Objective To study the characteristics of shrub communities in the process of vegetation restoration and reconstruction in the burned areas of spruce-fir forest on the northeast edge of Qinghai-Tibetan Plateau, and clarify the ecological process of diversity pattern and maintenance mechanism of shrub communities in burned areas. Method In spatial instead of time method, the species composition characteristics, α species diversity and β species diversity of shrub communities in 5 a and 15 a of burned areas and understory shrub communities in unburned areas were studied.Result There are differences in plant species composition among shrub communities in burned areas after 5 a and 15 a of restoration, and understory shrub communities in unburned areas, There are 24 species of shrubs belonging to 17 genera in 11 families in the burned areas of 5 a, 17 species of shrubs belonging to 10 genera in 8 families in the burned areas of 15 a, and 35 species of shrubs belonging to 19 genera in the unburned forest areas. The species richness index and Pielou evenness index of 5 a and 15 a burned areas and unburned woodland, and the correlation between species richness index and Simpson index and Shannon-Wiener index of 5 a burned areas are not strong (P < 0.1 or P > 0.1),but the correlation between other indexes in the three communities was strong (P < 0.001 or P < 0.01). The species richness index restored 5 a burned areas > restored 15 a burned areas > unburned forest areas, the Shannon-Wiener index and Simpson index are all restored 15 a burned areas > unburned forest areas > restored 5 a burned areas, the Pielou evenness index 15 a burned areas > unburned forest areas > 5 a burned areas. The Species composition of shrub communities in restored 5 a and 15 a are the most similar, and the understory shrub layer species composition and recovery 15 a are more similar than recovery 5 a burn areasConclusion After severe forest fire disturbance, the species composition of spruce-fir forest on the northeast edge of Qinghai- Tibetan Plateau is different in different restoration time gradients. In a short time after the fire, the species diversity and dominance are low in the burned areas, and the species distribution was uneven. With the succession, the species richness began to decrease, and the species diversity and dominance increased, and the species distribution was relatively uniform. With the normal succession of the burned areas, the similarity of species composition between the shrub community in the burned areas and the unburned areas are increasing, and the shrub community in the burned areas are in the forward succession.

Objective To construct the maximum density-size line and explore the self-thinning rule of oak natural forest, the study aims to enrich the theory of population ecology and provide a theoretical reference for the management and control of forest stand density in natural forests.Method Using data from 265 continuous inventory plots of oak mixed forests in Hunan Province, the stand density index was improved. The applicability of Reineke density index and the improved density index in constructing the maximum density line of oak natural forests was evaluated using quantile regression and stochastic frontier analysis. The self-thinning rule of oak natural forest with different stand types were also analyzed.Result Compared with Reineke’s stand density model, the improved stand density model significantly reduced prediction errors (P<0.05). The improved stand density model, based on mean diameter at breast height and mean height of dominant tree species, could better interpret the meaning of self-thinning in forest stands. The stochastic frontier model was more objective and accurate in simulating the maximum density-size model, and the quantile regression method can also provide a valuable supplement. The self-thinning process of natural mixed forest was determined by the average diameter and the average height of dominant tree species. The larger the mean stand diameter was, the faster the rate of self-thinning was. The higher the average height of dominant tree species, the more plants could be accommodated. Moreover, the rate of self-thinning showed significantly different among different types of oak stands (P<0.05), and the oak pure forest showed a faster rate and a higher mortality. Conclusion The study of maximum density-size model and self-thinning rule can provide a quantitative basis for the identification of the self-thinning state of the oak natural forest, and help to improve the quality of the oak natural forest and grasp the dynamics of the self-thinning.

