Semi-natural Stands Research Articles

Comparative analysis of Quercus suber L. acorns in natural and semi-natural stands: Morphology characterization, insect attacks, and chemical composition

Comparative analysis of Quercus suber L. acorns in natural and semi-natural stands: Morphology characterization, insect attacks, and chemical composition

Lower alpha, higher beta, and similar gamma diversity of saproxylic beetles in unmanaged compared to managed Norway spruce stands.

Strong anthropogenic pressures on global forests necessitate that managed forests be evaluated as habitat for biodiversity. The complex pattern of habitat types created in forestry systems is ideal for analyses through the theoretical framework of alpha (local), gamma (total) and beta (compositional) diversity. Here I use saproxylic beetles, a species-rich threatened group, to compare four Norway spruce-dominated habitats representative of the boreal forest landscape of northern Europe: unmanaged semi-natural stands, nature reserves, unthinned middle-aged production stands and commercially thinned production stands. The beetles (in total 38 085 individuals of 312 species), including red-listed ones and three feeding guilds (wood consumers, fungivores and predators) were studied in 53 stands in central-southern Sweden, in two regions with differing amounts of conservation forest. Alpha diversity of saproxylic, but not red-listed, beetles was higher in the thinned stands than in the semi-natural stands, and did not differ for the other forest types. Beta diversity of saproxylic beetles was higher in unmanaged semi-natural stands than in the other forest types, but species composition did not differ noticeably. Furthermore, red-listed saproxylic beetles had higher gamma diversity in unmanaged semi-natural stands in the region with more conservation forest, but not in the one with less such forest. The local factors dead wood volume and dead wood diversity did not influence alpha diversity of beetles, but increasing canopy openness had a minor negative influence on saproxylic and red-listed beetles. While the local scale (alpha diversity) indicates the potential for managed forests to house many saproxylic beetle species associated with spruce forests in this boreal landscape, the larger scales (beta and gamma diversity) indicate the value of unmanaged forests for the conservation of the entire saproxylic beetle fauna. These results show the importance of analyses at multiple levels of diversity (alpha, beta, gamma) for identifying patterns relevant to conservation.

Modeling gas turbine electro power station typical operating modes using pre-trained artificial neural network

The article discusses the gas turbine electric power stations model creation on the converted aircraft engines basis. Simulation is necessary for the development and control algorithms computer testing for such electric power stations. For this, the developed control algorithms must be tested in various situations arising during the power stations operation. It is well known that it is difficult or impossible to reproduce the most critical modes in real operation and on test benches. Therefore, such studies are carried out on mathematical models, using various designs semi-natural stands, in which real control equipment is interfaced with a mathematical model that reproduces the electrical system behavior. The article discusses a possible solution to this problem: for individual characteristic modes, simplified, fast-solving models with a limited adequacy area, but with high performance, are built. The article proposes to assign the task of constructing such models to an artificial neural network. This opens up additional opportunities for reducing the time required to obtain such models, for example, by using neural networks that have already been trained for a different mode, which in the future will allow expanding the adequacy area of the created neural network models.

Bryophyte species composition at the stand scale (1 ha) – Differences between secondary stands half a century after clear-cutting and older semi-natural boreal forests

