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In 2005–2016, we investigated a secondary succession of small mammal communities in forest ecosystems in High Tatras (Slovakia) disturbed by windstorm and fire. This long-term ecological study confirmed the occurrence of significant temporal and spatial changes in species composition and number of dominant small mammal species. A comparison between disturbed and undisturbed plots indicated notable differences in species richness and abundance. The gradations of dominant small mammal species in disturbed habitats were asynchronous and showed a wider range of amplitude than in the undisturbed plots. An analysis of the temporal and spatial changes in the structure of small mammal communities in relation to selected environmental gradients confirmed the statistically significant effect of secondary succession on species composition, abundance, and exchange in forest ecosystems in the High Tatra Mountains following a disturbance.

The Kenyan tropical rain forest is under imminent threat of degradation due to the changes in climatic condition and rapid growing human population. This study determined the changes in woody species diversity between natural forest (secondary forest) and plantation forest during different stages of plant succession. The secondary data from three forest blocks was obtained from Kenya Forest Research Institute and used to derive species diversity. Variation in species diversity and abundance was analyzed by SPSS software. Species richness was significantly different between plantation and secondary forest types (P

Peatlands are a significant landscape component in temperate mountain ranges and serve multiple functions. However, many peatlands were damaged, altered, or drained over the past centuries, and knowledge about their development is needed for their protection and sustainable management. In our study, we analysed two peat cores from a bog site located in the Black Forest (Southwest Germany) using high-resolution multi-proxy palaeoecological analysis, including biological indicators (plant macrofossils, pollen, testate amoebae), macro-and micro-charcoal as well as geochemical analyses (peat stoichiometry and stable isotopes (δ13C, δ15N)) supported by radiocarbon dating. We tracked the development of the peatland and forest ecosystem to (i) determine their current ecological state, and to (ii) assess the role of different agents of change at the catchment scale on peatland development. The overall objective was to determine natural reference conditions as a basis for the restoration of degraded mountain bogs in the Black Forest Mountains and other temperate mountain ranges. Our results revealed that: i) the bog developed on mineral bedrock of slight slope through paludification around ca. 10,000 cal. BP; ii) the pristine plant populations dominated by Sphagnum fuscum occurring from 6200 cal. BP were replaced by Sphagnum medium/divinum and Eriophorum vaginatum since ca. 3300 cal. BP, most likely due to hydrological disturbances and possible dust deposition on the bog; iii) peat formation at the study site seems still active despite relatively deep water levels (ca. 22–26 cm below surface) and was active over the last 8000 years also when WTD varied between 12 and 26 cm; iv) the self-recovery of peat formation at this mountain bog is possible; v) the protection and restoration of mountain bog ecosystems should also consider land cover changes in the surrounding catchment, serving as further indicators or drivers of mountain bog development.

Abstract Background Experimental manipulations of tree diversity have often found overyielding in mixed-species plantations. While most experiments are still in the early stages of stand development, the impacts of tree diversity are expected to accumulate over time. Here, I present findings from a 31-year-old tree diversity experiment (as of 2018) in Japan. Results I find that the net diversity effect on stand biomass increased linearly through time. The species mixture achieved 64% greater biomass than the average monoculture biomass 31 years after planting. The complementarity effect was positive and increased exponentially with time. The selection effect was negative and decreased exponentially with time. In the early stages (≤ 3 years), the positive complementarity effect was explained by enhanced growths of early- and mid-successional species in the mixture. Later on (≥ 15 years), it was explained by their increased survival rates owing to vertical spatial partitioning — i.e. alleviation of self-thinning via canopy stratification. The negative selection effect resulted from suppressed growths of late-successional species in the bottom layer. Conclusions The experiment provides pioneering evidence that the positive impacts of diversity-driven spatial partitioning on forest biomass can accumulate over multiple decades. The results indicate that forest biomass production and carbon sequestration can be enhanced by multispecies afforestation strategies.

Sand shore ecosystems are extremely vulnerable to alien plant invasions. While most of the abiotic drivers of alien success have been identified, less is known on the role of biological processes driving the invasion. Studying the interactions between alien and native plant communities across different habitats and along the ecological succession (i.e. community maturity) can elucidate the dynamics of alien invasions in dune systems.In this study, we sampled alien and native plant communities in 100 patches across 10 natural coastal landscapes in NE Italy. The patches represented three main habitat types (foredune, backdune and salt marsh, which differ in terms of sea storm-related disturbance and soil salinity) distributed along a gradient of community maturity (i.e. number of years since the plant community was completely eroded by a sea storm). We analysed the effects of alien/native status, habitat type and maturity on species richness and colonization potential of plant species pools. Colonization potential was estimated by applying for the first time on plant data a species-habitat network approach, which allowed us to assess in detail the effect of each plant community on the others.In backdune habitats, alien plant species richness was negatively related with community maturity, which in turn had a positive effect on native species richness. Colonization potential was positively influenced by age for native communities and negatively for alien communities in salt marshes. Among habitat types, backdune patches were also particularly prone to alien invasions and very efficient donors of alien plants to other patches. Salt marshes were in general very resistant to invasion but potentially acting as secondary reservoirs for some backdune alien species.This study identified backdune habitats as key nodes for alien plant introduction and spread in coastal ecosystems, underlining the importance of maintaining mature undisturbed patches as a barrier to alien invasions. This information could prove pivotal in optimizing monitoring and management efforts of alien plant species in these ecosystems, as well as in conservation prioritization.

