Interactive effects of composted green waste and earthworm activity on tree growth and reclaimed soil quality: a mesocosm experiment

On reclaimed landfill sites, the addition of organic matter such as composted green waste (CGW) to soil-forming materials can support tree survival and growth. CGW addition may also assist the establishment of sustainable earthworm populations, and in turn these organisms can promote further soil development through their burrowing and feeding activity. Despite such potentially mutual benefits, little research has been carried out into CGW and earthworm interactions with trees on reclaimed land. A twelve month, open field nursery experiment revealed the responses of the interactions between two tree species; Alnus cordata (Betulaceae) and Acer platanoides (Sapindaceae), CGW and the earthworms Aporrectodea longa (Lumbricidae) and Allolobophora chlorotica (Lumbricidae) in reclaimed soil. Controlled mesocosm conditions permitted a detailed investigation into the factors affecting tree growth and nutrient uptake, soil nutrient cycling and earthworm population dynamics. Results revealed that A. cordata growth was unaffected by CGW or earthworm addition. There was, however, a significant positive synergistic effect of earthworm activity and CGW addition on A. platanoides growth. CGW addition significantly increased levels of organic carbon and essential plant macro-nutrients in reclaimed soil while earthworm activity assisted decomposition of both leaf litter and CGW. Findings showed that CGW may serve as a suitable early source of organic matter to support earthworm population establishment on reclaimed sites. This experiment demonstrates that CGW improves reclaimed soil quality, thereafter supporting tree establishment and growth on reclaimed landfill

Looking for Earthworms in Deadwood

Fallen branches, logs, and tree stumps are a valuable habitat in forests, giving food and shelter to many organisms, including earthworms. Unfortunately, deadwood is often removed from forests because its value is not fully appreciated. We wanted to overcome this by developing a sampling method for earthworms living in deadwood in forests. By testing our new sampling method in oak forests, we found that including deadwood in earthworm surveys improves our knowledge of forest earthworm populations. We also found a greater number of young earthworms in deadwood, where conditions were warmer and moister than in the soil. By surveying deadwood for invertebrates, such as earthworms, we can better understand the important role that deadwood in forests plays in maintaining biodiversity

Investigating tree foliar preference by the earthworms Aporrectodea longa and Allolobophora chlorotica in reclaimed and loam soil

Afforestation can improve the delivery of ecosystem services from reclaimed landfill sites. Tree health is a key determinant of ecosystem service delivery, and is directly impacted by soil quality; which is driven by biological processes in the soil, reliant on leaf litter inputs to function. Different tree species have different litter quality, affecting the degree to which they support biological processes in soils and the development of abundant and diverse soil faunal communities. In recognition of their key role in improving soil structure and fertility - key attributes of soil quality, earthworms have often been the subject of research as a part of land reclamation, and these organisms have displayed preferences for specific types of leaf litter. This work utilised a choice chamber design to measure the foliar material palatability of two tree species used in land restoration (Alnus cordata and Acer platanoides) as a food source for two common European earthworm species (Aporrectodea longa and Allolobophora chlorotica), and the effect of a reclaimed soil quality on earthworm growth, survival and feeding preferences. The research revealed that both earthworm species initially preferred the foliar material of A. cordata over A. platanoides, with the leaves of the latter requiring higher degradation to become palatable to earthworms. The consumption of fresh leaves showed these are a suitable food source for earthworms in choice chamber experiments, which historically have instead relied on senescent leaf litter. Finally, high survival rates of both A. longa and A. chlorotica in the reclaimed soil treatment, in addition to consumption of leaf material of two tree species now widely used on reclaimed landfill sites, demonstrated that these earthworm species are suitable candidates for inoculation to reclaimed land

KEYLINK: towards a more integrative soil representation for inclusion in ecosystem scale models. I. review and model concept

