Settlements as a source for the spread of non-native plants into Central European suburban forests

Urbanization is considered as a major driver for biotic homogenization. Urbanization also promotes the dispersal of non-native species. This study examined the roles of suburban settlements and of the surrounding landscape composition for the spread of non-native plant species into adjacent mixed deciduous forests in Southern and Northwestern Switzerland. The number and abundance of native and non-native vascular plant species in both the ground vegetation and shrub layer were recorded in 15 forest sites situated adjacent to settlements and 15 control sites far from settlements. Various site and landscape characteristics were assessed in the surroundings (100 m radius) of the study sites. In both regions we found a higher number and larger abundance of non-native plant species in forest sites adjacent to settlements than in control forest sites. Furthermore, non-native plants were more frequently recorded close to roads and in sites surrounded by a large percentage cover of garden. All these effects were more pronounced in Southern Switzerland, a region with milder winter climate, than in Northwestern Switzerland. Our study showed that settlements are a source for the spread of non-native plant species into Central European suburban forests, and that the composition of the surrounding landscape matrix (e.g. traffic infrastructure, percentage cover of gardens) also affects the establishment of non-native plants.     

Poplar plantations along regulated rivers may resemble riparian forests after abandonment: a comparison of passive restoration approaches

Abandoning hybrid poplar plantations may be an alternative strategy for enlarging natural riparian corridors along regulated rivers where forest regeneration no longer takes place. Despite the generally high local diversity of plants in poplar plantations, their capacity to converge towards riparian forests following abandonment remains largely untested and uncertain, because maintenance‐related disturbance of plantations favors ruderal, not strictly riparian specialists. We assessed the spontaneous recolonization of vegetation in abandoned hybrid poplar plantations following two management strategies: harvesting or simple abandonment of standing trees. The floristic composition in four chronosequences of 10 active (1–15 years), 17 harvested (1–15 years), and 10 abandoned (8–20 years) hybrid poplar plantations, as well as 10 riparian sites established at gravel bars that appeared following the cessation of in‐channel gravel mining (8–25 years) along the highly regulated Garonne River (SW France) was assessed in the framework of ecological disturbance theory. Both harvested and abandoned sites still resembled active plantations more than riparian forests. When poplar resprouting was low after harvesting, sites were dominated by light‐demanding, nitrophilous herbs, sub‐shrubs, and vines showing both competitive and ruderal traits, and vegetation composition remained stable over time. Abandoned and harvested sites with high poplar resprouting developed forest communities in which competitive species that tolerate and generate shade dominated, and tree species recruitment was higher. Riparian sites hosted the highest number of indicator species, mainly wetland and exotic. Simple passive restoration strategies like abandonment of plantations can help create valuable ecosystems, although ones that diverge from riparian forests colonizing new fluvial landforms.     

Dynamics of food resources for beavers in settlements colonized and abandoned several times

The state of food resources for Eurasian beavers (Castor fiber Linnaeus, 1758) after several cycles of habitat colonization and abandonment has been analyzed in three beaver settlements on small rivers of Novgorod oblast. It has been shown that tree stands surrounding the settlements differ in composition and degree of damage but are similar in that they contain no forage for beavers: aspen is absent, and birch trees are large and require great efforts to cut them down and utilize. The undergrowth and understory also contain no aspen, while abundant willows and birch are represented by young, thin-stemmed plants unevenly distributed over the area. Tree species prevailing in abandoned settlements are not favored by beavers, implying that the animals must have expended extra energy for foraging. Supposedly, populations of beavers on small rivers in the southern taiga subzone, in habitats modified by their activities, will maintain their abundance far below the maximum possible level, depending on the rate of forage plant regrowth against the background of deteriorating habitat quality.     

