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.     

An integrated approach for measuring urban forest restoration success

Rapid urban growth has increased the importance of restoring degraded vegetation patches within these areas. In this study, we reforested a site that was previously dominated by exotic grasses within an urban area. The goal of this study was to evaluate restoration success in a reforested site using four variables of vegetation structure, five groups of organisms, and eight variables of ecosystem processes, and compare these values with a pre-reforested site and a forested reference site using the Subjective Bray Curtis Ordination. The change in vegetation structure provided arboreal habitats that increased species diversity and ecosystem processes in the reforested site. Specifically, the development of a vertical vegetation structure was associated with: (1) a decrease in herbaceous cover, which allowed the colonization of woody seedlings; (2) a change in microclimatic conditions, which enhanced the colonization of ants and amphibians; (3) colonization of arboreal reptiles and birds; and (4) an increase in litter production, which enhanced nutrient inputs. Moreover, the Subjective Bray Curtis Ordination demonstrated an overall recovery of approximately 70%. Planting woody species was sufficient to stimulate rapid recovery of many ecosystem attributes. Future restoration projects should include multiple variables that reflect important ecosystem attributes to determine the success of a project and to direct future management efforts.     

Is colourful self-sustaining forb vegetation mere fantasy?

Biodiversity in urban and suburban environments can be supported through establishment of low maintenance-requiring herbaceous vegetation types. Here, we attempt to provide a perspective on the possibilities and limitations of establishing forb-dominated vegetation to support local biodiversity and contribute to changing public aesthetics concerning green spaces. Plant ecological theories, methods and experiences are the foundation for the design and establishment of such vegetation types. We emphasise the importance of high plant density and recurrent disturbance for the maintenance of forb communities. Well-established ecological theory tells us that totally self-sustaining herbaceous vegetation is not a realistic possibility. Without intervention, herbaceous vegetation will change over time and eventually be colonized by woody species through the process of succession. However, by applying a creative and strategic approach to establishment and subsequent management involving small scale disturbances, rather than solely a uniform maintenance regime, it may be possible to maintain a colourful, aesthetically appealing and species-rich forb dominated community that will support biodiversity and increase public acceptance of alternatives to conventional lawns in urban and suburban environments.     

Dispersal of woody plants in forest edges and hedgerows in a Southern Swedish agricultural area: the role of site and landscape structure

The distribution of woody vegetation was studied in forest edges and hedgerows in a 28 km² southern Swedish agricultural area, characterised by species-rich edge zones. The occurrence of 21 selected woody species (taxa) was related to differences in both edge structure and landscape structure. All the species studied were represented in both edge types, but a higher frequency of animal-dispersed species was found in hedgerows.Animal dispersed species were more affected by edge width and density than wind dispersed species. A higher number of wind-dispersed species were more frequent in forest edges, in hedgerows near to forest, or with a high proportion of forest within 500 m. A clear relationship was found between the number of physically connected elements in hedgerow networks and increasing frequency of occurrence for Corylus avellana, Crataegus spp., Euonymus europaeus, and Quercus robur; which indicate the ecological significance of connectedness for certain animal dispersed species. The study supports the general principle that woody species distribution and landscape structure are linked in a positive feedback loop. The results match findings from studies in other countries and are interpreted in the context of landscape processes and the ecological characteristics of woody plant species. We emphasise the importance of understanding dispersal mechanisms of woody species for the design and improvement of edge habitats in agricultural landscapes.     

Toward a rule-based biome model

Current projections of the response of the biosphere to global climatic change indicate as much as 50% to 90% spatial displacement of extratropical biomes. The mechanism of spatial shift could be dominated by either 1) competitive displacement of northern biomes by southern biomes, or 2) drought-induced dieback of areas susceptible to change. The current suite of global biosphere models cannot distinguish between these two processes, thus determining the need for a mechanistically based biome model. The first steps have been taken towards the development of a rule-based, mechanistic model of regional biomes at a continental scale. The computer model is based on a suite of empirically generated conceptual models of biome distribution. With a few exceptions the conceptual models are based on the regional water balance and the potential supply of water to vegetation from two different soil layers, surface for grasses and deep for woody vegetation. The seasonality of precipitation largely determines the amount and timing of recharge of each of these soil layers and thus, the potential mixture of vegetative life-forms that could be supported under a specific climate. The current configuration of rules accounts for the potential natural vegetation at about 94% of 1211 climate stations over the conterminous U.S. Increased temperatures, due to global warming, would 1) reduce the supply of soil moisture over much of the U.S. by reducing the volume of snow and increasing winter runoff, and 2) increase the potential evapotranspiration (PET). These processes combined would likely produce widespread drought-induced dieback in the nation’s biomes. The model is in an early stage of development and will require several enhancements, including explicit simulation of PET, extension to boreal and tropical biomes, a shift from steady-state to transient dynamics, and validation on other continents.     

