A field and laboratory study was made to determine the effect of alternate year rest rotation grazin in stem bases and root crowns of crested wheatgrass. Analyses for carbohydrate reserves and total nitrogen were made for the following treatments: (1) exclosures; (2) open range; (3) agronomy cages. Both carbohydrate concentration and total nitrogen content showed differences between sampling dates but did not show differences as a result of grazing treatment on individual dates. Differences between sampling dates were associated with season and growth stage of plants. Although differences due to grazing teatment were not shown for individual dates the combined average carbohydrate concentration for plants rested or protected from grazing for one season was higher than from protected plants inside exclosures or from plants grazed during the study. Despite the short duration of this study these results indicate that alternate year rest rotation grazing as practiced on Diamond Mountain is not adversely affecting storage of food reserves in crested wheatgrass.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

The composition of a community and the environmental conditions in which they exist fundamentally influence productivity and responses of systems to change. In the Northern Gulf of Mexico (NGoM), the relationships between nutrients, salinity, and phytoplankton populations are complex and have been changing over time. This work focuses on describing and analyzing: 1) a case study of diversity and recommendations for change within an academic institution; 2) spatial and temporal trends in surface dissolved inorganic nitrogen (DIN) and phosphorus (DIP) in the NGoM over 35 years; 3) nutrient addition experiments (NAEs) to determine prevailing NGoM surface slope region nutrient limitation; and 4) NGoM surface continental slope phytoplankton community composition and dynamics. Over time, academic institutions have not made progress toward increasing diversity, equity, and inclusion (DEI) in the geosciences. The first chapter of this work serves as a roadmap for other institutions to make progress toward ingraining DEI frameworks into the foundations of our institutional systems. Toward explaining trends in nutrients from 1985 to 2019, I compiled the largest data set of NGoM surface dissolved nutrient concentrations to date and analyzed it to delineate spatiotemporal trends and identify potential drivers of nutrient change. DIP concentrations in both the Mississippi-Atchafalaya River system (MAR) and in the NGoM increased over time, but the increase of NGoM DIP exceeded the DIP loads coming from only the MAR, suggesting additional sources of P to the NGoM. To determine nutrient controls on surface slope NGoM phytoplankton growth and populations, we calculated growth rates and pigment composition using redundancy analyses and a variety of nutrient limitation criteria for each nutrient amendment over 48 hours. Nutrient limitation criteria concluded predominant NP limitation in the NGoM, though single N and P limitation and nutrient replete conditions were also present. In individual NAEs with N and NP amendments, phytoplankton pigment changes were driven by the growth of diatoms and Synechococcus (Syn). Though release from nutrient limitation stimulated responses in some phytoplankton groups, nutrient limitation of phytoplankton growth could not fully be predicted by the criteria and response thresholds evaluated in this study. Additionally, an analysis of environmental variables and phytoplankton pigments was conducted for the surface slope region of the NGoM to determine how phytoplankton community composition varies spatially with the influence of the MAR plume using group-specific chlorophyll a (Chl-a) calculations, bivariate linear regression, multivariate redundancy analysis, and cluster analysis. The largest proportion of Chl-a occurred in the nano/microphytoplankton group, followed by Syn, with both peaking at the high and low ends of the salinity gradient. Redundancy and cluster analyses showed that nutrients and salinity alone cannot predict or subdivide phytoplankton community composition; however, with the addition of pigments, we can characterize specific regions based on shared environmental variables (i.e., low salinity, high biomass) and pigment abundance. In sum, this work produced a straightforward and reproducible guide to leading a DEI task force, the largest NGoM surface nutrient data set to date, and characterizations of NGoM continental slope nutrient limitation and pigment composition and their relation to environmental variables.

