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Context: Forest–grassland ecotones, the transitional zones between forests and grasslands, often harbor high levels of biodiversity. According to the portfolio theory, communities with such high biodiversity should exhibit high stability in ecosystem functioning. On the contrary, the theory of 'bi-stability' or 'multistability' predicts that ecosystems exhibiting multiple states or regimes (e.g. forest and grassland) are less stable. Understanding the stability of forest–grassland ecotone has broad implications for forest management and restoration. Objectives: In this study, by quantifying landscape heterogeneity and temporal invariability of regional climatic and vegetational metrics, we aimed to reveal how landscape diversity influences the stability of ecosystem functioning in the forest–grassland ecotone. Methods: We focused on the forest–grassland ecotone in northern China (i.e. from the forest belt in the Greater Khingan Mountains to the steppe grassland in Inner Mongolia) and used remote sensing data of land cover dynamics from 1992 to 2015 to analyze the landscape diversity and ecosystem dynamics at different grain sizes. To measure the temporal stability of climatic variables and vegetational dynamics, we calculated the interannual variation of temperature (T), wind speed (WS), precipitation (P), and the net primary productivity (NPP) on the grided sampling cells at different spatial scale over the same period. Results: Our results showed that landscape diversity across this forest–grassland ecotone was positively related to the stability of T and NPP, but negatively related to that of WS and P. These opposite patterns may be explained by the differential nature of ecosystem variables, namely whether they involve transporting substance across space (WS and P) or not (T and NPP). We also found that as the spatial scale increases, the diversity-stability relationships strengthened for all three climatic variables (i.e., T, P, WS). However, the stabilizing effects of landscape diversity on NPP first increased but then decreased with increasing grain size, peaking at ~ 30 km. Conclusions: Our empirical analyses demonstrate strong, but context-dependent diversity-stability relationships, shedding light on the paradox in the stability of ecosystem functioning in the ecotone. These findings also have implications for the management of landscape resources to maintain the sustainability of forest–grassland ecotones. [ABSTRACT FROM AUTHOR]

Introduction: Continuous nitrogen deposition increases the nitrogen content of terrestrial ecosystem and affects the geochemical cycle of soil nitrogen. Forestgrassland ecotone is the interface area of forest and grassland and is sensitive to global climate change. However, the structure composition and diversity of soil microbial communities and their relationship with soil environmental factors at increasing nitrogen deposition have not been sufficiently studied in forestgrassland ecotone. Methods: In this study, experiments were carried out with four nitrogen addition treatments (0 kgN·hm-2·a-1,10 kgN·hm-2·a-1,20 kgN·hm-2·a-1 and 40 kgN·hm-2·a-1) to simulate nitrogen deposition in a forest-grassland ecotone in northwest Liaoning Province, China. High-throughput sequencing and qPCR technologies were used to analyze the composition, structure, and diversity characteristics of the soil microbial communities under different levels of nitrogen addition. Results and discussion: The results showed that soil pH decreased significantly at increasing nitrogen concentrations, and the total nitrogen and ammonium nitrogen contents first increased and then decreased, which were significantly higher in the N10 treatment than in other treatments (N:0.32 ~ 0.48 g/kg; NH4 +-N:11.54 ~ 13 mg/kg). With the increase in nitrogen concentration, the net nitrogen mineralization, nitrification, and ammoniation rates decreased. The addition of nitrogen had no significant effect on the diversity and structure of the fungal community, while the diversity of the bacterial community decreased significantly at increasing nitrogen concentrations. Ascomycetes and Actinomycetes were the dominant fungal and bacterial phyla, respectively. The relative abundance of Ascomycetes was negatively correlated with total nitrogen content, while that of Actinomycetes was positively correlated with soil pH. The fungal community diversity was significantly negatively correlated with nitrate nitrogen, while the diversity of the bacterial community was significantly positively correlated with soil pH. No significant differences in the abundance of functional genes related to soil nitrogen transformations under the different treatments were observed. Overall, the distribution pattern and driving factors were different in soil microbial communities in a forest-grassland ecotone in northwest Liaoning. Our study enriches research content related to factors that affect the forest-grassland ecotone. [ABSTRACT FROM AUTHOR]