The calcareous substrate of spring-fed fens makes them unique islands of biodiversity, hosting endangered, vulnerable, and protected vascular plants. Hence, spring-fed fens ecosystems require special conservation attention because many of them are destroyed (e.g. drained, forested) and it is extremely difficult or even impossible to restore the unique hydrogeological and geochemical conditions enabling their function. The long-term perspective of paleoecological studies allows indication of former wetland ecosystem states and provides understanding of their development over millennia. To examine the late Holocene dynamics of a calcareous spring-fed fen (Raganu Mire) ecosystem on the Baltic Sea coast (Latvia) in relation to environmental changes, substrate and human activity, we have undertaken high-resolution analyses of plant macrofossils, pollen, mollusc, stable carbon (δ13C) and oxygen (δ18O) isotopes combined with radiocarbon dating (AMS) in three coring locations. Our study revealed that peat deposits began accumulating ca. 7000 cal. yr BP and calcareous deposits (tufa) from 1450 cal. yr BP, coinciding with regional hydrological changes. Several fire events occurred between 4000 and 1600 cal. yr BP, which appeared to have had a limited effect on local vegetation. The most significant changes in the forest and peatland ecosystems were at 3200 cal. yr BP associated with a dry climate stage and high fire activity, and then between 1400 and 500 cal. yr BP potentially associated with temperature changes during the Medieval Climate Anomaly (MCA) and Little Ice Age. Hydrological disturbances in the peatland catchment from 1400 cal. yr BP were most likely strengthened by human activity (deforestation) in this region. The relationship between the development of this peatland and changes in its catchment area, such as land cover changes or fluctuations in groundwater levels, suggest that protection and restoration of spring-fed fen ecosystems should also include the surrounding catchment. The presence of calcareous sediments, as well as appropriate temperature and local hydrological conditions appear to be the most crucial factors controlling Cladium marisus populations in our site - currently at the eastern limit of its distribution in Europe.

Abstract Changing climatic conditions prompt concerns about vegetation response to disturbance under future compared to past conditions. In this long‐term study, we examined soil climate and vegetation differences at lower, mid, and upper elevations in two separate locations in the Great Basin, USA. We hypothesized that soil climate and vegetation associations across the elevational gradient could help predict responses under future warming and drying. We measured soil water availability, soil temperatures, and vegetation cover in relation to fire and perennial herb removal at each elevation for 13–17 yr after treatment. Seasonal soil water availability increased, while soil temperature‐related variables decreased with increasing elevation. Soil water availability in spring was positively correlated with October through June precipitation (r2 = 0.53), while water availability in spring through fall was positively correlated with perennial plant cover (r2 = 0.65). Partition models separated low, mid, and high elevations by spring soil water availability and growing degree days when soil water was available (R2 = 0.93). Current soil climate and vegetation conditions at lower elevations could indicate future conditions at higher elevations under a warmer and drier climate. During the first years after removal of perennial grasses and forbs, there was an increase in soil water availability in spring at 13–30 cm soil depth that was associated with sagebrush establishment, particularly at upper elevations. In subsequent years, sagebrush continued to dominate even though little difference in soil water availability existed between disturbed and undisturbed plots. This indicates that quickly establishing sagebrush preempted resources and reduced perennial herb recovery. Resource preemption after disturbance will likely be a major driver of plant succession in the future as in the past. Species that establish best under future warmer and drier conditions are most likely to dominate after disturbance. A negative correlation (r2 = 0.34) between the standard deviation of annual spring soil water availability and perennial vegetation cover, which helps resist annual grass invasion, supports the hypothesis that greater resource fluctuation is associated with greater plant community invasibility. Current responses to fire and loss of native plant cover across elevational gradients can indicate future responses under a warmer and drier climate.

Habitat degradation and fragmentation are recognized as major causes of biodiversity loss, and effective management to conserve habitats is highly dependent on our ability to assess their conservation status. In this study we introduce a new index (VCS, for vegetation conservation status) to assess the conservation status of plant communities, which reflect the identity of habitat types. The VCS index is based on the same probabilistic approach than the classical Simpson’s diversity index, but uses the concept of species pools to integrate the influence of ‘typical’ and ‘non-typical’ species on habitat conservation status. In addition to the effect of species identity, this index also allows the detection of change in conservation status because of variation in species-abundance distribution. As an example we applied the VCS index to two heathland habitats in French Brittany and we compared the values provided by the index to qualitative assessments by heathland experts. We also compared the performance of the VCS index against three other indices: species richness, species diversity and a more recent index of ‘favourable conservation status’. Among the four indices tested, the VCS index was the most effective in assessing the vegetation conservation status when compared against qualitative assessment by heathland experts. Moreover the VCS index, coupled with variance partitioning methods, allowed to quantify the contribution of expected causes of habitat degradation. This study demonstrates that the use of habitat-specific species pools to distinguish between typical and non-typical species, as well as the consideration of species abundances, are critical for an accurate assessment of the vegetation conservation status. The VCS index should therefore be a valuable tool for both managers and researchers involved in habitat conservation.

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The occurrence of old-growth forests is quite limited in Mediterranean islands, which have been subject to particularly pronounced human impacts. Little is known about the carbon stocks of such peculiar ecosystems compared with different stages of secondary succession. We investigated the carbon variation in aboveground woody biomass, in litter and soil, and the nitrogen variation in litter and soil, in a 100 years long secondary succession in Mediterranean ecosystems. A vineyard, three stages of plant succession (high maquis, maquis-forest, and forest-maquis), and an old growth forest were compared. Soil samples at two soil depths (0–15 and 15–30 cm), and two litter types, relatively undecomposed and partly decomposed, were collected. Carbon stock in aboveground woody biomass increased from 6 Mg ha-1 in the vineyard to 105 Mg ha-1 in old growth forest. Along the secondary succession, soil carbon considerably increased from about 33 Mg ha-1 in the vineyard to about 69 Mg ha-1 in old growth forest. Soil nitrogen has more than doubled, ranging from 4.1 Mg ha-1 in the vineyard to 8.8 Mg ha-1 in old growth forest. Both soil parameters were found to be affected by successional stage and soil depth but not by their interaction. While the C/N ratio in the soil remained relatively constant during the succession, the C/N ratio of the litter strongly decreased, probably following the progressive increase in the holm oak contribution. While carbon content in litter decreased along the succession, nitrogen content slightly increased. Overall, carbon stock in aboveground woody biomass, litter and soil increased from about 48 Mg ha-1 in the vineyard to about 198 Mg ha-1 in old growth forest. The results of this study indicate that, even in Mediterranean environments, considerable amounts of carbon may be stored through secondary succession processes up to old growth forest. [ABSTRACT FROM AUTHOR]

