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At least 451 records · Page 25Linked to original sources

USGS2009

Climate alters response of an endemic island plant to removal of invasive herbivores

Islands experience higher rates of species extinction than mainland ecosystems, with biological invasions among the leading causes; they also serve as important model systems for testing ideas in basic and applied ecology. Invasive removal programs on islands are conservation efforts that can also be viewed as powerful manipulative experiments, but few data are available to evaluate their effects. We collected demographic and herbivore damage data for Castilleja mollis Pennell, an endangered plant endemic to Santa Rosa Island, California, over a 12-year period before, during, and after the implementation of control for introduced cattle, deer, and elk. We used these long-term data to explore mechanisms underlying herbivore effects, assess the results of herbivore reduction at the scales of both individual plants and populations, and determine how temporal variability in herbivory and plant demography influenced responses to herbivore removals. For individual plants, herbivore effects mediated by disturbance were greater than those of grazing. Deer and elk scraping of the ground substantially increased plant mortality and dormancy and reduced flowering and growth. Stem damage from browsing did not affect survivorship but significantly reduced plant growth and flower production. Herbivore control successfully lowered damage rates, which declined steeply between 1997 and 2000 and have remained relatively low. Castilleja mollis abundances rose sharply after 1997, suggesting a positive effect of herbivore control, but then began to decline steadily again after 2003. The recent decline appears to be driven by higher mean growing season temperatures; interestingly, not only reductions in scraping damage but a period of cooler conditions were significant in explaining increases in C. mollis populations between 1997 and 2002. Our results demonstrate strong effects of introduced herbivores on both plant demography and population dynamics and show that climate-driven variation may counteract and mask positive responses to herbivore removal. Regional mean temperatures already have risen significantly over the last 50 years, suggesting that climate change could increasingly swamp the effects of management targeted at other environmental problems. Similar interactions between climate and invasive species will play an even greater role in future management, with long-term data sets like this critical to quantifying such effects. ?? 2009 by the Ecological Society of America.

Ecological Applications↗

USGS2016

Tolerance to multiple climate stressors: A case study of Douglas-fir drought and cold hardiness

Drought and freeze events are two of the most common forms of climate extremes which result in tree damage or death, and the frequency and intensity of both stressors may increase with climate change. Few studies have examined natural covariation in stress tolerance traits to cope with multiple stressors among wild plant populations. We assessed the capacity of coastal Douglas‐fir ( Pseudotsuga menziesii var. menziesii ), an ecologically and economically important species in the northwestern USA, to tolerate both drought and cold stress on 35 populations grown in common gardens. We used principal components analysis to combine drought and cold hardiness trait data into generalized stress hardiness traits to model geographic variation in hardiness as a function of climate across the Douglas‐fir range. Drought and cold hardiness converged among populations along winter temperature gradients and diverged along summer precipitation gradients. Populations originating in regions with cold winters had relatively high tolerance to both drought and cold stress, which is likely due to overlapping adaptations for coping with winter desiccation. Populations from regions with dry summers had increased drought hardiness but reduced cold hardiness, suggesting a trade‐off in tolerance mechanisms. Our findings highlight the necessity to look beyond bivariate trait–climate relationships and instead consider multiple traits and climate variables to effectively model and manage for the impacts of climate change on widespread species.

California, Oregon, Washington↗

USGS2011

The influence of stream channels on distributions of Larrea tridentata and Ambrosia dumosa in the Mojave Desert, CA, USA: Patterns, mechanisms and effects of stream redistribution

