Diversity, functional structure and functional redundancy of woodland plant communities: How do mixed tree species plantations compare with monocultures?

Managing forest plantation stands in a way that retains productivity targets, but that also fosters biodiversity and stand resilience are key sustainable forest management goals. Current forestry policy advocates a diversification of forest stands to achieve these goals, favouring mixed age structures and polycultures over single-aged monocultures. Evidence is lacking, however, to support this management recommendation for biodiversity gains and related ecosystem service delivery. We used indices of taxonomic diversity and functional structure to compare ground vegetation communities in mixed and pure stands of Scots pine (Pinus sylvestris) and pedunculate oak (Quercus robur) in each of three study regions. We categorised the 91 vascular plant species identified into functional effect and response groups. We tested the hypotheses that ground vegetation communities (i) differ significantly in structure and composition between Scots pine and oak monocultures and (ii) show enhanced levels of taxonomic and functional diversity and functional redundancy in mixed stands of Scots pine and oak compared with monocultures. We explored the implications of any differences in the functional structure of ground vegetation communities in the different stand types on two ecosystem services: nutrient availability and levels of resource provisioning for herbivores. Nine functional response groups (RG) and seven functional effect groups (EG) were identified with considerable overlap in the RG and EG species grouping. Three RGs had traits characteristic of forests (spring flowering herbs, tree saplings and shrubs/ climbers), one RG had traits characteristic of open habitats (annual ruderals) and the remaining RGs had more generalist traits (anemochorous perennials, graminoids and short perennials). No significant differences were found among stand types in terms of taxonomic diversity or richness of the different functional trait groups. Ground vegetation communities in the three study regions also had similar levels of functional redundancy across stand types. However, Scots pine and oak monocultures harboured significantly different abundances of species with distinct functional traits. In all three study regions, anemochorous perennials were significantly more abundant in Scots pine monocultures than oak monocultures, while two core forest groups (shrubs/ climbers, spring flowering herbs) were significantly more abundant in oak monocultures. Mixed stands had intermediate abundances of these functional groups. These differences have implications for the comparative availability of food resources and shelter for wildlife, but also the mobilisation and temporal availability of nutrients in the two monocultures. Thus, mixtures of Scots pine and pedunculate oak can temper significant tree species identity influences on ground vegetation functional diversity

Structural Changes are More Important than Compositional Changes in Driving Biomass Loss in Ugandan Forest Fragments

Aboveground biomass (AGB) contained in privately-owned forests is less frequently measured than in forest reserves despite their greater likelihood of degradation. We demonstrate how density changes in contrast to species compositional changes have driven AGB changes in privately-owned fragments in Uganda over two decades. Data on tree assemblages in fragments were obtained by re-sampling a 1990 dataset in 2010 and AGB estimated using generalised allometric equation that incorporates diameter at breast height (DBH) and species-specific wood density. AGB were highly variable between fragments and over time. Structural changes contributed a higher proportion of change in AGB than species compositional changes in all forests. Non-pioneer species constituted over 50% of AGB in reserve forest, in contrast to private forests where pioneer species dominated. Our study demonstrates the potential of private forests to hold comparable AGB to plantation. Reduction in exploitation pressure is required if fragments are to mitigate carbon emissions

The handbook for standardised field and laboratory measurements in terrestrial climate-change experiments and observational studies

Climate change is a worldwide threat to biodiversity and ecosystem structure, functioning, and services. To understand the underlying drivers and mechanisms, and to predict the consequences for nature and people, we urgently need better understanding of the direction and magnitude of climate‐change impacts across the soil–plant–atmosphere continuum. An increasing number of climate‐change studies is creating new opportunities for meaningful and high‐quality generalisations and improved process understanding. However, significant challenges exist related to data availability and/or compatibility across studies, compromising opportunities for data re‐use, synthesis, and upscaling. Many of these challenges relate to a lack of an established “best practice” for measuring key impacts and responses. This restrains our current understanding of complex processes and mechanisms in terrestrial ecosystems related to climate change

Changes in the functional connectivity of woodland habitats across Great Britain between 1990 and 2007

In order to monitor progress towards international biodiversity conservation targets the UK has developed a suite of 18 biodiversity indicators. One indicator, which is aligned to CBD and EU indicators, is intended to assess the change in the impacts of habitat fragmentation on habitat connectivity and biodiversity. In common with much of Europe, the habitats and landscapes of the UK have undergone considerable loss and fragmentation through a long history of human activity. Habitat loss and fragmentation is regarded as a serious threat to biodiversity conservation. The UK connectivity indicator adopts a species-based perspective to examine functional connectivity. Firstly, the indicator accounts for edge impacts (i.e. negative effects of adjoining land cover that differs from the habitat of interest) by applying an internal edge buffer, weighted by the intensity of surrounding land cover. The indicator then calculates the probability of movement within and between the remaining habitat patches. These potential movements are weighted by the area of the patch; a negative exponential dispersal curve; and a least-cost distance measure (which indicates greater potential movement through permeable, ecologically similar, landscape features, as opposed to intensive, urban features). This paper reports on changes in functional connectivity of woodland habitats in 591 1km sample squares across Britain between 1990, 1998 and 2007

