In this study, seven LysM-RLK subfamily genes were systematically identified in the whole genome of papaya using bioinformatics methods, and the chromosome distribution, gene structure, protein physical and chemical properties, and subcellular localization information were analyzed. Familial evolutionary analysis showed that papaya LysM-RLK could be further divided into three subgroups (Lym-II, Lym-III, Lym-IV), distributed on four chromosomes. Recent gene replication is the main driver of the evolution of the papaya LysM-RLK subfamily. The analysis of promoter sequence regulatory elements found that it contained multiple photoresponse elements and elements involved in low temperature response and stress related hormone signal response. Large-scale comparative transcriptome analysis systematically analyzed the gene expression patterns of LysM-RLK under papaya biostress and abiotic stress and different tissues, revealing its specific expression patterns and potential biological functions. The expression differentiation of replicating gene pairs, differences in domain composition, and changes in the tertiary structure of proteins suggest subfunctionalization in the process of evolution. Core co-expression network analysis under biotic and abiotic stress conditions identified 27 core genes strongly associated with LysM-RLK3, revealing the potential transcriptional regulatory patterns of LysM-RLK3. The results would provide important insights into the evolution, functional differentiation and role of the papaya LysM-RLK subfamily in adversity response and growth and development.

To confirm the characteristics and difference of the chloroplast (cp) genome of Colocasia esculenta var. Redbud and Colocasia esculenta var. Lipu, the two taros were taken as experimental materials in the study, their genomic DNA were first extracted form fresh leaves using an improved CTAB method and the two complete cp genomes were obtained using high-throughput sequencing technology and bioinformatics analysis, simple sequence repeat (SSR) identification, multiple sequence alignment, sliding window analysis on DNA polymorphism and phylogenetic tree analysis were then conducted on two complete cp genomes. The results showed that the length of the complete cp genomes of Redbud and Lipu was 162 478 bp and 162 453 bp, respectively, exhibiting the typical cyclic quadripartite structure. A total of 131 genes were annotated both in the two, including 86 protein-coding genes, 37 tRNA genes and 8 rRNA genes, of which 18 genes had two copies and 23 genes had introns. A total of 130 and 124 SSR sites were identified in Redbud and Lipu respectively, the content of A/T in the SSR repeats was 63.08% and 61.29% respectively. 15 SSR polymorphic primers were identified. A total of 236 cp single nucleotide polymorphism (SNP) sites were detected between Redbud and Lipu, of which 26.7% were in the gene coding region, which leading to 25 missense variant genes, the variation of the genes may promote the difference between the two varieties. Compared with the representative species from 13 genus of Aroideae showed that the structure, types, and numbers of gene were relatively conservative. The trnS-trnG and ndhF-rpl32 were the highest variation sites in SSC and LSC region, respectively. The phylogenetics analysis using maximum likelihood method (ML) showed that the genus Colocasia had the closest relationship with the genus Steudnera, but the farthest relationship with the genus Sauromatum in the Ariodeae. The results would provide a theoretical basis for the germplasm resource exploitation,genetic diversity evaluation and phylogenetic analysis of C. esculenta.

Cyperus esculentus is a special oil crop, with its underground tuber accumulating a large amount of oil, and also having the advantages of wide adaptability and strong stress resistance. This crop is a superior germplasm material for studying plant stress resistance and oil enrichment in the underground vegetative organs. Transport inhibitor response protein 1 (TIR1) can regulate plant growth and development and abiotic stress response as an auxin receptor. However, few reports on CeTIR1 have been reported. In this study, four TIR1 genes, namely CeTIR1-1, CeTIR1-2, CeTIR1-3 and CeTIR1-4, were identified from C. esculentus transcriptome data and the ORFs were further cloned by RT-PCR. All the four CeTIR1 proteins contained a typical F-box protein domain, AMN1 superdomain and Transp_inhibit domain, revealed by bioinformatics analysis. No significant difference was detected among the four CeTIR1 proteins in regarding sequence length, relative molecular weight, isoelectric point and other physicochemical properties. The four CeTIR1s were closely related to TIR1s derived from plants of Cyperaceae, Oleaceae and Cruciferae in the evolution. Gene expression profiling showed that the expression levels of CeTIR1 family genes were significantly different in different tissues of C. esculentus, with the highest expression in tuber tissues and lower expression in root and leaf tissues. The antioxidant enzyme activity and MDA content of C. esculentus seedlings increased under salt stress. After adding exogenous IBA treatment, the antioxidant enzyme activity of C. esculentus seedlings under salt stress further increased whereas the MDA content decreased. This indicated that IBA could alleviate the adverse effects of salt stress on the growth of C. esculentus seedlings. qRT-PCR results showed that expression levels of the four CeTIR1 genes increased in C. esculentus seedlings treated with salt stress, and exogenous addition of IBA could significantly up-regulate the expression of CeTIR1-2 gene. Comprehensive analysis demonstrates that CeTIR1-2 may be an important gene involved in regulating the response of C. esculentus seedlings to salt stress. Together, the results would provide the scientific basis and important reference for exploring the related function genes involved in auxin regulating the growth and development and stress resistance of C. esculentus, as well as the C. esculentus cultivation in the saline-alkali land.

