Mixed-Species Plantation Effects on Soil Biological and Chemical Quality and Tree Growth of a Former Agricultural Land

Tree planting on abandoned agricultural land could both restore the soil quality and increase the productivity of economically valuable woody species. Here, we assess the impact of mixed-species tree plantations on soil quality at a site in Central Italy where tree intercropping systems were established 20 years ago on a former agricultural land. These intercropping systems include two species of economic interest, Populus alba and Juglans regia, and one of three different nurse trees, i.e., Alnus cordata, Elaeagnus umbellata, both of which are N-fixing species, and Corylus avellana. We measured tree growth and compared how soil organic matter, soil extracellular enzymes, and nematodes of different feeding groups varied among the intercropping systems and relative to a conventional agricultural field. Our results indicate that tree plantation led to an increase in soil carbon and nitrogen, and enhanced enzyme activities, compared with the agricultural land. The proportion of nematode feeding groups was heterogeneous, but predators were absent from the agricultural soil. Multivariate analysis of soil properties, enzymatic activity, nematodes, and tree growth point to the importance of the presence N-fixing species, as the presence of A. cordata was linked to higher soil quality, and E. umbellata to growth of the associated valuable woody species. Our findings indicate that intercropping tree species provide a tool for both restoring fertility and improving soil quality

Forecasting tillage and soil warming effects on earthworm populations

1. Healthy soils are crucial for sustainable food production, but tillage limits the biological regulation of essential ecosystem services. Better understanding of the mechanisms driving management effects on soil ecosystem engineers is needed to support sustainable management under environmental change. 2. This paper presents the EEEworm (Energy–Environment–Earthworm) model, a mechanistic individual-based model (IBM) of Lumbricus terrestris populations. L. terrestris is a dominant earthworm species in undisturbed habitats and is closely associated with numerous ecosystem services such as water flow regulation, soil structure and crop production. In reduced tillage agriculture a decline in mechanical disturbance allows for L. terrestris proliferation, whilst the activities of L. terrestris can replace many of the soil functions provided by tillage. 3. Extensive EEEworm validation with eight published studies (average R2 = 0.84) demonstrates a mechanistic approach which can extrapolate between diverse soil, management and weather conditions. EEEworm simulation experiments elucidate that a combination of direct and indirect tillage effects lead to population declines in tilled fields, with litter removal from the soil surface being the main driver. 4. We investigate the effects of different tillage intensities under historical and projected soil warming conditions, and find that future warmer and drier soils in our simulation exacerbate the effects of deep ploughing on L. terrestris population declines. These effects result from warmer and drier soil conditions increasing individual metabolic rates and tillage reducing food availability to meet energy demands. 5. Synthesis and applications. Pre-emptive strategies to mitigate climate change impacts on soil health in agroecosystems should focus on decreasing tillage intensity and retention of crop residues following tillage. EEEworm has the potential to benefit land managers, policy makers, risk assessors and regulators by providing a tool to forecast how soil systems respond to combinations of land management and environmental change. To allow better cost-benefit analysis of contrasting land management systems a future aim of mechanistic models like EEEworm is to incorporate the links between earthworm populations, soil functions and ecosystem services

Organic matter composition and the protist and nematode communities around anecic earthworm burrows

By living in permanent burrows and incorporating organic detritus from the soil surface, anecic earthworms contribute to soil heterogeneity, but their impact is still under-studied in natural field conditions. We investigated the effects of the anecic earthworm Lumbricus centralis on fresh carbon (C) incorporation, soil organic matter composition, protists, and nematodes of a Cambisol under grassland. We used plant material labelled with stable isotope tracers to detect fresh C input around earthworm-occupied burrows or around burrows from which the earthworm had been removed. After 50 days, we sampled soil (0–10 cm depth) in concentric layers around the burrows, distinguishing between drilosphere (0–8 mm) and bulk soil (50–75 mm). L. centralis effectively incorporated fresh C into the drilosphere, and this shifted soil organic matter amount and chemistry: total soil sugar content was increased compared to unoccupied drilosphere and bulk soil, and the contribution of plant-derived sugars to soil organic matter was enhanced. Earthworms also shifted the spatial distribution of soil C towards the drilosphere. The total abundance of protists and nematodes was only slightly higher in earthworm-occupied drilosphere, but strong positive effects were found for some protist clades (e.g. Stenamoeba spp.). Additional data for the co-occurring anecic earthworm species Aporrectodea longa showed that it incorporated fresh C less than L. centralis, suggesting that the two species may have different effects on soil C distribution and organic matter quality

Soil faunal and structural responses to the settlement of a semi- sedentary earthworm Lumbricus terrestris in an arable clay field