Land application of domestic and industrial wastewaters provides an effective means of recycling water and its components into the ecosystem. Successful treatment by soil requires that wastewater is applied in quantities that both maintain infiltrative capacity of the soil and do not exceed the capacity of the soil-plant system to assimilate biological and chemical contaminants. Application of N-rich wastewaters requires that consideration be given to both the ability of the soil to transmit the hydraulic load and remove sufficient N to maintain groundwater quality standards. A textile wastewater containing high concentrations of organic N was spray-irrigated to tall fescue (Festuca arunindinacea) to determine optimum N application levels. Nitrogen balances were determined at each N level and and the potential for predicting the leaching component of the excess N applied was investigated. Historically on-site wastewater disposal systems (OSWDS) for treating septic tank effluent (STE) have been designed on a hydraulic loading basis with N pollution potential essentially ignored. Many soils have been deemed unsuitable for application of STE because of textural, water table, or landscape restrictions. The relations between soil properties, hydraulic performance of OSWDS, and N distribution around OSWDS are evaluated. Wastewater from a nylon processing plant was applied to 'Ky 31' tall fescue at total Kjeldahl nitrogen (TKN) levels of approximately 250, 430, and 1900 kg ha⁻¹ during 1982 and 1983. Fescue yield and N removal was comparable to agricultural yields at similar N application levels. Nitrogen balances indicate that plant uptake efficiency decreased with increasing organic N levels above the 250 kg ha⁻¹ level and that maximum uptake occurred at the 450 kg ha⁻¹ level. Most of the N not recovered in plant tissue mineralized rapidly to the nitrate NO₃⁻ form and leaching was noted during the winter and spring. This data is evaluated with quasi-transient analytical solution of the convection-dispersion equation. The movement of the solute center of mass is predicted on the basis of assumptions of piston flow as well as alternative assumptions of mixing via plate layer theory. Prediction of the location of the center of solute mass (α) provides a moving lagrangian coordinate solution around which dispersion of solute is calculated. The assumptions made about the sequence of evaporation and infiltration events significantly influence the prediction of α and hence the agreement between predicted and measured solute distribution. Both approaches give results which are within experimental error and provide a rational basis for predicting leaching losses and carry-over NO₃⁻ available to future crops. Prototype OSWDS with low pressure distribution installed in three clayey limestone-derived soils were dosed with STE at flux densities ranging from 0.4 to 3.6 cm d⁻¹ on a trench bottom area basis. Ponding was noted in OSWDS at all sites dosed at the 3.6 cm d⁻¹ flux due to both underlying hydraulic restrictions and resultant anaerobic conditions. It is concluded that clayey B horizons low in swelling clays but moderately well structured can be dosed at flux densities up to 2 cm d⁻¹ if low pressure distribution of STE is used. Nitrification was found to be quite limited in soils where effluent was ponded above a restrictive layer but occurred readily within 30 cm below trenches which were freely drained or had matric potentials of at least 40 cm of water. Ratios of NO₃⁻ to Cl⁻ indicate that only limited denitrification can be expected and that substantial NO₃⁻ does leach from below OSWDS in the direction of water flow. / Ph. D.

