191 research outputs found
Rapid transfer of photosynthetic carbon through the plant-soil system in differently managed grasslands
No full textPlant-soil interactions are central to short-term
carbon (C) cycling through the rapid transfer of recently
assimilated C from plant roots to soil biota. In grassland
ecosystems, changes in C cycling are likely to be influenced
by land use and management that changes vegetation and
the associated soil microbial communities. Here we tested
whether changes in grassland vegetation composition resulting
from management for plant diversity influences shortterm
rates of C assimilation and transfer from plants to soil
microbes. To do this, we used an in situ 13C-CO2 pulselabelling
approach to measure differential C uptake among
different plant species and the transfer of the plant-derived
13C to key groups of soil microbiota across selected treatments
of a long-term plant diversity grassland restoration experiment.
Results showed that plant taxa differed markedly
in the rate of 13C assimilation and concentration: uptake was
greatest and 13C concentration declined fastest in Ranunculus
repens, and assimilation was least and 13C signature
remained longest in mosses. Incorporation of recent plantderived
13C was maximal in allmicrobial phosopholipid fatty
acid (PLFA) markers at 24 h after labelling. The greatest incorporation
of 13C was in the PLFA 16:1!5, a marker for arbuscular
mycorrhizal fungi (AMF), while after 1 week most
13C was retained in the PLFA18:2!6,9 which is indicative of
assimilation of plant-derived 13C by saprophytic fungi. Our
results of 13C assimilation and transfer within plant species
and soil microbes were consistent across management treatments.
Overall, our findings suggest that plant diversity
restoration management may not directly affect the C assimilation
or retention of C by individual plant taxa or groups
of soil microbes, it can impact on the fate of recent C by
Correspondence to: G. B. De Deyn
([email protected])
changing their relative abundances in the plant-soil system.
Moreover, across all treatments we found that plant-derived
C is rapidly transferred specifically to AMF and decomposer
fungi, indicating their consistent key role in the cycling of
recent plant derived C.
Plant and soil data from the last year of the biodiversity experiment
No full textData from: Wen-feng Cong, Jasper van Ruijven, Liesje Mommer, Gerlinde De Deyn, Frank Berendse and Ellis Hoffland. (2014) Plant species richness promotes soil carbon and nitrogen stocks in grasslands without legumes. Data were collected in the 11-year grassland biodiversity experiment in Wageningen, the Netherlands, in 2010 and 2011. Abbreviated headlines are as follows: “”BLK”= block; “PT”= plot; "SR" = plant species richness; “MI” = monoculture identity (Ac = Agrostis capillaris; Ao = Anthoxanthum odoratum; Cj = Centaurea jacea; Fr = Festuca rubra; Hl = Holcus lanatus; Lv = Leucanthemum vulgare; Pl = Plantago lanceolata; Ra = Rumex acetosa); "AAB" = average aboveground biomass from 2000 to 2010 (g m-2); "RB" = standing root biomass (g fresh weight m-2) up to 50 cm depth in June 2010; "CS" = soil carbon stocks (g C m-2) in April 2011; "NS" = soil nitrogen stocks (g N m-2) in April 2011. "CD" = soil organic carbon decomposition (mg CO2-C kg-1 soil) measured in soil collected in April 2011; "NM" = potential net N mineralization rate (µg N kg-1 soil day-1) measured in soil collected in April 2011
The effect of cover crop mixtures on N mineralization and on spring barley (Hordeum vulgare) performance
