Historical development of karst evergreen broadleaved forests in East Asia has shaped the evolution of a hemiparasitic genus Brandisia(Orobanchaceae)

Brandisia is a shrubby genus of about eight species distributed basically in East Asian evergreen broadleaved forests(EBLFs),with distribution centers in the karst regions of Yunnan,Guizhou,and Guangxi in southwestern China.Based on the hemiparasitic and more or less liana habits of this genus,we hypothesized that its evolution and distribution were shaped by the development of EBLFs there.To test our hypothesis,the most comprehensive phylogenies of Brandisia hitherto were constructed based on plastome and nuclear loci(nrDNA,PHYA and PHYB);then divergence time and ancestral areas were inferred using the combined nuclear loci dataset.Phylogenetic analyses reconfirmed that Brandisia is a member of Orobanchaceae,with unstable placements caused by nuclear-plastid incongruences.Within Brandisia,three major clades were well supported,corresponding to the three subgenera based on morphology.Brandisia was inferred to have originated in the early Oligocene(32.69 Mya)in the Eastern Himalayas-SW China,followed by diversification in the early Miocene(19.45 Mya)in karst EBLFs.The differentiation dates of Brandisia were consistent with the origin of keystone species of EBLFs in this region(e.g.,Fagaceae,Lauraceae,Theaceae,and Magnoliaceae)and the colonization of other characteristic groups(e.g.,Gesneriaceae and Mahonia).These findings indicate that the distribution and evolution of Brandisia were facilitated by the rise of the karst EBLFs in East Asia.In addition,the woody and parasitic habits,and pollination characteristics of Brandisia may also be the important factors affecting its speciation and dispersal.

Effect of Slash Burning on Nutrient Removal and Soil Fertility in Chinese Fir and Evergreen Broadleaved Forests of Mid-Subtropical China

A Chinese fir forest (Cunninghamia lanceolata, CF) and an evergreen broadleaved forest (EB) located inFujian Province, southeastern China, were examined following slash burning to compare nutrient capital andtopsoil properties with pre-burn levels. After fire, nutrient (N, P and K) removal from burning residues wasestimated at 302.5 kg ha-1 in the CF and 644.8 kg ha-1 in the EB. Fire reduced the topsoil capitals of totalN and P by about 20% and 10%, respectively, in both forests, while K capital was increased in the topsoils ofboth forests following fire. Total site nutrient loss through surface erosion was 28.4 kg (N) ha-1, 8.4 kg (P)ha-1 and 328.7 kg (K) ha-1 in the CF. In the EB, the losses of total N, P and K were 58.5, 10.5 and 396.3kg ha-1, respectively. Improvement of soil structure and increase in mineralization of nutrients associatedwith increased microbe number and enzyme activities and elevated soil respiration occurred 5 days after fire.However, organic matter and available nutrient contents and most of other soil parameters declined one yearafter fire on the burned CF and EB topsoils. These results suggest that short-term site productivity canbe stimulated immediately, but reduced subsequently by soil and water losses, especially in South China,where high-intensity precipitation, steep slopes and fragile soil can be expected. Therefore, the silviculturalmeasurements should be developed in plantation management.

Distribution and quantification of Pb in an evergreen broadleaved forest in three hydrological years

The distribution,quantification and fluxes of Pb were examined in an evergreen broadleaved forest in western Greece for three hydrological years.More specifically,concentrations and annual fluxes of Pb were determined in bulk and throughfall deposition as well as litterfall.The Pb concentrations were also measured in forest floor and mineral soil up to 80 cm and the isotopic ratios of 206Pb/207Pb were determined in soil layers and the parent rock material.High variability in the fluxes of the metal among the three hydrological years were found,evidence of the variability of Pb deposition in time.Litterfall fractions with a large surface area,like holm oak flowers,had high Pb concentrations.Applying a steady state model and considering the Pb amounts in throughfall and litterfall as inputs on the forest floor,the mean residence time of Pb in the forest floor was 94 years with a coefficient of variation equal to 41%.More observations are needed to lower the variability of the mean residence time.The isotopic ratio in the rock material was defined as the lithogenic ratio.The statistical tests showed that the petrol derived Pb migrated to the depth of 20 cm and its percentages in the soil pedon was in the range of 62%in the L horizon to 11%in the 10–20cm layer.In higher depths(>40 cm)preindustrial anthropogenic Pb affected the isotopic ratio.As the forest under consideration is remote from industrial activities,the results can serve as a baseline for future studies on Pb distribution and quantification.