Drainage channels are among the most conspicuous surficial features of deserts, but little quantitative analysis of their influence on plant distributions is available. We analysed the effects of desert stream channels (‘washes’) on Larrea tridentata and Ambrosia dumosa density and cover on an alluvial piedmont in the Mojave Desert, based on a spatial analysis of transect data encompassing a total length of 2775 m surveyed in 5 cm increments. Significant deviations from average transect properties were identified by bootstrapping. Predictably, shrub cover and density were much reduced inside washes, and elevated above average levels adjacent to washes. Average Larrea and Ambrosia cover and density peaked 1·2–1·6 m and 0·5–1·0 m from wash edges, respectively. We compared wash effects in runon-depleted (−R) sections, where washes had been cut off from runon and were presumably inactive, with those in runon-supplemented (+R) sections downslope from railroad culverts to help identify mechanisms responsible for the facilitative effect of washes on adjacent shrubs. Shrub cover and density near washes peaked in both + R and − R sections, suggesting that improved water infiltration and storage alone can cause a facilitative effect on adjacent shrubs. However, washes of < 2 m width in + R sections had larger than average effects on peak cover, suggesting that plants also benefit from occasional resource supplementation. The data suggest that channel networks significantly contribute to structuring plant communities in the Mojave Desert and their disruption has notable effects on geomorphic and ecological processes far beyond the original disturbance sites.

California↗

USGS2007

Species-area curves indicate the importance of habitats' contributions to regional biodiversity

We examined species-area curves, species composition and similarity (Jaccard's coefficients), and species richness in 17 vegetation types to develop a composite index of a vegetation type's contribution to regional species richness. We collected data from 1 to 1000 m2 scales in 147 nested plots in Rocky Mountain National Park, Colorado, USA to compare three species-area curve models' abilities to estimate the number of species observed in each vegetation type. The log(species)-log(area) curve had the largest adjusted coefficients of determination (r2 values) in 12 of the 17 types, followed by the species-log(area) curve with five of the highest values. When the slopes of the curves were corrected for species overlap among plots with Jaccard's coefficients, the species-log(area) curves estimated values closest to those observed. We combined information from species-area curves and measures of heterogeneity with information on the area covered by each vegetation type and found that the types making the greatest contributions to regional biodiversity covered the smallest areas. This approach may provide an accurate and relatively rapid way to rank hotspots of plant diversity within regions of interest.

Colorado↗

USGS2016

Fluctuating water depths affect American alligator ( Alligator mississippiensis ) body condition in the Everglades, Florida, USA

Successful restoration of wetland ecosystems requires knowledge of wetland hydrologic patterns and an understanding of how those patterns affect wetland plant and animal populations.Within the Everglades, Florida, USA restoration, an applied science strategy including conceptual ecological models linking drivers to indicators is being used to organize current scientific understanding to support restoration efforts. A key driver of the ecosystem affecting the distribution and abundance of organisms is the timing, distribution, and volume of water flows that result in water depth patterns across the landscape. American alligators (Alligator mississippiensis) are one of the ecological indicators being used to assess Everglades restoration because they are a keystone species and integrate biological impacts of hydrological operations through all life stages. Alligator body condition (the relative fatness of an animal) is one of the metrics being used and targets have been set to allow us to track progress. We examined trends in alligator body condition using Fulton’s K over a 15 year period (2000–2014) at seven different wetland areas within the Everglades ecosystem, assessed patterns and trends relative to restoration targets, and related those trends to hydrologic variables. We developed a series of 17 a priori hypotheses that we tested with an information theoretic approach to identify which hydrologic factors affect alligator body condition. Alligator body condition was highest throughout the Everglades during the early 2000s and is approximately 5–10% lower now (2014). Values have varied by year, area, and hydrology. Body condition was positively correlated with range in water depth and fall water depth. Our top model was the “Current” model and included variables that describe current year hydrology (spring depth, fall depth, hydroperiod, range, interaction of range and fall depth, interaction of range and hydroperiod). Across all models, interaction between range and fall water depth was the most important variable (relative weight of 1.0) followed by spring and fall water depths (0.99), range (0.96), hydroperiod (0.95) and interaction between range and hydroperiod (0.95). Our work provides additional evidence that restoring a greater range in annual water depths is important for improvement of alligator body condition and ecosystem function. This information can be incorporated into both planning and operations to assist in reaching Everglades restoration goals.