Objective Point cloud density is a critical factor affecting the cost of airborne LiDAR data acquisition and pre-processing. Therefore, exploring the influence of point cloud density on the estimation accuracy of forest inventory attributes can provide a reference for optimizing technical schemes for airborne LiDAR-based large-area forest inventory and monitoring. Method In this study, we used airborne LiDAR data and field plot data collected in a subtropical mountainous and hilly region in Guangxi, China. Firstly, the original point clouds with a density of 4.35 points·m⁻² were reduced to 4.0, 3.5, 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.2, and 0.1 points·m⁻² using a systematic thinning method, respectively, resulting in 11 plot-level point cloud datasets, including one full-density point cloud dataset and ten reduced-density point cloud datasets. Secondly, a paired sample t-test was used to analyze the differences in 12 LiDAR-derived metrics between reduced-density point clouds and full-density point clouds in four forest types (Chinese fir, pine, eucalyptus, and broad-leaved). Thirdly, using a multiplicative power model formulation with fixed variables and stable structure, the stand volume (VOL) and basal area (BA) were estimated using various density datasets of point clouds, respectively, and their goodness-of-fit statistics, including coefficient of determination (R²), relative root square error (rRMSE), and mean prediction error (MPE), were compared. Finally, a t-test was used to analyze the differences in the means of the estimates between the reduced-density point clouds and full-density point clouds. Result 1) When the point cloud density was low, the means of the 25^th, 50^th, and 75^th height percentiles (ph25, ph50, and ph75) of the reduced-density point clouds showed statistically significant differences from those of the corresponding variables of the full-density point clouds. However, when statistically significant differences were found for different variables in various forest types, the point cloud densities differed. There were no statistically significant differences in the means of mean point cloud height (H_mean) and coefficient of variation of point cloud height distribution (H_cv) between the reduced-density point clouds and full-density point clouds in all forest types, but there were statistically significant differences in the means of maximum height (H_max) of point clouds between the reduced-density point clouds and full-density point clouds for all forest types. 2) The means of canopy cover (CC) and 25^th density percentile (dh25) of the reduced-density point clouds were not statistically significantly different from those of the corresponding variables of the full-density point clouds for all forest types (except dh25 for broadleaf forests), but statistically significant differences existed for the 50^th and 75^th density percentiles (dh50 and dh75). 3) The means of the mean leaf area density (LAD_mean) of reduced-density point clouds were statistically significantly different from those of the LAD_mean of full-density point clouds in all forest types, and while the means of the coefficient of variation of leaf area density (LAD_cv) of reduced-density point clouds were significantly different from those of the LAD_cv of full-density point clouds when point cloud density was low. 4) The differences in the estimates of VOL and BA for different density point clouds were small among the forest types, and none of the estimates were statistically significantly different from each other. However, as the density of point clouds decreased, the R² of the estimation models for VOL and BA for fir, pine, and eucalyptus forests slowly decreased, and the rRMSE and MPE slowly increased, indicating that the estimation accuracy of forest inventory attributes gradually decreased. The R², rRMSE, and MPE of the estimation models for VOL and BA for the broad-leaved forests were not obviously affected by the change in point cloud density. Conclusion The decrease in the density of point clouds leads to an increase in the standard deviation of the LiDAR-derived metrics, which is the main reason for the decrease in the estimation accuracy of forest inventory attributes. In the operational forest resources investigation and monitoring, the airborne LiDAR point cloud density should be greater than 0.5 points·m⁻².

Objective Forest structure characteristic is an important index to evaluate forest ecological function, which can directly present the growth status of forest. It is not only the research object in the fields of forestry, ecology and geoscience, but also an important input parameter of many terrestrial ecological models. How to obtain the characteristics of large-scale forest structure effectively has important scientific research value. Based on MISR(multi-angle imaging spectro-radiometer) satellite remote sensing data and UAV(unmanned aerial vehicle) photogrammetry data, SGM(simple geometric optical model) and the optimization methods of GRG(generalized reduced gradient) were used to obtain the key structure information of Populus euphratica forest in Tarim River, so as to provide a new method for the quantitative study of forest remote sensing.Method Taking the typical riparian forest near Yingsu in the lower reaches of Tarim River as the study area, based on field investigation, UAV remote sensing aerial survey, multi-angle satellite remote sensing, the inversion of SGM is carried out, the process is divided into three steps: firstly, the multi-angle reflectance data and forest structure parameters of the train dataset are input into the SGM model as known fixed variables, and the coefficients of Walthall model are retrieved by GRG optimization algorithm. Secondly, the regression equation of