Pattern-process Relationships Research Articles

Consistently heterogeneous structures observed at multiple spatial scales across fire-intact reference sites

Yellow pine and mixed-conifer (YPMC) forests of California’s Sierra Nevada have experienced widespread fire suppression for over a century, resulting in ingrowth and densification of trees, heavy fuel accumulation, and shifts in species composition. Under warmer and drier climates, these forests are primed for stand-replacing fires and severe drought mortality, requiring management interventions to improve their resilience and mitigate future impacts. Observations from functioning frequent-fire systems (e.g., contemporary reference sites) can provide key insights about pattern-process relationships in fire-intact systems, which can be used to inform regional management efforts. In this study, we used airborne lidar data to quantify and compare forest structure at multiple spatial scales between contemporary reference sites (i.e., forests with a restored frequent, low-intensity fire regime) and control sites (i.e., typical fire-suppressed forests). We evaluated structures at the neighborhood- (∼1 ha), site- (∼100–1,000 ha), and among-site- (∼10,000–100,000 ha) levels. In reference sites, high proportions of individual trees, small clumps of 2–4 trees, and open space formed mostly open canopy structures at the neighborhood-level, and patches of these neighborhood-level structures were arranged in heterogeneous spatial patterns within sites. We observed low variability in site-level structures among reference sites, indicating a stabilizing effect of frequent, low-intensity fire across broad, ecosystem scales. In fire-suppressed control sites, edaphic factors and other non-fire disturbances occasionally produced heterogeneity at the neighborhood- and site-level, but the degree of heterogeneity was not consistent across sites. Structural patterns in contemporary reference sites suggest improved resilience to future disturbances and climate change, and increased provisioning of ecosystem services relative to control sites. We suggest applying these metrics to help inform multi-scale and multi-resource management in Sierra Nevada forests.

Studying the spatial evolutionary behavior of urban forest patches from the perspective of pattern-process relationships

Urban forest dynamics can influence the provision of ecosystem services provision. Considerable research has been conducted to understand how these dynamics respond to urbanization, from individual patches to entire landscapes. However, most of these are cross-sectional studies based on landscape metrics, and research using a process-based perspective in this context is scarce. In this study, we present a “pattern-process” analytical framework to quantify the evolutionary behavior of urban forest patches. We combine this framework with land cover classification data based on high-resolution remote sensing images (< 1 m) from 2002, 2013, and 2019 to detect the dynamic characteristics of four processes of forest patches in Beijing urban areas. These dynamic characteristics include: size distribution, aggregation and fragmentation, transfer, and self-stabilization. The results showed that 1) the average size of the patches in the study area is increasing, and patches larger than 50 m2 have a more positive influence on the process of patch structure evolution, 2) patch fragmentation shifts with the direction of urban sprawl, 3) transfer between urban forest and bare land is increasing, and 4) urban forest network construction positively enhances the stability of patches. This framework can provide a useful basis for understanding the spatial and temporal evolution of urban forest landscapes during urban development and contribute to the sustainable management of urban forests.

Perspectives on Applications of Geospatial Technology and Landscape Ecology for Conservation Planning in the Global South

Rapidly changing landscapes and disturbance regimes in the Global South impact the viability of conservation planning. Although conservation planning processes benefit from reliable multi-scale and multi-temporal data on landscape changes, this is not widely understood. In this paper, the authors examine landscape change dynamics and disturbance regimes in the Global South and discuss the methodological needs of characterizing pattern-process relationships of landscape disturbance to facilitate effective conservation planning. For example, geospatial analysis of Nairobi-Namanga Road, in the Kaputei Plains of Kenya, was used to highlight impacts of road infrastructure on wooded grassland and open grasslands, on wildlife migration corridors and livelihoods. The authors discuss how integration of geospatial technologies and landscape ecology metrics could enhance conservation planning and decision-making in the Global South. The benefits of coupling the decision-making process with stakeholder engagements and nature-based solutions to ensure viable conservation of biodiversity were also discussed.