Microhabitat preferences of butterflies in urban parks: Both vegetation structure and resources are decisive

Urban parks comprise diverse microhabitats, such as vegetation units of lawn and arbour forests, with differing biodiversity potentials. However, the influences of microhabitats on butterfly diversity and the mechanisms involved remain unclear. This study used butterfly survey data from 112 plots in 27 urban parks in the central metropolitan area of Beijing, China, from June to September 2020. Based on the growth form of larval host plants, recorded butterfly species were classified into three functional groups: woody plant-feeding taxa (WF), herb-feeding taxa (HF), and feeding on multiple plant growth forms taxa (MF). We analysed the effects of 11 variables among three facets, namely, vegetation composition, vegetation structure, and human activity, on the butterfly diversity (species richness and abundance) of the whole community, three functional groups using generalised linear mixed models. Twenty-five butterfly species observed mainly feed on herbs rather than on woody plants. Our results demonstrated that vegetation community characteristics explain up to 24% and 43% variation in butterfly species richness and abundance, respectively. Of this, vegetation structure facets crucially affected butterfly species richness, and vegetation composition facets had the most significant influence on the abundance of the whole butterfly community. However, the impact of human activity factors was minimal. Light availability and herb height belonging to vegetation structure factors and nectar plant species richness and nectar abundance which belonged to vegetation composition factors showed the most important and positive effects on butterfly diversity. The positive impact of the above significant factors was found especially on herb-feeding butterfly diversity. In contrast, the diversity of butterflies feeding on woody plants was most positively influenced by herb height. We thus suggest that it is necessary to guarantee the presence of a well-developed herb layer, which provides abundant nectar sources and maintain specific open spaces to ensure light availability. In conclusion, our findings imply that the critical role of the spatial structure of vegetation community is conspicuous in the formation of suitable microhabitats for butterflies, and managers could combine vegetation management practices with the needs of specific functional groups.     

Interrelationships between plant functional types and soil moisture heterogeneity for semiarid landscapes within the grassland/forest continuum: a unified conceptual model

In semiarid landscapes, the ratio of herbaceous to woody plant biomass is a major determinant of ecosystem properties. This ratio depends to a large extent on the amount and spatial distribution of soil moisture that is available to plants, and these variables, in turn, are determined primarily by climate and land use. Current conceptual models for determining the ratio of herbaceous to woody plant biomass in semiarid plant communities are based either on differences in soil moisture with depth (vertical heterogeneity) from one site to another (Walter's two-layer model) or on differences in soil moisture between canopy and intercanopy patches at the same site (horizontal heterogeneity) that result from disturbances associated with land use (Schlesinger et al.'s model of desertification). We developed a model that unifies these two perspectives by relaxing two assumptions of Walter's two-layer model. First, our model recognizes that soil moisture varies horizontally between canopy and intercanopy patches, not only due to land-use disturbance, a general assumption of the Schlesinger et al. model, but also due to the physical nature of the canopy itself. Second, while retaining the general assumption of Walter that woody plants obtain moisture from deeper soil layers than do herbaceous plants, our model recognizes the existence of two types of woody plants: those that extract a substantial proportion of their moisture from deeper layers and those that extract mainly from shallower layers. By modifying the two-layer hypothesis to include four soil compartments and distinguishing between shallow- and deeper-rooted woody species, our model integrates three key concepts in semiarid ecology: (1) the proportion of woody cover increases as moisture in the deeper soil layers increases (Walter's two-layer hypothesis for coexistence of herbaceous and woody plants); (2) land use practices that cause a reduction in herbaceous vegetation and compaction of intercanopy soils lead to a long-term increase in the proportion of woody plants (Schlesinger et al.'s concept, or more generally, that at a given site multiple variations in the proportions of herbaceous and woody plant biomass are possible); and (3) changes in the ratios of herbaceous to woody plant biomass exhibit complex behavior (changes can happen quickly and are not directly reversible without intensive management). This integration of concepts results because rather than assuming a simple, one-way dependence of plant functional types on soil moisture heterogeneity, our model assumes an interdependence between the two: soil moisture heterogeneity constrains the composition of the plant community, which in turn modifies soil moisture heterogeneity. The four-compartment model that we propose enables, for the first time, an integrated picture of both dimensions of soil moisture heterogeneity – horizontal and vertical – and of the interdependence between soil moisture heterogeneity and the proportions of the plant functional types that make up a given plant community. This unified conceptual model can be applied to provide insight into the individual and the combined effects of climate and land use on semiarid plant communities within the grassland/forest continuum, which vary in the proportions of canopy and intercanopy patches.     

