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Author: Kevin Robert Welch Publisher: ISBN: 9781321807653 Category : Languages : en Pages :
Book Description
This study examines postfire regeneration patterns in low to mid-elevation forests of northern and central California where conifers co-exist and compete with hardwoods and shrubs in the postfire environment. Due to fire suppression policies, timber harvest, and other management practices over the last century, many low- to mid-elevation forests in California have accumulated high fuel loads and dense, multi-layered canopies that are dominated by shade-tolerant and fire-sensitive conifers. These conditions promote high-intensity fires, which have major effects on forest structure, function, and composition. We established 1,854 survey plots in nineteen wildfires on ten National Forests across a range of elevations, forest types, and fire severities in central and northern California to provide insight into factors that promote natural tree regeneration after wildfires and the differences in post-fire responses of the most common conifer species and hardwood species. We developed a zero-inflated negative binomial mixed model with random effects to understand the importance of ten environmental variables in predicting conifer regeneration. This model identified as important factors distance to potential seed tree, annual precipitation, presence of regenerating shrubs, litter cover, fire severity and pre-existing forest type. We documented widespread conifer regeneration failure with nearly 50% of all plots devoid of conifer regeneration. When regeneration did occur, it was dominated by shade-tolerant but fire-sensitive firs, Douglas-fir and incense cedar. Active forest restoration (planting, brush control, reduction of undesirable species, etc.) may be necessary in more severely burned areas farther from seed trees where natural regeneration is insufficient to restore forest composition and structure, increasing forest resiliency in the face of climate change and augmented levels of fire disturbance. However, conifers do not exist in isolation in these forests and the interaction with other functional woody plant types must be considered. This study adds a unique contribution to understanding postfire regeneration dynamics by comparing the relative success of hardwoods to conifers across a fire severity gradient and in the first decade after mixed-severity fires. By utilizing vegetative sprouting (and to a lesser extent sexual reproduction), hardwood trees and shrubs are able to quickly capitalize on available resources and this ability may confer a competitive advantage to hardwoods. The results of this study indicate that increased fire severity leads to greater relative density of hardwoods via a combined impact of resprouts and seedlings, creating alternative states where hardwoods and shrubs (that suppress the relatively few conifer seedlings that do establish) may dominate for many years after disturbance. To a great extent, the future status of California's forests will depend on tree species' responses to patterns and trends in fire activity and behavior and post-fire management decisions.
Author: Kevin Robert Welch Publisher: ISBN: 9781321807653 Category : Languages : en Pages :
Book Description
This study examines postfire regeneration patterns in low to mid-elevation forests of northern and central California where conifers co-exist and compete with hardwoods and shrubs in the postfire environment. Due to fire suppression policies, timber harvest, and other management practices over the last century, many low- to mid-elevation forests in California have accumulated high fuel loads and dense, multi-layered canopies that are dominated by shade-tolerant and fire-sensitive conifers. These conditions promote high-intensity fires, which have major effects on forest structure, function, and composition. We established 1,854 survey plots in nineteen wildfires on ten National Forests across a range of elevations, forest types, and fire severities in central and northern California to provide insight into factors that promote natural tree regeneration after wildfires and the differences in post-fire responses of the most common conifer species and hardwood species. We developed a zero-inflated negative binomial mixed model with random effects to understand the importance of ten environmental variables in predicting conifer regeneration. This model identified as important factors distance to potential seed tree, annual precipitation, presence of regenerating shrubs, litter cover, fire severity and pre-existing forest type. We documented widespread conifer regeneration failure with nearly 50% of all plots devoid of conifer regeneration. When regeneration did occur, it was dominated by shade-tolerant but fire-sensitive firs, Douglas-fir and incense cedar. Active forest restoration (planting, brush control, reduction of undesirable species, etc.) may be necessary in more severely burned areas farther from seed trees where natural regeneration is insufficient to restore forest composition and structure, increasing forest resiliency in the face of climate change and augmented levels of fire disturbance. However, conifers do not exist in isolation in these forests and the interaction with other functional woody plant types must be considered. This study adds a unique contribution to understanding postfire regeneration dynamics by comparing the relative success of hardwoods to conifers across a fire severity gradient and in the first decade after mixed-severity fires. By utilizing vegetative sprouting (and to a lesser extent sexual reproduction), hardwood trees and shrubs are able to quickly capitalize on available resources and this ability may confer a competitive advantage to hardwoods. The results of this study indicate that increased fire severity leads to greater relative density of hardwoods via a combined impact of resprouts and seedlings, creating alternative states where hardwoods and shrubs (that suppress the relatively few conifer seedlings that do establish) may dominate for many years after disturbance. To a great extent, the future status of California's forests will depend on tree species' responses to patterns and trends in fire activity and behavior and post-fire management decisions.
Author: Max Bencomo Publisher: ISBN: Category : Languages : en Pages :
Book Description
Wildfire is a necessary part of ecosystem function in California, but fire suppression and the spread of invasive species have endangered many ecosystems. The North Coast bioregion of California has seen dramatic shifts in forest ecology and vegetative density, largely due to the disruption of historic fire regimes. Historic fire regimes were previously maintained through indigenous land management, but the arrival of European settlers in the 1850's initiated the changes reflected in current fire regimes. Not only is the North Coast bioregion the hotbed of recent fire activity, it is experiencing decreased counts of heterogeneity within forests while also seeing increased amounts of fuel loads that contribute to more severe fires. This paper utilizes a comparative analysis of mixed conifer forest and oak woodland ecozones, describing the vegetative outcomes of their altered fire regimes. Through the synthesis of case studies, government reports, impact assessments, and management plans, I investigated the current state of these landscapes and developed recommendations for future management. The combination of fire suppression and increasing invasive populations have led to numerous shifts in forest systems. Invasive species heavily influence forest fuel loads and can change ecosystem structure, which can subsequently alter the area's fire regime. Once a fire regime has changed it can imperil the livelihood of historic plant populations. Conifer forests are seeing shifts from resilient species to more fire-sensitive species, which can lead to the decimation of entire populations by high-severity fires. Oak woodlands are also suffering from fire regime changes, as conifers are encroaching and overtaking the forest canopy, drowning out oaks and reducing them to shrub species. Both mixed conifer forests and oak woodlands are threatened by changes in their respective fire regimes. These shifts in vegetation patterns can be amended through integrative management initiatives, notably the application of prescribed burns to aid the restoration of historical fire regimes.
