An assessment of soil compaction caused by machinery used in stump and/or logging residue extraction for energy on soils typical of Ireland. We determined unaffected soil conditions and to find the compaction grade after timber harvesting and bundling activities, and to compare those results with stands where timber harvesting was followed by stump extraction for energy. The investigation was carried out in Ireland on three different locations which had a slightly different proportion of stones in their soils. Two of the soils were purely mineral soils, and the third was a mineral soil affected by anthropogenic activities. To ensure comparable results as much as possible, the moisture content of the soil on wet basis was investigated. Each location was purposely treated. Therefore, on each location plots were identified as follows: plots unaffected by operation (reference area), plots after timber harvesting, plots after timber harvesting and bundling operation, and plots after timber harvesting and stump extraction operation. According to the experimental design 40 repetitions on each of the three different treatments were set. The results showed that the compaction of soil occurred on plots after timber harvesting, but there was not a significant difference between compaction grades with and without logging residue bundling operation. However, once the site was extracted of stumps, the soil became too loose and no significant difference was found compared to unaffected soil.

The mineralization of the soil organic matter may be accelerated by productive activities as grazing and pasture management. The objective of this study was to evaluate the impact of grazing on soil organic carbon (COS) in the high plateau of Anaime, Tolima, Colombia. An unbalanced completely randomized design was used, selecting three treatments: 1) pastures with 20 years in conservation; 2) pastures currently in use; and 3) Andean high-land native forests. The COS storage was estimated using organic carbon concentration and bulk density at a depth of 0-30 cm. Aboveground biomass (AB) of forage plants was also estimated in the case of pastures. Correlation and regression analysis were carried out between COS and time of use, occupation period and stocking rate. The pastures in use stored more COS than those conserved and native forests (P<0.05; 34.4 vs 22.0 vs 21.6 tC/ha, respectively). In contrast, conserved pastures stored more carbon in AB that those in use (P<0.05; 8.3 vs 2.1 tC/ha). It was found that extensive livestock management had a positive impact in the COS in the Páramo of Anaime. However, a change from forests to pastures would cause a CO2 emission by effect of burns and/or decomposition of the organic matter and the loss of other environmental services as water regulation and those derived from conservation of biodiversity.

Biofuel crops are an accepted alternative to fossil fuels, but little is known about the ecological impact of their production. The aim of this contribution is to study the effect of native (Salix viminalis and Phalaris arundinacea) and introduced (Helianthus tuberosus, Reynoutria sachalinensis and Silphium perfoliatum) biofuel crop plantations on the soil biota in comparison with cultural meadow vegetation used as control. The study was performed as part of a split plot field experiment of the Crop Research Institute in the city of Chomutov (Czech Republic). The composition of the soil meso- and macrofauna community, composition of the cultivable fraction of the soil fungal community, cellulose decomposition (using litter bags), microbial biomass, basal soil respiration and PLFA composition (incl. F/B ratio) were studied in each site. The C:N ratio and content of polyphenols differed among plant species, but these results could not be considered significant between introduced and native plant species. Abundance of the soil meso- and macrofauna was higher in field sites planted with S. viminalis and P. arundinacea than those planted with S. perfoliatum, H. tuberosus and R. sachalinensis. RDA and Monte Carlo Permutation Test showed that the composition of the faunal community differed significantly between various native and introduced plants. Significantly different basal soil respiration was found in sites planted with various energy crops; however, this difference was not significant between native and introduced species. Microbial biomass carbon and cellulose decomposition did not exhibit any statistical differences among the biofuel crops. The largest statistically significant difference we found was in the content of actinobacterial and bacterial (bacteria, G+ bacteria and G− bacteria) PLFA in sites overgrown by P. arundinacea compared to introduced as well as native biofuel crops. In conclusion, certain parameters significantly differ between various native and introduced species of biofuel crops; however, the functional importance of these differences requires further research.

AIMS: We assessed the temporal changes on microbial biomass in relation to changes in soil moisture, dissolved organic carbon and plant biomass during the summer season in a Mediterranean high-mountain grassland. METHODS: Temporal variations were tested by two-way ANOVA. The relationships among microbial biomass, plant biomass, soil water content, soil organic carbon, dissolved organic carbon and total soil nitrogen during the summer season were assessed by means of structural equation modeling. RESULTS: Microbial biomass did not show variation, while dissolved organic carbon and root biomass decreased throughout the summer. Aboveground plant biomass peaked in the middle of the summer, when soil water content was at its minimum. Soil water content directly and negatively affected soil microbial biomass, and positively affected dissolved organic carbon. Moreover soil microbial biomass and dissolved organic carbon were negatively related. Plant biomass effects on soil microbial biomass were driven by root biomass, which indirectly affected soil microbial biomass through effects on soil organic carbon and soil nitrogen. CONCLUSIONS: The temporal dynamic of microbial biomass during the summer season appeared to differ from previous observations in temperate alpine communities, and indicated the drought resistance of the microbial community during the summer in Mediterranean high-mountain grasslands. During the dry period, microbial biomass may play an alternative role in soil carbon conservation.

The impact of land-use change on soil microbial biomass carbon (C) and nitrogen (N) was studied through two annual cycles involving natural forest, degraded forest, agroecosystem and Jatropha curcas plantation. Soil microbial biomass C and N, soil moisture content and soil temperature were analysed at upper (0–10cm), middle (10–20cm) and lower (20–30cm) soil depths during the rainy, winter and summer seasons. The levels of microbial biomass C and N were highest in the natural forest, followed in decreasing order by Jatropha curcas plantation, degraded forest and the agroecosystem. The highest level of soil microbial biomass C and N was observed during summer, decreasing through winter to the minimum during the rainy season. Soil microbial biomass C and N decreased with increasing soil depth for all land-use types, and for all seasons. Seasonal variation in soil microbial biomass was better correlated with the soil moisture content than with soil temperature. The microbial biomass C/N ratio increased with the soil depth for all land-use types, indicating changes in the microbial community with soil depth. It is concluded that the change in land-use pattern, from natural forest to other ecosystems, results in a considerable decrease in soil microbial biomass C and N. Jatropha plantation may be an alternative for the restoration of degraded lands in the dry tropics.

