Defoliation and soil compaction jointly drive large-herbivore grazing effects on plants and soil arthropods on clay soil
Klink, R. van; Schrama, M. ; Nolte, S. ; Bakker, J.P. ; Wallis de Vries, M.F. ; Berg, M.P. - \ 2015
Ecosystems 18 (2015)4. - ISSN 1432-9840 - p. 671 - 685.
salt-marsh - nitrogen mineralization - wadden sea - mountain pastures - grassland - collembola - management - diversity - growth - cow
In addition to the well-studied impacts of defecation and defoliation, large herbivores also affect plant and arthropod communities through trampling, and the associated soil compaction. Soil compaction can be expected to be particularly important on wet, fine-textured soils. Therefore, we established a full factorial experiment of defoliation (monthly mowing) and soil compaction (using a rammer, annually) on a clay-rich salt marsh at the Dutch coast, aiming to disentangle the importance of these two factors. Additionally, we compared the effects on soil physical properties, plants, and arthropods to those at a nearby cattle-grazed marsh under dry and under waterlogged conditions. Soil physical conditions of the compacted plots were similar to the conditions at cattle-grazed plots, showing decreased soil aeration and increased waterlogging. Soil salinity was doubled by defoliation and quadrupled by combined defoliation and compaction. Cover of the dominant tall grass Elytrigia atherica was decreased by 80% in the defoliated plots, but cover of halophytes only increased under combined defoliation and compaction. Effects on soil micro-arthropods were most severe under waterlogging, showing a fourfold decrease in abundance and a smaller mean body size under compaction. Although the combined treatment of defoliation and trampling indeed proved most similar to the grazed marsh, large discrepancies remained for both plant and soil fauna communities, presumably because of colonization time lags. We conclude that soil compaction and defoliation differently affect plant and arthropod communities in grazed ecosystems, and that the magnitude of their effects depends on herbivore density, productivity, and soil physical properties.
Temperate forest development during secondary succession: effects of soil, dominant species and management
Bose, A.K. ; Schelhaas, M. ; Mazerolle, M.J. ; Bongers, F. - \ 2014
European Journal of Forest Research 133 (2014)3. - ISSN 1612-4669 - p. 511 - 523.
organic-matter accumulation - net primary production - pinus-sylvestris l. - age-related decline - land-use change - scots pine - carbon sequestration - tree height - nitrogen mineralization - practical implications
With the increase in abandoned agricultural lands in Western Europe, knowledge on the successional pathways of newly developing forests becomes urgent. We evaluated the effect of time, soil type and dominant species type (shade tolerant or intolerant) on the development during succession of three stand attributes: above-ground biomass, stand height (HT) and stem density (SD). Additionally, we compared above-ground biomass (AGB) in natural and planted forests, using ten chronosequences (8 from the literature and 2 from this study). Both AGB and HT increased over time, whereas SD decreased. HT, SD and AGB differed among species types. For example, birch had greater HT than alder, willow and ash at a similar age and had higher SD than pine and oak at a similar age. However, birch showed lower AGB than pine. HT and AGB differed among soil types. They were higher in rich soil than in poor soils. Comparative analysis between chronosequences showed an effect of the regeneration method (natural regeneration vs plantation) on above-ground biomass. Planted sites had higher AGB than natural regeneration. Time, soil type, species and regeneration method influenced the mechanism of stand responses during secondary succession. These characteristics could be used to clarify the heterogeneity and potential productivity of such spontaneously growing temperate forest ecosystems.
Production-ecological modelling explains the difference between potential soil N mineralisation and actual herbage N uptake
Rashid, M.I. ; Goede, R.G.M. de; Brussaard, L. ; Bloem, J. ; Lantinga, E.A. - \ 2014
Applied Soil Ecology 84 (2014). - ISSN 0929-1393 - p. 83 - 92.
winter-wheat fields - nitrogen mineralization - organic-matter - food webs - grassland soils - forest soils - community - manure - earthworms - management
We studied two different grassland fertiliser management regimes on sand and peat soils: above-ground application of a combination of organic N-rich slurry manure and solid cattle manure (SCM) vs. slit-injected, mineral N-rich slurry manure, whether or not supplemented with chemical fertiliser (non-SCM). Measurements of field N mineralisation as estimated from herbage N uptake in unfertilised plots were compared with (i) potential N mineralisation as determined from a standard laboratory soil incubation, (ii) the contribution of groups of soil organisms to N mineralisation based on production-ecological model calculations, and (iii) N mineralisation calculated according to the Dutch fertilisation recommendation for grasslands. Density and biomass of soil biota (bacteria, fungi, enchytraeids, microarthropods and earthworms) as well as net plant N-uptake were higher in the SCM input grasslands compared to the non-SCM input grasslands. The currently used method in Dutch fertilisation recommendations underestimated actual soil N supply capacity by, on average, 102 kg N ha-1 (202 vs. 304 kg ha-1 = 34%). The summed production-ecological model estimate for N mineralisation by bacteria, fungi, protozoa, and enchytraeids was 87–120% of the measured potential soil N mineralisation. Adding the modelled N mineralisation by earthworms to potential soil N mineralisation explained 98–107% of the measured herbage N uptake from soil. For all grasslands and soil biota groups together, the model estimated 105% of the measured net herbage N uptake from soil. Soil biota production-ecological modelling is a powerful tool to understand and predict N uptake in grassland, reflecting the effects of previous manure management and soil type. The results show that combining production ecological modelling to predict N supply with existing soil N tests using aerobic incubation methods, can add to a scientifically based improvement of the N fertilisation recommendations for production grasslands.
