Morphological and population responses to deer grazing for herbaceous species in Nara Park, western Japan

Abstract

To quantify the morphological and population responses of plants to grazing by deer, we conducted two deer-exclusion experiments in Nara Park, western Japan. The first experiment assessed the morphological differences in 10 traits of two species with erect growth (Oxalis corymbosa and Cyperus brevifolius. var. leiolepis) and two species with prostrate growth (Oxalis corniculata and Hydrocotyle maritima) between shoots inside and outside of the exclosures at the end of a growing season (late autumn). The size and weight of the leaves, stems and reproductive organs of the four perennials were significantly smaller outside the exclosures. The degree of size reduction was highest for an erect species, O. corymbosa, compared with the other three species, and was similar between the two prostrate species. The second experiment, using 11 erect species and 15 prostrate species, demonstrated that erect species exhibited greater reduction in leaf length and cover in the grazing environments compared with prostrate species, suggesting that the erect species suffered more from grazing. In conclusion, many of the plant species reduced their size under grazing pressure during the growing season, but the nature of the changes depended on the growth form of each species. It remains unclear whether the morphological reduction was an adaptive response to grazing.

Distance-dependent shifts in net effects by an unpalatable nettle on a palatable plant species

“…Mett. ex Kuhn, and Urtica thunbergiana) were particularly abundant in this environments (Suzuki et al, 2009). These tall species are unpalatable to deer because of their physical and chemical defences (Kato et al 2008).…”

Morphological adaptation of a palatable plant to long-term grazing can shift interactions with an unpalatable plant from facilitative to competitive

“…Meanwhile, a long evolutionary history of grazing often selects for small plant phenotypes (Detling and Painter 1983;McKinney and Fowler 1991;McNaughton 1984;Polley and Detling 1988;Fahnestock and Detling 2000;Kotanen and Bergelson 2000;Ishikawa et al 2006;Suzuki 2008;Suzuki et al 2009). While the small plants experience reduced grazing damage, they tend to have reduced competitive abilities (Briske and Anderson 1992;Hartvigsen and McNaughton 1995;Osem et al 2004;McGuire and Agrawal 2005).…”

Selection on plant height through the interplay of landscape and large herbivores

“…As such, significant selection is exerted on the size of plants within these environments (Ruiz et al 2006). Individuals from numerous grass and forb species have been observed to exhibit lower stature from grazed populations than conspecifics from non‐grazed populations (Carman and Briske 1985, Suzuki et al 2009). Many of such studies cultivated plants starting from seed so as to tease apart genetic variation from phenotypic plasticity, and demonstrated that genetic differentiation is indeed commonly involved (Linhart and Grant 1996, Suzuki 2008).…”