Chan, Wing Shing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 201-222). / Abstracts in English and Chinese. / Abstract --- p.i / Abstract (in Chinese) --- p.iv / Acknowledgements --- p.vi / Table of contents --- p.viii / List of tables --- p.xii / List of figures --- p.xiv / List of plates --- p.xvi / Chapter Chapter One --- Introduction / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Research background --- p.2 / Chapter 1.3 --- Conceptual framework --- p.6 / Chapter 1.4 --- Objectives of the study --- p.10 / Chapter 1.5 --- Significance of the study --- p.11 / Chapter 1.6 --- Organization of the thesis --- p.12 / Chapter Chapter Two --- Literature Review / Chapter 2.1 --- Land degradation: an overview --- p.14 / Chapter 2.2 --- Land degradation in Hong Kong --- p.17 / Chapter 2.3 --- Ecological rehabilitation --- p.20 / Chapter 2.4 --- Role of plantation in ecological rehabilitation --- p.22 / Chapter 2.5 --- Reforestation history in Hong Kong and species selection --- p.25 / Chapter 2.6 --- Nutrient requirements of native species --- p.31 / Chapter 2.7 --- The geology and soils of Hong Kong --- p.35 / Chapter 2.7.1 --- Geology --- p.35 / Chapter 2.7.2 --- Soils --- p.35 / Chapter 2.8 --- Greenhouse approach in nutrient requirement study --- p.37 / Chapter 2.9 --- Nitrogen mineralization --- p.38 / Chapter 2.10 --- Chlorophyll fluorescence --- p.40 / Chapter 2.11 --- Summary --- p.41 / Chapter Chapter Three --- Inherent Characteristics and Properties of Decomposed Granite and Fire-affected Soil / Chapter 3.1 --- Introduction --- p.42 / Chapter 3.2 --- Materials and methods --- p.42 / Chapter 3.2.1 --- Sources of soil and sampling --- p.43 / Chapter 3.2.2 --- Soil pre-treatment --- p.44 / Chapter 3.3 --- Laboratory analysis --- p.45 / Chapter 3.3.1 --- Reaction pH and conductivity --- p.45 / Chapter 3.3.2 --- Texture --- p.46 / Chapter 3.3.3 --- Organic carbon --- p.46 / Chapter 3.3.4 --- Total Kjeldahl nitrogen (TKN) --- p.47 / Chapter 3.3.5 --- Carbon: nitrogen ratio --- p.47 / Chapter 3.3.6 --- Total phosphorus (TP) --- p.47 / Chapter 3.3.7 --- Exchangeable Al and H --- p.48 / Chapter 3.3.8 --- "Exchangeable cations, base saturation percentage (BSP) and exchangeable Al percentage" --- p.48 / Chapter 3.4 --- Results and discussion --- p.49 / Chapter 3.4.1 --- Texture --- p.49 / Chapter 3.4.2 --- Reaction pH and conductivity --- p.49 / Chapter 3.4.3 --- "Soil organic matter, total Kjeldhal nitrogen and total phosphorus" --- p.51 / Chapter 3.4.4 --- Exchangeable cations --- p.52 / Chapter 3.4.5 --- DG as a representative soil of soil destruction sites --- p.54 / Chapter 3.4.6 --- FAS as a representative soil of vegetation disturbance sites --- p.56 / Chapter 3.5 --- Summary --- p.58 / Chapter Chapter Four --- Nitrogen Fluxes of Decomposed Granite and Fire-affected Soil Amended with Urea / Chapter 4.1 --- Introduction --- p.59 / Chapter 4.2 --- Materials and methods --- p.62 / Chapter 4.2.1 --- Experimental design --- p.62 / Chapter 4.2.2 --- Soil incubation and sampling --- p.63 / Chapter 4.2.3 --- Analysis of mineral nitrogen (NH4-N and NO3-N) --- p.64 / Chapter 4.2.4 --- Statistical analysis --- p.64 / Chapter 4.3 --- Results and discussion --- p.64 / Chapter 4.3.1 --- Variation of NH4-N in DG and FAS --- p.64 / Chapter 4.3.2 --- Variation of N03-N in DG and FAS --- p.68 / Chapter 4.3.3 --- Variation of mineral N in DG and FAS --- p.74 / Chapter 4.3.4 --- NH4-N fluxes in DG and FAS --- p.78 / Chapter 4.3.5 --- NO3-N fluxes in DG and FAS --- p.80 / Chapter 4.3.6 --- Mineral N fluxes in DG and FAS --- p.82 / Chapter 4.4 --- Summary --- p.86 / Chapter Chapter Five --- Growth Performance of Native Species in Decomposed Granite and Fire-affected Soil / Chapter 5.1 --- Introduction --- p.88 / Chapter 5.2 --- Materials and