Plant Population Dynamics and Conservation in Wooded Hay-Meadows – Effects of Intensified Management

• Main Author: Wallin, Lotta
• Format: Doctoral Thesis
• Language: English
• Published: Uppsala universitet, Ekologisk botanik 2007
• Subjects: Biology; coordinates; demographic model; dispersal; hay-meadow; Hypochoeris maculata; litter; management; Polygala amarella; stochastic modelling; Succisa pratensis; Biologi
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7743; http://nbn-resolving.de/urn:isbn:978-91-554-6829-3

The decrease in number and area of managed hay-meadows over the last century, in combination with the reduction of traditional management, threatens the biodiversity connected to these habitats. I experimentally examined how management intensity affected meadow characteristics and long-term population viability of three vascular plant species in wooded hay-meadows on the Swedish island of Gotland in the Baltic Sea. I discovered that intensified management (extra raking and/or extra mowing) reduced the amount of litter and biomass, even in well-managed meadows. The effects of intensified management on population growth rate varied among species. Deterministic demographic models revealed that intensified management increased population growth rate in Succisa pratensis. Stochastic modelling confirmed this; all meadows displayed larger projected population sizes 50 years into the future with intensified management. Polygala amarella responded with lower growth rates in raked plots, a consequence of the plant’s morphology, which makes it prone to being pulled out by raking. Hypochoeris maculata had population growth rates close to unity, and showed no response to an increase in management. Examination of the life-history characteristics of Polygala amarella showed that the species’ strategy is aimed at reproduction and fast growth, which is in contrast to the other two species, with their success relying on the survival of older plants. The species-specific responses to management show that several species should be considered when evaluating management practices for conservation of semi-natural grasslands. Furthermore, I suggest that data on stage distributions alone may not be sufficient for identifying threatened populations. In a study of artificial dispersal between meadows, I found that establishment was twice as successful for planted plug-plants compared to sown seeds. Both methods may be useful for introducing or augmenting meadow populations, depending on access to seed sources and possibilities to nurse plants. An electronic coordinate measurement device for gathering location data to be used in demographic studies was developed. In the field, the device proved to be a simple and reliable method for locating individuals in permanent plots.