Authors:G. Koncz, P. Török, M. Papp, G. Matus, and B. Tóthmérész
Intensification of land use in the last few decades resulted in an increased rate of fragmentation of natural forest habitats. With decreased patch size but increased total borderline length the influence of the surroundings also increased. The extent of influence is especially crucial where the forest stands are adjacent to agricultural lands. We studied the vegetation (cover) and seed bank (soil samples, seedling emergence) along adjacent stands of an abandoned vineyard and edge and interior of an oak forest community (Quercetum petraeae-cerris) widespread in Central-Europe, using five transects (16 m2 plots along each transect). We asked the following questions: (i) How do vegetation and seed bank composition differ between the vineyard and forest interior and (ii) which weeds are able to penetrate into the forest herbaceous understorey vegetation and seed banks from the vineyard? In total, 15 phanaerophytes and 147 herbs were detected. Negatively associated with canopy shading, herb cover proved the lowest in the forest inferior. Few weeds and other ruderals recorded in vineyard penetrated into the forest interior. Mean seed density decreased one order of magnitude from the vineyard to the forest interior (from 20,831 to 2,159 seed/m2). The seed banks of the abandoned vineyard and edge and forest interior were dominated by ruderals, but decreasing proportion of weeds was detected from the vineyard to the forest interior. Characteristic forest herbs possessed at most sparse seed banks. Our results suggest that high canopy cover mitigates the negative impact of surrounding weedy vegetation on the forest herb layer. Therefore, the effect of surroundings is detectable mostly in the seed banks. We can assume that the formation of an increased ruderal herb cover can be foreseen if canopy opens, because the local propagule sources of forest species are missing from vegetation and soil seed banks.
Authors:M. Gobbi, M. Caccianiga, B. Cerabolini, F. Bernardi, A. Luzzaro, and S. Pierce
Little is known of how changes in plant function may influence adaptive traits amongst animals further up the food chain. We addressed the hypothesis that shifts in plant functional traits are associated with the adaptive function of animal species which have an indirect trophic link. We compared community characteristics and functional traits of two trophically detached biotic groups (vascular plants and carabid beetles) along a primary succession on terrain at the Cedec glacier in the Alps, where deglaciation events following post-Little Ice Age climate warmings are marked by moraine ridges. Morphofunctional traits were recorded: canopy height (CH), leaf dry matter content (LDMC), leaf dry weight (LDW) and specific leaf area (SLA) (for plants) and the number of brachypterous, autumn-breeding and predator species, and average body length (for carabid beetles). We found that vegetation cover and plant species richness gradually increased throughout early succession, with an abrupt increase between 40 and 150 years after deglaciation. At the early stages of the succession plant traits were typical of ruderal species (high SLA, low CH, LDW) whilst a shift in traits towards stress-tolerance (low SLA) occurred >150 years. Carabid communities and traits changed alongside changes in plant species richness and cover, with late successional vegetation hosting larger, more diverse, less mobile carabid species with longer larval development. Thus, ruderal plant strategies are the main contributors during vegetation development, determining vegetation quantity, and probably have the greatest impact on changes in carabid assemblages by regulating resource availability. Plants then require greater stress-tolerance to survive in stable vegetation, which supports high carabid diversity. This suggests that different plant strategies may affect ground beetle communities via contrasting mechanisms: both quantities (biomass, species richness) and qualities (functional traits, adaptive strategies) should be taken into account during studies of plant-animal interactions within ecosystems.
This study is part of a general project to analyse the biological and ecological mechanisms that influence the invasion of Mediterranean sand dune ecosystems by alien plants. In this paper we analyse the morphological and functional traits of coastal dune wild species (natives and aliens) based mainly on information from the literature. The most common 130 wild species occurring on the recent (Holocenic) coastal dunes were included considering the invasive status of alien plants. A comparative analysis of functional groups was performed through ordination techniques (PCoA using the Gower index). This reveals four functional groups related to the most important plant communities in coastal vegetation zonation. Alien plants were found in all functional groups and no trait or set of traits was specifically related to them. This indicates that aliens show similar traits to those natives growing in different communities of the coastal dune zonation, from the small beach annuals to the evergreen taller shrubs of the Mediterranean macchia. When the invasive status of alien species was taken into account, however, some differences emerged: a) casual aliens were found in almost all groups but their traits were not interpreted as being due to any particular adaptive strategy; b) naturalised aliens were only found in the less fluctuating habitats of the inner coastal zones; c) invasive alien species were connected with two major plant strategies: annual invasive aliens (quick-to-mature low grasses and herbs) and perennial invasive aliens (taller and often strongly clonal).
Authors:D. Palhares, J. E. de Paula, and C. E. dos Santos Silveira
Although Brosimum gaudichaudii occurs in Amazon forest
and in Atlantic forest, it is the only species from the genus Brosimum found in
cerrado vegetation, with a very common occurrence. This species has been
exploited by pharmaceutical industry due to large accumulation of psoralens in
its roots. The stems and subterranean systems of seven fertile plants were
characterised in this study. At early stage of development the stems are
scandent and grow slowly before reaching arboreal size. The subterranean system
is composed of a xylopodium and a taproot. The xylopodium continuously produces
shoots that are able to turn into trunks. The taproot may grow up to one or two
metres deep. There are few lateral roots, but many radicles along the surface
of root system. Abundant latex is found in the pith and bark of branches and
young stems as well in the bark of the subterranean system. However, it is
scarce in the bark of mature trunks. The stem bark is grey, rough and thin,
while the bark of the root and xylopodium is orange, corrugated with laminate
surface. The xylopodium is a fundamental structure to understand the plant
strategies to successfully adapt to the cerrado environment condition.
Clonal populations are hierarchically organized: genetic individuals (genets) can consist of many physiological individuals (ramets). Each ramet takes up resources from its local environment, but the resource pattern can be reorganized within the clone by transport between ramets. Thus, an integrated clone is not directly subject to the pattern of resource availability in its habitat. Local shortages can be compensated, hence, the clone can buffer itself against spatio-temporal heterogeneity in the habitat. We modelled a series of habitat types, assuming that one limiting resource was patchily distributed in space, and could fluctuate over time. Habitat types differed in the density, size and persistence of resource patches, and in the contrast between resource-rich patches and the resource-poor background. We applied an individual-based, spatially explicit population dynamic model to compare the performance of two plant strategies in these habitat types. In the Integrator, ramets that were interconnected distributed the resource evenly. In the Splitter, no resource translocation occurred. First we observed population growth of the two strategies separately, then in competition. We found a range of habitat types, where none of the strategies was viable, because of the scarcity of resource patches. As the density of resource patches was increased, first only the Integrator could persist. Then, at intermediate densities of resource patches, the Splitter became viable, and, being a stronger competitor, excluded the Integrator. Finally, at high resource-patch densities, the Integrator occupied the area again. Since the Splitter was viable at high density of resource patches when growing alone, its disappearance is more due to spontaneous extinction, due to competitive exclusion by the Integrator. We predict, therefore, the dominance of integrated clones both in extremely unproductive and productive environments, but for different reasons. It is important to note that this trend was observable only at high spatial and temporal variation in resource availability. Less contrast between patches of different quality, smaller patch sizes, or longer persistence of patches facilitated the dominance of the Splitter. Thus, buffering is advantageous in many but not all habitat types.