Long-term effects of eight soil health treatments to control plant-parasitic nematodes and Verticillium dahliae in agro-ecosystems
Korthals, G.W. ; Thoden, T.C. ; Berg, W. van den; Visser, J.H.M. - \ 2014
Applied Soil Ecology 76 (2014). - ISSN 0929-1393 - p. 112 - 123.
root-knot nematode - pratylenchus-penetrans - meloidogyne-hapla - tagetes-patula - nitrogen mineralization - biological-control - damping-off - cover crops - pyrrolizidine alkaloids - glucosinolate-profiles
There is an urgent need to test and develop sustainable methods for management of soil pathogens, such as the root-lesion nematode Pratylenchus penetrans and the soil fungus Verticillium dahliae. Ultimately this should be investigated with a multidisciplinary approach, with long-term measurements of biological and chemical parameters and their final impact on crop yield under field conditions. The present study focusses on eight soil health treatments (compost, chitin, marigold, grass–clover, biofumigation, anearobic soil disinfestation, a physical control method and a combination of marigold, compost and chitin) and two control treatments (a chemical control with 300 L/ha Metam sodium and un untreated control). These 10 treatments were studied for their effects on soil chemical quality, soil pathogens and their impact on the yield of potato, lily and carrots during 6 years. The present study did demonstrate that in comparison to chemical control, additions of chitin, anaerobic soil disinfestation and marigold are already excellent alternatives for the control of plant-parasitic nematodes and V. dahliae. We also demonstrated that grass–clover, biofumigation, Cultivit and compost are not effective alternatives for chemical control yet and further development is needed. All treatments caused a yield increase in comparison with the control. The biggest increases of more than 60% were found for the treatments with chitin. Furthermore it was demonstrated that these yield increases were probably less influenced by changes in chemical soil properties, but the consequence of changes in the soil biota, in this case especially the effective control of P. penetrans and V. dahliae. Furthermore it has been demonstrated that most of these soil health treatments could already be implemented in an arable crop rotation and probably adapted for many areas of the world where other alternatives, such as solarisation or soil flooding, are not feasible or too risky.
Interactions between microbial-feeding and predatory soil fauna trigger N2O emissions
Thakur, M.P. ; Groenigen, J.W. van; Kuiper, I. ; Deyn, G.B. de - \ 2014
Soil Biology and Biochemistry 70 (2014). - ISSN 0038-0717 - p. 256 - 262.
nitrogen mineralization - enchytraeid worms - trophic cascades - food webs - raw humus - decomposition - biodiversity - nitrification - oligochaeta - microarthropods
Recent research has shown that microbial-feeding invertebrate soil fauna species can significantly contribute to N2O emissions. However, in soil food webs microbial-feeding soil fauna interact with each other and with their predators, which affects microbial activity. To date we lack empirical tests of whether or not these interactions play a significant role in N2O emissions from soil. Therefore we studied how interactions between soil microbes, two groups of microbial-feeding soil fauna (enchytraeids and fungivorous mites) and their predators (predatory mites) affect soil N2O emissions. We hypothesized that: 1) the presence of two microbial-feeding fauna groups (enchytraeids and fungivorous mites) together increase N2O emissions more than when only a single group is present; and 2) the addition of predatory mites further enhances N2O emissions. We assembled soil food webs consisting of soil microbes, enchytraeids, fungivorous and predatory mites in microcosms with sandy loamy soil and sterilised hay as a substrate for the soil microbes. N2O emissions were measured during 56 days. We found no support for our first yet support for our second hypothesis. Addition of predatory mites to microcosms with enchytraeids and fungivorous mites increased N2O emissions significantly from 135.3 to 482.1 mg N m-2, which was also significantly higher than the control without fauna (83 mg N m-2) (P <0.001). In presence of enchytraeids, fungivorous and predatory mites, we found much higher nitrate availability at the time of the N2O peak on Day 35 (10.9 versus 5.5 mg N per kg soil without soil fauna), indicating that the major increase in N2O emissions in this treatment may be due to increased nitrification. Increased nitrification may be attributed to higher availability of N from the dead tissues of fungivorous mites and increased activity of the enchytraeids that might also have affected soil structure and contributed to increased N2O emissions. This study demonstrates the importance of interactions between microbial-feeding invertebrate soil fauna and their predators in understanding N2O emissions.