Cross scale spatial and temporal indicators for measuring the effects of landscape heterogeneity on pollination service

Spatial heterogeneity as well as landscape services’ provision are a function of spatio-temporal scales, therefore, pattern–process relationships must be assessed at the multiple scales. In this context, this research aims at: (1) analyzing at the regional scale how pollination service can be affected by landscape heterogeneity, using two landscape indicators useful to quantify the multiscale landscape composition and landscape configuration simultaneously; and (2) assessing the effect that the infection of Xylella fastidiosa has exerted on the pollination services. The multi-scale spatial assessment has been focused on two land-covers: forests and olive groves that can act as source of pollination services. The multi-temporal analysis, based on the annual NDVI, has been used to assess the functionality of olive groves before and at the beginning of the infection of Xylella fastidiosa, and currently. The results have shown that in 2012 the most representative cluster (C1) (73.6% for forests and 63% for olive groves) is in the lower left part of the multiscale metric space, meaning that both land-covers show a fragmented spatial configuration at small spatial scales and tend to be aggregated at large scales. The multi-temporal analysis has allowed to show the evident change in the landscape functioning in the provinces interested by the infection of Xylella fastidiosa (Lecce, Brindisi and Taranto) from 2013 to 2021, highlighting that the stability of the landscape has resulted completely changed for the loss of permanent land-covers (olive groves). In this study the spatio-temporal analyses have helped in giving a more complete indication in the assessment of landscape services where different factors can play a crucial role. The analysis of spatial patterns along a continuum of scale has been implemented by the analysis of multi-temporal dynamics to consider the effect of Xylella fastidiosa infection on pollination. The temporal behavior of NDVI has resulted completely changed in the provinces interested by this infection, meaning that recovering policies need to be undertaken to regenerate the landscape. When studying landscape services, some considerations must be considered in choosing the suitable spatial and temporal scale for its assessment. One of the recent drivers of change, represented by the infection of Xylella fastidiosa, and the planning of landscape functionality recovery interest higher spatial scales and will affect the scale at which landscape services, included pollination, are delivered.

Studying the Spatial Evolutionary Behavior of Urban Forest Patches from the Perspective of Pattern–Process Relationships

Studying the Spatial Evolutionary Behavior of Urban Forest Patches from the Perspective of Pattern–Process Relationships

Linear downscaling from MODIS to landsat: connecting landscape composition with ecosystem functions

The open and free access to Landsat and MODIS products have greatly promoted scientific investigations on spatiotemporal change in land mosaics and ecosystem functions at landscape to regional scales. Unfortunately, there is a major mismatch in spatial resolution between MODIS products at coarser resolution (≥ 250 m) and landscape structure based on classified Landsat scenes at finer resolution (30 m). Based on practical needs for downscaling popular MODIS products at 500 m resolution to match classified land cover at Landsat 30 m resolution, we proposed an innovative modelling approach so that landscape structure and ecosystem functions can be directly studied for their interconnections. As a proof-of-concept of our downscaling approach, we selected the watershed of the Kalamazoo River in southwestern Michigan, USA as the testbed. MODIS products for three fundamental variables of ecosystem function are downscaled to ensure the approach can be extrapolated to multiple functional measurements. They are blue-sky albedo (0–1), evapotranspiration (ET, mm), and gross primary production (GPP, Mg C ha−1 year−1). An object-oriented classification of Landsat images in 2011 was processed to generate a land cover map for landscape structure. The downscaling model was tested for the five Level IV ecoregions within the watershed. We achieved satisfactory downscaling models for albedo, ET, and GPP for all five ecoregions. The adjusted R2 was > 0.995 for albedo, 0.915–0.997 for ET, and 0.902–0.962 for GPP. The estimated albedo, ET, and GPP values appear different in the region. The estimated albedo was the lowest for water (0.076–0.107) and the highest for cropland (0.166–0.172). Estimated ET was the highest for the built-up cover type (525.6–687.1 mm) and the lowest for forest (209.7–459.7 mm). The estimated GPP was the highest for the build-up cover type (8.65–9.85 Mg C ha−1 year−1) and the lowest for forest. Estimated values for albedo, ET, and GPP appear reasonable for their ranges in the Kalamazoo River region and are consistent with values reported in the literature. Despite these promising results, the downscaling approach relies on strong assumptions and can carry substantial uncertainty. It is only valid at a spatial scale where similar climate, soil, and landforms exist (i.e., values in isolated patches of the same cover type are similar). Plausibly, the uncertainties associated with each estimation, as well as the model residuals, can be explored for other pattern-process relationships within the landscape.

