Land use history, hurricane disturbance, and the fate of introduced species in a subtropical wet forest in Puerto Rico

Tropical forests are suffering from increasing intensities and frequency of disturbances. As a result, non-native species accidentally introduced or intentionally planted for farming, plantations, and ornamental purposes may spread and potentially invade undisturbed native forest. It is not known if these introduced species will become invasive, as a result of recurrent natural disturbances such as hurricanes. Using data from three censuses (spanning 15 years) of a 16-ha subtropical wet forest plot, we investigated the impact of two hurricanes on populations of plant species that were planted in farms and plantations that were then abandoned and from the natural spread of species introduced into Puerto Rico in the past. The populations of four species (Citrus paradis, Mangifera indica, Musa sp., and Simarouba glauca) changed little over time. Six species (Artocarpus altilis, Calophyllum calaba, Genipa americana, Hibiscus pernambucensis, Syzygium jambos, and Swietenia macrophylla) declined between the first two censuses after Hurricane Hugo, then increased again in Census 3 after Hurricane Georges. Spathodea campanulata gradually increased from census to census, while Coffea arabica declined. These introduced species represent only a small part of the forest basal area and few show signs of increasing over time. The number of stems per plant, new recruits, and the growth rates of these introduced species were within the ranges of those for native plant species. The mortality rates over both census intervals were significantly lower for introduced species (<5% year⁻¹) than for native ones (15% year⁻¹). Many new recruits established after Hurricane Hugo (prior to this study) had opened the forest canopy and these high mortality rates reflect their death as the canopy recovered. Only Swietenia macrophylla and Syzygium jambos showed an increase in stem numbers in the closed canopy area of forest that had suffered limited human disturbance in the past. A future increase in frequency of disturbance may enable greater stem numbers of introduced species to establish, while lower-mortality rates compared to native species, may allow them to persist during inter-hurricane intervals. An increase in the population of introduced species, especially for those that grow into large trees, may have an impact on this tropical forest in the future.     

Fragment shape and tree species composition in tropical forests: a landscape level investigation

Fragmentation of tropical forest alters community composition as a result of changes in forest shape. This paper uses 22 hypotheses to test the effect of fragment shape on tree species composition in Ghana, West Africa, within biological categories of regeneration guild, rarity, phenology and dispersal. For both regenerating and mature trees, relationships between species composition and the shape of forest fragments were complex; almost half were significant but many failed to support the established hypotheses. Irregular shaped fragments had high proportions of regenerating, light‐demanding pioneers and mature, animal‐dispersed species. Species common to Ghana formed the foundation of communities in fragments of all shapes. Investigation at the landscape level indicated broad patterns of species change. Rigorous hypothesis testing is needed, following extensive demographic work on the ground, before population dynamics within tropical forest fragments can be comprehended fully and applied to conservation management.     

Woody plants diversity,floristic composition and land use history in the Amazonian rain forests of Madidi National Park,Bolivia

A floristic inventory of woody plants was carried out to analyse the relationships between floristic similarity and geographical distance, and to compare the effect of land use history on the floristic composition between sites. Three lowland and two submontane sites were studied in Madidi, Bolivia. In one site, there is evidence of an Inca ruin. A total of 877 species and 12,822 individuals of woody plants with a diameter at breast height ≥2.5 cm were recorded in 44 0.1–ha plots. Fisher’s Alpha index values were slightly higher for the lowlands than for the submontane. Floristic similarity was higher within sites than between sites as measured by both Sørensen and Steinhaus indexes. The fact that the 30 most important species per site (totalling 94 species) accounted for 61.7% of total individuals, support the hypothesis that Amazonian plant communities are dominated by a limited set of species, genera and families. On the other hand, 18 out of the 94 species were reported in a single site, suggesting that some species are patchy in distribution and may be environmentally determined. Both the oligarchy and environmental-determinism hypotheses can be complementary in order to understand floristic patterns of this region. The Ruins submontane site is floristically the most distinct, and past human disturbance is likely to be the main reason. Since species diversity (ranging from 53 to 122 species per plot) and density (ranging from 157 to 503 per plot) are highly variable in Madidi, to characterize the diversity of a site, it is necessary to quantify an average of 10 0.1-ha plots in a relatively small geographical area.     

