Degree Of Forest Fragmentation Research Articles

Modeling honeybee flower visitation rates in the fragmented agricultural landscapes based on Lévy-flight behavior

AbstractTypically, honeybees (Apis mellifera L.), rely on waggle dances performed by scout bees to communicate information about fruitful nectar and pollen sources across the landscape. However, when this communication is absent, inaccurate, or when resources become depleted, bees resort to alternative search strategies. Field experiments utilizing harmonic radar have revealed that honeybees follow flight patterns that demonstrate a scale-free (Lévy-flight) behavior, representing an optimal search strategy for relocating the original feeder location. If honeybees adhere to a Lévy flight pattern to discover resources, where would honeybees demonstrate the highest flower visitation rates in agricultural landscapes? We generated simulated landscapes with varying proportions of forest cover scenarios, ranging from 5 to 50% of the total landscape area, along with different levels of fragmentation per se. Subsequently, we constrained the richness of flower farm cells in each landscape. To predict honeybee visitation rates, three different methodologies based on random movement were utilized: (1) moving window, (2) random walk, and (3) Lévy flight. We found that honeybee visitation rates were influenced by the degree of forest fragmentation in each scenario. Across all visitation scenarios, the highest average number of visited flowers per cell was observed in landscapes with maximum fragmentation per se. In landscapes with lower forest cover and higher fragmentation, honeybees were more likely to visit a greater number of flowers due to the increased probability of traversing the landscape and encountering more flower cells. honeybee visitation rates in agricultural landscapes are significantly influenced by the degree of forest fragmentation. The study highlights the importance of considering landscape structure, specifically forest fragmentation, when predicting honeybee visitation rates and underscores the need for further research to better understand the intricate relationship between landscape characteristics and pollinator behavior.

Spatial variation in risk for tick-borne diseases in residential areas of Dutchess County, New York

Although human exposure to the ticks that transmit Lyme-disease bacteria is widely considered to occur around people’s homes, most studies of variation in tick abundance and infection are undertaken outside residential areas. Consequently, the patterns of variation in risk of human exposure to tick-borne infections in these human-dominated landscapes are poorly understood. Here, we report the results of four years of sampling for tick abundance, tick infection, tick encounters, and tick-borne disease reports on residential properties nested within six neighborhoods in Dutchess County, New York, USA, an area of high incidence for Lyme and other tick-borne diseases. All properties were within neighborhoods that had been randomly assigned as placebo controls in The Tick Project; hence, none were treated to reduce tick abundance during the period of investigation, providing a unique dataset of natural variation within and between neighborhoods. We estimated the abundance of host-seeking blacklegged ticks (Ixodes scapularis) in three types of habitats on residential properties–forests, lawns, and gardens. In forest and lawn habitats, some neighborhoods had consistently higher tick abundance. Properties within neighborhoods also varied consistently between years, suggesting hot spots and cold spots occurring at a small (~ 1-hectare) spatial scale. Across neighborhoods, the abundance of nymphal ticks was explained by neither the amount of forest in that neighborhood, nor by the degree of forest fragmentation. The proportion of ticks infected with three common tick-borne pathogens did not differ significantly between neighborhoods. We observed no effect of tick abundance on human encounters with ticks, nor on either human or pet cases of tick-borne diseases. However, the number of encounters between ticks and outdoor pets in a neighborhood was negatively correlated with the abundance of questing ticks in that neighborhood. Our results reinforce the need to understand how human behavior and neglected ecological factors affect variation in human encounters with ticks and cases of tick-borne disease in residential settings.

