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

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

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

Data_Andriuzzi_Wall_J_Animal_Ecol

Nematode body size and abundance data for article "Grazing and resource availability control soil nematode body size and abundance-mass relationship in semi-arid grassland

Data from: Grazing and resource availability control soil nematode body size and abundance-mass relationship in semi-arid grassland

1. Body size is a central functional trait in ecological communities. Despite recognition of the importance of above-belowground interactions, effects of aboveground herbivores on size and abundance-size relationships in soil fauna are almost uncharted. Depending on climate and soil properties, herbivores may increase basal resources of soil food webs, or reduce pore space, mechanisms expected to have contrasting effects on soil animal body size. 2. We investigated how body size and shape of soil nematodes responded to mammalian grazers in three semi-arid grassland sites, along a gradient of soil texture and organic matter (OM) in a long-term herbivore removal study. We analysed nematode mass, length, diameter, body size distribution, and biomass distribution. We formulated two mechanistic hypotheses to assess whether resource availability or pore space was the dominant abiotic control and modulated the effects of grazing. 3. In ungrazed soils, average and maximum nematode size, as well as abundance and biomass of large nematodes, were greater in the high-OM than in the low-OM soil, and intermediate in the medium-OM soil. Grazing promoted larger sizes in the low-OM soil, where it had been shown to increase organic matter and microbial biomass, and led to more homogeneous average size and body size distribution across sites. The results support the hypothesis that nematode size was controlled by basal resource availability rather than by pore space. However, body shape might have been constrained by small pores in the fine-texture, high-OM soil, where nematodes were more elongated. 4. Grazing may facilitate larger sizes in soil nematode communities by boosting basal resources where these are limiting, with important implications for estimations of nematode biomass and contribution to carbon and nutrient cycling. These findings contribute to the insofar-limited mechanistic understanding of how herbivores can shape functional traits of soil fauna, and demonstrate that animals at one trophic level may control patterns in body size and abundance-size relationships in other trophic levels without a direct predator-prey or competitive linkage between them

Comparison of two widely used sampling methods in assessing earthworm community responses to agricultural intensification

To assess whether different sampling protocols provide similar results on earthworm community responses to land use, comparisons across different environments are required. Using an ongoing experiment in France, we assessed whether two protocols, widely used in international projects and global databases, provide similar estimates of earthworm abundance, and detect the same community responses to agricultural intensification. Method A consisted of hand-sorting composite samples of three soil monoliths 35 × 35 × 20 cm each, and applying formalin in the resulting holes. Method B consisted of applying formalin over a 1 m2 contiguous area and subsequently hand-sorting a 25 × 25 × 25 cm soil monolith within it. Higher abundance was obtained from Method A than from Method B, but the two methods led to the same ecological conclusions. Firstly, they both showed that earthworm biomass and density decreased with agricultural intensification. Secondly, they showed similar land use effects on earthworm ecological group proportions, age structure, and body size distribution, pointing to a relative loss of large-bodied earthworms with agricultural intensification. These findings suggest that data from the two methods are both suitable to investigate the community response of earthworms, whereas assessments of earthworm abundance per se are more sensitive to the sampling protocol. Merits and drawbacks of the methods in terms of time and labour needed and of statistical variation are discussed.</p

Earthworm functional traits and interspecific interactions affect plant nitrogen acquisition and primary production

We performed a greenhouse experiment to test how the functional diversity of earthworms, the dominant group of soil macro-invertebrates in many terrestrial ecosystems, affects nitrogen cycling and plant growth. Three species were chosen to represent a range of functional traits: Lumbricus terrestris (large, mainly detritivorous, makes vertical permanent burrows open at the surface), Aporrectodea longa (medium-large, feeds on both detritus and soil, makes burrows more branched than L. terrestris), and Allolobophora chlorotica (small, geophagous, makes ephemeral burrows below the soil surface). Mesocosms with ryegrass (Lolium perenne) were inoculated with none to all three species (similar total biomass), using an experimental design (Simplex) suited to partition single species and diversity effects. Two contrasting N sources, urea or mammalian dung, were labelled with 15N so that the acquisition by plants and earthworms and recovery of applied 15N could be estimated.Over 3 months, plant production was higher with urea applications, but there were also species-specific earthworm effects: A. chlorotica and, to a lesser extent, A. longa increased shoot biomass, whereas L. terrestris increased root biomass. Earthworms did not affect soil N concentrations or leaching losses, whereas more N was leached under urea. A. chlorotica tended to increase dung-15N recovery in grass shoots, but in interaction with A. longa had the opposite effect, possibly through increased N immobilization in the microbial biomass. Earthworms assimilated negligible amounts of urea-15N but a substantial proportion (17% on average) of the dung-15N, with no clear-cut differences between species. Our findings show that earthworm species may have similar trophic response to N sources and yet different effects on plant N uptake and primary production, and that inter-specific earthworm interactions can result in non-additive diversity effects

Anecic earthworms (Lumbricus terrestris) alleviate negative effects of extreme rainfall events on soil and plants in field mesocosms

Background and aims - Intense rains are becoming more frequent. By causing waterlogging, they may increase soil erosion and soil surface compaction, hamper seedling establishment, and reduce plant growth. Since anecic earthworms make vertical burrows that improve water infiltration, we hypothesised that they can counteract such disturbance. Methods - In a field experiment, intact soil mesocosms with ryegrass (Lolium multiflorum), with or without introduced adult Lumbricus terrestris, underwent either a precipitation regime with two intense rain events (36 mm, at beginning and end of spring), or a control regime with the same cumulative rainfall but no intense events. Short-term response of soil moisture and lagged response of plant growth were measured, and soil macroporosity was quantified. Results - Intense rains reduced ryegrass shoot biomass (by 16–21 % on average) only in the absence of earthworms. Waterlogging duration aboveground was not affected, whereas soil moisture contents after intense rainfall tended to drop faster with earthworms present. Continuous vertical macropores were found only in the mesocosms to which earthworms had been added. The number of such macropores was 2.4 times higher under the intense precipitation regime, despite similar earthworm survival. Conclusions - We found that anecic earthworms can offset negative effects of intense rainfall on plant growth aboveground. Underlying mechanisms, such as macropore formation and enhanced nutrient cycling, are discussed. We also observed that altered precipitation patterns can modify earthworm burrowing behaviour, as earthworms had produced more burrows under the intense regim

Knox et al. data

Full dataset for Knox et al. (2017) Ecology Letter