29 research outputs found
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Ecological effects of alternative fuel-reduction treatments: highlights of the National Fire and Fire Surrogate study (FFS)
The 12-site National Fire and Fire Surrogate study (FFS) was a multivariate experiment that evaluated ecological consequences of alternative fuel-reduction treatments in seasonally dry forests of the US. Each site was a replicated experiment with a common design that compared an un-manipulated control, prescribed fire, mechanical and mechanical + fire treatments. Variables within the vegetation, fuelbed, forest floor and soil, bark beetles, tree diseases and wildlife were measured in 10-ha stands, and ecological response was compared among treatments at the site level, and across sites, to better understand the influence of differential site conditions. For most sites, treated stands were predicted to be more resilient to wildfire if it occurred shortly after treatment, but for most ecological variables, short-term response to treatments was subtle and transient. Strong site-specificity was observed in the response of most ecosystem variables, suggesting that practitioners employ adaptive management at the local scale. Because ecosystem components were tightly linked, adaptive management would need to include monitoring of a carefully chosen set of key variables. Mechanical treatments did not serve as surrogates for fire for most variables, suggesting that fire be maintained whenever possible. Restoration to pre-settlement conditions will require repeated treatments over time, with eastern forests requiring more frequent applications.Keywords: Oak, Prescribed fire, Frequent fire regimes, Pine, Mechanical treatment, Forest thinning, Dry forest management, Seasonally dry forest
Intronic and plasmid-derived regions contribute to the large mitochondrial genome sizes of Agaricomycetes
Root-infecting fungi associated with a decline of longleaf pine in the southeastern United States
symptoms A 35year-old longleaf pine stand exhibited trees in various stages of decline. A study was conducted to determine root-infecting fungi and other abnormalities associated with varying degrees of crown symptoms. A four-class crown symptom rating system was devised according to ascending symptom severity. Leptographium procerum and L. terebrantis were significantly associated with increasing crown symptom severity. Heterobasidion annosum was also isolated in higher frequency as crown symptoms increased. Also, evidence of insects on roots increased as did amount of resinosis observed. Edaphic and silvicultural factors may interact with these pathogens and insects to pose a pathological limitation on longer-term management objectives. Further research is needed to determine relationships among various edaphic, silvicultural, and biological factors associated with the decline syndrome on this site. t
A shift in nuclear state as the result of natural interspecific hybridization between two north american taxa of the basidiomycete complex Heterobasidion
Biological and Management Implications of Fire-Pathogen Interactions in the Giant Sequoia Ecosystem
An overriding management goal for national parks is the maintenance or, where necessary, the restoration of natural ecological processes. In Sequoia-Kings Canyon and Yosemite National Parks, there is concern about the effects of fire suppression on the giant sequoia-mixed conifer forest ecosystem. The National Park Service is currently using prescribed fire management and prescribed burning as tools to reintroduce fire as a natural process. However, there are questions about the positive and negative effects of reintroducing fire in the giant sequoia-mixed conifer ecosystem. Reintroducing fire in the Sierra Nevada forests needs critical evaluation with respect to the pathogens that affect giant sequoias. We designed a 3-year study, funded by the U.S. Department of the Interior, National Park Service, to: (1) determine the effects of fire scars and their re-burning on the incidence, extent, and survival of fungi in giant sequoia; (2) identify pathogens, insects, location of decay, and other characteristics present in standing old-growth giant sequoia fire scars; (3) evaluate host specialization and cross infectivity of isolates of Heterobasidion annosum from white fir (Abies concolor), red fir (Abies magnipca), and giant sequoia (Sequoia gigantea); and (4) develop criteria and recommendations for monitoring the effects of fire on pathogens in giant sequoia stands. The total circumference of giant sequoia trees affected by fire scars ranged from 3.3% to 69.5%. Cross-sectional area affected by fire scars ranged from 3.2% to 53.7%. The season of year in which prescribed burning takes place could influence the effect fire has on giant sequoia. A survey of 90 fire scars for the presence of resin, MycocaIicium, carpenter ants, other insects, Arachnids, decay above and below groundline, and bird activity (i.e., cavities) yielded a high presence of each factor when all burn groups were combined. Statistically significant differences in bird cavity activity, decay above groundline, and carpenter ant activity were noted among the unburned group, 1-year burn group, and 5-year burn group. The Pilodyn wood tester was effective in determining the presence of decay above and below groundline. A variety of microfungi were found associated with giant sequoia fire scars. The fungi most frequently isolated were: Byssochlamys fulva from 34 out of 90 fire scars (38%), Acrodontium intermissum from 22 out of 90 fire scars (24%), and Tritirachium sp. from 14 out of 90 fire scars (16%). Several other microfungi and Basidiomycetes were also identified. H. annosum acts as both a saprophyte and a pathogen in the giant sequoia-mixed conifer ecosystem. The results of these experiments have demonstrated H. annosum can spread from true fir to giant sequoia and vice versa, given that they are of the same ”S” intersterility group
Genetic Structure of Heterobasidion annosum in White Fir Mortality Centers in California
The structure of Heterobasidion annosum populations was studied in 1.5 mixed-conifer sites in central and northern California. Study sites displayed mortality of white fir trees in enlarging discrete patches (mortality centers). At each site, fungal genotypes were defined by somatic compatibility tests. In two sites, further genetic and molecular analyses were performed on field genotypes and on homokaryons obtained by dedikaryotization of field heterokaryons. Isolates were found to be colonizing mostly the roots and the bole sapwood of white fir trees, and no significant infections of other tree species were observed. Each mortality center was characterized by the presence of several fungal genotypes, all belonging to the S intersterility group. Both homokaryotic and heterokaryotic strains were present in all sites. Multiple genotypes were retrieved in individual trees or stumps. Out of 228 fungal genotypes, 86 % were found only within a single tree or stump, while 14 % had spread to adjacent trees. The two largest genotypes had diameters of 9 and 10 m, and had colonized fiv
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Root Disease, Longleaf Pine Mortality, and Prescribed Burning
Study to determine factors involved in decline of longleaf pine associated with prescribed burning. Trees having symptoms were recorded by crown rating system based upon symptom severity-corresponded to tree physiological status-increased in hot burn plots. Root pathogenic fungi widespread throughout the study site. Histological studies show high fine root mortality rate in the hot burn treatment. Decline syndrome is complexed by root pathogens, soil factors, root damage and dysfunction