Unmined Land Research Articles

Estimating Ecological Responses to Climatic Variability on Reclaimed and Unmined Lands Using Enhanced Vegetation Index

Climatic impact on re-established ecosystems at reclaimed mined lands may have changed. However, little knowledge is available about the difference in vegetation–climate relationships between reclaimed and unmined lands. In this study, ecological responses to climatic variability on reclaimed and neighbouring unmined lands were estimated using remote-sensing data at the Pingshuo Mega coal mine, one of the largest coal mines with long-term reclamation history in China. Time-series MODIS enhanced vegetation index (EVI) data and meteorological data from 1997 to 2017 were collected. Results show significantly different vegetation–climate relationships between reclaimed and unmined lands. First, the accumulation periods of all climatic variables were much longer on reclaimed mining lands. Second, vegetation on reclaimed lands responded to variabilities in temperature, rainfall, air humidity, and wind speed, while undisturbed vegetation only responded to variabilities of temperature and air humidity. Third, climatic variability made a much higher contribution to EVI variation on reclaimed land (20.0–46.5%) than on unmined land (0.7–1.7%). These differences were primarily caused by limited ecosystem resilience, and changed site hydrology and microclimate on reclaimed land. Thus, this study demonstrates that the legacy effects of surface mining can critically change on-site vegetation–climate relationships, which impacts the structure, functions, and stability of reclaimed ecosystems. Vegetation–climate relationships of reclaimed ecosystems deserve further research, and remote-sensing vegetation data are an effective source for relevant studies.

Rehabilitating open-cut coal mine spoil for a pasture system in south east Queensland, Australia: Abiotic soil properties compared with unmined land through time

Rehabilitation of mined land intends to support food and biomass production, with open cut mines required to return the land to a safe, stable and productive state in Queensland, Australia. The aim of this investigation was to assess the potential for soil that was previously farmed, then mined and rehabilitated to support pasture for commercial cattle production. The study was focussed on abiotic properties of the rehabilitated soils, in comparison to properties of a range of unmined soil profiles supporting pastures within the immediate vicinity. Three hypotheses were tested: 1) the abiotic properties of rehabilitated soils would fall within the range of those from nearby unmined soils; 2) that rehabilitated soils would support viable pasture production; and 3) that the mine-spoil would restrict root function. The mine was situated near Acland, Queensland, with rehabilitated land sown to pasture 1, 3 and 6 years prior to the initiation of the study in 2013. The investigation followed these rehabilitated sites, in comparison to a Control site, and 18 proximal unmined sites, through a five year period. All sites were used to support cattle grazing, with soil nutrients, structural condition and pasture growth (8 sites) monitored. Evidence from pasture production and root exploration obtained through soil pit investigations demonstrated that the mine spoil was capable of supporting root growth beyond the replaced soil layer. There were few differences between the Control and rehabilitated sites with regard to benefits or constraints to pasture production, with exception that two rehabilitated sites had simillar or higher plant-available phosphorus and nitrogen. It was concluded that: 1) abiotic properties of rehabilitated soils fell within the range of unmined soils; 2) viable pasture production was achieved from the rehabilitated sites; and 3) both the replaced soil layer and the mine spoil supported root exploration and pasture production.

Sustainability of beef production from brigalow lands after cultivation and mining. 1. Sown pasture growth and carrying capacity

