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Results for “Biology and Fertility of Soils”

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At least 19 recordsLinked to original sources
USGS2003

Soil fertility in deserts: A review on the influence of biological soil crusts and the effect of soil surface disturbance on nutrient inputs and losses

Sources of desert soil fertility include parent material weathering, aeolian deposition, and on-site C and N biotic fixation. While parent materials provide many soil nutrients, aeolian deposition can provide up to 75% of plant-essential nutrients including N, P, K, Mg, Na, Mn, Cu, and Fe. Soil surface biota are often sticky, and help retain wind-deposited nutrients, as well as providing much of the N inputs. Carbon inputs are from both plants and soil surface biota. Most desert soils are protected by cyanobacterial-lichen-moss soil crusts, chemical crusts and/or desert pavement. Experimental disturbances applied in US deserts show disruption of soil surfaces result in decreased N and C inputs from soil biota by up to 100%. The ability to glue aeolian deposits in place is compromised, and underlying soils are exposed to erosion. The ability to withstand wind increases with biological and physical soil crust development. While most undisturbed sites show little sediment production, disturbance by vehicles or livestock produce up to 36 times more sediment production, with soil movement initiated at wind velocities well below commonly-occurring wind speeds. Soil fines and flora are often concentrated in the top 3 mm of the soil surface. Winds across disturbed areas can quickly remove this material from the soil surface, thereby potentially removing much of current and future soil fertility. Thus, disturbances of desert soil surfaces can both reduce fertility inputs and accelerate fertility losses.

Conference Paper↗
USGS2018

Plant and microbial biomarkers suggest mechanisms of soil organic carbon accumulation in a Mojave Desert ecosystem under elevated CO2

We investigated how properties of soil organic matter (SOM) were altered after 10 years exposure to elevated atmospheric CO 2 concentration ([CO 2 ]) in a Mojave Desert ecosystem, using plant and microbial biomarkers. We focused on roles of Larrea tridentata , the dominant evergreen shrub which form islands of fertility, and biological soil crusts which have extensive cover in plant interspace. Soils to 5 cm in depth were collected under L. tridentata and plant interspace, and biological soil crusts to 0.5 cm in depth under three cover types, Pleuraphis rigida , a C 4 grass, shrubs and plant interspace. Soil organic carboncontents were not significantly different between elevated and ambient [CO 2 ]. However, significantly higher abundance of n -alkanes, a major constituent of foliage wax material, occurred in the elevated compared to ambient [CO 2 ] plots in the soils collected under L. tridentata , but no such difference was found in the soils at plant interspace or the biological soil crusts. There was no significant difference in abundance of microbial phospholipid fatty acids between the CO 2 treatments in the soils of either cover types. However, neutral lipid fatty acid abundance was significantly higher under elevated than ambient [CO 2 ] in the soils under L. tridentata , whereas no such significant difference was observed at plant interspace. These results emphasize important roles of the dominant shrubs in SOM formation under elevated [CO 2 ] in arid ecosystems. Elevated [CO 2 ] stimulated growth of L. tridentata in wet years, and aboveground litter deposition via senescence contributed to SOM formation in islands of fertility. In addition, elevated [CO 2 ] stimulated soil microbial turnover rates in rhizosphere of L. tridentata , which left more soil microbial necromass, a major SOM source. We concluded that responses of dominant shrubs to elevated [CO 2 ] can stimulate SOM formation in arid ecosystems, but biological soil crusts may have limited capacity.