Untangling the positive and negative effects of shrubs on herbaceous vegetation in drylands

Woody vegetation, as an ecosystem engineer, can modulate the landscape such that the levels of resources in its vicinity undergo positive and negative changes as far as the herbaceous vegetation is concerned. To better understand how these processes play out in a semi-arid ecosystem, we examined resource modulation by woody vegetation, and the response of herbaceous vegetation to that modulation, at a fine spatial scale. Experimental manipulations were employed to separate the positive and negative effects of water, light and seed dispersal in determining herbaceous species density and biomass in three patch types within and adjacent to the shrub (core, periphery and open). We synthesized our results into a multilayered landscape diversity (MLLD) model. Woody vegetation creates distinct multilayered resource patches at its core and periphery which do not correspond to the dichotomous structural pattern of shrub canopy versus intershrub background. The combined effect of these multilayered resource patches had higher herbaceous species density (8.2 vs. 4.0 species 400?cm^?2) and herbaceous biomass (5.4 vs. 1.0?g 400?cm^?2) in the periphery than in the core (3-yr averages). The periphery??s net positive effects are due to enhancement of soil properties (water infiltration depth of 11.1?cm at periphery vs. 8.1?cm at core), while the core??s net negative effects are due to modulation of seed (seed abundance per seed trap of 44.2 at periphery vs. 3.0 at core) and light availability (PAR transmittance of 41.9?% at periphery vs. 16.5?% at core) by the shrub canopy. Thus, when examined at this fine spatial resolution, woody vegetation has both net positive and net negative effects on herbaceous vegetation. Analysis of our results by means of the MLLD model emphasizes the importance of examining the landscape at the spatial scale of the modulated resources and of recognizing different patch types and their differing effects on herbaceous vegetation.     

Bioreceptivity of living walls: Interactions between building materials and substrates,and effect on plant growth

Bringing nature into urban areas is largely recognized as one of the multiple benefits of green walls. Among the existing types of living walls, those made from durable building materials have a longer lifespan and require less maintenance than many typical green wall systems. In that context, there is a need to study the bioreceptivity of materials, i.e., their ability to host living organisms. This paper presents a novel method to study the bioreceptivity of materials, by enhancing the biological and physicochemical exchanges in different mixtures of crushed materials and substrates, and by measuring their effect on plant growth. For this experiment, we crushed and sieved four different building materials (3 types of concretes and 1 brick) to increase their contact surface. We then mixed them with substrate with or without compost additions. The mixtures were used as growing media for the cultivation of two wild mural plant species in a glasshouse. Plant growth and the physicochemical evolution of the mixtures were monitored for one year. The study shows the physical and chemical differences between the building materials, their interactions with substrate composition, and their effect on plant growth. Two main results appeared: (i) high pH (>8) was the major constraint against plant growth (ii) compost additions significantly compensated for adverse characteristics of the materials. Assuming that higher plant growth is associated with better bioreceptivity, this experiment introduces a quantitative method that could contribute to the evaluation of the agronomic properties of building materials. The results allow us to make recommendations for Living wall and Technosol design.     