In order to reveal the genome characteristics of HNU24, which has excellent antagonistic ability to Ralstonia solanacearum, its complete genome was sequenced by the BGISEQ-500 and ONT PromethION technology, and the genome assembly, gene prediction, function annotation, and protein homology analysis also were conducted. Phylogenetic analysis results demonstrated that HNU24 belonged to Bacillus velezensis. Its completed genomic sequence length was 3 932 768 bp, GC content was 46.48%, and had 3822 genes. A total of 43 carbohydrate active enzyme gene families were identified in the genome, and the cellulase activity experiment further confirmed that the strain HNU24 had the ability to degrade cellulose. Thirteen clusters of secondary metabolite biosynthesis genes were predicted in genome, including eight compounds: surfactin, fengycin, plantazolicin, butirosin A/butirosin B, macrolactin, bacillaene, difficidin, bacillibactin and bacilysin, which have been reported as the antibacterial components. Five unknown components, which were found no homologous genes or were less similar to the known database sequences, may be new compounds that have not been identified and reported. In addition, greenhouse experiment demonstrated that HNU24 had significant growth promoting effect on tomato plants. Thus, HNU24 may antagonize R. solanacearum and promote tomato growth by secreting active compounds, and it is a potential biofertilizer strain. The relevant results would lay a foundation for further research and application of HNU24 in biological control.

Two genuses and species of Orchidaceae, Taeniophyllum glandulosum Blume and Tainia dunnii Rolfe, together with other two species, Bulbophyllum henanense J. L. Lu and Goodyera yangmeishanensis T. P. Lin, were reported as new records to Hubei province. The morphological characteristics were briefly described, and color photos were provided. The new records enrich the wild orchid resources and are of great significance for further study of orchid plants and biodiversity conservation in Hubei province.

Trachoma Garay, originally described from northern India，was recently collected from Motuo, Tibet Autonomous Region, China. The flowers are similar to those of Tuberolabium Yamamoto, but in that genus the flowers open simultaneously along an elongate rachis and with deeply cleft separated by a hyaline flange poliionia, whereas in Trachoma they open in successive clusters on an abbreviated rachis and with entire or obscurely sulcate pollinia.

In three Camellia vietnamensis producing areas of southwest tropical rainforest in Hainan Province, Baomeiling Ecological Protection Reserve (JB), Bawangling Gibbon Reserve (QS), and Jiangpai Village (XS), Baisha Li Autonomous County, 22 high-yielding single strains were selected, for primary screening and comparison. Observe fruit yield per unit area, oil content rate of fresh fruit, grude oil yield per unit of crown area, peroxide value, iodine value, acid value, saponification value and the contents of palmitic acid, stearic acid, oleic acid, linoleic acid, myristic acid, palmitoleic acid, linolenic acid, arachidic acid, eiconsenoic acid in seed oil for 3 years, after the data was treated with the methods of ANOVA, gray association analysis, and cluster analysis, then screen out the more superior single strains. There existed significant difference in grude oil yield per unit of crown area, oil content rate of fresh fruit and fruit yield per unit area, among them, fruit yield per unit area might be the key indicator of high-yield screening. The physicochemical nature and fatty acid content of camellia seed oil both meet the requirements of “oil-tea camellia seed oil” (GB/T 11765—2018), but there existed some significant difference in some indicators, and there existed the linear correlations between some saturated and unsaturated fatty acids, then there existed the phenomena of the saturated acids changed into unsaturated acids, indicating that the camellia seed oil has no quality problems, and the different tree had its specific characteristic, so the breeding target should be mainly high yield and stable yield, and iodine value, saponification value and the contents of oleic acid might be the effective indicators for selection. Known from the grey association analysis data, the single strains with superior integrated traits were successively JB2, JB7, QS6, JB1, QS5, XS2, JB4, XS4, JB9 and XS5 respectively; Known from the clustering results, it is better to gather all the individual strains into 9 categories (r=0.904), among them, the top seven single strains of comprehensive traits were clustered in Ⅰ, Ⅸ, Ⅶ and Ⅵ respectively, indicating it was expected to screen out the characteristic diverse varieties. JB2, JB7, QS5, XS2 and XS4 belonged to the expected individual strains whose comprehensive behaviors in economic traits were excellent, and JB2 among them was the best one and rare.

