Understory species interactions in mature boreal mixedwood forests

Botany ◽  
2010 ◽  
Vol 88 (10) ◽  
pp. 912-922 ◽  
Author(s):  
Virginia Chávez ◽  
S. Ellen Macdonald
Keyword(s):  
Environmental Factors ◽  
Species Interactions ◽  
Common Species ◽  
Herbaceous Layer ◽  
Competition Intensity ◽  
Understory Species ◽  
Mixedwood Forests ◽  
Natural Logarithm ◽  
Cornus Canadensis ◽  
Herb Species

We explored interactions among plant growth forms in the understory of mature boreal mixedwood forests in western Canada by investigating the competitive influence of erect shrubs on herbs (forbs and grasses). We established 10 pairs of plots; all erect shrubs were removed in one plot of each pair (removals) and left intact in the other plot (controls). Two years later, we harvested all aboveground biomass of the herbaceous layer (herb biomass: this included graminoids, forbs, trailing shrubs, and species with a woody base but not woody stems) from the 20 plots. We tested for significant differences in understory species biomass and composition between control and removal plots and examined the influence of 25 environmental factors on species composition of the herbaceous layer. Competition intensity was measured by the natural logarithm of response ratio (ln RR) index based on herb biomass. After erect shrub removal, there was a significant increase in herb biomass, mostly due to an increase of the most common species (e.g., Cornus canadensis Linnaeus, Linnaea borealis Linnaeus). The values of competition intensity (ln RR) varied among herb species but were, overall, positive, indicating a release from competition following shrub removal. Composition of the herbaceous layer was significantly different between removal and control plots and was also significantly related to seven environmental factors, which explained 40% of the variation in composition. Our study suggests that there is asymmetric competition for light between erect shrub and herb species in boreal ecosystems.

scholarly journals Histology of the liver of Oligosarcus jenynsii (Ostariophysi, Characidae) from Los Padres Lake, Argentina

2006 ◽  
Vol 96 (2) ◽  
pp. 205-208 ◽  
Author(s):  
Gladys M. Petcoff ◽  
Alcira O. Díaz ◽  
Alicia H. Escalante ◽  
Adriana L. Goldemberg
Keyword(s):  
Environmental Factors ◽  
Portal Vein ◽  
Exocrine Pancreas ◽  
Histological Analysis ◽  
Buenos Aires ◽  
Marine Species ◽  
Common Species ◽  
Pancreatic Tissue ◽  
Buenos Aires Province ◽  
Pancreatic Cells

The liver is an organ notable for its sensitivity to a great variety of environmental factors. It is composed of a parenchyma divided into irregular lobules by the exocrine pancreas or hepatopancreas; the pancreatic cells are arranged around a branch of the portal vein. The hepatocytes are radially arranged in cords around a central sinusoid. The liver histomorphology and the organization of exocrine pancreatic tissue of O. jenynsii (Günther, 1864) is similar to the acinar morphology of many teleosts, including freshwater and marine species. The aim of the present work was to carry out the histological analysis of the liver of Oligosarcus jenynsii, one of the most common species inhabiting Los Padres Lake (Buenos Aires Province, Argentina).

Heat tolerance of rhizomes of several understory species

1983 ◽  
Vol 61 (2) ◽  
pp. 452-457 ◽  
Author(s):  
Marguerite A. Flinn ◽  
Joan K. Pringle
Keyword(s):  
Temperature Tolerance ◽  
Pteridium Aquilinum ◽  
Tolerance Index ◽  
Understory Species ◽  
Chamaedaphne Calyculata ◽  
Cornus Canadensis ◽  
Shoot Number ◽  
Different Temperatures ◽  
Maianthemum Canadense ◽  
Study Sites

Rhizomes of eight understory species: Gaultheria procumbens, Maianthemum canadense, Vaccinium angustifolium, Cornus canadensis, Pteridium aquilinum, Kalmia angustifolia, Chamaedaphne calyculata, and Rhododendron canadense were subjected to treatments of 45, 50, 55 and 60 °C for 5 min in a water bath. Selection of these species for study was based on differences in the depth of the rhizomes, in habitat, and in rhizome morphology. Samples were collected from study sites located near Halifax, in the Nova Scotia Acadian Forest region.Maximum shoot growth occurred at different temperatures for the various species: 45 °C for Cornus canadensis; 50 °C for Chamaedaphne calyculata, R. canadense, and V. angustifolium; 55 °C for G. procumbens and M. canadense. Death occurred at or below 60 °C for most species. For comparative purposes, a temperature tolerance index (TTI) was calculated for each species. The TTI indicated that R. canadense and V. angustifolium showed the greatest tolerance to higher temperatures and that K. angustifolia and P. aquilinum showed the least tolerance. Mean shoot number increased significantly following spring treatments for all species except for Cornus canadensis which showed greater increase following autumn treatments.