Floristic composition and diversity of mixed primary and secondary forests in northwest Guyana

The adequate protection and sustainable management of a tropical rain forest requires a good knowledge of its biodiversity. Although considerable parts of Guyana's North-West District have been allocated as logging concessions, little has been published on the forest types present in this region. The present paper reviews the floristic composition, vegetation structure, and diversity of well-drained mixed and secondary forests in northwest Guyana. Trees, shrubs, lianas, herbs and hemi-epiphytes were inventoried in four hectare plots: two in primary forests, one in a 20-year-old secondary forest and one in a 60-year-old secondary forest. The primary forests largely corresponded with the Eschweilera–Licania association described by Fanshawe, although there were substantial variations in the floristic composition and densities of dominant species. The late-succession forest contained the highest number species and was not yet dominated by Lecythidaceae and Chrysobalanaceae. There is a need for updating the existing vegetation maps of northwest Guyana, as they were based on limited information. Large-scale forest inventories may provide a fair indication of species dominance and forest composition, but do not give a reliable insight in floristic diversity. Although previous reports predicted a general low diversity for the North-West District, the forests plots of this research were among the most diverse studied in Guyana so far. These results will hopefully influence the planning of protected areas in Guyana.     

喀斯特常绿落叶阔叶混交林木本植物组成特征

喀斯特常绿落叶阔叶混交林是我国西南喀斯特地区分布的典型森林植被类型之一,由于富钙偏碱的地球化学背景及多样性的生境类型,该森林具有群落结构多样、树种组成丰富、优势物种突出等特点,基于大型动态监测样地的群落特征分析是揭示其生物多样性维持机制的基础。该研究在木论国家自然保护区建立了25 hm2的样地,依照CTFS全球森林生物多样性监测规范,定位并调查了样地内每一棵胸径≥1 cm的木本植物。结果表明：(1)样地内有监测树种254种,隶属于64科161属;独立个体总数为110370株(含分枝为144679株),平均胸径为4.14 cm。(2)个体数最多的15个树种的个体数之和占到总个体数的78.46％,稀有种有100种,占总树种数的39.37％。(3)群落结构稳定且更新良好,木本植物整体径级结构呈倒“J”形。(4)样地内重要值≥1的树种有26种,占总树种数量10.24％;重要值排名前三的物种分别是小果厚壳桂、栀子皮和香叶树。(5)样地中共有萌生木本植物204种34309株,分属于127属51科,分别占样地总物种、个体数量、属及科数的80.32％、14.42％、78.88％和79.69％。此结果表明木论喀斯特常绿落叶阔叶混交林物种组成丰富、群落成熟稳定、更新良好,反映了亚热带非地带性喀斯特顶极群落常绿落叶阔叶混交林的典型特征。     

毛竹扩张对次生常绿阔叶林物种组成、结构与多样性的影响

毛竹(Phyllostachys edulis)向邻近次生常绿阔叶林扩张现象明显, 极大地影响了常绿阔叶林的生态功能, 但关于其扩张对常绿阔叶林的群落结构与生物多样性影响的后效研究较少。本文采用时空替代法, 在江西井冈山国家级自然保护区沿毛竹扩张方向, 依次设置毛竹林、竹阔混交林和常绿阔叶林样地, 比较分析了扩张前后群落物种相似性、群落结构和多样性指数等特征。结果表明: (1)毛竹林与常绿阔叶林乔木层、灌木层和草本层的Bray-Curtis相似性指数很小, 分别为0.003、0.046和0.030。(2)毛竹林的垂直结构呈“>”型, 高度12-14 m区间的多度百分比达33.3%, 径级结构集中分布于5-10 cm区间, 达总数的90.0%; 常绿阔叶林的垂直结构为“L”型, 高度2-4 m的物种数占54.3%, 径级分布范围较广, 4个较大径级区间的平均百分比为10.3%。(3)乔木层的Shannon-Wiener指数由常绿阔叶林的2.56降至毛竹林的0.06, 降幅高达98%; 灌木层也由2.58降至2.03, 降幅21%。以上结果说明, 毛竹扩张会导致次生常绿阔叶林群落组成和结构简化、物种多样性下降, 对森林生态系统功能产生负面影响。     

