Objective: In order to explore water use strategies and competition/complementarity relationships of arbors and shrubs under different magnitudes of rainfall in the same stand, we analysed the soil water use resource and water niche characteristics of dominant species in arbor layer and shrub layer in the Robinia pseudoacacia and Pinus tabulaeformis plantations in the Loess region of Western Shanxi Province, it is expected to provide a theoretical basis for vegetation restoration and management in the Loess region. Method: We collected the xylem of upper story arbors (R. pseudoacacia and P. tabulaeformis) and lower story shrubs (Rosa xanthina and Abelia biflora), the soil of 0-10, 10-20, 20-30, 30-40, 40-60, 60-80, and 80-120 cm layers and rainfall samples to study¹⁸O characteristics and dynamic changes before and after rainfall events. The MixSIAR model was adopted to calculate the contribution rate of soil water at different soil layers to different plant species, and the niche width and niche overlap were calculated using the Levins index and Levins overlap formula. Result: The results showed that the soil water content, ¹⁸O of soil water, water absorption depth of trees and shrubs, and niche characteristics of water were affected by rainfall, but the impact and duration of different rainfalls were different. Before and after 12.7 and 33.4 mm precipitation, P. tabulaeformis and the understory shrubs R. xanthina mainly took water from 0-80 cm soil layers, but the utilization ratio of 0-40 cm soil water after rainfall was significantly higher than that before rainfall. The rainfall of 3.1 mm had no significant effect on the water use of R. pseudoacacia and A. biflora. After 106.6 mm precipitation, R. pseudoacacia increased the absorption proportion of 0-40 cm soil water, but it had a time lag. A. biflora responded quickly to rainfall, it increased the absorption proportion of 0-40 cm soil water to 49.3%-62.5% after rainfall. We also found that the water niche breadth of upper story trees kept stable during the study period, but that of lower story shrubs changed with rainfall and soil water content; different magnitudes of rainfall were able to change the niche overlap degrees. Conclusion: Except for rainfall of 3.1 mm, the water use strategies and water niche characteristics of the upper story trees (P. tabulaeformis and R. pseudoacacia) and the lower story shrubs (R. xanthina and A. biflora) in the same community were different at different rainfall levels. Our research suggested that the influence of rainfall on the niche width of the lower story shrubs was greater than that of the upper story trees. The water use strategies of P. tabulaeformis was similar to the lower story shrub R. xanthina; R. pseudoacacia and its lower story shrubs A. biflora had different water use strategies. For vegetation restoration, deep-rooted plants can be planted in combination with shallow-rooted plants to reduce water competition.

Objective: Due to the special geographical location, the ecological environment of alpine region in Qinghai Province is fragile and the growth of vegetation is poor. The objective of this research was to investigate seasonal variation and vertical distribution of fine root biomass and nutrient storage of typical plantations in this region. The result would provide a theoretical basis for vegetation restoration and plantation management in alpine region in Qinghai Province. Method: Four typical plantations namely Betula platyphylla, Populus cathayana, Larix principis-rupperchii, and Picea crassifolia were selected in the Taergou watershed of Datong County, Qinghai Province. Samples of fines roots in 0-60 cm soil layer were collected from May to October in 2019 from each plantation type. The fine root biomass and their C (carbon), N (nitrogen), and P (phosphorus) contents were analyzed. We used variance analysis to explore the effect of seasons, plantation types and soil layers on fine root biomass and nutrient storage. Result: During the growing season, the fine root biomass of B. platyphylla, P. cathayana, L. principis-rupperchii, and P. crassifolia in the 0-60 cm soil layer was 7.63, 6.89, 6.11, and 19.31 t·hm^-2, respectively. The fine root biomass of P. crassifolia was significantly higher than that of the other plantations. The fine root biomass of the four plantations were all decreased in the order of autumn > summer > spring, with significant difference between seasons (P < 0.05). With the increase of depth of the soil layer, the fine root biomass of the four plantations decreased exponentially. Fine root biomass mainly concentrated in the surface soil layer (0-20 cm), accounting for more than 68% of the total for all the four plantations. The fine root nutrient content of broad-leaved forest was relatively higher than that in coniferous forest, indicating that broad-leaved forest needs more nutrients for its growth. The fine root C content of the four plantations were all decreased in the order of autumn > summer > spring, while the fine root N and P contents in autumn were significantly higher during the growing season (P < 0.05). In vertical variation, the fine root nutrient content generally showed a trend of decreasing with the increase of soil depth. The fine root nutrient storage of P. crassifolia was significantly higher than that of the other species during the growing season. The fine root nutrient storage was the highest in autumn. Conclusion: The fine root biomass, fine root nutrient content and storage of the four plantations in the alpine region of Qinghai Province had significant seasonal variation and vertical distribution pattern. The fine root biomass in autumn was the highest. The fine roots were mainly concentrated in the surface soil layer and decreased with the depth of soil layer, showing an obvious property of surface-aggregation. The seasonal variation and vertical distribution of fine root C, N, and P storage were consistent with the fine root biomass. Among the four plantations, the fine root C, N, and P storage of P. crassifolia were relatively high. Therefore, we suggested that the plantation management in this area should be combined with seasonal characteristics. It is important to promote the growth and development of fine roots by reasonable management measures in the early growing seasons, and to protect the accumulation of surface fine roots in order to ensure vegetation resilience can be improved.