Scientists Reveal Historical Assembly of East Asian Subtropical Evergreen Broadleaved Forests

The subtropical evergreen broadleaved forests(EBLFs),ranging in occurrence from c.23°N to 39°N and 97°E to 141°E,are amongst the most characteristic biomes in East Asia and are common in South China.They contribute fundamentally to both the biodiversity function and ecosystem services of the East Asiatic floristic kingdom.The East Asian subtropical EBLFs are considered as unique zonal vegetation that might have developed in concert with the Asian monsoons,particularly

Forest vegetation of Xishuangbanna,south China

Xishuangbanna of southern Yunnan is biogeographically located at a transitional zone from tropical southeast （SE） Asia to subtropical east Asia and is at the junction of the Indian and Burmese plates of Gondwana and the Eurasian plate of Laurasia. The region, though surprisingly far from the equator and at a relatively high altitude, has a rich tropical flora and a typical tropical rain forest in the lowland areas. Based on physiognomic and ecological characteristics, floristic composition and habitats combined, the primary vegetation in Xishuangbanna can be organized into four main vegetation types： tropical rain forest, tropical seasonal moist forest, tropical montane evergreen broad-leaved forest and tropical monsoon forest. The tropical rain forest can be classified into two subtypes, i.e. a tropical seasonal rain forest in the lowlands and a tropical montane rain forest at higher elevations. The tropical seasonal rain forest has almost the same forest profile and physiognomic characteristics as equatorial lowland rain forests and is a type of truly tropical rain forest. Because of conspicuous similarity on ecological and floristic characteristics, the tropical rain forest in Xishuangbanna is a type of tropical Asian rain forest. However, since the tropical rain forest of Xishuangbanna occurs at the northern edge of tropical SE Asia, it differs from typical lowland rain forests in equatorial areas in having some deciduous trees in the canopy layer, fewer megaphanerophytes and epiphytes but more abundant lianas and more plants with microphyll. It is a type of semi-evergreen rain forest at the northern edge of the tropical zone. The tropical montane rain forest occurs at wet montane habitats and is similar to the lower montane rain forest in equatorial Asia in floristic composition and physiognomy. It is a type of lower montane rain forests within the broader category of tropical rain forests. The tropical seasonal moist forest occurs on middle and upper limestone slopes. It is similar to the tropical montane evergreen broad-leaved forest in the region in physiognomy, but differs from the latter in floristic composition. It is a vegetation type on limestone at high elevations. The monsoon forest in Xishuangbanna is a tropical deciduous forest under the influence of a strong monsoon climate and is considered to be a transitional vegetation type between a tropical rain forest and savanna in physiognomy and distribution. The tropical montane evergreen broad-leaved forest is the main montane vegetation type in the region. It is dominated largely by the families Fagaceae, Euphorbiaceae, Theaceae and Lauraceae. It differs from tropical lower montane rain forests in its lack of epiphytes and in having more abundant lianas and plants with compound leaves. It is considered to be a distinct vegetation type from the northern margin of mainland southeastern Asia, controlled by a strong seasonal climate, based on its floristic and physiognomic characteristics.

Habitat fragmentation impacts on biodiversity of evergreen broadleaved forests in Jinyun Mountains,China

The plant communities and their microclimates were surveyed and observed,and the soil fertilities were determined in six plots of evergreen broadleaved forests of different sizes and similar slope aspects on Jinyun Mountains of Chongqing in China from April to October,2003.The relationships of biotic and abiotic factors were analyzed using the Simpson,Shannon-Wiener,and Hill diversity indices,and stepwise multilinear regression analyses techniques.The results showed that compared with continuous evergreen broadleaved forests,five fragmentations had a lower species diversity index,and different life forms showed differences in diversity index.With the decrease in patch areas,the daily differences in air temperature(ΔTa),ground surface temperature(ΔTs),daily differences in relative humidity(ΔRH),maximum wind velocity(Vmax),differences in photosynthetic available radiation(ΔPAR)(at noon)of both edges and interiors,all tended to increase.Maximum wind velocity(Vmax)and photo effective radiation in forest edges were higher than those in interior forest,which presented a stronger temperature-gained edge effect.In all the fragmentations of evergreen broadleaved forests,the depth of the edge effect was the nearest from interior forest in the biggest patch(about 15 meters away from interior forest),while the depth of the edge effect was the farthest from interior forest in the smallest patch(about 25 meters away from interior forest).With regard to the water conservation function,soil water content improved along with increasing species diversity.Some of the nutritional function substances of soil increased with increasing species diversity.The elements of microclimate,such as Ta,ΔTa,ΔTs,ΔRH,Vmax,and PAR,changed along with the extent of fragmented forest.

