Forest plant community as a driver of soil biodiversity: experimental evidence from collembolan assemblages through large‐scale and long‐term removal of oak canopy trees Quercus petraea

Plant–soil interactions are increasingly recognized to play a major role in terrestrial ecosystems functioning. However, few studies to date have focused on slow dynamic ecosystems such as forests. As they are vertically stratified by multiple vegetation strata, canopy tree removal by thinning operations could alter forest plant community through tree canopy opening. Very little is known about cascading effects on soil biodiversity. We conducted a large‐scale, multi‐site assessment of collembolan assemblage response to long‐term canopy tree removal in sessile oak Quercus petraea temperate forests. A total of 33 experimental plots were studied covering a large gradient of canopy tree basal area, stand age and local abiotic contexts. Collembolan abundance strongly declined with canopy tree removal in early forest successional stage and this was mediated by negative effect of understory plant community composition changes, i.e. shift from moss and forb to tree seedling, fern, shrub and grass species. Negative effect of this composition shift on collembolan species richness was largely offset by positive effect of the increase in understory plant species richness. This gives support to both the plant mass‐ratio and functional diversity hypotheses. Collembolan functional groups had contrasting response patterns, which were mediated by different ecological factors. Epedaphic (r‐strategist) abundance and species richness increased with canopy tree removal in relation with the increase in understory plant species richness. In contrast, euedaphic (K‐strategist) abundance and species richness declined with canopy tree removal in early forest successional stage in relation with changes in understory plant community composition and species richness, as well as microclimatic conditions. Overall, our study provides experimental evidence that forest plant community can be a strong driver of collembolan assemblages. It also emphasizes the role of trees as foundation species of forest ecosystems that can shape soil biodiversity through their regulation of understory plant community and ecosystem abiotic conditions.     

Changes in woody vegetation abundance and diversity after natural disturbances causing different levels of mortality

Questions: How does woody vegetation abundance and diversity differ after natural disturbances causing different levels of mortality? Location: Abies balsamea–Betula papyrifera boreal mixed‐wood stands of southeast Quebec, Canada. Methods: Woody vegetation abundance and diversity were quantified and compared among three disturbance‐caused mortality classes, canopy gap, moderate‐severity disturbances, and catastrophic fire, using redundancy analysis, a constrained linear ordination technique, and diversity indices. Results: Substantial changes in canopy tree species abundance and diversity only occurred after catastrophic fire. Shade‐tolerant, late‐successional conifer species remained dominant after canopy gap and moderate‐severity disturbances, whereas shade‐intolerant, early‐successional colonizers dominated canopy tree regeneration after catastrophic fire. Density and diversity of mid‐tolerant and shade‐intolerant understory tree and shrub species increased as the impact of disturbance increased. Highest species richness estimates were observed after catastrophic fire, with several species establishing exclusively under these conditions. Relative abundance of canopy tree regeneration was most similar after canopy gap and moderate‐severity disturbances. For the sub‐canopy tree and shrub community, relative species abundances were most similar after moderate‐severity disturbances and catastrophic fire. Vegetation responses to moderate‐severity disturbances thus had commonalities with both extremes of the disturbance‐caused mortality gradient, but for different regeneration layers. Conclusions: Current spatio‐temporal parameters of natural disturbances causing varying degrees of mortality promote the development of a complex, multi‐cohort forest condition throughout the landscape. The projected increase in time intervals between catastrophic fires may lead to reduced diversity within the system.     

Effect of gap size and age on climber abundance and diversity in Budongo Forest Reserve, Uganda

A study of the effects of gap size and age on climber abundance and diversity was carried out in Budongo Forest Reserve in Uganda. Data were collected from compartments N5, W21, B1 and B3. Stump records were used to locate and estimate the ages of 78 gaps. Sample plots 5 × 5 m were set up in the gaps to assess climber abundance and diversity.
Climbers were more abundant and diverse in gaps that were more than 400 m², 15 months old and had more than 25% canopy opening. Momordica foetida was the most abundant climber species occurring on stems, branches and crowns of seedlings and saplings. Therefore, in order to keep natural regeneration free from climber tangles and produce good quality timber, climber control should be a major activity in tropical high forest management.     

