Critical Ecological Functions Research Articles

Elevated ground-level O3 negatively influences paddy methanogenic archaeal community.

The current knowledge regarding the effect of global climate change on rice-paddy methane (CH4) emissions is incomplete, partly because information is limited concerning the mechanism of the microbial response to elevated ground-level ozone (O3). A field experiment was conducted in the China Ozone Free-Air Concentration Enrichment facility in a rice–wheat rotation system to investigate the responses of methanogenic archaeal communities to elevated ground-level O3 by culture-independent and -reliant approaches. We found that elevated ground-level O3 inhibited methanogenic activity and influenced the composition of paddy methanogenic communities, reducing the abundance and diversity of paddy methanogens by adversely affecting dominant groups, such as aceticlastic Methanosaeta, especially at the rice tillering stage. Our results indicated that continuously elevated ground-level O3 would negatively influence paddy methanogenic archaeal communities and its critical ecological function. These findings will contribute to a comprehensive understanding of the responses and feedbacks of paddy ecosystems to global climate change.

Key herbivores reveal limited functional redundancy on inshore coral reefs

Marine ecosystems are facing increasing exposure to a range of stressors and declines in critical ecological functions. The likelihood of further loss of functions and resilience is dependent, in part, on the extent of functional redundancy (i.e. the capacity of one species to functionally compensate for the loss of another species) within critical functional groups. We used multiple metrics; species richness, generic richness, abundance and reserve capacity (i.e. the relative number of individuals available to fulfil the function if the numerically dominant species is lost), as indicators to assess the potential functional redundancy of four functional groups of herbivorous fishes (browsers, excavators, grazers and scrapers) in two of the worlds’ most intact coral reef ecosystems: the Great Barrier Reef (GBR) and Ningaloo Reef in Western Australia. We found marked variations in potential redundancy among habitats within each reef system and functional groups. Despite negligible fishing of herbivorous fishes, coastal habitats in both reef systems had lower functional redundancy compared to offshore locations for all herbivorous fishes collectively and the four functional groups independently. This pattern was consistent in all four indicators of redundancy. The potential vulnerability of these coastal habitats is highlighted by recent shifts from coral to macroalgal dominance on several coastal reefs of the GBR. Our approach provides a simple yet revealing evaluation of potential functional redundancy. Moreover, it highlights the spatial variation in potential vulnerability and resilience of reef systems.

Tuberculosis infection in wildlife from the Ruaha ecosystem Tanzania: implications for wildlife, domestic animals, and human health

Mycobacterium bovis, a pathogen of conservation, livestock, and public health concern, was detected in eight species of wildlife inhabiting protected areas bordering endemic livestock grazing lands. We tested tissues from 179 opportunistically sampled hunter-killed, depredation, road-killed, and live-captured wild animals, representing 30 species, in and adjacent to Ruaha National Park in south-central Tanzania. Tissue culture and PCR were used to detect 12 (8.1%) M. bovis-infected animals and 15 (10.1%) animals infected with non-tuberculosis complex mycobacteria. Kirk's dik-dik, vervet monkey, and yellow baboon were confirmed infected for the first time. The M. bovis spoligotype isolated from infected wildlife was identical to local livestock, providing evidence for livestock-wildlife pathogen transmission. Thus we advocate an ecosystem-based approach for bovine tuberculosis management that improves critical ecological functions in protected areas and grazing lands, reduces focal population density build-up along the edges of protected areas, and minimizes ecological stressors that increase animals' susceptibility to bovine tuberculosis.

Comparing Aboveground Biomass Predictions for an Uneven-Aged Pine-Dominated Stand Using Local, Regional, and National Models

Sequestration by Arkansas forests removes carbon dioxide from the atmosphere, storing this carbon in biomass that fills a number of critical ecological and socioeconomic functions. We need a better understanding of the contribution of forests to the carbon cycle, including the accurate quantification of tree biomass. Models have long been developed to predict aboveground live tree biomass, but few of these have been derived from Arkansas forests. Since there is geographic variability in the growth and yield of pine as a function of genetics, site conditions, growth rate, stand stocking, and other factors, we decided to compare aboveground tree biomass estimates for a naturally regenerated, uneven-aged loblolly pine (Pinus taeda)-dominated stand on the Crossett Experimental Forest (CEF) in southeastern Arkansas. These predictions were made using a new locally derived biomass equation, five regional biomass equations, and the pine model from the National Biomass Estimators. With the local model as the baseline, considerable biomass variation appeared across a range of diameters—at the greatest diameter considered, the minimum value was only 69% of the maximum. Using a recent inventory from the CEF’s Good Farm Forty to compare each model, stand-level biomass estimates ranged from a low of 76.9 Mg/ha (a different Arkansas model) to as much as 96.1 Mg/ha (an Alabama model); the local CEF equation predicted 82.5 Mg/ha. A number of different factors contributed to this variability, including differences in model form and derivation procedures, geographic origins, and utilization standards. Regardless of the source of the departures, their magnitude suggests that care be used when making large-scale biomass estimates.