No full textDissertação de Mestrado em Engenharia AgronómicaCover crop mixture residues, through complementarity, can supply a larger biomass to the soil than monoculture cover crops resulting in a higher nitrogen (N) input into the soil. Moreover, one can control the cover crops quality by mixing species with different N content. By doing this, N can also be transferred between the species residues, avoiding soil N immobilization, potentially resulting in higher N availability for the next crop. We hypothesised that N mineralization in mixtures would be higher than the expected based on sole cover crops, resulting in a better than expected performance of the following crop. A field experiment was conducted to assess the ability of 3 cover crop species, oat (Avena strigosa), radish (Raphanus sativus), and vetch (Vicia sativa), and all possible 2 and 3- species mixtures to provide mineral N to spring barley (Hordeum vulgare). Besides this, a laboratory incubation was performed to investigate if the residue quality, in terms of the N, carbon (C), lignin, N in the cell wall, N in the readily decomposable fraction and cellulose content, could explain the observed N mineralization of mixed residues. In the field experiment, only the vetch-oat mixture has shown a higher than expected N mineralization. However, differences in quantity (biomass) or quality (C:N ratio) of the cover crop did not explain this difference. Conversely, barley performance was higher than expected only when preceded by the oat-radish mixture. The mixtures in the laboratory incubation did not present signs of enhanced N mineralization, not giving a clear explanation for the observed enhanced N mineralization in the field. Although the C:N ratio was a good predictor of N mineralization in the laboratory incubation, cellulose and the N content in the cell wall also showed a high correlation, indicating that the C:N ratio may not be enough to predict N mineralization in mixed residues. Cover crop mixtures do not perform consistently better than expected at providing mineral N to the main crop, however similar yields as the corresponding best performing sole crop can be reached.Através de complementaridade, misturas de culturas de cobertura podem fornecer mais
biomassa do que só uma espécie. Isto pode resultar num maior retorno de azoto (N) ao solo
quando incorporadas. Ao usar misturas também é possível controlar a qualidade dos resíduos
ao usar espécies com diferentes concentrações de N. Neste caso, o N pode ser transferido entre
os resíduos das diferentes espécies, evitando assim imobilização de N do solo e potencialmente
aumentar a disponibilidade de N para a cultura seguinte. Colocou-se a hipótese que a
mineralização de N de misturas seria mais elevada do que o esperado com base na média
ponderada das monoculturas. Por sua vez, isto resultaria numa performance mais elevada da
cultura seguinte. Para testar a hipótese, foi feito um ensaio de campo com 3 espécies de culturas
de cobertura, aveia (Avena strigosa), rabanete forrageiro (Raphanus sativus) e ervilhaca-vulgar
(Vicia sativa), e todas as possíveis combinações de misturas com 2 e 3 espécies. Após estas
terem sido incorporadas, foi semeada uma cultura de cevada de primavera (Hordeum vulgare)
Foi ainda conduzida uma incubação em laboratório, para investigar se a qualidade dos resíduos
podem explicar a mineralização de N em misturas de resíduos, através de determinados
parâmetros bioquímicos (conteúdo de N, carbono (C), lenhina, N na parede celular, N na fração
facilmente degradável e celulose). Os resultados no ensaio de campo demonstraram que apenas
houve uma mineralização de N mais intensa do que o esperado na mistura ervilhaca-aveia.
