Dispersal by cattle of salt-marsh and dune species into salt-marsh and dune communities

Seed dispersal via ingestion and defecation by large herbivores (endozoochory) plays a potentially important role in structuring plant communities. In the present study we tested whether cattle disperse seeds between different plant communities in a heterogeneous coastal habitat. We surveyed the seed contents of cattle dung collected from two habitat types within a grazing system, one in dunes and the other in salt-marsh. The dunes are characterized by sandy soil, and infrequent inundation by the sea, whereas the salt-marsh features clay deposited during inundations. Seeds of both salt-marsh and dune species were dispersed into salt-marsh and dune habitats. The seed content of cattle dung collected in salt-marsh and dunes was similar with respect to species composition and seed density. However, dispersal of dune species into salt-marsh and vice-versa did not result in establishment in those communities. Seed traits per se did not differ between dune species and salt-marsh species. Species abundance in the established vegetation and seed density in dung were positively correlated. Seed abundance for most species found in dung was consistent with the availability of viable seeds during the growing season. Seed mass, seed 'roundness' and seed release height were all negatively correlated with seed numbers in dung. An indirect factor, namely, forage quality of the plant, and hence attractiveness for herbivores, could explain the higher likelihood of seed dispersal of salt-marsh species than of dune species. The salt-marsh harbours species with higher forage quality than the dune species, as derived from Ellenberg nitrogen indicator values

Praktijkervaringen met waterberging in natuur(ontwikkelings)gebieden : hoofdrapport pilotprogramma waterberging en natuur

In 2002 is het “Pilotprogramma Waterberging-Natuur”gestart. Het hoofddoel van het pilotprogramma was waterbeheerders, terreinbeherende instanties en provincies te ondersteunen in het koppelen van de functies waterberging en natuur. Daarbij is het pilotprogramma primair gericht geweest op het opdoen en verspreiden van ervaringskennis. Dit rapport geeft een overzicht van de belangrijkste resultaten van het pilotprogramma waterberging-natuur. Naast dit hoofdrapport is er per pilot een achtergrondrapport beschikbaar waar in meer detail wordt ingegaan op aanpak van de monitoring en de resultaten. Een samenwerking tussen vele partijen: WUR, Deltares, Natuurmonumenten, Staatsbosbeheer, RU Groningen, Twentse Vogelwerkgroep, waterschappen, Rijkswaterstaat en LNV (Natuur, Kennis

Creation and preservation of vegetation patterns by grazing

Structural patterns of tall stands ("tussock") and short stands ("lawn") are observed in grazed vegetation throughout the world. Such structural vegetation diversity influences plant and animal diversity. A possible mechanism for the creation and preservation of such patterns is a positive feedback between grazing and plant palatability. Although some theoretical studies have addressed this point in a non-spatial setting, the spatial consequences of this feedback mechanism on the stability and spatial characteristics of vegetation structure patterns have not been studied. We addressed this issue by analyzing a spatially explicit individual-based plant-grazer simulation model, based on published empirical relations and the assumption of optimal foraging. In the model, the selection by the grazer of short stands (that have a higher energy content and are more palatable) is affected by traveling costs and the spatial organization of swards. Nevertheless, the most selected biomass in this type of short stands was the optimal biomass predicted by cropping and digestion constraints. As a result of the optimal foraging strategy, the grazers displayed Levy-flight traveling behavior during the simulations with characteristic exponent mu approximate to 2. Patterns of short and tall stands created by grazing were preserved for at least a decade. Even in seasonal habitat, the spatial organization of the patterns remained relatively constant, despite fluctuations in the area of short stands. Heterogeneity of initial vegetation increased heterogeneity of the grazing-induced pattern, but did not affect its stability. The area of short stands that was preserved by grazing scaled with the herbivore mass to the power 0.4 and with the carrying capacity of the vegetation to the power -0.75. Patterns of tall and short stands can be created and perpetuated by optimally grazing ruminants, irrespective of possible underlying soil patterns. The simulations generate predictions for the stability and spatial characteristics of such structural vegetation patterns. (C) 2008 Elsevier B.V. All rights reserved

The dispersal of vascular plants in a forest mosaic by a guild of mammalian herbivores

Endozochorous seed dispersal by herbivores can affect plant spatial dynamics and macroecological patterns. We have investigated the number and species composition of viable seeds deposited in faeces of a full guild of macroherbivores (four deer and two lagomorph species) in a forest in eastern Britain. One hundred and one plant species germinated from faecal pellet material, 85 of which were among the 247 vascular plant species recorded in the forest. However, three species – Chenopodium album, Urtica dioica and Agrostis stolonifera – comprised 56% of the seedlings recorded. Of the species recorded in faecal samples, 36% had no recognised dispersal mechanism, while very few (7%) were adapted to endozoochorous dispersal (fleshy fruit or nut). The number of species dispersed by the herbivores was ranked Cervus elaphus and Dama dama (96) > Capreolus capreolus (40) > Muntiacus reevesi (31) > Oryctolagus cuniculus (21) > Lepus europaeus (19), with the other taxa dispersing subsets of those dispersed by C. elpahus and D. dama. The invasive M. reevesi deposited the fewest seeds per gram of faecal pellet material (0.4 g−1) and hence fewer seeds per unit area than other deer species despite their numerical dominance, while C. elaphus/D. dama deposited the most (0.43 seeds m−2 year−1). Due to differences in faecal seed density among habitats combined with the ranging behaviour of animals, more seeds were deposited in younger stands, enhancing the potential contribution of macroherbivores to population persistence by dispersal and colonisation in a successional mosaic