Effects Of Landscape Context Research Articles

Interacting effects of farming practice and landscape context on bumble bees

Organic farming has been suggested to counteract declines in farmland biodiversity, but comparisons to conventional farming have produced variable outcomes. To examine whether this is due to the landscape context farms are situated in and traits of the studied organisms, we surveyed bumble bees in cereal field borders and margins at 12 pairs of matched organic and conventional farms, with half the pairs located in heterogeneous farmland and the remaining in homogeneous plains. Species richness and abundance of bumble bees were significantly positively related to both organic farming and landscape heterogeneity. However, there was an interaction effect between farming practice and landscape context so that species richness and abundance were only significantly higher on organic farms in homogeneous landscapes. The higher abundance of bumble bees on organic farms was partly related to higher flower abundance on these sites. The effect of landscape context on bumble bee abundance was stronger for species with medium sized colonies than for those with smaller and larger colony sizes. These patterns may reflect that species with medium sized foraging ranges are most affected by fragmentation of foraging habitat, because colony size reflects the spatial scale at which bumble bees utilize resources. We conclude that both organic farming and landscape heterogeneity can be used to increase bumble bee species richness and abundance, but that organic farming has a larger effect in homogeneous landscapes and landscape heterogeneity a larger effect on conventional farms. The effects differed between species, suggesting that a single prescription to increase pollinator abundance may not be valid.

Multi-scale site and landscape effects on the vulnerable superb parrot of south-eastern Australia during the breeding season

The threatened superb parrot of south-eastern Australia exemplifies many of the challenges associated with research on wide-raging organisms which live ‘off-reserve’. Challenges include that most land is privately owned and that landscape use by such organisms does not always conform to traditional schematic and categorical landscape/fragmentation models. A multi-scale approach for embedding the detection of site-level and landscape context effects into landscape sampling design and subsequent statistical analysis is presented. The superb parrot was found scattered at varying densities throughout the agricultural landscapes of the South-West Slopes, much of which was privately owned. It responded to site-level variables and the surrounding landscape context. Overall, the superb parrot favoured lower elevation sites which were dominated by scattered, open woodlands, where Blakely’s red gum was a significant component. Mean plant productivity within 2 km, levels of woody tree cover within 3 km and (with caveats) length of roads within 3 km had a major effect on site-level response, indicating conditions in the surrounding local landscape are important to the superb parrot. This multi-scale response requires a multi-scale conservation and restoration strategy. The importance of open tree cover and amounts of Blakely’s red gum are a matter for concern, due to a general lack of tree regeneration and the particular susceptibility of Blakely’s red gum to dieback. The scattered trees in the agricultural matrix were important to the superb parrot, suggesting that it views these landscapes as a continuum of usable habitat. Strategies for restoration of larger habitat remnants should also include regeneration of trees in scattered pattern in the wider landscape, and Blakely’s red gum should be part of any strategy along with other key species such as yellow and white box. The landscape sampling approach successfully addressed the challenges of whole-landscape research. This highlights the value of ‘off-reserve’ studies across whole landscapes.

Forest fragmentation and matrix effects: the matrix does matter

Forest fragmentation and matrix effects: the matrix <i>does</i> matter

Effect of landscape context on anuran communities in breeding ponds in the National Capital Region, Canada

Land cover change, predominantly habitat conversion to agricultural use and urbanization, has recently been recognized as the primary cause of biodiversity loss in terrestrial ecosystems. We evaluated the relative effects of urban and agricultural landscapes on anuran species richness and the abundance of six anuran species found at breeding ponds in and around the cities of Ottawa, Ontario and Gatineau, Quebec. We performed six call surveys at 29 permanent focal ponds surrounded by one of three landscape contexts: primarily urban, primarily agricultural, and primarily forested. We also measured three local pond variables to control for the effects of local habitat quality in our analyses. We found that anuran species richness was significantly lower in breeding ponds in urban landscapes compared to forested and agricultural landscapes, which exhibited no significant difference in species richness. The abundances of individual anuran species were also consistently lower in urban landscapes for all species except one, which exhibited no response to landscape type. Three species had their highest abundances in ponds in forested landscapes, whereas two species had their highest abundances in ponds in agricultural landscapes. We conclude that ponds embedded in urban landscapes support lower biodiversity than ponds in agricultural settings. We suggest that landscapes composed of a mosaic of forest and open habitats surrounding wetlands would hold the highest biodiversity of these species.