Plant–pollinator metanetworks in fragmented landscapes: a simulation study

BackgroundThe topology of the plant–pollinator network can be explained by the species’ abundance and their random interactions. Plant–pollinator networks can be studied in the context of a landscape, because each patch can accommodate a certain local network. Local populations of pollinators in the landscape can be connected through migration and then constitute a metanetwork that is known as a combination of spatial and ecological networks. In this regard, habitat fragmentation can affect the topology of plant–pollinator metanetworks through changes in the species abundance and limiting their interactions. However, it is not clear what pattern (fragmented or aggregated) of the landscape structure can accommodate networks with a higher degree of specialization.Methodswe created simulated landscapes with different forest proportions scenarios (from 5% to 50% of the total landscape) and degrees of fragmentation. Then, for each landscape, we limited the proportion of pollinators to the forest patch. We assumed that plants and pollinators are randomly distributed around the landscape and interact randomly. We used landscape metrics to measure different aspects of landscape structure and bipartite metrics for calculating the degree of specialization in plant–pollinator networks.ResultsThe statistical relationship between bipartite and landscape metrics showed that the relationship between the topology of plant–pollinator networks and the landscape structure is affected by the forest amount in the landscape and the degree of forest fragmentation. We also found that according to the nestedness and H2 (a measure of specialization) metrics, fragmented landscapes contain more general plant–pollinator networks.ConclusionsOur findings suggest that fragmented landscapes, characterized by scattered forest patches, can promote higher levels of interaction between limited pollinators and diverse flowers, leading to more general plant–pollinator networks.

Financial compensation for natural forest logging ban: Standard calculation based on willingness to accept.

To alleviate the deteriorating environment and protect biodiversity, China has implemented a natural forest protection system, demonstrating the importance of sustainable forest management for ecological conservation and socio-economic development, including the complete cessation of commercial logging of natural forests. Financial compensation is adopted to increase farmers' enthusiasm within the commercial Logging Ban of Natural Forests framework. This study used the contingent valuation method and the Heckman two-stage model to explore farmers' willingness to participate in the Logging Ban of Natural Forests and the willingness to accept by survey data on 486 farming households. 72% of farmers are willing to join the Logging Ban of Natural Forests. Their willingness to accept is 517.95 yuan/ha per year, higher than the current state subsidy standard (225 yuan/ha per year). The key factors influencing willingness to accept include the education and degree of fragmentation of woodland and village collective willingness to accept. The age of the rural household head, the fragmentation of the forest, and the evaluation of the Logging Ban of Natural Forests policies have inhibited the increase of farmers' compensation. Farmers' assessment of the Logging Ban of Natural Forests policy only impacts the medium level of compensation. The age and the degree of forest fragmentation would affect the higher compensation amount. The results from this study suggest more financial sources and increased compensation standards are needed. The government should also strengthen ecological awareness and adopt different compensation standards for other groups to achieve sustainable forestry.

Estimating landscape structure effects on pollination for management of agricultural landscapes

BackgroundThe growing human population around the world is creating an increased demand for food. In agricultural landscapes, forests are cleared and turned into agricultural land to produce more food. Increasing the productivity of agricultural land per unit area may prevent extreme forest degradation. Since many agricultural products are dependent on pollinators, it is possible to increase crop production by increasing the pollination rate in the agricultural landscapes. Pollinators are highly dependent on forest patches in agricultural landscapes. Therefore, by creating new forest patches around agricultural fields, we can increase the pollination rate, and thus the crop production. In this regard, estimating the effects of different scenarios of forest fragmentation helps us to find an optimized pattern of forest patches for increasing pollination in an agricultural landscape.MethodsTo investigate the effect of different forest fragmentation scenarios on pollination, we used simulated agricultural landscapes, including different forest proportions and degrees of fragmentation. Using landscape metrics, we estimated the relationship between pollination and landscape structure for each landscape.ResultsOur results showed that for increasing pollination, two significant factors should be considered: habitat amount and capacity of small patches to supply pollination. We found that when the capacity of small patches in supplying pollination was low, fragmented patterns of forest patches decreased pollination. With increasing capacity, landscapes with a high degree of forest fragmentation showed the highest levels of pollination. There was an exception for habitat amounts (the proportion of forest patches) less than 0.1 of the entire landscape where increasing edge density, aggregation, and the number of forest patches resulted in increasing pollination in all scenarios.ConclusionThis study encourages agriculturists and landscape planners to focus on increasing crop production per unit area by pollinators because it leads to biodiversity conservation and reduces socio-economic costs of land-use changes. We also suggest that to increase pollination in agricultural landscapes by creating new forest patches, special attention should be paid to the capacity of patches in supporting pollinators.

