Water balance, transpiration and canopy conductance in two beech stands

Measurements of sap flow, vapour fluxes, throughfall and soil water content were conducted for 19 months in a young beech stand growing at low elevation, in the Hesse forest. This experiment is part of the Euroflux network, covering 15 representative European forests. Study of the radial variation of sap flow within tree trunks, showed a general pattern of sap flux density in relation to the depth below cambium. Among-tree variation of sap flow was also assessed, in order to determine the contribution of the different crown classes to the total stand transpiration. Stand sap flow and vapour flux, measured with eddy covariance technique, were well correlated, for half hourly as well for daily values, the ratios of the fluxes for both averaging periods being 0.77. A strong canopy coupling to the atmosphere was found, omega factor ranging between 0.05 and 0.20 relative to the windspeed. Canopy conductance variation was related to a range of environmental variables: global radiation, vapour pressure deficit, air temperature and soil water deficit. In addition to the effect of radiation and of vapour pressure deficit often found in various other tree species, here beech exhibited a strong reduction in canopy conductance when air temperature decreased below 17°C. The model of transpiration was calibrated using data measured in the Hesse forest and applied to another beech stand under mountainous conditions in the Vosges mountains (east France). Measured and modelled stand transpiration were in good agreement.     

A yield-independent, 15N-isotope dilution method to estimate legume symbiotic dependence without a non-N2-fixing reference plant

The proportional contribution of atmospheric N₂ to the N nutrition of lupin (P _atm) was estimated in a field experiment following addition of NH₄Cl of KNO₃ to unconfined microplots (1.5 m²) at 2.5 g N m^-2 (10 atom% ¹⁵N). The integrated ¹⁵N enrichment, or mean pool abundance, of nitrate extracted from 0- to 15-cm samples taken under the lupin crop on eight occasion between 28 and 190 days after sowing was used as the reference criterion to estimate P _atm by the ¹⁵N-isotope dilution technique. Estimates of P _atm were similar to those obtained using canola as a non-fixing reference plant, but were higher than estimates obtained using a yield-dependent model. Use of mean pool abundance obviates the need for a non-fixing reference plant, and the frequent sampling and isotope-ratio analysis of the legume biomass required with the yield-dependent model is unnecessary. However, further work is needed to validate a sampling strategy commensurate with the growth of the legume roots.     

Moisture conservation for rainfed wheat production with alternative mulches and conservation tillage in the hills of north-west India

In the hills of north–west India, maize (Zea mays L.)-wheat (Triticum aestivum L.) is the dominant cropping system. However, rainfed wheat suffers from lack of optimum moisture at sowing. Field experiments were conducted for 3 years on a silty clay loam (Typic Hapludalf) to evaluate the effectiveness of mulches and conservation tillage for rainfed wheat in mitigating this problem. The treatments were ten factorial combinations of five mulch-tillage practices and two nitrogen levels (N₆₀ and N₁₂₀ kg ha⁻¹). Mulch treatments consisted of application of 10 Mg ha⁻¹ (dry weight basis), to previous standing maize, of either wild sage (Lantana camara L.) or eupatorium (Eupatorium adenophorum Sprengel) in combination with either conventional or conservation (minium) tillage prior to wheat sowing. These alternative practices were compared to the conventional farmer practice of soil tillage after harvest of maize with no mulch. The application of these weed mulches to standing maize maintained friable soil structure owing to a five fold higher mean population of earthworms underneath mulch. Mulches resulted in 0.06–0.10 m³ m⁻³ higher moisture in the seed-zone when wheat was sown compared with the conventional farmer practice of soil tillage after maize harvest. Mulch-conservation tillage treatments favourably moderated the hydro-thermal regime for growing a wheat crop. The mean root mass density under these treatments at wheat flowering was higher by 1.27–1.40 times over the conventional farmer practice during the 3 year study. Conservation tillage holds promise because it does not require elaborate tillage and may ultimately reduce animal draught in the hilly regions. Recycling available organic materials having no fodder value coupled with conservation tillage may help enrich the soil environment in the long-term. The practice also offers gainful use of these obnoxious weeds that cause great menace in grass and forest lands in the region.     

Nitrate leaching loss following application of organic manures to sandy soils in arable cropping.

Abstract. Experiments were set up at two sites to measure nitrogen (N) leaching loss from applications of separated pig/cattle slurry and cattle farmyard manure(FYM), during winters 1990/91–1993/94 (site A) and from broiler litter and FYM, during winters 1990/91–1992/93 (site B). The manures were applied at a target rate of 200 kg ha^-1 total N during the autumn and winter to overwinter fallow or top dressed onto winter rye. The total N in leachate was calculated from leachate N concentrations, in samples collected using ceramic cups buried at 90 cm, and an estimate of drainage volume. Nitrogen losses were greatest following manure applications in September, October and November but losses following applications in December or January were not significantly elevated above those from untreated controls. Losses were consistently lower from FYM than from broiler litter or separated slurry. The presence of a cover crop (winter rye) significantly reduced overall N leaching compared with the fallow, but only reduced the manure N leaching losses at one site during one winter when a high proportion of drainage occurred late. The incorporation of a nitrification inhibitor (DCD) with manures applied in October did not significantly reduce the manure N leaching.     

