Landscape Pattern Response to Changes in the Pattern Generation Rules: Land-use Legacies in Forestry

The Pacific Northwest of the United States is currently embroiled in an acrimonious debate over the management of federal forest lands. Constructive resolution of this debate will require better information on a broad range of forest management issues. This study focuses on one such issue: the development of landscape pattern in response to alternative forest cutting plans and the degree to which established landscape patterns can be changed. Dispersed cutting has been conducted on federal lands in the western United States for \u3e40 yr, but alternative cutting plans are now being considered. To assess the effects of different disturbance processes on the development of landscape pattern, we compare dispersed- and aggregated-cutting plans using a simple, rule-based simulation model that incorporates realistic regulatory and logistic constraints. Our results indicate that, once established, the landscape pattern created by dispersed disturbances is difficult to erase without a substantial reduction in the disturbance rate or a reduction in the minimum stand age eligible for disturbance. Change in landscape pattern can lag substan­tially behind change in the rules governing pattern generation

The forgotten stage of forest succession: early-successional ecosystems on forest sites

Early-successional forest ecosystems that develop after stand-replacing or partial disturbances are diverse in species, processes, and structure. Post-disturbance ecosystems are also often rich in biological legacies, including surviving organisms and organically derived structures, such as woody debris. These legacies and postdisturbance plant communities provide resources that attract and sustain high species diversity, including numerous early-successional obligates, such as certain woodpeckers and arthropods. Early succession is the only period when tree canopies do not dominate the forest site, and so this stage can be characterized by high productivity of plant species (including herbs and shrubs), complex food webs, large nutrient fluxes, and high structural and spatial complexity. Different disturbances contrast markedly in terms of biological legacies, and this will influence the resultant physical and biological conditions, thus affecting successional pathways. Management activities, such as post-disturbance logging and dense tree planting, can reduce the richness within and the duration of early-successional ecosystems. Where maintenance of biodiversity is an objective, the importance and value of these natural early-successional ecosystems are underappreciated

The Forgotten Stage of Forest Succession: Early-Successional Ecosystems on Forest Sites

Early-successional forest ecosystems that develop after stand-replacing or partial disturbances are diverse in species, processes, and structure. Post-disturbance ecosystems are also often rich in biological legacies, including surviving organisms and organically derived structures, such as woody debris. These legacies and post-disturbance plant communities provide resources that attract and sustain high species diversity, including numerous early-successional obligates, such as certain woodpeckers and arthropods. Early succession is the only period when tree canopies do not dominate the forest site, and so this stage can be characterized by high productivity of plant species (including herbs and shrubs), complex food webs, large nutrient fluxes, and high structural and spatial complexity. Different disturbances contrast markedly in terms of biological legacies, and this will influence the resultant physical and biological conditions, thus affecting successional pathways. Management activities, such as post-disturbance logging and dense tree planting, can reduce the richness within and the duration of early-successional ecosystems. Where maintenance of biodiversity is an objective, the importance and value of these natural early-successional ecosystems are underappreciated

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

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

Effects of volcanic and hydrologic processes on forest vegetation: Chaitén Volcano, Chile

The 2008-2009 eruption of Chaitén Volcano (Chile) involved a variety of volcanic and associated hydrologic processes that damaged nearby forests. These processes included coarse (gravel) and fine (silt to sand) tephra fall, a laterally directed blast, fluvial deposition of remobilized tephra, a variety of low-temperature mass-movement processes, and a pyroclastic flow. Each of these geophysical processes constitutes a type of ecosystem disturbance which involves a distinctive suite of disturbance mechanisms, namely burial by tephra and sediment, heating, abrasion, impact force, and canopy loading (accumulation of tephra in tree crowns). Each process affected specific areas, and created patches and disturbance gradients in the forest landscape. Coarse tephra (‘gravel rain’, >5 cm depth) abraded foliage from tree canopies over an area of approximately 50 km2 north-northeast of the vent. Fine tephra (>10 cm depth) accumulated in tree crowns and led to breakage of branches in old forest and bowing of flexible, young trees over an area of about 480 km2. A directed blast down the north flank of the volcano damaged forest over an area of 4 km2. This blast zone included an area of tree removal near the crater rim, toppled forest farther down the slope, and standing, scorched forest around the blast perimeter. Fluvial deposition of >100 cm of remobilized tephra, beginning about 10 days after initiation of the eruption, buried floodplain forest in distinct, elongate streamside patches covering 5 km2 of the lower 19 km of the Rayas River and several km2 of the lower Chaitén River. Across this array of disturbance processes the fate of affected trees varied from complete mortality in the tree removal and pyroclastic flow areas, to no mortality in areas of thin tephra fall deposits. Tree damage included defoliation, loss of branches, snapping of tree trunks, abrasion of bark and ephiphytes, and uprooting. Damaged trees sprouted from epicormic buds located in trunks and branches, but sprouting varied over time among disturbance mechanisms and species. Although some effects of the Chaitén eruption are very similar to those from the 1980 eruption of Mount St. Helens (USA), interactions between biota and geophysical processes at Chaitén produced some unique effects. Examination of vegetation response helps interpret geophysical processes, and disturbance mechanisms influence early stages of biotic response to an eruption

Recent geomorphic history in the area of experimental watersheds 1, 2, 3, 9, and 10, H. J. Andrews Forest

Studies in the lower Lookout Creek-Blue River area have revealed a geomorphic history including glaciation and the development of three alluvial surfaces, presently active alluvial cones and older, deeply dissected cone remnants. Results are based on landform mapping, analysis of the types and distributions of surficial sediments, and the distribution of Mazama ash. Presence of the ash makes it possible to date geomorphic features relative to a time horizon about 8,000 years in age. This work has served to identify individual cones which will be studied further to learn the erosional histories of specific watersheds

Ecosystem Stewardship: Sustainability Strategies for a Rapidly Changing Planet

Ecosystem stewardship is an action-oriented framework intended to foster social-ecological sustainability of a rapidly changing planet. Recent developments identify three strategies that make optimal use of current understanding in an environment of inevitable uncertainty and abrupt change: reducing the magnitude of, and exposure and sensitivity to, known stresses; focusing on proactive policies that shape change; and avoiding or escaping unsustainable social-ecological traps. All social-ecological systems are vulnerable to recent and projected changes but have sources of adaptive capacity and resilience that can sustain ecosystem services and human well-being through active ecosystem stewardship