章古台沙地松树人工林土壤无机氮、微生物生物量碳及微生物生物量氮

The dynamics of soil inorganic nitrogen （NH4^＋ -N and NO3^- -N） and microbial biomass carbon （Cmic） and nitrogen （Nmic） under 30-year-old fenced Pinus sylvestris L. var. mongolica Litvin （SF）, unfenced P. sylvestris L. var. mongolica Litvin （SUF）, and unfenced Pinus densiflora Siebold et Zucc. （DUF） plantations in the Zhanggutai sandy soil of China were studied during Apr. to Oct. 2004 by the in situ closed-top core incubation method. All mentioned C and N indices in each stand type fluctuated over time. The ranges of inorganic N, Cmic, and Nmic contents in the three stand types were 0.7-2.6, 40.0-128.9, and 5.4-15.2 μg g^-1, respectively. The average contents of soil NH4^＋ -N and Cmic under the three 30-year-old pine plantations were not different. However, soil NO3^ -N and total inorganic N contents decreased in the order of SUF ≥ SF ≥ DUF, the Nmic content was in the order of SF = SUF 〉 DUF, and the Cmic：Nmic ratio was in the order of SUF = DUF 〉 SF. Seasonal variations were observed in soil inorganic N, microbial biomass, and plant growth. These seasonal variations had certain correlations with microbe and plant N use in the soil, and their competition for NH4^＋ -N was mostly regulated by soil N availability. The influence of tree species on inorganic N and Nmic were mainly because of differences in litter quality. Lack of gazing decreased the Cmic：Nmic ratio owing to decreased carbon output and increased the ability of soil to supply N. The soil N supply under the P. sylvestris var. mongolica plantation was lower than under the P. densiflora plantation.     

Organic carbon in soil physical fractions under different-aged plantations of Mongolian pine in semi-arid region of Northeast China

In order to understand the changes of surface soil carbon (C) storage following the afforestation of sandy grasslands, we used physical fractionation procedures to quantify C concentrations and sucrase enzyme activity in bulk soil and different particle fractions along two replicate chronosequences of Mongolian pine (Pinus sylvestris var. mongolica Litv.) plantations in the southeastern Keerqin Sand Lands, Northeast China. Carbon concentration in bulk topsoil (0–15 cm) initially decreased following afforestation of grassland and subsequently increased as the forest matured. In general, this pattern of C concentration changes was associated with all particle-size fractions (except clays) and both macro- and microaggregates. The patterns of topsoil C were also influenced by wind erosion and deposition, with marked increases in the relative mass of silt and fine sand fractions occurring during forest development. The loss of aggregates immediately following afforestation was counteracted by formation of aggregates as the forests developed, contributing to the stabilization of carbon. To enhance soil C storage during afforestation of sandy soils in such semi-arid regions it is recommended to minimize disruption of grassland vegetation during the planting stage.     

Effects of weed control and fertilization on soil carbon and nutrient pools in an exotic pine plantation of subtropical Australia

Purpose  

Soil carbon (C) and nutrient pools under different plantation weed control and fertilizer management treatments were assessed in a 7-year-old, F₁ hybrid (Pinus elliottii var. elliottii × Pinus caribaea var. hondurensis) plantation in southeast Queensland, Australia. This research aimed to investigate how early establishment silvicultural treatments would affect weed biomass, soil C, nitrogen (N) and other nutrient pools; and soil C (δ¹³C) and N isotope composition (δ¹⁵N) to help explain the key soil processes regulating the soil C and nutrient pools and dynamics.     