Deriving Fire Behavior Metrics from UAS Imagery

The emergence of affordable unmanned aerial systems (UAS) creates new opportunities to study fire behavior and ecosystem pattern—process relationships. A rotor-wing UAS hovering above a fire provides a static, scalable sensing platform that can characterize terrain, vegetation, and fire coincidently. Here, we present methods for collecting consistent time-series of fire rate of spread (RoS) and direction in complex fire behavior using UAS-borne NIR and Thermal IR cameras. We also develop a technique to determine appropriate analytical units to improve statistical analysis of fire-environment interactions. Using a hybrid temperature-gradient threshold approach with data from two prescribed fires in dry conifer forests, the methods characterize complex interactions of observed heading, flanking, and backing fires accurately. RoS ranged from 0–2.7 m/s. RoS distributions were all heavy-tailed and positively-skewed with area-weighted mean spread rates of 0.013–0.404 m/s. Predictably, the RoS was highest along the primary vectors of fire travel (heading fire) and lower along the flanks. Mean spread direction did not necessarily follow the predominant head fire direction. Spatial aggregation of RoS produced analytical units that averaged 3.1–35.4% of the original pixel count, highlighting the large amount of replicated data and the strong influence of spread rate on unit size.

Hierarchy theory reveals multiscale predictors of Arkansas darter (Etheostoma cragini) abundance in a Great Plains riverscape

Abstract Landscape ecology and its emphasis on relationships between spatial heterogeneity, scale, and ecological processes can be applied to manage stream ecosystems as riverscapes. Hierarchy theory, a central tenet of riverscape ecology, allows for investigating ecological relationships between aquatic organisms and habitat by exploring the nested interactions inherent in reaches, segments, and basins. Arkansas darter Etheostoma cragini is a Great Plains fish endemic to the Arkansas River basin and is listed as in need of conservation in all five states within its range in North America. The aim of this study was to develop empirical models describing relationships between Arkansas darter abundance and local habitats, and identify the appropriate scale(s) for assessing and managing populations. We used Arkansas darter abundance data collected from stream sample units as a fixed grain size (102 m) and compiled datasets at three hierarchical spatial extents, including reach (103 m), nested within segment (104 m), nested within basin (105 m) in southcentral Kansas. We fit generalised linear mixed models (GLMMs) to assess scale‐specific relationships between Arkansas darter abundance and local habitat dimensions (stream depth and width) and heterogeneity (canopy cover, overhanging vegetation, and woody structure). Habitat parameters included in best‐supported GLMMs differed among extents. Variation in Arkansas darter abundance was explained by canopy cover and channel depth at the reach (54% explained) and segment (56%) extents, and stream width and depth at the basin extent (37%). Partial dependence plots from multiple regression GLMMs revealed that Arkansas darter abundance was negatively correlated with increasing channel depth across all extents, increasing canopy cover at reach and segment extents, and increasing channel width at the basin extent. Our results highlight scale‐specific relationships between Arkansas darter abundance and local habitats across multiple spatial extents. These findings provide direction for assessing stream fish ecology pattern‐process relationships at the appropriate spatial scales and benefit native fish conservation by highlighting the application of hierarchy theory to address management challenges.

