Native Ecosystem Function Research Articles

BIOGEOGRAPHY AND INVASION BIOLOGY- A THEORETICAL STUDY

Biogeography is a 19th-century discipline of geography that analyses the spatial distribution of creatures such as plants and animals. Biogeography is the scientific study, description, and documentation of the distribution and spread of species around the globe, as well as their environmental variables. Since, Invasion Invading species biology is one of the more recently created fields of biology that deals with the problem of invasive species. The phrase "invasive species" refers to plant and animal species that have been brought to new geographies and ecosystems and compete fiercely with native species that are infringing on their ecological area. They acquire and use space, soil, sunlight, nourishment, and other natural resources disproportionately, depriving native species of all available resources. They reproduce quickly and consistently, replacing native creatures. There has been transportation of species, consciously or unknowingly, since the geographical voyages, mainly during the 17th and 19th centuries. Many animals and birds migrate as a natural part of their life cycle, driven by physiological needs and environmental changes. This natural migration is not a factor in species introduction, which is mostly due to human activity. One of the major causes of biodiversity loss is biological invasions. As biological invasion threats grow, identifying high-vulnerability locations is becoming increasingly important. Biological invasions continue to have a significant negative influence on the environment and the economy. It's vital to understand why some introduced species become invasive before they can be managed. The ecology and physiology of the species in the invaded range have been studied in order to determine the processes underlying invasion success. However, a rising corpus of research highlighting insights derived from investigating invasion success as a biogeographic issue is highlighting the use of biogeographic techniques. Invaders have the ability to drastically alter the species composition and function of native ecosystems through competition, predation, and habitat disruption. Biological invasions have a significant economic impact on the world economy, with annual costs in the United States alone estimated at over $100 billion. Invasions occur when organisms are introduced outside of their native or historic range, either purposefully or unintentionally, and then spread effectively in their new surroundings. Exotic species, which include cattle, crops, and garden plants, are any species that isn't native to a specific location. Biological invaders are non-native creatures that spread outside of an ecosystem dominated by humans. The distinguishing characteristics of invasions, such as some marine species, plant species, and animals, are some remarkable instances. In addition, we document the biogeographic distribution of invasive species, as well as the diversity of species, habitats, and climate zones studied. A fact study and prediction analysis of key records and data related to our research aim were included in our research, which let us come to a decision on the obstacles, potential difficulties and future prospects of "Biogeography and Invasion Biology- A Theoretical Study."

Multiple invasion routes have led to the pervasive introduction of earthworms in North America.

Soil-dwelling organisms play a key role in ecosystem functioning and the delivery of ecosystem services. As a consequence, soil taxa such as earthworms are iconic in good land management practices. However, their introduction in places where species did not co-evolve with them can trigger catastrophic changes. This issue has been largely ignored so far in nature management policies because of the positive image of soil taxa and the lack of knowledge of the magnitude of soil fauna introductions outside their native range. Here we address this gap with a large spatio-temporal database of introduced alien earthworms. We show that 70 alien earthworm species have colonized the North American continent. They have larger geographical ranges than native species and novel ecological functions, representing a serious threat to the biodiversity and functioning of native ecosystems. The probably continuous introduction of alien earthworms, from a variety of sources and introduction pathways, into many distant and often empty niches, contrasts with the classical patterns of invasions in most aboveground taxa. This suggests that earthworms, and probably other soil organisms, constitute a major but overlooked pool of invasive species that are not adequately managed by existing control and mitigation strategies.

Phenological and physiological advantages of invasive annuals are strengthened by nitrogen enrichment

Abstract Anthropogenic nitrogen (N) deposition exerts profound influence on the composition and function of native ecosystems, commonly resulting in reduced plant richness and increases in nonnative plant invasion. Identifying differences in plant N responses and functional traits could help to explain the ongoing invasion and biological impoverishment of ecosystems subject to N deposition. We compared the growth, emergence phenology and functional traits of 30 native and invasive annual plant species under high and low N availability, with the goal of evaluating if invasives exhibit functionally dissimilar responses to N compared with the native species they displace. Invasives grew larger than natives, especially under increased N availability. Overall, invasives and natives did not differ in emergence phenology. However, these groups of species differed in relationships between growth and days to emergence, and N addition further strengthened these differences; invasives consistently grew larger than natives that emerged around the same time, whereas natives showed a strong negative effect of delayed emergence on plant growth. Relative N responses for measures of plant growth and allocation did not differ between native and invasive species, but invasives exhibited greater plasticity in physiological traits. This included significantly lower leaf N content, higher CN ratios and greater water‐use efficiency (WUE) in plants grown under high N. Invasives also showed functionally different patterns of growth and water use. Across species, invasives showed a positive relationship between shoot growth and WUE. Native species showed a trade‐off between root allocation and WUE, whereas invasives displayed high values for WUE even despite reduced root: shoot ratios under high N. Our results highlight the ability of invasives to rapidly accrue biomass, disproportionately benefit from early emergence and N addition and use water efficiently despite rapid growth. Natives, on the other hand, pay a higher cost for delayed emergence and may experience trade‐offs between growth and water use. The more pronounced functional differences between natives and invasives observed under high N likely play an important role in driving invasion and reduced species diversity under N enrichment. These differences could be used to inform successful management strategies for N‐impacted and water‐limited ecosystems. Read the free Plain Language Summary for this article on the Journal blog.