Soil food web properties explain ecosystem services across European land use systems
Vries, F.T. de; Thebault, E.M.C. ; Liiri, M. ; Birkhofer, K. ; Tsiafouli, M. ; Bjornlund, L. ; Jorgensen, H.B. ; Brady, M.V. ; Christensen, S. ; Ruiter, P.C. de; Hertefeldt, T. d'; Frouz, J. ; Hedlund, K. ; Hemerik, L. ; Hol, W.H.G. ; Hotes, S. ; Mortimer, S.R. ; Setälä, H. ; Sgardelis, S.P. ; Uteseny, K. ; Putten, W.H. van der; Wolters, V. ; Bardgett, R.D. - \ 2013
Proceedings of the National Academy of Sciences of the United States of America 110 (2013)35. - ISSN 0027-8424 - p. 14296 - 14301.
nitrogen mineralization - carbon sequestration - bacterial community - mycorrhizal fungi - biomass - scale - intensification - decomposition - biodiversity - agriculture
Intensive land use reduces the diversity and abundance of many soil biota, with consequences for the processes that they govern and the ecosystem services that these processes underpin. Relationships between soil biota and ecosystem processes have mostly been found in laboratory experiments and rarely are found in the field. Here, we quantified, across four countries of contrasting climatic and soil conditions in Europe, how differences in soil food web composition resulting from land use systems (intensive wheat rotation, extensive rotation, and permanent grassland) influence the functioning of soils and the ecosystem services that they deliver. Intensive wheat rotation consistently reduced the biomass of all components of the soil food web across all countries. Soil food web properties strongly and consistently predicted processes of C and N cycling across land use systems and geographic locations, and they were a better predictor of these processes than land use. Processes of carbon loss increased with soil food web properties that correlated with soil C content, such as earthworm biomass and fungal/bacterial energy channel ratio, and were greatest in permanent grassland. In contrast, processes of N cycling were explained by soil food web properties independent of land use, such as arbuscular mycorrhizal fungi and bacterial channel biomass. Our quantification of the contribution of soil organisms to processes of C and N cycling across land use systems and geographic locations shows that soil biota need to be included in C and N cycling models and highlights the need to map and conserve soil biodiversity across the world.
Calibration and validation of models for short-term decomposition and N mineralization of plant residues in the tropics
Nascimento, A.F. do; Mendona, E.D. ; Leite, L.F.C. ; Scholberg, J.M.S. ; Neves, J.C.L. - \ 2012
Scientia agricola 69 (2012)6. - ISSN 0103-9016 - p. 393 - 401.
soil organic-matter - nitrogen mineralization - nutrient release - simulation - lignin - litter - polyphenol - quality - systems - forest
Insight of nutrient release patterns associated with the decomposition of plant residues is important for their effective use as a green manure in food production systems. Thus, this study aimed to evaluate the ability of the Century, APSIM and NDICEA simulation models for predicting the decomposition and N mineralization of crop residues in the tropical Atlantic forest biome, Brazil. The simulation models were calibrated based on actual decomposition and N mineralization rates of three types of crop residues with different chemical and biochemical composition. The models were also validated for different pedo-climatic conditions and crop residues conditions. In general, the accuracy of decomposition and N mineralization improved after calibration. Overall RMSE values for the decomposition and N mineralization of the crop materials varied from 7.4 to 64.6 % before models calibration compared to 3.7 to 16.3 % after calibration. Therefore, adequate calibration of the models is indispensable for use them under humid tropical conditions. The NDICEA model generally outperformed the other models. However, the decomposition and N mineralization was not very accurate during the first 30 days of incubation, especially for easily decomposable crop residues. An additional model variable may be required to capture initial microbiological growth as affected by the moisture dynamics of the residues, as is the case in surface residues decomposition models.
Long-term dynamics of soil C and N in intensive rice-based cropping systems of the Indo-Gangetic Plains (IGP): A modelling approach
Shibu, M.E. ; Keulen, H. van; Leffelaar, P.A. - \ 2012
Ecological Modelling 232 (2012)5. - ISSN 0304-3800 - p. 40 - 63.