Stratification in a New Zealand rain forest

An undisturbed podocarp-broadleaved rain forest was sampled in eight strata (synusiae): canopy, small tree, shrub, low shrub, herb, ground, epiphyte and liane. Independent classifications of the quadrats were performed using the eight strata, and the classifications were correlated. Relations between strata were significant, but weak. Using records of plants of all ages, the relations largely reflected the presence of seedlings of woody species in the ground and herb strata. Using only records of species present as adults, the relations were quite different, and at least some seemed to reflect sociological interactions. Relations between a tree and a herb stratum was lower than in McCune & Antos' (1981) investigation, probably because of the narrow ecological range of the present study area.     

大兴安岭呼中地区3种林分的群落特征、物种多样性差异及其耦合关系

准确理解天然林林分群落特征及其与物种多样性耦合关系是提升天然林管理、达到多样性保护的关键。选择大兴安岭呼中地区典型落叶松林、杂木林、白桦落叶松林为研究对象,分别对乔木层、灌木层和草本层特征(高度、胸径、冠幅、盖度等)进行调查并计算丰富度指数、多样性指数和均匀度指数,旨在探究林分间差异及其耦合关系变化。结果表明:(1)乔木层的树高、枝下高表现出杂木林落叶松林白桦落叶松(P0.05);落叶松林的胸径比白桦落叶松林和杂木林的高出6%和11%;灌木层的高度、盖度、地径、冠幅和草本层多度、盖度、高度在森林类型间均未表现出显著差异。(2)3个森林类型的乔、灌、草丰富度指数R、Shannon-Wiener指数及Simpson指数均表现出杂木林最大,乔木层和草本层呈相同规律,即杂木林白桦落叶松林落叶松林,而灌木层表现出杂木林落叶松林白桦落叶松林;白桦落叶松林和杂木林的乔木层均匀度Pielou指数和Alatalo指数约为落叶松林的3倍左右,而在灌木层和草本层在森林类型间差异不显著(P0.05)。(3)典范对应分析(CCA)结果表明林分群落特征和生物多样性关系存在明显森林类型间差异。总体表现为灌木特征(冠幅、地径)、草本层特征(盖度、多度和高度)对多样性均有较大影响;白桦落叶松林和杂木林的胸径对多样性影响明显,而落叶松林的乔木高度(树高、枝下高)对多样性影响较大。杂木林随着灌木盖度、草本高度的增加,草本物种多样性降低、乔木多和灌木物种多样性增加;而落叶松林相同的多样性变化多伴随草本高度增加、多度和盖度变小。灌木层物种多样性增加多与乔木和草本物种多样性降低相伴随,在杂木林中同时伴随着乔木胸径和草本的盖度、多度增大、灌木冠幅变小,而白桦落叶松林则伴随灌木冠幅和草本多度盖度的减小。以上结果表明,林分群落特征与物种多样性存在耦合关系,上述解耦合结果为通过维持良好森林结构、多样性保护具有实践意义。     

When do nurse plants stop nursing? Temporal changes in water stress levels in Austrocedrus chilensis growing within and outside shrubs

Question: Does the proximity of shrubs affect seasonal water stress of young Austrocedrus chilensis trees (a native conifer of the Austral Temperate Forest of South America) in xeric sites? Location: A. chilensis xeric forest in northwest Patagonia, Argentina. Methods: We examined the dependence of predawn twig water potential on tree development (seedling to adult) and proximity to nurse shrubs during spring and summer. We analysed spatial associations of seedlings, saplings and adult trees with nurse shrubs, and also evaluated if trees affected shrub canopy vitality. Results: Water stress in Austrocedrus trees was affected by shrub presence. Small trees (i.e.<0.5 m in height) growing in the open were most stressed, particularly in summer. Small trees growing within a shrub canopy had low water stress and little change between spring and summer. The opposite trend, however, was true for the medium‐height category (i.e. 0.5‐1.5 m in height); trees in this size category were more stressed when growing within the shrub canopy than in the open. Larger Austrocedrus trees (i.e.>2 m in height) were not affected by shrub presence. Austrocedrus trees were spatially associated with shrubs in all height classes; however, the percentage of living shrub canopy decreased with tree height. Conclusions: In xeric areas of northwest Patagonia, the strength and direction of interactions between A. chilensis and shrubs, in terms of tree water stress, are dynamic and modulated by tree size and environmental conditions. Overall, positive effects of shrubs on early developmental stages appear to be more important than subsequent negative interactions, since nursing effects could generate a spatial association of shrubs and Austrocedrus trees that persists through later successional stages. These findings shed light on mechanisms behind successional changes, and have important conservation and management implications.     

