Dynamics and pattern of a managed coniferous forest landscape in Oregon

We examined the process of fragmentation in a managed forest landscape by comparing rates and patterns of disturbance (primarily clear-cutting) and regrowth between 1972 and 1988 using Landsat imagery. A 2589-km(exp 2) managed forest landscape in western Oregon was classified into two forest types, closed-canopy conifer forest (CF) (typically, greater than 60% conifer cover) and other forest and nonforest types (OT) (typically, less than 40 yr old or deciduous forest). The percentage of CF declined from 71 to 58% between 1972 and 1988. Declines were greatest on private land, least in wilderness, and intermediate in public nonwilderness. High elevations (greater than 914 m) maintained a greater percentage of CF than lower elevations (less than 914 m). The percentage of the area at the edge of the two cover types increased on all ownerships and in both elevational zones, whereas the amount of interior habitat (defined as CF at least 100 m from OT) decreased on all ownerships and elevational zones. By 1988 public lands contained approximately 45% interior habitat while private lands had 12% interior habitat. Mean interior patch area declined from 160 to 62 ha. The annual rate of disturbance (primarily clear-cutting) for the entire area including the wilderness was 1.19%, which corresponds to a cutting rotation of 84 yr. The forest landscape was not in a steady state or regulated condition which is not projected to occur for at least 40 yr under current forest plans. Variability in cutting rates within ownerships was higher on private land than on nonreserve public land. However, despite the use of dispersed cutting patterns on public land, spatial patterns of cutting and remnant forest patches were nonuniform across the entire public ownership. Large remaining patches (less than 5000 ha) of contiguous interior forest were restricted to public lands designated for uses other than timber production such as wilderness areas and research natural areas

Measuring forest landscape patterns in the Cascade Range of Oregon, USA

This paper describes the use of a set of spatial statistics to quantify the landscape pattern caused by the patchwork of clearcuts made over a 15-year period in the western Cascades of Oregon. Fifteen areas were selected at random to represent a diversity of landscape fragmentation patterns. Managed forest stands (patches) were digitized and analyzed to produce both tabular and mapped information describing patch size, shape, abundance and spacing, and matrix characteristics of a given area. In addition, a GIS fragmentation index was developed which was found to be sensitive to patch abundance and to the spatial distribution of patches. Use of the GIS-derived index provides an automated method of determining the level of forest fragmentation and can be used to facilitate spatial analysis of the landscape for later coordination with field and remotely sensed data. A comparison of the spatial statistics calculated for the two years indicates an increase in forest fragmentation as characterized by an increase in mean patch abundance and a decrease in interpatch distance, amount of interior natural forest habitat, and the GIS fragmentation index. Such statistics capable of quantifying patch shape and spatial distribution may prove important in the evaluation of the changing character of interior and edge habitats for wildlife

Regional variation in stand structure and development in forests of Oregon, Washington, and inland Northern California

Despite its importance to biodiversity and ecosystem function, patterns and drivers of regional scale variation in forest structure and development are poorly understood. We characterize structural variation, create a hierarchical classification of forest structure, and develop an empirically based framework for conceptualizing structural development from 11,091 plots across 25 million ha of all ownerships in Oregon, Washington, and inland Northern California, USA. A single component related to live tree biomass accounted for almost half of the variation in a principal components analysis of structural attributes, but components related to live tree density and size, dead wood, and understory vegetation together accounted for as much additional variation. These results indicate that structural development is more complex than a monotonic accumulation of live biomass as other components may act independently or emerge at multiple points during development. The classification revealed the diversity of structural conditions expressed at all levels of live biomass depending on the timing and relative importance of a variety of ecological processes (e.g., mortality) in different vegetation zones. Low live biomass structural types (100 Mg/ha) substantiated the diversity of later developmental stages and exhibited considerable variation in the abundance of dead wood and density of big trees. Most structural types corresponded with previously described stages of development, but others associated with protracted early development, woodland/savannah transitions, and partial stand-replacing disturbance lacked analogs and indicated alternative pathways of development. We propose a conceptual framework that distinguishes among families of pathways depending on the range of variation along different components of structure, the relative importance of different disturbances, and complexity of pathways. Our framework is a starting point for developing more comprehensive models of structural development that apply to a wider variety of vegetation zones differing in environment and disturbance regimes

Disturbance, tree mortality, and implications for contemporary regional forest change in the Pacific Northwest

Tree mortality is an important demographic process and primary driver of forest dynamics, yet there are relatively few plot-based studies that explicitly quantify mortality and compare the relative contribution of endogenous and exogenous disturbances at regional scales. We used repeated observations on 289,390 trees in 3673 1 ha plots on U.S. Forest Service lands in Oregon and Washington to compare distributions of mortality rates among natural disturbances and vegetation zones from the mid-1990s to mid-2000s, a period characterized by drought, insect outbreaks, and large wildfires. Endogenous disturbances (e.g. pathogens, insects) were pervasive but operated at relatively low levels of mortality (1%/yr in over half of the plots in late and old-growth stages corroborate previous findings of elevated mortality during the same period and indicate the potential for pervasive structural change across all vegetation zones. Partial- and stand-replacing fire were associated with most mortality, but affected a relatively small proportion of dry vegetation zones (3.1–7.1% and 2.1–5.1%, respectively). These disturbances have likely affected regional biodiversity through the creation of early seral habitat, increased within-stand heterogeneity, and restored some aspects of historical fire regimes, but there is a need to better understand corresponding structural and compositional changes. We demonstrate the variability in the drivers, magnitude, and extent of mortality across a biophysically diverse region and highlight the need to incorporate and characterize the effects of mortality at intermediate levels to develop a more comprehensive understanding of regional forest dynamics.Keywords: Tree mortality, Pacific Northwest, Regional forest dynamics, Insects, Disturbance, Fir