Pyric herbivory, scales of heterogeneity and drought

Abstract Understanding how extreme drought alters spatial patterns and temporal stability in grassland biomass will become increasingly important by the end of the century when climate model forecasts suggest drought events will occur more frequently. In grassland landscapes where grazing is driven by fire (termed pyric herbivory), temporal stability in above‐ground plant biomass at landscape scales typically coincides with greater spatial variability across local communities (time‐since‐fire patches), whereas variability within local communities is associated with lower temporal stability. We assess the robustness of this relationship during one of the most severe droughts on modern record in the southern Great Plains. We use a long‐term pyric herbivory experiment to test whether extreme drought (1) changes patterns of spatial variability in above‐ground plant biomass among or within local communities, (2) changes the temporal stability in above‐ground plant biomass and the relationship between spatial variability and temporal variability and (3) changes the underlying feedback mechanisms associated with pyric herbivory. Ordination revealed a shift from spatially distinct patches before drought to a convergence of patches during drought in terms of above‐ground plant biomass and crude protein. Permutation tests revealed that within‐patch variability in above‐ground plant biomass significantly increased during drought compared to pre‐drought levels. Temporal stability in above‐ground plant biomass decreased during drought and indeed corresponded with reduced variability in biomass among local communities and increased variability within local communities compared to pre‐drought levels. The results from this study strongly suggest that both positive and negative feedback loops responsible for pyric herbivory were maintained by scale‐switching during periods of extreme drought and further reinforce the importance of scale in the study of pattern–process relationships. A plain language summary is available for this article.

Evidence and Opportunities for Integrating Landscape Ecology into Natural Resource Planning across Multiple-Use Landscapes

Enhancing natural resource management has been a focus of landscape ecology since its inception, but numerous authors argue that landscape ecology has not yet been effective in achieving the underlying goal of planning and designing sustainable landscapes. We developed nine questions reflecting the application of fundamental research topics in landscape ecology to the landscape planning process and reviewed two recent landscape-scale plans in western North America for evidence of these concepts in plan decisions. Both plans considered multiple resources, uses, and values, including energy development, recreation, conservation, and protection of cultural and historic resources. We found that land use change and multiscale perspectives of resource uses and values were very often apparent in planning decisions. Pattern-process relationships, connectivity and fragmentation, ecosystem services, landscape history, and climate change were reflected less frequently. Landscape sustainability was considered only once in the 295 decisions reviewed, and outputs of landscape models were not referenced. We suggest six actionable opportunities for further integrating landscape ecology concepts into landscape planning efforts: 1) use landscape sustainability as an overarching goal, 2) adopt a broad ecosystem services framework, 3) explore the role of landscape history more comprehensively, 4) regularly consider and accommodate potential effects of climate change, 5) use landscape models to support plan decisions, and 6) promote a greater presence of landscape ecologists within agencies that manage large land bases and encourage active involvement in agency planning efforts. Together these actions may improve the defensibility, durability, and sustainability of landscape plan decisions.

Land change and loss of landscape diversity at the Caatinga phytogeographical domain – Analysis of pattern-process relationships with MODIS land cover products (2001–2012)

Tropical dry forests are increasingly threatened by land degradation. For the Caatinga seasonally dry forests in Northeast Brazil, recent studies revealed both woody vegetation loss and (re-)gain. A conclusive analysis of land cover and landscape diversity changes is still lacking. To fill this gap, we surveyed pattern-process relationships for the Caatinga phytogeographical domain on different spatial levels for the years 2001–2012 from MODIS land cover data. By a landscape pattern analysis, a set of five landscape metrics was calculated using FRAGSTATS. The spatio-temporal results revealed a general decrease of fragmentation and diversity. The savanna class which comprises also Caatinga dry forests covered large parts of the landscape and gained considerably, whereas other vegetation classes decreased. The distribution of the low vegetated shrublands and grasslands implied degradation risks, in particular at the São Fransisco River valley. Large-scaled agriculture was found in the proximity to water reservoirs in the lowlands, which led to local increases of the landscape’s diversity. We quantified both gains and losses of woody vegetation with a notable net gain of 6.7% of the study area. Main changes may be attributed to socio-economic shifts from local to large-scaled agriculture and water infrastructural activities. Overall, our study shows that a multi-temporal, global dataset along with a landscape pattern analysis provides valuable contributions to landscape research and for detecting land cover and landscape diversity changes.