Organic versus conventional arable farming systems: Functional grouping helps understand staphylinid response

The response of different feeding groups of staphylinid beetles to organic management, distance to perennial boundary and landscape context was studied in 42 paired organic and conventional winter wheat fields. Management effects were found to strongly depend on feeding group. While the activity-density of predators was higher in the conventional fields, both activity-density and species richness of detritivores were higher in the organic fields. Activity-density and species richness of detritivores were positively correlated to crop yield in the conventional but not in the organic fields. Unexpectedly, species richness as high as in the less productive organic fields was thus found in intensified conventional systems. No significant effects of landscape context could be found on activity-density or species richness of the different feeding groups. More species were caught near the field edge than in the middle, showing the importance of spill-over from field boundaries into arable crops for diversity. In conclusion, separation of species into feeding groups revealed patterns that have not been shown before. Decomposer diversity (but not that of predators and fungivores) was higher in organic fields, but reached similar levels in high-yielding conventional fields. Thus resource quality (purely organic or organic/synthetic fertiliser) and quantity appear to play a major role for this functional group.

Interacting effects of landscape context and habitat quality on flower visiting insects in agricultural landscapes

Summary Landscape context and habitat quality may have pronounced effects on the diversity of flower visiting insects. We investigated whether the effects of landscape context and habitat quality on flower visiting insects interact in agricultural landscapes in the Netherlands. Landscape context was expressed as the area of semi-natural habitats or the density of linear landscape features, and was quantified at spatial scales ranging from 250 to 2000 m. Habitat quality was determined as flower abundance. Species richness and abundance of hoverflies and bees were determined along 16 stream banks experiencing similar environmental conditions but situated in areas with contrasting landscape context. Only flower abundance and the area of semi-natural habitats within 500–1000 m were significantly related to species richness of hoverflies and bees and these factors had interacting effects on both species groups. Our results suggest that the regional area of semi-natural habitats had a positive effect on hoverfly species richness when flower abundance was relatively high, but not when flower abundance was low. Moreover, flower abundance had positive effects on hoverfly species richness only in areas with relatively many semi-natural habitats. Contrastingly, flower abundance had a more positive effect on bee species richness in landscapes with few semi-natural habitats compared to landscapes with more semi-natural habitats. Our results suggest that the importance of landscape context for the species richness of flower visiting insects depends upon the quality of the habitat patches.

Effects of progressive catchment harvesting on stream invertebrates in two contrasting regions of New Zealand's North Island

We examined changes in stream habitat and benthic invertebrate communities in two contrasting regions of New Zealand’s North Island over a 9–10-year period as pine forest harvesting progressed through the catchments. Increases in streambed cover by sand/silt, wood and macrophytes were recorded as harvesting progressed, but little change was observed in qualitative periphyton abundance. Despite similar high-level taxonomic structure of invertebrate communities between the two regions, differences in percentage and log-transformed abundance indicated an effect of landscape context that reflected different hydrologies and bed-substratum stabilities. Within regions, ordination plots indicated broadly distinct site clusters that persisted through time and reflected variations in stream size, substratum composition, periphyton abundance and degree of catchment harvesting. Generally, few of the invertebrate community metrics examined showed clear responses to progressive catchment or onsite harvesting relative to previous intra- and inter-annual variation. The most noticeable exceptions were percentage Ephemeroptera, Plecoptera and Trichoptera (excluding Hydroptilidae) abundance and percentage Elmidae abundance, which were negatively and positively correlated, respectively, with percentage catchment harvested. We identify three broad response categories to catchment harvesting that reflect subsidy–stress effects as logging progressed and discuss the relevance of these findings to potential pine forest harvesting effects in southern Australia.