Context New Acland coal mine in south-eastern Queensland is seeking to rehabilitate mined land to pastures that are safe, stable and sustainable for beef production. Little is known of the productivity and sustainability of grazing previously mined land in the Darling Downs study region. Additionally, information is required to specify management guidelines for sustainable grazing of regional land types retired from cultivation. Aims Identify pasture growth characteristics, rainfall use efficiencies and long-term carrying capacities of subtropical sown pastures established on lands rehabilitated after open-cut coal mining in comparison to sown pastures established on un-mined but previously cultivated lands. Methods Pasture growth and quality (% nitrogen) were observed using the Swiftsynd methodology in ungrazed exclosures with three sites on rehabilitated lands of the Acland Grazing Trial over a 5-year period (2014–2018), and 13 sites on unmined lands over periods of 2–5 years providing data for modelling pasture growth. Key results Peak pasture yield (TSDM for autumn harvests) averaged for 2017 and 2018 was greater (P < 0.1) on rehabilitated sites than unmined Poplar Box land type sites (5957 and 2233 kg/ha respectively) but similar to Brigalow Uplands and Mountain Coolibah land type sites (3946 and 3413 kg/ha respectively). Pasture rundown was evident, with pasture N uptake decreasing over 5 years at some sites. Soil mineral N supply (potentially mineralisable N and mineral N) in spring was a useful indicator of N uptake over the following growing season. Simulations using the GRASP pasture growth model for the grazing trial period predicted rainfall use efficiencies of 12.0, 7.0, 9.1 and 4.8 kg/ha.mm rainfall for rehabilitated sites and unmined sites on Brigalow Uplands, Mountain Coolibah and Poplar Box land types respectively. Long-term carrying capacities based on estimates of long-term median pasture growth and 30% utilisation were 4.39, 3.58 and 5.92 ha/adult equivalent respectively for the unmined land types, and 2.45 ha/adult equivalent for the rehabilitated lands. Conclusions Rehabilitated land can be as productive as unmined but previously cultivated land. Implications Grazing management plans for sustainable management of mined and unmined lands can be developed using data from the present study. The plans will assist with the transition of rehabilitated lands to commercial agriculture.

Sustainability of beef production from brigalow lands after cultivation and mining. 3. Pasture rundown, climate and grazing pressure effects

Context The Acland Land System overlying the Walloon sandstone coal deposits in southern Queensland is generally marginal for cropping but well suited to grazing, and thus cultivated land is commonly returned to pasture. Rehabilitation of these lands after open-cut coal mining seeks to be safe, stable and self-sustaining to satisfy requirements for ecologically sustainable development. Aims The present paper evaluates the sustainability and economic viability of beef production on (a) lands retired from cultivation and then rehabilitated with sown pastures after open-cut coal mining at the New Acland mine site, and (b) similar nearby pasture lands that were not mined but were also retired from cultivation. Methods The GRASP grazing systems model was modified and calibrated with short-term (5-year) grazing trial data (soil, pasture and cattle observations), and then used with long-term (60-year) weather data to estimate effects of land type, pasture rundown, climate and grazing pressure on productivity and economic returns. The productivity of three rehabilitated sites and 15 unmined sites were evaluated, including pastures on six commercial properties. Key results Estimates of long-term mean annual growth of pastures on unmined lands retired from cultivation on three land types (Mountain Coolibah, Brigalow Uplands and Poplar Box) were 3398, 2817 and 2325 kg/ha respectively. Pasture growth was greater on rehabilitated lands; 3736 kg/ha on the site most typical of rehabilitated lands and a mean of 4959 kg/ha across three sites. Seasonal conditions had large effects on cattle liveweight gain (133–213 kg/head per year during the trial); however, pasture growth was the main driver of beef production and economic returns per hectare. In GRASP, potential nitrogen uptake was used to influence key pasture growth processes and accounted for 64% of variation in observed annual growth. The short-term lift and subsequent rundown in productivity typically associated with sown pastures was estimated to have increased mean annual pasture and cattle productivity during the 2014–2018 trial period by up to 17% and 25% respectively. Estimates of long-term mean annual beef production and economic returns for the unmined lands were less than estimated for rehabilitated lands and were 139 kg/head.year (45 kg/ha.year) and AU$154/adult equivalent. Conclusions Rehabilitated lands were found to be sustainable for beef production at grazing pressures up to 30% utilisation of annual pasture growth, and comparable with grazing systems on native and sown pastures in good condition. Pastures on unmined lands retired from cultivation had reduced productivity. Implications Overgrazing is a significant and on-going residual risk to sustainable production. Grazing regimes need to continually adjust for changes in novel landscapes, pasture condition and climate. The methods used in the present study could be applied more generally.

