Vegetation Patterns In Landscapes Research Articles

Colonial management drives ecological change following the exclusion of Indigenous stewardship in a Stoney Iyethka montane grassland, Canadian Rocky Mountains

Abstract For millennia, Indigenous Peoples and their ecological stewardship have kept culturally important landscapes open, diverse and productive. Under colonization which suppresses stewardship activities, landscape vegetation patterns shift and areas previously stewarded by Indigenous Peoples are now undergoing successional change. As a case study, we document ecological change on the homelands of the Stoney Iyethka Nations in the Canadian Rocky Mountains, where landscapes have changed dramatically over the past century of colonial management. On the Stoney Iyethka traditional montane Egnuck Wida grasslands, we analysed vegetation change on both the landscape and plot level. Using oblique photographs taken in 1924 paired with 2021 satellite imagery, we compared past and present landscape vegetation cover and assessed drivers of succession. We also examined differences in vegetation class cover and plant community structure between surveys conducted in 1981, 1995 and 2020. Nearly half (47%) of the landscape surveyed showed seral progression in vegetation class, which was not explained by topography, geology or climate warming. Grassland area decreased four‐fold between 1924 and 2021. Grassland retention was strongly related to management zoning, with greater losses in the crown‐managed ecological reserve than on lands that remain under Stoney Iyethka stewardship. Vegetation plots surveyed reveal changes to plant community composition and shifts in dominant vegetation class. In plots previously composed primarily of forbs and graminoids, shrubs have become the dominant groundcover. Declines in historic vegetation include a loss of culturally important food, medicine and ceremonial plants to the Stoney Iyethka Nations. The most likely explanation for these results is the displacement of Indigenous Peoples and their stewardship from the landscape. We demonstrate that the past century of colonial environmental management has altered ecological processes maintained on this landscape for millennia by Indigenous Peoples. Read the free Plain Language Summary for this article on the Journal blog.

Adapting a multiscale approach to assess the compositional diversity of landscapes

ContextThe role of landscape diversity and structure is crucial for maintaining biodiversity. Both landscape diversity and structure have often been analysed on one thematic layer, focusing on Shannon diversity. The application of compositional diversity, however, has received little attention yet.ObjectivesOur main goal was to introduce a novel framework to assess both landscape compositional diversity and structure in one coherent framework. Moreover, we intended to demonstrate the significance of the use of a neutral model for landscape assessments.MethodsBoth entire Hungary and nine of its regions were used as study areas. Juhász-Nagy’s information theory-based functions, i.e. “compositional diversity” and “associatum”, were introduced and applied in landscape context. Potential and actual landscape characteristics were compared by analysing a probabilistic representation of potential natural vegetation (multiple PNV, MPNV) and actual vegetation (AV), treating MPNV as a neutral model.ResultsA significant difference was found between the MPNV- and AV-based, maximal compositional diversity estimates. MPNV-based maximal compositional diversity was higher and the maximum appeared at a finer spatial scale. The differences were more prominent in human-modified regions. Associatum implied the spatial aggregation of both MPNV and AV. Fragmentation of AV was indicated by larger units carrying maximal compositional diversity and maximal associatum values.ConclusionsApplying the multiscale Juhász-Nagy’s functions to landscape composition allowed more precise characterization of the landscape state than traditional Shannon diversity. Our results underline, that increasingly transformed landscapes host decreasing complexity of vegetation type combinations and increasing grain that carries the richest information on landscape vegetation patterns.

Fire Has a Positive Effect on the Abundance of Sun Spiders (Arachnida: Solifugae) in the Cerrado-Pantanal Ecotone

Fire is an important disturbance factor in shrublands, grasslands, and savannas. It alters the habitat of a multitude of species and, under natural dynamics, is a major determinant of landscape vegetation patterns. Here, we evaluate the effects of different wildfire regimes on the abundance of sun spiders in the Cerrado-Pantanal ecotone. To study how different fire regimes affect the number of individual sun spiders, we considered the frequency of fire occurrences in the last 20 years and classified locations as high frequency or low frequency. We also classified the time of the last fire in 2020 as occurring in the first or second half of the year. In addition, we compared the number of individual sun spiders before and after fire. We found no effects of fire frequency and period when the fire occurred in 2020, but the number of individual sun spiders was higher after wildfires. Although ground-dwelling are considered fire sensitive, some can employ strategies to tolerate fire so that they are able to not only survive, but also reproduce in fire-prone landscapes. Thus, we suggest that sun spiders are resilient, can explore sites under different fire regimes, and can be considered pyrophilous species.

