The Rodeo-Chediski Wildfire the largest in Arizona's history at the time of burning damaged and disrupted ecosystems resources and functioning in a largely mosaic pattern throughout the ponderosa pine (Pinus Ponderosa) forests exposed to the burn. Impacts of this wildfire on ecosystems resources and functioning were studied from shortly after the cessation of the wildfire in late summer of 2002 through the spring of 2007 on two previously instrumented watersheds located on sandstone derived soils within the burn. One watershed was burned by a high severity (stand-replacing fire), while the other watershed burned in a low severity (stand-modifying) fire. This dissertation focuses on the effects fire severity had on watersheds resources and functioning in terms of the tree overstories, herbaceous understories, large and small mammals, avifauna, hydrologic functioning, soil water repellency, hillslope soil movement, and fuel loadings. The results of these studies indicated the cumulative impacts incurred to ecosystem resources, hydrologic functioning, and flammable fuels were much greater on the watershed exposed to the high severity (stand-replacing) fire. It is anticipated that the overall ecological and hydrologic function on the watershed burned by a high severity will not approach pre-fire conditions for many years. The watershed burned at a low severity, however, was approaching pre-fire conditions nearly five years after fire and is expected to be recovered within the next few years.

Coloradia pandora (Blake) is a phytophagous insect that defoliates Pinus ponderosa (Dougl. ex Laws.) in south-central Oregon. Little is known about the extent of damage this insect inflicts upon its host trees during an outbreak. In this paper, we present stem analyses on four dominant Pinus ponderosa trees that enable us to determine the amount of volume lost during each Coloradia pandora outbreak on this site for the past 450 years. We found that on average an outbreak inhibits radial growth so that an individual tree produces 0.057 m³ less wood volume than the potential growth for the duration of an individual outbreak. A total of 0.549 m³ of growth per tree was inhibited by 10 outbreaks during the lifetime of the trees, which, in this stand, equates to 9.912 m³/ha (1,700 board feet/acre) of wood suppressed over the last 450 years throughout the stand. Our results do not support previous findings of a lag in suppression onset between the canopy of the tree versus the base. Crossdating of stem analysis samples is paramount to definitively examine the potential for a lagged response throughout the

Increment cores are invaluable for assessing tree attributes such as inside bark diameter, radial growth, and sapwood area. However, because trees accrue growth and sapwood unevenly around their pith, tree attributes derived from one increment core may not provide sufficient precision for forest management/research activities. To assess the variability in a tree’s inside bark radius, sapwood radius, and 10-year radial growth estimated by tree cores, two increment cores at 90 degree angles were collected from ponderosa pine (Pinus ponderosa) trees in eastern Montana (n = 2,156). Paired core measurements varied substantially with 13% mean difference for inside bark radius, 19% mean difference for sapwood radius, and 23% mean difference for estimates of radial increment. Furthermore, decreasing crown ratio, decreasing diameter, and increasing site slope were all found to increase differences in estimates derived from paired cores. Whether for management or research purposes, the number of cores that should collected per tree depend on a stand’s susceptibility to reaction wood, required measurement precision, and budgetary constraints.

This dissertation describes arthropod responses to and effects on decay processes in ponderosa pine, a dominant forest canopy tree in northern California. We used both descriptive and experimental field techniques to establish how arthropod assemblages depend on and are important to the disintegration of woody structures in forests of this type. The first study used pitfall traps placed within and on the outsides of fallen, large old ponderosa pine trees to establish the effects of microenvironments created during tree death. We studied the internal and external structures of fallen trees as well as the forest floor in canopy gaps and in the surrounding undisturbed forest. Five trees were surveyed, representing a decay sequence from newly dead and with distinct canopy gap, to well-decayed with recovering canopy. Arthropod assemblages were distinct among the different microenvironments, but were less so with increasing tree/gap age. Differences between tree and soil faunae decreased with increasing decay, as did the differences between gap and non-gap catches from the forest floor. The second study used experimental exclusion techniques to examine how longitudinal (bark beetle) and transverse (woodboring) insect colonists could influence rates of mass loss and carbon respiration from young, dead ponderosa pine. We found that both groups enhanced the prevalence of staining fungi in the sapwood, which in turn was negatively related to the degree of structural failure in the sapwood, associated with decay fungi. Carbon respiration was positively related to sapwood structural failure and we believe that the two insect groups act in concert to suppress wood decomposition in this system. This is contrary to prevailing wisdom among forest practitioners who have suspected that decay and insect activity are positively correlated, but in agreement with laboratory studies showing antagonism between stain and decay fungi. Lastly, we observed that neither forest harvesting nor fire had strong effects on the development of exemplar taxa from decay communities in ponderosa pine two years post-treatment. Though time since treatment did affect all functional groups inside of logs, only undisturbed old-growth treatments showed a reduced variability in composition, leading us to suspect effects to emerge at longer time intervals. / Graduation date: 2004