Interacting Factors Driving a Major Loss of Large Trees with Cavities in a Forest Ecosystem

Large trees with cavities provide critical ecological functions in forests worldwide, including vital nesting and denning resources for many species. However, many ecosystems are experiencing increasingly rapid loss of large trees or a failure to recruit new large trees or both. We quantify this problem in a globally iconic ecosystem in southeastern Australia – forests dominated by the world's tallest angiosperms, Mountain Ash (Eucalyptus regnans). Tree, stand and landscape-level factors influencing the death and collapse of large living cavity trees and the decay and collapse of dead trees with cavities are documented using a suite of long-term datasets gathered between 1983 and 2011. The historical rate of tree mortality on unburned sites between 1997 and 2011 was >14% with a mortality spike in the driest period (2006–2009). Following a major wildfire in 2009, 79% of large living trees with cavities died and 57–100% of large dead trees were destroyed on burned sites. Repeated measurements between 1997 and 2011 revealed no recruitment of any new large trees with cavities on any of our unburned or burned sites. Transition probability matrices of large trees with cavities through increasingly decayed condition states projects a severe shortage of large trees with cavities by 2039 that will continue until at least 2067. This large cavity tree crisis in Mountain Ash forests is a product of: (1) the prolonged time required (>120 years) for initiation of cavities; and (2) repeated past wildfires and widespread logging operations. These latter factors have resulted in all landscapes being dominated by stands ≤72 years and just 1.16% of forest being unburned and unlogged. We discuss how the features that make Mountain Ash forests vulnerable to a decline in large tree abundance are shared with many forest types worldwide.

Predicaments and Protective Actions of Giant Panda Habitat of Baoxing County in Sichuan Province, China

The giant panda habitat of Baoxing County, located in the transition zone from Sichuan Basin to the edge of southeastern Qinghai-Tibet Plateau, is the critical and key ecological function areas. At present, the puzzled problems present that the whole ecological system was interrupted by ecological management from different local department policy and the long merits for protecting giant habitat was weaken by short-term economic profits from natural resources. Exploring marbles and constructing hydropower plants and the livelihood activities of residents in the world heritage protection zone threatened to the protection for giant panda habitats. The government and people have taken a series of measures in recent years to deal with conflict: setting up nature reserves, establishing ecological protection projects, speeding up adjustment of industrial structure and international cooperation. The development practice of Baoxing County over the years shows that it is a sustainable and effective measure to grow economy while simultaneously protecting the giant panda habitats through Integrated Ecosystem Management (IEM). However, giant panda protection is destined a protracted battle in economy development process.

Global Monthly Water Scarcity: Blue Water Footprints versus Blue Water Availability

Freshwater scarcity is a growing concern, placing considerable importance on the accuracy of indicators used to characterize and map water scarcity worldwide. We improve upon past efforts by using estimates of blue water footprints (consumptive use of ground- and surface water flows) rather than water withdrawals, accounting for the flows needed to sustain critical ecological functions and by considering monthly rather than annual values. We analyzed 405 river basins for the period 1996–2005. In 201 basins with 2.67 billion inhabitants there was severe water scarcity during at least one month of the year. The ecological and economic consequences of increasing degrees of water scarcity – as evidenced by the Rio Grande (Rio Bravo), Indus, and Murray-Darling River Basins – can include complete desiccation during dry seasons, decimation of aquatic biodiversity, and substantial economic disruption.

Marine Viruses: Truth or Dare

Over the past two decades, marine virology has progressed from a curiosity to an intensely studied topic of critical importance to oceanography. At concentrations of approximately 10 million viruses per milliliter of surface seawater, viruses are the most abundant biological entities in the oceans. The majority of these viruses are phages (viruses that infect bacteria). Through lysing their bacterial hosts, marine phages control bacterial abundance, affect community composition, and impact global biogeochemical cycles. In addition, phages influence their hosts through selection for resistance, horizontal gene transfer, and manipulation of bacterial metabolism. Recent work has also demonstrated that marine phages are extremely diverse and can carry a variety of auxiliary metabolic genes encoding critical ecological functions. This review is structured as a scientific "truth or dare," revealing several well-established "truths" about marine viruses and presenting a few "dares" for the research community to undertake in future studies.