In this paper, a combination of traditional morphological features and modern molecular phylogenetic analysis was used to identify and describe a gasteroid fungus collected from Guangdong. The studied specimens is Asperosporus subterraneus Karlsen-Ayala, Gazis & M.E. Sm., a member of the new genus Asperosporus Karlsen-Ayala, Gazis & M.E. Sm. of Agaricaceae which newly reported from Florida, USA, and firstly reported from China. A. subterraneus was mainly characterized by its irregular spherical basidiomata, white to grayish white at first, then becoming brownish when mature, rapidly stain pinkish-red when cut or bruised, earthy smell, Basidiospores, 14-18 μm×11-16 μm, broadly elliptical to subglobose and thick-walled basidiospores ornamented with larger pyramidal to irregular warts, turn to orange brown in 5% KOH solution and dark brown when added to Melzer solution, and the spores were often attached with sterigma remnants. Specimens were deposited in the Fungarium of Guangdong Institute of Microbiology (GDGM).

Three tapping time during the daytime of six rubber cultivars was set to explore the rubber yield, latex quality and raw rubber properties of different rubber varieties. The two-way analysis of variance showed that rubber production was significantly affected by the interaction between tapping time and rubber variety, and the response of each physiological parameter to the variety was significantly different, but there was no significant difference to the tapping time. The most suitable time for daytime rubber tapping is 6:00 am in the three daytime rubber tapping time treatment. Reken 524 and Reken 525 were the most suitable daytime rubber tapping variety judged by latex volume, dry rubber yield and physiological parameters. 7-33-97 and Reken 501 were the most suitable daytime rubber tapping variety judged by common raw latex properties. Considering the purpose of improving labor efficiency and increasing the income of rubber workers, Reken 524 and Reken 525 could be used for daytime rubber tapping at 6:00 am during the peak rubber production period in Maoming Reclamation Area, Guangdong, China.

At present, the difficulty and pain point that sugarcane mechanical harvesting cannot be widely promoted is that mechanical rolling has a negative effect on sugarcane growth. In order to explore the effects of mechanical harvesting on the main agronomic traits and important physiological indexes of GT47 and GT31 at seedling stage, and provide theoretical reference for the evaluation of physiological adaptability of sugarcane mechanical harvesting and selection of suitable mechanical harvesting varieties, a randomized block design was used to compare and analyze the differences of plant growth rate, tiller rate, main components of leaves, root activity and related enzymes between mechanical and artificial harvesting treatments. The results showed that mechanical harvesting had a great effect on the rate of plant initiation and tillering of GT31, but not on the rate of plant initiation of GT47. There was a significant difference in nitrogen content between the two varieties during artificial harvesting, and the two harvesting methods had no obvious effect on the nitrogen content of GT47. The difference of total P content between GT47 and GT31 was extremely significant in artificial harvest, while there was no significant difference in total P content between the two varieties in mechanical harvest. Potassium content was greatly affected by different fertilization methods and different sugarcane varieties, and there was a significant difference in total potassium content between GT47 and GT31 regardless of mechanical or artificial harvesting. The root activity of GT47 and GT31 was 0.53 mg/(g·h) and 0.82 mg/(g·h) respectively in mechanical harvesting, but there was no significant difference in the root activity of the two varieties in artificial harvesting. After mechanical milling, the MDA content of GT31 root was significantly higher than that of artificial harvesting, while the MDA content of GT47 root showed no significant difference between the two harvesting methods. The CAT activity in root system of GT47 was 688.07 nmol/(min·g), which was significantly higher than that of GT31. There was no significant difference in Pro content and POD activity in roots among different varieties and different harvesting methods of the same variety. The adaptability of different sugarcane varieties in different harvest way differed. GT47 responded more quickly in tillering and other agronomic traits, and leaf nutrition, root activity, root art related enzymes after mechanical compaction. GT47 is more suitable for mechanical harvest.