Soil legacies determine the resistance of an experimental plant-soil system to drought

This study examines the effects of climate and the degree of forest fragmentation legacies on response of oak to drought. A microcosm approach was set up with holm oak seedlings from three provenances grown in soils coming from two regions of contrasting climate (drier vs. wetter), and three scenarios of forest fragmentation (low, mid, and high agricultural matrix influence). We measured different indicators of the plant-soil system functioning such as ecosystem respiration, net ecosystem exchange, gross primary productivity, stomatal conductance, quantum yield, biomass allocation, and mycorrhization. Legacies of the bioclimatic region and the degree of forest fragmentation on soil properties drove the response to drought of an experimental plant-soil system, masking the effects of seedling provenance. The system was functionally more resistant to drought in soils from forest fragments with more agricultural influence and from the drier region. Our results indicate that the degree of forest fragmentation and bioclimatic legacies on soil properties exerted a much more decisive effect on the response of the plant-soil system to drought than holm-oak seedling provenance.

Landscape composition is more important than landscape configuration for phyllostomid bat assemblages in a fragmented biodiversity hotspot

Human-modified landscapes are composed of different types of land covers in differing proportions (landscape composition), and each with differing spatial physiognomy (landscape configuration). Unfortunately, the information on the relative impact of these two components of landscape structure on biological assemblages is scarce, but urgently needed to improve conservation strategies. We assessed the relative influence of the composition (landscape forest cover and matrix composition) and configuration (degree of forest fragmentation and forest edge density) of 100-ha and 500-ha landscapes on the abundance, diversity, and evenness of phyllostomid bat assemblages in the Lacandona rainforest, Mexico. We assessed the complete bat assemblage and frugivorous bats separately, and we grouped frugivores into understory foragers and canopy foragers. Landscape forest cover was the main predictor of the complete bat assemblage, positively affecting species diversity, particularly the number of rare species. Thus, community evenness decreased in landscapes with higher forest cover. Although weaker, species diversity was positively related to fragmentation and negatively associated with edge density. Landscape composition also was relatively more important than configuration for frugivores. The number of common and dominant frugivorous species and the abundance of understory frugivores increased in landscapes with lower forest cover and dominated by secondary forests in the matrix. The abundance of canopy frugivores showed the opposite response. Thus, to preserve bat assemblages and their important functional roles, conservation initiatives should prioritize a reduction in deforestation and the increase of secondary forests in the matrix. Maintaining all remaining forest patches is needed to favor landscape complementation and supplementation dynamics.

Proximal and Distal Predictors of the Spider Monkey's Stress Levels in Fragmented Landscapes.

The rapid loss, fragmentation and degradation of tropical forests threaten the survival of many animal species. However, the way in which these phenomena affect animal health has been poorly explored, thus limiting the design of appropriate conservation strategies. To address this, here we identified using linear mixed models the effect of proximal (diet, activity pattern, hunting and logging) and distal (sum of the basal areas of fruiting-tree species [SBAFS], landscape forest cover and degree of forest fragmentation) variables over fecal glucocorticoid metabolite (fGCM) levels–hormones associated with animal health and fitness–of six groups of spider monkeys (Ateles geoffroyi) inhabiting six landscapes with different spatial structures in Mexico. Proximal variables showed a stronger predictive power over fGCMs than distal. In this sense, increases in travel time, the occurrence of hunting, and reductions in rest time and fruit consumption resulted in higher fGCM levels. Regarding distal variables, increases in SBAFS were negatively related to fGCM levels, thus suggesting that food scarcity increases stress hormone levels. Nevertheless, contrary to theoretical expectations, spider monkeys living in smaller tracts of forest spent less time travelling, but the same time feeding on fruit as those in more forested areas. The lower net energy return associated with this combination of factors would explain why, contrary to theoretical expectations, increased forest cover was associated with increased levels of fGCMs in these groups. Our study shows that, at least in the short term, spider monkeys in fragmented landscapes do not always present higher levels of stress hormones compared to those inhabiting continuous forest, and the importance of preserving fruit sources and controlling hunting for reducing the levels of stress hormones in free ranging spider monkeys.