Effects of landscape context on herbivory and parasitism at different spatial scales

Local community structure and interactions have been shown to depend partly on landscape context. In this paper we tested the hypothesis that the spatial scale experienced by an organism depends on its trophic level. We analyzed plant‐herbivore and herbivore‐parasitoid interactions in 15 agricultural landscapes differing in structural complexity using the rape pollen beetle (Meligethes aeneus), an important pest on oilseed rape (Brassica napus), and its parasitoids. In the very center of each landscape a patch of potted rape plants was placed in a grassy field margin strip for standardized measurement. Percent non‐crop area of landscapes was negatively related to plant damage caused by herbivory and positively to the herbivores’ larval mortality resulting from parasitism. In a geographic scale analysis, we quantified the structure of the 15 landscapes for eight circular sectors ranging from 0.5 to 6 km diameter. Correlations between parasitism and non‐crop areas as well as between herbivory and non‐crop area were strongest at a scale of 1.5 km, thereby not supporting the view that higher trophic levels experience the world at a larger spatial scale. However, the predictive power of non‐crop area changed only slightly for herbivory, but greatly with respect to parasitism as scales from 0.5 to 1.5 km and from 1.5 to 6 km diameter increased. Furthermore, the effect of non‐crop area tended to be stronger in parasitism than herbivory suggesting a greater effect of changes in landscape context on parasitoids. This is in support of the general idea that higher trophic levels should be more susceptible to disturbance.

Birds in North American Great Lakes coastal wet meadows: is landscape context important?

Landscape context can influence species richness, abundance, or probability of patch-use by birds. Little is known, however, about the effects of landscape context on birds in wetland-dominated landscapes. This lack of knowledge is alarming because many wetlands are threatened by development and other human impacts, while serving critical functions as migratory, breeding and foraging habitat. To address this lack of knowledge, we censused birds in North American Great Lakes coastal wet meadows located along the northern Lake Huron shoreline in Michigan (USA) during 1997 and 1998. Using a suite of multivariate techniques, we first accounted for effects of area and within-patch habitat characteristics before testing for effects of landscape context. Most bird variables were significantly related to landscape context, and two major patterns were apparent. First, avian species richness, abundance, and probability of patch-use by some species were higher for wet meadows located in complex contexts (adjacent to many patch types) compared to simpler contexts (adjacent to only one patch type). Second, these variables were higher for wet meadows located in wetland contexts compared to contexts that were terrestrial and road-impacted, dominated by open water habitats, or dominated by forested wetland habitats. Conservation plans for wetlands have focused on saving large wetlands and creating the vegetative habitat structure required by birds, but they should go further and explicitly consider the landscape context of wetlands as well. Specifically, wetlands located in complex and/or wetland contexts should have a higher conservation value than similar wetlands located in simpler, more terrestrial contexts.

SCALE-DEPENDENT EFFECTS OF LANDSCAPE CONTEXT ON THREE POLLINATOR GUILDS

Most ecological processes and interactions depend on scales much larger than a single habitat, and therefore it is important to link spatial patterns and ecological processes at a landscape scale. Here, we analyzed the effects of landscape context on the distribution of bees (Hymenoptera: Apoidea) at multiple spatial scales with respect to the following hypotheses: (1) Local abundance and diversity of bees increase with increasing proportion of the surrounding seminatural habitats. (2) Solitary wild bees, bumble bees, and honey bees respond to landscape context at different spatial scales. We selected 15 landscape sectors and determined the percentage of seminatural habitats and the diversity of habitat types at eight spatial scales (radius 250-3000 m) by field inspections and analyses of vegetation maps using two Geographic Information Systems. The percentage of semi- natural habitats varied between 1.4% and 28%. In the center of each landscape sector a patch of potted flowering plants (four perennial and two annual species) was placed in the same habitat type, a grassy field margin adjacent to cereal fields. In all, 865 wild bee individuals and 467 honey bees were observed and an additional 475 individuals were caught for species identification. Species richness and abundance of solitary wild bees showed a close positive correlation with the percentage of seminatural habitats at small scales up to 750 m, whereas bumble bees and honey bees did not respond to landscape context at these scales. In contrast, honey bees were correlated with landscape context at large scales. The densities of flower-visiting honey bees even increased with decreasing proportion of seminatural habitats at a radius of 3000 m. We are not aware of any empirical studies showing contrasting foraging patterns related to landscape context at different spatial scales. We conclude (1) that local landscape destruction affects solitary wild bees more than social bees, possibly changing mutualistic plant-pollinator and competitive wild bees- honey bees interactions and (2) that only analyses of multiple spatial scales may detect the importance of the landscape context for local pollinator communities.