Identifying Policy-relevant Indicators for Assessing Landscape Vegetation Patterns to Inform Planning and Management on Multiple-use Public Lands

Understanding the structure and composition of landscapes can empower agencies to effectively manage public lands for multiple uses while sustaining land health. Many landscape metrics exist, but they are not often used in public land decision-making. Our objectives were to (1) develop and (2) apply a process for identifying a core set of indicators that public land managers can use to understand landscape-level resource patterns on and around public lands. We first developed a process for identifying indicators that are grounded in policy, feasible to quantify using existing data and resources, and useful for managers. We surveyed landscape monitoring efforts by other agencies, gathered science and agency input on monitoring goals, and quantified the prevalence of potential indicators in agency land health standards to identify five landscape indicators: amount, distribution, patch size, structural connectivity, and diversity of vegetation types. We then conducted pilot applications in four bureau of land management (BLM) field offices in Arizona, California, and Colorado to refine procedures for quantifying the indicators and assess the utility of the indicators for managers. Results highlighted the dominance of upland and the limited extent of riparian/wetland vegetation communities, moderate connectivity of priority vegetation patches, and lower diversity of native vegetation types on BLM compared to non-BLM lands. Agency staff can use the indicators to inform the development of quantitative resource management objectives in land use plans, evaluate progress in meeting those objectives, quantify potential impacts of proposed actions, and as a foundation for an all-lands approach to landscape-level management across public lands.

Change in Vegetation Patterns Over a Large Forested Landscape Based on Historical and Contemporary Aerial Photography

Changes to vegetation structure and composition in forests adapted to frequent fire have been well documented. However, little is known about changes to the spatial characteristics of vegetation in these forests. Specifically, patch sizes and detailed information linking vegetation type to specific locations and growing conditions on the landscape are lacking. We used historical and recent aerial imagery to characterize historical vegetation patterns and assess contemporary change from those patterns. We created an orthorectified mosaic of aerial photographs from 1941 covering approximately 100,000 ha in the northern Sierra Nevada. The historical imagery, along with contemporary aerial imagery from 2005, was segmented into homogenous vegetation patches and classified into four relative cover classes using random forests analysis. A generalized linear mixed model was used to compare topographic associations of dense forest cover on the historical and contemporary landscapes. The amount of dense forest cover increased from 30 to 43% from 1941 to 2005, replacing moderate forest cover as the most dominant class. Concurrent with the increase in extent, the area-weighted mean patch size of dense forest cover increased tenfold, indicating greater continuity of dense forest cover and more homogenous vegetation patterns across the contemporary landscape. Historically, dense forest cover was rare on southwesterly aspects, but in the contemporary forest, it was common across a broad range of aspects. Despite the challenges of processing historical air photographs, the unique information they provide on landscape vegetation patterns makes them a valuable source of reference information for forests impacted by past management practices.

Linking carbon balance to establishment patterns: comparison of whitebark pine and Engelmann spruce seedlings along an herb cover exposure gradient at treeline

There is increasing evidence that landscape vegetation patterns near species’ range limits are associated with positive biotic interactions, such as in the alpine-treeline ecotone. In the northern Rocky Mountains, whitebark pine (Pinus albicaulis) is considered an early-successional species, able to establish in exposed microsites, while late-successional species such as Engelmann spruce (Picea engelmannii) are more dependent on neighboring vegetation to facilitate establishment. We compared ecophysiological traits associated with carbon balance of newly germinated seedlings of whitebark pine and Engelmann spruce along an herb cover gradient to (1) infer which ecophysiological properties explain the establishment success of seedlings, and (2) to assess differences in establishment patterns with respect to distance from neighboring vegetation. We measured survival over 2 years, and concurrently measured gas exchange and water relations (photosynthesis, respiration, and transpiration), morphology [specific leaf area (SLA)], and biochemistry [chlorophyll fluorescence (F v /F m) and nonstructural carbohydrates]. Both species initially established in the most exposed microsites away from vegetation during their first growing season, but only pine persisted in exposed microsites to the end of the second growing season. Pine exhibited phenotypic traits to increase stress tolerance (e.g., higher soluble sugar concentrations, lower SLA) and improve carbon balance (e.g., greater water use efficiency, lower respiration, higher F v /F m) compared to spruce in exposed sites, but had lower carbon balance under herb cover. Superior establishment success of pine in exposed microsites at treeline could thus be attributed to a suite of intrinsic physiological advantages that are apparent at the earliest stage of development.

