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1.
Landscape metric scalograms (the response curves of landscape metrics to changing grain size) have been used to illustrate the scale effects of metrics for real landscapes. However, whether they detect the characteristic scale of hierarchically structured landscapes remains uncertain. To address this question, the scalograms of 26 class-level metrics were systematically examined for a simple random landscape, seven hierarchical neutral landscapes, and the real landscape of the Xilin River Basin of Inner Mongolia, China. The results show that when the fraction of the focal patch type (P) is below a critical value (P c), most metric scalograms are sensitive to change in single-scale and lower-level hierarchical structure and insensitive to change in higher-level hierarchical structure. The scalograms of only a few metrics measuring spatial aggregation and connectedness are sensitive to change in intermediate-level hierarchical structure. Most metric scalograms explicitly identify the characteristic scale of a single-scale landscape and fine or intermediate characteristic scales of a multi-scale landscape for both simulated and real landscapes. When P exceeds P c, only some metrics detect scale and change in structure. The scalograms of total class area and Euclidean nearest-neighbor distance cannot detect scale or change in structure in either case. Landscape metric scalograms are useful for addressing scale issues, including illustrating the scale effects of spatial patterns, detecting multi-scale patterns, and developing possible scaling relations.
相似文献2.
Knowledge on environmental variability and how it is affected by disturbances is crucial for understanding patterns of biodiversity
and determining adequate conservation strategies. The aim of this study is to assess environmental variability in patches
undergoing post-fire vegetation recovery, identifying trends of change and their relevant drivers. We particularly evaluate:
the value of three spectral indices derived from Landsat satellite data [Normalized Burn Ratio (NBR), Normalized Difference
Vegetation Index (NDVI) and Wetness Component of the Tasseled Cap Transformation (TCW)] for describing secondary succession;
the effectiveness of three metrics (diversity, evenness and richness) as indicators of patch variability; and how thematic
resolution can affect the perception of environmental variability patterns. While the system was previously characterised
as highly resilient from estimations of vegetation cover, here we noted that more time is required to fully recover pre-fire
environmental variability. Using mean diversity as indicator of patch variability, we found similar patterns of temporal change
for the three spectral indices (NBR, NDVI and TCW). Analogous conclusions could be drawn for richness and evenness. Patch
variability, measured as diversity, showed consistent patterns across thematic resolutions, although values increased with
the number of spectral classes. However, when the variance of diversity was plotted against thematic resolution, different
scale dependencies were detected for those three spectral indices, yielding a dissimilar perception of patch variability.
In general terms, NDVI was the best performing spectral index to assess patterns of vegetation recovery, while TCW was the
worst. Finally, burned patches were classified into three classes with similar trends of change in environmental variability,
which were strongly related to fire severity, elevation and vegetation type. 相似文献
3.
Rune H. Økland Harald Bratli Wenche E. Dramstad Anette Edvardsen Gunnar Engan Wendy Fjellstad Einar Heegaard Oddvar Pedersen Heidi Solstad 《Landscape Ecology》2006,21(7):969-987
Knowledge of variation in vascular plant species richness and species composition in modern agricultural landscapes is important
for appropriate biodiversity management. From species lists for 2201 land-type patches in 16 1-km2 plots five data sets differing in sampling-unit size from patch to plot were prepared. Variation in each data set was partitioned
into seven sources: patch geometry, patch type, geographic location, plot affiliation, habitat diversity, ecological factors,
and land-use intensity. Patch species richness was highly predictable (75% of variance explained) by patch area, within-patch
heterogeneity and patch type. Plot species richness was, however, not predictable by any explanatory variable, most likely
because all studied landscapes contained all main patch types – ploughed land, woodland, grassland and other open land – and
hence had a large core of common species. Patch species composition was explained by variation along major environmental complex
gradients but appeared nested to lower degrees in modern than in traditional agricultural landscapes because species-poor
parts of the landscape do not contain well-defined subsets of the species pool of species-rich parts. Variation in species
composition was scale dependent because the relative importance of specific complex gradients changed with increasing sampling-unit
size, and because the amount of randomness in data sets decreased with increasing sampling-unit size. Our results indicate
that broad landscape structural changes will have consequences for landscape-scale species richness that are hard or impossible
to predict by simple surrogate variables. 相似文献
4.