EFFECTS OF FOREST FRAGMENTATION ON BIRD ASSEMBLAGES IN A NOVEL LANDSCAPE CONTEXT

We report findings of a large-scale study in a 100 000-ha subsection of the Tumut region in southern New South Wales, southeastern Australia. The study was designed to measure the effects of landscape context and habitat fragmentation on forest birds. The study region consisted of a forest mosaic characterized by different landscape contexts: large, continuous areas of native Eucalyptus forest, extensive stands of exotic softwood (radiata pine, Pinus radiata) plantation, and remnant patches of native Eucalyptus forest scattered throughout the extensive areas of radiata pine plantation. A set of 85 eucalypt remnants was randomly selected across several stratifying variables: four patch size classes (1-3 ha, 4-10 ha, 11-20 ha, and .20 ha), two isolation age classes (,20 years and .20 years since fragmentation), and five dominant eucalypt forest type classes. In addition to the 85 eucalypt remnants, a further 80 3-ha sites were selected for study: 40 in large, continuous areas of eucalypt forest and 40 in radiata pine stands. Point-interval counts of forest birds at the 165 sites were conducted in 1996 and 1997. Of 90 species recorded, 23.1 species (95% confidence interval, 22.0, 24.2 species), on average, were present in continuous eucalypt forest, 20.6 (19.5, 21.7) species in patch- shaped eucalypt remnants, 20.6 (19.5, 21.7) species in strip-shaped eucalypt remnants, and 16.7 (15.6, 17.8) species in radiata pine. Strong gradients in bird assemblages were found. These gradients were governed by a combination of landscape context, remnant size, and remnant shape effects, and, in the case of radiata pine sites, the extent of native forest surrounding the pine. These gradients could, in part, be explained by bird life history attributes such as foraging guild and nesting height. For example, birds more often detected in patch-shaped remnants were smaller, produced smaller clutches, were more likely to be migratory, and typically had cup nests or burrows. The results of our study showed that eucalypt fragments of all sizes and shapes have significant conservation value. This is because they contain many native species of birds, some of which are more abundant in fragments than they are in continuous eucalypt forests, and also because they increase native bird populations in nearby non-native pine plantations.

Effects of Forest Fragmentation on Bird Assemblages in a Novel Landscape Context

We report findings of a large-scale study in a 100 000-ha subsection of the Tumut region in southern New South Wales, southeastern Australia. The study was designed to measure the effects of landscape context and habitat fragmentation on forest birds. The study region consisted of a forest mosaic characterized by different landscape contexts: large, continuous areas of native Eucalyptus forest, extensive stands of exotic softwood (radiata pine, Pinus radiata) plantation, and remnant patches of native Eucalyptus forest scattered throughout the extensive areas of radiata pine plantation. A set of 85 eucalypt remnants was randomly selected across several stratifying variables: four patch size classes (1–3 ha, 4–10 ha, 11–20 ha, and >20 ha), two isolation age classes (<20 years and >20 years since fragmentation), and five dominant eucalypt forest type classes. In addition to the 85 eucalypt remnants, a further 80 3-ha sites were selected for study: 40 in large, continuous areas of eucalypt forest and 40 in radiata pine stands. Point-interval counts of forest birds at the 165 sites were conducted in 1996 and 1997. Of 90 species recorded, 23.1 species (95% confidence interval, 22.0, 24.2 species), on average, were present in continuous eucalypt forest, 20.6 (19.5, 21.7) species in patch-shaped eucalypt remnants, 20.6 (19.5, 21.7) species in strip-shaped eucalypt remnants, and 16.7 (15.6, 17.8) species in radiata pine. Strong gradients in bird assemblages were found. These gradients were governed by a combination of landscape context, remnant size, and remnant shape effects, and, in the case of radiata pine sites, the extent of native forest surrounding the pine. These gradients could, in part, be explained by bird life history attributes such as foraging guild and nesting height. For example, birds more often detected in patch-shaped remnants were smaller, produced smaller clutches, were more likely to be migratory, and typically had cup nests or burrows. The results of our study showed that eucalypt fragments of all sizes and shapes have significant conservation value. This is because they contain many native species of birds, some of which are more abundant in fragments than they are in continuous eucalypt forests, and also because they increase native bird populations in nearby non-native pine plantations.

