Amur tigers and leopards returning to China: direct evidence and a landscape conservation plan

Context

The Amur tiger and leopard, once roaming over the Eurasian continent, are now endangered and confined to the Sikhote-Alin Mountains, Russia—a landscape that has been increasingly fragmented due to human activities. The ultimate fate of these big cats depends on whether they can resettle in their previous main historical range in NE China. Recent sightings of these animals along the China–Russia border have aroused new hope, but direct evidence is lacking.

Objectives

The main objectives of our study were (1) to determine the abundance and spatiotemporal patterns of tigers, leopards, and primary prey; (2) to investigate factors influencing the resettlement of the two big cats; and (3) to propose a landscape-scale conservation plan to secure the long-term sustainability of the Amur tiger and leopard.

Methods

We monitored the two felids, their prey, and human activities, with 380 camera-trap stations, for a total of 175,127 trap days and over an area of 6000 km² in NE China. We used the constraint line method to characterize cattle grazing and human influences on tigers, leopards, and their prey species.

Results

Our results show that, unexpectedly, at least 26 tigers and 42 leopards are present within China, which are confined primarily to a narrow area along the border with Russia. We have further identified that cattle grazing and human disturbances are the key hurdles to the dispersal of the tigers and leopards farther into China where suitable habitat is potentially available.

Conclusions

Amur tigers and leopards are returning to China, indeed, but their long-term resettlement is not likely without active and timely conservation efforts on landscape and regional scales. To overcome the hurdles to the resettlement of tigers and leopards in China, we propose a “Tiger and Leopard Resettlement Program” that will engage the government, local communities, and researchers, so that the long-term sustainability of the Amur tigers and leopards can be ensured.

     

Differentiating anthropogenic modification and precipitation-driven change on vegetation productivity on the Mongolian Plateau

Context

The Mongolian Plateau, comprising Inner Mongolia, China (IM) and Mongolia (MG) is undergoing consistent warming and accelerated land cover/land use change. Extensive modifications of water-limited regions can alter ecosystem function and processes; hence, it is important to differentiate the impacts of human activities and precipitation dynamics on vegetation productivity.

Objectives

This study distinguished between human-induced and precipitation-driven changes in vegetation cover on the plateau across biome, vegetation type and administrative divisions.

Methods

Non-parametric trend tests were applied to the time series of vegetation indices (VI) derived from MODIS and AVHRR and precipitation from TRMM and MERRA reanalysis data. VI residuals adjusted for rainfall were obtained from the regression between growing season maximum VI and monthly accumulated rainfall (June–August) and were used to detect human-induced trends in vegetation productivity during 1981–2010. The total livestock and population density trends were identified and then used to explain the VI residual trends.

Results

The slope of precipitation-adjusted EVI and EVI2 residuals were negatively correlated to total livestock density (R² = 0.59 and 0.16, p < 0.05) in MG and positively correlated with total population density (R² = 0.31, p < 0.05) in IM. The slope of precipitation-adjusted EVI and EVI2 residuals were also negatively correlated with goat density (R² = 0.59 and 0.19, p < 0.05) and sheep density in MG (R² = 0.59 and 0.13, p < 0.05) but not in IM.

Conclusions

Some administrative subdivisions in IM and MG showed decreasing trends in VI residuals. These trends could be attributed to increasing livestock or population density and changes in livestock herd composition. Other subdivisions showed increasing trends residuals, suggesting that the vegetation cover increase could be attributed to conservation efforts.

     

Integrating models across temporal and spatial scales to simulate landscape patterns and dynamics in mountain pasture-woodlands

Context

Pasture-woodlands are semi-natural landscapes that result from the combined influences of climate, management, and intrinsic vegetation dynamics. These landscapes are sensitive to future changes in land use and climate, but our ability to predict the impact on ecosystem service provisioning is limited due to the disparate scales in time and space that govern their dynamics.

Objectives

To develop a process-based model to simulate pasture-woodland landscapes and the provisioning of ecosystem services (i.e., livestock forage, woody biomass and landscape heterogeneity).

