Zonal transition of evergreen,deciduous, and coniferous forests along the altitudinal gradient on a humid subtropical mountain,Mt. Emei,Sichuan, China

Altitudinal zonation of evergreen, deciduous and coniferous forests on Mt. Emei (3099 m asl, 29°34.5' N, 103°21.5' E), Sichuan, China was studied to understand the transition of vegetation zonation from tropical to temperate mountains in humid Asia. On the basis of quantitative data on floristic composition and community structure sampled at ten plots selected in different altitudes on the eastern slope of the mountain, forest zonation and the inter-relationships among different life-forms of trees in each zonal forest community were studied quantitatively. Three forest zones were identified physiognomically along the altitudinal gradient, viz. (i) the evergreen broad-leaved forest zone (660–1500 m asl), (ii) the mixed forest zone (1500–2500 m asl), and (iii) the coniferous forest zone (2500–3099 m asl). Great compositional changes were observed along elevation, and the zonal forest communities were characterized by their dominants and floristic composition. Maximum tree height decreased from 33 m at lower middle altitude (965 m asl) to 13 m near the summit (2945 m asl). There was no apparent deciduous forest zone along the altitudinal gradient, but true mixed forests of three life-forms (evergreen, deciduous, and coniferous) were formed around 2000–2500 m asl. Patches of deciduous forest were found in a lower part of the mixed forest zone, particularly on scree slopes, between 1450 m and 1900 m asl. These patches were dominated by the Tertiary relic deciduous trees, such as Davidia involucrata, Tetracentron sinense, and Cercidiphyllum japonicum var. sinense. High species diversity in the mixed forest zone resulted from the overlapping of different life-forms at middle altitudes, which is partly due to wider variety of temperature-altitude correlations. A comparison of the altitudinal zonation with the other east Asian mountain vegetation clarified that Mt. Emei is located exactly at the ecotone between tropical and temperate zonation types in eastern Asia.     

Successional change of forest pattern along topographical gradients in warm-temperate mixed forests in Mt Kiyosumi,central Japan

Forest patterns along topographical gradients were compared between second- and old-growth forested watersheds in a warm-temperate zone of Mt Kiyosumi, central Japan. Three community types were distinguished depending on the topographical habitat type in each watershed, for example, conifer forest was dominated byAbies firma andTsuga sieboldii on ridge sites, evergreen broad-leaved forest was dominated byQuercus acuta, Q. salicina andCastanopsis cuspidata var.sieboldii on slope sites, and deciduous forest was dominated byEuptelea polyandra andCornus controversa in valley sites. Beta diversity and distinctiveness of each topographical community type increased with progression of secondary succession. Conifers and evergreen broad-leaved trees, which were intermingled with each other on ridges and slopes of the second-growth watershed, were in turn restricted to the ridge and slope habitat type, respectively, in the old-growth watershed. The process of this differentiation can be explained by the continuous regeneration of conifers on ridge sites, and its absence on slope sites due to different light conditions caused by progressive canopy closure of evergreen trees on the slope sites toward the old-growth watershed. In the valley type habitat, frequent soil disturbance, such as landslides and soil creep, hinder the continuous growth of late successional evergreen trees, and thus seral or pioneer deciduous trees can persist in the habitat.     

广西石灰岩山地常绿落叶阔叶混交林分类的研究

石灰岩山地在广西占有相当大的面积,在亚热带范围形成一种独特的石灰岩常绿落叶阔叶混交林,常常与砂页岩山地的常绿阔叶林镶嵌分布。本文主要论述它的系统分类和地理分布规律。     

Coexistence mechanisms of evergreen,deciduous and coniferous trees in a mid-montane mixed forest on Mt. Emei,Sichuan, China

