人工与自然恢复条件下地被层优势种大羽藓的遗传多样性比较

基于随机扩增多态性DNA(RAPD)方法比较了川西米亚罗地区3个人工云杉林样地和3个天然次生林样地大羽藓(Thuidium cym bifolium)种群的遗传多样性及分化程度。人工林种群的平均多态位点百分比(PPL)为12.7%,Ne i’s基因多样性(HE)为0.042,Shannon’s信息指数(S)为0.064,种群内遗传一致度(I)为0.952;天然次生林种群则依次为10.0%、0.027、0.043和0.960。人工林种群和天然次生林种群Gst分别为0.592和0.702,Fst分别为0.639和0.695;结合UPGMA聚类和PCA分析,发现种群间的基因交流极少。单因素方差分析显示,人工林下大羽藓种群的遗传多样性水平显著高于天然次生林下种群(p<0.05),表明在皆伐迹地上通过人工造林能有效地促进林下物种遗传多样性的恢复。     

Nitrogen Uptake by Trees and Mycorrhizal Fungi in a Successional Northern Temperate Forest: Insights from Multiple Isotopic Methods

Forest succession may cause changes in nitrogen (N) availability, vegetation and fungal community composition that affect N uptake by trees and their mycorrhizal symbionts. Understanding how these changes affect the functioning of the mycorrhizal symbiosis is of interest to ecosystem ecology because of the fundamental roles mycorrhizae play in providing nutrition to trees and structuring forest ecosystems. We investigated changes in tree and mycorrhizal fungal community composition, the availability and uptake of N by trees and mycorrhizal fungi in a forest undergoing a successional transition (age-related loss of early successional tree taxa). In this system, 82–96% of mycorrhizal hyphae were ectomycorrhizal (EM). As biomass production of arbuscular mycorrhizal (AM) trees increased, AM hyphae comprised a significantly greater proportion of total fungal hyphae, and the EM contribution to the N requirement of EM-associated tree taxa declined from greater than 75% to less than 60%. Increasing N availability was associated with lower EM hyphal foraging and ¹⁵N tracer uptake, yet the EM-associated later-successional species Quercus rubra was nonetheless a stronger competitor for ¹⁵N than AM-associated Acer rubrum, likely due to the more extensive nature of the persistent EM hyphal network. These results indicate that successional increases in N availability and co-dominance by AM-associated trees have increased the importance of AM fungi in the mycorrhizal community, while down-regulating EM N acquisition and transfer processes. This work advances understanding of linkages between tree and fungal community composition, and indicates that successional changes in N availability may affect competition between tree taxa with divergent resource acquisition strategies.     

海岛森林不同演替阶段土壤和植物的碳、氮、磷化学计量特征

该研究采用空间代替时间的方法,对福建省东部海域的平潭岛林区不同演替阶段群落(灌草丛、针叶林、针阔混交林、常绿阔叶林)的土壤和植物的C、N、P含量进行测定,分析不同演替阶段土壤和植物的C、N、P及生态化学计量特征的变化规律,并探讨植物与土壤养分之间的相互关系。结果表明:(1)由于土壤C、N、P的来源不同,导致土壤有机碳(SOC)和全氮(STN)含量随着演替进行逐渐增加,土壤全磷(STP)含量呈先下降后上升的趋势;土壤C∶N随演替进行呈增加趋势,土壤C∶P和N∶P呈先升高后下降的趋势。(2)植物叶片碳(LC)含量随着演替进行呈先升高后下降的趋势,叶片氮(LN)和磷(LP)含量呈先下降后升高的趋势,反映了各演替阶段植物采取不同的生态适应性;植物叶片C∶N和C∶P随演替进行呈先升高后下降的趋势,植物叶片N∶P呈逐渐增加的趋势。(3)相关分析表明,土壤SOC与STN呈显著正相关关系,表明土壤C、N元素有较强的耦合关系;植物LN与LP呈显著正相关关系,共同反映植物的光合作用;植物叶片LP与土壤STP呈显著正相关关系,且植物叶片N∶P在各演替阶段均大于16,说明平潭岛植物生长主要受到土壤P限制。     