Role of urban remnant evergreen broad-leaved forests on natural restoration of artificial forests in Chongqing metropolis

The effects of urban remnant natural evergreen broad-leaved forest (EBLF) on the restoration of artificial pine forests surrounding it were studied with reference to species composition,biodiversity,dominant species and stand structure on Mt. Tieshanping in Chongqing metropolis,Southwest China. The seeds from the remnant EBLF naturally facilitate the restoration process of artificial Pinus massoniana forests near it. The similarity of species composition between the artificial Pinus massoniana forests and the remnant EBLF and biodiversity index of the artificial Pinus massoniana forests decrease as the distance from the remnant EBLF increases. Castanopsis carlesii var. spinusa is the dominant species in the ground vegetation,shrub layer and sub-tree layer of the Pinus massoniana forests near the remnant EBLF. However,the natural restoration processes of those farther away from the remnant EBLF are restricted for the absence of seed source of the inherent components of the remnant EBLF,and the anthropogenic measures should be taken to facilitate the restoration process.

Comparative Study of Carbon Storage and Allocation Characteristics of Mature Evergreen Broad-leaved Forest

Evergreen broad-leaved forest is an important forest type in China.This paper analyzes the allocation characteristics of vegetation and soil carbon pool of evergreen broad-leaved forest,to understand the current status of research on the carbon storage of evergreen broadleaved forest as well as shortcomings.In the context of global climate change,it is necessary to carry out the long-term research of evergreen broad-leaved forest,in order to grasp the formation mechanism of evergreen broad-leaved forest productivity,and the impact of climate change on the carbon sequestration function of evergreen broad-leaved forest ecosystem.

Quantitative indicative significance of pollen assemblages on vegetation coverage in deciduous Quercus forest in the central Loess Plateau, China

We compared the pollen assemblages of surface moss samples and corresponding vegetation inventory data from 34 sites in the Huangling region of the central Loess Plateau. Our aims were to determine the characteristics of the pollen assemblages from the deciduous broadleaved forest climax community and its significance in terms of vegetation type and species composition. The pollen assemblages are dominated by woody plants such as Quercus(42% of total terrestrial pollen),Betula(16%) and Pinus(12%), with minor differences between different plant communities. The pollen assemblages of individual sampling sites differed from the vegetation composition within the 0–100 m scope and were more similar to the vegetation coverage within the 0–1000 m scope. This indicates that the surface pollen assemblages mainly reflect the comprehensive information from the vegetation composition of a large area, rather than the vegetation composition close to the sampling site. The contents of Quercus, Betula and Pinus pollen are high, and close to their vegetation coverage; whereas the contents of deciduous broadleaved arbor taxa(such as Malus and Acer) are lower, but their corresponding regional vegetation cover is higher. This suggests that the vegetation information conveyed by poorly-represented pollen taxa should be considered when interpreting stratigraphic pollen assemblages. Using the observed quantitative relationships between pollen and vegetation of the main taxa, we reconstructed the regional vegetation composition in the Gonghai Lake area of the northeastern Loess Plateau during the middle Holocene(7300–5000 yr BP). The results indicated that Quercus-dominated deciduous broadleaved forest climax community developed in the mountains surrounding the lake.

