefore, an in—depth study on them has a far—reachingsignificance for the regional desertification combating.

Mots clés : Ordos Plateau Tangut Nitraria sand mounds Spatial heterogeneity Geostatistics Biodiversity

Présentation (Dissertationtopic)

Page publiée le 1er mai 2013, mise à jour le 10 janvier 2018