Structure and regeneration of a mid-montane (2200 m a.s.l.)mixed forest codominated by evergreen (Lithocarpuscleistocarpus), deciduous (Acer flabellatum)andconiferous (Tsuga chinensis, Abies fabri, andTaxus chinensis) trees were analyzed in a 40m× 60 m plot on Mt. Emei, Sichuan, China. Plant communitystructure and composition varied depending on topographic micro-habitat withinthe plot. Four topographic communities (topo-communities) were distinguishedwith dominant species corresponding to topography: (1)Abies – valley bank, (2) Acer– lower steep slope, (3) Lithocarpus – uppergentle slope, and (4) Tsuga – ridge. The coexistencemechanisms of the evergreen, deciduous, and coniferous trees were determined byidentifying the regeneration process characteristic of each dominant species,asrepresented by their seedling dispersion patterns and seedling establishmentalong the topographic gradients. The saplings and seedlings of the dominantswere distributed differently according to the topography:Lithocarpus under the canopy of parent trees and in gapsofthe upper gentle slope and ridge, Acer mainly in bothwell-lit and shady sites on the lower steep slope and on fallen logs,Abies on the valley bank but only in well-lit sites,Tsuga on the ridge, Taxus mostly onrock and well-lit sites on the slopes. Distribution of surviving saplings andseedlings was also related to the species of nearby canopy trees. We suggestthat Lithocarpus, Tsuga and Acer tendto be self-replacing in their own topographic habitats, andAbies survives as a fugitive by occupying occasionalsuitable gaps. The variation in soil conditions, particularly nutrients, withtopography affected seedling establishment and the growth of trees. Thesuccessional change of quantitative species composition, as predicted by theMarkovian model, shows the mixed forest to be in a sustained climax stage.     

Effects of canopy gaps on the demography of the subcanopy tree Styrax obassia

Abstract. To evaluate the gap dependency of the subcanopy tree species Styrax obassia, we estimated the demographic parameters of this species in a permanent plot in the Ogawa Forest Reserve, Central Japan, a temperate deciduous forest. From the data collected over eight years, we constructed four transition matrix models of Styrax: a whole population; a shaded subpopulation; a gap-site subpopulation; a compound population of shaded and gap-site subpopulations. The whole-population model suggested that the population structure of Styrax is stable in its present condition. The asymptotic population growth rate of the shaded subpopulation was larger than 1, suggesting that this species can maintain its population even under shaded conditions. The elasticity analyses showed the relative importance of survival of adult individuals that stay mostly under a closed canopy. Since the subpopulation in gaps is very small in a mature forest, the contributions of high seedling survival and high fecundity of adult trees in gaps to the whole population growth were smaller than the survival of adult individuals in the shade. Although we showed that this species has the potential to increase its population in larger disturbances, it actually dominates in the study site where the disturbance scale is relatively small. Styrax should be classified as a typical shade-tolerant species, and it also takes good advantage of small scale disturbance. It can sufficiently maintain its population in a mature forest with small-scale disturbances and has the adaptive characteristics of species that live under a closed canopy.     

Distribution and regeneration strategies of major canopy dominants in species-rich subtropical/warm temperate rainforests in south-western Japan

The distribution and regeneration strategy of the major canopy dominants in species-rich subtropical/warm temperate rainforests in south-western Japan was studied in a hilly zone below 1100 m a.s.l. Using the patch sampling method, four dominance-community types were numerically identified and they corresponded to four habitats which represented a combination of topography and altitude (i.e. ridgesvs slopes, and belowvs above 500 m a.s.l.) Seven major canopy dominants had their respective distributional core in one of these topo-altitudinal habitats. The seven canopy dominants could be classified into three species groups according to their size structure and growth habits. Group A (Tsuga sieboldii andQuercus gilva) and group B (Quercus acuta, Quercus salicina, Machilus thunbergii) were restricted to the emergent and canopy layer, respectively. These two groups had only a few subcanopy trees and saplings. Saplings of group B showed a rapid growth rate in canopy gaps. Group C (Distylium racemosum) was characterized by many subcanopy trees and saplings that grew steadily under the closed canopy.Castanopsis sieboldii showed intermediate characteristics between group B and C in the size structure and growth habit of its saplings. The density ofD. racemosum canopy trees was markedly reduced on ridges and slopes above 500 m and on slopes below 500 m. In these marginal habitats, the three species groups coexisted by sharing different strata within a community. This situation was possible due to the differences in regeneration strategies among the canopy species.     

