Tommaso Sitzia

Using forest management to control invasive alien species: helping implement the new European regulation on invasive alien species

On 1 January 2015 a new European regulation on invasive alien species entered in force. Key aspects of this regulation are the adoption of a list of invasive alien species which are of European Union concern, the requirement for specific prevention measures, the establishment of early detection and fast eradication measures, and the management of the widely spread invasive alien species. We highlight the potential contribution of the forestry sector to promote the implementation of this regulation. There is a wealth of experience on positive and negative responses of invasive alien species to forestry interventions. This knowledge should be synthesized and further developed to help prevent and manage invasions in forests and adjacent habitats and to minimize the risks of invasive alien species. We thus recommend that decisions regarding the application of the regulation will include actors responsible for, or involved in, the management and use of forests and related semi-natural habitats.

High cover of hedgerows in the landscape supports multiple ecosystem services in Mediterranean cereal fields

Summary Field-margin diversification through conservation and restoration of hedgerows is becoming a prominent intervention for promoting biodiversity and associated ecosystem services in intensive agricultural landscapes. However, how increasing cover of hedgerows in the landscape can affect ecosystem services has rarely been considered. Here, we assessed the effect of increased field-margin complexity at the local scale and increasing cover of hedgerows in the landscape on the provision of pest control, weed control and potential pollination. Locally, three types of field margin were compared as follows: (i) standard grass margin, (ii) simple hedgerow and (iii) complex hedgerow, along two independent gradients of hedgerow cover and arable land cover in the landscape. We performed an exclusion experiment to measure biological control of cereal aphids and assessed natural enemy and pest abundance in the field. We sampled plant weed communities and performed a phytometer experiment to test the effects of pollinators on plant reproductive success. At the local scale, planting a new hedgerow or improving its structural complexity and vegetation diversity did not enhance the delivery of ecosystem services in the neighbouring field. However, high cover of hedgerows in the landscape enhanced aphid parasitism (from 12 to 18%) and potential pollination (visitation rate and seed set increased up to 70%) irrespective of local margin quality. The cover of arable land in the landscape reduced the abundance of plant-dwelling predators and weed diversity, but did not affect the delivery of the investigated ecosystem services. Synthesis and applications. Our results highlight the key importance of the surrounding landscape context, rather than local factors, to the delivery of ecosystem services. This suggests a need for new policies that pay particular attention to the conservation of hedgerows at large scales for promoting multiple ecosystem services in agroecosystems. Specifically, hedgerows can serve to develop a network of ecological corridors that can facilitate the movement of beneficial organisms, such as pollinators and natural enemies in the agricultural matrix. Such interventions may be a ‘low cost–high benefit solution’, since farmers can create or conserve high-quality habitats taking little or no land from crop production and without the need to change their crop management.

Ecological risk and accessibility analysis to assess the impact of roads under Habitats Directive

We propose a method for the appropriate assessment of adverse effects of roads in compliance with the European Union Habitats Directive. The method incorporates an analysis of ecological risk of edge effects by the proposed roads with the related increase in accessibility. The method was tested on 30 km of planned forest roads inside an 8,000-ha reserve included in two Natura 2000 sites. As a result, the cumulative effect of 19 road segments was judged as not significantly affecting the integrity of the sites, although they made accessible an extra 314 ha. On the basis of the accessibility calculation, 20 ha of land were set aside from forest exploitation as a mandatory mitigation measure. The method objectively determined the cumulative adverse effects, enabled comparison of plan revisions and alternatives and proved to measure direct and indirect significant effects with a realistic effort in terms of field survey and geographic information system processing.

