Small Landscape Scale Research Articles

Local and landscape factors shape alpha and beta trophic interaction diversity in urban gardens.

Promoting urban green spaces is an effective strategy to increase biodiversity in cities. However, our understanding of how local and landscape factors influence trophic interactions in these urban contexts remains limited. Here, we sampled cavity-nesting bees and wasps and their natural enemies within 85 urban gardens in Zurich (Switzerland) to identify factors associated with the diversity and dissimilarity of antagonistic interactions in these communities. The proportions of built-up area and urban green area at small landscape scales (50 m radius), as well as the management intensity, sun exposure, plant richness and proportion of agricultural land at the landscape scale (250 m radius), were key drivers of interaction diversity. This increased interaction diversity resulted not only from the higher richness of host and natural enemy species, but also from species participating in more interactions. Furthermore, dissimilarity in community structure and interactions across gardens (beta-diversity) were primarily influenced by differences in built-up areas and urban green areas at the landscape scale, as well as by management intensity. Our study offers crucial insights for urban planning and conservation strategies, supporting sustainability goals by helping to understand the factors that shape insect communities and their trophic interactions in urban gardens.

CHANGES IN VEGETATION AT SMALL LANDSCAPE SCALES AND CAPTIVITY ALTER THE GUT MICROBIOTA OF BLACK HOWLER MONKEYS (<i>Alouatta pigra</i>: Atelidae)

The healthy function of the gastrointestinal system is influenced by changes in the microbiota and the adaptability of the host to different habitat conditions and food availability. We isolated and identified 64 bacterial morphospecies from rectal swabs from five captive black howler monkeys (CM) and 15 wild individuals (WM) from groups living in fragments with different compositions and vegetation structures (height, density, canopy width) in flooded and non-flooded areas. Low microbial diversity in CM and WM from the flooded area was observed while in WM from the non-flooded area, there was a higher microbial diversity and evenness. Free-ranging monkeys from different areas showed a significant difference in the replacement of morphospecies of gut microbiota (p = 0.0006); however, the bacterial communities are not differentiated as particular entities. The intestinal microbial community can be an indicator of howler monkeys’ health and habitat quality. The change in the composition of the plant community into small landscape scales, as well as fragmentation and natural heterogeneity of the landscape, can affect the intestinal microbial community of howler monkeys.

Building resilient landscapes in a semi-arid watershed: Anthropogenic and natural burning histories in Late Holocene Tesuque Creek, northern New Mexico

As mega-fires have swept the North American West in recent decades, studies of past fire events have gained academic interest. Deep-time perspectives are necessary to better understand the periodicity of fire events and to identify basic drivers of frequent fire episodes through time, including potential anthropogenic fire use. Our study contributes to the growing field of archeological fire ecology in the Southwest with an examination of a high-resolution geobotanical dataset for Holocene fire regimes as indicated within sediments from an alluvial section from Tesuque Creek in northern New Mexico. Using phytolith, geochemical, and sedimentological data, we reconstruct indices for burn cycle seasonality and destabilization of riparian vegetation communities that suggest potential anthropogenic land use and possible patterns distinguishing human burning from lightning ignitions. Through this study, we consider the potential role of hunter-gatherer behavior in producing fire landscapes as part of their strategies for managing risks in the fragile environments of the Middle-Late Holocene in northern New Mexico. We suggest that combining geo and botanical datasets from alluvial sections with archeological evidence will allow researchers to fine-tune the resolution of local climate sequences and their environmental impacts on small landscape scales. When such small-scale studies can be aggregated, they may further contribute to testing models of regional patch-burning, either natural or anthropogenic. We further posit that human relationships with fire in the past should be considered as collaborative efforts with lightning-ignited burns, to manage the risks associated with both too much and too little fire in fragile dryland ecosystems.