Author: Neil G. Sugihara Publisher: Univ of California Press ISBN: 0520246055 Category : Business & Economics Languages : en Pages : 613
Book Description
Focusing on California and issues specific to fire ecology and management in the state's bioregions, this work provides scientific information for use in land restoration and other management decisions made in the field. It introduces the basics of fire ecology, and includes an overview of fire, vegetation and climate in California; and more.
Author: Natalie Pawlikowski Publisher: ISBN: Category : Languages : en Pages :
Book Description
This research quantifies forest structure and examines how post-fire succession alters pine-oak composition, group-gap spatial structure, and wildfire resilience in an old-growth ponderosa pine (Pinus ponderosa) forest that was resilient to recent wildfires and exhibits a heterogeneous forest structure thought to be similar to forests before fire exclusion. To quantify forest structure and spatial patterns, trees were aged, mapped, and measured in the year 2000 six-years after a wildfire and in 2016 22-years post-fire in six, 1-hectare, stem map plots in the Beaver Creek Pinery, located in the Ishi Wilderness, Southern Cascades, California. Regeneration seedlings and saplings were tallied in 10x10m cells. Rates of tree recruitment, mortality, and growth for the sites two co-dominant species ponderosa pine and California black oak (Quercus kelloggii) were estimated using demographic models. Local patterns in group structure was quantified using spatial clump algorithms and gap area was quantified using the empty space function. Potential fire behavior and effects were modeled for a range of fuel and weather conditions.Stand density and basal area in both 2000 and 2016 were within the historical range of variability for pre-fire exclusion ponderosa pine forests. Initially, wildfire promoted California black oak; however, oak abundance and regeneration has declined while pine abundance and regeneration has increased in the subsequent 22 years without fire. In 2000, ~15% of trees were classified as individuals and tree group sizes ranged from 2 to 75 trees. Small tree groups (2-4 trees) consist of similar-aged trees while larger groups are multi-aged. In 2016, the percent of trees classified as individuals decreased by ~30%, and the scale and intensity of clustering increased. The greatest change in spatial patterns occurred in plots with the highest rates of post-fire recruitment. The size and frequency of canopy gaps was similar in 2000 and 2016; however, higher densities of seedlings and saplings were associated with canopy gaps in 2016 which suggests, without future fire, canopy gaps will be infilled. Fire behavior models indicate the Beaver Creek Pinery is still resilient to high severity wildfire. Overall, this research broadens our understanding on the persistent effects of fire on spatial heterogeneity and demonstrates that wildfires can be used to restore resiliency to forests where wildfires have been suppressed for nearly a century.
Author: United States. Congress. House. Committee on Resources. Subcommittee on Forests and Forest Health Publisher: ISBN: Category : Nature Languages : en Pages : 100
Author: Dani Niziolek Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Contemporary fires in California are becoming larger, more frequent, and increasingly severe, and this trend is expected to continue in the coming decades. Increases in area burned and area burned at high severity generate larger high severity patches without a tree canopy, which can impede forest recovery by limiting seed dispersal from live trees and triggering vegetation type change. Although there is an emerging body of research on post-fire conifer regeneration, there is uncertainty in how landscape and local site conditions interact to influence regeneration. This thesis identifies dominant drivers of postfire conifer regeneration in Lassen Volcanic National Park in the southern Cascades. We studied post-fire conifer regeneration in the footprint of nine fires, between 7 and 26 years after the burn, quantifying pre- and post-fire forest condition, topography and topoclimate, and local terrain and ground cover at each plot. Random Forest models assessed the relationship between these environmental conditions and regeneration stocking or species occurrence. We found that post-fire conifer regeneration was relatively abundant in Lassen Volcanic National Park, and abundance was related toto topography, vegetation type, and characteristics of the pre- and post-fire forest. Regeneration was densest in cooler, wetter topographic positions, and although overall regeneration did not respond to post fire water balance, species showed different responses to moisture availability. Regeneration responded positively to proximity to forest edge and longer time since fire, with the strongest regeneration occurring within 200 m of forest edge and >10 years since fire. Though high levels of shrub cover inhibited regeneration, at lower levels shrub cover supported more dense tree regeneration. These findings support trends found in the literature, and highlight the importance of studying regeneration over longer periods after fire, and incorporating characteristics of the local environment in studies of post-fire conifer regeneration.
Author: Jose M. Moreno Publisher: Springer Science & Business Media ISBN: 1461383951 Category : Science Languages : en Pages : 219
Book Description
Fire has been recognized as a vital agent influencing the diversity and vigor of landscapes. It is particularly important in Mediterranean ecosystems, such as those of California. This book is of interest to ecologists, policy makers, and land managers.
Author: Kevin Robert Welch
Author: Kevin Robert Welch
Author: Justin S. Crotteau
Author: J. M. Buck
Author: Max Bencomo
Author: Robert W. Cermak
Author: Neil G. Sugihara
Author: Natalie Pawlikowski
Author: United States. Congress. House. Committee on Resources. Subcommittee on Forests and Forest Health
Author: Dani Niziolek
Author: Jose M. Moreno