- About
-
The Global ETD Search service is a free service for researchers
to find electronic theses and dissertations. This service is
provided by the
Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
Search results
Showing 1 to 5 of 5 (0.047 seconds)Spelling suggestions: "subject:"step density""
| 1 |
Effect of Rate and Season of Application of Aminocyclopyrachlor on the Control of Acacia Farnesiana (L.) Willd. in South TexasMcGinty, Joshua 2012 May 1900 (has links)
This study was conducted on two rangeland sites in south Texas with large populations of huisache (Acacia farnesiana (L.) Willd.); the Bush Ranch in Goliad County, and the Hitchcock Ranch in Bee County. The purpose of the study was to evaluate the effect of three herbicide treatments and three seasons of application on 1) apparent mortality of huisache, 2) huisache canopy cover, 3) huisache stem density, and 4) herbaceous ground cover.
Herbicide treatments included aminocyclopyrachlor alone at a rate of 0.315 kg a.i. ha-1, aminocyclopyrachlor + triclopyr at a rate of 0.210 kg a.i. ha-1 + 0.420 kg a.e. ha-1, and triclopyr + picloram at a rate of 0.560 kg a.e. ha-1 + 0.560 kg a.e. ha-1. Herbicide treatments were applied over 3 x 30 m plots containing previously mowed huisache in May, July, and October of 2010 with ground-broadcast equipment at a rate of 140 L ha-1. Randomly selected huisache individuals and herbaceous ground cover at randomly selected points were monitored for the duration of the study.
Statistical analyses of huisache mortality, canopy area, and stem densities revealed that at both sites one year after treatment, huisache mortality across the three seasons of application was consistently higher in plots treated with aminocyclopyrachlor + triclopyr (50 to 99%) versus those treated with aminocyclopyrachlor alone (16 to 78%) or triclopyr + picloram (4 to 70%). This mixture also provided the greatest reductions in huisache canopy area (60 to 99% reduction) and stem density (61 to 99% reduction). Also at both sites, spring applications consistently provided the greatest huisache control and canopy and stem reductions. Herbicide treatment and season of application had little effect on post-treatment herbaceous ground cover, likely due to extreme drought conditions in 2011.
Of the possible combinations of seasons of application and herbicide treatments, the application in the spring of aminocyclopyrachlor plus triclopyr provided the most desirable results in terms of huisache mortality, canopy reduction, and stem density reduction. However, for sites invaded by huisache that are located near to potentially susceptible crops, the application of aminocyclopyrachlor plus triclopyr or aminocyclopyrachlor alone in the fall after the harvest of those crops may be more appropriate in order to avoid non-target injury while still providing acceptable huisache control.
|
| 2 |
Estimating forest attributes using laser scanning data and dual-band, single-pass interferometric aperture radar to improve forest managementPeduzzi, Alicia 27 September 2011 (has links)
The overall objectives of this dissertation were to (1) determine whether leaf area index (LAI) (Chapter 2), as well as stem density and height to live crown (Chapter 3) can be estimated accurately in intensively managed pine plantations using small-footprint, multiple-return airborne laser scanner (lidar) data, and (2) ascertain whether leaf area index in temperate mixed forests is best estimated using multiple-return airborne laser scanning (lidar) data or dual-band, single-pass interferometric synthetic aperture radar data (from GeoSAR) alone or both in combination (Chapter 4). In situ measurements of LAI, mean height, height to live crown, and stem density were made on 109 (LAI) or 110 plots (all other variables) under a variety of stand conditions. Lidar distributional metrics were calculated for each plot as a whole as well as for crown density slices (newly introduced in this dissertation). These metrics were used as independent variables in best subsets regressions with LAI, number of trees, mean height to live crown, and mean height (measured in situ) as the dependent variables. The best resulting model for LAI in pine plantations had an R2 of 0.83 and a cross-validation (CV) RMSE of 0.5. The CV-RMSE for estimating number of trees on all 110 plots was 11.8 with an R2 of 0.92. Mean height to live crown was also well-predicted (R2 = 0.96, CV-RMSE = 0.8 m) with a one-variable model. In situ measurements of temperate mixed forest LAI were made on 61 plots (21 hardwood, 36 pine, 4 mixed pine hardwood). GeoSAR metrics were calculated from the X-band backscatter coefficients (four looks) as well as both X- and P-band interferometric heights and magnitudes.
Both lidar and GeoSAR metrics were used as independent variables in best subsets regressions with LAI (measured in situ) as the dependent variable. Lidar metrics alone explained 69% of the variability in temperate mixed forest LAI, while GeoSAR metrics alone explained 52%. However, combining the LAI and GeoSAR metrics increased the R2 to 0.77 with a CV-RMSE of 0.42. Analysis of data from active sensors shows strong potential for eventual operational estimation of biophysical parameters essential to silviculture. / Ph. D.
|
| 3 |
Use of Landsat Data to Characterize Burn Severity, Forest Structure and Invasion by Paulownia (Paulownia Tomentosa) in an Eastern Deciduous Forest, KentuckyUpadhaya, Suraj 01 January 2015 (has links)
Landsat imagery has been used successfully to assess burn severity and monitor post-fire forest structure in a variety of ecosystems, but to date there are few documented studies on its application in the eastern deciduous forests of the eastern United States. The occurrence of a wildfire in the Daniel Boone National Forest in2010 provided a rare opportunity for research into the use of Landsat data for assessing burn severity and its ecological effects. We used differenced normalized burn ratio (∆NBR) to quantify burn severity. The ∆NBR based burn severity classification had 70% agreement with a qualitative ground-based burn severity assessment. We also examined the relationship between the presence of an invasive species (Paulownia tomentosa), and our assessment of burn severity, where we found a weak but statistically significant relationship (adj R2 0.13, p<0.0001). We also examined the relationship between the normalized difference vegetation index (NDVI) and forest structure measurements. The relationship between NDVI and basal area was strongly and significantly related (adj R2 0.41, p<0.0001). The relationship of NDVI with stem density was weak but significant (adj R2 0.23. p=0.004). These results indicate that data from Landsat imagery have great potential for quantifying burn severity, identifying potential hotspots for invasive species, and assessing post fire forest structure in the eastern deciduous forest.
|
| 4 |
Analysis of Amur honeysuckle Stem Density as a Function of Spatial Clustering, Horizontal Distance from Streams, Trails, and Elevation in Riparian Forests, Greene County, OhioGrierson, Greg Michael, Jr. 28 May 2021 (has links)
No description available.
|
| 5 |
Relationships between soil chemical properties and forest structure, productivity and floristic diversity along an altitudinal transect of moist tropical forest in Amazonia, Ecuador. / Beziehungen zwischen bodenchemischen Eigenschaften und Waldstruktur, Produktivität und floristischer Diversität tropischer Regenwälder Amazoniens entlang eines Höhengradienten in Ecuador.Unger, Malte Arne 30 April 2010 (has links)
No description available.
|
Page generated in 0.0518 seconds