Individual tree and stand-level carbon and nutrient contents across one rotation of loblolly pine plantations on a reclaimed surface mine

While reclaimed loblolly pine (Pinus taeda L.) plantations in east Texas, USA have demonstrated similar aboveground productivity levels relative to unmined forests, there is interest in assessing carbon (C) and nutrients in aboveground components of reclaimed trees. Numerous studies have previously documented aboveground biomass, C, and nutrient contents in loblolly pine plantations; however, similar data have not been collected on mined lands. We investigated C, N, P, K, Ca, and Mg aboveground contents for first-rotation loblolly pine growing on reclaimed mined lands in the Gulf Coastal Plain over a 32-year chronosequence and correlated elemental rates to stand age, stem growth, and similar data for unmined lands. At the individual tree level, we evaluated elemental contents in aboveground biomass components using tree size, age, and site index as predictor variables. At the stand-level, we then scaled individual tree C and nutrients and fit a model to determine the sensitivity of aboveground elemental contents to stand age and site index. Our data suggest that aboveground C and nutrients in loblolly pine on mined lands exceed or follow similar trends to data for unmined pine plantations derived from the literature. Diameter and height were the best predictors of individual tree stem C and nutrient contents (R ≥ 0.9473 and 0.9280, respectively) followed by stand age (R ≥ 0.8660). Foliage produced weaker relationships across all predictor variables compared to stem, though still significant (P ≤ 0.05). The model for estimating stand-level C and nutrients using stand age provided a good fit, indicating that contents aggrade over time predictably. Results of this study show successful modelling of reclaimed loblolly pine aboveground C and nutrients, and suggest elemental cycling is comparable to unmined lands, thus providing applicability of our model to related systems.

The development of topsoil properties under different reclaimed land uses in the Pingshuo opencast coalmine of Loess Plateau of China

A better knowledge on soil development under different land use/cover is critical for restoring eco-environmental integrity in degraded mining areas. This study aims at evaluating the impacts of different reclaimed land uses on topsoil properties over time in an opencast coalmine located at Pingshuo, Shanxi province, China. Over two hundred soil samples at the depth of 0–30cm were collected and analyzed by using descriptive statistic, spatial statistic, and geostatistical method. The results showed that significant differences existed in soil particle distribution, organic carbon (OC), total nitrogen (N), available potassium (AK), and cation exchangeable capacity (CEC) between reclaimed and unmined lands. However, pH, N, total phosphorus (P), available phosphorus (AP) and AK significantly differentiated from each other under different reclaimed land uses, while OC and N were the highest in cultivated soil, followed by forest, grass and barren soils. In addition, the results showed a strong global autocorrelation for pH, OC, N, P, AP and AK. Moreover, the changes of OC and N exhibited U-shape trajectory under forest and grass land, indicating that approximate 20 years were required for reclaimed forest and grass land to restore OC and N comparable to unmined land.

Laboratory-Scale Apparatus for Semi-Continuous Electrokinetic Dewatering of Phosphatic Clay Suspensions