A Tropical Macroalga (Halimeda incrassata) Enhances Diversity and Abundance of Epifaunal Assemblages in Mediterranean Seagrass Meadows

The introduction and successful expansion of tropical species into temperate systems is being exacerbated by climate change, and it is particularly important to identify the impacts that those species may have, especially when habitat-forming species are involved. Seagrass meadows are key shallow coastal habitats that provide critical ecosystem services worldwide, and they are threatened by the arrival of non-native macroalgae. Here, we examined the effects of Halimeda incrassata, a tropical alga that has recently colonized the Mediterranean Sea, on epifaunal assemblages associated with Cymodocea nodosa seagrass meadows of Mallorca Island (Western Mediterranean Sea). This invasive macroalga is an ecological engineer and thus has a high potential of modifying native habitats. A seagrass meadow colonized by H. incrassata exhibited important changes on associated epifaunal assemblages, with an increase in abundance and diversity, particularly driven by higher abundances of Gammaridae, Polychaeta, Copepoda and Caprellidae. Given the key ecological contribution of epifauna to food webs, these alterations will likely have important implications for overall food web structure and ecosystem functioning of native ecosystems.

Forests Without Frugivores and Frugivores Without Forests – An Investigation Into the Causes of a Paradox in One of the Last Archipelagos Colonized by Humans

The Mascarenes are sadly famous worldwide for the massive extinction of their native vertebrates since recent human colonization. However, extinction patterns show astonishing disparities between the two main islands and between lineages of forest vertebrates. On Réunion (2,512 km2, 3,070 m) where about a third of native habitats remains, most large-bodied vertebrates, especially frugivores, collapsed by the first half of the 18th century, while several have survived longer and some still exist on Mauritius (1,865 km2, 828 m) where more than 95% of native habitats have been transformed. Considering lineages of forest vertebrates shared by both islands (23 genera, 53 species), we test the hypothesis that differing patterns of lowland suitable habitat destruction is the main cause behind this paradox. Before that, we assess the potential impact of other major drivers of extinctions since first contact with humans. Firstly, Mauritius shows earlier and more numerous introductions of mammal predators known for their devastating impact (except northern islets which have thus become important sanctuaries for several squamates). Secondly, settlers were inveterate hunters on both islands, but while Réunion was overhunted before Mauritius, the burst of human population in the latter in late 18th century has not led to the rapid extinction of all large native vertebrates. These two factors alone therefore cannot explain the observed paradox. Rather, the early destruction of lowland habitats (<400 m) on Réunion is concomitant with most extinctions of forest vertebrate, notably frugivores that rapidly lost most lowland habitats dominated by large fleshy-fruited plants. Moreover, landform-induced fragmentation has likely decreased the ability of adjacent habitats to act as effective refuges. Conversely, Mauritius retained suitable low-fragmented habitats until the late 19th which probably allowed, at least for a time, several native vertebrates to escape from multiple human-induced disturbances. Despite the almost total destruction of native habitats since then on Mauritius, conservation actions have saved several threatened vertebrate species that play a fundamental role in the functioning of native ecosystems. The fact that there are now more favorable habitats on Réunion than on Mauritius argues for the rewilding of Réunion with these extant large vertebrates.