Florida↗

USGS2011

Macroinvertebrate communities associated with three aquatic macrophytes (Ceratophyllum demersum, Myriophyllum spicatum, and Vallisneria americana) in Lake Onalaska, Wisconsin

The standing crop and species diversity of macroinvertebrates associated with wild celery (Vallisneria americana), Eurasian watermilfoil (Myriophyllum spicatum), and coontail (Ceratophyllum demersum) were examined in Lake Onalaska, Pool 7 of the upper Mississippi River, during summer 1983. Although Ceratophyllum generally supported the largest invertebrate standing crop (number per g plant dry weight), differences in invertebrate abundance among plant species were not consistent across time. However, the distribution of several taxa were significantly affected by plant species. Hyalella azteca (overall the most abundant species) and Enallagma spp. (the most abundant predator) were consistently most numerous in Ceratophyllum samples and least abundant in Vallisneria samples. Generally, invertebrate community composition differed significantly among plant species throughout the summer.

Wisconsin↗

USGS2013

Gradients of microhabitat and crappie ( Pomoxis spp.) distributions in reservoir coves

Embayments are among the most widespread littoral habitats found in Mississippi flood-control reservoirs. These macrohabitats represent commonly used nursery zones for age-0 crappies, Pomoxis spp., despite barren and eroded shorelines formed over 60–70 years of annual water level fluctuations. We tested if embayments displayed microhabitat gradients linked to the effect of water level fluctuations on riparian vegetation and if these gradients were paralleled by gradients in age-0 crappie distribution. Habitat composition changed longitudinally along the embayments with the most pronounced gradient representing a shift from nonvegetated mudflats near the mouth of embayments to herbaceous material upstream. The degree of habitat change depended on the water level. Similarly, catch rates of crappies increased upstream toward the rear of embayments, differing among water levels and reservoirs, but the longitudinal pattern persisted. Our results indicate that habitat composition gradients occur in embayments of northwest Mississippi flood-control reservoirs and that these gradients may influence a similar gradient in age-0 crappie distribution. While the biotic interactions behind the gradients may be less clear, we speculate that water level is the main factor influencing the observed gradients in habitat composition and fish. Management to benefit age-0 crappies may involve habitat improvement along embayment shorelines and water level regimes that foster growth of herbaceous plants.

Mississippi↗

USGS2004

Demographic analysis of dormancy and survival in the terrestrial orchid Cypripedium reginae

1. We use capture-recapture models to estimate the fraction of dormant ramets, survival and state transition rates, and to identify factors affecting these rates, for the terrestrial orchid Cypripedium reginae . We studied two populations in West Virginia, USA, for 11 years and investigated relationships between grazing and demography. Abe Run's population was small, with moderate herbivory by deer and relatively constant population size. The population at Big Draft was of medium size, with heavy deer grazing, and a sharply declining number of flowering plants up to the spring before our study started, when the population was fenced. 2. We observed dormant episodes lasting from 1 to 4 years. At Abe Run and Big Draft, 32.5% and 7.4% of ramets, respectively, were dormant at least once during the study period for an average of 1.6 and 1.3 years, respectively. We estimated the annual fraction of ramets in the dormant state at 12.3% (95% CI 9.5-15.8%) at Abe Run and at 1.8% (95% CI 1.2-2.6%) at Big Draft. Transition rates between the dormant, vegetative and flowering life-states did not vary between years in either population. Most surviving ramets remained in the same state from one year to the next. Survival rates were constant at Abe Run (0.96, 95% CI 0.93-0.97), but varied between years at Big Draft (0.89-0.99, mean 0.95). 3. At Big Draft, we found neither a temporal trend in survival after cessation of grazing, nor relationships between survival and the number of spring frost days or cumulative precipitation during the current or the previous 12 months. However, analysis of precipitation on a 3-month basis revealed a positive relationship between survival and precipitation during the spring (March-May) of the previous year. 4. Relationship between climate and the population dynamics of orchids may have to be studied with a fine temporal resolution, and considering possible time lags. Capture-recapture modelling provides a comprehensive and flexible framework for demographic analysis of plants with dormancy. 4. Relationship between climate and the population dynamics of orchids may have to be studied with a fine temporal resolution, and considering possible time lags. Capture-recapture modelling provides a comprehensive and flexible framework for demographic analysis of plants with dormancy.

