Nick A. Littlewood

Science into practice – how can fundamental science contribute to better management of grasslands for invertebrates?

Abstract.  1. Grasslands are diverse and extensive but are declining in extent in some parts of the globe. Grassland invertebrates can be numerically abundant and are crucial to ecosystem functioning through their roles in herbivory, nutrient cycling and pollination. Most European grasslands are modified through agricultural practices. Indeed, semi‐natural grasslands, which often host the most diverse invertebrate assemblages, have suffered catastrophic losses over the last century.

Grazing impacts on moth diversity and abundance on a Scottish upland estate

Abstract.  1 Livestock grazing is the most important direct management impact on grasslands in upland areas of the UK. For phytophagous species, such as Lepidoptera, the impact is primarily through grazing altering the species composition and structure of the vegetation. However, specific impacts related to different grazing regimes are not well understood for this group of insects. 2 Within a replicated controlled grazing experiment, nocturnal adult moths were sampled by light trapping in the fifth year after establishment. Sampling effort was standardised between the four grazing treatments by simultaneously using identical traps in each treatment. 3 The highest‐intensity grazing treatment produced the lowest moth abundance and species richness. Ungrazed and low‐intensity sheep grazing treatments produced the highest moth abundance and species richness. 4 Moths that feed exclusively on graminoids and moths that overwinter as larvae were disproportionately well represented in the ungrazed treatment. 5 A sub‐set of species for which large declines have recently been documented in the UK were most abundant in the ungrazed treatment. However, they made up the largest proportion of the overall assemblage in the high‐intensity grazing treatment. 6 Increased grazing inversely affects moth abundance and species richness. However, effects are not even across all moth species. An absence of grazing is likely to negatively affect the abundance of some moths, especially those that overwinter in the egg stage.

The cascading impacts of livestock grazing in upland ecosystems: a 10‐year experiment

Livestock grazing is a major driver of land-use change, causing significant biodiversity loss globally. Although the short-term effects of livestock grazing on individual species are well studied, a mechanistic understanding of the long-term, cascading impacts is lacking. We manipulated livestock densities using a unique, replicated upland experiment over a 10-year period and found significant effects of grazing treatment on plant and arthropod biomass; the number of Anthus pratensis breeding bird territories; the amplitude of Microtus agrestis population cycles and the activity of a top predator, Vulpes vulpes. Lower plant biomass as a result of higher stocking densities led to cascades across trophic levels, with fewer arthropods and small mammals, the latter affecting predator activity. Breeding bird territories were a function of arthropod abundance and vegetation structure heterogeneity. Our results provide a novel food-web analysis in a grazing experiment to provide a mechanistic understanding of ho...

Grazing impacts on Auchenorrhyncha diversity and abundance on a Scottish upland estate

Abstract.  1. Livestock grazing impacts on insect populations in a variety of ways. For phytophagous insects the impact is primarily a result of altering the structure and species assemblage of vegetation. However not all species react in similar ways and even within an order there may be winners and losers from different grazing regimes.

A field assessment of the success of moorland restoration in the rehabilitation of whole plant assemblages

ABSTRACT Question: How successful is restoration that is focused on a single dominant plant at enabling the reassembly of the whole vegetation assemblage and what factors affect the relative success of such restoration? Location: Moorlands in England and Scotland, UK. Methods: Vegetation composition was sampled in grass-dominated (degraded), restored and long established Calluna vulgaris-dominated (target) areas within eight moorland restoration sites. Additional soil and biogeographic data were collected. Data were analysed by Canonical Correspondence Analysis, which allowed the impact of moorland management to be examined. Results: All sites showed good restoration success when the dominant managed species (Calluna vulgaris, Molinia caerulea and Nardus stricta) were considered. Restoration success of the remainder of the plant assemblage, disregarding these dominant species, was lower with restored samples at some sites differing little from their respective degraded samples. Moors restored solely by grazing exclusion were more similar to their respective targets than were those restored by more intensive mechanical means. The most important factors in explaining vegetation assemblages were management status (i.e. whether samples represented degraded, restored or target parts of the moor) and latitude. Conclusions: The project demonstrates that, where possible, restoration should be attempted by grazing exclusion alone. Furthermore the importance of applying local restoration targets and of monitoring the whole plant assemblages when assessing the success of moorland restoration is highlighted. Nomenclature: Species names follow Stace (1991) for higher plants and Smith (2004) for bryophytes. Abbreviations: CCA = Canonical Correspondence Analysis, LOI = Loss on Ignition

How to Replicate the Functions and Biodiversity of a Threatened Tree Species? The Case of Fraxinus excelsior in Britain

