黑龙江省不同地点蒙古栎林生态特点研究

通过对黑龙江省６个地点的天然蒙古栎林的结构和更新特点的分析,蒙古栎林可划分为不同特点的蒙古栎群落,即纯蒙古栎群落、蒙古栎桦树群落、蒙古栎槭树群落、蒙古栎红松群落和蒙古栎松混交林群落,其演替趋势如下：红蒙古栎群落、蒙古栎桦树群落至蒙古栎槭树落、蒙古栎红松群落,再至蒙古栎红松混交林群落,蒙古栎群落类型的多样性主要反应群落不同的演替阶段,造成蒙古栎群落多样的原因是人类活动和自然因素作用的结果,随着群落的演替,蒙古栎的优势地位逐渐被消弱,乔木种类丰富度增多,草本种类丰富度增多;蒙栎的相对密度下降,林内环境由于干燥逐渐变中性至较湿润,蒙古栎幼苗和幼树在总幼苗和幼树中所占的比例下降,耐荫物中色木槭等的幼苗和幼树所占比例上升;在演替过程中,蒙古栎分布格局－聚集分布的聚集程度逐渐降低,并向随机分布的方向发展。     

秦岭山地油松群落更新特征及影响因子

采用样方法,对秦岭山地油松次生林群落更新特性和相关环境因子进行了研究.结果表明:油松次生林更新层乔木树种共36种,占总种数的51.4%;优势种有短柄枹栎、锐齿栎和榛子等;幼苗库丰富,高度级及龄级较小;更新方式以实生为主,该森林群落处于演替中期、林分密度对林下乔木幼苗、幼树数量影响极显著(P<0.01),当林分密度从580株.hm-2增加到1500株.hm-2时,林下更新的幼苗、幼树密度呈增加趋势,随着林分密度的继续增加,其密度逐渐减少;坡向对幼苗、幼树密度的影响显著(P<0.05),当坡向由南偏西10°到南偏西40°,林下幼树密度逐渐减少,至阴坡(北偏东10°)幼树数量又逐渐增加.不同坡位林分更新特征各异,平坡林分中幼苗、幼树密度均较大;从坡下向上,幼苗密度逐渐减少,而幼树密度逐渐增大;海拔从1159 m增至1449 m,幼树密度逐渐增加,至1658 m时,幼树密度逐渐减小,而幼苗密度则一直呈现增加趋势.处于阴坡的中密度林分更新效果最佳.合理调整林分密度是加快林分更新的有效途径之一.     

Composition and Dynamics of Functional Groups of Trees During Tropical Forest Succession in Northeastern Costa Rica

We compared the functional type composition of trees ≥10 cm dbh in eight secondary forest monitoring plots with logged and unlogged mature forest plots in lowland wet forests of Northeastern Costa Rica. Five plant functional types were delimited based on diameter growth rates and canopy height of 293 tree species. Mature forests had significantly higher relative abundance of understory trees and slow-growing canopy/emergent trees, but lower relative abundance of fast-growing canopy/emergent trees than secondary forests. Fast-growing subcanopy and canopy trees reached peak densities early in succession. Density of fast-growing canopy/emergent trees increased during the first 20 yr of succession, whereas basal area continued to increase beyond 40 yr. We also assigned canopy tree species to one of three colonization groups, based on the presence of seedlings, saplings, and trees in four secondary forest plots. Among 93 species evaluated, 68 percent were classified as regenerating pioneers (both trees and regeneration present), whereas only 6 percent were classified as nonregenerating pioneers (trees only) and 26 percent as forest colonizers (regeneration only). Slow-growing trees composed 72 percent of the seedling and sapling regeneration for forest colonizers, whereas fast-growing trees composed 63 percent of the seedlings and saplings of regenerating pioneers. Tree stature and growth rates capture much of the functional variation that appears to drive successional dynamics. Results further suggest strong linkages between functional types defined based on adult height and growth rates of large trees and abundance of seedling and sapling regeneration during secondary succession.
Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp     

Biodiversity values of abandoned teak,Tectona grandis plantations in southern Western Ghats: Is there a need for management intervention?