Patterns of woody plant abundance,recruitment, mortality,and growth in a 65 year chronosequence of old-fields

We surveyed vegetation along forest margins in a 65-year chronosequence of old-fields at the Cedar Creek Natural History Area in east-central Minnesota, USA, to identify successional patterns of woody plants and to determine if these were correlated with soil nitrogen. We predicted that shrub and tree abundance, size, and distance of occurrence from the forest edge would be correlated with field age or soil nitrogen. Instead we did not find successional trends in the abundance or composition of woody species. Even in the oldest field the abundance of trees and shrubs was low and concentrated in areas close to the forest. Though trees were larger and present further from the forest edges in older fields, average tree height was less than 126 cm in all fields.Since we did not find successional trends we looked at various local factors (local seed sources, deer browsing, and forest edge aspect) and their relation to recruitment, mortality, or growth to explain variation among fields in abundance of trees or shrubs. The three most common tree species (Quercus rubra, Q. macrocarpa,and Populus tremuloides) all had a higher relative abundance of seedlings, and two (Q. rubra and Q. macrocarpa) had a higher relative abundance of large trees adjacent to forests with a high abundance of conspecific adults. Most trees taller than 20 cm were browsed by deer and were shorter in 1995 than they were in 1993. Mortality was higher for trees less than 30 cm indicating that mortality was size-dependent. Forest edge aspect did not significantly influence the abundance or demography of any species. Our results suggest that the patterns of seedling recruitment were largely determined by the proximity of seed sources and that these patterns may persist so that tree communities in old-fields resemble adjacent forests. Deer may be a significant factor in the suppression of tree populations in old-fields through repeated browsing which reduces tree growth and elevates tree mortality by prolonging the period of time trees remain susceptible to size-dependent mortality.     

Tropical Secondary Forest Management Influences Frugivorous Bat Composition,Abundance and Fruit Consumption in Chiapas,Mexico

Most studies on frugivorous bat assemblages in secondary forests have concentrated on differences among successional stages, and have disregarded the effect of forest management. Secondary forest management practices alter the vegetation structure and fruit availability, important factors associated with differences in frugivorous bat assemblage structure, and fruit consumption and can therefore modify forest succession. Our objective was to elucidate factors (forest structural variables and fruit availability) determining bat diversity, abundance, composition and species-specific abundance of bats in (i) secondary forests managed by Lacandon farmers dominated by Ochroma pyramidale, in (ii) secondary forests without management, and in (iii) mature rain forests in Chiapas, Southern Mexico. Frugivorous bat species diversity (Shannon H’) was similar between forest types. However, bat abundance was highest in rain forest and O. pyramidale forests. Bat species composition was different among forest types with more Carollia sowelli and Sturnira lilium captures in O. pyramidale forests. Overall, bat fruit consumption was dominated by early-successional shrubs, highest late-successional fruit consumption was found in rain forests and more bats consumed early-successional shrub fruits in O. pyramidale forests. Ochroma pyramidale forests presented a higher canopy openness, tree height, lower tree density and diversity of fruit than secondary forests. Tree density and canopy openness were negatively correlated with bat species diversity and bat abundance, but bat abundance increased with fruit abundance and tree height. Hence, secondary forest management alters forests’ structural characteristics and resource availability, and shapes the frugivorous bat community structure, and thereby the fruit consumption by bats.     

海南岛霸王岭热带山地雨林群落结构及树种多样性特征的研究

 以海南岛霸王岭自然保护区1 hm2老龄原始林样地的调查材料为基础,分析了热带山地雨林群落的组成、高度结构、径级结构及有关的树种多样性特征。结果表明：霸王岭热带山地雨林树种较丰富,物种多样性指数较高。树种数和树木的密度都随高度级、径级的增加而呈负指数或负幂函数递减;热带山地雨林不同高度级、不同径级和不同小样方斑块内的树种数都与树木密度呈显著的正相关关系。热带山地雨林经过自然的演替达到老龄顶极群落后,最后进入主林层的只是少部分树种的少数个体。     

Novelty predictors for shrub (and climbers) ecological niche modeling,based on their successional stage

