[Objective] To explore coexistence mechanism of species during community restoration process, we analyzed the spatial distribution pattern and inter- and intra-specific correlations of two dominant species in a 6 hm² forest dynamic plot (FDP) of subtropical evergreen and deciduous broad-leaved mixed forest in Qizimei Mountain, Hubei Province. This paper aims to provide a theoretical basis for forest ecosystem restoration and diversity conservation in this forest area. [Method]Two most dominant canopy tree species, deciduous tree Carpinus fargesiana and evergreen tree Cyclobalanopsis multinervis were selected based on abundance rank in the FDP. All individuals of two species were categorized into four DBH (diameter at breast height) classes: saplings (1 cm ≤ DBH < 2.5 cm), small trees (2.5 cm ≤DBH < 5 cm), medium trees (5cm ≤DBH <10 cm), and adult trees (DBH≥ 10cm). The population structure, spatial distribution, inter- and intra-specific correlations of four different DBH classes of the two dominant species were analyzed by using spatial point pattern analysis method. [Result] The stem abundance of C. fargesiana within four DBH classes were similar, but C. multinervis showed an inverted "J" shape. The individuals of different DBH classes of both species shared similar habitat preference. Most individuals of various DBH classes of C. fargesiana and C. multinervis showed aggregated distribution and extent of aggregation reduced gradually with the increase of DBH classes. In four different DBH classes of C. fargesiana, medium trees showed a trend from significantly positive to non-obvious associations with saplings. On the contrary, adult trees showed a trend from non-significant to negative associations with saplings. Positive spatial associations still dominated among different DBH classes (small trees to saplings, medium trees to small trees, adult trees to medium trees, adult trees to small trees). The C. multinervis showed positive associations among all four different DBH classes and along all spatial scales, but the positive associations were relatively weak. Different DBH classes of C. fargesiana showed positive associations to each DBH class of C. multinervis with the spatial scale. The medium and adult trees of C. multinervis showed a trend from non-significant to negative associations with saplings and small trees of C. fargesiana. Moreover, the extents of negative associations increased with the difference of DBH classes. [Conclusion] Although two dominant species (C. fargesiana and C. multinervis) had similar habitat preferences, but there was obvious suppression effect of C. multinervis (late successional species) on C. fargesiana (pioneer species). With the community restoration process, the secondary forest plot will gradually become dominant by C. multinervis. This study confirmed hypotheses that variation in the inter- and intra-species associations ultimately drives the community assemblages process.

[Objective] This research aims at investigating the variation patterns of tree morphology with different stand densities and mingling intensities in natural scenic forest, and clarifying the effects of stand density, mingling intensity and their interaction on tree morphology of different diameter classes.[Method]65 plots were set up in typical areas of Changbai Mountain, the forest spatial structures and tree morphological indicators were investigated. By using synthetic index method, four morphology indices were established, and the effects of stand density, mingling intensity and their interaction on these indices were analyzed with variance analysis method. [Result] Stand density had very significant effects (P<0.01) on all tree morphology indices. The increase of stand density had adverse effects on tree spatial occupancy index (U₁), stem and crown coordination index (U₂) and crown expansion index (U₃), while had a beneficial effect on stem straight index (U₄). The effects of stand density on U₁ and U₂ were very significant (P<0.000 5) in all three diameter classes, while the effect on U₃ were very significant (P<0.000 5) only in middle diameter class, and the effect on U₄ were significant (P=0.017) only in small diameter class. Mingling intensity was negatively correlated with U₁, U₂ and U₄, while positively correlated with U₃. The effect of mingling intensity on U₂ were very significant (P<0.000 5), and this effect showed extremely significant difference (P<0.000 5) and significant difference (P=0.038) in small diameter class and large diameter class, respectively. The interaction had a very significant influence (P<0.000 5) on U₃, and the influence of stand density on U₂ showed a trend of increasing first and then decreasing with the increase of mingling intensity, while the influence of mingling intensity on U₂ was on the contrary.[Conclusion] In scenic forest, stand density and mingling intensity significantly affected crown, stem and their coordination by changing the competition relationship of neighboring trees, and the stand density played a major role. Within the scope of the study, the stand density of more than 1 200 individual·hm^-2 had a significant suppression on the increase of tree volume and tree morphology coordination of all three diameter classes, while mingling intensity showed a significant influence on the tree morphology coordination in large diameter and small diameter trees when the density was more than 1 600 individual·hm^-2 or less than 800 individual·hm^-2, and the forest with low density and moderate mingling intensity were most beneficial to the coordinated development of trunk and crown morphology.