Effects of forest fragmentation on the mating system of a cool-temperate heterodichogamous tree Acer mono

Pollination is a key process for reproduction and gene flow in flowering plants. Anthropogenic habitat fragmentation, however, can disrupt plant–pollinator interactions, and may have a negative impact on the reproductive success and population viability of entomophilous plants. Heterodichogamous plants containing protandrous and protogynous individuals within a population may be susceptible to habitat fragmentation due to a lack of available mating partners. In this study, we investigated the effects of forest fragmentation on the mating system in the heterodichogamous plant Acer mono, a major constituent of cool-temperate deciduous forests in Japan. Microsatellite analysis was applied to 212 adult trees and 17 seed families from continuous and fragmented forests. Dispersal kernel modeling using the neighborhood model indicated that pollen dispersal of A. mono was highly fat-tailed. The estimated parameters of the model suggested that the siring success of a pollen donor increased approximately fivefold, with a 100 cm increase in its diameter at breast height (DBH), and that disassortative mating was five times more frequent than assortative mating. The mating system parameters of each mother tree, outcrossing rate (tm), biparental inbreeding (tm−ts), and paternity correlation (rpm) varied among sites and conditions, depending on the local density of potential pollen donors. Whereas A. mono was effectively outcrossed (tm=0.901, tm−ts=0.052, and the number of effective sires was 1/rpm=14.93) in the continuous forest, clumped trees within the fragmented forest showed increased biparental inbreeding and reduced pollen pool genetic diversity (tm=0.959, tm−ts=0.245,1/rpm=1.742) as a result of localized mating combined with spatial genetic structures. In contrast, the isolated trees had a higher selfing rate, but the pollen pool diversity was maintained (tm=0.801, tm−ts=0.022, and 1/rpm=15.63) due to frequent long-distance pollination. These results suggest that although pollen limitation following habitat fragmentation could result in negative genetic consequences, enhanced long-distance pollination across a fragmented landscape could partly compensate for this limitation depending on the degree of forest fragmentation.

Spatial analysis of forest fragments of the Rio da Prata subwatershed in Ibiraçu and Aracruz, ES, Brazil

The aim of this work was to map forest fragments in the Rio da Prata subwatershed, in Ibiraçu and Aracruz — ES, as well as to analyze the structure of the forest landscape by metric indexes and landscape ecology. Mapping was obtained by photo interpretation in a scale of 1:5,000. A hundred and sixty-four fragments were found, representing 40.69% of the Rio da Prata subwatershed total area. Very small fragments (<5 ha) were predominating in the subwatershed, totalizing 138 fragments. Therefore, the forest constitution in the subwatershed is mostly made up of fragments smaller than 5 ha, indicating an elevated degree of forest fragmentation.

Habitat loss, fragmentation and degradation effects on small mammals: Analysis with conditional inference tree statistical modelling