The identification of species' environmental predictors constitute a key challenge for decision making, especially when using ecological niche modeling based on these drivers and when presence points are limited. More specifically, shrub species are affected by ecosystem dynamics, and appear in degraded formations, in dense mid-stage vegetation formations, or under late climax-forest canopy. In this study, we tested novelty predictors to understand the drivers that affect the selected species distribution in the Mediterranean biome, targeting different vegetation successional stages, and further improve ecological models' performance, when presence points are limited. Land surface temperature (LST) in association with temperature related predictors, allowed differentiating between species thriving in the understory of the forest canopy, from those that are co-dominant with dense vegetation cover and a third group/species, thriving in degraded vegetation. In addition, the Normalized Difference Vegetation Level Index (NDVI) played a key role in the models for species growing in highly degraded ecological niches such as Spartium junceum, Calicotome villosa, but also forest-fringe vegetation like the climber Hedera helix. Our study highlights the importance of integrating remote sensed predictors, combined with appropriate climate drivers, when using ecological niche modeling.     

岷江冷杉林皆伐后次生群落结构和物种多样性的演替动态

为阐明岷江冷杉林皆伐后次生群落的演替过程,采用空间代替时间的方法,在川西米亚罗林区海拔3100—3600 m的阴坡选择岷江冷杉林皆伐后次生演替10、20、30、40和50a阶段的次生群落作为研究对象,对其群落结构和物种多样性的动态进行了研究。不同演替阶段的树木均呈显著聚集分布。按群落中优势种的重要值将该演替序列划分为3个类型:悬钩子-蔷薇灌丛、白桦阔叶林和桦木-岷江冷杉针阔混交林。随次生演替,乔木和灌木种的物种丰富度趋于增加,而草本种的物种丰富度趋于减少;乔木和灌木种的Shannon-Wiener多样性指数趋于增大,而草本的Shannon-Wiener多样性指数趋于减小;乔木、灌木和草本层的Pielou均匀度指数均趋于增大;乔木层的Simpson优势度指数趋于减小,灌木和草本层的Simpson优势度指数在演替0—40年阶段趋于增大,而在演替50a阶段趋于减小。在该演替序列中,乔木、灌木和草本层的物种组成均呈耐荫种替代非耐荫种的趋势。     

Species composition,diversity, and abundance of lianas in different secondary and primary forests in a subtropical mountainous area,SW China

The species composition, diversity, and abundance of lianas were studied in four secondary forests (a 100-year-old forest, a middle-aged forest, and two younger secondary forests), and compared with an undisturbed primary forest in the Ailao Mountains of subtropical SW China. The results showed that the species composition of lianas differed greatly from the secondary forests to the primary forest, which exhibit early and late-successional species. The abundance of lianas was relatively higher in the two younger and middle-aged secondary forests than in the old-growth secondary and primary forests. However, liana species richness was very limited in the four secondary forests as compared to the primary forest. Root climbers mainly grew in the primary forest, whereas tendril and hook climbers predominated in the four secondary forests, while stem twiners were common in both. The majority of lianas recorded in this study reproduced by animal dispersal, and there was no variation in dispersal modes across the five forest types. A step-wise regression showed that the abundance of small lianas (dbh <4 cm) was positively correlated with the abundance of small- and medium-sized tree stems and negatively correlated with the abundance of large-sized tree stems, whereas there is a strong positive correlation between the abundance of large lianas (dbh ≥4 cm) and large tree stems. Results from the CCA indicate that canopy openness, soil moisture, and average canopy height were the most important factors that influenced the abundance and distribution of lianas.     

Legacy effects of canopy gaps on liana abundance 25 years later in a seasonal tropical evergreen forest in northeastern Thailand

Lianas require host trees to reach and stay in the forest canopy, but as seedlings and juveniles, they benefit from canopy gaps created by treefalls. Here, we evaluated the relative importance of these two aspects, that is, the availability of potential hosts vs. the legacy effect of past treefall gaps, on the local abundance of liana stems in a seasonal tropical evergreen forest in the Sakaerat Biosphere Reserve in northeastern Thailand. Within a 2.5-ha plot for forest dynamics monitoring, canopy height was measured in 1993 and 2018 at 5-m intervals to distinguish areas of mature (canopy height ≥ 20 m), building (10–20 m), and gap phases (< 10 m). In 2017–2018, we surveyed all liana stems ≥ 1 cm in diameter at breast height within 50 subplots (10 m × 10 m each) and recorded their diameter and the diameter of the host tree. Of a total of 445 liana individuals, 242 could be identified at least to the family level, while the others had clear morphological traits of climbing mechanisms. The number of liana stems was higher in areas that had been at the building/gap phase than those at the mature phase in 1993. When this 25-year-old legacy of past gap locations was considered, there was a positive association of local abundance between lianas and trees in areas at the mature phase in 2018. In conclusion, liana abundance reflected a long-term legacy of past treefall gaps more than 25 years earlier in this seasonal evergreen forest.     