THE RESPONSE OF ARBOREAL MARSUPIALS TO LANDSCAPE CONTEXT: A LARGE-SCALE FRAGMENTATION STUDY

We describe a landscape-scale study of fragmentation effects on arboreal marsupials at Tumut, southeastern Australia. Embedded within a 55000-ha plantation of exotic Monterey pine (Pinus radiata) are 192 patches of remnant Eucalyptus forest, with large contiguous areas of eucalypt forest beyond the plantation boundary. We compared presence and estimated abundance of arboreal marsupials in three broad groups of sites: remnants of native Eucalyptus forest in the P. radiata plantation; P. radiata stands in the plantation; and large areas of contiguous Eucalyptus forest surrounding the plantation. The study animals were Trichosurus vulpecula, T. caninus, Petaurus breviceps, P. norfolcensis, P. australis, Acrobates pygmaeus, Pseudocheirus peregrinus, and Petauroides volans. We used randomized, replicated statistical procedures to sample 86 eucalypt remnants varying in size, shape, and other features. We matched 40 sites in large contiguous Eucalyptus forest to those remnants, based on environment, climate, terrain, and vegetation cover. In addition, 40 sites in P. radiata stands were matched to sites in the remnants and the large eucalypt forest on the basis of geology, climate, and terrain. We also surveyed 41 micropatches (remnants < 1 ha), where almost no animals were detected. These micropatches, smaller than the home ranges of most arboreal marsupials in the Tumut region, probably represent a minimum threshold patch size below which animals cannot survive. Highly significant landscape context effects were identified. P. radiata sites were excluded from analysis because few animals were detected there. P. australis and P. norfolcensis were not recorded in remnants. P. norfolcensis was recorded only once in contiguous eucalypt forest; P. australis was absent. Four species (P. volans, P. peregrinus, T. vulpecula, and T. caninus) occurred in sufficient numbers for statistical analyses of presence and abundance on remnants vs. large contiguous forest. P. volans was less likely to occur in remnants, whereas P. peregrinus was less likely to occur in contiguous eucalypt forest. Site context had no significant effect on presence of T. caninus, and arboreal marsupials per se, or on abundance of P. volans, T. vulpecula, T. caninus, and arboreal marsupials overall. P. peregrinus was significantly more abundant in remnants than in contiguous eucalypt forest. Statistical adjustment for environmental, climatic, terrain, and vegetation variables by regression modeling did not change animal abundance results. Similar outcomes were recorded for presence of T. vulpecula and T. caninus. However, context effects for presence of T. vulpecula, P. volans, and P. peregrinus could be explained by some of the vegetation, terrain, and landscape covariates. For P. volans, probability of occurrence was significantly greater in large remnants, sites on flat terrain, and sites dominated by particular eucalypt forest types. T. vulpecula was significantly more likely to occur in large remnants and sites with open understories. There was no evidence that P. peregrinus responded to remnant area, but it was significantly more likely to occur on sites with limited understories and trees with few cavities. Life history attributes of the eight marsupial species (e.g., home range, body size, diet, and social organization) provided no insight into the landscape context and fragmentation effects observed. However, the only two species detected in P. radiata stands surrounding the remnants displayed either a complete absence of context or fragmentation effects (T. caninus) or were more likely to occur in remnants than in large contiguous eucalypt forest (P. peregrinus). Thus, fragmentation effects may be related, in part, to how animals use the exotic softwood “matrix” around the remnants. Our investigation indicated that eucalypt forest remnants are valuable refugia for some arboreal marsupials. Future expansions of P. radiata plantations planned for degraded and partially cleared agricultural landscapes in many parts of southeastern Australia should ensure that existing Eucalyptus remnants are not cleared.