Walthall model coefficients is established by using the AMBRAL model coefficients of the train dataset and the multi-spectral reflectance data of MISR AN camera. Thirdly, an regression equation of the Walthall model coefficient is used to obtain the soil background reflectance of the test dataset, and the structural parameters of the test dataset are retrieved by GRG nonlinear optimization algorithm, Finally, the accuracy is verified and evaluated by UAV measurement data.Result The tree height, crown diameter and density data extracted by OBIA (object based image analysis) technology were compared with the measured samples. It was found that the R² of the height, crown diameter, density obtained by UAV oblique photogrammetry between the field-measured value was 0.90, 0.84, 0.94 and RMSE(root mean square error) was 0.45 m, 0.68 m and 4.25 trees·hm^-2 respectively. Compares the SGM simulated value with satellite observation reflection value of the train dataset, the maximum value of R² is 0.99, the minimum value of R² is 0.72 and the mean value of R² is 0.92. The tree height and coverage obtained from the inversion of the train dataset are consistent with the reference value. R² reaches 0.99 and RMSE is 0.73%. The consistency of tree height is slightly poor, R² is 0.66 and RMSE is 0.61m. c₁ parameter of Walthall model has the greatest impact on FVC and tree height, followed by c₄, c₂ and c₃. c₁-c₄ have relative little effect on the change of density. By establishing the multiple linear regression equation between the reflectance of AN camera multispectral band and AMBRALS model coefficients with c₁-c₄, the c₁-c₄ parameters of the train dataset are predicted. Compared with the inversion values, the adjusted R² of c₁-c₄ parameters are 0.78, 0.98, 0.59 and 0.75 respectively. Compared with the UAV measured data on the 275 m² scale, the R² of linear models of FVC, tree height, density and crown diameter of Populus euphratica obtained by MISR multi-angle satellite remote sensing were 0.54, 0.47, 0.41 and 0.24 respectively, and the RMSE were 3%, 0.76 m, 112 trees and 0.31 m respectively; MRE(mean relative error) was 24.7%, 8.9%, 22.5% and 10% respectively. When the power function model is used, the R² of FVC, tree height, density and crown diameter are 0.80, 0.53, 0.55 and 0.30; RMSE is 1%, 0.4m, 33 trees, 0.16 m; MRE is 10%, 5%, 6%, 6% respectively.Conclusion The structural data of Populus euphratica forest obtained by UAV can be used as the calibration parameters of the model and the accuracy verification instead of the field-measured data. SGM model can well simulate the anisotropic reflection characteristics of observation samples. The accuracy of background reflection simulated by Walthall model has a great impact on the final inversion results of structural parameters. The combination of MISR multi-angle satellite remote sensing and UAV technology can obtain more accurate forest structure information on a regional scale.

Objective This study aims to improve the water and nitrogen (N) use efficiency in fast-growing and high-yield Populus tomentosa stands and to provide a theoretical basis for long-term water and N management. Method In a field experiment, four N levels (N0, N1, N2 and N3 represented 0, 101.6, 203.2 and 304.8 kg·hm^-2, respectively) with a single application cycle, and three irrigation levels (W1, W2 and W3 represented 45%, 60% and 75% of the lower limit of soil water content of field water holding capacity, respectively) were applied. The correlations between soil mineral nitrogen content, ammonia volatilization rate, and urease activity were investigated. Result During a single N application cycle, both NO₃^--N and NH₄⁺-N contents increased and then decreased with the depth of soil layer, and increased and then decreased with time. They reached the maximum values on the 7th and 3rd day after N application (26.64–62.34 mg·kg^-1 and 26.61–51.32 mg·kg^-1), respectively. The accumulative contents of NO₃^--N and NH₄⁺-N from 0 to 100 cm soil layers in the stand was 56.84–104.88 kg·hm^-2 and 33.53–53.63 kg^-1·hm^-2, respectively. Mineral N in the soil was mainly accumulated in the form of NO₃^--N, and the accumulated amount was significantly lower than that in farmland and orchards. The NH₄⁺-N content was relatively low and stable (except for the surface layer). The content and accumulation of soil mineral N were positively correlated with the applied N rates. The W3 treatment was more prone to cause NO₃^--N transport to deeper soil layers. Total amount of NH₃ volatilization was significantly and positively correlated with N and water application levels, and the NH3 volatilization mainly occurred within 10 d after N application, reaching a peak (0.96–3.15 kg·hm^-2d^-1) in 1–2 days after N application. The ammonia volatilization loss in a single nitrogen application cycle was 1.57–18.29 kg·hm^-2, with a loss rate of 14.05%–18.97%. Soil urease activity was significantly (P < 0.01) positively correlated with the N and water application levels, and increased and then decreased with the time, reaching the maximum value (3.14–4.48 mg·g^-1) in 3 days after N application. The partial correlation analysis showed that there was a significantly negative correlation between the NO₃^--N content and NH₄⁺-N content in the soil surface layer, and a significant positive correlation between NH₄⁺-N content and NH₃ volatilization rate.Conclusion N and water application levels significantly affect the dynamics of soil NO₃^--N, NH₄⁺-N, NH₃ volatilization characteristics and urease activity in P. tomentosa stand. In order to reduce NH₃ volatilization loss and NO₃^--N leaching risk in forest land, we suggest that N application rate is 203.2 kg·hm^-2, and the soil water content should be controlled at 60%~75% of the field water holding capacity.