We studied the soil community and habitat consequences of introducing a deep-burrowing, sedentary life-style earthworm, Lumbricus terrestris (dew-worm) into arable zero-till clay. Seventeen years after introduction, which was originally aimed at improving the macroporosity and permeability of the heavy clay soil, we returned to the gradient of L. terrestris dispersal (well established, more recent and no settlement) and investigated the temporal development of the ecosystem engineering impacts on different faunal groups (earthworms, enchytraeids and nematodes) and soil porosity. The faunal re- sponses were examined both at L. terrestris midden scale (individual living site) and field scale. We found that L. terrestris middens sustained elevated densities of all three faunal groups. In the case of earth- worms, there was evidence for temporal development of the engineering impact as the difference be- tween the midden and non-midden areas was more pronounced in the well-established areas than close to the leading edge of dispersal. The earthworm community composition was not altered at L. terrestris midden sites. The settlement of L. terrestris had no discernible effects on field-scale earthworm and nematode abundances, but enchytraeids were practically absent beyond the leading edge of the dispersal. This effect might, however, be partly explained by a gradient of increasing clay content. Soil macroporosity at L. terrestris midden sites did not increase with the age of L. terrestris settlement. Our results suggest that L. terrestris settlement in a clay soil can significantly increase the spatial patchiness of soil fauna, but may not, except in the case of enchytraeids, affect their field-scale abundances or the macroporosity of the soil in the vicinity of L. terrestris living sites

Earthworm functioning in soil ecosystem services in relation to land use intensity

The FP7 EcoFINDERS project aimed to assess the relationship between soil biodiversity and ecosystem service provision. We studied functional responses for earthworms and fungi on soil formation and water regulation under different agricultural land uses representing a range in land use intensity. The aim was to establish and quantify these functional relationships by literature and field studies

Protist diversity on a nature reserve in NW England − with particular reference to their role in soil biogenic silicon pools

Soil protists play fundamental roles in many earth system processes, yet we are only beginning to understand the true diversity of the organisms involved. In this study we used conventional (microscopy-based) methods to characterise the diversity and estimate protist population sizes in soils from a variety of distinct habitats within Mere Sands Wood nature reserve in NW England. We produced population size data for over ninety soil protists belonging to two major eukaryotic functional groups: testate amoebae (TA) and diatoms, adding substantial ‘cryptic diversity’ to the nature reserves recorded biota. From these population size data we estimated relative contributions of TA and diatoms to soil biogenic silicon (BSi) pools and found significant correlations between taxon richness and the TA and diatom Si pool. This could indicate that protist functional diversity can influence terrestrial BSi pools, especially in early successional plant communities where TA and diatoms can potentially increase Si mineralisation and/or create Si ‘hot spots’ and hence, the biological availability of this element for subsequent plant uptake. TA were particularly abundant in mor humus type soils further supporting the idea that they could be important players in nutrient cycling in such soils. Overall, we demonstrate this is a useful approach in order to start to attempt to estimate the role of protists in the Si cycle and other ecological processes

Soil quality regeneration by grass-clover leys in arable rotations compared to permanent grassland: Effects on wheat yield and resilience to drought and flooding

Intensive arable cropping depletes soil organic carbon and earthworms, leading to loss of macropores, and impaired hydrological functioning, constraining crop yields and exacerbating impacts of droughts and floods that are increasing with climate change. Grass and legume mixes traditionally grown in arable rotations (leys), are widely considered to regenerate soil functions, but there is surprisingly limited evidence of their effects on soil properties, resilience to rainfall extremes, and crop yields. Using topsoil monoliths taken from four intensively cropped arable fields, 19 month-old grass-clover ley strips in these fields, and from 3 adjacent permanent grasslands, effects on soil properties, and wheat yield in response to four-weeks of flood, drought, or ambient rain, during the stem elongation period were evaluated. Compared to arable soil, leys increased earthworm numbers, infiltration rates, macropore flow and saturated hydraulic conductivity, and reduced compaction (bulk density) resulting in improved wheat yields by 42–95 % under flood and ambient conditions. The leys showed incomplete recovery compared to permanent grassland soil, with modest gains in soil organic carbon, total nitrogen, water-holding capacity, and grain yield under drought, that were not significantly different (P > 0.05) to the arable controls. Overall, grass-clover leys regenerate earthworm populations and reverse structural degradation of intensively cultivated arable soil, facilitating adoption of no-tillage cropping to break out of the cycle of tillage-driven soil degradation. The substantial improvements in hydrological functioning by leys will help to deliver reduced flood and water pollution risks, potentially justifying payments for these ecosystem services, especially as over longer periods, leys increase soil carbon sequestration

Conversation avec une marque : perception des modalités d'expression des marques sur les médias sociaux

International audienceBrands can now express themselves, literally, through conversations on social media. Based on a series of interviews, this research shows that conversational brands may seem more human and improve their image even without the physical representation of a speaker. However, neither their presence on social media nor their personification is sufficient. To be more human, brands must participate to a quality conversation. Consumers evaluate the conversation according to its context, content and form.Les marques peuvent désormais faire entendre leur voix, littéralement, grâce à l'utilisation du mode de la conversation sur les médias sociaux. En s'appuyant sur une série d'entretiens, cette recherche montre que les marques en conversation peuvent paraître plus humaines et améliorer leur image sans avoir besoin de la représentation physique d'un locuteur. Pour autant, ni leur simple présence sur les médias sociaux, ni leur personnification, ne suffisent à rendre les marques plus humaines : elles doivent avant tout participer à une conversation de qualité. Les internautes évaluent la conversation selon son contexte, son contenu et sa forme