methods --- p.91 / Chapter 5.2.1 --- Experimental design --- p.91 / Chapter 5.2.2 --- Nitrogen treatments --- p.94 / Chapter 5.2.3 --- Post-planting care --- p.95 / Chapter 5.2.4 --- "Measurement of survival rate, height, basal diameter, aboveground biomass and foliar nitrogen" --- p.95 / Chapter 5.2.4.1 --- Survival rate --- p.96 / Chapter 5.2.4.2 --- Height and basal diameter --- p.96 / Chapter 5.2.4.3 --- Aboveground biomass --- p.96 / Chapter 5.2.4.4 --- Foliar sampling --- p.97 / Chapter 5.2.4.5 --- Determination of foliar nitrogen --- p.97 / Chapter 5.2.5 --- Statistical analysis --- p.97 / Chapter 5.3 --- Results and discussion --- p.98 / Chapter 5.3.1 --- Survival rate --- p.98 / Chapter 5.3.2 --- Height growth of species in DG --- p.105 / Chapter 5.3.3 --- Effect of nitrogen on species height growth in DG --- p.112 / Chapter 5.3.4 --- Height growth of species in FAS --- p.117 / Chapter 5.3.5 --- Effect of nitrogen on species height growth in FAS --- p.118 / Chapter 5.3.6 --- Effect of DG and FAS on species height growth --- p.120 / Chapter 5.3.7 --- Basal diameter growth of species in DG --- p.122 / Chapter 5.3.8 --- Effect of N on basal diameter growth of species in DG --- p.124 / Chapter 5.3.9 --- Basal diameter growth of species in FAS --- p.126 / Chapter 5.3.10 --- Effect of N on basal diameter growth of species in FAS --- p.127 / Chapter 5.3.11 --- Effect of DG and FAS on species basal diameter growth --- p.127 / Chapter 5.3.12 --- Overall height and basal diameter growth of species in DG . --- p.129 / Chapter 5.3.13 --- Overall height and basal diameter growth of species in FAS --- p.131 / Chapter 5.3.14 --- Aboveground biomass of species in DG --- p.133 / Chapter 5.3.15 --- Effect of N on aboveground biomass of species in DG --- p.135 / Chapter 5.3.16 --- Aboveground biomass production in FAS --- p.138 / Chapter 5.3.17 --- Effect of N on aboveground biomass of species in FAS --- p.139 / Chapter 5.3.18 --- Effect of DG and FAS on aboveground biomass of species --- p.141 / Chapter 5.3.19 --- Foliar nitrogen --- p.143 / Chapter 5.3.19.1 --- Foliar N of species grown in DG --- p.143 / Chapter 5.3.19.2 --- Effect of N amendment on foliar N of species in DG --- p.147 / Chapter 5.3.19.3 --- Foliar N of species in FAS --- p.149 / Chapter 5.3.19.4 --- Effect of N amendment on foliar N of species in FAS --- p.151 / Chapter 5.3.19.5 --- Effect of DG and FAS on the foliar N of species --- p.152 / Chapter 5.4 --- Summary --- p.155 / Chapter Chapter Six --- Photosynthetic Efficiency of Native Species / Chapter 6.1 --- Introduction --- p.158 / Chapter 6.2 --- Materials and methods --- p.160 / Chapter 6.2.1 --- Measurement of chlorophyll fluorescence --- p.160 / Chapter 6.2.2 --- Statistical analysis --- p.162 / Chapter 6.3 --- Results and discussion --- p.162 / Chapter 6.3.1 --- Photosynthetic efficiency of species in DG --- p.162 / Chapter 6.3.2 --- Photosynthetic efficiency of species in FAS --- p.170 / Chapter 6.3.3 --- Effect of DG and FAS on photosynthetic efficiency of Species --- p.172 / Chapter 6.4 --- Summary --- p.175 / Chapter Chapter Seven --- Conclusions / Chapter 7.1 --- Introduction --- p.178 / Chapter 7.2 --- Summary of major findings --- p.179 / Chapter 7.3 --- Implications of the study --- p.187 / Chapter 7.3.1 --- Species selection for the rehabilitation of soil destruction sites --- p.187 / Chapter 7.3.2 --- Species selection for the rehabilitation of vegetation disturbance sites --- p.191 / Chapter 7.3.3 --- Fertilization practice in different degraded lands --- p.193 / Chapter 7.3.4 --- The importance of soil test in ecological rehabilitation Planting --- p.195 / Chapter 7.4 --- Limitations of the study --- p.197 / Chapter 7.5 --- Suggestions for further study --- p.198 / References --- p.201 / Appendices --- p.223