Remnant tree presence affects forest recovery after slash-and-burn agriculture. However, little is known about its effect on above-ground carbon stocks, especially in Africa. We focused our study on Sierra Leone, part of the Upper Guinean forests, an important centre of endemism threatened by encroachment and forest degradation. We studied 99 (20-m-radius) plots aged 2-10 years with and without remnant trees and compared their above-ground carbon stocks, vegetation structure (stem density, basal area) and tree diversity. Above-ground carbon stocks, stem density, basal area, species richness and tree diversity increased significantly with fallow age. Remnant tree presence affected significantly tree diversity, species dominance and above-ground carbon stocks, but not vegetation structure (stem density, basal area). Number of remnant trees and number of species of remnant trees were also important explanatory variables. Although other factors should be considered in future studies, such as the size and dispersal modes of remnant trees, our results highlight that more strategic inclusion of remnant trees is likely to favour carbon stock and forest recovery in old fallows. To our knowledge, this is the first study on early succession regrowing fallows in West Africa. [ABSTRACT FROM AUTHOR]

Classical old-field succession studies focused on vegetation changes after the abandonment of annual croplands or on succession after the elimination of cultivated crops. Perennial-crop-mediated succession, where fields are initially covered by perennial crops, reveals alternative aspects of old-field succession theories. We tested the validity of classical theories of old-field succession for perennial-crop-mediated succession. We formulated the following hypotheses: (1) functional diversity increases with increasing field age; (2) resource acquisition versus conservation trade-off shifts toward conservation at community level during the succession; (3) the importance of spatial and temporal seed dispersal decreases during the succession; and (4) competitiveness and stress-tolerance increases and ruderality decreases at community level during the succession. We studied functional diversity, trait distributions and plant strategies in differently aged old-fields using chronosequence method. We found increasing functional richness and functional divergence, but also unchanged or decreasing functional evenness. We detected a shift from resource acquisition to resource conservation strategy of communities during the succession. The role of spatial and temporal seed dispersal was found to be important not only at the initial but also at latter successional stages. We found an increasing stress-tolerance and a decreasing ruderality during succession, while the competitiveness remained unchanged at the community level. Despite the markedly different starting conditions, we found that classical and perennial-crop-mediated old-field successions have some similarities regarding the changes of functional diversity, resource acquisition versus conservation trade-off, and seed dispersal strategies. However, we revealed also the subsequent differences. The competitive character of communities remained stable during the succession; hence, the initial stages of perennial-crop-mediated succession can be similar to the middle stages of classical old-field succession. Moreover, the occupied functional niche space and differentiation were larger in the older stages, but resources were not effectively utilized within this space, suggesting that the stabilization of the vegetation requires more time. [ABSTRACT FROM AUTHOR]

Forest structural heterogeneity due to species composition, spatial relationships and tree size are widely studied patterns in forest systems, but their impacts on tree function are not as well documented. The objective of this study was to examine how stand composition, tree proximity relationships and tree size influence the leaf functional traits of aspen, an early successional species, and subalpine fir, a climax species. We measured foliar nutrients, nonstructural carbohydrates (aspen only), defense chemistry and xylem water potential of aspen and subalpine fir trees in three size classes growing in close proximity or independently from other trees under three stand conditions: aspen dominant, aspen-conifer mixed, and conifer dominant stands. Close proximity of subalpine fir to aspen reduced aspen’s storage of starch in foliar tissue by 17% suggesting that competition between these species may have small effects on carbon metabolism in aspen leaves. Simple sugar (glucose + sucrose) concentrations in aspen leaves were slightly higher in larger aspen trees than smaller trees. However, no differences were found in stem water potential, foliar concentrations of nitrogen, phosphorus, or secondary defense chemicals of aspen or subalpine fir across the gradients of stand composition, tree proximity or tree size. These results suggest that mechanisms of coexistence allow both aspen and subalpine fir to maintain leaf function across a wide range of stand structural characteristics. For aspen, resource sharing through its clonal root system and high resource storage capacity may partially contribute to its functional stability in mixed aspen-conifer stands. [ABSTRACT FROM AUTHOR]

In this study we characterised the development of caecal microbiota in egg laying hens over their commercial production lifespan, from the day of hatching until 60 weeks of age. Using pyrosequencing of V3/V4 variable regions of 16S rRNA genes for microbiota characterisation, we were able to define 4 different stages of caecal microbiota development. The first stage lasted for the first week of life and was characterised by a high prevalence of Enterobacteriaceae (phylum Proteobacteria). The second stage lasted from week 2 to week 4 and was characterised by nearly an absolute dominance of Lachnospiraceae and Ruminococcaceae (both phylum Firmicutes). The third stage lasted from month 2 to month 6 and was characterised by the succession of Firmicutes at the expense of Bacteroidetes. The fourth stage was typical for adult hens in full egg production aged 7 months or more and was characterised by a constant ratio of Bacteroidetes and Firmicutes formed by equal numbers of the representatives of both phyla. [ABSTRACT FROM AUTHOR]

