Plant presence reduces root and shoot litter decomposition rates of crops and wild relatives
Barel, J.M. - \ 2019
plant functional traits - litter decomposition - litter quality - rhizosphere priming - domestication
We tested coordination of above-and belowground litter traits and decomposition rates for six pairs of crops and closely related wild plants and studied the influence of plant presence on decomposition.
Effect of different magnesium sources on digesta and excreta moisture content and production performance in broiler chickens
Hangoor, E. ; Linde, I.B. van der; Paton, N.D. ; Verstegen, M.W.A. ; Hendriks, W.H. - \ 2013
Poultry Science 92 (2013)2. - ISSN 0032-5791 - p. 382 - 391.
foot pad dermatitis - dietary electrolyte balance - corn-soybean diets - litter quality - laying hens - gastrointestinal-tract - antidiarrheal activity - chloride requirements - growing turkeys - lower intestine
Reducing litter moisture is an effective measure to reduce the incidence of footpad dermatitis. Dietary mineral levels affect intestinal conditions with regard to osmolarity and water reabsorption. Magnesium is often used as a laxative, preventing reabsorption of water from the digesta, and as a consequence, more moisture in the excreta. The objective of the current experiment was to evaluate Mg in broiler diets as a model for reduced intestinal water reabsorption. Effects of magnesium source (magnesium sulfate, magnesium oxide, and magnesium chloride), each at 3 levels (0.255, 1.02, and 2.04 g·kg-1 diet), were studied. Measured effects were digesta moisture levels throughout the gastrointestinal tract and the moisture level of the excreta. The 10 treatments were randomly assigned to cages within 6 blocks, resulting in 6 replicates per treatments with 18 birds per replicate. Adding magnesium to the diet of broilers linearly increased the excreta moisture content, following the pattern MgCl > MgSO4 = MgO. This rejects the hypothesis that MgO and MgCl are less laxative sources compared with MgSO4. The magnesium sources most likely changed the water reabsorption in the distal gastrointestinal tract, as confirmed by the increased digesta moisture percentage in the ceca and colon. Increasing dietary MgSO4 linearly reduced BW gain and feed intake, though absolute differences were minor. The results of this experiment show that Mg addition in the diet may be used as a model to study wet litter caused by reduced intestinal water reabsorption.
Field Simulation of Global Change: Transplanting Northern Bog Mesocosms Southward
Breeuwer, A.J.G. ; Heijmans, M.M.P.D. ; Robroek, B.J.M. ; Berendse, F. - \ 2010
Ecosystems 13 (2010)5. - ISSN 1432-9840 - p. 712 - 726.
increased nitrogen deposition - increased n deposition - water-table depth - vascular plants - sphagnum mosses - litter quality - climate-change - boreal mire - peat bogs - mass-loss
A large proportion of northern peatlands consists of Sphagnum-dominated ombrotrophic bogs. In these bogs, peat mosses (Sphagnum) and vascular plants occur in an apparent stable equilibrium, thereby sustaining the carbon sink function of the bog ecosystem. How global warming and increased nitrogen (N) deposition will affect the species composition in bog vegetation is still unclear. We performed a transplantation experiment in which mesocosms with intact vegetation were transplanted southward from north Sweden to north-east Germany along a transect of four bog sites, in which both temperature and N deposition increased. In addition, we monitored undisturbed vegetation in control plots at the four sites of the latitudinal gradient. Four growing seasons after transplantation, ericaceous dwarf shrubs had become much more abundant when transplanted to the warmest site which also had highest N deposition. As a result ericoid aboveground biomass in the transplanted mesocosms increased most at the southernmost site, this site also had highest ericoid biomass in the undisturbed vegetation. The two dominant Sphagnum species showed opposing responses when transplanted southward; Sphagnum balticum height increment decreased, whereas S. fuscum height increment increased when transplanted southward. Sphagnum production did not differ significantly among the transplanted mesocosms, but was lowest in the southernmost control plots. The dwarf shrub expansion and increased N concentrations in plant tissues we observed, point in the direction of a positive feedback toward vascular plant-dominance suppressing peat-forming Sphagnum in the long term. However, our data also indicate that precipitation and phosphorus availability influence the competitive balance between Sphagnum, dwarf shrubs and graminoids.
