Soil carbon storage and stratification under different tillage/residue-management practices in double rice cropping system
Chen, Z. ; Zhang, H. ; dikgwatlhe, S.B. ; Xue, J. ; Qiu, K. ; Tang, H. ; Chen, F. - \ 2015
Journal of Integrative Agriculture 14 (2015)8. - ISSN 2095-3119 - p. 1551 - 1560.
no-tillage - organic-matter - conservation tillage - climate-change - sequestration - impacts - agriculture - phosphorus - nitrogen
The importance of soil organic carbon (SOC) sequestration in agricultural soils as climate-change-mitigating strategy has become an area of focus by the scientific community in relation to soil management. This study was conducted to determine the temporal effect of different tillage systems and residue management on distribution, storage and stratification of SOC, and the yield of rice under double rice (Oryza sativa L.) cropping system in the southern China. A tillage experiment was conducted in the southern China during 2005-2011, including plow tillage with residue removed (PT0), plow tillage with residue retention (PT), rotary tillage with residue retention (RT), and no-till with residue retention on the surface (NT). The soil samples were obtained at the harvesting of late rice in October of 2005, 2007 and 2011. Multiple-year residue return application significantly increased rice yields for the two rice-cropping systems; yields of early and late rice were higher under RT than those under other tillage systems in both years in 2011. Compared with PT0, SOC stocks were increased in soil under NT at 0-5, 5-10, 10-20, and 20-30 cm depths by 33.8, 4.1, 6.6, and 53.3%, respectively, in 2011. SOC stocks under RT were higher than these under other tillage treatments at 0-30 cm depth. SOC stocks in soil under PT were higher than those under PT0 in the 0-5 and 20-30 cm soil layers. Therefore, crop residues played an important role in SOC management, and improvement of soil quality. In the 0-20 cm layer, the stratification ratio (SR) of SOC followed the order NT>RT>PT>PT0; when the 0-30 cm layer was considered, NT also had the highest SR of SOC, but the SR of SOC under PT was higher than that under RT with a multiple-year tillage practice. Therefore, the notion that conservation tillage lead to higher SOC stocks and soil quality than plowed systems requires cautious scrutiny. Nevertheless, some benefits associated with RT system present a greater potential for its adoption in view of the multiple-year environmental sustainability under double rice cropping system in the southern China.
Intercropping enhances soil carbon and nitrogen
Cong, W. ; Hoffland, E. ; Li, L. ; Six, J. ; Sun, J.H. ; Bao, X.G. ; Zhang, F.S. ; Werf, W. van der - \ 2015
Global Change Biology 21 (2015)4. - ISSN 1354-1013 - p. 1715 - 1726.
organic-matter - crop-rotation - ecosystem processes - root distribution - northwest china - food security - nutrient-use - diversity - biodiversity - sequestration
Intercropping, the simultaneous cultivation of multiple crop species in a single field, increases aboveground productivity due to species complementarity. We hypothesized that intercrops may have greater belowground productivity than sole crops, and sequester more soil carbon over time due to greater input of root litter. Here, we demonstrate a divergence in soil organic carbon (C) and nitrogen (N) content over 7 years in a field experiment that compared rotational strip intercrop systems and ordinary crop rotations. Soil organic C content in the top 20 cm was 4% +- 1% greater in intercrops than in sole crops, indicating a difference in C sequestration rate between intercrop and sole crop systems of 184 +- 86 kg C ha-1 yr-1. Soil organic N content in the top 20 cm was 11% +- 1% greater in intercrops than in sole crops, indicating a difference in N sequestration rate between intercrop and sole crop systems of 45 +- 10 kg N ha-1 yr-1. Total root biomass in intercrops was on average 23% greater than the average root biomass in sole crops, providing a possible mechanism for the observed divergence in soil C sequestration between sole crop and intercrop systems. A lowering of the soil d15N signature suggested that increased biological N fixation and/or reduced gaseous N losses contributed to the increases in soil N in intercrop rotations with faba bean. Increases in soil N in wheat/maize intercrop pointed to contributions from a broader suite of mechanisms for N retention, e.g., complementary N uptake strategies of the intercropped plant species. Our results indicate that soil C sequestration potential of strip intercropping is similar in magnitude to that of currently recommended management practises to conserve organic matter in soil. Intercropping can contribute to multiple agroecosystem services by increased yield, better soil quality and soil C sequestration.