间伐和去除凋落物对马尾松林细根生产力和土壤有机碳含量的影响

Soils play a critical role in the global carbon cycle, and can be major source or sink of CO₂ depending upon land use, vegetation type and soil management practices. Fine roots are important component of a forest ecosystem in terms of water and nutrient uptake. In this study the effects of thinning and litter fall removal on fine root production and soil organic carbon content were examined in 20-year-old Masson pine (Pinus resinosa) plantations in Huitong, Hunan Province of China in the growing seasons of 2004 and 2005. The results showed that fine root production was significantly lower in the thinning plots than in the control plots, with a decrease of 58% and 14% in 2004 and 2005 growing seasons, respectively. Litter fall removal significantly increased fine root production by 14% in 2004. Soil temperature (T_soil) and soil moisture (M_soil) were higher in the thinning plots than those in the controls. Litter fall removal had significant effiects on T_soil and M_soil. Soil organic carbon content was higher in the thinning plots but was lower in the plots with litter fall removal compared with that in the controls. Our results also indicated that annual production of fine roots resulted in small carbon accumulation in the upper layers of the soil, and removal of tree by thinning resulted in a significant increase of carbon storage in Masson pine plantations.     

Land-use history,forest conversion,and soil organic carbon in pine plantations and native forests of south eastern Australia

Land-use history – the number, type, and duration of previous land uses – is relevant to many questions regarding land-use effects on soil carbon, but is infrequently reported. We examine the importance of land-use history variables, as well as topographic and edaphic variables, on soil C in a range of forest types – native forest, pine plantations, secondary forest and rehabilitated forest – at three contrasting locations in south eastern Australia. Our comparisons include a novel forest conversion of exotic pine plantations to native, broadleaf forest.Using nested ANOVAs, we detected few differences in soil C concentration indices (total C, microbial biomass C, K₂SO₄–C) and C content among eucalypt-dominated vegetation and pine plantations within each location (0–10 cm depth). However, planned contrasts indicated a 30% decrease in soil C content with conversion of native forest to pine plantation of age 37 years. The reverse land-use change – pine plantation to native, broadleaf forest – was associated with a decrease in soil C concentration and content at one location (40%; age 12–13 years) and no detectable changes at another (to age 7 years). Variable effect between locations of this novel land-use change on soil C could be due to differences in potential productivity, conifer species, and plantation age.We used correlation coefficients and general linear models to identify widely applicable variables for predicting soil C concentration and content at local scales (≤ 20 km²). Within-location relationships with topographic variables were weak and infrequent relative to those with edaphic and land-use history variables. Soil texture was strongly correlated with soil C at each location, although the relative significance of different particle size fractions differed among locations. Electrical conductivity appeared more widely applicable since it was included in C models at two locations. Combining land-use history and edaphic variables produced strong predictive models for soil C concentrations and content at two locations (total r² 0.83 to 0.95). Positive relationships were indicated between soil C and ‘age of current vegetation’ at one location, and negative relationships were indicated with ‘number of land uses’ at another. These data highlight a potential predictive role for land-use history variables in local-scale assessments of soil C in forested landscapes.     

Solubilization of iron and calcium phosphates by soil fungi isolated from coffee plantations

Almost 900 fungal isolates were obtained from eight coffee plantations in Colombia and Mexico. Of these, 76 isolates showed activity to solubilize Ca₃(PO₄)₂ (PCa) and FePO₄·H₂O (PFe), which had been added to agar in a plate test. Generally, PCa was better solubilized than PFe. Colombian isolates were generally somewhat less effective than Mexican isolates. The two most effective isolates from each country with apparent highest PFe, solubilization potential were selected and cultivated in liquid medium containing PFe, which is more prevalent in tropical soils. The pH value, solubilized P in the medium and P uptake in fungal biomass were determined. After 24 days, Cylindrocarpon didymum and C. obtusisporum (both from Colombia) had solubilized 9.9 and 6.4 mg PO₄ ^3--P L^?1 and took up 8.6 and 11.6 mg P in biomass. Penicillium janthinellum and Paecilomyces marquandii (both from Mexico) solubilized 7.0 and 1.9 mg PO₄ ^3--P L^?1 and took up 11.3 and 17.3 mg P in biomass. The potential practical use of the four fungal isolates for different strategies in making more P available for coffee growth is discussed.     