[Objective] This paper explores understory seedlings of different provenances of Machilus pauhoi and their response to geographical environment changes with the intention of providing theoretical and practical basis for artificial reforestation of natural forest and selection of suitable cultivation environment selection.[Method]Leaf samples were collected from understory seedlings of 9 provenances of M. pauhoi and variations of leaf C, N, P stoichiometry of different provenances were analyzed by one-way ANOVA and the correlations were calculated using Pearson method. Representative environmental factors were selected by combining both entropy-weight method and redundancy analysis method. Based on stepwise regression, fitting models of leaf stoichiometry and environmental factors were established. Using akaike information criterion, the best fitting models were chosen to analyze the influence of environmental factors on leaf stoichiometry of M. pauhoi understory seedlings. [Result] Firstly, leaf P concentrations, C:P and N:P of M. pauhoi understory seedlings of different provenances presented extremely significant differences (P < 0.01), while C and N concentrations as well as C:N presented little. For the variation coefficients of leaf stoichiometry, P concentrations, C:P, N:P, N concentrations, C:N and C concentrations were in descending order. Secondly, N concentrations were extremely significantly positively correlated to C and P concentrations (P < 0.01), but extremely significantly negatively correlated to C:N and C:P (P < 0.01). P concentrations demonstrated significant positive correlations with C concentrations (P < 0.05), but extremely significant negative with C:N, C:P and N:P (P < 0.01). And C:P displayed extremely significant positive correlations with C:N and N:P (P < 0.01). Thirdly, leaf C, N, P stoichiometry of M. pauhoi understory seedlings were mutually affected by longitude and mean annual temperature. Leaf C and N concentrations were significantly and extremely significantly positively correlated with longitude (P < 0.05 and P < 0.01, respectively), while C:N showed a significantly negative correlation (P < 0.05). Leaf P concentrations were extremely significantly positively correlated with longitude and mean annual temperature (P < 0.01), while C:P and N:P extremely significantly and significantly negatively correlated (P < 0.01 and P < 0.05, respectively). Longitude rather than mean annual temperature had greater effects on the three. [Conclusion] Differences were detected in leaf C, N and P stoichiometry of M. pauhoi understory seedlings of different provenances, which were mainly resulted from longitude and mean annual temperature. As a consequence, it is crucial to consider the adaptability of different provenances and environmental heterogeneity during the process of artificial reforestation of natural M. pauhoi forest and selection of suitable cultivation environment.

[Objective] This study investigated the growth and physiological adaption of the growth process of Populus×euramericana in different irradiation duration, in order to provide a theoretical basis for the early breeding and promotion of the superior varieties with high photosynthetic efficiency.[Method] In this paper, seedlings of 16 P.×euramericana clones were taken as experimental materials, and artificial light control tests were performed with LED-100W full spectrum plant growth lamp under all shading conditions to study the influence of different irradiation duration (11 h, 12 h, 13 h, 14 h and 15 h) on the seedlings growth, the biomass, the relative content of chlorophyll and the photosynthetic characteristics of P.×euramericana. [Result] 1)The results showed that relative growth rate of height and root diameter, and leaf biomass of seedlings under 14 h and 15 h irradiation were significantly higher than those under other irradiation duration (P<0.01). On the contrary, the root-shoot ratio and leaf SPAD value were relatively low. The trends of light-response curves of seedlings under different irradiation duration were basically consistent. With the increase of photosynthetically active radiation (PAR), the net photosynthetic rate (P_n) of leaves increased rapidly at first, and then began to flatten after reaching the light saturation point. The rectangular hyperbola was a favorable model for fitting the light-response curve data (R²≥0.948). 2)The maximum net photosynthetic rate (P_max) of leaves increased as the light time prolonged, and was 104.53% higher with 15 h irradiation than that with 11 h irradiation. Apparent quantum yield (AQY), dark respiration (R_d), and light compensation point (LCP) were the highest with 15 h irradiation. Light saturation point (LSP) was relatively higher under 14 h irradiation, with only lower than 13 h irradiation, while LCP and R_d were lower than all the other irradiation duration. 3) The chlorophyll fluorescence parameters showed that basis fluorescence (F_o) of seedlings under 11 h irradiation was the highest, and the maximum fluorescence (F_m) was not significantly different (P>0.01). Variable fluorescence (F_v) of seedlings under 13 h irradiation was relatively higher. The efficiency of solar energy conversion (F_v /F_m) and potential activity of PSⅡ(F_v /F_o) increased gradually with the increase of irradiation time, and the value of (F_v /F_m) ranged from 0.83 to 0.85.[Conclusion] Within the scope of this study, as the extension of light time, the P_max、F_m、F_v、F_v/F_o and F_v/F_m of P.×euramericana seedlings increased gradually, while F_o and root-shoot ratio decreased gradually. Besides, SPAD value, AQY, LSP, LCP, and R_d also had different responses to irradiation duration. Therefore, we suggest that the results can be used as an indicator of the early growth and the ecological adaption of P.×euramericana seedlings, also can be used as an important reference of the new varieties breeding, the application of breeding varieties and production practices.