The by-products of phosphatic clay suspensions are a major waste product of the phosphate mining industry. The phosphate clay suspensions produced from beneficiation are about 130,000 gallons per minute (GPM) at about a solids content of 2 wt%. After flocculation the settled clay suspensions at 10% solids content are pumped into the clay settling areas (CSAs) for natural settling. This natural clay settling process takes as much as 25 years to reach the demanded value of 40 wt% solids content. Therefore, the CSAs are frequently constructed on the unmined land and currently cover an area of over 100,000 acres in Florida. Disposal of the phosphatic clay suspensions has become the phosphate mining industry’s major challenge. Thus, it is necessary to develop a technique to increase the solids content of the effluent of phosphate clay suspensions from a phosphate mining beneficiation plant and thereby can save the land used for CSAs and recycling water. A semi-continuous electrokinetic dewatering apparatus for phosphatic clay suspensions has been designed and its performance has been evaluated. A 23 factorial design was applied to determine the optimum process parameters. The results show that the electric field was found to have the greatest positive influence on the solids content. The maximum change in solids content reached a plateau as a function of operating time at a given electric field. Moreover, the plateau occurred earlier at larger electric fields, indicating that for the maximum solids content the optimum parameters of the electric field and the operating time can be determined. The CEDA had lower energy consumption and continuously produced the thickened clay which had the highest solid content of about 33 wt%. The CEDA can be operated to cope with dilute initial solids content (3-10%) from a phosphate mining beneficiation plant. The CEDA has potential to replace existing thickening equipment.

An assessment of microbial communities associated with surface mining-disturbed overburden

To assess the microbiological changes that occur during the maturation of overburden that has been disturbed by surface mining of coal, a surface mining-disturbed overburden unit in southeastern Ohio, USA was characterized. Overburden from the same unit that had been disturbed for 37 and 16years were compared to undisturbed soil from the same region. Overburden and soil samples were collected as shallow subsurface cores from each subregion of the mined area (i.e., land 16years and 37years post-mining, and unmined land). Chemical and mineralogical characteristics of overburden samples were determined, as were microbial respiration rates. The composition of microbial communities associated with overburden and soil were determined using culture-independent, nucleic acid-based approaches. Chemical and mineralogical evaluation of overburden suggested that weathering of disturbed overburden gave rise to a setting with lower pH and more oxidized chemical constituents. Overburden-associated microbial biomass and respiration rates increased with time after overburden disturbance. Evaluation of 16S rRNA gene libraries that were produced by "next-generation" sequencing technology revealed that recently disturbed overburden contained an abundance of phylotypes attributable to sulfur-oxidizing Limnobacter spp., but with increasing time post-disturbance, overburden-associated microbial communities developed a structure similar to that of undisturbed soil, but retained characteristics of more recently disturbed overburden. Our results indicate that over time, the biogeochemical weathering of disturbed overburden leads to the development of geochemical conditions and microbial communities that approximate those of undisturbed soil, but that this transition is incomplete after 37years of overburden maturation.

Wyoming Big Sagebrush Seed Production from Mined and Unmined Rangelands

Wyoming Coal Rules and Regulations require shrubs be returned to mined land and that revegetation ...be self renewing. We evaluated seed production and seed quality of Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis (Beetle & Young)) by measuring the effect of mining, herbivory, and environmental modification on seed production at 5 sites on the Dave Johnston Coal Mine near Glenrock, Wyo. Mined-land stands ranged in age from 5 to >20 years. Single sagebrush plants on mined, and adjacent unmined land were treated by: (1) fabric mulch around the base, (2) windbreak on the north and west, (3) both mulch and windbreak, and (4) neither windbreak nor mulch. Plants were fenced and compared with unfenced, untreated, neighboring plants. Seeds were harvested for 3 years and data were collected on seed-stalk numbers, bulk weight of seeds produced, and seed quality. Fenced mined-land plants produced several times more seeds than fenced plants on adjacent unmined land. There was no difference in seed quality. Treatments to modify the plant environment resulted in some benefits but fencing had a greater effect on seed-quality parameters than did planned treatments. We conclude the sagebrush seed-production potential on reclaimed lands such as those of the Dave Johnston Coal Mine is equal to, and often several times greater than that of adjacent unmined lands. However, browsing by wild ungulates can eliminate the mined-land yield advantage. DOI:10.2458/azu_jrm_v56i5_booth