峨眉山世界遗产地表土孢粉组合及其生态和古环境启示

通过峨眉山40个样点表土孢粉组合及其与植物群落之间关系的分析,结果表明:(1)花粉组合中木本植物含量(83.3%)占绝对优势,松属、杉科、桤木属、蔷薇科、桦属、枫杨属、蒿属、毛茛科和水龙骨科为主要孢粉类型;(2)中山常绿阔叶林花粉组合未能反映植被的群落特征;低山常绿阔叶林间人工次生林和常绿落叶阔叶混交林花粉组合只能反映母体植被的部分组成;针叶林花粉组合基本可以指示母体植被的群落特征;灌丛草甸花粉组合能够较好地反映母体植被的群落组成;针阔混交林花粉组合不仅可以很好地指示群落特征,花粉高含量类型还可以与植物群落优势种很好地对应;(3)主要花粉类型冷杉属、杜鹃花科、蔷薇科、珙桐属、槭属和盐肤木属具低代表性;枫杨属、栲属/柯属、桤木属和杉科花粉具超代表性;(4) DCA表明,通过花粉百分含量,能较好地区分人类扰动植被、阔叶林和针叶林,但常绿阔叶林、常绿落叶阔叶混交林和针阔混交林之间,针叶林和灌丛草甸之间难以区分;(5)利用孢粉学恢复热带亚热带常绿阔叶代表类群樟科群落和第三纪孑遗落叶阔叶属种珙桐群落时,受其主体植物花粉外壁薄,易破碎影响,原生植被优势种缺失;因此,孢粉实验改良和保存环境研究,与其他生物学指标(植物大化石和气孔器)综合分析在重建古植物群落中具有重要意义;(6)植物(如冷杉)花粉含量一定程度上能够指示其林分结构。本研究可为热带亚热带山地及相似地区利用孢粉学进行地质时期气候与环境重建提供理论支持和基础资料,并对植被生态恢复提供实践和参考。     

茂兰喀斯特常绿落叶阔叶混交林群落组成和优势种更新类型

为探讨茂兰喀斯特森林群落结构和优势种更新机制,对茂兰自然保护区常绿落叶阔叶混交林群落进行了调查。结果表明,群落中有木本植物37科58属70种,以樟科、蔷薇科、无患子科和漆树科为主。常绿树种41种,占总种数的58.6%;落叶树种29种,占总种数的41.4%,这体现了喀斯特常绿落叶阔叶混交林的群落学性质。群落的优势乔木树种有轮叶木姜子(Litseaverticillata)、青冈栎(Cyclobalanopsisglauca)、狭叶润楠(Machilusrehderi)和翅荚香槐(Cladrastisplatycarpa)等。灌木优势种有皱叶海桐(Pittosporumcrispulum)、裂果卫矛(Euonymusdielsianus)、革叶铁榄(Sinosideroxylonwightianum)和南天竹(Nandina domestica)等。优势种种群结构有5种类型:单峰型,如樱桃(Cerasus pseudocerasus)、南酸枣(Choerospondias axillaris)等阳性乔木,为林窗更新种,随林窗的郁闭将衰退消失;逆J字型,如轮叶木姜子、香港四照花(Dendrobenthamia hongkongensis)、皱叶海桐等耐荫性强的常绿阔叶树种,更新能力较强,为顶极群落优势种;间歇型,如青冈栎、狭叶润楠、齿叶黄皮(Clausena dunniana)等树种,群落中的个体多集中在小径级阶段,能长期存在于群落中;L字型,如桂皮(Cinnamomumtamala)、梓叶槭(Acer catalpifolium)、革叶铁榄等;单柱型,如石岩枫(Mallotus repandus)、南天竹等常绿灌木树种,个体集中于幼苗、幼树阶段,为顶极群落亚乔木层和灌木层的主要组成种。因此,这表明调查区域的植物群落处于相对稳定的顶极阶段。     

Aspects of tissue water relations and seasonal changes of leaf water potential components of evergreen and deciduous species coexisting in tropical dry forests

