Abstract:The research on the interspecific relationship, niche status and community stability of dominant plants in evergreen broad-leaved forests in special habitats can provide scientific basis for the conservation of regional biodiversity and the conservation and management of nature reserves. Based on the filed investigation data of long-term plots in Guangdong Grand Canyon and 2×2 correlation tables, the importance value, niche width and niche overlap of dominant species were determined. The index of interspecific associations, OI index and DI index for dominant species were analyzed by using variance ratio method and χ² test. Moreover, the community stability was evaluated by Godron method. The results showed that there were 104 species, belonging to 39 families and 74 genera, in which the importance value and niche width of Schima superba were the biggest, followed by Machilus chinensis, Heptapleurum heptaphyllum, Diospyros morrisiana and Engelhardia roxburghiana. These five species occupied a dominant position in the competition for community resources and had a high niche overlap with other plants in the community (67.16% of the total). In 325 pairs of 26 dominant species, negative associations were greater than positive associations. χ² test showed that the species were relatively independent and loosely connected. However, the five dominant species showed close correlation, and the concomitant occurrence rate was high. Godron method analysis showed that the community was in an unstable state and there was a significant negative correlation between species. Therefore, it was revealed that the interspecific association of the community in broad-leaved evergreen forests in Guangdong Grand Canyon had weak interspecific association and unstable community, which needs to be strengthened for conservation and management.

Abstract:Leaf functional traits can reflect the adaptation strategies of plant to environment. Based on the sample survey, six wild Rosa anemoniflora communities at different altitude in Yanping District, Fujian Province were selected to study the effects of environment factors on leaf functional traits by using coefficient of variation, Pearson correlation analysis and redundancy analysis. The results showed that the habitat heterogeneity of R. anemoniflora communities was strong, the CV of soil factors under different environment ranged from 9.44% to 122.28%, among which soil pH was the smallest, and soil available phosphorus content was the largest. There are significant differences among soil factor indexes under different environment. The soil pH, contents of organic matter, total nitrogen (N), phosphorus (P) and potassium (K) and available nitrogen (AN), phosphorus (AP) and potassium (AK) were high in the middle altitude areas, and the soil stoichiometric ratio was low, while the soil moisture content and soil stoichiometric ratio were the highest in the high altitude areas. Under different environment, the CV of leaf functional traits of R. anemoniflora ranged from 2.49% to 97.58%, among which leaf water content was the smallest, and the specific leaf weight was the largest. Along the altitude, the contents of P, K, calcium (Ca) and magnesium (Mg) in leaves showed an increasing trend, indicating that the diversity of leaf functional traits was abundant, and had strong adaptability to heterogeneous habitats. Pearson correlation analysis showed that the dry matter content was significantly positively correlated with Ca content in leaves, and the contents of K and Mg were negatively correlated with C/N and N/P in leaves. Rosa anemoniflora at high altitude could increase stress resistance by improving the absorption of K, Ca and Mg to cope with habitat changes. The redundancy analysis showed that soil AK and water content were the main driving factors of leaf functional trait change with environment. Therefore, it was suggested that the leaf of R. anemoniflora adapted to the changes of altitude and habitat through functional trait variation and trait combination. The study on the functional traits of R. anemoniflora leaves and their relationship with environment factors would help to understand the impact of small-scale environmental changes on plant variation, and provide theoretical guidance for the conservation, development and genetic improvement of wild resources of R. anemoniflora.