An appraisal of management pathologies in the Great Lakes

Recent research has produced broad application of the health concept to regional ecosystems, including the Great Lakes. The attention is warranted, as new and recurring stresses on the health of the Great Lakes undermine our understanding and hinder our ability to manage and restore critical ecological functions. There is widespread agreement that the Great Lakes are presently exhibiting symptoms of extreme stress and potentially irreversible and catastrophic damage. Historical command and control management has resulted simultaneously in environmental benefits to people and a loss of resilience in Great Lakes ecosystems. Surprising system responses often prompt further control, and the continued decline in resilience has been called the pathology of natural resource management. The pathology is also suggested to affect human systems of organization such as management authorities. We use published criteria of institutional pathologies and illustrate their occurrence in the Great Lakes with evidence of non-existent program evaluation, program incompatibility, lack of coordination among programs, authorities that establish and then abandon public participatory initiatives, and inappropriate choice of policy mechanisms or inadequate level of support for an appropriate mechanism (either of which creates disincentives for stakeholders). Learning is an element of resilience, as managed systems are inherently dynamic and our understanding is therefore always incomplete. Policy mechanisms that mimic learning techniques to improve understanding are therefore central to avoiding pathologies in management. But learning (individually or institutionally) can be threatening and very difficult, and its proper conduct necessarily involves a continuous process of feedback, interpretation, and reformulation. Double-loop learning processes that institutionalize learning in policy are recommended, as these will be required to overcome pathologies in management and maintain resilience of the Great Lakes system.

Thinking and managing outside the box: coalescing connectivity networks to build region-wide resilience in coral reef ecosystems

As the science of connectivity evolves, so too must the management of coral reefs. It is now clear that the spatial scale of disturbances to coral reef ecosystems is larger and the scale of larval connectivity is smaller than previously thought. This poses a challenge to the current focus of coral reef management, which often centers on the establishment of no-take reserves (NTRs) that in practice are often too small, scattered, or have low stakeholder compliance. Fished species are generally larger and more abundant in protected reserves, where their reproductive potential is often greater, yet documented demographic benefits of these reproductive gains outside reserves are modest at best. Small reproductive populations and limited dispersal of larvae play a role, as does the diminished receptivity to settling larvae of degraded habitats that can limit recruitment by more than 50%. For “demographic connectivity” to contribute to the resilience of coral reefs, it must function beyond the box of no-take reserves. Specifically, it must improve nursery habitats on or near reefs and enhance the reproductive output of ecologically important species throughout coral reef ecosystems. Special protection of ecologically important species (e.g., some herbivores in the Caribbean) and size-regulated fisheries that capitalize on the benefits of NTRs and maintain critical ecological functions are examples of measures that coalesce marine reserve effects and improve the resilience of coral reef ecosystems. Important too is the necessity of local involvement in the management process so that social costs and benefits are properly assessed, compliance increased and success stories accrued.

Landscape responses to wetland eutrophication: loss of slough habitat in the Florida Everglades, USA

Much of the historical Everglades has been either lost or degraded as a result of human activities. Among the aquatic habitats that comprise the Everglades landscape mosaic, open-water sloughs support critical ecological functions and appear especially sensitive to both hydrologic and water-quality perturbations. We used a combination of remote sensing and on-the-ground sampling to document spatial changes in the extent and vegetative composition of sloughs along a phosphorus (P) gradient in the northern Everglades. Increasing levels of water and soil P were associated with a decline in slough coverage, loss of the abundant native periphyton community, and a shift in dominant macrophyte species. The characteristic slough macrophyte species Eleocharis cellulosa and Nymphaea odorata exhibited different sensitivities to P enrichment, but both species declined with enrichment as slough habitats were invaded by Typha domingensis, a species that is known to expand aggressively in response to enrichment. A limited amount of open-water habitat occurred in highly enriched areas, but these habitats were maintained largely as a result of airboat disturbance and did not contain characteristic slough vegetation. Many changes in slough coverage and composition occurred in areas where water and soil P concentrations were only marginally higher than background levels. Our findings support the need for Everglades hydrologic restoration efforts to adhere to strict water-quality standards for P to avoid further degradation of this key landscape feature.