West Virginia↗

USGS2013

Dendrometer bands made easy: using modified cable ties to measure incremental growth of trees

Dendrometer bands are a useful way to make sequential repeated measurements of tree growth, but traditional dendrometer bands can be expensive, time consuming, and difficult to construct in the field. An alternative to the traditional method of band construction is to adapt commercially available materials. This paper describes how to construct and install dendrometer bands using smooth-edged, stainless steel, cable tie banding and attachable rollerball heads. As a performance comparison, both traditional and cable tie dendrometer bands were installed on baldcypress trees at the National Wetlands Research Center in Lafayette, Louisiana, by both an experienced and a novice worker. Band installation times were recorded, and growth of the trees as estimated by the two band types was measured after approximately one year, demonstrating equivalence of the two methods. This efficient approach to dendrometer band construction can help advance the knowledge of long-term tree growth in ecological studies.

Louisiana↗

USGS2012

Five new records of ants (Hymenoptera: Formicidae) for Nebraska

Ants are ubiquitous and influential organisms in terrestrial ecosystems. About 1,000 ant species occur in North America, where they are found in nearly every habitat (Fisher and Cover 2007). Ants are critical to ecological processes and structure. Ants affect soils via tunneling activity (Baxter and Hole 1967), disperse plant seeds (Lengyel et al. 2009), prey upon a variety of insects and other invertebrates (Way and Khoo 1992, Folgarait 1998), are often effective primary consumers through their prodigious consumption of floral and especially extrafloral nectar, and honeydew (Tobin 1994), and serve as prey for invertebrates (Gotelli 1996, Gastreich 1999) and vertebrates (Reiss 2001).

Nebraska↗

USGS2011

LiDAR: Providing structure

Since the days of MacArthur, three-dimensional (3-D) structural information on the environment has fundamentally transformed scientific understanding of ecological phenomena (MacArthur and MacArthur 1961). Early data on ecosystem structure were painstakingly laborious to collect. However, as reviewed and reported in recent volumes of Frontiers(eg Vierling et al. 2008; Asner et al.2011), advances in light detection and ranging (LiDAR) remote-sensing technology provide quantitative and repeatable measurements of 3-D ecosystem structure that enable novel ecological insights at scales ranging from the plot, to the landscape, to the globe. Indeed, annual publication of studies using LiDAR to interpret ecological phenomena increased 17-fold during the past decade, with over 180 new studies appearing in 2010 (ISI Web of Science search conducted on 23 Mar 2011: [{lidar AND ecol*} OR {lidar AND fores*} OR {lidar AND plant*}]).

Frontiers in Ecology and the Environment↗

USGS2002

Research plan for lands administered by the U.S. Department of the Interior in the Interior Columbia Basin and Snake River Plateau