Soil Biology and Biochemistry↗
USGS2002

Effects of subsurface aeration and trinexapac-ethyl application on soil microbial communities in a creeping bentgrass putting green

The sensitivity of creeping bentgrass (Agrostis palustris Huds.) to the extreme heat found in the southeastern United States has led to the development of new greens-management methods. The purpose of this study was to examine the effects of subsurface aeration and growth regulator applications on soil microbial communities and mycorrhizal colonization rates in a creeping bentgrass putting green. Two cultivars (Crenshaw and Penncross), a growth regulator (trinexapacethyl), and subsurface aeration were evaluated in cool and warm seasons. Total bacterial counts were higher in whole (unsieved) soils than in sieved soils, indicating a richer rhizosphere soil environment. Mycorrhizal infection rates were higher in trinexapac-ethyl (TE) treated plants. High levels of hyphal colonization and relatively low arbuscule and vesicle occurrence were observed. Principal components analysis of whole-soil fatty acid methyl ester (FAME) profiles indicated that warm-season microbial populations in whole and sieved soils had similar constituents, but the populations differed in the cool season. FAME profiles did not indicate that subsurface aeration and TE application affected soil microbial community structure. This is the first reported study investigating the influences of subsurface aeration and TE application on soil microorganisms in a turfgrass putting green soil.

Biology and Fertility of Soils↗
USGS2005

Microbial responses and nitrous oxide emissions during wetting and drying of organically and conventionally managed soil under tomatoes

The types and amounts of carbon (C) and nitrogen (N) inputs, as well as irrigation management are likely to influence gaseous emissions and microbial ecology of agricultural soil. Carbon dioxide (CO2) and nitrous oxide (N2O) efflux, with and without acetylene inhibition, inorganic N, and microbial biomass C were measured after irrigation or simulated rainfall in two agricultural fields under tomatoes (Lycopersicon esculentum). The two fields, located in the California Central Valley, had either a history of high organic matter (OM) inputs ("organic" management) or one of low OM and inorganic fertilizer inputs ("conventional" management). In microcosms, where short-term microbial responses to wetting and drying were studied, the highest CO2 efflux took place at about 60% water-filled pore space (WFPS). At this moisture level, phospholipid fatty acids (PLFA) indicative of microbial nutrient availability were elevated and a PLFA stress indicator was depressed, suggesting peak microbial activity. The highest N 2O efflux in the organically managed soil (0.94 mg N2O-N m-2 h-1) occurred after manure and legume cover crop incorporation, and in the conventionally managed soil (2.12 mg N2O-N m-2 h-1) after inorganic N fertilizer inputs. Elevated N2O emissions occurred at a WFPS >60% and lasted <2 days after wetting, probably because the top layer (0-150 mm) of this silt loam soil dried quickly. Therefore, in these cropping systems, irrigation management might control the duration of elevated N2O efflux, even when C and inorganic N availability are high, whereas inorganic N concentrations should be kept low during times when soil moisture cannot be controlled.

Biology and Fertility of Soils↗
USGS2003

Differences in native soil ecology associated with invasion of the exotic annual chenopod, Halgeton glomeratus

Various biotic and abiotic components of soil ecology differed significantly across an area where Halogeton glomeratus is invading a native winterfat, [ Krascheninnikovia (= Ceratoides ) lanata ] community. Nutrient levels were significantly different among the native, ecotone, and exotic-derived soils. NO 3 , P, K, and Na all increased as the cover of halogeton increased. Only Ca was highest in the winterfat area. A principal components analysis, conducted separately for water-soluble and exchangeable cations, revealed clear separation between halogeton- and winterfat-derived soils. The diversity of soil bacteria was highest in the exotic, intermediate in the ecotone, and lowest in the native community. Although further studies are necessary, our results offer evidence that invasion by halogeton alters soil chemistry and soil ecology, possibly creating conditions that favor halogeton over native plants.