radiation-use efficiency - differently textured soils - organic-matter dynamics - microbial biomass-c - temperature-dependence - plant-material - nitrogen mineralization - legume material - jute corchorus - yield declines
We describe a summary model for the dynamics of carbon and nitrogen under varying weather, crop and soil conditions to investigate the role of soil organic carbon and nitrogen in yield formation in rice-based cropping systems of the Indo-Gangetic Plains (IGP). The model consists of three modules: soil organic matter (SOM), soil (SOIL), and crop growth (CROP). The SOM module consists of three pools: fresh, labile and stable. Carbon and nitrogen dynamics in the model are described in terms of carbon turnover, assimilation and dissimilation, with nitrogen linked through distinct C/N ratios. The SOIL module has two soil layers of variable depth (often 15 cm each), and the labile and stable pools are replicated for these two layers. Water, crop and soil management practices and aeration characteristics of these layers affect the C and N dynamics of their respective pools. The CROP module calculates potential and actual biomass, leaf area index (LAI), evapotranspiration, total N demand, actual N uptake and N stress. Actual biomass is first partitioned between above (leaves, stem and storage organs) and below ground (roots and rhizodeposition), and a harvest index (HI) is applied to the aboveground biomass to calculate the yield. Independent data sets of 9 long-term experiments (LTEs) from the IGP of India were used for calibration and validation of the model. After calibration and validation, the model was used to explore the impact of various crop and soil management practices in rice-based cropping systems on different sites of the IGP. Overall, the model satisfactorily reproduced observed crop yields, SOC dynamics and total soil N dynamics for various cropping systems at different sites. Nitrogen mineralized from soil organic nitrogen contributed 5–75% to total N uptake in fertilized and non-fertilized treatments. With a recommended NPK application, a trend of significant decrease in simulated rice yield was found only at Ludhiana-3, and Pantnagar. Similarly, the simulated wheat yield also showed a significant trend of decline at Ludhina-3, Pantnagar and Barrackpore. Simulated SOC had a significant decline at Pantnagar, whereas at Ludhiana-3, it showed a significant increase. An increase in SOM is not always associated with an increase in yield, as the factor(s) improved by an increase in SOM may not be the limiting factor for crop growth. Depletion of many major macro (NPK) and micro (Zn, Fe, Mn, etc.) nutrients, essential for plant growth even with a balanced NPK fertilizer application and a maintained SOC, can lead to a decline in productivity. --------------------------------------------------------------------------------
Predicting soil N mineralization using organic matter fractions and soil properties: A re-analysis of literature data
Ros, G.H. - \ 2012
Soil Biology and Biochemistry 45 (2012). - ISSN 0038-0717 - p. 132 - 135.
nitrogen mineralization - indexes - availability - management - relevance - systems
Extractable organic matter (EOM) fractions have been used to assess the capacity of soils to supply nitrogen (N), but their role in N mineralization and their potential to improve agricultural fertilizer management are still under debate. This paper shows evidence that the relationship between EOM and soil N supply is an indirect relationship reflecting the soils’ organic matter content. Data from 59 published experiments were re-analyzed using multivariate PLS modelling. Nitrogen mineralization was primarily related to the size of total and extractable organic matter fractions whereas variables reflecting soil texture and organic matter quality were less important. All EOM fractions reflected the soil organic matter content of the soil rather than a specific bioavailable fraction. There is strong need for research that explores the biochemical basis for relationships among total organic matter, extractable organic matter and soil N mineralization using mechanistic approaches.
Arctic warming on two continents has consistent negativ effects on lichen diversity and mixed effects on bryophyte diversity
Lang, S.I. ; Cornelissen, J.H.C. ; Shaver, G.R. ; Ahrens, M. ; Callaghan, T.V. ; Molau, U. ; Braak, C.J.F. ter; Hölzer, A. ; Aerts, R. - \ 2012
Global Change Biology 18 (2012)3. - ISSN 1354-1013 - p. 1096 - 1107.
simulated environmental-change - plant community responses - dwarf shrub heath - nitrogen mineralization - climate-change - tundra - vegetation - biomass - growth - ecosystems
Little is known about the impact of changing temperature regimes on composition and diversity of cryptogam communities in the Arctic and Subarctic, despite the well-known importance of lichens and bryophytes to the functioning and climate feedbacks of northern ecosystems. We investigated changes in diversity and abundance of lichens and bryophytes within long-term (9–16 years) warming experiments and along natural climatic gradients, ranging from Swedish subarctic birch forest and subarctic/subalpine tundra to Alaskan arctic tussock tundra. In both Sweden and Alaska, lichen diversity responded negatively to experimental warming (with the exception of a birch forest) and to higher temperatures along climatic gradients. Bryophytes were less sensitive to experimental warming than lichens, but depending on the length of the gradient, bryophyte diversity decreased both with increasing temperatures and at extremely low temperatures. Among bryophytes, Sphagnum mosses were particularly resistant to experimental warming in terms of both abundance and diversity. Temperature, on both continents, was the main driver of species composition within experiments and along gradients, with the exception of the Swedish subarctic birch forest where amount of litter constituted the best explanatory variable. In a warming experiment in moist acidic tussock tundra in Alaska, temperature together with soil ammonium availability were the most important factors influencing species composition. Overall, dwarf shrub abundance (deciduous and evergreen) was positively related to warming but so were the bryophytes Sphagnum girgensohnii, Hylocomium splendens and Pleurozium schreberi; the majority of other cryptogams showed a negative relationship to warming. This unique combination of intercontinental comparison, natural gradient studies and experimental studies shows that cryptogam diversity and abundance, especially within lichens, is likely to decrease under arctic climate warming. Given the many ecosystem processes affected by cryptogams in high latitudes (e.g. carbon sequestration, N2-fixation, trophic interactions), these changes will have important feedback consequences for ecosystem functions and climate
A Belowground Perspective on Dutch Agroecosystems: How Soil Organisms Interact to Support Ecosystem Services
Mulder, C. ; Boit, A. ; Bonkowski, M. ; Ruiter, P.C. de; Mancinelli, G. ; Heijden, M.G.A. van der; Wijnen, H.J. van; Vonk, J.A. ; Rutgers, M. - \ 2011
In: Advances in Ecological Research / Woodward, G., San Diego, USA : Elsevier Academic Press (Advances in Ecological Research 44) - ISBN 9780123747945 - p. 277 - 357.