Wyoming big sagebrush seed production from mined and unmined rangelands

Wyoming Coal Rules and Regulations require shrubs be returned to mined land and that revegetation "...be self renewing." We evaluated seed production and seed quality of Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis (Beetle Young)) by measuring the effect of mining, herbivory, and environmental modification on seed production at 5 sites on the Dave Johnston Coal Mine near Glenrock, Wyo. Mined-land stands ranged in age from 5 to >20 years. Single sagebrush plants on mined, and adjacent unmined land were treated by: (1) fabric mulch around the base, (2) windbreak on the north and west, (3) both mulch and windbreak, and (4) neither windbreak nor mulch. Plants were fenced and compared with unfenced, untreated, neighboring plants. Seeds were harvested for 3 years and data were collected on seed-stalk numbers, bulk weight of seeds produced, and seed quality. Fenced mined-land plants produced several times more seeds than fenced plants on adjacent unmined land. There was no difference in seed quality. Treatments to modify the plant environment resulted in some benefits but fencing had a greater effect on seed-quality parameters than did planned treatments. We conclude the sagebrush seed-production potential on reclaimed lands such as those of the Dave Johnston Coal Mine is equal to, and often several times greater than that of adjacent unmined lands. However, browsing by wild ungulates can eliminate the mined-land yield advantage.

Land restoration management after topsoil mining and implications for restoration policy guidelines in New Zealand

A three-year field trial on an upland loessial soil (Belmont silt loam) in New Zealand investigated the effects of ripping, application of fertilizer N and grazing management on the recovery of some physical, chemical and biochemical properties of soil and pasture productivity following removal (mining) of topsoil. Removing the top 31 cm of soil by mining (all of the A horizon and part of the AB horizon) also removed most of the soil's labile organic matter fractions, and to a lesser extent its total organic matter. After three years, the microbial C and mineralizable N in the 0–10 cm depth of mined soil had reached 65 and 62 per cent of the corresponding levels in unmined soil. Ripping to a depth of 30 cm, application of fertilizer N and lenient grazing of the pasture failed to enhance the recovery of soil fertility. A soil sampling depth of 20 cm provided a reasonable basis to assess the microbial biomass and potential fertility. Pasture productivity was, on average, 30 per cent lower on mined land than on unmined land over the first three years after mining. Application of N proved uneconomic in terms of farm production, although a good pasture response to N fertilizer was obtained. The results from this and related trials are summarized as a series of recommendations for the monitoring and regulation of topsoil mining. An incentive regime is also recommended to encourage land owners and/or topsoil miners to use successful restoration techniques on topsoil-mined land. Copyright © 1999 John Wiley & Sons, Ltd.

Radionuclides in Milk of Dairy Heifers Raised on Forages Harvested from Phosphatic Clay Soils on Reclaimed Mined Land

AbstractAlfalfa (AR; Medicago sativa L.) and corn (CSR; Zea mays L.) were grown in phosphatic clay soils on phosphate‐mined reclaimed land in central Florida. Corn (CSC) also was grown on unmined land and served as a control forage. Upon harvesting, plants were chopped and ensiled. Concentrations of 226Ra averaged 2.44, 0.26, and 0.15; 210Pb averaged 1.04, 0.63, and 0.52; and 210Po averaged 1.59, 0.59, and 1.26 Bq kg−1 DM for AR, CSR, and CSC, respectively. These forages were fed separately to Holstein dairy replacement heifers (Bos taurus) (n = 15 per forage) from approximately 9 to 25 mo of age. Heifers gave birth to calves at approximately 24 mo of age. Samples of milk were collected on d 1, 15, and 30 of lactation and analyzed for radionuclides. Averaged across sampling days, heifers fed AR had greater milk concentrations of 226Ra compared with those fed CSR (0.27 vs. 0.22 Bq kg−1 DM; P<0.10), which, in turn, had greater milk concentrations compared with heifers fed CSC (0.22 vs. 0.13 Bq kg−1 DM; P<0.05). Heifers fed AR also had greater milk concentrations of 210Po compared with heifers fed CSR (0.58 vs. 0.30 Bq kg−1 DM; P<0.10), but values of CSR‐fed heifers were not different from CSC‐fed heifers (0.45 Bq kg−1 DM). Lead‐210 was greater in milk from heifers fed CSR compared with those fed AR or CSC (1.38 vs. 0.94 and 0.92 Bq kg−1 DM; P<0.13), respectively. Plasma S and Cu concentrations suggested subclinical molybdenosis in heifers fed AR. However, all heifers grew at an acceptable rate, conceived normally, had normal gestation periods, gave high quality colostrum at calving, and produced similar amounts of milk.