Biology and Fertility of Soils↗
USGS2002

Nitrogen fixation in biological soil crusts from southeast Utah, USA

Biological soil crusts can be the dominant source of N for arid land ecosystems. We measured potential N fixation rates biweekly for 2 years, using three types of soil crusts: (1) crusts whose directly counted cells were >98% Microcoleus vaginatus (light crusts); (2) crusts dominated by M. vaginatus , but with 20% or more of the directly counted cells represented by Nostoc commune and Scytonema myochrous (dark crusts); and (3) the soil lichen Collema sp. At all observation times, Collema had higher nitrogenase activity (NA) than dark crusts, which had higher NA than light crusts, indicating that species composition is critical when estimating N inputs. In addition, all three types of crusts generally responded in a similar fashion to climate conditions. Without precipitation within a week of collection, no NA was recorded, regardless of other conditions being favorable. Low (<1°C) and high (>26°C) temperatures precluded NA, even if soils were moist. If rain or snow melt had occurred 3 or less days before collection, NA levels were highly correlated with daily average temperatures of the previous 3 days ( r 2 =0.93 for Collema crusts; r 2 =0.86 for dark crusts and r 2 =0.83 for light crusts) for temperatures between 1°C and 26°C. If a precipitation event followed a long dry period, NA levels were lower than if collection followed a time when soils were wet for extended periods (e.g., winter). Using a combination of data from a recording weather datalogger, time-domain reflectometry, manual dry-down curves, and N fixation rates at different temperatures, annual N input from the different crust types was estimated. Annual N input from dark crusts found at relatively undisturbed sites was estimated at 9 kg ha –1 year –1 . With 20% cover of the N-fixing soil lichen Collema , inputs are estimated at 13 kg ha –1 year –1 . N input from light crusts, generally indicating soil surface disturbance, was estimated at 1.4 kg ha –1 year –1 . The rates in light crusts are expected to be highly variable, as disturbance history will determine cyanobacterial biomass and therefore N fixation rates.

Biology and Fertility of Soils↗
USGS2003

Response of desert biological soil crusts to alterations in precipitation frequency

Biological soil crusts, a community of cyanobacteria, lichens, and mosses that live on the soil surface, occur in deserts throughout the world. They are a critical component of desert ecosystems, as they are important contributors to soil fertility and stability. Future climate scenarios predict alteration of the timing and amount of precipitation in desert environments. Because biological soil crust organisms are only metabolically active when wet, and as soil surfaces dry quickly in deserts during late spring, summer, and early fall, the amount and timing of precipitation is likely to have significant impacts on the physiological functioning of these communities. Using the three dominant soil crust types found in the western United States, we applied three levels of precipitation frequency (50% below-average, average, and 50% above-average) while maintaining average precipitation amount (therefore changing both timing and size of applied events). We measured the impact of these treatments on photosynthetic performance (as indicated by dark-adapted quantum yield and chlorophyll a concentrations), nitrogenase activity, and the ability of these organisms to maintain concentrations of radiation-protective pigments (scytonemin, beta-carotene, echinenone, xanthophylls, and canthaxanthin). Increased precipitation frequency produced little response after 2.5 months exposure during spring (1 April-15 June) or summer (15 June-31 August). In contrast, most of the above variables had a large, negative response after exposure to increased precipitation frequency for 6 months spring-fall (1 April-31 October) treatment. The crusts dominated by the soil lichen Collema, being dark and protruding above the surface, dried the most rapidly, followed by the dark surface cyanobacterial crusts (Nostoc-Scytonema-Microcoleus), and then by the light cyanobacterial crusts (Microcoleus). This order reflected the magnitude of the observed response: crusts dominated by the lichen Collema showed the largest decline in quantum yield, chlorophyll a, and protective pigments; crusts dominated by Nostoc-Scytonema-Microcoleus showed an intermediate decline in these variables; and the crusts dominated by Microcoleus showed the least negative response. Most previous studies of crust response to radiation stress have been short-term laboratory studies, where organisms were watered and kept under moderate temperatures. Such conditions would give crust organisms access to ample carbon to respond to imposed stresses (e.g., production of UV-protective pigments, replacement of degraded chlorophyll). In contrast, our longer-term study showed that under field conditions of high air temperatures and frequent, small precipitation events, crust organisms appear unable to produce protective pigments in response to radiation stress, as they likely dried more quickly than when they received larger, less frequent events. Reduced activity time likely resulted in less carbon available to produce or repair chlorophyll a and/or protective pigments. Our findings may partially explain the global observation that soil lichen cover and richness declines as the frequency of summer rainfall increases. ?? Springer-Verlag 2003.