Land‐use change and subalpine tree dynamics: colonization of Larix decidua in French subalpine grasslands

Summary In many places in Europe, trees are currently far below their theoretical altitudinal limit because of past land use. However, under the current crisis affecting mountain agriculture, trees are likely to recolonize the subalpine belt. Addressing the societal issues associated with such landscape change requires predictive tools to assess vegetation dynamics in relation to management strategies. This study aims to analyse the factors determining tree dynamics at the subalpine ecotone and to evaluate the impact of land‐use change on landscape vegetation patterns. We developed a hierarchical scaling approach and applied it to a European larch (Larix decidua Mill.) colonization in the French Alps. Our landscape case study focused on subalpine south‐facing grasslands of Villar d’Arêne (France). First, we used a habitat‐suitability model to delineate the climatic suitability habitats of larch in the French Alps. Then we used a landscape model (LaMoS) to determine whether larch is able to colonize these grasslands predicted to be climatically suitable, considering land use and local vegetation. The sensitivity of landscape colonization patterns to land‐use scenarios (abandonment, delayed mowing or traditional mowing) and biological attributes of larch were analysed with a factorial simulation experiment. The accuracy of the habitat‐suitability model at the French Alps scale allowed for the prediction that the grasslands of Villar d’Arêne were highly suitable for larch. Simulations highlighted the effect of land use on larch establishment at the local but not at the landscape scale. On the other hand, larch attributes such as dispersal capacity, juvenile tolerance to light interaction (competition and facilitation) and its capacity to survive on infertile soil were shown as essential for tree spatial dynamics. Synthesis and applications. Combining a habitat‐suitability model with a spatially and temporally explicit landscape model enhances the capacity to account for environmental factors acting at different overlapping scales. This modelling strategy increases the robustness and accuracy of predictions, a prerequisite for landscape management in a global change context. We conclude that ongoing and future agri‐environmental policies have to be quickly adapted to protect biodiversity and ecosystem services provided by subalpine grasslands.

Invasive Pathogens At Alpine Treeline: Consequences for Treeline Dynamics

The potential impact of invasive forest pathogens on alpine treeline dynamics has not previously been considered. Whitebark pine (Pinus albicaulis), a foundation and keystone species of subalpine forests and major component of alpine treeline in the northern Rocky Mountains of the United States and southern Canada, is infected nearly range-wide by the exotic pathogen Cronartium ribicola, which causes white pine blister rust. A major component of treeline in the northern Rocky Mountains, whitebark pine initiates tree islands on the eastern slope in northwestern Montana more than any other conifer species. Blister rust infects whitebark pine throughout the region, and both infection and mortality are already evident at treeline. We discuss the cascading ecological effects of the loss of treeline whitebark pine and expected changes in landscape vegetation patterns. Potential implications of the loss of whitebark pine for northwestern Montana treelines are examined in the context of climate change within a conceptual model. We speculate that exotic pathogens could potentially confound predictions of treeline responses to global warming in many geographic regions.

Spatially explicit modeling of mixed-severity fire regimes and landscape dynamics

Simulation models of disturbance and succession are being increasingly applied to characterize landscape composition and dynamics under natural fire regimes, and to evaluate alternative management strategies for ecological restoration and fire hazard reduction. However, we have a limited understanding of how landscapes respond to changes in fire frequency, and about the sensitivity of model predictions to assumptions about successional pathways and fire behavior. We updated an existing landscape dynamics model (LADS) to simulate the complex interactions between forest dynamics, fire spread, and fire effects in dry forests of the interior Pacific Northwest. Experimental model runs were conducted on a hypothetical landscape at fire rotations ranging from 5 to 50 years. Three sensitivity analyses were carried out to explore the responses of landscape composition to (1) parameters characterizing succession and fire effects on vegetation, (2) the probability of fire spread into different successional stages, and (3) the size and spatial pattern of static fire refugia. The area of old open-canopy forests was highest at the shortest fire rotations, and was particularly sensitive to the probability of stand-replacement fire in open-canopy forests and to the fire-free period required for ingrowth to occur in open-canopy forests. The area of old closed-canopy forests increased with lengthening fire rotation, but always comprised a relatively small portion of the landscape (<10%). The area of old closed-canopy forests increased when fire spread was more rapid in open-canopy forests than in closed-canopy forests, and when the physical landscape incorporated large “fire refugia” with low fire spread rates. Old closed-canopy forests appear to comprise a relatively minor landscape component in mixed-severity fire regimes with fire rotations of 50 years or less. However, these results are sensitive to assumptions about the spatial interactions between fire spread, landscape vegetation patterns, and the underlying physical landscape.