Methods

We modified a dynamic forest landscape model to simulate pasture-woodland landscapes in Switzerland. This involved including an annual herbaceous layer, selective grazing from cattle, and interactions between grazing and tree recruitment. Results were evaluated within a particular pasture, and then the model was used to simulate regional vegetation patterns and livestock suitability for a ~198,000 ha landscape in the Jura Vaudois region.

Results

The proportion of vegetation cover types at the pasture level (i.e., open, semi-open and closed forests) was well represented, but the spatial distribution of trees was only broadly similar. The entire Jura Vaudois region was simulated to be highly suitable for livestock, with only a small proportion being unsuitable due to steep slopes and high tree cover. High and low elevation pastures were equally suitable for livestock, as lower forage production at higher elevations was compensated by reduced tree cover.

Conclusions

The modified model is valuable for assessing landscape to regional patterns in vegetation and livestock, and offers a platform to evaluate how climate and management impact ecosystem services.

     

Fire legacies impact conifer regeneration across environmental gradients in the U.S. northern Rockies

Context

An increase in the incidence of large wildfires worldwide has prompted concerns about the resilience of forest ecosystems, particularly in the western U.S., where recent changes are linked with climate warming and 20th-century land management practices.

Objectives

To study forest resilience to recent wildfires, we examined relationships among fire legacies, landscape features, ecological conditions, and patterns of post-fire conifer regeneration.

Methods

We quantified regeneration across 182 sites in 21 recent large fires in dry mixed-conifer forests of the U.S. northern Rockies. We used logistic and negative binomial regression to predict the probability of establishment and abundance of conifers 5–13 years post-fire.

Results

Seedling densities varied widely across all sites (0–127,500 seedlings ha^?1) and were best explained by variability in distance to live seed sources (β = ?0.014, p = 0.002) and pre-fire tree basal area (β = 0.072, p = 0.008). Beyond 95 m from the nearest live seed source, the probability of seedling establishment was low. Across all the fires we studied, 75 % of the burned area with high tree mortality was within this 95-m threshold, suggesting the presence of live seed trees to facilitate natural regeneration.  

Conclusions

Combined with the mix of species present within the burn mosaic, dry mixed-conifer forests will be resilient to large fires across our study region, provided that seedlings survive, fire do not become more frequent, high-severity patches do not get significantly larger, and post-fire climate conditions remain suitable for seedling establishment and survival.

     

The heterogeneity of wooded-agricultural landscape mosaics influences woodland bird community assemblages

Context

Landscape heterogeneity (the composition and configuration of different landcover types) plays a key role in shaping woodland bird assemblages in wooded-agricultural mosaics. Understanding how species respond to landscape factors could contribute to preventing further decline of woodland bird populations.

Objective

To investigate how woodland birds with different species traits respond to landscape heterogeneity, and to identify whether specific landcover types are important for maintaining diverse populations in wooded-agricultural environments.

Methods

Birds were sampled from woodlands in 58 2 × 2 km tetrads across southern Britain. Landscape heterogeneity was quantified for each tetrad. Bird assemblage response was determined using redundancy analysis combined with variation partitioning and response trait analyses.

Results

For woodland bird assemblages, the independent explanatory importance of landscape composition and landscape configuration variables were closely interrelated. When considered simultaneously during variation partitioning, the community response was better represented by compositional variables. Different species responded to different landscape features and this could be explained by traits relating to woodland association, foraging strata and nest location. Ubiquitous, generalist species, many of which were hole-nesters or ground foragers, correlated positively with urban landcover while specialists of broadleaved woodland avoided landscapes containing urban areas. Species typical of coniferous woodland correlated with large conifer plantations.

Conclusions

At the 2 × 2 km scale, there was evidence that the availability of resources provided by proximate landcover types was highly important for shaping woodland bird assemblages. Further research to disentangle the effects of composition and configuration at different spatial scales is advocated.

