Comparing the impact of a grazing regime with European bison versus one with free-ranging cattle on coastal dune vegetation in the Netherlands

Substantial light woodland and open vegetation characterized the temperate forest biome before Homo sapiens

The extent of vegetation openness in past European landscapes is widely debated. In particular, the temperate forest biome has traditionally been defined as dense, closed-canopy forest; however, some argue that large herbivores maintained greater openness or even wood-pasture conditions. Here, we address this question for the Last Interglacial period (129,000-116,000 years ago), before Homo sapiens-linked megafauna declines and anthropogenic landscape transformation. We applied the vegetation reconstruction method REVEALS to 96 Last Interglacial pollen records. We found that light woodland and open vegetation represented, on average, more than 50% cover during this period. The degree of openness was highly variable and only partially linked to climatic factors, indicating the importance of natural disturbance regimes. Our results show that the temperate forest biome was historically heterogeneous rather than uniformly dense, which is consistent with the dependency of much of contemporary European biodiversity on open vegetation and light woodland.

Spatially associated or composite life traces from Holocene paleosols and dune sands provide evidence for past biotic interactions

Biotic interactions (e.g., predation, competition, commensalism) where organisms directly or indirectly influenced one another are of great interest to those studying the history of life but have been difficult to ascertain from fossils. Considering the usual caveats about the temporal resolution of paleontological data, traces and trace fossils in the sedimentary record can record co-occurrences of organisms or their behaviours with relatively high spatial fidelity in a location. Neoichnological studies and studies on recently buried traces, where direct trophic links or other connections between tracemakers are well-known, may help interpret when and where overlapping traces represented true biotic interactions. Examples from Holocene paleosols and other buried continental sediments in Poland include the tight association between mole and earthworm burrows, forming an ichnofabric representing a predator-prey relationship, and that of intersecting insect and root traces demonstrating the impact of trees as both ecosystem engineers and the basis for food chains. Trampling by ungulates, which leaves hoofprints and other sedimentary disturbances, may result in amensal or commensal effects on some biota in the short term and create heterogeneity that later trace-making organisms, such as invertebrate burrowers, can also respond to in turn, though such modified or composite traces may be challenging to interpret.

Metagenomics: A viable tool for reconstructing herbivore diet

Metagenomics can generate data on the diet of herbivores, without the need for primer selection and PCR enrichment steps as is necessary in metabarcoding. Metagenomic approaches to diet analysis have remained relatively unexplored, requiring validation of bioinformatic steps. Currently, no metagenomic herbivore diet studies have utilized both chloroplast and nuclear markers as reference sequences for plant identification, which would increase the number of reads that could be taxonomically informative. Here, we explore how in silico simulation of metagenomic data sets resembling sequences obtained from faecal samples can be used to validate taxonomic assignment. Using a known list of sequences to create simulated data sets, we derived reliable identification parameters for taxonomic assignments of sequences. We applied these parameters to characterize the diet of western capercaillies (Tetrao urogallus) located in Norway, and compared the results with metabarcoding trnL P6 loop data generated from the same samples. Both methods performed similarly in the number of plant taxa identified (metagenomics 42 taxa, metabarcoding 43 taxa), with no significant difference in species resolution (metagenomics 24%, metabarcoding 23%). We further observed that while metagenomics was strongly affected by the age of faecal samples, with fresh samples outperforming old samples, metabarcoding was not affected by sample age. On the other hand, metagenomics allowed us to simultaneously obtain the mitochondrial genome of the western capercaillies, thereby providing additional ecological information. Our study demonstrates the potential of utilizing metagenomics for diet reconstruction but also highlights key considerations as compared to metabarcoding for future utilization of this technique.