[Objective] This paper aimed to investigate the quality forming regularity of Ping'ou hybrid hazelnut(Corylus heterophylla×C.avellana) kernels and discuss the nutritional quality characteristics of the kernel during growth and development stages to provide important theoretical foundation for production and cultivation management, timely harvesting and efficient utilization of hazelnut.[Method]Ping'ou hybrid hazelnut at different developmental stages was used to measure the water content in husk, shell and kernel, main nutrition substance content and important bioactivators, in kernels, including fat content, protein content, sugar content, fatty acid content, VC and VE content, total phenols and total flavonoids content, and then analyze the quality forming regularity of hazelnut during development phase further. [Result] At the early stage of development, the water content of kernels decreased rapidly from 88.6% to 38.2%; the content of crude fat, total protein and VE increased rapidly from 29.9 g·kg^-1 FW, 37.3 g·kg^-1 FW and 0.038 g·kg^-1 oil to 362.4 g·kg^-1 FW, 96.7 g·kg^-1 FW and 0.35 g·kg^-1 oil, respectively. However, those substances all remained relatively stable level at the later stage of development. The VE in the kernel was mainly composed of α-configuration of VE, with a small amount of β-, γ- and σ-configuration. Sugar content gradually increased during the whole development period. Sucrose was the main component of sugars in hazelnut kernels and its content gradually increased during the whole development stages. VC reached the maximum content of 0.13 g·kg^-1 FW at the kernel-filling stage and then sharply decreased until 0.062 g·kg^-1 FW at the fully-mature of hazelnuts. The contents of total phenols (TPC) and total flavonoids (TFC) gradually increased in the early stage of development and reached the peak value at the kernel-filling period, being 1.49 g GAE·kg^-1 FW and 2.44 g RE·kg^-1 FW, respectively and then rapidly decreased until to the end of development phase. The final TPC and TFC contents were 34.0% and 23.7% of the peak values at the nut abscission period, respectively. [Conclusion] During the whole development period, the water content of kernels decreased gradually and main nutrition substances increased gradually. As the main component of fatty acid, the increase tendency of oleic acid content was in step with the decrease tendency of palmitic acid and linoleic acid contents. VE, mainly the α-configuration, was gradually accumulated; Main antioxidants substance VC, phonelic and flavonoid were rapidly accumulated and peaked at kernel-filling period and then decreased at the later stage. The early development phase was the significant time for nutrient substance formation of hazelnut kernels. Kernel-filling period was the important transition stage of development of hazelnut, during which hazelnut kernels completed the accumulation of the main nutrient substances and had higher antioxidant substance reserves.

[Objective] Chinese jujube (Ziziphus jujuba) fruit is easy to crack at ripening stage during rainy season, which brings huge economic loss to the production. This study aimed to clarify the main ways of water absorption leading to jujube fruit cracking, and provide a basis for further exploring the mechanism of fruit cracking and its prevention and control.[Method] The experiment was carried out from 2013 to 2015. Fruits of Z. jujuba ‘Huping’ with higher cracking susceptibility were used as test materials. The water absorption distribution of different parts of the jujube fruit was observed with dye tracer and stereoscope. The possible ways of water absorption of jujube fruits were determined, and the differences of water absorption per unit time in different parts of jujube fruits were determined by sealing the different parts of the fruit with wax and then incubating them in water. The surface structure characteristics of jujube fruit were observed with stereoscope and scanning electron microscope, and the relationship between surface structure characteristics and water absorption and fruit cracking of jujube fruit was analyzed as well.[Result] 1) The surface, stem and stalk cavity of ‘Huping’ jujube fruits were able to absorb water, and during the fruit coloring period, their relative water absorption accounted for 51%-54%, 31%-40% and 9%-18% of the total relative water absorption of the fruits, respectively. 2) In the process of fruit development and maturation, the fruit surface stomata were corked to form lenticels and some of the lenticels formed microcracks. At that time, water absorption on the fruit surface doubled and water could enter the fruit through open lenticels and microcracks by both symplastic and apoplastic pathways. 3) It was generally observed in both natural rainfall and water-incubation experiment that macroscopic cracks were connected in a line by more than two fruit points, and the cross point of cross cracks was the location of the fruit spot. The above results proved that jujube fruit surface stomata were the inducement of microcracks.[Conclusion] During the fruit maturation process, the lenticels and microcracks formed from stomata on jujube fruit surface were the main ways for the fruit to absorb water, and they were also the main causes of water absorption and cracking of jujube fruit. On the jujube fruit surface, there existed both symplastic and apoplastic pathways by which water entered the fruit.