A growing proportion of the boreal biome consists of managed even-aged secondary forest stands regenerated after clear-cutting. Many disturbance-intolerant species may not be able to recolonize or reach their original abundance in these stands before the next clear-cutting, potentially causing large-scale biodiversity losses. Boreal bryophytes (mosses and liverworts) include many species intolerant to clear-cutting, and at small spatial scales species richness and occupancy has been shown to remain changed in secondary stands half a century after logging. To assess if such persistent changes occur also at the stand scale, we listed and estimated cover of all bryophyte species in 1-ha plots, comparing 14 secondary stands originating from clear-cutting 40–60 years earlier with 14 older semi-natural stands. The large plots also made it possible to assess differences in occupancy and abundance for more bryophyte species than in previous studies. Species composition differed significantly for both mosses and liverworts, but unlike earlier studies, we could not detect any significant difference between stand types in species numbers. Thirteen species were significantly associated with semi-natural stands and the total cover of liverworts was less than half in secondary stands. Secondary stands had significantly fewer species typically occurring under shady conditions and/or mostly growing on “tree substrates” (dead wood and/or bases and stems of living trees). Ordination analysis further emphasized the importance of shade and suitable deadwood substrates; the among-plot variation in bryophyte species composition was related to amount of coarse deadwood as well as to gradients from shady spruce dominated to open pine dominated stands and from polar- to equator-facing slopes. Besides lack of suitable habitat conditions in secondary stands, dispersal limitation may have caused a colonization time lag for some species. The clear importance of stand scale habitat conditions for bryophyte species composition calls for management adaptions to facilitate life boating and/or recolonization by ensuring availability of shade, coarse decomposing logs, and specific deciduous tree species (Populus, Salix, Sorbus) in secondary stands.

СТЕНД-ИМИТАТОР АВИАДВИГАТЕЛЯ КАК УНИВЕРСАЛЬНОЕ СРЕДСТВО ОБЕСПЕЧЕНИЯ РАЗРАБОТКИ И ИСПЫТАНИЙ РЕГУЛЯТОРОВ

There is described the work on the project, carried out at the enterprise Element JSC for the creation of aircraft gas turbine engine simulator stands, for the maintenance and testing of some digital regulators for helicopter and aircraft engines (turboshaft and turboprops), which the company is the developer and manufacturer of. Compact simulator stands test all the functions of the regulator and allows you to abandon the use of bulky semi-natural stands, at least for 95% of the tests. The stand simulator is a hardware-software complex that simulates the engine as a system interacting with the regulator by simulating all analog, discrete and digital signals. The stand imitates the signals arriving at the regulator from sensors, aggregates, and engine systems that provide reception of control signals from the regulator. Besides, stand performs calculations and generates sets of interdependent parameter values (in the form of analog, discrete, and digital signals), each of which corresponds to one of the engine operating modes according to predetermined functional dependencies that reflect the characteristics of the engine – a mathematical model of the engine. The stands undergo certification in the scope of the program agreed with the State Enterprise “Zaporizhiastandardmetrology” and are verified by comparing the test results of the regulator on a simulator stand and as part of the motor stands of the Customer (engine developer). It is shown that the modular structure of the first of the simulator stands (basic) developed at the enterprise and the reserve provided for in its structure helped simplify its subsequent adaptation to the implementation of models of new types of engines. There is given the information on the stands simulating the AI-450M, AI-450S, AI-450S-1, AI-450T engines (for an unmanned aerial vehicle), and MS-500V-02S. It has been shown that simulator stands provide a set of tests for the development and serial production of regulators RDC-450M, RDTs-450M-S, RDTs-450M-S-1, RDTs-450M-C-T-P, RDTs-450S-500 at the enterprise.

Effect of salvage-logging on post-fire tree establishment and ground cover vegetation in semi-natural hemiboreal forests

Fire is a common disturbance in boreal forests causing changes in biological diversity at various spatial scales. In the past 100 years, forest management has limited fire outbreaks, but in the future, the fire-affected forest area is expected to increase in many regions due to climate change. Burned forests are typically salvage-logged, but the effect of this type of management versus natural regeneration on biological diversity is not well understood, particularly the mid-term effect to tree establishment and understory vegetation composition and diversity. Various management methods were used after a large fire in 1992 in a peatland-forest complex and neighbouring managed forests, which created an experimental setup for study of the effect of management after fire in the Sliteres National park, northwestern Latvia. Understory vegetation was described in plots using a design of four forest and three management types: natural regeneration (unmanaged) and managed sites with salvage logging followed by no further human intervention and salvage logging with planting. Post-fire management had different effect in each forest type. Species richness was higher in forest types with salvage logging than in natural regenerated sites on rich wet and rich dry forest types, but not for the poor forest types. Tree regeneration was generally greater in salvage-logged stands, but differed between forest types. Species composition was related to tree regeneration and canopy openness. In contrast to other studies, salvage logging had a positive mid-term effect to ground vegetation diversity and tree establishment in the studied stands, implying potential for concomitant management and conservation of ground cover vegetation in semi-natural stands.

