scholarly journals Analyzing long-term impacts of ungulate herbivory on forest-recruitment dynamics at community and species level contrasting tree densities versus maximum heights

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ursula Nopp-Mayr ◽  
Susanne Reimoser ◽  
Friedrich Reimoser ◽  
Frederik Sachser ◽  
Leopold Obermair ◽  
...  
Keyword(s):  
Tree Species ◽  
Life Stage ◽  
Tree Regeneration ◽  
Species Level ◽  
Ecosystem Dynamics ◽  
Stem Density ◽  
Maximum Height ◽  
Ungulate Herbivory ◽  
Over Time

AbstractHerbivores are constitutive elements of most terrestrial ecosystems. Understanding effects of herbivory on ecosystem dynamics is thus a major, albeit challenging task in community ecology. Effects of mammals on plant communities are typically explored by comparing plant densities or diversity in exclosure experiments. This might over-estimate long-term herbivore effects at community levels as early life stage mortality is driven by a multitude of factors. Addressing these challenges, we established a set of 100 pairs of ungulate exclosures and unfenced control plots (25 m2) in mixed montane forests in the Alps in 1989 covering a forest area of 90 km2. Investigations ran until 2013. Analogous to the gap-maker–gap-filler approach, dynamically recording the height of the largest trees per tree species in paired plots with and without exclosures might allow for assessing herbivore impacts on those individuals with a high probability of attaining reproductive stages. We thus tested if recording maximum heights of regenerating trees would better reflect effects of ungulate herbivory on long-term dynamics of tree regeneration than recording of stem density, and if species dominance patterns would shift over time. For quantifying the effects of ungulate herbivory simultaneously at community and species level we used principle response curves (PRC). PRCs yielded traceable results both at community and species level. Trajectories of maximum heights yielded significant results contrary to trajectories of total stem density. Response patterns of tree species were not uniform over time: e.g., both Norway spruce and European larch switched in their response to fencing. Fencing explained about 3% of the variance of maximum tree heights after nine years but increased to about 10% after 24 years thus confirming the importance of long-term surveys. Maximum height dynamics of tree species, addressed in our study, can thus reflect local dominance of tree species via asymmetric plant competition. Such effects, both within and among forest patches, can accrue over time shaping forest structure and composition.

Long-term effects of stump removal and tree species composition on the diversity and structure of soil fungal communities

2020 ◽  
Vol 96 (5) ◽  
Author(s):  
Dixi Modi ◽  
Suzanne Simard ◽  
Jean Bérubé ◽  
Les Lavkulich ◽  
Richard Hamelin ◽  
...  
Keyword(s):  
Species Composition ◽  
Fungal Community ◽  
Tree Species ◽  
Management Practice ◽  
Tree Regeneration ◽  
Root Disease ◽  
Fungal Communities ◽  
Tree Species Composition ◽  
The Impact

ABSTRACT Stump removal is a common forest management practice used to reduce the mortality of trees affected by the fungal pathogen-mediated root disease, Armillaria root rot, but the impact of stumping on soil fungal community structure is not well understood. This study analyzed the long-term impact of stumping and tree species composition on the abundance, diversity and taxonomic composition of soil fungal communities using internal transcribed spacer (ITS) marker-based DNA metabarcoding in a 48-year-old trial at Skimikin, British Columbia. A total of 108 samples were collected from FH (fermented and humus layers), and soil mineral horizons (A and B) from stumped and unstumped plots of six tree species treatments (pure stands and admixtures of Douglas-fir, western red-cedar and paper birch). Fungal α-diversity in the A horizon significantly increased with stumping regardless of tree species composition, while β-diversity was significantly affected by stumping in all the horizons. We also observed that the relative abundance of the saprotrophic fungal community declined while that of the ectomycorrhizal fungal community increased with stumping. In conclusion, increase in ectomycorrhizal fungal associations, which are positively associated with tree productivity, suggests that stumping can be considered a good management practice for mitigating root disease and promoting tree regeneration.