Objective: Excessive nitrogen addition can restrain the leaf photosynthesis and growth of woody plants. However, the underlying ecophysiological mechanism is still not very clear, which is important for precision fertilization to seedlings and plantation. Poplar (Populus spp.) is an important afforestation species and biological model tree. This study aims to investigate the photosynthetic and chlorophyll fluorescence characteristics, nonstructural carbohydrate (NSC) and nitrogen distribution of hybrid poplar seedlings under nitrogen addition for 2 consecutive years, in order to reveal the ecophysiological mechanism of trees in responding and adapting to nitrogen addition. Method: In this study, the potted cuttings of P. × euramericana 'Zhongjin7' were used as experimental materials, NH₄NO₃ was used as nitrogen source and 4 gradients (CK: 0 g·plant^-1a^-1, N3: 3 g·plant^-1a^-1, N6: 6 g·plant^-1a^-1, N9: 9 g·plant^-1a^-1) were set. After nitrogen addition for 2 years, changes of leaf photosynthetic characteristics, organ biomass accumulation, non-structural carbohydrate storage and distribution were investigated. Result: After nitrogen addition for consecutive 2 years, the nitrogen content and chlorophyll content in leaves and roots significantly increased, stomata became smaller but higher density, transient water use efficiency remarkably increased, but photosynthetic nitrogen use efficiency continuously decreased. Under moderate and low dose nitrogen addition, the net photosynthesis (P_n) of leaves on top twig was suppressed by sink and high carbohydrate feedback inhibition. But the P_n of lateral branch leaves was higher than that of the control. Under high nitrogen addition, P_n and starch content were significantly decreased, but with actual fluorescent quantum yield and electron transport rate increased significantly, suggesting that photorespiration and other processes supplied large amount energy for nitrate reduction and assimilation. Nitrogen addition continued to promote lateral branch growth and weaken the apical dominance. Under N9 conditions, the starch content in main stem decreased with a lower biomass, which maybe due to the source inhibition of P_n. The root drymass and biomass distribution percentage of N9 were no significantly different with those of N3 and N6. The results of organ growth, and carbon and nitrogen distribution implied that the decline of aux in synthesis and transport might play an important role in whole plant carbon and nitrogen relationships under excessive nitrogen addition. Conclusion: Nitrogen addition with moderate and low doses can significantly enhance carbon assimilation of leaves on the lateral branch and increase plant growth of whole poplar seedlings, with a sink limit on leaf net photosynthesis. But leaf photosynthesis may be inhibited by nitrogen assimilation under high dose nitrogen addition, with a declined apical dominance. And whole plant biomass accumulation could be restricted by source.

Objective: This study aims to explore the changes of respiration pathways of postharvest moso bamboo (Phyllostachys edulis)shoot and the effects of high concentration oxygen (H, 90%O₂+10%N₂) treatment on the respiration, in order to reveal the respiration and aging mechanisms of bamboo shoots and provide theoretical underpinnings of bamboo shoot preservation. Method: The 3-meter bamboo shoots were unexcavated and placed in the atmosphere (A, 21%O₂+79%N₂) and High-concentration oxygen environments(H, 90%O₂+10%N₂)in room temperature, respectively. The aging and decay of moso shoots and its ultrafine sections were examined. The respiration rate, activities of key enzymes involved in respiration metabolism were analyzed, including pyruvate kinase (PK), succinate dehydrogenase (SDH), glucose 6-phosphatedehydrogenase (G-6-PDH) and 6-phosphogluconate dehydrogenase (6-PGDH).Thekey metabolic substrates and metabolites such as nicotinamide adenine dinucleotide (NAD), nicotinamide adenine dinucleotide reduced (NADH), nicotinamide adenine dinucleotide phosphate (NADP) and nicotinamide adenine dinucleotide phosphate reduced (NADPH)) were measured, to study the respiration change sof the postharvested moso shoot and the impact of H treatment on them. Result: The mitochondrial structure in the basal part of moso shoots at the slow-growing stage was compact with a lot of cristae. At the fast-growing stage, the mitochondrial structure in the middle part of moso shoots appeared swollen vacuoles withless cristae. During the storage, the number of mitochondria in the shoots with air treatment decreased gradually and the vacuoles swelled on Day 4, but the number of mitochondria by hyperoxia treatment was significantly higher than that by air treatment. In the first 4 days, the oxygen contents in shoot bodies in both A and H treatments remained at a low level and showed little difference with each other. While the oxygen level increased drastically in Day 4-6. On Day 6, the oxygen content of shoot bodies with H treatment was 1.5 times of that withA treatment. The change trendof oxygen content was in accord with the rate of aging and decay. In both A and H treatments. The ethanol contents in moso shoots treated with A and H showed a "slow-fast-slow" increasing pattern. The ethanol content showed no significant difference between the two treatments and the ethanol contents in moso shoots treated with H did not decline significantly. In A treatment, The respiration rate of shoots treated with A decreased gradually, and the enzyme activities of SDH, PK, G-6-PDH and 6-PGDH increased. The content of NAD, a key substrate of glycolysis (EMP) and tricarboxylic acid cycle (TCA cycle), increased initially and decreased later, and the content of NADH increased gradually. The content of NADP, the key substrate of pentose phosphate pathway (PPP), decreased, but the content of NADPH increased. In H treatment, the respiration rate and the activities of key respiration-related enzymes increased significantly (P < 0.05), but the contents of NADH and NADPH, the key metabolites of respiration, significantly decreased (P < 0.05). Conclusion: The respiration pathways of postharvested moso shoots are definitely affected by the ambient oxygen concentration. In A treatment, the aging process of the moso shoot is mainly attributed to anaerobic respiration, not aerobic respiration. EMP, TCA and PPP pathways are changed alternately in aerobic metabolism of postharvested moso shoot. PPP pathway is dominant in Day 0-2, EMP and TCA peaked in Day 2-4, and all three pathways almost stopped in Day 4-6. In H treatment, moso shoot relies primarily on aerobic respiration, supplemented with anaerobic respiration.TCA and PPP metabolic processes are promoted, but anaerobic respiration is inhibited. It has been found that H treatment deterres the aging and decay of postharvested moso shoots by increasing respiration rate, enhancing PPP and TCA and lowering the ethanol content in moso shoot.