Topsoil organic matter properties in contrasted hedgerow vegetation types

Background and aimsHedges, semi-natural landscape components, have the ability to integrate both agronomic and environmental functions and to provide several ecosystem services. The aim of this study was to test whether hedgerow vegetation is a determinant of soil organic matter properties in ancient agricultural lands.MethodsWe complemented cluster analysis and ordination to determine the extent to which two types of hedges that were distinct in character-plant species also differed between each other in concentration and composition of two major constituents of soil organic matter, namely humic substances and dissolved organic matter.ResultsThe two types of hedges were associated with significant differences in humic carbon content, hormone-like activity and molecular size of humic substances, which, in general, were more similar to those typical of forest than of agricultural soils. Moreover, we detected between-group differences in several phenolic acids.ConclusionsVariation of the topsoil biochemical properties of hedges may be explained by variation in their vegetation characteristics, similar to other ecosystems. Spontaneous vegetation in hedges perform an important role in controlling the variability of surface soil properties that influence the evolution of soil organic matter and nutrient availability in agricultural lands.

To core, or not to core: the impact of coring on tree health and a best-practice framework for collecting dendrochronological information from living trees

Trees are natural repositories of valuable environmental information that is preserved in the growth and structure of their stems, branches and roots. Dendrochronological analyses, based on the counting, crossdating and characterisation of incrementally formed wood rings, offer powerful insights for diverse fields including ecology, climatology and archaeology. The application of this toolset is likely to increase in popularity over coming decades due to advances in the field and a reduction in the cost of analyses. In research settings where the continued value of living trees subject to dendrochronological investigation is important, the use of an increment bore corer to extract trunk tissue is considered the best option to minimise negative impacts on tree health (e.g. stress and fitness). A small and fragmented body of literature, however, reports significant after‐effects, and in some cases fatal outcomes, from this sampling technique. As it stands, the literature documenting increment bore coring (IBC) impacts lacks experimental consistency and is poorly replicated, making it difficult for prospective users of the method to assess likely tree responses to coring. This paucity of information has the potential to lead to destructive misuse of the method and also limits its safe implementation in circumstances where the risk of impacts may be appropriate. If IBC is to fulfil its potential as a method of choice across research fields, then we must first address our limited understanding of IBC impacts and provide a framework for its appropriate future use. Firstly, we review the historical context of studies examining the impacts of IBC on trees to identify known patterns, focal issues and biases in existing knowledge. IBC wound responses, particularly those that impact on lumber quality, have been the primary focus of prior studies. No universal treatment was identified that conclusively improved wound healing and few studies have linked wound responses to tree health impacts. Secondly, we build on literature insights using a theoretical approach to identify the most important factors to guide future research involving implementation of IBC, including innate tree characteristics and environmental factors. Thirdly, we synthesise and interrogate the quantitative data available through meta‐analysis to identify risk factors for wound reactions. Although poor reporting standards, restricted scopes and a bias towards temperate ecosystems limited quantitative insight, we found that complete cambial wound closure could still harbour high rates of internal trunk decay, and that conditions favouring faster growth generally correlated with reduced indices of internal and external damage in broadleaved taxa. Finally, we propose a framework for guiding best‐practice application of IBC to address knowledge gaps and maximise the utility of this method, including standardised reporting indices for identifying and minimising negative impacts on tree health. While IBC is an underutilised tool of ecological enquiry with broad applicability, the method will always incur some risk of negative impacts on the cored tree. We caution that the decision to core, or not to core, must be given careful consideration on a case‐by‐case basis. In time, we are confident that this choice will be better informed by evidence‐based insight.