Contudo, diferenças na quantidade (biomassa) e qualidade (relação C:N) desta cultura de
cobertura não foram suficientes para explicar esta diferença. Inversamente, a performance da
cevada foi mais elevada do que o esperado apenas quando precedida pela mistura de aveiarabanete. As misturas de resíduos na incubação em laboratório não apresentaram sinais de
sinergia na mineralização de N, não esclarecendo a causa para a mineralização de N observada
no campo. Apesar da relação C:N ter sido um bom preditor da mineralização de N na incubação
em laboratório, o conteúdo de celulose e de N na parede celular também mostraram uma elevada
correlação, indicando que a relação C:N pode não ser o único parâmetro para prever a
mineralização de azoto em misturas de resíduos. Misturas de culturas de cobertura nem sempre
apresentam melhor desempenho no fornecimento de N mineral à cultura principal do que o
esperado. No entanto, quando precedida por misturas, a cultura seguinte pode apresentar
produtividades semelhantes aquando precedida pela espécie com melhor desempenho em
monocultura
Increased plant carbon translocation linked to overyielding in grassland species mixtures
No full textPlant species richness and productivity often show a positive relationship, but the underlying mechanisms are not fully understood, especially at the plant species level. We examined how growing plants in species mixture influences intraspecific rates of short-term carbon (C-) translocation, and determined whether such short-term responses are reflected in biomass yields. We grew monocultures and mixtures of six common C3 grassland plant species in outdoor mesocosms, applied a 13C-CO2 pulse in situ to trace assimilated C through plants, into the soil, and back to the atmosphere, and quantified species-specific biomass. Pulse derived 13C enrichment was highest in the legumes Lotus corniculatus and Trifolium repens, and relocation (i.e. transport from the leaves to other plant parts) of the recently assimilated 13C was most rapid in T. repens grown in 6-species mixtures. The grass Anthoxanthum odoratum also showed high levels of 13C enrichment in 6-species mixtures, while 13C enrichment was low in Lolium perenne, Plantago lanceolata and Achillea millefolium. Rates of C loss through respiration were highest in monocultures of T. repens and relatively low in species mixtures, while the proportion of 13C in the respired CO2 was similar in monocultures and mixtures. The grass A. odoratum and legume T. repens were most promoted in 6-species mixtures, and together with L. corniculatus, caused the net biomass increase in 6-species mixtures. These plant species also had highest rates of 13C-label translocation, and for A. odoratum and T. repens this effect was greatest in plant individuals grown in species mixtures. Our study reveals that short-term plant C translocation can be accelerated in plant individuals of legume and C3 grass species when grown in mixtures, and that this is strongly positively related to overyielding. These results demonstrate a mechanistic coupling between changes in intraspecific plant carbon physiology and increased community level productivity in grassland systems
Enhancement of late successional plants on ex-arable land by soil inoculations
No full textRestoration of species-rich grasslands on ex-arable land can help the conservation of biodiversity but faces three big
challenges: absence of target plant propagules, high residual soil fertility and restoration of soil communities. Seed
additions and top soil removal can solve some of these constraints, but restoring beneficial biotic soil conditions remains a
challenge. Here we test the hypotheses that inoculation of soil from late secondary succession grasslands in arable receptor
soil enhances performance of late successional plants, especially after top soil removal but pending on the added dose. To
test this we grew mixtures of late successional plants in arable top (organic) soil or in underlying mineral soil mixed with
donor soil in small or large proportions. Donor soils were collected from different grasslands that had been under
restoration for 5 to 41 years, or from semi-natural grassland that has not been used intensively. Donor soil addition,
especially when collected from older restoration sites, increased plant community biomass without altering its evenness. In
contrast, addition of soil from semi-natural grassland promoted plant community evenness, and hence its diversity, but
reduced community biomass. Effects of donor soil additions were stronger in mineral than in organic soil and larger with
bigger proportions added. The variation in plant community composition was explained best by the abundances of
nematodes, ergosterol concentration and soil pH. We show that in controlled conditions inoculation of soil from secondary
succession grassland into ex-arable land can strongly promote target plant species, and that the role of soil biota in
promoting target plant species is greatest when added after top soil removal. Together our results point out that
transplantation of later secondary succession soil can promote grassland restoration on ex-arable land.