Centromea pubescens is an important tropical leguminous forage. It is of great significance to study the salt tolerance mechanism of the plant for breeding excellent varieties and improving forage yield. In order to study the difference of salt tolerance of different seeds of C. pubescens in the germination period, the salt tolerance of 75 germplasms was identified in the germination period. NaCl with 150 mmol/L, and 14 indexes such as germination rate, germination potential, root length, bud length and fresh weight were measured, and membership function, principal component analysis, correlation analysis and cluster analysis were carried out to comprehensively evaluate the salt tolerance of germplasm resources of pteromea and to screening salt tolerant germplasm. Under salt stress concentration of 150 mmol/L, the coefficient of variation of relative root shoot ratio was the highest (67.75%), which could be used as one of the evaluation indicators of salt tolerance. The correlation analysis showed that there was a very significant (P<0.01) relationship between any two germination indicators of the germination rate and germination potential, and the other indicators were related to each other to a certain extent. Four principal component as the main component analysis of the direction of the cumulative contribution rate of 83.17% could replace most of the information of all indicators, comprehensively reflecting the germination characteristics during germination under salt stress, and determine the germination index, relative root shoot ratio, relative germination rate and root shoot ratio as the evaluation indicators of salt tolerance through the load matrix. The average membership function and comprehensive score were comprehensively evaluated for salt tolerance, and the 75 germplasm resources were divided into four categories by clustering based on the comprehensive score value of salt tolerance (Z), including 1 highly salt tolerant germplasm (Centrosema 050321057), 17 salt tolerant germplasm, 7 low salt tolerant germplasm and 50 salt sensitive germplasm. In this study, the salt tolerance evaluation system and material evaluation and screening methods were established, which could provide a basis for the study of salt tolerance and salt tolerance gene screening of the genus.

Morinda officinalis How is a plant of the Rubiaceae, whose dried roots are used as medicine It can strengthen bones and muscles, nourish kidney-yang and remove wind and moisture. It is mainly distributed in Guangdong, Guangxi, Fujian and Hainan provinces. It is one of the four major southern medicines in China. In the main production areas of China, it is mainly propagated by cuttings. In the process of variety breeding, it is often disturbed by plant viruses. The viruses are transmitted and accumulated in plants through asexual propagation of plants, resulting in the inhibition of plant growth and the decline of yield and quality. Therefore, for the purpose of tissue culture detoxification of M. officinalis, the tissue culture detoxification research of M. officinalis was carried out. Thereby improving the yield and quality of M. officinalis, which is beneficial to the protection of M. officinalis species. It is of great practical significance to provide technical support for quality resources and the factory-based seedlings of M. officinalis. Using the stem segments as the explants, an efficient and stable M. officinalis tissue rapid propagation system was established, and suitable plant regeneration methods were screened out. Using 1/2MS as the basic medium, M. officinalis stem axillary buds were used to induce clustered buds to obtain the virus-free seedlings and successfully domesticated and transplanted, the virus detection of M. officinalis tissue culture seedlings and transplanted seedlings were carried out by PCR technology. The semi-lignified stem segments as the explants were suitable to induce axillary buds, the most suitable medium was 1/2MS+6-BA 0.2 mg/L, and the axillary bud induction rate was 70%. Taking the axillary buds to induce fascicled bud, the most suitable medium was 1/2MS+6-BA 0.2 mg/L, and the fascicled bud induction rate was 86.36%. The suitable medium for rooting was 1/2MS+IBA 0.5 mg/L, with a root rate of 100%. The tissue culture seedlings were transplanted in the 1∶1 peat soil-perlite matrix for 8 days with the highest survival rate, reaching 93.3%. The reverse transcript PCR was used to determine the Cucumber mosaic virus isolate M. officinalis How (CMVMO) in the tissue cultured seedlings and transplanted seedlings, the plantlets of M. officinalis How detoxified was obtained. In this study, virus-free seedlings of M. officinalis were successfully cultivated through direct organogenesis, and an in vitro rapid propagation and regeneration system of M. officinalis was established, which would not only improve the yield and quality of M. officinalis, but also provide a reference for virus-free rapid propagation and commercial production and seedling raising of M. officinalis.