International principles and standards for the practice of ecological restoration. Second edition

Ecological restoration, when implemented effectively and sustainably, contributes to protecting biodiversity; improving human health and wellbeing; increasing food and water security; delivering goods, services, and economic prosperity; and supporting climate change mitigation, resilience, and adaptation. It is a solutions-based approach that engages communities, scientists, policymakers, and land managers to repair ecological damage and rebuild a healthier relationship between people and the rest of nature. When combined with conservation and sustainable use, ecological restoration is the link needed to move local, regional, and global environmental conditions from a state of continued degradation, to one of net positive improvement. The second edition of the International Principles and Standards for the Practice of Ecological Restoration (the Standards) presents a robust framework for restoration projects to achieve intended goals, while addressing challenges including effective design and implementation, accounting for complex ecosystem dynamics (especially in the context of climate change), and navigating trade-offs associated with land management priorities and decisions.

Avian biodiversity across Auckland’s volcanic cone reserves

ABSTRACTAuckland, a city with a population of approximately 1.7 million, is located directly on the Auckland Volcanic Field, a late Quaternary-era monogenetic field. There are at least 53 volcanoes across the field, many of which are of geological, cultural and ecological significance, such as for being reserves for native species; however, few assessments of the richness of avian biodiversity across the volcanoes have been made. To address this data shortfall, we conducted avian biodiversity surveys using stationary point counts within nine of Auckland's volcanic cone reserves. Thirty-eight species were detected across the sites, of which 18 were native. Our estimates of relative species abundances and detection probabilities revealed that the most common native birds within these reserves were silvereyes, tui and southern black-backed gulls, while common mynas, house sparrows, Eurasian blackbirds and eastern rosellas were the most common introduced species. In addition to tui and silvereyes, the presence of other natives critical to the functioning of native ecosystems, such as New Zealand fantails, grey warblers and New Zealand pigeon, suggest that the volcanoes possess a diverse native avifauna supported by native flora that warrant continued and intensified restoration efforts. We discuss several feasible strategies for improving faunal and floral biodiversity across the volcanic cone reserves. Continued avian biodiversity surveys are also of critical importance as they will enable us to further evaluate and prioritise restoration projects within Auckland's multitude of diverse volcanic cone reserves.

Soil Organic Carbon Contents and Stocks in Coastal Salt Marshes with Spartina alterniflora Following an Invasion Chronosequence in the Yellow River Delta, China

Plant invasion alters the fundamental structure and function of native ecosystems by affecting the biogeochemical pools and fluxes of materials and energy. Native (Suaeda salsa) and invasive (Spartina alterniflora) salt marshes were selected to study the effects of Spartina alterniflora invasion on soil organic carbon (SOC) contents and stocks in the Yellow River Delta. Results showed that the SOC contents (g/kg) and stocks (kg/m2) were significantly increased (P < 0.05) after Spartina alterniflora invasion of seven years, especially for the surface soil layer (0–20 cm). The SOC contents exhibited an even distribution along the soil profiles in native salt marshes, while the SOC contents were gradually decreased with depth after Spartina alterniflora invasion of seven years. The natural ln response ratios (LnRR) were applied to identify the effects of short-term Spartina alterniflora invasion on the SOC stocks. We also found that Spartina alterniflora invasion might cause soil organic carbon losses in a short-term phase (2–4 years in this study) due to the negative LnRR values, especially for 20–60 cm depth. And the SOCD in surface layer (0–20 cm) do not increase linearly with the invasive age. Spearman correlation analysis revealed that silt + clay content was exponentially related with SOC in surface layer (Adjusted R2 = 0.43, P < 0.001), suggesting that soil texture could play a key role in SOC sequestration of coastal salt marshes.

Effects ofSpartina alternifloraInvasion on the Diet of Mangrove Crabs (Parasesarma plicata) in the Zhangjiang Estuary, China

Gao, X.; Wang, M.; Wu, H.; Wang, W., and Tu, Z., 2018. Effects of Spartina alterniflora invasion on the diet of mangrove crabs (Parasesarma plicata) in the Zhangjiang Estuary, China.Spartina alterniflora, an exotic invasive plant, has become the most serious threat colonizing mangrove areas in China in the past two decades. The diets of a dominant mangrove crab, Parasesarma plicata, in two mangrove habitats (Kandelia obovata forest and Avicennia marina forest) and adjacent S. alterniflora marsh in a subtropical mangrove estuary in Fujian, China, were investigated using stable isotopes, while a feeding experiment was carried out. The results showed that in the Avicennia forest, Parasesarma was herbivorous, feeding mainly on macroalgae. In the Kandelia forest, the contribution of mangrove leaves, macroalgae, and sediment to the diet of Parasesarma were about 75.5%, 24.2%, and 0.2%, respectively. While Parasesarma had a higher δ13C value and also a higher δ15N value in the Spartina marshes relative to the two mangrove habitats, suggesting that they were feeding on Spartina detritus as well as some small invertebrates. The feeding experiment showed that the δ13C value of Parasesarma after 90-day feeding only on Spartina leaves was very close to the δ13C value of the crab caught from the Spartina marshes, indicating that Spartina was the main carbon source. These results demonstrated that the invasion of Spartina has changed the main food resources of native crabs by providing food resources, which could affect the impact of crabs as ecological engineers and eventually affect the integrity and function of native ecosystems.

