| 1. |
- Kehoe, Laura, et al.
(författare)
-
Make EU trade with Brazil sustainable
- 2019
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 2. |
- Ahlberg, Erik, et al.
(författare)
-
"Vi klimatforskare stödjer Greta och skolungdomarna"
- 2019
-
Ingår i: Dagens nyheter (DN debatt). - 1101-2447.
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- DN DEBATT 15/3. Sedan industrialiseringens början har vi använt omkring fyra femtedelar av den mängd fossilt kol som får förbrännas för att vi ska klara Parisavtalet. Vi har bara en femtedel kvar och det är bråttom att kraftigt reducera utsläppen. Det har Greta Thunberg och de strejkande ungdomarna förstått. Därför stödjer vi deras krav, skriver 270 klimatforskare.
|
|
| 3. |
- Andresen, Louise C., 1974, et al.
(författare)
-
Shifting Impacts of Climate Change: Long-Term Patterns of Plant Response to Elevated CO2, Drought, and Warming Across Ecosystems
- 2016
-
Ingår i: Large-Scale Ecology: Model Systems to Global Perspectives. - : Elsevier. - 9780081009352 ; , s. 437-473
-
Bokkapitel (refereegranskat)abstract
- Field experiments that expose terrestrial ecosystems to climate change factors by manipulations are expensive to maintain, and typically only last a few years. Plant biomass is commonly used to assess responses to climate treatments and to predict climate change impacts. However, response to the treatments might be considerably different between the early years and a decade later. The aim of this data analysis was to develop and apply a method for evaluating changes in plant biomass responses through time, in order to provide a firm basis for discussing how the ‘short-term’ response might differ from the ‘long-term’ response. Across 22 sites situated in the northern hemisphere, which covered three continents, and multiple ecosystems (grasslands, shrublands, moorlands, forests, and deserts), we evaluated biomass datasets from long-term experiments with exposure to elevated CO2 (eCO2), warming, or drought. We developed methods for assessing biomass response patterns to the manipulations using polynomial and linear (piecewise) model analysis and linked the responses to sitespecific variables such as temperature and rainfall. Polynomial patterns across sites indicated changes in response direction over time under eCO2, warming, and drought. In addition, five distinct pattern types were confirmed within sites: ‘no response’, ‘delayed response’, ‘directional response’, ‘dampening response’, and ‘altered response’ patterns. We found that biomass response direction was as likely to change over time as it was to be consistent, and therefore suggest that climate manipulation experiments should be carried out over timescales covering both short- and long-term responses, in order to realistically assess future impacts of climate change.
|
|
| 4. |
- Hovenden, Mark J., et al.
(författare)
-
Globally consistent influences of seasonal precipitation limit grassland biomass response to elevated CO2
- 2019
-
Ingår i: Nature Plants. - : Springer Science and Business Media LLC. - 2055-0278. ; 5, s. 167-173
-
Tidskriftsartikel (refereegranskat)abstract
- © 2019, The Author(s), under exclusive licence to Springer Nature Limited. Rising atmospheric carbon dioxide concentration should stimulate biomass production directly via biochemical stimulation of carbon assimilation, and indirectly via water savings caused by increased plant water-use efficiency. Because of these water savings, the CO 2 fertilization effect (CFE) should be stronger at drier sites, yet large differences among experiments in grassland biomass response to elevated CO 2 appear to be unrelated to annual precipitation, preventing useful generalizations. Here, we show that, as predicted, the impact of elevated CO 2 on biomass production in 19 globally distributed temperate grassland experiments reduces as mean precipitation in seasons other than spring increases, but that it rises unexpectedly as mean spring precipitation increases. Moreover, because sites with high spring precipitation also tend to have high precipitation at other times, these effects of spring and non-spring precipitation on the CO 2 response offset each other, constraining the response of ecosystem productivity to rising CO 2 . This explains why previous analyses were unable to discern a reliable trend between site dryness and the CFE. Thus, the CFE in temperate grasslands worldwide will be constrained by their natural rainfall seasonality such that the stimulation of biomass by rising CO 2 could be substantially less than anticipated.
|
|
| 5. |
- Andresen, Louise C., 1974, et al.