Forest Carbon Offsets Revisited: Shedding Light on Darkwoods
Kooten, G.C. van; Bogle, T. ; Vries, F.P. de - \ 2015
Forest Science 61 (2015)2. - ISSN 0015-749X - p. 370 - 380.
land management - policy design - sequestration - emissions - redd - implementation - deforestation - framework - prospects - programs
This paper investigates the viability of carbon offset credits created through forest conservation and preservation. A detailed forest management model based on a case study of a forest estate in southeastern British Columbia, owned by The Nature Conservancy of Canada (NCC) is used to demonstrate the challenging nature of estimating forest carbon offsets. For example, the NCC management plan creates substantial carbon offset credits because the counterfactual is that of a private forest liquidator, but when sustainable management of the site is assumed, the commercial operator would sequester much more carbon than under the NCC plan. The broader message is that the creation of carbon offsets is highly sensitive to ex ante assumptions and whether physical carbon is discounted. We demonstrate that more carbon gets stored in wood products as the discount rate on carbon rises (addressing climate change is more urgent). A high discount rate on carbon favors greater harvests and processing of biomass into products, while a low rate favors reduced harvest intensity. Further, since carbon credits earned by protecting forests may find their way onto world carbon markets, they lower the costs of emitting CO2 while contributing little to mitigating climate change.
Soil inorganic carbon stock under different soil types and land uses on the Loess Plateau region of China
Tan, W.F. ; Zhang, R. ; Cao, H. ; Huang, C.Q. ; Yang, Q.K. ; Wang, M.K. ; Koopal, L.K. - \ 2014
Catena 121 (2014). - ISSN 0341-8162 - p. 22 - 30.
organic-carbon - storage - sequestration - grasslands - deposition - dynamics - patterns - nitrogen - climate - caliche
The soil carbon reservoir is the largest carbon reservoir in terrestrial ecosystems and consists of soil organic and inorganic carbon stocks. Previous studies have mainly focused on the soil organic carbon (SOC) stock, and limited information is available about the soil inorganic carbon (SIC) stock. The Chinese Loess Plateau (CLP), which is located in the arid and semi-arid region of China, is an important inorganic carbon reservoir, with a thick soil layer that is rich in calcium carbonate. However, there are few reports on the SIC stock and its spatial distribution in this region. In the current study, the SIC densities and stocks for various soil types and land use patterns were evaluated based on 495 profiles with 2470 soil samples across the CLP, which were collected from the Chinese Second National Soil Survey. The results showed that in the top 1 m of soil across the CLP, the average SIC density is 17.04 kg/m(2), and the total SIC stock is approximately 10.20 Pg C (1 Pg = 10(15) g). The SIC stock of the CLP accounts for approximately 18.4% of the total SIC stock throughout China. The average values of the SIC stock in the 0-20, 20-50 and 50-100 cm depths of the CLP are 2.39, 2.92 and 4.89 Pg, respectively. Under different land use patterns, the order of the average SIC density is farmland approximate to grassland > forest in all soil layers. For the various soil types, the SIC density in the 0-100 cm layer is the highest in alkaline soil and lowest in subalpine meadow soil, whereas the SIC stock is highest in loessial soil, eolian sandy soil and sierozem, and the lowest in subalpine meadow soil. These differences are largely a result of the area occupied by each soil type and the climate conditions. The results of this study provide basic information about carbon reservoir in China and contribute to our understanding of the SIC stock on the CLP as it relates to the carbon balance of terrestrial ecosystems. (C) 2014 Elsevier B.V. All rights reserved.
Sustainability of meat production beyond carbon footprint: a synthesis of case studies from grazing systems in Uruguay
Picasso, V.D. ; Modernel Hristoff, P.D. ; Becona, G. ; Salvo, L. ; Gutierrez, L. ; Astigarraga, L. - \ 2014
Meat Science 98 (2014)3. - ISSN 0309-1740 - p. 346 - 354.
life-cycle assessment - impact assessment - sequestration - emissions - climate - grasslands - balance
Livestock production has been challenged as a large contributor to climate change, and carbon footprint has become a widely used measure of cattle environmental impact. This analysis of fifteen beef grazing systems in Uruguay quantifies the range of variation of carbon footprint, and the trade-offs with other relevant environmental variables, using a partial life cycle assessment (LCA) methodology. Using carbon footprint as the primary environmental indicator has several limitations: different metrics (GWP vs. GTP) may lead to different conclusions, carbon sequestration from soils may drastically affect the results, and systems with lower carbon footprint may have higher energy use, soil erosion, nutrient imbalance, pesticide ecotoxicity, and impact on biodiversity. A multidimensional assessment of sustainability of meat production is therefore needed to inform decision makers. There is great potential to improve grazing livestock systems productivity while reducing carbon footprint and other environmental impacts, and conserving biodiversity.