The ecological mechanisms driving community succession are widely debated, particularly for microorganisms. While successional soil microbial communities are known to undergo predictable changes in structure concomitant with shifts in a variety of edaphic properties, the causal mechanisms underlying these patterns are poorly understood. Thus, to specifically isolate how nutrients – important drivers of plant succession – affect soil microbial succession, we established a full factorial nitrogen (N) and phosphorus (P) fertilization plot experiment in recently deglaciated (∼3 years since exposure), unvegetated soils of the Puca Glacier forefield in Southeastern Peru. We evaluated soil properties and examined bacterial community composition in plots before and one year after fertilization. Fertilized soils were then compared to samples from three reference successional transects representing advancing stages of soil development ranging from 5 years to 85 years since exposure. We found that a single application of +NP fertilizer caused the soil bacterial community structure of the three-year old soils to most resemble the 85-year old soils after one year. Despite differences in a variety of soil edaphic properties between fertilizer plots and late successional soils, bacterial community composition of +NP plots converged with late successional communities. Thus, our work suggests a mechanism for microbial succession whereby changes in resource availability drive shifts in community composition, supporting a role for nutrient colimitation in primary succession. These results suggest that nutrients alone, independent of other edaphic factors that change with succession, act as an important control over soil microbial community development, greatly accelerating the rate of succession. [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jhg.2005.05.017 Byline: David Matless (a), Laura Cameron (b) Abstract: The paper considers the geographies of scientific knowledge produced around a pool dug at Long Gores, Hickling, Norfolk, England in 1953. Designed by ecologist and artist Marietta Pallis as a swimming pool and symbolic site, the pool also became a scientific experiment in landscape, through which Pallis pursued general ecological principles and specific theories on the landscape history and ecology of the Norfolk Broads. The digging of the pool coincided with the publication of research establishing the broads' artificial origin in medieval peat diggings. The paper begins by developing arguments concerning the cultural geographies of scientific knowledge. We then trace Pallis's presentation of the pool as equivalent for the broads in its origins and development, her discussion of the relationship between pool, marsh and North Sea, the connection between Pallis and local scientific culture, and the pool's place in a landscape of ecological succession. The paper concludes with further theoretical discussion, and reflection on the remains of Pallis and her reputation. Author Affiliation: (a) School of Geography, University of Nottingham, University Park, Nottingham NG7 2RD, UK (b) Department of Geography, Queen's University, Kingston, Ontario, Canada

On semi-open pre-alpine fen pastures Alder encroachment creates a dynamic mosaic of grassland and woodland, which is rich in ecotones from fen to Carr. The structural diversity in colonisation patterns of Alder on fens suggests a dependency on multiple environmental drivers. Unidirectional progressive ecotone development provides an opportunity to address a current deficit in understanding successional patterns, i.e. process–pattern relationships in a multiple factor regime. We developed an individual-based model of Alder establishment on fen grassland to investigate the dependency of encroachment patterns upon seed production, dispersal distances and safe site availability. The purpose of the model is to provide a causal understanding of establishment patterns of Alder. In the model, all life processes of Alder individuals were parameterised with field data. This allowed us to strictly perform bottom–up simulations and successfully check plausibility by comparing simulated establishment patterns of cohorts with observed ecotone structures. Simulation results show that establishment patterns strongly depend on environmental drivers. Spatial progression of Alder encroachment and width of ecotones, respectively, mainly depend on wind speed during seed dispersal. Dense establishment of Alder leading to community change from fen grassland to Carr, requires windows of opportunity, which are defined by the rare coincidence of widespread dispersal, high seed production and favorable establishment conditions. Life-history traits of Alder (mast year cycle, high seed weight, weak establishment in fen) spatially and temporarily constrain the encroachment process. The structural diversity of long-term encroachment patterns is explained by the event-driven character of encroachment. Modelling individual establishment pathways of seedlings starting from germination revealed an endogenous stochasticity in establishment patterns emerging from low seed densities in the tail of the dispersal function. We conclude an inherent stochastic structure of dispersal-limited tree line ecotones, which limits reconstruction of processes from patterns. In order to describe long-term successional patterns of Alder encroachment at landscape scale, we propose the combination of two concepts: deterministic “patch-movement” of Alder woodland driven by continuous ecotone migration together with rare and stochastic “infiltration” of single Alder trees into open fen grasslands. Conservation management can control predictable “patch-movement” by cutting off maturing saplings around existing Alder woods. But the preservation of the actual large proportion of open grassland in fen pastures from infiltrating Alder seedlings and from the subsequent shift of the pasture to a densely wooded state would require mowing additionally to extensive grazing. [Copyright &y& Elsevier]

The savanna biome is defined by the codominance of grasses and trees, the precise ratio of which is a function of numerous variables, both natural and anthropogenic. Fire is a critical determinant of the tree-to-grass ratio because it can suppress tree establishment and growth. Despite the fact that nearly all fires have human causes, most savanna fire ecology models are based solely on ecological variables and fail to integrate human land and fire use patterns. To understand how human burning practices, land cover patterns, and fire regimes are linked I combined the results of an image-based burn scar analysis and land cover maps generated from a Landsat database covering thirty years with interview and survey results. I documented the spatially explicit fire regime for an area of Sudan savanna in southern Mali and linked it to human practices and land cover patterns. The study concludes that burning creates a seasonal mosaic in which some patches regularly burn early and others late, whereas some areas rarely if ever burn. Ecologists attribute mosaic fire regimes to natural factors such as plant succession, but this research demonstrates that the regime is a function of the combined effects of edaphic conditions, vegetation patterns, land use, and widespread burning practices. The anthropogenic burning regime documented here differs from the one based on ecological theory in that its spatiotemporal pattern is relatively consistent from year to year. The findings demonstrate the need to 'humanize' savanna models by breaking nature-society dichotomies and synthesizing natural and social science explanations. [ABSTRACT FROM AUTHOR]

Understanding how species interactions drive succession is a key issue in ecology. In this study we show the utility of combining the concepts and methodologies developed within the biodiversity-ecosystem functioning research program with J. H. Connell and R. O. Slatyer's classic framework to understand succession in assemblages where multiple interactions between early and late colonists may include both inhibitory and facilitative effects. We assessed the net effect of multiple species interactions on successional changes by manipulating the richness, composition, and abundance of early colonists in a low-shore assemblage of algae and invertebrates of the northwestern Mediterranean. Results revealed how concomitant changes in species richness and abundance can strongly alter the net effect of inhibitory vs. facilitative interactions on succession. Increasing richness of early colonists inhibited succession, but only under high levels of initial abundance, probably reflecting the formation of a highly intricate matrix that prevented further colonization. In contrast, increasing initial abundance of early colonists tended to facilitate succession under low richness. Thus, changes in abundance of early colonists mediated the effects of richness on succession. [ABSTRACT FROM AUTHOR]