The model of the servo piston of the fuel metering unit using matrix approach and neural network

In the paper, the model of a servo piston of a fuel metering unit based on a matrix approach using neural networks is considered. To develop the model of a servo piston, the dependence of the initial piston deviation on the control signal for different values of the nozzles is used. This dependence is represented in the form of a matrix and is used in the neural network. This approach allows describing the movement of the servo piston with a sufficient degree of accuracy. As a record of change squares adjustment of the nozzles is a source of parametric uncertainty in the operation of the automatic control system can lead to a drop in the quality of control, such accounting is relevant. The model of the servo piston is proposed to be used in the structure of the automatic control system for a gas turbine engine and for semi-natural stands.

An allometry-based approach for understanding forest structure, predicting tree-size distribution and assessing the degree of disturbance

Tree-size distribution is one of the most investigated subjects in plant population biology. The forestry literature reports that tree-size distribution trajectories vary across different stands and/or species, whereas the metabolic scaling theory suggests that the tree number scales universally as −2 power of diameter. Here, we propose a simple functional scaling model in which these two opposing results are reconciled. Basic principles related to crown shape, energy optimization and the finite-size scaling approach were used to define a set of relationships based on a single parameter that allows us to predict the slope of the tree-size distributions in a steady-state condition. We tested the model predictions on four temperate mountain forests. Plots (4 ha each, fully mapped) were selected with different degrees of human disturbance (semi-natural stands versus formerly managed). Results showed that the size distribution range successfully fitted by the model is related to the degree of forest disturbance: in semi-natural forests the range is wide, whereas in formerly managed forests, the agreement with the model is confined to a very restricted range. We argue that simple allometric relationships, at an individual level, shape the structure of the whole forest community.

Effects of thinning on seed rain, regeneration and understory vegetation in a Pinus canariensis plantation (Tenerife, Canary Islands)

Stand density management in even-aged coniferous plantations may increase biodiversity and enhance natural tree regeneration. Thinning of pine plantations has only recently been started on the Canary Islands, yet the ecological effects of this treatment are relatively unknown. Our objective was to investigate the impact of thinning on pine seed rain, natural pine regeneration and diversity of understory vegetation in Pinus canariensis plantations. Seven years after thinning, we sampled 60-year old plantations thinned by 60% of basal area, unthinned stands and adjacent semi-natural old-growth forests. Thinning significantly increased pine seed rain to levels similar to semi-natural stands. This is probably a result of fast crown development and enhanced cone production due to the immediate release of resources and reduction in competition. In contrast, plantations with the highest tree densities had very low seed production, limiting pine regeneration. Seed rain showed seasonal fluctuations with clear summer peaks of seed release. Thinning also significantly increased seedling, sapling and juvenile densities. However, thinned plantations still differed from old-growth forests in seedling and juvenile densities. Thinning promoted understory plant diversity, including typical endemic pine forest species, without triggering plant invasion, which is of great conservation interest. This study provides evidence that heavy thinning represents an important management tool to enhance naturalization and local biodiversity of Canary pine plantations, common in large areas of this Archipelago.