Oecologia↗
USGS2016

Human land-use and soil change

Soil change refers to the alteration of soil and soil properties over time in one location, as opposed to soil variability across space. Although soils change with pedogensis, this chapter focuses on human caused soil change. Soil change can occur with human use and management over long or short time periods and small or large scales. While change can be negative or positive; often soil change is observed when short-term or narrow goals overshadow the other soil’s ecosystem services. Many soils have been changed in their chemical, physical or biological properties through agricultural activities, including cultivation, tillage, weeding, terracing, subsoiling, deep plowing, manure and fertilizer addition, liming, draining, and irrigation. Assessing soil change depends upon the ecosystem services and soil functions being evaluated. The interaction of soil properties with the type and intensity of management and disturbance determines the changes that will be observed. Tillage of cropland disrupts aggregates and decreases soil organic carbon content which can lead to decreased infiltration, increased erosion, and reduced biological function. Improved agricultural management systems can increase soil functions including crop productivity and sustainability. Forest management is most intensive during harvesting and seedling establishment. Most active management in forests causes disturbance of the soil surface which may include loss of forest floor organic materials, increases in bulk density, and increased risk of erosion. In grazing lands, pasture management often includes periods of biological, chemical and physical disturbance in addition to the grazing management imposed on rangelands. Grazing animals have both direct and indirect impacts on soil change. Hoof action can lead to the disturbance of biological crusts and other surface features impairing the soil’s physical, biological and hydrological function. There are clear feedbacks between vegetative systems and soil properties; when vegetation is altered because of grazing or other disturbances, soil property changes often follow. Some soils are very sensitive to management and disturbance and can undergo rapid change: cropping led to massive gully formation in the southeastern USA, exposure of acid-sulfate soils led to irreversible changes in soil minerology and thawing of cold soils has created thermokarst features. These soil changes alter soil properties and functions and may impact soil ecosystem services far into the future.

World Soils Book Series↗
USGS2010

Phosphorus dynamics in soils irrigated with reclaimed waste water or fresh water - A study using oxygen isotopic composition of phosphate

Transformations of phosphate (Pi) in different soil fractions were tracked using the stable isotopic composition of oxygen in phosphate ( δ 18 O p ) and Pi concentrations. Clay soil from Israel was treated with either reclaimed waste water (secondary, low grade) or with fresh water amended with a chemical fertilizer of a known isotopic signature. Changes of δ 18 O p and Pi within different soil fractions, during a month of incubation, elucidate biogeochemical processes in the soil, revealing the biological and the chemical transformation impacting the various P pools. P in the soil solution is affected primarily by enzymatic activity that yields isotopic equilibrium with the water molecules in the soil solution. The dissolved P interacts rapidly with the loosely bound P (extracted by bicarbonate). The oxides and mineral P fractions (extracted by NaOH and HCl, respectively), which are considered as relatively stable pools of P, also exhibited isotopic alterations in the first two weeks after P application, likely related to the activity of microbial populations associated with soil surfaces. Specifically, isotopic depletion which could result from organic P mineralization was followed by isotopic enrichment which could result from preferential biological uptake of depleted P from the mineralized pool. Similar transformations were observed in both soils although transformations related to biological activity were more pronounced in the soil treated with reclaimed waste water compared to the fertilizer treated soil.