Modelling potential conservation easement locations using physical and socio-economic factors: A case-study from south-east Michigan

Conservation easements are an important tool for land stewardship by managing existing land use on private lands while allowing for continued private ownership and management. Conservation easements have been used to address a variety of conservation goals such as preserving wetlands for wildlife or constraining urban growth to conserve agricultural landscapes. Since conservation easements serve not just environmental but also social goals, understanding the pattern-process relationships of conservation easement placement can help illustrate current landscapes compared to future scenarios potential by linking current locations across the social and physical landscape. This paper examines the relationships of two types of conservation easements (i.e. environmental and farm) and projects similar potential locations based on just the physical landscape compared to both physical and social landscape by adapting the ecological model, Maxent, to land use modelling. Our results found that current conservation easement locations are modelled equally well using only environmental variables as social and environmental variables together. However, a comparison between projected potential conservation easement locations based on environmental versus socio-economic and environmental factors revealed little difference for environmental conservation easement, but a substantially different distribution for open space conservation easements. These results indicate potential areas to expand open space conservation easements that will serve different socio-economic groups than current locations and demonstrate the potential utility of this methodology for modelling current and future landscapes using the Maxent approach.

Multi-scale network analysis shows scale-dependency of significance of individual protected areas for connectivity

The problem of how ecological mechanisms create and interact with patterns across different scales is fundamental not only for understanding ecological processes, but also for interpretations of ecological dynamics and the strategies that organisms adopt to cope with variability and cross-scale influences. Our objective was to determine the consistency of the role of individual habitat patches in pattern-process relationships (focusing on the potential for dispersal within a network of patches in a fragmented landscape) across a range of scales. Network analysis was used to assess and compare the potential connectivity and spatial distribution of highland fynbos habitat in and between protected areas of the Western Cape of South Africa. Connectivity of fynbos patches was measured using ten maximum threshold distances, ranging from five to 50 km, based on the known average dispersal distances of fynbos endemic bird species. Network connectivity increased predictably with scale. More interestingly, however, the relative contributions of individual protected areas to network connectivity showed strong scale dependence. Conservation approaches that rely on single-scale analyses of connectivity and context (e.g., based on data for a single species with a given dispersal distance) are inadequate to identify key land parcels. Landscape planning, and specifically the assessment of the value of individual areas for dispersal, must therefore be undertaken with a multi-scale approach. Developing a better understanding of scaling dependencies in fragmenting landscapes is of high importance for both ecological theory and conservation planning.

Thermodynamics in landscape ecology: the importance of integrating measurement and modeling of landscape entropy

Entropy and the second law of thermodynamics are the central organizing principles of nature. Or perhaps more accurately, the second law is the central disorganizing principle. Hot things cool down. Cold things warm up. You cannot get something for nothing. You always pay more than you get. Things fall apart. You cannot repeat the past. We grow old and die. It is all downhill from here to the heat death of the universe. While at first these seem like grim and pessimistic ideas, a deeper understanding reveals that the disequilibrial processes of increasing entropy are what enables all organizing actions, such as the formation of a molecule, building of a cell, birth of a child, organization of an ecosystem. Yet strangely, the ideas and implications of the second law are poorly developed in the landscape ecology literature. This is particularly strange given the focus of landscape ecology on understanding pattern-process relationships across scales in space and time. Every interaction between entities leads to irreversible change which increases the entropy and decreases the free energy of the closed system in which they reside. This is the essence of the entropy principle. Descriptions of landscape patterns, processes of landscape change, propagation of pattern-process relationships across space and through time are all governed, constrained, and in large part directed by thermodynamics. This direct linkage to thermodynamics and entropy was noted in several of the pioneering works in the field of landscape ecology (e.g. Forman and Godron 1986; O'Neill et al. 1986; Naveh 1987; O'neill et al. 1989). Yet in the subsequent decades our field has largely failed to embrace and utilize these relationships and constraints, with a few exceptions (see Wu and Loucks 1995; Zhang and Wu 2002; Zurlini et al. 2013).

Influence of urban edges on stress in an arboreal mammal: a case study of squirrel gliders in southeast Queensland, Australia