     

Spatial and temporal variability of fragmentation effects in a long term,eucalypt forest fragmentation experiment

Context

Although forest fragmentation is generally thought to impact tree growth and mortality negatively, recent work suggests some forests are resilient. Experimental forests provide an opportunity to examine the timing and extent of forest tree resilience to disturbance from fragmentation.

Objectives

We used the Wog Wog Habitat Fragmentation Experiment in southeastern Australia to test Eucalyptus growth and survivorship responses to forest fragmentation over a 26 year period.

Methods

We measured 2418 tree diameters and used spline-regression techniques to examine non-monotonic fragmentation effect over two time periods.

Results

Over the first 4 years after fragmentation, individual eucalypt tree growth was greater than in continuous forest for large trees and mortality rates were higher only within 10 m of edges. Over the following 22 years only the effects on tree growth remained and on average all fragments rebounded so that their biomass and mortality rates were equivalent to continuous forest. Importantly non-monotonic patterns were observed in growth and mortality with respect to area and distance from edge in both study periods, demonstrating that fragmentation impacts on trees can be strong in localized areas (greatest in 3 ha fragments and 0–30 m edges) and over short time periods.

Conclusions

Dry-sclerophyll eucalypt forests join the set of forest types that display resilient growth dynamics post fragmentation. Moreover, persistent non-monotonic impacts on tree growth with respect to tree size, fragment area, and fragment distance from edge, highlighting landscape fragmentation as a driver of habitat heterogeneity within remnant forest fragments.

     

Multi-scale prediction of landscape resistance for tiger dispersal in central India

Context

Connectivity models for animal movement frequently use resistance surfaces, but rarely incorporate actual movement data and multiple scale drivers of landscape resistance.

Objectives

Using GPS data, we developed a multi-scale model of landscape resistance for tiger (Panthera tigris) dispersal in central India and evaluated the performance, interpretation and predictions against single scale models.

Methods

Six dispersing tiger paths were subjected to a path level analysis with conditional logistic regression to parameterize a resistance surface. We evaluated for 21 scales of available habitat and selected the best scale for each variable. We derived a scale-optimized multivariate path selection function and predicted landscape resistance across the landscape.

Results

The tigers preferred to move along areas with forest cover at relatively high elevations along the ridges with rugged topography at broad scale, while avoiding areas with agriculture-village matrix at fine scale. We found that the scale that was most supported by Akaike’s information criterion was not always the scale that maximized the magnitude (effect size) of the relationship. Further, the multi-scale optimized model differed substantially from the single scale models in terms of variable importance, magnitude of coefficients and predictions of connectivity.

Conclusions

Our results demonstrate that the variables in landscape resistance models produce markedly different predictions of population connectivity depending on the scales of analyses and interpretation. Thus, scale optimization in parameterization is critical for appropriate inferences and sound management strategies.

     

Policy impacts on regulating ecosystem services: looking at the implications of 60 years of landscape change on soil erosion prevention in a Mediterranean silvo-pastoral system

Context

Policy decisions form a major driver of land use change, with important implications for socially and environmentally susceptible regions. It is well known that there can be major unintended consequences, especially where policies are not tailored to regionally specific contexts.

Objectives

In this paper we assess the implications of 60 years of agricultural policies on soil erosion prevention (SEP) by vegetation, an essential regulating ecosystem service in Mediterranean Europe.

Methods

To assess these implications we produced and analysed a time series of land cover/use and environmental conditions datasets (from 1951 to 2012) in relation to changing agricultural policies for a specific region in the southern Portugal. A set of indicators related to SEP allowed us to identify that land use intensification as increased soil erosion in the last 60 years.

Results

Particularly in the last 35 years, as a consequence of headage payments for cattle, the agricultural policy had a significant effect in the density and renewal of the tree cover, resulting in drastic effects for the provision of the SEP service. These are more significant after 1986, coinciding with the implementation of several Common Agricultural Policy instruments focused on increasing the modernization and productivity capacity of farm systems.