Habitat isolation can affect the distribution and abundance of wildlife, but it is an ambiguous attribute to measure. Presumably, isolation is a characteristic of a habitat patch that reflects how spatially inaccessible it is to dispersing organisms. We identified four isolation metrics (nearest-neighbor distance, Voronoi polygons, proximity index, and habitat buffers) that were representative of the different families of metrics that are commonly used in the literature to measure patch isolation. Using simulated data, we evaluated the ability of each isolation metric to predict animal dispersal. We examined the simulated movement of organisms in two types of landscapes: an artificially-generated point-pattern landscapes where patch size and shape were consistent and only the arrangement of patches varied, and realistic landscapes derived from a geographic information system (GIS) of forest-vegetation maps where patch size, shape, and isolation were variable. We tested the performance of the four isolation metrics by examining the strength of the correlation between observed immigration rate in the simulations and each patch isolation metric. We also evaluated whether each isolation metric would perform consistently under varying conditions of patch size/shape, total amount of habitat in the landscape, and proximity of the patch to the landscape edge. The results indicate that a commonly-used distance-based metric, nearest-neighbor distance, did not adequately predict immigration rate when patch size and shape were variable. Area-informed isolation metrics, such as the amount of available habitat within a given radius of a patch, were most successful at predicting immigration. Overall, the use of area-informed metrics is advocated despite the limitation that these metrics require parameterization to reflect the movement capacity of the organism studied.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
5.
Henrik von Wehrden David J. Abson Michael Beckmann Anna F. Cord Stefan Klotz Ralf Seppelt 《Landscape Ecology》2014,29(6):941-948
The “land sharing versus land sparing” concept provides a framework for comparing potential land use patterns in terms of trade-offs between biodiversity conservation and agricultural yields at a landscape scale. Here, we raise two additional aspects to be considered in the sparing/sharing debate, supported by a review of available literature. First, beta and gamma (instead of alpha) diversity measures capture landscape scale variance in biodiversity in response to land use changes and should be considered for the long-term management of agricultural landscapes. Moreover, beta and gamma diversity may better account for comparisons of biodiversity between spared and shared land use options. Second, land use history has a pronounced influence on the complexity and variance in agricultural habitat niches at a landscape scale, which in turn may determine the relevance of sparing or sharing land use options. Appropriate and comparable biodiversity metrics and the recognition of landscape history are two vital preconditions in aligning biological conservation goals with maximized yields within the sparing/sharing framework. 相似文献
6.
Context
Deforestation is a major driver of biodiversity loss, mainly due to agriculture. As rice is among the world’s most important crops, determining how agricultural communities are shaped is imperative. However, few studies have addressed the factors that alter community assembly in human-modified landscapes. We aim to quantify taxonomic, functional, trait and phylogenetic diversity of an anuran community from rice crops on a biodiversity hotspot.Objectives
Identify local and landscape characteristics responsible for variations in multiple dimensions of anuran diversity in rice crops.Methods
This study was performed in Tocantins, Brazil. We chose 36 lentic waterbodies on rice fields for anuran sampling. We quantified taxonomic diversity (TD), functional diversity (FD) and phylogenetic diversity (PD) for each waterbody. We also estimated the mean functional differences among species for each trait separately. To evaluate how local and landscape scale features affect anurans, we performed generalized linear mixed models in 500, 1000 and 1500 m buffers around each waterbody.Results
We found increased PD and FD in waterbodies closer to many other waterbodies and large forest patches. Anuran biomass decreased with increasing distance to the closest waterbody. Trait diversity varied with waterbody abundance and closeness, percentage of bare ground and marginal vegetation.Conclusions
Our study emphasizes the importance of waterbody and forest patch networks for maintaining high anuran FD and PD in agricultural landscapes. As both metrics are known to be related to ecosystem resilience, understanding these patterns is pivotal for biodiversity management, especially in the tropics, where agricultural expansion is unrelenting and biodiversity is especially unique.7.