This study aimed to explore the ecological stoichiometric characteristics of soil carbon ( C ), nitrogen ( N), and phosphorus( P) in a northern forest-grass ecotone and evaluate its response to influencing factors to reveal the limiting factors of soil nutrients and the driving mechanism of ecosystem evolution in the region. Sampling points were set up at an interval of 25 km from north to south in the study area for field investigation and soil sample collection. The soil ecological stoichiometric characteristics and their relationship with environmental factors were analyzed using statistics and redundancy analysis( RDA). The results showed that: the average concentration of soil organic carbon( SOC), total nitrogen( TN), and total phosphorus( TP) in the 0-20 cm soil layer was 36.76, 2.65, and 0.60 g • kg-1, respectively, and the C N P ratio was 61:4:1. In the 20-30 cm soil layer, the contents of SOC, TN, and TP decreased, they were 27.95, 2.30, and 0.55 g•kg-1, respectively, and the C: N: P ratio was 51:4:1. The region was characterized by N deficiency. For different vegetation types, the contents of SOC, TN, and TP were in the following order: forest>forest and sandy grassland>sandy grassland, and there were significant differences among the three vegetation areas( P<0.05). The contents of SOC, TN, and TP increased with an increase in precipitation, altitude, and temperature. In the 0-20 cm soil layer, the C: N, C: P, and N: P ratios increased with an increase in precipitation and altitude, but decreased with an increase in temperature. In the 20-30 cm soil layer, C: P and N: P ratios increased with an increase in precipitation and altitude but did not change significantly with temperature. C: N ratio increased with an increase altitude but did not change significantly with precipitation and temperature. RDA indicated that the main driving factor of soil ecological stoichiometry in the area was vegetation, followed by soil, terrain, and climate. The results revealed the response mechanism of soil ecological stoichiometry to influencing factors, and this is an important guide to ecological restoration and soil quality health development in forest-grassland ecotones in northern China. [ABSTRACT FROM AUTHOR]

Context: Montane grasslands and forest-grassland ecotones are unique and dynamic components of many landscapes, but the processes that regulate their dynamics are difficult to observe over ecologically relevant time spans. Objectives: We aimed to demonstrate the efficacy of using grassland-forest ecotone trees to reconstruct spatial and temporal properties of the historical fire regime in a complex landscape of montane forests and adjacent grasslands. Methods: We sampled and crossdated fire-scarred trees along ecotones and compared variations in historical fire occurrence within and among nine adjoining valle basins in a 10,158 ha landscape. We analyzed fire year extensiveness, climate regulation, and the occurrence of consecutive fire years. Results: The resulting tree-ring record covers 1240–2005 AD, with 296 trees recording 125 replicated fire years during the analysis period 1601–1902 AD. Mean fire intervals for all events recorded on two or more trees ranged from 4.7 to 13.6 years in individual valles, and a mean of 2.4 ± 1.7 (SD) years at the landscape scale. Between 1660 and 1902, extensive fires occurring in six or more valles occurred 15 times, on average at ~ 17-year intervals; 29 moderately widespread fires (3–5 valles) occurred during this period, at 8.7 year intervals on average. Widespread events occurred in years with a significantly lower Palmer Drought Severity Index (PDSI) preceded by years of significantly positive PDSI, indicating conditions favorable for fine fuel production. Spatial reconstruction of fire extent revealed multiple occurrences of consecutive-year fires burning non-overlapping areas, associated with persistent low PDSI anomalies preceded by positive conditions in antecedent years. Conclusions: A landscape spatiotemporal approach to reconstructing fire regimes of montane forest-grassland complexes provides a valuable baseline for guiding prescribed and natural fire management at large spatial scales. [ABSTRACT FROM AUTHOR]

