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1.
National forests have a wealth of natural amenities that attract over 175 million recreational visitors a year. Although natural amenities draw visitors to national forests, many of the recreational activities that they engage in require built amenities, such as roads, campgrounds, boat ramps, and trails. We estimate regression models of the effect of two common built amenities—campgrounds and picnic areas—on national-forest visitation controlling for natural amenities and accounting for the endogenous relationship between visitation and built amenities. We found that campgrounds and picnic areas are significantly and positively correlated with visitation.  相似文献   

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Dead wood is an important element of forests both for biodiversity and ecosystem functions. Due to intensive silviculture, however, dead wood usually is strongly underrepresented in European forests. Forest reserves cannot fully compensate for this because they comprise only a small proportion of forested areas and are often isolated. Retaining a certain number of dead trees in managed forests is important, but may cause safety problems for lumbermen and visitors and still does not necessarily lead to an amount and incidence (i.e., probability of occurrence) of dead wood that might be required for many species and certain ecosystem functions. Our studies concentrate on a third and complimentary dead wood management strategy: dead wood islands, i.e. small unmanaged islands distributed throughout managed forests. As an example, we focus on European beech forests (Fagus sylvatica). An important question related to this strategy is: how do amount, quality, and incidence of dead wood depend on the island’s size? To provide an answer, we use the spatially explicit, rule-based simulation model BEFORE-CWD that was developed to analyse dead wood dynamics in natural beech forests. This model and its predecessor, BEFORE, are well-verified and validated. They reproduce a suite of observed patterns and generate valid secondary and independent predictions. We found that islands that are too small, i.e. smaller than 0.33 and 0.08 ha for standing and lying dead wood, respectively, can fail to provide dead wood for several decades. The shape of the islands has only a minor effect. Extreme storm events temporarily increase and then decrease the amount of standing dead wood. In terms of the amount and incidence of dead wood, it makes no difference if one big or several small islands are set aside from management, unless the islands are not too small. We conclude that even relatively small unmanaged islands within managed forests can reliably provide dead wood and therefore should be considered as a management option. Our results can be used, for example by using metapopulation models of species of interest, to develop management plans for creating networks of dead wood islands.  相似文献   

4.

Context

Mediterranean landscapes are composed of different interacting vegetation patches. Pine and oak ecosystems form contiguous patches within these landscapes, in pure stands, or as mixed pine?Coak ecosystems. During the nineteenth century, pine forest distribution in the Mediterranean Basin increased dramatically as a result of large-scale re-forestation and spontaneous forest regeneration. At the same time, secondary succession of abandoned agricultural land allowed development of pine and oak ecosystems. Consequently, a pine?Coak mosaic has developed, which created opportunities for cross-colonization, i.e. species colonization from one ecosystem in the reciprocal system. Pines shed their wind-dispersed seeds and colonize Mediterranean oak vegetation. Oaks regenerate in different ecosystems, including pine forest understories.

Research question

This paper reviews fire-free landscape-scale dynamics of pine?Coak Mediterranean mosaics and analyze how landscape-scale interactions are leading to pine?Coak ecosystems by different processes.

Results

Published information from the Mediterranean Basin illustrates pathways of pine?Coak ecosystems formation. Using Mediterranean literature, I try to elucidate the factors that (1) control colonization potential and (2) modulate the resistance to colonization, in different habitats, land uses, and landscape settings.

Conclusion

Management implications for these mixed pine?Coak ecosystems are suggested. The question of whether they are novel ecosystems is discussed.  相似文献   

5.
Are current estimates of silicate minerals weathering rates precise enough to predict whether nutrient pools will recover after forest harvesting? Answering this question seems crucial for sustainable forestry practices on silicate dominated soils. In this paper, we synthesize estimated Ca and K weathering rates (derived using seven different approaches) from a forested area in northern Sweden (the Svartberget-Krycklan catchment) to evaluate the precision of weathering rate estimates. The methods were: mass-balance budgets (catchment and pedon-scale); long-term weathering losses inferred from weathered soil profiles (using zirconium as a conservative tracer); strontium isotopes (86Sr/85Sr) as proxy for catchment export of geogenic Ca; climate based regressions; a steady-state, process-based weathering model (PROFILE) and a dynamic, conceptual catchment geochemistry model (MAGIC). The different methods predict average weathering rates of 0.67 ± 0.71 g Ca m−2 year−1 (mean ± stdev) and 0.39 ± 0.38 g K m−2 year−1, suggesting a cumulative weathering release during a forest rotation period of 100 years that is the same magnitude as losses induced by forest harvesting at the end of the period. Clearly, forestry practices have the capacity to significantly alter the long-term nutrient status of the soil and cation concentrations in soil-water runoff. However, the precision in weathering estimates are lower than that needed to distinguish between effects on nutrient pools by different forest practices (complete-tree harvesting versus conventional stem only harvest). Therefore, we argue that nutrient budgets, where weathering rates play a crucial role, cannot be used as basis for resolving whether different harvesting techniques will allow nutrient pools to recover within one rotation period. Clearly, this hampers the prerequisite for sound decision making regarding forestry practices on silicate mineral dominated soils.  相似文献   

6.
New Forests - Elms (Ulmus spp.) were once dominant trees in mixed broadleaf forests of many European territories, mainly distributed near rivers and streams or on floodplains. Since ancient times...  相似文献   

7.
New Forests - Author had ordered for open access after the article went online in Springer link. The article was changed to open access article.  相似文献   

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