The effect of an agro-pasture landscape on diversity and migration patterns of frugivorous butterflies in Chiapas, Mexico

Few relevant data are available to analyze how landscape structure and composition affect the abundance and movement patterns of tropical insects. Using mark-release recapture experiments we examine the effect of an agro-pasture matrix on changes in diversity and migration of frugivorous butterflies in a tropical fragmented landscape in southern Mexico. In total, 53 frugivorous butterfly species were recorded in the entire landscape. Butterfly species composition was much more similar between sites than plant composition. A total of 3,501 individuals belonging to 41 butterfly species were captured, out of which 23 species (56%) were recaptured at least once. A large fraction of individuals was recaptured at the site of release (91%). We failed to find a significant relationship between the proportion occupied by the matrix and rates of residence, emigration, and immigration. Our results suggest that matrix quality in this and other traditionally managed agro-pasture landscapes plays a key role in both keeping important levels of biodiversity and maintaining constant movements of butterflies between otherwise isolated habitat patches.     

Effects of dispersal,population delays,and forest fragmentation on tree migration rates

Examining the relation between the dispersal of seeds across landscapes and the migration of species can inform studies of processes such as invasions and response to climatic change. In this research a spatially explicit model is used to analyze the effects of dispersal probability, limits on establishment, generation time, seed crop probability, and varying proportions and patterns of landscape fragmentation on migration rate. Comparisons are made with rates inferred for migrations based on isopols of species range changes in the Holocene (20–200 km/century). The effects of the parameters on migration rate in the model are additive. Dispersal probability, related to diaspore type, is the most influential factor. Limits on establishment show effects only if severe. Lower seed crop probabilities can slow migration slightly. Generation times of 10 to 40 yr reduce migration rate moderately, while generations set long enough to reflect population doubling times would slow migration greatly. Extensive fine-scale fragmentation slows migration more than a single large barrier, but not greatly; multiple large barriers have greater effects. The factors have their greatest absolute and relative effects at higher dispersal probabilities; this result indicates that combinations of low dispersal probability and slow population development could increase the differences in migration rate among species while fragmentation could reduce these differences.     

森林干扰生态研究

陆地上80％的生态系统都已受到了来自人类和自然的各种干扰,森林生态系统也不例外．在各种干扰作用下,尤其是人类不合理的干扰导致世界范围内的森林退化／衰退已成为一个十分严峻的事实,因此,以维持、恢复森林生态系统固有的多种功能为基础,实现高效、稳定、可持续就成为经营森林生态系统的总目标．随着干扰的加剧,近年来生态学界更加关注的是“受干扰”生态系统的研究．干扰对森林生态系统主要生态过程的影响以及森林生态系统对干扰的响应等问题,已成为森林生态研究领域的国际前沿与热点．因此,系统地研究干扰条件下森林生态系统的生态过程,并在此基础上确立干扰森林的经营理论与技术,对中国天然林资源保护等林业工程实施及国家生态安全建设具有重要的科学和现实意义．本文在广泛收集国内外有关森林干扰研究结果的基础上,总结了森林干扰的基本概念,分析了干扰与森林经营的关系,探讨了森林干扰研究领域所涉及的内容和关注的基础问题,提出了森林干扰生态研究的主要内容与方向,对今后干扰森林生态研究和中国天然林保护等林业工程建设具有参考价值．     

Extinction debt and the role of static and dynamical fragmentation on biodiversity

The mass-extinction events caused by human-driven habitat loss are a current concern in conservation science. However, the observed number of extinctions is considerably smaller than predicted. The overestimation of extinction rates comes from the time-delay which depends on the species sensitivity to habitat changes. The standard method of predicting the effect of habitat loss on biodiversity is to use the species–area relationship and progressively following it backwards to smaller areas. The difference between the actual number of species and the one provided by the backwards species–area relationship is dubbed extinction debt. Previous studies in general adopt a static view for the spatial distribution of species. Nonetheless, a precise understanding of the problem urges us to adopt a dynamic framework to this issue since the time between disturbances of the landscape plays an active role in influencing the strength of the extinction debt. In this context, here we address two distinct approaches for this question: a static and a dynamic view of fragmentation. In the former we quantify the extinction debt in a quenched spatial distribution of species, whereas in the latter the community is let to evolve between disturbance events of the landscape. Here we show that the size of the extinction debt depends on the pattern of the fragmentation. It is found that random distributions of destroyed habitats provide larger extinction debts than those obtained for contiguous areas of fragmentation. Furthermore, in the dynamic approach it is observed that dispersal can lead to unexpected outcomes such as lower biodiversity levels than ones inferred from the backwards species–area relationship.     