Development of a generalist predator, Podisus maculiventris, on glucosinolate sequestering and nonsequestering prey
Geem, M. van; Harvey, J.A. ; Gols, R. - \ 2014
Naturwissenschaften 101 (2014)9. - ISSN 0028-1042 - p. 707 - 714.
sawfly athalia-rosae - plant-chemical defense - pyrrolizidine alkaloids - insect herbivore - multitrophic interactions - specialist herbivore - trophic levels - trade-offs - sequestration - host
Insect herbivores exhibit various strategies to counter the toxic effects of plant chemical defenses. These strategies include the detoxification, excretion, and sequestration of plant secondary metabolites. The latter strategy is often considered to provide an additional benefit in that it provides herbivores with protection against natural enemies such as predators. Profiles of sequestered chemicals are influenced by the food plants from which these chemicals are derived. We compared the effects of sequestration and nonsequestration of plant secondary metabolites in two specialist herbivores on the development of a generalist predator, Podisus maculiventris. Profiles of glucosinolates, secondary metabolites characteristic for the Brassicaceae, are known to differ considerably both inter- and intraspecifically. Throughout their immature (=nymphal) development, the predator was fed on larval stages of either sequestering (turnip sawfly, Athalia rosae) or nonsequestering (small cabbage white butterfly, Pieris rapae) prey that in turn had been feeding on plants originating from three wild cabbage (Brassica oleracea) populations that have previously been shown to differ in their glucosinolate profiles. We compared survival, development time, and adult body mass as parameters for bug performance. Our results show that sequestration of glucosinolates by A. rosae only marginally affected the development of P. maculiventris. The effects of plant population on predator performance were variable. We suggest that sequestration of glucosinolates by A. rosae functions not only as a defensive mechanism against some predators, but may also be an alternative way of harmlessly dealing with plant allelochemicals.
Woody biomass on farms and in the landscapes of Rwanda
Ndayambaje, J.D. ; Mugiraneza, T. ; Mohren, G.M.J. - \ 2014
Agroforestry Systems 88 (2014)1. - ISSN 0167-4366 - p. 101 - 124.
agroforestry practices - aboveground biomass - tropical forests - carbon stocks - systems - conservation - management - india - sequestration - agroecosystem
Scattered trees and woodlots are a prominent feature of agricultural landscapes of Rwanda. However, little is known about their characteristics and their contribution to farmers’ wood needs. Here, we present the results of a survey of (a) the abundance, composition, and size of trees and woodlots in the low, medium and high altitude regions of Rwanda, (b) total woody biomass and biomass for fuelwood at farm and landscape levels, and (c) opportunities for their sustainable use. Scattered trees occurred in all landscapes at minimum densities ranging from 20 to 167 trees ha-1. Of the 56 tree genera recorded, a handful of tree species dominated, with the ten most common species accounting for over 70 % of all trees recorded. Most of them provided fuelwood, fruit and timber to farm owners. Woodlots occurred on about 40 % of the survey farms and consisted for 90 % of eucalyptus coppice. Woody biomass dry weight of scattered trees on agricultural landscape was 0.7 t ha-1 in low altitude region (LAR), 3 t ha-1 in medium altitude region (MAR), and 1 t ha-1 in high altitude region (HAR). Dry weight woody biomass in woodlots (
Plant species richness promotes soil carbon and nitrogen stocks in grasslands without legumes
Cong, W. ; Ruijven, J. van; Mommer, L. ; Deyn, G.B. de; Berendse, F. ; Hoffland, E. - \ 2014
Journal of Ecology 102 (2014)5. - ISSN 0022-0477 - p. 1163 - 1170.
diversity-productivity relationship - functional composition - biodiversity experiment - ecosystem function - elevated co2 - communities - impacts - time - complementarity - sequestration
1.The storage of carbon (C) and nitrogen (N) in soil is important ecosystem functions. Grassland biodiversity experiments have shown a positive effect of plant diversity on soil C and N storage. However, these experiments all included legumes, which constitute an important N input through N2-fixation. Indeed, the results of these experiments suggest that N2 fixation by legumes is a major driver of soil C and N storage. 2.We studied whether plant diversity affects soil C and N storage in the absence of legumes. In an 11-year grassland biodiversity experiment without legumes, we measured soil C and N stocks. We further determined above-ground biomass productivity, standing root biomass, soil organic matter decomposition and N mineralization rates to understand the mechanisms underlying the change in soil C and N stocks in relation to plant diversity and their feedbacks to plant productivity. 3.We found that soil C and N stocks increased by 18% and 16% in eight-species mixtures compared to the average of monocultures of the same species, respectively. Increased soil C and N stocks were mainly driven by increased C input and N retention, resulting from enhanced plant productivity, which surpassed enhanced C loss from decomposition. Importantly, higher soil C and N stocks were associated with enhanced soil N mineralization rates, which can explain the strengthening of the positive diversity–productivity relationship observed in the last years of the experiment. 4.Synthesis. We demonstrated that also in the absence of legumes, plant species richness promotes soil carbon (C) and nitrogen (N) stocks via increased plant productivity. In turn, enhanced soil C and N stocks showed a positive feedback to plant productivity via enhanced N mineralization, which could further accelerate soil C and N storage in the long term.