Recovery of Plant Species Richness and Composition in an Abandoned Forest Settlement Area in Kenya

Cultivation of annual crops in the initial stage of reforestation has been commonly practiced in the tropics. In recent decades, however, cultivation of such areas has been discontinued, resulting in widespread abandoned settlements. In this article we used a former forest village settlement in Kenya, which had been cleared, cultivated and then abandoned, to study how natural vegetation recovers after such disturbances. Species richness, abundance, and composition of tree seedlings, saplings, adult trees, shrubs, and herbs were recorded in different zones, from a heavily degraded zone in the center of the settlement, through less disturbed transition zones (TZs), and in the surrounding secondary forest (SF). Species richness and abundance of tree seedlings, saplings, and adult trees increased gradually from the heavily degraded zone to the SF, whereas shrub and herb richness were the same for TZs and SF and abundance was lowest in the SF. Total species richness was highest in the SF. Some pioneer tree species were highly associated with the TZs, whereas sub‐canopy tree species were associated with the SF. A group of tree species were not particularly associated with any of the four zones. Thus, these species might have good potential as restoration species. The results of our study contribute to the knowledge of natural regeneration in general, and of individual species characterizing the different stages of recovery of abandoned settlements in particular. Such information is urgently needed in designing ecologically sound management strategies for restoring abandoned forest settlements in tropical areas.     

Role of infrastructure and other environmental factors affecting the distribution of alien plants in the Tatra Mts

Alien plants, although usually rare in mountain habitats, can significantly impact native species diversity. The aim of this study was to analyse patterns of alien plant distribution in the Tatra Mts (Slovakia), focusing primarily on comparison of various transportation routes as a conduit for the spread of alien plants. We collected data on transects along: (i) railways, (ii) paved roads with unlimited access, (iii) tourist routes in mountain valleys (paved and unpaved roads, footpaths) with limited access and (iv) plots in areas surrounding mountain chalets. The majority of alien plants were found in locations at lower elevations and with intensive human activity. Patterns of distribution along the main corridors in the Tatras reflect the intensity and manner of use of each transportation route. Paved roads with unlimited access and railways are used most frequently and host the greatest number of alien species. Our observations show that the mode of access of these routes is more important than the road surface. Roads with limited vehicular access, be it unpaved and paved, are very similar in their alien species richness, while paved roads with limited and unlimited access significantly differ. Footpaths that cannot be accessed by vehicles are almost free of alien plants, even though they are found in the widest elevation range and often parallel to roads in the same valley. Other factors significantly negatively affiliated with alien species richness were elevation, cover of the tree and moss layer and moisture, and positively affiliated with the amount of nutrients.     

Remnant habitats for grassland species in an abandoned Swedish agricultural landscape

Questions: Which factors influence the persistence of vascular grassland plants in long‐abandoned (at least 50 yr) arable fields and meadows? What might be the implications of current levels of species richness on abandoned arable fields and meadows for future restoration? Location: Forested highlands of Kilsbergen, south central Sweden. Methods: The abundance of all vascular plant species was investigated in three habitat types: former arable fields, hay meadows and outlands (pastures) at 27 farms, abandoned for either approximately 50 yr or 90 yr. Time since abandonment, tree cover, soil depth, degree of soil podsol development, size of the infield area and two measures of connectivity were used as predictors for species richness and species composition. Results: Former outland had denser tree cover, fewer species and fewer grassland species than former arable fields and hay meadows, irrespective of time since abandonment. Former hay meadows and arable fields with a longer time since abandonment were less rich in species, more wooded and had greater podsolization than meadows and fields abandoned at a later stage. Species richness was higher in hay meadows and arable fields at farms with larger infield area and deeper soils compared with farms with smaller infield area and shallower soils. The greatest richness of species and most open habitat were former arable fields at larger farms abandoned 50 yr before the study. Former arable fields had the highest number of grassland species. Conclusion: After 50 yr of abandonment, former arable fields were the most important remnant habitats for grassland species and may be a more promising target for restoration than formerly managed grasslands.     