Objective This study aims to explore the influence mechanism of environmental factors on the CO₂ concentration and δ¹³C dynamics in Larix gmelinii ecosystem, which would help to deeply understand the process and mechanism of carbon exchange in ecosystems, so as to provide reference for simulating and predicting the mutual feedback mechanism between global change and ecosystems, as well as for scientific assessment of carbon sink capacity of cold temperate forest ecosystems.Method The off-axis integral cavity output spectroscopy was used to perform continuous high-frequency observations to the CO₂ concentration and δ¹³C value at different heights in different phenological periods of L. gmelinii ecosystem, and thereby analyze the relationship between environmental factors and CO₂ concentration. Result 1) The CO₂ concentration at different heights of L. gmelinii ecosystem showed a single peak variation in the growth season and daily scale. The peak value appeared in the leaf spreading period (522.34 μmol·mol^-1) and at night (782.81 μmol·mol^-1), respectively. The valley value appeared in the leaf falling period (406.07 μmol·mol^-1) and at noon (379.72 μmol·mol^-1), respectively. The δ¹³C variation was opposite to CO₂ concentration. 2) The CO₂ concentration decreased with the increase of vertical height, while δ¹³C increased with the increase of vertical height. The CO₂ concentration and δ¹³C at different heights had obvious stratification. The increase of atmospheric stability at night (Ri ≥ 0.083) increased the difference inside and outside the canopy. 3) On the 0.5 h scale, air temperature (T_a) was the main factor affecting the variation of CO₂ concentration at different heights in day and night (0.714 < PC < 1.288). On a daily scale, soil temperature (T_s5) in 5 cm depth layer was the main factor determining the variation of CO₂ concentration at different heights in the growing season (0.473 < PC < 0.718). Conclusion There is a very significant negative correlation between δ¹³C and CO₂ concentration at different heights of L. gmelinii ecosystem. The increase of atmospheric stability at night aggravates their layering phenomenon. The influence level of soil factors on the variation of CO₂ concentration at different heights in different phenological periods of L. gmelinii ecosystem is greater than that of meteorological factors. The soil temperature has greater influence on the variation of CO₂ concentration than the soil water. The study area is located in a sensitive area to global climate change. Frozen soil is an indispensable environmental factor for forest vegetation in this area. Global warming will have a significant impact on the carbon exchange process of L. gmelinii ecosystem through direct temperature effect and indirect changes in soil physical and chemical properties and biological processes.

Objective This study aims to explore the resuscitation of uncultured endophytic bacteria in Eucalyptus urophylla, so as to lay a foundation for the application of resuscitated endophytic bacteria to control eucalypt bacterial wilt. Method Pseudomonas putida WCS358r, P. fluorescens WCS374r and their siderophore-minus mutants JM218, Mut2, and P. fluorescens WCS417r and its lipopolysaccharide-minus mutant WCS417OA-(B4) were used as the resuscitation strains. In a gnotobiotic system, sterile E. urophylla seedlings were co-cultured with the different resuscitation strains to study the revitalization of uncultured eucalypt endophytic bacteria, and the resuscitated endophytic bacteria were identified by rifampicin assay, Gram staining and molecular methods.Result After co-culture of homologous E. urophylla seedlings with three exogenous applied bacterial strains WCS358r, WCS374r and WCS417r, resuscitated bacteria were isolated from E. urophylla seedlings treated with strains WCS358r and WCS417r, and it was found that strain WCS358r was able to colonize in the seedlings of E. urophylla, and resuscitate two Bacillus amyloliquefaciens strains in different parts of eucalypt seedlings. WCS417r was able to colonize in the root, stem and leaf of E. urophylla, and the colonization amount in the roots and stems was significantly higher than in the leaves, but it was unable to resuscitate the uncultured endophytic bacteria in E. urophylla seedlings. After co-culture of E. urophylla seedlings germinated from different seeds with WCS358r, different endophytic procaryotic organisms, such as Streptomyces sp., B. thuringiensis, B. amyloliquefaciens and other Bacillus spp., were resuscitated. It was found that WCS358r could colonize in root and stem, and the colonization number followed a decreasing pattern from root to stem, and failed to colonize in leaf. After co-cultivation of different concentrations of exogenous bacterium WCS358r with homologous eucalypt seedlings, the results showed that strain WCS358r at the density of 10⁷ CFU·mL^-1 or less did not resuscitate the non-cultured endophytic bacteria in E. urophylla. When the population density of bacterial suspension reached 10⁹ CFU·mL^-1, it did not only colonize in E. urophylla but also resuscitate B. amyloliquefaciens and Bacillus sp. The three mutants JM218, Mut2 and WCS417OA-(B4) could neither colonize in E. urophylla nor resuscitate uncultured endophytic bacteria in E. urophylla after co-cultured with the homologous E. urophylla seedlings. Conclusion The resuscitation of uncultured endophytic bacteria in E. urophylla is influenced by the species and their densities of exogenous applied bacteria, and seeds of E. urophylla. The colonization in E. urophylla of exogenous bacteria is mostly influenced by the strains of bacteria. The siderophore and lipopolysaccharide mutants of exogenous bacteria lose the abilities to resuscitate uncultured bacteria and colonize in E. urophylla seedlings, respectively, demonstrating that the bacterial siderophore is the key factor of exogenous bacteria for resuscitating the uncultured endophytic bacteria, and the bacterial lipopolysaccharide is the key factor of exogenous bacteria to colonize in E. urophylla seedlings.