Soil organic carbon stocks in the Limpopo National Park, Mozambique: Amount, spatial distribution and uncertainty.
Cambule, A. ; Rossiter, D.G. ; Stoorvogel, J.J. ; Smaling, E.M.A. - \ 2014
Geoderma 213 (2014). - ISSN 0016-7061 - p. 46 - 56.
residual maximum-likelihood - optimal sampling schemes - regionalized variables - land-use - terrain attributes - local estimation - data sets - sequestration - geostatistics - variability
Many areas in sub-Saharan African are data-poor and poorly accessible. The estimation of soil organic carbon (SOC) stocks in these areas will have to rely on the limited available secondary data coupled with restricted field sampling. We assessed the total SOC stock, its spatial variation and the causes of this variation in Limpopo National Park (LNP), a data-poor and poorly accessible area in southwestern Mozambique. During a field survey, A-horizon thickness was measured and soil samples were taken for the determination of SOC concentrations. SOC concentrations were multiplied by soil bulk density and A-horizon thickness to estimate SOC stocks. Spatial distribution was assessed through: i) a measure-and-multiply approach to assess average SOC stocks by landscape unit, and ii) a soil-landscape model that used soil forming factors to interpolate SOC stocks from observations to a grid covering the area by ordinary (OK) and universal (UK) kriging. Predictions were validated by both independent and leave-one-out cross validations. The total SOC stock of the LNPwas obtained by i) calculating an area-weighted average from the means of the landscape units and by ii) summing the cells of the interpolated grid. Uncertainty was evaluated by the mean standard error for the measure-and-multiply approach and by the mean kriging prediction standard deviation for the soil-landscape model approach. The reliability of the estimates of total stockswas assessed by the uncertainty of the input data and its effect on estimates. The mean SOC stock from all sample points is 1.59 kg m-2; landscape unit averages are 1.13–2.46 kg m-2. Covariables explained 45% (soil) and 17% (coordinates) of SOC stock variation. Predictions from spatial models averaged 1.65 kg m-2 and are within the ranges reported for similar soils in southern Africa. The validation root mean square error of prediction (RMSEP) was about 30% of the mean predictions for both OK and UK. Uncertainty is high (coefficient of variation of about 40%) due to short-range spatial structure combined with sparse sampling. The range of total SOC stock of the 10,410 km-2 study area was estimated at 15,579–17,908 Gg. However, 90% confidence limits of the total stocks estimated are narrower (5–15%) for the measure-and-multiply model and wider (66–70%) for the soil-landscape model. The spatial distribution is rather homogenous, suggesting levels are mainly determined by regional climate.
Seasonal phenology of interactions involving short-lived annual plants, a multivoltine herbivore and its endoparasitoid wasp
Fei, M. ; Gols, R. ; Harvey, J.A. - \ 2014
Journal of Animal Ecology 83 (2014)1. - ISSN 0021-8790 - p. 234 - 244.