Analysis of forest naturalness and tree mortality patterns in Estonia

New methods for evaluating structural properties of stands and individual tree mortality within forests are needed to enhance biodiversity assessment in forest inventories. One approach is to assess the degree of naturalness in a forest. We assessed forest naturalness by examining patterns and causes of mortality and deadwood amount and spatial distribution as indicators of naturalness, or degree of anthropogenic disturbance. This study is based on 5-year interval measurement using 294 permanent samples plots from a forest growth network in Estonia. The average annual mortality was 1.3% from stem number counting 29% of Scots pine, 27% of silver and downy birch and 20% of Norway spruce. Most common reasons for the individual tree death were growth-dependent reasons (45%), fungi (23%) and wind damage (16%). Modelling showed that relative diameter of a tree in a stand is significantly related to mortality probability. Modelling the reasons of tree death showed that with increasing relative diameter there was a greater probability that mortality was caused by wind or damage from game (mostly moose ( Alces alces L.)), insect or fungi and a lower probability that mortality was due to competition between trees. Use of structural variable such as deadwood mingling, which was based on the neighbouring trees, improved the assessment of forest naturalness and helped to distinguish recent disturbances. A comparison of deadwood mingling and nature value scores in managed and semi-natural forests showed that dead trees were more dispersed and the naturalness score was higher in semi-natural forest stands. The nature score was significantly correlated with the diversity of mortality causes indicating that mortality causes are more diverse in semi-natural stands. Mean values and distribution of the deadwood mingling index in managed and semi-natural forests were not significantly different. In middle-aged semi-natural forests, mortality is spatially more random than in managed forests, thus there is no evidence of gap formation yet.

Soil organic matter in soil physical fractions in adjacent semi-natural and cultivated stands in temperate Atlantic forests

Changes from natural tree species to rapidly growing exotic species as well as intensification of forestry operations with heavy machinery can lead to changes in the quantity and quality of organic matter inputs to soil and to disruption of soil physical structure. These two ecosystem properties are tightly linked to organic matter dynamics. Five adjacent forest stands were selected to study soil organic matter dynamics in soil physical fractions. On one hand, two semi-natural broadleaved forests ( Quercus robur, Fagus sylvatica) and an adult radiata pine plantation (40-year-old,) in order to study the effect of species change on these parameters, and on the other, a chronosequence of Pinus radiata plantations (40-year-old; 3-year-old; 16-year-old), to study the effect of mechanization during harvesting and intense site preparation. Samples of intact topsoil (0–5 cm) were collected and aggregate-size distribution, mean weight diameter (MWD), total C and N, particulate organic matter (POM)-C, POM-N and microbial biomass-C were determined in each aggregate size fraction. Microbial respiration and nitrogen mineralization were also assessed in each aggregate size fraction, during a 28 day incubation period. Losses of POM-C and POM-N in the bulk soil due to mechanical site preparation were high relative to total soil C and N, which suggests that POM is a sensitive parameter to the effect of mechanization. The ratio C-POM:SOM was significantly related to MWD ( R 2 = 0.75, P < 0.001) reflecting that POM may play a key role in the topsoil aggregate formation in these stands. Semi-natural stands had a higher proportion of macroaggregates (0.25–2 mm) than the cultivated adult one. Megaaggregates (>2 mm) were the most abundant class in mature stands (82–92%), whereas macro- and microaggregates (<2 mm) were the most abundant ones in the intensely soil prepared P. radiata plantation (49%). Indicators for sustainable forest management related to soil organic matter should not only be assessed in terms of total C stocks but also with respect to sensitive organic matter and its degradability in different size classes.

Re-evaluation of Phytophthora citricola isolates from multiple woody hosts in Europe and North America reveals a new species, Phytophthora plurivora sp. nov.

During large-scale surveys for soilborne Phytophthora species in forests and semi-natural stands and nurseries in Europe during the last decade, homothallic Phytophthora isolates with paragynous antheridia, semipapillate persistent sporangia and a growth optimum around 25 degrees C which did not form catenulate hyphal swellings, were recovered from 39 host species in 16 families. Based on their morphological and physiological characters and the similarity of their ITS DNA sequences with P. citricola as designated on GenBank, these isolates were routinely identified as P. citricola. In this study DNA sequence data from the internal transcribed spacer regions (ITS1 and ITS2) and 5.8S gene of the rRNA operon, the mitochondrial cox1 and beta-tubulin genes were used in combination with morphological and physiological characteristics to characterise these isolates and compare them to the ex-type and the authentic type isolates of P. citricola, and two other taxa of the P. citricola complex, P. citricola I and the recently described P. multivora. Due to their unique combination of morphological, physiological and molecular characters these semipapillate homothallic isolates are described here as a new species, P. plurivora sp. nov.

