Premium
Colonization of limestone grasslands by woody plants: the role of seed limitation and herbivory by vertebrates
Author(s) -
Laborde J.,
Thompson K.
Publication year - 2013
Publication title -
journal of vegetation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 115
eISSN - 1654-1103
pISSN - 1100-9233
DOI - 10.1111/j.1654-1103.2012.01463.x
Subject(s) - grassland , seedling , biology , herbivore , germination , seed dispersal , biological dispersal , resistance (ecology) , woody plant , grazing , colonization , agronomy , botany , ecology , population , demography , sociology
Questions Why are some woody species able to colonize open grassland while others are not? How important are seed limitation and grazing by vertebrates for the colonization of grasslands by woody species? What are the effects of the grassland turf on seedling emergence, growth and survival? How frequently are seedlings killed by grazers, and how different are woody species in their resistance to herbivory? Location Limestone grassland of C ressbrook D ale, D erbyshire, in the P eak D istrict N ational P ark, UKMethods The emergence, growth and survival of the seedlings of eight scrub species were evaluated using sheep exclosures and paired open plots in the grassland. The grassland turf was clipped in half the area of each plot, to determine the effect on seedling establishment. Seeds of the selected species were sown in the field during autumn 2001 and followed through spring 2004. Results Dense grassland turf reduces the germination of some woody species and also slows growth of all seedlings. Seeds germinate better in short turf and, having germinated, the most important factor for seedling survival is resistance to browsing, which varies widely among species. The two most successful colonizers – C orylus avellana and C rataegus monogyna – have different routes to establishment. C orylus has very successful seed dispersal and is moderately resistant to herbivory. C rataegus is less successful in dispersal but its seedlings are very resistant to browsing. Other species, such as P runus spinosa , are as resistant to browsing as C rataegus , but are limited by seed availability. Conclusions Grazing by vertebrates exerts a dual control on scrub invasion. Livestock maintains a dense, compact turf that interferes with the seed germination and seedling growth of woody plants. Grazing also gives rise to differential survival of woody species as a function of their ability to resist browsing. The density and composition of the heterogeneous patchwork of developing scrub vary continually in accordance with the differential success of species in seed dispersal into the open grassland and the mortality of woody seedlings caused by the temporal and spatial variability of grazing.