Effects of ENSO and Temporal Rainfall Variation on the Dynamics of Successional Communities in Old-Field Succession of a Tropical Dry Forest

The effects of temporal variation of rainfall on secondary succession of tropical dry ecosystems are poorly understood. We studied effects of inter-seasonal and inter-year rainfall variation on the dynamics of regenerative successional communities of a tropical dry forest in Mexico. We emphasized the effects caused by the severe El Niño Southern Oscillation (ENSO) occurred in 2005. We established permanent plots in sites representing a chronosequence of Pasture (abandoned pastures, 0–1 years fallow age), Early (3–5), Intermediate (8–12), and Old-Growth Forest categories (n = 3 per category). In total, 8210 shrubs and trees 10 to 100-cm height were identified, measured, and monitored over four years. Rates of plant recruitment, growth and mortality, and gain and loss of species were quantified per season (dry vs. rainy), year, and successional category, considering whole communities and separating seedlings from sprouts and shrubs from trees. Community rates changed with rainfall variation without almost any effect of successional stage. Mortality and species loss rates peaked during the ENSO year and the following year; however, after two rainy years mortality peaked in the rainy season. Such changes could result from the severe drought in the ENSO year, and of the outbreak of biotic agents during the following rainy years. Growth, recruitment and species gain rates were higher in the rainy season but they were significantly reduced after the ENSO year. Seedlings exhibited higher recruitment and mortality rate than sprouts, and shrubs showed higher recruitment than trees. ENSO strongly impacted both the dynamics and trajectory of succession, creating transient fluctuations in the abundance and species richness of the communities. Overall, there was a net decline in plant and species density in most successional stages along the years. Therefore, strong drought events have critical consequences for regeneration dynamics, delaying the successional process and modifying the resilience of these systems.     

Community Assembly of Biological Soil Crusts of Different Successional Stages in a Temperate Sand Ecosystem, as Assessed by Direct Determination and Enrichment Techniques

In temperate regions, biological soil crusts (BSCs: complex communities of cyanobacteria, eukaryotic algae, bryophytes, and lichens) are not well investigated regarding community structure and diversity. Furthermore, studies on succession are rare. For that reason, the community assembly of crusts representing two successional stages (initial, 5 years old; and stable, >20 years old) were analyzed in an inland sand ecosystem in Germany in a plot-based approach (2 × 18 plots, each 20 × 20 cm). Two different methods were used to record the cyanobacteria and eukaryotic algae in these communities comprehensively: determination directly out of the soil and enrichment culture techniques. Additionally, lichens, bryophytes, and phanerogams were determined. We examine four hypotheses: (1) A combination of direct determination and enrichment culture technique is necessary to detect cyanobacteria and eukaryotic algae comprehensively. In total, 45 species of cyanobacteria and eukaryotic algae were detected in the study area with both techniques, including 26 eukaryotic algae and 19 cyanobacteria species. With both determination techniques, 22 identical taxa were detected (11 eukaryotic algae and 11 cyanobacteria). Thirteen taxa were only found by direct determination, and ten taxa were only found in enrichment cultures. Hence, the hypothesis is supported. Additionally, five lichen species (three genera), five bryophyte species (five genera), and 24 vascular plant species occurred. (2) There is a clear difference between the floristic structure of initial and stable crusts. The different successional stages are clearly separated by detrended correspondence analysis, showing a distinct structure of the community assembly in each stage. In the initial crusts, Klebsormidium flaccidum, Klebsormidium cf. klebsii, and Stichococcus bacillaris were important indicator species, whereas the stable crusts are especially characterized by Tortella inclinata. (3) The biodiversity of BSC taxa and vascular plant species increases from initial to stable BSCs. There are significantly higher genera and species numbers of cyanobacteria and eukaryotic algae in initial BSCs. Stable BSCs are characterized by significantly higher species numbers of bryophytes and vascular plant species. The results show that, in the investigated temperate region, the often-assumed increase of biodiversity in the course of succession is clearly taxa-dependent. Both successional stages of BSCs are diversity “hot spots” with about 29 species of all taxa per 20 × 20 cm plot. (4) Nitrogen and chlorophyll a concentrations increase in the course of succession. The chlorophyll a content of the crusts (cyanobacteria, eukaryotic algae, bryophyte protonemata) is highly variable across the studied samples, with no significant differences between initial and stable BSCs; nor were ecologically significant differences in soil nutrient contents observed. According to our results, we cannot confirm this hypothesis; the age difference between our two stages is probably not big enough to show such an increase. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