The angiosperm radiation revisited, an ecological explanation for Darwin's 'abominable mystery'
Berendse, F. ; Scheffer, M. - \ 2009
Ecology Letters 12 (2009)9. - ISSN 1461-023X - p. 865 - 872.
crato formation brazil - nitrogen mineralization - vascular plants - litter quality - wet heathlands - n deposition - ecosystems - decomposition - sphagnum - diversification
One of the greatest terrestrial radiations is the diversification of the flowering plants (Angiospermae) in the Cretaceous period. Early angiosperms appear to have been limited to disturbed, aquatic or extremely dry sites, suggesting that they were suppressed in most other places by the gymnosperms that still dominated the plant world. However, fossil evidence suggests that by the end of the Cretaceous the angiosperms had spectacularly taken over the dominant position from the gymnosperms around the globe. Here, we suggest an ecological explanation for their escape from their subordinate position relative to gymnosperms and ferns. We propose that angiosperms due to their higher growth rates profit more rapidly from increased nutrient supply than gymnosperms, whereas at the same time angiosperms promote soil nutrient release by producing litter that is more easily decomposed. This positive feedback may have resulted in a runaway process once angiosperms had reached a certain abundance. Evidence for the possibility of such a critical transition to angiosperm dominance comes from recent work on large scale vegetation shifts, linking long-term field observations, large scale experiments and the use of simulation models.
Response of Sphagnum species mixtures to increased temperature and nitrogen availability
Breeuwer, A.J.G. ; Heijmans, M.M.P.D. ; Berendse, F. ; Gleichman, J.M. ; Robroek, B.J.M. ; Limpens, J. - \ 2009
Plant Ecology 204 (2009)1. - ISSN 1385-0237 - p. 97 - 111.
n-deposition - water-level - nutritional constraints - decomposition rates - northern peatlands - litter quality - climate-change - peat formation - growth - bogs
To predict the role of ombrotrophic bogs as carbon sinks in the future, it is crucial to understand how Sphagnum vegetation in bogs will respond to global change. We performed a greenhouse experiment to study the effects of two temperature treatments (17.5 and 21.7°C) and two N addition treatments (0 and 4 g N m¿2 year¿1) on the growth of four Sphagnum species from three geographically interspersed regions: S. fuscum, S. balticum (northern and central Sweden), S. magellanicum and S. cuspidatum (southern Sweden). We studied the growth and cover change in four combinations of these Sphagnum species during two growing seasons. Sphagnum height increment and production were affected negatively by high temperature and high N addition. However, the northern species were more affected by temperature, while the southern species were more affected by N addition. High temperature depressed the cover of the `wet¿ species, S. balticum and S. cuspidatum. Nitrogen concentrations increased with high N addition. N:P and N:K ratios indicated P-limited growth in all treatments and co-limitation of P and K in the high N treatments. In the second year of the experiment, several containers suffered from a severe fungal infection, particularly affecting the `wet¿ species and the high N treatment. Our findings suggest that global change can have negative consequences for the production of Sphagnum species in bogs, with important implications for the carbon sequestration in these ecosystems
The effect of increased temperature and nitrogen deposition on decomposition in bogs
Breeuwer, A.J.G. ; Heijmans, M.M.P.D. ; Robroek, B.J.M. ; Limpens, J. ; Berendse, F. - \ 2008
Oikos 117 (2008)8. - ISSN 0030-1299 - p. 1258 - 1268.
plant-mediated controls - swedish raised bog - litter quality - sphagnum mosses - mass-loss - growth - carbon - rates - decay - fertilization
Despite their low primary production, ombrotrophic peatlands have a considerable potential to store atmospheric carbon as a result of their extremely low litter decomposition rates. Projected changes in temperature and nitrogen (N) deposition may increase decomposition rates by their positive effects on microbial activity and litter quality, which can be expected to result in enhanced mass loss and N release from Sphagnum and vascular plant litter. This is the first study that examines the combined effects of increased temperature and N deposition on decomposition in bogs. We investigated mass loss and N release at four bog sites along a gradient from north Sweden to northeast Germany in which both temperature and N deposition increased from north to south. We performed two litterbag experiments: one reciprocal experiment with Eriophorum vaginatum litter and one experiment using recalcitrant (Sphagnum fuscum) and more degradable (Sphagnum balticum) Sphagnum litter collected from the most northern site. We measured mass loss and N release during two (Sphagnum) and three (E. vaginatum) years. The N concentration and decomposability of the E. vaginatum litter did not differ between the sites. Mass loss from E. vaginatum litter increased over the gradient from north to south, but there was no such effect on Sphagnum litter. N loss of all litter types was affected by collection site, incubation site and time and all interactions between these factors. N release in Sphagnum was positively related to N concentration. We conclude that decomposition of vascular plants and Sphagnum litter is influenced by different environmental drivers, with enhanced temperatures stimulating mass loss of vascular plant litter, but not of Sphagnum. Enhanced N deposition increases Sphagnum litter N loss. As long-term consequences of climate change will presumably entail a higher vascular plant production, overall litter decomposition rates are likely to increase, especially in combination with increased temperature
The effect of temperature on growth and competition between Sphagnum species
Breeuwer, A.J.G. ; Heijmans, M.M.P.D. ; Robroek, B.J.M. ; Berendse, F. - \ 2008
Oecologia 156 (2008)1. - ISSN 0029-8549 - p. 155 - 167.