From the backyard to the backcountry: how ecological and biological traits explain the escape of garden plants into Mediterranean old fields

To explain current ornamental plant invasions, or predict future ones, it is necessary to determine which factors increase the probability of an alien species becoming invasive. Here, we focused on the early phases of ornamental plant invasion in order to identify which plant features and cultivation practices may favor the escape of ornamental plants from domestic gardens to abandoned agricultural land sites in the Mediterranean Region. We used an original approach which consisted in visiting 120 private gardens in an urbanizing rural area of the French Mediterranean backcountry, and then visited surrounding old fields to determine which planted species had escaped out of the gardens. We built a database of 407 perennial ornamental alien species (most of which were animal-dispersed), and determined nineteen features that depicted the strength of species’ propagule pressure within gardens, the match between species requirements and local physical environment, and each species’ reproductive characteristics. Using standard and phylogenetic logistic regression, we found that ornamental alien plants were more likely to have escaped if they were planted in gardens’ margins, if they had a preference for dry soil, were tolerant to high-pH or pH-indifferent, and if they showed a capacity for clonal growth. Focusing only on animal-dispersed plants, we found that alien plants were more likely to have escaped if they were abundant in gardens and showed preference for dry soil. This suggests that gardening practices have a primary impact on the probability of a species to escape from cultivation, along with species pre-adaptation to local soil conditions, and capacity of asexual reproduction. Our results may have important implications for the implementation of management practices and awareness campaigns in order to limit ornamental plants to becoming invasive species in Mediterranean landscapes.     

Land-Use History and Forest Regeneration in the Cayey Mountains, Puerto Rico

Although deforestation continues to be a major threat to tropical biodiversity, abandonment of agricultural land in Puerto Rico provides an opportunity to study long-term patterns of secondary forest regeneration. Using aerial photographs from 1937, 1967, and 1995, we determined land-use history for 2443 ha in the Cayey Mountains. Pastures were the dominant land cover in 1937 and <20% of the area was classified as forest. Between 1937 and 1995, forest cover increased to 62% due to widespread abandonment of agriculture. To examine the effect of historic land use on current forest structure and species composition, we sampled secondary forests in 24 abandoned pastures, 9 abandoned coffee plantations and 4 old-growth forest sites. Sites were located on two soil types along an elevational gradient (125–710 m) and included a chronosequence from 4 to over 80 years old. After 25–30 years, basal area and species richness in secondary forest sites derived from abandoned pastures and coffee plantations were similar to old-growth forest sites. The species composition of secondary forests derived from abandoned pastures and coffee plantations remained distinct from old-growth forest. In addition to historic land use, age and elevation were important environmental variables explaining variation in secondary forest species composition. Non-indigenous species were common in recently abandoned pastures and coffee plantations, but their importance declined in the older sites. This study demonstrates that secondary forests on private land can be an important component of the conservation of tropical tree biodiversity. Received 16 June 1999; Accepted 8 October 1999.     

Cross-scale management strategies for optimal control of trees invading from source plantations

Biological invasion by non-native tree species can transform landscapes, and as a consequence, has received growing attention from researchers and managers alike. This problem is driven primarily by the naturalisation and invasion of tree species escaping from cultivation or forestry plantations. Furthermore, these invasions can be strongly influenced by the land-use matrix of the surrounding region, specific management of the source populations, and environmental conditions that influence seed dispersal or habitat quality for the invader. A major unresolved challenge for managing tree invasions in landscapes is how management should be deployed to contain or slow the spread of invading populations from one or more sources (e.g. plantations). We develop a spatial simulation model to test: (1) how to best prioritise the control of invasive tree populations spatially to slow or contain the biological invader when habitat quality varies in the landscape, and (2) how to allocate control effort among different management units when trees spread from many source populations. We first show that to slow down spread effectively, management strategy is less important than management effort. We then identify the conditions affecting the relative performance of different management strategies. At the landscape scale, targeting peripheral stands consistently yielded the best results whereas at the regional scale, management strategies needed to account for both habitat quality and tree life-history. Overall, our findings demonstrate that knowledge of how habitat affects tree life-history stages can improve management to contain or slow tree invasions by improving the spatial match between management effort and efficacy.     