Objective: This study aims to explore the impact of flower traits and mating system on sexual reproduction of Acer griseum, an endangered species endemic in China, by investigating the possible causes of low seed setting rate. This study would lay a theoretical foundation for formulating effective measures to improve sexual reproduction, in order to alleviate the current contradiction between supply and demand of seedlings. Method: In this study, the cultivated A. griseum was targeted, and the flowering dynamics, floral traits and mating system were investigated through phenological observation, flower morphological characteristics determination, calculation of outcrossing index (OCI) and pollen-ovule ratio (P/O), and determination of pollen vitality and stigma receptivity. An artificial pollination and bagging experiment was carried out to explore the mating system. Result: 1) The sex expression of A. griseum florets was complicated and the florets were divided into two types based on their functions: male floret and female floret. Male florets were divided into male floret type Ⅰ and male floret type Ⅱ according to the degree of pistil degeneration. The male floret I only had stamens, while male floret Ⅱ had stamens and vestigial pistil. The length of stamens was much longer than that of the pistils. They were both male due to lack of ovary. Female florets were pseudohermaphrodite. The stigmas were longer than those of the anthers. Throughout the opening process, the stigmas were able to make curving movement, while the anthers were not dehiscent and did not release pollens. 2) The flowering process for one floret could be divided into five periods: bud stage, budding, anther or stigma appearing, blooming and withering. It took an averaged time of 7.6 days for male florets from opening to shedding, while the averaged time for female flowers from opening to fruiting was 11.6 days. The cyme usually consisted of three florets. In the inflorescences that were composed of male and female florets, the female florets usually bloomed earlier than male florets. 3) A. griseum bloomed once a year in April. Generally, the flowering lasted about 19.5 days. Protandry and protogyny coexisted for an individual tree and there was a certain overlapping time for the opening of male florets and female florets. The number of female florets was more than that of male flowers on an individual tree with the mean ratio of about 3.71∶1. 4) The duration of pollen viability was relatively short. When the pollen was stored at room temperature and dry, the maximum viability of pollens reached 63.86%±5.35% within 24 hours and then decreased to 1.03%±0.13% after 24 hours, almost losing viability. It indicated that pollens could keep their viability for a short time at room temperature. The stigma of female florets became receptive when it was out of the corolla before florets blooming. The receptivity of stigma reached its highest at full open and maintained throughout the entire opening process of female floret. Male flower pollens had viability during stigma fertile period of female florets. 5) There were 45 900-58 900 pollens for each male floret and 4 ovules of each female floret. The P/O was 3 093-3 969 based on the ratio of male and female floret per plant, and the OCI was 4. Combining the results of artificial pollination, mating system of A. griseum was facultative outcrossing and partially self-compatible, thus pollinators were necessary for the pollination process. Acer griseum showed a strong parthenocarpic tendency. Conclusion: The flower of A. griseum is functionally unisexual, monoecious and incomplete dichogamous. Its mating system is facultative outcrossing with low pollination efficiency. It shows strong parthenocarpy tendency. All the above traits are the important reasons for its low seed setting rate.