The growth of spring barley related to soil tilth produced on restored opencast and unmined land

The main limitations to crop growth posed by restored opencast mine land derive from physical changes in the soil. The loss of soil structure makes the land prone to waterlogging and reduces soil workability. For spring cereals the main soil-management problem will be the production of an adequate seedbed. An experiment was therefore conducted on a clay loam soil to examine three alternative cultivation regimes for spring-barley production, these regimes contrasted autumn and spring ploughing and a tined cultivation on unmined land and restored land with and without drainage. Final yields were found to be determined by final ear numbers. This in turn derived from the initial plant population established, which varied with aggregate size distribution in the seedbed tilth. Unmined land produced more favourable tilths and hence higher yields, than either restored site irrespective of the tillage system. On all sites, autumn ploughing produced finer tilths than either spring working treatment. These trends persisted over 4 years and the tilth on all sites deteriorated over this period, though most noticeably on the unmined land. The stability of seedbed aggregates was correlated with soil organic-matter content, which varied across sites. Straw incorporation over 4 years was found to give only a minor enhancement of soil organic-matter concentration over straw burning. This difference did not noticeably affect crop yields or soil aggregation.

Status and trends of freshwater wetlands in the coal-mining region of Pennsylvania, USA

The impact of surface mining for coal on the nature and extent of freshwater wetlands was assessed on 73,200 ha in western Pennsylvania. The influence of mining on wetlands was not uniform across physiographic regions, varying with regional differences in hydrology and soils. Overall, mined lands supported 18% more palustrine wetlands than unmined lands, primarily because of a 270% gain in permanent, open-water wetlands on mined lands in the glaciated region. Open-water wetlands declined on mined lands in unglaciated regions owing to unfavorable hydrologic conditions. The number and size of emergent wetlands declined as a result of mining. Mined lands supported 81% fewer riverine wetlands than unmined lands. This was caused primarily by avoidance of lands containing streams, and secondarily by a 10% reduction in replacement of riverine wetlands during reclamation. Land managers need to develop land use policies that maximize the ecological and social benefits that can be derived from developing diverse wetland communities on mined lands.