应用Wenner结构原理估计沙地松树人工林土壤含水量

To estimate the mean value of surface soil water content rapidly, accurately, and nonintrusively, field investigations on soil electrical resistivity （SER） with the Yokogawa 324400 earth resistivity meter and the surface （0-150 cm） soil water content （SWC） with time domain reflectometry （TDR）, together with the abiotic factors including soil texture, structure, and salinity concentrations were conducted in the Mongolian pine （Pinus sylvestris var. mongolica） plantations on a sandy land. The measurement of SER was based on the 4-probe Wenner configuration method. Relationships between the values of SWC and SER were obtained based on analysis of the abiotic factors of the research site, which play a key role in affecting the soil electrical resistivity. Results indicate that the SER meter could be used to estimate the mean value of SWC in the Mongolian pine plantations on the sandy land during the growing seasons. The bulky nature of the equipment simplified the cumbersome measurements of soil water content with the general methods. It must be noted that the Wenner configuration method could only provide the mean values of the SWC, and the soil texture, structure, temperature, and solute concentrations influenced the SER and further affected the estimation of the SWC by the SER meter. Therefore, the results of this study could be applied on a sandy land during the growing seasons only. However, the SWC of other soil types also may be obtained according to the individual soil types using the procedures of this study.     

Field inoculation effectiveness of native and exotic arbuscular mycorrhizal fungi in a Mediterranean agricultural soil

In sustainable agriculture, arbuscular mycorrhizal (AM) fungal inoculation in agronomical management might be very important, especially when the efficiency of native inocula is poor. Here, we assessed the effect of native and exotic selected AM fungal inocula on plant growth and nutrient uptake in a low input Trifolium alexandrinum-Zea mays crop rotation. We evaluated the effects of four exotic AM fungal isolates on T. alexandrinum physiological traits in greenhouse. Then, the field performances of T. alexandrinum inoculated with the exotic AMF, both single and mixed, were compared to those obtained with a native inoculum, using a multivariate analysis approach. Finally, we tested the residual effect of AM fungal field inoculation on maize as following crop. Multivariate analysis showed that the field AM fungal inoculation increased T. alexandrinum and Z. mays productivity and quality and that the native inoculum was as effective as, or more effective than, exotic AM fungal isolates. Moreover, the beneficial effects of AMF were persistent until the second year after inoculation. The use of native AMF, produced on farm with mycotrophic plants species, may represent a convenient alternative to commercial AM fungal inocula, and may offer economically and ecologically important advantages in sustainable or organic cropping systems.     

Soil water depletion and replenishment during first- and early second-rotation Eucalyptus globulus plantations with deep soil profiles

Eucalyptus globulus plantations are thought to use stored soil water when planted on ex-agricultural sites, and we hypothesized that this is likely to affect productivity of 2nd and later rotation plantations because the next rotations have access to less stored soil water. We used a combination of experiments and modeling to understand the impact of E. globulus plantations on soil water stores over the first rotation and early second rotation. The experiments were conducted at 3 contrasting sites in south-western Australia, and modeling was used to extrapolate the results to other climatic zones. Soil water dynamics were assessed to 8 m depth under a range of management options, including spacing and nitrogen addition in the first rotation, and coppice or seedling re-establishment in the 2nd rotation. We found that soil water stores declined over the course of the first rotation at all sites, with some (incomplete) annual replenishment evident at the higher rainfall sites, but less replenishment at depth, especially in the lower rainfall sites. Only the wettest of the 3 sites fully replenished with soil water after harvest of the 1st rotation. Plots with higher stocking rates had higher soil water depletion early in the rotation, although by the end of the first rotation, most treatments had similar soil water deficits of around 800 mm at all of the sites. Of the sites that were responsive to N fertilizer, there was a strong differential in the degree of soil water deficit between N treatments, with N fertilized trees using more of the soil water store each year, but also producing more wood. A process-based plantation growth model, CABALA, was found to be adequate for predicting soil water dynamics under the range of management options that we explored, and we applied it to understanding the potential replenishment of soil under 2nd rotation plantations in a range of climatic zones within the E. globulus estate in south-western Australia. This modeling showed that most sites with soil depths of more than 4 m (i.e., most of the estate) are unlikely to be fully replenished in the 2nd rotation, and that this is likely to have a significant impact on the capacity of sites to achieve similar productivity levels in the second rotation as the first unless the sites are given an opportunity for soil water replenishment between rotations. The results from this study suggest that plantation managers will need to understand soil water dynamics at any given site to be able to predict productivity in 2nd and later rotations, and may need to explore novel management options like fallowing between rotations to allow for soil water replenishment.     