Objective: Membrane steroid-binding protein (MSBP) is a type of membrane-associated steroid receptor protein located on the cytoplasmic membrane, and it affects multiple processes of plant growth and development by initiating cell response to hormone regulatory signals, regulating steroid transport and metabolism. This study aims to study the role of MSBP during the poplar growth and development, especially its effect on wood formation, so as to provide a basis for the improvement of poplar wood quality. Method: AtMSBP1 protein sequence of Arabidopsis was used for homologous sequence alignment against the genome database of Populus trichocarpa and P. alba × P. glandulosa '84K' to obtain the nucleotide and amino acid sequences of poplar MSBP, and then aphylogenetic tree was constructed and the gene structure was analyzed. qPCR was used to analyze the tissue specific expression of MSBP genes in top buds, roots, stems and leaves of 84K poplar. The expression patterns of P. trichocarpa homologous genes in wood formation tissues were searched against the Aspwood database. The 35 S∷GFP-PagMSBP1/2a plant expression binary vector was constructed and transiently transformed into tobacco leaves by Agrobacterium. The subcellular localization of PagMSBP1/2a was observed by laser confocal microscope. 35 S∷PagMSBP1/2a plant expression binary vector was constructed and transformed into poplar 84K by Agrobacterium-mediated leaf disk method. The difference of xylem between PagMSBP1/2a-OE and control plants was investigated through cross-sections examined with microscopy. The content of lignin and the distribution of lignin in the vascular tissues of transgenic and control poplar stems were analyzed by acetyl bromide method and phloroglucinol staining respectively. Result: In this study, 7 poplar MSBP members were identified through homologous comparison, and the poplar genes were named according to evolutionary relationship and gene structure. Ameng them the homologous genes of AtMSBP1 and AtMSBP2 in poplar were named PtMSBP1/2a, PtMSBP1/2b and PtMSBP1/2c respectively, and PtMSBP1/2a had the most homology with AtMSBP1. The result of qPCR analysis showed that the three genes were all expressed in roots, stems, and leaves. The expression of PagMSBP1/2c in tissues was significantly lower than that of PagMSBP1/2a and PagMSBP1/2b, while the expression of PagMSBP1/2a was the highest in old stems, which was nearly 6 times higher than that in young stems. It is consistent with the high expression of PtMSBP1/2a in xylem during the process of wood formation as shown in the Aspwood data. The MSBP1/2a ortholog (PagMSBP1/2a) of 84K poplar was cloned and its encoded protein contained the trans-membrane domain at the N-end. The subcellular localization analysis showed that PagMSBP1/2a was localized in the endoplasmic reticulum membrane. The vector used for over-expression of PagMSBP1/2a was constructed and the gene was transformed into 84K poplar by Agrobacterium mediated leaf disk method. The transgenic poplars more grew slow and were shorter than the control. The lignin content in stems of PagMSBP1/2a overexpressed poplar was significantly lower than that of the control, and the soluble lignin content of acetylbromide decreased by 34.6%. Conclusion: PagMSBP1/2a is a steroid receptor protein located on the endoplasmic reticulum membrane, which is involved in regulating the lignin biosynthesis during the wood formation of poplar. Therefore, it can be used as a target gene in the poplar breeding for lignin content alteration.

Objective: The aim of this study is to explore the genetic variation, population genetic differentiation, and demographic history of Cryptomeria populations in East Asia, so as to provide a scientific basis for the flora evolution study of East Asia and the conservation of this species genetic resources. Method: Fourteen nuclear microsatellite markers (nSSR) were used to detect the genetic variation of 18 natural (or ancient) populations of Cryptomeria from China and Japan. The level and pattern of genetic differentiation were analyzed, and the demographic history of the populations was simulated by DIY ABC. Result: The results showed that Cryptomeria in East Asia had moderate genetic diversity (H_o = 0.472, H_e = 0.488), and high genetic differentiation existed among populations (F_ST = 0.136). Molecular analysis of variance (AMOVA) showed that the genetic variation of Cryptomeria in East Asia was mainly from individuals within the populations (86.37%, P < 0.001). Consistent with the geographic origin, Cryptomeria in East Asia was able to be divided into two geographical populations of C. japonica var. sinensis and C. japonica var. japonica, as well as four lineages including southeast (CHS) and Lushan populations in China (LS), and the sea coast (Ura-sugi) and Pacific coast populations (Omote-sugi) in Japan by STRUCTURE and DAPC analyses. The genetic diversity of C. japonica var. sinensis (N_a = 4.571, H_o = 0.442) was lower than that of C. japonica var. japonica (N_a = 4.634, H_o = 0.510), but there was high genetic differentiation among populations. The results of the DIY ABC simulation showed that the divergence event of populations and lineages of Cryptomeria in East Asia occurred between 110 000 ~ 340 000 years ago. Conclusion: Affected by the third glacial period of Quaternary (Lushan glacial substage), the effective populations of Cryptomeria in East Asia were decreased rapidly, retreated to the refuges in Southeast China and Southwest Japan, and diverged into two populations (C. japonica var. sinensis and C. japonica var. japonica) with independent evolutionary routes. Our findings suggest that climate change in Quaternary, geographical isolation and human disturbance since Holocene play an important role in the formation of genetic variation pattern of Cryptomeria in East Asia. Compared with C. japonica var. japonica, C. japonica var. sinensis has abundant resources in China, but its genetic diversity is low, natural forest populations are seriously damaged, and scientific and effective conservation is urgently needed.

Objective: Paracarophenax alternatus is a newly found parasitic mite species that can feed on and kill the eggs of Monochamus alternatus, the main vector of pine wilt disease in China. Clarification of its biological characteristics can provide a basis for the applications of this mite to control M. alternatus. Method: The behavioral habits, parasitism rate, development duration, fecundity and longevity of P. alternatus were investigated through indoor breeding and microscopic observation under controlled conditions. Result: P. alternatus is a phoretic mite and the adults usually attached on the thorax and abdomen of the adult of M. alternatus. Phoretic mites crawled into the oviposition grooves and then parasitized to kill the eggs of M. alternatus. P. alternatus reproduced as gamogenesis and viviparism mode. After parasitizing the egg, the abdomen of female adult mite gradually expanded into physogastry. The nymphs grew in the physogastry, and the adults crawled out from the physogastry one by one. The male adult mites crawled out first and then stayed aside the physogastry waiting for mating. The mating process lasted for 3-6 s commonly. Usually, a female mite reproduced only 1 to 2 male mites, and the rest were all females.The parasitism rate of P. alternatus to M. alternatus egg reached 80.85%, and all parasitized eggs became shriveled and died. Temperature played a significant role on the developmental duration, longevity and the physogastry volume of P. alternatus. With the increase of temperature, both development duration and longevity of P. alternatus significantly shortened. Averagely, the development duration was 6.9 d at 17 ℃ and then decreased to 2.2 d at 33 ℃. Its developmental threshold temperature was (10.44 ± 0.09) ℃, and the effective accumulated temperature was (46.28 ± 0.28) d·℃. The adult female mites could survive 70.3 d at 15 ℃ and 10.7 d at 30 ℃. The volume of the physogastry was 1.54 mm³ at 21 ℃, however, decreased to 0.72 mm³ at 17 ℃. P.alternatus showed a high fecundity, and each female adult reproduced averagely 71.2 offspring at 25 ℃, with a minimum of 14 and a maximum of 139. Its fecundity exhibited significantly positive correlation with the volume of its physogastry. The physogastry with the volume less than 1.0 mm³ was able to just reproduce averagely 32.2 offspring, however, the physogastry with the volume more than 3.0 mm³ could reproduce averagely 110.9 offspring. Conclusion: P. alternatus is an important biological factor for controlling M. alternatus, due to its high parasitic and lethal rate on M. alternatus eggs, short developmental cycle, high fecundity and easy propagation and spread.

