Browsing by Subject "Forests"
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Item Environment and development: essays on the link between household welfare and the environment in developing countries(2014-07) Rogers, Martha H.In this dissertation, I present three methods of evaluating local populations' interactions with their natural environments using household-level data from Tanzania. To date, little effort has been made to evaluate the non-market benefits of natural resources for local populations and this dissertation makes important contributions to this budding research area. First, I apply a travel cost model and estimate that households in Kagera, Tanzania are willing to pay approximately $200 per year (2012 U.S. dollars) for local community forests access, a value equal to roughly 25 percent of annual total household expenditures. Second, using a long-term panel data set I estimate that an additional hour required to collect firewood when a child is young translates into $475 (2010 USD) in lost earnings over 30 years, roughly 1.7 percent of income. Finally, I show evidence of significant interdependencies between a household's agricultural production and food consumption decisions. This inter-dependency implies that programs aimed at environmental conservation through agricultural intensification may have important unintended consequences on a household's food consumption and subsequent micronutrient levels. In sum, the results in this dissertation indicate that households in Tanzania interact with their environments in complex ways and receive significant non-market benefits from natural resources.Item Libraries Offer Key Resources for Managing Private Forests(Minnesota Forest Association, 1991) Sandy, John HThis article promotes the role of Minnesota libraries in helping private forest landowners manage their woodlands.Item Population genetic structure, pollen dispersal, and local adaptation in Quercus oleoides forests of Costa Rica(2010-08) Deacon, NicholasRecent and ongoing anthropogenic land use has altered natural landscapes and resulted in isolated patches of native vegetation across the globe. This process of habitat fragmentation reduces continuous habitat into small remnants in a matrix of altered terrain. The impetus for this research was to contribute to the growing body of work on the effects of habitat fragmentation while simultaneously gaining a better understanding of the specific role that recent fragmentation played in the evolution and demography of the most ubiquitous species in one particular region. My goal was to understand the evolutionary history of Quercus oleoides in Costa Rica in order to more effectively conserve and possibly restore the region’s seasonally dry forest in the future. How has the conversion of the seasonally dry forest of Costa Rica to an agricultural mosaic affected Quercus oleoides (live oak), the dominant tree species of remnant forest fragments? Although studies addressing the genetic consequences of habitat fragmentation are becoming more common, assessments of genetic structure and population viability that inform management decisions for conservation and restoration are rare. This study combined analyses of genetic diversity, pollen dispersal, and the growth and survival of various seedling families to provide an integrated evaluation of the response of a critical dry forest species to fragmentation and will help guide management and restoration efforts in the Aréa de Conservación Guanacaste (ACG). v The Q. oleoides forests of Guanacaste province, Costa Rica are something of a biological enigma: they are geographically disjunct and genetically distinct from conspecifics and similar species, and geographically quite restricted within Costa Rica while spanning a broad range of environments and associations within that range. Quercus oleoides is ectomycorrhizal in a habitat dominated by endomycorrhizal associations, possesses an atypical developmental process with regard to germination and emergence system, produces a fruit type that is extremely rare in the tropics, is wind pollinated in a habitat dominated by insectpollinated species, is evergreen in a habitat where most species are deciduous or semi-deciduous, and its reproductive phenology is largely mismatched to the seasonally dry environment of Guanacaste, producing large crops of dessicationsusceptible acorns at the beginning of a dry season more severe than what the species encounters anywhere else in its range. Despite this seeming mismatch between traits and environment, Q. oleoides is by far the most common large tree wherever it occurs. As such it is an extremely important structural species in Guanacaste dry forest. Its seeds are consumed by a wide range of mammalian and avian seed predators and its evergreen habit undoubtedly has a large effect on the abiotic environment experienced by many dry forest organisms. The subsequent chapters describe three previously unanswered questions about the past, present, and future status of Q. oleoides in the ACG. In Chapter 1, I characterized the standing genetic diversity of 13 Q. oleoides populations vi and the geographic structuring of that diversity. The pattern of that diversity was compared to geographic distance, flowering time similarity, and environmental similarity among populations. The structuring of genetic diversity was also compared between two age cohorts representing pre-fragmentation individuals and post-fragmentation individuals. I found that Q. oleoides in Costa Rica contained a high level of genetic diversity as well as genetic variation that is geographically structured across the landscape. The degree to which this structuring is due to fragmentation, however, is small in comparison to the genetic structure that has existed prior to fragmentation. This is somewhat counterintuitive due to the expectations provided from population genetic theory that can be applied to fragmented landscapes. If habitat fragments are isolated from one another such that gene flow no longer occurs among them, inbreeding may reduce offspring fitness and limit the viability of populations in those fragments. Isolated habitat fragments then become genetically differentiated over time due to the random process of genetic drift. Genetic diversity may also be affected because the amount of genetic variability in a population decreases due