Habitat fragmentation is considered a major cause of biodiversity loss, both on terrestrial and marine environments. Understanding the effects of habitat fragmentation on the structure and dynamics of natural communities is extremely important to support management actions for biodiversity conservation. However, the effects of habitat fragmentation on marine communities are still poorly understood. Here we evaluated whether habitat fragmentation affects the structure of epifaunal communities in the sublittoral zone, in the northern coast of São Paulo state, Brazil. Five experimental landscapes were constructed, each one forming a large continuous patch. After 4 weeks, each landscape was cut on three patches of different sizes. Epifaunal macroinvertebrate communities were sampled at the edge and interior of experimental landscapes before manipulation to evaluate edge effects. After four more weeks, communities from the three patch sizes were also sampled to evaluate patch size effects. We compared the diversity of communities at different levels of fragmentation by total abundance, rarefied taxon richness, Shannon–Wiener diversity index, Simpson’s dominance index, and abundance of dominant taxa. Higher taxon richness and gastropod abundance were recorded in the patch edges, but no significant differences were found among patch sizes. We found a significant effect of habitat fragmentation, with lower abundances of Gammaridea (the dominant taxon), Ophyuroidea, and Pycnogonida after the experimental fragmentation. Lower abundances of dominant taxa resulted in higher diversity and lower dominance in fragmented landscapes when compared to integral, pre-manipulation landscapes. Our results suggest that fragmentation of landscapes in the system studied can reduce dominance, and that even small patch sizes can be important for the conservation of macroinvertebrate diversity. 相似文献
8.
We argue that thematic resolution, i.e., the level of categorical detail of a thematic map expressed by the number of classes
included in the map legend, is an inherent component of the scale at which a landscape is analyzed. Changing the number of
classes can change the configuration of the patch mosaic as much as changing the grain does. We address recent calls in this
and other journals to deepen research in this topic. In particular, we report how thematic resolution affects the patchiness
of mosaics representing natural landscapes, which have seldom been studied in this respect. We selected seven 50 × 50 km landscapes
within national parks, each representative of a world biome. We applied an object-based unsupervised classification to Landsat
TM imagery of these landscapes using increasing numbers of classes, between 2 and 50, and derived curves of mean patch size
and patch density for each site. Our results are consistent with previous findings in that the patchiness of output mosaics
increases monotonically with increasing thematic resolution, with a higher rate of increase up to eight classes that declines
until it becomes roughly constant for more than 16 classes. However, this constant rate of increase is still considerable,
meaning that, at least for natural landscapes, there is no threshold beyond which the patch-mosaic model is independent of
the conceptual filter applied. This dependence on human fiat calls for re-thinking the patch-mosaic paradigm. 相似文献
9.
Measuring landscape configuration with normalized metrics 总被引：1，自引：1，他引：0
Natural and anthropogenic disturbances on natural landscapes reduce the abundance and alter the spatial arrangement of certain
habitat types. Measuring and modeling such alterations, and their biological effects, remains challenging in part because
many widely used configuration metrics are correlated with habitat amount. In this paper, we consider the sources of such
correlation, and distinguish process or sample-based correlation from functional correlation that may be an artifact of the
metrics themselves. Process correlation is not necessarily a serious problem for statistical inference, but functional correlation
would be. We propose that functional correlation may be reduced by normalizing metrics by habitat abundance. We illustrate
with normalized versions of total core area, mean nearest neighbor distance, and mean shape index, and show informally that
the standard versions of these metrics should exhibit functional correlation. We evaluate the normalized metrics on samples
of harvested and undisturbed forested landscapes, and on simulated landscapes generated with varying degrees of spatial autocorrelation.
Normalization markedly reduced correlations with habitat abundance on natural landscapes, but not on simulated landscapes.
The reasons for this appear to be a combination of differing variances in metric values within levels of habitat abundance,
and of the precise form of the relationships between habitat abundance and the un-normalized metrics. In all cases, the normalization
changes the ordering of landscapes by metric values across levels of habitat abundance. In consequence, normalized and standard
metrics cannot both be accurate measures of configuration. We conclude that statistical modeling of ecological response data
is needed to finally determine the merits of the normalizations. 相似文献
10.