Objective Based on the field trial on the triploid progeny produced from crossing between tetraploid and diploid birches, several superior parents and their combinations were selected with excellent growth and wood properties. This study aims to provide a scientific basis for parent selection in establishing birch seed orchards. Method This experiment was conducted in a field trial forest of 10-year-old progeny of 40 full-sib families derived from different parental combinations. Tree height (H), diameter at breast height (DBH), single tree volume, wood basic density, cellulose content, hemicellulose content, lignin content, fiber aspect ratio traits and retention rate of planted trees were measured respectively. SPSS 22.0 and WinNCII were used analyze variance, general combining ability (GCA) and specific combining ability (SCA) of each trait. Membership function and principal component analysis (PCA) were also used to identify the best overall performance of parental combinations. Result 1) Except the traits of wood basic density and tree retention rate, the variance of parental combination, GCA and SCA of remaining seven traits reached significant or extremely significant levels. The coefficient of variation of the seven traits ranged from 6.34% to 55.29%, and the broad-sense and narrow-sense heritability were between 38.83%–73.72% and 22.23%–68.48%, respectively. Some traits had significant variation and strong genetic ability among families, indicating that the selection opportunities were expected in this study. 2) Further analysis on the seven traits showed that the differences in the GCA and SCA effects of tree height, DBH, volume, lignin content and fiber length/width reached significant or extremely significant levels. The additive effect of parents was significant on traits of DBH, volume, cellulose hemicellulose content and fiber length/width ratio. By comparing the additive effect of maternal parent and paternal parent, it was found that the maternal parent had much greater effect on the observed traits than the paternal parent effect. The variance component of maternal parent was 43.11%–94.15%, while that of paternal parent was 0–4.86%. It was found that the lignin content and tree height traits were strong controlled by SCA effect only, which accounted for 52.03% and 44.55%, respectively. 3) Based on the combined analysis of membership function and PCA with GCA and SCA effect, F4, F7 and F10 were selected as superior male parents and Q19 with Q103 as superior female parents for growth or wood fiber traits, of which the volume genetic gain of Q103 reached 8.60%. Q33×F1, Q103×F10, Q13×F12 and Q19×F11 were selected as superior parental combinations, of which the volume genetic gain of Q33×F1 and Q103×F10 were 16.33% and 15.62% , respectively. Conclusion The main contributor to the performance of traits in this study is the additive effect of birch maternal parents. Based on growth and wood property measurements of birch triploid families and statistical analysis, three excellent male parents, two female and four superior parental combinations have finally been selected. This study provides a scientific basis for the establishing next generation birch seed orchard.

Objective This study aims to explore the early growth and carbon sequestration potential of cypress clones and families, so as to lay the foundation for the selection and breeding of fast-growing and high carbon sequestration varieties. Method The 9-year-old clonal and family test forests established in Kaihua County Forest Farm, Zhejiang Province, were used as materials to analyze the variation pattern of growth traits, analyze the distribution difference of biomass and carbon content, construct the allometric growth equation of carbon content, and analyze and estimate the carbon fixation potential. Result The growth advantage of cypress clones was obvious, and the average tree height, DBH and individual volume were 47.81%, 28.39% and 120.83% higher than those at the family level. There were significant differences in tree height, diameter at breast height and individual volume between clones and families (P<0.01). Regardless of the level of families and clones, diameter at breast height and tree height were significantly positively correlated with biomass and carbon content, and had no significant linear relation with carbon content rate. The proportion of biomass allocation of cypress trunk was the highest, with the highest proportion of carbon content, while leaves had the highest carbon content rate. Clones maintained their growth advantage mainly by sacrificing the biomass distribution of coarse roots (3.45% lower than that of families), increasing the biomass of branches (5.55% higher than that of families) and fine roots (1.34% higher than that of families). The fitted carbon content model (lnTBS=k₀+k₁lnD+k₂lnH+k₃lnUBH) had the best prediction effect with tree height, DBH and the height under branches as independent variables (except for the carbon content of clone roots). The estimation accuracy was able to be improved by including the height under branches as independent variables in the model. According to the selection rate of 20%, it was estimated that the genetic gain of carbon content in the clonal test forest was 51.48%, and that in the family test forest was 16.14%. Six clones and families with fast growth and excellent carbon fixation were selected by combining the volume traits. Conclusion Cypress clones have higher carbon fixation capacity than families, and their carbon fixation capacity can be improved by screening good growing genotypes. At the early growth stage, the height under branches as an important evaluation index is used to construct the allometric growth model, which is helpful to improve the estimation accuracy of plant carbon content. In combination with the growth characteristics, clones and families with fast growth and high carbon content can be screened to improve the carbon fixation potential of cypress.