Modification of soil enzyme activities as a consequence of replacing meadows by pine plantations under temperate climate

Changes in land use frequently modify the capacity of ecosystems to provide services. The purpose of this study was to investigate the effects of a specific land-use change, i.e. from meadows to pine plantations under temperate climate, on soil enzyme activities. To this aim, the variation of five key soil enzyme activities (dehydrogenase, β-glucosidase, arylsulphatase, acid phosphatase and urease) was evaluated in different sites located in the Urdaibai Reserve of the Biosphere (northern Spain). Lower values of dehydrogenase [effect size, computed as 100 × (1 − mean value from pine plantations/mean value from meadows), was 82.9%], β-glucosidase (52.9%) and urease (52.5%) activity were observed in soils from pine plantations versus meadows. Acid phosphatase and arylsulphatase activity showed a pattern of variation that was not dependent on land-use. The largest variation in enzyme activity values was due to changes at the small scale, not between the studied sites, an encouraging finding for the suitability of enzyme activities as bioindicators of the impact of land-use changes on soil functioning. Our results suggest that nutrient cycling (as reflected by the values of soil enzyme activities) might have been modified as a consequence of replacing meadows by pine plantations.     

Activated carbon amendments to soil alters nitrification rates in Scots pine forests

The influence of charcoal on biotic processes in soils remains poorly understood. Charcoal is a natural product of wildfires that burned on a historic return interval of ∼100 years in Scots pine (Pinus sylvestris L.) forests of northern Sweden. Fire suppression and changes in forest stand management have resulted in a lack of charcoal production in these ecosystems. It is thought that charcoal may alter N mineralization and nitrification rates, however, previous studies have not been conclusive. Replicated field studies were conducted at three late-succession field sites in northern Sweden and supporting laboratory incubations were conducted using soil humus collected from these sites. We used activated carbon (AC), as a surrogate for natural-occurring fire-produced charcoal. Two rates of AC (0 and 2000 kg ha⁻¹), and glycine (0 and 100 kg N as glycine ha⁻¹) were applied in factorial combination to field microplots in a randomized complete block pattern. Net nitrification, N mineralization, and free phenol concentrations were measured using ionic and non-ionic resin capsules, respectively. These same treatments and also two rates of birch leaf litter (0 and 1000 kg ha⁻¹) were applied in a laboratory incubation and soils from this incubation were extracted with KCl and analyzed for NH₄⁺ and NO₃⁻. Nitrification rates increased with AC amendments in laboratory incubations, but this was not supported by field studies. Ammonification rates, as measured by NH₄⁺ accumulation on ionic resins, were increased considerably by glycine applications, but some NH₄⁺ was apparently lost to surface sorption to the AC. Phenolic accumulation on non-ionic resin capsules was significantly reduced by AC amendments. We conclude that charcoal exhibits important characteristics that affect regulating steps in the transformation and cycling of N.     

