Native Woodland Restoration Research Articles

Conversion of Pinus radiata plantations to native forest after harvest operations: a north Iberian Peninsula case study

There is broad consensus on restoration of native woodlands in places where intensive forestry is nowadays not profitable. However, this consensus is lost when stakeholders need to implement forest management practices as restoration tool, especially because there is a substantial lack of empirical evidence about its feasibility. In this context, we assess the impact of two different harvest treatments on understorey plant species composition of Pinus radiata plantations as tools to recover native woodland vegetation in northern Iberian Peninsula. Here, common clear-cut treatment and restoration-clear-cut where only pine trees were removed (i.e. reducing the disturbance effect over understorey vegetation) were compared against understorey plant species composition of young and old plantations and restored tracks. The aim was to identify which treatment is more suitable to recover native woodland vegetation. The results reveal that both clear-cuts maintained species composition plus important understorey native species, some of them being restoration targets. However, both clear-cuts showed diversity reductions compared with old plantations, although there were not apparent retention effects on compositional change towards native communities at least two years after harvest. It seems that the remaining vegetation established by natural succession after both clear-cut treatments could be used to achieve initial restoration objectives for some native tree and understorey plant species at relatively low costs. In any case, it would be interesting to implement supplementary management measures to accelerate this conversion, such as invasive species elimination or target species seeding, to maintain local biodiversity and introduce native woodland species not present in the area.

Upland land use predicts population decline in a globally near‐threatened wader

Summary Changes in large‐scale land use may fragment and degrade habitats, affecting animal species adapted to these habitats. In the UK uplands for example, changes in sheep and game management, and afforestation, have altered the configuration of internationally important moorland habitat and are predicted to have increased predation pressure for a globally unique suite of breeding birds of international conservation importance. Some of these upland bird species have declined, with particular concern over ground‐nesting waders. Using resurveys of the rapidly declining Eurasian curlew Numenius arquata as a focal species of global conservation concern, we investigate whether upland land use predicts low nesting success and population decline. Curlew population changes over an 8‐ to 10‐year period were positively related to gamekeeper density (a surrogate of predator control intensity) and inversely to the area of woodland surrounding sites, as a likely source of predators to adjacent open ground. Model predictions suggest that increasing woodland cover from 0% to 10% of the land area within 1 km of populated sites requires an increase in human predator control effort of about 48%, to a level associated with high‐intensity grouse production, to achieve curlew population stability. Curlew nesting success, known to be a key driver of population trends, was also positively related to gamekeeper density and inversely to woodland area surrounding sites, providing a plausible mechanistic link between land use and population change. Synthesis and applications. Upland land use is associated with curlew declines, with predation a likely mechanism, and this may apply to other breeding waders. The removal of isolated woodland plantations from otherwise unafforested landscapes may help reduce predation pressure across a range of systems including moorland. However, direct predator control may also be important to conserve ground‐nesting birds in these landscapes, for example, where moorland management and forestry coexist as major land uses. Predator control may also mitigate climate change effects by enhancing wader productivity, particularly where climate effects coincide with changing land use. Emerging land uses in open landscapes, including native woodland restoration and wind farms, require careful siting to minimize further impacts on open‐area breeding birds.

Rewilding – A New Paradigm for Nature Conservation in Scotland?

Rewilding is a strategy for the conservation of complete, self-sustaining ecosystems, primarily involving the protection and, where necessary, reintroduction, of populations of keystone species in large, connected reserve networks. A potential method of preserving ecosystem functions and biodiversity, it is now receiving a great deal of practical and political attention, particularly in North America. In Scotland, where many native species have been extirpated in the relatively recent past, rewilding has clear relevance and may provide an overarching set of objectives for current programmes of native woodland restoration and species reintroductions. Nevertheless, rewilding is not widely used as a term or strategy in Scottish conservation. This review considers the development of the concept and its possible application in Scotland, and identifies substantial scope for rewilding, in terms of the restoration and protection of large areas of wild land, and of the reintroduction of native species which have been driven to extinction by human activity. As the environmental, social and economic benefits which are likely to result from a programme of rewilding in Scotland outweigh the potential drawbacks, the adoption of rewilding is recommended as one aim of environmental policy.

Long-term approaches to native woodland restoration: Palaeoecological and stakeholder perspectives on Atlantic forests of Northern Europe

