Response of the herbaceous layer to natural disturbance in North American forests

2004 ◽  
Vol 82 (9) ◽  
pp. 1273-1283 ◽  
Author(s):  
Mark R Roberts
Keyword(s):  
North American ◽  
Natural Disturbance ◽  
Anthropogenic Disturbances ◽  
Tree Canopy ◽  
Natural Disturbances ◽  
Herbaceous Layer ◽  
Response Factors ◽  
Full Spectrum ◽  
Long Term Studies

Most work on the disturbance ecology of North American forests has focused on the tree canopy and woody understory, with little consideration of the herbaceous layer. Understanding how this species-rich and ecologically important layer responds to natural disturbances is needed as a guide for conservation. As a framework for this review, selected natural disturbances common to North American forests are evaluated in terms of a three-axis model of disturbance severity: percentage of tree canopy removed, percentage of understory vegetation removed, and percentage of forest floor and soil removed or disrupted. Eight factors, which control herbaceous-layer response, are linked to the three axes; these factors vary in dominance, depending on disturbance type and severity. The relative importances of different species' regeneration mechanisms also vary along severity gradients. The disturbance-severity model, along with the linked response factors and regeneration mechanisms, provide a framework for evaluating impacts of both natural and anthropogenic disturbances. Long-term studies of herbaceous-layer response to disturbance are needed, particularly mechanistic studies that focus on the relative importance of the eight factors controlling response. The conceptual model proposed herein needs to be tested across the full spectrum of severity levels. Finally, comparisons between natural and anthropogenic disturbances are needed.Key words: disturbance, forests, herbaceous layer, life-history characteristics, succession, understory.

Can forest management based on natural disturbances maintain ecological resilience?

2006 ◽  
Vol 36 (9) ◽  
pp. 2285-2299 ◽  
Author(s):  
C Ronnie Drever ◽  
Garry Peterson ◽  
Christian Messier ◽  
Yves Bergeron ◽  
Mike Flannigan
Keyword(s):  
Nutrient Dynamics ◽  
Multiple Scales ◽  
Critical Role ◽  
Natural Disturbance ◽  
Ecological Resilience ◽  
Natural Disturbances ◽  
Resilience Theory ◽  
Managed Forests ◽  
Spatial And Temporal Scales

Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance.

Implications of Long-Term Studies of Three Model Preschool Programs for Head Start

2008 ◽  
Author(s):  
Lawrence J. Schweinhart ◽  
Elena V. Malofeeva ◽  
Lawrence J. Schweinhart ◽  
Michelle M. Englund ◽  
Arthur J. Reynolds ◽  
...  
Keyword(s):  
Head Start ◽  
Preschool Programs ◽  
Long Term Studies

Primary varicose veins

Phlebologie ◽  
2010 ◽  
Vol 39 (03) ◽  
pp. 133-137
Author(s):  
H. Partsch
Keyword(s):  
Varicose Veins ◽  
Compression Therapy ◽  
Daily Practice ◽  
Clinical Severity ◽  
Compression Stockings ◽  
Primary Varicose Veins ◽  
The Cost ◽  
Convincing Data ◽  
Long Term Studies

SummaryBackground: Compression stockings are widely used in patients with varicose veins. Methods: Based on published literature three main points are discussed: 1. the rationale of compression therapy in primary varicose veins, 2. the prescription of compression stockings in daily practice, 3. studies required in the future. Results: The main objective of prescribing compression stockings for patients with varicose veins is to improve subjective leg complaints and to prevent swelling after sitting and standing. No convincing data are available concerning prevention of progression or of complications. In daily practice varicose veins are the most common indication to prescribe compression stockings. The compliance depends on the severity of the disorder and is rather poor in less severe stages. Long-term studies are needed to proof the cost-effectiveness of compression stockings concerning subjective symptoms and objective signs of varicose veins adjusted to their clinical severity. Conclusion: Compression stockings in primary varicose veins are able to improve leg complaints and to prevent swelling.

Habitat fragmentation causes collapse of kelp recruitment

2020 ◽  
Vol 648 ◽  
pp. 111-123
Author(s):  
C Layton ◽  
MJ Cameron ◽  
M Tatsumi ◽  
V Shelamoff ◽  
JT Wright ◽  
...  
Keyword(s):  
Habitat Fragmentation ◽  
Patch Size ◽  
Life Stage ◽  
Extended Period ◽  
Anthropogenic Disturbances ◽  
Anthropogenic Sources ◽  
Kelp Forests ◽  
Natural Disturbances ◽  
Short Term ◽  
Turf Algae

