To complement and improve the community composition and structural characteristics of the summit mossy dwarf forests in Southwest China， based on the community survey data of the 1 hm² forest dynamic plot（FDP）， the Center for Tropic Forest Sciences（CTFS） standard was used to investigate all woody trees with DBH ≥ 1 cm in the plot. Then， ten standard plots（a total of 0.6 hm²， 20 m×30 m each） were selected from the 1 hm² FDP， and all vascular plants within the 0.6 hm² plot were investigated and counted by plant community inventory. The species composition and community structure were analyzed by the aspects of species richness and quantitative characters， and the diameter class structure of the dominant tree species. The main results were as follows： （1）there were 3 614 woody individuals from 42 species， 32 genera， 20 families， with DBH≥1 cm within the 1 hm² FDP； in the 0.6 hm² plot， there were 103 species of vascular plants in 42 families， 67 genera and 1 536 individuals of 24 woody species with height≥3 m； （2）Rhododendron sinofalconeri was， absolutely dominant in the community， with important values 3-4 times higher than those of the secondary dominant species； （3）The age structure of the whole community showed a “L” shape； however， Rhododendron sinofalconeri was dominant in adult individuals， being different from other dominant species； （4）The community was composed of tree， shrub and herb layers as well as epiphytes and parasitic plants， and named as Rhododendron sinofalconeri， Clethra delavayi var. yuiana， Illicium tsaii summit mossy dwarf forests. In the Bozhu Mountain， Wenshan county， Yunnan， China， the mossy dwarf forest community was rich in species， stable in composition， prominent in dominant species and good in their regeneration. The canopy appearance of the community was flat， and the community succession was in a mature forest state.

Seeds of 18 F. mandshurica clones were used as materials， the germination performances of clones at suitable temperatures after different stratification treatments were compared， and the relationships between germination performances and seed embryo growth changes were analyzed. The results showed that the germination performances of seeds were different among F. mandshurica clones after different stratification treatments. Seed dormancy of clones 1， 2 and 6 was shallow and could be broken after variable temperature stratification treatments for a short time（a total 18 weeks）， which the germination rate of clones 2 and 6 reached more than 75%. Seed dormancy of clones 13， 14， 15 and 16 were broken by 20-week stratification treatment （cold temperature extended for two weeks）， and clones 4， 8， 11 and 12 by 20-week stratification treatment （warm temperature extended for two weeks）. Seeds dormancy of clones 5 and 18 was deep-degree， it could be broken by extending the stratification（warm and cold temperature） time to 22 weeks. Seed dormancy of clones 3， 7， 9， 10 and 17 could be broken by stratification treatment for 20 weeks， without significant difference in the dormancy between seeds treated by extending warm and cold stratification time. The changes of embryo length， embryo rate and embryo mass ratio in the process of stratification were different in different clones， and relative extension time（two weeks） of cold temperature stratification in clones 6， 7 and 11 was conducive to embryo growth， and extension time（two weeks） of warm temperature stratification in clones 2， 5 and 17 was conducive to embryo growth. Differences in seed dormancy of different clones could not be accurately judged by changes in seed embryo growth during the stratification process， which should be judged mainly by the germination performances. The results could provide a reference for the selection of mother clones with shallow seed dormancy in production practice.

To address the problem of the rooting ability of Fraxinus mandshurica cuttings significantly decreasing after three years due to age effect， four-year-old F. mandshurica seedlings were used to investigate the role of cycle rejuvenation through cuttings in overcoming age effect in this study. The impact of the number of cycles and topping treatment on the sprouting， growth， and rooting of F. mandshurica cuttings， as well as the physiological changes during its rejuvenation process were examined. The results showed that the measurement of increasing the number of rejuvenation cycles and topping treatment both enhanced the degree of rejuvenation in F. mandshurica， which were characterized by an increased number of sprouted branches， finer branches， and shorter internodes， while significantly improved the regeneration ability of the cuttings. When the number of rejuvenation cycles reached three and was combined with topping treatment， the number of sprouted branches increased by 6.56 times， and the rooting rate increased by 7.44 times compared to non-rejuvenated treatment. During one to three rejuvenation cycles， the indole acetic acid（IAA） and cytokinin（CTK） levels in the plants increased， the gibberellin（GA₃） levels significantly increased only at the third cycle， and the abscisic acid （ABA） levels decreased gradually. After rejuvenation， the activities of catalase（CAT）， peroxidase（POD）， and superoxide dismutase（SOD） and the contents of malondialdehyde（MDA） and soluble sugars decreased in the regenerated plants. These physiological changes were consistent with the juvenile state of the plants. Cycle rejuvenation can effectively restore the juvenile state， induce the formation of sprouts with higher IAA and GA₃ levels and lower ABA levels， and simultaneously reduce the oxidative state and soluble sugar content in F. mandshurica. These changes are beneficial for achieving rejuvenation of F. mandshurica， thereby increasing the rooting rate of F. mandshurica cuttings and enabling rapid and efficient clonal propagation of superior F. mandshurica varieties.