Abstract A method for characterizing aggregate stability with repeated laser diffraction measurements was tested on soils spanning the prairie-forest ecotone in northern Minnesota, USA. These soils formed in similar parent material but display a wide range of upper horizon morphology, organic carbon content, and chemistry, allowing assessment of the method's performance over a wide range of aggregate stability and its utility in identifying factors influencing aggregate behavior. Equations representing fine material release through breakdown of two aggregate populations as first-order processes were fit to experimental data. The best-fit parameters for these equations, and an additional index of persistent water-stable aggregate content, indicated distinct differences in aggregate behavior among the major horizons of Mollisols and Alfisols. Linear models were developed to explore the relationships between these parameters and soil physicochemical characteristics for the dataset as a whole and for subsets corresponding to four zones with different vegetation history, soil orders, and major soil horizons. The relationships identified were relatively weak (R2 = 0.30 to 0.70). The best predictors for the parameters representing early disintegration of less stable aggregates were cation exchange capacity (CEC) and effective CEC (ECEC) for the whole dataset, although organic carbon and nitrogen contents also emerged as predictors for forest and Alfisol subsets. The best predictors for the index of persistent water-stable aggregate content were organic carbon content, base saturation, or exchangeable Ca/Mg ratio, depending on the particular subset and fine material size fraction used in the analysis. The relatively weak explanatory power of organic carbon content as a predictor of aggregate behavior in these experiments was somewhat surprising, given prior work on aggregate stability. Both CEC and ECEC may serve as proxies for the various combinations of organic matter and clay content that influence aggregate stability in these samples, explaining their importance as predictors. It is likely that other factors not examined in this research contributed to aggregate stability, including carbonate content, clay mineralogy, and differing frequency and types of pedoturbation under grassland and forest. The results of this study are relevant to reconstructing the development of texture-contrast profiles as forest invaded grassland over the past 4000 in the study area, as documented by paleoecological research. In particular, loss of organic matter below a thin A horizon may have facilitated initial development of an E horizon in which weak aggregation favored clay eluviation; loss of clay would then have weakened aggregate stability still further. We suggest this new method for assessing aggregate stability can also be applied to research on soil erosion and runoff potential as affected by land use and management. Highlights • Soil aggregate behavior assessed using repeated laser diffraction measurements. • Dynamics of aggregate disintegration can be modeled as first-order processes. • Method applied to comparison of aggregate behavior in grassland and forest soils. • Aggregate's stability and disintegration dynamics vary by soil order and horizon. • Disintegration rates and water-stable aggregate content related to soil properties. [ABSTRACT FROM AUTHOR]

Phytoliths are a useful tool for reconstructing paleovegetation and paleoenvironments and grass short cell phytoliths (GSCPs), in particular, can provide important paleoenvironmental information. Although herbaceous phytoliths from non-grass species in forests also provide important paleovegetation information, they have not been investigated in as much detail as GSCPs, especially in Northeast China. In this study, we examined herbaceous phytolith morphotypes and assemblages from both forested and grassland areas in NE China, comprising three vegetation types. The phytoliths in 60 herbaceous quadrats were divided into seven morphotype groups. Cross-shaped phytoliths, bilobate type-C with long shank and papillate echinate morphotypes were only observed in grassland (GRA); complex saddle and bilobate type-A were only observed in non-understory vegetation in forested areas (NON); and phytoliths with scrobiculate decoration, elongate curved, silicified stoma (F), silicified stoma (D), globular granulate and oblong ruminate were only observed in forest understory (UND). Papillate (39.7%) was the dominant phytolith type in UND assemblages, and bilobate was dominant in NON (27.2%) and GRA (55.0%). According to the results of Discriminant Analysis (DA) and Detrended Correspondence Analysis (DCA), there was no similarity between UND and GRA, while NON had similarities with both UND and GRA. We conclude that herbaceous phytolith morphotypes and assemblages from forest and grassland in NE China are substantially different, which potentially enables their use for paleovegetation reconstruction in the region. Overall, our findings provide a new approach for determining past forest–grassland boundaries in NE China. [ABSTRACT FROM AUTHOR]