A watershed approach to upgrade rainfed agriculture in water scarce regions through Water System Innovations: an integrated research initiative on water for food and rural livelihoods in balance with ecosystem functions

The challenge of producing food for a rapidly increasing population in semi-arid agro-ecosystems in Southern Africa is daunting. More food necessarily means more consumptive use of so-called green water flow (vapour flow sustaining crop growth). Every increase in food production upstream in a watershed will impact on water user and using systems downstream. Intensifying agriculture has in the past often been carried out with negative side effects in terms of land and water degradation. Water legislation is increasingly incorporating the requirement to safeguard a water reserve to sustain instream ecology. To address the challenges of increasing food production, improving rural livelihoods, while safeguarding critical ecological functions, a research programme has recently been launched on “Smallholder System Innovations in Integrated Watershed Management” (SSI). The programme takes an integrated approach to agricultural water management, analysing the interactions between the adoption and participatory adaptation of water system innovations (such as water harvesting, drip irrigation, conservation farming, etc.), increased water use in agriculture and water flows to sustain ecological functions that deliver critical ecosystem services to humans. The research is carried out in the Pangani Basin in Tanzania and the Thukela Basin in South Africa. A nested scale approach is adopted, which will enable the analysis of scale interactions between water management at the farm level, and cascading hydrological impacts at watershed and basin scale. This paper describes the integrated research approach of the SSI programme, and indicates areas of potential to upgrade rainfed agriculture in water scarcity-prone agro-ecosystems while securing water for downstream use.

Climate change impacts on freshwater wetland habitats

Wetland ecosystems are important habitats for flora and fauna and hence are of national and international importance for conservation. Wetlands can be defined as areas of high groundwater environments that are characterised by permanent (shallow water bodies) or temporary inundation, or soils having hydric properties. They provide a number of critical ecological functions, including the regulation of water regimes, and support a significant percentage of the world's biodiversity that have adapted to life in saturated conditions. Wetland ecosystems depend on water levels and therefore climate change, especially changes in precipitation, is likely to have a significant impact on these habitats and associated species. A modelling assessment of water balance was undertaken for the UK and Ireland using current and future climate scenarios. Results showed that water availability could increase in winter across the whole region, and northwest Ireland and northwest Scotland could have a small increase in water availability in the summer. Other regions would experience little change or have decreased water availability during the summer months; this being most severe in southeast England. A local-scale study of a wetland habitat in East Anglia indicated that significant seasonal stresses could occur due to climate change and the associated lowering of water levels.

FUNCTIONAL VARIABILITY OF HABITATS WITHIN THE SACRAMENTO–SAN JOAQUIN DELTA: RESTORATION IMPLICATIONS

We have now entered an era of large-scale attempts to restore ecological functions and biological communities in impaired ecosystems. Our knowledge base of complex ecosystems and interrelated functions is limited, so the outcomes of specific restoration actions are highly uncertain. One approach for exploring that uncertainty and anticipating the range of possible restoration outcomes is comparative study of existing habitats similar to future habitats slated for construction. Here we compare two examples of one habitat type targeted for restoration in the Sacramento–San Joaquin River Delta. We compare one critical ecological function provided by these shallow tidal habitats—production and distribution of phytoplankton biomass as the food supply to pelagic consumers. We measured spatial and short-term temporal variability of phytoplankton biomass and growth rate and quantified the hydrodynamic and biological processes governing that variability. Results show that the production and distribution of phytopl...

Declining Woody Vegetation in Riparian Ecosystems of the Western United States

Abstract Riparian ecosystems serve critical ecological functions in western landscapes. The woody plant components in many of these keystone systems are in serious decline. Among the causes are invasion by exotic species, stress-induced mortality, increases in insect and disease attack, drought, beaver, fire, climatic changes, and various anthropogenic activities. The latter include agricultural development, groundwater depletion, dam construction, water diversion, gravel mining, timber harvesting, recreation, urbanization, and grazing. This article examines the factors implicated in the decline and discusses the importance of interactions among these factors in causing decline. It also clarifies issues that need to be addressed in order to restore and maintain sustainable riparian ecosystems in the western United States, including the function of vegetation, silvics of the woody plant species involved, hydrologic condition, riparian zone structure, and landscape features, geomorphology, and management objectives. West. J. Appl. For. 16(4):169-181.