Showing papers in "Ecological Applications in 2000"

Biotic invasions: causes, epidemiology, global consequences, and control

Abstract: Biotic invaders are species that establish a new range in which they proliferate, spread, and persist to the detriment of the environment. They are the most important ecological outcomes from the unprecedented alterations in the distribution of the earth's biota brought about largely through human transport and commerce. In a world without borders, few if any areas remain sheltered from these im- migrations. The fate of immigrants is decidedly mixed. Few survive the hazards of chronic and stochastic forces, and only a small fraction become naturalized. In turn, some naturalized species do become invasive. There are several potential reasons why some immigrant species prosper: some escape from the constraints of their native predators or parasites; others are aided by human-caused disturbance that disrupts native communities. Ironically, many biotic invasions are apparently facilitated by cultivation and husbandry, unintentional actions that foster immigrant populations until they are self-perpetuating and uncontrollable. Whatever the cause, biotic invaders can in many cases inflict enormous environmental damage: (1) Animal invaders can cause extinctions of vulnerable native species through predation, grazing, competition, and habitat alteration. (2) Plant invaders can completely alter the fire regime, nutrient cycling, hydrology, and energy budgets in a native ecosystem and can greatly diminish the abundance or survival of native species. (3) In agriculture, the principal pests of temperate crops are nonindigenous, and the combined expenses of pest control and crop losses constitute an onerous "tax" on food, fiber, and forage production. (4) The global cost of virulent plant and animal diseases caused by parasites transported to new ranges and presented with susceptible new hosts is currently incalculable. Identifying future invaders and taking effective steps to prevent their dispersal and establishment con- stitutes an enormous challenge to both conservation and international commerce. Detection and management when exclusion fails have proved daunting for varied reasons: (1) Efforts to identify general attributes of future invaders have often been inconclusive. (2) Predicting susceptible locales for future invasions seems even more problematic, given the enormous differences in the rates of arrival among potential invaders. (3) Eradication of an established invader is rare, and control efforts vary enormously in their efficacy. Successful control, however, depends more on commitment and continuing diligence than on the efficacy of specific tools themselves. (4) Control of biotic invasions is most effective when it employs a long-term, ecosystem- wide strategy rather than a tactical approach focused on battling individual invaders. (5) Prevention of invasions is much less costly than post-entry control. Revamping national and international quarantine laws by adopting a "guilty until proven innocent" approach would be a productive first step. Failure to address the issue of biotic invasions could effectively result in severe global consequences, including wholesale loss of agricultural, forestry, and fishery resources in some regions, disruption of the ecological processes that supply natural services on which human enterprise depends, and the creation of homogeneous, impoverished ecosystems composed of cosmopolitan species. Given their current scale, biotic invasions have taken their place alongside human-driven atmospheric and oceanic alterations as major agents of global change. Left unchecked, they will influence these other forces in profound but still unpredictable ways.

The vertical distribution of soil organic carbon and its relation to climate and vegetation

Abstract: As the largest pool of terrestrial organic carbon, soils interact strongly with atmospheric composition, climate, and land cover change. Our capacity to predict and ameliorate the consequences of global change depends in part on a better understanding of the distributions and controls of soil organic carbon (SOC) and how vegetation change may affect SOC distributions with depth. The goals of this paper are (1) to examine the association of SOC content with climate and soil texture at different soil depths; (2) to test the hypothesis that vegetation type, through patterns of allocation, is a dominant control on the vertical distribution of SOC; and (3) to estimate global SOC storage to 3 m, including an analysis of the potential effects of vegetation change on soil carbon storage. We based our analysis on .2700 soil profiles in three global databases supplemented with data for climate, vegetation, and land use. The analysis focused on mineral soil layers. Plant functional types significantly affected the vertical distribution of SOC. The per- centage of SOC in the top 20 cm (relative to the first meter) averaged 33%, 42%, and 50% for shrublands, grasslands, and forests, respectively. In shrublands, the amount of SOC in the second and third meters was 77% of that in the first meter; in forests and grasslands, the totals were 56% and 43%, respectively. Globally, the relative distribution of SOC with depth had a slightly stronger association with vegetation than with climate, but the opposite was true for the absolute amount of SOC. Total SOC content increased with precipitation and clay content and decreased with temperature. The importance of these controls switched with depth, climate dominating in shallow layers and clay content dominating in deeper layers, possibly due to increasing percentages of slowly cycling SOC fractions at depth. To control for the effects of climate on vegetation, we grouped soils within climatic ranges and compared distributions for vegetation types within each range. The percentage of SOC in the top 20 cm relative to the first meter varied from 29% in cold arid shrublands to 57% in cold humid forests and, for a given climate, was always deepest in shrublands, inter- mediate in grasslands, and shallowest in forests ( P , 0.05 in all cases). The effect of vegetation type was more important than the direct effect of precipitation in this analysis. These data suggest that shoot/root allocations combined with vertical root distributions, affect the distribution of SOC with depth. Global SOC storage in the to p3mo fsoil was 2344 Pg C, or 56% more than the 1502 Pg estimated for the first meter (which is similar to the total SOC estimates of 1500-1600 Pg made by other researchers). Global totals for the second and third meters were 491 and 351 Pg C, and the biomes with the most SOC at 1-3 m depth were tropical evergreen forests (158 Pg C) and tropical grasslands/savannas (146 Pg C). Our work suggests that plant functional types, through differences in allocation, help to control SOC distributions with depth in the soil. Our analysis also highlights the potential importance of vegetation change and SOC pools for carbon sequestration strategies.