scholarly journals Effect of environmental factors on understory species diversity in Southwest Guangxi Excentrodendron tonkinense forests

2019 ◽  
Vol 27 (9) ◽  
pp. 970-983 ◽  
Author(s):  
Tan Yibo ◽  
Shen Wenhui ◽  
Fu Zi ◽  
Zheng Wei ◽  
Ou Zhiyang ◽  
...  
Keyword(s):  
Species Diversity ◽  
Environmental Factors ◽  
Understory Species

scholarly journals SOME MAINE SPECIES OF HALICTUS

1905 ◽  
Vol 37 (8) ◽  
pp. 299-300 ◽  
Author(s):  
John. H. Lovell
Keyword(s):  
British Museum ◽  
Common Species ◽  
Sagittaria Latifolia ◽  
Cornus Canadensis

This paper continues the enumeration of the species of Halictus found in Maine, begun in the Canadian Entomologist for February, 1905, page 40.Halictus similis, Smith, ♀ ♂.— A very common species in this locality, taken from June 19th to August 24th. It visits a great variety of flowers, as the blackberry, Iris versicolor, Sagittaria latifolia, Aralia hispida, Cornus Canadensis, and teh thistles and goldenrods. Professor Cockerell, who has examined Smith's type in the British Museum, states that the Maine specimens agree with it in all the more important characters.

Prescribed fire effects on the herbaceous layer of mixed-oak forests

2005 ◽  
Vol 35 (4) ◽  
pp. 877-890 ◽  
Author(s):  
Todd F Hutchinson ◽  
Ralph EJ Boerner ◽  
Steve Sutherland ◽  
Elaine Kennedy Sutherland ◽  
Marilyn Ortt ◽  
...  
Keyword(s):  
Prescribed Fire ◽  
Fire Effects ◽  
Common Species ◽  
Small Scale ◽  
Oak Forests ◽  
Compositional Variation ◽  
Herbaceous Layer ◽  
Moisture Index ◽  
Burned Areas ◽  
Species Frequencies

In 1994, a multidisciplinary project was established to study the effects of prescribed fire on oak forests in southern Ohio. Here we describe the herbaceous layer response to fires over a 5-year period. In four study sites, treatments imposed were unburned, periodic (1996 and 1999), and annual (1996–1999) fires. Sample plots (n = 108) were stratified by an integrated moisture index. Species' frequencies were recorded annually, and a total of 452 species (97% native) were documented. Though species composition was significantly affected by fire, the effects were shown by ordination to be small in magnitude relative to overall compositional variation. Burned areas developed greater small-scale species richness as grasses, summer forbs, and seed-banking species increased in frequency; however, these changes were also not large in magnitude. Though a few species increased substantially via germination after fire, most common species exhibited frequency increases or decreases of <10% on burned units. Fire effects on vegetation were largely similar between annual and periodic burns and also among integrated moisture index classes. Direct fire effects on vegetation were limited by the dormant-season timing of burns and the resprouting of woody plants. Indirect effects were limited, as fires caused relatively minor changes in forest structure and resource availability in these long-unburned forests.

scholarly journals Sensitivity and resistance of communities: Evaluation on the example of the influence of edaphic, vegetation and spatial factors on soil macrofauna

2017 ◽  
Vol 25 (4) ◽  
Author(s):  
O. V. Zhukov ◽  
O. M. Kunah ◽  
Y. Y. Dubinina
Keyword(s):  
Environmental Factors ◽  
Species Interactions ◽  
Community Response ◽  
Ecological System ◽  
Environmental Stability ◽  
Relative Role ◽  
Soil Macrofauna ◽  
Floodplain Soil ◽  
Main Components