Secondary succession in disturbed Pinus-Quercus forests in the highlands of Chiapas,Mexico

We present floristic and structural data on serai plant communities (Old-Field, Grassland, Shrubland, and Early Successional, Mid-Successional, and Mature Forest) resulting from the current land use pattern in the Pinus-Quercus forests in the highlands of Chiapas, Mexico. The number of species ranged from 24 in the Old-Field stage up to 100 in the Mature Forest, and the shrub layer was richest in all the forested stands. An almost complete floristic replacement exists between the open and the forested communities. Quercus and Pinus dominate the canopy of old-growth stands, but their recruitment does not occur or is very low in the shade. Vigorous seedlings and saplings of these species are found only in the open serai stages or in forest gaps. Demographic and phytosociological data are used to indicate the successional role of dominant species in the forested stages. Some implications of the regional land use patterns for conservation and succession are discussed.     

Functional trait variation of forest understorey plant communities across Europe

Global environmental changes are expected to alter the functional characteristics of understorey herb-layer communities, potentially affecting forest ecosystem functioning. However, little is known about what drives the variability of functional traits in forest understories. Here, we assessed the role of different environmental drivers in shaping the functional trait distribution of understorey herbs in fragmented forests across three spatial scales. We focused on 708 small, deciduous forest patches located in 16 agricultural landscape windows, spanning a 2500-km macroclimatic gradient across the temperate forest biome in Europe. We estimated the relative effect of patch-scale, landscape-scale and macroclimatic variables on the community mean and variation of plant height, specific leaf area and seed mass. Macroclimatic variables (monthly temperature and precipitation extremes) explained the largest proportion of variation in community trait means (on average 77% of the explained variation). In contrast, patch-scale factors dominated in explaining community trait variation (on average 68% of the explained variation). Notably, patch age, size and internal heterogeneity had a positive effect on the community-level variability. Landscape-scale variables explained only a minor part of the variation in both trait distribution properties. The variation explained by shared combinations of the variable groups was generally negligible. These findings highlight the importance of considering multiple spatial scales in predictions of environmental-change effects on the functionality of forest understories. We propose that forest management sustainability could benefit from conserving larger, historically continuous and internally heterogeneous forest patches to maximise ecosystem service diversity in rural landscapes.     

A forest habitat network for the Atlantic Oakwoods in Highland region,Scotland

Summary

The need to conserve biological diversity and ensure the future viability and integrity of Atlantic oakwoods in a fragmented landscape has led to strategies that facilitate a more holistic view of biodiversity conservation across extensive areas. The Scottish Forestry Strategy contains a major aspiration to develop forest habitat networks through the restoration and improvement of existing woodland and the expansion of new woodland. The Forest Research landscape ecology model BEETLE (Biological and Environmental Evaluation Tools for Landscape Ecology) uses a focal species approach to assess the functional connectivity of habitat within the wider landscape matrix. This model has been used to predict the current habitat network for Atlantic oakwood specialists in the Highland region of Scotland. The analysis outputs are presented with an approach to help practitioners and planners visualise the opportunities to target expansion, conversion or restoration of Atlantic oakwoods and their intrinsic biodiversity.     

Spatial and temporal variability in fire occurrence within the Las Bayas Forestry Reserve, Durango, Mexico

Patterns of fire occurrence within the Las Bayas Forestry Reserve, Mexico are analyzed in relation to variability in climate, topography, and human land-use. Significantly more fires with shorter fire return intervals occurred from 1900 to 1950 than from 1950 to 2001. However, the frequency of widespread fire years (25% filter) was unchanged over time, as widespread fires were synchronized by climatic extremes. Widespread fire years occurred during dry years that lagged wet years. Widespread fire years lagged the negative El Niño phase (wet winters) of the Southern Oscillation by 1 year, but were not synchronized by the positive, La Niña phase (dry winters) of the Southern Oscillation. The smaller, localized fires that occurred more frequently during the first half of the 20th century were attributed to changes in land tenure with the introduction of the ejido system in the early 1950s. Ejido management strategies lowered fire frequencies by suppressing fires and reducing anthropogenic fires. There were likely more ignitions prior to the arrival of the ejido system as fires were ignited by lightning and indigenous people. As the movement of indigenous peoples across the landscape has been restricted by changes in land tenure, numbers of human-ignited fires subsequently decreased post 1950. After 1950, fires occurred less frequently, were more synchronized, and more restricted to years of extreme climate.     