Anette Edvardsen Rune Halvorsen Ann Norderhaug Oddvar Pedersen Knut Rydgren 《Landscape Ecology》2010,25(7):1071-1083
Habitat specificity analysis provides a tool for partitioning landscape species diversity on landscape elements by separating
patches with many rare specialist species from patches with the same number of species, all of which are common generalists
and thus provide information of relevance to conservation goals at regional and national levels. Our analyses were based upon
species data from 2201 patch elements in SE Norwegian modern agricultural landscapes. The context used for measuring habitat
specificity strongly influences the results. In general the gamma diversity contribution and core habitat specificity calculated
from the patch data set were correlated. High values for both measures were observed for woodland, pastures and road verges
whereas midfield islets and boundary transitional types were ranked low, as opposed to findings in traditional, extensively
managed agricultural landscapes. This is due to our study area representing intensively used agricultural landscape elements
holding a more trivial species composition, in addition to ruderals being favoured by fertility and disturbance, a finding
also being supported by the semi-natural affiliation index. Results obtained by use of checklist data from the same study
area diverged from patch data. Caution is needed in interpretation of habitat specificity results obtained from checklist
data, because modern agricultural landscapes contain several land types which are seldom surveyed by botanists, thus being
under-represented in the data set. We propose the use of core habitat specificity and gamma diversity contribution in parallel
to obtain a value neutral diversity assessment that addresses patch uniqueness and other properties of conservation interests. 相似文献
11.
Surface metrics: an alternative to patch metrics for the quantification of landscape structure 总被引：6，自引：3，他引：3
Modern landscape ecology is based on the patch mosaic paradigm, in which landscapes are conceptualized and analyzed as mosaics
of discrete patches. While this model has been widely successful, there are many situations where it is more meaningful to
model landscape structure based on continuous rather than discrete spatial heterogeneity. The growing field of surface metrology
offers a variety of surface metrics for quantifying landscape gradients, yet these metrics are largely unknown and/or unused
by landscape ecologists. In this paper, we describe a suite of surface metrics with potential for landscape ecological application.
We assessed the redundancy among metrics and sought to find groups of similarly behaved metrics by examining metric performance
across 264 sample landscapes in western Turkey. For comparative purposes and to evaluate the robustness of the observed patterns,
we examined 16 different patch mosaic models and 18 different landscape gradient models of landscape structure. Surface metrics
were highly redundant, but less so than patch metrics, and consistently aggregated into four cohesive clusters of similarly
behaved metrics representing surface roughness, shape of the surface height distribution, and angular and radial surface texture.
While the surface roughness metrics have strong analogs among the patch metrics, the other surface components are largely
unique to landscape gradients. We contend that the surface properties we identified are nearly universal and have potential
to offer new insights into landscape pattern–process relationships.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
12.
Quantifying the speed, growth modes, and landscape pattern changes of urbanization: a hierarchical patch dynamics approach 总被引：1，自引：1，他引：0
Urbanization transforms landscape structure and profoundly affects biodiversity and ecological processes. To understand and solve these ecological problems, at least three aspects of spatiotemporal patterns of urbanization need to be quantified: the speed, urban growth modes, and resultant changes in landscape pattern. In this study, we quantified these spatiotemporal patterns of urbanization in the central Yangtze River Delta region, China from 1979 to 2008, based on a hierarchical patch dynamics framework that guided the research design and the analysis with landscape metrics. Our results show that the urbanized area in the study region increased exponentially during the 30 years at the county, prefectural, and regional levels, with increasing speed down the urban hierarchy. Three growth modes—infilling, edge-expanding, and leapfrogging—operated concurrently and their relative dominance shifted over time. As urbanization progressed, patch density and edge density generally increased, and the connectivity of urban patches in terms of the average nearest neighbor distance also increased. While landscape-level structural complexity also tended to increase, the shape of individual patches became increasingly regular. Our results suggest that whether urban landscapes are becoming more homogenous or heterogeneous may be dependent on scale in time and space as well as landscape metrics used. The speed, growth modes, and landscape pattern are related to each other in complicated fashions. This complex relationship can be better understood by conceptualizing urbanization not simply as a dichotomous diffusion-coalescence switching process, but as a spiraling process of shifting dominance among multiple growth modes: the wax and wane of infilling, edge-expansion, and leapfrog across the landscape. 相似文献
13.