Changes in soil properties related to conversion of savannah woodland into pine and eucalyptus plantations,Northern Nigeria

Soil properties associated with six age-grade plantations of Pinus oocarpa Schiede and Eucalyptus camaldulensis Dehnh., respectively, including nearby natural vegetation, were compared in the savannah zone of Nigeria. The soil organic matter, total nitrogen and exchangeable nutrients first show declining values with the increasing age of the plantation, then an increase and finally steady or declining values in the 0–15 cm soil depth. Usually the differences between the two youngest plantations and the oldest plantations, and the natural vegetation, were significant. In the 20–30 cm soil depth the properties showed a decrease or steady values over time, with the three oldest plantations showing significant differences from the natural vegetation. The soil pH showed an increased acidity over time. There was little difference in the soil properties between the two tree species. The implications of the results are discussed in relation to sustaining productivity and soil fertility. © 1998 John Wiley & Sons, Ltd.     

丛枝菌根真菌介导的土壤有机碳稳定机制研究进展

土壤有机碳(SOC)的稳定是陆地生态系统碳循环的关键过程之一,对维持土壤肥力和减少温室气体排放具有重要意义。以往认为植物残体中难降解性物质的物理保护和腐殖质影响土壤中有机碳库的稳定性。最近的研究结果表明,微生物介导的碳循环过程在土壤有机碳稳定中发挥着重要作用。丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)作为土壤中一类重要的共生微生物,参与植物光合碳向土壤的转运和分配,是陆地生态系统碳循环的重要一环,但其在土壤有机碳稳定中的作用潜力还未得到充分挖掘。基于此,本文估算了植物光合碳在AMF根外菌丝的分配量;总结了AMF介导的土壤有机碳稳定机制,主要包括AMF活体菌丝对碳的截留,分泌物及残体的分子结构抗性和土壤矿物吸附,提高植物源碳的质量和数量,菌丝分泌物及残体的激发效应和稳定土壤团聚体;探讨了影响AMF介导的稳定性有机碳形成的非生物(气候因子、土壤养分和土壤矿物)和生物因子(植物和AMF种类);提出了AMF与土壤有机碳周转互作机理进一步的研究方向,包括探究菌根植物光合碳转化为稳定性SOC的机制,解析不同生态系统中AMF对稳定性SOC的贡献及影响因素,并厘清...     

Different impacts of native and exotic earthworms on rhizodeposit carbon sequestration in a subtropical soil

Earthworms are known to regulate the sequestration of soil and leaf litter carbon (C). However, their impacts on the more accessible rhizospheric C, which represents a major energy source for soil food webs and an essential factor for C sequestration, are still unclear. Previous studies indicate that earthworms regulate the dynamics of SOC and leaf litter-C by increasing C accessibility to microbiota. However, in the case of labile rhizodeposit-C, microbiota might not require any pre-conditioning by earthworms and may rapidly metabolize most of this root-derived C. Consequently, potential pathways by which earthworms may affect the fate of rhizodeposit-C would be to regulate the biomass and/or activity of rhizosphere microbiota and, further, to mineralize/stabilize microbial products. A ¹³CO₂ labelling experiment was performed to determine the impacts of four different earthworm species on the fate of tree rhizodeposit-C in a subtropical soil. We hypothesized that endogeic earthworm species, representing primarily geophagous species, would closely interact with soil microbiota and sequester the microbially metabolized rhizodeposit-C more efficiently than epigeic and anecic earthworm species. We found that irrespective of ecological group affiliation, the three native earthworms did not affect rhizodeposit-C sequestration. In contrast, the exotic endogeic species stimulated the immobilization of rhizodeposit-C in the biomass of root-associated bacteria and/or arbuscular mycorrhizal fungi and, further, accessed the microbiota-metabolized rhizodeposit-C more efficiently. As a consequence, the exotic endogeic earthworm species transiently tripled rhizodeposit-C retention in soil. We propose that the weak linkages between native earthworms and rhizodeposits-related microbiota limit earthworm impacts on rhizodeposit-C sequestration. However, the exotic endogeic species Pontoscolex corethrurus may potentially alter rhizodeposit-C dynamics in invaded areas by shifting rhizosphere microbial community composition. This work highlights a distinct mechanism by which earthworms can regulate C dynamics and indicates a significant contribution of invasive earthworm species to belowground processes.     