Abstract:Understory plant diversity and soil physicochemical properties are the key indicators of soil and water conservation stability and growth ability. Five typical stand types on Pingtan Island were selected, including Acacia confusa forest (I), Pinus thunbergii forest (II), A. confusa + Casuarina equisetifolia forest (III), P. thunbergii + A. confusa forest (IV) and P. thunbergii + Eurya emarginata forest (V), the differences of understory plant diversity and soil physicochemical properties in different stand types were analyzed, and explored their relationships through redundancy analysis (RDA). The results showed that the mixed forest of P. thunbergii + A. confusa was more beneficial to enrich the species diversity in the understory, while the community structure of A. confuse + C. equisetifolia forest was simple with low species diversity. The soil physicochemical properties of different mixed forests were different. Compared with pure forest, the mixed planting of tree species was beneficial to increase the total potassium content of soil, and A. confuse + C. equisetifolia and P. thunbergii + E. emarginata forest were beneficial to enhance soil organic matter content, total nitrogen, alkali-hydrolytic nitrogen and available phosphorus. Soil total K and water soluble salt had the greatest influence on species diversity in understory, and total K was negatively correlated with species diversity index in shrub layer and herbaceous layer. The total water soluble salt was positively correlated with the species diversity index of shrub layer and negatively correlated with the species diversity index of herbaceous layer. Therefore, in order to improve the species diversity of the understory, the mixed planting of P. thunbergii + A. confusa could be considered. To improve soil fertility, mixed planting of A. confusa + Casuarina equisetifolia, P. thunbergii + A. confuse could be considered. At the same time, tree species coordination was carried out through artificial tending, thinning and replanting, so as to reduce allelopathy of Casuarina equisetifolia, control total potassium and water soluble salt content in soil for promote long-term stable development of community.

Abstract:To explore the formation and maintenance mechanisms of the understory plant diversity, the ecological stoichiometric characteristics of leaves of understory trees, shrubs, herbs and vines and their relationship with phylogeny were studied by conventional and phylogenetic comparison methods in Maoershan subtropical evergreen broad-leaved forest, Guangxi. The results showed that the phylogenetic signals (Blomberg’s K) of leaf stoichiometric characteristics ranged from 0.020 to 0.183. The contents of N and P and the phylogenetic signals of C/P, P/Ca and K/Ca in leaves were significant, indicating that phylogenetic conservation existed in the process of species diversification. The contents of C, N, K and Mg in leaves and most of stoichiometric ratios were significantly affected by life form. The contents of N, K and Mg in leaves of vines were the highest, while the contents of C, Mg, C/N and C/P in leaves of herb were the lowest, which indicated that there were differences in the requirement and proportion of nutrient elements in leaves of different life forms. The stable selection of the optimal ecological stoichiometric characteristic values of leaves of different life forms was the optimal evolutionary model, which indicated that plants of different life forms chose the optimal combination of leaf stoichiometric characteristics to adapt to themselves in the evolutionary process. In addition, there was a close correlation between the stoichiometric characteristics of leaves during evolution. Therefore, phylogenetic conservation of leaf ecological stoichiometric characteristics and optimal stable selection in the process of species diversification jointly promoted the formation and maintenance of understory plant diversity in subtropical evergreen broad-leaved forests.

Abstract:Acacia mangium is an important fast-growing tree in South China, but mature forest shows phosphorus deficiency which may reduce forest efficiency, so it needs to be reconstructed. Phosphorus, including four levels as control treatment (CK), low phosphorus addition (LP), medium phosphorus addition (MP), and high phosphorus addition (HP), were added into two forest reconstruction mode, such as M1 (Ormosia pinnata + Castanopsis hystrix + Cinnamomum camphora + Magnolia glauca) and M2 (Michelia macclurei + Carallia brachiata + Schima superba + Mytilaria laosensis) in a mature A. mangium plantation of Longyandong Forestry Farm of Guangdong Province. The growth and leaf nutrients of the modified tree species were measured after 39 months. The results showed that the total biomass of M1 species was the highest in MP (29.91 kg), and that of M2 species was the highest in HP (29.98 kg). The biomass of Michelia macclurei, Carallia brachiata and Mytilaria laosensis was the highest in HP, which was 5.97, 10.3 and 10.69 kg, respectively. The biomass of Ormosia pinnata, Castanopsis hystrix and Magnolia glauca was the highest at MP (5.12, 6.91 and 11.46 kg, respectively), the biomass of Cinnamomum camphora was the highest at LP (10.4 kg), and the biomass of Schima superba was the highest at CK (4.45 kg). The average phosphorus content of leaves of M2 species was higher than that of M1, but the average N:P in leaves of M2 species was lower than that of M1. Therefore, the phosphorus addition increased the phosphorus content and decreased N:P in the leaves of all modified tree species, which provided a scientific reference for the phosphorus addition gradient and the selection of modified tree species in mature A. mangium plantations in South Asia.