Effects of dispersal barriers and geographic distance on the genetic structure of a narrowly distributed frog in a spatially structured landscape

AbstractLandscape features (e.g., mountains and rivers) can act as barriers to dispersal and gene flow, and therefore impede population connectivity, increasing genetic differentiation between populations. The concave‐eared torrent frog (Odorrana tormota) is a rare, stream‐associated species in eastern China. In this study, we investigated the genetic structure and population demography of this narrowly distributed frog based on mitochondrial Cyt b gene and seven nuclear microsatellite loci. As a result, we found that the rare frog still preserved a relatively high level of genetic diversity compared to some other amphibia. Population structure analyses distinctly identified three or four tentative genetic clusters for the species in the study area. Additionally, by fine‐scale spatial autocorrelation analysis, significant positive genetic structure was uncovered in the shortest distance classes (0–5 km, 5–10 km). Demographic analyses revealed a population expansion (0.075–0.017 Mya) and 15 times population decline (c. 9000 years ago). In conclusion, we supposed that stable montane environments and associated historical population expansion might provide an opportunity for the species to harbor high genetic diversity. The relatively recent population decline might be correlated with climate change as well as genetic differentiation among populations. In addition, our results showed that, on a small landscape scale, dispersal is closely linked to geographic distance and the presence of river systems may not substantially affect the genetic structure for the narrowly distributed O. tormota.

Positive effect of environmentally friendly farming on paddy field odonate assemblages at a small landscape scale

Odonata species can be used to indicate the effects of anthropogenic disturbance on agrobiodiversity. In Japan, populations of some odonate species inhabiting rice paddy fields have decreased strongly owing to their high susceptibility to insecticides, and they therefore need to be conserved. To identify effective conservation strategies, we investigated how agricultural practices (conventional vs. environmentally friendly: EF) and surrounding landscape (area of forest at three spatial scales, namely 50, 100 and 200 m from the edge of the paddy field) influenced the abundance of odonates in rice paddies in Tochigi Prefecture, Japan. Generalized linear mixed-effect models revealed that EF farming increased the abundance of odonate adults and the number of nymphal exuviae, suggesting a strong negative effect of insecticides. The influence of forest area at the local scale on the numbers of odonate adults and nymphal exuviae was small, with the exception of a strong negative influence on adult Sympetrum infuscatum: the presence of a large area of forest within 200 m of the edge of the paddy field reduced their abundance, probably reflecting this dragonfly’s oviposition site preference. Our results suggest that EF farming could generally support the conservation and recovery of local populations of odonates, but its effectiveness potentially varies depending on the ecological aspects of each species.

Local and landscape level variables influence butterfly diversity in critically endangered South African renosterveld

Severe losses in biodiversity hotspots reduce global insect diversity. Renosterveld is a critically endangered and biologically diverse ecosystem occurring only in the fynbos biome of the Cape Floristic Region (CFR), a recognized global biodiversity hotspot. Following agricultural intensification, less than 5% natural renosterveld vegetation remains in the Swartland of South Africa’s Western Cape. Remaining renosterveld is highly fragmented and confined to land less suited to agriculture, including steep slopes and rocky outcrops. These fragments vary in their environmental conditions at the local (e.g. microhabitat, floral diversity and density) and the landscape (e.g. patch size, habitat connectivity and surrounding crop cover) level. The influence of these environmental variables on butterfly diversity at a landscape scale in the CFR is not fully understood. We selected 32 sites across the Swartland and surveyed for butterflies to determine the effect of environmental variables on butterfly diversity, specifically butterfly species richness, abundance and composition. Overall, we found 2861 individuals of 27 species. Our findings suggest that crop cover in the surrounding landscape affects butterfly diversity at a small landscape scale (< 500 m radius) in the CFR. Flower species richness and microhabitat type impact species richness and abundance. Patch size is a key predictor of species diversity particularly for endemics and site quality may influence species composition. All renosterveld patches regardless of size and site quality can be considered valuable for butterflies in this highly fragmented landscape.