Conclusions

The results show some unintended effects of agricultural policy mechanisms on ecosystem service provision and highlight the need for context-based policies, tailored to the environmental constrains and potentials of each region.

     

Spatial heterogeneity of subsurface soil texture drives landscape-scale patterns of woody patches in a subtropical savanna

Context

In the Rio Grande Plains of southern Texas, subtropical savanna vegetation is characterized by a two-phase pattern consisting of discrete woody patches embedded within a C₄ grassland matrix. Prior trench transect studies have suggested that, on upland portions of the landscape, large woody patches (groves) occur on non-argillic inclusions, while small woody patches (clusters) are dispersed among herbaceous vegetation where the argillic horizon is present.

Objective

To test whether spatial heterogeneity of subsurface soil texture drives the landscape-scale pattern of woody patches in this subtropical savanna.

Methods

Landscape-scale spatial patterns of soil texture were quantified by taking spatially-specific soil samples to a depth of 1.2 m in a 160 m × 100 m plot. Kriged maps of soil texture were developed, and the locations of non-argillic inclusions were mapped.

Results

Visual comparison of kriged maps of soil texture to a high resolution aerial photograph of the study area revealed that groves were present exclusively where the non-argillic inclusions were present. This clear visual relationship was further supported by positive correlations between soil sand concentration in the lower soil layers and total fine root biomass which mapped the locations of groves.

Conclusions

Subsurface non-argillic inclusions may favor the establishment and persistence of groves by enabling root penetration deeper into the profile, providing greater access to water and nutrients that are less accessible on those portions of the landscape where the argillic horizon is present, thereby regulating the distribution of grove vegetation and structuring the evolution of this landscape.

     

Influences of scale on bat habitat relationships in a forested landscape in Nicaragua

Context

Scale dependence of bat habitat selection is poorly known with few studies evaluating relationships among landscape metrics such as class versus landscape, or metrics that measure composition or configuration. This knowledge can inform conservation approaches to mitigate habitat loss and fragmentation.

Objectives

We evaluated scale dependence of habitat associations and scaling patterns of landscape metrics in relation to bat occurrence or capture rate in forests of southwestern Nicaragua.

Methods

We captured 1537 bats at 35 locations and measured landscape and class metrics across 10 spatial scales (100–1000 m) surrounding capture locations. We conducted univariate scaling across the 10 scales and identified scales and variables most related to bat occurrence or capture rate.

Results

Edge and patch density, at both landscape and class levels, were the most important variables across species. Feeding guilds varied in their response to metrics. Certain landscape and configuration metrics were most influential at fine (100 m) and/or broad (1000 m) spatial scales while most class and composition metrics were influential at intermediate scales.

Conclusions

These results provide insight into the scale dependence of habitat associations of bat species and the influence of fine and broad scales on habitat associations. The effects of scale, examined in our study and others from fine (100 m) to broad (5 km) indicate habitat relationships for bats may be more informative at larger scales. Our results suggest there could be general differences in scale relationships for different groups of landscape metrics, which deserves further evaluation in other taxonomic groups.

     

Forest recovery since 1860 in a Mediterranean region: drivers and implications for land use and land cover spatial distribution

Context

Land use and land cover (LULC) change is a major part of environmental change. Understanding its long-term causes is a major issue in landscape ecology.

Objectives

Our aim was to characterise LULC transitions since 1860 and assess the respective and changing effects of biophysical and socioeconomic drivers on forest, arable land and pasture in 1860, 1958 and 2010, and of biophysical, socioeconomic and distance from pre-existing forest on forest recovery for the two time intervals.

Methods

We assessed LULC transitions by superimposing 1860, 1958 and 2010 LULCs using a regular grid of 1 × 1 km points, in a French Mediterranean landscape (195,413 ha). We tested the effects of drivers using logistic regressions, and quantified pure and joint effects by deviance partitioning.

