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Disturbance Effect Of Dominant Rodents On Haloxylon Ammodendron In The South Edge Of Gurbantunggut Desert

Posted on:2021-05-15Degree:MasterType:Thesis
Country:ChinaCandidate:Y L XiangFull Text:PDF
GTID:2370330620972822Subject:Biology
Abstract/Summary:PDF Full Text Request
In desert ecosystem,the assimilated branch of Haloxylon ammodendron has high nutritional value and is an ideal source of water and nutrition for desert rodens.Rodents often burrow and build burrow systems under the bush of H.ammodendron,and collect assimilated branches and seeds of H.ammodendron near the burrow systems.The activities of herbivores can change the morphological characteristics of plants,the content of nutrients and the physical and chemical properties of soil.After being fed by herbivores,plants will adopt various defense strategies to maintain their normal growth and development.To some extent,changes in plant morphology and nutrient content can be regarded as a low-cost defense mechanism.Age can affects the best defensive strategy of plants.H.ammodendron of different ages stage may show different physiological and ecological responses under the disturbance of rodents.Moreover,in the southern edge of the Gurbantunggut Desert,the physiological and ecological responses of different age groups of H.ammodendron to the disturbances by rodents are not clear.In our study,the physical and chemical properties of soil under shrubs,above-ground morphological characteristics along with physiological and biochemical features of assimilating branches in different height of H.ammodendron?young,30-100cm;middle-aged,100-200cm;mature,>200cm?in burrowed areas and non-burrowed areas were compared in he southern edge of the Gurbantunggut Desert.We found that:?1?The disturbance of rodents makes the proportion of young and mature H.ammodendron in the burrowed areas greatly reduced.The decrease of the proportion of mature H.ammodendron showed that the mortality of H.ammodendron was high during the transition period from middle aged H.ammodendron to mature H.ammodendron.But the proportion of middle aged H.ammodendron?0.44?increased.It shows that the mortality of H.ammodendron was low in the process of transition from young H.ammodendron to middle aged H.ammodendron.?2?The disturbance of rodents can strengthen the"Fertile Island"effect of H.ammodendron,and has a certain impact on the"Salt Island"effect of H.ammodendron.This is mainly reflected in the increase of soil SOM,TN,an and AP content under shrub,especially the content of AN,TN and AK in the surface soil?0-20cm?.The pH value of soil in the depth of 20-40 cm increased significantly under the H.ammodendron shrub.?3?The disturbance of rodents promoted the basal diameter,branch and crown of H.ammodendron,but slightly inhibited the plant height.The changes of morphological characteristics of young and middle-aged H.ammodendron were more extensive than that of mature H.ammodendron.In the burrowed areas,the increase of basal diameter was only significant in the young H.ammodendron.The crown diameter and total branching rate of H.ammodendron increased significantly in both young and middle aged H.ammodendron.For mature H.ammodendron,rodents disturbance only significantly increased the total branching rate.More branches and larger crown size help to absorb more light energy,CO2 and O2,which shows that H.ammodendron has a morphological plasticity in response to rodents disturbance.The content of AN and AK in soil was positively correlated with the height,base diameter and crown of H.ammodendron,which were the main soil nutrient factor affecting the above-ground morphological characteristics in burrowed areas.?4?Rodent disturbance significantly reduced the photosynthetic pigment content of the annual assimilating branches,except for the carotenoids of the assimilating branches of mature H.ammodendron.The effect of rodent disturbance on nutrient content of assimilating branch was more significant in the younger H.ammodendron.The contents of total soluble sugar,reducing sugar,crude fiber and calcium in the assimilating branches of young H.ammodendron were significantly reduced.The contents of crude fat and calcium in the assimilating branches of H.ammodendron decreased significantly in the burrow areas,but the contents of soluble sugar and reducing sugar increased significantly,and there was no significant correlation with the content of photosynthetic pigment,which may be used as osmoregulation substance.The content of nutrients in assimilating branches of mature H.ammodendron was not significant affected by rodents except phosphorus except phosphorus.?5?The activities of SOD,POD and CAT in the assimilating branches increased to some extent under the disturbance of rodents?except for the young H.ammodendron?.However,for different age groups of H.ammodendron,the strategies of antioxidant system response to rodent disturbance are different.The effects of rodent disturbance on the activities of antioxidant enzymes in the assimilating branches of middle aged H.ammodendron were the most significant and the activities of these three enzymes increased significantly.But only SOD activity of mature H.ammodendron increased significantly.For the young H.ammodendron,the enzyme activities of three antioxidants were not significantly increased.In a word,different growth stages of H.ammodendron will affect its best defense strategy.In the early stage of growth,H.ammodendron mainly responded positively,and in the later stage,it tended to endure passively.Young H.ammodendron tends to choose more low-cost defensive measures.It can resist the feeding of rodents by changing the shape?increasing the branch and crown?,reducing the palatability?reducing the content of nutrients?of assimilating branches to rodents.The main defensive measures of middle-aged H.ammodendron were to change the shape?increase the branch and crown?,increase the content of soluble sugar and reducing sugar,and increase the activity of antioxidant enzyme.Rodents disturbance had little effect on the above-ground morphological characteristics and physiological characteristics of mature H.ammodendron.Under the condition of this study,the disturbance of rodents is not enough to have a great impact in eco-physiological traits of the mature H.ammodendron.The effect of rodent disturbance on H.ammodendron will gradually weaken with its growth.
Keywords/Search Tags:Haloxylon ammodendron, age groups, population structure, assimilating branches physiological and biochemical features, soil physical and chemical properties
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