Comparing forest structure and biodiversity on private and public land: secondary tropical dry forests in Costa Rica

Secondary forests constitute a substantial proportion of tropical forestlands. These forests occur on both public and private lands and different underlying environmental variables and management regimes may affect post‐abandonment successional processes and resultant forest structure and biodiversity. We examined whether differences in ownership led to differences in forest structure, tree diversity, and tree species composition across a gradient of soil fertility and forest age. We collected soil samples and surveyed all trees in 82 public and 66 private 0.1‐ha forest plots arrayed across forest age and soil gradients in Guanacaste, Costa Rica. We found that soil fertility appeared to drive the spatial structure of public vs. private ownership; public conservation lands appeared to be non‐randomly located on areas of lower soil fertility. On private lands, areas of crops/pasture appeared to be non‐randomly located on higher soil fertility areas while forests occupied areas of lower soil fertility. We found that forest structure and tree species diversity did not differ significantly between public and private ownership. However, public and private forests differed in tree species composition: 11 percent were more prevalent in public forest and 7 percent were more prevalent in private forest. Swietenia macrophylla, Cedrela odorata, and Astronium graveolens were more prevalent in public forests likely because public forests provide stronger protection for these highly prized timber species. Guazuma ulmifolia was the most abundant tree in private forests likely because this species is widely consumed and dispersed by cattle. Furthermore, some compositional differences appear to result from soil fertility differences due to non‐random placement of public and private land holdings with respect to soil fertility. Land ownership creates a distinctive species composition signature that is likely the result of differences in soil fertility and management between the ownership types. Both biophysical and social variables should be considered to advance understanding of tropical secondary forest structure and biodiversity.     

云南哀牢山原生林及次生林群落附生地衣物种多样性与分布

附生地衣是森林附生植物的重要类群之一, 在维护森林生态系统的物种多样性以及水分和养分循环等方面发挥着重要作用。作者于2005年12月至2006年5月利用树干取样法调查了云南哀牢山徐家坝地区原生山地常绿阔叶林及其次生群落栎类萌生林、滇山杨(Populus bonatii)林和花椒(Zanthoxylum bungeanum)人工林中525株不同种类和径级树木距地面 0–2.0 m处附生地衣的组成和分布, 并收集了各个群落地面上凋落的地衣, 分析了林冠层附生地衣的物种组成。研究结果表明, 该区森林中附生地衣物种比较丰富。共收集到附生地衣61种, 分属17科29属, 其中原生林、栎类萌生林、滇山杨林和花椒人工林分别有51、53、46和23种。在树干距地面 0–2.0 m位置, 各群落中的附生地衣组成明显不同;但在林冠层中, 各群落内的附生地衣基本相似。原生林中附生地衣种类较多, 但分布不均匀。树干附生地衣的Shannon-Wiener和Simpson多样性指数以栎类萌生林最高, 分别为2.71和0.89;花椒林和滇山杨林次之, 分别为2.43–2.45和0.88–0.89;原生林最低, 为1.25和0.67。树干方位、宿主种类和宿主径级等都对附生地衣的物种组成和多样性有着重要影响, 附生地衣更多地出现于树干南向方位, 云南越桔(Vaccinium duclouxii)的附生地衣最为丰富, 胸径5.0–25.0 cm的树木上附生地衣较多。哀牢山山地森林群落中丰富的附生地衣种类及物种多样性在维系本区山地森林生态系统生物多样性格局方面具有重要的作用。     

Species richness in deciduous forests: Effects of species pools and environmental variables