(författare)
-
Amino acid and N mineralization dynamics in heathland soil after long-term warming and repetitive drought
- 2015
-
Ingår i: Soil. - : Copernicus GmbH. - 2199-3971 .- 2199-398X. ; 1:1, s. 341-349
-
Tidskriftsartikel (refereegranskat)abstract
- Monomeric organic nitrogen (N) compounds such as free amino acids (FAAs) are an important resource for both plants and soil microorganisms and a source of ammonium (NH4+) via microbial FAA mineralization. We compared gross FAA dynamics with gross N mineralization in a Dutch heathland soil using a 15N tracing technique. A special focus was made on the effects of climate change factors warming and drought, followed by rewetting. Our aims were to (1) compare FAA mineralization (NH4+ production from FAAs) with gross N mineralization, (2) assess gross FAA production rate (depolymerization) and turnover time relative to gross N mineralization rate, and (3) assess the effects of a 14 years of warming and drought treatment on these rates. The turnover of FAA in the soil was ca. 3 h, which is almost 2 orders of magnitude faster than that of NH4+ (i.e. ca. 4 days). This suggests that FAA is an extensively used resource by soil microorganisms. In control soil (i.e. no climatic treatment), the gross N mineralization rate (10 ± 2.9 μg N g−1 day−1) was 8 times smaller than the total gross FAA production rate of five AAs (alanine, valine, leucine, isoleucine, proline: 127.4 to 25.0 μg N g−1 day−1). Gross FAA mineralization (3.4 ± 0.2 μg N g−1 day−1) contributed 34% to the gross N mineralization rate and is therefore an important component of N mineralization. In the drought treatment, a 6–29% reduction in annual precipitation caused a decrease of gross FAA production by 65% and of gross FAA mineralization by 41% compared to control. On the other hand, gross N mineralization was unaffected by drought, indicating an increased mineralization of other soil organic nitrogen (SON) components. A 0.5–1.5 °C warming did not significantly affect N transformations, even though gross FAA production declined. Overall our results suggest that in heathland soil exposed to droughts a different type of SON pool is mineralized. Furthermore, compared to agricultural soils, FAA mineralization was relatively less important in the investigated heathland. This indicates more complex mineralization dynamics in semi-natural ecosystems.
|
|
| 6. |
- Andresen, Louise C., 1974, et al.
(författare)
-
Depolymerization and mineralization – investigating N availability by a novel 15N tracing model
- 2016
-
Ingår i: SOIL. - : Copernicus GmbH. - 2199-398X. ; 2:3, s. 433-442
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Depolymerization of soil organic matter such as proteins and peptides into monomers (e.g. amino acids) is currently thought to be the rate limiting step for N availability in terrestrial N cycles. The mineralization of free amino acids (FAA), liberated by depolymerization of peptides, is an important fraction of the total N mineralization. Accurate assessment 10 of peptide depolymerization and FAA mineralization rates is important in order to gain a better understanding of the N cycle dynamics. Due to the short time span, soil disturbance and unnatural high FAA content during the first few hours after the labelling with the traditional 15N pool dilution experiments, analytical models might overestimate peptide depolymerization rate. In this paper, we present an extended numerical 15N tracing model Ntrace which incorporates the FAA pool and related N processes in order to 1) provide a more robust and coherent estimation of production and mineralization rates of FAAs; 2) 15 and 2) suggest an amino acid N use efficiency (NUEFAA) for soil microbes, which is a more realistic estimation of soil microbial NUE compared to the NUE estimated by analytical methods. We compare analytical and numerical approaches for two forest soils; suggest improvements of the experimental work for future studies; and conclude that: i) FAA mineralization might be as equally an important rate limiting step for gross N mineralization as peptide depolymerization rate is, because about half of all depolymerized peptide N is consecutively being mineralized; and that ii) FAA mineralization and FAA 20 immobilization rates should be used for assessing NUEFAA.
|
|
| 7. |
- Andresen, Louise C., 1974, et al.
(författare)
-
Simultaneous quantification of depolymerization and mineralization rates by a novel 15N tracing model
- 2016
-
Ingår i: SOIL. - : Copernicus GmbH. - 2199-398X. ; 2, s. 433-442
-
Tidskriftsartikel (refereegranskat)abstract
- The depolymerization of soil organic matter, such as proteins and (oligo-)peptides, into monomers (e.g. amino acids) is currently considered to be the rate-limiting step for nitrogen (N) availability in terrestrial ecosystems. The mineralization of free amino acids (FAAs), liberated by the depolymerization of peptides, is an important fraction of the total mineralization of organic N. Hence, the accurate assessment of peptide depoly- merization and FAA mineralization rates is important in order to gain a better process-based understanding of the soil N cycle. In this paper, we present an extended numerical 15 N tracing model Ntrace , which incorporates the FAA pool and related N processes in order to provide a more robust and simultaneous quantification of de- polymerization and gross mineralization rates of FAAs and soil organic N. We discuss analytical and numerical approaches for two forest soils, suggest improvements of the experimental work for future studies, and conclude that (i) when about half of all depolymerized peptide N is directly mineralized, FAA mineralization can be as important a rate-limiting step for total gross N mineralization as peptide depolymerization rate; (ii) gross FAA mineralization and FAA immobilization rates can be used to develop FAA use efficiency (NUEFAA), which can reveal microbial N or carbon (C) limitation.
|
|
| 8. |
- Holmstrup, Martin, et al.
