Understory Vegetation (understory + vegetation)

Distribution by Scientific Domains

Selected Abstracts

Effect of Hydrologic Restoration and Lonicera maackii Removal on Herbaceous Understory Vegetation in a Bottomland Hardwood Forest

Rebecca M. Swab
Abstract Amur honeysuckle (Lonicera maackii (Rupr.) Herder), a large deciduous shrub from China, has invaded many forests in eastern/central United States. The species was removed by cutting and herbicide application from a recently hydrologically restored section of a bottomland hardwood forest in central Ohio, and the response of understory plants, especially herbaceous species, was measured. Plots were established in uncleared and cleared sections, and percent cover of each herbaceous understory species was estimated monthly. One season after several years of Lonicera removal efforts, no significant association was discovered between percentage of Lonicera cover and total understory species abundance. There was, however, a direct correlation between elevation and honeysuckle abundance; L. maackii abundance was negatively associated with low elevations, likely due to hydrologic factors. Plant species diversity (H) and richness (s) increased with elevation but were not significantly different on plots with honeysuckle removal (H = 0.86 ± 0.08 vs. 0.78 ± 0.09 and s = 4.4 ± 0.19 vs. 4.2 ± 0.2 species/m2, respectively) despite the fact that understory light levels measured by densiometer were significantly higher (,= 0.003) in cleared versus uncleared sections. Native and invasive species were found in similar proportions in the two sections, and significant sprouting and regrowth of L. maackii were observed throughout the cleared section. Although the removal of L. maackii altered the characteristics of the plant species assemblage, the value of this management remains questionable in the years immediately following treatment. [source]

Inter- and intraspecific variation of stemflow production from Fagus grandifolia Ehrh. (American beech) and Liriodendron tulipifera L. (yellow poplar) in relation to bark microrelief in the eastern United States,

ECOHYDROLOGY, Issue 1 2010
J. Toland Van Stan II
Abstract Stemflow is a spatially concentrated hydrologic input at the tree base. Prior work has documented the differential effects of stemflow from a wide range of plant species on ecohydrological processes, such as the alteration of soil pH and spatial patterning of understory vegetation. No known work has coupled stemflow yield with high resolution measurements of bark microrelief that definitively ascribe differential stemflow yield to bark microrelief. As such, our research objectives were to: (1) correlate inter- and intraspecific variation in stemflow yield to a quantitative bark microrelief scale and (2) compare and contrast stemflow for two co-occurring deciduous species,Fagus grandifolia Ehrh. (American beech) and Liriodendron tulipifera L. (yellow poplar). Using a newly developed instrument to measure bark microrelief, namely the LaserBarkÔ automated tree measurement system, in combination with an 11-month stemflow database for a broadleaved deciduous forest in eastern North America, it was found that bark microrelief values significantly differed between the two species [P = 0·000, F (1,19) = 49·32]. Funneling ratios [P = 0·000, H (1, 990) = 339·20] and stemflow generation [P = 0·000, H (1, 990) = 146·75] also significantly differed between the two species. Our results indicate that bark microrelief exerts a considerable effect on stemflow yield from F. grandifolia and L. tulipifera, possibly affecting water and solute flux to the forest floor. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Russell J. Anderson
ABSTRACT: An extensive group of datasets was analyzed to examine factors affecting widths of streams and rivers. Results indicate that vegetative controls on channel size are scale dependent. In channels with watersheds greater than 10 to 100 km2, widths are narrower in channels with thick woody bank vegetation than in grass lined or nonforested banks. The converse is true in smaller streams apparently due to interactions between woody debris, shading, understory vegetation, rooting characteristics, and channel size. A tree based statistical method (regression tree) is introduced and tested as a tool for identifying thresholds of response and interpreting interactions between variables. The implications of scale dependent controls on channel width are discussed in the context of stable channel design methods and development of regional hydraulic geometry curves. [source]

Realized gene flow within mixed stands of Quercus robur L. and Q. petraea (Matt.) L. revealed at the stage of naturally established seedling

Abstract The estimates of contemporary gene flow assessed based on naturally established seedlings provide information much needed for understanding the abilities of forest tree populations to persist under global changes through migration and/or adaptation facilitated by gene exchange among populations. Here, we investigated pollen- and seed-mediated gene flow in two mixed-oak forest stands (consisting of Quercus robur L. and Q. petraea [Matt.] Liebl.). The gene flow parameters were estimated based on microsatellite multilocus genotypes of seedlings and adults and their spatial locations within the sample plots using models that attempt to reconstruct the genealogy of the seedling cohorts. Pollen and seed dispersal were modelled using the standard seedling neighbourhood model and a modification,the 2-component seedling neighbourhood model, with the later allowing separation of the dispersal process into local and long-distance components. The 2-component model fitted the data substantially better than the standard model and provided estimates of mean seed and pollen dispersal distances accounting for long-distance propagule dispersal. The mean distance of effective pollen dispersal was found to be 298 and 463 m, depending on the stand, while the mean distance of effective seed dispersal was only 8.8 and 15.6 m, which is consistent with wind pollination and primarily seed dispersal by gravity in Quercus. Some differences observed between the two stands could be attributed to the differences in the stand structure of the adult populations and the existing understory vegetation. Such a mixture of relatively limited seed dispersal with occasional long distance gene flow seems to be an efficient strategy for colonizing new habitats with subsequent local adaptation, while maintaining genetic diversity within populations. [source]

Understory vegetation response to mechanical mastication and other fuels treatments in a ponderosa pine forest

Jeffrey M. Kane
Abstract Questions: What influence does mechanical mastication and other fuel treatments have on: (1) canopy and forest floor response variables that influence understory plant development; (2) initial understory vegetation cover, diversity, and composition; and (3) shrub and non-native species density in a second-growth ponderosa pine forest. Location: Challenge Experimental Forest, northern Sierra Nevada, California, USA. Methods: We compared the effects of mastication only, mastication with supplemental treatments (tilling and prescribed fire), hand removal, and a control on initial understory vegetation response using a randomized complete block experimental design. Each block (n=4) contained all five treatments and understory vegetation was surveyed within 0.04-ha plots for each treatment. Results: While mastication alone and hand removal dramatically reduced the midstory vegetation, these treatments had little effect on understory richness compared with control. Prescribed fire after mastication increased native species richness by 150% (+6.0 species m2) compared with control. However, this also increased non-native species richness (+0.8 species m2) and shrub seedling density (+24.7 stems m2). Mastication followed by tilling resulted in increased non-native forb density (+0.7 stems m2). Conclusions: Mechanical mastication and hand removal treatments aided in reducing midstory fuels but did not increase understory plant diversity. The subsequent treatment of prescribed burning not only further reduced fire hazard, but also exposed mineral soil, which likely promoted native plant diversity. Some potential drawbacks to this treatment include an increase of non-native species and stimulation of shrub seed germination, which could alter ecosystem functions and compromise fire hazard reduction in the long-term. [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]