Spontaneous succession is often underappreciated in restoration after the cessation of intensive agricultural management. Spontaneous succession could improve the success of restoration programmes, and offers a cost-effective option with little active intervention. We studied the spontaneous recovery of loess grasslands in extensively managed lucerne Medicago sativa fields mown twice a year using space for time substitutions to highlight the importance of spontaneous processes in grassland restoration. With increasing field age a gradual replacement of lucerne by perennial native grasses and forbs and increase of mean species richness was detected. As the age of fields increased, lucerne decreased from 75% to 2% of total vegetation cover, whereas perennial graminoids increased from 0·5 to 50% cover. Mean total cover showed no significant differences between the age groups; weed cover was less than 10%. The phytomass of lucerne was negatively correlated with graminoid phytomass. As the age of the fields increased, lucerne phytomass decreased and grass phytomass increased. We found a negative correlation between litter and forb phytomass but there was no relationship with the age of the field. There was no litter accumulation and no increase of mean total phytomass as the age of fields increased. Synthesis and applications. Native grasses within loess grasslands recovered within 10 years, but characteristic native forbs remained rare. The advantages of spontaneous succession in lucerne fields compared to technical reclamation include: (i) no early stages dominated by weeds, (ii) minimal litter accumulation, (iii) a spontaneous decrease in lucerne over time, and (iv) negligible cost. In addition, the requirement for twice yearly mowing in the early years will guarantee farmer involvement because of the high forage value of lucerne. The complete restoration of species rich grasslands will require more active management such as propagule transfer by hay and/or moderate grazing to encourage the return of native forbs. [ABSTRACT FROM AUTHOR]

Temperatures in southwestern North America are projected to increase 3.5–4 °C over the next 60–90 years. This will precipitate ecological shifts as the ranges of species change in response to new climates. During this shift, rapid-colonizing species should increase, whereas slow-colonizing species will at first decrease, but eventually become reestablished in their new range. This successional process has been estimated to require from 100 to over 300 years in small areas, under a stable climate, with a nearby seed source. How much longer will it require on a continental scale, under a changing climate, without a nearby seed source? I considered this question through an examination of the response of fossil plant assemblages from the Grand Canyon, Arizona, to the most recent rapid warming of similar magnitude that occurred at the start of the Holocene, 11,700 years ago. At that time, temperatures in southwestern North America increased about 4 °C over less than a century. Grand Canyon plant species responded at different rates to this warming climate. Early-successional species rapidly increased, whereas late-successional species decreased. This shift persisted throughout the next 2700 years. I found two earlier, less-extreme species shifts following rapid warming events around 14,700 and 16,800 years ago. Late-successional species predominated only after 4000 years or more of relatively stable temperature. These results suggest the potential magnitude, duration, and nature of future ecological changes and have implications for conservation plans, especially those incorporating equilibrium assumptions or reconstituting past conditions. When these concepts are extended to include the most rapid early-successional colonizers, they imply that the recent increases in invasive exotics may be only the most noticeable part of a new resurgence of early-successional vegetation. Additionally, my results challenge the reliability of models of future vegetation and carbon balance that project conditions on the basis of assumptions of equilibrium within only a century. [ABSTRACT FROM AUTHOR]

Motivation: The Buell-Small Succession Study (BSS) is the longest running study of post agricultural succession in North America. To honor this program, a symposium at the Ecological Society of America meetings was organized to explore the state of succession theory and its contribution to the field of ecology and its application to restoration. The BSS was originally motivated by two controversies in the literature during the 1950's. The first was between a community versus and individual basis of secondary succession. The second was the validity of the Initial Floristic Composition hypothesis. Location: Hutcheson Memorial Forest, Somerset, New Jersey, USA Methods: Vegetation composition and cover has been continuously quantified in permanent plots established in 10 old fields. Continued Research Motivation: The rich data set has documented population and community dynamics and the spatio-temporal controls and historical contingencies that influence those dynamics. The regulation of community dynamics continues to be a line of inquiry as does the application of results to restoration and understanding the dynamics of non-native species. Conclusions: Long term vegetation studies are uncommon in ecology yet they are uniquely valuable for understanding system dynamics - particularly if the studies capture periodic events or system shifts such as droughts and invasions by non-native species. Resilient long term studies, of which the BSS is an example, maintain methods and data structure while allowing motivating questions to evolve along side advancements in the theoretical and conceptual realms of the field. Succession continues to serve as a basic tenet of ecology which is demonstrated by the papers making up this special issue. [ABSTRACT FROM AUTHOR]

1. Classical ecological theory predicts a succession towards plant communities that are determined by environmental conditions. However, in ecological restoration, species composition often remains different from the predicted target community, compromising the success of restoration measures. 2. We analysed the relative importance of environmental conditions, management and distance to source populations for floodplain grassland succession following re-conversion from intensive to traditional use. The study was established at 33 grassland sites in central German river valleys. Species composition, environmental variables, past and current management, and the distance to source populations of characteristic species of traditional management (indicator species) were recorded and compared using multivariate statistics. We further tested the speed of colonization by two indicator species, Silaum silaus and Serratula tinctoria, along transects from source populations into unoccupied fields. 4. The species composition of the successional grassland was mainly determined by elevation, total soil nitrogen, distance to remnant species-rich grasslands and frequency of mowing or grazing. Elevation and distance were negatively, and frequency was positively related to the occurrence of late successional species. 5. Colonization by indicator species was only dependent on the distance to source populations; other explanatory variables were not significant. Migration from adjacent source sites of S. silaus and S. tinctoria into re-converted grasslands was slow, reaching only 40 m and 15 m after 15 years. 6. Synthesis and applications. The results demonstrated the limitations of the deterministic view on plant succession and the high relative importance of propagule availability in grassland restoration. Natural colonization will only be successful if source populations of the target species are adjacent to the restoration sites. Artificial introduction techniques are recommended to overcome dispersal barriers. [ABSTRACT FROM AUTHOR]