Post-fire tree establishment and early cohort development in conifer forests of the western Cascades of Oregon, USA

Early‐seral ecosystems make important contributions to regional biodiversity by supporting high abundance and diversity of many plant and animal species that are otherwise rare or absent from closed‐canopy forests. Therefore, the period of post‐fire tree establishment is a key stage in forest stand and ecosystem development that can be viewed in the context of competing management interests in diverse early‐seral ecosystems vs. rapid forest development for ecological or commercial objectives. Previous work in Douglas‐fir/western hemlock forests of the Pacific Northwest suggests stands initiate either with abrupt establishment (100 years. To improve understanding of how post‐fire tree establishment and early cohort development have varied in space and over time and elucidate some of the factors contributing to that variation, we analyzed forest structure, tree ages, and Douglas‐fir growth across the central western Cascades of Oregon where cohort ages span nearly eight centuries. The number of post‐fire cohorts was estimated per stand, and establishment trajectories were evaluated by cohort. On average, it took 43.5 years to reach establishment of 90% of the trees per cohort. The rate and duration of establishment were surprisingly consistent across variation in topography (elevation, slope position, and aspect), among cohorts initiated from the late 12th to the early 20th century, and regardless of the severity of the cohort‐initiating fire or the timing of establishment by shade‐tolerant species. Only 8% of cohorts completed establishment within 20 years and 12% had establishment lasting >80 years. Douglas‐fir growth (basal area increment) exhibits high plasticity in relation to different competitive interactions within uni‐specific and multi‐species cohorts and between cohorts of different age, suggesting wide variation in the structure and dynamics of early‐seral ecosystems and an ability to tolerate moderate competition when young. This study illustrates that post‐fire establishment in Douglas‐fir/western hemlock forests of the central western Cascades historically was a multi‐decadal process. Limited regeneration in a short window did not necessarily lead to persistent shrublands. In fact, post‐fire forest development appears resilient to considerable variation in the fire regime and climatic and biotic constraints on tree establishment

Fire-mediated pathways of stand development in Douglas-fir/ western hemlock forests of the Pacific Northwest, USA

Forests dominated by Douglas-fir and western hemlock in the Pacific Northwest of the United States have strongly influenced concepts and policy concerning old-growth forest conservation. Despite the attention to their old-growth characteristics, a tendency remains to view their disturbance ecology in relatively simple terms, emphasizing infrequent, stand-replacing (SR) fire and an associated linear pathway toward development of those old-growth characteristics. This study uses forest stand- and age-structure data from 124 stands in the central western Cascades of Oregon to construct a conceptual model of stand development under the mixed-severity fire regime that has operated extensively in this region. Hierarchical clustering of variables describing the age distributions of shade-intolerant and shade-tolerant species identified six groups, representing different influences of fire frequency and severity on stand development. Douglas-fir trees >400 years old were found in 84% of stands, yet only 18% of these stands (15% overall) lack evidence of fire since the establishment of these old trees, whereas 73% of all stands show evidence of at least one non-stand-replacing (NSR) fire. Differences in fire frequency and severity have contributed to multiple development pathways and associated variation in contemporary stand structure and the successional roles of the major tree species. Shade-intolerant species form a single cohort following SR fire, or up to four cohorts per stand in response to recurring NSR fires that left living trees at densities up to 45 trees/ha. Where the surviving trees persist at densities of 60-65 trees/ha, the postfire cohort is composed only of shade-tolerant species. This study reveals that fire history and the development of old-growth forests in this region are more complex than characterized in current stand-development models, with important implications for maintaining existing old-growth forests and restoring stands subject to timber management.Keywords: forest age structure, Douglas-fir, western hemlock, Pseudotsuga menziesii, developmental pathways, Pacific Northwest, Tsuga heterophylla, USA, mixed-severity fire regimeKeywords: forest age structure, Douglas-fir, western hemlock, Pseudotsuga menziesii, developmental pathways, Pacific Northwest, Tsuga heterophylla, USA, mixed-severity fire regim

EEG microstate quantifiers and state space descriptors during anaesthesia in patients with postoperative delirium: a descriptive analysis.