Abandoned plantations could potentially support a large number of native tree species through succession and restore the original tree community. In order to assess the ability of abandoned teak plantations to recover through regeneration, teak stands from 29 to 80 years old were sampled for seedling and sapling density, species richness and the use by large ungulates in the southern Western Ghats using 10 m circular plots. The influence of the forest-plantation edge was also studied. There was regeneration of a species-rich tree community in the understorey of abandoned teak plantations. However, regeneration was arrested, and thereby the large girth-class tree community remained species-poor. There was no significant change in the tree species richness with distance from natural forest, suggesting that the forest-plantation edge had little influence on the penetration of native tree species inside plantations. Asian elephant and Indian gaur dung densities were significantly lower in the plantations than in the forest. Indian gaur and sambar used the younger plantations intensively, and the density of their dung was negatively correlated with age of the plantation. Abandonment of mature teak stands arrested the succession of native trees. We provide evidence that abandoned teak plantations might not serve as suitable habitats for large herbivores during the dry months of the year in the region. The study highlights the need for active management of mature teak plantations inside wildlife reserves, in order to promote succession and improve the habitat for wild flora and fauna in the Western Ghats.     

黑龙江省大兴安岭林区火烧迹地森林更新及其影响因子

林火干扰是大兴安岭森林更新的影响因子之一,研究火烧迹地森林更新的影响因子(立地条件、火前植被、火干扰特征)对理解生态系统的结构、功能和火后演替轨迹具有重要意义。选取呼中及新林林业局55个代表性火烧样地,利用增强回归树分析法分析了火烧迹地森林更新的影响因素。结果表明:(1)立地条件是影响针、阔叶树更新苗密度的主要因素;海拔对针叶树更新苗密度的影响最大;坡度对阔叶树更新苗密度影响最大;(2)距上次火烧时间对针叶树更新苗比重影响最大,其次是林型;(3)中度林火干扰后森林更新状况好于轻度和重度火烧迹地。根据火烧迹地森林更新调查分析可知:林型影响火后演替模式,火前为针叶树或阔叶树纯林,火后易发生自我更新(火后树种更新组成与火前林型相同),而针阔混交林在火干扰影响下易于发生序列演替(火后初期以早期演替树种更新为主)。     

中国东北小兴安岭阔叶红松林更新及其恢复研究

研究了中国东北小兴安岭地区阔叶红松林的更新和红松的生长及其影响因素。研究结果表明由于成树树冠的遮蔽作用所导致的光照减少是制约幼树生长和存活的关键因素。阔叶红松林是该区最典型和稳定的植被类型,但是在过去的50a中,由于皆伐和更新不良导致了它的分布面积和蓄积量的减少。阔叶红松林是地带性“顶极”植被,并通过具有连续性年龄结构的树种有规律的替代和演替过程中不同阔叶树种组成而处于优势地位。这种林型无疑应作为一种重要的基因库加以保护。次生阔叶林是在阔叶红松林受干扰后出现的,但它的种类组成简单,而且结构也很不稳定。因此,必须对现有的林分结构加以调整以利于林分的长期稳定和高产。同时,提出了红松阔叶林的恢复和重建的经营方式。     

Variation in structural diversity and regeneration potential of tree species in different tropical forest types of Similipal Biosphere Reserve,Eastern India