Exploring the coupling relationship among stand structure， site conditions， protection intensity， and plant diversity is helpful to improve the effect of plant diversity protection in protected areas. Based on this， the forest community of the Chuona River National Nature Reserve in Daxing’anling Mts was selected as the research object， the plant diversity and stand structure characteristics of the arbor， shrub， and herb layers were investigated， and the soil samples were collected and the soil physicochemical properties were determined. The frequency distribution， redundancy ranking and variance analysis were used to reveal the characteristics of plant diversity and its coupling relationship with influencing factors. The results showed that：（1）Larix gmelinii was the dominant tree species in the tree layer of Chuona River Reserve， with a relative abundance of 64.35%， followed by Betula platyphylla. The proportion of lingonberry（Vaccinium vitis-idaea） in shrubs was the highest， reaching 72.70%. A total of 77 herbs were recorded， of which Carex callitrichos accounted for the largest proportion（23.72%）. （2）The order of richness index and diversity index was herb layer>arbor layer>shrub layer， and the shrub layer had the highest evenness index. （3）Redundancy analysis and variance decomposition analysis showed that the independent effects of stand structure explained the most changes in plant diversity. Herbaceous coverage， shrub density， tree height and soil bulk density were most closely related to plant diversity changes. Adjusting stand structure would be a simple and reliable way to improve plant diversity， and the above results provided data support for stand management in Daxing’anling Mts.

The fixed monitoring plot was conducted in the Xilinhe National Nature Reserve to analyze tree species diversity， dominant species niche， interspecific associations and community stability in the Piceakoraiensis-Abies nephrolepis-Pinus koraiensis forest community by using a series of analysis methods including the α diversity index， the niche determination， the variance ratio（V_R）， the Chi-square test（χ² test）， the Spearman’s rank correlation coefficient test and the M. Godron stability. The results showed that： （1）the plot encompassed 20 tree species， 14 families and 14 genera， with a balanced distribution of trees， and the α diversity index was high； （2）the community niche overlap index was relatively high， but the cases with large （>0.7） or small（<0.4） niche overlap index were rare with a moderate degree of niche differentiation； （3）the overall correlation of the community was nonsignificant positive， and the interspecific correlations among the main tree species were mainly positive and nonsignificant correlation with strong interspecific independence； （4）the stability of M. Godron analysis fell to the point（32.79， 67.21） and was far from the stable point （20， 80）， indicating poor community stability； （5）P. koraiensis had the highest importance value and niche width in the sample plot， the average niche overlap index with other tree species was higher than the average value of the sample plot； the species was dominated by large-diameter individuals， and the relative frequency among tree species was low. Therefore， during the restoration process of Piceakoraiensis-Abies nephrolepis-Pinus koraiensis forest， the appropriate artificial intervention should be carried out to promote the recovery of Pinus koraiensis population， to regulate interspecies relationships， to enhance interspecies association strength， and to strengthen monitoring and protection of rare plant populations when community stability declined.