Climate change and extreme events, such as drought, threaten ecosystems world-wide and in particular mountain ecosystems, where species often live at their environmental tolerance limits. In the European Alps, plant communities are also influenced by land-use abandonment leading to woody encroachment of subalpine and alpine grasslands., In this study, we explored how the forest-grassland ecotone of Alpine tree lines will respond to gradual climate warming, drought events and land-use change in terms of forest expansion rates, taxonomic diversity and functional composition. We used a previously validated dynamic vegetation model, FATE- HD, parameterized for plant communities in the Ecrins National Park in the French Alps., Our results showed that intense drought counteracted the forest expansion at higher elevations driven by land-use abandonment and climate change, especially when combined with high drought frequency (occurring every 2 or less than 2 years)., Furthermore, intense and frequent drought accelerated the rates of taxonomic change and resulted in overall higher taxonomic spatial heterogeneity of the ecotone than would be expected under gradual climate and land-use changes only., Synthesis and applications. The results from our model show that intense and frequent drought counteracts forest expansion driven by climate and land-use changes in the forest-grassland ecotone of Alpine tree lines. We argue that land-use planning must consider the effects of extreme events, such as drought, as well as climate and land-use changes, since extreme events might interfere with trends predicted under gradual climate warming and agricultural abandonment. [ABSTRACT FROM AUTHOR]

Distinct guidelines have been proposed in Romania and Switzerland for the management of pasture-woodlands that either focused on the regulation of grazing pressure (Romanian production perspective) or overall tree cover (Swiss conservation perspective). However, the landscape structural diversity and the cover of forest-grassland ecotones, which are both crucial for nature conservation value, were not explicitly considered. We aimed to compare the country-specific management guidelines regarding their efficiency for the conservation of the structurally diverse forest-grassland mosaics in the light of recent land-use and climate change. In strategic simulation experiments using the process-based model of pasture-woodland ecosystems WoodPaM, we analyzed the relationships among drivers for the formation of mosaic patterns (grazing intensity, climate change) and the resulting landscape properties (tree cover, forest-grassland ecotones, mosaic structure) during the past until today (2000 AD). The results showed that tree canopy densification following recent climate warming is likely to trigger landscape structural shifts. Medium grazing pressure promoted the development of the full range of pasture-woodland habitats and is therefore confirmed as a management strategy that balances agronomic demands and nature conservation value. Tree cover is rejected as a criteria to monitor pasture-woodland conservation status, because its relationship to landscape structural diversity and to the cover of forest-grassland ecotones did not hold for changing climate. Our results suggest “experimental-retrospective” analysis as a useful tool to test conclusions from expert knowledge. [ABSTRACT FROM AUTHOR]

Ecotones are frequently associated with habitat fragmentation, one of the main causes of biodiversity loss. Conifer reforestations are assumed to enhance connectivity between forest remnants, buffering negative effects of fragmentation (edge effect). Conversion of agricultural lands into conifer plantations is commonly considered a good practice, although its implications on biodiversity are still unclear., We compare effects of two matrices (non-native conifer reforestations and semi-natural grasslands) on epigeic centipedes of native forests in central Italy. Assemblages were sampled at progressive distances from the edge, both in the matrix and the native forest. Basing on habitat-matrix similarity, reforestations should show lower edge effects compared to grasslands. Consequently reforestations could act as secondary habitat, while grasslands as barrier or semipermeable matrix., Several species occurred in both native forest and matrix: 47% of species at the forest-reforestation ecotone, 16% at the forest-grassland ecotone. Both reforestation and grasslands affected forest indicators ( Lithobius castaneus and L. tylopus). L. castaneus showed reforestations had a lower magnitude (0.95) and a greater depth of edge effect (53 m into the forest). Conversely, grasslands had a higher magnitude (1.00) and a lower depth of edge effect (17 m)., Our findings show reforestations can act as secondary habitat, while grasslands as semipermeable matrix. Secondly, grasslands mainly threat forest species by isolation, while conifer reforestations by edge-effect penetration. In conclusion, the establishment of non-native conifer reforestation, although enhances connectivity, is not risk free and further comparative studies are due to evaluate positive and negative effects on biodiversity. [ABSTRACT FROM AUTHOR]