Objective Bursaphelenchus xylophilus (pine wood nematode) has a short generation, large egg production, and strong population reproductive ability. At 25 ℃, it only takes 5 days for pine wood nematodes to complete a generation, and a pair of nematodes can reproduce 200 000 offsprings within 20 days, showing that the growth and development speed is very fast. In this paper, by studying the spatiotemporal expression characteristics and biological functions of B. xylophilus Bxy-cul-1, the role of this gene in the growth and development of B. xylophilus is clarified, so as to provide a theoretical basis for exploring specific measures for controlling nematode population growth from the perspective of growth and development.Method Based on the genome data of B. xylophilus, primers were designed and the Bxy-cul-1 gene was cloned. Bioinformatics analysis such as sequence, phylogenetic analysis and protein structure prediction of Bxy-cul-1 was performed. Real-time quantitative PCR technology and in situ hybridization technology were used to explore the expression level and expression site of Bxy-cul-1 gene in various instars of B. xylophilus, to clarify its spatiotemporal dynamic expression characteristics. RNA interference technology was used to explore the role of this gene in nematode growth and development. Result The results of bioinformatics analysis showed that the CDS of Bxy-cul-1 gene was 2 292 bp in full length, encoding 763 amino acids, belonging to the Cullin protein family. The results of in situ hybridization showed that Bxy-cul-1 gene was expressed in different developmental stages of B. xylophilus, expressed in the whole embryo in the embryonic stage, widely expressed in the second instar, and mainly in the intestine and body wall muscles and tail in the third and fourth instars. In the adult stage, the gene was expressed in oocytes and vulva of females, and abdomen, copulatory spines and tail of males. The results of real-time quantitative PCR showed that the expression level of Bxy-cul-1 gene was the highest in the second instar stage of B. xylophilus, followed by the embryonic stage, and decreased in turn in the third instar, fourth instar and adult stages. After interference of B. xylophilus embryos, it was found that the hatching rate of B. xylophilus embryos decreased by 10.44%, and most of the unhatched embryos stayed at the end of the first instar, and the abdomen of the worm was deformed and swollen, and the worm was not able to break through the egg shell. The instar larvae also appeared deformed, the deformed worms was not able to stretch normally, the middle esophagus glands were abnormally enlarged, and the tail curled up. Interference of the 2nd instar larvae resulted in a significant decrease in the viability of the worm body, with the head swing frequency dropped about 5 times every 30 seconds. Some 2nd instar larvae also appeared deformed, such as short and small body shape, abnormal enlargement of the head and esophageal glands, twisting of the tail and abdomen, and inability to normally move, and hence the worms could not move normally. The results of the developmental progress experiment showed that after silencing the Bxy-cul-1 gene, the developmental progress of B. xylophilus slowed down, and the second instar in the interference group developed to adult 4 days later than the control group.Conclusion Bxy-cul-1 gene of B. xylophilus is a member of the Cullin protein family, and its expression level and expression site are specific at different developmental stages. Silencing this gene can reduce the hatching rate of B. xylophilus embryos and cause deformities, and also reduce the movement ability and developmental progress of B. xylophilus, indicating that the Bxy-cul-1 gene plays an important role in the growth and development of B. xylophilus.