[Objective] C-glycosyl flavonoids are abundant in Phyllostachys edulis leaves and possess vital biological activities. C-glycosyltransferase (CGT) is the key C-glycosylation enzyme in C-glycosyl flavonoid biosynthesis. However, no reports currently exist on the C-glycosylation pathway and C-glycosyl flavonoid CGT from P. edulis leaves. In this work, The main aims of this work were to analyse and confirm the predominant C-glycosylation pathway, enzymatic properties, primary amino acid sequence and gene sequence of CGT and to provide a good foundation for further studying CGT from P. edulis leaves.[Method] The CGT of a C-glycosyl flavonoid from P. edulis leaves was first purified by ammonium sulfate fractionation precipitation, dialysis, gel chromatography and diethylaminoethyl anion exchange, and detected using SDS-PAGE. Three possible substrates (eriodictyol chalcone, eriodictyol and luteolin) were selected as substrates to analyse the possible C-glycosylation pathways using the established C-glycosylation reaction system and to confirm which pathway was predominant. Using Q-TOF analysis and database searching, the gene and amino acid sequences of P. edulis CGT were analysed and confirmed.[Result] The results suggested that the molecular weight of P. edulis CGT is about 50 kDa, and the optimal incubation time, incubation temperature, buffer pH and substrate (luteolin) concentration for the CGT reaction system was 40 min, 28 ℃, 8.1 and 31.76 μmol·L^-1, respectively. A large amount of the luteolin underwent CGT-catalysed C-glycosylation was converted into isoorientin in reaction system 3, while a large amount of eriodictyol chalcone and eriodictyol in reaction system 1 and 2 were converted into unknown products, only a small portion was converted into isoorientin. According to fragmenting law and the diagnostic fragments of the protein peptide ions, four CGT peptide ions were analysed and confirmed, which was aligned with the amino acid sequence encoded by the gene from P. edulis gene (PH01000603G0510), the amino acid sequence of the four CGT peptide ions perfectly matched the amino acid sequence encoded by the P. edulis gene (PH01000603G0510). The matching rate of P. edulis gene sequence (PH01000603G0510) with rice (Oryza sativa Japonica Group) CGT gene sequence (PH01000603G0510) was 81%.[Conclusion] Through separation, purification and structural identification of CGT from P. edulis, the possible gene (PH01000603G0510) and amino acid sequences of C-glycosyl flavonoid CGT from P. edulis leaves were analysed and confirmed. The C-glycosylation pathways of flavonoids in P. edulis were also determined. The main C-glycosylation pathway of isoorientin in P. edulis leaves is via the direct synthesis of isoorientin from luteolin and UDP-glucose, and the secondary pathway is via the indirect synthesis of isoorientin from eriodictyol chalcone and UDP-glucose, or eriodictyol and UDP-glucose. The C-glycosyl flavonoid CGT in P. edulis leaves catalyzes the accumulation of flavone 6-C-glucosides (isoorientin) but seldom catalyzes the accumulation of flavone 8-C-glucosides (orientin).

[Objective] MYB protein is one of the important transcription factors, which play critical roles in regulating the syntheses of cellulose and lignin. In order to identify those MYB genes involved in wood formation of Betula luminifera, four BlMYB genes were cloned and their sequence characteristics, expression patterns and downstream regulatory genes were also analyzed. These results would provide a theoretical basis and genetic resources for further gene function analysis and molecular assisted breeding.[Method] cDNA fragments of four BlMYB genes of B. luminifera were isolated by using RACE technology. Their sequence features were analyzed by bioinformatic tools, and then, the relative expression levels of these BlMYB genes and seven downstream regulatory genes in different organs/tissues (female inflorescence, male inflorescence, bud, young leaf, mature leaf, stem, phloem, cambium, inner and outer xylem) and early stage of tension wood(TW) were analyzed by real-time quantitative PCR. Furthermore, two xylem specific expressed BlMYB were used as the guide genes to construct a co-expression network by mutual ranking method and Cytoscape software. Cis-elements in the promoter regions of the putative downstream genes were analyzed by using the Plant CARE website.[Result] The full-length cDNA of four BlMYB genes were isolated and were named BlMYB1, BlMYB2, BlMYB3 and BlMYB4, respectively. These four BlMYB genes encode 395, 252, 258, 320 amino acid residues, respectively, and all these proteins contain R2R3 domains near the N-terminus. The four BlMYB protein sequences show 27%-37% identity with each other, but exhibit higher identity (39%-55%) with their homologs in Arabidopsis thaliana. There are one or two introns in these BlMYB genes. The phylogenetic analysis revealed that the four BlMYB belonged to different branches, and BlMYB2 and BlMYB4 belonged to two branches which contained MYB genes involved in the formation of secondary cell wall. BlMYB1 and BlMYB3 dominantly expressed in mature leaf, and their expression levels increased with the maturation of leaf, which suggested that they may be associated with development of leaf. BlMYB2 strongly expressed in the xylem of lignified stem, while weakly expressed in leaves, phloem and other tissues. During the early stages of TW formation, the expression of BlMYB2 in TW was down-regulated, especially after 48 hours and 7 days bending treatment. BlMYB4 predominantly expressed in the xylem and male inflorescence, and its expression levels were relatively low in root and leaves. And, its expression was up-regulated in TW and down-regulated in OW (Opposite Wood). In addition, according to co-expression analysis and specific AC element screening, seven Unigenes annotated as cellulose and lignin biosynthesis enzyme genes (FRK, COMT, HCT, CesA3, CesA4, 4CL and CCoAOT) might be regulated by BlMYB2 and BlMYB4.[Conclusion] Four BlMYB genes belonging to the R2R3-MYB family were cloned from B.luminifera and showed different gene structures. The expression patterns of BlMYB indicated that they might participate in different metabolic pathways. In consideration of tension wood feature and the result of co-expression analysis, it could be speculated that the BlMYB2 and BlMYB4 might regulate the wood formation of B. luminifera.