Context
Human appropriation of net primary productivity (HANPP) is employed as a measure of human pressures on biodiversity, though largely at global and national scales rather than landscape to regional scales where many conservation decisions take place. Though gaining in familiarity, HANPP is not widely utilized by conservation professionals.
ObjectivesThis study, encompassing the US side of the Great Lakes basin, examines how regional distributions of HANPP relate to landscape-based biodiversity proxy metrics used by conservation professionals. Our objectives were (1) to quantify the HANPP of managed lands at the county scale; and (2) to assess spatial patterns of HANPP in comparison to landscape diversity and local habitat connectedness to determine if the metric can provide useful information to conservation professionals.
MethodsWe aggregated forest and cropland NPP data between 2005 and 2015 and coupled it with previously published potential vegetation maps to quantify the HANPP of each county in the study region. We mapped the outputs at 500 m resolution to analyze spatial relationships between HANPP and landscape metrics of biodiversity potential.
ResultsArea-weighted HANPP across our study region averaged 45% of NPP, down to 4.9% in forest-dominated counties. Greater HANPP correlated with reduced landscape diversity (p?<?0.001, r2?=?0.28) and reduced local habitat connectedness (p?<?0.001, r2?=?0.36).
ConclusionHANPP could be used as an additional tool for conservation professionals during regional-scale land use planning or conservation decision-making, particularly in mixed-use landscapes that both support important biodiversity and have high levels of primary production harvest.
相似文献14.
Gap Analysis takes a proactive landscape-level approach to conserving native species by identifying nodes of high biological diversity. It uses vertebrate species richness as an index of overall biological diversity. However, it remains unknown whether or not the spatial distribution of vertebrate diversity corresponds with the diversity of other taxa. We tested whether landscape-level diversity patterns corresponded between a vertebrate and an invertebrate taxon, mammals and ants, across the southern half of the Florida peninsula, USA. Composite digital maps with a 30-m spatial resolution were produced for each taxon. Spatial correspondence between the taxa was determined by normalizing and then subtracting the composite maps. There were large areas of spatial correspondence – indicating that richness between mammals and ants was similar over much of southern Florida. However, spatial correspondence occurred where the richness of both taxa was low or moderate, and areas with the highest species richness (highest 20%) for each taxon, the explicit focus of Gap Analyses, corresponded over only 8752 ha. Gap Analysis provides a much needed assessment of landscape-level diversity patterns and proactive reserve design, but it must be explicit that the results are applicable for vertebrate diversity, which does not necessarily correspond with diversity patterns of other taxa. The two taxa investigated differ by orders of magnitude in the scale that they perceive their environment, and it is likely that diversity hotspots vary as the scale of investigation – and the taxa mapped – vary. 相似文献
15.
Karen Riva-Murray Rachel Riemann Peter Murdoch Jeffrey M. Fischer Robin Brightbill 《Landscape Ecology》2010,25(10):1489-1503
Widespread and increasing urbanization has resulted in the need to assess, monitor, and understand its effects on stream water
quality. Identifying relations between stream ecological condition and urban intensity indicators such as impervious surface
provides important, but insufficient information to effectively address planning and management needs in such areas. In this
study we investigate those specific landscape metrics which are functionally linked to indicators of stream ecological condition,
and in particular, identify those characteristics that exacerbate or mitigate changes in ecological condition over and above
impervious surface. The approach used addresses challenges associated with redundancy of landscape metrics, and links landscape
pattern and composition to an indicator of stream ecological condition across a broad area of the eastern United States. Macroinvertebrate
samples were collected during 2000–2001 from forty-two sites in the Delaware River Basin, and landscape data of high spatial
and thematic resolution were obtained from photointerpretation of 1999 imagery. An ordination-derived ‘biotic score’ was positively
correlated with assemblage tolerance, and with urban-related chemical characteristics such as chloride concentration and an
index of potential pesticide toxicity. Impervious surface explained 56% of the variation in biotic score, but the variation
explained increased to as high as 83% with the incorporation of a second land use, cover, or configuration metric at catchment
or riparian scales. These include land use class-specific cover metrics such as percent of urban land with tree cover, forest
fragmentation metrics such as aggregation index, riparian metrics such as percent tree cover, and metrics related to urban
aggregation. Study results indicate that these metrics will be important to monitor in urbanizing areas in addition to impervious
surface. 相似文献
16.
