K. J. Kirby

Microclimate moderates plant responses to macroclimate warming

Significance Around the globe, climate warming is increasing the dominance of warm-adapted species—a process described as “thermophilization.” However, thermophilization often lags behind warming of the climate itself, with some recent studies showing no response at all. Using a unique database of more than 1,400 resurveyed vegetation plots in forests across Europe and North America, we document significant thermophilization of understory vegetation. However, the response to macroclimate warming was attenuated in forests whose canopies have become denser. This microclimatic effect likely reflects cooler forest-floor temperatures via increased shading during the growing season in denser forests. Because standing stocks of trees have increased in many temperate forests in recent decades, microclimate may commonly buffer understory plant responses to macroclimate warming. Recent global warming is acting across marine, freshwater, and terrestrial ecosystems to favor species adapted to warmer conditions and/or reduce the abundance of cold-adapted organisms (i.e., “thermophilization” of communities). Lack of community responses to increased temperature, however, has also been reported for several taxa and regions, suggesting that “climatic lags” may be frequent. Here we show that microclimatic effects brought about by forest canopy closure can buffer biotic responses to macroclimate warming, thus explaining an apparent climatic lag. Using data from 1,409 vegetation plots in European and North American temperate forests, each surveyed at least twice over an interval of 12–67 y, we document significant thermophilization of ground-layer plant communities. These changes reflect concurrent declines in species adapted to cooler conditions and increases in species adapted to warmer conditions. However, thermophilization, particularly the increase of warm-adapted species, is attenuated in forests whose canopies have become denser, probably reflecting cooler growing-season ground temperatures via increased shading. As standing stocks of trees have increased in many temperate forests in recent decades, local microclimatic effects may commonly be moderating the impacts of macroclimate warming on forest understories. Conversely, increases in harvesting woody biomass—e.g., for bioenergy—may open forest canopies and accelerate thermophilization of temperate forest biodiversity.

An inventory of ancient woodland for England and Wales

Abstract Since 1981 the Nature Conservancy Council has been compiling an inventory of ancient woodland for England and Wales. We describe the methods used and problems encountered. The current area of ancient woodland and the looses of ancient semi-natural woodland over the last 50 years are quantified for each county. Ancient woodland covers about 2·6% of England and Wales. Some 7% of the area of ancient woodland present in c. 1930 has been cleared for other land uses while 38% by area has been replaced with plantations, usually of non-native species. The extent of these losses varies from county to county and between woods of different sizes; large woods, for example, are more likely to have been replanted. The inventories form the basis for further more detailed surveys and have contributed to the development of woodland conservation policies. They provide a baseline against which the success of these policies can be monitored.

Seasonal and observer differences in vascular plant records from British woodlands

(1) The variations between vascular plant lists produced from the same wood by different observers, at different seasons and using different methods are described. (2) Three British woods were examined during 1982, with two observers per wood and at least two recording times (April-May and August-September). The methods used were to list the species seen either on a walk through the wood or found in randomly placed quadrats. Each method was used at two of the three woods. (3) No significant differences were found in the number of species recorded at a particular wood by either method by either observer between May and September. Lower numbers of species were recorded in early April and October. (4) Differences were found in the frequency with which particular species were recorded both between seasons and between observers. Some of these differences could be related to the phenology of the species concerned. (5) The relation between the time spent on a survey (the sampling intensity) and the number of species recorded is illustrated. (6) The implications of the results for other woodland surveys are discussed.

Changes in the ground flora in Wytham Woods, southern England from 1974 to 1991 – implications for nature conservation

. The ground flora (vascular plants < 2 m high, excluding trees and shrubs) was recorded in 1974 and 1991 from 163 permanent 10 m x 10 m plots arranged on a systematic grid across Wytham Woods, near Oxford (UK). The Woods cover about 320 ha, are predominantly deciduous, but of varying ages and management types. The total number of species found (173, 167 respectively), the mean richness per plot (16.7, 17.2) and the breakdown of the species list between different species types (ancient woodland indicators, other woodland species, non-woodland species) showed no significant differences between 1974 and 1991, but mean ground cover declined from 80% to 64%. Ancient woodland indicators as a group showed less change between the years than species associated with the open glades and grassland patches in the wood. Some species increased in frequency across the woodland including Arum maculatum, Brachypodium sylvaticum, Deschampsia cespitosa and Poa trivialis; while others such as Ajugareptans, Angelica sylvestris and Circaea lutetiana declined. Mean cover of Rubus fruticosus per plot declined from 35% to 6% and of Mercurialis perennis from 32 to 24%. More species were lost from plantations than from semi-natural stands. The results are based on only two times, so inferences on possible causes must be drawn with caution. However the results are consistent with the effects of (1) the changing conditions associated with stand growth, particularly in the plantations, and (2) an increase in browsing/grazing by deer. No evidence was found for an effect of changing soil nitrogen levels on the vegetation. Changes in the ground flora as well as the woody layers, and in managed as well as unmanaged stands should be monitored, if nature conservation objectives are to be met.