arable farming systems - stable-isotope ratios - ecological community description - direct counting method - belowground food webs - winter-wheat fields - body-size - fatty-acids - species richness - nitrogen mineralization
1. New patterns and trends in land use are becoming increasingly evident in Europe's heavily modified landscape and else whereas sustainable agriculture and nature restoration are developed as viable long-term alternatives to intensively farmed arable land. The success of these changes depends on how soil biodiversity and processes respond to changes in management. To improve our understanding of the community structure and ecosystem functioning of the soil biota, we analyzed abiotic variables across 200 sites, and biological variables across 170 sites in The Netherlands, one of the most intensively farmed countries. The data were derived from the Dutch Soil Quality Network (DSQN), a long-term monitoring framework designed to obtain ecological insight into soil types (STs) and ecosystem types (ETs). 2. At the outset we describe STs and biota, and we estimate the contribution of various groups to the provision of ecosystem services. We focused on interactive effects of soil properties on community patterns and ecosystem functioning using food web models. Ecologists analyze soil food webs by means of mechanistic and statistical modelling, linking network structure to energy flow and elemental dynamics commonly based on allometric scaling. 3. We also explored how predatory and metabolic processes are constrained by body size, diet and metabolic type, and how these constraints govern the interactions within and between trophic groups. In particular, we focused on how elemental fluxes determine the strengths of ecological interactions, and the resulting ecosystem services, in terms of sustenance of soil fertility. 4. We discuss data mining, food web visualizations, and an appropriate categorical way to capture subtle interrelationships within the DSQN dataset. Sampled metazoans were used to provide an overview of below-ground processes and influences of land use. Unlike most studies to date we used data from the entire size spectrum, across 15 orders of magnitude, using body size as a continuous trait crucial for understanding ecological services. 5. Multimodality in the frequency distributions of body size represents a performance filter that acts as a buffer to environmental change. Large differences in the body-size distributions across ETs and STs were evident. Most observed trends support the hypothesis that the direct influence of ecological stoichiometry on the soil biota as an independent predictor (e.g. in the form of nutrient to carbon ratios), and consequently on the allometric scaling, is more dominant than either ET or ST. This provides opportunities to develop a mechanistic and physiologically oriented model for the distribution of species' body sizes, where responses of invertebrates can be predicted. 6. Our results highlight the different roles that organisms play in a number of key ecosystem services. Such a trait-based research has unique strengths in its rigorous formulation of fundamental scaling rules, as well as in its verifiability by empirical data. Nonetheless, it still has weaknesses that remain to be addressed, like the consequences of intraspecific size variation, the high degree of omnivory, and a possibly inaccurate assignment to trophic groups. 7. Studying the extent to which nutrient levels influence multitrophic interactions and how different land-use regimes affect soil biodiversity is clearly a fruitful area for future research to develop predictive models for soil ecosystem services under different management regimes. No similar efforts have been attempted previously for soil food webs, and our dataset has the potential to test and further verify its usefulness at an unprecedented space scale.
Predicting soil N mineralization: Relevance of organic matter fractions and soil properties.
Ros, G.H. ; Hanegraaf, M.C. ; Hoffland, E. ; Riemsdijk, W.H. van - \ 2011
Soil Biology and Biochemistry 43 (2011)8. - ISSN 0038-0717 - p. 1714 - 1722.
nitrogen mineralization - microbial biomass - chemical methods - grassland soils - forest soils - indexes - availability - carbon - respiration - temperature
Distinct extractable organic matter (EOM) fractions have been used to assess the capacity of soils to supply nitrogen (N). However, substantial uncertainty exists on their role in the N cycle and their functional dependency on soil properties. We therefore examined the variation in mineralizable N and its relationship with EOM fractions, soil physical and chemical properties across 98 agricultural soils with contrasting inherent properties and management histories. Mineralizable N was determined by aerobic incubation at 20 °C and optimum moisture content for 20 weeks. We used multivariate statistical modelling to account for multi-collinearity, an issue generally overlooked in studies evaluating the predictive value of EOM fractions. Mineralization of N was primarily related to the size of OM pools and fractions present; they explained 78% of the variation in mineralizable N whereas other soil variables could explain maximally 8%. Both total and extractable OM expressed the same soil characteristic from a mineralization perspective; they were positively related to mineralizable N and explained a similar percentage of the variation in mineralizable N. Inclusion of mineralizable N in fertilizer recommendation systems should be based on at least one OM variable. The most appropriate EOM fraction can only be identified when the underlying mechanisms are known; regression techniques are not suitable for this purpose. Combination of single EOM fractions is not likely to improve the prediction of mineralizable N due to high multi-collinearity. Inclusion of texture-related soil variables or variables reflecting soil organic matter quality may be neglected due to their limited power to improve the prediction of mineralizable N.
