Seth Nii-Annang

Microbial Actvity and 13C/12C Ratio as Evidence of N-Hexadecane and N-Hexadecanoic Acid Biodegradation in Agricultural and Forest Soils

The dynamics of microbial degradation of exogenous contaminants, n-hexadecane and its primary microbial oxidized metabolite, n-hexadecanoic (palmitic) acid, was studied for topsoils, under agricultural management and beech forest on the basis the changes in O2 uptake, CO2 evolution and its associated microbial and non-microbial carbon isotopic signature, the respiratory quotient (RQ) and the priming effect (PE) of substrates. Soil microbial communities in agricultural soil responded to the n-hexadecane addition more rapidly compared to those of forest soil, with lag-periods of about 23 ± 10 and 68 ± 13 hours, respectively. Insignificant difference in the lag-period duration was detected for agricultural (tlag = 30 ± 13 h) and forest (tlag = 30 ± 14 h) soils treated with n-hexadecanoic (palmitic) acid. These results demonstrate that the soil microbiota differed in metabolic activities for using n-hexadecane as a reductive hydrocarbon and n-hexadecanoic acid as a partly oxidized hydrocarbon. The corresponding δ13C of respired CO2 after the addition of the hydrocarbon contaminants to soils indicates a shift in microbial activity towards the consumption of exogenous substrates with a more complete degradation of n-hexadecane in the agricultural soil, for which some initial contents of hydrocarbons are inherent. It was reflected in the carbon isotope signature of microbial biomass. It is supposed that the observed deviation of RQ from theoretically calculated value under microbial substrate mineralization is determined by difference in the time (Δti) of registration of CO2 production and O2 consumption. Positive priming effect (PE) of n-hexadecane and negative PE of n-hexadecanoic (palmitic) acid were detected in agricultural and forest soils. It is suggested that positive PE of n-hexadecane is conditioned by the induction of microbial enzymes that perform hydroxylation/oxygenation of stable SOM compounds mineralized by soil microbiota to CO2. The microbial metabolism coupled with oxidative decarboxylation of n-hexadecanoic acid is considered as one of the most probable causes of the revealed negative PE value.

Soil Respiratory Indicators Including Carbon Isotope Characteristics in Response to Copper

The human impact on soil functions with reference to environmental pollution and climatic changes have received great attention during the last decades. A widespread and integral environmental indicator is the soil microbial respiration and can be estimated either on the basis of carbon dioxide evolution or of oxygen uptake. In accordance with many previous studies, we found that soil respiration decreased in the presence of heavy metals such as Cu. The Cu spiking of an acid and unpolluted, organic-rich pine forest soil at approximately the limits for sewage sludge (100 to 200 μ g Cu g −1 soil) led to high concentrations of up to 0.35 μ g Cu per ml in the soil solution and reduced carbon dioxide evolution by 27% and the oxygen uptake by 18% during basal respiration. Thus, the respiratory quotient (RQ) which is defined as the carbon dioxide evolution related to oxygen uptake was reduced with increasing Cu levels. The Cu effect was also detected after the addition of glucose as a readily available substrate. In the soil investigated, the carbon isotope characteristic of the 13 C-CO 2 evolved did not give any indication of specific carbon use and fractionation processes during basal metabolism as indicated by enrichment or depletion of 13 C values. However, carbon isotope characteristic of the 13 C-CO 2 evolved showed that glucose addition stimulated mineralization of the soil organic matter (SOM) which derived from either increased biomass turnover or simulated dead SOM degradation and is defined as priming effect. The results showed that (1) the evaluation of heavy metal effect on soil respiratory indicators and the transformation of active SOM are method-dependent and (2) under aerobic conditions, soil microbial communities consumed relatively more oxygen in the presence of Cu than in its absence in this acid, unpolluted and organic rich soil under pine forest.

Ecosystem Manipulation and Restoration on the Basis of Long-Term Conceptions

Ecosystems are affected by anthopogenic activities at a global level and, thus, are manipulated world-wide. This chapter addresses the impacts of apparent and non-apparent manipulations and restoration by human activities in Europe with a focus on the temperate zone. Agricultural management practices induced evident site-specific modification of natural ecosystem structures and functions whereas forests and natural grasslands and also aquatic systems are considered as being less manipulated. Ecosystems such as mires, northern wetlands and the tundra, have received attention due to their vulnerability for conserving carbon and biodiversity and for identifying the role of non-apparent manipulations on ecosystem functioning. Drastic types of ecosystem manipulation include open-cast mining activities that occur worldwide and induce perturbation of large areas across landscapes. Such harsh human impacts create the need for remediation and restoration measures for mining regions that address classical food and fodder services and also nature conservation and novel social benefits. Recultivation therefore offers the opportunity to introduce new land-use types and to study processes of initial ecosystem development that are still poorly understood.

