|Emery, Keith - UNIV. OF GEORGIA - ATHENS|
|English, James - UNIV. OF MISSOURI|
Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 1999
Publication Date: N/A
Interpretive Summary: Birdsfoot trefoil is a plant that is grown as a high-quality feed for livestock. Birdsfoot trefoil plants are perennial, but persistent stands of trefoil are comprised of new and old plants, because natural reseeding accounts for new seedlings to replace plants that die. With new and old plants in any stand of birdsfoot trefoil, researchers look at stands as a dynamic population; i.e., the ages of the plants and their condition are always changing. Weather, disease, and other stresses can influence the condition of the plant population and the mix of new and old plants. In Missouri, birdsfoot trefoil population survival often is limited primarily by fungal diseases that can cause serious damage to birdsfoot trefoil leaves and shoots. The objective of our research was to test changes observed in a population of birdsfoot trefoil that was either clipped to remove foliage or left unclipped. The information derived from studying the clipping effects during establishment and mature plant stages was used to develop a mathematical model to assist in explaining how a management treatment like mowing can effect the age mix of a birdsfoot trefoil stand. We learned that during the establishment stages, the death of seedlings and young plants was high, and this is important because these plants are too young to produce seed that could replace dying plants. In contrast, once a plant survived past the establishment phase, the amount of death of the remaining plants in the population decreased, and they were able to produce seeds to provide replacement plants. The impact of these findings will allow producers to develop better management practices that lead to persistent and productive stands of birdsfoot trefoil.
Technical Abstract: The population dynamics of perennial plant populations are influenced by numerous factors including weather and disease. The objective of this study was to model the population dynamics of birdsfoot trefoil (Lotus corniculatus), a perennial legume, in relation to clipping treatments. The plant growth stages represented in the model were seeds, seedlings, mature vegetative, and reproductive plants. Environmental conditions in the fiel vary from year to year and such models are useful for evaluating population behavior in relation to patterns of weather or disease development. In Missouri, birdsfoot trefoil population survival often is limited by leaf and shoot blight caused primarily by Rhizoctonia solani. Two phases of population growth were evaluated in clipped and unclipped birdsfoot trefoil stands. Establishment-phase populations were characterized by relatively high mortality and low reproduction. Elasticity analysis indicated that growth of these populations was most sensitive to the survival of vegetative plants. Mature vegetative plants and seeds comprised the majority of surviving individuals in clipped and unclipped populations, respectively; however, establishment-phase populations in both management treatments tended toward extinction. Populations in the post establishment-phase of growth were characterized by relatively low mortality and high reproduction. Population growth in these populations was most sensitive to seed production, and most individuals in these populations were in the seed stage of development.