In order to reveal the mechanism of selenium alleviating the cadmium stress in Astragalus membranaceus， the traditional medicinal plant A. membranaceus was used as materials， and the roles of ion antagonism， antioxidant enzyme system， heavy metal chelates and isoflavones in alleviating the Cd stress by Se were clarified comprehensively using hydroponic cultivation method. The results showed that 10 μmol·L^-1 Se significantly improved the growth of A. membranaceus seedlings under 50 μmol·L^-1 Cd stress， and reduced the accumulation of reactive oxygen species and membrane lipid peroxidation levels. The addition of Se significantly reduced the Cd content in all parts of A. membranaceus under Cd treatment. Meanwhile， the addition of Cd also reduced the Se content， indicating that it has a significant antagonistic effect on the absorption of Se and Cd. Se reduced the activities of POD， SOD， APX， CAT and GR in all parts of A. membranaceus under Cd stress. Correlation analysis showed that various antioxidant enzymes activities were significantly positively correlated with {\mathrm{O}}_{\mathrm{2}}^{•-} content， suggesting that the changes of antioxidant enzyme activity were more adapted to the level of reactive oxygen species in the plants. In addition， the addition of Se also reduced the content of non-protein sulfhydryl groups and metallothionein in all parts of A. membranaceus exposed to Cd treatment， and the contents showed a good positive correlation with the Cd content in corresponding part， indicating that the content of heavy metal chelates was regulated by the Cd content in various parts. Unlike antioxidant enzymes and metallothionein， the contents of three isoflavone components were significantly increased by Se addition in the roots of A. membranaceus seedlings under Cd stress. Furthermore， the expression levels of key enzyme genes in the isoflavone synthesis pathway， including CHS， IFS， I3'H， IOMT and UCGT， were significantly upregulated by Se under Cd stress. In summary， Se decreased the content of Cd in A. membranaceus seedlings under Cd treatment by antagonizing Cd during the absorption process， and reduced the degree of plant stress. At the same time， Se improved the tolerance of plant to Cd stress by upregulating the synthesis of secondary metabolites such as isoflavones.

To investigate the dormancy type and physiological and metabolic characteristics of Acanthopanax senticosus seeds during germination， the seeds from northeast China were treated with sand accumulation for 140 days under different temperature conditions（20 ℃， 4 ℃， 20 ℃/4 ℃） respectively. Five distinct stages were identified based on embryo phenotypic changes，and the dynamic changes in endogenous hormones， main nutrient substances and their hydrolases， antioxidant system， and metabolomics during these five stages were examined respectively. The results revealed that： （1）A. senticosus seeds exhibited good water absorption； while the constant temperature of 20 ℃ only promoted embryo elongation， but not germination. There was no increase in embryo rate at 4 ℃， and the embryo rate increased and the seeds germinated only when the temperature was maintained at 20 ℃ for 0-110 d and 4 ℃ for 110-140 d. （2）As the embryo growth rate increased， gibberellic acid content increased while abscisic acid content decreased. The levels of indoleacetic acid， indolebutyric acid， and naphthenic acetic acid all decreased. Fat content decreased while soluble sugar content increased. Fat content showed a significant negative correlation with lipohydrolase activity as well as a highly significant negative correlation with soluble sugar content. （3）A total of 92 differential metabolites were screened， and the carbon metabolism， energy metabolism， and antioxidant metabolism were the major differential metabolic pathways. Additionally， there were difference in sesquiterpene and triterpene biosynthesis， fatty acid biosynthesis and glyceride metabolism. In conclusion， seeds of A. senticosus were morphological and physiological dormancy， and variable temperature stratification was a necessary condition to break seed dormancy， and endogenous hormones might regulate seed dormancy and germination. Macromolecular nutrients such as fat were decomposed by hydrolases to provide material and energy for seed germination， which was also one of the necessary conditions for seed germination. This study provided theoretical guidance for identifying seed dormancy types and artificial propagation of A. senticosus.