Lam Lai-yee. / Thesis submitted in: November 2004. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 124-140). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.vii / Table of contents --- p.viii / List of Tables --- p.xi / List of Figures --- p.xiii / List of Plates --- p.xiv / Chapter CHAPTER ONE --- Introduction / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Background and ecological impact of hill fires in Hong Kong --- p.2 / Chapter 1.3 --- Conceptual framework of study --- p.4 / Chapter 1.4 --- Objectives of the study --- p.10 / Chapter 1.5 --- Significance --- p.11 / Chapter 1.6 --- Organization of the thesis --- p.12 / Chapter CHAPTER TWO --- The study area / Chapter 2.1 --- Introduction --- p.14 / Chapter 2.2 --- Geographical setting of Hong Kong --- p.14 / Chapter 2.2.1 --- Climate of Hong Kong --- p.14 / Chapter 2.2.2 --- Geology of Hong Kong --- p.15 / Chapter 2.2.3 --- Soils of Hong Kong --- p.16 / Chapter 2.2.4 --- Vegetation of Hong Kong --- p.17 / Chapter 2.3 --- Site selection --- p.18 / Chapter 2.4 --- Grassy Hill --- p.20 / Chapter CHAPTER THREE --- Heating effect on the properties of ash / Chapter 3.1 --- Introduction --- p.23 / Chapter 3.2 --- Experimental design and methodology / Chapter 3.2.1 --- Selection of simulation heating --- p.26 / Chapter 3.2.2 --- "Heating intensity at 200°-600°C for 1,5 and 15 minutes" --- p.27 / Chapter 3.2.3 --- Field work --- p.27 / Chapter 3.2.4 --- Heating method --- p.28 / Chapter 3.2.5 --- Chemical analysis --- p.28 / Chapter 3.2.6 --- Analysis of data --- p.32 / Chapter 3.3 --- Results and Discussion / Chapter 3.3.1 --- Heating effect on ash weight and pH --- p.33 / Chapter 3.3.2 --- "Heating effect on ash organic C, N and P" --- p.33 / Chapter 3.3.3 --- Heating effect on ash available cations --- p.40 / Chapter 3.4 --- Conclusion --- p.42 / Chapter CHAPTER FOUR --- The effect of heat and ash on soil / Chapter 4.1 --- Introduction --- p.44 / Chapter 4.2 --- Methodology / Chapter 4.2.1 --- Field work --- p.48 / Chapter 4.2.2 --- Soil heating methods --- p.48 / Chapter 4.2.3 --- Chemical analysis --- p.49 / Chapter 4.2.4 --- Statistical analysis --- p.52 / Chapter 4.3 --- Results and Discussion / Chapter 4.3.1 --- The effect of heat and ash on soil pH --- p.53 / Chapter 4.3.2 --- "The effect of heat and ash on soil organic matter, N and P" --- p.55 / Chapter 4.3.3 --- The effect of heat and ash on soil cations --- p.62 / Chapter 4.4 --- Conclusion --- p.65 / Chapter CHAPTER FIVE --- Nitrogen and phosphorus mineralization after heating / Chapter 5.1 --- Introduction --- p.67 / Chapter 5.2 --- Methodology / Chapter 5.2.1 --- Heating and incubation method --- p.70 / Chapter 5.2.2 --- Laboratory methods --- p.72 / Chapter 5.2.3 --- Statistical analysis --- p.72 / Chapter 5.3 --- Results and discussion / Chapter 5.3.1 --- Temporal changes of N mineralization in heated bare soils --- p.72 / Chapter 5.3.2 --- The effect of ash on N mineralization --- p.78 / Chapter 5.3.3 --- Comparison of N mineralization with other studies --- p.79 / Chapter 5.3.4 --- Temporal changes of P mineralization in the heated bare soils --- p.81 / Chapter 5.3.5 --- The effect of ash on P mineralization --- p.83 / Chapter 5.3.6 --- Comparison of P mineralization to other studies --- p.84 / Chapter 5.4 --- Conclusion --- p.85 / Chapter CHAPTER SIX --- Vertical movement of mineral N in ash-covered soil columns / Chapter 6.1 --- Introduction --- p.87 / Chapter 6.2 --- Methodology / Chapter 6.2.1 --- Package of soil columns --- p.89 / Chapter 6.2.2 --- Water addition and extraction of pore water --- p.90 / Chapter 6.2.3 --- Statistical analysis --- p.92 / Chapter 6.3 --- Results and Discussion / Chapter 6.3.1 --- Mineral N in the pore water --- p.92 / Chapter 6.3.2 --- The effect of ash on mineral N in pore water --- p.97 / Chapter 6.3.3 --- The leaching loss of mineral N --- p.98 / Chapter 6.3.4 --- Comparisons with other studies --- p.103 / Chapter 6.4 --- Conclusion --- p.105 / Chapter CHAPTER SEVEN --- Integrative discussion / Chapter 7.1 --- Summary of major findings --- p.107 / Chapter 7.2 --- Clarifying some misconceptions about the effect of fire --- p.110 / Chapter 7.3 --- Estimated losses of N and P from heating --- p.112 / Chapter 7.4 --- Nutrient supplying capacity of soils after heating --- p.115 / Chapter 7.5 --- Why are repeatedly burnt areas reduced to grassland? --- p.118 / Chapter 7.6 --- Implication on the restoration of fire-affected areas --- p.119 / Chapter 7.7 --- Limitations of the study --- p.121 / Chapter 7.8 --- Suggestions for future research --- p.122 / References --- p.124 / Appendices --- p.141