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Questions: Spatial characteristics of ecotones can affect ecotone function and define their role in ecological systems. Identifying ecotone location is necessary to quantify the relationship between spatial characteristics and function, yet there is no standard approach, particularly for compositionally complex ecotones where binary classification for the two adjacent systems is difficult to assign. We tested a new approach for identifying ecotone location based on the co‐occurrence property, which recognizes ecotones as areas where species from adjacent systems co‐occur. We assessed whether the approach can objectively identify the location of the Tension Zone in Wisconsin. Location: Wisconsin, USA. Methods: Ecotone Co‐occurrence Mapping (ECoMap) is a multi‐step approach: (a) indicator species analysis identifies representative species of two adjacent systems; (b) a ratio map constructed from the spatial densities of the indicator species identifies high co‐occurrence areas; and (c) contour lines encapsulate highest co‐occurrence areas. We applied this approach to identify the Tension Zone location using point locations of witness trees from the mid‐1800s Public Land Survey. We assessed the approach by examining results of multiple permutations, testing sensitivity to different initial boundary configurations, and comparing it to a subjectively derived map, the Curtis Tension Zone. Results: The location of the Tension Zone was identified consistently in multiple permutations, though there is minor variability in certainty of final ecotone location. Ecotone width varied substantially along the Tension Zone. The location was similar to the Curtis Tension Zone but slightly farther north and more spatially detailed. Sensitivity to initial boundary configuration was low. Conclusions: The ECoMap approach was robust and identified a spatially detailed Tension Zone location. This approach is broadly applicable and can be used to identify the location of simple or compositionally complex ecotones where spatial data of species occurrences and modest prior knowledge of general boundary location are available. [ABSTRACT FROM AUTHOR]

Aim Moving split-window ( MSW) analysis is a frequently used tool for vegetation boundary detection. The statistical test of the method is, however, not satisfactory. We aimed to identify reliable confidence limits of MSW statistics. Methods Multivariate transect data (representing forest, grassland and forest-steppe habitats and some artificial data sets) were analysed using five dissimilarity functions and two randomization methods to find the most efficient procedure. We tested the normality of distribution of the dissimilarity values, and then compared the effect of plot randomization and random shift randomization on the power of the statistic. We evaluated the scale dependence of the dissimilarity/distance values and confidence limits. Results The distribution of expected dissimilarity values deviated from a normal distribution, and in all analyses appeared to be skewed to the right. The rate of deviation depends on the data set, on the spatial scale (window size) and on the type of randomization. Expected mean dissimilarity decreased considerably with increasing window width when plot randomization was applied, but was more balanced if random shift was used. Consequently, normalized dissimilarity values increased rapidly with window width in plot randomization, causing extreme scale dependence and false significance. The analysis with random shift distinguished between significant and non-significant peaks at every window size. Conclusions We suggest the use of the random shift permutation as a new method in the MSW analysis, since it minimizes the scale dependence of standardized dissimilarity values, making a clear distinction between significant and non-significant discontinuities. [ABSTRACT FROM AUTHOR]

Questions Does seed mass influence the tolerance of seeds to the effects of heating in fires? Is the tolerance to heat shocks during fire events dependent mostly on seed mass itself or to other traits linked to the species ecological origin, e.g. non-fire-prone (forest) and fire-prone (savanna) environments? Location Savanna and forest ecosystems of the Cerrado biome, Brazil. Methods Heat shocks were applied to seeds of 17 selected common tree species in savanna (ten species) or forest ecosystems (seven species) of the Cerrado biome. After being submitted to a heat shock, seeds were allowed to germinate in chambers set at 30 °C. Germination percentage was calculated for each treatment and species. For comparison purposes, species were grouped into two functional groups (forest and savanna) and also into seed size classes (small, medium and large). We used generalized linear model to analyse heat shock effects on seed germination of savanna and forest tree species, and how seed size affected the germination response. Results Seed mass influenced seed tolerance to heat shock. Larger seeds had higher survival when subjected to heat shock, independent of species' ecological origin. In addition, seeds from species occurring in fire-prone environments (savanna) were more tolerant to high levels of heat shock than seeds from species occurring in non-fire-prone environments (forest). Conclusion In response to global climatic change, fire regimes in savannas of South America are expected to become more frequent and intense, even expanding into currently non-fire-prone environments. In this sense, our findings indicate that species from savannas (fire-prone environments) might have an adaptive advantage to these consequences of climatic changes, potentially leading to expansion of the savanna ecosystems. [ABSTRACT FROM AUTHOR]