南亚热带不同演替阶段森林优势树种叶片构建成本与机械抗性的协同关系

为探究不同演替阶段森林优势种叶片资源获取策略的差异以及叶片构建成本与机械抗性的关系,对我国南亚热带不同演替阶段森林14优势种的叶片构建成本、机械抗性、角质层厚度和比叶重等结构性状进行测定。结果表明,与演替早期相比,演替晚期优势种具有更高的单位面积叶片构建成本、叶片撕裂力以及穿透力,但其叶片最大光合速率较低;同时,单位面积叶片构建成本与机械抗性呈显著正相关关系,而叶片角质层厚度、比叶重等结构性状也与叶片构建成本、机械抗性均呈显著正相关。因此,从叶片能量投资策略上反映了南亚热带森林演替进程中叶片构建成本与机械抗性的协同关系。     

Succession of Ephemeral Secondary Forests and Their Limited Role for the Conservation of Floristic Diversity in a Human-Modified Tropical Landscape

Both local- and landscape-scale processes drive succession of secondary forests in human-modified tropical landscapes. Nonetheless, until recently successional changes in composition and diversity have been predominantly studied at the patch level. Here, we used a unique dataset with 45 randomly selected sites across a mixed-use tropical landscape in central Panama to study forest succession simultaneously on local and landscape scales and across both life stages (seedling, sapling, juvenile and adult trees) and life forms (shrubs, trees, lianas, and palms). To understand the potential of these secondary forests to conserve tree species diversity, we also evaluated the diversity of species that can persist as viable metapopulations in a dynamic patchwork of short-lived successional forests, using different assumptions about the average relative size at reproductive maturity. We found a deterministic shift in the diversity and composition of the local plant communities as well as the metacommunity, driven by variation in the rate at which species recruited into and disappeared from the secondary forests across the landscape. Our results indicate that dispersal limitation and the successional niche operate simultaneously and shape successional dynamics of the metacommunity of these early secondary forests. A high diversity of plant species across the metacommunity of early secondary forests shows a potential for restoration of diverse forests through natural succession, when trees and fragments of older forests are maintained in the agricultural matrix and land is abandoned or set aside for a long period of time. On the other hand, during the first 32 years the number of species with mature-sized individuals was a relatively small and strongly biased sub-sample of the total species pool. This implies that ephemeral secondary forests have a limited role in the long-term conservation of tree species diversity in human-modified tropical landscapes.     

The Early Stages of Speciation in Amazonian Forest Frogs: Phenotypic Conservatism Despite Strong Genetic Structure

Phylogeographic perspectives incorporating multiple classes of characters, especially those relating to sexual signals, are promising for the elucidation of recent evolutionary mechanisms driving speciation. Here, forest frogs were used as a model system to access distinct stages in the process of evolutionary differentiation. We studied 280 individuals assigned to three species: Allobates paleovarzensis, A. nidicola and A. masniger. Samples were collected at 20 localities arranged in two study systems, along the middle Amazon and the lower Madeira Rivers, in Central Amazonia. Mantel tests, analyses of molecular variance, and the spatial distribution of haplogroups indicated that the distribution of genetic variability, as inferred from a mitochondrial DNA marker, was determined by a combination of isolation-by-distance effects and the transposition of large Amazonian rivers. These two factors had contrasting relative influences in each of the study systems, which also differed regarding the estimated time of the major cladogenetic events. Pronounced population genetic structure was observed. However, multivariate discriminant function analyses revealed that the phenotypic (morphological and acoustic) divergence was loosely related with genetic differentiation and did not successfully predict assignment of individuals to genetic groups. The observed distribution of genetic variability showed the important role of genetic drift in the diversification of the mitochondrial marker studied. The phenotypic conservatism among populations was surprising in view of the high genetic structuring observed, and indicates a prevailing role of stabilizing selective forces in the process of sexual signal and morphological differentiation.     

