Browsing by Author "Marcia Gumpertz, Member"

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Ecological and Political Implications of Conversion from Shade to Sun Coffee in Puerto Rico
(2002-01-10) Borkhataria, Rena Rebecca; Jaime Collazo, Chair; Martha Groom, Member; Marcia Gumpertz, Member; Harold Heatwole, Member; Robert Rice, Member
Recent studies have shown that biodiversity is greater in shaded plantations than in sun coffee plantations, yet many farmers are converting to sun coffee varieties to increase short-term yields or to gain access to economic incentives. Through conversion, ecosystem complexity may be reduced and ecological services rendered by inhabitants may be lost. I attempted to quantify differences in abundances and diversity of predators in sun and shade coffee plantations in Puerto Rico and to gain insight into the ecological services they might provide. I also interviewed coffee farmers to determine the factors influencing conversion to sun coffee in Puerto Rico and to examine their attitudes toward the conservation of wildlife. Avian abundances were significantly higher in shaded coffee than in sun (p = 0.01) as were the number of species (p = 0.09). Avian species that were significantly more abundant in shaded coffee tended to be insectivorous, whereas those in sun coffee were granivorous. Lizard abundances (all species combined) did not differ significantly between plantations types, but Anolis stratulus was more abundant in sun plantations and A. gundlachi and A. evermanni were present only in shaded plantations. Insect abundances (all species combined) were significantly higher in shaded coffee (p = 0.02). I used exclosures in a shaded coffee plantation to examine the effects of vertebrate predators on the arthropods associated with coffee, in particular the coffee leaf miner (Leucoptera coffeela) and the flatid planthopper Petrusa epilepsis, in a shaded coffee plantation in Puerto Rico. Treatments included exclusion of birds, lizards, birds and lizards, and no exclusion. I found that birds had a significant effect on the abundance of Petrusa epilepsis and on insects > 5 mm in length. Combined insect species abundance as well as abundance of insects 2-5 mm and 5-10 mm varied significantly by treatment and removal of both birds and lizards had a larger effect than the removal of either taxa alone. Vertebrate predators exerted little influence over the coffee leaf miner, nor did they appear to appear with the leaf miner's natural enemies, a complex of parasitoid wasps. In the survey of 100 coffee farmers, I found that sun coffee was substantially more prevalent than shaded coffee, both in number of farms and in land area devoted to its production. The average sun coffee plantation was significantly larger than the average shaded plantation (p = 0.02). Reasons for conversion from shade to sun coffee included higher yields, recommendations by agronomists, and incentives from the government. Farmers placed high conservation value on species that are rare or provide services to humans. Vertebrate insectivores were more diverse and abundant in shaded coffee and may provide a service to farmers by depressing total insect numbers and preventing outbreaks of the planthopper Petrusa epilepsis. Furthermore, they did not interfere with parasitism of the coffee leaf miner by parasitoid wasps. I conclude that governmental incentives for shaded coffee have a high probability of success, since coffee growers are highly dependent upon assistance from the government.
Effects of Nutrient Amendments and Genotype on Stand Productivity and Crown Characteristics in Loblolly Pine(Pinus taeda L.)
(2002-01-24) Handest, Joshua A.; Steve McKeand, Co-Chair; H. Lee Allen, Co-Chair; Marcia Gumpertz, Member
Two provenances of loblolly pine, with five open-pollinated families from each were analyzed fordifferences in height, volume, leaf area, and various crown characteristics. Families from the North Carolina and South Carolina Coastal Plain (ACP) and from the 'Lost-Pines' area of Texas(LPT) were included in the study. In addition to studying potential genetic variation, half of theplots received fertilization treatments so that potential nutrient and genotype x environment(GxE) interactions could be assessed. The stands were established in 1993 and height wasmeasured annually until year 3 when both height and diameter at breast height were measured.Leaf area measurements were made in 1999 using the LI-CORE LAI-2000 PCA and destructiveand non-destructive sampling of individual branches was done to estimate the crown characteristics. Nutrient additions starting at stand establishment resulted in large gains in juvenile developmentin height, volume, leaf area, and growth efficiency. Fertilization also dramatically increasedfoliage and branch biomass at all crown levels, and also contributes to an early shift of foliage from the lower crown to the middle. This is most likely due to early canopy closure. The AtlanticCoastal Plain provenance consistently outperformed the Lost Pine Texas provenance in height,volume, and growth efficiency. The ACP provenance had more foliage, predominately in themiddle crown than the LPT provenance, which may explain some of the productivity differences.There was a significant amount of variation in height, volume, leaf area, and growth efficiencybetween the families of both provenances. Both the vertical distribution and quantity of foliage inthe ACP families may explain some of the variation in volume growth and growth efficiency,though neither show enough of a direct correlation to explain all of it. The crown characteristicsstudied seem to indicate that distribution of foliage itself is more important in explainingdifferences among the LPT families.
