What does the term early seral bring to mind? Why should we even worry about early seral wildlife species if we can just harvest an older stand and instantly create early seral habitats? What elements of early seral habitat are important to wildlife? How have past and current management practices influenced those elements?
Structure and composition --- therefore FUNCTION --- of young managed conifer stands differs from early seral stages that result from natural disturbance Different structure and composition translates to different function 2 important influences on wildlife
Residual trees and snags are a critical component of early seral habitat for many species; the presence of many species depends on the availability of these legacy structures. In particular, Woodpeckers love disturbance: it creates food for their prey: ants and beetles Species such as (NOFL, LEWO, BBWO) specialize in open, post-disturbance habitats; create habitat for secondary cavity nesters
The combination of dead and dying trees in open habitats creates habitat that is uniquely suitable for Aerial insectivores (many are cavity nesters); swallows, puma, wifl, bats, webl, atfl
Reptiles in early seral habitats: open for sunning; lots of prey
Dead wood created by disturbances provides refugia for species with low mobility, such as amphibians Large dead wood important in providing cover in otherwise exposed habitat; allows persistence of populations Dead wood in combination with dense cover and abundant seed production from pioneer species in a high-light environment creates suitable habitat for many granivores; e.g., mice, voles, sparrows, finches...
Vegetation in early seral stages tends to be fast growing and reproducing; i.e., lots of foliage, seeds, and fruits produced. Large diversity of vegetation offers more food resources for more species than monoculture of young conifers Haven’t even mentioned ARTHROPODS
All of these species rely on food resources from a large diversity of non-coniferous plants in early seral stages May use seedling and sapling conifers for cover or food, but that is probably not the main resource that attracts these species to early seral habitats
The reason we can’t just clear cut a forest and instantly have quality early seral habitat that meets the needs of the previously mentioned species is that Shrub development takes time for shrubs to become old enough to produce flowers and fruit; C. Harrington: stem diameter positively correlated with number of flowers; large shrubs more likely to flower and produce seed Many intolerant shrub species can exist under closed canopies, but won’t flower and fruit unless sufficient light is available. So if canopy closes too soon, production is lost. Takes time for shrubs to develop thick stems and to be colonized by epiphytes, which add another whole layer of biological complexity to the system
Early seral stages also offer an abundance and diversity of arthropods for insectivores and small carnivores Several species of shrew are associated with herbaceous, shrubby, and deciduous habitats; Insects can periodically be abundant on conifers, e.g. during outbreaks, but a diversity of herbs, shrubs, and hardwood trees ensures a diverse and stable resource for insectivores.
Early seral habitats are primary breeding habitat for some species. Probable reasons: abundant food and cover; forage primarily on deciduous shrubs and trees MGWA and OCWA are common in early successional forests, but not in closed canopy mid-seral and old forests. Other shrub-associated species may be present throughout all stages of forest development as long as suitable habitat is present. Several species of neotropical migrant birds that rely on early seral or shrubby habitats have been experiencing population declines.
Other species that breed in older forests may use early seral habitat during the non-breeding season Studies from eastern hardwood forests have shown that early seral stages are important habitat for some bird species during the post-breeding season. Fledglings find cover and food Some species fatten up on bountiful fruit before migration Several species strongly associated with mature forest are among those that are abundant in early seral during the post-breeding season To my knowledge, post-breeding habitat use has not been well-studied for many PNW species
Understory vegetation has not been favored by past and present forest practices aimed at timber production In order to get conifers established quickly, and to ensure their dominance, Managers traditionally have “controlled” shrubs and hardwoods in young forests Shrubs are viewed as competitors for resources that should be going to the crop trees, but for many species of wildlife, non-coniferous vegetation is the essential, defining element of early seral. OFP rules mandate that conifers are reestablished on harvest units to specified densities within a specified time frame
By focusing on the rapid establishment and dominance of conifers, the diversity and duration of the shrub stage is reduced Under natural forest development scenario (i.e., without “vegetation control”) early seral habitat would be suitable for OCWA from stand age 5 - > 30 (>25 generations).
By the time a D-fir stand is 30-40 years old, the conifer canopy makes up the main layer of vegetation, and any understory that survived early control has long been shaded out....
Summary: Focus on conifer establishment has Reduced abundance of flowering, seed-producing vegetation reduced temporal span of early seral habitats = shortened duration of shrub dominance; consequences for migratory species that return to the same breeding location year after year?
We are seeing declines in populations of some shrub-associated species, No direct evidence that these declines are related to changes in the availability and quality of early seral habitat, but a connection does seem plausible. These declines suggest the need for a critical evaluation of the habitat requirements of early-seral and shrub–associated species
Structural diversity is important for maintaining wildlife diversity; However, it is important to remember that the forest is more than just conifer trees This stand is missing a critical habitat element for many species: vegetation diversity Grasses, herbs, shrubs, and hardwoods provide FUNCTIONAL as well as structural diversity in early seral habitats and throughout forest development.
Joan Hagar - Birds and Mammals and Herps
Effects of Forest Management on Wildlife Use of Early Seral Habitats Joan Hagar USGS-FRESC
Following Natural Disturbance ... <ul><li>Structure </li></ul><ul><ul><li>Legacy trees and snags </li></ul></ul><ul><ul><li>Open (low tree density) </li></ul></ul><ul><ul><li>Large wood </li></ul></ul><ul><li>Composition </li></ul><ul><ul><li>Herbs and Grasses </li></ul></ul><ul><ul><li>Shrubs </li></ul></ul><ul><ul><li>Hardwoods </li></ul></ul>Bob Altman
Arthropods <ul><li>Insect diversity correlated with plant diversity </li></ul><ul><li>Deciduous species support more insects </li></ul><ul><li>Influence of deciduous litter on soil food webs? </li></ul>
Consequences of reduced temporal span of early seral habitats <ul><li>Limit on shrub size and age </li></ul><ul><li>Shortens duration of shrubby habitat </li></ul><ul><li>Reduced persistence of shrubs into mid-aged forests </li></ul>
Effects of Conifer-centric Forest Management on Early Seral Habitat <ul><li>Fewer residual structures </li></ul><ul><li>Altered vegetation composition </li></ul><ul><ul><li>Alters patterns of food abundance </li></ul></ul><ul><ul><li>Reduces diversity of food resources </li></ul></ul><ul><ul><li>Alters food webs </li></ul></ul><ul><li>Reduced temporal span </li></ul>
30 Year Trend for Swainson’s Thrush from Tillamook S.F. BBS Route