Rediscovery of traditional ecological knowledge as adaptive management

Abstract: Indigenous groups offer alternative knowledge and perspectives based on their own locally developed practices of resource use. We surveyed the international literature to focus on the role of Traditional Ecological Knowledge in monitoring, responding to, and managing ecosystem processes and functions, with special attention to ecological resilience. Case studies revealed that there exists a diversity of local or traditional practices for ecosystem management. These include multiple species management, resource rotation, succession management, landscape patchiness management, and other ways of responding to and managing pulses and ecological surprises. Social mechanisms behind these traditional practices include a number of adaptations for the generation, accumulation, and transmission of knowledge; the use of local institutions to provide leaders/stewards and rules for social regulation; mechanisms for cultural internalization of traditional practices; and the development of appropriate world views and cultural values. Some traditional knowledge and management systems were characterized by the use of local ecological knowledge to interpret and respond to feedbacks from the environment to guide the direction of resource management. These traditional systems had certain similarities to adaptive management with its emphasis on feedback learning, and its treatment of uncertainty and unpredictability intrinsic to all ecosystems.

Using traditional ecological knowledge in science: methods and applications

Abstract: Advocates of Traditional Ecological Knowledge (TEK) have promoted its use in scientific research, impact assessment, and ecological understanding. While several examples illustrate the utility of applying TEK in these contexts, wider application of TEK- derived information remains elusive. In part, this is due to continued inertia in favor of established scientific practices and the need to describe TEK in Western scientific terms. In part, it is also due to the difficulty of accessing TEK, which is rarely written down and must in most cases be documented as a project on its own prior to its incorporation into another scientific undertaking. This formidable practical obstacle is exacerbated by the need to use social science methods to gather biological data, so that TEK research and application becomes a multidisciplinary undertaking. By examining case studies involving bowhead whales, beluga whales, and herring, this paper describes some of the benefits of using TEK in scientific and management contexts. It also reviews some of the methods that are available to do so, including semi-directive interviews, questionnaires, facilitated workshops, and collaborative field projects.

Age of soil organic matter and soil respiration: radiocarbon constraints on belowground c dynamics

Abstract: Radiocarbon data from soil organic matter and soil respiration provide pow- erful constraints for determining carbon dynamics and thereby the magnitude and timing of soil carbon response to global change. In this paper, data from three sites representing well-drained soils in boreal, temperate, and tropical forests are used to illustrate the methods for using radiocarbon to determine the turnover times of soil organic matter and to partition soil respiration. For these sites, the average age of bulk carbon in detrital and Oh/A-horizon organic carbon ranges from 200 to 1200 yr. In each case, this mass-weighted average includes components such as relatively undecomposed leaf, root, and moss litter with much shorter turnover times, and humified or mineral-associated organic matter with much longer turnover times. The average age of carbon in organic matter is greater than the average age predicted for CO2 produced by its decomposition (30, 8, and 3 yr for boreal, temperate, and tropical soil), or measured in total soil respiration (16, 3, and 1 yr). Most of the CO 2 produced during decomposition is derived from relatively short-lived soil organic matter (SOM) components that do not represent a large component of the standing stock of soil organic matter. Estimates of soil carbon turnover obtained by dividing C stocks by hetero- trophic respiration fluxes, or from radiocarbon measurements of bulk SOM, are biased to longer time scales of C cycling. Failure to account for the heterogeneity of soil organic matter will result in underestimation of the short-term response and overestimation of the long-term response of soil C storage to future changes in inputs or decomposition. Comparison of the 14 C in soil respiration with soil organic matter in temperate and boreal forest sites indicates a significant contribution from decomposition of organic matter fixed.2 yr but ,30 yr ago. Tropical soil respiration is dominated by C fixed ,1 yr ago. Monitoring the 14 C signature of CO2 emitted from soils give clues as to the causes of

Carbon isotope ratios in belowground carbon cycle processes

Abstract: Analyses of carbon isotope ratios (δ13C) in soil organic matter (SOM) and soil respired CO2 provide insights into dynamics of the carbon cycle. δ13C analyses do not provide direct measures of soil CO2 efflux rates but are useful as a constraint in carbon cycle models. In many cases, δ13C analyses allow the identification of components of soil CO2 efflux as well as the relative contribution of soil to overall ecosystem CO2 fluxes. δ13C values provide a unique tool for quantifying historical shifts between C3 and C4 ecosystems over decadal to millennial time scales, which are relevant to climate change and land-use change issues. We identify the need to distinguish between δ13C analyses of SOM and those of soil CO2 efflux in carbon cycle studies, because time lags in the turnover rates of different soil carbon components can result in fluxes and stocks that differ in isotopic composition (disequilibrium effect). We suggest that the frequently observed progressive δ13C enrichment of SOM may be related to a g...

Entering an era of water scarcity: the challenges ahead.