Amy E. Frazier 《Landscape Ecology》2016,31(2):351-363
Context
Considerable research has examined scale effects for patch-based metrics with the ultimate goal of predicting values at finer resolutions (i.e., downscaling), but results have been inconsistent. Surface metrics have been suggested as an alternative to patch-based metrics, although far less is known about their scaling relationships and downscaling potential. If successful, downscaling would enable integration of disparate datasets and comparison of landscapes using different resolution datasets.Objectives
(1) Determine how surface metrics scale as resolution changes and how consistent those scaling relationships are across landscapes. (2) Test whether these scaling relationships can be accurately downscaled to predict metric values for finer resolutions.Methods
Various scaling functions were fit to 16 surface metrics computed for multiple resolutions for a set of landscapes. Best-fitting functions were then extrapolated to test downscaling behavior (i.e., predict metric value for a finer resolution) for an independent set of validation landscapes. Relative error was assessed between the predicted and true values to determine downscaling robustness.Results
Seven surface metrics (Sa, Sq, S10z, Sdq, Sds, Sdr, Srwi) fit consistently well (R2 > 0.99) with a 3rd order polynomial or power law. Of those, the scaling functions for Sa, Sq, and S10z were able to predict metric values at a finer resolution within 5 %. Three metrics, (Ssk, Sku, Sfd) were also notable in terms of fit and downscaling.Conclusions
Many metrics exhibit consistent scaling relations across resolution, and several are able to accurately predict values at finer resolutions. However, prediction accuracy is likely related to the amount of information lost during aggregation.17.
Riparian ecosystems are interfaces between aquatic and terrestrial environments recognized for their nutrient interception
potential in agricultural landscapes. Stream network maps from a broad range of map resolutions have been employed in watershed
studies of riparian areas. However, map resolution may affect important attributes of riparian buffers, such as the connectivity
between source lands and small stream channels missing in coarse resolution maps. We sought to understand the influence of
changing stream map resolution on measures of the river network, near-stream land cover, and riparian metrics. Our objectives
were: (1) to evaluate the influence of stream map resolution on measures of the stream network, the character and extent of
near-stream zones, and riparian metrics; (2) to compare patterns of variation among different physiographic provinces; and
(3) to explore how predictions of nutrient retention potential might be affected by the resolution of a stream map. We found
that using fine resolution stream maps significantly increased our estimates of stream order, drainage density, and the proportion
of watershed area occurring near a stream. Increasing stream map resolution reduced the mean distance to source areas as well
as mean buffer width and increased the frequency of buffer gaps. Measures of percent land cover within 100 m of streams were
less sensitive to stream map resolution. Overall, increasing stream map resolution led to reduced estimates of nutrient retention
potential in riparian buffers. In some watersheds, switching from a coarse resolution to a fine resolution stream map completely
changed our perception of a stream network from well buffered to largely unbuffered. Because previous, broad-scale analyses
of riparian buffers used coarse-resolution stream maps, those studies may have overestimated landscape-level buffer prevalence
and effectiveness. We present a case study of three watersheds to demonstrate that interactions among stream map resolution
and land cover patterns make a dramatic difference in the perceived ability of riparian buffers to ameliorate effects of agricultural
activities across whole watersheds. Moreover, stream map resolution affects inferences about whether retention occurs in streams
or riparian zones. 相似文献
18.