A Demographic Approach to Evaluating Tree Population Sustainability

Quantitative criteria for assessing demographic sustainability of tree populations would be useful in forest conservation, as climate change and a growing complex of invasive pests are likely to drive forests outside their historic range of variability. In this paper, we used CANOPY, a spatially explicit, individual‐tree model, to examine the effects of initial size distributions on sustainability of tree populations for 70 northern hardwood stands under current environmental conditions. A demographic sustainability index was calculated as the ratio of future simulated basal area to current basal area, given current demographic structure and density‐dependent demographic equations. Only steeply descending size distributions were indicated to be moderately or highly sustainable (final basal area/initial basal area ≥0.7 over several tree generations). Five of the six principal species had demographic sustainability index values of &lt;0.6 in 40%–84% of the stands. However, at a small landscape scale, nearly all species had mean index values &gt;1. Simulation experiments suggested that a minimum sapling density of 300 per hectare was required to sustain the initial basal area, but further increases in sapling density did not increase basal area because of coincident increases in mortality. A variable slope with high q‐ratios in small size classes was needed to maintain the existing overstory of mature and old‐growth stands. This analytical approach may be useful in identifying stands needing restoration treatments to maintain existing species composition in situations where forests are likely to have future recruitment limitations.

Landscape effects on plants in forests: Large-scale context determines local plant response

Most studies of landscape effects on plants in forests have explored only relatively small landscape scales (size of spatial extent) considering the poor-dispersal ability generally reported for forest plants, or failed to verify confidently that the scales at which landscape is considered best predicts plant patterns. We investigated the effect of landscape composition on response of plant communities according to three scales - 400 ha, 100 ha and 25 ha - in 263 forests in the northern half of France. We hypothesized that landscape composition at the 400-ha scale better predicted plant responses than smaller scales. We built models to compare the effects of each scale on individual species response and plant composition of 1902 700-m2 vegetation plots, considering the shared and pure effects of scales. Only landscape composition at the 400-ha scale showed a critical pure effect on plant composition. Similarly, the 400-ha scale better predicted individual species response. Using a large dataset, we brought evidence that landscape composition further than 100 ha and at least up to 400 ha had more effects on local plant diversity in forests, which means that smaller-scale investigations may miss the influence of landscape on plant patterns. The effects of large spatial scale may reflect the legacies of past landscape or the long-distance dispersal capacity of plants. Our findings call for better consideration of the large-scale effects of landscape on plants both in scientific studies and management plans.

Is habitat amount important for biodiversity in rocky shore systems? A study of South African mussel assemblages

Habitat-forming species on rocky shores are often subject to high levels of exploitation, but the effects of subsequent habitat loss and fragmentation on associated species and the ecosystem as a whole are poorly under - stood. In this study, the effects of habitat amount on the fauna associated with mussel beds were investigated, test- ing for the existence of threshold effects at small landscape scales. Specifically, the relationships between mussel or algal habitat amount and: associated biodiversity, associ- ated macrofaunal abundance and density of mussel recruits were studied at three sites (Kidd's Beach, Kayser's Beach and Kini Bay) on the southern and south-eastern coasts of South africa. Samples, including mussel-associated macro- fauna, of 10 × 10 cm were taken from areas with 100 % mussel cover (Perna perna or a combination of P. perna and Mytilus galloprovincialis) at each site. The amount of habitat provided by mussels and algae surrounding the

Multi-scale assessment of pollination of Lotus corniculatus (L.) in a peri-urban fringe

Background: The plant pollination service provided by pollinators is crucial for ecosystem maintenance, especially in highly fragmented landscapes, such as urban areas. Aims: We assessed at multiple spatial scales the influence of the degree of urbanisation on pollinator communities and pollination success. Methods: Artificial populations of Lotus corniculatus (Fabaceae) were established along an urbanisation gradient in gardens where pollinator communities were surveyed. We described the plant and pollinator composition of gardens (local scale) and measured landscape structure in nested buffers (small and large landscape scales). Results: At the local scale, species richness and abundance of pollinators increased with the number of spontaneous plants and the size of semi-natural areas, while at the large landscape scale pollinators were more diverse and abundant in diversified landscapes with extensive green space and low cover of impervious surfaces. At the small landscape scale, the pollination success was favoured by agricultural areas, and disfavoured by housing density and fragmentation. It was also favoured by green space cover at the large landscape scale. Conclusions: The variables that affect pollination differ across spatial scales. Local and landscape variables have different effects according to spatial scale, suggesting different underlying causes, such as the presence of flower resources or of suitable habitats in the surroundings. Our results emphasise the importance of accounting for all spatial scales when managing pollination services.