Spatial structure of semi-natural and plantation stands of Scots pine (Pinus sylvestris L.) in northern Scotland

The success of current initiatives to maintain and enhance the area of and the special habitats provided by the remnant semi-natural pinewoods of northern Scotland will depend upon foresters' ability to foster more natural structures in even-aged plantations through stand manipulation. However, there is little information on the structures and spatial patterns that can be found in Scottish pinewoods; such knowledge could be used to design appropriate silvicultural regimes. A study was carried out to compare spatial structure in three 0.8–1.0 ha plots in the Cairngorms National Park; one plot was a 78-year-old plantation stand, the other two were semi-natural stands with trees up to 300 years old. Basic mensurational data showed that the semi-natural stands were characterized by a wider range of tree sizes and more large (>50 cm d.b.h.) trees. Spatial structure was evaluated with a range of different indices: the aggregation index of Clark–Evans (CE), the uniform angle and diameter differentiation indices, Ripley's L function of tree spatial distribution, pair and mark correlation functions and experimental variograms of tree diameter. The CE revealed a regular distribution in the plantation with the semi-natural stands having a random pattern. Further analysis of the latter stands indicated that, in each case, the older trees in the stand were regularly distributed while the younger ones were clustered. There was little difference in uniform angle values between the stands while the diameter differentiation distributions suggested greater variety in diameter within the semi-natural stands than in the plantation. The Ripley's L function showed that trees in the plantation were regularly distributed at close distances but clustered over wider distances. There were differences in pattern between the semi-natural stands; in one, trees were clustered because the positions of the younger trees were influenced by past regeneration trials, whereas in the other stand a random pattern was observed. Similarly, the variogram indicated widespread homogeneity in diameter within the plantation, while the semi-natural stands showed high variation at close spacing because of competition followed by spatial autocorrelation up to ∼20 m distance. Thereafter, one of these stands had a very different pattern because of a more intensive regeneration history. All the indices, apart from uniform angle, were able to discriminate between the plantation and the two semi-natural stands, but only the more detailed spatial indices were capable of identifying differences within the latter. The implications of these results for management strategies in plantations are discussed.

Succession of understory vegetation in managed and seminatural Scots pine forests in eastern Finland and Russian Karelia

The aim of this study was to compare the understory vegetation in chronosequences representing seminatural and managed Scots pine (Pinus sylvestris L.) forests on dryish heaths of the Vaccinium type. The data represent the middle boreal vegetation zone and were collected in eastern Finland and the Dvina area of Karelia, on both sides of the border between Finland and the Russian Federation. Species diversity and the coverage of the various life-form groups (ground lichens, mosses, liverworts, grasses, herbs, dwarf shrubs, and tree seedlings) were used to analyse the properties of the ground vegetation over the succession from open forest land to closed forest communities. The clearest differences in diversity between the seminatural forests mainly influenced by fire and managed forests occurred in the early stages of succession. Forest management appeared to increase the species richness at the beginning of succession. The seminatural stands were rich in Cladonia lichens and dwarf shrubs up until tree canopy closure; however, the abundance of mosses was lower in the seminatural stands. Forest management favoured an abundance of grasses, notably Deschampsia flexuosa, which was common after clear-cutting. The use of prescribed burning in silviculture could result in more natural vegetation succession dynamics in managed stands.