What are the main climate drivers for shrub growth in Northeastern Siberian tundra?
Blok, D. ; Sass-Klaassen, U. ; Schaepman-Strub, G. ; Heijmans, M.M.P.D. ; Sauren, P. ; Berendse, F. - \ 2011
Biogeosciences 8 (2011)5. - ISSN 1726-4170 - p. 1169 - 1179.
plant functional types - alaskan arctic tundra - summer temperature - nitrogen mineralization - tree growth - manipulation experiment - environmental-change - cassiope-tetragona - vegetation types - northern alaska
Deciduous shrubs are expected to rapidly expand in the Arctic during the coming decades due to climate warming. A transition towards more shrub-dominated tundra may have large implications for the regional surface energy balance, permafrost stability and carbon storage capacity, with consequences for the global climate system. However, little information is available on the natural long-term shrub growth response to climatic variability. Our aim was to determine the climate factor and time period that are most important to annual shrub growth in our research site in NE-Siberia. Therefore, we determined annual radial growth rates in Salix pulchra and Betula nana shrubs by measuring ring widths. We constructed shrub ring width chronologies and compared growth rates to regional climate and remotely sensed greenness data. Early summer temperature was the most important factor influencing ring width of S. pulchra (Pearson's r=0.73, p
Modelling C and N mineralisation in soil food webs during secondary succession on ex-arable land
Holtkamp, R. ; Wal, A. van der; Kardol, P. ; Putten, W.H. van der; Ruiter, P.C. de; Dekker, S.C. - \ 2011
Soil Biology and Biochemistry 43 (2011)2. - ISSN 0038-0717 - p. 251 - 260.
nitrogen mineralization - fungal biomass - ecosystem - chronosequence - nematodes - dynamics - decomposition - biodiversity - restoration - abandonment
The rate of secondary succession after land abandonment depends on the interplay between aboveground and belowground processes. Changes in vegetation composition lead to altered amounts and composition of soil organic matter (SOM) with consequences for the abundance and functioning of the soil food web. In turn, soil food web structure determines the mineralisation rate of nutrients that can be taken up by plants. This study analyses changes in the C and N mineralisation rates along with soil food web structure during secondary succession after land abandonment. In a previous study, changes in soil food web structure and SOM quantity and quality were measured at different stages of secondary succession on abandoned arable fields (abandoned for 2, 9 and 22 years and a heathland, which is the assumed target of the secondary succession). Based on these measurements we expected the C and N mineralisation rates to increase during secondary succession. The key hypothesis is that with a description of the soil food webs in terms of quantified biomasses, natural death rates, energy conversion efficiencies and diets enables a calculation of C and N mineralisation rates in soils. The basic assumptions connected to this hypothesis are that on a time-scale of years the population sizes are in steady state. We also calculated mineralisation rates per trophic level and energy channel. Based on the same measurements we expected that the contributions by the lower trophic level groups will increase as well as the mineralisation rates by bacterial and fungal energy channels. Measured C and N mineralisation indeed increased during the 22-year period of abandonment. The calculated C and N mineralisation rates showed the same trend after land abandonment as the measured values. Calculated contributions to mineralisation of organisms at trophic level 1 increase during secondary succession following land abandonment. The fungal decomposition channel contributed more to N mineralisation than the bacterial decomposition channel, whereas both channels contributed equally to C mineralisation rates. Direct contributions by higher trophic levels to mineralisation decreased during secondary succession. However, higher trophic levels were direct important for N mineralisation and indirect for both C and N mineralisation due to their effect on biomass turnover rates of groups at lower trophic levels. The increasing total N mineralisation rate of the soil food web, however, does not benefit plants, as during succession plant species that mainly grow under high nutrient availability are replaced by species that can grow in nutrient poor condition
Organic amendments and their influences on plant-parasitic and free-living nematodes: a promising method for nematode management?