[Objective] Pinus massoniana is a commercially important conifer for timber and oleoresin in South China. This paper studies genetic variation among origins and clones within origins and their relationship with other economic traits of P. massoniana, so as to lay a theoretical basis for breeding high-yield and high-quality P. massoniana clones.[Method] 34 years old clonal plantations of P. massoniana from different habitats were used to estimate the genetic variation among origins and clones within origins and the correlations among growth, oleoresin yield and compositions.[Result]A total of 26 chemical compositions were identified by gas chromatography-mass spectrometry analysis. The result of ANOVA revealed significant differences among origins and clones within origins for the capability of oleoresin yield and oleoresin compositions. The variation of clones within origins with the variance components ranging from 30.93% to 80.89% was the main source of genetic variation. However, the significant differences were only observed among origins for all studied growth traits except crown width with the variance components of 40.13% to 52.89%. Diameter at breast height (DBH) exhibited positive genetic correlation with the capability of oleoresin yield (r_G=0.67). Among oleoresin compositions, only six compositions were moderately correlated with oleoresin yield. Strong genetic correlations were found mainly among the compositions within the same class of terpenes, especially for the sesquiterpenes. The hierarchical cluster analysis revealed monoterpenes are closely related to diterpenes, and clearly distant from sesquiterpenes. Finally,taking into account the capability of oleoresin yield,growth and oleoresin compositions,eleven high pinene and nine high abietic acid content of superior clones were selected.[Conclusion]Our results revealed that greater variation is among clones within origins for oleoresin yield and compositions, indicating the importance of within origins selection in improving oleoresin traits. DBH and six oleoresin compositions can be used to indirect selection of the capability of oleoresin yield. Strong genetic correlations existed mainly among composition within the same class of terpene. Based on growth and the capability of oleoresin yield,eleven high pinene and nine high abietic acid content of superior clones were selected.

[Objective] This study aimed to reveal the response characteristics of soil microbial community structure to different disturbance types in Masson pine (Pinus massoniana) plantation, and to explore the microbial mechanism of soil quality change, and to evaluate the effects of different tree removal disturbance types on underground ecosystems. [Method] Four different treatments of shrub removal (SR), light disturbance (LD) (removal of non-Masson pine tree with DBH>4 cm, i.e. 15% of basal area removed), heavy disturbance (HD) (removal of Masson pine tree with DBH>17.9 cm, i.e. 70% of basal area removed), and control (CK) were conducted in a P. massoniana plantation. The topsoil of 0-10 cm was collected in all plots on July 13, 2015, and Illumina Miseq high-throughput sequencing method was used to analyze the response characteristics of soil microbial community composition and structure under different disturbances. And the response mechanism of microbial was preliminarily explored by combining similarity and phylogenetic index. [Result] 1) Proteobacteria, Acidobacteria and Actinobacteria were the dominant bacteria in the soil of P. massoniana plantation, and Basidiomycota, Ascomycota and Zygomycota were the dominant fungi. Significant differences in the relative abundance of bacterial communities were tested at the phylum level, and the result showed that the relative abundance of Bacterioids, Beaproteobacteria, DeltaProteobacteria and Gammaproteobacteria were significantly different (P < 0.05). The soil microbes with different interference types were compared with the control plot. Compared with Control (CK), the relative abundance of Proteobacteria, Betaproteobacteria, Deltaproteobacteria and Gammaproteobacteria in LD was significantly decreased, and the relative abundance of Bacterioids and Deltaproteobacteria in HD was significantly lower (P < 0.05), but there was no significant change at the level of phylum and class in SR plots. 2) The results of principal component analysis showed that the soil microbial (bacterial and fungal) community structure could be distinctly separated in different disturbed plots, and the non-parametric multivariate analysis of variance (PMANOVA) showed that there were significant differences between the bacterial and fungal community structure in different disturbed plots (P < 0.05). The community structure of soil microorganisms in different disturbed plots except SR plots was significantly different from that in control plots (P < 0.05), and there was significant difference in the fungi community structure between the disturbed plots and the control (P < 0.05). 3) Compared with CK, the similarity of bacteria decreased significantly in LD and HD (P < 0.05). Also, the similarity of fungi was significantly different in SR, LD and HD (P < 0.05). 4) The analysis based on the zero model showed that only the changes of Phylogenetic abundance and Phylogenetic diversity of soil microbial communities with LD reached a significant level (P < 0.05). [Conclusion] The disturbance of P. massoniana plantation significantly affected the composition and structure of soil microbial community, and the disturbance reduced soil nutrient availability; the disturbance significantly reduced the similarity of soil microbial community, resulting in the decline of soil microbial community stability; In addition, the disturbance changed the Phylogenetic diversity of soil microorganism, that is, the nutrient content and niche diversity of soil microorganism was changed, which reduced the stability of the ecosystem. Both LD and HD significantly reduced soil quality, resulting in a decrease of soil nutrient content, therefore, LD and HD in Masson pine plantations should not be used.

