Community structure and species diversity dynamics of a subtropical evergreen broad-leaved forest in China:2005 to 2020

Here,we characterize the temporal and spatial dynamics of forest community structure and species diversity in a subtropical evergreen broad-leaved forest in China.We found that community structure in this forest changed over a 15-year period.Specifically,renewal and death of common species was large,with the renewal of individuals mainly concentrated within a few populations,especially those of Aidia canthioides and Cryptocarya concinna.The numbers of individual deaths for common species were concentrated in the small and mid-diameter level.The spatial distribution of community species diversity fluctuated in each monitoring period,showing a more dispersed diversity after the 15-year study period,and the coefficient of variation on quadrats increased.In 2010,the death and renewal of the community and the spatial variation of species diversity were different compared to other survey years.Extreme weather may have affected species regeneration and community stability in our subtropical monsoon evergreen broad-leaved forests.Our findings suggest that strengthening the monitoring and management of the forest community will help better understand the long-and short-term causes of dynamic fluctuations of community structure and species diversity,and reveal the factors that drive changes in community structure.

N-fixing tree species promote the chemical stability of soil organic carbon in subtropical plantations through increasing the relative contribution of plant-derived lipids

Biodiversity experiments have shown that soil organic carbon(SOC)is not only a function of plant diversity,but is also closely related to the nitrogen(N)-fixing plants.However,the effect of N-fixing trees on SOC chemical stability is still little known,especially with the compounding effects of tree species diversity.An experimental field manipulation was established in subtropical plantations of southern China to explore the impacts of tree species richness(i.e.,one,two,four and six tree species)and with/without N-fixing trees on SOC chemical stability,as indicated by the ratio of easily oxidized organic carbon to SOC(EOC/SOC).Plant-derived C components in terms of hydrolysable plant lipids and lignin phenols were isolated from soils for evaluating their relative contributions to SOC chemical stability.The results showed that N-fixing tree species rather than tree species richness had a significant effect on EOC/SOC.Hydrolysable plant lipids and lignin phenols were negatively correlated with EOC/SOC,while hydrolysable plant lipids contributed more to EOC/SOC than lignin phenols,especially in the occurrence of N-fixing trees.The presence of N-fixing tree species led to an increase in soil N availability and a decrease in fungal abundance,promoting the selective retention of certain key components of hydrolysable plant lipids,thus enhancing SOC chemical stability.These findings underpin the crucial role of N-fixing trees in shaping SOC chemical stability,and therefore,preferential selection of N-fixing tree species in mixed plantations is an appropriate silvicultural strategy to improve SOC chemical stability in subtropical plantations.

Seedling potential of trees species along the elevational gradient in temperate hill forest of central Nepal

Regeneration status of tree species along elevation gradient in temperate hill forest was not understood greatly.Present research examined the tree diversity and its regeneration patterns along an elevation gradient in temperate hill forest,central Nepal.Data were collected from 300 sample plots within vertical elevation bands of 10,ranging from 1365 to 2450 m asl.A random sampling method was used for data collection in three seasons,winter,pre-monsoon and post monsoon seasons.Diameter at breast height(DBH)was used to broadly categorize the plant individual into trees,saplings and seedlings.The tree species richness ranged from 12 to 25 with density of 350 to 1200 individuals per hectare.Species richness of tree and sapling showed statistically significant unimodal pattern,which peaked at mid-elevation.Elevation showed a strong and positive linear correlation with the seedling density(Deviance=0.99,p<0.001)and a significant hump-shaped relationship with sapling density(Deviance=0.95,p<0.001).Similarly,elevations showed a statistically significant negative hump-shaped relationship with all trees,saplings and seedling stages(Deviances=0.89,0.87 and 0.57).The highest values of the Shannon-Wiener index and the lowest value of the Simpson index were found at mid-elevation for all growth forms.Nearly 92%of tree species were found at regenerating stage;49%in a good renewal regeneration status,32%in fair renewal regeneration,and 11%at a poor regenerating condition.Nevertheless,4%of tree species were reported as non-regenerating stages and 4%were newly introduced species.Hence,the regeneration status of the study area was considered fairly well since sapling(78.5%)>seedling(10.6%)≤mature(10.9%).Among tested environmental variables,elevation and annual mean rainfall were the most influential factors in the regeneration of tree species.

