Assessing multiple novel tracers to improve the understanding of the contribution of agricultural farm waste to diffuse water pollution

A study was undertaken on drained and undrained 1 ha grassland lysimeters to assess the effectiveness of multiple novel tracing techniques in understanding how agricultural slurry waste moves from land to water. Artificial fluorescent particles designed to mimic the size and density of organic slurry particles were found to move off the grassland via inter-flow (surface + lateral through-flow) and drain-flow. Where both pathways were present the drains carried the greater number of particles. The results of the natural fluorescence and δ13C of water samples were inconclusive. Natural fluorescence was higher from slurry-amended lysimeters than from zero-slurry lysimeters, however, a fluorescence decay experiment suggested that no slurry signal should be present given the time between slurry application and the onset of drainage. The δ13C values of >0.7 microm and <0.7 microm material in drainage were varied and unrelated to discharge. The mean value of >0.7 microm δ13C in water from the drain-flow pathways was higher from the lysimeter which had received naturally enriched maize slurry compared to the lysimeter which received grass slurry indicating a contribution of slurry-derived material. Values of <0.7 microm δ13C from the same pathway, however, produced counter intuitive trends and may indicate that different fractions of the slurry have different δ13C values.     

Using Microsimulation to Maximise Scarce Survey Data: Applications for Catchment Scale Modelling and Policy Analysis

Microsimulation can be used to extend the use of scarce survey resources by creating simulated populations whose characteristics are close to those of the real population. The technique involves merging detailed survey observations with variables from more extensive data sets in order to create a simulated population. We illustrate how microsimulated data enable analysis of the economic and environmental impact of different policies on a catchment for which detailed farm level data was unavailable. Use of microsimulation for agri-environmental policy analysis is applicable to diverse problems from simulation of nitrogen trading to modelling of agent response to policy shocks. Scale flexibility is easily implemented since data can be aggregated or disaggregated to the preferred scale. Simulated catchment data allows better understanding of the effects of policies on different types of farm and should be extremely valuable to organisations that want to minimise the economic impact of environmental policies.     

Effect of food type and ration on growth of juvenile Capitella sp. I (Annelida: Polychaeta): macro- and micronutrients

Growth rates of juvenile Capitella sp. I were determined on different rations of six food types: Gerber's mixed cereal, TetraMin fish flakes, benthic diatoms, Ulva sp., spring detritus, and summer detritus. A simple growth model estimated maximum growth rate and maintenance ration for each food. There were differences in the growth response among foods relative to nitrogen content. As juveniles increased in size, differences in growth between foods became more pronounced. For all juveniles, growth rates were correlated with levels of the amino acids histidine, phenylalanine, threonine, and valine, and the polyunsaturated fatty acid 20:5w3; correlations with histidine and phenylalanine levels were the most significant. Regressions of growth rates as a function of these two amino acids suggest a daily maintenance ration of 300 pg histidine and phenylalanine mg^-1 nitrogen biomass. Juvenile worms grew on spring detritus but not on summer detritus, indicating the probable importance of micronutrients (polyunsaturated fatty acids, amino acids) for growth of juvenile Capitella sp. I in the field.     

Hydrogeomorphic considerations in development planning and stormwater management,central Texas Hill Country,USA

Watershed ordinances in Austin, Texas, USA, are intended to protect streams from stormwater degradation. Their adequacy is being questioned, however, where development is advancing into the Hill Country northwest and southwest of the city. Detailed investigation into hillslope runoff reveals that several important facts were overlooked in the ordinances, including locally high infiltration rates and drainage basins, which function as partial area systems. As a result, development planning is not taking advantage of the natural mitigation potential of the land. Roads cut across infiltration and moisture retention areas on side slopes, enlarging the partial area system feeding streams with stormflows. In addition, most residential planning is not responsive to the stepped microtopography of Hill Country drainage basins and the critical scale at which local runoff processes operate. Recommendations include adjusting the scale and configuration of development to conform with local runoff processes and features and taking advantage of the water-absorbing capacities of basin side slopes. The lesson for ordinance writers is that standard models of community stormwater ordinances are not appropriate for all terrains, especially complex ones like the Texas Hill Country.     

Response and resilience of <Emphasis Type="Italic">Spartina alterniflora</Emphasis> to sudden dieback

We measured an array of biophysical and spectral variables to evaluate the response and recovery of Spartina alterniflora to a sudden dieback event in spring and summer 2004 within a low marsh in coastal Virginia, USA. S. alterniflora is a foundation species, whose loss decreases ecosystem services and potentiates ecosystem state change. Long-term records of the potential environmental drivers of dieback such as precipitation and tidal inundation did not evidence any particular anomalies, although Hurricane Isabel in fall 2003 may have been related to dieback. Transects were established across the interface between the dieback area and apparently healthy areas of marsh. Plant condition was classified based on ground cover within transects as dieback, intermediate and healthy. Numerous characteristics of S. alterniflora culms within each condition class were assessed including biomass, morphology and spectral attributes associated with photosynthetic pigments. Plants demonstrated evidence of stress in 2004 and 2005 beyond areas of obvious dieback and resilience at a multi-year scale. Resilience of the plants was evident in recovery of ground cover and biomass largely within 3 y, although a small remnant of dieback persisted for 8 y. Culms surviving within the dieback and areas of intermediate impact had modified morphological traits and spectral response that reflected stress. These morphometric and spectral differences among plant cover condition classes serve as guidelines for monitoring of dieback initiation, effects and subsequent recovery. Although a number of environmental and biotic parameters were assessed relative to causation, the reason for this particular dieback remains largely unknown, however.