Physical,chemical and microbiological soil attributes influence soil greenhouse gases fluxes in Atlantic Forest and pine (Pinus taeda) plantations in Brazil

Forest soils can be sources or sinks of greenhouse gases (GHGs) depending on soil attributes that affect biomass and activity of soil micro-organisms involved in GHGs fluxes. In this work, we tested the hypothesis that soil physical, chemical and microbiological attributes, under different forests ecosystems, affect the soil GHGs [nitrous oxide (N₂O), carbon dioxide (CO₂) and methane (CH₄)] fluxes. The study was carried out in two locations in southern Brazil in 2019, with three experimental plots of 900 m² in native forests of the Atlantic Forest biome and in loblolly pine (Pinus taeda) plantations. Air samples released from the soil surface were analysed for concentration and flux of CO₂, N₂O and CH₄. Soil samples were analysed for chemical attributes, density (Ds), soil microporosity (MiPs), soil macroporosity (MaPs), total porosity (TP), water-filled pore space (WFPS), microbial biomass carbon (MB-C), basal respiration (BR), microbial (qMic) and metabolic (qCO₂) quotient and activities of soil urease and β-glucosidase enzymes. The seasons influenced the CO₂ and N₂O emissions, probably because of the changes in seasonal conditions. However, native forests consumed more CH₄ than pine plantations. Meanwhile, the native forests presented soils with lower Ds (average 21.5% lower), more TP (average 12.5% higher) and more moisture (average 33% higher), which improved the microbiological attributes of the soil (20% to 60% more MB-C, 67% higher urease activity and 30% higher β-glucosidase activity) compared with pine plantations. Native forests contributed more intensely to CH₄ consumption than pine plantations because they present better physical, chemical and microbiological soil conditions. Therefore, it is possible that forestry practices that improve soil physical attributes are likely to contribute to increase CH₄ consumption, and to reduce GHGs emissions in forest ecosystems.     

Extramatrical mycelia of ectomycorrhizal fungi as moderators of carbon dynamics in forest soil

Extramatrical mycelia (EMM) of ectomycorrhizal (ECM) fungi are potentially extensive in soil and receive significant allocations of plant-derived carbon. Although losses from living EMM occur via respiration and exudation, EMM represents a considerable biomass component and potential carbon sink in many forest soils. ECM root tips and rhizomorphs may persist in soil for many months, but interactions between grazing arthropods and decomposers probably facilitate more rapid turnover of diffuse EMM. Elevated atmospheric CO₂ concentration [CO₂] is likely to increase carbon allocation to ECM fungi by their tree hosts. This will probably increase root colonization by ECM fungi and drive changes in their communities in soil. The likely effects of elevated [CO₂] and other climate change factors on the production and turnover of EMM production are difficult to predict from current evidence, and this hampers our understanding of their potential value as future carbon sinks. Responses of grazing soil arthropods to future climate change will have a strong influence on EMM turnover, along with the abilities of ECM fungi to store carbon in below-ground, and this should be seen as a priority area for future research.     

Dynamics and stratification of bacteria and fungi in the organic layers of a scots pine forest soil