There is growing recognition that ecological research must expand its focus beyond inference based on pattern-process relationships to the direct measurement of ecological and physiological processes. Physiological assessment is important because vertebrates cope with unpredictable and noxious stimuli by initiating a stress response. However, an over-activation of the acute stress response by numerous novel and potentially stressful anthropogenic pressures, including those associated with urban edges, has the potential to generate chronic stress and a greater susceptibility to disease, reduce fecundity and survivorship. An individual’s physiological response to edge habitats with varying degrees of contrast to the adjacent disturbed urban matrix (e.g. major vs. minor roads), may provide insight into their survival likelihood in fragmented urban landscapes. Although demographic changes in wildlife resulting from urbanization have been documented, only recently have physiological consequences been examined. We addressed this problem using a case study of the squirrel glider (Petaurus norfolcensis) in the fragmented urban landscape of southeast Queensland, Australia. Hair samples were used to enable a comparison of hair cortisol levels in individual squirrel gliders, providing an indication of potential stress. We applied a linear mixed-effect modeling approach clustered by patch to quantify the influence of site-level habitat factors and relative abundance comparative to edge contrast on hair cortisol levels. We found that edge type had a strong positive effect on hair cortisol levels; but this depended on the availability of abundant nest hollows at a site. We conclude that individual hair cortisol concentration, providing an index of stress, was lowest in interior habitats and highest in edge habitats adjacent to major roads. Furthermore, gliders occupying low edge contrast habitats adjacent to residential areas and minor roads, and containing abundant tree nest hollows, had low-moderate hair cortisol levels. This highlights the potential importance of these habitats for the conservation of arboreal mammals such as the squirrel glider in urban landscapes.

Spatial complexity in fragmenting Amazonian rainforests: Do feedbacks from edge effects push forests towards an ecological threshold?

Deforestation and resulting landscape fragmentation are important concerns in many tropical areas. Deforestation is a complex process with many potential feedback loops, many of which are ignored in models that attempt to interpolate forest loss based on past deforestation rates. In addition, most ecological studies of the impacts of deforestation have focused on landscapes that are already fragmented. These studies ignore the fact that edge effects, such as anthropogenic fire, reach their maximum well before habitat connectivity is lost and may create positive feedbacks that result in further fragmentation. We developed a simple model to explore the potential influence of edge effects on fragmentation rates and used remotely sensed data from the MAP (Madre de Dios, Acre, and Pando) region of the Brazilian Amazon to parameterize the relationships of interest. Under reasonable real-world parameter combinations, edge effects can have a significant impact on deforestation rates, supporting the hypothesis that the true tipping point in a forest to pasture regime shift occurs earlier (i.e., ∼50% forest loss) than analysis of a loss in connectivity would suggest (i.e., ∼60% forest loss). Our results have important implications for understanding deforestation, edge-driven processes, regime shifts, and the management of complex pattern-process relationships.

Associations between soil carbon and ecological landscape variables at escalating spatial scales in Florida, USA

The spatial distribution of soil carbon (C) is controlled by ecological processes that evolve and interact over a range of spatial scales across the landscape. The relationships between hydrologic and biotic processes and soil C patterns and spatial behavior are still poorly understood. Our objectives were to (i) identify the appropriate spatial scale to observe soil total C (TC) in a subtropical landscape with pronounced hydrologic and biotic variation, and (ii) investigate the spatial behavior and relationships between TC and ecological landscape variables which aggregate various hydrologic and biotic processes. The study was conducted in Florida, USA, characterized by extreme hydrologic (poorly to excessively drained soils), and vegetation/land use gradients ranging from natural uplands and wetlands to intensively managed forest, agricultural, and urban systems. We used semivariogram and landscape indices to compare the spatial dependence structures of TC and 19 ecological landscape variables, identifying similarities and establishing pattern–process relationships. Soil, hydrologic, and biotic ecological variables mirrored the spatial behavior of TC at fine (few kilometers), and coarse (hundreds of kilometers) spatial scales. Specifically, soil available water capacity resembled the spatial dependence structure of TC at escalating scales, supporting a multi-scale soil hydrology-soil C process–pattern relationship in Florida. Our findings suggest two appropriate scales to observe TC, one at a short range (autocorrelation range of 5.6 km), representing local soil-landscape variation, and another at a longer range (119 km), accounting for regional variation. Moreover, our results provide further guidance to measure ecological variables influencing C dynamics.