Relative importance of climate vs local factors in shaping the regional patterns of forest plant richness across northeast China

Northeast (NE) China covers three climatic zones and contains all the major forest types of NE Asia. We sampled 108 forest plots in six nature reserves across NE China to examine the influence of climate and local factors (canopy seasonality, successional stage, topography and forest structure) on geographic patterns of plant richness. We analyzed the relative effects of different factors at two spatial scales: the regional scale (across both latitude and altitude) and the local scale (along the altitudinal gradient within site). Our results showed that the relative importance of climate vs local factors differed remarkably depending on scale and functional group. While total and tree species richness were mainly limited by climate, herb and shrub richness was more related to local factors (especially at the local scale). In the climatic factors, heat sum was the major correlate of tree, shrub and total species richness, while herb richness was more associated with winter coldness. Precipitation was not a limiting factor for forest plant richness in NE China. Climate accounted for 34–76% of variation in richness at the regional scale, but explained only 0–44% at the local scale. Among the local factors, shrub species richness was sensitive to seasonal canopy openness, with higher richness in deciduous forests than in the evergreen needle-leaf forest. On the other hand, herb richness was sensitive to forest successional stage, with higher richness in middle- successional forests than in the early and late-sucessional forests. Local topography (aspect and position on slope) and forest structure (tree density) also showed remarkable influence on species richness. Our results suggest the importance of including local factors when examining large scale diversity gradient (especially for understory species), and the necessity of comparing diversity patterns among functional groups at different spatial scales.     

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     

Abundance of climbing plants in a southern temperate rain forest: host tree characteristics or light availability?

Question: In a southern temperate rain forest, we addressed three questions: (1) Does the abundance of climbing plants increase with light availability? (2) Do host tree species differ in their susceptibility to vine infestation? (3) How does the relationship between host tree trunk diameter and relative abundance of vines vary with their climbing mechanism? Location: Two sites in the temperate evergreen rain forest of southern Chile: Puyehue (40°39′S, 72°09′W; 350 m a.s.l.) and Pastahue (42°22′S, 73°49′W; 285 m a.s.l.). Methods: We sampled vines in 60 25‐m² plots, with 20 plots in each of three light environments: mature forest, forest edges and canopy gaps. In each plot, for every tree ≥1.50‐m tall of any diameter we counted and identified all climbing plant individuals at a height of 1.30 m. We also counted, measured (trunk diameter at 1.30 m) and identified all these trees, and determined prevalence of vine infestation for each tree species. Results: Light availability in forest plots did not affect vine abundance when the number and size of host trees was taken into account. Overall, vine abundance increased with host tree trunk diameter. Tree species did not differ in the prevalence of vine infestation. The relative abundance of stem twiners and adhesive climbers decreased and increased with trunk diameter, respectively. The densities of stem twiners and adhesive climbers were negatively correlated across the forest. Conclusion: We provide further evidence that the pattern of vine abundance is independent of light availability in southern temperate rain forests, in contrast to results commonly reported for tropical rain forests. We also show that support suitability across the forest varies with the mechanism by which vines climb, probably due in part to biomechanical constraints and in part to vine interspecific competition, a virtually unexplored ecological factor.     

Invertebrate communities in a tropical rain forest canopy in Puerto Rico following Hurricane Hugo