Historically, where forest habitats are deemed as the pristine landscape state, anthropogenic habitats such as managed grasslands or open spaces are often perceived to be antagonistic and of secondary conservation priority. Traditionally, studies on biodiversity responses to ecological variation, i.e. edge effect, have mostly focused on forest habitats. Yet recently there has been increased attention on communities beyond the forest edge in an effort to better understand how interactions between forests and adjacent habitats may potentially affect regional biodiversity. However, in Europe and the Mediterranean basin (a biodiversity hotspot), areas with high landscape heterogeneity and high edge density, there is a paucity of studies analysing the community responses across forest and 'beyond edge' habitats across ecotones. In a protected area of central Italy, we investigated the responses of ground-dwelling arthropods [Araneae (spiders), Chilopoda (centipedes) and Carabidae (ground beetles)], which were differentiated into habitat-specific guilds (forest, edge and grassland species) across a forest-grassland ecotone. We investigated the extent to which a habitat edge influenced communities of arthropods associated with either the forest or grassland, and how far from the edge this effect penetrated into each habitat. Twelve 150 m-transects perpendicular to a forest-grassland edge were established and arthropods were sampled at nine progressive distances across the ecotone. An indicator species analysis was used to detect species significantly associated with forest, edge-belt or grassland habitats, which were assumed representative of the respective communities. Logistic models of indicator species richness and abundances were used to describe responses of grassland and forest communities across the ecological boundaries. We found that grassland and edge habitats had habitat specialists and higher species richness compared to the forest habitat. Moreover, the occurrence of grassland-specific species was influenced by the presence of an edge up to 15 m from the habitat border. In contrast forest-associated indicator species were not affected by proximity to the habitat edge, rather individuals typical of forest habitats tended to 'spill over' into grassland habitats. These findings support the hypothesis that in a forest-grassland mosaic, forest species are less sensitive to an edge and influence the community beyond the forest edge and into the grassland more than the reverse, i.e. the effect was asymmetric. From these data, we estimated that a minimum grassland habitat width of 600 m is necessary for grassland species to maintain a core area that is relatively unaffected by the spillover of species from adjacent forest habitats. Incorporating the directional influences of adjacent communities on each other allows for an empirical assessment of habitat vulnerability that doesn't a priori value the conservation of one habitat over another. [ABSTRACT FROM AUTHOR]

Resprouting of trees and shrubs in forest-grassland ecotones is a key process to understand the dynamics of these systems under different disturbance regimes. This study integrates resprouting of grassland shrubs and pioneer forest trees ('gullivers'), burned in subtropical lowland grassland and cut in temperate highland grassland of Rio Grande do Sul, Brazil. Per grassland site, 20 individuals each of 1-2 grassland shrub species (Asteraceae) and two forest tree species (Myrsinaceae, Myrtaceae) were tagged, and post-disturbance survival and growth monitored for 1 year at 2-4 month intervals. Differences in resprouting vigour (summed-up basal area of resprouted shoots per pre-disturbance summed-up area of basal stems), and in density and allometry of resprouted shoots (allocation mode) were compared between tree and shrub species by linear mixed effects modelling and multiple comparisons, using the Tukey test. All grassland shrub individuals resprouted and regained 73-142 % (species average) of pre-disturbance basal area within one year, as opposed to 14-24 % in trees. All Myrtaceae 'gullivers' resprouted, but up to two-thirds of Myrsine individuals did not survive disturbance. Tree species tended to produce either many slender or few stout shoots, while shrub species were intermediate between these extremes. Forest trees regained 22-46 % of pre-disturbance height, independent of allocation mode, and grassland shrubs up to 73 %. This suggests that grassland fires allow grassland shrubs but not forest trees to persist and to grow to reproductive size. Differing sprout allocation modes may reflect allometric constraints rather than strategies to outgrow the fire-prone grass matrix. [ABSTRACT FROM AUTHOR]

