2 results
Recruitment biology of cleavers (Galium spp.) populations in western Canada
- Andrea De Roo, Eric Tozzi, Dilshan I. Benaragama, Christian J. Willenborg
-
- Journal:
- Weed Science / Volume 70 / Issue 6 / November 2022
- Published online by Cambridge University Press:
- 29 September 2022, pp. 669-679
-
- Article
-
- You have access Access
- Open access
- HTML
- Export citation
-
Two species of cleavers, Galium aparine L. and Galium spurium L., are known to inhabit croplands in western Canada. The latter is the more abundant of the two species. An increased abundance of these species over the most recent decades warrants a more comprehensive understanding of their developmental phenology and the cause of this increase. This study aimed to identify the base temperature and emergence characteristics of Galium spp. across different populations from western Canada. A thermal gradient plate experiment was conducted using five G. spurium populations collected from various Saskatchewan (SK) and Alberta (AB) locations. One known G. aparine reference sample was also included. A common garden experiment was conducted using the six Galium spp. populations to determine emergence characteristics. The base germination temperature identified was 2 C for all populations of G. spurium and 4 C for G. aparine. The median germination temperature for G. aparine was 8.34 C, whereas G. spurium had a similar median germination temperature of 6.5 C. Despite similar germination characteristics, the field emergence study revealed differences between populations’ initiation of emergence (150 to 250 growing degree days [GDD]) and time to 50% emergence (275 to 470 GDD) in spring. Highly variable emergence among years and populations within the year (200 to 600 GDD in 2013 and 100 to 200 GDD in 2014) were observed during fall, probably due to differences in moisture availability. Cumulative emergence among populations in fall was very low (1% to 9%) compared with spring emergence (2% to 17%). Overall, this study provides evidence for a low base temperature and differences in emergence periodicity among populations, both of which may be significant factors contributing to the seasonal success of this species.
7 - Nitrogen processes in aquatic ecosystems
- from Part II - Nitrogen processing in the biosphere
-
- By Patrick Durand, INRA, France, Lutz Breuer, Institute for Landscape Ecology and Resources Management, Penny J. Johnes, University of Reading, Gilles Billen, University Pierre & Marie Curie, Andrea Butturini, University of Barcelona, Gilles Pinay, University of Birmingham, Hans van Grinsven, Netherlands Environmental Assessment Agency, Josette Garnier, UMR Sisyphe UPMC ' CNRS, Michael Rivett, University of Birmingham, David S. Reay, University of Edinburgh, Chris Curtis, University College London Environmental Change Research Centre, Jan Siemens, University of Bonn Institute of Crop Science and Resource Conservation – Soil Sciences, Stephen Maberly, Centre for Ecology and Hydrology, Øyvind Kaste, Norwegian Institute for Water Research, Christoph Humborg, Stockholm University, Roos Loeb, B-ware Research Centre, Jeroen de Klein, Wageningen University and Research Centre, Josef Hejzlar, Institute of Hydrobiology, Nikos Skoulikidis, Pirkko Kortelainen, Finnish Environment Institute, Ahti Lepistö, Finnish Environment Institute, Richard Wright, Norwegian Institute for Water Research
- Edited by Mark A. Sutton, NERC Centre for Ecology and Hydrology, UK, Clare M. Howard, NERC Centre for Ecology and Hydrology, UK, Jan Willem Erisman, Gilles Billen, Albert Bleeker, Peringe Grennfelt, Hans van Grinsven, Bruna Grizzetti
-
- Book:
- The European Nitrogen Assessment
- Published online:
- 16 May 2011
- Print publication:
- 14 April 2011, pp 126-146
-
- Chapter
- Export citation
-
Summary
Executive summary
Nature of the problem
Freshwater ecosystems play a key role in the European nitrogen (N) cycle, both as a reactive agent that transfers, stores and processes N loadings from the atmosphere and terrestrial ecosystems, and as a natural environment severely impacted by the increase of these loadings.
Approaches
This chapter is a review of major processes and factors controlling N transport and transformations for running waters, standing waters, groundwaters and riparian wetlands.
Key findings/state of knowledge
The major factor controlling N processes in freshwater ecosystems is the residence time of water, which varies widely both in space and in time, and which is sensitive to changes in climate, land use and management.
The effects of increased N loadings to European freshwaters include acidification in semi-natural environments, and eutrophication in more disturbed ecosystems, with associated loss of biodiversity in both cases.
An important part of the nitrogen transferred by surface waters is in the form of organic N, as dissolved organic N (DON) and particulate organic N (PON). This part is dominant in semi-natural catchments throughout Europe and remains a significant component of the total N load even in nitrate enriched rivers.
In eutrophicated standing freshwaters N can be a factor limiting or co-limiting biological production, and control of both N and phosphorus (P) loading is often needed in impacted areas, if ecological quality is to be restored.