Understanding the regeneration potential of tree species in natural forest ecosystems is crucial to deliver suitable management practices for conservation of biodiversity. We studied the variation in structural diversity and regeneration potential of tree species in three different tropical forest types, namely: Dry Deciduous forest (DDF), Moist Deciduous forest (MDF) and Semi-evergreen forest (SEF) of Similipal Biosphere Reserve (SBR), Eastern India. Random sample plots were laid for studying the diversity and distribution pattern of tree, sapling, and seedling stages of the tree species. A total of 84 species belong to 73 genera and 35 families were recorded from the study area. The highest species richness was reported for tree (54 species) in DDF, sapling (24 species) in MDF and seedling (22 species each) in SEF and DDF. The overall density of trees with GBH (Girth at Breast Height) ≥ 10 cm was 881 individuals/ha. The regeneration potential of tree species was poor in DDF (39%) where as it was fair in SEF (43%) and MDF (49%). Most of the dominant tree species at each forest type performed good regeneration. The species such as Ehretia laevis Roxb., Bridelia retusa (L.)A.Juss., Mitragyna parviflora (Roxb.) Korth., Terminalia tomentosa Wight & Arn., Terminalia chebula Retz., Terminalia bellirica (Gaertn.) Roxb.etc. had either no regeneration or poor regeneration potential need immediate attention for conservation measures. The diversity of standing trees did not correlate with seedling or sapling diversity in all the cases but there was significant correlation among seedling and sapling diversity found in DDF (r = 0.67, p ≤ 0.05) and SEF (r = 0.83, p ≤ 0.05). Further, the diversity of tree species increased with their age (trees > saplings > seedlings) and the stem density decreased with their age (trees < saplings < seedlings) in all three forest types. The results of our study would be helpful in understanding the structural attributes, diversity and regeneration potential of different tropical forest types of India for their better conservation and management.     

Regeneration of monsoon rain forest in northern Australia: the sapling bank

Abstract. As part of a wider study examining regeneration pathways in monsoon rain forest vegetation in northern Australia, a one-off, dry season census of saplings was undertaken along transects sampled at each of 33 relatively undisturbed sites broadly representative of the range of regional monsoon rain forest vegetation. Four floristic quadrat groups were derived through TWINSPAN classification. Subsequent analyses involved: (1) comparison of mean dry season stockings of juveniles occurring in different rain forest types, and their structural and environmental correlates; (2) comparison of the contributions of different life forms, and the influence of clonal reproduction in the sapling regeneration banks of different forest types; and (3) exploration of relationships between the distributions of saplings of common tree species with respect to seed bank, floristic, structural, and environmental variables. While data presented here require cautious interpretation given that processes of seedling/sapling recruitment and mortality are highly dynamic, sapling banks were found to be most dense on coarse-textured, moist soils, and least dense on coarse-textured, seasonally dry soils. Canopy cover and fire impact were shown to be highly influential on sapling distribution, especially for saplings of tree species and those growing on seasonally dry sites. Sapling densities were little influenced by proximity to rain forest margins, except for shrubs. The potential for clonal reproduction was significantly greater on dry sites, especially for trees. The majority of saplings sampled were derived from relatively few common, non-clonal, canopy tree species. Sapling distributions of 20 out of 23 common tree species were clumped in the vicinity of conspecific adults; for most species the strength of this relationship was greater than that for any other variable. These data support observations in the literature concerning the distribution of sapling banks in moist and dry tropical forests.     

Long-term changes in a Wisconsin Fagus-Acer forest in relation to glaze storm disturbance

Changes in the composition of a Fagus-Acer (Beech-Sugar maple) forest in southeastern Wisconsin over a 16-yr period from 1971 to 1987 are analyzed in relation to a severe glaze (ice) storm disturbance occurring within the census period. Landscape topography created ‘windward’ and ‘leeward’ forest aspects with respect to storm severity, which resulted in greater canopy opening on the windward aspect. In the tree stratum, most species remained stable in density and most of the common species increased in basal area into larger size classes. However, Fagus grandifolia, Ulmus rubra, and the small tree Ostrya virginiana suffered net losses that suggest synergistic effects between glaze storm disturbance and other factors upon tree mortality. In the sapling stratum, canopy opening strongly promoted release of shade-to levant Acer sac-charum. On the windward forest aspect, sapling densities of less shade-tolerant species also increased, in contrast to the absence of such increases on the leeward forest aspect. In the shrub (regeneration) stratum, species responses were heterogeneous. Regeneration of most species increased over the 16-yr period, and some less shade-tolerant species showed increased regeneration differentially on the windward forest aspect. Overall, disturbance appears to have accelerated forest succession toward increased dominance by A. saccharum and persistence of both Fagus and Tilia americana through their capacities for root sprouting. However, forest succession was retarded somewhat on the windward aspect through increased recruitment of less-shade tolerant species. These results parallel those of other studies of glaze storm disturbance, and they illustrate how spatially heterogeneous disturbance intensity may contribute to maintenance of forest diversity.     