Dominant woody plant species recognition with a hierarchical model based on multimodal geospatial data for subtropical forests

Since the launch of the Google Earth Engine(GEE)cloud platform in 2010,it has been widely used,leading to a wealth of valuable information.However,the potential of GEE for forest resource management has not been fully exploited.To extract dominant woody plant species,GEE combined Sen-tinel-1(S1)and Sentinel-2(S2)data with the addition of the National Forest Resources Inventory(NFRI)and topographic data,resulting in a 10 m resolution multimodal geospatial dataset for subtropical forests in southeast China.Spectral and texture features,red-edge bands,and vegetation indices of S1 and S2 data were computed.A hierarchical model obtained information on forest distribution and area and the dominant woody plant species.The results suggest that combining data sources from the S1 winter and S2 yearly ranges enhances accuracy in forest distribution and area extraction compared to using either data source independently.Similarly,for dominant woody species recognition,using S1 winter and S2 data across all four seasons was accurate.Including terrain factors and removing spatial correlation from NFRI sample points further improved the recognition accuracy.The optimal forest extraction achieved an overall accuracy(OA)of 97.4%and a maplevel image classification efficacy(MICE)of 96.7%.OA and MICE were 83.6%and 80.7%for dominant species extraction,respectively.The high accuracy and efficacy values indicate that the hierarchical recognition model based on multimodal remote sensing data performed extremely well for extracting information about dominant woody plant species.Visualizing the results using the GEE application allows for an intuitive display of forest and species distribution,offering significant convenience for forest resource monitoring.

Variations and determinants of tissue carbon concentration of 32 sympatric temperate tree species

Plant carbon(C)concentration is a fundamental trait for estimating C storage and nutrient utilization.However,the mechanisms of C concentration variations among different tree tissues and across species remains poorly understood.In this study,we explored the variations and determinants of C concentration of nine tissues from 216 individuals of 32 tree species,with particular attention on the effect of wood porosity(i.e.,non-porous wood,diffuse-porous wood,and ring-porous wood).The inter-tissue pattern of C concentration diverged across the three porosity types;metabolically active tissues(foliage and fine roots,except for the foliage of ring-porous species)generally had higher C levels compared with inactive wood.The poor inter-correlations between tissue C concentrations indicated a necessity of measuring tissue-and specific-C concentrations.Carbon concentration for almost all tissues generally decreased from non-porous,to diffuse-porous and to ring-porous.Tissue C was often positively correlated with tissue(foliage and wood)density and tree size,while negatively correlated with growth rate,depending on wood porosity.Our results highlight the mediating effect of type of wood porosity on the variation in tissue C among temperate species.The variations among tissues were more important than that among species.These findings provided insights on tissue C concentration variability of temperate forest species.

Aboveground biomass stocks of species-rich natural forests in southern China are influenced by stand structural attributes,species richness and precipitation

Forests,the largest terrestrial carbon sinks,play an important role in carbon sequestration and climate change mitigation.Although forest attributes and environmental factors have been shown to impact aboveground biomass,their influence on biomass stocks in species-rich forests in southern China,a biodiversity hotspot,has rarely been investigated.In this study,we characterized the effects of environmental factors,forest structure,and species diversity on aboveground biomass stocks of 30 plots(1 ha each) in natural forests located within seven nature reserves distributed across subtropical and marginal tropical zones in Guangxi,China.Our results indicate that forest aboveground biomass stocks in this region are lower than those in mature tropical and subtropical forests in other regions.Furthermore,we found that aboveground biomass was positively correlated with stand age,mean annual precipitation,elevation,structural attributes and species richness,although not with species evenness.When we compared stands with the same basal area,we found that aboveground biomass stock was higher in communities with a higher coefficient of variation of diameter at breast height.These findings highlight the importance of maintaining forest structural diversity and species richness to promote aboveground biomass accumulation and reveal the potential impacts of precipitation changes resulting from climate warming on the ecosystem services of subtropical and northern tropical forests in China.Notably,many natural forests in southern China are not fully stocked.Therefore,their continued growth will increase their carbon storage over time.