specialist herbivore - brassica-oleracea - trophic levels - quality - evolution - sequestration - consequences - constraints - parasitoids - coleoptera
Spatial-temporal realism is often missing in many studies of multitrophic interactions, which are conducted at a single time frame and/or involving interactions between insects with a single species of plant. In this scenario, an underlying assumption is that the host-plant species is ubiquitous throughout the season and that the insects always interact with it. We studied interactions involving three naturally occurring wild species of cruciferous plants, Brassica rapa, Sinapis arvensis and Brassica nigra, that exhibit different seasonal phenologies, and a multivoltine herbivore, the large cabbage white butterfly, Pieris brassicae, and its gregarious endoparasitoid wasp, Cotesia glomerata. The three plants have very short life cycles. In central Europe, B. rapa grows in early spring, S. arvensis in late spring and early summer, and B. nigra in mid to late summer. P. brassicae generally has three generations per year, and C. glomerata at least two. This means that different generations of the insects must find and exploit different plant species that may differ in quality and which may be found some distance from one another. Insects were either reared on each of the three plant species for three successive generations or shifted between generations from B. rapa to S. arvensis to B. nigra. Development time from neonate to pupation and pupal fresh mass were determined in P. brassicae and egg-to-adult development time and body mass in C. glomerata. Overall, herbivores performed marginally better on S. arvensis and B. nigra plants than on B. rapa plants. Parasitoids performance was closely tailored with that of the host. Irrespective as to whether the insects were shifted to a new plant in successive generations or not, development time of P. brassicae and C. glomerata decreased dramatically over time. Our results show that there were some differences in insect development on different plant species and when transferred from one species to another. However, all three plants were of generally high quality in terms of insect performance. We discuss ecological and evolutionary constraints on insects that must search in new habitats for different plant species over successive generations.
Projected changes in soil organic carbon stocks upon adoption of recommended soil and water conservation practices in the upper Tana river catchment, Kenya
Batjes, N.H. - \ 2014
Land Degradation and Development 25 (2014)3. - ISSN 1085-3278 - p. 278 - 287.
climate-change - land-use - agricultural soils - data requirements - sequestration - management - uncertainty - impacts - world - dynamics
Large areas in the Upper Tana river catchment, Kenya, have been over-exploited, resulting in soil erosion, nutrient depletion and loss of soil organic matter (SOM). This study focuses on sections of the catchment earmarked as being most promising for implementing Green Water Credits, an incentive mechanism to help farmers invest in land and soil management activities that affect all fresh water resources at source. Such management practices can also help restore SOM levels towards their natural level. Opportunities to increase soil organic carbon (SOC) stocks, for two broadly defined land use types (croplands and plantation crops, with moderate input levels), are calculated using a simple empirical model, using three scenarios for the proportion of suitable land that may be treated with these practices (low¿=¿40¿per¿cent, medium¿=¿60¿per¿cent, high¿=¿80¿per¿cent). For the medium scenario, corresponding to implementation on ~348¿000¿ha in the basin, the eco-technologically possible SOC gains are estimated at 4·8 to 9·3¿×¿106¿tonnes (Mg) CO2 over the next 20¿years. Assuming a conservative price of US$10 per tonne CO2-equivalent on the carbon offset market, this would correspond to ~US$48–93 million over a 20-year period of sustained green water management. This would imply a projected (potential) payment of some US$7–13¿ha-1 to farmers annually; this sum would be in addition to incentives that are being put in place for implementing green water management practices and also in addition to the benefits that farmers would realize from the impact on production of these practices themselves
Silicate minerals for CO2 scavenging from biogas in Autogenerative High Pressure Digestion
Lindeboom, R.E.F. ; Ferrer, I. ; Weijma, J. ; Lier, J.B. van - \ 2013
Water Research 47 (2013)11. - ISSN 0043-1354 - p. 3742 - 3751.
anaerobic-digestion - calcium-carbonate - waste-water - steel slag - sequestration - sludge - ph - precipitation - degradation - dissolution
Autogenerative High Pressure Digestion (AHPD) is a novel concept that integrates gas upgrading with anaerobic digestion by selective dissolution of CO2 at elevated biogas pressure. However, accumulation of CO2 and fatty acids after anaerobic digestion of glucose resulted in pH 3–5, which is incompatible with the commonly applied high-rate methanogenic processes. Therefore, we studied the use of wollastonite, olivine and anorthosite, with measured composition of CaSi1.05O3.4, Mg2Fe0.2Ni0.01Si1.2O5.3 and Na0.7Ca1K0.1Mg0.1Fe0.15Al3.1Si4O24, respectively, to scavenge CO2 during batch AHPD of glucose. Depending on the glucose to mineral ratio the pH increased to 6.0–7.5. Experiments with wollastonite showed that Ca2+-leaching was caused by volatile fatty acid (VFA) production during glucose digestion. At 1, 3 and 9 bar, the CH4 content reached 74%, 86% and 88%, respectively, indicating CO2 scavenging. Fixation of produced CO2 by CaCO3 precipitation in the sludge was confirmed by Fourier Transferred-InfraRed, Combined Field emission Scanning Electron Microscopy-Energy-dispersive X-ray spectroscopy and Thermogravimetric Analysis-Mass Spectroscopy.
The contribution of nitrogen deposition to the photosynthetic capacity of forests.