Distribution patterns of alien invasive plants and their influences on native plants of Hainan Island

 以国家农业部指定的20种恶性入侵植物为目的种, 在海南岛开展其分布特征与入侵强度的调查研究, 重点研究了陆域环境中6种广布入侵植物——飞机草(Chromolaena odorata)、假臭草(Praxelis clematidea)、含羞草(Mimosa pudica)、苏门白酒草(Conyza sumatrensis)、三裂叶蟛蜞菊(Wedelia trilobata)、马缨丹(Lantana camara)在7种生态系统(天然次生林、农田、村落、种植园、林缘、弃耕地、草地)中的入侵频率及入侵植物对本地植物的影响。结果表明: 1)海南岛有恶性入侵植物11种, 占调查目的种总数的55.0%。2)海南岛的东北、西南部分布的入侵植物种数较多, 东南部次之, 中部地区最少。3) 6种入侵植物的整体入侵强度为: 假臭草>飞机草>含羞草>三裂叶蟛蜞菊>马缨丹>苏门白酒草; 苏门白酒草、马缨丹在不同生态系统中的入侵频率无显著差异; 而假臭草在种植园及弃耕地, 含羞草在农田, 三裂叶蟛蜞菊在种植园生态系统中的入侵频率均显著高于其他生境。4)种植园、弃耕地和农田生态系统是植物入侵的主要生境类型, 而林缘和天然次生林生态系统均对植物入侵表现出抵御作用。5)植物入侵对当地植物多样性的影响存在正、负及无关联效应, 并主要影响群落中的草本植物功能群; 样地中入侵植物盖度总值与本地植物平均种数在种植园、农田和村落生态系统中无相关性, 在林缘和弃耕地生态系统中, 两者呈显著负相关关系; 而在草地生态系统中, 在一定盖度范围内, 入侵植物盖度总值与本地植物平均种数呈显著正相关关系。     

Qualitative variation in roadside weed vegetation along an urban–rural road gradient

Information on mechanisms of differentiation or homogenization of urban floras is deficient, despite their importance for urban nature conservation and urban land management. Roads, as a major human promoter of urbanization, can be an initial habitat for plants dispersed by transportations. We assumed that variation in weed vegetation along urban–rural roadside gradients is small, particularly in curbside cracks. We classified vegetation occurring in curbside cracks along the National Route 3 in southern Japan and compared the characteristics of the vegetation types recognized. Species in curbside cracks were recorded on 40 plots. Three vegetation types were classified, in part related to surrounding land-use types. Although the Shannon–Wiener diversity index and the number of native species clearly differed among the vegetation types in the curbside cracks, no significant differences between the three floristic vegetation types were found in the number of non-natives and invasive alien species. This may result from the small specificity and complexity of landscape structures, due to the continuity and connectivity of paved-road networks. Of the 122 species, 44 were non-natives or invasive alien species. The vegetation types generally involved the same plant families, with large numbers of species from the Asteraceae and Poaceae, regardless of vegetation types, but frequency of occurrence of the two families clearly differed between natives and non-natives and invasive alien species. Ephemeral non-natives and invasive alien species, particularly Asteraceae and Poaceae, seem to have advantageous dispersal strategies or low habitat dependency facilitating their occurrence in curbside cracks, regardless of adjacent land uses and the urban–rural landscape gradient. Expansion of these species may cause a homogenization of regional floras along roads.     

