The Effect of Lake-Water Infiltration on the Acidity and Base Cation Status of Forest Soil

In this article, the effects of the artificialrecharging of groundwater by infiltrating surface water throughforest soil, i.e. sprinkling infiltration, on the acidity andbase cation status of the soil are described. The study wascarried out in the Ahvenisto esker area, Hämeenlinna,southern Finland, during 1996–1998. The sample plots werelocated in a 110- to 160-yr-old Scots pine (Pinussylvestris L.) stand. The site was classified as the Oxalis-Maianthemum type. The soil consisted of a mixture oftill and glaciofluvial sediments. The pH of the organic layerincreased from 4.7 to >6.5 soon after the start of irrigationon the infiltration plot. The pH of the 0–10 cm mineral soillayer also increased from 4.9 to 6.4 as a result ofinfiltration. Sprinkling infiltration increased theexchangeable Ca and Mg concentrations in the organic anduppermost mineral soil layers. The output of Ca and Mg inpercolation water from the 0–100 cm thick layer was lower thanthe input to the soil surface via irrigation in 1996. Theretention of Ca and Mg on cation exchange sites took placewithin a relatively short period of time, since retention wasobserved only in 1996 but no longer in 1997 or 1998 indicatingsaturation of the cation exchange sites by base cations. Lakewater infiltration leads to the neutralisation of forest soilacidity, and increases the capacity of the soil to withstandacidic inputs by increasing the concentrations of exchangeablebase cations on cation exchange sites in the soil.     

Animal treading stimulates denitrification in soil under pasture

The effects of animal treading on denitrification in a mixed ryegrass-clover pasture were studied. A single treading event of moderate or severe intensity was applied in plots during spring by using dairy cows at varying stocking rates (4.5 cows 100 m⁻² for 1.5 or 2.5 h, respectively). Treading caused a significant short-term 21 days) increase in denitrification. Denitrification rates reached a maximum of 52 g N₂O-N ha⁻¹ day⁻¹ at 8 days after severe treading compared to 2.3 g N₂O-N ha⁻¹ day⁻¹ under nil treading. Thereafter, denitrification rates declined, and were similar to non-trodden control plots after 28 days. Soil aeration, was significantly reduced by treading as expressed by water-filled porosity. In addition, soil NH₄⁺-N and NO₃⁻-N concentrations were also increased by treading. We propose that the underlying processes involved in increasing denitrification under treading were two-fold. Firstly, treading caused a temporary (e.g. 3 days after treading) reduction in soil aeration through soil physical damage, and secondly, reduced soil N utilisation prompted by reduced plant growth led to increased soil NH₄⁺-N and NO₃⁻-N availability. This study shows that treading, without the influence of other grazing animal factors (e.g. excretion), can cause a large short-term stimulation of denitrification in grass-clover pastures.     

Using auction mechanisms to reveal costs for water quality improvements in Great Barrier Reef catchments in Australia

There is increasing interest in the use of market-based instruments such as tenders and trading systems to address water quality issues. While the focus is typically on the improvements in resource allocation that are generated, these instruments also play an important role in addressing issues of asymmetric information. The use of water quality tenders to reveal the opportunity costs of changing agricultural practices can help policy makers to understand the potential costs of misallocating public resources and to design better ways of achieving water quality improvements. This role of water quality tenders to reveal opportunity costs is demonstrated by reporting four pilot applications to improve water quality into the Great Barrier Reef in Australia. The results demonstrate the potential for opportunity costs to vary substantially between agricultural producers, and across industries, catchments and pollutants. The results from these case studies indicate that the most cost-effective water quality improvements may be generated from the horticulture and dairy sectors. In contrast, the opportunity costs of reducing emissions from the cane and grazing industries appear to be higher.     

Effects of increasing acidity on aquatic protozoan communities

Laboratory tests were conducted to evaluate the chronic effects of increased acidity on protozoan communities. Taxonomic richness of the protozoan component of these communities was severely affected at pH ≤ 5.33. Taxonomic composition was significantly affected at much higher pH. A permissible concentration was defined as the pH affecting no more than 20% of the species and estimated from concentration-response regression as 6.92 (5.92 to 8.04) pH units. A similar value estimated from more conventional chronic toxicity tests was 6.28 (6.16 to 6.45) pH units. Bacterial abundance decreased at pH levels ≤ 5.34 pH units. Other nontaxonomic responses (e.g., biomass, algal biomass, fungal biomass, net oxygen metabolism) were not sensitive to increases in acidity.     

Antifungal activity and fungal metabolism of steroidal glycosides of Easter lily (Lilium longiflorum Thunb.) by the plant pathogenic fungus, Botrytis cinerea

Botrytis cinerea Pers. Fr. is a plant pathogenic fungus and the causal organism of blossom blight of Easter lily (Lilium longiflorum Thunb.). Easter lily is a rich source of steroidal glycosides, compounds which may play a role in the plant-pathogen interaction of Easter lily. Five steroidal glycosides, including two steroidal glycoalkaloids and three furostanol saponins, were isolated from L. longiflorum and evaluated for fungal growth inhibition activity against B. cinerea, using an in vitro plate assay. All of the compounds showed fungal growth inhibition activity; however, the natural acetylation of C-6' of the terminal glucose in the steroidal glycoalkaloid, (22R,25R)-spirosol-5-en-3β-yl O-α-L-rhamnopyranosyl-(1→2)-[6-O-acetyl-β-D-glucopyranosyl-(1→4)]-β-D-glucopyranoside (2), increased antifungal activity by inhibiting the rate of metabolism of the compound by B. cinerea. Acetylation of the glycoalkaloid may be a plant defense response to the evolution of detoxifying mechanisms by the pathogen. The biotransformation of the steroidal glycoalkaloids by B. cinerea led to the isolation and characterization of several fungal metabolites. The fungal metabolites that were generated in the model system were also identified in Easter lily tissues infected with the fungus by LC-MS. In addition, a steroidal glycoalkaloid, (22R,25R)-spirosol-5-en-3β-yl O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside (6), was identified as both a fungal metabolite of the steroidal glycoalkaloids and as a natural product in L. longiflorum for the first time.     

Differentiation of physical from chemical toxicity in solid waste fish bioassays

This study showed that particulate (i.e., physical) toxicity was responsible for rainbow trout deaths in bioassays with two separate solid wastes. This conclusion was based on: (1) fish necropsies which indicated physical damage to gills but no evidence of chemical damage to liver or kidney, (2) chemical analyses which indicated that levels of Priority Pollutants and other target compounds were too low to cause the observed toxicity, (3) structural and chemical analyses of the waste particles which showed that these consisted of inert materials, and (4) the use of centrifugation techniques to remove most of the suspended particulate material in bioassay tanks resulting in an elimination of most of the toxicity. The particles associated with the lethal effects were approximately 5 to 10 μm in size. Regulatory testing of solid wastes must distinguish physical and chemical toxicity since disposal options can vary depending on the mode of toxicity. For instance, chemical toxicity raises concern regarding leaching through soils into groundwater, whereas if physical particles are responsible for toxicity, such leaching is not of concern.