Due to the small sample size, our results also were variable and inconclusive regarding the general belief that mixed species plantations support more native species abundance and diversity than monocultures Hartley ; Stephens and Wagner Older plantations established on previously forested lands, are generally expected to support higher levels of diversity given additional time to develop structural complexity Lugo ; Munro et al.
Other studies, however, have found high levels of species richness in younger plantations, but have primarily attributed this to an increase in light-demanding ruderal and often exotic species, with native forest species increasing with plantation age Ito et al.
Our results provide some support for this idea, with a significant negative relationship with plantation age and species richness in the shrubland to plantation category and an insignificant but similar trend with grassland afforestation.
Clearly, this would also depend on the particular growth rate of the plantation species used, the ecological characteristics of native understory species, and other environmental and site conditions including adequate seed sources and climate conditions Hartley ; Cusack and Montagnini Discussions of management strategies to conserve biodiversity in plantations are generally focused on enhancing habitat for forest species.
In a synthesis of management recommendations to improve biodiversity outcomes of plantations established on previously forested lands, Hartley suggests 1 leaving remnant native trees, snags, and cavity trees during harvest, 2 managing plantations on longer rotations, 3 utilizing native species over exotics and polycultures over monocultures, 4 avoiding intensive site preparation, and 5 thinning some plantations heavily and others not to maintain a mosaic of open to non-open areas to encourage native species colonization.
Of these recommendations we found clear support for using native species over exotic species. While we did not have sufficient information on the amount of remnant native vegetation left in plantations, this, in addition to proximity to native forest, is likely a key control on biodiversity outcomes Goldman et al. In some cases, regeneration of native species in plantations may depend on colonization from adjacent or nearby native ecosystems Senbeta et al.
Relatively few publications reported sufficient detail on distance, making this factor difficult to analyze. Canopy openness is also regarded as an important factor influencing understory richness where plantations with wider spacing either due to plantation species or management practices , and thus more open canopies, allow more light to reach the understory Michelsen et al.
While thinning generally facilitates the establishment of shrubs and herbaceous flora, it also can favor primarily generalist and exotic species which thrive with increased light and moderate which than compete with native species, such as forest herbs and native late seral woody species Herault et al. Moderate levels of disturbance are generally seen as beneficial for biodiversity, but severe disturbance creates conditions few plants can tolerate Battles et al.
Unfortunately, there was not adequate information on spacing, thinning, and canopy cover provided in the studies included in the database to conduct a detailed analysis on the effects of canopy openness on plant diversity.
We found no significant relationship between whether canopy cover was greater or lesser in plantations versus the paired land-use, although small sample size made this difficult to analyze. The fact that all native plantations in the secondary to plantation category had a lower canopy cover than the paired land use may be indicative of increased management particularly thinning in plantations compared to naturally regenerating forest and may result in increasing species richness of some species Nagaike et al.
While we did not find significant relationships between measures of biodiversity and management, plantation age, and other factors, greater availability of data on these topics could help to clarify the role they play. While species richness is an often-used proxy for biodiversity it does not take into account which species are increasing or decreasing and thus does not reflect changes in species composition Nagaike et al.
While in some cases plantations support more species than paired land covers, it is important to take into account which species benefit from plantation establishment and which are negatively affected by it, which depends largely on the functional characteristics of particular species, such as seed size, dispersal agent, shade tolerance, and maximum plant height Nagaike ; Gomez-Aparicio et al. It is also important to consider changes in specialist or narrow and native especially endemic species richness, as these species are often the most sensitive to land-use change Ogden et al.
The relatively short rotation of plantations can be particularly discriminating against old forest succession species, decreasing the value of plantations as compared to natural forests Richardson and Van Wilgen ; Alrababah et al. It is also critical to consider how plantations affect the number and abundance of exotic species since non-native species, when invasive, can compete with indigenous species and change ecosystem functioning Richardson et al. While the limited number of studies precludes drawing strong conclusions, the results of this synthesis support past research that suggests that plantations tend to lead to an increase in exotic species Fig.