Based on the fact that soil microorganisms can enhance the adaptability of plants to global change， the effects of soil microorganisms on the ecological stoichiometric characteristics of rhizosphere soil microorganisms were studied under the background of nitrogen deposition， and then the regulation of changes in ecological stoichiometric characteristics on the soil microbial nutrient limitation was explored. Under the premise of soil sterilization treatment（sterilized soil（+S） and non-sterilized soil（-S））， one-year-old potted seedlings of Caragana korshinskii were inoculated in two ways（inoculation（+M） and without inoculation（-M））， and nitrogen addition treatments（no nitrogen application（CK）， low nitrogen（LN， 3 g·m^-2·a^-1）， high nitrogen（HN， 6 g·m^-2·a^-1）） were set up. Compared with the original microbial community composition in non-sterilized soil without fungus inoculation， the correlation between ecological stoichiometric characteristics of microhabitat and microbial nutrient limitation under different treatments was explored.Results were as follows： （1）In sterilized soil treatment， the relative abundance of fungi in the rhizosphere soil of C. korshinskii mycorrhizal seedlings was significantly increased by 82.20%， 25.00% and 59.84% under CK， LN and HN treatments than that of non-mycorrhizal seedlings， respectively. （2）In the treatment of non-sterilized soil， the microbial biomass carbon-to-phosphorus ratio in the rhizosphere soil of non-mycorrhizal C. korshinskii seedlings under LN treatment was lower by 46.28% compared to CK treatment（P<0.05）， while that of mycorrhizal seedlings was 56.76% higher compared to CK treatment（P<0.05）. （3）Under the nitrogen addition treatments， stoichiometry of carbon and nitrogen-related soil enzyme activity， stoichiometry of carbon and phosphorus-related soil enzyme activity， and vector length in the rhizosphere soil of C. korshinskii non-mycorrhizal seedlings under sterilized soil treatment were significantly lower than those of mycorrhizal seedlings（P<0.05）. （4）PLS-PM path analysis showed that the total effect coefficient of microbial regulation on microbial nutrient limitation was greater than that of nitrogen addition treatment. In summary， soil indigenous microorganisms and mycorrhizal fungi synergistically regulated the enzymatic stoichiometric ratio of rhizosphere soil， and enhanced the adaptation of soil microbial nutrient limitation to nitrogen addition.

To provide a theoretical basis for the timely harvesting of Aralia elata， the cultivated A.elata was used as experimental materials， and the biomass， photosynthetic pigment content， total phenolic content， total flavonoid content， and antioxidant capacity of A. elata leaves in different harvesting periods（S1 period， April 10th， 2023； S2 period， April 30th， 2023； S3 period， May 20th， 2023； S4 period， June 9th， 2023） were analyzed respectively. Meanwhile， the high-performance liquid chromatographic（HPLC） method was established to determine the contents of araloside X， araloside V， and araloside A. Based on high-performance liquid chromatography-mass spectrometry metabolomics technology， the differences in secondary metabolites of A. elata at different harvesting periods were compared and analyzed. The results showed that： （1）The fresh weight， dry weight， and photosynthetic pigment content of A. elata leaves increased with growth， and reached the maximum value in the S4 period. （2）The contents of total phenol and total flavone reached the maximum value in the S1 period（1.36 mg·g^-1， 29.38 mg·g^-1）. （3）The scavenging ability of DPPH radical was the strongest in the S1 period（IC₅₀ of 0.262 g·L^-1） and the scavenging ability of ABTS radical was the strongest in the S2 period （IC₅₀ of 0.511 g·L^-1）. （4）The content of araloside A reached a maximum of 12.90 mg·g^-1 in the S4 period. The contents of araloside V and X in the S2 period were significantly higher than those in other periods， which were 1.53 and 3.30 mg·g^-1 respectively. （5）A total of 24 phenolic metabolites were identified， and the total amount of phenolic compounds in the four periods were 64.84， 119.31， 101.95 and 89.32 mg·g^-1， respectively. Among the total phenolic compounds， the C6C1 backbone compounds （protocatechuic acid and gentisic acid）， the C6C3C6 backbone compounds （rutin）， and the C6C3 backbone compounds （caffeic acid） were significantly accumulated in the S2 period. In conclusion， considering the content of functional components， antioxidant activity， and edibility， the S2 period is the most suitable time for harvesting.

