Matching Items (5)
Filtering by
- All Subjects: Soil Ecology
- All Subjects: Saguaro
- Creators: Green, Douglas
Description
The Cave Creek Complex fires of June and July of 2005 north of Phoenix, Arizona, U.S.A. burned 248,310 acres of Sonoran desert, primarily on the Tonto National Forest, USFS. The fires consumed multiple stands of the keystone species Carnegiea gigantea, the saguaro cactus. Restoration efforts in late spring 2007 involved the monitoring of 200 transplanted saguaro cacti over a two year period for overall establishment and success. Observation of local saguaro distribution suggests that soil factors might influence saguaro growth. Therefore, soil samples were collected from each transplant location and analyzed for percentage coarse fragments, texture, pH and electrical conductivity as soil collection and analysis of these variables are relatively inexpensive and expedient. Regression analysis was used to determine which, if any of these soil characteristics significantly correlated with plant growth. The results of this study found significant correlation between saguaro transplant growth and the soil variables of clay content and pH, but no correlation between saguaro growth and coarse fragment percentages or electrical conductivity.
ContributorsElliott, Todd (Author) / Green, Douglas (Thesis advisor) / Steele, Kelly (Committee member) / Alford, Eddie (Committee member) / Arizona State University (Publisher)
Created2013
Description
Livestock-grazing, in particular cattle grazing, is a common use of public and private lands in western North America. As a result, the effects of grazing on both plants and animals are widely studied. Few studies, however, look directly at the long-term effects that cattle grazing may have on a particular species. The goal of this experiment was to continue research begun in 1988, to determine if the effects of cattle grazing are still seen in the age structure of two populations of saguaros (Carnegiea gigantea [Engelm.] Britton & Rose) at Saguaro National Park - Rincon Mountain District (SNP-RMD). The null hypothesis stated that enough time has elapsed since the cessation of grazing, and there is no difference in the age distribution of the saguaros of the two populations. The study area was comprised of a former fence line where grazing ceased on the western side of the fence in 1958 and the eastern side in 1978. Belt transects were laid on each side of the fence line and height was measured for each saguaro encountered in a transect. Approximate age of the individual was then calculated using an age-height correlation for SNP-RMD. Individuals were then placed into age classes of 10 year increments and a Log-Likelihood test was performed. The resulting calculated P value of 0.12 meant the null hypothesis was not rejected and there was no statistical difference between the age structure of the two populations. After 34 and 54 years rest from grazing, the negative effects of cattle grazing on the retention and recruitment of saguaro seedlings have ended, and replenishment of the populations is now dependent upon factors such as temperature and precipitation. Other factors such as climate change, increasing fire frequency, encroachment by invasive species, and poaching are sources of concern and increased mortality for these and other saguaros.
ContributorsKrone, Elizabeth AnnMarie Stewart (Author) / Alford, Eddie (Thesis advisor) / Brady, Ward (Committee member) / Green, Douglas (Committee member) / Arizona State University (Publisher)
Created2013
Description
Mycorrhizal fungi form symbiotic relationships with plant roots, increasing nutrient and water availability to plants and improving soil stability. Mechanical disturbance of soil has been found to reduce mycorrhizal inoculum in soils, but findings have been inconsistent. To examine the impact of restoration practices on riparian mycorrhizal inoculum potential, soil samples were collected at the Tres Rios Ecosystem Restoration and Flood Control Project located at the confluence of the Salt, Gila, and Agua Fria rivers in central Arizona. The project involved the mechanical removal of invasive Tamarix spp.( tamarisk, salt cedar) and grading prior to revegetation. Soil samples were collected from three stages of restoration: pre-restoration, soil banks with chipped vegetation, and in areas that had been graded in preparation for revegetation. Bioassay plants were grown in the soil samples and roots analyzed for arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) infection percentages. Vegetations measurements were also taken for woody vegetation at the site. The mean number of AM and EM fungal propagules did not differ between the three treatment area, but inoculum levels did differ between AM and EM fungi with AM fungal propagules detected at moderate levels and EM fungi at very low levels. These differences may have been related to availability of host plants since AM fungi form associations with a variety of desert riparian forbs and grasses and EM fungi only form associations with Populus spp. and Salix spp. which were present at the site but at low density and canopy cover. Prior studies have also found that EM fungi may be more affected by tamarisk invasions than AM fungi. Our results were similar to other restoration projects for AM fungi suggesting that it may not be necessary to add AM fungi to soil prior to planting native vegetation because of the moderate presence of AM fungi even in soils dominated by tamarisk and exposed to soil disturbance during the restoration process. In contrast when planting trees that form EM associations, it may be beneficial to augment soil with EM fungi collected from riparian areas or to pre-inoculate plants prior to planting.