Objective: This study aims to investigate the adaptation and physiological response of Hyphantria cunea (Lepidoptera: Arctiidae) to Populus alba × P. berolinensis colonized with arbuscular mycorrhizae fungi (AMF). Method: The cuttings of P. alba × P. berolinensis were inoculated with Glomus mosseae (GM), and when the GM infection rate reached the highest (90 days), the leaves were harvested and fed to the larvae of H. cunea. Result: After feeding on GM infected leaves of the popular, the body weight of 3^rd-6^th instar larvae was lower than that of the control, but the difference was not significant. The development duration of 2^nd-5^th instar larvae was significantly prolonged, and the relative growth rates of 3^rd and 5^th instar larvae were significantly decreased. There was no significant difference in food digestion rate of 5^th instar larvae of H. cunea, but food conversion rate and utilization rate were inhibited. There was no significant difference in food consumption rate, conversion rate and utilization rate of 6^th instar larvae. The activity of lipase in 5^th instar larvae was significantly increased, the activity of glutathione S-transferase (GSTs) was inhibited, and the activities of protease, amylase and carboxylesterase (CarE) were not significantly different from those in the control group. The activities of lipase, protease, amylase, GSTs and CarE of 6^th instar larvae were significantly higher than those of the control. Conclusion: The P. alba × P. berolinensis inoculated with GM has a certain inhibitory effect on the growth, development and food utilization of H. cunea in a short period of time, and H. cunea can break through this inhibition by increasing the activities of digestive enzymes and detoxification enzymes, and maintain normal growth and development. The results can lay a theoretical foundation for the future study of AMF-forest-herbivorous insect system.

Objective: Massicus raddei is widely distributed in eastern Asia, but the insects only outbreak in regional oak forests in Jilin and Liaoning provinces of China. This study aims to ascertain potential effects of host plants with different preference levels on the spread and outbreak of M. raddei in China, so as to provide theoretical guidance for ecological management in outbreak regions and early warning in distribution-free regions. Method: A total of 137 distributional points of M. raddei in China were obtained based on literature, database search, and field investigation. Eight climate variables with correlation coefficients < |0.9| and relatively larger contribution rate to the potential distribution of M. raddei were screened out from 19 environmental variables downloaded from WorldClim between 1970 and 2000 by ArcGIS 10.0. Then the data were converted into the ASCII format data required for Maxent. Through database search and further artificial screening, 2 548 host distributional points of M. raddei were obtained in China. Based on the feeding preference degree of host species distributed in every counties of China, the suitability degrees of M. raddei in each county were assigned as specific values, and then the ASCII format data of risk map of hosts was obtained by using ArcGIS. In the MaxEnt model, two files of distribution points of M. raddei and environmental variables and two files of distribution points of M. raddei and the risk map of hosts were successively imported, and the average predictive results of repeated 10 runs by MaxEnt were regarded as the potential suitable areas of M. raddei based on only climate factors or host distribution, respectively. By applying ArcGIS, aforementioned two layers were overlapped to obtain a new potential distribution combining climate with host distribution, and then the precision of the three predicted models was all evaluated through actual distribution points obtained from field surveys. In the three predicted results, the habitat of M. raddei in China was divided into four categories: non-suitable areas, low suitable areas, moderate suitable areas, high suitable areas, according to the suitability index. Finally, the areas of regions of four suitability levels in three prediction results were calculated and plotted. Result: Under current climatic conditions, the high suitable areas of M. raddei were mainly concentrated in Jilin, Liaoning, Beijing, Hebei, Tianjin and northern Zhejiang, whereas the suitable areas failed in including some distribution points in Yunnan obtained from the field survey. Under the current host distribution, obvious distinction in host preference was observed between southern and northern China. Two susceptible hosts (Quercus mongolica and Q. wutaishanica) were distributed in the northern provinces, where the borer would show high suitability, whereas the secondary preferred hosts were mainly distributed in the southern provinces, accordingly, the borer would show low and moderate suitability. The potential distribution of M. raddei based on the combination of climatic and host factors would be more concordant with its actual distribution and infestation conditions, that is, the suitable area covers all distribution points obtained from field surveys. Most regions of China were climatically suitable for M. raddei except for Xinjiang autonomous region and Qinghai province. The total suitable areas were larger than those only based on climatic or host factors. Therein, the range of low and moderate suitable regions became wider and the range of high suitable regions reduced. Conclusion: Host species and distribution are the dominant ecological drivers which determine the suitability level of M. raddei. Both preferable host plants and suitable climate are potential ecological drivers which result in regional outbreak of M. raddei in northeastern China. In addition, all non-distribution areas of China are facing risks of spread and colonization of M. raddei.