Contrasting patterns in the invasions of European terrestrial and freshwater habitats by alien plants,insects and vertebrates

Aim To provide the first comparative overview on the current numbers of alien species that invade representative European terrestrial and freshwater habitats for a range of taxonomic groups. Location Europe. Methods Numbers of naturalized alien species of plants, insects, herptiles, birds and mammals occurring in 10 habitats defined according to the European Nature Information System (EUNIS) were obtained from 115 regional data sets. Only species introduced after ad 1500 were considered. Data were analysed by ANCOVA and regression trees to assess whether differences exist among taxonomic groups in terms of their habitat affinity, and whether the pattern of occurrence of alien species in European habitats interacts with macroecological factors such as insularity, latitude or area. Results The highest numbers of alien plant and insect species were found in human‐made, urban or cultivated habitats; if controlled for habitat area in the region, wetland and riparian habitats appeared to support relatively high numbers of alien plant species too. Invasions by vertebrates were more evenly distributed among habitats, with aquatic and riparian, woodland and cultivated land most invaded. Mires, bogs and fens, grassland, heathland and scrub were generally less invaded. Habitat and taxonomic group explained most variation in the proportions of alien species occurring in individual habitats related to the total number of alien species in a region, and the basic pattern determined by these factors was fine‐tuned by geographical variables, namely by the mainland–island contrast and latitude, and differed among taxonomic groups. Main conclusions There are two ecologically distinct groups of alien species (plants and insects versus vertebrates) with strikingly different habitat affinities. Invasions by these two contrasting groups are complementary in terms of habitat use, which makes an overall assessment of habitat invasions in Europe possible. Since numbers of naturalized species in habitats are correlated among taxa within these two groups, the data collected for one group of vertebrates, for example, could be used to estimate the habitat‐specific numbers of alien species for other vertebrate groups with reasonable precision, and the same holds true for insects and plants.     

Forest regeneration in abandoned coffee plantations and pastures in the Cordillera Central of Puerto Rico

Forest structure and species composition were described in abandonedshade and sun coffee plantations and abandoned pastures in Puerto Rico. Foreststructural characteristics were similar to older forest sites afterapproximately 30 yr of recovery. The historical presence of shadecoffee plantations as the dominant agricultural activity in the region hasresulted in the homogenization of secondary forest composition. The continuousdominance of Coffea arabica and species used for shade inabandoned shade coffee contributed to a slower rate of species compositionchange in comparison to abandoned pastures. Abandoned pastures were initiallycolonized by a group of light demanding and/or wind dispersed species and thenby shade tolerant species characteristic of abandoned shade coffee plantations,suggesting that the secondary forests of abandoned shade coffee plantation arethe major source of species in this landscape. The presence of a few isolatedbig trees in sun coffee plantations appeared to facilitate colonization ofwoodyspecies similar in composition to abandoned shade coffee plantations. In amultivariate analysis, time since abandonment and elevation were the variablesthat explained the majority of variability in species composition among sites.However, a few native species (e.g. Guarea guidonia,Casearia sylvestris, Ocotealeucoxylon) were common regardless of land use history or elevation.In contrast, important old forest species (e.g. Sloaneaberteriana, Dacryodes excelsa,Manilkara bidentata) were rare or absent from most of thesecondary forest stands suggesting the need to reintroduce these species. Landmanagement and conservation efforts can be improved by incorporating theeffectsof land use history on secondary forest dynamics.     

Frequent burning promotes invasions of alien plants into a mesic African savanna

Fire is both inevitable and necessary for maintaining the structure and functioning of mesic savannas. Without disturbances such as fire and herbivory, tree cover can increase at the expense of grass cover and over time dominate mesic savannas. Consequently, repeated burning is widely used to suppress tree recruitment and control bush encroachment. However, the effect of regular burning on invasion by alien plant species is little understood. Here, vegetation data from a long-term fire experiment, which began in 1953 in a mesic Zimbabwean savanna, were used to test whether the frequency of burning promoted alien plant invasion. The fire treatments consisted of late season fires, lit at 1-, 2-, 3-, and 4-year intervals, and these regularly burnt plots were compared with unburnt plots. Results show that over half a century of frequent burning promoted the invasion by alien plants relative to areas where fire was excluded. More alien plant species became established in plots that had a higher frequency of burning. The proportion of alien species in the species assemblage was highest in the annually burnt plots followed by plots burnt biennially. Alien plant invasion was lowest in plots protected from fire but did not differ significantly between plots burnt triennially and quadrennially. Further, the abundance of five alien forbs increased significantly as the interval (in years) between fires became shorter. On average, the density of these alien forbs in annually burnt plots was at least ten times as high as the density of unburnt plots. Plant diversity was also altered by long-term burning. Total plant species richness was significantly lower in the unburnt plots compared to regularly burnt plots. These findings suggest that frequent burning of mesic savannas enhances invasion by alien plants, with short intervals between fires favouring alien forbs. Therefore, reducing the frequency of burning may be a key to minimising the risk of alien plant spread into mesic savannas, which is important because invasive plants pose a threat to native biodiversity and may alter savanna functioning.     