Tree allometry responses to competition and complementarity in mixed-species plantations of Betula alnoides

Tree allometry plays a crucial role in tree survival,stability,and timber quantity and quality of mixed-species plantations.However,the responses of tree allometry to resource utilisation within the framework of interspecific competition and complementarity remain poorly understood.Taking into consideration strong-and weakspace competition(SC and WC),as well as N_(2)-fixing and non-N_(2)-fixing tree species(FN and nFN),a mixedspecies planting trial was conducted for Betula alnoides,a pioneer tree species,which was separately mixed with Acacia melanoxylon(SC+FN),Erythrophleum fordii(WC+FN),Eucalyptus cloeziana(SC+nFN)and Pinus kesiya var.langbianensis(WC+nFN)in southern China.Six years after planting,tree growth,total nitrogen(N)and carbon(C)contents,and the natural abundances of^(15)N and^(13)C in the leaves were measured for each species,and the mycorrhizal colonisation rates of B.alnoides were investigated under each treatment.Allometric variations and their relationships with space competition and nutrient-related factors were analyzed.The results showed a consistent effect of space competition on the height-diameter relationship of B.alnoides in mixtures with FN or nFN.The tree height growth of B.alnoides was significantly promoted under high space competition,and growth in diameter at breast height(DBH),tree height and crown size were all expedited in mixtures with FN.The symbiotic relationship between ectomycorrhizal fungi and B.alnoides was significantly influenced by both space competition and N_(2) fixation by the accompanying tree species,whereas such significant effects were absent for arbuscular mycorrhizal fungi.Furthermore,high space competition significantly decreased the water use efficiency(WUE)of B.alnoides,and its N use efficiency(NUE)was much lower in the FN mixtures.Structural equation modeling further demonstrated that the stem allometry of B.alnoides was affected by its NUE and WUE via changes in its height growth,and crown allometry was influenced by the mycorrhizal symbiotic relationship.Our findings provide new insights into the mechanisms driving tree allometric responses to above-and belowground resource competition and complementarity in mixed-species plantations,which are instructive for the establishment of mixed-species plantations.

Absorption capacity of major urban afforestation species in north-eastern China to heavy metal pollutants in the atmosphere

Totally 24 arbor tree species and 6 shrub species were measured on their absorption capacities to heavy metal Pb, Cd, Cr, and Hg by collecting and analyzing the leaves of trees along different streets in Harbin city in Sept. to Oct. of 2003. The results showed that all the measured species had certain absorbency to the pollutants (Pb, Cd, Cr and Hg), but there existed significant difference in absorption capacity for different species to different pollutants. The measured tree species were classified into three categories by their absorption quantum of heavy metal pollutants. Among the species measured,Betula platyphylla, Ulmus pumila var.pendula, andPrunus persicaf.rubro-plena had high capacity in absorbing Pb;Populus xiahei, P. nigra var.Italica, P. alba x P. berolinensis andSalix matsudana had had high capacity in absorbing Cd;Phellodendron amurense, Syringa oblata, Salix matsudana, Pinus tabulaeformis var.mukdensis, Picea koraiensis, Prunus persica f.rubro-plena, P. triloba andAcer negundo, etc. had high capacity in absorption of Cr;Prunus triloba, Quercus mongolica, Salix matsudana, Sambucus williamsii, Pyrus ussuuriensis andSpiraea fritschiana were good at absorption of Hg. This study might offer scientific foundation for selection of urban afforestation species in different polluted conditions caused by heavy metals. Keywords Greening tree species - Heavy metal - Pollutants - Plumbum - Cadmium - Chromium - Mercury - Absorptivity CLC number S731.2 - X501 Document code A Foundation item: This study is financially supported by the Special Programme for Agriculture under Ministry of Chinese Science and Technology (No. 2002BA516A15-01).Biography: MU Li-qiang (1966-), female, Associate professor in Northeast Forestry University, Harbin 150040, P. R. China.Responsible editor: Zhu Hong