Objective: This study aims to reveal the influencing factors, inter-layer relationship and change trend of the flammability of surface litter, in order to provide data support for the assessment of the flammability of the northern forest burned area and its ecological restoration. Method: In this paper, the burned slash of natural Larix gmelinii forest in Tahe forestry bureau of Daxing'an Mountains was targeted. The physical and chemical properties (ash content, fat content and calorific value) and enzyme content (cellulase, hemicellulase and ligninase) of the aboveground litter were investigated. One way ANOVA was used to compare the significant differences in litter flammability and enzyme activities in each recovery period since fire. Pearson correlation and redundancy analysis were used to explore the correlation of each factor. Paired sample t-test was used to compare the temporal change trend of flammability and enzyme activity in litter and fermentative layer. Linear regression equation was used to fit the coupling model of crude fat, ash content and calorific value, and the linear slope significance test was used to verify the consistency of inter-layer slope. Result: 1) The flammability of litter layer increased with the recovery time, and the crude fat content and high calorific value were significantly higher than those of the control group in the late recovery period, while the ash content was significantly lower than that of the control group. The indexes of semi-decomposition layer changed obviously. In addition, the content of enzymes in the litter ranged as cellulase > hemicellulase > ligninase, and all the three enzymes showed a decreasing trend in the recovery period after fire. 2)The aspect and position of slope were important factors affecting the burning property of litter layer. The crude fat content and high calorific value of litter layer were higher in shady slope and bottom of slope, while ash content was opposite. 3)The crude fat content and higher heating value in litter were significantly higher than that in fermentative layer, and there was not significant correlation between them. The ash content in litter was significantly lower than that in fermentative layer, and there was significant positive correlation between them. The ash free calorific value, hemi cellulase, ligninase and cellulase content in litter were higher than those in fermentative layer, and there was no significant correlation between layers. There was a significant positive correlation between the content of cellulase in litter and fermentative layer. 4) There was a very significant linear relationship between crude fat content, ash content and higher heating value in litter. The slope of the model of crude fat content and higher heating value in fermentative layer was significantly higher than that in Litter, and the slope of the model of ash content and higher heating value was the same in two layers. Conclusion: The flammability of aboveground litter in burned area have recovered and exceeded the original habitat 16-27 years after the fire. The combustibility in litter is stronger than that in fermentative layer, and the difference between layers decreases as the recovery time increases. Terrain factors have a significant impact on the flammability of aboveground litter, thus it is necessary to make a comprehensive assessment of forest combustibility by multi factors in accordance with local conditions. Cellulase content can affect the ash content, crude fat and higher heating value of aboveground litter. The linear model of ash content and high calorific value of aboveground litter is y = 21.225 - 0.207 x (y is high calorific value, x is ash content, P < 0.001, R² = 0.908), which has a good goodness of fit. After further verification, it can be used as a reference to add a new way to rapidly estimate calorific value and combustibility of surface fuel and predict forest fire occurrence.

Objective: This study was carried out to explore the shear bearing capacity of an oblique screw connecting steel plate and CLT joint, to explore the failure mode and force mechanisms of steel plate and CLT joints connected by self-tapping screws, and to analyze the influences of angle on shear strength and stiffness. The development and application of new connectors would be expected to provide theoretical models and scientific bases. Method: Using Douglas fir as the study object and domestic full-threaded self-tapping screws as materials, the included angle between the main shaft of the self-tapping screw and the steel plate, those were 75°, 60° and 45°, respectively, was selected as the variable. The screw cap pulled in the tensile direction of the steel plate was shear force (T-S: tensile-shear), and the compression direction of the screw cap toward the steel plate was the compressive-shear force (C-S: compressive-shear). Referring to the American Standard (ASTM D1761-12) and loading at a constant speed of 1 mm ·min^-1, the stress of the node, the maximum load reached during the failure process, the deformation of the nail and the failure characteristics of the wood were observed and recorded. Result: For T-S and 90° shear force mode, the failure modes of nails were both that one side of the tapping screw was sheared. For C-S mode, the nail had three fracture modes under the 45° force mode, whereas the self-tapping screw on the one side produced two obvious plastic hinges and that on the other side was sheared at a distance of 8 mm from the nail cap under the 60° and 75° force modes. The bearing capacity under the T-S state increased gradually with the decreasing angle, and the opposite was observed under the C-S state; the stiffness under the T-S state increased gradually with the decrease of the angle. Conclusion: The bearing capacity of 45°, 60° and 75° joints under T-S state is 1.46, 1.35 and 1.22 times that of 90°, respectively, all higher than those of C-S state. The stiffness of 45°, 60° and 75° joints under T-S state is 3.58, 2.42 and 2.08 times that of 90°, respectively, and all higher than those of C-S state, of which the energy dissipation of 75° is the largest.