Silver fir sapling bank in seminatural stand: Individuals architecture and vitality

The relations between age, crown architecture, height and height increment of silver fir ( Abies alba Mill.) saplings were analysed using a multivariate method. Individuals from the saplings bank in mixed, unevenly aged, seminatural stands in Western Poland were investigated. Examined features were analysed with respect to light availability, which varied between 5.9 and 25.8% of full sunlight. The age of firs in the saplings bank varied from 11 up to 101 years. Under shade, growth is suspended and saplings tend to form a flat crown. Reduction of growth of a sapling did not influence its mortality, and did not diminish its ability to vigorously grow for up to 90-year-old saplings. Results of the PCA showed that age was not connected with sapling size, growth or crown morphology. Height increment is related to the relative crown length (RCL) and to the size of the sapling. In looking for an objective and quantitative indicator of growth potential, results suggest the RCL as a feature not influenced by sapling size. It should be pointed out that the vitality defined in this way reflects only the current growth, but not the potential to survive or the ability for rapid growth along with a changing light environment. The apical dominance ratio (ADR) value seems to be an indicator of light conditions in the understorey, but this trait is influenced by the height of the sapling.

Dead wood in semi-natural temperate broadleaved woodland: contribution of coarse and fine dead wood, attached dead wood and stumps

Dead wood is essential for biodiversity in forests and is therefore often surveyed in conservation inventories. Usually only coarse downed trees (logs) and standing dead trees (snags) are surveyed, but dead wood also occurs on living trees, in stumps, and in fallen branches. Attached, standing (including stumps) and downed dead wood with a diameter of more than 1 cm was surveyed in 25 semi-natural stands of temperate broadleaved woodland dominated by oak in southern Sweden (most trees younger than 70 years but with an older generation of Quercus , and often Corylus scrub). This study is primarily motivated by the rising interest in biofuel harvesting by thinning which will affect dead wood structure in forests, especially the finer dead wood fractions. The sites in this study contained on average 14.3 m 3 /ha coarse dead wood (defined as wood with a diameter >10 cm), which is more than twice as much as in production woodland. Fine dead wood (diameter 1–10 cm) made up another 12.2 m 3 /ha (45% of the total dead wood volume). Of the fine dead wood, on average 20% was oak wood and 71% was wood from other broadleaved trees. The coarse dead wood fraction consisted equally of oak wood (46%) and wood from other broadleaved species (47%). Coniferous wood amounted to 7% (coarse dead wood) or 8% (fine dead wood). The total dead wood volume was dominated by downed (66%) and standing dead wood (22%), while attached dead wood and stumps amounted to smaller fractions (6% each). The total volume of fine dead wood did not correlate with the total volume of coarse dead wood. These results therefore suggest that fine dead wood cannot be predicted from conservation surveys of coarse dead wood. The value for biodiversity of fine dead wood is discussed, and should not be overlooked in conservation work due to the fact that for example, many fungi and insects are associated with it.

Dead wood in semi-natural temperate broadleaved woodland: contribution of coarse and fine dead wood, attached dead wood and stumps

Dead wood is essential for biodiversity in forests and is therefore often surveyed in conservation inventories. Usually only coarse downed trees (logs) and standing dead trees (snags) are surveyed, but dead wood also occurs on living trees, in stumps, and in fallen branches. Attached, standing (including stumps) and downed dead wood with a diameter of more than 1 cm was surveyed in 25 semi-natural stands of temperate broadleaved woodland dominated by oak in southern Sweden (most trees younger than 70 years but with an older generation of Quercus, and often Corylus scrub). This study is primarily motivated by the rising interest in biofuel harvesting by thinning which will affect dead wood structure in forests, especially the finer dead wood fractions. The sites in this study contained on average 14.3 m 3/ha coarse dead wood (defined as wood with a diameter >10 cm), which is more than twice as much as in production woodland. Fine dead wood (diameter 1–10 cm) made up another 12.2 m 3/ha (45% of the total dead wood volume). Of the fine dead wood, on average 20% was oak wood and 71% was wood from other broadleaved trees. The coarse dead wood fraction consisted equally of oak wood (46%) and wood from other broadleaved species (47%). Coniferous wood amounted to 7% (coarse dead wood) or 8% (fine dead wood). The total dead wood volume was dominated by downed (66%) and standing dead wood (22%), while attached dead wood and stumps amounted to smaller fractions (6% each). The total volume of fine dead wood did not correlate with the total volume of coarse dead wood. These results therefore suggest that fine dead wood cannot be predicted from conservation surveys of coarse dead wood. The value for biodiversity of fine dead wood is discussed, and should not be overlooked in conservation work due to the fact that for example, many fungi and insects are associated with it.