Comparison of establishment methods for extensive green roofs in southern Sweden

The most common technique for establishment of thin extensive green roofs in Sweden has been using prefabricated vegetation mats. Our study investigated (1) how the establishment of green roofs in Sweden was influenced by the establishment method (prefabricated vegetation mat, plug-plant, shoot), substrate composition and species mixture, and (2) whether on-site construction was a possible alternative. The establishment of the vegetation, which in all cases consisted of succulent species, was recorded using the quadrate point intercept method in fixed plots and the success measured as frequency cover.Prefabricated vegetation mats had higher succulent plant cover than on-site constructed roofs. There was no difference in succulent plant cover between plots established using plug-plants compared to shoots. Shoot-established plots had more moss than the other establishment methods. The commercial substrate ‘Roof soil’ had significantly higher succulent plant cover than the other substrates, which might be related to a higher nutrient content. The organic content of the non-commercial substrates was rapidly decomposed. The standard species mixture produced a higher cover than both the mix developed for northern conditions and the mix with an increased proportion of big leaved species. The total cover of the plots was mainly dependent on the cover of two species: Sedum album (L.) and Sedum acre (L.). Few species managed to establish spontaneously but the establishment of woody species highlighted the need for proper maintenance.     

Evaluation and correction of nutrient availability to Gerbera jamesonii H. Bolus in various compost-based growing media

Nutrient deficiencies usually constrain the use of some composted materials as peat-substitute growing media even if some fertilizer is applied to the media. In this work, we assessed the suitability of various composted materials as such or mixed with peat for potted plant production, with special emphasis on their effects on nutrient availability to plants. Further, we examined the effect of vivianite [Fe₃(PO₄)₂·8H₂O] as a fertilizer and its mixture with humic substances (HS) on these growing media (particularly their effectiveness in preventing Fe deficiency chlorosis in alkaline substrates). A completely randomized experiment design was developed involving the growth of gerber (Gerbera jamesonii H. Bolus) and two factors, namely (i) the growing medium, specifically composted cork residue (C), compost obtained from a mixture of olive husk and cotton gin trash mixed with rice hulls and peat in a 1:1:1 volume proportion (OH), composted grape marc (GM), Sphagnum peat mixed with spent mushroom compost (M), coconut fibre (CF), and Sphagnum peat; and (ii) the Fe source (control without Fe, Fe-EDDHA, vivianite and vivianite + HS in a weight ratio of 10:1).     

Historical influences dominate the composition of regenerating plant communities in abandoned citrus groves in north-central Florida

The question of what determines plant community composition is fundamental to the study of plant community ecology. We examined the relative roles of historical land use, landscape context, and the biophysical environment as determinants of plant community composition in regenerating citrus groves in north-central Florida. Results were interpreted in light of plant functional traits. Herbaceous and woody plants responded differently to broad-scale variables; herbs correlated most strongly with surrounding land cover at a scale of 8 km, while the only significant determinant of woody species distributions was local land use history. There were significant correlations between herbaceous species and spatial context, habitat isolation, environmental variables, and historical variables. Partial Mantel tests indicated that each variable provided a unique contribution in explaining some of the variation in the herbaceous dataset. The correlation between woody plants and local historical variables remained significant even with other effects corrected for. In the herbaceous community, species composition was linked to functional traits much as expected from classical theory. While spatial influences in our study system are important for both woody and herbaceous plants, the primary determinant of plant community composition in regenerating citrus groves is historical land use. Our results suggest that the fine-scale mechanisms of local competition, tolerance and facilitation invoked by many classical studies may ultimately be less important than land use history in understanding current plant community composition in regenerating agricultural areas.     

Almond shell waste: possible local rockwool substitute in soilless crop culture

This industrial residue is the woody endocarp of the almond fruits. This material is normally incinerated or dumped without control. Almond shell used (100% pure) as growing media can be more ecologically-friendly and less expensive than traditional rockwool since it can be locally produced. Three commercially produced random samples of two different textures and two volumes (19 and 25 L) were evaluated as growing media for soilless production. Three experiments were conducted to evaluate the effects of volume and texture and to compare this substrate with rockwool in terms of yield and quality characteristics of fruits in melon and tomato culture. The physical, physico-chemical and chemical properties studied did not differ significantly between both textures. Tomato plants grown in almond shell residue used 21% less water compared to rockwool over the course of production. We found non-limiting in comparison to rockwool for melon and tomato crops in relation to fertigation parameters, water uptake and yield. Significant differences of yield were found when we used the big size, specially in melon crop where commercial yield and soluble solids of plants growing on 25 L bags was higher than that on small one. The results suggested that almond shells seem to be an acceptable growing media as rockwool substitute for soilless vegetable production.     