千岛湖区马尾松林改造后的林下植物多样性和群落稳定性

[目的]马尾松针叶林阔叶化改造有利于提升森林生态系统结构和功能,对林下植被的更新和演替也有着重要影响。分析林分改造后的林下植物多样性和稳定性特征,可为森林的可持续经营提供参考。[方法]以淳安县千岛湖林区马尾松不同改造林分(Ⅰ疏伐促新、Ⅱ疏伐补阔、Ⅲ皆伐促新、Ⅳ皆伐补阔)为对象,周边无改造措施林分(Ⅴ)为对照,进行植被调查、土壤采样与测定,分析了林下植被物种组成和多样性与林地特征因子的关系,并探究了林下群落稳定性与物种多样性的关系。[结果]样地间的林下灌木层优势种的差异低于草本层,Ⅴ的林下物种多样性显著低于改造后林地(p <0.05),Ⅳ的草本层物种多样性显著高于其它林地(p <0.05)。林地特征因子能解释林下植物种变化的40%,且对草本层的影响程度高于灌木层,其中郁闭度是最主要的影响因素。在马尾松林分改造初期,林下植物群落稳定性Ⅴ>Ⅰ>Ⅱ>Ⅲ>Ⅳ,林下灌木层稳定性与物种多样性的相关程度较低,而草本层稳定性与物种多样性呈显著负相关(p <0.05)。[结论]千岛湖区马尾松林阔叶化改造初期,主要通过降低郁闭度显著提高了林下草本层多样性,但皆伐措施的林下植物群落稳定性较低。因此,综合考虑植物多样性和稳定性维持,对马尾松林采取适当间伐等抚育措施能促进其林下植被的发展。

新安江森林公园阔叶林木本植物生态位与种间联结性

通过建立和调查植物多样性长期监测样地,探讨植物种间关系、生态位及群落稳定性,掌握群落演替规律,为森林公园的植物多样性保育、森林资源管理和植被恢复提供基础。在新安江森林公园内选取1 hm2的阔叶林动态监测样地,选取重要值排名前13的优势木本物种,通过计算生态位宽度(BS、BL)和生态位重叠指数(Oik),并运用方差比率法、χ^(2)检验、皮尔逊相关系数及斯皮尔曼秩相关系数等方法,分析物种生态位重叠指数与物种联结性之间的关系。研究发现,重要值排序与生态位宽度排序之间无显著相关性。木荷(Schima superba)的重要值最高,其次是青冈(Quercus glauca)、苦槠(Castanopsis sclerophylla)和石栎(Lithocarpus glabra),这4个树种在群落资源竞争中占据优势地位,且优势物种间生态位重叠度较高。13个优势物种的总体联结性表现为显著正联结。χ^(2)检验结果表明种间相对独立性强,只有1对种对联结性显著,联结较为松散;Pearson相关系数中显著水平为24.4%, Spearman秩相关系数中也仅有28.2%种对表现为显著联结;生态位重叠指数与物种联结性之间呈正相关。综上所述,群落整体处于稳定状态,目前朝着正向演替的中后期阶段发展。建议对现在森林进行严格保护的同时,对于密度较高的林分可适当间伐部分苦槠、杉木(Cunninghamia lanceolata),以促进高质量森林群落的形成。

星斗山天然次生林优势种的生态位和种间联结动态

[目的]常绿落叶阔叶混交林是我国特有的天然林类型,作为亚热带山地的主要植被类型。探讨典型亚热带常绿落叶阔叶混交林优势种的生态位和种间联结动态变化,阐明短期群落发展中优势种的适应能力、种间关系和变化规律,为亚热带地区生物资源保护、恢复和森林管理提供理论依据。[方法]本研究以湖北星斗山国家级自然保护区天然次生林为研究对象,结合2013年和2018年的两次固定样地(48个)调查监测数据,对比分析重要值排名前10名的优势种(重要值大于2%)的生态位宽度、生态位重叠指数、方差比率法、χ^(2)检验、联结系数、Jaccard指数和Spearman秩相关系数的动态变化。[结果](1)2013年和2018年物种组成变化较小,物种株数、科属种数减少;重要值排名前10名的优势种仅1名物种发生变动。(2)两次调查结果的生态位重叠指数均以0.2~0.5之间为主,种对数随群落发展而增加,大部分物种对生境需求具有一定相似性、互补性。随着群落发展,多数优势种的生态位重叠程度逐渐降低、生态位宽度逐渐变窄、利用资源能力逐渐减弱。(3)5年间,重要值排序与生态位宽度排序并不完全相同,群落资源未被完全充分利用。水榆花楸和翅柃一直占据优势地位,与其他优势种的生态位重叠指数呈现稳定或增加趋势。(4)两次调查中优势种的总体联结性均为显著正关联,χ^(2)检验、联结系数、Jaccard指数和Spearman秩相关系数的结果基本一致:正关联种对数大于负关联种对数,极显著或显著正关联种对数比极显著或显著负关联种对数多,不显著关联种对数也占有重要比例。随着群落发展,总体联结性的显著正关联逐渐增强,正相关对数和正负比值逐渐增加,负相关对数逐渐减少。[结论]湖北星斗山国家级自然保护区天然次生林处于自然演替的早期至中期阶段,种间联结松散、不紧密,水榆花楸和翅柃竞争力强,长蕊杜鹃、多脉青冈和包果柯常绿树种对环境资源利用能力不断提高。

