| 1. |
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| 2. |
- Eckersten, Henrik, et al.
(författare)
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Comparison of monocultures of perennial sow-thistle and spring barley in estimated shoot radiation-use and nitrogen-uptake efficiencies
- 2010
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Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 60, s. 126-135
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Tidskriftsartikel (refereegranskat)abstract
- Shoot radiation-use efficiency (RUE) and nitrogen-uptake efficiency (UPE) of monocultures of perennial sow-thistle (Sonchus arvensis L.) and spring barley (Hordeum distichon L.) were quantified to assess the significance of these traits for the relative performance of the two species. RUE and UPE were derived for shoot growth and N uptake by calibrating a mechanistic model to above-ground biomass and N observations in an outdoor box experiment, conducted during two years at two soil nitrogen levels in Central Sweden. The model, which is driven by climate variables, predicts above-ground biomass and nitrogen increment as a function of intercepted radiation, temperature, and nitrogen availability. Observed values of leaf area and root development are used as input. Shoot RUE in S. arvensis was only 56% of the RUE in spring barley (1.35 and 2.40 g dry weight MJ-1, respectively). On the other hand, shoot UPE in S. arvensis at low N supply during early season was seven times higher than in barley (0.07 and 0.01 d-1, respectively). For S. arvensis, UPE was higher at the low soil nitrogen level than at high level, while the reverse was found for barley, at a given amount of biomass per area unit. We suggest that the higher shoot UPE in S. arvensis at low nitrogen supply, in comparison with the low UPE of annual small grain crops at low soil nitrogen levels, is a contributing cause for the observed increase in S. arvensis in organic farming.
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| 3. |
- Eckersten, Henrik, et al.
(författare)
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Crop yield trends in relation to temperature indices and a growth model
- 2010
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Ingår i: Climate Research. - : Inter-Research Science Center. - 0936-577X .- 1616-1572. ; 42, s. 119-131
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Tidskriftsartikel (refereegranskat)abstract
- Annual variability and trends in winter wheat yields were evaluated for relationships to climate in 6 long-term experiments (in total 1915-2005) and regionally in 3 counties (1965-2008) in southern and central Sweden. The annual yield was predicted as function of a climate index and year. Alternative indices were used based on either monthly temperatures or yield predicted by a simple weather-driven crop growth simulation model. The main results were as follows. (1) The yield predictions were better for regions than for the long-term experiments. (2) The time variable accounted for more of the yield trend in regions than in the experiments, and more in southern than in central Sweden. (3) The models based on a simple temperature index were often better yield predictors than the growth model. (4) The relations to winter temperatures became gradually weaker after ca. 1970. (5) The yield relation to simple temperature indices differed between locations, similarly for experimental and regional yields. (6) The strongest influence of climate was estimated by means of the growth model predictions of regional yields in Gotland County. (7) The fraction of regional yield trends (1965-1996; ranging from 57 to 90 kg ha(-1) yr(-1)) that could be attributed to climate was estimated greatest in the Gotland region (27 to 64%). For climate change assessments of winter wheat yield in central Sweden, the growth model considering temperature, radiation and water conditions during spring and summer would also need to include processes of overwintering.
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| 4. |
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| 5. |
- Eckersten, Henrik, et al.