Abstract: Fresh water is a renewable resource, but it is also finite. Around the world, there are now numerous signs that human water use exceeds sustainable levels. Groundwater depletion, low or nonexistent river flows, and worsening pollution levels are among the more obvious indicators of water stress. In many areas, extracting more water for human uses jeopardizes the health of vital aquatic ecosystems. Satisfying the increased demands for food, water, and material goods of a growing global population while at the same time protecting the ecological services provided by natural water ecosystems requires new ap- proaches to using and managing fresh water. In this article, I propose a global effort (1) to ensure that freshwater ecosystems receive the quantity, quality, and timing of flows needed for them to perform their ecological functions and (2) to work toward a goal of doubling water productivity. Meeting these challenges will require policies that promote rather than discourage water efficiency, as well as new partnerships that cross disciplinary and professional boundaries.

Ecological Principles and Guidelines for Managing the Use of Land

Abstract: Decision-making levels in the United States and examples of their land-use management powers, both regulatory and nonregulatory (Dale et al, 2000, Reproduced with permission of Ecological Society of America, Redraivn by Travis Witt, 2014).

Traditional ecological knowledge and wisdom of aboriginal peoples in british columbia

Abstract: This paper discusses the characteristics and application of Traditional Eco- logical Knowledge and Wisdom (TEKW) of aboriginal peoples in British Columbia, Canada. Examples are provided from various groups, most notably, the Secwepemc (Shuswap) Interior Salish and Kwakwaka'wakw and Nuu-Chah-Nulth peoples of the Northwest Coast, covering a range of features comprising TEKW: knowledge of ecological principles, such as succession and interrelatedness of all components of the environment; use of ecological indicators; adaptive strategies for monitoring, enhancing, and sustainably harvesting re- sources; effective systems of knowledge acquisition and transfer; respectful and interactive attitudes and philosophies; close identification with ancestral lands; and beliefs that rec- ognize the power and spirituality of nature. These characteristics, taken in totality, have enabled many groups of aboriginal peoples to live sustainably within their local environ- ments for many thousands of years. In order for TEKW to be incorporated appropriately into current ecosystem-based management strategies, the complete context of TEKW, in- cluding its philosophical bases, must be recognized and respected. A case study of ecological and cultural knowledge of the traditional root vegetables yellow avalanche lily (Erythronium grandiflorum) and balsamroot (Balsamorhiza sagittata) illustrates ways in which these components can be integrated.

Spillover of exploitable fishes from a marine park and its effect on the adjacent fishery

Abstract: The role of a marine protected area in enhancing local fisheries, through the emigration or spillover of exploitable fishes, was studied in a coral reef park (Mombasa Marine Park, Kenya) and fishery over a seven-year period during a time when the park's border changed and pull seines were eliminated. We measured catches before and after the park's establishment and during the management changes and compared these catches with the unmanaged side of the park. Additionally, we placed baited traps on both sides of the park over a full tidal cycle which allowed us to measure the spillover from the park compared to the deeper, rougher, and less fished reef edge. The total wet mass of catches per trap, the mean size of the trapped fish, and the number of fish species caught per trap declined as a function of the distance away from the park edge on both the southern and northern sides. However, this relationship was truncated on the unmanaged side which also had smaller catches, smaller fish, and fewer species th...

Biosphere responses to CO2 enrichment.

Abstract: Atmospheric changes such as elevated CO2 are of global extent, exert prime influences in the remaining wilderness areas, and are second in importance only to effects of land use on ecosystems in most parts of the world. This study is an attempt to summarize, from a biological viewpoint, knowledge of the influences of atmospheric CO2 enrichment on terrestrial ecosystems, as derived from empirical data. I first briefly recall key aspects of the global carbon cycle, mention important conceptual aspects and research tools, and then discuss in greater depth how elevated CO2 is likely to affect vegetation processes. Besides a stimulation of photosynthesis, the most robust findings on plant responses to elevated CO2 are changes in active tissue quality (wider C/N ratio) and effects on community dynamics. Results of experimental work offer a number of plausible projections with respect to future ecosystem processes and organismic interactions, but manipulative experiments appear unsuitable to prove or disprove C sequestration by terrestrial ecosystems. In certain regions, consequences of climatic changes and soluble-nitrogen deposition are likely to be greater than direct CO2 effects on the carbon balance of vegetation. The significance of the ecosystem approach, the use of fully coupled plant–soil systems, and the consideration of nonlinear responses are highlighted. The current understanding of the CO2 problem offers sufficient justification to urge measures for moderating human forcing of atmospheric change.

Climatic and human influences on fire regimes in ponderosa pine forests in the Colorado Front Range.