Summary This study compared the tissue water relations and seasonal changes in leaf water potential components of an evergreen tree,Morisonia americana, and two evergreen shrubs,Capparis verrucosa andC. aristiquetae, with two deciduous trees,Humboltiella arborea andLonchocarpus dipteroneurus, and the deciduous vineMansoa verrucifera. All these species coexist in a tropical dry forest in Venezuela. Leaves of the evergreen species are sclerophyllous, while those of the deciduous species are mesophytic. Leaf area to leaf weight ratios of fully mature leaves were about 75 and 170 cm² g^–1 in evergreen and deciduous species, respectively. Seasonal fluctuations of leaf water content per unit of dry weight, water potential, and turgor pressure were smaller in evergreen than in deciduous species. The analysis of tissue water relations using pressurevolume curves showed that evergreen species could develop a higher leaf turgor and lose turgor at lower leaf water potentials than deciduous species. This was related to a lower osmotic potential at full turgor in evergreen (-3.0 MPa)_than in deciduous (-2.0 MPa) species, rather than to the elastic properties of leaf tissue. The volumetric modulus of elasticity was 14 MPa in evergreen compared with 7–10 MPa in deciduous species. Thus, leaf characteristics are important in determining the drought resistance of evergreen species of this tropical dry forest.     

乌蒙山峨眉栲、华木荷群落特征研究

乌蒙山位于中国西部半湿润常绿阔叶林与东部湿润常绿阔叶林交界区,是云南省唯一分布峨眉栲、华木荷群系(Formation Castanopsis platyacantha,Schima sinensis)的地区,该群系处于中国西部常绿阔叶林向东部常绿阔叶林过渡的地带,群落更加复杂多样。为了更深入地了解该群系的群落特征,同时找出其与东部湿润常绿阔叶林的联系,该文对该类型群落进行了数量分类研究,分析了聚类归并的各群落类型的乔灌优势种特征(径级结构、高度结构和重要值),同时采用DCA,CCA和DCCA排序分析进行群落特征分异的环境解释,并与四川峨眉山同类群落进行特征对比。结果表明:(1)乌蒙山峨眉栲、华木荷群落可划分为6个类型:峨眉栲群落,峨眉栲、华木荷群落,峨眉栲、十齿花群落,水青冈(Fagus longipetiolata)、华木荷、峨眉栲群落,华木荷、硬斗石栎(Lithocarpus hancei)群落,十齿花(Dipentodon sinicus)、华木荷群落。(2)乌蒙山峨眉栲、华木荷群落中,峨眉栲大树比例较高,华木荷小苗数量巨大,灌木层常以竹类为优势种。(3)海拔、坡度和太阳年辐射值是影响群落分布的主导因素。(4)峨眉山同类群落中优势种种群呈稳定型或增长型,而乌蒙山峨眉栲、华木荷群落中,峨眉栲和水青冈呈现下降型的特点。     

Vegetation structure in relation to micro-landform in an evergreen broad-leaved forest on Amami Ohshima Island,south-west Japan

The relationship between micro-landform and vegetation structure was studied in a plot that was established on a slope from the ridge to the valley bottom in an evergreen broad-leaved forest on Amami Ohshima Island, south-west Japan. Five micro-landform units recognized in the plot were grouped into the upper and lower slopes by their location in relation to the erosion front, and plant distributions and vegetation structure were compared between them. Although small trees with d.b.h. less than 10 cm occurred almost all over the plot, the occurrence of larger trees was limited mostly to the upper slope. Based on the spatial distribution pattern in the plot, woody species are classified into three groups: group A mostly or strictly confined to the upper slope; group B confined to the lower slope; and group C associated statistically with neither slope. A well-developed forest stand, whose dominant species wereCastanopsis sieboldii ssp.lutchuensis andSchima wallichii, was seen on the upper slope, whereas only a poorly developed stand was seen on the lower slope. The difference in stability of the land surface is likely to be the major cause of the observed differences in stand structure between the upper and lower slopes. It is suggested that the erosion front is important as a line demarcating different habitats within a slope from the ridge to the valley bottom.     