The establishment of shelter forests in the northeastern region of Ulan Buh Desert is a crucial ecological barrier to protect agricultural productivity within the eastern Hetao Plain. However， the lack of attention towards scientific research on artificial afforestation has resulted in a decline tendency in many shelter forest systems. The investigation of ecological adaptability of indigenous tree species after artificial cultivation was a crucial approach to guide the establishment and sustainable management of plantations. In order to further investigate the ecological adaptability of native tree species in Ulan Buh Desert after artificial cultivation， three native tree species： Ammopiptathus mongolicus， Zygophyllum xanthoxylon and Prunus mongolica were used as materials. By measuring the epidermal morphology， anatomical structure， and physiological indices of functional leaves， in conjunction with local meteorological data， the adaptive mechanisms of these plants to arid desert environments were clarified. The results showed that each of three plants exhibited distinct adaptations to arid desert environment in different ways. A. mongolicus enhanced light exposure and photosynthetic efficiency by augmenting leaf area， strengthened leaf mechanical defenses through dense epidermal hairs and well-developed cuticle， reduced light-induced damage and water transpiration， and maintained cellular water balance to minimize lipid peroxidation. The leaves of P. mongolica were clustered， by increasing number of leaves， the light receiving area was increased and the photosynthetic efficiency was improved， and by curling the leaves to avoid strong light burns， the water transpiration was reduced and the cell water balance was maintained by specializing the stomatal position（all the stomata were distributed on the lower surface of the leaves）， developed vascular bundles and rich mucous cells and crystal structures， and reduced cell membrane lipid peroxidation. The leaves of Z. xanthoxylon showed a cylindrical strip structure. By reducing the wind resistance， the probability of wind-sand flow damage to the leaves was reduced. The antioxidant enzyme activity and osmotic adjustment substance content in leaves was enhanced by physiological metabolic regulation， and the balance of cell water and reactive oxygen species metabolism was maintained. These findings suggested the different adaptation strategies adopted by the three plants in response to the desert environment， and provided the new ideas for introduction and domestication of native tree species in the northeastern Ulan Buh Desert.

Alpine meadows exhibited environmental characteristics such as intense radiation， low air pressure， strong winds and sudden changes in diurnal temperature， which were unfavorable for plant growth. In order to explore the ecological adaptability of Cynanchum forrestii， an endemic species of China to the alpine meadow environment（altitudes of 3 100-3 500 m） in Jiulong County， southwest Sichuan Province， the anatomical features of various organs of C. forrestii were examined by optical microscopy and scanning electron microscopy， and the pollen and seed viability were analyzed by the TCC method. The results showed that the leaves， stems and flowers of C. forrestii were covered with epidermis composed of rich single-row cells； the cuticle of leaf and stems epidermis was thick； the stomata were large and located on the lower surface of the leaves， palisade tissue and sponge tissue were developed； the stem epidermal cells were small and the cell wall was thick， and the cortex was composed of seven layers of cells， which were closely arranged， there were rich substances stored in the stem cells， and the vascular columns accounted for a large proportion of stem， the pith was developed and rich in stored substances； the root vascular tissue was well-developed， rich storage substances in cortical cells； the characteristics of high seed and pollen vitality， combined corolla， combined pistil column， the seed had seed hair， and thick and hard seed coat provide guaranteed for improving reproductive efficiency. The above results indicated that C. forrestii possessed a comprehensive array of external and internal structural characteristics， which enabled adaption to high-altitude cold environments while maintaining elevated levels of radiation resistance， drought resistance， and cold tolerance， and laid a structural foundation for the successful survival and reproduction of C. forrestii in the alpine environment.

Functional traits of the leaf and fine root play an important role in plant invasion. It was of great significance for understanding the biological invasion mechanism to investigate the differences and connections between the functional traits of leaf and fine root functional traits and to illustrate the responses of plants parts above and below ground to heterogeneous habitats. In this research， 20 functional traits in leaves and fine roots of Alternanthera philoxeroides in three habitats（xeric， wet， and aquatic） were measured and their differences and correlations in different habitats were analyzed by field investigation methods. The results indicated that： （1）There were significant differences（P<0.05） in plant functional traits among the three habitats， with the largest differences in leaf fresh weight（（1.12±0.14） g）， leaf area（（4.80±0.57） cm²）， and leaf volume（（1.12±0.16） cm³） in the xeric habitat， while the ratio of leaf length to width（2.95±0.22） and root tissue density （（4.14±0.52） g·cm^-3） in aquatic habitat， respectively. （2）A. philoxeroides had the highest coefficient of variation in leaf relative water content（0.603） in hydric habitat， while the lowest coefficient of variation for the ratio of leaf length to width（0.057）. In addition， it had the highest coefficient of variation for root branch number（0.453） in xeric habitat and the lowest coefficient of variation for root average diameter（0.065）. （3）Similar to leaf， fine root traits were closely related， but there were less related between root and leaf traits. （4）A. philoxeroides preferred the acquisitive strategy（high input-low return） in the xeric habitat， while it preferred the resource conservative strategy（low input-high return） in the wet and aquatic habitats.