The abundance and micro-stratification of bacteria and fungi inhabiting the organic layers of a Scots pine forest (Pinus sylvestris L.) were investigated. An experiment using stratified litterbags, containing organic material of four degradation stages (fresh litter, litter, fragmented litter and humus) was performed over a period of 2.5 years. Dynamics and stratification of fluorescent stained bacteria and fungi, ratios between bacterial and fungal biomass, and relationships with moisture and temperature are described. Average bacterial counts in litter and fragmented litter were similar, i.e., approximately 5×10⁹ bacteriag^–1 (dry weight) organic matter, and significantly exceeded those in humus. The mean bacterial biomass ranged from 0.338 to 0.252mg carbon (C) g^–1 (dry weight) organic matter. Lengths of mycelia were significantly below the usually recorded amounts for comparable temperate coniferous forests. The highest average hyphal length, 53mg^–1 (dry weight) organic matter, was recorded in litter and decreased significantly with depth. The corresponding mean fungal biomass ranged from 0.050 to 0.009mg Cg^–1 (dry weight). The abundance of bacteria and fungi was influenced by water content, that of fungi also by temperature. A litterbag series with freshly fallen litter of standard quality, renewed bimonthly, revealed a clear seasonal pattern with microbial biomass peaks in winter. The mean hyphal length was 104mg^–1 (dry weight) and mean number of bacteria, 2.40×10⁹ bacteria g^–1 (dry weight). Comparable bacterial and fungal biomass C were found in the freshly fallen litter [0.154 and 0.132mgCg^–1 (dry weight) organic material, respectively]. The ratio of bacterial-to-fungal biomass C increased from 1.2 in fresh litter to 28.0 in humus. The results indicate the existence of an environmental stress factor affecting the abundance of fungi in the second phase of decomposition. High atmospheric nitrogen deposition is discussed as a prime factor to explain low fungal biomass and the relatively short lengths of fungal hyphae in some of the forest soil layers under study. Received: 26 June 1997     

Alteration of soil labile organic carbon by invasive earthworms (Pontoscolex corethrurus) in tropical rubber plantations

The invasive earthworm (Pontoscolex corethrurus) is commonly found in rubber plantations of Xishuangbanna, southwestern China. To understand the long-term impact of this invasive earthworm on soil labile organic carbon (LOC), we examined changes in LOC that was protected and unprotected by soil aggregates during a worm-exclusion experiment in rubber plantations of Xishuangbanna. We found that the presence of this invasive earthworm for 20 months increased LOC (up to 35%) protected by aggregates in surface soil layer (0–5 cm). In contrast, the presence of this earthworm increased LOC unprotected by the aggregates and the turnover rate of LOC protected by the aggregates in subsurface soil layer (5–15 cm). Soil total LOC did not differ between the control and worm-exclusion treatments. These findings suggest that the invasion of P. corethrurus can redistribute LOC along soil vertical profiles with accumulation of protected LOC on surface soil layer and unprotected LOC on subsurface soil layer. Earthworms' redistribution of LOC between the protected and unprotected forms and along soil profile may affect long-term soil carbon cycling.     

A modelling analysis of the potential for soil carbon sequestration under short rotation coppice willow bioenergy plantations

Abstract. Rising atmospheric CO₂ concentrations and their association with global climate change have led to several major international initiatives to reduce net CO₂ emissions, including the promotion of bioenergy crops such as short rotation coppice (SRC) willow. Although the above-ground harvested bio-fuel is likely to be the major contributor to the CO₂ mitigation potential of bioenergy crops, additional carbon may be sequestered through crop inputs into plantation soils.   Here, we describe a process-based model specifically designed to evaluate the potential for soil carbon sequestration in SRC willow plantations in the UK. According to the model predictions, we conclude that the potential for soil carbon sequestration in these plantations is comparable to, or even greater than, that of naturally regenerating woodland. Our preliminary, site-specific model output suggests that soil carbon sequestration may constitute about 5% of the overall carbon mitigation benefit arising from SRC plantations. Sensitivity analyses identified the following factors as the principal controls on rates and amounts of soil carbon sequestration under SRC: carbon inputs (net primary production), decomposition rates of the major soil carbon pools, initial soil carbon content (an inverse relationship with rates of soil carbon sequestration), crop/plantation management, and depth of soil being influenced by the bioenergy crop. Our results suggest that carbon sequestration potential is greatest in soils whose carbon content has been depleted to relatively low levels due to agricultural land use practices such as annual deep ploughing of agricultural soils.