景观指数分类、应用及构建研究

在景观生态学研究中,理解与把握景观格局变化的生态学原则至关重要,用景观指数描述景观格局及变化,建立格局与景观过程之间的联系,是景观生态学最常用的定量化研究方法,本文在综合前人对景观指数的基础上,对景观指数研究从景观指数的分类研究,指数对景观格局的描述研究,指数之间的相关性研究及指数构建研究等4方面进行了总结,并从单个景观指数与指数体系两个层次上提出了判定景观指数优劣及景观指数应用的一般性原则。     

Keepers of maize in Chiapas,Mexico

This study concerns the knowledge and selection of biological diversity of maize (Zea mays) within its center of domestication in Mesoamerica. Maize farmers in central Chiapas of Southern México keep local varieties (landraces) belonging to six races and four race mixtures. Fifteen local varieties are recognized. In spite of widespread adoption of a modern, high yielding variety, maize farmers continue to select local varieties for specific soils and because of agronomic and use criteria. Farmers maintain maize varieties primarily through seed selection. Spatial and temporal separation do not seem sufficient to maintain varieties. The management of improved varieties can lead from a uniform population to a heterogeneous one as hybridization with local maize populations occurs.     

Wildfires in the western Canadian boreal forest: Landscape patterns and ecosystem management

Abstract. Mimicking of natural disturbance for ecosystem management requires an understanding of the disturbance processes and the resulting landscape patterns. Since fire is the major disturbance in the boreal forest, three widely held beliefs about fire behavior and resulting landscape patterns are examined in light of the empirical evidence available. These beliefs are: (1) that there is a ‘natural’ fire frequency for boreal ecosystems; (2) that the landscape mosaic created by wildfire is generally one of small, younger patches embedded within a matrix of older forest; and (3) that forest flammability is largely controlled by fuel accumulation. Despite the apparently logical basis for such beliefs, they are not well supported by empirical evidence. This discrepancy is explained by problems such as failure to appreciate the relationship between number of fires and area burned and inappropriate extrapolations or generalizations from other regions and vegetation types. The most important implications for management are that the natural disturbance processes producing landscape patterns in the boreal forest generally operate at much larger scales than management units, and that humans may have more indirect (through landuse change) rather than direct (through fire suppression) effects on the frequency of wildfires.     

Large-scale forest fragmentation increases the duration of tent caterpillar outbreak

I examined historical data (1950–1984) on the duration of outbreaks of the forest tent caterpillar (Malacosoma disstria) in northern Ontario, Canada. Outbreak duration was compared to host tree species dominance and forest structure over large areas of boreal forest partially cleared for agriculture. Abundance of the principal host tree species Populus tremuloides had no consistent effect on duration of outbreak within forest districts, and was negatively correlated with duration of outbreaks among the eight forest districts examined. The amount of forest edge per km² was the best, and most consistent, predictor of the duration of tent caterpillar outbreaks both within individual forest districts and among forest districts. Because forest tent caterpillar populations are driven largely by the impact of parasitoids and pathogens, results here suggest that large-scale increase in forest fragmentation affects the interaction between these natural enemies and forest tent caterpillar. Increased clearing and fragmentation of boreal forests, by agriculture and forestry, may be exacerbating outbreaks of this forest defoliator.     

Species richness and composition of amphibians and reptiles in a fragmented forest landscape in northeastern Bolivia

We quantified patterns of species richness and species composition of frogs and reptiles (lizards and snakes) among three habitats (continuous forest, forest islands, and a seasonally flooded savannah) and between forest island size and isolation classes in a floristic transition zone in northeastern Santa Cruz Department, Bolivia. Species richness was similar across macrohabitats, as was faunal composition of forested habitats, although savannah harbored a distinct herpetofauna. On forest islands, richness and composition of forest frogs was largely related to isolation, whereas reptiles were affected by both isolation and habitat. The observation that isolation rather than area was the primary driver of distribution patterns on forest islands stands in contrast to many studies, and may be a function of (1) the greater range in forest island isolation values compared to area or (2) the long history of isolation in this landscape.     