A meta-analysis on the impact of different matrix structures on species movement rates

Many biodiversity conservation strategies aim to increase species movement by changing the landscape between suitable areas of habitat. We applied systematic review and meta-analytical methods to robustly assess evidence on the impact of matrix structure on movement rates, with the hypothesis that movement will be greater through matrix of a more similar structure (vegetation height and cover) to the home habitat. Twenty studies of movement through two or more different matrix types provided 107 effect sizes, expressing the difference between the relative movement rates in different matrix types. The studies were all on animals, including relatively mobile taxa such as birds and butterflies but also rodents and amphibians. We were able to detect that on average, movement was greater through matrix of a more similar structure to the species� habitat despite the variation in studies in terms of matrix types, species and methods. The effect size was larger when there was a greater difference in the structure of the two matrix types being compared (e.g. comparing grassland to forest rather than short grass to long grass). However, there was a high degree of covariation between matrix contrast and studies and other significant subgroupings such as taxonomic group and matrix openness. The biological significance of the increase in movement is not clear; however, ecological theory predicts dispersing individuals are important for population dynamics. Changes to the structure of landscapes intended to improve permeability to movement are supported by the findings of this study, particularly for relatively mobile species. However, research over longer timescales, greater distances and range of taxonomic groups is necessary

Functionally richer communities improve ecosystem functioning: Dung removal and secondary seed dispersal by dung beetles in the Western Palaearctic

International audienceAim: In several ecosystems, the diversity of functional species traits has been shown to have a stronger effect on ecosystem functioning than taxonomic diversity alone. However, few studies have explored this idea at a large geographical scale. In a multisite experiment, we unravelled the relationship between ecosystem function and functional completeness of species assemblages using dung beetles as a model group, focusing on dung removal and secondary seed dispersal. Location: Seventeen grassland locations across the Western Palaearctic. Methods: We used a randomized block design with different exclosure types to control the dung and seed removing activities of individual functional groups of the local dung beetle assemblage. We classified dung beetle species according to resource specialization and into functional groups based on dung processing behaviour (dwellers, tunnellers, rollers) and body size (small, large). Additionally, we assessed the role of other soil macro-invertebrates. By sampling the dung beetle community and measuring the remaining dung and seeds after the experiment, the impact of each functional group was estimated. Results: Dung beetle assemblages differed along a north-south and east-west gradient. Dwellers dominated northernmost sites, whereas at lower latitudes we observed more tunnellers and rollers indicating a functional shift. Resource specialists were more abundant in southern and eastern areas. Overall, functional group diversity enhanced dung removal. More dung (+46.9%) and seeds (+32.1%) were removed in the southern sites and tunnellers and rollers were more effective. At the northernmost sites, where tunnellers were scarce or absent, other soil macro-invertebrates removed the majority of dung. Main conclusions: The conservation of functionally complete dung beetle assemblages is crucial to maintain the ecosystem functions provided by dung beetles. Given the latitudinal variation in functional group diversity, it is reasonable to expect compositional changes due to climate change. These changes could lead to increased dung removal and a higher secondary seed dispersal rate in northern regions

Relationships between the species composition of forest field-layer vegetation and environmental drivers, assessed using a national scale survey

Simulation models of forest stand dynamics have increased understanding of over-storey vegetation functioning, and have facilitated the development of tools capable of assessing possible successional trajectories. However, few models incorporate the response of the field layer vegetation despite it being another key component of forest ecosystems. Our main objective was to assess the degree to which field-layer vegetation composition in forests is determined by variables operating at different scales, from regional (e.g. climate, location) to local factors (e.g. basal area of canopy trees, management). We used data gathered during a nationwide forest survey to assess the relative effects of a broad spectrum of environmental variables on species composition. Variation partitioning was used to examine the relative contribution of subsets of environmental variables such as site spatial variation, boundary type and presence of herbivores. Ordination confirmed hypotheses that field layer vegetation is primarily structured by two composite geo-climatic gradients. However, variation partitioning demonstrated that site- and plot-scale management factors also strongly influence the floristic composition of forest patches. Disturbance variables (site boundary type/regional presence of deer) accounted for considerable species variation, exceeding that due to either site spatial variation or forest structure. This is the first time variation attributable to such a comprehensive range of environmental variables has been quantified for forests surveyed at a national scale. We thus provide a context within which regional studies, or analyses considering a more limited range of factors, can be viewed, and a framework from which robust models of floristic response to gradual and episodic natural and anthropogenic disturbances may be developed. The methodology we present, including a novel technique for the identification and removal of outliers in large data sets, provides a unique and standardized means of assessing the relative importance of diverse environmental drivers across a range of habitat types at the landscape scale, and is readily applicable elsewher