In order to explore the obstacle factors of regeneration of Amygdalus ledebouriana in Xinjiang， and to better protect the germplasm resources and population， the seeds of A. ledebouriana in Barluk Mountain of Xinjiang were used as experimental materials， and the effects of seed water absorption characteristics， different stacking time， different concentrations of GA₃ and different substrate treatments on the dormancy and germination characteristics of A. ledebouriana seeds and the germination inhibitors in A. ledebouriana were explored respectively. The results showed that： （1）The natural dormancy of whole seeds was relieved after 80 days stratification， while the decorticated seeds could germinate without stratification， and the addition of 300 mg·L^-1 G_A3 could break the dormancy of decorticated seeds in advance and improve the germination rate. （2）The germination inhibitors in A. ledebouriana seeds mainly existed in exocarp and mesocarp. （3）The germination rate of A. ledebouriana seeds in the original habitat soil was higher than that in the nutrient soil.

In order to reveal the characteristics of fine root（diameter ≤2 mm） morphology and vertical distribution of biomass from different provenances and families of 24-year-old Picea koraiensis， the soil core method was used to determine fine root morphology and biomass at different soil layers（surface layer： 0<h≤ 10 cm， subsurface layer： 10 cm<h≤20 cm， bottom layer： 20 cm<h≤30 cm） in 30 families from four provenances（Muling， Linkou， Jinshantun， and Wuyiling from low to high latitude） in Qingshan Forest Farm， Linkou County， Heilongjiang Province， China. The results showed that there were significant differences in all fine root morphological traits among different provenances， and specific root length and root tissue density exhibited significant differences among families within provenance. At the provenance level， the average root diameter of Wuyiling provenance was the thickest at all soil layers， whereas specific root length and root tissue density of Linkou provenance were the largest. At the family level， in 0<h≤10 cm soil layer， root diameter of W035 was the thickest， that of CK-2 was the thinnest， specific root length of CK-2 was the longest， that of W043 was the shortest， root tissue density of J082 was the highest， that of M515 was the lowest. Root tissue density and specific root length of different provenances and families of P. koraiensis decreased with the increase of soil layer， while root diameter increased. The total fine root biomass（all three soil layers） across the four provenances was 33.56 g·m^-2 on average， with the maximum occurring in Linkou provenance （39.04 g·m^-2） and the minimum in Jinshantun provenance（32.52 g·m^-2）， showing inconsecutive geographical distribution. Fine root biomass decreased with soil layer increasing， and root biomass at the surface soil layer accounted for 77% of the total biomass on average. In comparison， the low-latitude provenance of Muling tended to distribute greater fine root biomass at the subsurface and bottom soil layers， while the high-latitude provenances of Wuyiling and Jinshantun had higher fine root biomass at the surface soil layer， indicating that P. koraiensis originated from cold site tended to allocate more fine roots at the fertile surface soil.

To explore whether the fungi from Parametarhizium， namely P. hingganense or P. changbaiense， a newly discovered fungus from forest litters in northeast China， could improve plant growth under salt and alkali stress， the mung bean seeds were treated with the fungi， followed by the examinations on the phenotypic changes， and alterations on the photosynthesis， chlorophyll fluorescence parameters， osmolyte contents， ROS levels， and antioxidant enzyme activities were detected respectively. The results showed that the biomass of mung bean plants treated with P. hingganense or P. changbaiense were higher under no-stress， salt and alkali stress conditions than untreated plants. Under salt and alkali stress， two fungus-treated plants maintained a high photosynthetic activity， elevated proline content， decreased malondialdehyde（MDA） content， and increased the activities of antioxidant enzymes POD， SOD and CAT in different degrees. In conclusion， through maintenance of photosynthesis， raising osmotic potential， and antioxidant capacity， treatment of the fungi from Parametarhizium alleviated the salt and alkali stress on mung bean. P. hingganense might significantly alleviate salt stress damage， while P. changbaiense might significantly improve the growth of mung bean under alkali stress.

