Natural Disturbance Processes

Author(s):  
Craig Delong ◽  
Philip Burton ◽  
Marten Geertsema
1982 ◽  
Vol 3 (2) ◽  
pp. 89-111 ◽  
Author(s):  
Jack L. Hofman

Nine historic sheepherder camps in northern Wyoming are the basis for this study of intrasite artifact patterning and intersite assemblage variation. The sites all represent a single functional type. Variation between sites results from natural disturbance processes and cultural factors such as idiosyncrasies in occupants' behaviors, differential curation of artifacts, chance occurrences of artifact loss and discard, and length, season and number of occupations. Intrasite patterning is evident and a drop, toss and throw zone can be defined for most sites. This aids in determining the prior location and orientation of the herders' wagons on the sites. The density of the material aids in determining the number of occupations. Assemblage differences between sites are significant and should caution us of potential problems in studies comparing small assemblages from sites such as temporary collecting stations of hunters and gatherers.


ISRN Forestry ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Christine S. Olsen ◽  
Angela L. Mallon ◽  
Bruce A. Shindler

Growing emphasis on ecosystem and landscape-level forest management across North America has spurred an examination of alternative management strategies which focus on emulating dynamic natural disturbance processes, particularly those associated with forest fire regimes. This topic is the cornerstone of research in the Blue River Landscape Study (BRLS) on the Willamette National Forest in the McKenzie River watershed of western Oregon. As scientists and managers work to unravel the ecological and economic implications of disturbance-based forest management, they must also consider public acceptance for such an approach. In this study, citizen opinions from the local attentive public in McKenzie River watershed communities are examined. Results suggest the attentive public has moderate to low levels of knowledge about landscape-level disturbance processes and terms. Further, public confidence in agencies and the information they provide appears to be low, though respondents indicated a somewhat higher level of trust for local agency personnel than agencies as institutions. Overall, respondents display cautious support of disturbance-based management (DBM), but many are still undecided. Findings also demonstrate support may be improved through transparent and inclusive decision-making processes that demonstrate the use of sound science in project planning, frank disclosure of risks and uncertainties, and clear management objectives.


The Holocene ◽  
2020 ◽  
Vol 30 (8) ◽  
pp. 1115-1128
Author(s):  
Valentina Álvarez-Barra ◽  
Thomas Giesecke ◽  
Sonia L. Fontana

Natural disturbance processes such as volcanic eruptions, fire and human activities are important vegetation drivers in north Patagonia. Here, we tested the impact of volcanic ash fall and fire on vegetation composition analysing two sediment records, Lake Avutarda and Lake Bruja, located in the forest-steppe transition at 40°S. In addition, our analysis provides the first account on the history of Nothofagus alpina at its eastern distribution limits. Our results comprise the last 3000 years, indicating the persistence of the vegetation despite evident volcanic activity documented by numerous tephra layers in both records. Eleven fire episodes were identified, while redundancy analysis indicates a non-significant influence of fire activity on the vegetation. The population increase of Nothofagus alpina represents the most important change in vegetation composition in the last three millennia. We speculate that the presumed change in climate, which led to the expansion of Austrocedrus chilensis south of the study area, also caused the increase of Nothofagus alpina populations in the region.


Forests ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 990
Author(s):  
Casey A. Lott ◽  
Michael E. Akresh ◽  
Bridgett E. Costanzo ◽  
Anthony W. D’Amato ◽  
Shengwu Duan ◽  
...  

Forest management planning requires the specification of measurable objectives as desired future conditions at spatial extents ranging from stands to landscapes and temporal extents ranging from a single growing season to several centuries. Effective implementation of forest management requires understanding current conditions and constraints well enough to apply the appropriate silvicultural strategies to produce desired future conditions, often for multiple objectives, at varying spatial and temporal extents. We administered an online survey to forest managers in the eastern US to better understand how wildlife scientists could best provide information to help meet wildlife-related habitat objectives. We then examined more than 1000 review papers on bird–vegetation relationships in the eastern US compiled during a systematic review of the primary literature to see how well this evidence-base meets the information needs of forest managers. We identified two main areas where wildlife scientists could increase the relevance and applicability of their research. First, forest managers want descriptions of wildlife species–vegetation relationships using the operational metrics of forest management (forest type, tree species composition, basal area, tree density, stocking rates, etc.) summarized at the operational spatial units of forest management (stands, compartments, and forests). Second, forest managers want information about how to provide wildlife habitats for many different species with varied habitat needs across temporal extents related to the ecological processes of succession after harvest or natural disturbance (1–2 decades) or even longer periods of stand development. We provide examples of review papers that meet these information needs of forest managers and topic-specific bibliographies of additional review papers that may contain actionable information for foresters who wish to meet wildlife management objectives. We suggest that wildlife scientists become more familiar with the extensive grey literature on forest bird–vegetation relationships and forest management that is available in natural resource management agency reports. We also suggest that wildlife scientists could reconsider everything from the questions they ask, the metrics they report on, and the way they allocate samples in time and space, to provide more relevant and actionable information to forest managers.


Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 755
Author(s):  
Eric B. Searle ◽  
F. Wayne Bell ◽  
Guy R. Larocque ◽  
Mathieu Fortin ◽  
Jennifer Dacosta ◽  
...  

In the past two decades, forest management has undergone major paradigm shifts that are challenging the current forest modelling architecture. New silvicultural systems, guidelines for natural disturbance emulation, a desire to enhance structural complexity, major advances in successional theory, and climate change have all highlighted the limitations of current empirical models in covering this range of conditions. Mechanistic models, which focus on modelling underlying ecological processes rather than specific forest conditions, have the potential to meet these new paradigm shifts in a consistent framework, thereby streamlining the planning process. Here we use the NEBIE (a silvicultural intervention scale that classifies management intensities as natural, extensive, basic, intensive, and elite) plot network, from across Ontario, Canada, to examine the applicability of a mechanistic model, ZELIG-CFS (a version of the ZELIG tree growth model developed by the Canadian Forest Service), to simulate yields and species compositions. As silvicultural intensity increased, overall yield generally increased. Species compositions met the desired outcomes when specific silvicultural treatments were implemented and otherwise generally moved from more shade-intolerant to more shade-tolerant species through time. Our results indicated that a mechanistic model can simulate complex stands across a range of forest types and silvicultural systems while accounting for climate change. Finally, we highlight the need to improve the modelling of regeneration processes in ZELIG-CFS to better represent regeneration dynamics in plantations. While fine-tuning is needed, mechanistic models present an option to incorporate adaptive complexity into modelling forest management outcomes.


1―The effect of natural disturbance on the earth’s magnetic field at any one place is at least twofold: (i) to introduce a regular variation (S d ) periodic within the day and additional to, as well as different in type from (except in a limited region round the magnetic axis pole), the variation associated with quiet days (S q ); and (ii) to suppose on S d irregular changes which may either be of the distinctive type peculiar to large storms especially in low latitudes and generally preceded by the particular type of perturbation known as a sudden commencement, or the changes in the field may be of the apparently nondescript class which comprises an unlimited variety of short-period irregular oscillations. Of these effects of disturbances S d is definitely a local time phenomenon: the sudden commencement with subsequent depression in the horizontal component of the field as definitely follows universal time. For the irregular and unclassified oscillations in moderate and high latitudes a diurnal variation in their incidence has been shown to exist for a few isolated localities. But in the general view it is not known whether this aspect of disturbance is controlled by local or universal time. Nor is it known whether the form of the diurnal variation in disturbance (which variation we shall denote by D) varies in any systematic way with latitude.


1999 ◽  
Vol 29 (4) ◽  
pp. 424-433 ◽  
Author(s):  
Glen W Armstrong

The annual area burned on an 8.6 × 106 ha study area in the boreal mixedwood forest of northeastern Alberta, Canada, was characterised as a serially independent random draw from a lognormal distribution. This characterisation was applied in Monte Carlo simulations, which showed that estimates of the mean annual burn rates, even with long sample periods, are highly imprecise. Monte Carlo simulation was also used to simulate the development of a forest subject to lognormally distributed annual burn rate in an attempt to characterise the equilibrium age-class structure. No equilibrium age-class structure could be identified from the simulation results. The validity of equilibrium age-class distribution models (e.g., the negative exponential and Weibull) and analysis that relies on these models is questioned for forests where the annual burn rate is highly variable.


1999 ◽  
Vol 29 (1) ◽  
pp. 106-114 ◽  
Author(s):  
Quanfa Zhang ◽  
Kurt S Pregitzer ◽  
David D Reed

The General Land Office (GLO) survey notes (1840-1856) were used to examine the interaction among natural disturbance, vegetation type, and topography in the presettlement forests of the Luce District, an ecological unit of approximately 902 000 ha in the Upper Peninsula of Michigan, U.S.A. The surveyors recorded 104 fire and 126 windthrow incidences covering 3.1 and 2.8% of the total length of the surveyed lines, respectively. The rotation periods over the entire landscape were 480 years for fire and 541 years for windthrow, but these varied with vegetation type and topographic position. Fire occurred more frequently on southerly aspects and at elevations where pinelands were concentrated. The density of windthrow events increased with elevation and slope, with the highest occurrence on westerly aspects. Based on the estimated rotation periods, we calculated that 7.5, 24.4, and 68.1% of the presettlement forest were in the stand initiation, stem exclusion, and old forest (including both understory reinitiation and old growth) stages, respectively. Pinelands and mixed conifers were the major components in both the stand initiation (34.5 and 31.1%) and the stem exclusion stage (20.9 and 39.8%), while mixed conifers (39.3%) and northern hardwoods (34.7%) were the major old-forest cover types. The diverse mosaic of various successional stages generated by natural disturbance suggests a "shifting-mosaic" landscape in this region.


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