Memoria para optar al Título Profesional de Ingeniero Forestal

An infiltration-wetting agent study, using the wetting agent "WATER-IN", was conducted in the ponderosa pine forest type of east central Arizona, near McNary, Arizona. An application rate of 10 gallons of wetting agent per surface acre was used both on bare mineral soil and on ponderosa pine litter. The infiltration rate was measured by a modified North Fork infiltrometer. It was found that "WATER-IN" significantly increased water runoff, when applied to litter, but when applied to bare mineral soil, "WATER-IN" caused a significant increase in water infiltration. The wetting agent did not significantly affect antecedent moisture, soil particle distribution, litter water holding capacity, or litter bulk density. It is presently hypothesized that the increase in water infiltration on treated bare mineral soil is due to a decrease in the average bulk density of the surface inch of soil. The data strongly suggests this hypothesis to be correct. The increase in runoff when litter is treated is probably due to an interaction, either physical, chemical, or both, between the humus layer and "WATER-IN", creating a hydrophobic condition where one did not exist before.

Attempts at reforestation of many sites in the southwestern United States have repeatedly failed. Experience and research show that moisture stress is the primary cause of seedling mortality. Therefore, it is of utmost importance to produce planting stock for these areas that are as drought tolerant as possible. Seedlings with high ratios of root mass to shoot mass and adequate mycorrhizal infections should be more resistant to harsh conditions than most seedlings currently produced in nurseries and greenhouses. Inferences from other research indicated that the root-shoot ratios of seedlings could be increased solely by decreasing the amount of nitrogen supplied to them. Mycorrhizal formation would also be enhanced by minimal nitrogen levels. Containerized ponderosa pine seedlings (Pinus ponderosa Lawson var. scopulorum Engelm.) were grown in commercial greenhouses at various levels of nitrogen fertilization and treated with several mycorrhizal inoculums. Mycorrhizal treatments significantly increased shoot height and diameter, but no other seedling parameters. The inoculums did not affect the root-shoot ratio or the percent of short roots that became infected. Nitrogen levels significantly affected all parameters measured. As nitrogen concentration increased, shoot height, diameter, and weight increased, while root weight, root-shoot ratios, and mycorrhizal infections decreased. The inverse relationship between fertilizer nitrogen concentration and the resulting root-shoot ratios of the seedlings was linear and highly correlated. Nitrogen and percent mycorrhizal infection was nearly linear and also inversely correlated. The results of this research are immediately applicable to current greenhouse and nursery operations. When stock is to be planted on sites where seedling survival may be compromised by harsh environmental conditions, production methods should be modified to yield seedlings with maximum root-shoot ratios and heavily infected with mycorrhizae.

Study objectives included determining whether prescribed burning affected ponderosa pine growth; mathematically modeling the growth response to burning; and determining whether forest management history affected growth response. I sampled 188 trees from two areas near Flagstaff, Arizona; one area (Brannigan Flat) had been logged and thinned, and the other (Chimney Spring) had not; both were burned in 1976. Within each study area, control and burned plots were of similar age, vigor, height, and competition index. Trees at Chimney Spring were older, less vigorous, and taller, and had a higher competition index than at Brannigan. For each tree, periodic basal area increment (PBAI) was calculated for the years 1974-1984. To determine which variable would best model growth, postfire PBAI (individual years, 1977-1984) was correlated with previous growth (average PBAI 1974-1976); crown ratio; competition index; thinning index; and diameter. Two models of growth response were developed; one oriented toward satisfying theoretical and research goals, and the other, toward management applications. Growth was modeled using stepwise multiple linear regression, and the dependent variable was postfire PBAI. Research Model independent variables were previous growth, years (climate), and treatment-year interaction, and 72% of total variance was explained. Fire affected growth significantly and negatively for two years, and then burned trees grew similarly to control trees. Management Model independent variables were crown ratio, competition index, crown ratio, subject tree diameter, year, and treatment, and 52% of total variance was explained. This model, too, indicated a slight negative effect of burning on growth. Management history was not a significant determinant of growth response. Both models validated well; the ratio of observed-to-predicted residual mean square was 1.04 and 0.91 (Research and Management Models, respectively). Thinning index was not significantly related to postfire growth, but a change in carbohydrate allocation from stem wood to crown and root expansion could have resulted in observed burning effects. Management implications include (1) short-term growth decline may result from burning, (2) management history did not affect growth response, and (3) burning impact is greatest in dense stands of small trees.