Net Primary Production and Canopy Nitrogen in a Temperate Forest Landscape: An Analysis Using Imaging Spectroscopy, Modeling and Field Data

Understanding spatial patterns of net primary production (NPP) is central to the study of terrestrial ecosystems, but efforts are frequently hampered by a lack of spatial information regarding factors such as nitrogen availability and site history. Here, we examined the degree to which canopy nitrogen can serve as an indicator of patterns of NPP at the Bartlett Experimental Forest in New Hampshire by linking canopy nitrogen estimates from two high spectral resolution remote sensing instruments with field measurements and an ecosystem model. Predicted NPP across the study area ranged from less than 700 g m⁻² year⁻¹ to greater than 1300 g m⁻² year⁻¹ with a mean of 951 g m⁻² year⁻¹. Spatial patterns corresponded with elevation, species composition and historical forest management, all of which were reflected in patterns of canopy nitrogen. The relationship between production and elevation was nonlinear, with an increase from low- to mid-elevation deciduous stands, followed by a decline in upper-elevation areas dominated by evergreens. This pattern was also evident in field measurements and mirrored an elevational trend in foliar N concentrations. The increase in production from low-to mid-elevation deciduous stands runs counter to the generally accepted pattern for the northeastern U.S. region, and suggests an importance of moisture limitations in lower-elevation forests. Field measurements of foliar N, wood production and leaf litterfall were also used to evaluate sources of error in model estimates and to determine how predictions are affected by different methods of acquiring foliar N input data. The accuracy of predictions generated from remotely sensed foliar N approached that of predictions driven by field-measured foliar N. Predictions based on the more common approach of using aggregated foliar N for individual cover types showed reasonable agreement in terms of the overall mean, but were in poor agreement on a plot-by-plot basis. Collectively, these results suggest that variation in foliar N exerts an important control on landscape-level spatial patterns and can serve as an integrator of other underlying factors that influence forest growth rates.     

High Conservation Value of Forest Fragments for Plant and Frugivore Communities in a Fragmented Forest Landscape in South Africa

Fragmentation is a major threat factor for plant–frugivore communities in tropical and subtropical forests. Resulting changes in the distribution of traits within these communities, e.g., a loss in large‐bodied frugivores, may lead to strong changes in plant–frugivore interactions in fragmented forests. Yet, we still lack a thorough understanding of the interplay between forest fragmentation, the trait‐composition of communities and resulting plant–frugivore interactions on a community‐scale. In a fragmented South African landscape comprising different forest categories—i.e., continuous natural forest, forest fragments surrounded by natural grassland, and forest fragments surrounded by sugarcane—we investigated the relationship between communities of fruiting plants and their frugivore visitors in response to forest fragmentation, as well as the interactive effects of forest fragmentation and fruit size of the plants on the number of frugivore visitors and their body size. Neither the fruit size of plant nor the body mass of frugivore communities differed between natural forest sites and forest fragments. Moreover, in‐depth analyses of frugivore assemblages visiting plant species revealed no effect of forest category on the number of frugivore visits or their mean body mass. The number of visits and body mass of frugivores were merely determined by the crop and fruit size of the focal plant species. Overall, our results suggest that frugivory of plant species with differently sized fruits was not reduced in forest fragments. Thus, fragments with high fruit availability may be key elements maintaining the functional connectivity of a heterogeneous forest landscape.     

