The growing demand for bioenergy has raised concerns about the sustainability of intensive forest biomass removal. Less attention has been paid to the ash generated when forest biomass is combusted to produce energy. In Canada, this ash is often landfilled, but in some countries, wood ash is applied to the soil to maintain or improve soil fertility and forest health. AshNet is a network of Canadian scientists, foresters, policy makers and industry representatives that has formed to address opportunities for and challenges to the use of wood ash as a forest soil amendment. To date, AshNet collaborators have produced a guide to navigating the regulatory approval process, and completed a techno-economic analysis of the costs associated with landfilling wood ash versus using it as a forest soil amendment. Practical methods for optimizing ash quality and applying it on forested sites are being investigated. Applications of wood ash are also being examined as a tool for emulating some of the effects of wildfire on soil chemistry. The results of research trials established by AshNet collaborators across Canada will be shared to help develop and refine forest management policies and practices surrounding soil applications of wood ash. Updates on AshNet’s activities are available at (http://cfs.nrcan.gc.ca/projects/140 (English); http://scf.rncan.gc.ca/projets/140?lang=fr_CA (French)).

Soil properties are thought to affect annual plant productivity in rangelands, and thus soil variables that are consistently correlated with plant biomass may be general indicators of rangeland health. Here we measured several soil properties (e.g. aggregate stability, organic carbon, total nitrogen) and tested each as a would-be predictor of local variation in peak aboveground grassland biomass. Individual properties explained a slight (≤10%) amount of variation in plant biomass. Plant biomass was mainly (negatively) associated with two soil properties, subsurface soil carbonate concentration and the stability of soil macroaggregates near the soil surface. Less important predictive variables included: elevation, plant community composition, surface soil organic carbon, and soil carbon:nitrogen. Plot-to-plot variation in plant biomass is seemingly difficult to predict based on soil properties, including popular indicators of soil and rangeland health and even root biomass. While protection of soil is critical to overall rangeland ecosystem function, our findings suggest that the relationship between soil properties and plant biomass in natural grasslands is complex. Thus, there may not be one or even several soil properties that consistently predict appreciable variation in peak grassland biomass, especially variation within an ecosystem independent of precipitation.

Excess salinity may lead to degradation of arable land and exclusion from agricultural production by worsening of their properties. The evaluation of the characteristics of saline soils is very important from the point of view of the use of agricultural soil. The aim of this study was to determine changes in the physicochemical properties of soil, the content and activity of soil microbial biomass (SMB) and the thermokinetics of glucose biodegradation in soil samples containing different doses of sodium chloride and sodium bromide (0.0263; 0.0526; 0.1052; 0.1578; 0.2104; 0.2630mmolg−1 DM soil), and to compare the effects of both salts. The pH values of soil samples decreased (from 6.1 to 5.4 for NaCl and NaBr) and electrical conductivity increased (from 0.20dSm−1 to 2.61dSm−1for NaCl and 2.30dSm−1 for NaBr) with increasing doses of both salts. SMB content, determined based on substrate-induced respiration (SIR), decreased with increasing doses of NaCl and NaBr (from 737mg C to 348mg C for NaCl and 379mgCkg−1 DM soil for NaBr). Both salts inhibited glucose biodegradation processes in soil proportionally to their increasing doses (NaBr exerted a greater inhibitory effect). This was confirmed by lower values of the maximum rate of heat production (RHPmax) and the apparent growth rate constant (k), and by higher values of peak time (PT), generation time (tG) and the inhibitory ratio (I). Changes in pH, SIR-SMB and Qtmax (total heat production) were modeled based on the applied doses of NaCl and NaBr. The empirical data were well approximated by the proposed mathematical models representing relationships between soil pH, SIR-SMB and Qtmax vs. the applied doses of NaCl and NaBr. They can be used to reliably predict the effects of the analyzed salts on the tested soil parameters.

Plateau pika (Ochotona curzoniae) is an endemic mammal in the Qinghai-Tibetan Plateau, and its activities create extensive disturbances on vegetation and soil of alpine meadow. Field surveys at two sites were conducted to determine the effects of plateau pika disturbances on important soil factors and plant biomass of vegetated land, and their relationships of the same alpine meadow type. Our study showed that plateau pika disturbances significantly increased soil organic carbon, soil total nitrogen, graminoid biomass and the number of plant species, and significantly decreased soil moisture and forb biomass, although they had no significant impacts on soil total phosphorus, soil total potassium and total biomass on vegetated land. Our study further showed that soil organic carbon, soil total nitrogen, graminoid biomass and the number of plant species were much higher at intermediate disturbance intensities than those at low and high disturbance intensities in the disturbed areas, and soil moisture showed a decreasing trend with the increase of disturbance intensity. Plateau pika disturbances altered the contribution of some important soil nutrients and moisture to plant biomass, and had different impact on the best models between plant biomass (total biomass, graminoid biomass and forb biomass) and predominant soil factors. Our results demonstrated that the optimal disturbance intensities of plateau pika were beneficial to alpine meadow. These results highlighted the influence of the presence of plateau pika and its disturbance intensity on key soil nutrients and plant productivity on vegetated land of the same alpine meadow type, which will help us better understand the role of plateau pika in the alpine meadow ecosystem.