浙江仙居俞坑森林群落优势种群结构与分布格局研究

以浙江仙居俞坑森林群落为研究对象,用“空间序列代替时间变化”的方法,对该群落优势种群的结构和动态进行了分析,结果是：各优势种群中常绿阔叶树种的大小级分布图的形状基本相似,种群存活曲线均表现为极显著的线性关系,种群的年龄结构为稳定型。地树种拟赤杨的年龄结构为衰退型。甜槠、青冈栎、红楠种群的分布格局均呈集群分布,木荷、虎皮楠种群的分布格局多为随机分布,拟赤杨呈随机分布或均匀分布。甜槠种群的幼苗、幼树的     

Differences in nitrogen use efficiency between leaves from canopy and subcanopy trees

We examined the effects of increasing light availability along a vertical gradient within a forest community on the efficiency of leaf nitrogen (N) use in individual trees. The N contents of green and senescent leaves in canopy and subcanopy trees of an evergreen coniferous species, Podocarpus nagi, and an evergreen hardwood species, Neolitsea aciculata, were analyzed in a mixed forest community at Mt Mikasa, Nara City, Japan. The inverse of N concentration (N_C) in senescent leaves was used as an index of N use efficiency (NUE) at the leaf-level. The leaf-level NUE was higher in canopy trees than in subcanopy trees in both P.nagi and N.aciculata, although soil N mineralization rates around canopy and subcanopy trees did not differ significantly. The N_C in green leaves was lower in canopy trees than in subcanopy trees. The ratio of resorbed N in senescent leaves to the N content in green leaves was higher in canopy trees than in subcanopy trees. The higher leaf-level NUE of canopy trees was partly a result of lower N_C in living tissues and partly because of greater N resorption during senescence. The present study suggested that the leaf-level NUE could be increased in response to an imbalance between soil N and light availability caused by spatial community structure.     

亚热带常绿阔叶林和暖温带落叶阔叶林叶片热值比较研究

植物干重热值(GCV)是衡量植物生命活动及组成成分的重要指标之一,反映了植物光合作用中固定太阳辐射的能力。利用氧弹量热仪测定了亚热带和暖温带两个典型森林生态系统常见的276种常见植物叶片的干重热值,探讨了亚热带和暖温带植物热值分布特征,以及不同生活型、乔木类型间植物热值的变化规律。实验结果发现:亚热带常绿阔叶林和暖温带落叶阔叶林叶片热值的平均值分别为17.83 k J/g(n=191)和17.21k J/g(n=85),整体表现为亚热带植物暖温带植物。不同地带性植被的植物叶片热值在不同生活型间表现出相似的规律,其中亚热带常绿阔叶林表现为:乔木(19.09 k J/g)灌木(17.87 k J/g)草本(16.65 k J/g);暖温带落叶阔叶林表现为:乔木(18.41 k J/g)灌木(17.94 k J/g)草本(16.53 k J/g);不同乔木类型间均呈现常绿乔木落叶乔木、针叶乔木阔叶乔木的趋势。落叶阔叶乔木表现为亚热带暖温带,而常绿针叶乔木则呈现亚热带暖温带的趋势。此外,我们对于两个分布区域内的4种针叶树种叶片热值进行了比较,发现华北落叶松(19.32 k J/g,暖温带)杉木(19.40 k J/g,亚热带)马尾松(19.82 k J/g,亚热带)油松(20.95 k J/g,暖温带)。亚热带常绿阔叶林和暖温带落叶阔叶林植物热值的特征及其变化规律,为森林生态系统的能量流动提供了理论基础。     

基于地形因子的天童地区常绿树种和落叶树种共存机制研究

位于亚热带的浙江天童和古田山常绿阔叶林大样地分布有较高比例的落叶树种,那么它们与常绿树种的共存机制是什么?常绿树种和落叶树种生态习性差异较大,二者对生境的选择应有所不同,我们推测生境分化可能是两类植物实现共存的主要机制。为检验该假设,我们以天童20ha动态样地调查数据为依托,选择个体数≥20的55个常绿树种和42个落叶树种作为分析对象,用典范对应分析(CCA)研究了地形因子对二者分布的影响差异,用torus转换检验来分析常绿树种和落叶树种与各类地形生境的关联。结果如下:(1)CCA分析表明地形因子对常绿树种分布的解释量为19.2%,对落叶树种分布的解释量为7.0%。(2)torus转换检验结果表明,与沟谷成正关联的常绿树种和落叶树种的比例分别为16.4%和28.6%,成负关联的比例分别为40%和7%;与山脊成正关联的常绿树种和落叶树种的比例分别为41.8%和4.8%,成负关联的比例分别为10.9%和47.6%;与受干扰生境成正关联的常绿树种和落叶树种的比例分别为16.4%和42.9%。上述结果说明地形对常绿树种分布的影响大于落叶树种;两个植物类群对生境的选择多呈现相反格局,尤其是在沟谷生境和山脊生境,这进一步表明生境分化是常绿树种和落叶树种共存的重要机制之一,生态位理论在一定程度上能较好地解释亚热带常绿阔叶林物种多样性的维持。     