Lower treeline ecotones are influenced by several processes, including fire, grazing, and climatic variables, but rocky substrate is an under-recognized factor affecting their patterns and dynamics. On the Northern Range of Yellowstone National Park, we hypothesized that north-facing slopes and riparian zones would explain the distribution of most forested areas, but that rocky substrate would explain a substantial additional portion of the lower treeline, and that advancement of conifers into grassland has occurred along rocky substrate. We used GIS software and change detection analysis to assess the spatial distribution and change of the forest with respect to north-facing slopes, riparian areas, and rocky substrate. As in other lower treeline studies, we found that north-facing slopes and riparian zones contained the majority of forested land (63%). However, areas with rocky substrate accounted for more forested area than north-facing slopes and riparian zones combined (67.4%), including 28% of forest that was not explained by the first two variables. Change detection analysis between 1954 and 2006 revealed that conifer advancement was insignificant but the number of forested patches increased and the mean size of patches decreased. These results suggest a more fragmented lower treeline environment that may indicate forest advancement in small patches. Field surveys revealed that rocky substrate did not provide conifers with protection from browsing ungulates or fire, yet conifers preferentially established on rocky areas. Our landscape analysis suggests that weathered rock increases soil coarseness in a landscape dominated by fine glacial till, which improves conditions for seedling establishment by reducing competition with grasses and shrubs sufficiently to overcome the negative influence of dry, nutrient-poor microsites in a moisture-stressed environment. [ABSTRACT FROM AUTHOR]

We conducted a study on small-mammal composition, abundance and diversity across altitudinal and vegetational gradients in the Urucum Mountains (from 150 to 1000 m asl) in western Brazil, a complex biogeographic region. Small mammals were collected in 31 sampling units distributed along altitudinal and vegetational gradients (forest and grassland), totalling 18 112 trap-nights for pitfall and 3500 trap-nights for live-trap. Community variation among sampling units was assessed by randomization tests, setting altitude, vegetation, locality and time as factors, and using presence/absence data. Correlation and logistic regression analyses were run for species and diversity along gradients of altitude and vegetation, according to abundance and presence/absence data. Nineteen species (seven marsupial and 12 rodent) and 355 individuals were recorded. The species composition of small mammals differed according to altitude, vegetation type, locality and time. Species diversity varied significantly according to altitude. Species were influenced solely by altitude or vegetation, or by both vegetation and altitude concomitantly. The small-mammal community was divided in two groups according to biogeographic affinities. The grassland group is capable of invading forest habitats. The results are discussed in light of current hypotheses that attempt to explain community variation along altitudinal gradients around the world. [ABSTRACT FROM PUBLISHER]

• Pixels with greater subpixel percent tree cover generally had earlier greenup dates (GUDs). • A large area of significantly earlier GUD was observed across the Hulunbuir forest-grassland ecotone. • Increases in spring temperature and percent tree cover contributed to the earlier trends in GUD. Changes in climate and land cover are potential drivers of land surface phenology changes. Here, we investigate whether subpixel percent tree cover (PTC) change is an important driver of trends in satellite derived vegetation spring greenup date (GUD) across the Hulunbuir temperate forest-grassland ecotone in northeastern China. GUD was estimated using the MODIS-derived enhanced vegetation index time series during 2001–2020 with a spatial resolution of 500 m. To understand the influential mechanisms of PTC on GUD, we examined relationships between the spatial variations in GUD and PTC at multiple spatio-temporal extents. Forested pixels with greater PTC were found to have generally earlier GUDs for all forest types. The GUD of forests was also generally earlier than that of grassland. On the other hand, we observed approximately 23.7% and 1.2% significantly earlier and later trends in GUD across the region, respectively. Meanwhile, widespread increases in preseason land surface temperature (LST) and PTC were detected. Both increases in LST and PTC contributed to the earlier GUD in the forested region. Specifically, we found negative correlations (Spearman correlation coefficient -0.17 to -0.55) between the change slopes of GUD and PTC in every forest and grassland type. The results highlight the important impacts of subpixel PTC on GUD variations, and improve the understanding of ecosystem changes under the effects of climate and human activities (e.g., afforestation) over the Hulunbuir temperate forest-grassland ecotone. [ABSTRACT FROM AUTHOR]