Changes in Deadwood and Understory Vegetation 12 Years after Partial and Clearcut Harvesting in Mixedwood Stands of Western Quebec, Canada

2020 ◽  
Vol 66 (3) ◽  
pp. 337-350
Author(s):  
Kobra Maleki ◽  
Benoit Lafleur ◽  
Brian D Harvey ◽  
Marc J Mazerolle ◽  
Nicole J Fenton
Keyword(s):  
Timber Harvesting ◽  
Tree Regeneration ◽  
Understory Vegetation ◽  
Ecosystem Dynamics ◽  
Ecosystem Functions ◽  
Moderate Intensity ◽  
Stem Density ◽  
Natural Ecosystem ◽  
Study Objective ◽  
Understory Plant

Abstract Ecosystem management promotes the integration of knowledge of natural ecosystem dynamics into forest-management planning and practices, and provides a useful framework for understanding and mitigating the impacts of timber harvesting on biodiversity and ecosystem functions. Understory vegetation and deadwood are involved in many ecosystem functions including nutrient and carbon, and tree-regeneration dynamics. The study objective was to compare the 12-year post-treatment effects on forest floor attributes of two intensities of partial harvesting (gap harvesting [62 percent basal area retention; BAR] and diameter-limit harvesting [35 percent BAR]) to clearcutting (10 percent BAR). We quantified the standing and downed deadwood abundance and the understory plant community composition in mixed, northern temperate forests, in western Québec, Canada. Our results suggest that moderate-intensity gap harvesting can best preserve a standing deadwood stem density and a diameter structure comparable to unmanaged stands. Downed deadwood abundance of all diameter classes was not altered, 12 years following the gap harvesting. Finally, understory plant communities in the gap treatment were more similar to those of unmanaged stands than those in diameter-limit and clearcutting treatments. These results illustrate the importance of tree retention levels for the maintenance of deadwood and understory plant species associated with closed-canopy or old-growth forests.

scholarly journals Concerted changes in tropical forest structure and dynamics: evidence from 50 South American long-term plots

2004 ◽  
Vol 359 (1443) ◽  
pp. 421-436 ◽  
Author(s):  
S. L. Lewis ◽  
O. L. Phillips ◽  
T. R. Baker ◽  
J. Lloyd ◽  
Y. Malhi ◽  
...  
Keyword(s):  
Tropical Forest ◽  
Net Primary Productivity ◽  
Basal Area ◽  
Mortality Rates ◽  
Stem Density ◽  
Cross Sectional ◽  
The Cross ◽  
Stem Mortality ◽  
Over Time

Several widespread changes in the ecology of old–growth tropical forests have recently been documented for the late twentieth century, in particular an increase in stem turnover (pan–tropical), and an increase in above–ground biomass (neotropical). Whether these changes are synchronous and whether changes in growth are also occurring is not known. We analysed stand–level changes within 50 long–term monitoring plots from across South America spanning 1971–2002. We show that: (i) basal area (BA: sum of the cross–sectional areas of all trees in a plot) increased significantly over time (by 0.10 ±; 0.04 m 2 ha −1 yr −1 , mean ± 95%CI) as did both (ii) stand–level BA growth rates (sum of the increments of BA of surviving trees and BA of new trees that recruited into a plot); and (iii) stand–level BA mortality rates (sum of the cross–sectional areas of all trees that died in a plot). Similar patterns were observed on a per–stem basis: (i) stem density (number of stems per hectare; 1 hectare is 10 4 m 2 ) increased significantly over time ( 0.94 ± 0.63 stems ha −1 yr −1 ); as did both (ii) stem recruitment rates; and (iii) stem mortality rates. In relative terms, the pools of BA and stem density increased by 0.38 ± 0.15% and 0.18 ± 0.12% yr −1 , respectively. The fluxes into and out of these pools—stand–level BA growth, stand–level BA mortality, stem recruitment and stem mortality rates—increased, in relative terms, by an order of magnitude more. The gain terms (BA growth, stem recruitment) consistently exceeded the loss terms (BA loss, stem mortality) throughout the period, suggesting that whatever process is driving these changes was already acting before the plot network was established. Large long–term increases in stand–level BA growth and simultaneous increases in stand BA and stem density imply a continent–wide increase in resource availability which is increasing net primary productivity and altering forest dynamics. Continent–wide changes in incoming solar radiation, and increases in atmospheric concentrations of CO 2 and air temperatures may have increased resource supply over recent decades, thus causing accelerated growth and increased dynamism across the world's largest tract of tropical forest.

scholarly journals Habitation Sites Influence Tree Community Assemblages in the Great Bear Rainforest, British Columbia, Canada

2022 ◽  
Vol 9 ◽  
Author(s):  
Kyle Schang ◽  
Kieran Cox ◽  
Andrew J. Trant
Keyword(s):  
Community Composition ◽  
Tree Species ◽  
Indigenous Communities ◽  
Sitka Spruce ◽  
Forest Community ◽  
Western Hemlock ◽  
Maximum Height ◽  
Western Redcedar ◽  
Shannon Diversity