The structural integrity of fire-dependent ecosystems, such as ponderosa pine (<i>Pinus ponderosa </i> Dougl.) and Interior Douglas-fir (<i>Pseudotsuga menziesii </i> (Mirb.) Franco) biogeoclimatic zones in Interior British Columbia (BC) is changing. The problems within these ecosystems include decreased rangeland area, reduced carrying capacity and loss of biodiversity due to tree encroachment and forest ingrowth caused mainly by fire suppression. The goal of this study was to determine the effect of burning and thinning on understory vegetation of grassland and forested sites. The burning experiment took place at Dew Drop (Tranquille Ecological Reserve) located 20 km northwest of Kamloops, BC. Thinning was done at two upper grassland sites near Cache Creek, BC; Coal Mine Pasture and Gladys Lake Pasture. Species evenness and values of the Shannon-Weiner Diversity Index (H) were reduced (13 and 27%, respectively) within three years following burning (P = 0.014 and P = 0.038, respectively). Burning reduced canopy cover of shrubs on grassland sites (P = 0.005) and it reduced graminoid cover on forest sites (P = 0.014) immediately after the treatment (1999) but both functional groups had recovered by 2002. Litter depth and total canopy cover of plants were reduced in grasslands and forests immediately following burning (1999) but litter depth and canopy cover had recovered by 2002. Litter cover and litter depth beneath the tree canopy were reduced by burning (P = 0.037 and P = 0.009, respectively). Trends in the data indicate forb standing crop increased and total understory standing crop increased following burning in the grassland compared to the control. Graminoid standing crop was reduced 47% by burning in the forests (P = 0.049). Thinning reduced species richness in the first (P = 0.033) and fourth (P = 0.030) years, and H in the first year (P = 0.037) following the thinning at Coal Mine Pasture. Trends in the data suggest understory standing crop increased at Coal Mine and Gladys Lake Pastures following thinning. At both locations, thinning reduced litter depth. Therefore, burning and thinning kills trees, reduces fuel loads, and increases standing crop of the understory.

The structural integrity of fire-dependent ecosystems, such as ponderosa pine (<i>Pinus ponderosa </i> Dougl.) and Interior Douglas-fir (<i>Pseudotsuga menziesii </i> (Mirb.) Franco) biogeoclimatic zones in Interior British Columbia (BC) is changing. The problems within these ecosystems include decreased rangeland area, reduced carrying capacity and loss of biodiversity due to tree encroachment and forest ingrowth caused mainly by fire suppression. The goal of this study was to determine the effect of burning and thinning on understory vegetation of grassland and forested sites. The burning experiment took place at Dew Drop (Tranquille Ecological Reserve) located 20 km northwest of Kamloops, BC. Thinning was done at two upper grassland sites near Cache Creek, BC; Coal Mine Pasture and Gladys Lake Pasture. Species evenness and values of the Shannon-Weiner Diversity Index (H) were reduced (13 and 27%, respectively) within three years following burning (P = 0.014 and P = 0.038, respectively). Burning reduced canopy cover of shrubs on grassland sites (P = 0.005) and it reduced graminoid cover on forest sites (P = 0.014) immediately after the treatment (1999) but both functional groups had recovered by 2002. Litter depth and total canopy cover of plants were reduced in grasslands and forests immediately following burning (1999) but litter depth and canopy cover had recovered by 2002. Litter cover and litter depth beneath the tree canopy were reduced by burning (P = 0.037 and P = 0.009, respectively). Trends in the data indicate forb standing crop increased and total understory standing crop increased following burning in the grassland compared to the control. Graminoid standing crop was reduced 47% by burning in the forests (P = 0.049). Thinning reduced species richness in the first (P = 0.033) and fourth (P = 0.030) years, and H in the first year (P = 0.037) following the thinning at Coal Mine Pasture. Trends in the data suggest understory standing crop increased at Coal Mine and Gladys Lake Pastures following thinning. At both locations, thinning reduced litter depth. Therefore, burning and thinning kills trees, reduces fuel loads, and increases standing crop of the understory.

Thesis (M.S.)--Oregon State University, 2003. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

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