1. Canopy invertebrate responses to Hurricane Hugo, tree species, and recovery time were examined at the Luquillo Experimental Forest in Puerto Rico during 1991–92 and 1994–95. Six tree species representing early and late successional stages were examined in paired plots representing severe hurricane disturbance (most trees toppled) and light hurricane disturbance (all trees standing and most branches intact). 2. Hurricane disturbance affected invertebrate abundances significantly. Sap-suckers and molluscs were more abundant, and defoliators, detritivores, and emergent aquatic insects were less abundant in recovering tree-fall gaps than in intact forest during this 5-year period. These changes in functional organisation are consistent with comparable studies of arthropod responses to canopy removal during harvest in temperate forests. 3. Tree species also affected invertebrate abundances significantly, but invertebrate communities did not differ significantly between the three early successional and three later successional tree species. 4. Most taxa showed significant annual variation in abundances, but only two Homoptera species showed a significant linear decline in abundance through time, perhaps reflecting long-term trends during recovery. 5. Leaf area missing, an indicator of herbivore effect on canopy processes, showed significant seasonal and annual trends, as well as differences among tree species and hurricane treatments. Generally, leaf area missing peaked during the wet season each year, but reached its highest levels during an extended drought in 1994. Leaf area missing also tended to be higher on the more abundant tree species in each disturbance treatment. 6. Herbivore abundances and leaf area missing were not related to concentrations of nitrogen, phosphorous, potassium, or calcium in the foliage. 7. This study demonstrated that invertebrate community structure and herbivory are dynamic processes that reflect the influences of host species and variable environmental conditions.     

Resilience of tropical rain forests: tree community reassembly in secondary forests

Understanding the recovery dynamics of ecosystems presents a major challenge in the human-impacted tropics. We tested whether secondary forests follow equilibrium or non-equilibrium dynamics by evaluating community reassembly over time, across different successional stages, and among multiple life stages. Based on long-term and static data from six 1-ha plots in NE Costa Rica, we show that secondary forests are undergoing reassembly of canopy tree and palm species composition through the successful recruitment of seedlings, saplings, and young trees of mature forest species. Such patterns were observed over time within sites and across successional stages. Floristic reassembly in secondary forests showed a clear convergence with mature forest community composition, supporting an equilibrium model. This resilience stems from three key factors co-occurring locally: high abundance of generalist species in the regional flora, high levels of seed dispersal, and local presence of old-growth forest remnants.     

The potential of small exclosures in assisting regeneration of coffee shade trees in South‐Western Ethiopian coffee forests

Ethiopian Afromontane moist forests where coffee grows as understorey shrub are traditionally managed by the local communities for coffee production through thinning of the shade tree canopy and slashing of competing undergrowth. This management practice has a negative impact on the coffee shrubs, because the removal of shade tree saplings and seedlings reduces the succession potential of the shade tree canopy, which threatens the very existence of the shade coffee production system. We assessed the functionality of small exclosures to initiate coffee shade tree canopy restoration through natural regeneration. Our results show that small exclosures have a strong restoration potential for the coffee shade trees preferred by farmers (Albizia schimperiana, A. gummifera and Millettia ferruginea), as evidenced from their seedling abundance, survival and growth. The regeneration of late‐successional tree species of the moist Afromontane forest was not successful in the small exclosures, most probably due to the low abundance or absence of adult trees as seed sources for regeneration. Therefore, temporary establishment of small exclosures in degraded coffee forest fragments where shade trees are getting old or dying is recommended for sustainable shade coffee production.     

大兴安岭不同演替阶段天然林物种多度格局模拟

为实现大兴安岭地区落叶松天然林的全周期可持续经营,以新林林业局翠岗林场3块100m×100m不同演替阶段(白桦林、落叶松-白桦混交林和落叶松林)的天然林固定调查样地数据为基础,采用统计模型(对数正态模型)、生态位模型(断棍模型、生态位优先占领模型、Zipf模型、Zipf-Mandelbrot模型)和中性模型(群落零和多项式模型、Volkov模型)对不同演替阶段天然林的乔木层、幼苗层和由乔木层划分的不同林层的物种多度格局进行拟合,并用χ² 检验和Kolmogorov-Smirnov检验选择最佳模型。结果表明:(1) 在大兴安岭地区不同演替阶段的落叶松天然林群落中,Zipf-Mandelbrot模型的拟合效果均最好。(2) 对数正态模型对于稳定的演替阶段白桦林和落叶松林的群落相较于过渡阶段群落落叶松-白桦混交林的物种多度分布的拟合效果更好。(3) 在大兴安岭地区落叶松天然林中,生境过滤主导群落构建,随着群落不断演替生境过滤和中性过程减弱。(4) 天然林群落乔木层的群落构建过程与乔木层内不同生长阶段林层的构建过程不同,生境过滤过程在落叶松林乔木层中逐渐减弱,而在落叶松林不同生长阶段的林层和更新层中增强。