Ecological land classification: A survey approach

A landscape approach to ecological land mapping, as illustrated in this article, proceeds by pattern recognition based on ecological theory. The unit areas delineated are hypotheses that arise from a knowledge of what is ecologically important in the land. Units formed by the mapper are likely to be inefficient or irrelevant for ecological purposes unless he possesses a sound rationale as to the interactions and controlling influences of the structural components of ecosystems. Here is the central problem with what have been called objective multivariate approaches to mapping based on grid units and the sometimes arbitrary attributes thereof; they tend to conceal the importance of ecological theory and the necessity for theory-based supervision of pattern recognition. Multivariate techniques are best used iteratively to verify and refine map units initially recognized and delineated by theoretical considerations. These ideas are illustrated by an example of a reconnaissance survey in the Northwest Territories of Canada.     

EFFECT OF URBANIZATION ON ALTERNATIVE FLOOD CONTROL STRATEGIES1

ABSTRACT: The effect of urbanization on alternative flood control strategies was investigated for a large developing watershed in Texas. Urban and rural areas were modeled separately using a geographically-referenced data base and the U.S. Corps of Engineers HEC-1 and HEC-2 programs, and results yielded a double-peaked hydrograph. Hydrograph input parameters were modified to predict the effects of a wide range of management alternatives including on-site storage, reservoirs, channelization, and development controls. Results indicated a combination of alternatives is required to protect existing and future developments.     

Swine effluent irrigation rate and timing effects on bermudagrass growth,nitrogen and phosphorus utilization,and residual soil nitrogen

Maximizing utilization of effluent nutrients by forage grasses requires a better understanding of irrigation rate and timing effects. This study was conducted in 1998 and 1999 on a Vaiden silty clay (very-fine, smectitic, thermic Aquic Dystrudert) soil to determine the effects of swine lagoon effluent irrigation rate and timing on bermudagrass [Cynodon dactylon (L.) Pers.] growth, nitrogen (N) and phosphorus (P) recovery, and postseason soil profile NO3(-)-N. Treatments consisted of swine effluent irrigation at the rates of 0, 5, 10, 15, and 20 ha-cm. Two additional treatments included 2.5 ha-cm applied on 1 September and 1 October in addition to a base summer rate of 10 ha-cm. In both years for early to mid-season irrigation, bermudagrass dry matter yield quadratically increased with increasing swine effluent irrigation rates. Averaged across years, effluent irrigation in October resulted in 30% less dry matter than in September. For late-season irrigation, apparent N recovery averaged 59% less and P recovery averaged 46% less with a delay in irrigation from 1 September to 1 October. The greatest quantity of soil NO3(-)-N was associated with both the greatest effluent rate and October irrigation treatments. Minimal yield benefit was obtained when effluent was applied at rates greater than 10 ha-cm during the summer months. Late-season irrigation, especially after 1 October for areas with similar climatic conditions, should be avoided to maximize synchronization of nutrient availability with maximum growth rates to minimize potential offsite movement of residual soil N and P.     

The economic effects of stratospheric ozone depletion on U.S. agriculture: a preliminary assessment

The adverse effects of stratospheric ozone depletion on human health and welfare is a major environmental concern. One potential welfare effect is reduction in plant productivity, including agricultural crops, due to increased UV-B radiation and tropospheric ozone formation. This paper evaluates the economic effects of potential changes in crop yields due to hypothetical depletions in stratospheric ozone over regions of the U.S.A. Results suggest that increases in tropospheric ozone due to a 15 per cent stratospheric ozone depletion may cause economic losses of around 0·9 billion dollars. Combined effects of both tropospheric ozone and UV-B radiation range from 1·3 to 2·5 billion dollars. These estimates are preliminary, given the high degree of uncertainty in key plant science and aerometric data.     

DEVELOPMENT OF WATER QUALITY MANAGEMENT INDICES1

ABSTRACT: In a joint undertaking by The MITRE Corporation and the EPA Office of Water Programs Operations, three indices were developed: (1) An index of water quality; (2) An index of the need for abatement action; and (3) An index of the need for water quality management planning. These indices were evaluated for some 1000 planning areas (sub basins, regional planning jurisdictions, metropolitan areas, etc.) which together cover essentially all of the area of the 48 contiguous states.     

Initial tree establishment on blocky quarry waste ameliorated with hydrogel or slate processing fines

Pocket planting reclamation techniques developed in the 1970s for revegetating blocky quarrying waste have met with very limited success, often because the low water-holding capacity of the waste and limited root development within a small volume of planting pocket material result in severe drought mortality. We tested pocket planting approaches for waste tip reclamation at Europe's largest slate quarry, and compared materials for enhancing the continuity of water- and nutrient-holding down into the interior of the waste tip. When small compost-filled pocket planting bags were placed above slate processing fines (SPF) or water absorbent cross-linked polyacrylamide gel ("hydrogel"), tree growth rates increased in comparison with pocket planting bags alone. The SPF significantly improved tree survival especially during severe drought, but survival was not enhanced by the use of hydrogel. The sorption characteristics of hydrogel indicated that its presence may help to reduce nutrient leaching, but that it may have a negative effect on nitrogen availability. A more likely explanation for the poor performance of pure hydrogel is that it did not maintain sufficient available water, because of discontinuities caused by shrinkage and movement of the hydrogel, and/or degradation of water-holding capacity with environmental exposure. However, the root growth observed in the hydrogel treatments suggests that this technique, if adapted to reduce the effects of hydrogel shrinkage by using finer-grade hydrogel, mixing it with other soil-forming material, and reducing its exposure to extremes of temperature or sunlight, might have the potential to improve the growth and survival of trees planted on sites where delivery of heavy materials such as SPF is impractical. Fine mineral processing waste is freely available at active quarries and should be seen as a key resource for reclamation schemes.     