This document presents a long-term research strategy designed to address current and future research needs for management of Department of the Interior-administered ecosystems in the Intermountain West. Although the research plan was developed in the context of the Interior Columbia Basin Ecosystem Management Project, the plan addresses many high-priority issues facing land managers throughout the Intermountain West. These issues pose management challenges that may be addressed with applied research both currently and in upcoming decades. Possessing a particular focus on semiarid ecosystems, the plan is a collection of research questions under five categories of research emphases: 1) restoration; 2) rangeland health; 3) aquatic-terrestrial connections; 4) development of monitoring and evaluation protocols; and 5) species and habitats at risk. The goal of the research strategy is to provide ideas for integrating emerging scientific understanding into future management in order to restore and maintain long-term ecosystem health and ecological integrity; provide consistent management direction over broad spatial and temporal scales; emphasize adaptive management over the long term; restore and maintain habitats for plant and animal species; and support economic and social needs of people, without compromising the above goals. Research questions are prioritized into three categories based on the immediacy of their need, feasibility of addressing the question rigorously under varying funding budgets, and magnitude of risk posed by not addressing the issue. The research strategy is intended to support and integrate with existing management efforts and strategies. As such, it melds observational studies with experimental manipulation, treating management actions as experiments whenever feasible. The research strategy focuses on disturbance processes and events that have been the primary drivers of change, to provide a predictive model for future changes. These drivers include fire, nonnative plants, herbivory, roads and associated human influences, and climate change. Whereas management in the western United States has striven to move from an inefficient species-based approach to a habitat-based approach, the plan focuses on ecosystem function and ecological processes as critical measures of habitat response. Because of the large amount and contiguity of public lands in the western United States, the region presents both a compelling opportunity to implement landscape-level science and a challenge to underst

Information and Technology Report↗

USGS2023

Species and physiographic factors drive Indian cucumber root and Canada mayflower plant chemistry: Implications for white-tailed deer forage quality

Nutrition is fundamental to white-tailed deer ( Odocoileus virginianus ) management given its relationship to habitat carrying capacity and population productivity. Ecological Sites (ESs) are a United States federal landscape management unit of specific land potential due to unique soils, topography, climate, parent material, and perhaps deer forage nutritional value. We present results of a study that extends the use of ESs to inform white-tailed deer management by evaluating indicator plant chemistry in two spring forb species, Indian cucumber root ( Medeola virginiana) and Canada mayflower ( Maianthemum canadense ), across the northcentral Appalachians. We sampled spring forbs and underlying soils across two ESs: Dry, upland, oak–maple–hemlock hardwood forest (OMH) and Deep soil, high slope, northern hardwood forests (NHF). Plant elemental content, soil pH, and site aspect, slope and elevation were measured. Our results show that forb chemistry differs between species and within a species geographically. Indian cucumber root, as compared to Canada mayflower, has significantly higher Mg, Na, Cu, Fe, and Zn, and lower Mn. Canada mayflower in the NHF ES, versus OMH ES, was found to have significantly higher K, Mn, and B. Indian cucumber root in the NHF ES, versus the OMH ES, was found to have significantly higher Mg, Al, Fe, and Ca:P ratio but lower K. Linear discriminant analysis shows that plant tissue Mn was the best discriminator between species, and between ESs, Canada mayflower plant tissue Mn and Indian cucumber plant tissue P, K, Ca, Mg and Mn were best discriminators. Given that nutrition determines habitat carrying capacity, differences in forage nutrition between ESs may have different potentials to support deer. Forage nutrition is an important aspect of deer habitat conditions and carrying capacity, thus ESs are likely to support deer populations with different growth potential, which means that even if the same plant species occur in different ESs their nutritional value to deer may differ.

Journal of Environmental Management↗

USGS2022

Spatially explicit management of genetic diversity using ancestry probability surfaces