Thoden, T.C. ; Korthals, G.W. ; Termorshuizen, A.J. - \ 2011
Nematology 13 (2011)2. - ISSN 1388-5545 - p. 133 - 153.
bacterial-feeding nematodes - root-knot nematode - soil microbial communities - nitrogen mineralization - pratylenchus-penetrans - cover crops - biological-control - food-web - bacterivorous nematodes - pyrrolizidine alkaloids
The use of organic soil amendments, such as green manures, animal manures, composts or slurries, certainly has many advantageous aspects for soil quality and is suggested as a promising tool for the management of plant-parasitic nematodes. However, during a recent literature survey we also found numerous studies reporting an increase of plant-parasitic nematodes after the use of organic amendments. Therefore, we critically re-evaluated the usefulness of organic amendments for nematode management and suggest possible mechanisms for a stimulation of plant-parasitic nematodes, as well as mechanisms that might be causing a reduction of plant-parasitic nematodes. In addition, we also elucidate a possible mechanism that might be responsible for the observed overall positive effects of organic amendments on crop yields. It is likely that a significant part of this is, inter alia, due to the proliferation of non-pathogenic, free-living nematodes and their overall positive effects on soil microbial populations, organic matter decomposition, nutrient availability, plant morphology and ecosystem stability.
The contribution of mineralization to grassland N uptake on peatland soils with anthropogenic A horizons
Sonneveld, M.P.W. ; Lantinga, E.A. - \ 2011
Plant and Soil 340 (2011)1-2. - ISSN 0032-079X - p. 357 - 368.
nitrogen mineralization - cattle dung - management - level - fluxes - model
Peatland soils contain large amounts of nitrogen (N) in the soil and mineralization can contribute substantially to the annual mineral N supply of grasslands. We investigated the contribution of N mineralization from peat with respect to the total annual N uptake on grasslands with anthropogenic A horizons and submerged tile drains. The study included i) a pot experiment to determine potential N mineralization from the topsoil and the subsoil, ii) a 1-year field experiment to study herbage yields and N uptake under fertilized and non-fertilized conditions and iii) a 3-year field study where herbage yield and N uptake from the top 30 cm and the entire soil profile were monitored. The 3-year field study yielded an average N uptake of 342 kgha(-1) under non-fertilized conditions but the contribution of subsoil peat N mineralization to the total N uptake was found to be negligible. Our calculations demonstrate that peat N mineralization contributed only 10% to 30% to the total N-uptake, mainly coming from the top 30 cm. Most of the N uptake under unfertilized conditions appears to be largely the result of mineralization from long-term inputs of dung, ditch sludge, farmyard manure, cow slurry and non-harvested herbage.
Assessing denitrification and N leaching in a field with organic amendments
Radersma, S. ; Smit, A.L. - \ 2011
NJAS Wageningen Journal of Life Sciences 58 (2011)1-2. - ISSN 1573-5214 - p. 21 - 29.
nitrate vulnerable zone - paper-mill sludge - crop yields - nitrogen mineralization - plant residues - barley straw - forest soils - decomposition - management - release
Denitrification and leaching of nitrogen (N) from agriculture are a loss of nutrients to farmers and sources of pollution to water and air, and should therefore be minimized. In a field experiment on loamy soil, denitrification and N leaching were measured after late summer incorporation of fodder radish residues with or without paper pulp as N-immobilizing organic material. A set of relatively simple methods were used to measure and calculate denitrification and N leaching during the first two weeks after application and during the rest of the winter period. The methods were acetylene inhibition of nitrification, anion-exchange resin, the mineralization model MINIP, and inorganic-N balance calculations. Paper pulp increased N immobilization after the first day of application throughout the winter. This led to a 63–70% reduction in N losses compared with the sole fodder radish field and with the control. Denitrification was highest in the sole fodder radish treatment, at 65% of its total N losses. N leaching during the winter period was highest in the control, at 70% of its total N losses. This N was mainly liberated by mineralization of soil organic matter after ploughing in late summer. The application of paper pulp plus fodder radish did not affect sugar beet yields in the next year. The methodology for determining leaching and denitrification enabled the assessment of differences among treatments. It showed clearly that paper pulp strongly reduced N losses on this type of soil. The anion resin method that was used to measure leaching during the winter period showed clear and consistent differences between treatments, but may need additional calibration before fully relying on the absolute amounts of N leached
Effect of vermicompost on the growth and production of amashito pepper, interactions with earthworms and rhizobacteria
Huerta, E. ; Vidal, O. ; Jarquin, A. ; Geissen, V. ; Gomez, R. - \ 2010
Compost Science & Utilization 18 (2010)4. - ISSN 1065-657X - p. 282 - 288.