Nocturnal movements of phototactic zooplankton in shallow waters

Downwardly directed light-traps were used by night, over seagrass and coral sand to investigate the existence and significance of nocturnal peaks in phototactic zooplankton. Samples each half-hour from sunset to sunrise showed that small invertebrates, mostly copepods, were trapped in large numbers once or twice a night. Each period of high catches lasted only 1 to 2 h and was often associated with periods of failing natural light (evening twilight, moonset). This pattern and its variations are explained in terms of nocturnal vertical migration, in which plankton move towards light in response to decreasing light intensity, move away from light in response to increasing light intensity, and disperse at constant light intensity. Some morning peaks are unexplained.     

Evolution of clog formation with time in columns permeated with synthetic landfill leachate

Laboratory column tests conducted to gain insight regarding the biological and chemical clogging mechanisms in a porous medium are presented. To seed the porous medium with landfill bacteria, a mixture of Keele Valley Landfill and synthetic leachate permeated through the column under anaerobic conditions for the first 9 days of operation. After this, 100% synthetic leachate was used. The synthetic leachate approximated Keele Valley Landfill leachate in chemical composition but contained negligible suspended solids and bacteria compared with real leachate. The removal of volatile fatty acids (VFAs), primarily acetate, in leachate as it passed through the medium was highly correlated with the precipitation of calcium carbonate (CaCO(3(s))) from solution. The columns experienced a decrease in drainable porosity from an initial value of about 0.38 to less than 0.1 after steady state chemical oxygen demand (COD) removal, resulting in a five-order magnitude decrease in hydraulic conductivity. The decrease in drainable porosity prior to steady state COD removal was primarily due to the growth of a biofilm on the medium surface. After steady state COD removal, calcium precipitation was at least equally responsible for the decrease in drainable porosity as biofilm growth. Clog composition analyses showed that CaCO(3(s)) was the dominant clog constituent and that 99% of the carbonate in the clog material was bound to calcium.     

The deadly effects of "nonlethal" predators

Nonconsumptive predator effects are widespread and include plasticity as well as general stress responses. Caged predators are often used to estimate nonconsumptive effects, and numerous studies have focused on the larval stages of animals with complex life cycles. However, few of these studies test whether nonconsumptive predator effects, including stress responses, are exclusively sublethal. Nor have they assessed whether these effects extend beyond the larval stage, affecting success during stressful life-history transitions such as metamorphosis. We conducted experiments with larvae of a dragonfly (Leucorrhinia intacta) that exhibits predator-induced plasticity to assess whether the mere presence of predators affects larval survivorship, metamorphosis, and adult body size. Larvae exposed to caged predators with no ability to attack them had higher levels of mortality. In the second experiment, larvae reared with caged predators had higher rates of metamorphic failure, but there was no effect on adult body size. Our results suggest that stress responses induced by exposure to predator cues increase the vulnerability of prey to other mortality factors, and that mere exposure to predators can result in significant increases in mortality.     

Application of the probability-based Maryland Biological Stream Survey to the state’s assessment of water quality standards

The Clean Water Act presents a daunting task for states by requiring them to assess and restore all their waters. Traditional monitoring has led to two beliefs: (1) ad hoc sampling (i.e., non-random) is adequate if enough sites are sampled and (2) more intensive sampling (e.g., collecting more organisms) at each site is always better. We analyzed the 1,500 Maryland Biological Stream Survey (MBSS) random sites sampled in 2000–2004 to describe the variability of Index of Biotic Integrity (IBI) scores at the site, reach, and watershed scales. Average variability for fish and benthic IBI scores increased with increasing spatial scale, demonstrating that single site IBI scores are not representative at watershed scales and therefore at best 25% of a state’s stream length can be representatively sampled with non-random designs. We evaluated the effects on total taxa captured and IBI precision of sampling for twice as many benthic macroinvertebrates at 73 MBSS sites with replicate samples. When sampling costs were fixed, the precision of the IBI decreased as the number of sites had to be reduced by 15%. Only 1% more taxa were found overall when the 73 sites where combined. We concluded that (1) comprehensive assessment of a state’s waters should be done using probability-based sampling that allows the condition across all reaches to be inferred statistically and (2) additional site sampling effort should not be incorporated into state biomonitoring when it will reduce the number of sites sampled to the point where overall assessment precision is lower.