Selection of Fire-resistant Tree Species for Southwestern China

Selection of fire resistant tree species for the southwestern China and the planting of those species can effectively prevent large area's fire damage. In this paper the components and flammability of leaves, twigs and barks of 12 tree species in the mountain area of southwestern China have been tested and analyzed in the laboratory. The test and analysis indicate the results as follows:(1) for all the tree species, the fire resistance of leaves is much weaker than that of twigs and barks, and the broad leaves are stronger than those of conifers in fire resistance. (2) Heat value, moisture, ignition point and ash content are main indexes to affect fire resistance. Heat value relates to lignose content and benzene ethanol extractive content linearly.(3) Of all the 12 tree species, Schima superba,Castanopsis hystrix, Myrica rubra have the strongest resistance to fire; Machilus pauhoi, Michelia macclurei, Mytilaria laosensis, Camellia olifera and Manglietia tenuipes are relatively strong in fire resistance, and Lithocapus thalassica, Tsoongiodendron odorum, Cunninghamia lanceolata and Pinus massoniana are weak in fire resistance.

Seed Germination and Storage of Woody Species in the Lower Subtropical Forest

The dimension, water content and germination of the seeds from 90 woody species in the lower subtropical forest were analyzed in this study. Out of 90 species, germination analysis was performed in 45 species (in which there were enough germinating individuals), and the effect of storage of seed and fruit on germination of seed was studied in 41 species (in which there were enough seeds and germinating individuals). Most of the species began to germinate within 60 d. Hypogeal species had longer dormancy than epigeal species. Dormancy of fleshy seeds and seeds in pulpy fruit was also longer than that of dry seeds. There were no significant differences in length of dormancy (LD, days from sowing to germination) between fleshy seeds ripening in summer and those ripening in winter and spring, and between big seeds and small seeds. Seeds in pulpy fruit or fleshy seeds had more germination than the dry seeds ( P <0.05), however, percentage germination was not significantly correlated with water content of fresh seeds. Water loss in the seeds could obviously affect percentage germination, especially during the early three days when the seeds were laid open in air in the laboratory. When water content of the seeds decreased to about 20% (fresh weight basis), percentage germination became very low, this happened when the seeds were laid open in air for 10-14 d. Percentage germination decreased with the length of storing in refrigerator ((4±1) ℃), but it was not markedly affected for one month's storage, with a decrease by 8.3% in comparison with the fresh seeds, and it was greatly affected by storing for more than three months, with values decreasing by 37%, 63%, and 81% for three months', six months' and 12 months' storage respectively. Difference in percentage germination as well as in LD was not significant for most lots after different storing periods between big seeds and small seeds, between fruit storage and seed storage, and between seeds in pulpy fruits or fleshy seeds and dry seeds.

Spatial Characteristics and Change for Tree Species (Genera) Along Northeast China Transect (NECT)

The 16 tree species on Northeast China Transect (NECT) were analyzed from the change of geographical distribution, frequency and dominance pattern and the spatial correlation at landscape scale in 1986 and 1994. Pinus koraiensis Sieb. et Zucc. and Fraxinus rhynchophylla Hemsl. had spread rapidly towards west and east, respectively. The frontier form of species had close relation with its movement. The patch size of Pinus koraiensis , Populus davidiana Dode., Phellodendron amurense Rupr., Juglans mandshurica Maxim., Fraxinus mandshurica Rupr., Betula dahurica Pall., Picea koraiensis Nakai, Abies nephrolepis Maxim. and Larix olgeusis var. koreana Nakai decreased, however, Quercus mongolica Fisch., Betula costata Trautv., Acer mono Maxim., Tilia spp., Ulmus spp., Betula platyphylla Suk. and Fraxinus rhynchophylla increased. The frequency pattern of Populus davidiana , Betula platyphylla , Fraxinus rhynchophylla and Betula dahurica changed significantly. The dominance pattern of Populus davidiana , Tilia spp., Juglans mandshurica , Betula platyphylla , Betula dahurica and Abies nephrolepis changed significantly. The spatial correlation between Quercus mongolica and Betula dahurica , Betula costata and Picea spp., Betula costata and Abies nephrolepis , Picea spp. and Abies nephrolepis declined, however, the spatial correlation between Larix spp. and Betula platyphylla , Acer mono and Ulmus spp. increased.