Lichens and bryophyte communities of planted and semi-natural forests in Britain: the influence of site type, stand structure and deadwood

Lichen and bryophyte communities of spruce and pine plantations in different parts of Britain were surveyed and compared to those of semi-natural pine and oak woodlands. In total, 202 lichen species and 111 bryophytes were recorded. Community composition and species-richness were related to measures of climate, stand structure and deadwood (snags, logs and stumps). Plantations had a less species-rich lichen flora than semi-natural stands related to reduced light availability and lack of old trees. Bryophyte species-richness was similar in plantations and semi-natural stands, and was positively correlated with large diameter (>20 cm), well-decayed logs and stumps. Lichens species-richness was higher on decorticate snags (especially in semi-natural Scots pine stands in the Scottish Highlands). Early successional stands were often the richest for lichens, stumps being important for Calicium and Cladonia species. Three strategies are suggested for enhancing lower plant diversity in planted forests: (1) extending felling rotations; (2) introducing alternative silvicultural systems to clear-felling (e.g. single-tree selection) to foster continuity of woodland conditions and increase deadwood volumes; (3) modifying restocking practices on clear-fells to avoid excessive shading of deadwood.

Relationships between insect diversity and habitat characteristics in plantation forests

A methodological approach to the identification of biodiversity indicators in commercial forest stands is illustrated by analysis of the relationships between syrphid (hoverflies) and carabid (ground beetles) community composition and diversity, and stand structure and field layer vegetation. Data were collected from 12 commercial forest sites encompassing a range of climatic conditions and different crop types (Scots pine, Sitka spruce, Norway spruce and Corsican pine) across the UK. Comparisons were also made between unmanaged semi-natural Scots pine woods and Scots pine plantations. For both syrphids and carabids, no differences in species richness and diversity were recorded between semi-natural stands and plantations; one rare syrphid considered to be restricted to semi-natural pine stands was also found in spruce. Syrphid species diversity and richness was higher in southern spruce sites than in the northern sites. Northern sites had distinctive carabid communities, as did sites in the New Forest, a large ancient woodland in southern England. Of the measured habitat variables, vertical stand structure showed the best correlation with species richness and diversity of both carabids and syrphids. Richness and diversity were less in stands with high vertical cover values for canopy layers. Stands with higher field layer cover supported greater syrphid diversity, but lower carabid diversity. Measures of stand structure could be used as potential indicators of syrphid and carabid diversity, but additional habitat parameters also need to be tested.

Effects of drought on beech in Lady Park Wood, an unmanaged mixed deciduous woodland

The effects over 16 years of the 1976 drought on the beech (Fagus sylvatica L.) population in mature, mixed deciduous, semi-natural stands in Lady Park Wood are described. Individual trees were recorded within sample transects at intervals from 1945 onwards, so it was also possible to examine responses in relation to previous growth. Many mature beeches were killed immediately or severly damaged. Growth of survivors was negligible until about 1985 and never recovered to pre-drought rates. Damaged trees were still dying 15 years later from drought-induced damage. Sub-canopy beech in those parts of the wood which suffered most canopy mortality grew rapidly after 1983. Through its effects on beech, the drought had a marked impact on the structure and successional trajectory of the wood.