Effects of fragmentation on parasite burden (nematodes) of generalist and specialist small mammal species in secondary forest fragments of the coastal Atlantic Forest,Brazil

Parasites are considered to play an important role in the regulation of wild animal populations. We investigated parasite burden of gastrointestinal nematodes and body condition in specialist and generalist small mammal species in secondary forest fragments in the highly endangered coastal Atlantic Forest. We hypothesized that body condition decreases with increasing parasite load and that parasite burden increases with increasing fragmentation in specialist species but not in generalist species as a consequence of differing responses to fragmentation effects. Investigated species were Akodon montensis, Oligoryzomys nigripes, and Delomys sublineatus (rodents) and the marsupials Marmosops incanus and Gracilinanus microtarsus. Prevalence of parasites was high in all species except for the arboreal G. microtarsus, presumably because of decreased infection probability. No correlation was found between body condition and parasite load in any of the species. Contrary to our expectations, body condition of the specialists D. sublineatus and M. incanus increased in both species with increasing fragmentation. In D. sublineatus, parasite burden increased and body condition decreased in fragments with relatively high density probably due to increased contact rates and facilitation of infection with nematodes. In all generalist species, low or no correlation between parasite burden and fragmentation was detected, suggesting little effect of fragmentation on population health.     

Introducing a new method for assessing spatially explicit processes of landscape fragmentation

Landscape fragmentation is commonly defined as having five distinct phases (perforation, dissection, subdivision, shrinkage, and attrition). Previous studies focus on using landscape pattern metrics to interpret the phase of the landscape. A critical but underinvestigated aspect is that these five phases are also spatially explicit processes. This study proposes a new method to map and measure the different spatially explicit processes of landscape fragmentation. Unlike previous studies that are based on landscape pattern metrics, this current study measures landscape change directly. The new method is applied to Bao’an District in Shenzhen, China, to investigate forest land fragmentation under rapid urbanization. Landsat data were used to map the land use distributions from 1978 to 2009. Results show that different spatial processes occur simultaneously throughout the study area as well as in different study periods of forest fragmentation. Shrinkage was the dominant spatial process in the early period. In the later period, subdivision played a more important role, followed by attrition. Interestingly, urban land was not the leading land use that directly encroached on forest land, as many other studies have shown. Instead, forest land was first converted to orchard land, and orchard land was converted to urban land. The study contributes to Forman's general model of spatially explicit processes of landscape fragmentation and holds implications for urban planning policy and practice. The study concludes that the new method is effective in understanding and assessing forest land fragmentation, especially in the context of rapid urbanization.     

Dung beetle (Coleoptera: Scarabaeidae: Scarabaeinae) diversity in continuous forest,forest fragments and cattle pastures in a landscape of Chiapas,Mexico: the effects of anthropogenic changes

We studied the diversity of dung beetles in three different habitats in the Lacandona Forest, Chiapas, Mexico. We found a total of 49 species. Of these, 44 were in well-preserved forests (SC) within the limits of the Montes Azules Biosphere Reserve, 42 in fragmented forests (SF), and 13 in cattle pastures (PZ). These two latter habitats were part of a fragmented landscape. Even though the species richness between the two forest habitats is similar, there is a change in guild composition and structure. About 12% of the species were exclusively found in SC, while 4.1% and 2% were exclusive of SF and PZ respectively. β diversity was the most important element for overall diversity (γ), above that of the local richness (α). Within well-preserved forests, species composition changes substantially, even among neighboring sites. Species diversity within the landscape seems to depend on canopy coverage, soil temperature and geographic distance between sites. Functional groups vary with the habitat. Large-bodied, nocturnal species with specific requirements of soil temperature and compaction are more sensitive to anthropogenic changes. In cattle pastures there is a larger number of heliophilic species, with a higher percentage of small-bodied and roller beetles.     

A large-scale forest fragmentation experiment: the Stability of Altered Forest Ecosystems Project

Opportunities to conduct large-scale field experiments are rare, but provide a unique opportunity to reveal the complex processes that operate within natural ecosystems. Here, we review the design of existing, large-scale forest fragmentation experiments. Based on this review, we develop a design for the Stability of Altered Forest Ecosystems (SAFE) Project, a new forest fragmentation experiment to be located in the lowland tropical forests of Borneo (Sabah, Malaysia). The SAFE Project represents an advance on existing experiments in that it: (i) allows discrimination of the effects of landscape-level forest cover from patch-level processes; (ii) is designed to facilitate the unification of a wide range of data types on ecological patterns and processes that operate over a wide range of spatial scales; (iii) has greater replication than existing experiments; (iv) incorporates an experimental manipulation of riparian corridors; and (v) embeds the experimentally fragmented landscape within a wider gradient of land-use intensity than do existing projects. The SAFE Project represents an opportunity for ecologists across disciplines to participate in a large initiative designed to generate a broad understanding of the ecological impacts of tropical forest modification.     