Objective In this study, the effects of different pruning treatments on the trunk growth, crown changes and trunk shape of young forests of Michelia macclurei, Castanopsis hystrix and Castanopsis fissa were investigated to select their best pruning methods respectively, so as to provide theoretical basis for their pruning techniques.Method The pruning experiment was carried out in 5-year-old pure forests of M. macclurei, C. hystrix and C. fissa. Three pruning treatments and one control were set up: pruning 1/3 (trim the branches below 1/3 of the tree height), pruning 1/2 (trim the branches below 1/2 of the tree height), pruning 2/3 (trim the branches below 1/2 of the tree height), CK (no pruning). After 4 years of pruning, the effects of different pruning treatments on trunk growth, crown changes and trunk shape conditions of M. macclurei, C. hystrix and C. fissa were measured and determined. The analytic hierarchy process was used to comprehensively evaluate their form quality of different pruning treatments.Result Different pruning treatments had no significant effects on the height, DBH, volume and growth percentage of M. macclurei. Pruning 2/3 reduced the DBH, DBH growth percentage and volume growth percentage of C. hystrix. Pruning 1/2 and 2/3 reduced the tree height growth percentage of C. fissa, and pruning 2/3 reduced the volume growth percentage of C. fissa. With the strengthening of pruning degree, the under-branch height and dead branch height of M. macclurei, C. hystrix and C. fissa became higher, while the height of tree crown moving upward and the depth of dead branch layer became smaller. Pruning 1/2 reduced the crown diameter of C. hystrix, and pruning 1/3, 1/2 and 2/3 reduced the crown diameter of C. fissa. With the strengthening of pruning degree, the tree tapering, number of branches and probability of bifurcation of M. macclurei and C. hystrix decreased, while the bifurcation height increased. Pruning 1/3, 1/2 and 2/3 reduced the tree tapering, number of branches and probability of bifurcatione of C. fissa. The comprehensive evaluation scores of different pruning treatments were as follows: for M. macclurei, pruning 2/3 > pruning 1/2 > CK > pruning 1/3; for C. hystrix, pruning 1/2 > pruning 2/3 > pruning 1/3 > CK; for C. fissa, pruning 1/3 > pruning 1/2 > pruning 2/3 > CK.Conclusion The compensation threshold of different tree species is different. At the early-aged stage, the compensation threshold of M. macclurei is higher than pruning 2/3, while that of C. hystrix and C. fissa is lower than pruning 2/3. If pruning exceeds the threshold, it will reduce the growth of tree height or DBH, and ultimately reduce the growth of volume. Different pruning treatments have no significant effect on the crown diameter of M. macclurei during the early age. Pruning 1/2 significantly reduces the crown diameter of C. hystrix during early age, and pruning 1/2 and 2/3 significantly reduced the crown diameter of C. fissa during early age. The under-branch height and dead branch height are characterized that the greater the pruning intensity, the higher the height. Pruning can significantly improve the forest sanitation, outturn percentage, trunk shape quality and form quality of M. macclurei, C. hystrix and C. fissa during early age. At the early-aged stage, the best pruning treatment for M. macclurei is pruning 2/3, for C. hystrix is pruning 1/2, and for C. fissa is pruning 1/3.

Objective Based on indoor simulation of ignition, the characteristics of smoldering of sub-surface fires in wind-caused disaster area of Changbaishan Mountain were mastered, and a probability model was established to provide a theoretical basis for the prevention and control of sub-surface fires in this area. Method The sub-surface fuel in the Changbai Mountain wind disaster area with different recovery degrees (recovery area, semi recovery area and non restored area) was used as the research object, and different moisture content gradients (0%, 5%, 10% and 15%) of sub-surface fuel were set up. Through underground fire simulation ignition experiments, the characteristics of smoldering temperature and spreading rate of sub-surface fires with different recovery degrees were mastered. A two-factor analysis method was used to determine the influence of different recovery degrees and moisture contents on the smoldering peak temperature and spread rate of sub-surface fires. A probability prediction model of smoldering of sub-surface fires in wind disaster area was established based on logistic regression model by using two factors of moisture content and depth. Result The limit moisture content of smoldering of sub-surface fires in the recovery area and non restored area from wind disaster in Changbai Mountain was 10%, and the limit moisture content of smoldering of sub-surface fires in the semi recovery area was 15%. The smoldering temperature of sub-surface fires with different recovery degrees was lower, and the self-sustaining combustion time increased with the increase of moisture content of fuel, and the extinction time was the shortest under the condition of high moisture content. The smoldering spread rate of sub-surface fires was slow, with the fastest being only 3.25 cm·h^–1. The interaction of different recovery degrees and moisture contents on the smoldering peak temperature of sub-surface fires was significantly different, among which there was a significant difference in the peak temperatures of different recovery degrees between the conditions of 0% and 5% moisture content, and there was a significant difference in the peak temperatures of different moisture contents among the differently restored area. The spread rate of smoldering of sub-surface fires was affected by the recovery degree and moisture content respectively, but there was no significant difference in the impact of their interaction on the spread rate. The established prediction model of smoldering probability of sub-surface fires had good fitting effect and high prediction accuracy (P<0.01，AUC=0.917). Conclusion The smoldering temperature of sub-surface fires in the recovery area and the semi recovery area of Changbai Mountain wind disaster area is relatively high, with the highest temperature of 640.57 ℃ and 602.02 ℃, respectively. The smoldering spread rate of sub-surface fires in the nonrestored area is the fastest （3.25 cm·h^–1）. The probability prediction model of sub-surface fires based on logistic regression has high prediction accuracy.