(författare)
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Modelling species competition in mixtures of perennial sow-thistle and spring barley based on shoot radiation use efficiency
- 2011
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Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 61, s. 739-746
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Tidskriftsartikel (refereegranskat)abstract
- Perennial sow-thistle (Sonchus arvensis L.) may be a serious weed in organic and conventional farming. To assess the effects of radiation acquisition and resource allocation on competitive ability, S. arvensis was grown together with spring barley (Hordeum distichon L.) in six mixtures in a replacement series with initial above-ground biomass proportions of S. arvensis ranging from 2% to 96%. A one-season experiment was made outdoors in boxes in Uppsala, Sweden, at a low level of nitrogen supply (5 g N m(-2)). The study tested the predictability of shoot biomass of each species based on two principal assumptions: (i) growth model parameters derived from species in monocultures could be applied in mixtures, and (ii) radiation in the mixed stand was partitioned between species proportional to their leaf area. Calibration of two parameters, for scaling of shoot radiation use efficiency and radiation partitioning respectively, were the base for the evaluation. When the coefficients were close to unity, which was the case for all mixtures dominated by barley, and for one of the mixtures with high proportion of S. arvensis in the early season, observed and predicted shoot biomass coincided well. For the evenly composed mixtures, total shoot biomass was underestimated (the scaling coefficient of shoot radiation use efficiency was > 1), whereas the relative composition among species was predicted well. In the late season the principal model assumptions were not applicable to S. arvensis, likely due to increasing root allocation not accounted for in the model. Sonchus arvensis in mixtures with high proportions was planted early in relation to sowing of barley, which resulted in a comparably late development stage of S. arvensis. Consequently the relation between species development stages varied with species composition suggesting a need to introduce effects of differences in development stage into the model.
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| 6. |
- Eckersten, Henrik, et al.
(författare)
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Radiation-use efficiency in leys: influences of growth period and clover proportion
- 2009
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Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 59, s. 465-474
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Tidskriftsartikel (refereegranskat)abstract
- Acquisition of carbohydrates and their partitioning to storage organs are decisive attributes for the persistence of perennial leys. It was therefore of interest to analyse radiation-use efficiency (RUE) and root allocation (br) in one-, two-, and three-year-old red clover-grass leys as functions of growth period (first and second growth, ley age), proportion of clover, and site properties (location, soil type, humus content). By calibrating RUE and br, the ley yields simulated with a growth model were adjusted to the values observed during two consecutive years at 33 organic farms located in the southern and the northwestern coastal regions of Finland. Driving variables of the simulations were daily measurements of weather. RUE declined from the first to the second growth and further with ley age, while its variability increased. The value of br decreased from the first to the second growth, and was positively correlated with RUE. The high variability of RUE between different sites, and the absence of correlations between site properties and RUE, were mainly attributable to differences in overwintering and regrowth conditions. Early measurements of above-ground biomass subsequent to overwintering and cutting, and the inclusion of site-specific measurements of soil properties would have increased the general validity of the calibrated parameter values. RUE correlated positively with proportion of clover. However, the increase of the proportion of clover from the first to the second growth was not strong enough to balance the concurrent decline of RUE. With increasing ley age there were two concurrent and reinforcing patterns, namely a decrease in proportion of clover and in RUE. Thus, both symbiotic N fixation and vigour of perennial red clover-grass leys declined with ley age. With regards to RUE, however, three-year-old leys were still productive.
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| 7. |
- Torssell, Bengt, et al.
(författare)
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Modelling below-ground shoot elongation and emergence time of Sonchus arvensis shoots
- 2015
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Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 65, s. 582-588
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Tidskriftsartikel (refereegranskat)abstract
- To assess emergence time of shoots from roots of the perennial weed Sonchus arvensis as a function of root weight and soil temperature, we performed an experiment to which linear models were fitted. Root parts of three distinct initial weight classes were grown in pots in the dark at constant temperatures of 4, 8 and 18 degrees C, respectively. During five harvest occasions, prior to or at shoot emergence, below-ground shoot length was measured. Root planting depth (3, 10 and 17 cm) did not influence shoot elongation rate. The below-ground shoot elongation rate for a given initial root-weight class was estimated from the observations to be constant with time, but to increase with temperature and initial root weight. By expressing shoot length for a given day as a linear function of the number of days from planting date, and elongation rate as a linear function of temperature, we calculated (1) the accumulated temperature-sum requirement for emergence, (2) emergence time for variable temperature conditions in a clay soil using soil temperature recordings at 5-cm depth for seven seasons in central Sweden and (3) the emergence time at three elevated temperature levels and initial root-weight classes. The accumulated temperature-sum requirements for below-ground shoots of S. arvensis to reach soil surface are independent of temperature regime for roots of a given initial weight but lower for heavier than lighter roots. The temperature limit for below-ground shoot elongation to occur is about 2.0-2.5 degrees C. Between-year variations in temperature under field conditions cause larger variation to emergence time than initial root-weight differences. An average temperature increase of 3 degrees C would cause an earlier emergence time, in the same range (about 2 weeks) as the difference between the earliest and latest year in the current weather conditions.