Reforestation of abandoned pasture on Hokkaido, northern Japan: effect of plantations on the recovery of conifer-broadleaved mixed forest

When pasture land is abandoned, there are, in many cases, inhibitory factors that slow the rate of transition to a natural vegetation. Accordingly, the planned management of restoration has become an important issue in various parts of the world, where environmental conditions can vary widely. Although tree plantations are widely used as a management tool for restoration, there have been few studies addressing the practical aspects of the procedure. I examined effects of tree plantations within the framework of an evaluation of methods for restoring abandoned pasture on Hokkaido, northern Japan. I developed and analyzed vegetation maps spanning the past 57 years for the old-growth site influenced by artificial disturbance; the procedure revealed the pattern of change in the vegetation cover. Matrix model analysis showed that intensive use of plantations contributed to reduction of the area occupied by dwarf bamboo and pasture land (i.e., superior to simple abandonment). Furthermore, the field study of vegetation types and changes in species composition over 20 years suggests that plantations have contributed to a reduction in the effects of factors that inhibit revegetation. However, the establishment of monoculture plantations is frequently viewed skeptically as a procedure that is applied without fundamental ecological knowledge. For sustained management, adequate historical and ecological information on the restoration site should be provided to all stakeholders. An erratum to this article can be found at     

Structure and dynamics of pollination networks: the role of alien plants

Research on ecological communities, and plant–pollinator mutualistic networks in particular, has increasingly benefited from the theory and tools of complexity science. Nevertheless, up to now there have been few attempts to investigate the interplay between the structure of real pollination networks and their dynamics. This study is one of the first contributions to explore this issue. Biological invasions, of major concern for conservation, are also poorly understood from the perspective of complex ecological networks. In this paper we assess the role that established alien species play within a host community by analyzing the temporal changes in structural network properties driven by the removal of non‐native plants. Three topological measures have been used to represent the most relevant structural properties for the stability of ecological networks: degree distribution, nestedness, and modularity. Therefore, we investigate for a detailed pollination network, 1) how its dynamics, represented as changes in species abundances, affect the evolution of its structure, 2) how topology relates to dynamics focusing on long‐term species persistence; and 3) how both structure and dynamics are affected by the removal of alien plant species. Network dynamics were simulated by means of a stochastic metacommunity model. Our results showed that established alien plants are important for the persistence of the pollination network and for the maintenance of its structure. Removal of alien plants decreased the likelihood of species persistence. On the other hand, both the full network and the subset native network tended to lose their structure through time. Nevertheless, the structure of the full network was better preserved than the structure of the network without alien plants. Temporal topological shifts were evident in terms of degree distribution, nestedness, and modularity. However the effects of removing alien plants were more pronounced for degree distribution and modularity of the network. Therefore, elimination of alien plants affected the evolution of the architecture of the interaction web, which was closely related to the higher species loss found in the network where alien plants were removed.     

