Forest Herbs (forest + herb)

Distribution by Scientific Domains

Selected Abstracts

Antagonistic effects of seed dispersal and herbivory on plant migration

Mark Vellend
Abstract The two factors that determine plant migration rates , seed dispersal and population growth , are generally treated independently, despite the fact that many animals simultaneously enhance plant migration rate via seed dispersal, and decrease it via negative effects of herbivory on population growth. Using extensive empirical data, we modelled the antagonistic effects of seed dispersal and herbivory by white-tailed deer on potential migration rates of Trillium grandiflorum, a forest herb in eastern North America. This novel antagonistic interaction is illustrated by maximum migration rates occurring at intermediate, but low herbivory (< 15%). Assuming herbivory < 20% and favourable conditions for population growth during post-glacial migration, seed dispersal by deer can explain rates of migration achieved in the past, in contrast to previous models of forest herb migration. However, relatively unfavourable conditions for population growth and increasingly intense herbivory by deer may compromise plant migration in the face of present and future climate change. [source]

Unravelling the effects of temperature, latitude and local environment on the reproduction of forest herbs

GLOBAL ECOLOGY, Issue 6 2009
P. De Frenne
ABSTRACT Aim, To investigate the effect of temperature, latitude and local environment on the reproductive traits of widespread perennial forest herbs to better understand the potential impacts of rising temperatures on their population dynamics and colonization capacities. Location, Six regions along a latitudinal gradient from France to Sweden. Methods, Within each region, we collected data from three to five populations of up to six species. For each species, several variables were recorded in each region (temperature, latitude) and population (local abiotic and biotic environmental variables), and seed production and germination were estimated. Resource investment in reproduction (RIR) was quantified as seed number seed mass, while germinable seed output (GSO) was expressed as seed number germination percentage. We performed linear regression and mixed effect models to investigate the effects of temperature (growing degree hours), latitude and local abiotic and biotic environment on RIR and GSO. Results, Temperature and latitude explained most of the variation in RIR and GSO for early flowering species with a northerly distribution range edge (Anemone nemorosa, Paris quadrifolia and Oxalis acetosella). Reproduction of the more southerly distributed species (Brachypodium sylvaticum, Circaea lutetiana and Primula elatior), in contrast, was independent of temperature/latitude. In the late summer species, B. sylvaticum and C. lutetiana, variation in RIR and GSO was best explained by local environmental variables, while none of the investigated variables appeared to be related to reproduction in P. elatior. Main conclusions, We showed that reproduction of only two early flowering, northerly distributed species was related to temperature. This suggests that the potential reproductive response of forest herbs to climate warming partly depends on their phenology and distribution, but also that the response is to some extent species dependent. These findings should be taken into account when predictions about future shifts in distribution range are made. [source]

Forest herb colonization of postagricultural forests in central New York State, USA

Rhine Singleton
Summary 1,The recovery of forest vegetation following abandonment of agriculture was followed by surveying forest herbs in central New York State at 25 sites where postagricultural forest occurred directly adjacent to old-woods (forest that has never been ploughed). 2,The abundance, richness and diversity of 50 forest herbs were on average lower in postagricultural forests than in old-woods. 3,Thirty of 39 forest herbs that were found in at least four stands were less frequent (number of plots present out of 60) in postagricultural forests than in old-woods. Three species (Aster divaricatus, Dryopteris intermedia and Polystichum acrostichoides) had significantly higher frequency in old-woods, while none was significantly more common in postagricultural forests. 4,Although differences among species in their frequency in the two forest types were not strongly related to dispersal mode, species with rapid clonal expansion were significantly more frequent in postagricultural stands. 5,Several species that were less frequent in postagricultural forests than in old-woods showed decreases in density in postagricultural forests with increasing distance from the adjacent old-woods. [source]

Temperature conditions control embryo growth and seed germination of Corydalis solida (L.) Clairv., a temperate forest spring geophyte

