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- De Frenne, Pieter, et al.
(author)
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Plant movements and climate warming : intraspecific variation in growth responses to nonlocal soils
- 2014
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In: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 202:2, s. 431-441
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Journal article (peer-reviewed)abstract
- Most range shift predictions focus on the dispersal phase of the colonization process. Because moving populations experience increasingly dissimilar nonclimatic environmental conditions as they track climate warming, it is also critical to test how individuals originating from contrasting thermal environments can establish in nonlocal sites. We assess the intraspecific variation in growth responses to nonlocal soils by planting a widespread grass of deciduous forests (Milium effusum) into an experimental common garden using combinations of seeds and soil sampled in 22 sites across its distributional range, and reflecting movement scenarios of up to 1600km. Furthermore, to determine temperature and forest-structural effects, the plants and soils were experimentally warmed and shaded. We found significantly positive effects of the difference between the temperature of the sites of seed and soil collection on growth and seedling emergence rates. Migrant plants might thus encounter increasingly favourable soil conditions while tracking the isotherms towards currently colder' soils. These effects persisted under experimental warming. Rising temperatures and light availability generally enhanced plant performance. Our results suggest that abiotic and biotic soil characteristics can shape climate change-driven plant movements by affecting growth of nonlocal migrants, a mechanism which should be integrated into predictions of future range shifts.
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- Rütting, Tobias, 1977, et al.
(author)
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Increased fungal dominance in N2O emission hotspots along a natural pH gradient in organic forest soil
- 2013
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In: Biology and Fertility of Soils. - : Springer Science and Business Media LLC. - 0178-2762 .- 1432-0789. ; 49:6, s. 715-721
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Journal article (peer-reviewed)abstract
- Drained organic forest soils represent a hotspot for nitrous oxide (N2O) emissions, which are directly related to soil fertility, with generally higher emissions from N-rich soils. Highest N2O emissions have been observed in organic forest soils with low pH. The mechanisms for these high emissions are not fully understood. Therefore, the present study was conducted to gain a deeper insight into the underlying mechanisms that drive high N2O emissions from acid soils. Specifically, we investigated the microbial community structure, by phospholipid fatty acid analysis, along a natural pH gradient in an organic forest soil combined with measurements of physico-chemical soil properties. These were then statistically related to site-specific estimates of annual N2O emissions along the same natural pH gradient. Our results indicate that acidic locations with high N2O emissions had a microbial community with an increased fungal dominance. This finding points to the importance of fungi for N2O emissions from acid soils. This may either be directly via fungal N2O production or indirectly via the effect of fungi on the N2O production by other microorganisms (nitrifiers and denitrifiers). The latter may be due to fungal mediated N mineralization, providing substrate for N2O production, or by creating favourable conditions for the bacterial denitrifier community. Therefore, we conclude that enhanced N2O emission from acid forest soil is related, in addition to the known inhibitory effect of low pH on bacterial N2O reduction, to a soil microbial community with increased fungal dominance. Further studies are needed to reveal the exact mechanisms.
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- Rütting, Tobias, 1977, et al.
(author)
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Recent developments in labelling and data analysis approaches for 15N tracing experiments
- 2012
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In: Joint European Stable Isotope Users Group Meeting JESIUM 2012 • 2–7 September 2012 • Leipzig • Germany.
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Conference paper (other academic/artistic)abstract
- The microbial mediated soil nitrogen (N) cycle is often investigated using stable isotope (15N) labelling. The main objective of these studies is to quantify gross rates of simultaneously occurring N transformations. In this paper we will give an overview on recent progress in 15N tracing methodologies, including both in-situ 15N label application as well as data analysis. In most studies investigating gross N transformations, soils are disturbed before incubation, leading to alteration of soil properties compared to field conditions. In-situ studies typically disrupt the soil-rootmycorrhiza system by inserting cylinders into the soil. A novel in-situ 15N labelling approach, coined ‘Virtual Soil Core’[1], was developed in order to allow the soil properties as well as the plant root and mycorrhizal activity to remain unaltered during the course of the 15N experiment. Most investigations have used analytical 15N tracing models[2] for data analysis, which though allow only the quantification of total production and consumption rates[3, 4]. To achieve a process based quantification of simultaneously occurring N transformation rates, numerical 15N tracing models are required. Recent progress in these models, by implementing Monte Carlo methods[5], overcome the limitations of earlier models, which restricted the number of considered transformations as well as the chosen kinetics. In summary, using case studies in different ecosystems, we show that 15N labelling techniques in combination with robust data analysis tools provide us with a deeper insight in N cycling processes. Therefore, 15N tracing techniques are an essential tool to increase our understanding of the soil N cycling.
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- Staelens, Jeroen, et al.
(author)
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Nitrogen dynamics in contrasting forest ecosystems exposed to enhanced atmospheric N deposition
- 2009
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In: Working Papers of the Finnish Forest Research Institute. - 1795-150X. - 9789514021763 ; 128
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Conference paper (peer-reviewed)abstract
- Despite chronically enhanced nitrogen (N) deposition to forest ecosystems in Europe and NE America, considerable N retention by forests has been observed. It is still unclear which factors determine N retention in forest soils. However, this knowledge is crucial to assess the impact of changing anthropogenic N emissions on future N cycling and N loss of forests. For coniferous and deciduous forest stands at comparable sites, it is known that both N deposition to the forest floor as well as N loss by leaching below the rooting zone are significantly higher in coniferous stands (De Schrijver et al., 2007). In addition, the N loss in coniferous stands is often more enhanced than can be explained by the higher N input only, which suggests lower N retention by coniferous stands and may be related to differences in litter quality, microbial activity, and N uptake by plant roots. To test this hypothesis, we studied the effect of forest type on N retention. N dynamics were examined for two adjacent forest stands (pedunculate oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.)) on a well-drained soil type and with a similar stand history, which are located in a region with high N deposition (Belgium). Firstly, input-output N budgets were established by quantifying atmospheric deposition and leaching, which confirmed the above finding of higher N deposition and disproportionately higher N loss by the pine stand than the oak stand. Secondly, the fate of inorganic N within the ecosystems was studied by spraying dissolved 15N onto the forest floor, both as ammonium (NH4+) and nitrate (NO3-). The 15N recovery over time in organic and mineral soil layers, tree roots, water leaching, ferns, foliage, and stem wood was compared between the two forest stands and N treatments. Thirdly, in situ gross N transformation rates in undisturbed mineral forest soils were determined via a 15N tracing approach (Müller et al., 2007). Meaningful differences between the two forest stands were found for the rates of mineralisation, heterotrophic and autotrophic nitrification, and NH4+ and NO3- immobilisation. Unexpectedly, dissimilatory NO3- reduction to NH4+ (DNRA) was detected in the oak soil. This process has mainly been described for unpolluted soils (e.g., Huygens et al., 2008), and to the best of our knowledge, this is the first report of DNRA under field conditions in a temperate forest soil under high N deposition.
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