Objective Xichang City is a high-risk area of forest fire in China, and establishing a forest fire obstructing network is the most effective way to prevent and control forest fires. According to the relevant standards and specifications, the regional natural geographical elements and existing fire prevention infrastructure that can comprehensively affect the occurrence and development of forest fires were studied. With the help of GIS spatial analysis, a suitable spatial location of the integrated forest obstructing network is proposed to provide a reference for improving the forest fire obstructing network in Xichang City.Method By analyzing the forest fire risk level, the effective obstructing network density and control area were determined. The geostatistics and hydrological analysis, SVM (support vector machine), and factor correlation analysis were used to obtain main factors affecting the layout of the forest fire comprehensive obstructing network. Then, based on various factors and current conditions, in terms of the principles of efficiency, ecology and cost, the cost factor weight analysis was used to quantitatively select the location for the spatial layout of the comprehensive obstructing network. Finally, the potential for spatial optimization was analyzed based on natural geographical factors and existing fire prevention and obstructing facilities.Result 1) During the forest fire prevention period in Xichang City, the highest fire risk level is set as Level I. The effective density of the comprehensive obstructing network should be greater than 17.88 m·hm^–2, and the control area should be less than 500 hm². The existing obstructing does not meet the standard requirements. 2) The factors selected through research are closely related to the layout of forest fire obstructing. Multi factor characteristics are taken into consideration to make the layout of the obstructing network more comprehensive and complete. 3) The natural obstructing network is suitable for layout on ridges, valleys, rivers, and waters that meet the width and orientation, and mainly distributed in the southeast and northeast mountains of Xichang City and around Lushan Mountain. The biological obstructing network can be arranged at forest edges and in open spaces suitable for afforestation, and mainly distributed in the periphery and interior of large areas of forests and around forest settlements. The engineering obstructing network is suitable for low cost areas such as low wind speed, slope, and bare land with low altitude. 4) The suitable area of the comprehensive obstructing network in Xichang City can basically cover the existing forest land, and effectively block flammables from concentrated forest area. The existing forest fire obstructing layout in the northwest and southeast regions is relatively weak, and the construction of the comprehensive barrier network should be strengthened according to local conditions.Conclusion The layout and function of the existing fire obstructing network in Xichang City are not perfect, and a scientific obstructing system should be established by comprehensively considering various relevant factors and actual conditions. This study quantitatively and visually analyzes the layout of the comprehensive obstructing network in Xichang City, which has practical significance for improving the regional fire prevention and extinguishing capacity, maintaining ecological security, and has certain reference value for related networks planning.

Objective This study aims to promote the coordinated and sustainable development of regional forest eco-nature-economic-society complex system. Method Based on 28 indexes data of the forest ecology-nature-economy-society complex system in Changsha City from 1980 to 2020, the coupling degree and coupling coordination degree of the regional forest ecology-nature-economy-society complex system were measured and analyzed by using entropy model, coupling degree model and coupling coordination degree model. Result From 1980 to 2020, the coupling degree of forest ecology-natural environment-economy-society complex system showed an "inverted U shape", with an overall upward trend. In Changsha City, the coupling coordination degree between forest ecosystem, natural environment system and social system showed an "S-shaped" increasing trend year by year, and the coupling coordination degree between forest ecosystem and economic system showed an "N-shaped" trend, with first increasing, then decreasing and then increasing again. However, after 2015, the rising trend of the coupling coordination degree of all systems slowed down. Conclusion From 1980 to 2020, the coupling coordination degree of the forest ecosystem-natural environment-economic-social complex system and its subsystems is not high. At present, it is mainly at the moderate coordination stage, basically in the transition period from moderate coupling coordination to high coupling coordination, and there is still a lot of room for improvement. From 1980 to 2020, the coupling coordination degree of forest ecosystem-natural environment-economy-society complex system and forest eco-system with natural environmental system, socio-cultural system and economic system in Changsha City has increased to different degrees, but the rising trend has slowed down. It is suggested that the coupling and coordination degree of regional forest ecosystem should be improved from three aspects: constructing fine natural environment subsystem for regional forest growth, establishing high-quality and sustainable economic development subsystem, and building social subsystem for supporting reasonable and green consumption, to realize the sustainable development of regional forest ecology-nature-economy-society complex system.