Edge Effects and Seedling Bank Depletion: The Role Played by the Early Successional Palm Attalea oleifera (Arecaceae) in the Atlantic Forest

In this study, we examined the impacts of Attalea oleifera on the structure of seedling bank and discuss potential mechanisms of palm influence. Seed rain, seedling bank, and palm leaf fall were assessed beneath the canopy and in the vicinity of 16 adult palms across the edges of a large fragment (3500 ha) of the Atlantic forest. Moreover, we examined A. oleifera impacts on seed germination and seedling mortality by experimentally submitting seeds and seedlings to prolonged palm-leaf covering. As expected, seedling bank beneath the adults exhibited reduced abundance and species richness at local and habitat scale. Small to large seeds (3.1–30 mm) were underrepresented in the seed rain below adults palms, while experimental leaf covering drastically reduced both seed germination and seedling survivorship. A. oleifera leaf fall occurred over the whole year (3.6±2.7 leaves/individual/yr), which resulted in deep leaf litter mounds (10.7±9.2 cm). Finally, adult palm density (21.6±11.9 individuals/ha) correlated negatively with seedling density across Attalea clusters. Our results suggest that A. oleifera exerts negative effects on the seedling bank by reducing seedling abundance and richness as a consequence of two complementary mechanisms: impoverished and size-biased seed rain plus reduced seed germination and increased seedling mortality due to prolonged covering by fallen leaves.     

Macrofaunal Loss and Microhabitat Destruction: The Impact of Trampling in a Temperate Mangrove Forest, NSW Australia

Trampling paths are a feature of estuarine habitats in southeastern Australia. An experimental investigation quantified the impact of trampling over a 3 year period on the microhabitat features and macrofaunal assemblages in a temperate mangrove forest in New South Wales, Australia. The magnitude of the impact varied between 0 and 25 passes (representing a visit by 25 people), which reduced the biomass of the Bostrychia–Caloglossa algal association by 50%. The frequency of trampling varied between one and four, simulating a single and seasonal visits by a group of people to the mangrove forest. The main impact of trampling was an alteration to the microhabitat structures of the forest floor including a decrease in the number and vertical height of pneumatophores, an increase in the proportion of bent and broken pneumatophores in trampled lanes and a decrease in the biomass of the epiphytic Bostrychia–Caloglossa algal association. The macrofauna most impacted by trampling were the gastropods most commonly associated with the pneumatophores and algal assemblages and included Ophicardelus spp. and Assiminea buccinoides. Those gastropods least impacted by trampling were commonly associated with the surface of the sediment or were known to move over the surface and included Bembicium auratum and Cassidula zonata. There was little impact on the main burrowing crab, Heloecius cordiformis. There were some indirect impacts of trampling with the recruitment of Ophicardelus spp. Assiminea buccinoides and Salinator solida reduced in the subsequent year after trampling had ceased. People can create walking paths in mangrove forests that have long term effects on the habitat. An appropriate management emphasis may lie in maintaining the structural features of the habitat.     

The Spatial-Temporal Heterogeneity of Understory Light Availability in a Temperate Forest of North China

The spatial-temporal variation of understory light availability has important influences on species diversity and community assembly. However, the distribution characteristics and influencing factors of understory light availability have not been fully elucidated, especially in temperate deciduous, broad-leaved forests. In this study, the understory light availability was monitored monthly (May–October) in a temperate deciduous, broad-leaved forest in Henan Province, China. Differences in the light availability among different months and habitat types were statistically analyzed using Kruskal–Wallis method, respectively. Partial least squares path modeling (PLS-PM) was used to explore the direct and/or indirect effects of stand structure, dominant species and topographic factors on the light environment. Results showed that there were differences in light environments among the four habitat types and during the studied six months. The PLS-PM results showed that the stand structure and the dominant species were negatively correlated with the light environment, and the path coefficient values were −0.089 (P = 0.042) and −0.130 (P = 0.004), respectively. Our result indicated that the understory light availability exhibit a distinct spatial and temporal heterogeneity in temperate deciduous, broad-leaved forest of north China. The characteristics of woody plant community, especially the abundance of one of the dominant plant species, were the important factors affecting the understory light availability.     