Study on the Planning of Garden Greening Tree Species in Liuzhou City

By analyzing the application situation of greening tree species in Liuzhou City,this study aimed to put forward several strategies and suggestions for garden tree species planning in Liuzhou City according to relevant theories and principles.

干旱胁迫对胡杨、沙枣幼苗的生理影响

筛选高抗逆树种并优化防护林树种配置是解决极端干旱区农田防护林大面积顶梢干枯、衰败的有效途径。以塔里木荒漠乡土树种胡杨、沙枣幼苗为试验材料,采用盆栽控水法研究两树种幼苗抗氧化酶活性、渗透调节物质对干旱胁迫程度、胁迫时间的动态响应及抗旱性差异。结果表明:(1)随干旱胁迫程度加剧与胁迫时间延长,胡杨、沙枣叶游离脯氨酸(Pro)质量分数、可溶性蛋白(SP)质量分数、丙二醛(MDA)质量摩尔浓度、叶饱和亏缺及胡杨叶超氧化物歧化酶(SOD)活性均呈增加趋势;两树种幼苗叶过氧化物歧化酶(POD)活性、叶相对含水量呈降低趋势。(2)随干旱胁迫程度加剧,沙枣叶Pro、SP质量分数显著高于胡杨,胡杨叶SOD活性高于沙枣,POD活性相反。胡杨、沙枣幼苗均以Pro、SP维持叶细胞渗透压,并通过SOD清除活性氧(ROS)来协同适应干旱胁迫。(3)综合分析表明沙枣幼苗的抗旱能力优于胡杨幼苗。建议干旱区绿洲农田防护林建设中优先选择沙枣或以沙枣、胡杨为主要树种营建混交林,以及退化防护林改造修复时配置补植沙枣,恢复农田防护林的生态功能。

Growth and Influencing Factors of Three Native Tree Species in Coastal Casuarina equisetifolia Plantation

[Objective] The aim was to study the growth and environment factors of three native tree species（Thespesia lampas,Calophyllum inophyllum and Hernandia sonora）in Hainan in coastal Casuarina equisetifolia plantation.[Method] The coastal sandy soil was treated by adding wood chips,bagasse and the control without adding anything in the plant pits.The growth of three native tree species planted for one year was analyzed.[Result] ① One year later,the survival rate showed an order of T.lampasH.sonoraC.inophyllum;the net increase of basal diameter showed an order of H.sonoraT.lampasC.inophyllum;while the net increase of plant height showed an order of T.lampasC.inophyllumH.sonora.The difference of survival rate between T.lampas and C.inophyllum was extremely significant,the difference of survival rate between H.sonora and C.inophyllum was significant,but the survival rate between T.lampas and H.sonora showed no significant difference.The difference on net growth of plant height among T.lampas,C.inophyllum and H.sonora was extremely significant,and the different on the net growth of basal diameter between T.lampas and C.inophyllum was significant.② Among different soil treatments,the survival rate of three native tree species in the treatment by adding wood chips,bagasse were higher than the treatment without adding anything,and the difference of survival rate of T.lampas between the treatment by adding wood chips,bagasse and the treatment without adding anything was extremely significant,but the treatment by adding wood chips and bagasse had not significant difference.③ The growth of three native tree species showed some correlation with environment factors（∣r∣0.3）.The survival rate of T.lampas showed higher correlation with soil pH value and soil moisture,and the basal diameter and height of T.lampas showed some correlation with soil pH value and soil temperature.The survival rate of C.inophyllum showed higher correlation with soil pH value,soil temperature and light intensity,while the basal diameter and height of C.inophyllum showed some correlation with soil temperature.The survival rate of H.sonora showed higher correlation with soil salinity and soil temperature,while the basal diameter and height of H.sonora showed some correlation with soil temperature.The basal diameter and height of three native tree species had higher correlation（r0.5）,which had reached a significant level.[Conclusion] In the one-year growth period in C.equisetifolia forest,the native tree species of T.lampas grew best and it was the most potential forest species mixed with C.equisetifolia.