Mapping, Measuring, and Modeling Cultural Intelligence as the Capacity for Success in the Global Knowledge Economy: A Series of Meta-Analyses.
(2018-04-05) Irvine, Christina Bode; Mattie Fleener, Chair; James Bartlett, Member; Marcia Gumpertz, Member; Bradley Mehlenbacher, Member
New Approaches for Crossover and Screening Optimal Design.
(2020-08-07) Allen, Katherine Nicole; Jonathan Stallrich, Chair; Alyson Wilson, Member; Marcia Gumpertz, Member; Bradley Jones, External; He Huang, Member
Predicting the Dimensional Impact of Pitch Stitches.
(2021-01-18) Vekert, Jennifer Star; Lisa Parrillo-Chapman, Chair; Marcia Gumpertz, Member; Marguerite Moore, Member; Lori Rothenberg, Member
Using Generalized Linear Models to Enhance Satellite Based Land Cover Change Detection
(1997-04-29) Morisette, Jeffrey Thomas; Siamak Khorram, Chair; Marcia Gumpertz, Member; Hugh Devine, Member; Thomas Mace, Member; Joseph Roise, Member
A popular satellite based land cover change detection technique is to compare the spectral information for each pixel, from two images acquired at different dates. For each pixel, if there is a big enough difference between the reflectance values from the two images, the area represented by that pixel is considered to have changed. The change detection methods are different in how they determine a "big enough difference". The analyst is left to choose which function of the reflectance values to use and where to set the "change" threshold. These choices are often subjective and affect the accuracy of the change detection. In this dissertation we describe and defend the thesis that Generalized Linear Models can be used to enhance satellite based land cover change detection. This is done by first presenting some background on satellite based change detection and then describing how the Generalized Linear Models relate to existing satellite based change detection algorithms. This is followed by an example change detection, which utilizes Generalized Linear Models. The example uses subset images from Landsat Thematic Mapper Data. The data are from 1988 and 1994. For each time period there are overlapping subset images for an area over Raleigh, North Carolina and two overlapping subset images for an area over a coastal region of North Carolina. In each region we collect a sample at 260 ground locations. For each location, land cover changes are determined from high-resolution air photo reference data. This is coupled with the satellite radiance values for the corresponding area. Generalized Linear Models are then used to regress the binary response of change/no-change (as determined from the air photos) on the radiance values extracted from the satellite imagery. In doing so, the models help determine the most appropriate function of the reflectance values to use for predicting change. For the data in this study, the GLMs indicated a combination of radiance values to be more accurate than a single band or single index. Also, the models indicate that different combinations of radiance values should be used for the different study areas. Next, the models are used to produce "accuracy assessment curves". These curves show the relationship between the location of the "change threshold" and the accuracy of the associated change classification. These curves can be used to compare two models across all possible change thresholds. Finally, the models are incorporated into the satellite imagery to produce "probability of change" (POC) images and "variability" images. In the POC image the pixels contain continuous values ranging from zero to one, representing the probability that the area has changed. The pixels in the variability image contain values corresponding to the variability of the estimated POC. Results indicate that incorporating Generalized Linear Models into satellite based land cover change detection yields a more quantitative change detection procedure and more informative change detection products. There are three ways to utilize the models. First GLMs can help select the most significant set of explanatory variables to use in the change detection. Next, the output from the GLMs can be used to produce what we will refer to as "accuracy assessment curves". These curves show the relationship between the threshold value used to classify change areas and the accuracy of this classification. The third use is through incorporate the modeling into the image data to produce continuous "probability of change" images in which the pixel values range from zero to one. These values represent the probability that the area represented by that pixel has changed.