1. Conceptual models of ecosystem development commonly predict a phase of initial colonization characterized by the nucleation, growth and coalescence of discrete patches of pioneer plants. Spatiotemporal dynamics during subsequent development may follow one of three different models: the classical model, in which initially discrete patches of competitive dominant (secondary) colonists coalesce to form a homogeneous cover; the patch dynamics model, in which renewal mechanisms such as disturbance create a shifting mosaic of patches at different stages; and the geoecological model, in which the vegetation gradually differentiates along edaphic gradients related to the underlying physical template. 2. These models of spatiotemporal dynamics were tested using vegetation and soil data from an 850-year chronosequence, comprised of seven lava flows on Mt Hekla, Iceland. The scale and intensity of spatial pattern were quantified on each flow using spatial analyses (mean-variance ratios, quadrat variance techniques and indices of autocorrelation). Changes in spatial pattern with increasing terrain age were compared with predicted trajectories, in order to identify which of the models of spatiotemporal dynamics was most consistent with the observations. 3. The early stages of ecosystem development were characterized by colonization of the pioneer species, especially Racomitrium mosses, in discrete patches (‘Pioneer colonization stage’, < 20 years), which then grew laterally and coalesced to form a continuous, homogeneous carpet (‘Pioneer expansion stage’, 20–100 years). Later in the sequence, higher plants established in discrete patches within this pioneer matrix (‘Higher plant colonization stage’, 100–600 years). Over time, heterogeneity re-emerged at a larger spatial scale as the vegetation differentiated according to topographic variations in the underlying substrate (‘Differentiation stage’, > 600 years). 4. Synthesis. The spatiotemporal dynamics observed in the early stages of this succession were consistent with a model of pioneer nucleation in micro-scale safe sites, followed by growth, coalescence and eventual fragmentation of pioneer patches. The spatial patterns which emerged later in development support the geoecological model, with spatial differentiation of vegetation related to meso-scale substrate topography. The findings provide insight on how vegetation patterns emerge at different stages of ecosystem development in response to differing scales of heterogeneity in the underlying physical environment. [ABSTRACT FROM AUTHOR]

We present methods for estimating the base proportion of introduced alien species that will naturalize, and the distribution of time until naturalization occurs. The approach is Bayesian, incorporating prior estimates of the probability of naturalization and the time from introduction to naturalization. A worked example uses data on the introduction and time to recorded naturalization of woody perennials introduced to South Australia. Up until 2007, 188 of 2230 (8.4%) woody perennials listed in nursery catalogues between 1843 and 1985 were recorded as having naturalized. If prior information on naturalization rates from elsewhere is ignored, the available data suggest that the most likely proportion of introduced plants that will naturalize is large (0.93) though uncertain (95% CI 0.51–0.99), with the corresponding mean time to recorded naturalization being protracted (522 years) and similarly uncertain (95% CI 360–678 years). Alternatively, if informative prior estimates of both the naturalization probability and the time to recorded naturalization are incorporated, the most likely probability of naturalization is estimated to be 18.6% (95% CI 15.5–23.4%). For those plants that do naturalize, the most likely value for the mean time from importation to recorded naturalization is 149 years (95% CI 130–174 years). Our results illustrate the potentially long timescale of the naturalization process, and the challenges this presents for obtaining accurate estimates of naturalization parameters. [ABSTRACT FROM AUTHOR]

Question: What is the impact of prescribed fires on the cover and composition of vegetation in Artemisia tridentata ssp. vaseyana steppe? Location: United States Department of Agriculture, Agricultural Research Service, United States Sheep Experiment Station, eastern Idaho (44°14'44" N, 112°12'47'' W). Methods: Multiple prescribed fires were lit in 2002 and 2003 in an Artemisia tridentata ssp. vaseyana (mountain big sagebrush) steppe ecosystem that was relatively free of exotic plants. Measurements of cover components and plant species frequencies were taken pre- and for 2 to 3 years post-fire. Results: Cover of forbs and grasses returned to pre-fire levels after two years. Shrub cover declined from 36 to 6% in the first year post-fire. Fire reduced the frequencies of three species, A. tridentata ssp. vaseyana, Festuca idahoensis, and Cordylanthus ramosus, of rangeland plants. Frequencies of four plant species, Hesperostipa comata, Polygonum douglasii, Chenopodium fremontii and Chenopodium leptophyllum increased, but only P. douglasii increased for more than a year. Conclusion: This study demonstrates that in an Artemisia tridentata ssp. vaseyana steppe ecosystem without significant non-native species or anthropogenic disturbances vegetative cover and species composition of the herbaceous community are only minimally altered by fire. The herbaceous component returned to pre-fire conditions within three years of a fire. [ABSTRACT FROM AUTHOR]

The colonization of novel habitats involves complex interactions between founder events, selection, and ongoing migration, and can lead to diverse evolutionary outcomes from local extinction to adaptation to speciation. Although there have been several studies of the demography of colonization of remote habitats, less is known about the demographic consequences of colonization of novel habitats within a continuous species range. Populations of the Eastern Fence Lizard, Sceloporus undulatus, are continuously distributed across two dramatic transitions in substrate color in southern New Mexico and have undergone rapid adaptation following colonization of these novel environments. Blanched forms inhabit the gypsum sand dunes of White Sands and melanic forms are found on the black basalt rocks of the Carrizozo lava flow. Each of these habitats formed within the last 10,000 years, allowing comparison of genetic signatures of population history for two independent colonizations from the same source population. We present evidence on phenotypic variation in lizard color, environmental variation in substrate color, and sequence variation for mitochondrial DNA and 19 independent nuclear loci. To confirm the influence of natural selection and gene flow in this system, we show that phenotypic variation is best explained by environmental variation and that neutral genetic variation is related to distance between populations, not partitioned by habitat. The historical demography of colonization was inferred using an Approximate Bayesian Computation (ABC) framework that incorporates known geological information and allows for ongoing migration with the source population. The inferences differed somewhat between mtDNA and nuclear markers, but overall provided strong evidence of historical size reductions in both white sand and black lava populations at the time of colonization. Populations in both novel habitats appear to have undergone partial but incomplete recovery from the initial bottleneck. Both ABC analyses and measures of mtDNA sequence diversity also suggested that population reductions were more severe in the black lava compared to the white sands habitat. Differences observed between habitats may be explained by differences in colonization time, habitat geometry, and strength or response to natural selection for substrate matching. Finally, effective population size reductions in this system appear to be more dramatic when colonization is accompanied by a change in selection regime. Our analyses are consistent with a demographic cost of adaptation to novel environments and show that it is possible to infer aspects of the historical demography of local adaptation even in the presence of ongoing gene flow. [ABSTRACT FROM AUTHOR]