"September 2001" / Bibliography: leaves 144-159. / xix, 159 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The two main aims of this study were: 1) to determine if the presence of Calcium carbonate in soil was the reason behind soils from Yorke Peninsula having relatively high OC (organic carbon) contents, given local farming practices, and 2) to determine the effect that the composition of the soils' OC has on the mineralisation rates. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 2002

Rotating wheat with other crops is a common practice in the Willamette Valley of western Oregon. Depending upon previous crop and soil type, current N fertilizer recommendations for wheat in the Willamette Valley vary widely. Excessive fertilizer poses environmental risk, whereas lower N inputs than required by the crop represent economic losses to growers. Growers and their advisors face the challenge to minimize the environmental risk, and at the same time to maintain or increase economic returns. Questions are often raised concerning the efficient use of N fertilizer and accurately predicting the amount of N needed by wheat following different crops. The first study measured growth, N uptake and N use efficiency (NUE) of winter wheat grown after either a legume or oat for three years. In all three growing seasons, winter wheat showed higher biomass, N uptake and NUE when grown after a legume than after oat. The contribution of legume was evident before the wheat was fertilized in spring, indicating that legume N had mineralized in fall or winter. Contribution of soil N to wheat suggested that fertilizer N can be reduced by 44 kg N ha����� if a legume is grown previously. Nitrogen use efficiency estimated 50 to 70 days after N application by isotopic method (24 to 94%) was comparable with that estimated simply by difference (21 to 94%) at the same time. The second study predicted gross mineralization rates using analytical models. Comparable N mineralization was predicted by a model assuming remineralization and a model assuming no remineralization, suggesting that remineralization was negligible. In the spring, mineralization-immobilization turnover was at a lower pace than expected in both rotations. In two growing seasons, gross mineralization rates were higher where the previous crop was legume (0.37 to 0.74 kg����� ha����� day�����) as compared to where oat was grown previously (0.14 to 0.6 kg����� ha����� day). Negative net mineralization indicated that fertilizer N was immobilized in the oat-wheat rotation. The third study evaluated calibration and digestion techniques used to determine elemental concentration in grasses. Use of a dry ashed standard to calibrate the ICP spectrometer generated highly variable calibration curves and was not a viable calibration method. Good agreement was found between chemical and microwave digested standards. Dry ashing resulted in considerable S and Mn losses, whereas, perchloric acid digestion and microwave digestion showed similar results. Our study suggests that if routine analysis are to be performed for macro nutrients or involve trace level work, the best method is microwave digestion with chemical standard calibration of ICP spectrometer. / Graduation date: 1999