Foliar nutrients shape fungal endophyte communities in Western white pine (Pinus monticola) with implications for white-tailed deer herbivory

Asymptomatic fungal endophytes colonize tissues of woody plants worldwide, with largely unknown ecological effects. Using culture-based methods and ITS1-5.8S-ITS2 rDNA sequence analysis, we investigated differences between foliar endophyte communities in disease-resistant hybrid and wild-type Pinus monticola (Western white pine) trees with observed variation in tree growth, vigor, and browsing damage by white-tailed deer (Odocoileus virginianus). We isolated 69 phylotypes of endophytic fungi in at least 39 genera, including 26 that have not previously been reported in P. monticola. Principal components analysis revealed that endophyte communities differed between browsed seedlings, unbrowsed seedlings, and unbrowsed adult trees. Sulfur, nitrate and calcium concentrations correlated with endophyte community differences among tree groups based on a distance-based redundancy analysis. Our results indicate that foliar nutrient variation influences endophyte community assembly and deer herbivory in P. monticola on a small landscape scale (80 hectares).

Anthropogenic effects on the biodiversity of riparian wetlands of a northern temperate landscape

Land uses such as forestry and agriculture are presumed to degrade the biodiversity of riparian wetlands in the northern temperate regions of the United States. In order to improve land use decision making in this landscape, floral and faunal communities of 15 riparian wetlands associated with low-order streams were related to their surrounding land cover to establish which organismal groups are affected by anthropogenic disturbance and whether these impacts are scale-specific. Study sites were chosen to represent a gradient of disturbance. Vascular plants of wet meadow and shrub carr communities, aquatic macro-invertebrates, amphibians, fish and birds were surveyed, and total abundance, species richness and Shannon diversity were calculated. For each site, anthropogenic disturbances were evaluated at local and landscape scales (500, 1000, 2500 and 5000 m from the site and the site catchment) from field surveys and a geographic information system (GIS). Land use data were grouped into six general land use types: urban, cultivated, rangeland, forest, wetland and water. Shrub carr vegetation, bird and fish diversity and richness generally decrease with increasing cultivation in the landscape. Amphibian abundance decreases and fish abundance increases as the proportions of open water and rangeland increases; bird diversity and richness increase with forest and wetland extent in the landscape. Wet meadow vegetation, aquatic macro-invertebrates, amphibians and fish respond to local disturbances or environmental conditions. Shrub carr vegetation, amphibians and birds are influenced by land use at relatively small landscape scales (500 and 1000 m), and fish respond to land use at larger landscape scales (2500, 5000 m and the catchment). Effective conservation planning for these riparian wetlands requires assessment of multiple organismal groups, different types of disturbance and several spatial scales.1998 Academic Press

Characteristics of vegetation phenology over the Alaskan landscape using AVHRR time-series data

AbstractAdvanced Very High Resolution Radiometer (AVHRR) satellite data were acquired and composited into twice-a-month periods from 1 May 1991 to 15 October 1991 in order to map vegetation characteristics of the Alaskan landscape. Unique spatial and temporal qualities of the AVHRR data provide information that leads to a better understanding of regional biophysical characteristics of vegetation communities and patterns. These data provided synoptic views of the landscape and depicted phenological diversity, temporal vegetation phenology (green-up, peak of green, and senescence), photosynthetic activity, and regional landscape patterns. Products generated from the data included a phenological class map, phenological composite maps (onset, peak, and duration), and photosynthetic activity maps (mean and maximum greenness). The time-series data provide opportunities to study phenological processes at small landscape scales over time periods of weeks, months, and years. Regional patterns identified on some of the maps are unique to specific areas; others correspond to biophysical or ecoregional boundaries. The data provide new insights to landscape processes, ecology, and landscape physiognomy that allow scientists to look at landscapes in ways that were previously difficult to achieve.