Abstract. The study was conducted in deciduous forests of two Swedish regions, Öland and Uppland. It had two objectives: to (1) test the species pool hypothesis by examining if differences in small‐scale species richness are related to differences in large‐scale species richness and the size of the regional species pool, and (2) to examine the relationship between species richness and productivity and its scale‐dependence. The first data set comprised 36 sites of moderate to high productivity. In each site, we recorded the presence of vascular plant species in nested plots ranging from 0.001 to 1000 m² and measured several environmental variables. Soil pH and Ellenberg site indicator scores for nitrogen were used as estimators of productivity. The second data set included 24 transects (each with 20 1‐m² plots) on Öland in sites with low to high productivity. Species number, soil pH and relative light intensity were determined in each plot. The forest sites on Öland were more species‐rich than the Uppland sites on all spatial scales, although environmental conditions were similar. Small‐scale and large‐scale species richness were positively correlated. The results present evidence in favour of the species pool hypothesis. In the nested‐plots data set, species number was negatively correlated with pH and nitrogen indicator scores, whereas a unimodal relationship between species number and pH was found for the transect data set. These results, as well as previously published data, support the hump‐shaped relationship between species richness and productivity in Swedish deciduous forests. Two explanations for the higher species richness of the sites with moderate productivity are given: first, these sites have a higher environmental heterogeneity and second, they have a larger ‘habitat‐specific’ species pool.     

关帝山寒温性云杉次生林样地树种组成、结构和空间分布

云杉次生林是关帝山的优势森林植被类型,也是华北亚高山地区寒温性常绿针叶林的代表类型.为更好地了解其物种组成、群落结构等基本特征及其潜在的生态学过程和机制,于2010年在关帝山庞泉沟国家自然保护区建立了4 hm²的云杉次生林固定监测样地(GDS样地).本文以第一次本底调查数据为基础,分析了样地树种组成、结构和空间分布.结果表明: 样地共有木本植物30种,隶属于11科22属.包括分枝的总个体数为26218(其中独立个体数为10266).植物区系组成属北温带成分;不同树种个体数、平均胸径和胸高断面积差异较大,导致群落成层分明,各层优势种明显.乔木层第一亚层树种径级结构呈双峰偏正态分布,乔木层第二亚层树种径级呈近似正态分布,灌木层树种径级呈“L”型分布.乔木优势树种青杄和华北落叶松的空间分布无论在个体数量还是聚集程度上均随径级变化而呈现不同的格局特征.相同径级的两树种,胸径(DBH)≥30 cm的华北落叶松在样地居多且聚集分布于样地中部,而DBH≥30 cm的青杄则相对较少,没有表现出空间聚集性.DBH≤10 cm的华北落叶松个体很少且散生于样地,而DBH≤10 cm的青杄大量聚集于样地中部.DBH≤10 cm的青杄在样地偏西北区域也有大量分布,而DBH≤10 cm的红桦主要分布于样地偏东南区域.灰栒子、土庄绣线菊和四川忍冬等灌木树种也表现出一定的异质性空间分布特征.树种分布格局受生境条件影响,同时与自身发育规律、更新特征及生态习性等相关.     

Effects of environmental heterogeneity on species diversity and composition of terrestrial bryophyte assemblages in tropical montane forests of southern Ecuador

Background: Most studies on tropical bryophytes deal with epiphytic species. This is the first ecological study of tropical forests that focuses specifically on terrestrial bryophytes.

Aim: To investigate the differences between slope and ridge environments in upper montane forests of southern Ecuador in terms of species diversity (richness, abundance), species composition and life forms of terrestrial bryophytes.

Methods: We used Non-metric Multidimensional Scaling (NMDS) to group bryophyte relevés by study location, habitat type and exposure class. Species indicator values were calculated and compared for different habitats.

Results: In total, 140 species were recorded, the majority being liverworts. NMDS analyses and Mantel correlations clearly separated between slope and ridge relevés, and between sunny and shaded microhabitats on ridges. Bryophyte life forms also showed different distribution patterns in slope and in ridge habitats. Mosses were more prominent in sunny than in shaded microhabitats.

Conclusions: Environmental differentiation between ridges and slopes, and small-scale variation in microclimatic conditions caused by differences in exposure, were stronger predictors of species richness and composition than geographical distance between study sites.     

Species richness and vertical stratification of epiphytic lichens in subtropical primary and secondary forests in southwest China

An entire-tree investigation was conducted in two primary and three secondary forest types in the subtropical Ailao Mountains of southwest China to determine whether species richness and vertical stratification of epiphytic lichens responded to forest type and host attributes. Lichen species number, composition and cover differed significantly among forest types and tree species, while tree diameter and tree height had a modest influence. Epiphytic lichen species and functional groups showed clear vertical stratification. Epiphytic lichens were richer in canopies than on trunks and exhibited a great preference for the intermediate zones of trees, while five lichen groups showed distinct vertical diversification. The stratification patterns are clearly related to forest type and may reflect the microclimatic requirements of individual species, e.g. light availability and humidity.     