Questions How do early secondary successional forest species that grow in savannas differ in their tolerance to surface fires? What are the consequences of these fire tolerances for savanna-forest dynamics and landscape management? Location Anthropogenic savannas in the New Caledonian biodiversity hotspot ( SW Pacific). Methods We estimated the range of fire intensity in New Caledonian savannas using field survey of fuels and the Behave Plus fire behaviour model. Within the predicted range of fire line intensity, we assessed theoretical fire injury to the cambium and crown for 11 species: the dominant tree of New Caledonian savannas ( Melaleuca quinquenervia) and early secondary successional forest species. Using empirical models, for each species we estimated cambium damage from depth of necrosis (as a function of fire line intensity and fire residence time) and bark thickness, and crown damage from scorch height (as a function of fire line intensity) and tree height. We compared bark thickness and tree height increment patterns among species as well as species potential fire tolerance. Results The 11 species had very contrasting capacity to avoid fire injury to the bole cambium due to differences in bark investment patterns, but were all very exposed to scorching and crown injury. Overall, most of sampled individuals are likely top-killed by low intensity fires (<1000 kW·m−1), which are frequent according to our simulations. Conclusions The early secondary successional forest species growing in New Caledonian savannas are poorly adapted to fire, in comparison with literature on worldwide trees in savannas. As a result, their juveniles are unlikely to reach adult size in fire-prone areas. Restoration using the most fire-tolerant species and fire prevention may be complementary strategies to manage such tropical landscapes in order to conserve biodiversity and ecosystem services. [ABSTRACT FROM AUTHOR]

Questions: How are plant species distributed along grazing gradients? What is the shape of species richness patterns? How can we test for the existence of potential discontinuities in species turnover pattern? Location: Semi-deserts in the eastern Caucasus, Azerbaijan, Gobustan district. Methods: We studied the distribution of vascular plant species along transects 900-m long, perpendicular to five farms, and estimated grazing intensity as current livestock units per distance. We modelled species response curves with Huismann-Olff-Fresco (HOF) models and calculated species turnover by accumulating the first derivatives of all response curves. To test for potential discontinuities in changes of vegetation composition along the grazing gradient, we introduce a new null model based on the individualistic continuum concept that uses permutations of the observed pattern of species responses. Results: Most species show a sigmoidal negative response to grazing intensity, while a few species respond with a unimodal pattern. The monotonic decrease in species richness with increasing grazing intensity marks a process of overgrazing that leads to the complete extirpation of plant species. Although the species turnover pattern shows a clear peak, it does not deviate significantly from the null model of individualistic continuous changes. Conclusions: Our approach offers a method for differentiating between transition zones and continuous shifts in species composition along ecological gradients. It also provides a valuable tool for rangeland management to test state-and-transition concepts and gives deeper insights into ecological processes affected by grazing. [ABSTRACT FROM AUTHOR]

Question: What are the importance of elevation and fire in maintaining ecotones of Florida scrub assemblages along a gradual topographic gradient? Location: Archbold Biological Station (ABS), 12 km south of Lake Placid, Florida, USA. Methods: Vegetation cover of upland Florida shrublands was quantified using the line-intercept method along 20 transects traversing similar elevation gradients, stratified by time since fire (TSF). We objectively identified shrubland ecotones using a split moving windows boundary analysis (SMW) with three different window widths. Non-metric multidimensional scaling ordination was used to determine relationships among plant assemblages defined by SMW. Results: We located up to four ecotones per transect, the majority of which were wide, highly heterogeneous zones. Relative elevation controlled the distribution of plant assemblages in upland Florida shrublands. Ecotones in shrublands >30 years TSF had relatively low dissimilarity values in SMW, indicating that previously discrete plant assemblages with longer TSF were becoming more similar with time. Conclusions: Split Moving Windows (SMW) analysis identified ecotones relatively well although patches generated by oak clonal growth were sometimes identified as ecotones. Fire suppression caused ecotones to become more diffuse, suggesting that without fire at least every 30 years, discrete plant assemblages within upland Florida shrublands will be more continuous. [ABSTRACT FROM AUTHOR]

Question: How do properties of different vegetation components vary along ecotones of semi-deciduous forest islands, and can the depth of edge influence (DEI) of the components be detected using a novel combination of analyses? Location: Comoé National Park (CNP), NE Ivory Coast. Methods: Along eight transects at semi-deciduous forest islands tree individuals > 20 cm DBH were mapped. At one transect, tree and shrub individuals down to 1 cm DBH were measured and cover of species was estimated. Split moving window dissimilarity analysis (SMWDA) and moving window regression analysis (MWRA) were combined to detect statistical significance of borders in multivariate vegetation data along continuous transects, to determine the width of associated ecotones, and, thus, the DEI towards the forest interior. Results: For trees > 20 cm DBH, a distinct boundary formation was detected, dominated by the semi-fire resistant tree species Anogeissus leiocarpus. The median of DEI towards the forest interior was 55 m. Ecotone detection with all species present revealed an interlocked sequence of ecotones for grasses, herbs, woody climbers, shrubs and trees, with each of these ecotones being narrower than the overall ecotone. DEI ranged from 10 m for grasses up to 120 m for trees and shrubs. Conclusions: The coherent set of analyses applied proved to be an objective method for detecting borders and the width of associated ecotones. The patterns found may be explained by successional processes at the forest-savanna border. The DEI measured for the forest islands in the nearly undisturbed seminatural system of the CNP is of relevance to concepts of corearea analysis and the protection of forest interior species in semi-deciduous forests in tropical West Africa. [ABSTRACT FROM AUTHOR]