Predictability of plant-soil feedback
No full textABSTRACT In my thesis project I studied the role of soil biota as possible drivers of linkages between plant community diversity and plant productivity. My study was carried out in the framework of a large grassland biodiversity experiment in Jena, the so-called Jena Experiment. In chapter 1 I explain how soil biota may exert control over plant community productivity by recycling organic material and by intimately interacting with plant roots, either acting as antagonists to plants or as plant growth-promoting symbionts. Reciprocal interactions between plant and soil communities are an important component of so-called ‘plant-soil feedbacks’ (PSFs). In the PSF loop, plant community composition drives changes in belowground communities and abiotic conditions, which can subsequently alter plant community composition and productivity. Such PSF interactions have been proposed to play a major role in plant community composition and functioning. In the second chapter I review studies that use an experimental approach of inoculating live soils into sterilized background soils to study the effects of root symbionts on plant growth. I demonstrate that we make many assumptions when translating results of controlled studies to natural systems. I propose that we should continuously and carefully consider these assumptions and aim for rigid hypothesis testing by cross-talking between different levels of ecological realism. In chapter 3 I test how plant traits relate to PSF using a 49 grassland plant species of the Jena Experiment. First, I grew individuals of all species for two months in sterilized soil inoculated with field soil. In the subsequent feedback phase, I grew all plant species for 6 weeks in sterilized soil inoculated with (I) species-specific inoculum (conspecific conditioned soil), (II) sterilized species-specific inoculum, or (III) a mixture of all 49 species-specific inoculums (mixed conditioned soil). Subsequently I compared biomass production in conspecific conditioned soil to biomass production in sterilized soil (PSFsterilized) and in mixed conditioned soil (PSFmixed). Species with increasing specific root length (SRL) were increasingly susceptible to antagonistic interactions in conspecific conditioned soil (i.e. they had strong negative PSFsterilized), while thick-rooted plants had both positive PSFsterilized and high colonization rates of arbuscular mycorrhizal fungi (AMF). Finally, I showed that species ranking of PSFmixed was similar to species ranking of PSFsterilized, indicating that plants with increasingly negative net interactions in conspecific conditioned soil increasingly benefit from growing in mixed conditioned soil. With these findings, I made a first important step in placing PSFs in plant ecological strategy frameworks: high SRL is typical for plants that adopt a ‘fast’ growth strategy, characterized by fast resource acquisition but poor defense against antagonists and little reliance on AMF. In chapter 4, I test the relation between phylogenetic relatedness and the feedback effect of one (soil conditioning) plant species to another (responding) plant species. This is named indirect PSF. I grew eleven focal plant species, chosen to represent plants that had negative, neutral and positive PSFsterilized, in soils that were conditioned by conspecifics and soils conditioned by three to four other species with a varying degree of phylogenetic relatedness to the focal plant species. I found that plant species with negative PSF had no different or slightly better growth when growing in soil conditioned by plant species with larger phylogenetic distance to the focal plant. In contrast, plant species with neutral PSF grew less well, and species with positive PSF even worse, in soil conditioned by plant species with increasing phylogenetic distance to the focal plant. I conclude that the effect of phylogenetic relatedness on PSF interactions between plant species may depend on the tendency of the focal plant species to develop detrimental or beneficial interactions with soil microbes. In chapter 5, I use the PSFmixed values of chapter 3 in a correlational analysis to test how short-term PSFs relate to longer-term species’ performances in the field, using established monocultures and species-rich (60 species) plant communities of the Jena Experiment. Based on some recently published studies I expected that plants with more negative PSFmixed would benefit most from growing in mixtures; these plant species were expected to overyield most in mixed plant communities. However, opposite to the expectation, plant species with the most negative PSF produced least biomass in the 60-species plant communities, whereas plant performance in monoculture was not related to its short-term PSF. I conclude that species-specific overyielding was positively related to species-specific PSF, and that community overyielding was mostly driven by plant species with a neutral to positive PSF. Finally, in chapter 6 I examine the role of quality and quantity of plant biomass in driving nematode feeding group abundance and diversity. I found strong positive effects of both plant species- and plant functional group-richness on abundances of plant feeding, bacterial feeding and fungal feeding nematodes, as well as omnivores, but not for predators. Structural equation modeling (SEM) analysis showed that the positive effect of plant diversity on the abundance of microbial feeding nematodes (fungal plus bacterial feeders) could not be explained by increased microbial biomass. Similarly, the abundance of plant feeding nematodes was not driven by the higher plant biomass in species rich plant communities. Instead, increased plant biomass explained the positive relation between plant species richness and the abundance of microbial feeding nematodes, while for plant feeding nematodes, increased C to N ratio of aboveground plant biomass appeared to explain the positive relation between the abundance of plant feeding nematodes and plant species and functional group richness. Importantly, the density of plant feeding nematodes per unit root biomass decreased with increasing plant diversity, indicating a root feeder dilution effect. I conclude that plant diversity does not explain nematode community composition primarily by simple bottom-up relations, but that other aspects, such as quality of resource and microhabitats quality, may play a role as well.</p
Cascading spatial and trophic impacts of oak decline on the soil food web
No full textTree defoliation and mortality have considerably increased world-wide during the last decades due to global change drivers such as increasing drought or invasive pests and pathogens. However, the effects of this tree decline on soil food webs are poorly understood. In this study, we evaluated the impacts of Quercus suber decline on soil food webs of Mediterranean mixed forests invaded by the exotic oomycete pathogen Phytophthora cinnamomi, using soil nematodes as bioindicator taxa. We used a spatially explicit neighbourhood approach to predict the characteristics of the nematode community (diversity, trophic structure, and several indices indicative of soil food web conditions) as a function of the characteristics of the tree and shrub community (species composition, size, and health status). Our results indicate that the process of defoliation and mortality of Q. suber caused significant alterations in the nematode trophic structure increasing the abundance of lower trophic levels (bacterivores, fungivores, and herbivores) and decreasing the abundance of higher levels (predators and omnivores). Furthermore, Q. suber decline altered the functional composition of soil communities, producing a setback of the ecological succession in the soil food web to an earlier stage (decrease in the maturity index and increase in the plant parasitic index), simplified soil food webs (decrease in the structure index), and shifts in the predominant decomposition channel (increase in the fungivores/bacterivores ratio). We also detected contrasting characteristics of the nematode community in neighbourhoods dominated by coexisting woody species, which suggests potential for long-term indirect effects on soil food webs due to the substitution of Q. suber by non-declining species. Synthesis. Our study provides novel results that show the major impacts that ongoing health deterioration of dominant tree species can have on the structure and composition of soil food webs in forest systems invaded by exotic pathogens, with cascading consequences for soil biogeochemical processes in both the short- and long term
Impacts of plant domestication on soil microbial and nematode communities during litter decomposition
No full textPlant domestication altered leaf litter quality. Since litter traits relate to soil functions and organisms (i.e., litter decomposition and soil decomposer communities), in this study we explore if domestication-induced changes in litter quality have affected their decomposability, and bacterial, fungal, and nematode communities in the soil. Methods: We collected leaf litter from herbaceous crops and their wild progenitors, and measured litter chemical and physical traits. Then, we performed a litter decomposition assay on a common soil. After three months of litter incubation, we measured mass loss, nematode richness and community composition in ten crops. We also measured soil bacterial and fungal richness and community composition in six crops. Results: Domesticated litters had less carbon (C) and leaf dry matter content (LDMC), which accelerated decomposition in comparison to wild litters. Fungal richness was higher in microcosms incubated with domesticated litters, while the effects of domestication on bacterial richness differed among crops. Domestication did not affect nematode richness. The effects of domestication on bacterial and fungal community compositions differed among crops. Soils with domesticated litters tended to have nematode communities with a higher abundance of bacterial feeding nematodes, in comparison to soils fed with wild litters. Conclusion: Domestication altered decomposition at different levels. Leaf litter decomposability increased with domestication, which might alter resource inputs into the soil. Feeding soils with domesticated litters had idiosyncratic effects on soil microbes, but consistent effects on soil nematodes. Overall, domestication altered the linkages between crop residues and soil communities differently for bacteria, fungi, and nematodes
Data belonging to Oram et al. Plant community flood resilience in intensively managed grasslands and the role of the plant economic spectrum.
No full textThese data belong to Oram et al. (2020) Plant community flood resilience in intensively managed grasslands and the role of the plant economic spectrum. Published in Journal of Applied Ecology
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