A review of the impacts of major terrestrial invasive alien plants in Ireland

Invasive alien plants represent a major threat to Ireland's biodiversity and ecosystems, not only in productive or disturbed areas but also in habitats of high conservation value. With a focus on the major terrestrial invasive alien plants occurring in Ireland, we performed a systematic review of current knowledge on a wide range of environmental impacts of plant invasions. These include modifications to native or resident plant communities, alterations in the functioning of native ecosystems and associated ecosystem services, including supporting, regulating, provisioning and cultural services, as well as any positive effects. Overall, we found that rigorous quantitative assessments of the ecological impacts of these species, including comparative studies, are available for few species only and mainly focus on changes in the standing vegetation, while there is a paucity of data on how or if they contribute to alterations in the services provided by native ecosystems, even in protected areas. We conclude by highlighting the need for information on the long-term impacts of plant invasions in Ireland, including potential local, regional, or national extinctions, and the regeneration potential of native plant communities in invaded areas, which ultimately depend on the reversibility of these impacts.

Asymmetric effects of native and exotic invasive shrubs on ecology of the West Nile virus vector Culex pipiens (Diptera: Culicidae).

BackgroundExotic invasive plants alter the structure and function of native ecosystems and may influence the distribution and abundance of arthropod disease vectors by modifying habitat quality. This study investigated how invasive plants alter the ecology of Culex pipiens, an important vector of West Nile virus (WNV) in northeastern and midwestern regions of the United States.MethodsField and laboratory experiments were conducted to test the hypothesis that three native leaf species (Rubus allegheniensis, blackberry; Sambucus canadensis, elderberry; and Amelanchier laevis, serviceberry), and three exotic invasive leaf species (Lonicera maackii, Amur honeysuckle; Elaeagnus umbellata, autumn olive; and Rosa multiflora, multiflora rose) alter Cx. pipiens oviposition site selection, emergence rates, development time, and adult body size. The relative abundance of seven bacterial phyla in infusions of the six leaf species also was determined using quantitative real-time polymerase chain reaction to test the hypothesis that variation in emergence, development, and oviposition site selection is correlated to differences in the diversity and abundance of bacteria associated with different leaf species, important determinants of nutrient quality and availability for mosquito larvae.ResultsLeaf detritus from invasive honeysuckle and autumn olive yielded significantly higher adult emergence rates compared to detritus from the remaining leaf species and honeysuckle alleviated the negative effects of intraspecific competition on adult emergence. Conversely, leaves of native blackberry acted as an ecological trap, generating high oviposition but low emergence rates. Variation in bacterial flora associated with different leaf species may explain this asymmetrical production of mosquitoes: emergence rates and oviposition rates were positively correlated to bacterial abundance and diversity, respectively.ConclusionsWe conclude that the displacement of native understory plant species by certain invasive shrubs may increase production of Cx. pipiens with potential negative repercussions for human and wildlife health. These findings may be relevant to mosquito control and invasive plant management practices in the geographic range of Cx. pipiens. Further, our discovery of a previously unknown ecological trap for an important vector of WNV has the potential to lead to novel alternatives to conventional insecticides in mosquito control by exploiting the apparent “attract-kill” properties of this native plant species.

Soil biota affect mycorrhizal infection and growth ofImpatiens capensisand alter the effects ofLonicera maackiirhizosphere extracts1

Abstract Invasive plant species are one of the leading threats to the structure and function of native ecosystems. Increased attention has been given to the mechanisms that drive successful invasions, including those influencing belowground interactions between invasive and native plant species. To determine how the prominent invasive shrub Lonicera maackii (Rupr.) Herder affects a co-occurring native plant, we examined how a root/rhizosphere extract from L. maackii affected growth and mycorrhizal infection of Impatiens capensis Meerb. using epifluorescence microscopy of live roots. We also examined how the presence of a live soil microbial community influenced growth and mycorrhizal infection of I. capensis and how it the altered the effect of L. maackii extracts on these variables. In live soils, exposure to L. maackii extracts reduced mycorrhizal infection, reduced height, and slightly reduced shoot mass. In sterilized soils, exposure to L. maackii extracts slightly increased mycorrhizal infection, red...