Plant invasions are a serious threat to natural and semi-natural ecosystems worldwide. Most management-orientated research on invasions focuses on invaders that are already widespread and often have major impacts. This paper deals with “emerging” invaders—those alien species with the potential to become important problems without timely intervention. A climate matching procedure was developed to define areas of South Africa, Lesotho and Swaziland that could be invaded by 28 plant species that had previously been classified as emerging invaders. Information on the location of populations of these species in the study area was combined with information on their distributions (as native or alien) in parts of Australia and the United States of America. These two countries had the best available distribution data for this study. They also share many invasive alien plant species with South Africa. Climatic data obtained for weather stations near points of known occurrence in these countries were used to define the climatically suitable areas for each species in the study area. Almost 80% of the remaining natural environment in southern Africa was found to be vulnerable to invasion by at least one of these species, 50% by six or more and 24% by 16 or more species. The most vulnerable areas are the highveld grasslands and the eastern escarpment. The emerging invaders with the greatest potential range included Acacia podalyriifolia and Cortaderia selloana. The globally important invaders Ulex europaeus and Lythrum salicaria had a more limited invasion potential but could still become major invaders. There was no relationship between the extent of the climatically suitable areas for the different species and an expert ranking of their invasion potential, emphasising the uncertainties inherent in making expert assessments based on very little information. The methods used in this analysis establish a protocol for future modelling exercises to assess the invasion potential of other emerging invaders. [Copyright &y& Elsevier]

A growing body of literature has led to the debate in invasion biology whether exotic species perform within communities differently than native taxa due to inherent advantages. To address this issue, the population dynamics of native and exotic plant species were assessed from a 48-year record of permanent plot data from the Hutcheson Memorial Forest Center (New Jersey, USA) to determine rate of increase, lag time, maximum frequency, and the year of peak frequency. Overall, native and exotic species exhibited very similar population dynamics. Rates of increase and length of lag times were similar between native and exotic taxa but were strongly influenced by plant life form. Short-lived species were characterized by rapid population growth rates and short lag times. Growth rates decreased and lag times increased with species longevity. Overall, correlations between population metrics were the same in native and exotic taxa, suggesting similar trade-offs in life history patterns. The one difference observed was that, in native species, peak frequency was negatively associated with the year of peak frequency (i.e., early-successional species tended to become more abundant), while there was no relationship in exotic species. These analyses show that exotic species behave in essentially the same way as native taxa within dynamic communities. This suggests that abundant native and exotic plant species are exploiting the same range of ecological strategies resulting in similar roles within communities. [ABSTRACT FROM AUTHOR]

Question: This paper studies the establishment and performance of Cortaderia selloana (Pampas grass), an alien South American ornamental species that is invading many parts of the world. We asked whether (1) early successional stages were the most susceptible to C. selloana invasion; (2) soil microdisturbances increased invasion at any point of succession, and (3) C. selloana invasion of later successional stages was modulated by vegetation type Location: Delta del Llobregat (Catalonia, NE Spain). Methods: We monitored survival and growth of transplanted C. selloana seedlings in disturbed and non-disturbed plots throughout a successional gradient with an age range of< 1 to > 10 years in different vegetation types and within the area of influence of coexisting species with similar growth form. Results: Although seedling survival was extremely low in all treatments, our results revealed that early successional stages were not the most easily invaded since we found no significant differences in the percentage survival of C. selloana along the successional gradient. However, survival and seedling biomass were enhanced by soil disturbance at any seral stage. This result suggested that inhibition ruled C. selloana invasion. Invasibility neither depended on the invaded vegetation type nor on the co-existing species with similar growth form. Finally, C. selloana invasion was not enhanced by decreasing competition with Phragmites australis, a native coexisting species because survival rates after a year were not significantly different. However, Phragmites increased C. selloana leaf length probably due to shading. Conclusions: C. selloana recruitment appears to be positively affected by soil disturbance but it is independent of successional stage or vegetation type. [ABSTRACT FROM AUTHOR]

Ecologists are searching for models, frameworks, and principles that provide a bridge between theory and the practice of restoration. Successional management has been proposed as a useful model for managing and restoring invasive-plant-dominated rangeland because it provides a framework in which ecological processes can be manipulated by managers to achieve a desired plant community. Successional management identifies three general causes of succession (site availability [disturbance], species availability [colonization], and species performance) and suggests that managers address the ecological process influencing each general cause in a coordinated fashion to direct plant community dynamics. We tested successional management using various techniques to restore invasive-weed-dominated rangeland. Our hypothesis was that successively modifying the factors influencing the causes of succession in an integrated fashion would favor the establishment and abundance of native grasses over singularly applied treatments. Thus, we anticipated that the majority of responses to multiple treatments would be explained by higher order interactions, especially in the final year of the study (2004). To test this hypothesis; we used a model system within a Festuca campestris/Pseudoroegneria spicata habitat among pothole wetlands dominated by Centaurea maculosa and Potentilla recta, two invasive species. We used three herbicide treatments (none, 2,4-D, and picloram) to influence species performance; two seeding methods (imprinting, i.e., creating a small depression and broadcasting, and no-till drilling) to influence disturbance; three seeding rates (977, 1322, and 1557 seeds/m2) to influence colonization; and two cover crop treatments (with and without Triticum aestivum) to influence soil N and favor native grasses. Treatments were factorially arranged and replicated four times in a randomized complete block design in 2001 and sampled in 2002 and 2004. As predicted, plant response to treatments was dominated by two- and three-way interactions in 2004. The highest seeding rate (colonization) combined with no-till drilling (disturbance) produced the highest native grass density in 2002. These effects persisted into 2004 for P. spicata. but not for F. campestris or F. idahoensis. Combining picloram with no-till drill seeding also produced a high density of P. spicata. Drill seeding at 977 seeds/m2 favored F. idahoensis density, while no-till drilling at 1322 seeds/m2 favored its biomass in 2004. F. idahoensis established well after drill seeding with a cover crop and applying 2,4-D. Herbicides reduced native forb density and/or biomass, with early season forbs being more sensitive topicloram and summer forbs being more sensitive to 2,4-D. Herbicides increased exotic grasses’ density and biomass but had no effect on native grasses. In most cases, integrating treatments that addressed multiple causes of succession favored a desired plant community. Thus, we accomplished our goal of using successional management to direct plant communities toward native desired species, but the treatments used did not improve species richness. Since naturally occurring native forbs did not respond favorably to any treatment combination, ecological restoration using successional management may best be thought of as an iterative procedure where various components and processes of the system are methodically repaired or replaced over time. [ABSTRACT FROM AUTHOR]