Hippeastrum is a new kind of flower introduced in large scale from abroad in recent years, but its seedlings are expensive, regular scale cuttage propagation speed is slow and needs a large number of mother bulbs. Cross breeding, a common method for its new varieties, however, has poor orientation. This aim of this study was to establish an efficient callus regeneration system for rapid propagation and factory production of seedlings, which can also be used for the orientation breeding of Hippeastrum. The effects about different plant growth regulators on callus induction and plantlet regeneration were studied with the leaves of Hippeastrum ‘Bankkok Rose’ plantlet in vitro. The highest induction rate of callus (39.67%) was observed when the basal leaves of the buds in vitro were cultured on MS+2,4-D 2.00 mg/L+ TDZ 0.50 mg/L medium for 45 days. The optimal medium for callus proliferation was MS+6-BA 2.00 mg/L, and the average proliferation was 4.01 times every 20 days. The optimal medium for callus differentiation was MS+ KT 0.50 mg/L. After 60 days, the adventitious bud differentiation coefficient reached 10.59, and the seedling formation coefficient was 5.67. The rooting rate reached 100% after 30 days in MS+IBA 0.50 mg/L. After 30 days of root culture, the small plants were transplanted to the coir: peat soil: vermiculite =1 : 1 : 1 substrate, and the survival rate reached 93.33% after 30 days. This study could provide technical support for industrial propagation of Hippeastrum seedlings, and also provide excellent receptor materials for subsequent molecular breeding.

The southern ecological type of Chinese yam variety Guihuai5 was used to investigate the mutagenic effect of ⁶⁰Co-γ radiation. In a certain dose range, ⁶⁰Co-γ radiation had highly significant inhibitory effect on the germination and seedling growth of Chinese yam bulbils. The linear regression equation between the radiation dose and germination rate was y =-0.8776x+103.37. According to this, the half-lethal-dose and 40%-lethal-dose was 60.8 Gy and 72.2 Gy respectively. 40 Gy radiation treatment had no inhibitory effect on the germination, growth and development of the M₁ generation population of the bulbils. On the contrary, it showed a promoting effect in some extent. Radiation treatment induced increased tuber length, diameter and weight in the off spring plants of M₁ generation. The radiation treatment induced fascicular branching in some individual tubers in the M₁ generation, which resulted in the tuber change from long-column-shaped shape to irregular-block-shaped shape, and the weight of single tuber increased greatly. This occurred particularly in 90% of the plants harvested in the 100 Gy treatment. ⁶⁰Co- γ treatment induced mutations with twin tubers in the M₁ generation of the treated bulbils. The occurrence probability of the twin mutation was the highest in the 60 Gy treatment, accounting for 8% of the plants harvested. From the M₁ generation, 18 mutants with twin tubers, 11 mutants with large tubers and 1 mutant with female flowers were obtained. The results of this experiment indicate a bright prospect for radiation induction breeding of Chinese yam, and would provide basic materials for the further breeding of new Chinese yam varieties and lines.

To effectively monitor the occurrence and damage of dangerous pests in Zhaoshu Island, a systematic survey and risk assessment on all the pests of 90 plants in Zhaoshu Island was conducted. The results showed that there were 19 insects and mintes of 8 wild halophytes including 5 alien invasive pests and 7 world dangerous pests occurred and harmed seriously; 24 insects and mintes of 29 landscape plants including 9 alien invasive pests and 6 world dangerous pests occurred and harmed seriously; 36 insects and mintes of 31 salt-tolerant fruits and vegetables including 7 alien invasive pests and 6 world dangerous pests occurred and harmed seriously; 16 insects and mintes of 22 sand-bander plants including 5 alien invasive pests and 2 world dangerous pests occurred and harmed seriously. The results of risk assessment showed that Brontispa longissima, Paracoccus marginatus, Phenacoccus solenopsis and Opisina arenosella were all high-risk pests in Zhaoshu Island with R value 2.12, 2.12, 2.09 and 2.02, while Dysmicoccu neobrevipes, Diaspis boisduvalii, Tetranychus urticae, Thrips palmi, Bemisia tabaci, Liriomyza sativae and Bactrocera cucuribita were all moderate risk pests in Zhaoshu Island with R value 1.92, 1.89, 1.82, 1.79, 1.79, 1.74 and 1.61, respectively. The results were the first report on the occurrence and damage of plant pests in Zhaoshu Islan, which would provide an important basic information support for the effective protection of the biosafety in Zhaoshu Island.