Patterns and driving factors of leaf C,N,and P stoichiometry in two forest types with different stand ages in a mid-subtropical zone

Background:Carbon(C),nitrogen(N),and phosphorus(P)stoichiometry is a key indicator of nutrient utilization in plants,and C/N/P ratios are related to the life histories and adaptation strategies of tree species.However,no consensus has been reached on how leaf stoichiometric characteristics are affected by forest type and stand ages.The relationships between leaf stoichiometry and geographical,meteorological,and soil factors also remain poorly understood.Methods:Leaf and soil were sampled from forest stands of different age groups(young,middle-aged,near-mature,and mature)in two forest types(Chinese fir(Cunninghamia lanceolata)forests and evergreen broadleaved forests).The relationships between leaf C,N,and P stoichiometric parameters and geographical,meteorological,and soil factors were analysed by using redundancy analysis(RDA)and stepwise linear regression analysis.Results:Leaf C concentrations peaked in the near-mature stands with increasing age irrespective of forest type.Leaf N and P concentrations fluctuated with a rising trend in Chinese fir forests,while decreased first and increased later from young to mature phases in natural evergreen broadleaved forests.Chinese fir forests were primarily limited by N and P,while natural evergreen broadleaved forests were more susceptible to P limitation.Leaf C,N,and P stoichiometric characteristics in Chinese fir forests were mainly affected by the soil total P concentration(SP),longitude(LNG),growing season precipitation(GSP)and mean temperature in July(JUT).The leaf C concentration was mainly affected by GSP and JUT;leaf N and P concentrations were both positively correlated with LNG;and leaf P was positively correlated with SP.In evergreen broadleaved forests,however,leaf stoichiometric parameters displayed significant correlations with latitude(LAT)and mean annual precipitation(MAP).Conclusions:Leaf stoichiometry differed among forest stands of different age groups and forest types.Leaf C,N,and P stoichiometry was primarily explained by the combinations of SP,LNG,GSP and JUT in Chinese fir forests.LAT and MAP were the main controlling factors affecting the variations in the leaf C,N,and P status in natural evergreen broadleaved forests,which supports the temperature-plant physiological hypothesis.These findings improve the understanding of the distribution patterns and driving mechanisms of leaf stoichiometry linked with stand age and forest type.

Comparison of litterfall production in three forest types in Jeju Island, South Korea

Litterfall, which is influenced by physical and biological factors, is a major pathway for carbon and nutrient cycling in forest ecosystems. The purpose of this study was to investigate monthly litterfall production in three forests in Jeju Island differentiated by forest composition and precipitation: Cheongsu(Quercus glauca as the dominant species;low precipitation), Seonheulb(Q. glauca as the dominant species;high precipitation), and Seonheulm(Q. glauca and Pinus thunbergii as the dominant species;high precipitation). Litterfall was collected monthly from April to December 2015 and divided into leaf litter, twig, bark, seeds, and unidentified materials.Seasonal patterns of litterfall production varied across stands according to their species composition. However,the amount of leaf litterfall and total litterfall were comparable among stands, ranging from 362 to 375 g m-2 for leaf litter and 524 g m-2 to 580 g m-2 for total litterfall.Oak leaf litter in May was the highest in all stands, while needle litter was the highest in December in Seonheulm.High twig litterfall in July may be attributable to high rainfall with strong winds and storms during the rainy season. Although forest type and climate factor had no influence on litterfall amounts in this study, the pattern of litterfall production was species dependent, suggesting diverse effects on carbon and nutrient cycling in these forests.