Environmental stability is a multifaceted concept and includes properties such as asymptotic stability, robustness, persistence, variability, elasticity and resistance. Resistance reflects the ability of a community or population to remain in a substantially unaltered state under external influence. The reverse of resistance is sensitivity. This article suggests a way to assess the sensitivity of animal communities to factors of various character and explain sensitivity and resistance of the macrofauna community near the floodplain of the river Dnieper within the "Dnipro-Orelsky" Nature Reserve to the effects of edaphic and plant factors, as well as spatial variables. It is shown that the regulatory impact of environmental factors is refracted through the properties of ecological systems themselves, namely resistance and sensitivity. If an ecological system does not react to changing environmental factors, such a system is indifferent with respect to these factors. In the case of regulatory influence of factors, there may be resistance, sensitivity and the proportionality of the response of the ecological system. The ratio of the specific role of a factor in the variability of a community to the contribution of the main components of the total variability of the attributive space makes it possible to assess the resistance, sensitivity and proportionality of response the ecological system to the action of that factor. If the ratio is >1, then this indicates sensitivity: level of variability of a community is higher than the relative role of environmental factors in the changing of the attributive space. If <1, this indicates resistance: the level of variability of a community is lower than the relative role of environmental factors in the changing of the attributive space. If the ratio =1 (≈1), changes in the community are proportional to the level of the main components of variation in comparison with other components. Ecological factors (both external environmental and internal due to species interactions and which have a neutral nature) cause different levels of community response to their impact. These differences refracted through different aspects of stability of a community can be described using the categories resistance, sensitivity and proportionality. The proposed procedure for quantification of specified properties of sustainability has established that the floodplain soil macrofauna is endowed with resistance to factors that prevail on the level of its variation. However, macrofauna is highly sensitive to minor factors. The community of the soil inhabitants is sensitive to fine-scale variations, which have a neutral nature.

scholarly journals Susceptibility of Eight Herbs to Common Root-Knot Nematodes

2002 ◽  
Vol 20 (2) ◽  
pp. 101-103
Author(s):  
Jerry T. Walker
Keyword(s):  
Meloidogyne Incognita ◽  
Mass Production ◽  
Root Systems ◽  
Common Species ◽  
Egg Mass ◽  
Common Root ◽  
Root Knot Nematode ◽  
Root Knot Nematodes ◽  
Gall Index ◽  
Herb Species

Abstract Eight herb species were inoculated with two common species of root-knot nematode and grown for 2 months in a greenhouse. Root systems were examined for galls and egg mass production. All herb species were susceptible but developed fewer galls and had lower gall indices than Rutgers tomato. Burnet, chives, valerian and winter savory had few galls or low gall indices. Eggs were produced on all. Chamomile had a high gall index. Chicory, parsley, and sorrel had intermediate indices. Herbs were equally susceptible to the southern (Meloidogyne incognita) and peanut root-knot nematodes (M. arenaria), particularly at the highest inoculum densities. Mean dry weights of inoculated herbs were not always significantly less than the non-inoculated plants, suggesting that some herbs may be tolerant to root-knot nematodes.

scholarly journals On the inference of positive and negative species associations and their relation to abundance

2021 ◽  
Author(s):  
Andrew J Rominger
Keyword(s):  
Rare Species ◽  
Species Interactions ◽  
Positive Association ◽  
Common Species ◽  
Type I ◽  
Species Association ◽  
Abundance Data ◽  
Negative Density Dependence ◽  
The Subject ◽  
Species Being

Why do rare species persist in ecosystems? Rare species seem to be at a disadvantage by pure probabilistic odds and perhaps also from poorly adapted species-environment and species-species interactions, though negative density-dependence may help rare species persist. The question of rarity and persistence thus remains unresolved. In a recent paper, Calatayuda et al. (CEA) inferred species-species association networks from spatially replicated abundance data across many taxa and environments. CEA found that rare species were over-represented in positive association networks whereas common species were over-represented in negative association networks. However, the use of abundance and co-occurrence data to infer true species associations is difficult and often inaccurate. This issue arises in no small part because the underlying null models used to infer associations themselves are known to have type I and II error problems in real world applications. Here, I show that the finding of rare species being more represented in positive association networks as found by CEA can be explained by statistical artifacts in the inference of species associations from abundance data. It would therefore not be supported to assign biological interpretations to these findings until more data can be brought to bear on the subject or association types and the persistence of rare species.

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