Fleischer, K. ; Rebel, T. ; Molen, M.K. van der; Erisman, J.W. ; Wassen, M.J. ; Loon, E.E. ; Montagnani, L. ; Gough, C.M. ; Herbst, M. - \ 2013
Global Biogeochemical Cycles 27 (2013)1. - ISSN 0886-6236 - p. 187 - 199.
net primary productivity - terrestrial carbon sink - leaf-area index - ecosystem respiration - boreal forests - temperate - co2 - sequestration - biosphere - trends
 Global terrestrial carbon (C) sequestration has increased over the last few decades. The drivers of carbon sequestration, the geographical spread and magnitude of this sink are however hotly debated. Photosynthesis determines the total C uptake of terrestrial ecosystems and is a major flux of the global C balance. We contribute to the discussion on enhanced C sequestration by analyzing the influence of nitrogen (N) deposition on photosynthetic capacity (Amax) of forest canopies. Eddy covariance measurements of net exchange of carbon provide estimates of gross primary production, from which Amax is derived with a novel approach. Canopy Amax is combined with modeled N deposition, environmental variables and stand characteristics to study the relative effects on Amax for a unique global data set of 80 forest FLUXNET sites. Canopy Amax relates positively to N deposition for evergreen needleleaf forests below an observed critical load of¿~¿8¿kg¿N ha–1¿yr–1, with a slope of 2.0¿±¿0.4 (S.E.) µmol CO2 m–2¿s–1 per 1¿kg¿N ha–1¿yr–1. Above this threshold canopy Amax levels off, exhibiting a saturating response in line with the N saturation hypothesis. Climate effects on canopy Amax cannot be separated from the effect of N deposition due to considerable covariation. For deciduous broadleaf forests and forests in the temperate (-continental) climate zones, the analysis shows the N deposition effect to be either small or absent. Leaf area index and foliar N concentration are positively but weakly related to Amax. We conclude that flux tower measurements of C fluxes provide valuable data to study physiological processes at the canopy scale. Future efforts need to be directed toward standardizing measures N cycling and pools within C monitoring networks to gain a better understanding of C and N interactions, and to disentangle the role of climate and N deposition in forest ecosystems.
Soil and freshwater and marine sediment food webs: their structure and function
Krumins, J.A. ; Oevelen, D. van; Bezemer, T.M. ; Deyn, G.B. de; Hol, W.H.G. ; Donk, E. van; Boer, W. de; Ruiter, P.C. de; Middelburg, J.J. ; Monroy, F. ; Soetaert, K. ; Thébault, E. ; Koppel, J. van de; Veen, J.A. van; Viketoft, M. ; Putten, W.H. van der - \ 2013
Bioscience 63 (2013)1. - ISSN 0006-3568 - p. 35 - 42.
global carbon-cycle - terrestrial ecosystems - real ecosystems - climate-change - biodiversity - stability - communities - limitation - patterns - sequestration
The food webs of terrestrial soils and of freshwater and marine sediments depend on adjacent aboveground or pelagic ecosystems for organic matter input that provides nutrients and energy. There are important similarities in the flow of organic matter through these food webs and how this flow feeds back to primary production. In both soils and sediments, trophic interactions occur in a cycle in which consumers stimulate nutrient cycling such that mineralized resources are made available to the primary producers. However, aquatic sediments and terrestrial soils differ greatly in the connectivity between the production and the consumption of organic matter. Terrestrial soils and shallow aquatic sediments can receive organic matter within hours of photosynthesis when roots leak carbon, whereas deep oceanic sediments receive organic matter possibly months after carbon assimilation by phytoplankton. This comparison has implications for the capacity of soils and sediments to affect the global carbon balance.
Hydrological implications of desertification: Degradation of South African semi-arid subtropical thicket
Luijk, G. van; Cowling, R.M. ; Riksen, M.J.P.M. ; Glenday, J. - \ 2013
Journal of Arid Environments 91 (2013). - ISSN 0140-1963 - p. 14 - 21.
succulent thicket - eastern cape - interception loss - land-use - runoff - savanna - carbon - water - transformation - sequestration
Almost half of the 16,942 km2 of South Africa's subtropical thicket with a substantial Portulacaria afra (spekboom) component has been heavily degraded by domestic herbivores. The subtropical thicket biome is a drought-prone and water-stressed area, and many of the region's watersheds comprise of eroded landscapes clothed in degraded spekboom thicket. The objective of this study was to determine the impact of degradation of spekboom thicket on hydrological processes. We hypothesised that degradation of spekboom thicket would reduce infiltration and, hence, reduce soil moisture retention and increase run-off and erosion. We tested this hypothesis by collecting data on rainfall, infiltration, soil moisture retention and run-off in degraded thicket, and – as a reference site – in an adjacent stand of relatively intact thicket. The results showed clear trends in the impacts of spekboom thicket degradation on hydrological processes. The more than hundred-fold lower infiltration in soils associated with degraded thicket relative to the soils beneath the intact, spekboom canopy, resulted in lower levels and less retention of soil moisture, almost double the amount of runoff, and an almost six-fold increase in sediment load. Thus, restoring degraded thicket will reduce erosion and likely improve baseflows, in addition to sequestering carbon.