1. Ecological restoration and conservation efforts are increasing worldwide and the management of intraspecific genetic variation in plants and animals, an important component of biodiversity, is increasingly valued. As a result, tailorable, spatially explicit approaches to map genetic variation are needed to support decision-making and management frameworks related to the recovery of threatened and endangered species and the maintenance of genetic resources in species utilized by humans, such as for restoration or agricultural purposes. 2. Here, we describe and demonstrate a workflow to spatially interpolate patterns of genetic differentiation using novel functions in the R package POPMAPS ( Pop ulation M anagement using A ncestry P robability S urfaces). Our approach uses empirical genetic data to estimate ancestry coefficients across a user-defined landscape correlated with patterns of differentiation in the focal species. The resulting surface, which we term the ancestry probability surface, includes two components: hard population boundaries and estimations of uncertainty that represent confidence in population assignments (i.e., ancestry probabilities). 3. An ancestry probability surface developed for Hilaria jamesii , an important graminoid utilized in restoration across the western United States, demonstrates the functionality of POPMAPS . Genetic distances among empirical sites correlated better with least-cost distances across suitable habitat than with geographic distances, informing the surface over which the interpolation was conducted (i.e., a model indicating habitat suitability). A jackknifing procedure identified parameter values resulting in robust population assignments across the species’ range, which were utilized in downstream analyses to estimate ancestry coefficients from empirical data. Ancestry coefficients were translated into ancestry probabilities, which tended to be low for cells that were intermediate in distance between empirical sampling locations representing different populations or when influenced by empirical sampling locations with mixed genetic ancestry. 4. POPMAPS allows users to tailor parameter values and analytical approaches and thereby incorporate species-specific biological characteristics and desired levels of uncertainty into maps illustrating patterns of genetic differentiation. Ancestry probability surfaces may be used to guide management or investigate further ecological or evolutionary hypotheses. We discuss how maps produced by POPMAPS can inform multiple management challenges including species recovery planning and the utilization of commonly used species in restoration.

Methods in Ecology and Evolution↗

USGS2003

Natural and anthropogenic factors affecting the structure of the benthic macroinvertebrate community in an effluent-dominated reach of the Santa Cruz River, AZ

This study provides an assessment of the ecological conditions of a 46-km effluent-dominated stream section of the Santa Cruz River in the vicinity of the International Waste Water Treatment Plant, Nogales, AZ. We associated changes in the structure of the macroinvertebrate community to natural and anthropogenic chemical and physical variables using multivariate analysis. The analysis shows that biological criteria for effluent-dominated streams can be established using macroinvertebrate community attributes only with an understanding of the contribution of three classes of variables on the community structure: (1) low flow hydrological discharge as affected by groundwater withdrawals, treatment plant discharge, and subsurface geomorphology; (2) chemical composition of the treatment plant discharge and natural dilution; and (3) naturally produced floods resulting from seasonality of precipitation. ?? 2003 Elsevier Science Ltd. All rights reserved.

Ecological Indicators↗

USGS2025

Fungi, fire, and feedbacks: Grasses and wildfire interact to alter ectomycorrhizal fungal communities and decrease tree seedling growth

Wildfire and its effects, including changes to soil biota and the introduction of invasive or seeded grasses, can cause long-term shifts in ecological communities. Post-wildfire establishment of long-lived trees and shrubs is a critical bottleneck to recovering native plant communities. Ectomycorrhizal fungi (EMF) can improve plant responses to stressors and influence seedling establishment following wildfire, but little is known about how introduced grasses alter plant-fungal relationships and influence woody plant recovery. We investigated how piñon pine ( Pinus edulis ) EMF colonization and growth responded to soil wildfire history and novel grasses. Piñon seedlings were grown in soils from areas that burned in a stand-replacing fire nearly two decades prior or in soils from unburned piñon-juniper woodlands. Each piñon was grown with an invasive grass ( Bromus tectorum ), a native rhizomatous grass ( Pascopyrum smithii ) or another piñon seedling. Even ∼20 years after fire, EMF community composition in burned areas differed from that of unburned woodlands. Fire history and plant neighbor identity interacted to affect EMF abundance. Piñon seedling biomass was positively associated with EMF abundance in unburned woodland soils, but not in post-burn soils, suggesting that the EMF community in unburned woodlands is more beneficial. Importantly, the presence of either an invasive or native grass had a negative effect on seedling growth and EMF abundance, resulting in an average 61.4 % drop in EMF abundance and altered EMF community composition. Our findings suggest that plant species interactions, long-term effects of fire on soil, and EMF may determine the trajectory of woodland recovery following wildfire.