Growth strategies of main trees and forest architecture of aFagus-Magnolia forest in Florida, USA

Growth strategies of six species of trees are compared and used to analyze forest architecture. They included the overstory speciesFagus grandifolia, Magnolia grandiflora, Pinus glabra andLiquidambar styraciflua, and the understory speciesOstrya virginiana andIlex opaca. The six species were abundant in Woodyard Hammock, an old-growth forest in northern Florida, USA. Height, stem diameter, crown projection and radial growth were measured in trees between 5 and 35 m tall. Three different, but non-exclusive, growth strategies were identified for the tree species: survival (Fagus grandifolia, Magnolia grandiflora, Ilex opaca), occupy open space (Fagus grandifolia, Ostrya virginiana, Ilex opaca), and reach above competitors (Liquidambar styraciflua, Pinus glabra). In two transects (0.42 ha) and one quadrat (1 ha), heights of dominant trees were used to distinguish different phases of forest development, which were mapped. In the quadrat, juvenile canopy trees in the undergrowth were mapped. The combination of presence of different developmental phases, presence of juveniles in the undergrowth, growth strategies of main tree species, and disturbance regime was used to assess forest development in the near future.Fagus grandifolia is predicted to become the main dominant species, but the frequent hurricanes open the forest canopy and provide opportunities for understory species (Ostrya virginiana andIlex opaca), and light-demanding overstory species (Liquidambar styraciflua andPinus glabra).     

Tolerance to habitat fragmentation influences the colonization of new habitat by forest birds

We examined the relationship between the ability of bird species to persist in fragmented forests and their ability to colonize new forest habitat. Using a long-term data set on the colonization of a forest plantation, we tested the hypothesis that bird species tolerant to habitat fragmentation would detect and colonize the new habitat faster than intolerant species. The forest plantation under study is situated on an area of land reclaimed from the sea (a polder) in the central part of The Netherlands. We constructed an index of tolerance to habitat fragmentation and included it as a predictor variable in a set of three logistic regression models that compared the probability of colonization over four consecutive time periods. After controlling statistically for the effects of regional incidence, preferred habitat and life-history characteristics, there was a significant effect of tolerance to fragmentation on the ability of species to colonize the plantation, and a marginal effect on the timing of colonization. We then examined the effect of the same index of tolerance to fragmentation on colonization patterns over a larger spatial scale. Multivariate regression models showed that the proportion of three polders of different ages occupied by forest bird species was dependent upon the regional incidence of a species, its preferred habitat and its tolerance to fragmentation. The results support the hypothesis that species tolerant to habitat fragmentation detect and colonize new habitat faster than those intolerant to habitat fragmentation.     

Tree species richness complementarity, disturbance and fragmentation in a Mexican tropical montane cloud forest

Tropical montane cloud forest exhibits great heterogeneity in speciescomposition and structure over short geographic distances. In central Veracruz,Mexico, the conservation priority of seven cloud forest fragments was assessedby considering differences in woody plant species richness and complementarityof species among sites, forest structure, tree mortality, and timber andfirewood extraction as indicators of anthropogenic disturbance. Densities oftrees 5 cm dbh (360–1700 trees/ha) weredifferent among the sites, but basal area (35.3–89.3m²/ha) did not differ among fragments. The number of dead trees rangedfrom 10–30 to 170–200 trees/ha. The fragments'species composition was different but complementary. The Morisita–Hornindex indicated low similarity between fragments. A non-parametric estimator ofspecies richness indicated that more sampling effort would be necessary tocomplete the inventory (15 additional trees and two understory shrub species).Unfortunately, most of the fragments are threatened with deforestation. The numberof cut trees was similar among sites (0–15 cut trees/0.1 ha).Sites with immediate need for conservation were close to settlements, with highnumbers of cut trees and no legal protection. The selected sites represent thevariety of situations that exist in the region. Given the high complementarityobserved between fragments, a regional conservation approach will be required topreserve the last repositories of part of the tremendous biodiversity of theonce continuous forest in this region.