Abstract: In the northern Colorado Front Range, fire suppression during the 20th cen- tury is believed to have created a high hazard of catastrophic fire in ponderosa.pine (Pinus ponderosa) forests. Since the early 1990s, resource managers have increased the use of prescribed fires to re-create fire regimes and forest structures similar to those of the pre- Euro-American settlement period in order both to reduce fire hazard and to improve forest health. To improve understanding of historical fire regimes, we conducted a study of fire history along an elevational gradient from -1830 to 2800 m in ponderosa pine forests in the northern Front Range. Fire-scar dates were determined from 525 partial cross sections from living and dead trees at 41 sample sites. Fire frequencies and fire intervals were analyzed in relation to changes in human activities and interannual climatic variability as recorded in instrumental climatic records and tree-ring proxy records. Prior to modern fire suppression, the low elevation, open ponderosa pine forests of the northern Front Range were characterized by frequent surface fires, similar in frequency to many other ponderosa pine ecosystems in the West. In contrast, in higher elevation forests (above -2400 m) where ponderosa pine is mixed with Douglas-fir (Pseudotsuga menziesii) and lodgepole pine (Pinus contorta), the fire regime was characterized by a much lower fire frequency and included extensive stand-replacing fires as well as surface fires. In the mid-1800s there was a marked increase in fire occurrence that can be related both to Euro- American settlement and increased climatic variability. This episode of increased fire left a legacy of dense, even-aged stands in higher elevation ponderosa pine forests, whereas increased stand densities in low elevation forests are attributed mainly to fire exclusion during the 20th century. Warmer and drier spring-summers, indicated in instrumental climatic records (1873- 1995) and in tree-ring proxy records of climate (1600-1983), are strongly associated with years of widespread fire. Years of widespread fire also tend to be preceded two to four years by wetter than average springs that increase the production of fine fuels. Alternation of wet and dry periods over time periods of 2-5 years is conducive to fire spread and is strongly linked to El Niiio-Southern Oscillation (ENSO) events. The warm (El Niiio) phase of ENSO is associated with greater moisture availability during spring that results in a peak of fire occurrence several years following El Ninlo events. Conversely, dry springs associated with La Nifia events were followed by more widespread fire during the same year. The 1600-1920 fire-scar record indicates that individual years during which high per- centages of the 41 sample sites synchronously recorded fire have occurred at least several times per century. The association of these years of widespread fire with very strong ENSO events demonstrates the importance of ENSO-related climatic variabililty in creating ex- treme fire hazard at a landscape scale.

Effect of human development on bacteriological water quality in coastal watersheds

Abstract: Human development along the land–seawater interface is considered to have significant environmental consequences. Development can also pose an increased human health risk. In a rapidly developing coastal region we investigated this phenomenon throughout a series of five estuarine watersheds, each of which differed in both the amount and type of anthropogenic development. Over a four-year period we analyzed the abundance and distribution of the enteric pathogen indicator microbes, fecal coliform bacteria and Escherichia coli. We also examined how these indicator microbes were related to physical and chemical water quality parameters and to demographic and land use factors throughout this system of coastal creeks. Within all creeks, there was a spatial pattern of decreasing enteric bacteria away from upstream areas, and both fecal coliform and E. coli abundance were inversely correlated with salinity. Turbidity was positively correlated with enteric bacterial abundance. Enteric bacterial abundance was strongly correlated with nitrate and weakly correlated with orthophosphate concentrations. Neither fecal coliforms nor E. coli displayed consistent temporal abundance patterns. Regardless of salinity, average estuarine fecal coliform abundance differed greatly among the five systems. An analysis of demographic and land use factors demonstrated that fecal coliform abundance was significantly correlated with watershed population, and even more strongly correlated with the percentage of developed land within the watershed. However, the most important anthropogenic factor associated with fecal coliform abundance was percentage watershed-impervious surface coverage, which consists of roofs, roads, driveways, sidewalks, and parking lots. These surfaces serve to concentrate and convey storm-water-borne pollutants to downstream receiving waters. Linear regression analysis indicated that percentage watershed-impervious surface area alone could explain 95% of the variability in average estuarine fecal coliform abundance. Thus, in urbanizing coastal areas waterborne health risks can likely be reduced by environmentally sound land use planning and development that minimizes the use of impervious surface area, while maximizing the passive water treatment function of natural and constructed wetlands, grassy swales, and other “green” areas. The watershed approach used in our study demonstrates that the land–water interface is not restricted to obvious shoreline areas, but is influenced by and connected with landscape factors throughout the watershed.

Estimating animal abundance using noninvasive dna sampling: promise and pitfalls

Abstract: Advances in molecular biology offer promise to the study of demographic characteristics of rare or hard-to-capture species, because individuals can now be identified through noninvasive sampling such as fecal collection or hair snags. However, individual genotyping using such methods currently leads to a novel problem that we call a ''shadow effect,'' because some animals not captured previously are believed to be recaptures due to their DNA profile being an indistinguishable shadow of previously captured animals. We evaluate the impact of the shadow effect on the two methods most commonly used in applied population ecology to estimate the size of closed populations: Lincoln-Petersen and multiple-recapture estimators in program CAPTURE. We find that the shadow effect can cause a negative bias in the estimates of both the number of different animals and the number of different genotypes. Furthermore, with Lincoln-Petersen estimators, the shadow effect can cause estimated confidence intervals to decrease even as bias increases. Because the bias arises from heterogeneity in apparent ''capture'' probabilities for animals with genetic shadows vs. those without, a model in program CAPTURE that is robust to capture heterogeneity (M h-jackknife) does not underestimate the number of genotypes in the population and only slightly underestimates the total number of individuals. As the shadow effect increases, CAPTURE is better able to correctly identify heterogeneity in capture probability and to pick Mh-jackknife, so that the higher levels of shadow effect have less bias than medium levels. The shadow effect will occur in all estimates of demographic rates (including sur- vival) that use DNA sampling to determine individual identity, but it can be minimized by increasing the number of individual loci sampled.