Low net primary productivity of dominant tree species in a karst forest, southwestern China： first evidences from tree ring width and girth increment

Aboveground net primary productivity(ANPP)of two dominant species, one deciduous tree(Platycarya strobilacea) and one evergreen tree(Machilus cavaleriei),was estimated based on the tree-ring width and the girth increment as well as allometric functions in a karst evergreen and deciduous broadleaved mixed forest in central Guizhou Province, southwestern China. Results showed that the ANPP increased from 1961 to 2015, especially during the last 20–30 years, but with strong variations. The deciduous tree had higher ANPP than the evergreen tree according to two kinds of estimates by the tree ring and girth increment. The averaged ANPP for these two mature trees was 2.27 kg/individual/year, ca. 8 t/ha/year considering the normal stand density. Such karst forest productivity was lower than the natural subtropical forests in China and in the world.

湖北七姊妹山亚热带常绿落叶阔叶混交林主要木本植物的生态位与种间联结

[目的]探究亚热带常绿落叶阔叶混交林的生态位特征和种间联结,阐明主要木本植物种间关系及对环境适应状况,为亚热带地区生物资源保护和森林管理提供理论依据。[方法]本研究基于湖北七姊妹山国家级自然保护区6 hm2(300 m×200 m)标准大样地数据,从物种组成、生态位宽度、生态位相似性系数、生态位重叠指数、方差比率法、χ^(2)检验、联结系数、Jaccard指数等方面研究了16种主要木本植物(重要值大于1%)的生态位和种间联结。[结果](1)2020年湖北七姊妹山亚热带常绿落叶阔叶混交林共有64科140属266种木本植物,主要有桦木科、壳斗科和金缕梅科等,物种组成逐渐复杂。(2)川陕鹅耳枥的物种重要值和生态位宽度最高,占据绝对优势地位,与其他主要木本植物之间具有较高的生态位重叠和生态位相似性。四照花、灯台树和尖叶四照花的优势地位次之。生态位重叠指数和生态位相似系数均以0.2~0.5之间为主,大部分物种对生境需求具有一定相似性、互补性。物种重要值排序与生态位宽度排序并不完全相同。(3)湖北七姊妹山亚热带常绿落叶阔叶混交林内物种间总体关联性呈现显著正联结,且正负联结比值大于1。16种主要木本植物的χ2检验、联结系数、Jaccard指数、Pearson相关系数和Spearman秩相关系数的结果基本一致:正关联种对数大于负关联种对数,极显著或显著正关联种对数比极显著或显著负关联种对数多,不显著关联种对数也占有重要比例。[结论]亚热带常绿落叶阔叶混交林物种丰富,群落处于演替早期至中期阶段,种间关系松散、不紧密。

木果柯功能性状的种内变异及其与遗传·环境和个体发育的关系

依托哀牢山按公里网格布设的20个亚热带常绿阔叶林1 hm^(2)动态样地,选取样地内所有胸径(Diameter at breast height,DBH)≥10 cm的木果柯(Lithocarpus xylocarpus)个体作为研究对象,测量其6个功能性状(叶面积、比叶面积、叶片厚度、叶干物质含量、叶绿素含量和枝条木质密度),利用基于距离矩阵的多元回归解析遗传变异、环境距离、个体发育阶段差异对木果柯功能性状种内变异的相对作用。结果表明:木果柯的功能性状均存在不同程度的种内变异,叶面积变异最大,其次是比叶面积和叶片厚度,木质密度、叶干物质含量和叶绿素含量变异较小;对种内变异程度最大的叶面积来说,个体发育阶段差异的正效应最强,其次是遗传变异,环境距离的正效应最弱;遗传变异对叶绿素含量种内变异的正效应在所有性状中最强,而环境距离对比叶面积的正效应在所有性状中最强。

雪灾对哀牢山中山湿性常绿阔叶林木质藤本幼苗更新的影响

为探讨雪灾对木质藤本幼苗更新的影响,研究了雪灾前后,云南哀牢山中山湿性常绿阔叶林木质藤本幼苗的组成、物种多样性与多度的变化、多度与冠层光照指数的关系。雪灾前(2014年)后(2016年)分别在林内设置20个4 m×4 m的样方,调查样方内木质藤本幼苗(高度或长度≤50 cm)的种类、数量、基径,并测定冠层光照指数。结果表明:①雪灾前后的木质藤本幼苗分别为502株(17种)、1022株(25种);木质藤本幼苗在雪灾前(2014年)的优势种为耐荫种,雪灾后(2016年)的优势种除了葡萄酸藤子外均为喜光的物种;②木质藤本幼苗在雪灾后(2016年)的多度、物种丰富度显著高于雪灾前(2014年)。在11种最常见木质藤本幼苗物种中,雪灾后(2016年)5个喜光种的多度显著高于雪灾前(2014年),而其他6个耐荫种的差异性不显著;③雪灾前后的冠层光照指数从1.58增加到2.88(t=-5.394,p<0.05),木质藤本幼苗的多度与冠层光照指数呈显著正相关(r=0.956,p<0.01)。