to the loss of rare alleles when the individuals carrying them are removed. This is termed a genetic bottleneck because the genetic variability of future generations is contained in the few surviving individuals. Small populations are vulnerable to stochastic environmental and demographic occurrences because adaptation by an organism to a changing environment depends on the genetic variability present in the population. The loss of genetic diversity reduces future evolutionary options and can lead to extinction. Population genetic variation consists of the sum of all genetic variation among individuals within the population. It can be measured by parameters including allelic richness (A) and expected heterozygosity (He). Allelic richness is the average number of alleles per locus and observed heterozygosity is compared to expected heterozygosity under Hardy-Weinberg equilibrium conditions. Wright’s F-statistics are means of describing how genetic diversity is partitioned in a population. High values for FST indicate that subpopulations have very different gene frequencies than the total population. A loss in heterozygosity can occur with inbreeding due to the higher chance that offspring of a mating event between two individuals with the same common ancestor may share the same alleles. One method for quantifying genetic variation within species is to assay highly variable regions of repeated DNA units called microsatellites. Individuals of a population were characterized by the differences in length of 11 of these non-coding genetic units. Although I observed no significant correlations between genetic distance and geographic distance, flowering time similarity, or environmental similarity in Chapter 1; I analyzed pollen dispersal more rigorously in Chapter 2 in order to better calculate contemporary pollen dispersal distance estimates. It is not unusual for studies of plant populations in fragmented landscapes to report few of the negative consequences predicted by theory, and that is because pollen may actually disperse father in fragmented landscapes. My results from two separate molecular analyses of pollen dispersal distance using 8 of the microsatellite markers from Chapter 1, however, indicated that the average pollen dispersal that resulted in viable offspring predominately occurred over very short distances. Both the paternity exclusion and two-generation methods yielded similarly short dispersal distance estimates. Evidence from the physical trapping of pollen in one location indicated that pollen was capable of moving much farther, however, so the importance of long distance pollen dispersal may rely more on phenology. I observed staminate and pistillate flowering times in 10 sites over two years, but the lack of strong seasonality in flowering obscured any obvious patterns. The geographic structuring of genetic diversity and the short average pollen dispersal distance provide a sound foundation for testing for local adaptation in Q. oleoides populations. In Chapter 3, I compared the growth and survival of upland and lowland maternal families in their native and foreign environments. The native environment of the populations of families differs most notably in their elevations and the lack of precipitation during the 4-5 month dry season in the lowlands. Seedlings planted in the lowland garden from both populations experienced a much higher level of mortality than seedlings planted in the upland garden, but using the aster models approach for comparing the likelihood of various models of combined growth and survival data, we did not identify evidence for local adaptation. Overall, these experiments indicate that contemporary Q. oleoides in Costa Rica have a rich and complicated population genetic history that despite obvious and extensive habitat fragmentation has not severely affected genetic variation or demographic processes. The long term outlook for the recovery of the tropical dry forests in general and the Q. oleoides stands, in particular, is good. Little direct action by managers is required and any active planting efforts do not seem to be encumbered by site-specific seed requirements. I do recommend local seed sources, however, out of an abundance of caution. These results not only add to the field fragmentation studies by examining a common, tropical tree over multiple habitats; this work also provides applicable information to an actively managed region that is in a transitory successional state.Item Predicting breeding habitat of the Connecticut Warbler (Oporornis agilis)(2010-05) Lapin, CarlyThe Connecticut warbler (Oporornis agilis) is an uncommon Neotropical migrant that breeds in the north-central United States and south-central Canada. Breeding populations of this species are reported to be declining. I analyzed habitat and landscape at three spatial scales (buffer radii of 100 m, 500 m, and 1,000 m) for 86 sites within 28 forest stands in northern Minnesota for Connecticut Warblers sampled over an 18-year period. I regressed combinations of habitat variables with two response variables, Connecticut Warbler abundance (the total number ever recorded at a site or stand) and Connecticut Warbler frequency (the number of years recorded out of 18 years) using a zero-inflated negative binomial distribution and logistic regression, respectively. A subset of models with #1;AICc ≤ 4.0 was retained and model-averaged predictions were calculated for each combination of buffer size and response variable. When comparing model-averaged predictions to observed data, the best models were those using Connecticut Warbler frequency at the 1,000 m buffer (r2 = 0.52). These models were used to create a map of predicted Connecticut Warbler breeding habitat in the two national forests sampled. At the 1,000 m scale, Connecticut Warblers were positively associated with large, simple patches of upland coniferous and lowland black spruce forest, and were negatively associated with upland deciduous forest.Item Riparian Forest Buffers for Trout Habitat Improvement(2010-06-30) Bongard, Phyllis; Wyatt, Gary; Nerbonne, BrianCreating an educational program that promotes the benefits of riparian forest buffers. The approach includes developing educational materials based on a literature review and establishing a demonstration on an existing DNR-designated trout stream, the Vermillion River in Dakota County.