| Titre : |
Population dynamics and functional traits of annual plants - a comparative study on how rare and common arable weeds persist in agroecosystems |
| Type de document : |
Imprimé |
| Auteurs : |
Arne Saatkamp |
| Editeur : |
Regensburg : Universität Regensburg |
| Année de publication : |
2009 |
| Importance : |
220 p. |
| Langues : |
Anglais (eng) |
| Catégories : |
[CBNPMP-Thématique] Banque de semences dans le sol
[CBNPMP-Thématique] Climax, succession plantes, dynamique végétation
[CBNPMP-Thématique] Mauvaises herbes
|
| Résumé : |
The continuing industrialisation of agriculture leads to important changes in composition and decrease of plant diversity in European agro-ecosystems. Remnants of traditional agriculture conserved many but declining rare cereal weeds in South Eastern France. Conservation efforts for them are hampered by the little evidence on which differences in their biology are related to population persistence, abundance and rarity among species. Data on longevity of seeds in the soil, an important factor for annual plant population dynamics, can help to prioritise conservation efforts. The main aim of the present thesis was therefore to study the relations between long-term population persistence, abundance and rarity together with life history, physiologic and seed traits in order to identify species most at risk. We studied annual plants -simple and rapidly reacting- in arable fields -an environment with rapid and drastic changes. First, we analysed plant α- and β-diversity in vineyards at different spatial scales, using additive diversity partitioning. We identified habitat types, intensity of agriculture, landscape type and land use history as main determinants for plant diversity and maintenance of species of conservation interest. Nearly all target species are known to be cereal weeds; we therefore restricted the study on rare and common relatives of annual cereal weeds for the remainder of the study. Soil seed banks are known to be an important life stage in annual plants for population dynamics. Therefore, we did a comparative seed burial experiment with 38 species to study soil seed survival and levels of dormancy. The striking differences with previous data motivated us to re-evaluated current methods. This showed that the soil seed bank persistence estimates from seedling emergence method and derived seed longevity index (L.I.) are correlated to seed production but not to soil seed mortality. Third, we re-analysed soil seed survival with data from germination experiments. Light requirement, degree of dormancy, reaction to diurnally fluctuating temperatures and seed size were related to survival of seeds in the soil giving insights into how long-lived species can stay ungerminated while buried. Fourth, we compared data on soil seed survival, degree of dormancy, seed size and number, specific leaf area, leaf dry matter content and pollen:ovule ratio (P/O) to data on local population extinction and turnover from 1983 to 2005 and 2006, in an approach using phylogenetically independent contrasts (PICs). This revealed that soil seed survival was a major correlate of extinction on the long time step and that this could not be explained by directional changes in edaphic factors. Finally, we studied two axes of rarity, local population size and regional frequency of populations and their relation to biological and life history traits. This yielded few results consistent among different dates. An exception was soil seed survival; probably in relation with increased effective population size. Both analyses -on rarity and on regression- emphasised also the role of P/O –a monitor for gene exchange via pollen- for rarity and regression of annual cereal weeds. In conclusion, species with high soil seed mortality and low P/O are most at risk of local extinction and should be considered in conservation efforts. The germination ecology together with the soil seed survival indicated that temporal variability and unfavourable years can trigger annual cereal weed diversity through storage effect. However, there are striking differences between species. For the most regressing species seed dispersal via uncleaned seed material is necessary to conserve them at the long run in rapidly changing agro-ecosystems. |
| En ligne : |
https://epub.uni-regensburg.de/14995/ |
| Permalink : |
https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=81174 |
Saatkamp, Arne
, 2009.
Population dynamics and functional traits of annual plants - a comparative study on how rare and common arable weeds persist in agroecosystems.
Universität Regensburg, Regensburg.
220 pp.
|
Population dynamics and functional traits of annual plants - a comparative study on how rare and common arable weeds persist in agroecosystems (2009)