50 years of change in a Swedish boreal old-growth Picea abies forest

Abstract. Changes in the tree layer (> 1.3m) and sapling layer (< 1.3m, including seedlings) of a Swedish boreal old-growth Picea abies (Norway spruce) forest from the 1930s to the 1980s were studied in permanent plots. The plots were established in 1938–1939 and re-analysed in 1983–1988. Regeneration, mortality, turnover rate in the tree layer and amount of decomposing logs as well as the time required for complete decomposition of logs were investigated using the detailed data from the 1930s. Ca. 25 % of the trees present during the first analysis were no longer alive. This mortality was balanced by recruitment from the sapling layer. The rate of mortality suggests a turnover time for the tree layer of ca. 200 yr. The number of spruces in the sapling layer has increased by ca. 85 %, hypothetically in response to an increase in amount of decomposing wood that can serve as nurse logs and stumps. The mean time for total decomposition was calculated as ca. 200 yr. Spruce regeneration on logs does not occur until the log is at least ca. 50 yr old. The survival pattern in the sapling layer suggests a high mortality rate at the seedling stage (≤ 1 yr) and a low mortality rate at the sapling stage. In conclusion, it is suggested that the amount of coarse woody debris available for regeneration, the occurrence of seedlings, and seedling mortality constitute concurrent factors through which climatic fluctuations, in a long-term perspective, direct stand recruitment and density. As a consequence, these boreal forests will be kept in a dynamical equilibrium.     

Recovery of plant species richness and composition after slash-and-burn agriculture in a tropical rainforest in Madagascar

Slash-and-burn agriculture is an important driver of deforestation and ecosystem degradation, with large effects on biodiversity and carbon sequestration. This study was conducted in a forest in Madagascar, which consists of fragments of slash-and-burn patches, within a matrix of secondary and primary forest. By recording species richness, abundance, and composition of trees, shrubs, and herbs in fallows of various age and slash-and-burn history, and in the secondary and primary forest, we show how slash-and-burn intensity (number of cycles, duration of abandonment), years since last abandonment, and environmental factors (distance to primary forest and topography) affect the natural succession and recovery of the forest ecosystem. We used ordination analyses to examine how the species composition varied between the different successions stages, and to examine tree recruitment. Our results show shrub dominance the first years after abandonment. Thereafter, a subsequent increase in species richness and abundance of tree seedlings and saplings suggests a succession towards the diversity and composition of the secondary and primary forest, although a big gap between the oldest fallows and the secondary forest shows that this will take much more than 30 years. A high number and frequency of slash-and-burn cycles decreased tree seedling and sapling richness and abundance, suggesting that reducing slash-and-burn intensity will increase the speed of tree recruitment and fallow recovery. Trees can be planted into fallows to speed up vegetation and soil recovery, such that fallows can be usable within needed time and thus the extension of cultivated areas reduced. We recommend further testing of six potential species for restoration based on their early colonization of the fallows and their survival through vegetation succession.     

Spatial structure of the abiotic environment and its association with sapling community structure and dynamics in a cloud forest

Analyzing the relationship between the spatial structures of environmental variables and of the associated seedling and sapling communities is crucial to understanding the regeneration processes in forest communities. The degree of spatial structuring (i.e., spatial autocorrelation) of environmental and sapling community variables in the cloud forest of Teipan, S Mexico, were analyzed at a 1-ha scale using geostatistical analysis; after fitting semivariogram models for each set of variables, the association between the two sets was examined through cross-variograms. Kriging maps of the sapling community variables (density, cover, species richness, and mortality and recruitment rates) were obtained through conditional simulation method. Canopy openness, total solar radiation, litter depth, soil temperature and soil moisture were spatially structured, as were sapling density, species richness and sapling mortality rate. Mean range in semivariograms for environmental and sapling community variables were 13.14 ± 3.67 and 12.68 ± 5.71 m (±SE), respectively. The spatial structure of litter depth was negatively associated with the spatial structures of sapling density, species richness, and sapling community cover; in turn, the spatial structure of soil moisture was positively associated with the spatial structure of recruitment rate. These associations of the spatial structures of abiotic and sapling community variables suggest that the regeneration processes in this cloud forest is driven by the existence of different microsites, largely characterized by litter depth variations, across which saplings of tree species encounter a range of opportunities for successful establishment and survival.     