Objective: Aiming at the problems of low efficiency of directional sorting before rough milling, poor sorting effect and high degree of manual dependence, we designed and developed a continuous directional feeding system for rough milling of bamboo slices to realize the mechanization, automation and continuity. Method: Taking the bamboo slices after breaking the bamboo and removing the bamboo joints as the research objects, the technical scheme of the continuous directional feeding system for rough milling of the bamboo slices was proposed, the inclined vibration lifting chain, step separation system, recognition and turnover system of bamboo green and yellow surface and mechanical structure such as automatic feeding system were designed. By analyzing the movement characteristics of the bamboo slices in the vibration sorting process and the throwing process, the mathematical model of the bamboo slice movement trajectory in the vibration sorting process was established, the trajectory of the bamboo slice parabolic movement was described, and the main influencing factors of the bamboo slice selection process were determined. Selecting the lift chain speed, the inclination angle and the length of the bamboo slices as the inspection factors, the optimization experiment of the three-factor five-level quadratic regression orthogonal rotation combination was designed. The equipment, using the bamboo slice sorting rate and the bamboo green and yellow surface recognition rate as the evaluation index, was tested and set up at the Jian'ou Pilot Test Base in Fujian. Result: The single factor test showed that the bamboo slice sorting rate increased first and then decreased with the increasing speed of the lifting chain. When the speed of the lifting chain increased from 1.5 m·s^-1 to 2.7 m·s^-1, the separation rate of bamboo slices showed a trend of increasing first and then decreasing. The inclination angle of the lifting chain increased from 25° to 45°, and the separation rate of bamboo slices improved significantly. As the length of bamboo slices increased, the rate of separation of bamboo slices increased first and then decreased. However, compared with the influences of the speed of the lifting chain and the inclination angle of the lifting chain on the adhesion and separation rate, the length of the bamboo slice had a smaller influence on the adhesion and separation of the bamboo slice. The recognition rate of the bamboo green and yellow surface was mainly affected by the speed of the lifting chain. When the speed of the lifting chain was slow, the recognition system could obtain a clearer image of the bamboo green and yellow surface, and the recognition rate of the bamboo green and yellow surface was higher. The quadratic regression orthogonal rotation combination test showed that the order of the three test factors on the bamboo slices sorting effect was: ascending chain inclination angle > lifting chain speed > bamboo length. The speed range of the lifting chain was 1.6-2.0 m·s^-1, the inclination angle of the lifting chain was 35°-42°, and the length of the bamboo slice was 1 750-1 850 mm, the bamboo slice separation and conveying effect was the best, and the bamboo slice separation rate reached 96.5%-96.8%. Conclusion: 1) Based on the analysis of the actual operation situation of bamboo slices sorting, a continuous directional feeding system for rough milling of bamboo slices based on vibration and step separation design was designed. 2) In the application test of the continuous directional feeding system for rough milling of bamboo slices, the rotating speed of the elevator chain was 1.6-2.0 m·s^-1, the inclination angle of the elevator chain was 35°-42°, the length of bamboo slices was 1 750-1 850 mm, the sheet separation and conveying effect was the best, and the separation rate was 96.5%~96.8%. In actual production, the rotating speed and the inclination angle of the elevator chain could be selected to be 2.0 m·s^-1 and 40°, respectively. Under the conditions with the above parameters, the separation effect of bamboo slices with a length of 1 800 mm was the best, and the separation rate reached 96.7%, the recognition rate of bamboo green and yellow surface was 97.6%. At this time, the separation of bamboo slices and the identification of green and yellow surfaces of bamboo were better, which could meet the needs of on-site applications.

Objective: This study aims to explore the non-linear impact of forestry element input and production efficiency on forestry economic growth, especially the decisive role played by labor remuneration. Method: In this study, 40 forestry bureaus in Heilongjiang state-owned forest regions were targeted. The panel threshold regression model with labor remuneration as the threshold variable was used to analyze the stage characteristics of the impact of forestry capital input, forestry labor input, forestry land input, and forestry production efficiency on forestry economic growth. Furthermore, the mediating effect model and the moderating effect model were used to explore the unique role of labor remuneration in the process of forestry economic growth. Result: 1) The test results of F statistics of the double threshold effect were significant at the level of 1%, and each of the threshold regression model had a better fitting effect than the ordinary panel regression model. Furthermore, the threshold coefficient of each variable had an upward trend. 2) The test results of the total effect and the mediating effect were both significant at the level of 1%, and the test results of the direct effect were that the coefficients of forestry capital input and production efficiency were significant at the level of 1%, and the coefficient of forest land input was significant at the level of 5%, while the coefficient of forestry labor input was not significant. 3) The test results of moderating effect were that the coefficients of the interaction terms of forestry capital input and labor remuneration, labor input and labor remuneration were significant at the level of 1%, and the coefficients of the interaction terms of forestry land input and labor remuneration, forestry production efficiency and labor remuneration were not significant. The analysis results showed that each impact of forestry capital input, forestry labor input, forest land input, and forestry production efficiency on forestry economic growth had a double threshold effect with labor remuneration changing, and with the continuous increasing of labor remuneration, the marginal contribution of forestry factor input and production efficiency to forestry economic growth continues to rise. The labor remuneration had a partial mediating effect in the impact of forestry capital input, forest land input and forestry production efficiency on forestry economic growth, while there was a complete mediating effect in the impact of forestry labor input on forestry economic growth. Approximately 69.88% of the impact of various factors on forestry economic growth was achieved through labor remuneration. The labor remuneration had a positively strengthened moderating effect in the impact of forestry capital input on forestry economic growth, and a negatively strengthened moderating effect in the impact of forestry labor input on forestry economic growth, while there were no significant moderating effects in the impact of forest land input and forestry production efficiency. Conclusion: Generally speaking, the influence of forestry factor input and production efficiency on forestry economic growth is non-linear, and the labor remuneration exerts a significant threshold, mediating and moderating effects. There is an inherent consistency and deep causal relationship between the increase in labor remuneration and forestry economic growth.