Abstract:To understand the niche characteristics and succession status of subtropical evergreen broad-leaved secondary forest community in Dongguan, Guangdong Province, three 1 hm² plots were set up. Levins niche width and Pianka niche overlap are used to analyze the niche characteristics of the dominant tree species of the evergreen broad-leaved secondary forest community in Mashan and Yinpingshan Nature Reverses in Dongguan. The results showed that the secondary forest communities in Mashan and Yinpingshan were mainly composed of Lauraceae, Rutaceae, Theaceae, Iteaceae, Rubiaceae. The niche width of Acronychia pedunculata, Shichima superb, Machilus chinensis, Cinnamomum parthenoxylon, Itea chinensis in communities was large, and the niche width was closely related to the frequency. The niche overlap of dominant tree species ranged from 0 to 0.53, indicating that the competition of dominant tree species was weak. The succession stages of the three plots are different. The niche width and the niche overlap of heliophytes were large in Yinpingshan communities, while those of mesophytes in Mashan community were relatively larger, reflecting the replacement process of evergreen broad-leaved forest from heliophytes to mesophytes, these would provide scientific basis for the protection and management of secondary forest in this area.

Abstract:To understand the similarities and differences in the rhizosphere bacterial communities of different limestone endemic plants, five species of limestone endemic plants in northern Guangdong were studied, including Saxifraga daqiaoensis, Begonia leprosa, Primulina alutacea, P. polycephala and P. yangshanensis. The rhizosphere bacterial community characteristics and functional component of five limestone endemic plants were analysed by using high-throughput 16S rDNA sequencing and bioinformatics methods. The results showed that 42 phyla, 113 classes, 250 orders, 315 families, and 498 genera bacteria were detected in rhizosphere soil of five plants. Chloroflexi, Bacteroidetes, Actinobacteria, Planctomycetes, Proteobacteria and Acidobacteria were the dominant phyla. Heatmap analysis indicated that the soil physical and chemical factors, including available phosphorus, exchangeable calcium, ammonium nitrogen, soil organic matter, pondus hydrogenii and total nitrogen, played important roles in the composition of bacterial community. The LEfSe analysis showed that different plants enriched different rhizosphere bacterial population. The composition and function of the rhizosphere bacterial community of B. leprosa was significantly different from those of the other four plants. The prediction of PICRUSt2 function showed that the rhizosphere bacterial communities of five plants were the most active in metabolism. The function prediction of FARPOTAX showed that chemoheterotrophy, aerobic chemoheterotrophy, nitrification and aerobic ammonia oxidation were the common dominant functional population in the rhizosphere bacteria of five plants. These functional bacteria play an important role in helping plants grow and develop. It would provide soil microenvironment data for the introduction and domestication of endemic plants in limestone.

Abstract:In order to investigate the effects of exogenous silicon addition on the growth of Phoebe bourneiseedlings under light stress, the changes of different light intensity and silicon addition in the growth, biomass, leaf morphology and photosynthetic parameters of P. bourneiseedlings were analyzed. The results showed that shading and silicon addition had significant effects on the growth and photosynthetic traits of seedlings. Moderate shading and silicon addition were beneficial to the growth of seedling height, ground diameter, biomass of organs and leaf morphology (length, width and area) of seedlings. The decrease of light intensity was conducive to the accumulation of chlorophyll in leaves, and the addition of silicon further promoted the accumulation of chlorophyll in the 15%-60% light intensity, which made seedlings better adapt to light stress. The addition of 1 000 to 2 000 mg/kg silicon under 15% to 40% light intensity could improve the chlorophyll fluorescence parameters in leaves and promote photosynthesis. The addition of 1 000~2 000 mg/kg silicon under 40% light intensity was more conducive to improving the net photosynthetic rate, stomatal conductance and transpiration rate of leaves, reducing the intercellular CO₂ concentration, promoting the improvement of photosynthetic capacity of seedlings, and improving the adaptability of seedlings to light stress. Therefore, the regeneration of P. bournei seedlings was suitable under certain shade conditions, and the addition of silicon was conducive to alleviating light stress, improving the leaf morphology and photosynthetic efficiency of seedlings under different light intensity, improving their growth adaptability to light stress, and then promoting the growth of seedlings, which is conducive to the improvement of afforestation and regeneration effect.