plant-growth - humic substances - nitrogen mineralization - pig manure - take-all - soil - greenhouse - casts - decomposition - lumbricus
Increasing yield is one of the goals in the tropics. Traditional farming is replaced in many cases by agroindustrial production which often leads to environmental pollution due to the marked use of pesticides and fertilizers. In Tabasco, Amashito pepper (Capsicum annum var. glabriusculcum) is cultivated in the traditional way in backyards or cocoa fields with no chemical inputs. The germination of these kind of peppers is difficult to achieve, since wild peppers seeds have a large range of dormancy. Plant-growth-promoting rhizobacteria (PGPRs) are used as inoculants for biofertilization, phytostimulation and biocontrol. Soil fauna has an important function in regulating rhizosphere microbial processes and therefore significantly affects plant growth. Earthworms produce indirect effects through changes in the environment of the roots or via interactions with organisms that affect root growth and production. Our aim was to study the effects of different fresh organic matter, earthworms (P. corethrurus, oligochaeta) and rhizobacteria (A. brasiliensis) on plant growth, and yield production of amashito pepper (Capsicum annuum var. glabriusculum). We established a three factorial outdoors mesocosms experiment. We tested the effects of 3 substrates (dry cocoa husks (C), Panicum sp grass-cocoa husks vermicompost (V), cocoa husks with cow manure (CC) (type of germination substrate, factor 1), the presence (E) and absence of P. corethrurus (WE) (earthworm, factor 2) and the absence (WB) or presence (B) of A. brasiliensis (rizobacteria, factor 3). After 173 days, fruit production was significantly more in plants raised in vermicompost. Vermicompost significantly enhanced the highest weight (23.4g), height (26.7 cm) and production of leaves per plant (20.6 leaves per plant). Further studies are required in order to understand the interactions between vermicompost, plants, earthworms and rhizobacteria.
The nitrate response of a lowland catchment: on the relation between stream concentration and travel time distribution dynamics
Velde, Y. van der; Rooij, G.H. de; Rozemeijer, J.C. ; Geer, F.C. van; Broers, H.P. - \ 2010
Water Resources Research 46 (2010). - ISSN 0043-1397 - 17 p.
nitrogen mineralization - grassland soils - organic-matter - groundwater - transport - scale - model - texture - uncertainty - netherlands
Nitrate pollution of surface waters is widespread in lowland catchments with intensive agriculture. For identification of effective nitrate concentration reducing measures the nitrate fluxes within catchments need to be quantified. In this paper we applied a mass transfer function approach to simulate catchment-scale nitrate transport. This approach was extended with time-varying travel time distributions and removal of nitrate along flow paths by denitrification to be applicable for lowland catchments. Numerical particle tracking simulations revealed that transient travel time distributions are highly irregular and rapidly changing, reflecting the dynamics of rainfall and evapotranspiration. The solute transport model was able to describe 26 years of frequently measured chloride and nitrate concentrations in the Hupsel Brook catchment (6.6 km2 lowland catchment in the Netherlands) with an R2 value of 0.86. Most of the seasonal and daily variations in concentrations could be attributed to temporal changes of the travel time distributions. A full sensitivity analysis revealed that measurements other than just surface water nitrate and chloride concentrations are needed to constrain the uncertainty in denitrification, plant uptake, and mineralization of organic matter. Despite this large uncertainty, our results revealed that denitrification removes more nitrate from the Hupsel Brook catchment than stream discharge. This study demonstrates that a catchment-scale lumped approach to model chloride and nitrate transport processes suffices to accurately capture the dynamics of catchment-scale surface water concentration as long as the model includes detailed transient travel time distributions
Soil carbon balance of rice-based cropping systems of the Indo-Gangetic Plains
Shibu, M.E. ; Keulen, H. van; Leffelaar, P.A. ; Aggarwal, P.K. - \ 2010
Geoderma 160 (2010)2. - ISSN 0016-7061 - p. 143 - 154.
organic-matter - climate-change - nitrogen mineralization - cycle feedbacks - jute corchorus - yield declines - oryza-sativa - dynamics - wheat - management
An agricultural land use system centred on rice-based cropping systems as common in the Indo-Gangetic Plains (IGP), with its annual cycles of wet and dry, puddling and ploughing, is unique and exerts a specific influence on soil organic matter (SOM) dynamics. Reports of yield ‘stagnation’ in some parts of the IGP with a decline in SOM quantity and quality raises concerns about the sustainability of the rice–wheat system in the region. Proper understanding of the soil carbon balance and of measures required to build up or maintain the soil carbon status of such a production system is therefore important for its sustainable production. Long-term experiments conducted in this region are especially useful in gaining understanding of soil carbon dynamics, since the processes affecting carbon dynamics are slow in nature. We used a simple analytical model—Yang's model—to calculate carbon balances in the rice-based cropping systems of the IGP in India. We used eight data sets from rice-based cropping systems from different sub-regions in the IGP, with different crop managements applied to rice, wheat or a third crop. Carbon input into the soil from crop biomass was calculated using data on crop yield and Harvest Index (HI). The values of soil organic carbon content predicted by the model were comparable to the observed values (r = 0.91). The model performs well in situations with porous soils (low clay content), with a pH values in the neutral range (7–7.5) and low annual rainfall as in the situation of Ludhiana-1 and 2. However, it underperforms in situations with heavy clay soils with high rainfall, causing severe anaerobic conditions. The model projections for the long-term (by 2080) show a decline in SOC at all sites in the IGP. Hence, the yield stagnation in the IGP, which has been attributed to a decline in SOC and the associated reduction in nutrient supply, could lead to further decreases in SOC levels, aggravated by climate change-induced higher temperatures.