Species site matching: Selecting palms (Arecaceae) for urban growing spaces

Palms (Arecaceae) are part of many urban environments in warmer climatic zones where they are mainly planted for their aesthetical value. Due to physiological and morphological characteristics they provide many common services at lower levels than trees, putting them in danger of being replaced. To avoid this, it is necessary to adequately match them to available sites so that costs remain small in comparison to their benefits. To determine what factors might be related to palm health, and therefore aesthetic value, information on the total palm population in Olhão, Portugal, was collected and statistically analysed for relationships between crown state and variables like palm height, distance to the nearest road or objects located within a species-specific growing space. While city-scape related variables showed no or only very weak correlations, it was found that the three most common species differed significantly from each other as comparatively many Phoenix canariensis palms were in poor state due to red palm weevil damage. The results of the study suggest that, in order to reduce financial inputs required to create high levels of desired benefits, a focus should be on macro-environmental conditions which cannot easily be manipulated or only with considerable costs associated. In addition to often discussed general climatic suitability of different species it is also necessary to consider the factor ‘pests and diseases’ when evaluating the appropriateness of certain plant types for designated growing spaces.     

Stormwater quality improvement potential of an urbanised catchment using water sensitive retrofits into public parks

Urban stormwater management is undergoing a transition from centralised hydrologically efficient systems to collections of dispersed, multi-functional elements. In response to a better understanding of impervious surface areas, the adoption of water sensitive urban design is promising for new large urban developments. However, spatial and economic constraints prohibit its adoption in established urban areas. We explore the potential for improvement to stormwater quality if 10% of existing parks in an established urban catchment are reserved for stormwater filtration. Spatially explicit hydrologic modelling is used to model the effects of parks in an existing urban catchment in South Australia as networks of bioretention devices. The allocation of 10% of parks that cover less than 16% of the landscape for bioretention devices may result in a 62% reduction (7.8 tonnes per year) of nitrogen from stormwater. The sources and destinations of stormwater pollutants are mapped to explore the strength and weaknesses of park size and distribution within each sub-catchment. Large parks situated lower in the catchment along the main trunk, and distributed smaller parks higher along the secondary stormwater network are shown to be effectively located. The potential for increasing the utilitarian value of many public parks by demonstrating the capacity for significantly improving urban stormwater quality is illustrated in this exploratory model. Opportunities for targeted improvements to stormwater quality are examined in the discussion.     

Environmental,historical, and contextual determinants of vegetation cover: a landscape perspective

We formulated and tested models of relationships among determinants of vegetation cover in two agroforested landscapes of eastern North America (Haut Saint-Laurent, Quebec, Canada) that differed by the spatial arrangement of their geomorphic features and intensity of agricultural activities. Our landscape model compared the woody plots of each landscape in terms of the relative influence of environmental attributes, land use history (1958 – 1997), and spatial context (i.e., proximity of similar or contrasting land cover). Our vegetation model evaluated the relative contribution of the same sets of variables to the distributions of herbs, trees, and shrubs. Relationships were assessed using partial Mantel tests and path analyses. Significant environmental and contextual differences were found between the vegetation plots of the two landscapes, but disturbance history was similar. Our vegetation model confirms the dominant effect of historical factors on vegetation patterns. Whereas land-use history overrides environmental and contextual control for trees, herbaceous and shrub species are more sensitive to environmental conditions. Context is determinant only for understory species in older, less-disturbed plots. Results are discussed in relevance to vegetation dynamics in a landscape perspective that integrates interactions between environmental and human influences.     

Elephants,termites and mound thermoregulation in a progressively warmer world

Context

With global change, microclimates become important refuges for temperature-sensitive, range-restricted organisms. In African savannas, woody vegetation on Macrotermes mounds create widely-dispersed microclimates significantly cooler than the surrounding matrix, which buffer against elevated temperatures at the finer scale of mounds, allowing species to persist at the landscape scale. Termite colonies cultivate symbiotic fungi to digest lignin, but the fungi require temperatures between 29 and 32 °C, which termites strive to maintain. Mound-associated vegetation is a hot-spot for elephant herbivory, so removal of woody species cover by elephants could influence mound-associated microclimates, impacting temperature regulation by termites.