Results

Over the whole period, the three main LULCs were spatially structured according to land accessibility and soil productivity. LULC was driven more by socioeconomic than biophysical drivers in 1860, but the pattern was reversed in 2010. A widespread forest recovery mainly occurred on steeper slopes, far from houses and close to pre-existing forest, due to traditional practice abandonment. Forest recovery was better explained by biophysical than by socioeconomic drivers and was more dependent on distance from pre-existing forest between 1958 and 2010.

Conclusions

Our results showed a shift in drivers of LULC and forest recovery over the last 150 years. Contrary to temperate regions, the set-aside of agricultural practices on difficult land has strengthened the link between biophysical drivers and LULC distribution over the last 150 years.

     

Climate change amplifies the interactions between wind and bark beetle disturbances in forest landscapes

Context

Growing evidence suggests that climate change could substantially alter forest disturbances. Interactions between individual disturbance agents are a major component of disturbance regimes, yet how interactions contribute to their climate sensitivity remains largely unknown.

Objectives

Here, our aim was to assess the climate sensitivity of disturbance interactions, focusing on wind and bark beetle disturbances.

Methods

We developed a process-based model of bark beetle disturbance, integrated into the dynamic forest landscape model iLand (already including a detailed model of wind disturbance). We evaluated the integrated model against observations from three wind events and a subsequent bark beetle outbreak, affecting 530.2 ha (3.8 %) of a mountain forest landscape in Austria between 2007 and 2014. Subsequently, we conducted a factorial experiment determining the effect of changes in climate variables on the area disturbed by wind and bark beetles separately and in combination.

Results

iLand was well able to reproduce observations with regard to area, temporal sequence, and spatial pattern of disturbance. The observed disturbance dynamics was strongly driven by interactions, with 64.3 % of the area disturbed attributed to interaction effects. A +4 °C warming increased the disturbed area by +264.7 % and the area-weighted mean patch size by +1794.3 %. Interactions were found to have a ten times higher sensitivity to temperature changes than main effects, considerably amplifying the climate sensitivity of the disturbance regime.

Conclusions

Disturbance interactions are a key component of the forest disturbance regime. Neglecting interaction effects can lead to a substantial underestimation of the climate change sensitivity of disturbance regimes.

     

Land cover influences boreal-forest fire responses to climate change: geospatial analysis of historical records from Alaska

Context

Wildfire activity in boreal forests is projected to increase dramatically in response to anthropogenic climate change. By altering the spatial arrangement of fuels, land-cover configuration may interact with climate change to influence fire-regime dynamics at landscape and regional scales.

Objectives

We evaluate how land cover interacts with weather conditions to influence boreal-forest burning from 2012 to 2014 in Alaska.

Methods

Using geospatial fire and land-cover data, we quantify relationships between area burned and land cover, and test whether observed patterns of burning differ from random under varying weather conditions and fire sizes.

Results

Mean summer moisture index was correlated with annual area burned (ρ = ?0.78, p < 0.01), the total number of fires (ρ = ?0.68, p = 0.01), and the number of large fires (>500 km²; ρ = ?0.58, p = 0.04). Area burned was related positively to percent cover of coniferous forest and woody wetlands, and negatively to percent cover of shrub scrub, dwarf scrub, and open water and barren areas. Fires preferentially burned coniferous forest, which represented 50.1 % of the area burned in warmer/drier summers and 40.3 % of area burned in cooler/wetter summers, compared to the 34.5 % (±4.2 %) expected by random selection of land-cover classes. Overall vegetation tended to burn more similarly to random in warmer/drier than cooler/wetter years.

Conclusions

Land cover exerted greater influences on boreal fire regimes when weather conditions were less favorable for forest burning. Reliable projections of boreal fire-regime change thus require consideration of the interactions between climate and land cover, as well as feedbacks from land-cover change.

     

Tropical forest regeneration following land abandonment is driven by primary rainforest distribution in an old pastoral region

Context

Tropical forest regeneration is increasingly prominent as agro-pastoral lands are abandoned. Regeneration is characterised as favouring ‘marginal’ lands; however, observations of its drivers are often coarse or simple, leaving doubt as to spatial dynamics and causation.