Objective: The responses of rhizosphere soil stoichiometry of 1-year-old mycorrhizal and non-mycorrhizal Clematis fruticosa seedlings in relation to nitrogen (N) deposition were investigated. The regulatory mechanisms of mycorrhizal biotechnology on micro-ecological environment in rhizosphere soil were analyzed to provide a theoretical basis for exploring the stability of ecosystem under the background of global climate change. Method: The 1-year-old mycorrhizal and non-mycorrhizal C. fruticosa seedlings were selected for pot experiments. The inoculation treatments included single inoculation (inoculated with Rhizophagus intraradices or Funneliformis mosseae), mixed inoculation (inoculated with the mixed fungi inoculum of R. intraradices and F. mosseae with the mass ratio of 1∶1), and no inoculation as the control. Four N deposition treatments were established: 0N (0N, 0 g·m^-2a^-1); low N (LN, 3 g·m^-2a^-1); medium N (MN, 6 g·m^-2a^-1); and high N (HN, 9 g·m^-2a^-1). The soil available nutrients stoichiometry, microbial biomass stoichiometry, ecoenzymatic stoichiometry, and microbial nutrient limitation (i.e., vector length represents the microbial C relative limitation, vector angle represents the microbial N or P relative limitation) were measured, in order to explore the regulatory mechanisms of microbial metabolism in rhizosphere soil in response to AMF inoculation and N deposition treatments. Result: 1) Comparing with the control, all of the AMF inoculation treatments increased the ratio of dissolved organic C and available N, and the ratio of dissolved organic C and available P in the rhizosphere soil under all N deposition treatments. The ratio of available N and available P in HN treatment was the highest and significantly higher than that in LN treatment in all of the AMF inoculation treatments. The ratio of available N and available P in MN treatment was the highest and significantly higher than that in LN treatment in the control. 2) Under 0N treatment, the ratio of microbial biomass N and microbial biomass P in the control was significantly higher than that in all of the AMF inoculation treatments. Under MN and HN treatments, the ratio of microbial biomass N and microbial biomass P in the control was notably lower than that in all of the AMF inoculation treatments. Under LN treatment, the ratio of microbial biomass C and microbial biomass N in the F. mosseae inoculation treatment was significantly increased by 208.5%, 109.2% and 209.4% than that in the non-inoculated, R. intraradices inoculation and mixed inoculation treatments, respectively. 3) Under 0N treatment, the stoichiometry of enzymes related to C and N acquisition, the stoichiometry of enzymes related to C and P acquisition, vector angle and vector length in all of the AMF inoculation treatments were significantly higher than those in the control. Under HN treatment, there was no significant differences of vector length among all of the four inoculation treatments. 4) The total effects of microbial C and P limitations of inoculation treatments was higher than that of N deposition treatments. The inoculation treatments significantly increased the microbial C and P limitations. Conclusion: AMF inoculation effectively regulates the responses of stoichiometry in rhizosphere soil to low N deposition, and the ability of the regulation of F. mosseae was the best. The regulatory effect of AMF inoculation was greater than nitrogen deposition on the microbial C and P limitations in rhizosphere soil.

Objective: Sex ratio adjustability is a widespread ecological phenomenon in parasitic wasps. A female-biased sex ratio has long been asserted as the evolutionary stable strategy for some gregarious parasitic wasps on account of the theory of local mate competition (LMC). This evolutionary stable sex ratio can only be equalized as the increasing of foundresses numbers. The bethylid wasps have been widely used as biocontrol agents for several cerambycid and buprestid larvae, and their sex ratio structures are the basis of biocontrol. This study aims to clarify the sex ratios of the bethylid wasps and to prove whether the LMC model was applicable to the prediction of their sex ratios under different foundress densities. Method: In this study, Sclerodermus guani, S. pupariae, and S. alternatusi were selected as the experimental objects. The changes of offspring sex ratio and the brood size per female of three bethylid wasps were analyzed when the foundress densities ranged from one to eight respectively. The measured sex ratio of these three parasitoids and their predicted sex ratio based on LMC model under different foundress densities were comparatively studied. Result: The results indicated that the sex ratio of these three parasitoids were highly female-biased. Brood size per foundress significantly reduced when the numbers of foundress increased from one to eight. The sex ratio of these bethylid parasitoids exhibited slightly increase with the increasing foundress densities and negatively related to the brood size per foundress. Meanwhile, the predicted sex ratios based on the LMC model of these bethylid parasitoids deviated significantly from their measured sex ratios. Conclusion: The extremely female-biased sex ratio is an evolutionary stable biological characteristic for the bethylid parasitoids. This female bias of the bethylid parasitoids cannot be equalized, even though it would become a slightly less biased, with increasing numbers of foundress. The LMC model cannot accurately reflect the fluctuations of bethylid sex ratio under different foundress densities.