Impact of European Bison Grazing (Bison bonasus (L.)) on Species and Functional Traits of Carabid Beetle Assemblages in Selected Habitats in Poland

Simple Summary

Currently, we are observing a drastic decline in insect biodiversity. The aim of this study was to determine whether grazing by European bison (Bison bonasus (L.)) has potential for the implementation of conservation measures. Therefore, a study on a free-ranging European bison population and captive herds in enclosures was carried out in order to determine whether this animal’s grazing activity impacts species composition and the ecological characteristics of carabid beetle assemblages. No notable influence on the numbers of individuals of carabid beetles could be detected, but there was an indication that high-intensity grazing may cause an increase in the number of species. Increased grazing activity had a stronger influence on the ecological characteristics of the species assemblages than on the species composition. This result indicates that using European bison grazing as a method for nature conservation may have more potential in regulating properties and functions of the ecosystem than in the conservation of specific species or species assemblages of carabid beetles.

Abstract

Currently we are observing a drastic decline in insect fauna on a large scale. Grazing is regularly used as an ecological method of protecting or restoring special biotopes that are important for species conservation. The European bison (Bison bonasus (L.)) is the largest living wild terrestrial animal in Europe; therefore, a large impact on flora and fauna as a result of its grazing activity can be assumed. There might be potential for implementing conservation measures that employ active grazing. Therefore, a study on a free-ranging European bison population and captive herds in enclosures was carried out in order to determine whether European bison grazing has an impact on carabid beetle assemblages and whether the degree of this impact (if any) depends on the intensity of grazing. No notable influence on numbers of individuals of carabid beetles could be detected, but there was an indication that high-intensity grazing may cause an increase in the number of species. Increased intensity of grazing seems to have only a weak impact on the species assemblage structure, but it has a stronger impact on the composition of functional traits in the assemblage, as demonstrated in particular by the significant impact of captive herds. The stronger relation between grazing intensity and the functional traits of the carabid beetle assemblages than between grazing intensity and assemblage structure indicates that using European bison grazing as a method of ecological engineering in the context of nature conservation may have more potential in regulating properties and functions of the ecosystem than in the conservation of specific species or species assemblages of carabid beetles.

Can Vegetation Removal Successfully Restore Coastal Dune Biodiversity?

Coastal dune habitats have been declining globally over the last several decades due to rapid urbanization. Within remaining dune systems, dune fixation has resulted in further losses of mobile dunes with negative impacts on their associated species. Some studies suggest vegetation removal can initially promote habitat heterogeneity, and increase availability of suitable habitats for psammophile, xeric and endemic mobile dune species, but longer-term responses are generally unknown. We investigated the temporal trends of four taxonomic groups to determine the effect of vegetation removal on dune assemblages over a 12-year period at an LTER site. Three different forms of removal are investigated here—removal in a grid form on fixed dunes, removal of the wind-facing slope vegetation on semi-fixed dunes and opportunistic off-road driving on disturbed dunes. Results were varied across taxa, highlighting the need for multi-taxa monitoring in conservation and restoration management. Overall, fixed dune treatment had very little effect, while a stronger response was found in semi-fixed treatments in particular for mobile dune indicator species, which showed evidence of recolonization within a few years following treatment. Disturbed dunes were most similar to mobile dunes for animal taxa indicating that pulse removal may not be as effective as continuous press disturbance. Nevertheless, a less destructive form of disturbance such as re-introduction of grazing might be preferable and requires further investigation.

Effects of white-tailed deer (Odocoileus virginianus) exclusion on plant recovery in overwash fans after a severe coastal storm

We documented the impacts of an abundant deer population on dune vegetation recovering from severe storm surge on a barrier island through use of permanent plots and a repeated measures analysis. Three years after landfall of the storm, vegetation cover was dominated by American beachgrass, Ammophila breviligulata, though we observed 12 plant species among plots surveyed. We documented significantly greater vegetation cover in fenced than unfenced plots in overwash fans in two consecutive years. The difference in species richness between fenced and unfenced plots was significant, though richness was consistently low (≤4 species per plot) and we did not detect a statistically significant difference between years. Both deer trampling and foraging effects were captured in this study, though separation between these effects was not possible. Because trampling effects are often exacerbated on sandy soils, trampling and foraging effects should be isolated and investigated in future assessments of deer impacts on coastal vegetation. Managing deer to lower abundance may enhance coastal resilience if vegetation is allowed to recover unimpeded by foraging and trampling, though a better understanding of the precise nature of deer impacts on dune vegetation is necessary.