Postoperative delirium is a serious sequela of surgery and surgery-related anaesthesia. One recommended method to prevent postoperative delirium is using bi-frontal EEG recording. The single, processed index of depth of anaesthesia allows the anaesthetist to avoid episodes of suppression EEG and excessively deep anaesthesia. The study data presented here were based on multichannel (19 channels) EEG recordings during anaesthesia. This enabled the analysis of various parameters of global electrical brain activity. These parameters were used to compare microstate topographies under anaesthesia with those in healthy volunteers and to analyse changes in microstate quantifiers and EEG global state space descriptors with increasing exposure to anaesthesia. Seventy-three patients from the Surgery Depth of Anaesthesia and Cognitive Outcome study (SRCTN 36437985) received intraoperative multichannel EEG recordings. Altogether, 720 min of artefact-free EEG data, including 210 min (29.2%) of suppression EEG, were analysed. EEG microstate topographies, microstate quantifiers (duration, frequency of occurrence and global field power) and the state space descriptors sigma (overall EEG power), phi (generalized frequency) and omega (number of uncorrelated brain processes) were evaluated as a function of duration of exposure to anaesthesia, suppression EEG and subsequent development of postoperative delirium. The major analyses involved covariate-adjusted linear mixed-effects models. The older (71 ± 7 years), predominantly male (60%) patients received a median exposure of 210 (range: 75-675) min of anaesthesia. During seven postoperative days, 21 patients (29%) developed postoperative delirium. Microstate topographies under anaesthesia resembled topographies from healthy and much younger awake persons. With increasing duration of exposure to anaesthesia, single microstate quantifiers progressed differently in suppression or non-suppression EEG and in patients with or without subsequent postoperative delirium. The most pronounced changes occurred during enduring suppression EEG in patients with subsequent postoperative delirium: duration and frequency of occurrence of microstates C and D progressed in opposite directions, and the state space descriptors showed a pattern of declining uncorrelated brain processes (omega) combined with increasing EEG variance (sigma). With increasing exposure to general anaesthesia, multiple changes in the dynamics of microstates and global EEG parameters occurred. These changes varied partly between suppression and non-suppression EEG and between patients with or without subsequent postoperative delirium. Ongoing suppression EEG in patients with subsequent postoperative delirium was associated with reduced network complexity in combination with increased overall EEG power. Additionally, marked changes in quantifiers in microstate C and in microstate D occurred. These putatively adverse intraoperative trajectories in global electrical brain activity may be seen as preceding and ultimately predicting postoperative delirium

Canopy gaps affect long-term patterns of tree growth and mortality in mature and old-growth forests in the Pacific Northwest

Canopy gaps created by tree mortality can affect the speed and trajectory of vegetation growth, species’ population dynamics, and spatial heterogeneity in mature forests. Most studies focus on plant development within gaps, yet gaps also affect the mortality and growth of surrounding trees, which influence shading and root encroachment into gaps and determine whether, and how quickly, a gap becomes occupied by recovering vegetation. The objective of this study was to determine the effect of canopy gap size on mortality and growth of surrounding trees over a 16-year period in mature and old-growth Douglas-fir dominated forests in the coastal Pacific Northwest, USA. Replicates of four sizes of experimental gaps and controls were created in two mature stands (90 and 145-years old) and two old-growth stands (overstory trees 350–525-years old); mortality and diameter of surrounding trees were measured periodically over 16 years. A subset of trees was cored to compare growth increment before and after gap creation. There was no difference between mortality rates of trees within 8 m of gaps and trees in closed-canopy controls, although mortality causes did differ for understory trees. Mortality of understory trees was higher at gap edges than in controls, but lower several meters into the forest, suggesting a shift from negative to positive effects with the gradient in exposure. Diameter growth rates of trees were greater next to gaps than in controls, with the greatest difference ranging from 39% for overstory trees to 111% for understory trees in mature stands. Growth rates of trees in old-growth stands differed by crown class and position around gap, suggesting an effect of direct solar radiation. Growth rates of trees in mature stands were relatively insensitive to gap size and position, suggesting that increased soil moisture drove responses in these stands. Somewhat unexpectedly, there were rapid increases in growth in some old-growth trees, but not in the largest gap sizes. Results suggest canopy gaps can create heterogeneity of ecosystem function through spatial variation in effects on growth and mortality across mature and old-growth stands.Keywords: Structural diversity, Canopy gaps, Disturbance, Mortality, Spatial pattern, GrowthKeywords: Structural diversity, Canopy gaps, Disturbance, Mortality, Spatial pattern, Growt

Science and society: The Role of Long-term Studies in Environmental Stewardship

Long-term research should play a crucial role in addressing grand challenges in environmental stewardship. We examine the efforts of five Long Term Ecological Research Network sites to enhance policy, management, and conservation decisions for forest ecosystems. In these case studies, we explore the approaches used to inform policy on atmospheric deposition, public land management, land conservation, and urban forestry, including decisionmaker engagement and integration of local knowledge, application of models to analyze the potential consequences of policy and management decisions, and adaptive management to generate new knowledge and incorporate it into decisionmaking. Efforts to enhance the role of long-term research in informing major environmental challenges would benefit from the development of metrics to evaluate impact; stronger partnerships among research sites, professional societies, decisionmakers, and journalists; and greater investment in efforts to develop, test, and expand practice-based experiments at the interface of science and society