Potassium (K) in microbial cells, microbial biomass K, in soil has been recently recognized as a K pool for plant growth. We determined soil microbial biomass K in paddy fields to reveal its importance as a K pool in paddy field soil for the first time. Microbial biomass K ranged from 5 to 21 mg K kg ⁻¹ in the soil samples periodically collected from a paddy field and the value corresponded to 41% of the exchangeable K on average. Both microbial biomass K and exchangeable K increased conspicuously due to the long-term application of livestock manure compost or rice straw compost. Biomass K was higher than exchangeable K under K-deficient conditions in the long-term experimental plots without K application. The present study revealed that the microbial biomass contained considerable amounts of K in paddy field soil, indicating the need for evaluation of the microbial biomass K as a source and a stock of K in soil that has been overlooked.

With the rapid urbanization of natural lands, researchers have begun to examine the capacity of urban soils to store carbon (C), with recent attention to residential yards. We performed a case study to examine four potential influences on soil C levels in residential yards. In 67 yards containing trees, we examined the relationship of soil C (kg m⁻²) to tree aboveground biomass, home age (3–87 years), yard maintenance (fertilization, irrigation, mulching or bagging lawn clippings), and soil texture (% clay, % sand, % silt), at three depths (0–15 cm, 15–30 cm, and 30–50 cm). Six tree aboveground biomass data sets were developed: 1) biomass, 2) biomass*(1/distance from tree), 3) biomass ≤ 15 m from sample site, 4) biomass ≤ 10 m, 5) biomass ≤ 5 m, and 6) biomass ≤ 4 m. Biomass ≤ 5 m and biomass ≤ 4 m had the greatest explanatory power for soil C at 30–50 cm depth (P = 0.001, R² = 0.28; P = 0.05 R² = 0.39, respectively). The relationship between soil C and home age was positive at 0–15 cm (P = 0.0003, R² = 0.19), but constant at the two lower depths. Yard maintenance had no significant influence on soil C levels across home age. At 0–15 cm, soil C increased with % silt (P = 0.006, R² = 0.12). Overall, trees in turfgrass yards may have a stabilizing effect on soil C levels below 15 cm but minimal influence above 15 cm.

The present study was aimed to evaluate the soil carbon sequestration and reclamation potential of Jatropha curcas L. (JCL) growing in varying soil conditions. For this, a study was conducted during 2008–2012 at four different sites of Jatropha plantations (Banthara, Gajaria, Bakshi ka talab and NBRI) growing in central India. Periodic sampling was done for plant biomass, litter turn over, microbial biomass, soil enzymes and carbon and nutrients stock of JCL plantations. The analytical studies clearly indicate that irrespective of the soil sites, the Jatropha plantations significantly enhanced (α=5%; p≤0.05) the total organic carbon, total Kjeldahl nitrogen, available phosphorus and potassium content n the soil. During the fourth year of plantations, the total plant biomass (including the above and below ground biomass) of JCL growing in various plantation sites has been increased from 15.20±4.60 to 203.00±40.60tha−1year−1 with a subsequent total biomass carbon content of 7.60±2.30 to 101.50±13.52tha−1year−1, respectively. Similarly, the soil carbon stock of the plantation sites varied from 20.59 to 50.45Mgha−1year−1. Furthermore, the microbial biomass carbon content of the four different sites varied from 132.64±9.28 to 641.32±38.48μgg−1 soils. Therefore, the study clearly indicates that JCL plantations can significantly (p≤0.01) enhance the soil quality including the soil carbon pool and microbial biomass carbon and can be used for the concurrent initiatives on biofuel production, soil carbon sequestration and soil reclamation.

Soil carbon (C) is crucial for maintaining soil functions, and it increases after conversion of an agricultural field from conventional tillage management to no-tillage management due to decreasing human-induced soil disturbance and the modification of soil structure through ecosystem engineers such as earthworms. To improve soils and prevent degradation, understanding the effects of no-tillage management over time in changing water stable aggregates (WSA) and soil C is important. We investigated the changes in WSA and soil C at a site in Akame, Mie, Japan, operating a no-tillage with weed mulch management (NWM) system over a chronosequence from 0 to 17years after conversion from conventional tillage practices (NWM for 0, 5, 10, 15, and 17years). We measured weed aboveground biomass, litter accumulation, and root and earthworm density and biomass, and analyzed the WSA and C of bulk soil and each WSA size fraction. Weed aboveground biomass increased with site age, while litter accumulation, root biomass (soil depth of 0–4cm), and earthworm density and biomass did not appear to be related to site age. Endogeic earthworm density and biomass tended to increase at year 5 of NWM compared to year 0. The WSA >2mm and soil C stock in WSA of >2mm increased over time under NWM at a soil depth of 0–15cm, while the soil C stock of 0.25–1-mm WSA decreased at soil depths of 0–5cm. The total soil C accumulation rate was 60gCm−2yr−1 at a soil depth of 0–25cm over the NWM chronosequence. Therefore, our results indicated that by adopting NWM, C inputs to the soil from weed aboveground biomass, as well as increases in the WSA of >2mm, might be responsible for soil C sequestration.