Identifying how past human actions have influenced their environment is essential for understanding the ecological factors that structure contemporary ecosystems. Intertidal resource use by Indigenous Peoples for thousands of years has led to habitation sites containing vast shell midden deposits and facilitating long-term impacts on soil chemistry and drainage. Here we examine how these shell middens have impacted various forest metrics, such as species diversity, community composition, canopy height, and regeneration recruitment to determine if forests on habitation sites differ from the surrounding matrix. We surveyed known habitation sites with archeological evidence indicating past year-round human occupation, within the Hakai Lúxvbálís Conservancy on Calvert and Hecate Islands within the Great Bear Rainforest along British Columbia’s Central Coast. Our results demonstrate that habitation sites exhibit lower tree species richness, less relative species abundances, as such, displayed lower Shannon diversity and inverse Simpson values. The composition of tree communities on habitation sites was statistically different, with western hemlock and western redcedar densities increasing on non-habitation sites. Conversely, regeneration diversity at habitation sites was more even and exhibited elevated Shannon diversity and inverse Simpson values. The community composition of regeneration was more consistent among habitation and non-habitation sites; however, western redcedar, western hemlock and Sitka spruce were more abundant at habitation sites. For all tree species, maximum height was higher within the habitation sites; however, this trend was the most notable in western redcedar and Sitka spruce, which increased by an average of 4.8 m relative to non-habitation sites. Collectively, our findings suggest that long-term habitation alters forest community compositions. The landscape alterations within habitation sites promote conditions needed to support diverse, even, and abundant regeneration communities and consequently increase the height of the dominant coastal tree species. Thus, our results offer evidence that long-term influence by Indigenous communities have a persistent influence on coastal forests.

scholarly journals Canopy gaps promote selective stem-cutting by small mammals of two dominant tree species in an African lowland forest: the importance of seedling chemistry

2015 ◽  
Vol 32 (1) ◽  
pp. 1-21 ◽  
Author(s):  
Julian M. Norghauer ◽  
Gregory Röder ◽  
Gaëtan Glauser
Keyword(s):  
Small Mammals ◽  
Tree Species ◽  
Species Difference ◽  
Basal Area ◽  
Tree Regeneration ◽  
Stem Cutting ◽  
Canopy Openness ◽  
Stem Density ◽  
Lowland Forest ◽  
Adult Trees

Abstract:Small mammals can impede tree regeneration by injuring seedlings and saplings in several ways. One fatal way is by severing their stems, but apparently this type of predation is not well-studied in tropical rain forest. Here, we report on the incidence of ‘stem-cutting’ to new, wild seedlings of two locally dominant, canopy tree species monitored in 40 paired forest understorey and gap-habitat areas in Korup, Cameroon following a 2007 masting event. In gap areas, which are required for the upward growth and sapling recruitment of both species, 137 seedlings of the long-lived, light-demanding, fast-growing large tropical tree (Microberlinia bisulcata) were highly susceptible to stem-cutting (83% of deaths) — it killed 39% of all seedlings over a c. 2-y period. In stark contrast, seedlings of the more shade-tolerant, slower-growing tree species (Tetraberlinia bifoliolata) were hardly attacked (4.3%). In the understorey, however, stem-cutting was virtually absent. Across the gap areas, the incidence of stem-cutting of M. bisulcata seedlings showed significant spatial variation that could not be explained significantly by either canopy openness or Janzen–Connell type effects (proximity and basal area of conspecific adult trees). To examine physical and chemical traits that might explain the species difference to being cut, bark and wood tissues were collected from a separate sample of seedlings in gaps (i.e. not monitored for stem-cutting). These analyses suggested that, compared with T. bifoliolata, the lower stem density, higher Mg and K and fatty acid concentrations in bark, and fewer phenolic and terpene compounds in M. bisulcata seedlings made them more palatable and attractive to small-mammal predators, likely rodents. We conclude that selective stem-cutting is a potent countervailing force to the current local canopy dominance of the grove-forming M. bisulcata by limiting the recruitment and abundance of its saplings. Given the ubiquity of gaps and ground-dwelling rodents in pantropical forests, it would be surprising if this form of lethal browsing was restricted to Korup.

scholarly journals Serial invasions can disrupt the time course of ecosystem recovery

2021 ◽  
Author(s):  
Vadim A Karatayev ◽  
Lars G Rudstam ◽  
Alexander Y Karatayev ◽  
Lyubov E Burlakova ◽  
Boris V Adamovich ◽  
...  
Keyword(s):  
Time Course ◽  
Zebra Mussels ◽  
Ecosystem Dynamics ◽  
Ecosystem Recovery ◽  
Ecosystem Impacts ◽  
Quagga Mussels ◽  
Species Invasions ◽  
Invasion Impacts ◽  
Over Time