Winter wheat is commonly grown in rotation with leguminous and non-leguminous crops in the Willamette Valley. For agronomic, economic, and environmental reasons it is important to understand the influence of previous crops on availability of N and other nutrients. Objectives of this study were: (1) to evaluate the effects of long-term rotations on winter wheat response to N fertilizer, and (2) to evaluate the use of Plant Root Simulator���(PRS) probes for measuring soil N mineralization and N availability to winter wheat. Field experiments were conducted over three growing seasons in plots of `Stephens' soft white winter wheat at Hyslop farm. Plots receiving 0, 50, 100, 150 and 200 kg N ha����� at Feekes GS 4 were sampled to determine above ground N uptake, grain yield, and grain protein. In spring 1998, PRS probes were placed in 0 kg N ha����� plots and removed at one-week or two-week intervals. In autumn 1998, probes were placed in unfertilized plots and removed at 1-week, 4-week, and 8-week intervals. Probes measured the availability of NH������-N, NO������-N, K���, Ca�����, Mg�����, and P0��������-P. Grain yield and N uptake were greater for wheat following clover as compared to following oats. Three-year average fertilizer equivalent values calculated from N uptake and grain yield data were 44.5 kg N h����� and 49.0 kg N h�����, respectively. The similarity of these independent measurements suggest that differences in N availability were the primary reason for the rotation effect. PRS probes also detected rotational differences in N availability. Average N recovered by probes sampled at 1-week intervals indicated that there was 63% as much NO������-N available to wheat following oat as compared to clover. Wheat recovered 64% as much N following oats as compared to clover. This suggests that PRS probes are an effective method for predicting relative amounts of plant available N. PRS probes also detected rotational differences in plant available potassium. Agronomic responses are useful for assessing the availability of nutrients that are limiting plant growth. PRS probes, on the other hand, are effective for assessing the availability of both limiting and non-limiting nutrients. / Graduation date: 2000

Graduation date: 1996

Graduation date: 1992

Concerns for environmental quality stimulate the development of various management strategies that mitigate nutrient losses to the environment. / Field experiments were conducted at St. Emmanuel, Quebec, from 1998 to 2000 to investigate the combined effects of water table management and N fertilizer application rates on corn yield, concentrations of NO3- -N in the soil profile and tile subsurface drainage water, denitrification and N2O production rates, and N2O:N2O+N 2 production ratios in the soil profile. There were two water table treatments: free drainage (FD) with open drains at a 1.0 m depth from the soil surface and subirrigation (SI) with a water table depth of 0.6 m below the soil surface, and two N fertilization rates: 120 kg N ha-1 (N120) and 200 kg N ha-1 (N 200) arranged in a split-plot design. Compared to FD, subirrigation reduced NO3--N concentration in the soil by up to 50% and in drainage water by 55 to 73%. Water table had little effect on corn yield during the study period. Greater denitrification rates under SI were not accompanied with greater N2O emissions as ratios of N2O:N2O+N2 were lower under SI than in FD plots. Denitrification rate, N2O emissions, and their ratios were unaffected by N rate. / A second field experiment was initiated from 1999 to 2000 to assess impacts of tillage systems on NO3--N, denitrification, N2O, and ratios of denitrification end-products (N2O:N 2O+N2). The experiment was conducted on long-term momocropped corn experimental plots under conventional tillage (CT), reduced tillage (RT), and no-till (NT), located at the Macdonald Research Farm, McGill University. Soil NO3--N concentrations tended to be lower under RT than under NT or CT. Denitrification and N2O were similar among tillage systems. / Approximately 50% of soil denitrification activity was measured within the 0.15--0.45 m soil layer. Consequently, we propose that sampling the 0--0.15 m soil layer alone, as is usually done, may not give an accurate picture of soil denitrification activity. Dissolved organic carbon concentrations remained high in all soil depths sampled, but was not affected by water table, N rate or tillage system.

The effect of species, parent material, and stand age on nitrogen mineralization were examined during aerobic lab and field incubations. The experimental design consisted of 3 tree species (birch (Betula papyrifera Marsh.); poplar (Populus tremuloides Michx.); and conifers (Abies balsamea (L.) Mill. and Picea glauca (Moench) Voss.)); two parent materials (lacustrine clay and glacial till); and three stand ages (50, 75, and 124 years of age). The strongest determinant of nitrogen mineralization potential was species. The effects of parent material and stand age were variable. Total nitrogen, pH, and soil moisture also affected N mineralization. Nitrogen mineralization dynamics may be largely affected by annual changes in quality of organic matter or climate. Available nitrogen inherent in forest stands must be taken into consideration when replacing hardwood stands with softwoods, because eliminating stages of boreal mixedwood succession could have detrimental effects on available nitrogen and forest productivity in the long-term.