Regeneration process of coniferous forests in northern Hokkaido I.Abies sachalinensis forest andPicea glehnii forest

Regeneration of natural forests was studied in the Nakagawa Experiment Forest of Hokkaido University using age distribution surveys made by the clear felling method. In Plot 1 (30 m × 65 m),Abies sachalinensis dominated the canopy layer but there were also a fewBetula ermanii trees.Sasa senanensis densely covered the forest floor. Most of the canopy trees were from 122 to 195 years old. Seedlings younger than 50 years old ofA. sachalinensis were found on fallen logs and root bases. There were, however, few trees from 50 to 120 years old. The present canopy trees seemed to have regenerated after competitive pressure from old canopy andSasa disappeared 180 years ago. Plot 2 (50 m × 100 m) on serpentinite soil was dominated byPicea glehnii. Sasa kulirensis covered the floor but not as densely asS. senanensis in Plot 1. The ages ofP. glehnii ranged from 1 to 586 years old, and the age distribution ofA. sachalinensis was L-shaped. A small gap in the canopy formed about 290 years ago, and it gradually extended. Conifers regenerated continuously in the extending gap butB. ermanii did not. One hundred thirty years ago, part of Plot 2 was again destroyed andA. sachalinensis andB. ermanii regenerated. Thus, two types of regeneration were found. One regenerated both conifers andBetula after a sudden disturbance of canopy layer or death ofSasa, and the other, under an extending gap, regenerated only conifers.     

哀牢山中山湿性常绿阔叶林木径向生长季节动态及其对气候因子的响应

研究采用树木生长环在哀牢山中山湿性常绿阔叶林持续9年(2009—2017年)监测了2个常绿树种(厚皮香,Ternstroemia gymnanthera;南亚枇杷,Eriobotrya bengalensis)和2个落叶树种(西桦,Betula alnoides;珍珠花,Lyonia ovalifolia)的树干月生长量,采用逻辑斯蒂生长模型(Logistic model)模拟树木径向生长量和物候参数,并分析了年、季尺度上径向生长与主要气候因子的关系。结果表明:1)4个树种年平均生长量为6.3 mm,落叶树种年平均生长量(10.6 mm/a)显著高于常绿树种(3.0 mm/a);2)雨季(5—10月)是哀牢山中山湿性常绿阔叶林树木生长的主要时期,4个树种雨季平均生长量为5.9 mm,占全年总生长量的93%,其中落叶树种雨季生长量占全年的96%,而常绿树种雨季生长量占全年的86%;3)常绿树种生长季长度为169天,长于落叶树种(137天),而落叶树种最大生长速率(0.14 mm/d)显著高于常绿树种(0.03 mm/d),最大径向生长速率能很好地预测树种年生长量;4)低温、雾日和光合有效辐射是影响哀牢山亚热带常绿阔叶林4个研究树种径向生长的重要环境因子,其中温度对常绿树种径向生长具有显著影响,而雨日、雾日与空气湿度等水分因子对落叶树种径向生长更为重要。常绿树种年生长量对旱季气候因子的响应相比落叶树种更为敏感,树木旱季生长量除了受低温限制外,也受到水分供给的影响。气候变化可能改变不同物候类型树种在哀牢山中山湿性常绿阔叶林中的生长状态与分布格局。     

Impacts of land-use history on the diversity of a riparian forest landscape in warm-temperate Kyushu,southern Japan