Kelp forests in many regions are experiencing disturbance from anthropogenic sources such as ocean warming, pollution, and overgrazing. Unlike natural disturbances such as storms, anthropogenic disturbances often manifest as press perturbations that cause persistent alterations to the environment. One consequence is that some kelp forests are becoming increasingly sparse and fragmented. We manipulated patch size of the kelp Ecklonia radiata over 24 mo to simulate persistent habitat fragmentation and assessed how this influenced the demography of macro- and microscopic juvenile kelp within the patches. At the beginning of the experiment, patch formation resulted in short-term increases in E. radiata recruitment in patches <1 m2. However, recruitment collapsed in those same patches over the extended period, with no recruits observed after 15 mo. Experimental transplants of microscopic and macroscopic juvenile sporophytes into the patches failed to identify the life stage impacted by the reductions in patch size, indicating that the effects may be subtle and require extended periods to manifest, and/or that another life stage is responsible. Abiotic measurements within the patches indicated that kelp were less able to engineer the sub-canopy environment in smaller patches. In particular, reduced shading of the sub-canopy in smaller patches was associated with proliferation of sediments and turf algae, which potentially contributed to the collapse of recruitment. We demonstrate the consequences of short- and longer-term degradation of E. radiata habitats and conclude that habitat fragmentation can lead to severe disruptions to kelp demography.

Diatoms and aquatic palynomorphs in the sediments of the Eurasian Arctic seas and their significance for paleooceanological investigations in the Arctic

2019 ◽  
pp. 246-251
Author(s):  
Yelena I. Polyakova ◽  
Yekaterina I. Novichkova ◽  
Tatiana S. Klyuvitkina ◽  
Elizaveta A. Agafonova ◽  
Irina M. Kryukova
Keyword(s):  
Bering Sea ◽  
Surface Sediments ◽  
Sea Water ◽  
The Arctic ◽  
Marginal Filter ◽  
Arctic Seas ◽  
Hydrological Parameters ◽  
The Arctic Ocean ◽  
Long Term Studies

Presented the results of long-term studies of diatoms and aquatic palynomorphs in surface sediments of the Arctic seas and the possibility of their use for the reconstructions of paleocirculation water masses, advection of Atlantic and Bering sea water into the Arctic ocean, changes in the river runoff to the seas, sedimentary processes in the marginal filter of the largest rivers, seasonal sea ice cover and other hydrological parameters.

Aspects of the Evolution of the Romanian Tourists’ Preferences Concerning the Domestic Tourist Destinations

2019 ◽  
Vol 10 (1) ◽  
pp. 21-28
Author(s):  
Aniela Bălăcescu ◽  
Radu Șerban Zaharia
Keyword(s):  
Logistic Model ◽  
Local Level ◽  
Medium Term ◽  
Tourist Destinations ◽  
Tourism Management ◽  
Production And Consumption ◽  
On Line ◽  
The One ◽  
Long Term Studies

Abstract Tourist services represent a category of services in which the inseparability of production and consumption, the inability to be storable, the immateriality, and last but not least non-durability, induces in tourism management a number of peculiarities and difficulties. Under these circumstances the development of medium-term strategies involves long-term studies regarding on the one hand the developments and characteristics of the demand, and on the other hand the tourist potential analysis at regional and local level. Although in the past 20 years there has been tremendous growth of on-line booking made by household users, the tour operators agencies as well as those with sales activity continue to offer the specific services for a large number of tourists, that number, in the case of domestic tourism, increased by 1.6 times in case of the tour operators and by 4.44 times in case of the agencies with sales activity. At the same time, there have been changes in the preferences of tourists regarding their holiday destinations in Romania. Started on these considerations, paper based on a logistic model, examines the evolution of the probabilities and scores corresponding to the way the Romanian tourists spend their holidays on the types of tourism agencies, actions and tourist areas in Romania.

Planning a system of permanent sample plots for integrated long-term studies of community-based forest management

1970 ◽  
Vol 16 (2) ◽  
pp. 3-11 ◽  
Author(s):  
H Meilby ◽  
L Puri ◽  
M Christensen ◽  
S Rayamajhi
Keyword(s):  
Forest Management ◽  
Key Words ◽  
Research Note ◽  
Managed Forests ◽  
Community Based ◽  
Permanent Sample Plots ◽  
Long Term Studies

To monitor the development of four community-managed forests, networks of permanent sample plots were established in 2005 at sites in Chitwan, Kaski and Mustang Districts, Nepal. This research note documents the procedures used when preparing for establishment of the plot networks, evaluates the applied stratification of the forest on the basis of data gathered in pilot surveys conducted in the early 2005, and provides a discussion on the implications of the choices made. Key words: Community-managed forests; permanent sample plots; stratification; allocation; estimates Banko Janakari Vol.16(2) 2006 pp.3-11

Budapest airport air quality long-term studies by remote sensing with DOAS and FTIR with focus upon runway emissions

2007 ◽  
Author(s):  
Klaus Schäfer ◽  
Gregor Schürmann ◽  
Carsten Jahn ◽  
Candy Matuse ◽  
Herbert Hoffmann ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Air Quality ◽  
Long Term Studies
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