Objectives

We quantified the spatial dynamics of forest regeneration relative to marginality and remnant forest cover in a 3000 km² pastoral region in northern tropical Australia.

Methods

Classification and regression trees related the extent and distribution of regeneration to soil agricultural potential, land-cover history, terrain slope, distance to primary forest, and primary forest fragment size, as defined by aerial photography.

Results

Secondary forest extent and distribution overwhelmingly reflect the proximity and size of primary forest fragments. Some 85 % of secondary forest area occurs <1 km of primary forest, and 86 % of secondary forest patches >50 ha are <400 m from primary forest and coincident with historic primary forest fragments. Where primary forest fragments are >8.5 ha, secondary forest area declines less rapidly with increasing distance from primary forest up to 1.5 km. Marginality inferred by soil potential and slope had no bearing on regeneration, except at the coarsest of spatial scales where regeneration is a proxy for primary forest cover.

Conclusion

Findings underline the need to conserve even modest rainforest patches as propagule reservoirs enabling regeneration. Marginality per se may have a limited role in regeneration. As most secondary forest was an extension of primary forest, its unique conservation value relative to that of primary forest may likewise merit reconsideration.

     

A network model framework for prioritizing wetland conservation in the Great Plains

Context

Playa wetlands are the primary habitat for numerous wetland-dependent species in the Southern Great Plains of North America. Plant and wildlife populations that inhabit these wetlands are reciprocally linked through the dispersal of individuals, propagules and ultimately genes among local populations.

Objective

To develop and implement a framework using network models for conceptualizing, representing and analyzing potential biological flows among 48,981 spatially discrete playa wetlands in the Southern Great Plains.

Methods

We examined changes in connectivity patterns and assessed the relative importance of wetlands to maintaining these patterns by targeting wetlands for removal based on network centrality metrics weighted by estimates of habitat quality and probability of inundation.

Results

We identified several distinct, broad-scale sub networks and phase transitions among playa wetlands in the Southern Plains. In particular, for organisms that can disperse >2 km a dense and expansive wetland sub network emerges in the Southern High Plains. This network was characterized by localized, densely connected wetland clusters at link distances (h) >2 km but <5 km and was most sensitive to changes in wetland availability (p) and configuration when h = 4 km, and p = 0.2–0.4. It transitioned to a single, large connected wetland system at broader spatial scales even when the proportion of inundated wetland was relatively low (p = 0.2).

Conclusions

Our findings suggest that redundancy in the potential for broad and fine-scale movements insulates this system from damage and facilitates system-wide connectivity among populations with different dispersal capacities.

     

Using operating area size and adjacency constraints to mitigate the effects of harvesting activities on boreal caribou habitat

Context

Sustained timber harvesting conflicts with the long-term viability of boreal caribou (Rangifer tarandus caribou) populations. The spatial arrangement of harvest blocks in the landscape could mitigate the impact of logging on caribou populations. For the forest industry, however, these measures represent constraints that reduce the annual allowable cut (AAC).

Objective

Estimate the long-term impacts of spatial constraints to harvesting, applied alone or in combination, on AAC and boreal caribou populations.

Methods

We divided a 30,000 km² region into 20 harvest block sizes varying from 50 to 1000 km², and modeled the implementation of spatially explicit harvest schedule plans in combination with wildfire and caribou population dynamics. We then evaluated the probability of persistence of boreal caribou populations.

Results

The probability of maintaining an AAC target declined with increasing target AAC, increasing size of operating area, and increasing adjacency constraints. In contrast, the probability of maintaining caribou populations declined with increasing AAC, decreasing size of operating areas, and decreasing adjacency constraints. An increase in operating area size from 50 to 300 km² produced a considerable gain in AAC for all adjacency constraints.

Conclusions

Because adjacency constraints led only to a small increase in the probability of maintaining caribou populations, we recommend adopting less constraining landscape management actions, such as a 70-year period between two consecutive harvests in the same ~300-km² operating area.