Ecosystem function differs between Old World bluestem invaded and native coastal prairie in South Texas

Exotic Old World bluestem grasses (OWBG) are invading prairie and savanna ecosystems of the southern Great Plains USA, yet little is known about whether or how this invasion alters ecosystem processes. We conducted a study in a south Texas coastal prairie to address the following questions: (1) Does litter production, quality, decomposition rates, and soil nutrient dynamics differ significantly between areas dominated by OWBG versus native prairie?; and, (2) Does soil texture influence the effects of OWBG dominance on ecosystem processes? Ecosystem parameters were measured in adjacent patches of native and OWBG invaded coastal prairie on two soil textures, sandy loam and clay. Our findings indicate that ecosystem function differed between OWBG and native prairie dominated areas, but these results were not consistent across soil textures. On sandy loam soil, the soil microclimate differed substantially between OWBG and native prairie, and areas dominated by OWBG had higher aboveground plant production, soil organic C and total N pools, soil inorganic N concentrations and mineralization rates, and litter decomposition rates than native prairie. In contrast, on clay soils, these ecosystem properties often varied little between OWBG and native prairie. Dominance of OWBG appears to have altered native ecosystem function; yet, in this study the directionality and extent of these OWBG effects were strongly soil texture dependent, suggesting that local edaphic factors will likely interact with OWBG dominance in determining ecosystem properties. Consideration of these results may be valuable for managing OWBG such that control or restoration efforts on coarse-textured soils may be given priority over finer-textured soils.

Aumento da disponibilidade de N via deposição atmosférica e fenologia reprodutiva de Habenaria caldensis Kraenzl. (Orchidaceae) no Parque Estadual do Itacolomi (PEIT) - MG, Brasil

Ao lado do aumento da concentração de CO2, a deposição atmosférica de N é atualmente considerada um dos mais importantes fatores de alteração do funcionamento dos ecossistemas nativos, tendo já provocado drásticas mudanças na composição florística e na ciclagem de nutrientes no hemisfério norte. Entretanto, em sistemas tropicais e subtropicais, pouco se sabe sobre os efeitos do enriquecimento de N via deposição atmosférica, sobre o seu funcionamento. A compreensão da amplitude e da direção das respostas de orquídeas ao aumento da concentração de N disponível pode ajudar a alimentar modelos de dinâmica de populações rupícolas em resposta às mudanças globais. Avaliamos as respostas de floração e frutificação em plantas de Habenaria caldensis Kraenzl. (Orchidaceae), espécie de ampla distribuição em Minas Gerais, em consequência do aumento da disponibilidade de N por meio de fertilizações com nitrato de amônio, in situ, por aspersão. Em resposta à adição de N, a antese foi adiantada em cerca de 15 dias em relação aos indivíduos do grupo controle. Pelos resultados obtidos, o aumento da disponibilidade de N via deposição atmosférica pode afetar em curto prazo a ecologia de orquídeas e possivelmente outras plantas de campos rupestres alterando seus padrões fenológicos e alométricos. Em médio e longo prazos, tais modificações podem ter relevante impacto sobre a dinâmica de populações e comunidades desse tipo vegetacional.

Priority Research and Management Issues for the Imperiled Great Basin of the Western United States

Abstract Like many arid and semiarid regions, the Great Basin of the western United States is undergoing major ecological, social, and economic changes that are having widespread detrimental effects on the structure, composition, and function of native ecosystems. The causes of change are highly interactive and include urban, suburban, and exurban growth, past and present land uses, climate change, altered fire regimes, and rapid expansion of invasive species. Cumulative effects include vegetation type conversions, loss of watershed functioning, loss of native species, and diminished economic potential. The diversity and magnitude of issues require consensus on priority issues, and new and innovative research and management approaches that address larger spatial scales and longer time scales than in the past. Primary research coupled with large‐scale assessments and effective monitoring strategies is needed to understand and track the ongoing changes. Prediction and modeling of alternative futures are needed for incorporation into the planning process and use as a basis for adaptive management, and management tools are needed to aid decision‐making and implementation. Historically, research and management in arid and semiarid regions such as the Great Basin have been severely under‐funded and altering current trajectories will require financial resources, political support, and effective policies and institutional mechanisms. Sustaining the ecosystems, resources, and human populations of these regions will require strong collaborative partnerships among research and management organizations to reduce overlap, leverage funds, and increase efficiency. Close involvement of all stakeholders is needed to obtain the needed support for making necessary changes in policies and management activities.