Geoderma↗
USGS2022

Vertical movement of soluble carbon and nutrients from biocrusts to subsurface mineral soils

Dryland ecosystems can be constrained by low soil fertility. Within drylands, the soil nutrient and organic carbon (C) cycling that does occur is often mediated by soil surface communities known as biological soil crusts (biocrusts), which cycle C and nutrients in the top ca. 0–2 cm of soil. However, the degree to which biocrusts are influencing soil fertility and biogeochemical cycling in deeper, subsurface mineral soils is unclear. The movement of dissolved resources from biocrusts to deeper soil layers in leachate may be one of the main mechanisms through which biocrust fertility is transferred downward towards deeper microbial communities and plant roots occurring within mineral soil. Here we examined the role of biocrust leachate in contributing to subsurface nutrient and soluble C pools and subsurface microbial cycling. We collected biocrusts from three biocrust successional stages and explored resource pools in situ at multiple soil depths, while collecting leachate and measuring nutrient and organic C concentrations and metabolite composition from each successional stage in the laboratory. After four leachate collections, we conducted an incubation of mineral soil collected from below each biocrust successional stage to measure heterotrophic microbial CO 2 flux and biomass. Overall, our findings observed that the degree of nutrient and C connectivity between biocrusts and the sub-crust mineral soil depended on the biocrust successional stage and the element being considered, and the influence of biocrust successional stage on mineral soil CO 2 flux is likely related to long-term resource build up. Together, our results suggest that the influence of biocrust leachate on subsurface mineral soil is complex and context dependent, but, over longer time periods and at later successional stages, can have measurable effects on dryland soil biogeochemical cycling with feedbacks to resource availability and CO 2 flux.

Geoderma↗
USGS2019

Interactions of microhabitat and time control grassland bacterial and fungal composition

Dryland grasslands are vast and globally important and, as in all terrestrial ecosystems, soil microbial communities play fundamental roles in regulating dryland ecosystem function. A typical characteristic of drylands is the spatial mosaic of vascular plant cover surrounded by interspace soils, where biological soil crusts (biocrusts)—a complex community of organisms including bacteria, fungi, algae, mosses, and lichens—are common. The implications of this heterogeneity, where plants and biocrust cover co-occur, are often explored in the context of soil fertility and hydrology, but rarely has the impact of these multiple microhabitat types been simultaneously explored to determine the influence on bacterial and fungal communities, key biological players in these ecosystems. Further, our understanding of the temporal dynamics of bacterial and fungal communities in grasslands, and of how these dynamics depend on the microhabitat within the ecosystem, is notably poor. Here we used a temporally and spatially explicit approach to assess bacterial and fungal communities in a grassland on the Colorado Plateau, and to link variation in these communities to edaphic characteristics. We found that microhabitat (e.g., vascular plant rhizosphere, biocrust, and below biocrust) was the strongest driver of differences in bacterial and fungal community richness, diversity, and composition. Microhabitat type also significantly mediated the impact of temporal change in shaping community composition. Taken together, 29% of the variation in bacterial community composition could be explained by microhabitat, date, and microhabitat-by-date interactions, while only 11% of the variation in fungal community composition could be explained by the same factors, suggesting important differences in community assembly processes. Soil microbial communities dictate myriad critical ecosystem functions, thus understanding the factors that control their compostition is crucial to considering and forecasting how terrestrial ecosystems work. Overall, this case study provides insights for future studies on the spatial and temporal dynamics of bacterial and fungal communities in dryland grasslands.

Frontiers in Ecology and Evolution↗
USGS2019

Temporal and abiotic fluctuations may be preventing successful rehabilitation of soil-stabilizing biocrust communities