C. camphora (L.) Presl is the most effective plant for extracting natural borneol in China. In order to help determine its proper habitat, this research plans to select branches and leaves of C. camphora (L.) Presl from eight habitats in China according to its habits, natural borneol of the leaves and branches of C. camphora (L.) Presl were extracted by steam distillation. The relative content of the chemical components in the extract was determined by GC-MS. The bacteriostatic circle diameter of Escherichia coli, Salmonella typhi and Salmonella enteritidis subsp was measured by the paper method, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by 96 micro well plates. Chemical composition determination showed that the content of natural borneol extracted from the branches and leaves from different habitats was different, among them, d-borneol, camphor, d-limonene, eucalyptol, d-α-pinene, camphene, α-humulene and terpinen-4-ol were the common components, and the content of d-borneol was the highest, then camphor. The highest content of d-borneol was found from Yuan’an, Hubei, China (82.47%), and the lowest content was found from Ruyuan, Guangdong, China (41.63%). The natural borneol extracted from various habitats showed bacteriostatic effect on the three tested strains, and the diameter range of bacteriostatic ring was 14.60 to 27.95 mm, the minimum inhibitory concentration (MIC) ranged from 250 to 1250 μg/mL, the minimum bactericidal concentration (MBC) ranged from 0 to 1000 μg/mL. The natural borneol from Yuan’an and Jishui, Jiangxi had the best bacteriostatic effect, while that from Guangdong had the worst on the whole. In conclusion, the bacteriostatic activity of the extracts from the branches and leaves of C. camphora (L.) Presl is correlated with the content of its main components, and the habitat with the highest content of d-bornol has the best bacteriostatic effect, while the other has poor bacteriostatic effect. The data obtained in this research are accurate and reliable, and would provide a basis for the quality evaluation of the extracts of C. camphora (L.) Presl branches and leaves and the development of natural borneol resources.

Paurocephala sauteri, characterized by small individuals, rapid reproduction and overlapped generations, is the most damaging pest of mulberry trees in tropical and subtropical areas. It happens in seedling period, leading to yield loss over 40%, or even out of harvest, and is very difficult to control. In order to accurately predict and efficiently control the pest, and to improve the yield and quality of mulberry leaves, the internal reproductive system of the male and female adults of the pest in different developmental periods was dissected and observed to clarify the morphological characteristics and changes of the internal reproductive system of male and female adults of the pest before and after mating. Except for 2 pairs of lateral oviducts the composition of the internal reproductive system of the female adults is similar to Trioza erytreae (Del guercio), and male adults is highly similar to Diaphorina citri (Kuwayama). Compared with the pre-mating period, the length of spermatheca in mating and post-mating periods reached nearly 1.63 times and 1.85 times, and the width increased by about 1.74 times and 1.84 times respectively, with significant differences in each period (P<0.05), the length and width of eggs increased rapidly, to mating period increased by nearly 2 times (P<0.05). At the same time, several large vesicles appeared inside the egg in mating period and disappeared in post-mating period, them should be trophoblasts, providing nutrition for oocytes. Compared with the pre-mating period, the testes of the male increased to the maximum in the mating period and shrank to the minimum in the post-mating period. There were significant differences in the three periods (P<0.05), while the length and width of the seminal vesicle both significantly increased to about twice (P<0.05) in mating and post-mating periods. This study has practical significance to precisely judge and determine the appropriate period of prevention and control, to clone reproductive-related genes, to develop new gene targeting agents, and to formulate efficient prevention and control measures of P. sauteri.