Management, under the concepts of multiple-use and adaptive management, requires the assessment of potentials and limitations of the natural ecosystems to provide satisfaction to human needs, to protect long term productivity, and preserve biological diversity. Overstory-understory relationships were developed for ponderosa pine (Pinus ponderosa) ecosystems to help managers to evaluate herbage production potentials. Secondary data sources from the Beaver Creek and the Heber Watersheds were divided as follows: igneous soils, igneous clay loam, igneous loam-sandy loam, sedimentary soils, alluvium, and sandstone. Regression models were fitted to the raw data by the least squared method. The dependent variables were herbage production (lb/ac) by component; namely total, grass and grass like plants, forbs and half shrubs, and shrubs. The independent variables were total and ponderosa pine basal area (ft 2 /ac). Semilogarithmic models fitted the data from igneous soils, while logarithmic transformations of hyperbolic models fitted the data from sedimentary soils. For igneous soils, ponderosa pine basal area suffice for adequate predictions of herbage production. Significant differences were found between equations for alluvium and sandstone. The resulting equations for ponderosa pine integrate the core of the model UNDER. Mathematical functions developed elsewhere are included in UNDER to compute herbage production in pinyon-juniper and mixed conifer ecosystems. UNDER is linked to other simulators by MICROSIM. MICROSIM, a multiple-resource simulation model, is a tool to assist in the assessment of potentials of forest and woodlands of Arizona. MICROSIM is a menu driven program for IBM or compatibles it contains the module Flora, for estimating plant responses, and module Fauna, to evaluate impacts on animals. Further development of MICROSIM should include the linkage to more modules and models, and to Geographical Information Systems.

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.

Time domain properties of 23 tree-ring chronologies derived from a large sample of Douglas-fir and ponderosa pine trees growing in closed-canopy forests of Colorado and New Mexico were analyzed using Box-Jenkins models. A variety of statistical criteria were employed during the identification and validation stages for evaluating the performance of different significant models, and the "best" Box-Jenkins model and its immediate "competitor" were reported for each tree-ring chronology. All series were stationary, and only one was approximately a white noise series. Overall, the ARMA(1,1) model was judged the best for 11 series, and the second for 7 of the remaining 12 series. The AR(2) model was considered the best for 6 series, and the second for 4 of the remaining 17 series. No statistical evidence was found for moving average models, nor for models with more than three different parameters. However, both cyclical (or seasonal) models and third-order autoregressive models with a null second-order parameter were chosen for some series. Fitted models explained from 7 to 51% of the variance of the original ring-index series, with an average of about 22 %. All parameter estimates were positive, and they varied within a relatively small range. From a comparison of all employed criteria, Akaike's Information Criterion (AIC) was the one that performed best in identifying Box-Jenkins models for tree-ring chronologies. Possible distinctions were recognized that would separate the selected models according to species and /or standardization option. Among the 12 chronologies from Colorado sites, all derived using the same standardization option, most Douglas-fir series were best fitted by the ARMA(1,1) model, while most ponderosa pine series were best fitted by the AR(2) model, suggesting a difference in the biological persistence of the two species. On the other hand, most of New Mexico chronologies, developed using various standardization options, were best fitted by the ARMA(1,1) model, and no difference was found between Douglas-fir and ponderosa pine series. Also, models fitted to Colorado chronologies explained a lower amount of variance than those for New Mexico chronologies (averages of 17 versus 29% respectively), and cyclical models were mainly selected for New Mexico series. Although periodicities in Douglas-fir series were probably caused by western spruce budworm outbreaks, similar periodic patterns in ponderosa pine series were more difficult to explain because pine trees in the study area had not been defoliated by that insect. Compared to the original tree-ring chronologies, prewhitened series showed similar short-term growth patterns, reduced long-term growth fluctuations, lower standard deviations, and higher mean sensitivities. Also, cross-correlations between chronologies from the same area usually increased after prewhitening. Since the autocorrelation problem is crucial in analyzing the relationships between different time series, and in removing the biological persistence included in tree-ring chronologies, the Box-Jenkins approach should facilitate the analysis of the dynamic relationships between tree growth and environmental variables.

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

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

This research examined the fire history of ponderosa pine (Pinus ponderosa Douglas ex P. Lawson & C. Lawson) forests in northwestern New Mexico. The study area included three sites in the Zuni Mountains of Cibola National Forest and one site along the boundary of El Malpais National Monument. I crossdated over 800 fire scars on 75 samples to reconstruct spatial and temporal characteristics of historic wildfire regimes. The Weibull Median Interval, Weibull Modal Interval, and Mean Fire Interval ranged from five to eight years across all sites and percent-scarred classes (all fires, 10% scarred, and 25% scarred) and indicated that low-severity wildfires occurred frequently in the study area during the period 1700 to 1880. Wildfires were historically driven by climatic variability. Superposed Epoch Analyses revealed that wetter conditions typically occurred one to three years prior to a fire event and were followed by drought during the fire year. No relationship was found between the Pacific Decadal Oscillation (PDO) and wildfire occurrence. These findings implied that shorter-term fluxes between wet and dry conditions, rather than longer-term climatic variability, were historically most conducive to fire occurrence. Fire frequency decreased suddenly in the late 19th century across the study area, and results indicated that fire has been absent at all sites since the 1920s. Anthropogenic disturbances including livestock grazing, timber harvesting, and fire suppression likely explain observed differences between historic and contemporary wildfire regimes in the Zuni Mountains. This research has important implications for forest management. In ponderosa pine forests of the southwestern United States, land managers often aim to restore historic ecological conditions. The reintroduction of a frequent, low-severity wildfire regime might restore some ecological patterns and processes, but given the strong legacy of human disturbances and the influences of human-induced climate change, a complete return to historic conditions may be neither possible nor desired.