Land degradation is a persistent ecological problem in many arid and semi-arid systems globally (drylands hereafter). Most instances of dryland degradation include some form of soil disturbance and/or soil erosion, which can hinder vegetation establishment and reduce ecosystem productivity. To combat soil erosion, researchers have identified a need for rehabilitation of biological soil crusts (biocrusts), a globally-relevant community of organisms aggregating the soil surface and building soil fertility. The impact of plant and biocrust cover was tested on soil erosion potential in the piñon-juniper woodlands of Bandelier National Monument, NM. Biocrusts were found to be similarly influential to vascular plants in reducing erosion, largely acting by promoting surface roughness. The potential to rehabilitate biocrusts within the Monument was also tested. In a full factorial design, plots were inoculated on eroding soils before the summer monsoon with greenhouse-cultured biocrusts, and administered the erosion intervention treatments of overland water flow barriers (flashing), slash placement, and seeding of vascular plants. Although significant and dynamic changes to soil stability, penetration resistance, and extractable soil nutrients were observed through time, no strong effects with the addition of inoculum, seeding, or erosion intervention treatments were seen. These results suggest possible ways forward to successfully rehabilitate biocrust, including varying the timing of biocrust application, amending inoculum application with different types of soil stabilization techniques, and adding nutrients to soils. The insights gleaned from the lack of response brings us closer to developing effective techniques to arrest soil loss in these important social-ecological dryland systems.

Ecological Applications↗
USGS2016

Low soil moisture during hot periods drives apparent negative temperature sensitivity of soil respiration in a dryland ecosystem: A multi-model comparison

Arid and semiarid ecosystems (drylands) may dominate the trajectory of biosphere-to-atmosphere carbon (C) exchange, and understanding dryland CO 2 efflux is important for C cycling at the global-scale. However, unknowns remain regarding how temperature and moisture interact to regulate dryland soil respiration ( R s ), while ‘islands of fertility’ in drylands create spatially heterogeneous R s . At a site in southeastern Utah, USA we added or removed litter (0–650 % of control) in plots associated with either shrubs or biological soil crust-dominated interspaces between vascular plants. We measured R s , soil temperature (T s ), and water content (θ) repeatedly from October 2013 to November 2014. R s was highest following rain in late summer at T s ~30 °C, and lowest mid-summer at T s > 40 °C, resulting in apparent negative temperature sensitivity of R s at high temperatures, and positive temperature sensitivity at low-moderate temperatures. We used Bayesian statistical methods to compare models capturing a range of hypothesized relationships between T s , θ, and R s . The best model indicates that apparent negative temperature sensitivity of R s at high T s reflects the control of water content, not high temperatures. Modeled Q 10 ranged from 2.7 to 1.4 between 5 and 45 °C. Litter addition had no effect on Q 10 or reference respiration ( R ref = R s at 20 °C and optimum θ) beneath shrubs, and little effect on R ref in interspaces, yet R ref was 1.5 times higher beneath shrubs than in interspaces. Altogether, these results suggest reduced R s often observed at high T s in drylands is dominated by the control of θ, and, on shorter-timescales, variable litter inputs exert minimal control over R s .

Biogeochemistry↗
USGS2002

Ecological effects on streams from forest fertilization: Literature review and conceptual framework for future study in the western Cascades

Fertilization of forests with urea-nitrogen has been studied numerous times for its effects on water quality. Stream nitrogen concentrations following fertilization are typically elevated during winter, including peaks in the tens-of-thousands of parts per billion range, with summer concentrations often returning to background or near-background levels. Despite these increases, water-quality criteria for nitrogen have rarely been exceeded. However, such criteria are targeted at fish toxicity or human health and are not relevant to concentrations that could cause ecological disturbances. Studies of the responses of stream biota to fertilization have been rare and have targeted either immediate, toxicity-based responses or used methods insensitive to ongoing ecological processes. This report reviews water-quality studies following forest fertilizations, emphasizing Cascade streams in the Pacific Northwest and documented biological responses in those streams. A conceptual model predicting potential ecological response to fertilization, which includes effects on algal growth and primary production, is presented. In this model, applied fertilizer nitrogen reaching streams is mostly exported during winter. However, some nitrogen retained in soils or stream and riparian areas may become available to aquatic biota during spring and summer. Biological responses may be minimal in small streams nearest to application because of light limitation, but may be elevated downstream where light is sufficient to allow algal growth. Ultimately, algal response could be greatest in downstream reaches, although ambient nutrient concentrations remain low due to uptake and benthic nutrient recycling. Ground-water flow paths and hyporheic processing could be critical in determining the fate of applied nitrogen. A framework is provided for testing this response in the Little River watershed, a tributary to the North Umpqua River, Oregon, at basic and intensive levels of investigation.