The long timeframes involved in woodland regeneration and adaptation introduce considerable uncertainty into management and conservation planning as most ecological datasets span only a small part of ecosystem dynamics. This is a particular concern in vulnerable habitats, such as Atlantic birch-oak woods in north-western Britain, where range edge populations are at risk from herbivory and climate change. This study combines historical palaeoecology and stakeholder observations to assess how multiple perspectives can inform existing models, expectations and goals for Atlantic woodland management. Long-term evidence for changing woodland composition addresses stakeholder uncertainties over the currently restricted distribution of oak, alder and hazel. Oak has remained a secondary component of birch-dominated woods and habitat definitions based on oak are too narrow to ensure sustainability. Birch has survived numerous periods of climatic and biotic adversity and shows the strongest positive response to historic reductions in grazing pressure. This has led to a pulse of regeneration since c. AD 1900, so current restoration efforts are taking place within the strongest period of woodland expansion in the last c. 500 years. Positive and negative cultural legacies are evident and intervention is considered a necessary restoration tool. Managed grazing at key stages of habitat development can support continued recruitment and regeneration. A more flexible and integrated management approach is recommended. Long-term ecology can provide direction and address uncertainties, while ecological and stakeholder evidence provide the detail necessary to develop effective management that incorporates ecosystem perspectives. This can help shape management strategies that balance possible conflicts over perceived short-term ‘damage’ to secure longer-term processes. Learning based on multiple temporal perspectives has the potential to contribute to conservation and restoration planning and practice. These principles are more widely applicable in adaptive management.

Woodland regeneration on grazed former arable land: A question of tolerance, defence or protection?

Ecological restoration of native woodlands and wooded pastures on former agricultural land is an important topic in modern conservation practice. The introduction of large herbivores is increasingly used to achieve these aims. We investigated how grazing, resistance traits of plants (concerning herbivory) and associational resistance interact and affect the establishment pattern of woody species on abandoned arable land (N-Belgium, W-Europe). In these early successional tree assemblages, we tested whether grazing increased or decreased spatial heterogeneity, which is supposed to be a crucial factor for biodiversity. With repeated measurements, 2-3 and 5-7 years after the cessation of agricultural use, we sampled 87 grazed and 56 ungrazed plots (314 m 2) in 14 sampling areas (former arable land) on nutrient rich, (sandy) loam soils. We recorded established tree frequencies, related to grazing, time, resistance traits and unpalatable/spiny vegetation cover in the herb and low shrub layer. We investigated horizontal and vertical heterogeneity using variances in establishment frequencies and variances in frequencies of trees that were able to grow beyond the browse line, respectively. We found massive colonisation of grazing tolerant and resistant woody species in early successional stages. Grazing decreased frequencies and height of the most abundant tolerant species (mainly Salix caprea L.). After 5-7 years, frequencies of defensive and tolerant species were equal, but the former (mainly Betula pendula Roth) were able to grow beyond the browse line. When the cover of unpalatable/spiny vegetation was high enough (>60% of plot size), it also provided suitable nurse sites for tolerant species to grow out. In early assemblages, grazing increased horizontal and vertical heterogeneity, resulting in intermediate successional stages. In the long-term, the mechanism of associational resistance will also allow non-resistant and tolerant species to grow beyond the browse line and promote forest succession and the order of species establishment and replacement.

Technological advances in temperate hardwood tree improvement including breeding and molecular marker applications

Hardwood forests and plantations are an impor- tant economic resource for the forest products industry worldwide and to the international trade of lumber and logs. Hardwood trees are also planted for ecological reasons, for example, wildlife habitat, native woodland restoration, and riparian buffers. The demand for quality hardwood from tree plantations will continue to rise as the worldwide consumption of forest products increases. Tree improve- ment of temperate hardwoods has lagged behind that of coniferous species and hardwoods of the genera Populus and Eucalyptus. The development of marker systems has become an almost necessary complement to the classical breeding and improvement of hardwood tree populations for superior growth, form, and timber characteristics. Molecular markers are especially valuable for determining the reproductive biology and population structure of natural forests and plantations, and the identity of genes affecting quantitative traits. Clonal reproduction of commercially important hardwood tree species provides improved plant- ing stock for use in progeny testing and production forestry. Development of in vitro and conventional vegetative propagation methods allows mass production of clones of mature, elite genotypes or genetically improved genotypes. Genetic modification of hardwood tree species could potentially produce trees with herbicide tolerance, disease and pest resistance, improved wood quality, and reproduc- tive manipulations for commercial plantations. This review concentrates on recent advances in conventional breeding and selection, molecular marker application, in vitro culture, and genetic transformation, and discusses the future challenges and opportunities for valuable temperate (or "fine") hardwood tree improvement.

Silviculture of Scottish Forests at a Time of Change

Summary During the 20th century, a sustained afforestation programme was carried out in Scotland, which increased the forest cover from about 4% of the country in 1900 to 17% in 2002. The expansion was achieved primarily through the establishment of evenaged plantations of fast-growing conifer species, most of which were not native to the British Isles. Many of these forests will reach financial maturity in the next two decades, thereby providing a valuable timber resource for the Scottish economy, and giving the opportunity to diversify the forests to meet the multifunctional objectives outlined in the recent Scottish Forestry Strategy. However, diversifying these forests requires the adoption of a range of silvicultural systems and not simply perpetuating the clearfelling and replanting system that has characterized plantation management. These new approaches include greater use of continuous cover forestry and the restoration of native woodlands on sites previously planted with conifers. A sustained period of low timber prices is also influencing this process, as managers are more aware both of the high replanting costs involved in plantation silviculture and of the subsidies given to manage stands for nonmarket benefits. The effect of these changes upon the structure and nature of Scottish forests is unclear, and a sectoral analysis should be undertaken to explore the potential impacts.