The suitability of alternative tree species to replace species that are either threatened by pests/disease or at risk from climate change is commonly assessed by their ability to grow in a predicted future climate, their resistance to disease and their production potential. The ecological implications of a change in tree species are seldom considered. Here, we develop and test 3 methods to assess the ecological suitability of alternative trees. We use as our case study the systematic search for an alternative tree species to Fraxinus excelsior (currently declining throughout Europe due to Hymenoscyphus fraxineus). Those trees assessed as most similar to F. excelsior in selected ecosystem functions (decomposition, leaf litter and soil chemistry) (Method A) were least similar when assessed by the number of ash-associated species that also use them (Method B) and vice versa. Method C simultaneously assessed ecosystem functions and species use, allowing trade-offs between supporting ecosystem function and species use to be identified. Using Method C to develop hypothetical scenarios of different tree species mixtures showed that prioritising ecosystem function and then increasing the mixture of tree species to support the greatest number of ash-associated species possible, results in a mixture of trees more ecologically similar to F. excelsior than by simply mixing tree species together to support the greatest number of ash-associated species. We conclude that establishing alternative tree species results in changes in both ecosystem function and species supported and have developed a general method to assess suitability that simultaneously integrates both ecosystem function and the ‘number of species supported’.

Changes in the phenology of the ground beetle Pterostichus madidus (Fabricius, 1775)

Abstract  A growing body of evidence shows that climate change can alter the phenology of plants and animals. In this study long‐term data from the UK Environmental Change Network (ECN) were analyzed to investigate whether there has been a change in the phenology of the ground beetle Pterostichus madidus (Fabricius, 1775). Pitfall trap data were available from 12 ECN sites across the United Kingdom, most of which have been in operation for more than 15 years. Weather and vegetation datasets were also utilized. Pitfall trap lines were categorized to eight vegetation types. Trend analysis over time was carried out first using all the available dates of capture events, then the datasets grouped by vegetation type and site. Shifts in high‐activity periods were also analyzed. P. madidus appearance dates advanced significantly at seven sites and in five vegetation types. Peak activity advanced at two sites. At one site the timing of activity became significantly later. The last day of activity did not change significantly, supporting the theory that the cessation of the activity period is more likely to be controlled by photoperiod than temperature. The relationships between phenological variables and climatic factors were also investigated. However, no significant correlations were detected. These results demonstrate that between 1992 and 2008, phenology of P. madidus at seven sites from the eight analyzed has changed. Global warming may be driving these changes and future work will investigate underlying processes.

Invertebrate species at risk from Ash Dieback in the UK

Abstract Ash Dieback, a disease of Ash (Fraxinus excelsior) trees caused by the ascomycete, Hymenoscyphus pseudoalbidus, was first noticed in the UK in February 2012 and has since been found through much of the country. Evidence from elsewhere in Europe suggests that most infected Ash trees succumb to the disease and, hence, UK woodlands and landscapes are at risk of large scale changes. A wide range of taxa either depends on Ash or makes significant use of it and is likely to be detrimentally affected if the UK’s Ash trees are seriously depleted. Invertebrate species that use Ash exclusively or are highly associated with the tree were identified from existing literature. We categorised 36 invertebrate species as “obligate” on Ash in the UK and a further 38 as “highly associated”. Hemiptera, Diptera and Lepidoptera were the most significant groups amongst the obligate species with Coleoptera, Lepidoptera and Diptera dominating the highly associated species. Most obligate species are phytophagous in their use of Ash. Highly associated species were evenly split between those that are phytophagous and those classified as saproxylic with a smaller number of species employing a range of additional feeding strategies. Among highly associated species that are phytophagous, Privet (Ligustrum sp.) was the most frequent alternative plant used. This and other alternative trees and shrubs could be used to help mitigate the effects of Ash Dieback in limited localised situations, where rare species might be affected. Additional suggestions for managing the impact of Ash Dieback on invertebrates are discussed.

Long-term changes in ground beetle (Coleoptera: Carabidae) assemblages in Scotland

1. One‐way, directional changes in both plant and animal associations are likely to be occurring as a result of changing climate. Current knowledge of long‐term cycles in insect communities is scarce, and therefore it is difficult to assess whether the observed changes in insect communities are the first part of a long‐term trend or parts of normal cycles.

A habitat suitability model for the narrow‐headed ant, Formica exsecta, evaluated against independent data

Abstract.  1 Predictive models are frequently used to assist forecasts of species’ distributions. For rare species, this approach can provide insights into habitat utilisation and potential habitat suitability that can assist conservation action. However the technique has seldom been used for invertebrates. 2 A habitat suitability model was constructed for the rare ant, Formica exsecta, at Glenmore, a pinewood site in Scotland that contains a significant proportion of the UK population of this species. A range of botanical and environmental variables were surveyed within cells in a grid structure. The model successfully re‐classified 87% of cells according to the presence/absence of ant nests. When subject to a jackknife procedure, 70% of cells were successfully re‐classified and the median predicted probability of presence in occupied cells was significantly greater than in unoccupied cells. 3 The model was further evaluated against three independent datasets with rates for successful predictions of 70%, 62.5% and 25%. The performance declined with increased distance from the area from which calibration data were collected. 4 We conclude that caution is required when a model is validated purely by reference to the data from which it was constructed and not against independent data. However, the process can provide useful insights into habitat suitability for rare invertebrates that can assist rapid assessment of potential ranges for conservation measures such as restoration of populations.