Effects of season and intensity of sheep grazing on tree regeneration in a British upland woodland

Abstract This paper reports some effects of experimental alteration of season (summer, winter) and intensity of sheep grazing on tree regeneration, growth and browsing damage in an upland broadleaved woodland in Cumbria, UK. During the first 3 years of grazing treatments, seedling recruitment was primarily Betula pubescens, Sorbus aucuparia and Fraxinus excelsior . After 7 years of grazing treatments, seedlings and saplings of many species were numerous, with fewer seedlings in winter-grazed plots but a higher proportion of these were browsed. More seedlings had reached sapling stage in winter-grazed plots. Sapling numbers increased with decreasing grazing intensity, with lower proportions browsed at low grazing intensities. Within the first 3 years grazing treatments, recruitment of Betula pubescens seedlings was greater in grazed than ungrazed plots, and greater in winter-grazed than in summer-grazed plots. Browsing damage to these seedlings increased with grazing intensity in winter, and height increments were greatest in ungrazed plots. After 7 years, B. pubescens seedlings and saplings showed no significant treatment effects. After 3 years, recruitment of Sorbus aucuparia seedlings was greater in grazed than ungrazed plots, and greater in summer-grazed than winter-grazed plots. Fewer seedlings were browsed in low grazing intensity plots, and seedling height increments were greatest in ungrazed plots. After 7 years, more S. aucuparia seedlings were browsed in winter than summer, but saplings showed no treatment effects. After 3 years, recruitment of F. excelsior was greatest in low grazing intensity plots and smallest in medium grazing intensity plots. More seedlings were browsed at higher grazing intensities, but in summer-grazed plots height increments tended to be greatest in the most heavily grazed plots. After 7 years, F. excelsior seedlings were more numerous in summer-grazed plots but were not differentially browsed; sapling numbers were not affected by grazing treatments but browsing damage was very high in all except summer low grazing plots. The implications of the results are discussed in relation to woodland grazing management issues.

The ecology of woodland creation.

To What Extent Can We Recreate Woodland? (J. Spencer). Planning and Designing New Woodlands for People (M. Sangster). New Woodlands in the Landscape (S. Bell). Biogeography and Woodland Design (I. Spellerberg). Vegetation Classification Systems as an Aid to Woodland Creation (J. Rodwell G. Patterson). Soils and Restoration Ecology (A. Moffat G. Buckley). Soil Biotic Communities and New Woodland (J. Harris T. Hill). Creating Woodlands: To Plant Trees or Not? (R. Harmer G. Kerr). Introduction of Plants and Manipulation of Field Layer Vegetation (J. Packham, et al.). Invertebrate Conservation and New Woodland in Britain (R. Key). Bird Populations in New Lowland Woods: Landscape, Design and Management Perspectives (R. Fuller, et al.). Population Dynamics of Small Mammals in New Woodlands (J. Flowerdew R. Trout). Do Woodland Mammals Threaten the Development of New Woods? (R. Gill, et al.). Ecological Planning in New Woodlands (R. Ferris-Kaan). Indexes.

Effects of forest management on stand structure and the quantity of fallen dead wood : some British and Polish examples

Abstract Examples of the effects of forest management for timber are illustrated through records of the stand structure, ground flora composition and amount of fallen dead wood in the Bialowieza Forest, Poland, and three English woods. Line intersect sampling, a technique not widely used in Britain, was adopted to assess the amount of fallen dead wood, and its potential in future nature conservation surveys is considered. Managed stands in the Bialowieza Forest had fewer large trees and much less dead wood than undisturbed stands. Worked coppice in English woods had the expected high number of small stems and low amounts of dead wood, particularly as large-diameter logs. In high forest, largely neglected for 100 years and promoted from coppice, there were more (and larger) fallen branches and trunks. However, the estimated volume of fallen dead wood was only about a third of that in the undisturbed areas of Bialowieza Forest.

Regional variation in the origin, extent and composition of Scottish Woodland

Summary Results from the Nature Conservancy Councils Inventory of Ancient Woodland show regional variations in the extent, origin and composition of Scottish woods and the degree to which they are recognized as important sites for nature conservation. Around 14.5% of Scotland is forested but not more than 2% of the land area is ancient woodland. Nearly half of the ancient area has been replanted, mainly with introduced conifers. Thus the area retaining ancient semi-natural woodland covers just 1 % of Scotland. Woodland within Sites of Special Scientific Interest or nature reserves covers 38,154 ha. The majority of this is ancient semi-natural woodland, but 68% of the total ancient semi-natural woodland area is not so protected. The value for nature conservation of many ancient sites has declined because of the extent of replanting and overgrazing. Recent beneficial changes in land use policies and practices need to be continued to prevent further decline in the nature conservation value of these importan...

A ROLE FOR LARGE HERBIVORES (DEER AND DOMESTIC STOCK) IN NATURE CONSERVATION MANAGEMENT IN BRITISH SEMI-NATURAL WOODS

Summary Large herbivores are a part of most natural woodland systems, but in Britain many of the species present in the wildwood some 7,000 years ago have been lost, while native woodland cover has...

The conservation of a fragmented ecosystem within a cultural landscape - the case of ancient woodland in England.

Abstract Ancient woodland (land continuously wooded since ad 1600) was identified in the 1970s (and confirmed in the 1994 UK Biodiversity Action Plan) as the most important category of woodland for nature conservation. It predominates within special protected sites, but the bulk of this resource (85%) lies outside such protection. Ownership by government and non-government bodies ensures that areas outside the protected site system are managed sympathetically, but the distribution of sites in such sympathetic ownership is very patchy. Hence, the nature conservation value of ancient woods must also be recognised in national forestry policies that apply to all such sites. In cultural landscapes such as in England, not all woodland species survive within the fragmented ancient semi-natural woodland resource. Plantations of introduced species and other, recent woodland must also be included in the conservation strategy. This paper explores the implications of these factors in the development of nature conservation policy and practice in England over the last 15 years.