Private Versus Common Property Forests: Forest Conditions and Tenure in a Honduran Community

Establishing secure tenure is widely recognized as a fundamental component of sustainable forest management. Policy-makers generally prefer privatization to achieve these ends, although common property institutions may also be appropriate. But if common property tenure is insecure and fails to control exploitation, theory predicts that private tenure should lead to better forest conditions. In this case study of a western Honduras community, forest mensuration data were collected from four private forests and two relatively open access common property forests. Statistical analyses failed to find consistent, significant differences in vegetation structure or soils related to tenure. Notable contrasts between forests reflected historical conditions and owner preferences. Neither form of tenure appeared to emphasize concerns for sustainable management, and ongoing processes of change constrained the possibility for limiting common property forest exploitation. The study adds to others which show that the outcomes of private or common property tenure relate substantially to the socioeconomic, political, and ecological context.     

南岳野生爬山虎属植物种质资源及园林应用

南岳风景名胜区现有野生爬山虎属植物5种,分别占国产种（含变种）、省种50%、62.5%;目前广泛应用的有爬山虎、五叶地锦,引种栽培的有异叶爬山虎和绿爬山虎,尚在野生状况是粉叶爬山虎。其攀附力强弱依次为爬山虎、王叶地锦与异叶爬山虎、绿爬山虎、粉叶爬山虎。     

我国的野生棕榈科园林观赏植物资源

我国原产棕榈科植物约有 18属 10 0种 ,可用于园林绿化及观赏的有 12属 4 4种 ,可作行道树、园景树、庭园树、室内观赏树和海滨、沙滩绿化树。虽然资源不太丰富、分布范围较为狭窄 ,但观赏价值较高 ,许多为国家重点保护植物。本文还重点介绍了部分种类 ,并对开发利用提出了建议     

Patterns of DON and DOC Leaching Losses Across a Natural N Availability Gradient in Temperate Hardwood Forests

Dissolved organic nitrogen (DON) is a potentially significant vector of N loss from forest ecosystems that has been characterized as an “N leak.” Although the term “leak” suggests a lack of regulation, it is clear DON losses are a function of biological and physicochemical processes that influence its production and retention across the landscape. In this study, we investigated how soil processes that influence DON cycling impact ecosystem patterns of DON loss in five northern hardwood forests that spanned a gradient of N availability, tree species composition, and moisture–edaphic characteristics. We collected soil leachate from the forest floor and at 15 and 100 cm soil depths and related solution chemistry to its physical environment. We found that DON losses were a function of ecosystem N status and increased modestly with soil N stock. We also found a unimodal pattern of DOC/DON losses across the gradient driven by low DOC/DON in the lowest N availability stand, likely due to the interaction between strongly sorbing DOM inputs from C-rich, oak-derived leaf litter with highly sorptive soils. We suggest DOM losses from forests depend on interactions between soil solution input chemistry from the forest floor, which reflects changes in tree species composition across the landscape, and soil sorptive processes where organic compounds are dynamically exchanged between solid and dissolved phases. These results emphasize the need to understand how fine-scale processes can interact to shape ecosystem patterns of DOM loss.     

Hunting Primates and Managing Forests: The Case of Iban Forest Farmers in Indonesian Borneo

Hunting by Iban forest farmers in West Kalimantan, Indonesia, is an important part of their subsistence economy, and as such became a focus of study as part of a conservation project in the Danau Sentarum Wildlife Reserve. In this paper, we examine Iban hunting of nonhuman primates with comparison to other large mammals. We analyze rates of encounter and capture, comparing encounters, hunting trips, and animal numbers. Information on habitats hunted shows the importance of secondary and old growth forest. Also examined are Iban attitudes, game preferences, and taboos. The significance of these findings is discussed with regard to the threats to wildlife from increases in the use of shotguns, human population, and habitat destruction, showing that conservation may be aided by promoting or enhancing certain aspects of the traditional Iban agroforestry system.