[Objective] The present paper aimed to study effects of elevated CO₂ concentration on the growth and development, nutrient utilization and in vivo detoxifying enzymes and protective enzymes of the serious forest defoliator, Lymantria dispar (Lepidoptera: Lymantridae). [Method] The different CO₂ concentrations (397, 550 and 750 μL·L^-1) were applied in the closed CO₂ artificial climate chamber, and the effects on growth and development of L. dispar were measured, and the effects on activities of detoxification enzymes and protective enzymes of L. dispar were determined by spectrophotometry. [Result] The elevated CO₂ concentration was able to prolong the egg hatching period of L. dispar, increased fecundity and hatching rate. At the same time, the elevated CO₂ concentration significantly prolonged the total larval developmental period, however, it had no significant effects on pupae and adult duration. Increased CO₂ concentration decreased the relative feeding rate and the approximate digestibility, but increased the food utilization rate and the conversion rate of digested food by L. dispar. The activities of superoxide dismutase (SOD) and catalase (CAT) in L. dispar larval body were significantly induced by 750 μL·L^-1 of CO₂ concentration, and increased by 32.05% and 13.47% compared with that at 397 μL·L^-1 CO₂ concentration, respectively; With the increase of CO₂ concentration, the activities of cytochrome P450 increased by 78.79% and 93.50% under 550 μL·L^-1 and 750 μL·L^-1 CO₂, respectively, compared with that at 397 μL·L^-1 CO₂. The GST activities were the highest under 550 μL·L^-1 CO₂ concentration, which was 71.03% and 50.00% higher than those in 397 μL·L^-1 and 750 μL·L^-1 treatment groups, respectively. [Conclusion] The elevated CO₂ concentration can affect the growth and physiological metabolism of the L. dispar larvae. At the same time, L. dispar can resist the high concentration of CO₂ through changing the developmental duration, increasing the food utilization and transformation, and changing the activities of detoxifying enzymes or/and protective enzymes to achieve the purpose of maintaining life.

[Objective] The combined use of abamectin and triflumuron has synergistic effect on the control of gypsy moths, but the synergy mechanism of abamectin and triflumuron is still unknown. In order to clarify the synergy mechanism of abamectin and triflumuron, 3rd-instar Lymantria dispar larvae were treated with abamectin and triflumuron alone or their combination, and then the activities of detoxification enzymes and protective enzymes were determined, which would provide theoretical basis for the mixture use of the two pesticides. [Method] Abamectin acetone solution of 9 000 μg·mL^-1 or triflumuron acetone solution of 25 000 μg·mL^-1, and the two combination were added to the artificial diet for preparation of poisonous feed for L. dispar larvae. In a low concentration group, the content of drugs was 0.50 μg·g^-1 abamectin or 8.30 μg·g^-1 triflumuron in single pesticide treatment group, and 0.50 μg·g^-1 abamectin plus 8.30 μg·g^-1 triflumuron in mixed pesticide group. In a high concentration group, the content of drugs was 1.10 μg·g^-1 abamectin or 16.60 μg·g^-1 triflumuron in single pesticide treatment group, and 1.10 μg·g^-1 abamectin plus 16.60 μg·g^-1 triflumuron in mixed pesticide group. The third instar L. dispar larvae were fed with the poisonous artificial diet for 24 h. Survivors were counted following activity determinations of detoxification enzyme and protective enzyme. [Result] Mortality analysis showed that all larvae of the control group, single abamectin treatment, and single triflumuron treatment survived from this experiment. The mortality of mixed pesticide treatment group was 1.15% at a low concentration, and 4.11% at a high concentration. There was no significant difference between low concentration group and control, but there was significant difference between the high concentration group and control. Detoxification enzyme activities analysis showed that the activities of CarE and GST of larvae treated with abamectin or triflumuron were significantly higher than those of the control group, while there were no significant differences in the enzymes activities between the mixed pesticide treatment and the control group. Protective enzyme activities assay showed that activities of SOD, CAT and PPO of larvae treated with abamectin, triflumuron, and the two combination were higher than those of control group, however POD activities of treated larvae were lower than that of the control. Meanwhile, activities of SOD, POD and CAT of larvae treated with the mixed pesticides were higher than that treated with either single pesticide, while the case for PPO activity was opposite. [Conclusion] It is concluded that the combined effect of abamectin and triflumuron on Lymantria dispar larvae is mainly through inhibiting the activity of the detoxifying enzymes CarE and GST, and supplemented by inhibiting the activities of protective enzymes PPO, so as to improve the toxicity effect.

[Objective] Site quality assessment is fundamental to forest management and important for understanding forest growth process, estimating forest growth and yield and making silviculture practices. However, most of studies focused on site index for site quality assessment and cannot predict potential site productivity because they used realized forest inventory data. The objective of this study is to develop a methodology for site quality assessment based on basal area- or volume-related potential increment.[Method] This study gave the definition of potential site productivity and developed the models for estimating potential and realized site productivity. The procedure for site quality assessment was put forward which included site unit-stand unit-stand growth type-potential and realized productivity models-mapping site quality at sub-compartment level. A case study for mixed conifer-broad-leaved forests was carried out with the application of the methodology and national forest inventory data in Jilin Province.[Result] Site factors affecting site productivity mainly included elevation, aspect, slope position, slope, soil type, and humus depth, respectively. Site types were classified as 5 site classes through stand height growth grouping with the constraints of these site factors. Growth models of stand mean height, basal area and volume were developed by site classes with biological and statistical reasonability. The coefficients of determination were 0.991 8, 0.986 6 and 0.984 2, respectively. The potential productivity varied from 3.6 to 5.8 m³·hm^-2a^-1. The optimal stand density at potential productivity was also estimated.[Conclusion] The methodology for potential site productivity estimation is applicable for both pure and mixed forest which could predict the maximum mean annual increment at specific sites and improve the realized productivity by stand density control. It is expected to be as a reference for forest quality improvement.