Plant diversity has been shown to determine the composition and functioning of soil biota. Although root-derived organic inputs are discussed as the main drivers of soil communities, experimental evidence is scarce. While there is some evidence that higher root biomass at high plant diversity increases substrate availability for soil biota, several studies have speculated that the quantity and diversity of root inputs into the soil, i.e.Though root exudates, drive plant diversity effects on soil biota. Here we used a microcosm experiment to study the role of plant species richness on the biomass of soil bacteria and fungi as well as fungal-To-bacterial ratio via root biomass and root exudates. Plant diversity significantly increased shoot biomass, root biomass, the amount of root exudates, bacterial biomass, and fungal biomass. Fungal biomass increased most with increasing plant diversity resulting in a significant shift in the fungal-To-bacterial biomass ratio at high plant diversity. Fungal biomass increased significantly with plant diversity-induced increases in root biomass and the amount of root exudates. These results suggest that plant diversity enhances soil microbial biomass, particularly soil fungi, by increasing root-derived organic inputs.

Plant diversity has been shown to determine the composition and functioning of soil biota. Although root-derived organic inputs are discussed as the main drivers of soil communities, experimental evidence is scarce. While there is some evidence that higher root biomass at high plant diversity increases substrate availability for soil biota, several studies have speculated that the quantity and diversity of root inputs into the soil, i.e. though root exudates, drive plant diversity effects on soil biota. Here we used a microcosm experiment to study the role of plant species richness on the biomass of soil bacteria and fungi as well as fungal-to-bacterial ratio via root biomass and root exudates. Plant diversity significantly increased shoot biomass, root biomass, the amount of root exudates, bacterial biomass, and fungal biomass. Fungal biomass increased most with increasing plant diversity resulting in a significant shift in the fungal-to-bacterial biomass ratio at high plant diversity. Fungal biomass increased significantly with plant diversity-induced increases in root biomass and the amount of root exudates. These results suggest that plant diversity enhances soil microbial biomass, particularly soil fungi, by increasing root-derived organic inputs.

Uncertainties remain as to the potential for tree plantations to affect soil microbial biomass. Our aim was to determine the factors accountable for the maintenance and the increase of soil microbial biomass following tree plantation. Based on mixed effect models, we conducted a meta-analysis with three fixed and two random factors to test the impact of tree plantation on soil microbial biomass. Previous land use was more important than climate or plant species in its effect on soil microbial biomass after tree plantation. There was a positive impact on soil microbial biomass for tree plantations on bare land but a negative impact for which on previously forested land. Climate and plant species were found to be not as important in their effects on soil microbial biomass. Our meta-analysis gives a general pattern that previous land use type is the major controlling factor of soil microbial biomass following tree plantations and promotes our understanding of the effects of rehabilitation of degraded sites on vegetation recruitment.

Soil-woody biomass interactions are relevant for the productivity of bioenergy plantations and biomass quality. In this context, the main objective of this study was to evaluate and to quantify possible relationships between chemical variables of the soil and the produced biomass through a multivariate approach. This latter approach allows to overcome the complex issue of multi-collinearity among variables. Soil and woody biomass samples were collected from two poplar short rotation coppices in Santarém (Portugal) and in Lochristi (Belgium). The results from the analyses of those samples were integrated into three databases with soil, woody biomass and site plots as cases, and 23 physical and chemical properties as variables. The databases were subjected to a multivariate sequence of calculations, which included correlation, principal components, factorial and hierarchical clustering analyses. The calculations showed that the site plots and the woody biomass of genotypes in Lochristi were more homogeneous as compared to Santarém; they also confirmed the high interconnection between soil and woody biomass variables. The higher heating value of the woody biomass correlated well with the soil concentrations of P2O5, Mg, Ca, Na and organic C. Linear equations related the higher heating value to the most important soil and woody biomass variables. Finally, the results suggest that the annual monitoring of soil and biomass in SRC systems should be performed to optimize both productivity and woody biomass quality as a fuel.