Soil mineral N and soil water content at planting, biomass accumulation, yield and grain quality parameters (hectolitermass and protein percentage) were measured on an unfertilized and recommended-N-application treatment during two consecutive growing seasons (1997-1998). The trials were planted in a fallow-wheat-wheat cropping system at three representative localities in the summer rainfall region of South Africa. High levels of available soil water and mineral N were measured following the fallow period preceding the start of the trials in 1997. For example, soil water content was 81.7%, 69.6%, and 78.2% of DUL at Bethlehem, Kroonstad and Petrusburg respectively. Although comparable total soil profile water contents to 1997 were measured in 1998 at all three sites, the cultivation zone (0-400 mm) had a substantially lower soil water content. This was due to erratic rainfall distribution during the fallow period, which prevented effective soil cultivation management, subsequent soil water conservation and residue decomposition. Undecomposed residue in the cultivation layer at planting appeared to affect availability of soil mineral N to the growing crop. At planting in 1998, undecomposed crop residue amounted to 53.6% at Bethlehem, 32.5% at Kroonstad and 46.9% at Petrusburg of that added at harvest in 1997. Soil mineral N was lower at planting in 1998 compared to 1997 due to decomposing residue (C:N ratio of above 73) in the cultivation zone immobilizing soil mineral N. This reduced initial growth, N accumulation, yield, and grain protein percentage without additional fertilizer N. Distribution of soil mineral N showed notable amounts in the 600-1200 mm soil layers, with limited changes over the trial period. This was linked to low root exploration of these soil layers (10-15% of total root distribution). The ratios of soil mineral NH(4+):N0(3)- for the different soil layers indicated similar values over the trial period. Climatic data for the localities indicated differences in the amount and distribution of rainfall and temperatures during the study period, which influenced crop development, yield and grain protein percentage. At Bethlehem above average in-season rainfall was measured during 1997, at Kroonstad average rainfall and at Petrusburg below average in-season rainfall. Response to applied N at the localities varied in magnitude during 1997. Nitrogen application significantly increased N concentrations of plant components, N uptake, yield and grain protein percentage, although values for all these parameters were lower in 1998 than in 1997. Indeed higher yields were produced in 1997 (mean=1.838 t ha(-1)) compared to 1998 (mean=0.980 t ha(-1)). A significant yield response to applied N was measured at the two higher yielding localities in both cropping years, but there was no significant response at the lower yielding locality. The limiting factors appeared to be the availability of soil water and residual soil mineral N. From the calculated response functions, the variables soil water content at planting, soil mineral N content at planting, in-season rainfall, and added fertilizer N explained the bulk of the variations in grain protein percentage, plant N uptake, and yields. It was concluded that the present fertilizer N recommendation system for dryland wheat production, which is based on fertilizer response curves for specific yield potentials, should be augmented by using initial soil mineral N and water contents in the profile measured prior to planting. / Thesis (M.Sc.Agric.)-University of Natal, Pietermaritzburg, 2002.

In an attempt to investigate the cause of change in the competitive ability between monocots and dicots in a pastureland in Farnham, Quebec under CO2 enrichment, I chose to study the response of Plantago major (dicot) and Poa pratensis (monocot) grown in ambient and elevated CO2 chambers, hypothesizing that a large increase in root biomass of dicots would be observed under elevated CO 2. A transient stimulation of root biomass of Plantago major was found during the first month of CO2 exposure but disappeared later. / The second objective of this study was to examine the effect of 5 years of CO2 enrichment both on root biomass and on total C and N content of roots and soil in the pasture. The largest belowground growth was recorded for Taraxacum officinale. Plantago major responded by achieving the highest aboveground growth. / N content of CO2 enriched roots was reduced. This change in the elemental composition of root tissues might negatively affect the process of decomposition and therefore, the nutrient availability to soil microbes and plants. The observed reduction of NO3 in CO2 enriched soil maybe due to greater N immobilization caused by the expected increase in microbial populations.