Effects of seed burial and fire on seedling and sapling recruitment, survival and growth of African savanna woody plant species

Seed predation and seedling mortality can act as strong demographic “bottlenecks” to sapling recruitment in African savanna woodlands. Fire also limits tree recruitment from saplings by suppressing their growth. I conducted field experiments with 13 woody plant species to assess the effects of seed burial on seedling emergence rates and effects of fire on seedling and sapling survival and growth rates over a period of 8 years at a savanna plot in central Zambia, southern Africa. Seed removal rates by small rodents varied among years and buried seeds had significantly higher emergence rates than seeds exposed to predators in most but not all the species. Annual burning reduced sapling growth in some species but in other species saplings experienced successive shoot die back even in the absence of fire. The findings show that for some woody species, seed predation is an important constraint to seedling recruitment but not for others and annual fires are important hindrances to demography and growth for some species but not others. Thus, demographic “bottlenecks” occur at different life history stages in different savanna woody species and these have the potential to alter woody tree competitive relationships and ultimately savanna structure.     

Non-native grass invasion suppresses forest succession

Multiple factors can affect the process of forest succession including seed dispersal patterns, seedling survival, and environmental heterogeneity. A relatively understudied factor affecting the process of succession is invasions by non-native plants. Invasions can increase competition, alter abiotic conditions, and provide refuge for consumers. Functional traits of trees such as seed size and life history stage may mediate the effects of invasions on succession. We tested the effects of the forest invader Microstegium vimineum on planted and naturally regenerating trees in a multi-year field experiment. We established plots containing nine species of small- and large-seeded tree species planted as seeds or saplings, and experimentally added Microstegium to half of all plots. Over 3 years, Microstegium invasion had an overall negative effect on small-seeded species driven primarily by the effect on sweetgum, the most abundant small-seeded species, but did not affect large-seeded species such as hickory and oak species, which have more stored seed resources. Natural regeneration was over 400% greater in control than invaded plots for box elder, red maple, and spicebush, and box elder seedlings were 58% smaller in invaded plots. In contrast to the effects on tree seedlings, invasion did not affect tree sapling survival or growth. Microstegium may be directly reducing tree regeneration through competition. Invaded plots had greater overall herbaceous biomass in 2006 and 2008 and reduced light availability late in the growing season. Indirect effects may also be important. Invaded plots had 120% more thatch biomass, a physical barrier to seedling establishment, and significantly greater vole damage to tree saplings during 2006 and 2007. Our results show that two tree functional traits, seed size and life history stage, determined the effects of Microstegium on tree regeneration. Suppression of tree regeneration by Microstegium invasions may slow the rate of forest succession and alter tree species composition.     

Recovery from clearing,cyclone and fire in rain forests of Tonga,South Pacific: Vegetation dynamics 1995–2005

Abstract In late 2001 a category 3 cyclone impacted forest plots that were established in Tonga in 1995, and additionally, one plot was accidentally burned by an escaped land‐clearing fire. Subsequent surveys provide observations of 10 years of forest dynamics in this poorly studied region, and the first reported observations of large interannual variation in juvenile (seedling and sapling) abundance in the western tropical Pacific. The severely disturbed (burned) plot was initially colonized by a non‐native early pioneer, Carica papaya L., but 3.5 years later a native pioneer, Macaranga harveyana (Muell. Arg.) Muell. Arg., was the most abundant tree species. The seedling layer included some long‐lived pioneers and shade‐tolerant species. Two mature forest plots affected only by the cyclone changed very little over a decade. Late‐successional shade‐tolerant species that dominated the overstory were also abundant as seedlings and saplings. This is in contrast with a 30‐ to 40‐year‐old, formerly cultivated, secondary forest plot that still shows no recruitment of late‐successional dominants, in spite of the proximity of remnant forest patches. This study suggests differing pathways of succession following shifting cultivation versus cyclone and fire disturbances in Tonga. Land use legacies appear to have a long‐lasting effect on community composition.     

