Population structures and individual performances of Trillium grandiflorum in hedgerow and forest habitats

Abstract

In agricultural landscapes, linear habitats, such as hedgerows at field margins increase structural connectivity among forest patches, potentially providing dispersal corridors for forest herbs. The spatial structure of linear habitats, however, also results in edge effects and perturbations that can influence the individual and population performance of forest plants. This study compares the stage structure and components of growth and reproduction of 14 Trillium grandiflorum populations in hedgerows and forests. Hedgerow Trillium tended to grow faster and, when mature, produced more flowers and more ovules per flowers than forest Trillium, a pattern possibly associated to differences in nutrients and light availability between the two habitats. Seed production and germination rate, however, did not differ between hedgerows and forests. At the population level, seedlings and juveniles were proportionally less abundant in hedgerows than in forests. Although well-established plants can thrive in hedgerows, reduced recruitment may eventually limit the capacity to establish new populations and therefore hamper migration along hedgerow-corridors. Considering the strategies by which plants persist in linear habitats becomes particularly relevant at a time when species are expected to be much in need of dispersal corridors because of climatic stress.

Seed dormancy in Trillium camschatcense (Melanthiaceae) and the possible roles of light and temperature requirements for seed germination in forests

“…Relatively few species have higher germination in darkness than in light (Baskin and Baskin, 1998). Studies on seeds with MPD that do not have double dormancy have found high percentages of germination in light (Hidayati et al, 2000a, 2000b, 2001; Baskin et al, 2002; Kondo et al, 2002, 2004, 2005, 2006; Walck and Hidayati, 2004b; Karlsson and Milberg, 2007; Kondo and Sato, 2007; Vandelook et al, 2007, 2009; Phartyal et al, 2009a, b; Vandelook and Assche, 2008, 2009). In seeds with double dormancy, studies on six plant species were conducted either in pots or (presumably) outdoors (Barton and Schroeder, 1942; Barton, 1944; Whigham, 1974), and we assume that seeds were in darkness while buried in soil.…”

“…Many aspects of the biology of T. camschatcense have been studied: phenology, seasonal growth pattern (Ohara and Kawano, 2005), genetic diversity, breeding system (Ohara et al, 1996, 2006; Ohara and Kawano, 2005; Kubota et al, 2008), resource allocation (Tomimatsu and Ohara, 2006b), and seed dispersal by myrmecochory (Ohara and Kawano, 2005). The seedling stage of T. camschatcense is highly affected by edge effects (Tomimatsu and Ohara 2004, 2006a) as is that of other Trillium species (Jules and Rathcke, 1999; Schmucki and de Blois, 2009). Tomimatsu and Ohara (2004) found that the density of T. camschatcense seedlings was considerably lower at the edge than in the interior of the forest, and they suggested that microclimatic conditions associated with the edge environment might be deleterious to seed germination.…”

Prediction of changes in the occurrence of forest herbs in hedgerow networks along a climate gradient in north-western Europe

“…The ranking was based on the results of studies previously conducted in this area and on related research from other countries (see above). It is known, for example, that hedgerows on average provide plants with a higher relative irradiance, higher soil nitrogen and lower soil moisture compared to forests (Schmucki and de Blois 2009). Therefore high Ellenberg values for light and nitrogen and low values for soil moisture were transformed into low rank scores.…”

Contrasting effects of different landscape characteristics on population growth of a perennial forest herb

“…In 2009-2010, the effects of forest cover on vital rates were smaller, resulting in smaller contributions (Fig. The larger light availability in these sites could favor resource acquisition and accumulation by adults in these areas (Schmucki and De Blois 2009), enhancing their re-growth ability and long-term survival. The LTRE contributions also indicated that in both yearly intervals, the increase in l with forest edge Figure 3.…”

“…However, we also found an increased probability of survival of reproductive adults in edge-rich sites. The larger light availability in these sites could favor resource acquisition and accumulation by adults in these areas (Schmucki and De Blois 2009), enhancing their re-growth ability and long-term survival. Overall, the effects of increased edge length tended to have a positive effect on vital rates.…”