Anthropogenic habitat loss, fragmentation and degradation often co-occur in a landscape and their relative influence on a native animals’ health and survival can be difficult to determine. We examined the influence of these environmental variables on the estimated relative abundance of some small mammal species in a large area (∼2500km2) of southeastern Australia. Using the agile antechinus (Antechinus agilis) as a model, we also examined the association between these variables and three population performance indices, mass-size residuals (MSR; indexing fat reserves), the neutrophil/lymphocyte ratio (N:L; indexing physiological stress) and red blood cell counts (RBC; indexing regenerative anaemia). Study sites were in either highly disturbed and fragmented, or relatively undisturbed, continuous Eucalyptus forest.We generated conditional inference tree statistical models to identify the relative importance of up to 49 ecological variables in explaining variation in small mammal abundance and performance indices. Habitat loss was important in explaining small mammal abundance, as were the abundances of the same species in neighbouring study sites. The models also suggested that the habitat area required to support a ‘healthy’ population was greater in the larger species examined. Autocovariates of neighbouring site same-species abundances and habitat fragmentation were the next most important influences on small mammal relative abundance, implying that metapopulations may be important for population persistence, especially in bush rats (Rattus fuscipes). Habitat degradation, reflected in structural and floristic features, was less important, but explained some variance in relative abundances. For agile antechinus populations, time of year, degree of forest fragmentation and extent of native tree cover were important in explaining performance indices. Results indicated that habitat reduction per se was a significant threatening process for small mammals. Habitat loss requires at least the same research attention as that currently devoted to anthropogenic habitat fragmentation and degradation.

Response of Bird Populations To Long-Term Changes In Local Vegetation and Regional Forest Cover

We analyzed data from a woodland site for a 59-year period to determine whether changes in bird populations are related to changes in the diversity and relative abundance of woody plant species even when vegetation structure, degree of forest fragmentation in the surrounding landscape, and regional changes in bird populations are taken into account. Principal component analyses generated vegetation factors encompassing variables such as total basal area, shrub density, basal area of common tree species, and measures of tree and shrub species diversity. We also calculated a forest edge/forest area index based on GIS analysis of the landscape within 2 km of the study site. Poisson regression models revealed relationships between these covariates and population changes for 19 bird species and for seven groups of species characterized by similar migration strategies or habitat requirements. All groups of habitat specialists showed a positive relationship with the first vegetation factor, which indicates that they declined as total basal area and dominance of oaks and maples increased and as tree and shrub diversity decreased. This suggests that floristic diversity may be important for determining habitat quality. Bird species associated with the shrub layer and with hemlock stands showed positive relationships with the second vegetation factor, suggesting that the recent decline in eastern hemlocks (Tsuga canadensis) because of hemlock woolly adelgid (Adelges tsugae) had an adverse impact on these species. Forest migrants, shrub-layer specialists, long-distance migrants and permanent residents showed negative relationships with the forest edge/forest interior index, indicating that conservation efforts to protect bird communities should take the wider landscape into account. The strongest relationship for most species and species groups was with the first vegetation factor, which suggests that species composition and diversity of trees and shrubs may be especially important in determining abundance of many forest bird species.

Monte Carlo simulation of false change in the overlay of misregistered forest vector maps

When an overlay of vector maps is performed, positional errors can cause a considerable overestimation of land cover change. When historical forest maps are used, this error can be high. It seems logical that the amount of false change is influenced by the degree of fragmentation of the landscape. This paper simulates positional error by using a rubbersheet procedure. Unlike in other studies, this approach does not perform a linear shift of the original map, but induced a positional error, heterogeneous in space. The spatial pattern of forest cover was quantified by means of pattern metrics and the relation between false change and spatial pattern was analyzed using a stepwise regression procedure. The results show that, when the positional error is kept constant, landscapes with a different degree of forest fragmentation contain diverging amounts of false change. False change was positively correlated with the mean nearest neighbour distance between forest fragments, the total forested area and the number of forest patches present. The results of this study also indicate that a coregistration with an RMSE inferior to 30 m is a real prerequisite in order to study change in a highly fragmented forest cover.