The relatively poor simulation of the below-ground processes is a severe drawback for many ecosystem models, especially when predicting responses to climate change and management. For a meaningful estimation of ecosystem production and the cycling of water, energy, nutrients and carbon, the integration of soil processes and the exchanges at the surface is crucial. It is increasingly recognized that soil biota play an important role in soil organic carbon and nutrient cycling, shaping soil structure and hydrological properties through their activity, and in water and nutrient uptake by plants through mycorrhizal processes. In this article, we review the main soil biological actors (microbiota, fauna and roots) and their effects on soil functioning. We review to what extent they have been included in soil models and propose which of them could be included in ecosystem models. We show that the model representation of the soil food web, the impact of soil ecosystem engineers on soil structure and the related effects on hydrology and soil organic matter (SOM) stabilization are key issues in improving ecosystem-scale soil representation in models. Finally, we describe a new core model concept (KEYLINK) that integrates insights from SOM models, structural models and food web models to simulate the living soil at an ecosystem scale

Reading tea leaves worldwide: decoupled drivers of initial litter decomposition mass‐loss rate and stabilization

The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large‐scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass‐loss rates and stabilization factors of plant‐derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy‐to‐degrade components accumulate during early‐stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass‐loss rates and stabilization, notably in colder locations. Using TBI improved mass‐loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early‐stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models

Effect of air-drying pre-treatment on the characterization of forest soil carbon pools

Archived soils could represent a valuable resource for the spatio-temporal inventory of soil carbon stability. However, archived soils are usually air-dried before storage and the impact of a drying pretreatment on physically and chemically-defined C fractions has not yet been fully assessed. Through the comparison of field-moist and corresponding air-dried (at 25oC for 2 weeks) forest soil samples, we examined the effect of air-drying on: a) the quantity and the quality of cold- (CWEC) and hot-water (HWEC) extractable C and b) the concentration of C in physically isolated fractions (free- and intra-aggregate light and organo-mineral). Soil samples were collected from the organic (O) and mineral (A and B) horizons of three different forest soils from southeastern England: (i) Cambisol under Pine (Pinus nigra); (ii) Cambisol under Beech (Fagus sylvatica) and (iii) Gleysol under oak (Quercus robur). CWEC concentrations for dry samples were up to 2 times greater than for corresponding field moist samples and had significantly (p 0.05) for most samples. Dried soils had significantly (p < 0.001) higher concentrations of free light-C while having lower concentrations of intra-aggregate-C when compared to moist samples (p < 0.001). However, fine silt and clay fractions were not significantly affected by the drying pretreatment (p=0.789). Therefore, based on the results obtained from gleysol and cambisol forest soils studied here, C contents in hot-water extractions and fine particle size physical fractions (< 25µm) seem to be robust measurements for evaluating C fractions in dried stored forest soils. Further soil types should be tested to evaluate the wider generality of these findings

Climate and atmospheric deposition effects on forest water-use efficiency and nitrogen availability across Britain

Rising atmospheric CO2 (ca) has been shown to increase forest carbon uptake. Yet, whether the ca- fertilization e ect on forests is modulated by changes in sulphur (Sdep) and nitrogen (Ndep) deposition and how ndep a ects ecosystem N availability remains unclear. We explored spatial and temporal (over 30\u2010years) changes in tree\u2010ring \u3b413C\u2010derived intrinsic water\u2010use e ciency (iWUE), \u3b418O and \u3b415N for four species in twelve forests across climate and atmospheric deposition gradients in Britain. The increase in iWUE was not uniform across sites and species\u2010speci c underlying physiological mechanisms re ected the interactions between climate and atmospheric drivers (oak and Scots pine), but also an age e ect (Sitka spruce). Most species showed no signi cant trends for tree\u2010ring \u3b415N, suggesting no changes in N availability. Increase in iWUE was mostly associated with increase in temperature and decrease in moisture conditions across the South\u2013North gradient and over 30\u2010years. However, when excluding Sitka spruce (to account for age or stand development e ects), variations in iWUE were signi cantly associated with changes in ca and Sdep. Our data suggest that overall climate had the prevailing e ect on changes in iWUE across the investigated sites. Whereas, detection of Ndep, Sdep and ca signals was partially confounded by structural changes during stand development