基于熵权与集成学习的半监督小样本树种分类研究

针对传统半监督自训练分类方法易导致数据集混乱,影响后续小样本树种分类精度这一问题,基于熵权法(en-tropy weight,EW)与集成学习(ensemble learning,EL)提出EW-EL的半监督小样本树种分类方法。EW-EL在传统半监督自训练分类方法的理论上引入EL的思想,以熵权法作为基础理论设计按基分类器当前训练周期下的F1分数计算的信息熵作为计算权重因子,再依信息熵越大基分类器越不稳定思想设计权重,使集成分类器分类概率更集中,减少集成分类器偏向性。结果显示,EW-EL较传统半监督自训练方法能更有效地均衡数据分布,使新加入数据的伪标签样本类别更准确。EW-EL所得到的小样本树种分类总精度(OA)为0.97、召回率(Recall)为0.96及Kappa系数为0.97,3种指标均优于监督分类、传统半监督自训练方法及利用传统EL机制所构建的半监督自训练方法。其中,EW-EL方法较融合软投票机制的半监督自训练方法,OA与Recall均提升了1%。EW-EL联合简单线性迭代聚类所制成的树种图在所选测试区内达到了94%。此外,进一步分析证明,EW-EL能通过集成诸多分类器,来实现更佳的小样本树种分类结果,更适用于低成本下的相关部门进行林业资源统计的工作。

应用优化最大熵模型的珍稀濒危玉兰属物种适生区预测

依据中国9种珍稀濒危玉兰属(Yulania spach)物种的地理分布数据及37个环境因子数据,利用R语言ENMeval包优化最大熵模型(MaxEnt)的正则化乘数(RM)和要素组合(FC)参数,提高模型模拟精度,以便更好的预测出各物种在基准期和未来3种气候情景的潜在适生区分布趋势,并分析影响其分布的主要环境因子。结果表明:(1)最大熵模型优化后,各珍稀濒危玉兰属物种的受试者工作特征曲线(ROC)下面积(AUC)值均在0.95以上,表明模型模拟效果极好,可用于中国珍稀濒危玉兰属物种地理分布模拟;(2)影响珍稀濒危玉兰属潜在分布的主要环境因子,贡献率从大到小依次为,最冷月最低温(BIO6,46.38%)、等温性(BIO3,13.83%)、坡度(SLO,8.03%)、最暖季降水量(BIO18,7.57%)、最干月降水量(BIO14,6.78%),其中,对各物种潜在适生区分布影响最大的影响因子为最冷月最低温,在存在概率最高时,各物种的最冷月最低温均在0℃左右;(3)在未来2061—2080年3种不同的气候情景时,光叶玉兰、青皮玉兰、凹叶玉兰及紫玉兰总适生区面积呈扩大趋势,增加面积在7 398~879 439 km^(2);景宁玉兰、罗田玉兰、天目玉兰、宝华玉兰、滇藏玉兰总适生区面积呈缩减趋势,减小面积在1 605~669 830 km^(2)。

Environmental Correlates of Distribution of the 25 Broad-leaved Tree Species Indigenous to Guangdong Province,China

Twenty-five tree species indigenous to Guangdong Province were chosen in this study to portray their distribution patterns in relation to environmental factors. Both data of species distribution and environmental factors were tabulated based on a digitized map of Guangdong Province gridded at 0.5° latitude × 0.5° longitude. Grid-based diversity was mapped using DMAP, a distribution mapping program, and horizontal patterns were assessed using Kruskal-Wallis tests. The diversity center of the indige- nous tree species under study is located north of 23° N. These tree species exhibit significant latitudinal variation (P = 0.007 4), but no significant longitudinal difference (P = 0.052 2). Non-metric Multidimensional Scaling (NMS) identified five different ecological species groups, while Canonical Correspondence Analysis (CCA) showed the distribution of tree species along each of the five envi- ronmental gradients. An understanding of the environmental correlates of distribution patterns has great implication for the introduc- tion of the indigenous tree species for afforestation.