Aggregation studied by laser diffraction in relation to plowing and liming in the Cerrado region in Brazil

In the Cerrado savanna region in Brazil, the effects of different land use on Oxisol aggregation were studied using laser diffraction grain size analyses. The topsoil of plowed systems had significantly lower amount of macroaggregates (2000–194 μm) and a significantly higher amount of soil in the microaggregate size and primary particle fraction (<76 μm) compared to pastures and the native Cerrado. In plowed systems low in soil organic carbon (SOC), lime had a negative effect on aggregate stability. Lime addition had no effect on topsoil aggregation in land use systems that were not plowed regularly and generally had a higher SOC content. For all the studied topsoils, pH_KCl was positively correlated with the amount of clay dispersed after 3 h of shaking in water. SOC did not influence clay dispersion in the range of soils studied. In continuous cropping systems in the Cerrado region, with a combination of mechanical stress and low SOC, liming will cause an increase in small aggregates and primary particles and hence contribute to a destabilization of the soil structure.     

Polyphenolic content in five tuscany cultivars of Olea europaea L.

In this study polyphenolic compounds extracted from olive fruits of five registered cultivars were analyzed. A solid-liquid extraction (LSE) procedure with Extrelut cartridge (diatomaceous earth) using different eluents was developed to obtain polyphenolic compounds. HPLC-DAD and HPLC-MS methods were applied for the quali-quantitative analysis of each fraction obtained from LSE. The results of this work show that the LSE procedure with diatomaceous earth cartridge supplies a rapid and reproducible fractioning method able to obtain a quantitative recovery of all compounds and to collect fractions directly analyzed by HPLC. A comparison among different cultivars shows significant quantitative differences in some polyphenols, such as verbascoside, anthocyanic compounds, and oleuropein derivatives.     

Impact of 1-methylcyclopropene and methyl jasmonate on apple volatile production.

Climacteric Fuji apples were treated with 10 microL x L(-1) MCP (1-methylcyclopropene), 2 mmol x L(-1) MJ (methyl jasmonate), or a combination of 10 microL x L(-1) MCP and 2 mmol x L(-1) MJ. Fruit were kept at 20 degrees C for 15 days after treatment. Production of ethylene and other volatile compounds was measured prior to and 3, 7, 11, and 15 days after treatment. Ethylene production decreased 3 days following MJ treatment and then increased. MCP treatment alone or in combination with MJ inhibited ethylene production. MJ and MCP inhibited production of many volatile alcohols and esters. The production of individual alcohols and esters appears to be differentially inhibited by MJ or MCP. MJ and MCP inhibited not only production of alcohols but also formation of esters from alcohols.     

Partial characterization of polyphenol oxidase activity in raspberry fruits.

A partial characterization of polyphenol oxidase (PPO) activity in raspberry fruits is described. Two early cultivars harvested in May/June (Heritage and Autumm Bliss) and two late cultivars harvested in October-November (Ceva and Rubi) were analyzed for PPO activity. Stable and highly active PPO extracts were obtained using insoluble poly(vinylpyrrolidone) (PVP) and Triton X-100 in sodium phosphate, pH 7.0 buffer. Polyacrylamide gel electrophoresis of raspberry extracts under nondenaturing conditions resolved in one band (R(f)()(1) = 0.25). Raspberry PPO activity has pH optima of 8.0 and 5.5, both with catechol (0.1 M). Maximum activity was with D-catechin (catecholase activity), followed by p-coumaric acid (cresolase activity). Heritage raspberry also showed PPO activity toward 4-methylcatechol. Ceva and Autumm Bliss raspberries showed the higher PPO activity using catechol as substrate.     

Distribution and Phytoavailability of Lead in a Soil Contaminated with Lead Shot

Water, Air, &; Soil Pollution - This paper presents a study of Pb contamination of soil at a clay target shooting facility in Canterbury, New Zealand. The spatial distribution of Pb...     

Oxidation-reduction regimes in some Oxisols of tropical China

The oxidation-reduction regimes of some Oxisols of tropical China were investigated on the basis of the Eh values and the amounts of reducing substances, both measured by newly devised methods. The Eh values in the surface layers of soil profiles under natural forest and commercial forest were 400–550 mV, lower by 100–200 mV than the deeper horizons. The concentrations of reducing substances in the surface layers corresponded to 0.5–5.0 · 10^?5M of Mn²⁺. In the cultivated layer of a submerged paddy soil the concentration of reducing substances was as high as 13·10^?5M, with an Eh value of less than 100 mV. There was a negative correlation between the Eh value and the logarithm of the concentration of reducing substances, showing that the intensity aspect and the capacity aspect of the oxidation-reduction status of a soil are closely interrelated.