(författare)
-
Long-term and realistic global change manipulations had low impact on diversity of soil biota in temperate heathland
- 2017
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- In a dry heathland ecosystem we manipulated temperature (warming), precipitation (drought) and atmospheric concentration of CO2 in a full-factorial experiment in order to investigate changes in below-ground biodiversity as a result of future climate change. We investigated the responses in community diversity of nematodes, enchytraeids, collembolans and oribatid mites at two and eight years of manipulations. We used a structural equation modelling (SEM) approach analyzing the three manipulations, soil moisture and temperature, and seven soil biological and chemical ariables. The analysis revealed a persistent and positive effect of elevated CO2 on litter C:N ratio. After two years of treatment, the fungi to bacteria ratio was increased by warming, and the diversities within oribatid mites, collembolans and nematode groups were all affected by elevated CO2 mediated through increased litter C:N ratio. After eight years of treatment, however, the CO2-increased litter C:N ratio did not influence the diversity in any of the four fauna groups. The number of significant correlations between treatments, food source quality, and soil biota diversities was reduced from six to three after two and eight years, respectively. These results suggest a remarkable resilience within the soil biota against global climate change treatments in the long term.
|
|
| 9. |
- Jansen-Willems, Anne B., et al.
(författare)
-
Long-term elevation of temperature affects organic N turnover and associated N2O emissions in a permanent grassland soil
- 2016
-
Ingår i: SOIL. - : Copernicus GmbH. - 2199-3971 .- 2199-398X. ; 2, s. 601-614
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract. Over the last century an increase in mean soil surface temperature has been observed, and it is predicted to increase further in the future. In order to evaluate the legacy effects of increased temperature on both nitrogen (N) transformation rates in the soil and nitrous oxide (N2O) emissions, an incubation experiment and modelling approaches were combined. Based on previous observations that gross N transformations in soils are affected by long-term elevated-temperature treatments we hypothesized that any associated effects on gaseous N emissions (e.g. N2O) can be confirmed by a change in the relative emission rates from various pathways. Soils were taken from a long-term in situ warming experiment on temperate permanent grassland. In this experiment the soil temperature was elevated by 0 (control), 1, 2 or 3 C (four replicates per treatment) using IR (infrared) lamps over a period of 6 years. The soil was subsequently incubated under common conditions (20 C and 50% humidity) and labelled as NO15 3 NH4 Gly, 15NO3NH4 Gly or NO3NH4 15N-Gly. Soil extractions and N2O emissions were analysed using a 15N tracing model and source-partitioning model. Both total inorganic N (NO3 CNHC 4 ) and NO3 contents were higher in soil subjected to the C2 and C3 C temperature elevations (pre and post-incubation). Analyses of N transformations using a 15N tracing model showed that, following incubation, gross organic (but not inorganic) N transformation rates decreased in response to the prior soil warming treatment. This was also reflected in reduced N2O emissions associated with organic N oxidation and denitrification. Furthermore, a newly developed source-partitioning model showed the importance of oxidation of organic N as a source of N2O. In conclusion, long-term soil warming can cause a legacy effect which diminishes organic N turnover and the release of N2O from organic N and denitrification.
|
|
| 10. |
- Rütting, Tobias, 1977, et al.
(författare)
-
Nitrogen cycle responses to elevated CO2 depend on ecosystem nutrient status
- 2015
-
Ingår i: Nutrient Cycling in Agroecosystems. - : Springer Science and Business Media LLC. - 1385-1314 .- 1573-0867. ; 101:3, s. 285-294
-
Tidskriftsartikel (refereegranskat)abstract
- Nitrogen (N) limitation of terrestrial ecosystems is a crucial factor for predicting how these ecosystems respond and feedback to climate change. Nitrogen availability for plants in terrestrial ecosystems depends on the internal soil N cycle and inputs to the ecosystem via biological N-2 fixation. We reviewed the effect of elevated atmospheric CO2 concentrations (eCO(2)) on gross soil N transformations to advance our understanding of ecosystem responses to eCO(2). Overall, neither gross mineralization nor gross nitrification was altered by eCO(2). However, emerging from ecosystem specific analysis, we propose a new conceptual model for eCO(2) effects on gross mineralization based on ecosystem nutrient status: gross mineralization is only stimulated in N limited ecosystems, but unaffected in phosphorus limited ecosystems. Moreover, the ratio of ammonium oxidation to immobilization is decreased under eCO(2), indicating a tighter N cycle with reduced ecosystem N losses. This new conceptual model on N cycle responses to eCO(2) should be tested in the future in independent experiments and it provides a new concept for refining mechanistic models of ecosystem responses to climate change.
|
|