interspecific competition - litter quality - tussock tundra - climate-change - water-level - mosses - bog - decomposition - mire - photosynthesis
Peat bogs play a large role in the global sequestration of C, and are often dominated by different Sphagnum species. Therefore, it is crucial to understand how Sphagnum vegetation in peat bogs will respond to global warming. We performed a greenhouse experiment to study the effect of four temperature treatments (11.2, 14.7, 18.0 and 21.4°C) on the growth of four Sphagnum species: S. fuscum and S. balticum from a site in northern Sweden and S. magellanicum and S. cuspidatum from a site in southern Sweden. In addition, three combinations of these species were made to study the effect of temperature on competition. We found that all species increased their height increment and biomass production with an increase in temperature, while bulk densities were lower at higher temperatures. The hollow species S. cuspidatum was the least responsive species, whereas the hummock species S. fuscum increased biomass production 13-fold from the lowest to the highest temperature treatment in monocultures. Nutrient concentrations were higher at higher temperatures, especially N concentrations of S. fuscum and S. balticum increased compared to field values. Competition between S. cuspidatum and S. magellanicum was not influenced by temperature. The mixtures of S. balticum with S. fuscum and S. balticum with S. magellanicum showed that S. balticum was the stronger competitor, but it lost competitive advantage in the highest temperature treatment. These findings suggest that species abundances will shift in response to global warming, particularly at northern sites where hollow species will lose competitive strength relative to hummock species and southern species.
Total soil C and N sequestration in a grassland following 10 years of free air CO2 enrichment
Kessel, C. van; Boots, B. ; Graaff, M.A. de; Harris, D. ; Blum, H. ; Six, J. - \ 2006
Global Change Biology 12 (2006)11. - ISSN 1354-1013 - p. 2187 - 2199.
elevated atmospheric co2 - trifolium-repens l - organic-matter - carbon-dioxide - lolium-perenne - n-15-labeled fertilizer - litter quality - nitrogen pools - forest soils - plant
Soil C sequestration may mitigate rising levels of atmospheric CO2. However, it has yet to be determined whether net soil C sequestration occurs in N-rich grasslands exposed to long-term elevated CO2. This study examined whether N-fertilized grasslands exposed to elevated CO2 sequestered additional C. For 10 years, Lolium perenne, Trifolium repens, and the mixture of L. perenne/T. repens grasslands were exposed to ambient and elevated CO2 concentrations (35 and 60 Pa pCO(2)). The applied CO2 was depleted in delta C-13 and the grasslands received low (140 kg ha(-1)) and high (560 kg ha(-1)) rates of N-15-labeled fertilizer. Annually collected soil samples from the top 10 cm of the grassland soils allowed us to follow the sequestration of new C in the surface soil layer. For the first time, we were able to collect dual-labeled soil samples to a depth of 75 cm after 10 years of elevated CO2 and determine the total amount of new soil C and N sequestered in the whole soil profile. Elevated CO2, N-fertilization rate, and species had no significant effect on total soil C. On average 9.4 Mg new C ha(-1) was sequestered, which corresponds to 26.5% of the total C. The mean residence time of the C present in the 0-10 cm soil depth was calculated at 4.6 +/- 1.5 and 3.1 +/- 1.1 years for L. perenne and T. repens soil, respectively. After 10 years, total soil N and C in the 0-75 cm soil depth was unaffected by CO2 concentration, N-fertilization rate and plant species. The total amount of N-15-fertilizer sequestered in the 0-75 cm soil depth was also unaffected by CO2 concentration, but significantly more N-15 was sequestered in the L. perenne compared with the T. repens swards: 620 vs. 452 kg ha(-1) at the high rate and 234 vs. 133 kg ha(-1) at the low rate of N fertilization. Intermediate values of N-15 recovery were found in the mixture. The fertilizer derived N amounted to 2.8% of total N for the low rate and increased to 8.6% for the high rate of N application. On average, 13.9% of the applied N-15-fertilizer was recovered in the 0-75 cm soil depth in soil organic matter in the L. perenne sward, whereas 8.8% was recovered under the T. repens swards, indicating that the N-2-fixing T. repens system was less effective in sequestering applied N than the non-N-2-fixing L. perenne system. Prolonged elevated CO2 did not lead to an increase in whole soil profile C and N in these fertilized pastures. The potential use of fertilized and regular cut pastures as a net soil C sink under long-term elevated CO2 appears to be limited and will likely not significantly contribute to the mitigation of anthropogenic C emissions.