Effects of saltmarsh invasion by Spartina alterniflora on arthropod community structure and diets

Invasive plants strongly affect physical and biotic environments of native ecosystems. Insects and other arthropods as one of the major components of many ecosystems are very sensitive to subtle changes in abiotic and biotic environments. We examined the effects of exotic Spartina alterniflora invasion on community structure and diets of arthropods in a saltmarsh previously dominated by native Phragmites australis in Yangtze River estuary through net sweeping and plant harvesting methods and stable isotope analysis. Our results showed that diversity indices were not significantly different between exotic and native plant communities, but the total abundance of insects estimated through plant harvesting method was found to be lower in Spartina monoculture than that in Phragmites monoculture. Community structure of insects in Spartina monoculture was dissimilar to that in Phragmites monoculture and Phragmites–Spartina mixture. Moreover, stable carbon isotope patterns of arthropods were significantly different between Phragmites and Spartina monocultures. Although some native arthropods (perhaps generalists) shifted their diets, many native taxa did prefer Phragmites to Spartina even in Spartina monoculture. Spartina invasions resulted in reduced abundances of some arthropds, and increased dominance of others feeding preferably on Spartina. This study provides evidence that invasive plants can change the community structure and diets of native arthropods, which will eventually alter the arthropod food web, and affect the integrity and functioning of native ecosystems within a nature reserve that has been set aside for conserving the native biodiversity and maintaining the ecosystem integrity. In this sense, Spartina invasions in the Yangtze River estuary need to be managed appropriately.

Integrating climate and trait models to predict the invasiveness of exotic plants in Canada’s Riding Mountain National Park

Invasive exotic species threaten the biodiversity and function of native ecosystems. Existing models, attempting to predict successful invaders, often emphasize isolated stages of biological invasions and fail to formalize interactions between exotic species and recipient environments. By integrating the native climatic range and biological traits of exotic vascular plants reported inside and outside Riding Mountain National Park, Manitoba, Canada, we present a model where invasion risk is predicted using the likelihood of establishment and proliferation of exotic species. Exotic vascular plants constituted 11.5% (77/669) of the total vascular flora of Riding Mountain National Park and approximately 14.2% (202/1418) of the flora of Manitoba. Based on their climatic range in Europe, 155 among 174 exotic species absent from the Park, including those found in Manitoba and other natural areas in Canada, were predicted to establish within its boundaries. Among the biological traits of exotic plants, perenniality and vegetative reproduction correctly identified 61% of documented invaders of natural areas in Canada and helped to further define a subset of 40 exotic plants with the highest potential to proliferate within the Park’s natural areas. Among these, 11 are still absent from inside its boundaries and 17 are not yet reported in Manitoba. Our results demonstrate that Riding Mountain National Park and natural areas in western Canada will continue to be impacted by exotic vascular plants. By integrating establishment and proliferation, key stages in the progress of biological invasions, our model offers a synthetic approach to the prediction and management of biological invasions inside natural areas; such integration is critical to the protection of Canada’s endemic biodiversity. Key words: Biological invasions, invasive alien plants, climate-matching model, life history, natural areas, risk assessment

REFERENCE CONDITIONS AND ECOLOGICAL RESTORATION: A SOUTHWESTERN PONDEROSA PINE PERSPECTIVE

Ecological restoration is the process of reestablishing the structure and function of native ecosystems and developing mutually beneficial human–wildland interactions that are compatible with the evolutionary history of those systems. Restoration is based on an ecosystem's reference conditions (or natural range of variability); the difference between reference conditions and contemporary conditions is used to assess the need for restorative treatments and to evaluate their success. Since ecosystems are highly complex and dynamic, it is not possible to describe comprehensively all possible attributes of reference conditions. Instead, ecosystem characteristics with essential roles in the evolutionary environment are chosen for detailed study. Key characteristics of structure, function, and disturbance—especially fire regimes in ponderosa pine ecosystems—are quantified as far as possible through dendroecological and paleoecological studies, historical evidence, and comparison to undisrupted sites. Ecological restoration treatments are designed to reverse recent, human-caused ecological degradation. Testing of restoration treatments at four sites in northern Arizona, USA, has shown promise, but the diverse context of management goals and constraints for Southwestern forest ecosystems means that appropriate applications of restoration techniques will probably differ in various settings.