On the other hand, we found a decrease in exotic species and an increase in native species in degraded or exotic pasture to plantation transitions, suggesting that plantations can be effective in shading out competitive exotic species under those conditions Carnus et al.
At local, national, and international levels, there is increasing emphasis on evaluating the impact of plantations on biodiversity and in enhancing biodiversity outcomes through land-use planning and forest management Kanowski et al. In evaluating plantations as a sustainable land use, it is important to consider how this type of land-use change will affect a range of environmental goods and services including forestry products, water supply, carbon cycling, and biodiversity.
The primary recommendation from this study is that plantations are more likely to positively benefit biodiversity particularly in terms of favoring native over exotic species when established on degraded or exotic land covers rather than as a replacement of natural ecosystems, whether those systems were originally forested or not. At the same time, this study makes clear that further research is needed on the biodiversity outcomes of shrubland and grassland afforestation as few studies were available in these categories.
In addition, the trends we found suggest that new plantations should utilize indigenous tree species to enhance within-plantation biodiversity, but more research is needed on the effects of afforestation in grasslands and shrublands using species that are native to nearby forests or woodlands versus exotic species Carnus et al. Thus, although plantations often support fewer specialist species than natural ecosystems, under some conditions they can play an important role in biodiversity conservation and recuperation, particularly at the landscape level.
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J Veg Sci — For instance, snails and other mollusks might seem expendable. However, scientists recently discovered that certain mollusks do not get cancer.
Scientists are searching for the chemicals that produce this natural immunity. Biodiversity is the basis for life-sustaining ecological services such as nutrient cycling, photosynthesis, decomposition, soil creation, climate regulation, removal of pollutants, and insect control. These processes contribute to the stability of the Earth's ecosystems and contribute to higher quality air, water, and food. Many people support biodiversity because it satisfies personal values.
These personal values are as varied as the people who hold them. Most people agree that we have a responsibility to ensure that future generations have all the pieces to sustain life on Earth. Biodiversity contributes to our enjoyment of natural beauty, outdoor recreation, and peace of mind.
People benefit from healthy forest ecosystems too, like this fisherman on the banks of a stream in autumn. As a good steward of the land, it is important to be aware of plant and animal species and ecological communities of concern designated as imperiled, critically imperiled, threatened, or endangered and how management activities in your forest may affect these species.
For Pennsylvania, G1 species include several freshwater mussels. G2 species potentially affected by forest management activities include the Indiana or social bat and the small-whorled pogonia. Both of these species, where they occur, are sensitive to forest-management activities. The Indiana Bat is an "imperiled" species native to Pennsylvania forests. Photo by Josh Johnson. In managing your forest, think about how your activities can improve important habitat features.
As you conduct harvesting activities, consider the following:. Fallen Maple leaves in autumn. To learn more about conserving biodiversity as you plan or conduct forest management, contact any one of the following organizations:. Box Harrisburg, PA Phone: Pennsylvania Natural Heritage Program. Let's Stay Connected. By entering your email, you consent to receive communications from Penn State Extension.
View our privacy policy. Thank you for your submission! This article provides strategies for conserving forest biodiversity, provides a brief overview of species of concern in Pennsylvania, and suggests ways you can conserve biodiversity in your forest. Large trees in forest. What Is Biodiversity? Genetic diversity --each individual organism is unique, even among their own species.
Species uniqueness is slow to develop and cannot be duplicated or retrieved once it is lost. A diverse gene pool increases a species' ability to adapt to changing environmental conditions. Pollinators also benefit from flowering trees and plants used in our projects. By mitigating soil compaction, the ground allows for greater water infiltration and storage, which reduces surface runoff which transports sediment.
Trees also uptake and intercept precipitation, further reducing inputs to streams and the trees can uptake metals and minerals that pose water quality concerns. Employment is generated for local, professional tree planters, equipment operators, and nurseries, and a renewable, sustainable, multi-use resource base is established for the future.
Appalachian forests are among the most diverse and valuable forests in the world.
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