Abandonment of timber harvesting favours European beech over silver fir: evidence from Val Tovanella Nature Reserve in the southern Dolomites (Northern Italy)

Historical data from forest management plans have the potential to shed light on changes driven by either the application or the abandonment of forestry practices. This information coupled with recent data allows temporal comparisons to be made between surveys at the same location. Here we present the temporal comparison of two forest compartments located in Val Tovanella (Oriented Nature Reserve [Riserva Naturale Orientata] and Site of Community Importance) in the south-eastern Italian Alps for which full callipering was available for two years (1957 and 2010), the first of which came from a management plan by the renowned forest ecologist Lucio Susmel (1914–2006). Both compartments currently host mixed silver fir, Norway spruce and beech stands, and have not been managed since 1948; but one was historically a high forest, whereas the other was an open wooded pasture. We aimed to reconstruct the changes in volume, number of stems and diameter classes for the two compartments by comparing species proportions and their changes over time. In both compartments, species composition changed. In general, a decrease in compositional importance of silver fir and an increase in beech were observed. Furthermore, in one compartment, Norway spruce showed a large increase. Volumetric changes confirmed such trends and highlighted a shift towards larger diameter classes. We conclude that the abandonment of traditional forest activities and, in particular, the avoidance of tending and coppicing activities are major factors favouring beech at the expense of silver fir in the study area. Traditional planning and inventory methods can help to understand long-term changes in forest structure and the effects of forestry in light of current scenarios of land-use and climate change in protected areas. Profile

Landscape metrics as functional traits in plants: perspectives from a glacier foreland

Spatial patterns of vegetation arise from an interplay of functional traits, environmental characteristics and chance. The retreat of glaciers offers exposed substrates which are colonised by plants forming distinct patchy patterns. The aim of this study was to unravel whether patch-level landscape metrics of plants can be treated as functional traits. We sampled 46 plots, each 1 m × 1 m, distributed along a restricted range of terrain age and topsoil texture on the foreland of the Nardis glacier, located in the South-Eastern Alps, Italy. Nine quantitative functional traits were selected for 16 of the plant species present, and seven landscape metrics were measured to describe the spatial arrangement of the plant species’ patches on the study plots, at a resolution of 1 cm × 1 cm. We studied the relationships among plant communities, landscape metrics, terrain age and topsoil texture. RLQ-analysis was used to examine trait-spatial configuration relationships. To assess the effect of terrain age and topsoil texture variation on trait performance, we applied a partial-RLQ analysis approach. Finally, we used the fourth-corner statistic to quantify and test relationships between traits, landscape metrics and RLQ axes. Floristically-defined relevé clusters differed significantly with regard to several landscape metrics. Diversity in patch types and size increased and patch size decreased with increasing canopy height, leaf size and weight. Moreover, more compact patch shapes were correlated with an increased capacity for the conservation of nutrients in leaves. Neither plant species composition nor any of the landscape metrics were found to differ amongst the three classes of terrain age or topsoil texture. We conclude that patch-level landscape metrics of plants can be treated as species-specific functional traits. We recommend that existing databases of functional traits should incorporate these type of data.

Selvicoltura nei tipi neoforestali del Trentino

The natural reforestation of the fallow lands, widely documented on the Alps and throughout Europe, has important consequences on the geomorphic and hydro-geological processes, on biodiversity and on the anthropogenic landscape; moreover the post-abandonment woodlands invading past cultivated lands and pastures, acquire several environmental functions. For these reasons, it is advisable to identify the best management techniques. This article deals with a synthesis of the major ecological and biometrical characteristics and accessibility of the neo-forest types of a region of the Eastern Italian Alps (Trentino). The analysis is based on the data surveyed during a two-stage sampling of the entire regional surface, which permitted the field survey of 291 post-abandonment woodlands. The present sylvicultural treatments can be grouped into four categories: a) thinning; b) coppicing with reserve of noble broadleaved species; c) planting of native species in the undercover; d) wildlife habitat improvement. Coppicing and planting follow consuetudinary or experimental techniques, which need to be parameterized. The experience in wildlife habitat improvement is wide and would deserve a large-scale monitoring program of its effects. The ecological analysis showed that the broadleaved species cover is much more higher than that of mature woodlands, and that many post-abandonment woodlands are invading herbaceous communities with high nature value (Festuco-Brometalia and Molinietalia). Finally, the not negligible cover of neophytes is noteworthy and its potential effects on genetic pollution should be studied in details.