Questions: What is the structure of the anthropogenic upper forest-grassland ecotone and are there differences in the spatial relationships between the tree species involved? Location: Valfurva Valley, Italian central Alps. Methods: We conducted a spatial distribution and structure analysis in three 1-ha permanent plots along an altitudinal gradient, from the treeline to the sub-alpine forest. We reconstructed the age structure from cores from each individual with diameter > 4 cm at 50 cm height. Results: All tree species and age classes examined had a clumped structure. The cluster tendency was more evident at the treeline where the environmental conditions are more severe. In the sub-alpine forest there was a repulsion between Pinus cembra and Pious mugo but at the treeline P. cembra was frequently found downslope from P. mugo. Conclusions: Although human influence has been the main driving force in shaping the present forest structure, in the last few decades natural dynamics have become the predominant force acting on forest structure and processes, showing a higher magnitude as altitude increases. Our results emphasize the existence of facilitating and interfering mechanisms between different species. P. cembra seems to be favoured compared to the other tree species. [ABSTRACT FROM AUTHOR]

This paper studied the occurrence of carabid beetles (Coleoptera: Carabidae) in the forest edge, the adjacent forest interior, and the surrounding grassland in southwestern China. Beetles were collected with pitfall traps along five replicated transects, Forest species rarely penetrated into the grassland from the forest interior, and the grassland specialists were not found in the forest interior. The forest edge hosted additional species from the adjacent grassland that increased its overall species richness. Nearly all forest species (23 of 24 species) and grassland species (13 of 15 species) can be found in the forest edge. Carabids of the forest edge were more similar to those of the forest interior than to those of the grassland by ordination and cluster analysis. Based on the specificity and fidelity, carabids can be distinguished into five species groups: habitat generalists, grassland-associated species, forest generalists, forest specialists, and edge-associated species. Multiple linear regression analysis showed that canopy cover and/or shrub cover were the most important factors in determining the richness, abundance, and diversity of carabids. The forest edge may serve as a transition zone for dispersal and re-colonization of carabid beetles from adjacent habitats and therefore is important for natural conservation. [ABSTRACT FROM AUTHOR]

Abstract: We studied five lower forest–grassland ecotones in the Darhad Valley in northern Mongolia and investigated the effects of 20th Century grazing regimes and changes in grazing management on ecotone dynamics at a local scale. A total of 2968 Siberian larch (Larix sibirica) trees were cored and tree-age distribution was constructed to determine 20th Century tree establishment. Tree age and location within the ecotones were correlated and seedling density and their distribution were explored to describe forest–grassland ecotone shift. To examine livestock herbivory effects on ecotone shift, the number of new trees was analyzed with five different grazing regimes and changes in grazing practices during the last 80 years in the Darhad Valley. We documented some evidence of ecotone shift into the adjacent grassland. Rates and patterns of ecotone shift varied with different grazing regimes. Siberian larch tree establishment was greater at overall grazing intensities of low and high levels, which were dominated by sheep and cattle grazing. In contrast, larch establishment was lower at overall grazing intensities of low and medium levels, which were dominated by goat grazing. Twentieth Century changes in grazing practices also influenced Siberian larch regeneration. An abrupt decline in Darhad Valley larch establishment during the 20th Century coincided with locally increased grazing pressure. Furthermore, regional climate variability showed important interaction with local grazing regimes in affecting larch regeneration. A 20th Century pulse in larch establishment coincided with a time period of regionally known warmer temperatures and locally reduced grazing pressure. Our results suggest that overall grazing intensity, livestock species composition, and changes in grazing patterns are important in understanding grazing effects on Siberian larch tree encroachment. [Copyright &y& Elsevier]

We assessed landscape-scale invasions of openings in mountain forests by native tree species since EuroAmerican settlement (ca. 1870-1899). We reconstructed historical openings across a 250,240 ha area in the Medicine Bow Mountains, Wyoming, using notes from the original General Land Office (GLO) surveys, and compared historical openings to modern openings interpreted from digital aerial photography. We constructed logistic regression models to describe and predict tree invasion, based on a set of environmental and land use predictors. Openings have decreased by about 7.3% in the last ca. 110 years. Invasion was more likely to occur on moister sites, indicated by high values for steady-state wetness, low values for evaporative demand, proximity to streams, and topographic settings in basins or channels. More invasion also occurred on unprotected public land, in openings surrounded by lodgepole pine and aspen, and on mesic soils. The relatively slow rates of invasion in the study area may be driven by climate and land use. [ABSTRACT FROM AUTHOR]