Differential effects of local habitat and landscape characteristics on bird communities in Mediterranean afforestations motivated by the EU Common Agrarian Policy

We investigated the effects of local habitat structure and surrounding landscape characteristics (proportion of land use types and connectedness) on species density and composition of bird communities inhabiting the interior of young tree plantations on former cropland in central Spain, which were motivated by the Common Agrarian Policy. Variation of species density (number of species/0.78 ha) among tree plantations showed different environmental associations across seasons: local habitat was more important than landscape characteristics during winter, whereas they were similarly important during spring. Species density increased with the development of the tree layer in winter and with the presence of urban areas around tree plantations and cover of the herbaceous layer within them in the breeding season. We identified 15 species that exhibit high relative abundance in woodland habitats within the Mesomediterranean region of Central Spain that were absent in both seasons in the studied tree plantations, which were an attractive habitat for urban exploiter species but an unfavorable habitat for the regional forest species pool except for forest generalist species. Composition of bird assemblages was more related to local habitat structure than to landscape characteristics around tree plantations and was rather similar in winter and spring seasons. The very different effects of local habitat and landscape characteristics on bird communities make difficult suggesting management practices with positive effects for all avifauna species during the entire year. We conclude that the small size and low maturity of the studied tree plantations do not contribute to enhancing the bird diversity value of current CAP aids to afforest former cropland with pines in the Mediterranean region.     

Community structure and diversity of bryophytes and vascular plants in abandoned fen meadows

We examined effects of abandonment on species diversity and species composition by comparing 21 calcareous fen meadows in the pre-alpine zone of central and northeastern Switzerland. Meadows were divided into three classes of successional stages (mown: annually mown in late summer, young fallow: 4–15 years, and old fallow: >15 years of abandonment). In each fen, we measured litter mass in four 20 cm×20 cm plots, as well as (aboveground) biomass and species density (number of species per unit area) of bryophytes and vascular plants. Bryophyte biomass was reduced in abandoned fens, whereas litter mass and aboveground biomass of vascular plants increased. Species density of both taxonomic groups was lower in abandoned than in mown fens. Young and old successional stages were not different except for bryophytes, for which old successional stages had higher species density than young stages. We used litter mass and aboveground biomass of vascular plants as covariables in analyses of variance to reveal their effects on species density of both taxonomic groups. For bryophytes, litter mass was more important than vascular plant biomass in explaining variance of species density. This indicates severe effects of burying by litter on bryophyte species density. For species density of vascular plants, both vascular plant biomass and litter mass were of similar importance in explaining the decreased species density. Canonical correspondence analyses showed that abandonment also had an effect on species composition of both bryophytes and vascular plants. However, young and old successional stages were not different indicating fast initial changes after abandonment, but slow secondary succession afterwards. Furthermore, indicator species analysis showed that there was no establishment of new species after abandonment that might dramatically alter fen communities. Re-introduction of mowing as a nature conservation strategy may thus be very promising – even for old fallows.     

Natural forest regeneration and ecological restoration in human‐modified tropical landscapes

In human‐modified tropical landscapes (HMLs) the conservation of biodiversity, functions and services of forest ecosystems depends on persistence of old growth forest remnants, forest regeneration in abandoned agricultural fields, and restoration of degraded lands. Understanding the impacts of agricultural land uses (ALUs) on forest regeneration is critical for biodiversity conservation in HMLs. Here, we develop a conceptual framework that considers the availability of propagules and the environment prevailing after field abandonment as two major determinants of forest regeneration in HMLs. The framework proposes that regeneration potential decreases with size, duration and severity of agricultural disturbance, reducing propagule availability and creating ill‐suited environmental conditions for regeneration. We used studies from Southern Mexico to assess this framework. First, we identify regeneration bottlenecks that trees face during transit from seed to follow‐up life stages, using demographic analysis of dominant pioneer species in recently abandoned fields. Then, we explore effects of ALUs on forest regeneration at the field and landscape scales, addressing major legacies. Finally, we integrate agricultural disturbance with landscape composition to predict attributes of successful second growth forests in HMLs, and provide indicators useful to select tree native species for active restoration. An indicator of disturbance inflicted by ALUs, based on farmers’ information, predicted better regeneration potential than measurements of soil and microclimate conditions at time of abandonment. Cover of cattle pastures in the landscape was a stronger indicator of forest regenerating attributes than cover of old growth forest remnants. To conclude, we offer recommendations to promote forest regeneration and biodiversity conservation in HMLs.