Biocomplexity from the Ground Up: Vegetation Patterns in a West African Savanna Landscape

Most studies of vegetation in African savannas have adopted reductionist approaches to research, mostly by looking at only “natural” or “anthropogenic” spaces in focal landscapes. Few have considered how social and biophysical factors interact to create vegetation patterns across landscapes. More holistic understanding of pattern–process relationships across savanna landscapes as wholes is needed to manage the ecological connections of global and local change. To understand how process interactions create vegetation patterns in a savanna landscape, I sampled vegetation in 217 sites in southwestern Mali, where conditions are similar to many parts of West Africa. For each site, I collected site-specific data on several biophysical factors as well as histories of settlement or cultivation, based on ethnographic interviews. Hierarchical clustering, indicator species analysis, multiresponse permutation procedures, and nonmetric multidimensional scaling revealed patterns of floristic variation across the landscape that related to patterns of biophysical variation and disturbance history. The results show complexity in terms of both pattern and process. Patterns evident at different scales of organization are not necessarily congruent, and vegetation heterogeneity is greater than expected based on any subset of biophysical or social processes. Soil moisture, bedrock lithology, and disturbance history are particularly important in shaping vegetation characteristics. Complex patterns arise because vegetation shows three different responses to settlement and cultivation—turnover, homogenization, and resilience—with actual outcomes that depend on site-specific biophysical and social conditions. This research shows that research epistemology can shape physical geographic knowledge and that savanna landscapes must be seen as entities with characteristics that are maintained through human–environment interaction.

Context-dependent vegetation dynamics in an African savanna

Understanding the spatio-temporal dynamics of ecological systems is fundamental to their successful management and conservation. Much research and debate has focused on identifying underlying drivers of vegetation change in savannas, yet few have considered the influence of spatial context and heterogeneity. Our goal was to develop deeper understanding of woody vegetation spatio-temporal dynamics through spatially explicit utilization of historical aerial photography and airborne LiDAR (light detection and ranging). We first assessed temporal change in woody vegetation cover through object-based image analysis of an aerial photography record that spanned 59 years from 1942 to 2001. Secondly, we tested the spatial relationships between environmental variables and patterns of woody structure and dynamics at broad (100 ha), medium (10 ha) and fine-scales (1 ha) through canonical correspondence analysis (CCA). Finally, we used LiDAR derived vegetation heights to explore current woody vegetation structure in the context of historical patterns of change. Total percentage woody cover was stable over time, but woody dynamics were highly variable at smaller scales and displayed distinct spatial trends across the landscape. Losses of woody cover on the diverse alluvial substrates were countered by increases of cover on the hillslopes. Analysis of current woody structure in the context of historical change revealed that the increases took place in the form of shrub encroachment and not the replacement of tall trees. We infer that mammalian herbivory contributed substantially to the losses on lowland alluvial soils, whilst shrub encroachment on the upland hillslopes likely stemmed from changes in fire regime and climate. Deeper reflection on spatial variability is needed in the debate around drivers of change in savanna systems, as spatial patterns of change revealed that different drivers underlie vegetation dynamics in different landscape contexts. Spatial heterogeneity needs explicit consideration in the exploration of pattern–process relationships in ecological systems.

Scale dependent inference in landscape genetics

Ecological relationships between patterns and processes are highly scale dependent. This paper reports the first formal exploration of how changing scale of research away from the scale of the processes governing gene flow affects the results of landscape genetic analysis. We used an individual-based, spatially explicit simulation model to generate patterns of genetic similarity among organisms across a complex landscape that would result given a stipulated landscape resistance model. We then evaluated how changes to the grain, extent, and thematic resolution of that landscape model affect the nature and strength of observed landscape genetic pattern–process relationships. We evaluated three attributes of scale including thematic resolution, pixel size, and focal window size. We observed large effects of changing thematic resolution of analysis from the stipulated continuously scaled resistance process to a number of categorical reclassifications. Grain and window size have smaller but statistically significant effects on landscape genetic analyses. Importantly, power in landscape genetics increases as grain of analysis becomes finer. The analysis failed to identify the operative grain governing the process, with the general pattern of stronger apparent relationship with finer grain, even at grains finer than the governing process. The results suggest that correct specification of the thematic resolution of landscape resistance models dominates effects of grain and extent. This emphasizes the importance of evaluating a range of biologically realistic resistance hypotheses in studies to associate landscape patterns to gene flow processes.