Interactive controls of herbivory and fluvial dynamics on landscape vegetation patterns on the Tanana River floodplain, interior Alaska

AbstractAim We examined the interactive effects of mammalian herbivory and fluvial dynamics on vegetation dynamics and composition along the Tanana River in interior Alaska.Location Model parameters were obtained from field studies along the Tanana River, Alaska between Fairbanks (64°50.50′ N, 147°43.30′ W) and Manley Hot Springs (65°0.0′ N, 150°36.0′ W).Methods We used a spatially explicit model of landscape dynamics (ALFRESCO) to simulate vegetation changes on a 1‐year time‐step. The model was run for 250 years and was replicated 100 times.Results Increases in herbivory decreased the proportion of early successional vegetation and increased the proportion of late successional vegetation on the simulated landscape. Erosion and accretion worked as antagonists to herbivory, increasing the amount of early successional vegetation and decreasing the amount of late successional vegetation. However, the interactive effects of herbivory and erosion/accretion were especially important in determining system response, particularly in early seral vegetation types. High erosion rates, when coupled with low herbivory, greatly increased the proportion of willow on the landscape. When coupled with high herbivory, however, they greatly increased the proportion of alder on the landscape. At low levels of herbivory, alder abundance peaked at intermediate levels of erosion/accretion.Main conclusions Neither erosion/accretion nor herbivory produced consistent landscape patterns that could be predicted independently of the other. These findings underscore the importance of the interactive effects of biotic and abiotic disturbances in shaping large‐scale landscape vegetation patterns in boreal floodplain ecosystems – systems traditionally thought to be driven primarily by abiotic disturbance alone.

Landscape pattern in topographically complex landscapes: issues and techniques for analysis

Ecological research provides ample evidence that topography can exert a significant influence on the processes shaping broad-scale landscape vegetation patterns. Studies that ignore this influence run the risk of misinterpreting observations and making inappropriate recommendations to the management community. Unfortunately, the standard methods for landscape pattern analysis are not designed to include topography as a pattern-shaping factor. In this paper, we present a set of techniques designed to incorporate the topographic mosaic into analyses of landscape pattern and dynamics. This toolbox includes adjustments to ‘classic’ landscape indices that account for non-uniform landscape topography, indices that capture associations and directionality in vegetation pattern due to topographic structure, and the application of statistical models to describe relationships between topographic characteristics and vegetation pattern. To illustrate these methods, we draw on examples from our own analysis of landscape pattern dynamics in logged and unlogged forest landscapes in southwestern British Columbia. These examples also serve to illustrate the importance of considering topography in both research and management applications.

Simulated dynamics of succession in a North American subtropical Prosopis savanna

Abstract. A transition matrix model was used to explore the dynamics, rate and potential extent of changes in landscape vegetation patterns on a southern Texas Prosopis savanna. Transitions between seven vegetation classes were determined for the periods 1941–1960 and 1960–1983 on aerial photographs of three sites. During these periods, the sites were heavily grazed by cattle and were fire‐free. Vegetation states assessed in grids of 20 m x 20 m cells superimposed on photographs ranged from grass‐dominated to woody plant‐dominated. The 1941–1960 period (denoted DRY) was characterized by prolonged drought, whereas annual rainfall during the 1960–1983 period (denoted WET) was typically normal to above‐normal. The 1941 landscape consisted of herbaceous zones (6% of cells), woodland (50% of cells) and savanna parkland (44% of cells with grass/woody plant mixtures). The woodland state was the most stable, with probabilities of no change being 0.970 and 0.873 in WET and DRY periods, respectively. The herbaceous state was least stable, with corresponding values of 0.074 and 0.353.Past and future landscape structure was modelled by randomly selecting DRY or WET transitions at 20 year time steps. The model was run under a series of rainfall scenarios where the probability of selecting the WET transition matrix (P[WET]) ranged from 0 (DRY always chosen) to 1 (WET always chosen). Historical records indicate P[WET] has approximated 0.3 to 0.4 in the region. The rate of succession to states of greater woody cover increased as P[WET] increased. Forward simulations based on P[WET] &gt; 0.2 suggest the present landscape is unstable and will develop into a closed‐canopy woodland within the next 180 years, assuming the processes operating between 1941 and 1983 continue (e.g. grazing by cattle and lack of fire). Reverse simulations concur with historical observations and projections derived from woody plant growth rates in other studies and suggest that 200 to 300 yr BP these landscapes contained a substantially greater proportion of cells dominated by grassland or grassland with scattered woody plants (43 to 74%) than was present in 1983 (19%). Based upon elapsed time between predicted past and future steady states, succession from open savanna to closed‐canopy woodland may occur in ca. 400 to 500 yr for P(WET) ≥ 0.33. Arresting or reversing the projected trend may require changes in climate and/or changes in livestock grazing and land management practices.The approaches employed in this study illustrate how time series maps, aerial photographs and satellite imagery can be analyzed and used to interpret, project and reconstruct local and regional changes in ecosystem structure. Difficulties and limitations associated with the use of Markov chains to model succession are identified and discussed.