Development and evaluation of predictive models for measuring the biological integrity of streams

Abstract: The ratio of the number of observed taxa to that expected to occur in the absence of human-caused stress (OIE) is an intuitive and ecologically meaningful measure of biological integrity. We examined how OIE ratios derived from stream invertebrate data varied among 234 unimpaired reference sites and 254 test sites potentially impaired by past logging. Data were collected from streams in three montane ecoregions in California. Two sets of River Invertebrate Prediction and Classification System (RIVPACS) predictive mod- els were built: one set of models was based on near-species taxonomic resolution; the other was based on family identifications. Two models were built for each level of taxonomic resolution: one calculated 0 and E based on all taxa with probabilities of capture (Pj) > 0; the other calculated 0 and E based on only those taxa with Pc ? 0.5. Evaluations of the performance of each model were based on three criteria: (1) how well models predicted the taxa found at unimpaired sites, (2) the degree to which OIE values differed among unimpaired reference sites and potentially impaired test sites, and (3) the degree to which test site OIE values were correlated with independent measures of watershed alteration. Predictions of species models were more accurate than those of family models, and pre- dictions of the PC ? 0.5 species model were more robust than predictions of the PC > 0 model. OIE values derived from both species models were related to land use variables, but only assessments based on the Pc > 0.5 model were insensitive to naturally occurring differences among streams, ecoregions, and years.

Arthropods in urban habitat fragments in southern California: Area, age, and edge effects

Abstract: The distribution of non-ant arthropods was examined in 40 urban habitat fragments in coastal San Diego County, California, USA, to look for effects of fragmen- tation, proximity to developed edge, and the non-native Argentine ant (Linepithema humile). Arthropods were sampled with pitfall traps and by vacuum sampling from California buck- wheat shrubs (Eriogonumfasciculatum). Individual arthropods were identified to order and Recognizable Taxonomic Unit (RTU), or morphospecies. At the fragment scale we looked for correlations in the point diversity and abundance of arthropods as a function of the age and area of the fragment being sampled. At the scale of the individual sample points we looked for correlations of abundance and diversity with variables that describe the species composition of the shrub vegetation and disturbance. As indicators of disturbance we used the cover of native woody and exotic non-woody vegetation, the distance to the nearest developed edge, and the abundance of Argentine ants. The following patterns were found: (1) In general, arthropods showed a fragmentation effect with point diversity and abundance positively correlated with fragment area and negatively correlated with fragment age. (2) The pitfall samples were dominated by three primarily non-native orders, Isopoda (pillbugs), Dermaptera (earwigs), and Blattaria (roaches). Over 35% of all pitfall-captured arthropods belonged to four species in these orders. Dermaptera and Blattaria increased in abundance in smaller and older fragments, respectively. Isopod abundance, in contrast, was unrelated to fragment attributes. None of these groups appeared to be associated with edges, but were distributed throughout the fragments. (3) Point diversity and abundance in ground-active spiders appears to be enhanced by fragmentation. (4) Total pitfall RTU richness and abun- dance, and abundance or richness in the Coleoptera (vacuum), Diptera, non-ant Hymenop- tera, Hemiptera, Microcoryphia, and Acarina had significant partial negative correlations with Argentine ant abundance. The Diptera and Coleoptera had this negative partial rela- tionship with the Argentine ants despite the fact that both they and the ants were positively associated with edges. (5) In general, diversity in most orders was higher in sampling locations dominated by coastal sage scrub habitat than in those with appreciable cover of chaparral shrub species. (6) There was a strong seasonal variation in abundance and diversity in most orders. Diversity and abundance were highest in spring, intermediate in winter, and lowest in the fall. (7) Although higher trophic levels are often considered to be more sensitive to fragmentation, two groups of arthropod predators, spiders and carabid beetles, increased in abundance in older fragments. Abundance of these predators was positively correlated with the abundance of Argentine ants and the non-native Isopods, Dermaptera, and Blattaria.

Shifts in arbuscular mycorrhizal communities along an anthropogenic nitrogen deposition gradient

Abstract: We evaluated arbuscular mycorrhizal (AM) species diversity and abundance in nine locations along an anthropogenic nitrogen deposition gradient in coastal sage scrub (CSS) vegetation in southern California. The primary pollutants were nitrogen oxides derived from vehicular emissions. Extractable soil N on the gradient ranged from 5 to 87 μg/g during the summer months. For comparative purposes, we also assessed AM communities in nitrogen-fertilized (60 kg N·ha−1·yr−1) and unfertilized plots. Nitrogen enrichment induced a shift in AM community composition. In particular, an increasing input of nitrogen was associated with the displacement of the larger-spored species of Scutellospora and Gigaspora (due to a failure to sporulate) with a concomitant proliferation of small-spored Glomus species (e.g., Glomus aggregatum, Glomus leptotichum). A subsequent reduction in species richness and diversity (as measured by Shannon–Wiener index) accompanied eutrophication. Nitrogen enrichment also significantly reduced spo...