Objectives

We explored the interaction between two prominent ecosystem engineers (termites and elephants) to ascertain whether elephant removal of mound woody cover affects (1) external mound-associated microclimate and (2) internal mound temperature.

Methods

We surveyed 44 mounds from three sites in Kruger National Park, South Africa, during an El Niño/Southern Oscillation-induced drought and heatwave, recording whether sub-canopy, external, mound-surface and internal mound temperatures varied with vegetation removal by elephant.

Results

Elephant damage to mound-associated vegetation reduces the fine-scale microclimate effect provided by vegetation on Macrotermes mounds. Despite this, termites were able to regulate internal mound temperatures, whereas internal temperatures of abandoned mounds increased with elevated surface temperatures.

Conclusions

Termites can persist despite loss of mound-associated microclimates, but the loss likely increases energetic costs of mound thermoregulation. Since mound vegetation buffers against drought, loss of widely-dispersed, fine-scale microclimates could increase as megaherbivores remain constrained to protected areas, impacting climate-sensitive organisms and ecosystem function at a range of scales.

     

A comparison of satellite data and landscape variables in predicting bird species occurrences in the Greater Yellowstone Ecosystem,USA

We compare the accuracy of predicting the occurrence of 11 bird species in montane meadows of the Greater Yellowstone National Park ecosystem, in the states of Montana and Wyoming, USA. We used remotely sensed, landscape, and habitat data. The meadow type, as determined from the remotely sensed data, was highly correlated with abundances of six of the 11 bird species. Landscape variables significant in predicting occurrence were selected using a stepwise multiple regression for each bird species. These variables were then used in a multiple regression with the variable meadow type. As expected, the abundances of the generalist species (American Robin, Dark-eyed Junco, White-crowned Sparrow, Brewer's Blackbird, and Chipping Sparrow) were not strongly correlated with landscape variables or meadow type. Conversely, abundances of the Common Snipe, Common Yellowthroat, Lincoln's Sparrow, Savannah Sparrow, Vesper Sparrow, and Yellow Warbler were highly correlated with meadow type and landscape variables such as percent cover of willow (Salix spp.), graminoid, woody vegetation, sagebrush (Artemisia spp.), and graminoid and shrub biomass. The results from our study indicate that remotely sensed data are applicable for estimating potential habitats for bird species in the different types of montane meadows. However, to improve predictions about species in specific sites or areas, we recommend the use of additional landscape metrics and habitat data collected in the field.     

Error assessment in decision-tree models applied to vegetation analysis

Methods were developed to evaluate the performance of a decision-tree model used to predict landscape-level patterns of potential forest vegetation in central New York State. The model integrated environmental databases and knowledge on distribution of vegetation. Soil and terrain decision-tree variables were derived by processing state-wide soil geographic databases and digital terrain data. Variables used as model inputs were soil parent material, soil drainage, soil acidity, slope position, slope gradient, and slope azimuth. Landscapescale maps of potential vegetation were derived through sequential map overlay operations using a geographic information system (GIS). A verification sample of 276 field plots was analyzed to determine: (1) agreement between GIS-derived estimates of decision-tree variables and direct field measurements, (2) agreement between vegetation distributions predicted using GIS-derived estimates and using field observations, (3) effect of misclassification costs on prediction agreement, (4) influence of particular environmental variables on model predictions, and (5) misclassification rates of the decision-tree model. Results indicate that the prediction model was most sensitive to drainage and slope gradient, and that the imprecision of the input data led to a high frequency of incorrect predictions of vegetation. However, in many cases of misclassification the predicted vegetation was similar to that of the field plots so that the cost of errors was less than expected from the misclassification rate alone. Moreover, since common vegetation types were more accurately predicted than rare types, the model appears to be reasonably good at predicting vegetation for a randomly selected plot in the landscape. The error assessment methodology developed for this study provides a useful approach for determining the accuracy and sensitivity of landscape-scale environmental models, and indicates the need to develop appropriate field sampling procedures for verifying the predictions of such models.