Seedling and Sapling Dynamics of Treefall Pits in Puerto Rico1

Seedling and sapling dynamics in a Puerto Rican rain forest were compared between forest understory and soil pits created by the uprooting of 27 trees during Hurricane Hugo. Soil N and P, organic matter, and soil moisture were lower and bulk densities were higher in the disturbed mineral soils of the pits than in undisturbed forest soils ten months after the hurricane. No differences in N and P levels were found in pit or forest soils under two trees with N–fixing symbionts (Inga laurina and Ormosia krugii) compared to soils under a tree species without N–fixing sym–bionts (Casearia arborea), but other soil variables (Al, Fe, K) did vary by tree species. Forest plots had greater species richness of seedlings (<10 cm tall) and saplings (10–100 cm tall) than plots in the soil pits (and greater sapling densities), but seedling densities were similar between plot types. Species richness and seedling densities did not vary among plots associated with the three tree species, but some saplings were more abundant under trees of the same species. Pit size did not affect species richness or seedling and sapling densities. Recruitment of young Cecropia schreberiana trees (>5 m tall) 45 months after the hurricane was entirely from the soil pits, with no tree recruitment from forest plots. Larger soil pits had more tree recruitment than smaller pits. Defoliation of the forest by the hurricane created a large but temporary increase in light availability. Recruitment of C. schreberiana to the canopy occurred in gaps created by the treefall pits that had lower soil nutrients but provided a longer–term increase in light availability. Treefall pits also significantly altered the recruitment and mortality of many understory species in the Puerto Rican rain forest but did not alter species richness.     

中国东北森林生长演替模拟模型及其在全球变化研究中的应用

 NEWCOP模型是一个新的适于模拟东北森林的种类组成动态的林窗类计算机模拟模型,它通过模拟在每一个林分斑块上的每株树木的更新、生长和死亡的全过程来反映森林群落的中长期生长和演替动态。由于 NEWCOP模型是一个由气候变量驱动的生态系统模型,故可用于评价气候变化对东北森林生长和演替的影响。在东北大兴安岭、小兴安岭和长白山地区对NEWCOP模型进行了验证和校准。沿环境梯度对NEWCOP模型的数字模拟实验表明：它能准确地再现顶极森林中树种组成及其在东北地区的垂直分布规律和水平分布规律;能准确地再现大兴安岭、小兴安岭和长白山的主要类型森林的生长和演替规律;在一定的场合NEWCOP还可反映林分的径级结构;NEWCOP模型还具有对现有森林的跟踪模拟能力。应用NEWCOP模型评估了东北森林生态系统对可能气候变化的敏感性。在GFDL 2×CO2和GISS 2×CO2气候变化情景下,东北森林的种类组成将发生很大变化,落叶阔叶树将取代目前长白山、小兴安岭的红松(Pinus koraiensis)和大兴安岭的兴安落叶松(Larix gmelinii)成为东北森林主要树种,而针叶树将在地带性森林中占很小的比重,阔叶树中蒙古栎(Quercus mongolica)将是最重要的树种,它将成为小兴安岭和大兴安岭最主要树种;东北地区适于森林生长的区域将大幅度减少,这些变化主要发生在气候变化过渡期。东北森林对不同的气候变化情景有不同响应。但是,总的趋势是未来东北森林中落叶阔叶树的比重将大幅度增加。这些结论对在全球气候变化背景下,我国东北合理地选择造林树种和制定现有森林的保护经营策略具有一定参考价值。     

