Marks E.A.N., Alcaniz J.M., Domene X. (2014) Unintended effects of biochars on short-term plant growth in a calcareous soil. Plant and Soil. : 0-0.LinkDoi: 10.1007/s11104-014-2198-2
Background and aims Biochar has demonstrably improved crop yields in weathered and acidic soils, but studies in calcareous soils are particularly lacking, so biochar effects on plant growth was investigated under these conditions. Methods Six biochars were obtained from different feedstocks and production technologies. Chemical characterization of fresh biochars included total and extractable nutrients, labile carbon, and Fourier transform infrared spectroscopy. Extractable nutrients were also evaluated in biochar-soil mixtures with a basic (pH >8.2) test soil. Bioassays with lettuce and ryegrass were carried out to relate biochar chemical properties to effects on plant biomass. Results A sewage sludge slow pyrolysis char was stimulatory to plant growth, as was a slow pyrolysis pine wood char at an intermediate concentration, while gasification and fast-pyrolysis pine and poplar wood chars were strongly inhibitory, with reductions in biomass at realistic application rates of 5-19 t ha-1. Conclusions Statistical comparison of plant responses with biochar composition led to the assessment that plant responses were most correlated with volatile matter content and total P content, whose availability was likely regulated by pH and Ca content. Potential effects of phytotoxins were considered, but these were seen to be much less probable than effects due to nutrient availability. © 2014 Springer International Publishing Switzerland.
Marks E.A.N., Mattana S., Alcaniz J.M., Domene X. (2014) Biochars provoke diverse soil mesofauna reproductive responses inlaboratory bioassays. European Journal of Soil Biology. 60: 104-111.LinkDoi: 10.1016/j.ejsobi.2013.12.002
Biochar application to soil has the potential to improve soil fertility under certain conditions. However, potential ecological effects remain largely unexplored and poorly understood, particularly those on soil biota. Six biochars were tested on two soil-dwelling invertebrates in short-term bioassays to determine effects on survival and reproduction. A pine wood gasification char increased collembolan adult mortality at high concentrations. Wood slow and fast pyrolysis biochars had a strong stimulatory effect on collembolan reproduction, but no strong effect on enchytraeids. A sewage sludge char was slightly stimulatory for both organisms, and a pine gasification char was inhibitory in both cases. Inhibitory effects were associated with biochars with high carbonate and Ca content and pH. In light of the high stimulation of collembolan reproduction, potential explanations such as soil microbial community shifts or gut symbiont use of biochar are suggested. © 2013 Elsevier Masson SAS.
Menges J., Huguet C., Alcaniz J.M., Fietz S., Sachse D., Rosell-Mele A. (2014) Influence of water availability in the distributions of branched glycerol dialkyl glycerol tetraether in soils of the Iberian Peninsula. Biogeosciences. 11: 2571-2581.LinkDoi: 10.5194/bg-11-2571-2014
The combined application of the MBT (degree of methylation) and CBT (degree of cyclization) indices, based on the distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in soils, has been proposed as a paleoproxy to estimate mean annual temperature (MAT). CBT quantifies the degree of cyclization of brGDGTs and relates to soil pH. MBT and the simplified version MBT' quantify the degree of methylation of brGDGTs and relate to MAT and soil pH. However, other factors such as soil water availability have also been suggested to influence MBT' and possibly restrict the combined application of the MBT' and CBT indices as a paleotemperature proxy. To assess the effect of hydrological conditions on MBT' and CBT, a set of 23 Iberian Peninsula soil samples, covering a MAT range from 10 to 18 °C and a mean annual precipitation (MAP) range of 405 mm to 1455 mm, was analyzed. We found that the CBT was indeed significantly correlated with soil pH in our sample set. In contrast, MBT' was not correlated with MAT but had a significant correlation with the aridity index (AI), a parameter related to water availability in soils. The AI can explain 50% of the variation of the MBT', and 70% of the residuals of MAT estimated with the MBT/CBT proxy as compared to instrumentally measured MAT. We propose that, in arid settings, where water may be an ecologically limiting factor, MBT' is influenced by hydrological conditions rather than temperature. Thus, our results suggest that the combination of MBT' and CBT indices should be applied with caution in paleotemperature reconstructions in soils from dry subhumid to hyperarid environments. copyright © Author(s) 2014.
Tarrason D., Ojeda G., Ortiz O., Alcaniz J.M. (2014) Can organic amendments be useful in transforming a mediterranean shrubland into a dehesa?. Restoration Ecology. 22: 486-494.LinkDoi: 10.1111/rec.12092
Transforming a shrubland into a dehesa system may be useful for recovering certain productive and regulatory functions of ecosystems such as grazing potential, soil erosion control, and also for reducing the risk of wildfire. However, the productivity of the herbaceous cover and tree development in the transformed system may be limited by soil fertility, especially after wildfire events. Previous studies have shown that adequate doses of sewage sludge may improve soil fertility and facilitate plant recovery, but few studies have focused on plant biodiversity assessment. Here, we compare the effects of sewage sludge that has undergone different post-treatments (dewatering, composting, or thermal drying) as a soil amendment used to transform a fire-affected shrubland into a dehesa, on tree growth and pasture composition (vegetation cover, species richness, and diversity). In the short term, sewage sludge causes changes in both pasture cover and tree growth. Although no major differences in vegetation species richness and composition have been detected, fertilization using sewage sludge was shown to modify the functional diversity of the vegetation community. Rapid replacement of shrubs by herbaceous cover and ruderal plants (e.g. Bromus hordeaceus and Leontodon taraxacoides) and of the three grass species sown (Festuca arundinacea, Lolium perenne, and Dactylis glomerata) was observed, whereas N-fixing species (leguminous) tended to be more abundant in nonfertilized soils and soils amended with composted sludge. These results indicate that sewage sludge modifies the functionality of vegetation when applied to soils, and that the response varies according to the treatment that the sludge has undergone. © 2014 Society for Ecological Restoration.
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