ContributorsArnold, Susanne (Author) / Stutz, Jean (Thesis advisor) / Alford, Eddie (Committee member) / Green, Douglas (Committee member) / Arizona State University (Publisher)
Created2012
Description
Microarthropods play important roles in the decomposition process of the detrital food web, where they break down organic matter and return nutrients to the soil. However, only a small percentage of the belowground microarthropod population has been studied or even discovered, leading to a decrease in the knowledge of all of the processes carried out by these organisms and their importance to the soil. This is because microarthropod extraction methods are not 100% effective at collecting specimens. This study aimed to find an ideal quantitative procedure to better record the number of microarthropods existing in the soil and to determine if a seasonal variation exists that effects the success of extraction. Two extraction methods, including dynamic extraction and heptane flotation extraction, were compared across two seasons, a dry season (June) and a wet season (September). Average biomasses and average richness were calculated for four different functional groups, including Prostigmata, Mesostigmata, Cryptostigmata, and Collembola, across the two seasons, and statistical analysis was performed to determine if any differences that existed were statistically significant. Results indicate that the dynamic extraction method was significantly more effective for the collection of microarthropods during the wet season, and the heptane extraction method was significantly more effective during the dry season. In addition, the heptane procedure recovered samples of higher average richness than the dynamic method during both seasons. The heptane procedure works best for extraction during the dry season because it is able to collect organisms that entered into an ametabolic anhydrobiotic state to escape desiccation. These organisms form a protective lipid layer around their exoskeletons to retain water, and the non-polar exoskeletons display a chemical affinity to the heptane fluid, allowing for collection out of the soil and into the heptane layer. Despite these results, no one method is entirely superior to the other, and the most efficacious procedure depends on the researcher's aim of study.
ContributorsAntol, Rachel Lynn (Author) / Sabo, John L. (Thesis director) / Hall, Sharon (Committee member) / Wyant, Karl A. (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2014-12
Description
ABSTRACT The February 2008 study of a Snowflake, Arizona site measured changes in soil organic carbon, total nitrogen, extractable phosphorus, and soil moisture, to determine what affect One-seed Juniper (Juniperus monosperma) trees have on surrounding soil, thus affecting native grass growth. Increasing juniper densities in grasslands also decrease populations of some grassland bird species. Measurements were taken each meter along a twelve meter line transect, moving from juniper trees, through a bare soil area and into a grassland. Non-linear relationships were examined, in regard to distance from the tree and juniper root mass. Relationships were examined to determine any affect of the juniper tree on soil characteristics along the transect. Organic carbon decreased as distance increased from the trees (F=4.25, df=46, p=0.020). Soil moisture increased with distance from the trees (F=5.42, df=46, p=0.008), and juniper root mass, of roots less than 1 mm diameter, significantly decreased with distance away from the trees (F=11.29, df=46, p=0.0001). Total nitrogen and extractable phosphorus did not significantly change with distance from the tree, or presence of juniper roots. This data is important as grassland restoration projects rely on the availability of soil nutrients and water for reestablishment of native grass species.
ContributorsWeller, Christopher (Author) / Green, Douglas (Thesis advisor) / Miller, William H. (Committee member) / Alford, Edward (Committee member) / Arizona State University (Publisher)
Created2010