We examined the impacts of land-use history on the species composition and diversity of a warm-temperate riparian forest landscape in Kyushu, southern Japan, focusing on the relationship between evergreen oaks and deciduous trees in natural and seminatural forests. The species composition of 59 plots was classified into four types (A to D). Type A, which showed a significant bias towards sites not subject to nonforest land use since 1947, had high species diversity consisting of (1) many lucidophyllous components of the region, including the rare indigenous oak Quercus hondae, and (2) summergreen tree species of varying dominance and number representing unique or locally rare elements of the riparian landscape in this warm-temperate region. Type B was dominated by a common species of oak, Q. glauca, and displayed less clear distribution bias with land-use history. In contrast to types A and B, types C and D, which were characterized by high dominance of deciduous trees, had negative bias away from sites that had been under forest land use in 1947. Presumably, intensive anthropogenic disturbances associated with nonforest land uses had expanded the habitats for deciduous trees. This phenomenon was represented by the establishment of forests (type D) dominated by Ulmus davidiana var. japonica (UDJ) after it had been released from the suppression of evergreen forest trees during a period of nonforest land use that prevents the successful recovery of evergreen trees. From these results we conclude that the impacts of land-use history on the diversity of warm-temperate riparian forest landscape are multiphased: a period of nonforest land use has a strong negative impact on lucidophyllous forest trees represented by the rare indigenous oak Q. hondae; release from the suppressive effects of the lucidophyllous species then encourages establishment of locally rare deciduous tree flora represented by UDJ, which continue to persist for decades after abandonment of nonforest land use.     

2011-2016年武夷山甜槠常绿阔叶林乔木层群落动态

武夷山保存了典型的中亚热带原生性森林生态系统。加强武夷山常绿阔叶林研究,对支撑武夷山生态保护实践具有重要意义。2016年,对按照美国史密森热带研究所热带森林研究中心调查技术规范建立的甜槠常绿阔叶林样地进行了首轮复查,并从物种组成、群落多样性、重要值、死亡率、补员率、胸径等方面分析了其群落动态。结果表明：2016年的乔木个体为25科44属88种,较2011年增加了2科2属7种。群落的优势种组成及其优势程度变化不大,在重要值大于1的21个常见树种中,10个树种的重要值增高,11个降低。甜槠仍为建群种,其重要值略下降。乔木个体增加到3888个,年死亡率为1.31%,年补员率为2.98%。43个树种出现死亡,46个出现补员。4个常见树种的种群数量下降,16个上升。群落的平均胸径从4.82 cm增大为4.89 cm,5个常见树种的平均胸径下降,16个上升。死亡个体的平均胸径为4.47 cm,补员个体为1.67 cm。甜槠仍然将在乔木层,马银花和鹿角杜鹃在亚乔木层保持优势地位。在短期内群落结构不会出现较大的变化,但黄绒润楠、厚皮香等阴生树种和中性树种优势度的增加可能预示群落将向中生群落（顶级群落）演替。     

Mass loss and nutrient release from decomposing evergreen and deciduous Nothofagus litters from the Chilean Andes

Abstract Leaf litter decomposition experiments were conducted on two deciduous (Nothofagus obliqua (roble)) and Nothofagus pumilio (lenga)) and one evergreen (Nothofagus dombeyi) Nothofagus (Nothofagaceae) species from a single Chilean forest in order to understand how congeneric trees with differing leaf lifespans impact the soil in which they grow. Single‐species litter samples were decomposed in a mixed hardwood forest in Ohio and in a deciduous‐evergreen Nothofagus forest in Chile. In the Ohio forest, the two deciduous species’ litters decomposed at k ≈ 1.00 per year and the evergreen at k ≈ 0.75 per year. In Chile k ranged from k ≈ 0.06 (N. obliqua) to k ≈ 0.23 (N. pumilio) per year. In both experiments, N and P were released faster from the deciduous litters than from evergreen litter. In Ohio, evergreen litter immobilized more N and P for a longer time period than did deciduous litter. As N. dombeyi stands tend to have lower available soil N and P in this particular mixed Nothofagus forest, the increased time of N and P immobilization by N. dombeyi litter suggests a feedback role of the tree itself in perpetuating low N and P soil conditions.