Big Game Habitat Use and Diets on a Surface Mine in Northeastern Wyoming

Seasonal habitat use and diets of mule deer (Odocoileus hemionus) and pronghorns (Antilocapra americana) were studied on a coal surface mine in northeastern Wyoming. Alfalfa (Medicago sativa) dominated mule deer diets from spring through fall, and fourwing saltbrush (Atriplex canescens) dominated in winter. Both plant species were well established on reclaimed land. Year-round, deer used reclaimed land more than unmined land. Pronghorn diets consisted of large proportions of native forbs in spring and summer; alfalfa in spring, summer, and fall; and sagebrush (Artemisia spp.) in fall and winter. The importance of native forages to pronghorns, as well as avoidance of reclaimed areas by fawns, resulted in greater year-round use of unmined land than of reclaimed land. Greatest dietary similarity between deer and pronghorns occurred in fall when diets of both species contained large quantities of alfalfa. Diet similarity was least in winter when deer consumed primarily saltbush and pronghorns consumed sagebrush. Improved establishment of native forbs and shrubs will reduce the potential for forage competition among native herbivores and livestock during times of low forage availability. J. WILDL. MANAGE. 50(1): 135-142 In the 10 years since large-scale surface mining activity peaked in the northern Great Plains, little data have been published on the uses of reclaimed land as grazing range and big game habitat. Mule deer, pronghorns, and livestock consume many plant species used to revegetate surface-mined land in the northern Great Plains and available forage, season, and topography influence range use patterns by these species (Bruns 1977, Amstrup 1978, Mackie et al. 1982). In some areas deer and pronghorns use mine spoils (Booth and Schuman 1981, McKell and Van Epps 1981), and livestock grazing of reclaimed land is common management (DePuit and Coenenburg 1979). Mule deer and pronghorns can compete with livestock for forage at certain times of the year, and grazing by domestic animals also can restructure the vegetation to the benefit of big game (Mackie 1978, Smith et al. 1979, Willms et al. 1979). Crockett Club, and the Natl. Wildl. Fed. We acknowledge the cooperation of the U.S. Fish and Wildl. Serv. Iowa Coop. Wildl. Res. Unit, R. B. Dahlgren, Leader, and thank D. G. Steward and D. W. Uresk for reviewing the manuscript. This is paper J-11617 of the Iowa Agric. and Home Econ. Exp. Stn., Proj. 2401.

MINE DRAINAGE AND ROCK TYPE INFLUENCES ON EASTERN OHIO STREAM WATER QUALITY1

ABSTRACT: Stream water during fair weather (base flow) is largely ground water discharge, which has been in contact with minerals of the underlying aquifer. Base flow water quality should therefore reflect aquifer mineralogy as well as upstream land use. Three upstream mining categories (unmined lands, abandoned coal mines, and reclaimed coal mines) differed in pH, specific conductance, sulfate, iron, aluminum, and alkalinity for 122 streams in eastern Ohio. Aquifer rock type influenced pH, specific conductance, sulfate, iron, and alkalinity. Reclamation returned many components of acid mine drainage to near unmined levels, although sulfate and specific conductance were not improved. Acid mine drainage problems were less severe in watersheds underlain by the calcareous Monogahela Formation. These results should ayply to other Appalachian coal regions having similar rock units.The water quality data distributions were neither consistently normal nor lognormal. Statistical tests utilizing ranks of the water quality data, instead of the data themselves, proved useful in analyzing the influences of mining category and rock type.

Coal mine drainage effects on a lotic ecosystem in Northwest Colorado, U.S.A.

An aquatic biological survey was conducted in 1979–1980 to determine the effects of drainage from an active coal strip-mine on Trout Creek, in northwest Colorado, U.S.A. Sampling was conducted over four seasons at four stations for periphyton, benthic invertebrates and fish. Periphyton in Trout Creek changed in the relative abundance of algae divisions in no apparent relation to mining. Diatoms were the predominant division at all sites. Golden-brown algae were abundant in spring at the stations upstream and adjacent to the mine. Blue-green algae were relatively important at stations upstream and downstream of the mine in winter. Benthic invertebrates exhibited a progressive increase in density, biomass and number of taxa from the upstream station to the downstream station. Shannon-Wiener diversity index for bethic invertebrates decreased slightly downstream of mine drainage but remained indicative of a clean water community. Aquatic insects (especially Trichoptera) were the predominant invertebrates at all stations. Analysis of functional groups of benthic invertebrates revealed increased importance of collector species at the lower sites while shredders were most important upstream of the mine. Unlike the invertebrates, fish exhibited slightly lower biomass at the station adjacent to the mine. The decrease was due to fewer salmonids. However, salmonid density and biomass increased substantially at the station just downstream of the mine. Non-game species (suckers and minnows) increased in numbers downstream and were most abundant at the lowest station. This coal strip-mine had little discernable adverse effects on the periphyton and invertebrates of Trout Creek. Fish populations did not appear to be significantly affected by the mine. Apparently, the presence of settling ponds and a buffer zone of unmined land between the mine and the stream helped to minimize adverse effects.