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| 8. |
- Torssell, Bengt, et al.
(författare)
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Modelling Sonchus arvensis root biomass allocation to below-ground shoot and fine root growth
- 2016
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Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 66, s. 476-482
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Tidskriftsartikel (refereegranskat)abstract
- Below-ground (bg) shoot emergence rates of Sonchus arvensis are dependent on temperature and root weight. However, it is unknown to what extent this is due to a root depletion rate that depends on initial root weight, or due to differences in resource allocation to fine root and bg shoot growth. To resolve this, we retrieved data from an experiment in which plants were grown in the dark at constant temperature (4 degrees C, 8 degrees C, and 18 degrees C) and harvested prior to or at shoot emergence. A dynamic mass-balance model, in which biomass of the initial root was allocated to bg shoot and fine root daily growth, and where respiration took place from all tissues, was used. The relative depletion rate of root biomass (RDR; d(-1)) and fraction of the depleted biomass allocated to bg shoots (SFRR) were estimated and calibrated to observed biomass. The RDR increased with initial root weight and temperature and SFFR was highest for light roots and lowest for heaviest roots, whereas the rest was allocated to fine root biomass. The length-to-biomass ratio of bg shoots decreased with initial root weight. Under betweenyear weather variations (2004-2010), the reduction in root biomass during the coldest AprilMay was simulated to be over 12 days delayed compared with the warmest spring. The influence of biomass allocation on bg shoot elongation of heavier roots was thus stimulated by a larger fraction of root biomass being depleted, but counteracted by a smaller fraction of it allocated into bg shoot elongation, compared with lighter roots. The complexity of shoot emergence based on root depletion estimates may be a reason why predictions based on only an accumulated root weight-specific temperature sum, as proposed by a previous study, are expected to be less uncertain than those based on root depletion estimates.
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| 9. |
- Verwijst, Theo, et al.
(författare)
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Weight loss in overwintering below-ground parts of Sonchus arvensis under current and temperature-elevated climate scenarios in Sweden
- 2013
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Ingår i: Weed Research. - : Wiley. - 0043-1737 .- 1365-3180. ; 53, s. 21-29
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Tidskriftsartikel (refereegranskat)abstract
- Weight loss in overwintering below-ground parts of perennial weeds has been attributed to respiration, but neither its temperature dependence nor its relevance for biomass dynamics under changing climate conditions have been investigated. In two experiments, we quantified weight loss of the perennial weed Sonchus arvensis, by measuring weight changes over time of sprouting roots in dark rooms at temperatures of 4, 8 and 18 degrees C. Dry weight loss rates were 0.47, 0.64 and 1.47% day-1 at 4, 8 and 18 degrees C, respectively, giving a half-life time of 149, 110 and 47 days, respectively. A factor by which weight loss rates increase for every 10 degrees rise in temperature (Q10) was equal to about 2.3. Cumulative weight loss may comprise >40% of the below-ground biomass during overwintering periods. Applying weight loss rates and Q10 to elevated soil temperature projections showed that losses during winter seasons in central Sweden will remain basically constant, the effect of increased weight loss at higher temperatures being balanced by shorter winters. This implies that need for control of S. arvensis in a changing climate will persist, but that shorter winter seasons will provide a longer time window for control of S. arvensis prior to sowing crops.
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