Despite intensive research, we still have no general understanding of why plant invasions occur. Many different mechanisms of plant invasions have been proposed, but studies designed to investigate them often produce inconsistent results. It remains unclear whether this unsatisfying state of affairs reflects the complexity of the real world (in which every invasion is unique) or the failure to identify the key processes driving most plant invasions. Here we argue that greater generalization is possible, but only if we recognize that the ecological and evolutionary processes enabling a species to advance into a new area change during the course of an invasion. In our view, an invasion can often usefully be subdivided into a primary phase, in which the abundance of an often preadapted species increases rapidly (typically in resource-rich, disturbed habitats), and a secondary phase, in which further spread is contingent upon plastic responses or genetic adaptation to new ecological circumstances. We present various examples to show how this partitioning of the invasion phase sensu stricto produces new hypotheses about the processes underlying plant invasions. Some of these hypotheses can be conveniently tested by investigating plant invasions along strong environmental gradients such as those that occur in mountainous regions. [ABSTRACT FROM AUTHOR]

Phalaris arundinacea L. (reed canarygrass) is one of the most noxious invasive species in North American wetlands, rivers, and lakes. As is true for many invasive species, detailed research may give insights into the ecological and evolutionary factors that promote reed canarygrass invasion. However, important insights into control strategies of reed canarygrass may be gleaned from a synthesis of all the relevant ecological and management studies. We assessed the control strategies previously applied to contain reed canarygrass invasions, the potential for new promising strategies, and the research that is still needed to improve its control in North America. We showed that no one method is sufficient, and that the most successful strategies require both physical and chemical methods, coupled with hydrological management. Moreover, subsequent restoration of the community structure and composition is needed to limit new infestations of reed canarygrass or other invaders. Biological control has not been developed yet for reed canarygrass. Finally, the current knowledge of ecological factors that enhance reed canarygrass invasion suggests that any attempt to eradicate it and limit its spread will be jeopardized if an integrated pest management strategy is not undertaken. Given the high sensitivity of wetlands to plant invasion, management of invasive species must switch from isolated efforts of stand eradication to a landscape approach, emphasizing infestation prevention and accounting for surrounding human activities and the socio-economic context. [ABSTRACT FROM AUTHOR]

In the southern California foothills and mountains, pronounced and complex topographic gradients support fire regimes that vary over short distances. We used LANDIS, a spatially explicit landscape model of disturbance and plant succession, to examine the resilience of dominant plant species, representing different disturbance response strategies, to the effect of varying fire rotation intervals (FRI). The simulated fire regimes represented natural, current and very long FRIs for the foothill shrublands less than 1,400 m (90, 30 and 150 years) and montane forest greater than 1400 m (30, 150, 500 years). The 30-year FRI allowed obligate resprouting shrubs to dominate over obligate seeders, whereas the 90-year FRI resulted in a stable spatial distribution of both of these shrub functional types. This is consistent with the literature that suggests that shifts in shrubland composition are most likely to result from human-caused increases in fire frequency at the low-elevation urban-wildland interface. An ecotone conifer, Pinus coulteri, showed dramatic shifts in distribution under different FRIs, and retreated to the portion of the landscape representing its temporal regeneration niche. Both low and high frequency fire maintained the fire tolerant dominant pine ( P. jeffreyi) in the montane zone. This contradicts the literature that suggests that a high frequency ground fire regime is required for the persistence of a pine-dominated forest, but is consistent with studies showing that conifer forests in the western U.S. have experienced, and are resilient to, a broad range of natural FRIs that include low frequency, high intensity crown fires. [ABSTRACT FROM AUTHOR]

The article provides information regarding plant invasion. The article defines an invader with the following attributes: is new to the region, has the potential to expand its range, and may have environment impacts in a range of ecosystems worldwide. The two important ecological factors that make a habitat prone to invasion are resource fluctuations and disturbance.

Abstract: The eastern Canary Islands constitute a region that is vulnerable to desertification processes, mainly due to its intensely arid climate and the action of man. Vegetation in the island of Fuerteventura has been profoundly transformed over the last few hundred years, and the greater part of the insular territory is presently covered by substitution brush. In this work, a study of soil degradation processes relating to plant cover transformation is presented. To this end, soils that characterize the present-day countryside of the island and those associated with enclaves of original vegetation are studied, and the sequential variation of soil properties along the plant succession is established by means of multivariant analysis of environmental gradients. The results indicate that the original vegetation was established on soils with a low natural quality, severely limited by natural aridity, salinity and sodicity as well as the water and wind erosion processes dominant in the island. These same ecological factors condition the quality of the island''s present soils, although the degradation of the plant cover has increased the severity of several soil degradation processes, particularly those of a physical and biological nature. [Copyright &y& Elsevier]