Succession of secondary forests affected by pine wilt disease in western Japan followed on vegetation maps

Abstract. Succession, changes in the distribution pattern of forest vegetation, and Pinus forest survival following pine wilt disease were clarified based on phytosociological analysis and vegetation maps. Survival of Pinus forests was restricted to the early successional stages, which were located on ridges and the upper part of slopes. Subsequent to pine wilt disease, the succession progressed from early to late substages of Pinus forest, mixed deciduous and evergreen Quercus, to evergreen Quercus forest. Succession occurs in abandoned pine forests which apparently are in a bad state and are vulnerable to attacks by pine wilt disease.     

Climate and land use changes will degrade the configuration of the landscape for titi monkeys in eastern Brazil

Land use changes have profound effects on populations of Neotropical primates, and ongoing climate change is expected to aggravate this scenario. The titi monkeys from eastern Brazil (Callicebus personatus group) have been particularly affected by this process, with four of the five species now allocated to threatened conservation status categories. Here, we estimate the changes in the distribution of these titi monkeys caused by changes in both climate and land use. We also use demographic‐based, functional landscape metrics to assess the magnitude of the change in landscape conditions for the distribution predicted for each species. We built species distribution models (SDMs) based on maximum entropy for current and future conditions (2070), allowing for different global circulation models and contrasting scenarios of glasshouse gas concentrations. We refined the SDMs using a high‐resolution map of habitat remnants. We then calculated habitat availability and connectivity based on home‐range size and the dispersal limitations of the individual, in the context of a predicted loss of 10% of forest cover in the future. The landscape configuration is predicted to be degraded for all species, regardless of the climatic settings. This include reductions in the total cover of forest remnants, patch size and functional connectivity. As the landscape configuration should deteriorate severely in the future for all species, the prevention of further loss of populations will only be achieved through habitat restoration and reconnection to counteract the negative effects for these and several other co‐occurring species.     

人为干扰对风水林群落林下木本植物组成和多样性的影响

华南地区的风水林是乡村聚落的一种特色林分, 具有守护村庄的象征意义。在过去的数百年中, 风水林在乡村的社会文化习俗的影响下而受到保护, 对当地的生物多样性保育有着重要作用。为揭示人为干扰对风水林的影响, 我们选择广东省东莞市大岭山镇同一林分起源的3个具有相似地形的风水林, 研究了在不同干扰强度下其林下木本植物种类组成和物种多样性。多响应置换过程(multi-response permutation procedures, MRPP)分析表明, 人为干扰显著改变了风水林林下木本植物组成(P = 0.001, A = 0.3886), 沿着干扰由弱至强的梯度呈现出中生性植物减少、阳生性植物递增的趋势。多样性指数变化趋势为重度干扰＞中度干扰＞轻度干扰, 但没有表现出统计学意义上的差异(P＞0.05)。随着干扰强度的增大, 3个风水林群落相互间的林下物种相似性降低, 物种替代率呈增加趋势。双向聚类分析较好地反映出林下物种因受不同人为干扰强度影响而表现出在空间分布上的差异。指示种分析进一步确定了不同干扰强度下具有显著指示值(IV ≥60)的指示种。综合分析表明, 人为干扰有利于阳性物种在风水林内定居生长, 并明显地改变了林下木本植物组成, 但未能引起物种多样性的显著差异。此外, 找出对人为干扰产生关键生态响应的林下指示种, 对增进风水林的生物多样性保育以及生态系统管理有着重要的理论意义和实践价值。     

Understorey plant species richness and composition in metropolitan forest archipelagos: effects of forest size, adjacent land use and distance to the edge