In the agroforestry system, the spatial distribution of the root system of each component determines its competitive ability to the resources in the system, which is an important basis for the design of an agroforestry system. In this paper, the root density and spatial distribution of Areca catechu and elephant grass in the compound system were studied by the zonal layered mining method, and the underground competition index of A. catechu and elephant grass was calculated by the niche overlap formula proposed by Levins. The biomass density of betel nut root (1343.88 g/m³) was 2.41 times that of elephant grass (558.53 g/m³). In the horizontal direction, the biomass density, root length density and competition index of fine roots (0-2 mm), middle roots (2-5 mm) and thick roots (> 5mm) of A. catechu decreased with the increase of the distance between roots and the base of A. catechu trunk. The root biomass density, root length density and competition index of elephant grass increased with the increase of distance, and the distribution was relatively uniform. In the horizontal direction, the root biomass density of A. catechu in 80cm from the trunk of A. catechu was significantly higher than that of elephant grass, and the root biomass density of elephant grass in 120-140 cm was significantly higher than that of A. catechu, but there was no significant difference between them in other distances. The root length density of A. catechu in 20-40 cm was higher than that of elephant grass, but the difference is not significant. The root length density of elephant grass in other horizontal distances was significantly higher than that of A. catechu. Except 20-60 cm from the trunk, the competition index of elephant grass in other areas was higher than that of betel nut. In the vertical direction, the biomass density, root length density and competition index of fine root, middle root, thick root and elephant grass root in 0-20 cm soil layer were significantly higher than those in 20-40 cm soil layer. In the two soil layers, the root length density of A. catechu root system was smaller than that of elephant grass, while the biomass density and competition index of A. catechu root system were larger than that of elephant grass. The results show that although the root distribution of A. catechu and elephant grass overlaps in space, they have their own advantages in a certain area, and neither can form an absolute competitive advantage over the other, thus both can grow healthily in the competition. Therefore, in order to effectively reduce the competition between betel nut and elephant grass, give full play to their respective advantages, and maximize their yield and benefit, we should appropriately increase the planting distance between elephant grass and betel nut trees, and appropriately strengthen the water and fertilizer input in the upper soil in the intercropping area.

In order to explore the effects of different rainfall and stand types in the same area on vegetation diversity, three regions with large annual rainfall differences in Hainan were selected to conduct vegetation diversity control experiments with different stand types. The results showed that 61 species, 58 genera, 45 families were present in the natural forests, 39 species, 37 genera, 26 families were present in the Eucalyptus plantations, and the vegetation diversity of Mangifera indica plantations, Acacia mangium plantations and Hevea brasiliensis plantations was relatively low due to frequent artificial management. The effects of rainfall on species diversity index of natural forest were significant (P<0.05), but no significant difference was found in Eucalyptus plantation (P>0.05). The species richness index (R) of natural forest and Eucalyptus plantation increased gradually with the increase of rainfall. The Shannon-Wiener diversity index (H), Simpson diversity index (D) and Pielou evenness index (J_sw) of tree layer and shrub layer of natural forest decreased with the increase of rainfall, while the herbaceous layer did the opposite. Shannon-Wiener diversity index, Simpson diversity index and Pielou evenness index of shrub layer and herb layer of Eucalyptus plantation increased with the increase of rainfall. The fluctuation of species diversity index was mainly in shrub layer and herb layer of natural forest and Eucalyptus plantation, and the change of tree layer was relatively stable. The rainfall and canopy shaded effect were the important reason for the differences in regional species diversity, compared with natural forest of Eucalyptus plantation tree layer the lack of ecological niche of the vegetation diversity was the main reason for the low and had nothing to do with the tree itself, specific provisions of other economic forest caused by frequent grass fertilizer management was relatively single species diversity. Therefore, the key to improve species diversity of the plantation is to establish a mixed or different-age forest to transform the existing pure forest to promote the release of the niche of the tree layer and change the management mode of other economic stands at the same time.

Species diversity is the most basic level of biodiversity, which not only reflects the richness of biological species, but also the spatial scope of species evolution and the ecological adaptability to specific environments. Structure is the basis for studying the historical dynamics of plants, and while understanding and clarifying the growth competition relationship between species, it reflects the trend of community succession. Based on the results of 62 plots with a total area of 3.72 hm², the species diversity and structure of tree populations of Dagangshan were analyzed. There were 486 species of plants in the community, belonging to 286 genera of 120 families, of which single species accounted for 66.43% of the total, and China fir were in a dominant position in the community. Dagangshan is located in the subtropical region and has the nature of transition zone. The genus of seed plants included 13 distribution types, and 9 genera with endemic components in China. Shannon-Weiner index, Simpson index and Pielou index were basically the same in the distribution trend of each growth layer. The advantage of shrub layer was obvious. The herbaceous layer was slightly higher than the arbor layer. The overall species diversity index of the community was higher and the species were more abundant. By sample belt, the 2nd sample was the most abundant, and the 1st sample was slightly lower than the others. However, the community similarity was the highest in the 1st and 2nd belts, and the difference in species diversity indices in the 3rd and 4th samples was small, but the community differences were the largest.