To explore the effects of different thinning intensity on the growth and wood properties of Populus pseudo-cathyana×Populus deltoids plantation， and to provide a theoretical basis for cultivating high-quality industrial resources of poplar in northeast China， the 18-year old Populus pseudo-cathyana×Populus deltoids was used as the material， and the initial plant row spacing of 2 m×3 m was used as the control， and the thinning treatments of 3 m×3 m， 6 m×3 m， 4 m×6 m were set up. The growth characteristics（tree height， DBH， 2 m diameter， crown width） and wood properties（basic density， fiber length， fiber width， hemicellulose content， cellulose content， semi-cellulose content， lignin content） of the experimental forest were measured in the 5th year after thinning， and the volume per tree and the storage per unit area were calculated using tree height and DBH. The results of variance analysis showed that all indexes were significantly different except basic density （P<0.01）. The results of mean analysis showed that the mean values of each growth index and lignin content reached the maximum when the row spacing was 6 m×3 m， and the other wood indexes reached the maximum when the row spacing was 4 m×3 m or 6 m×4 m. The variation of phenotypic coefficient of each index ranged from 3.35% to 29.87%. In addition to the basic density， the repetitive force of each index exceeded 0.590. The results of correlation analysis showed that there were significant positive correlations among the growth indicators（0.690<r<0.993）， but the correlation between wood traits and growth traits was weak. It was found that Q_i reached the maximum when the row spacing was 6 m×3 m， 4 m×6 m and 4 m×6 m， respectively， by using growth traits， wood traits and combined growth and wood traits as evaluation indexes. Thinning might promote the growth of stand and improve the wood property of the forest， and the wood property and the comprehensive improvement effect of the forest growth and wood would be better when the row spacing of the trees is 4 m×6 m. The best growth results were obtained when the row spacing was 6 m×3 m. Therefore， suitable thinning intensity might be selected according to different cultivation objectives for the cultivation of poplar high quality industrial resources in northeast China in the future.

To investigate the vertical distribution of root biomass（diameter≤2 mm） and root length density of Pinus tabulaeformis and Cupressus chengiana plantations in the arid valleys of the upper Minjiang River， and to analyze the carbon allocation strategy of fine root system in different soil layers， and to provide reference for vegetation restoration in the arid valleys of the upper Minjiang River. P. tabulaeformis and C. chengiana plantations were sampled by soil corer method， and the root biomass and root length density of absorptive roots（first to third order） and transport roots（≥fourth order） in different depth（h）（0 cm<h≤15 cm and 15 cm<h≤30 cm） were measured， as well as the proportions biomass and length density of absorptive roots to the total fine roots. The results showed that： the absorptive root biomass and root length density of P. tabulaeformis and C. chengiana were significantly higher in 0 cm<h≤15 cm than those in 15 cm<h≤30 cm， and the transport root biomass and root length density were not significantly different between soil layers； the proportions biomass and length density of absorptive roots to the total fine roots in 0 cm<h≤15 cm were significantly higher than that in 15 cm<h≤30 cm（P<0.05）； the proportions biomass and length density of absorptive roots to the total fine roots in 0 cm<h≤15 cm and 15 cm<h≤30 cm of C. chengiana were significantly higher than those of P. tabulaeformis（P<0.05）. These findings suggested that more carbon was allocated to the absorptive roots in the surface soil layers with the highest nutrient availability in P. tabulaeformis and C. chengiana root system.