E. J. Raynor C. D. Griffith D. Twidwell W. H. Schacht C. L. Wonkka C. P. Roberts C. L. Bielski D. M. Debinski J. R. Miller 《Landscape Ecology》2018,33(12):2103-2119
Context
Plant invasions of native ecosystems are one of the main causes of declines in biodiversity via system-simplification. Restoring native biodiversity can be particularly challenging in landscapes where invasive species have become dominant and where a new set of feedbacks reinforce an invaded state and preclude restoration actions. We lack an understanding of the response of invaded systems to landscape-level manipulations to restore pattern and process relationships and how to identify these relationships when they do not appear at the expected scale.Objectives
To better understand how fire and grazing influence landscape-level heterogeneity in invaded landscapes, we assess the scale at which grazing pressure and seasonality mediate the success of re-introducing a historical disturbance regime, grazing driven by fire (termed pyric herbivory), to an invasive plant-dominated landscape.Methods
We manipulated grazing timing and intensity in exotic grass-dominated grasslands managed for landscape heterogeneity with spring fire and grazing. In pastures under patch-burn grazing management, we evaluated the spatial and temporal variability of plant functional groups and vegetation structure among and within patches managed with separate grazing systems: season-long stocking and intensive early stocking.Results
Warm- and cool-season grasses exhibited greater among-patch variability in invasive-plant dominated grassland under intensive early grazing than traditional season-long grazing, but landscape-level heterogeneity, as measured through vegetation structure was minimal and invariable under both levels of grazing pressure, which contrasts findings in native-dominated systems. Moreover, within-patch heterogeneity for these functional groups was detected; contrasting the prediction that among-patch heterogeneity, in mesic grasslands, manifests from within-patch homogeneity.Conclusions
In invaded grasslands, manipulation of grazing pressure as a process that drives heterogeneous vegetation patterns influences native and non-native grass heterogeneity, but not heterogeneity of vegetation structure, within and among patches managed with fire. Fire and grazing-moderated heterogeneity patterns observed in native grass-dominated grasslands likely differ from invasive grass-dominated grasslands with implications for using pyric herbivory in invaded systems.19.
The woody plant communities found on residential properties constitute an integral component of cities’ green infrastructure and serve as a nexus between urban residents and the natural world. Despite this importance, residential landscapes are infrequently designed with principles of sustainability in mind, resulting in the extensive use of pesticides to suppress a diverse array of plant pests. In this study, we ask whether ecological theory can inform the sustainable design and management of woody plant communities on urban residential properties. The associational resistance and dilution effect hypotheses are analogous hypotheses, which posit that increasing biodiversity can inhibit the abundance of herbivores and pathogens, respectively. Importantly, theory suggests that it might not just be diversity that matters, but the right kind of diversity (i.e., community composition). Previous studies have demonstrated that herbivore abundance can be greater on native plants compared to exotic plants in residential landscapes. However, little is known regarding whether this translates into greater numbers of interventions to reduce damage associated with plant pests on native plants. To test these hypotheses, we utilized a multi-year, commercial plant health care program dataset. We examined, at the residential property scale, the relationships between woody plant diversity, the percentage of plants that were native, and pest management interventions. We found that the number of pest management interventions targeting phytophagous arthropods, but not plant pathogens, was negatively related to woody plant biodiversity. The percentage of native plants on a property had no relationship with the number of pest management interventions that occurred. Consequently, efforts to increase woody plant biodiversity in residential landscapes could result in increased phytophagous arthropod pest suppression, thereby reducing the need for pesticide applications and their associated adverse effects. 相似文献
20.
Chevonne Reynolds Robert J. FletcherJr. Celine M. Carneiro Nicole Jennings Alison Ke Michael C. LaScaleia Mbhekeni B. Lukhele Mnqobi L. Mamba Muzi D. Sibiya James D. Austin Cebisile N. Magagula Themba’alilahlwa Mahlaba Ara Monadjem Samantha M. Wisely Robert A. McCleery 《Landscape Ecology》2018,33(2):241-255