Oregon↗
USGS2023

Cultivating resilience in dryland soils: An assisted migration approach to biological soil crust restoration

Land use practices and climate change have driven substantial soil degradation across global drylands, impacting ecosystem functions and human livelihoods. Biological soil crusts, a common feature of dryland ecosystems, are under extensive exploration for their potential to restore the stability and fertility of degraded soils through the development of inoculants. However, stressful abiotic conditions often result in the failure of inoculation-based restoration in the field and may hinder the long-term success of biocrust restoration efforts. Taking an assisted migration approach, we cultivated biocrust inocula sourced from multiple hot-adapted sites (Mojave and Sonoran Deserts) in an outdoor facility at a cool desert site (Colorado Plateau). In addition to cultivating inoculum from each site, we created an inoculum mixture of biocrust from the Mojave Desert, Sonoran Desert, and Colorado Plateau. We then applied two habitat amelioration treatments to the cultivation site (growth substrate and shading) to enhance soil stability and water availability and reduce UV stress. Using marker gene sequencing, we found that the cultivated mixed inoculum comprised both local- and hot-adapted cyanobacteria at the end of cultivation but had similar cyanobacterial richness as each unmixed inoculum. All cultivated inocula had more cyanobacterial 16S rRNA gene copies and higher cyanobacterial richness when cultivated with a growth substrate and shade. Our work shows that it is possible to field cultivate biocrust inocula sourced from different deserts, but that community composition shifts toward that of the cultivation site unless habitat amelioration is employed. Future assessments of the function of a mixed inoculum in restoration and its resilience in the face of abiotic stressors are needed to determine the relative benefit of assisted migration compared to the challenges and risks of this approach.

Arizona, California, Utah↗
USGS1975

Some effects of pollutants in terrestrial ecosystems

Summary: Pollutants tend to simplify plant and animal communities by causing a progressive loss of species. At the extreme, this leads to erosion and loss of soil fertility. Weedy, broadly adapted species increase. Among animals, carnivorous species and groups are often the first to suffer. This is partly because of their exposure at the top of the food chain, and partly, it appears, because of physiological differences. Species differences in susceptibility are abundant and are often critical. One result is that when one pest is controlled another is likely to flare up. Resistance appears commonly in insects and is known in other fast-breeding forms, including fishes, frogs, and rodents. Resistant individuals can carry toxicant loads that make them dangerous food for other animals. Some groups, including mollusks and annelids, are naturally resistant to many organohalogens and tend to accumulate them. Animals such as birds may carry lipophilic pollutants in large amounts with apparent safety until forced to draw upon their fat. They may then suffer delayed mortality, and no doubt suffer reproductive or behavioral effects at sublethal levels. Lipophilic pollutants in the brain rise when body lipids decrease and fall when body lipids increase. Mutagenesis can be caused by some common pollutants and the mutagenic properties of most chemicals are far too little known. Fortunately, common pesticides are not likely to be strong mutagens. Mutagenicity may be affecting certain long-lived and slow-breeding species in the wild, but most species have enough population turnover to swamp an occasional mutagenic event. Behavioral changes can be caused by relatively low levels of contaminants, but it is often hard to demonstrate them without using high dosages. Reproduction may or may not be affected adversely by low exposures. At certain exposures that are below the toxic levels of a chemical, a biostimulatory effect is to be expected. Food chain accumulations definitely do occur when persistent chemicals enter organisms that eliminate them poorly. However, loss of chemicals in the food chain must be more common than accumulation. The great concentration from water to aquatic organism is chiefly a physical phenomenon, not a food chain effect, but it affords high starting levels for these chains. Terrestrial food chains often start at a high level with heavily contaminated, struggling prey. Litter feeders are another important base. Vegetation may be contaminated enough to be dangerous to animals that eat it. Dermal and respiratory routes of intoxication occur in the wild, but the oral route is far more important at most times and places. The organisms that govern soil fertility and texture are affected more by cultivation than by pesticides. Above ground, growing knowledge of resistance, species differences, and biological controls is leading to integrated control, in which use of chemicals is limited and specific. We do not know what is happening to most nontarget invertebrates. Amphibians and reptiles may be killed by applications of insecticides, but are not highly sensitive and can carry large residues. Effects of these residues on reproduction are little known. Heavy kills of birds by pesticides still occur in the field. Fish-eating and bird-eating birds also undergo shell thinning and related reproductive troubles in many areas, sometimes to the point of population decline and local or regional extermination. DDE most often correlates with shell thinning in the wild and in experiments. No other known chemical approaches DDE in causing severe and lasting shell thinning. Herbivorous birds seem to be largely immune to this effect. It is uncertain how much dieldrin and PCBs contribute to embryotoxicity in carnivorous birds. Mammals may be killed by the more toxic pesticides, but some of the commonest small rodents are so resistant, and lose their residues so rapidly, that they are of little