A large-scale “experiment” to examine the effects of landscape context and habitat fragmentation on mammals

A large-scale “experiment” was undertaken in a 100 000 ha region of south-eastern Australia to examine the response of mammals to landscape context, habitat fragmentation and other factors. The investigation examined the presence and abundance of mammals in three broad categories of sites for which there were strong contrasts in the composition of the surrounding landscape: • Large contiguous areas of Eucalyptus forest, • Areas dominated by exotic plantation softwood Radiata Pine ( Pinus radiata) trees, and • Fragments of eucalypt forest surrounded by an extensive P. radiata plantation. These sites provided the basis for assessing the effects of what we term “landscape context”. Eighty-six fragments of remnant eucalypt forest of varying size, shape, isolation age and other attributes were selected by a stratified, randomization process. Forty sites were located in large contiguous areas of Eucalyptus forest and these were matched to the sites in the remnants on the basis of forest type, geology and climatic conditions. A further 40 sites were selected in areas dominated by P. radiata trees and these also were matched to sites in the remnants and those in large contiguous areas of native forest on the basis of geology and climatic conditions. Two major surveys sampled mammals in the study. Hairtubing (a technique for detecting animals from the analysis of fur collected in a small portable bait station) was utilized at all 166 sites selected in the study. Trapping and a combination of different types of hairtubing was then employed at a subset of 58 sites. Data from these surveys was used to investigate the response of mammals to landscape context, habitat fragmentation and other attributes. A sub-theme of the study was to assess the efficacy of different methods to count mammals. There were large differences in the effectiveness of the different field techniques. The best technique (best in the sense of counting most animals) varied between species, particularly in relation to body size. Trapping and smaller-sized hairtubes were superior for small mammals such as Brown Antechinus ( Antechinus stuartii) and Bush Rat ( Rattus fuscipes). Large hairtubes performed best in the detection of large mammals like the Common Wombat ( Vombatus ursinus), Common and Mountain Brushtail Possums ( Trichosurus vulpecula and Trichosurus caninus), and Swamp Wallaby ( Wallabia bicolor). W. bicolor and V. ursinus showed no response to landscape context and were detected at similar rates in the remnants, sites in large contiguous areas of native forest and sites dominated by stands of P. radiata. Trichosurus spp. were recorded significantly less often in sites dominated by P. radiata trees. Landscape context effects for R. fuscipes and A. stuartii varied depending on the field methods employed to sample mammals. However, in general, R. fuscipes and A. stuartii were recorded significantly less frequently in P. radiata sites than sites in large contiguous areas of Eucalyptus forest or fragments of remnant eucalypt forest surrounded by the softwood plantation. An important finding of our work was that although some species were extremely rare in P. radiata stands, no significant differences were identified in mammal presence and abundance between sites located in large contiguous areas of Eucalyptus forest and sites in fragments of remnant eucalypt forest surrounded by the softwood plantation. This finding suggests that either: animals from potential population sources in contiguous eucalypt forest can move through the softwood plantation and colonise the remnants, or populations residing in the fragments of remnant eucalypt forest are large enough to resist local extinction. Softwood plantations are presently being expanded in south-eastern Australia, particularly on semi-cleared farmland that supports remnant fragments of native Eucalyptus forest and woodland. Our findings indicate that remnant native forest within plantations of exotic P. radiata trees are occupied by several species of native mammals even when these fragments are surrounded by extensive, largely unsuitable plantation forests that have been established for many decades. These fragments should not be cleared during efforts to expand the softwood plantation estate. Large remnants and those with particular habitat features such as a dense cover of vegetation should have priority for exemption from clearing.

Simulating Effects of Landscape Context and Timber Harvest on Tree Species Diversity

Simulating Effects of Landscape Context and Timber Harvest on Tree Species Diversity