Colorado↗

USGS1998

Walden Pond, Massachusetts: Environmental setting and current investigations

Introduction Walden Pond, in Concord, Massachusetts, is famous among lakes because of its unique social history. Walden was the setting for American naturalist Henry David Thoreau's well-known essay 'Walden; or, Life in the Woods,' first published in 1854. Thoreau lived and wrote at Walden Pond from July 1845 to September 1847. In 'Walden,' Thoreau combined highly admired writing on Transcendental philosophy with pioneering observations of aquatic ecology and physical aspects of limnology, the study of lakes. Because Thoreau also defended so effectively the value of living close to nature in the Walden woods, the pond is considered by many to be the birthplace of the American conservation movement. Visitors come from all over the world to the pond, which has been designated a National Historic Landmark, and its fame has resulted in a major fund drive to preserve the surrounding woods. Walden Pond has no surfacewater inflow or outflow, and much of its ground-water contributing area likely is preserved within the Walden Pond Reservation area (fig. 1). Only 15 miles from Boston, the pond is unusually clear and pristine for an urban-area lake. However, point sources of nutrients near the pond, and a large annual visitor attendance, concentrated during the summer when the swimming beach (fig. 2) is open, may contribute a nutrient load sufficient to change the pond environment. The occurrence of nuisance algal species, a recent beach closing, and an awareness of water-quality problems suffered by other ponds in the region raise concerns about the risk of ecological change at Walden Pond. Despite the role of Walden Pond as a cultural and environmental icon, little is known about the pond's ecological features, such as its internal nutrient cycling or the structure of its food web, nor have consistent measurements been made to determine whether these features are changing or are stable. Production rates of aquatic plants in lakes and ponds naturally undergo a slow increase as plant nutrients, organic matter, and soil are leached and eroded from the surrounding watershed. This process is known as eutrophication. The term 'cultural eutrophication' refers to an accelerated form of the natural process in which extra soil and nutrients are derived from people's use of fertilizer, rerouting of surface drainage, and disposal of domestic and industrial waste. Cultural eutrophication can lead to excessive growth of aquatic plants, pond filling by decayed plants and eroded soils, reduced water clarity, and depletion of dissolved oxygen in deep water with subsequent loss of cold-water fish habitat. In order to document the longterm ecological health of Walden Pond, the U.S. Geological Survey (USGS), working in cooperation with the Massachusetts Department of Environmental Management (MDEM), is investigating factors that could contribute to cultural eutrophication of Walden. Through measurements of mass balance of nutrients and oxygen in the pond's deep water, the investigation will establish a baseline data set on Walden's trophic state, which is a measure of the pond's ability to support plant growth. The baseline data will be used to detect trends and give early warning of trophic changes or trophic response to pond remediation projects. This Fact Sheet provides background information on the environmental setting, limnological features, and cultural eutrophication of Walden Pond, and describes the joint USGS/MDEM study.

Massachusetts↗

USGS2016

Integrative modelling reveals mechanisms linking productivity and plant species richness

How ecosystem productivity and species richness are interrelated is one of the most debated subjects in the history of ecology . Decades of intensive study have yet to discern the actual mechanisms behind observed global patterns . Here, by integrating the predictions from multiple theories into a single model and using data from 1,126 grassland plots spanning five continents, we detect the clear signals of numerous underlying mechanisms linking productivity and richness. We find that an integrative model has substantially higher explanatory power than traditional bivariate analyses. In addition, the specific results unveil several surprising findings that conflict with classical models . These include the isolation of a strong and consistent enhancement of productivity by richness, an effect in striking contrast with superficial data patterns. Also revealed is a consistent importance of competition across the full range of productivity values, in direct conflict with some (but not all) proposed models. The promotion of local richness by macroecological gradients in climatic favourability, generally seen as a competing hypothesis , is also found to be important in our analysis. The results demonstrate that an integrative modelling approach leads to a major advance in our ability to discern the underlying processes operating in ecological systems.

Nature↗