Atmospheric nitrogen deposition promotes carbon loss from peat bogs
Bragazza, L. ; Freeman, C. ; Jones, T. ; Rydin, H. ; Limpens, J. ; Fenner, N. ; Ellis, T. ; Gerdol, R. ; Hajek, M. ; Hajek, T. ; Iacumin, P. ; Kutnar, L. ; Tahvanainen, T. ; Toberman, H. - \ 2006
Proceedings of the National Academy of Sciences of the United States of America 103 (2006)51. - ISSN 0027-8424 - p. 19386 - 19389.
n-deposition - soil carbon - nutritional constraints - enzymatic-activity - ombrotrophic bogs - litter quality - organic-matter - climate-change - elevated co2 - mass-loss
Peat bogs have historically represented exceptional carbon (C) sinks because of their extremely low decomposition rates and consequent accumulation of plant remnants as peat. Among the factors favoring that peat accumulation, a major role is played by the chemical quality of plant litter itself, which is poor in nutrients and characterized by polyphenols with a strong inhibitory effect on microbial breakdown. Because bogs receive their nutrient supply solely from atmospheric deposition, the global increase of atmospheric nitrogen (N) inputs as a consequence of human activities could potentially alter the litter chemistry with important, but still unknown, effects on their C balance. Here we present data showing the decomposition rates of recently formed litter peat samples collected in nine European countries under a natural gradient of atmospheric N deposition from ¿0.2 to 2 g·m-2.yr -1. We found that enhanced decomposition rates for material accumulated under higher atmospheric N supplies resulted in higher carbon dioxide (CO2) emissions and dissolved organic carbon release. The increased N availability favored microbial decomposition (i) by removing N constraints on microbial metabolism and (ii) through a chemical amelioration of litter peat quality with a positive feedback on microbial enzymatic activity. Although some uncertainty remains about whether decay-resistant Sphagnum will continue to dominate litter peat, our data indicate that, even without such changes, increased N deposition poses a serious risk to our valuable peatland C sinks
Decomposition of 14C-labeled roots in a pasture soil exposed to 10 years of elevated CO2
Groenigen, C.J. van; Gorissen, A. ; Six, J. ; Harris, D. ; Kuikman, P.J. ; Groenigen, J.W. van; Kessel, C. van - \ 2005
Soil Biology and Biochemistry 37 (2005)3. - ISSN 0038-0717 - p. 497 - 506.
atmospheric carbon-dioxide - organic-matter dynamics - trifolium-repens l - microbial biomass - lolium-perenne - forest soils - tallgrass prairie - litter quality - fine roots - turnover
The net flux of soil C is determined by the balance between soil C input and microbial decomposition, both of which might be altered under prolonged elevated atmospheric CO2. In this study, we determined the effect of elevated CO2 on decomposition of grass root material (Lolium perenne L.). 14C-labeled root material, produced under ambient (35 Pa pCO2) or elevated CO2 (70 Pa pCO2) was incubated in soil for 64 days. The soils were taken from a pasture ecosystem which had been exposed to ambient (35 Pa pCO2) or elevated CO2 (60 Pa pCO2) under FACE-conditions for 10 years and two fertilizer N rates: 140 and 560 kg N ha¿1 year¿1. In soil exposed to elevated CO2, decomposition rates of root material grown at either ambient or elevated CO2 were always lower than in the control soil exposed to ambient CO2, demonstrating a change in microbial activity. In the soil that received the high rate of N fertilizer, decomposition of root material grown at elevated CO2 decreased by approximately 17% after incubation for 64 days compared to root material grown at ambient CO2. The amount of 14CO2 respired per amount of 14C incorporated in the microbial biomass (q14CO2) was significantly lower when roots were grown under high CO2 compared to roots grown under low CO2. We hypothesize that this decrease is the result of a shift in the microbial community, causing an increase in metabolic efficiency. Soils exposed to elevated CO2 tended to respire more native SOC, both with and without the addition of the root material, probably resulting from a higher C supply to the soil during the 10 years of treatment with elevated CO2. The results show the importance of using soils adapted to elevated CO2 in studies of decomposition of roots grown under elevated CO2. Our results further suggest that negative priming effects may obscure CO2 data in incubation experiments with unlabeled substrates. From the results obtained, we conclude that a slower turnover of root material grown in an `elevated-CO2 world¿ may result in a limited net increase in C storage in ryegrass swards.