Landscape-scale Edge Effect in Predation Risk in Forest-farmland Mosaics of Central Europe

Avian nest predation is known to increase with the degree of forest fragmentation. A common explanation is that farmland allows for high densities of generalist predators, and predators penetrating into the forest cause higher nest losses at forest-farmland edges than in forest interiors. In contrast to numerous patch-level studies of forest edge effects conducted earlier, we broadened the spatial extent to the landscape. We tested the hypothesis of increased predation near farmland over distances of >4 km from forest–farmland edges into forest interiors in five mountain ranges in Germany, using artificial ground nests. We considered two landscape settings: (1) Transitions between a forest matrix and a farmland matrix, and (2) farmland patches within a forest matrix. Nest losses were not significantly higher in vicinity to a farmland matrix, but proximity to a pasture within the forest matrix strongly increased predation risk. We speculate that these differences resulted from landscape geometry. Farmland patches and matrix alike are highly attractive to generalist predators, and are regularly visited by red foxes from the forest. Predators that traverse the forest and take prey along the way, will cause a concentration of predation risk towards a patch (pasture), but not towards an adjacent matrix (farming lowlands), of feeding habitat. Contrary to previous evidence that edge effects in nest predation level off after 50 m, nest fate was related to distance to pastures across the entire study extent of 4.1 km. Our results suggest that landscape context and predator mobility may greatly affect spatial predation patterns.

FOREST COVER–RAINFALL RELATIONSHIPS IN A BIODIVERSITY HOTSPOT: THE ATLANTIC FOREST OF BRAZIL

It is now generally accepted that the relationship between vegetation and climate is dynamic: vegetation is influenced by climate, but feedbacks between terrestrial ecosystems and the atmosphere mean that vegetation also affects climate. From this it follows that land-use changes may have climatic consequences. Specifically, it is widely believed that forest clearance may inhibit rainfall. Although models often support this view, this is not universally the case, and empirical evidence is scarce. We have compiled a database of forest cover and precipitation for the state of Sao Paulo, which lies within the diverse and highly endangered Atlantic forest region of Brazil. We do not find a strong relationship between forest cover and total rainfall, which appears to be influenced primarily by factors such as distance to the coast; but significant positive relationships between tree cover and the number of rain days consistently emerge. The degree of forest fragmentation seems to influence this relationship, w...

Estimating fragmentation effects on simulated forest net primary productivity derived from satellite imagery

Conversion of native forests to agriculture and urban land leads to fragmentation of forested landscapes with significant consequences for habitat conservation and forest productivity. When quantifying land-cover patterns from airborne or spaceborne sensors, the interconnectedness of fragmented landscapes may vary depending on the spatial resolution of the sensor and the extent at which the landscape is being observed. This scale dependence can significantly affect calculation of remote sensing vegetation indices, such as the Normalized Difference Vegetation Index (NDVI) and its subsequent use to predict biophysical parameters such as the fraction of photosynthetically active radiation intercepted by forest canopies (fPAR). This means that simulated above-ground net primary productivity (NPPA) using canopy radiation interception models such as 3-PG (Physiological Principles for Predicting Growth), coupled with remote sensing observations, can yield different results in fragmented landscapes depending on the spatial resolution of the remotely sensed data.We compared the amount of forest fragmentation in 1 km SPOT-4 VEGETATION pixels using a simultaneously acquired 20 m SPOT-4 multispectral (XS) image. We then predicted NPPA for New Zealand native forest ecosystems using the 3-PG model with satellite-derived estimates of the fPAR obtained from the SPOT-4 VEGETATION sensor, using NDVI values with and without correction for fragmentation. We examined three methods to correct for sub-pixel fragmentation effects on NPPA. These included: (1) a simple conversion between the broad 1 km scale NDVI values and the XS NDVI values; (2) utilization of contextural information from XS NDVI pixels to derive a single coefficient to adjust the 1 km NDVI values; and (3) calculation of the degree of fragmentation within each VEGETATION 1 km pixel and reduce NDVI by an empirically derived amount based on the proportional areal coverage of forest in each pixel. Our results indicate that predicted NPPA derived from uncorrected 1 km VEGETATION pixels was significantly higher than estimates using adjusted NDVI values; all three methods reduced the predicted NPPA. In areas of the landscape with a large degree of forest fragmentation (such as forest boundaries) predictions of NPPA indicate that the fragmentation effect has implications for spatially extensive estimates of carbon uptake by forests.