Dynamics of intermittent stream habitat regulate persistence of a threatened fish at multiple scales

Abstract: Traditionally, threatened species management has emphasized conservation of individual populations and has assumed that abundance within suitable habitats is primarily governed by local environmental factors. However, recent research has revealed that landscape-level processes such as disturbance, dispersal, and habitat patch mosaic structure may also strongly influence local populations. We studied the population and habitat dynamics of a threatened fish, the Arkansas darter (Etheostoma cragini) at four spatial scales (pool, reach, segment, watershed) in two intermittent Colorado plains streams. At each scale, information on hydrology, habitat, and fish populations was combined to evaluate factors influencing darter persistence. At the pool scale, Arkansas darters persisted in most permanent pools during summer drought, tolerated extremes of hyperthermia and hypoxia, and were extirpated only when pools dried. Deeper pools had a higher probability of persisting during summer drought. At the reach scale, s...

Heavy metals structure benthic communities in colorado mountain streams

Abstract: The development of field sampling designs that employ multiple reference and polluted sites has been proposed as an alternative to the traditional upstream vs. down- stream approach used in most biomonitoring studies. Spatially extensive monitoring pro- grams can characterize ecological conditions within an ecoregion and provide the necessary background information to evaluate future changes in water quality. We measured physi- cochemical characteristics, heavy-metal concentrations, and benthic macroinvertebrate com- munity structure at 95 sites in the Southern Rocky Mountain ecoregion in Colorado, USA. Most sites (82%) were selected using a systematic, randomized sampling design. Each site was placed into one of four metal categories (background, low, medium, and high metals), based on the cumulative criterion unit (CCU), which we defined as the ratio of the instream metal concentration to the U.S. Environmental Protection Agency criterion concentration, summed for all metals measured. A CCU of 1.0 represents a conservative estimate of the total metal concentration that, when exceeded, is likely to cause harm to aquatic organisms. Although the CCU was less than 2.0 at most (66.3%) of the sites, values exceeded 10.0 at 13 highly polluted stations. Differences among metal categories were highly significant for most measures of macroinvertebrate abundance and all measures of species richness. We observed the greatest effects on several species of heptageniid mayflies (Ephemeroptera: Heptageniidae), which were highly sensitive to heavy metals and were reduced by .75% at moderately polluted stations. The influence of taxonomic aggregation on responses to metals was also greatest for mayflies. In general, total abundance of mayflies and abundance of heptageniids were better indicators of metal pollution than abundance of dominant mayfly taxa. We used stepwise multiple-regression analyses to investigate the relationship between benthic community measures and physicochemical characteristics at the 78 randomly se- lected sites. Heavy-metal concentration was the most important predictor of benthic com- munity structure at these sites. Because of the ubiquitous distribution of heavy-metal pol- lution in the Southern Rocky Mountain ecoregion, we conclude that potential effects of

Traditional ecological knowledge: the third alternative (commentary)

Abstract: Contemporary Western attitudes concerning the management of natural re- sources, treatment of nonhuman animals, and the natural world emerge from traditions derived from Western European philosophy, i.e., they assume that humans are autonomous from, and in control of, the natural world. A different approach is presented by Traditional Ecological Knowledge (TEK) of indigenous peoples of North America. Although spiritually oriented, TEK converges on Western scientific approaches. TEK is based on close obser- vation of nature and natural phenomena; however, it is combined with a concept of com- munity membership that differs from that of Western political and social thought. TEK is strongly tied to specific physical localities; therefore, all aspects of the physical space can be considered part of the community, including animals, plants, and landforms. As a con- sequence, native worldviews can be considered to be spatially oriented, in contrast to the temporal orientation of Western political and historical thought. TEK also emphasizes the idea that individual plants and animals exist on their own terms. This sense of place and concern for individuals leads to two basic TEK concepts: (1) all things are connected, which is conceptually related to Western community ecology, and (2) all things are related, which changes the emphasis from the human to the ecological community as the focus of theories concerning nature. Connectedness and relatedness are involved in the clan systems of many indigenous peoples, where nonhuman organisms are recognized as relatives whom the humans are obliged to treat with respect and honor. Convergence of TEK and Western science suggests that there may be areas in which TEK can contribute insights, or possibly even new concepts, to Western science. TEK is inherently multidisciplinary in that it links the human and the nonhuman, and is the basis not only for indigenous concepts of nature, but also for concepts of indigenous politics and ethics. This multidisciplinary aspect sug- gests that TEK may be useful in resolving conflicts involving a variety of stakeholders and interest groups in controversies over natural resource use, animal rights, and conservation. TEK may also have implications for human behavior and obligations toward other forms of life that are often unrecognized, or at least not emphasized, in Western science. We present examples from community and behavioral ecology where a TEK-based approach yielded unexpected and nonintuitive insights into natural phenomena. Understanding of TEK may be useful in helping scientists respond to the changing public perceptions of science, and new cultural pressures in our society.