Ecological Species Groups and Interspecific Association of Dominant Tree Species in Daiyun Mountain National Nature Reserve

Abstract： Research on the ecological species groups and interspecific association of plant species are helpful to discover species coexistence processes and mechanisms, and to more fully understand plant community structure, function, and its taxonomy. However, little is known about the ecological species groups （ESG） and the interspecific association of dominant species in Daiyun Mountain National Nature Reserve of Fujian Province, China. Therefore, the main goal of this paper is to explore the ESG using maximal tree, and to analyze interspecific associations of 32 dominant species selected from lo2 sample plots using the chi-square test. The results show that： （1） 32 dominant species have a significant overall positive interspecific association, which indicates that the natural forest in Daiyun Mountain National Nature Reserve is stable, （a） The species pairs with weak associations, non-associations and positive associations account for lo.88%, 29.64% and 59.48% of the total 496 species pairs respectively, which suggests that the population distributions of the dominant species investigated are relatively independent, （3） The following species pairs may be useful for practical application, 〈Pinus taiwanensis, Rhododendron farrerae〉, 〈Castanopsis carlesii, Altingia chinensis〉, 〈C. carlesii, Castanopsis fargesii〉, 〈Castanopsis eyrei, C. fargesii〉, 〈P. taiwanensis, Fagus lucida〉 , 〈Machilus thunbergii, Castanopsis nigrescens〉, and （4） The results of clustering analysis based on the maximal tree method indicates that the 32 dominant species can be divided into 3 ESGs when A at o.6o, that is ESG I {Pinus massoniana, Cunning hamia lanceolata}, ESG II {P. taiwanensis, R. farrerae, Enkianthus quinqueflorus}, ESG III {C. carlesii, A. chinensis, C. eyrei, Castanopsis fabri, C. fargesii, Schima superba, Machilus thunbergii, Rhododendron latoueheae}. The results may be used for the selection of afforestation tree species in South China Forest Areas and guide the natural management of plantations.

THE EFFECT OF HEAT TREATMENT ON DIFFERENT SPECIES WOOD COLOUR

In this paper, the heat tratment of wood samples of 8 tree species with different colour were made at different temperature and time. Using SC-1 Model colorimeter, the colorimetric parameter was measured at quantitative measuring for treatment fore-and-after wood sampIes color. The effect of heat treatment conditions on wood color was analyzed. The results indicated: the temperature and time of heat treatment affected on big extent for wood samples color, in which the heat temperature was more evident than others. The luminance index of wood color parameter was more sensitive to treatment condition, which it reduced with temperature and time increasing, this kind of variation tendency was the same as all wood samples, but the variations extent was more different among the different wood species. After heat treatment the wood color hue and saturation variation direction were different for different wood species.This phenomenon had the relation to the migration and volatilization of color extract in heating process, or the rapid oxidation of lignin and some chemical element in high temperature.

Tree species richness enhances stand productivity while stand structure can have opposite effects, based on forest inventory data from Germany and the United States of America

Background： in recent studies, mixed forests were found to be more productive than monocultures with everything else remaining the same. Methods： To find out if this productivity is caused by tree species richness, by a more heterogeneous stand structure or both, we analyzed the effects of forest structure and tree species richness on stand productivity, based on inventory data of temperate forests in the United States of America and Germany. Results： Having accounted for effects such as tree size and stand density, we found that： （I） tree species richness increased stand productivity in both countries while the effect of tree size heterogeneity on productivity was negative in Germany but positive in the USA; （11） productivity was highest at sites with an intermediate amount of precipitation; and （111） growth limitations due water scarcity or low temperature may enhance structural heterogeneity. Conclusions： In the context of forest ecosystem goods and services, as well as future sustainable forest resource management, the associated implications would be：