The use of soil data in natural heritage planning and management

Abstract. Native woodland restoration is a conservation priority within the UK and there is an increasing awareness that a long‐term strategy is required to guide this process. A GIS‐based modelling approach has been developed, which links site conditions as expressed in an integrated soil and land cover dataset with the site requirements for different woodland types. There are three important aspects to the model – the parameter weightings, the added value of the integrated dataset, and the woodland categories which are described and predicted. The initial quantitative and qualitative validation has been encouraging although more is required and planned. The results indicate that for broad strategic planning purposes, predictions of woodland potential are not improved significantly when climatic factors are incorporated. The concept that soil acts as an integrator of other environmental variables is discussed alongside the practical application of the model by a range of users.

Using Geographical Information Systems to identify and target sites for creation and restoration of native woodlands: a case study of the Chiltern Hills, UK

Rare and threatened habitats in Europe must be restored and enhanced in accordance with the European Union’s Habitats and Species Directive. In the United Kingdom, conservation and expansion objectives for species and habitats are outlined in the Species Action Plans and Habitat Action Plans. Site identification for these measures has to date been ad hoc without consideration of either the existing “stock” of the natural resource or the ability of the surrounding land use to deliver the enhancement (enlargement) of a given habitat. Using a Geographical Information System, we outline a targeting system for creating new woodland in association with existing ancient woodland in the Chiltern Hills Area of Outstanding Natural Beauty. The aim was to create woodland blocks of at least 100ha, as being of the most benefit to biodiversity. We identified existing patches of woodland between 20 and 50ha as cores for habitat expansion and classified land use in terms of its suitability and proximity to these core areas for tree planting to meet the targets of the statutory body. Our results suggest that the targeting method employed is a useful tool for habitat restoration.

Current approaches to native woodland restoration in Scotland

Summary A large number of projects have recently been initiated in Scotland aiming to restore native woodland, which are being undertaken by a variety of organisations, often in partnership, with environmental NGOs playing a leading role. The objectives, constraints and methodologies of these projects are critically reviewed, partly through a questionnaire survey. Most aim to restore ‘natural’ woodland, but the lack of appropriate reference ecosystems and uncertainty about the characteristics of the original forest hinder the development of precise objectives, and consequently the criteria for success are poorly defined. Most projects face major practical constraints, particularly browsing by herbivores and invasion by exotic species, indicating that they will require long-term management interventions. Most woodlands are isolated from other woodlands, which threatens their long-term viability, restricting colonisation by woodland organisms. Greater reference to ecological theory in practical restoration ...

Estimating the non-market costs and benefits of native woodland restoration using the contingent valuation method

Summary The restoration of native forests is an important priority for forestry and conservation organizations in the United Kingdom. The economic case for public sector support for native woodland restoration in the United Kingdom rests almost entirely on the provision of non-market benefits related to wildlife, landscape and recreational opportunities. This paper describes a discrete choice contingent valuation (CV) to estimate the value of the non-market benefits of restoring two native pinewood forests in Affric and Strathspey. If only the willingness to pay (WTP) of those who supported the restoration plan was considered, the average benefit estimate per household was £35 for Affric and £53 for Strathspey. When the compensation required by a small proportion of respondents who preferred the! current moorland landscape, was estimated mean WTP was unchanged for Affric, but fell to £24 for Strathspey. The study highlights the need to take account of non-market benefits and costs when evaluating land use change, otherwise benefits may be overestimated and there is a possibility that the wrong projects will be selected. The sensitivity of CV values to the scope of the environmental change are also investigated and the issue of embedding discussed.

Restoration of Woody Plants to Capped Landfills: Root Dynamics in an Engineered Soil

AbstractClosed or abandoned landfills represent significant land areas, often in or near urban centers, that are potential sites for ecological restoration of native woodlands. But current guidelines in many jurisdictions do not allow for the installation of trees or shrubs above landfill clay caps, although these plants have many environmental, functional, and aesthetic advantages, including a rapid start to community succession. Typical closure procedures for capped landfills include only a grass cover to control moisture infiltration and impede soil erosion. The main concern that limits the application of a woody cover to a closed landfill is that roots may penetrate and weaken the clay cap. As part of a comprehensive experimental program on woodland restoration, we installed 22 tree and shrub species on Staten Island, New York (the Fresh Kills Sanitary Landfill). We found no evidence that roots of the transplanted woody plants penetrate caps used on these landfills. Root growth requirements and dynamics stop penetration of these materials. Anoxic and acidic conditions were found in the sandy subsoil above the cap, as indicated by corrosion patterns on steel test rods. Also, the intensity of mycorrhizal infection on the experimental plants was high in the surface soil and decreased progressively with increasing soil depth. The potential vertical rooting depth during this time period was greater than that occurring over the clay cap. This was shown from data collected on a nearby control site, where seven of the species were installed on an engineered soil lacking a clay barrier layer, and roots of all seven species penetrated deeper than on the landfill. The engineered landfill soils are poor growth media for roots, and below ground constraints that limit restoration on these sites must be addressed.