Belowground consequences of vegetation change and their treatment in models

Abstract: The extent and consequences of global land-cover and land-use change are increasingly apparent. One consequence not so apparent is the altered structure of plants belowground. This paper examines such belowground changes, emphasizing the interaction of altered root distributions with other factors and their treatment in models. Shifts of woody and herbaceous vegetation with deforestation, afforestation, and woody plant en- croachment typically alter the depth and distribution of plant roots, influencing soil nutrients, the water balance, and net primary productivity (NPP). For example, our analysis of global soil data sets shows that the major plant nutrients C, N, P, and K are more shallowly distributed than are Ca, Mg, and Na, but patterns for each element vary with the dominant vegetation type. After controlling for climate, soil C and N are distributed more deeply in arid shrublands than in arid grasslands, and subhumid forests have shallower nutrient dis- tributions than do subhumid grasslands. Consequently, changes in vegetation may influence the distribution of soil carbon and nutrients over time (perhaps decades to centuries). Shifts in the water balance are typically much more rapid. Catchment studies indicate that the water yield decreases 25-40 mm for each 10% increase in tree cover, and increases in transpiration of water taken up by deep roots may account for as much as 50% of observed responses. Because models are increasingly important for predicting the consequences of vegetation change, we discuss the treatment of belowground processes and how different treatments affect model outputs. Whether models are parameterized by biome or plant life form (or neither), use single or multiple soil layers, or include N and water limitation will all affect predicted outcomes. Acknowledging and understanding such differences should help constrain predictions of vegetation change.

Remote sensing of vegetation, plant species richness, and regional biodiversity hotspots

Abstract: Understanding mesoscale patterns of ecosystem properties is important if we are to effectively monitor ecosystem change due to land use and climate change Remote sensing provides the best tool for looking at large areas of the earth's surface to analyze, map, and monitor ecosystem patterns and processes Patterns of vegetation and variation in biodiversity are important ecosystem properties, with strong relationships to important ecosystem functions Species richness is the most widely used measure of biodiversity, and mapping patterns of species richness within a landscape can provide a basis for future monitoring and an ecological basis for land management and conservation decisions This study presents (1) a map of the vegetation of the Hood River region of the Central Canadian Arctic derived from a supervised classification of Landsat Thematic Mapper (TM) satellite imagery, (2) estimations and maps of regional variation in plant species richness, and (3) a comparison of three species richness estimat

Green turtle somatic growth model: evidence for density dependence

Abstract: The green turtle, Chelonia mydas, is a circumglobal species and a primary herbivore in marine ecosystems. Overexploitation as a food resource for human populations has resulted in drastic declines or extinction of green turtle populations in the Greater Caribbean. Attempts to manage the remaining populations on a sustainable basis are ham- pered by insufficient knowledge of demographic parameters. In particular, compensatory responses resulting from density-dependent effects have not been evaluated for any sea turtle population and thus have not been explicitly included in any population models. Growth rates of immature green turtles were measured during an 18-yr study in Union Creek, a wildlife reserve in the southern Bahamas. We have evaluated the growth data for both straight carapace length (SCL) and body mass with nonparametric regression models that had one response variable (absolute growth rate) and five potential covariates: sex, site, year, mean size, and recapture interval. The SCL model of size-specific growth rates was a good fit to the data and accounted for 59% of the variance. The body-mass model was not a good fit to the data, accounting for only 26% of the variance. In the SCL model, sex, site, year, and mean size all had significant effects, whereas recapture interval did not. We used results of the SCL model to evaluate a density-dependent effect on somatic growth rates. Over the 18 yr of our study, relative population density underwent a sixfold increase followed by a threefold decrease in Union Creek as a result of natural immigration and emigration. Three lines of evidence support a density-dependent effect. First, there is a significant inverse correlation between population density and mean annual growth rate. Second, the condition index (mass/(SCL)3) of green turtles in Union Creek is positively correlated with mean annual growth rates and was negatively correlated with population density, indicating that the green turtles were nutrient limited during periods of low growth and high population densities. Third, the population in Union Creek fluctuated around carrying capacity during our study and thus was at levels likely to experience density- dependent effects that could be measured. We estimate the carrying capacity of pastures of the seagrass Thalassia testudinum, the major diet plant of the green turtle, as a range from 122 to 4439 kg green turtles/ha or 16- 586 million 50-kg green turtles in the Caribbean. Because green turtle populations are probably regulated by food limitation under natural conditions, carrying capacity can serve as a baseline to estimate changes in green turtle populations in the Caribbean since pre- Columbian times and to set a goal for recovery for these depleted populations. Finally, we compare the growth functions for green turtle populations in the Atlantic and Pacific oceans. Not only does the form of the size-specific growth functions differ between the two regions (monotonic declining in the Atlantic and nonmonotonic in the Pacific), but also small juvenile green turtles in the Atlantic have substantially higher growth rates than those in the Pacific. Research is needed to evaluate the causes of these differences, but our results indicate that demographic parameters between ocean basins should only be extrapolated with great caution.

Dispersal limitations of epiphytic lichens result in species dependent on old-growth forests

Abstract: Epiphytic lichen biomass accumulates slowly in forest canopies. We eval- uated three alternative hypotheses for the slow accumulation of epiphytic lichens, using two experiments in tree crowns from 15 Douglas-fir forest stands representing three age classes: old growth, young, and recent clearcuts. The first experiment evaluated whether forest age, bark roughness, or dispersal rate limits the establishment of the dominant old- growth-associated lichen, Lobaria oregana. Surface-sterilized branches with either rough or smooth bark were repeatedly inoculated with propagules and compared 1 yr after the last inoculation. Dispersal affected rates of establishment: inoculated branches had 27X more newly established thalli than controls. Establishment on smooth bark was highest in clearcuts, intermediate in young forests, and lowest in old growth. There was as much or more establishment of sown propagules on smooth-barked branches as on rough-barked branches in all age classes. In the second, transplant-performance experiment, Lobaria oregana grew as rapidly in young forests as in old growth but lost biomass and suffered more injuries in clearcuts. In contrast, L. pulmonaria performed at least as well in clearcuts as in young forests and old growth. Poor dispersal and establishment limit the development of L. oregana populations in Douglas-fir forests. Particular substrates and microenviron- ments found only in old growth are not essential for Lobaria establishment and growth. Maximizing the number and dispersion of remnant trees in cutting units should maximize the rate of accumulation of L. oregana biomass in the regenerating forest. The single most important action promoting the accumulation of old-growth-associated epiphytes will be the retention of propagule sources in and near all cutting units.

