| The construction of sand control forest in the Kubuqi Desert has a history of more than 40 years,and the construction has been effective,among which poplar plays an important role,especially the desert edge area is the key area for the construction of the locking forest.In recent years,a series of decline phenomena such as over-ripe aging,withered and broken branches of poplar lock-edge forests have occurred.In this study,we quantified the growth status indexes of degraded poplar forests and evaluated the growth status of single poplar trees as well as poplar trees in different woodlands in the study area of South Yingzi,Baituliang,Haishin Gob,Bai Naijing and Qilimin Sha woodlands around Dalat Banner in Kubqi Desert,and established a chronology of poplar(Populus L.)tree whorl width at five sampling sites based on the tree whorl climatology method.The response of tree annual whorl width changes to climatic factors and the causes of poplar degradation were analyzed with climatic data;the main results are as follows:(1)From the 49 poplar samples and 2777 poplar individual growth state characteristics investigated,the morphological characteristics of the protection forest declined significantly.(1)From the 49 poplar samples and 2,777 poplar trees,we can see that the morphological characteristics of poplar forests have deteriorated significantly.The degradation of poplar forests in Nanyingzi woodland is serious,and most of the trees have died,showing significant degradation phenomena such as withered tips and broken branches,hollow trunks,falling bark and yellow hearts.The degradation of Bai Naijing Protected Forest is light,and the trees are beginning to decline,but the decline is not obvious;Qili Sha Protected Forest is less degraded,and the poplar trees are in good growth condition with obvious life characteristics.(2)The chronological period of poplar trees in Nanyingzi woodland(Area A)is1948-2022,with a reliable age of 74,and the age of poplar trees in Baituliang woodland and Haixingob woodland(Areas B and C)is not much different,with chronological periods of 1980-2022 and 1984-2022,with reliable ages of 42 and 38,respectively,and the chronological periods of poplar trees in Bai Naijing woodland(Area D)and Qilisha woodland(Area E)are 1986-2022 and 1984-2022,respectively.The chronological time periods of poplar woods were 1986-2022 and 1977-2022,with reliable ages of 36 and 45.The older the poplar trees in the other four woodlands except Bai Naijing woodland,the more serious the degradation.(3)The correlation between year-by-year and season-by-season climate data and the annual whorl index of poplar trees at the five sampling sites revealed that the increase of temperature in the early growing season of poplar trees in each forest site was beneficial to the radial growth of trees;on the contrary,the increase of temperature in summer during the growing season would inhibit the growth of trees;the average annual precipitation(April to October)had the strongest correlation with the whorl width index and was an important limiting factor for the radial growth of poplar trees in the forest sites.(4)The main reasons for the degradation of poplar trees along the Kubuqi Desert Dharat Banner are: over-mature aging of the forest trees,showing significant degradation phenomena such as withered tips and broken branches,hollow trunks,falling bark,and yellow cores;degradation of poplar forest growth due to the decline of the groundwater level and poor stand conditions,etc.,which is manifested by poor forest morphology and quality;followed by dryness of the climate,where the combined changes in temperature and precipitation lead to changes in soil The dryness of the climate and the combined changes in temperature and precipitation lead to changes in soil conditions,which have a more direct effect on the radial growth of poplar trees,as well as the attack of pests and diseases that lead to the degradation of the growth state of poplar trees. |
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