[Objective] This paper studies the applicability of the watershed algorithm, polynomial fitting method and Point cloud-based cluster segmentation for individual tree segmentation, analyzes the accuracy and explores the optimal selection of the key parameters of the three methods for individual tree segmentation.[Method] The field measured and visual interpretation data were combined to calculate the individual tree detection rate, precision of detected trees and overall accuracy index. In addition, the grid canopy height model(CHM, canopy height model)resolution of the watershed algorithm and polynomial fitting was changed and the distance threshold of point cloud-based cluster segmentation was adjusted to perform the sensitivity analysis of individual tree extraction.[Result] The result showed that: 1) The three segmentation methods used to segment individual trees in planted forests have relatively high overall accuracy(overall accuracy F=0.76-0.83).2) For "complex forest type" samples, point cloud-based cluster segmentation has a higher extracting accuracy(overall accuracy F=0.78)than the watershed algorithm(overall accuracy F=0.74)and polynomial fitting(overall accuracy F=0.53); for the "moderately complex forest type" samples, point cloud-based cluster segmentation has a higher extracting accuracy(overall accuracy F=0.89)than the watershed algorithm(overall accuracy F=0.84) and polynomial fitting(overall accuracy F=0.75); for the "simple forest type" samples, point cloud-based cluster segmentation(overall accuracy F=0.89), the watershed algorithm(overall accuracy F=0.89)and polynomial fitting(overall accuracy F=0.93)have similar precisions. 3) Sensitivity analysis result showed that when the CHM resolution is 0.5 m×0.5 m, the watershed algorithm and the polynomial fitting segmentation accuracy has the highest accuracy, whereas when the threshold approximately equals to the average of the crown projection radius, the point cloud-based cluster segmentation reaches the highest precision.[Conclusion] The individual tree segmentation of multiple types of plots reflects the applicability of the three methods to the planted forests. The accuracy of individual tree segmentation of planted forest by three methods is fully evaluated and compared with many types of plots. The sensitivities of the three methods were analyzed, and the optimal choice of key parameters during individual tree segmentation was described.

[Objective] In order to explore the more efficient method of predicting the wood density of Cunninghamia lanceolata, the near infrared spectroscopy was used. It could provide the theoretical basis for quantitative analysis of wood properties.[Method] Firstly, wood density and the near infrared spectroscopy data of 109 C. lanceolata samples were normalized. Of which,88 C. lanceolata samples constituted training set and 21 samples constituted test set. Secondly, the principal component analysis was used to extract the principal components of 2 151 dimensions of the C. lanceolata near infrared spectrum. Thirdly, the principal components set as the independent variable and the C. lanceolata density set as the dependent variable were used to establish the multiple linear regression(MLR)model and the support vector machine(SVM)model. In order to improve the prediction accuracy of C. lanceolata density model, the grey wolf optimizer(GWO)algorithm was applied to the SVM model for parameter optimization. Therefore the prediction of the C. lanceolata density based on the GWO-SVM was proposed. The determination coefficient(R²), the mean square error(MSE)and the mean absolute percentage error(MAPE)were adopted to measure the prediction result of the three models.[Result] Five principal components were obtained from the near infrared spectrum, and their cumulative contribution rate was 98.7%. The significant value P of the MLR model and the partial regression coefficient was both less than 0.05, which indicated that the MLR model was effective and the model can be used for the C. lanceolata density prediction. The R² of MLR model was 0.771 4, the MSE was 0.000 282 1, and the MAPE was 3.009 23%. At the same time, the R² of SVM model was 0.923 8, the MSE was 0.000 233 1, and the MAPE was 2.794 50%. The parameters of the SVM were optimized by the wolf group algorithm, and the optimal parameters were C=18.366 6, σ=0.043 3. In the GWO-SVM model, the R² was 0.919 2, the MSE was 0.000 183 4, and the MAPE was 2.496 37%.The MAPE of the three models were all within the acceptable range, and the prediction of the GWO-SVM model was the best.[Conclusion] The GWO-SVM model is superior to the MLR model and the SVM model on the prediction accuracy. The GWO-SVM and the SVM model are superior to the MLR model on determination coefficient analysis. So the approach of GWO-SVM combined with the near infrared spectroscopy to predict the C. lanceolata density is reasonable and efficient.

[Objective] In order to lay a foundation for the optimized wood dust,the size and shape distribution of particles emitted in panel furniture manufacturing was studied to clarify their influence on the particle flowability. [Method] The particle samples were collected in the panel cutting and paint sanding processes. The area diameter, aspect ratio, roundness, solidity and bluntness of the particles were investigated by means of image analysis to characterize their size and shape distribution. The influences of size and shape distribution on the particle flowability were then analyzed.[Result] The sawdust and sanding dust were mainly composed of fine particles with diameters of less than 100 μm, which could float long and travel wide in the air. Compared to the sawdust, the size of the sanding dust was smaller and the size distribution was narrower, making them more cohesive and adhesive. In terms of macroscopic shape, the sawdust and sanding dust were both irregular particles, exhibiting small aspect ratios and great inter-particle shape variation. However, they presented highly smoothed surface in mesoscopically, and the shape irregularity decreased with the falling particle size. Compared to the sanding dust, the sawdust showed higher shape irregularity and greater inter-particle shape variation.[Conclusion] The flowability of both particles was poor, which highly correlated with their size and shape characteristics. The small size of both particles causes high cohesive and adhesive forces, which in turn lower the flowability of the particles. With respect to the particle shape, the irregular larger particles tend to interlock with each other, while the relatively regular smaller particles are often trapped in the voids formed between the larger ones. This structure restricts the flow of particles with all sizes.