鼎湖山南亚热带常绿阔叶林20公顷样地群落特征研究

鼎湖山南亚热带常绿阔叶林是北回归线附近保存较完好的地带性植被,是在南亚热带季风湿润型气候条件下发育的植被类型,具有热带向亚热带的过渡性质,群落结构相对复杂,组成种类相对丰富。参照巴拿马巴洛科罗拉多岛(Barro Colorado Island,BCI)50hm2热带雨林样地的技术规范,采用中国森林生物多样性监测网络的统一调查研究方法,于2005年在鼎湖山南亚热带常绿阔叶林建立了20hm2固定监测样地,调查并鉴定了样方内胸径(Diameter at breast height,DBH)大于1cm的木本植物。首次调查结果表明,群落内共有木本植物210种,71617个活的个体,分属于56科119属。从乔木区系的组成及其特点可以看出,其南亚热带的区系成分占绝对优势,并呈现出由亚热带向热带过渡的趋势。群落垂直结构复杂,地上成层现象较明显,乔木可分为3层,其中重要值最大的锥(Castanopsis chinensis)、木荷(Schima superba)和黄杞(Engelhardtia roxburghiana)均是乔木上层的优势种;中层是群落的主要层,由厚壳桂(Cryptocarya chinensis)、黄叶树(Xanthophyllum hainanense)和华润楠(Machilus chinensis)等中生和耐阴树种组成;下层成分较复杂,物种多样性高,不同地段的物种组成差异较大。样地内物种十分丰富,种-面积曲线拟合显示其物种数量接近于BCI。稀有种比例极高,有110种,占总物种数的52.38%,其中有45%的稀有种源于物种本身的特性,有20%源于区系交汇,人为或自然干扰造成的稀有种占30%以上。样地中所有个体的径级分布(以1cm等级排列)明显呈倒"J"形,表示群落稳定与正常生长状态。根据对优势种径级结构的分布分析,将各树种的径级结构归纳为4种类型:1)峰型(中径级个体储备型),此类物种为乔木上层优势种;2)倒"J"型(正常型),此类物种为乔木中层的优势种;3)类倒"J"型(偏正常型),此类物种占据乔木的中、下层;4)"L"型(灌木型),此类物种分布于乔木下层和灌木层。点格局分析得出优势种在各个层上的绝大部分尺度都是聚集分布的,而不同径级的空间分布随物种的不同而呈现出明显的差异性,点格局显示了优势种在相同径级的分布(特别是DBH=10~40cm)具有一定的空间互补性。对大径级(DBH>40cm)的504个个体进行空间分布格局分析,结果表明,所有这些个体随机分布于整个样地,但不同的物种在空间分布上存在一定的规律。

中亚热带常绿阔叶林不同演替阶段土壤活性有机碳含量及季节动态

为探明不同演替阶段土壤碳吸存潜力,选取演替时间为15a(演替初期)、47a(演替中期)、110a(演替后期)3个中亚热带常绿阔叶林,分析了各演替阶段的土壤有机碳(SOC)含量以及土壤微生物量碳(MBC)、可溶性碳(DOC)和微生物熵(SMQ)的季节变化。结果表明:演替中、后期不同土层的土壤SOC、MBC、DOC含量和SMQ均显著高于演替初期(P<0.05);与演替中期相比,演替后期土壤MBC、DOC含量有所降低,SOC含量和SMQ无显著差异。土壤SOC、MBC和DOC含量随土层加深而显著性降低(演替初、中期DOC除外),并随演替进行逐渐向腐殖质层富集。不同演替阶段MBC、DOC和SMQ均有显著季节变化,最低值出现在秋季,最高值随演替进程由冬季逐步转向夏季。相关分析表明,不同演替阶段土壤活性有机碳含量与土壤有机碳含量极显著相关(P<0.01),且土壤活性有机碳(MBC、DOC)和SMQ对土壤碳库变化更为敏感。