     

Exploring dispersal barriers using landscape genetic resistance modelling in scarlet macaws of the Peruvian Amazon

Context

Dispersal is essential for species persistence and landscape genetic studies are valuable tools for identifying potential barriers to dispersal. Macaws have been studied for decades in their natural habitat, but we still have no knowledge of how natural landscape features influence their dispersal.

Objectives

We tested for correlations between landscape resistance models and the current population genetic structure of macaws in continuous rainforest to explore natural barriers to their dispersal.

Methods

We studied scarlet macaws (Ara macao) over a 13,000 km² area of continuous primary Amazon rainforest in south-eastern Peru. Using remote sensing imagery from the Carnegie Airborne Observatory, we constructed landscape resistance surfaces in CIRCUITSCAPE based on elevation, canopy height and above-ground carbon distribution. We then used individual- and population-level genetic analyses to examine which landscape features influenced gene flow (genetic distance between individuals and populations).

Results

Across the lowland rainforest we found limited population genetic differentiation. However, a population from an intermountain valley of the Andes (Candamo) showed detectable genetic differentiation from two other populations (Tambopata) located 20–60 km away (F _ST = 0.008, P = 0.001–0.003). Landscape resistance models revealed that genetic distance between individuals was significantly positively related to elevation.

Conclusions

Our landscape resistance analysis suggests that mountain ridges between Candamo and Tambopata may limit gene flow in scarlet macaws. These results serve as baseline data for continued landscape studies of parrots, and will be useful for understanding the impacts of anthropogenic dispersal barriers in the future.

     

The influence of landscape relative to site and patch variables on primate distributions in the Colombian Llanos

Context

Primates are an important component of biodiversity in tropical regions. However, many studies on the effects of habitat change on primates ignore the relative influence of landscape composition and configuration.

Objectives

This study addresses the question: how important are landscape-scale forest area and composition relative to patch-scale (1–1080 ha) and site-scale (transect of 1 km) habitat variables for the occupancy and abundance of four primate species in the Colombian Llanos.

Methods

Using a randomly stratified survey design, 81 fragments were surveyed for primate occupancy and abundance. We used zero-inflated models to test the relative influence of landscape-scale, patch-scale and site-scale variables on occupancy and abundance for each species. A 95% confidence set of models was constructed using the cumulative Akaike weight for each model and the relative importance of each set of variables calculated for each primate species.

Results

Occupancy was determined by a combination of site-scale, patch-scale and landscape-scale variables but this varied substantially among the primate species.

Conclusion

Our study highlights the importance of managing primates at a range of scales that considers the relative importance of site-, patch- and landscape-scale variables.

     

Regional patterns of nectar availability in subtropical eastern Australia

Context

There are few detailed data for short-term (≤?monthly) fluctuations in flowering and nectar availability at relatively large spatial scales. Such information is critical for understanding the governors of variation in flowering and for the management of floral resources assisting the persistence of nectar consumers in landscapes.

Objectives

To obtain monthly measurements of patterns of nectar availability in a 314,400 ha region, and to relate these patterns to potential environmental predictors.

Methods

Flowering was measured at 83 sites in natural vegetation and in eight domestic gardens in subtropical, eastern Australia. A nectar-availability index was developed was based on nectarivore visitation rates and plant-specific flowering patterns. Spatial–temporal patterns were related to environmental variables using boosted regression trees.

Results

The large between-year variation was due mostly to irregular flowering by several eucalypt species. There was a ‘lean season’ in the austral spring (August–September). Coastal vegetation was an important source of nectar for much of the year, including the lean season. Gardens produced prolific nectar throughout the year, peaking in August–October.

Conclusions

Nectar availability was most closely associated with primary productivity over the previous 12 months, average annual solar radiation, topographic wetness, and rainfall over the previous 6 months, although some relationships seemed counter-intuitive. There were large differences in nectar availabilities among broad vegetation types (especially rainforests vs. sclerophyllous forests), which partially accounted for the unintuitive results.