[Objective] In order to improve the design of the mill grinding disc, the fracture process of grinding the wood chips into fibers by the hot mill was studied in this paper. Based on ADAMS and ABAQUS, the process of grinding the wood chips by the hot mill was numerically simulated, and the process of gradual fracture of the wood chips with the force was explored. When the angle between the grinding and grinding teeth of the moving and stationary discs is constant, the amount of field change was recorded for the distance R from the wood piece to the center of the spindle. The influence of broken area size of the grinding piece on the energy consumption of fiber separation was theoretically analyzed.[Method] Combined with the theory of fracture mechanics, the method of numerical simulation is used. When the angle between the teeth of the moving and stationary discs α is 15°,the numerical simulation method is applied to solve the distance R between the wood chips and the spindle center by using ADAMS software to obtain R=370, 390, 410, 430, 450 mm in five cases, the size of the grinding pressure F_m and the shear force F_r. Then use ABAQUS software to load it on the wood chip and numerically simulate the fracture process.[Result] The ADAMS software was used to simulate the working process of grinding the wood chips by the hot mill, and the simulation result of the grinding pressure F_m and the shearing force F_r of the wood chips α=15° and R=450 mm were obtained. The field variable output result of α=15° and R=450 mm were obtained by using ABAQUS software. The variation trend of Mises stress, normal stress, Magnitude and node displacement of wood chips under different conditions was studied by using Excel scatter plot and regression analysis chart.[Conclusion] 1) The damage form of the wood chips during the grinding process is mainly separated by the shear force F_r along the transverse direction of the wood chips. Therefore, during the structural design and optimization analysis of the grinding plates, the grinding teeth should be increased as much as possible. The force of the cutting force F_r makes the fracture degree of the wood chip in the crushing zone more complete, and reduces the energy consumption of fiber separation in the rough grinding zone and the fine grinding zone. 2) When the hot mill grinds the wood chips, the larger the distance R from the wood chips to the center of the main shaft, the larger the area of the crushing area, the easier the fracture of the wood chips is. The reasonable design of the area of the crushing area of the grinding plate can reduce the energy consumption of fiber separation. 3) Using ABAQUS to simulate the field variable output when the distance from the wood chip to the center of the spindle is not equal, the influence of the area of the crushed area on the fiber separation energy consumption is theoretically analyzed, which can guide the optimized design of the grinding piece.

[Objective] Understanding the patterns of soil water movement under drip irrigation can provide supporting data and theoretical basis for developing precise drip irrigation strategies.[Method] A two-year-old Populus tomentosa plantation under surface drip irrigation on sandy loam soil was selected to measure the dynamics of soil water potential (ψ_s), wetting front and soil water content (θ) during irrigation and water redistribution periods. Then, the observed data in the field were used to evaluate the accuracy and feasibility of the HYDRUS-2D/3D model for simulating the short-term soil water movement. Besides, the validated model was used to simulate the dynamics of wetting front under different initial soil water content (θ_i).[Result] During irrigation, the variation of ψs, horizontal and vertical movement distances of the wetting front, and θ within the wetting volume with irrigation duration can be described by the logistic function (R² = 0.99), the logarithm function (R² = 0.99), the power function (R² = 0.82), and the polynomial function (R² = 0.99), respectively. At the end of irrigation, the horizontal and vertical movement distances of the wetting front reached 22.9 and 37.3 cm, respectively. The ψ_s and θ within the soil wetting volume were 61.6% and 30.9% higher than those at the start of the irrigation, respectively, but the ψ_s decreased to its initial level about 120 hours after the stop of irrigation. The average deviations of the horizontal and vertical wetting radius between the simulated and measured values were 1.3 and 4.5 cm, respectively. The mean RMSE and RMAE of HYDRUS-2D/3D for simulating θ at the end of irrigation and during water redistribution were 0.021 cm³·cm^-3 and 9.7%, respectively. The movement distances of wetting front in the experimental plantation under various soil drought degrees (soil water availabilities were 40%, 60%, 73%, and 80%) were obtained through scenarios simulations using HYDRUS-2D/3D. And it was found that the wetting front moved further under higher θ_i, and the movement distance of the wetting front was always smaller in the horizontal direction than in the vertical direction under different θ_i.[Conclusion] Consequently, HYDRUS-2D/3D can be used to well simulate the short-term soil water movement in drip-irrigated young P. tomentosa plantations in sandy loam soil. In addition, the constructed figure (describes the variations of the horizontal and vertical soil wetting distances with the irrigation duration) can be used to determine the reasonable irrigation duration for the plantations of P. tomentosa and other tree species in sandy loam soil.