Book chapter↗
USGS2000

Using multi-scale sampling and spatial cross-correlation to investigate patterns of plant species richness

Land managers need better techniques to assess exoticplant invasions. We used the cross-correlationstatistic, I YZ , to test for the presence ofspatial cross-correlation between pair-wisecombinations of soil characteristics, topographicvariables, plant species richness, and cover ofvascular plants in a 754 ha study site in RockyMountain National Park, Colorado, U.S.A. Using 25 largeplots (1000 m 2 ) in five vegetation types, 8 of 12variables showed significant spatial cross-correlationwith at least one other variable, while 6 of 12variables showed significant spatial auto-correlation. Elevation and slope showed significant spatialcross-correlation with all variables except percentcover of native and exotic species. Percent cover ofnative species had significant spatialcross-correlations with soil variables, but not withexotic species. This was probably because of thepatchy distributions of vegetation types in the studyarea. At a finer resolution, using data from ten1 m 2 subplots within each of the 1000 m 2 plots, allvariables showed significant spatial auto- andcross-correlation. Large-plot sampling was moreaffected by topographic factors than speciesdistribution patterns, while with finer resolutionsampling, the opposite was true. However, thestatistically and biologically significant spatialcorrelation of native and exotic species could only bedetected with finer resolution sampling. We foundexotic plant species invading areas with high nativeplant richness and cover, and in fertile soils high innitrogen, silt, and clay. Spatial auto- andcross-correlation statistics, along with theintegration of remotely sensed data and geographicinformation systems, are powerful new tools forevaluating the patterns and distribution of native andexotic plant species in relation to landscape structure.

Environmental Monitoring and Assessment↗
USGS1970

Chemical and biological conditions in Bald Eagle Creek and prognosis of trophic characteristics of Foster Joseph Sayers Reservoir, Centre County, Pennsylvania

Foster Joseph Sayers. Reservoir will b.e impounded on moderately fertile soils; however, its water source, Bald Eagle Creek, is a bicarbonate-water stream that is over~y-enriched with nutrients. About 650 of the 1,730 acres to be inundated in summer are subject to infestation with aquatic weeds. Nuisance algal "blooms" are expected to occur in summer. The reservoir will stratify in early summer and water · releas·ed for conservation purposes and acid neutralization will consist mostly of hypolimnetic water. This water will be nearly depleted in. dissolved oxygen and will, at times, contain relatively high concentrations of heavy metallic ions and hydrogen:!sulfide.

Pennsylvania↗