The impacts of species invasions can subside or amplify over time as ecosystems "adapt" or additional invaders arrive. These long-term changes provide important insights into ecosystem dynamics. Yet studies of long-term dynamics are rare, system-specific, and often confound species impacts with coincident environmental change. We track post-invasion changes shared across ecosystems and multiple decades, quantifying the response of seven key features to quagga and zebra mussels congeners that re-engineer and increasingly co-invade freshwaters. Six polymictic shallow lakes with long-term data sets reveal remarkably similar trends, with the strongest ecosystem impacts occurring within 5-10 years of zebra mussel invasion. Surprisingly, plankton communities then exhibited a partial, significant recovery. This recovery was absent, and impacts of initial invasion amplified, in lakes where quagga mussels outcompeted zebra mussels and more completely depleted phytoplankton. Thus, invasion impacts subside over time but can amplify with serial introductions of competing, even closely similar, taxa.

Enhancing community welfare through improved water quality: a case for applying staggered pollution charges in the river Musi sub-basin of Andhra Pradesh, India

Water Policy ◽  
2005 ◽  
Vol 7 (5) ◽  
pp. 469-483
Author(s):  
Tishya Chatterjee
Keyword(s):  
Andhra Pradesh ◽  
Relevant Literature ◽  
Pollution Prevention ◽  
Economic Benefits ◽  
Environmental Damage ◽  
Marginal Costs ◽  
Community Acceptance ◽  
Level Data ◽  
Over Time

In conditions of severe water-pollution and dormant community acceptance of accumulating environmental damage, the regulator's role goes beyond pollution prevention and more towards remediation and solutions based on the community's long-term expectations of economic benefits from clean water. This paper suggests a method to enable these benefits to become perceptible progressively, through participatory clean-up operations, supported by staggered pollution charges. It analyses the relevant literature on pollution prevention and applies a cost-based “willingness to pay” model, using primary basin-level data of total marginal costs. It develops a replicable demand-side approach imposing charge-standard targets over time in urban-industrial basins of developing countries.

The Short-Term and Long-Term Impacts of Sarbanes-Oxley Act on Composition and Characteristics of Corporate Board of Directors

2015 ◽  
Vol 5 (4) ◽  
Author(s):  
Halil Kaya ◽  
Gaurango Banerjee
Keyword(s):  
Board Composition ◽  
Corporate Boards ◽  
Corporate Accountability ◽  
Corporate Board ◽  
Short Term ◽  
Dual Roles ◽  
Board Characteristics ◽  
Sarbanes Oxley ◽  
Over Time

The paper examines the Sarbanes-Oxley (2002) Acts immediate impact on board composition and characteristics as well as possible reversals in its impact over time. Effects on directors age and tenure are analyzed over the 2001-06 sample period. Female participation in corporate boards is also studied in the pre-SOX and post-SOX periods. The dual roles of directors in being a member of the board as well as serving as either CEO, CFO, Chairman, Co-Chair, Founder, or Lead Director of their respective companies is also examined. We observe a short-term impact of SOX on board compositions due to changes seen in board characteristics between 2001 (pre-SOX), and 2003-05 short-term period (post-SOX). Also, we observe a reversal of board characteristics in 2006 to pre-SOX levels implying that the effects of SOX on board composition were short-lived, and needs to be monitored over time to ensure adherence to corporate accountability guidelines over the long-term.

A Downward Spiral? A Panel Study of Misinformation and Media Trust in Chile

2021 ◽  
pp. 194016122110252
Author(s):  
Sebastián Valenzuela ◽  
Daniel Halpern ◽  
Felipe Araneda
Keyword(s):  
News Media ◽  
Panel Study ◽  
Future Research ◽  
Panel Survey ◽  
Downward Spiral ◽  
The Media ◽  
Media Trust ◽  
People’S Attitudes ◽  
Over Time

Despite widespread concern, research on the consequences of misinformation on people's attitudes is surprisingly scant. To fill in this gap, the current study examines the long-term relationship between misinformation and trust in the news media. Based on the reinforcing spirals model, we analyzed data from a three-wave panel survey collected in Chile between 2017 and 2019. We found a weak, over-time relationship between misinformation and media skepticism. Specifically, initial beliefs on factually dubious information were negatively correlated with subsequent levels of trust in the news media. Lower trust in the media, in turn, was related over time to higher levels of misinformation. However, we found no evidence of a reverse, parallel process where media trust shielded users against misinformation, further reinforcing trust in the news media. The lack of evidence of a downward spiral suggests that the corrosive effects of misinformation on attitudes toward the news media are less serious than originally suggested. We close with a discussion of directions for future research.

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