PLANT BIOLOGY, Issue 6 2009
F. Vandelook
Abstract Spring is often the most suitable period for seedling establishment of temperate woodland species. Different physiological mechanisms resulting in spring emergence have evolved in seeds of such plants. The aim of this study was to determine the requirements for breaking dormancy and for seed germination of the European perennial spring geophyte Corydalis solida (Fumariaceae). Ripe seeds of C. solida contain an underdeveloped embryo, consisting of no more than a clump of cells. As a consequence, the embryo has to differentiate and grow to a critical length before germination can occur. In nature, seeds are dispersed in spring, while growth of the embryo starts in the autumn and continues in winter. Germination starts in late winter, immediately after embryo growth is completed, resulting in seedling emergence in the following spring. Experiments in controlled conditions showed that temperature is the main factor controlling dormancy and germination. Incubation at autumn temperatures (15/6 C; 20/10 C) for at least 8 weeks is required to initiate embryo growth, while a transfer to 5 C is needed for completion of embryo growth and germination. Growth of the embryo of C. solida occurs at different temperatures over an extended period, a feature typical of temperate forest herbs. Our results indicate that the dormancy mechanism in seeds of C. solida is very similar to mechanisms in other Corydalis species studied thus far, suggesting that stasis in the dormancy trait has occurred. [source]

Land-use legacies in a central Appalachian forest: differential response of trees and herbs to historic agricultural practices

James M. Dyer
Abstract Question: Are contemporary herb and tree patterns explained by historic land use practices? If so, are observed vegetation patterns associated with life-history characteristics, soil properties, or other environmental variables? Location: Southeastern Ohio, USA. Methods: Using archival records, currently forested sites were identified with distinct land use histories: cultivated, pasture (but not plowed), and reference sites which appear to have never been cleared. Trees were recorded by size and species on twenty 20 m 20 m plots; percent cover was estimated for each herb species in nested 10 m 10 m plots. Environmental characteristics were noted, and soil samples analysed for nutrient availability and organic matter. Nonmetric multidimensional scaling ordination was performed separately on both tree and herb datasets to graphically characterize community composition among plots. Life-history traits were investigated to explain observed compositional differences. Results: Vegetation patterns were explained by current environmental gradients, especially by land-use history. Cultivated and pasture sites had similar tree composition, distinct from reference sites. Herb composition of pasture and reference sites was similar and distinct from cultivated sites, suggesting the ,tenacity' of some forest herbs on formerly cleared sites. Tilling removes rhizomatous species, and disfavors species with unassisted dispersal. These life-history traits were underrepresented on cultivated sites, although ant-dispersed species were not. Conclusions: Historic land-use practices accounted for as much variation in species composition as environmental gradients. Furthermore, trees and herbs responded differently to past land-use practices. Life-history traits of individual species interact with the nature of disturbance to influence community composition. [source]

Understory vegetation response to thinning disturbance of varying complexity in coniferous stands

Adrian Ares
Abstract Question: Can augmented forest stand complexity increase understory vegetation richness and cover and accelerate the development of late-successional features? Does within-stand understory vegetation variability increase after imposing treatments that increase stand structural complexity of the overstory? What is the relative contribution of individual stand structural components (i.e. forest matrix, gaps, and leave island reserves) to changes in understory vegetation richness? Location: Seven study sites in the Coastal Range and Cascades regions of Oregon, USA. Methods: We examined the effects of thinning six years after harvest on understory plant vascular richness and cover in 40- to 60-year-old forest stands dominated by Douglas-fir (Pseudotsuga menziesii). At each site, one unthinned control was preserved and three thinning treatments were implemented: low complexity (LC, 300 trees ha,1), moderate complexity (MC, 200 trees ha,1), and high complexity (HC, variable densities from 100 to 300 trees ha,1). Gaps openings and leave island reserves were established in MC and HC. Results: Richness of all herbs, forest herbs, early seral herbs and shrubs, and introduced species increased in all thinning treatments, although early seral herbs and introduced species remained a small component. Only cover of early seral herbs and shrubs increased in all thinning treatments whereas forest shrub cover increased in MC and HC. In the understory, we found 284 vascular plant species. After accounting for site-level differences, the richness of understory communities in thinned stands differed from those in control stands. Within-treatment variability of herb and shrub richness was reduced by thinning. Matrix areas and gap openings in thinned treatments appeared to contribute to the recruitment of early seral herbs and shrubs. Conclusions: Understory vegetation richness increased 6 years after imposing treatments, with increasing stand complexity mainly because of the recruitment of early seral and forest herbs, and both low and tall shrubs. Changes in stand density did not likely lead to competitive species exclusion. The abundance of potentially invasive introduced species was much lower compared to other plant groups. Post-thinning reductions in within-treatment variability was caused by greater abundance of early seral herbs and shrubs in thinned stands compared with the control. Gaps and low-density forest matrix areas created as part of spatially variably thinning had greater overall species richness. Increased overstory variability encouraged development of multiple layers of understory vegetation. [source]