Impact of Soil Compaction on Bulk Density and Root Biomass of Quercus petraea L. at Reclaimed Post-Lignite Mining Site in Lusatia, Germany

The impact of soil compaction on bulk density and root biomass of Quercus petraea L. was assessed after 85 years of reclamation of post-lignite mining soil at Welzow-South, in Lusatia, Germany. Bulk density of core soils sampled from 20 to 25 cm, 100 to 105 cm, and 200 to 205 cm depths and oven-dried biomass of Q. petraea roots sampled from 0 to 30 cm and at successive depths of 20 cm, up to 210 cm depth at compacted and uncompacted sites were determined. Bulk density was significantly higher at 20 to 25 cm ( g cm−3) and 100 to 105 cm ( g cm−3) depths of the compacted site. Likewise, compaction induced significant greater root biomass within the 0 to 70 cm depth with higher bulk density; root biomass at this depth was 2-fold greater compared to the uncompacted site. Root biomass decreased with soil depth and showed significant relationship with depth at both sites. The result indicates that, after 85 years of reclamation, the impact of soil compaction persisted as evident in higher bulk density and greater root biomass.

Impacts of soil additives on crop yield and C-sequestration in post mine substrates of Lusatia, Germany.

Abstract Opencast lignite mining in the Lusatia region of Germany has resulted in large scale landscape disturbances, which require suitable recultivation techniques in order to promote plant growth and establishment in the remaining nutrient-poor substrates with low water-holding capacity. Thus, the effects of two commercial soil additives (CSA), a hydrophilic polymer mixed with volcanic rock flour and bentonite (a-CSA), and digester solids from biogas plants enriched with humic acids and bentonite (b-CSA), on soil organic carbon (SOC) storage, plant yields and root biomass were assessed after cultivating perennial crops (Dactylis glomerata L.) in monoculture and Helianthus annuus L.-Brassica napus L. in crop rotation systems. The CSA were incorporated into the top 20 cm soil depth using a rotary spader. The results indicated that a-CSA led to a significant increase in plant yield during the first year, and improved root biomass in the following year. As a result, SOC stocks increased, especially in the 0–10 cm soil layer. No significant sequestration of additional SOC was observed on b-CSA-amended plots at the end of both years. Bulk density values decreased in all treatments under the monoculture system. It can be concluded that application of a-CSA enhanced soil water availability for plant uptake and consequently promoted plant growth and organic carbon sequestration. The relative enrichment of organic matter without effects on water-holding capacities of b-CSA treatments suggested that it was not suitable for rapid land reclamation.

Impact of Commercial Soil Additives on Microbial Activity and Carbon Isotopic Characteristics of Recultivated Post Lignite Mine Soils

The impact of commercial soil additives (CSA) on post lignite mine soils was assessed after 14 months of field application by evaluating the changes in microbial respiration, the respiratory quotient and the isotopic signature of microbial respired CO2-C. Soil samples were randomly collected from 0 to 5 cm depths from: (1) tilled plots amended with polyacrylate hydrophilic polymer, mixed with zeolithes and bentonite (a-CSA) at 5,000 kg ha−1 dry mass; (2) tilled plots amended with a near-natural digester compost enriched with mineral additives, bentonite and synthesized humic acids (b-CSA) at 10,000 kg ha−1 dry mass; (3) plots tilled and without amendment (control), and (4) plots without tillage and amendment. All plots were seeded with orchard grass (Dactilus glomerata, L.). Soil microbial basal respiration was low and not significantly affected by the treatments presumably, due to low availability of CSA for microbial metabolism. Soil microbial respiration, respiratory quotients and 13C isotopic characteristics of the respired CO2 followed a similar trend for all treatments throughout the incubation period and was not significantly different between a-CSA and b-CSA amended plots compared to the control and untilled plots. The results indicate that the current soil microbial communities have similar eco-physiology and substrate utilisation patterns, and may have met their metabolic requirements mainly from the inherent and recent organic matter input from the vegetation cover. This may be due to the recalcitrant nature of the CSAs or the recommended application rates being too low to affect any significant short-term biochemical impact on these recultivated soils in early stages of development.

Potential of Igniscum sachalinensis L. and Salix viminalis L. for the Phytoremediation of Copper-Contaminated Soils

The potential of Salix viminalis L. and Igniscum sachalinensis L. for phytoremediation of copper- (Cu-) contaminated soils was studied under greenhouse conditions. Approximately 5 kg of potted agricultural and sewage amended soils sampled from the top 0 to 20 cm depth in Neuruppin, Germany, was treated with CuSO4 at concentrations 0 (control), 250, 750, and 1250 mg Cu kg−1 soil and ethylenediaminetetraacetic acid (EDTA) at 1000 mg kg−1 soil, respectively. Each plant species was grown on four replicates of each soil treatment. Copper accumulated in aboveground tissues tends to increase with increasing soil Cu concentration and was the lowest in stem and leaf of both plant species grown on control soils. At 750 and 1250 mg Cu kg−1 soil, Cu accumulated in stem and leaf of I. sachalinensis increased by over 12- and 20-fold, respectively, whereas there was no vegetative growth in S. viminalis beyond 250 mg Cu kg−1 soil. Application of EDTA to sewage amended soils increased Cu accumulated in the stem and leaf, especially in I. sachalinensis. In general, I. sachalinensis seems to have the potential to tolerate high soil Cu content and simultaneously bioaccumulate Cu in tissues and thus may have better prospects for phytoremediation.