The role of Mongolian nomadic pastoralists' ecological knowledge in rangeland management.

Abstract: Past stereotypes of indigenous pastoralists as ignorant and environmentally destructive are being revised as ecological and social science research advances. As yet, little documentation of pastoralists' ecological knowledge exists, and even less is known about how this knowledge is, or can be, applied to resource management. This paper outlines the ecological knowledge of Mongolian nomadic pastoralists and its role in rangeland management, showing how herders' knowledge is reflected in pasture use norms and attitudes toward pasture privatization, as well as herding practices. The paper explores the potentially contradictory roles of pastoralists' ecological knowledge and perceptions in the current management context.

Invasion dynamics of Cytisus scoparius: a matrix model approach.

Abstract: It is at the level of population dynamics that an invasion either fails or succeeds. By elucidating patterns of variation in population growth rates or demographic rates, it is possible to forge a connection between quantitative field data and theoretical ideas about invasiveness, invasibility, and rates of spread. Demographic models also provide a tool to guide control strategies for invasive pests. Here I report the results of a demographic study of Cytisus scoparius, an exotic shrub on the west coast of North America. I used matrix population models to describe demographic patterns in six populations (three in prairies and three in urban fields) and across advancing stages of invasion. At the edge of the invading front, all populations showed finite rates of increase (λ) >1; however, prairie populations were increasing much more rapidly than urban ones. While many individual vital rates differed between prairie and urban populations, Life Table Response Analysis revealed that seedling establishment mad...

Kincentric ecology: indigenous perceptions of the human-nature relationship

Abstract: Indigenous people view both themselves and nature as part of an extended ecological family that shares ancestry and origins. It is an awareness that life in any environment is viable only when humans view the life surrounding them as kin. The kin, or relatives, include all the natural elements of an ecosystem. Indigenous people are affected by and, in turn, affect the life around them. The interactions that result from this “kincentric ecology” enhance and preserve the ecosystem. Interactions are the commerce of ecosystem functioning. Without human recognition of their role in the complexities of life in a place, the life suffers and loses its sustainability. Indigenous cultural models of nature include humans as one aspect of the complexity of life. A Raramuri example of iwigara will serve to enhance understanding of the human–nature relationship that is necessary in order to fully comprehend the distinct intricacies of kincentric ecology.

Nitrogen saturation and retention in forested watersheds of the catskill mountains, new york

Abstract: The Catskill Mountains of southeastern New York receive relatively high rates of atmospheric N deposition, and NO3 2 concentrations in some streams have increased dramatically since the late 1960s. We measured the chemistry of 39 first- and second-order streams with forested watersheds to determine the variability of nitrogen concentrations within the Catskill Mountain area. We found that some streams have low NO3 2 concentra- tions throughout the year, some have seasonal cycles of varying amplitude, and some have relatively high concentrations year round. If the concentration and seasonality of NO 3 2 in stream water are used as indices of nitrogen saturation, then most stages of nitrogen sat- uration are evident in our survey of Catskill watersheds. Organic nitrogen was a small portion of the total nitrogen for streams with high NO3 2 concentration, but organic N was the dominant form of N (up to 73% of the total) in the streams with lowest nitrate. Estimated retention of N in these watersheds (based on total N in stream water) ranged from 49% to 90% of the atmospheric input. The variation in stream water NO3 2 concentration and the amplitude of the seasonal fluctuations did not appear to be attributable to differences among watersheds in atmospheric deposition, watershed topography, or groundwater influx to the stream. We hypothesize that differences among watersheds in forest species composition and forest history, which are interrelated, produce most of the variation in NO 3 2 concen- tration that we observed.

Effects of river regulation on river-margin vegetation : A comparison of eight boreal rivers

Abstract: Regulation and fragmentation by dams belong to the most widespread deliberate impacts of humans on the world's rivers, especially in the Northern Hemisphere. We evaluated the effects of hydroelectr ...

A new method for selection of umbrella species for conservation planning

Abstract: Umbrella species, species whose protection serves to protect many co-occurring species, have been proposed as a shortcut for conservation planning. Potential criteria for selection of umbrella species include rarity, sensitivity to human disturbance, and mean percentage of co-occurring species. Using butterflies in montane canyons in the Great Basin (USA) as a case study, we examined correlations among those three selection methods. We also developed a new index that specifically ranks species according to their potential to serve as umbrellas for their taxonomic group. Different methods for prioritizing species generally produced divergent rankings. Although rare butterflies tended to co-occur with more species than widespread butterflies, rare species may be poor umbrellas because their distributions are too highly restricted and often cannot be influenced by managers. Umbrella species are useful in meeting certain conservation challenges, particularly prioritization of habitat remnants for conservation...