Sapling dynamics in a southeastern Texas floodplain forest

Abstract. How much temporal variation in recruitment, mortality and change in size class occurs in the sapling layer of mature temperate forests in the absence of large‐scale exogenous disturbance? Using 15 years of data from a flood‐plain forest in Big Thicket National Preserve, we found that year‐to‐year variation in demographic parameters was greater than we originally expected. Death rates were generally more variable than recruitment rates, and were much more variable for large saplings than for small ones. Small saplings of the 10 most common species had at least one year when they experienced two to eight times their long‐term mean recruitment and death rates. Large saplings had at least one year when they experienced three to 10 times their long‐term mean death rates and at least one year with two to seven times the long‐term mean recruitment rate. Temporal patterns in sapling death rates were related to flooding patterns, while temporal patterns in recruitment were related to the Palmer Drought Severity Index, an indicator of drought severity and soil moisture availability. We also identified apparently synchronous patterns of demographic response among less flood‐tolerant species which differed from the responses of more flood‐tolerant species. We demonstrated the effects of both climatic variation and light variation in affecting stand‐wide sapling demographics in a forest where canopy gaps are important for regeneration, and where chronic understorey disturbance favours growth over survivorship as a sapling strategy.     

Effects of altitude and livestock on the regeneration of two tree line forming <Emphasis Type="Italic">Polylepis</Emphasis> species in Ecuador

Regeneration is known to be limited at many temperate tree lines, but very little data is available on the impacts of altitude and anthropogenic disturbance on regeneration patterns along tropical tree lines. The study focused on the reproductive traits of two Polylepis species in the Páramo de Papallacta in Ecuador along an altitudinal gradient, and involved different intensities of cattle trampling within subsequent altitudinal ranges. We analyzed flowering, fruit set, seed viability, germination, and seedling establishment as well as stand structure of Polylepis incana and P. pauta. The numbers of P. incana inflorescences and seedlings per m2 showed a marginally significant decrease with increasing altitude. Mean tree height was significantly lower at higher altitudes, while stem number increased. The number of P. pauta inflorescences also decreased significantly upslope. In both forest types, trampling was found to have a positive impact on seedling abundance, presumably due to the removal of the litter layer. Thus, there was no evidence of negative effects of moderate cattle grazing on both tree line species. However, sapling establishment was minimal inside the forest stands at all altitudes and grazing levels, and we consequently observed a low proportion of narrow stems within all investigated forests. Our results show that, along with vegetative growth limitations of adult trees, important regeneration traits such as seedling and inflorescence numbers are also influenced by altitude, which might contribute to the formation of the upper tree line. Nevertheless, recruitment in the forest interior was low overall indicating that further factors, such as light conditions, affect regeneration of the studied species.     

Species‐habitat associations change in a subtropical forest of China

Question: Do tree and shrub species in an evergreen broadleaf forest show similar habitat associations across different life stages? Location: A 24‐ha evergreen broadleaf forest plot in a heterogeneous landscape in Gutianshan National Nature Reserve, Zhejiang Province, Eastern China. Methods: Species having positive associations with four habitat types (low valley, low ridge, upper valley, and upper ridge) at three life stages (sapling, juvenile, and mature stages) were compared for 60 tree and shrub species using torus‐translation tests. Results: A total of 117 significant positive associations with the four habitats were observed at the three life stages (43, 41, and 33 at the sapling, juvenile, and mature stages, respectively). For the 52 species significantly associated with habitats, only 16 were associated with the same habitat across all three stages. The majority of associated species at the juvenile stage (34 out of 40) were associated with the same habitat at their sapling stage, whereas half of species at the mature stage had consistent associations with the same habitat at their sapling stage. More species were associated with the upper ridge at the sapling and juvenile stages compared to the mature stage. Conversely, more species were associated with the low valley at the mature stage compared to the sapling and juvenile stages. Conclusions: Our results indicate that species ecological habitat associations can differ between developmental stages beyond 1 cm DBH, as most species habitat preferences were consistent from the sapling stage to the juvenile stage but changed at the mature stage.