Since the regeneration of Tilia amurensis is difficult under full light conditions， and vegetation control can promote the growth of target species by changing light conditions and soil quality. In order to provide the support for the cultivation of T. amurensis， the effects of vegetation control intensity on root traits and soil factors of seedlings were investigated. T. amurensis monocultures（Five-year-old） with inter-row and intra-row spaces of 1.5 m×1.5 m were used as materials， and vegetation control treatments with different intensities T₃₀， T₅₀ and T₇₅（clearing vegetation in the radius of 30， 50， 75 cm around T. amurensis seedlings） and control treatment（CK） were set. The morphological traits， total nutrient content， and non-structural carbon content in the absorptive roots and transport roots of T. amurensis seedlings， as well as soil variables were measured under different treatments， and the effects of vegetation control on root traits and soil conditions were revealed. Vegetation control significantly changed the light intensity in the environment of T. amurensis seedlings， among which the light intensity under T₇₅ treatment was the maximum， and the light intensity decreased with the weakening of vegetation control intensity（P<0.05）. Vegetation control significantly reduced the contents of total carbon， total nitrogen， available nitrogen， and available phosphorus in the soil. With the decrease of vegetation control intensity， the fine root diameter， carbon to phosphorus ratio， soluble sugar and starch contents decreased， while the specific surface area， specific root length， total carbon， total nitrogen and total phosphorus contents increased. Soil variables factors to the variation of root traits for absorptive roots and transport roots were 43.2% and 37.9%， respectively. The greater the vegetation control intensity， the greater the light intensity obtained by T. amurensis saplings， and the root morphology， stoichiometry and physiological traits of T. amurensis saplings took adaptive changes with the change of vegetation control intensity. The root specific surface area， specific root length， total carbon， total nitrogen and total phosphorus contents were increased to enhance the adaptability to low light conditions. The changes of light conditions and soil factors under vegetation control might be the two main factors to explain the root trait changes of T. amurensis saplings.

In order to explore the difference and influencing factors of the number of regenerated seedlings of Pinus schrenkiana on different decomposed grades of fallen wood， the relationship between the number and height levels of regenerated seedlings on different decomposed grades of fallen wood， and the water content， surface area， slope， slope direction and elevation of fallen wood were investigated respectively. The results showed that the probability of seedlings appearing on fallen wood with different decay grades was different， but the seedlings survival rate increased with the increase the decay grade of fallen wood. The height level structure of fallen wood seedlings with different decomposition grades showed obvious growth characteristics， with seedlings at height of 0-5 cm being the most. The water content of fallen wood had a significant impact on the number of seedlings on grade Ⅰ and grade Ⅱ decayed fallen wood（P<0.05）， while the surface area of fallen wood had a significant impact on the number of seedlings on grade Ⅱ， Ⅲ and Ⅳ decayed fallen wood（P<0.01）， but the slope and altitude had no significant impact on the number of regenerated seedlings on each grade of decayed fallen wood（P<0.05）. Further analysis of the influencing factors on the number of seedlings at different height levels showed that water content had a very significant impact on the number of A₁（0-5 cm） and A₂（5.1-10.0 cm） height level regenerated seedlings on fallen wood with grade Ⅱ decay（P<0.01）， and the surface area of fallen wood had a significant impact on the number of A₁ height level seedlings on fallen wood with grade Ⅱ and Ⅲ decay（P<0.05）； On the fallen wood with grade Ⅳ decay， these factors had no significant impact on the number of regenerated seedlings at different height grades（P<0.05）. The surface area and slope direction of fallen trees had a significant impact on the number of dead seedlings on fallen trees. The water content on low-level decomposed fallen wood was the main factor affecting the number of regenerated seedlings， while for high-grade fallen wood， the surface area was the main factor. In contrast， seedlings with lower heights were more susceptible to the impact.

Understanding the growth dynamics of tree xylem in arid and semi-arid areas of China and its response to climatic factors is crucial for assessing and predicting forest productivity and carbon sequestration potential under climate change. In this study， the intra-annual xylem formation of four Quercus mongolica in Liupan Mountain Nature Reserve of Ningxia were monitored by micro-core sampling technique in two growing seasons（2019 and 2020）， and mixed linear model was used to explore the effects of temperature and precipitation on xylem growth rates. The results showed that there was no significant difference in intra-annual xylem formation dynamics between the two years（P>0.05）. The onset of xylem formation started from early April and ceased from mid-to-late September， resulting in a growing season length of （177±17） days（2019） and （165±24） days（2020）. The results of the mixed linear model showed that the annual xylem growth rate of Q. mongolica was positively correlated with the maximum， mean， minimum temperatures， as well as total precipitation in the preceding 7， 10 and 15 days（P<0.01）. Under global change， the xylem growth of Q. mongolica may benefit from future warm and humid climate conditions in Liupan Mountain Nature Reserve， Ningxia.