Variation in soil carbon stocks and their determinants across a precipitation gradient in West Africa
Saiz, G. ; Bird, M.I. ; Domingues, T.F. ; Schrodt, F. ; Schwartz, M. ; Veenendaal, E.M. - \ 2012
Global Change Biology 18 (2012)5. - ISSN 1354-1013 - p. 1670 - 1683.
land-use change - organic-matter - biotic controls - cycle feedback - savanna soils - forest soils - sequestration - texture - senegal - stabilization
We examine the influence of climate, soil properties and vegetation characteristics on soil organic carbon (SOC) along a transect of West African ecosystems sampled across a precipitation gradient on contrasting soil types stretching from Ghana (15°N) to Mali (7°N). Our findings derive from a total of 1108 soil cores sampled over 14 permanent plots. The observed pattern in SOC stocks reflects the very different climatic conditions and contrasting soil properties existing along the latitudinal transect. The combined effects of these factors strongly influence vegetation structure. SOC stocks in the first 2 m of soil ranged from 20 Mg C ha-1 for a Sahelian savanna in Mali to over 120 Mg C ha-1 for a transitional forest in Ghana. The degree of interdependence between soil bulk density (SBD) and soil properties is highlighted by the strong negative relationships observed between SBD and SOC (r2 > 0.84). A simple predictive function capable of encompassing the effect of climate, soil properties and vegetation type on SOC stocks showed that available water and sand content taken together could explain 0.84 and 0.86 of the total variability in SOC stocks observed to 0.3 and 1.0 m depth respectively. Used in combination with a suitable climatic parameter, sand content is a good predictor of SOC stored in highly weathered dry tropical ecosystems with arguably less confounding effects than provided by clay content. There was an increased contribution of resistant SOC to the total SOC pool for lower rainfall soils, this likely being the result of more frequent fire events in the grassier savannas of the more arid regions. This work provides new insights into the mechanisms determining the distribution of carbon storage in tropical soils and should contribute significantly to the development of robust predictive models of biogeochemical cycling and vegetation dynamics in tropical regions.
Forest inventories for carbon change assessments
Mohren, G.M.J. ; Hasenauer, H. ; Köhl, M. ; Nabuurs, G.J. - \ 2012
Current Opinion in Environmental Sustainability 4 (2012)6. - ISSN 1877-3435 - p. 686 - 695.
tropical forests - european forests - climate-change - root biomass - ecosystems - dioxide - sequestration - harmonization - mitigation - management
We give a general overview of forest inventory developments and their potential to estimate forest carbon budgets and GHG emissions. Forest inventories mostly focus on timber resources, but can be extended to cover other forest characteristics, such as forest biomass. From forest biomass, ecosystem carbon content can be derived. Forest inventory comprises of ground-based and space-based techniques, and the combination of the two provides a versatile scheme for carbon storage assessment. Large uncertainties remain in the estimation of soil carbon, as well as in the attribution and assessment of mitigation associated with the use of forest products, for example in substituting for high-energy building materials. Together, significant uncertainty remains in assessing and reporting of carbon storage and greenhouse mitigation with respect to forest-related land use and land use change.
Carbon balance for different management practices for fast growing tree species planted on former pastureland in southern Europe: a case study using the CO2 Fix model
Pérez-Crusado, C. ; Mohren, G.M.J. ; Merino, A. ; Rodríguez-Soalleiro, R. - \ 2012
European Journal of Forest Research 131 (2012)6. - ISSN 1612-4669 - p. 1695 - 1716.