In order to explore the pollution level and source of soil heavy metals in Haikou City, taking the agricultural land in Haikou City as the research object, the content of eight kinds of heavy metals such as Cd, Hg, As, Pb, Cr, Cu, Ni and Zn in soil surface samples were collected and determined, and the spatial distribution characteristics of heavy metals were clarified combined with geostatistical analysis method. The single factor pollution index method, geo-accumulation index method and potential ecological risk index method were used to evaluate soil pollution. The source of heavy metals was quantitatively analyzed by the correlation analysis and principal component analysis / absolute principal component fraction (PCA/APCS) receptor model. Six heavy metals such as Cd, Pb, Cr, Cu, Ni and Zn exceeded the risk screening value of agricultural land, and the proportion of exceeding the standard points from high to low was Cr, Ni (31.6%)>Cu (21.1%)>Cd (5.3%)>Pb and Zn (2.6%). The spatial distribution characteristics of Cu, Zn, Ni and Cr contents were basically the same, which were similar to the distribution of basic volcanic rocks in the study area. The evaluation results of heavy metal geo-accumulation index showed that the concentration of Cd in the soil was the highest, and the soil was greatly affected by Cd, followed by Cr, and other heavy metals were less affected. The potential ecological risk levels of soil heavy metal pollution were mainly mild and moderate risk levels, while As, Pb, Cr and Zn were slight ecological risks, and the potential ecological harm was small. The above points of Cd, Hg and Ni intensity ecological risk accounted for 52.6%, 15.8% and 5.3% respectively. The potential ecological risk of soil heavy metals in the study area was mainly caused by Cd and Hg. Eight kinds of heavy metal elements were identified as three sources. Cu, Ni, Cr and Zn were mainly from natural sources, which were mainly affected by the high soil background value of basic volcanic parent rock, Pb, Cd, As and Hg were mainly from industrial sources and traffic sources. As was also affected by agricultural sources. The source of heavy metals in Haikou soil was relatively single. As a result, it is necessary to strengthen the pollution control of Cd, Cr and Hg in the soil, with the focus on the pollution control of Cd.

In this paper, the bibliometrics approach in conjunction with the Research Leadership Index (RLI) was used to compare and assess the scientific research performance and innovation level of the major producing nations of natural rubber on 12 Research Fronts. The Research Fronts of each nation were revealed to enter the innovation excellence position, innovation forefront position, and innovation rank position, as well as the status of innovation catching up posi-tion and innovation gap, from three major research areas of agriculture and plant science, ecology and environmental science, chemistry and material science. China has grown to be a significant player in global natural rubber research, with the highest RLI score globally. The United States comes in second with a score roughly 65% of that of China. France, Germany, Thailand, India, and Malaysia are ranked third through seventh, respectively, with France, Germany, and Thailand being in the same active cascade as India and Malaysia. The United States and France are currently in the innovation excellence position in the majority of the Research Fronts (more than 50.00%), while China has entered the position in 100% of the Research Fronts. There is a large Research Front gap between the countries of Germany, Thailand, India, Malaysia and the countries of China, the United States, and France. 16.67% of the Research Front in Germany, Thailand, India, and Malaysia is still in the innovation catching up stage. In all three of these lucrative industries, where China excels at invention, the country has taken the lead. The performance of the other six nations varies in several areas. In the fields of agriculture and plant science, Germany, Thailand and Malaysia, have taken the innovation leadership and ranked positions, respectively, while India is in the innovation catching up position. The United States and France have entered the innovation excellence position. While India lags behind, the United States and France fare better than Germany, Thailand, and Malaysia. The United States and Germany have taken the top spots for innovation and excellence in the field of ecological and environmental science. France, Thailand, India, and Malaysia are still lagging behind in terms of innovation. The performance of the United States and Germany is superior, whereas that of France, Thailand, India, and Malaysia is subpar. In the fields of chemistry and materials science, the innovative excellence position has been attained by 50.00% of the Research Front in the United States and France, 30.00% in Thailand and India, 20.00% in Germany, and 10.00% in Malaysia. In the United States and France, 50.00% of the Research Front has joined the innovation forefront position and the innovation rank position, while India is at 70.00%. At 60.00%, 50.00%, and 80.00%, respectively, Germany, Thailand, and Malaysia are in the innovation forefront position and innovation rank position, but 20.00%, 20.00%, and 10.00% of the Research Front are still in the innovation catching up position. The six nations perform fairly evenly in this regard, but the United States, France, and India outperform Germany, Thailand, and Malaysia by a small margin.