Abstract:In order to analyze the variation pattern and genetic diversity of Choerospondias axillaris germplasms in typical distribution areas, fourteen fruit traits of 20 germplasms from 7 provinces were systematically analyzed and comprehensively evaluated. The results showed that there were variation and genetic diversity of 14 fruit traits in 20 germplasm resources. The variation coefficients of fruit traits except fruit shape index and edible rate were more than 10%, and the average genetic diversity index of fruit traits was 1.88. The correlation analysis showed that the single fruit weight of C. axillaris was positively correlated with the indexes of peel weight, kernel weight, pulp weight and transverse diameter, and the correlation coefficient was greater than 0.93. The 20 germplasms of C. axillaris were divided into 2 groups by cluster analysis, and the group II was further divided into 3 subgroups, and there were significant differences in fruit traits between 2 groups, and the biggest difference was single fruit weight. A comprehensive analysis model was established based on the principal component comprehensive scoring method. The 17#, 16#, 10#, 91# germplasms were selected, which had the characteristics of large fruit, high Vitamin C content, high total sugar content, and good comprehensive traits, and could be used as excellent germplasm resources for cultivation. Therefore, the fruit traits of C. axillaris germplasms had rich variation and genetic diversity, the selected 4 germplasm resources for fruit use had high breeding value and potential for development and utilization.

Abstract:In order to understand the effects of light intensity on growth of Cercidiphyllum japonicum seedlings, one-year-old seedlings were grown under 10% (L₁), 25% (L₂), 100% (L₃), 110% (L₄), and 125% (L₅) natural light intensity, and the adaptive ability in morphology and physiology of seedlings was studied. The results showed that the increase of plant height, biomass, leaf length, leaf width, and leaf area increased at first and then decreased with the increase of light intensity, and all of them reached the highest under L₂. The specific leaf area, leaf water content, and root shoot ratio continued to decrease, while the base diameter increased continuously. The peroxidase activity under L₁ and L₂ was significantly higher than that under L₄ and L₅, while the changes in malondialdehyde content was the opposite. With the increase of treatment time, the superoxide dismutase activity under L₂ increased at first and then decreased, which under L₁ continued to increase and was higher than that under L₃, L₄ and L₅. The contents of total chlorophyll, chlorophyll a and chlorophyll b decreased with the treatment time, and the stronger the light, the lower the content. Therefore, Cercidiphyllum japonicum seedlings could grow under both shade and strong light, and 25% natural light intensity was more suitable.

Abstract:A new species of Sophora(Leguminosae), S. elongata S. P. Chen & W. J. Lin, was found in Wuyishan National Park, Fujian Province, which was most similar to S. flavescens in morphology. Their difference between the two species was that the plant was short, the raceme was 40 cm, and the calyx was 2 mm×3 mm. The phylogenetic tree constructed based on three nuclear DNA fragment combinations (ETS, ITS, SQD1) and four chloroplast DNA fragment combinations (matK, rbcL, rpl32-trnL, trnL-F) showed that S. elongata had an independent position on the phylogenetic tree, which supported that S. elongata was a new species of Leguminosae, but its phylogenetic position was independent and there was nuclear-cytoplasmic conflict, presumably due to ancient hybridization or incomplete phylogenetic sorting.

Abstract:Vines are important components of tropical-subtropical forests ecosystems. Guangdong Province is located in the northern edge of the tropics to the middle subtropics, with abundant resources of climbing plants. Based on the literature of plant resources of Guangdong Province, the geographic composition of climbing plants, as well as their functional types and potentials for landscape applications, were systematically reviewed from a phylogeographic perspective. The results showed that there are 754 species (including varieties and forms) of climbing plants in 68 families and 216 genera in Guangdong, of which 48 families and 145 genera belonged to the tropics, with typical tropical characteristics. There are 651 species of native vines, 103 species of exotic vines, 341 species of vines with food and medicinal value, 138 species of ornamental vines commonly used in gardens, and 57 species with application potential. There were more species of woody rattan than grass rattan, and the climbing methods are mainly twining and tendrils. The zonality, functionality and species diversity of climbing plants in urban green spaces in Guangdong Province could be improved by increasing the application of native climbing plants, combining vines and lianas, and using climbing plants with high ornamental value.