north-western spain - soil organic-carbon - land-use change - wood-bark ash - forest management - eucalyptus-globulus - radiata pine - aboveground biomass - empirical-models - sequestration
Although it is known that forestry mitigates carbon emissions to some degree, there is still a need to investigate the extent to which changes in forest management regimes affect the carbon cycle. In a climate-change scenario, forest management schemes must be optimized to maximize product supply and minimize environmental impacts. It is difficult to predict the mitigating effects of different silvicultural regimes because of differences in the growth characteristics of each species, destination of products, and industrial efficiencies. The objective of the present study was to use a modeling approach to evaluate the effects of different management regimes for fast growing species in southern temperate Europe in relation to mitigating climate change. A comprehensive study was carried out considering the C sink effect in biomass, soil and wood products, the substitutive effect of bioenergy, and particular conditions of the forest industry in southern Europe. The mechanistic CO2Fix model was parameterized for three species used in fast growing plantations in southern Europe: Eucalyptus globulus, Eucalyptus nitens, and Pinus radiata. Data from 120 plots covering the complete age range observed for each species were used to calculate changes in C stocks in aboveground biomass and organic and mineral soil and to validate the parameterized model for these conditions. Additional information about the efficiency of forest industry processes in the region was also considered. A strong bias in soil organic carbon estimation was observed and attributed to overestimations in the decomposition rates of soil compartments. Slight bias was also observed in the carbon biomass estimation when forest-specific yield models were used to simulate afforestation over former pastureland. As regards the model sensitivity, the Yasso model was strongly robust to turnover of leaves, roots, and branches. The chip wood production alternative yielded higher carbon stock in biomass and products, as well as in bioenergy substitution effect, than the sawn wood production alternative. Nevertheless, the sawn wood alternative was the most effective as regards the C stock in the soil. Site index had an important effect for all species, alternatives, and compartments, and mitigating effects increased with site index. Harvesting of clearcutting and thinning slash for bioenergy use led to a slight decrease in the soil carbon equilibrium but significantly increased the mitigation effect through bioenergy use.
Olivine Weathering in Soil, and Its Effects on Growth and Nutrient Uptake in Ryegrass (lolium perenne L.): A Pot Experiment
Berge, H.F.M. ten; Meer, H.G. van der; Steenhuizen, J.W. ; Goedhart, P.W. ; Knops, P. ; Verhagen, J. - \ 2012
PLoS ONE 7 (2012)8. - ISSN 1932-6203
carbon-dioxide - plant - bioavailability - sequestration - phytotoxicity - serpentine - nickel - co2 - speciation - models
Mineral carbonation of basic silicate minerals regulates atmospheric CO2 on geological time scales by locking up carbon. Mining and spreading onto the earth's surface of fast-weathering silicates, such as olivine, has been proposed to speed up this natura
Predictions of soil surface and topsoil organic carbon content through the use of laboratory and field spectroscopy in the Albany Thicket Biome of Eastern Cape Province of South Africa
Nocita, M. ; Kooistra, L. ; Bachmann, M. ; Müller, A. ; Powell, M. ; Weel, S. - \ 2011
Geoderma 167-168 (2011). - ISSN 0016-7061 - p. 295 - 302.
infrared reflectance spectroscopy - least-squares regression - in-situ characterization - agricultural soils - river floodplains - nir spectroscopy - meta analysis - sequestration - spectrometry - nitrogen
In recent years it has been shown that laboratory and field visible near infrared spectroscopy (VNIRS) allows for the accurate prediction of soil organic carbon (SOC) — more rapidly, less expensively, and at larger scales than conventional soil laboratory methods. VNIRS might find application in the restoration assessment of the degraded, semi-arid subtropical thickets of the Albany Thicket Biome (ATB) of the Eastern Cape Province of South Africa. During the twentieth century, the semi-arid forms of the ATB suffered heavy browsing by goats, transforming the dense closed-canopy shrubland into an open savannah-like system. This paper presents a study dealing with SOC estimation of soil surface (0–5 mm) and topsoil (0–200 mm) in the degraded ATB, through the combination of soil spectroscopy and partial least square regression (PLSR). Spectroscopic measurements and soil samples were collected along a transect in the ATB. The PLSR models developed with laboratory and field spectra gave good predictions of SOC, with root mean square error of validation (RMSEV) <5.0 and 5.5 g C kg- 1, respectively. The use of the full visible near-infrared spectral range gave better SOC predictions than using either visible or near-infrared separately. The resampling simulation of the field surface spectra to the 232 channels of the satellite-born EnMAP sensor gave good SOC predictions for laboratory conditions (RPD > 2), but low accuracy (RMSE: 9.88 g C kg- 1) for field model. The results of this research study indicated that, for the ATB, (i) combining soil spectroscopy and PLSR does favor accurate prediction of SOC, (ii) the predictions of surface SOC can be used as a proxy of topsoil SOC, and (iii) there is potential for future application of satellite-born hyperspectral data for SOC content predictions. --------------------------------------------------------------------------------