Converting tropical rainforest to forest plantation in sabah,malaysia. Part II. Effects on nutrient dynamics and net losses in streamwater

Streamwater chemistry was monitored for five years in six streams in a paired catchment experiment in Mendolong, Sabah, Malaysia, comparing the effects of different ways to establish forest plantations with Acacia mangium. At the start of the monitoring in 1985 three catchments were covered with selectively logged rain forest (W4-W6) and three with secondary vegetation after forest fire (W1-W3). The treatments were: (1) clearing of secondary vegetation, burning and planting (W1 and W2); (2) clear-felling, crawler tractor extraction, burning and planting (W5); and (3) clear-felling, manual extraction, no burning and planting (W4). W3 and W6, with no treatment, were monitored as control catchments. Reference monitoring at all streams was for two years and was followed by treatments which lasted for nine months before the full establishment of a new vegetation cover. This paper covers monitoring for a further 2.5 years. The soil types of the catchments were Orthic Acrisol in W3, Gleyic Podsol in W6 and a mix of both soil types in the other catchments. The effect of treatments on streamwater chemistry was clear at both base- and stormflows. Concentrations of major plant nutrients (N, P and K.) became positively correlated to streamflow during treatments. The response of leaching from slash at clear-felling was fast and larger from the clear-felling residues (W4 and W5) than the cleared secondary vegetation (W1 and W2). The intense response to burning was more marked. The stormflow period mean nutrient concentrations were approximately 10-fold for N and K and 10-100 fold for P after burning compared with baseflow mean concentrations over the same period. Significant differences in baseflow concentrations in treated streams generally lasted one year for most elements, but elevated concentrations were still detectable after three years. The first large pulse of leaching was related to mineralization after tree-felling and particularly burning. The longer lasting elevated concentrations in baseflow were associated with the loss of weathering products. The amounts of nutrients lost, calculated by regression analysis as the effect of treatment compared with control, were found to be higher with the degree of vegetation killed and with increased soil disturbance. Consequently, normal forestry practices, with crawler tractor extraction and burning before planting, created the largest leaching losses. The total calculated effect of losses in total N, P and K were (i) W1 + W2 0.5, 1.8, 83.9; (ii) W4 0.8, 0.8, 105.6; and (iii) W5 1.3, 1.3, 189.4 kg ha^?1 for the period of 33 months during and after treatment. With normal forestry practice using crawler tractors and with burning before planting (W5), the treatment-induced loss of K was equivalent to 86% of the content of easily decomposed parts of the biomass (leaves, twigs, fine roots and ground vegetation) of the old forest, or larger than K removed by harvest. Exhaustion effects of lowered leaching after repeated burning (forest fire and pre-planting fire) was observed for several elements, indicating possible nutrient deficiencies.     

Responses of benthic macrofauna and biogeochemical fluxes to various levels of mussel biodeposition: An in situ “benthocosm” experiment

An in situ experiment was done to evaluate the dose-dependent response of mussel biodeposition on benthic communities and biogeochemical fluxes. Natural benthic communities were exposed to 7 different levels of mussel biodeposition (equivalent to that produced by 0-764 mussels m⁻²) over 50 days. Benthic communities responded as predicted from the Pearson, T.H., Rosenberg, R., 1978. Macrobenthic succession in relation to organic enrichment and pollution of the marine environment. Oceanogr. Mar. Biol. Annu. Rev. 16, 229-311 model of organic enrichment. Total abundance and species richness decreased with increasing biodeposition. The abundance and biomass of opportunistic species (Capitella spp.) increased in the mesocosms subject to the greatest biodeposition. Sensitive species Tellina agilis and Pherusa plumosa tended to decrease in abundance and biomass with increasing biodeposition. The biotic index M-AMBI responded clearly to increased biodeposition and may be a useful tool for assessing the effect of mussel biodeposition on the benthic environment. These results are important for the construction of predictive models for determining environmental carrying capacity for bivalve aquaculture.     

A case study of in situ oil contamination in a mangrove swamp (Rio De Janeiro, Brazil)

Mangroves are sensitive ecosystems of prominent ecological value that lamentably have lost much of their areas across the world. The vulnerability of mangroves grown in proximity to cities requires the development of new technologies for the remediation of acute oil spills and chronic contaminations. Studies on oil remediation are usually performed with in vitro microcosms whereas in situ experiments are rare. The aim of this work was to evaluate oil degradation on mangrove ecosystems using in situ microcosms seeded with an indigenous hydrocarbonoclastic bacterial consortium (HBC). Although the potential degradation of oil through HBC has been reported, their seeding directly on the sediment did not stimulate oil degradation during the experimental period. This is probably due to the availability of carbon sources that are easier to degrade than petroleum hydrocarbons. Our results emphasize the fragility of mangrove ecosystems during accidental oil spills and also the need for more efficient technologies for their remediation.     

Effects of CO2 on benthic biota: An in situ benthic chamber experiment in Storfjorden (Norway)

Carbon capture and storage (CCS) methods, either sub-seabed or in ocean depths, introduces risk of CO₂ leakage and subsequent interaction with the ecosystem. It is therefore important to obtain information on possible effects of CO₂. In situ CO₂ exposure experiments were carried out twice for 10 days during 2005 using a Benthic Chamber system at 400 m depth in Storfjorden, Norway. pCO₂ in the water above the sediment in the chambers was controlled at approximately 500, 5000 and 20,000 μatm, respectively. This article describes the experiment and the results from measured the biological responses within the chamber sediments. The results show effects of elevated CO₂ concentrations on biological processes such as increased nanobenthos density. Methane production and sulphate reduction was enhanced in the approximately 5000 μatm chamber.