Water-table management in lowland UK peat soils and its potential impact on CO2 emission

The rate of oxidation of peat soils is highly seasonal and varies with temperature and soil moisture content. Large variations in soil moisture content result in wet–dry cycles that can enhance peat degradation. Water‐table management plays a crucial role in controlling and damping the effect of these environmental factors. However, maintaining high ditch water levels in fields bounded by ditches does not guarantee a high field groundwater level. The effect of installing subsurface irrigation at different spacings on water table elevation was studied in a low‐lying peat grassland. The water table elevation data were compared against values predicted with a water balance model. In addition, greenhouse experiments were carried out on undisturbed soil core samples collected from the peat grassland as well as a low‐lying peatland under intensive arable faming to measure CO₂ evolution under different water regimes. The field data from the peat grassland suggest that sub‐irrigation spacing as low as 10 m is necessary during summer periods to maintain groundwater levels similar to those in the ditches. Over the same period of observation, the difference in water level between the ditches and the non‐irrigated fields is as high as 0.7 m. Modelled outputs are in good correlation with the field observations, and demonstrate that simple water balance models can provide an effective tool to study the effect of water management practices and potential changes in subsurface conditions, climate and land use on water‐table levels. The measurement of CO₂ emission from undisturbed peat soil columns shows that the rate of oxidation of soil organic matter from peat soils is highly seasonal and that drainage exacerbates the rate of peat mineralization.     

Effects of intensive harvesting on nutrient capitals of three forest types in New England

Effects of whole-tree clearcutting are being studied in three major forest types in the northeastern United States: a spruce-fir forest in central Maine, a northern hardwood forest in New Hampshire, and a central hardwood forest in Connecticut. At each site we sampled total and extractable nutrient capitals, inputs and outputs of nutrient ions in precipitation and streamflow, nutrient removals in harvested products, and nutrient accumulation in regrowth. Depending upon location, combined losses of nutrients in harvested products and increased leaching to streams were in the ranges of 374–558 kg ha⁻¹ for Ca, 135–253 kg ha⁻¹ for K, 50–65 kg ha⁻¹ for Mg, 248–379 kg ha⁻¹ for N, and 19–54 kg ha⁻¹ for P. Opportunities for replacing these losses over the next rotation are best for N. Data on inputs in precipitation versus outputs in streamflow indicate that, once effects of harvest subside, most N in precipitation will stay within the forest. By contrast, Ca shows a net output of 8–15 kg ha⁻¹ year⁻¹ from uncut watersheds, and the added leaching losses due to harvest may have a serious impact on Ca capital. This is especially the case for the Connecticut site, where total site capital for Ca is only about 4000 kg ha⁻¹.     

Variation in the C:N ratio of substrate mineralized during forest humus decomposition

Laboratory incubations of sieved (<2mm) forest humus were used to study the response of C and N mineralization to perturbation. Considerable variation in the ratio of mineralized C to mineralized N was observed. This ratio widened with increasing temperature. At constant temperature, addition of P stimulated CO₂-C evolution and reduced NH₄⁺-N production, also widening the C:N ratio of substrate mineralized. Addition of weak base stimulated mineralization of N more than C, reducing the C:N ratio of substrate mineralized. Addition of weak acid, mineral-N, or excessive amounts of water inhibited CO₂-C evolution while stimulating production of NH₄⁺-N, resulting in a “negative correlation” between the two, and reducing the C:N ratio of substrate mineralized still further.Results were interpreted in terms of effects on microbial biomass. A relatively benign treatment (P addition) may promote microbial growth and respiration, reducing net N availability. A moderate perturbation (addition of weak base) favors new organisms growing partly at the expense of microbial necromass. These organisms will mineralize some necromass-N, increase net N mineralization, and reduce the C:N ratio of substrate mineralized. Under severe conditions (addition of acid) the C:N ratio of substrate mineralized approaches that of the microbial biomass itself, suggesting that the biomass is the primary substrate mineralized. Microbial mortality is likely to be a significant factor affecting the supply of N in field situations, and should be included in any general model of soil N mineralization processes.     

Effect of meclofenamic acid on the response of parasite-naive lambs and adult sheep to Ostertagia circumcincta

Meclofenamic acid was used to inhibit prostaglandin synthesis in lambs challenged with Ostertagia circumcincta. It lowered the number of parasites which established in treated animals but not significantly. In treated animals plasma pepsinogen values were elevated at the time of parasite emergence but had dropped below the values achieved in control lambs towards the end of the experiment when parasites were at the adult, lumenal dwelling stage. Meclofenamic acid administered to adult immune ewes during challenge with third stage O circumcincta larvae did not significantly affect the establishment of the parasites, nor did it affect the rise in pepsinogen concentration associated with the challenge.     

Modified algorithm to determine localized modulus of elasticity of lumber

Summary A procedure has been developed to determine the cut-off frequency in an algorithm to evaluate the localized modulus of elasticity (MOE) in lumber. MOE profiles have been artificially generated to serve as input for evaluation of the procedure. A noise component has also been added to the input record to test the robustness and accuracy of the procedure. Good agreement between program predictions and the known localized MOE values has been obtained. The efficiency of the procedure has also been tested using MOE profiles collected from experiments. The program performed efficiently and program predictions seemed reasonable.     

Additional pregnane glycoside from Baseonema acuminatum

The isolation of baseonemoside C (1), a new pregnane glycoside from the aerial parts of Baseonema acuminatum is reported.