The large-scale diversity, distribution and environmental drivers of Europe's forest ectomycorrhizas

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Tamm Review: Influence of forest management activities on soil organic carbon stocks: A knowledge synthesis

International audienceAlmost half of the total organic carbon (C) in terrestrial ecosystems is stored in forest soils. By altering rates of input or release of C from soils, forest management activities can influence soil C stocks in forests. In this review, we synthesize current evidence regarding the influences of 13 common forest management practices on forest soil C stocks. Afforestation of former croplands generally increases soil C stocks, whereas on former grasslands and peatlands, soil C stocks are unchanged or even reduced following afforestation. The conversion of primary forests to secondary forests generally reduces soil C stocks, particularly if the land is converted to an agricultural land-use prior to reforestation. Harvesting, particularly clear-cut harvesting, generally results in a reduction in soil C stocks, particularly in the forest floor and upper mineral soil. Removal of residues by harvesting whole-trees and stumps negatively affects soil C stocks. Soil disturbance from site preparation decreases soil C stocks, particularly in the organic top soil, however improved growth of tree seedlings may outweigh soil C losses over a rotation. Nitrogen (N) addition has an overall positive effect on soil C stocks across a wide range of forest ecosystems. Likewise, higher stocks and faster accumulation of soil C occur under tree species with N-fixing associates. Stocks and accumulation rates of soil C also differ under different tree species, with coniferous species accumulating more C in the forest floor and broadleaved species tending to store more C in the mineral soil. There is some evidence that increased tree species diversity could positively affect soil C stocks in temperate and subtropical forests, but tree species identity, particularly N-fixing species, seems to have a stronger impact on soil C stocks than tree species diversity. Management of stand density and thinning have small effects on forest soil C stocks. In forests with high populations of ungulate herbivores, reduction in herbivory levels can increase soil C stocks. Removal of plant biomass for fodder and fuel is related to a reduction in the soil C stocks. Fire management practices such as prescribed burning reduce soil C stocks, but less so than wildfires which are more intense. For each practice, we identify existing gaps in knowledge and suggest research to address the gaps

Belowground biodiversity relates positively to ecosystem services of European forests

Biodiversity of ecosystems is an important driver for the supply of ecosystem services to people. Soils often have a larger biodiversity per unit surface area than what can be observed aboveground. Here, we present what is to our knowledge, the most extensive literature-based key-word assessment of the existing information about the relationships between belowground biodiversity and ecosystem services in European forests. The belowground diversity of plant roots, fungi, prokaryota, soil fauna, and protists was evaluated in relation to the supply of Provisioning, Regulating, Cultural, and Supporting Services. The soil biota were divided into 14 subgroups and the ecosystem services into 37 separate services. Out of the 518 possible combinations of biotic groups and ecosystem services, no published study was found for 374 combinations (72%). Of the remaining 144 combinations (28%) where relationships were found, the large majority (87%) showed a positive relationship between biodiversity of a belowground biotic group and an associated ecosystem service. However, for the majority of the combinations (102) there were only three or fewer studies. The percentage of cases for which a relationship was detected varied strongly between ecosystem service categories with 23% for Provisioning, 8% for Regulating, 40% for Cultural, and 48% for Supporting Services. We conclude that (1) soil biodiversity is generally positively related to ecosystem services in European forests; (2) the links between soil biodiversity and Cultural or Supporting services are better documented than those relating to Provisioning and Regulating services; (3) there is a huge knowledge gap for most possible combinations of soil biota and ecosystem services regarding how a more biodiverse soil biota is associated with a given ecosystem service. Given the drastically increasing societal demand for knowledge of the role of biodiversity in the functioning of ecosystems and the supply of ecosystem services, we strongly encourage the scientific community to conduct well-designed studies incorporating the belowground diversity and the functions and services associated with this diversity