Aim To address the relative role of adjacent land use, distance to forest edge, forest size and their interactions on understorey plant species richness and composition in perimetropolitan forests. Location The metropolitan area of Barcelona, north‐eastern Spain. Methods Twenty sampling sites were distributed in two forest size‐categories: small forest patches (8–90 ha) and large forest areas (> 18,000 ha). For each forest‐size category, five sites were placed adjacent to crops and five sites adjacent to urban areas. Vascular plant species were recorded and human frequentation was scored visually in 210 10 × 10 m plots placed at 10, 50 and 100 m from the forest edge, and additionally at 500 m in large forest areas. Plant species were grouped according to their ecology and rarity categories. A nonmetric multidimensional scaling (NMS) ordination was carried out to detect patterns of variation in species assemblage, and to explore the relationships between these patterns and the richness of the species groups and the studied factors. Factorial anovas were used to test the significance of the studied factors on the richness of species groups. Relationships between human frequentation and the studied variables were assessed through contingency tables. Results Forest‐size category was the main factor affecting synanthropic species (i.e. those thriving in man‐made or man‐disturbed habitats). Synanthropic species richness decreased with increasing distance from the forest edge and, when forests were adjacent to crops, it was higher in small forest patches than in large forest areas. Richness of rare forest species was lower in small forest patches than in large forest areas when forests were adjacent to urban areas. Richness of common forest species and of all forest species together were higher close to the forest edge than far from it when forests were adjacent to urban areas. Forests adjacent to urban areas were more likely to experience high human frequentation, particularly in those plots nearest to the forest edge. Main conclusions Forest‐size category and adjacent land use were the most important factors determining species richness and composition. The preservation of large forests adjacent to crops in peri‐urban areas is recommended, because they are less frequented by humans, are better buffered against the percolation of nonforest species and could favour the persistence of rare forest species.     

Effects of topography,soil moisture,wind and grazing on Festuca seedlings in a Patagonian grassland

Abstract. The effects of topography, soil moisture, wind and grazing on the emergence and survival of seedlings of Festuca spp. were examined in the steppe zone of Patagonia, Argentina. Ungrazed and grazed field treatment plots were established on a plain and a north-facing slope at the Media Luna Ranch (43° 36′S, 71° 25′W). On the leeward and windward sides of each of 15 Festuca plants, 0.1 m × 0.4 m quadrats were censused bimonthly for seedling emergence and survival over three growing seasons. Three categories were distinguished: recently germinated and up to the first leaf, two to four leaves, and from five leaves up to one tiller. Soil moisture content, litter cover and frost heaving effects were also determined for each treatment at each sampling date. Festuca spp. showed two emergence peaks, one in late fall and the other in early to mid-spring. Seedling emergence was significantly correlated with soil moisture content in the 0–5 cm of the soil during the three growing seasons. Seedlings that emerged in the fall had higher survivorship than those that emerged in spring. Seedling emergence and survival was significantly (p < 0.01) lower on slopes, in the grazing treatment, and on windward sides of adult plants. In this grassland, an increase in the availability of safe sites for seedling emergence and survival might be achieved by protecting vegetation from grazing, particularly on north-facing slopes.     

黔中北亚热带喀斯特次生林动态监测样地：物种组成与群落结构

多年来强烈的人为干扰导致我国西南喀斯特原生森林丧失殆尽并呈现植被灌丛化,甚至石漠化现象。贵州普定县残存的片段化喀斯特次生林是黔中地区北亚热带森林植被的典型代表,可作为监测该区域植被结构和动态的样本。在普定县天龙山建立2 hm~2(200 m×100 m)森林固定样地,对样地内胸径≥1 cm的所有木本植物进行了每木调查,分析了木本植物的物种组成、区系特征、径级结构和空间分布格局。结果表明,样地内有木本植物独立个体14,025株,隶属于34科55属66种。重要值最大的前3个科依次是壳斗科、胡桃科和樟科。在区系成分上,温带区系成分占总属数的52.7%,而热带区系成分占40.0%,温带成分多于热带成分。稀有种有21种,占总种数的31.82%。重要值≥1的物种共有13种,贡献了88.81%的重要值,重要值排名前三的物种分别是窄叶石栎(Lithocarpus confinis)、化香树(Platycarya strobilacea)和云南鼠刺(Itea yunnanensis)。样地内所有个体的平均胸径仅为5.12 cm,整体径级分布呈倒"J",表明群落更新良好。部分优势种的空间分布表现出较明显的...