A series of glasshouse and laboratory experiments was carried out to enable comparison of two woody perennial legumes, gorse and broom, with other legumes, nodulated non-legumes and other biological nitrogen fixing systems. Both species had distinct juvenile phases in which broom closely resembled herbaceous species in appearance, but adult plants of both species bore little resemblance to each other or to other legume species. Nodule development was similar to that of other legumes, but mature nodules exhibited structural adaptations to longevity - meristematic activity, a well developed vascular system and numerous cytoplasmic granules in cortical cells. Acetylene reduction and ¹⁵N₂ fixation continued for much longer following excision than has been observed in other legumes. In all experiments, broom nodules exhibited higher rates of acetylene reduction and nitrogen fixation than did gorse nodules. The first detectable product of nitrogen fixation in excised nodules - ammonia - was rapidly incorporated into amide and ∝ amino groups and another unidentified fraction. The principle free amino acid in nodules and sap was asparagine. Its preponderance increased as plants aged. Whole nodulated plants and excised nodules of both species exhibited a relatively low temperature optimum for growth and nitrogen fixation (22°C). They were very sensitive to elevated temperatures. Results indicated that gorse and broom have relatively low light requirements. When aeration was sufficient, combined nitrogen had little effect on growth of nodulated plants. Nodulation in both species was reduced by increasing amounts of combined nitrogen. High levels (100 mg/1) of nitrate and ammonia caused considerable inhibition of nitrogen function. Both species showed large responses to phosphate, but were able to grow and fix nitrogen when supplied with low amounts of phosphate. Boron deficiency reduced nitrogen fixation. Nodulation was increased to compensate for this. Considerable amounts of nitrogen can be contributed to the ecosystem in gorse end broom litter. Direct transfer between gorse or broom and Pinus radiate is likely to be small and may be masked by competition for other nutrients. These findings are discussed with respect to the use of gorse and broom to overcome nitrogen deficiency in reafforestation on the Moutere Gravels, in Nelson, N.Z.

Saltwater Forest is a Dacrydium cupressinum-dominated lowland forest covering 9000 ha in south Westland, South Island, New Zealand. Four thousand hectares is managed for sustainable production of indigenous timber. The aim of this study was to provide an integrated analysis of soils, soil-landform relationships, and soil-vegetation relationships at broad and detailed scales. The broad scale understandings provide a framework in which existing or future studies can be placed and the detailed studies elucidate sources of soil and forest variability. Glacial landforms dominate. They include late Pleistocene lateral, terminal and ablation moraines, and outwash aggradation and degradation terraces. Deposits and landforms from six glacial advances have been recognised ranging from latest Last (Otira) Glaciation to Penultimate (Waimea) Glaciation. The absolute ages of landforms were established by analysis of the thickness and soil stratigraphy of loess coverbeds, augmented with radiocarbon dating and phytolith and pollen analysis. In the prevailing high rainfall of Westland soil formation is rapid. The rate of loess accretion in Saltwater Forest (ca. 30 mm ka⁻¹) has been low enough that soil formation and loess accretion took place contemporaneously. Soils formed in this manner are known as upbuilding soils. The significant difference between upbuilding pedogenesis and pedogenesis in a topdown sense into an existing sediment body is that each subsoil increment of an upbuilding soil has experienced processes of all horizons above. In Saltwater Forest subsoils of upbuilding soils are strongly altered because they have experienced the extremely acid environment of the soil surface at some earlier time. Some soil chronosequence studies in Westland have included upbuilding soils formed in loess as the older members of the sequence. Rates and types of processes inferred from these soils should be reviewed because upbuilding is a different pedogenic pathway to topdown pedogenesis. Landform age and morphology were used as a primary stratification for a study of the soil pattern and nature of soil variability in the 4000 ha production area of Saltwater Forest. The age of landforms (> 14 ka) and rapid soil formation mean that soils are uniformly strongly weathered and leached. Soils include Humic Organic Soils, Perch-gley Podzols, Acid Gley Soils, Allophanic Brown Soils, and Orthic or Pan Podzols. The major influence on the nature of soils is site hydrology which is determined by macroscale features of landforms (slope, relief, drainage density), mesoscale effects related to position on landforms, and microscale influences determined by microtopography and individual tree effects. Much of the soil variability arises at microscales so that it is not possible to map areas of uniform soils at practical map scales. The distribution of soil variability across spatial scales, in relation to the intensity of forest management, dictates that it is most appropriate to map soil complexes with boundaries coinciding with landforms. Disturbance of canopy trees is an important agent in forest dynamics. The frequency of forest disturbance in the production area of Saltwater Forest varies in a systematic way among landforms in accord with changes in abundance of different soils. The frequency of forest turnover is highest on landforms with the greatest abundance of extremely poorly-drained Organic Soils. As the abundance of better-drained soils increases the frequency of forest turnover declines. Changes in turnover frequency are reflected in the mean size and density of canopy trees (Dacrydium cupressinum) among landforms. Terrace and ablation moraine landforms with the greatest abundance of extremely poorly-drained soils have on average the smallest trees growing most densely. The steep lateral moraines, characterised by well drained soils, have fewer, larger trees. The changes manifested at the landform scale are an integration of processes operating over much shorter range as a result of short-range soil variability. The systematic changes in forest structure and turnover frequency among landforms and soils have important implications for sustainable forest management.

Saltwater Forest is a Dacrydium cupressinum-dominated lowland forest covering 9000 ha in south Westland, South Island, New Zealand. Four thousand hectares is managed for sustainable production of indigenous timber. The aim of this study was to provide an integrated analysis of soils, soil-landform relationships, and soil-vegetation relationships at broad and detailed scales. The broad scale understandings provide a framework in which existing or future studies can be placed and the detailed studies elucidate sources of soil and forest variability. Glacial landforms dominate. They include late Pleistocene lateral, terminal and ablation moraines, and outwash aggradation and degradation terraces. Deposits and landforms from six glacial advances have been recognised ranging from latest Last (Otira) Glaciation to Penultimate (Waimea) Glaciation. The absolute ages of landforms were established by analysis of the thickness and soil stratigraphy of loess coverbeds, augmented with radiocarbon dating and phytolith and pollen analysis. In the prevailing high rainfall of Westland soil formation is rapid. The rate of loess accretion in Saltwater Forest (ca. 30 mm ka⁻¹) has been low enough that soil formation and loess accretion took place contemporaneously. Soils formed in this manner are known as upbuilding soils. The significant difference between upbuilding pedogenesis and pedogenesis in a topdown sense into an existing sediment body is that each subsoil increment of an upbuilding soil has experienced processes of all horizons above. In Saltwater Forest subsoils of upbuilding soils are strongly altered because they have experienced the extremely acid environment of the soil surface at some earlier time. Some soil chronosequence studies in Westland have included upbuilding soils formed in loess as the older members of the sequence. Rates and types of processes inferred from these soils should be reviewed because upbuilding is a different pedogenic pathway to topdown pedogenesis. Landform age and morphology were used as a primary stratification for a study of the soil pattern and nature of soil variability in the 4000 ha production area of Saltwater Forest. The age of landforms (> 14 ka) and rapid soil formation mean that soils are uniformly strongly weathered and leached. Soils include Humic Organic Soils, Perch-gley Podzols, Acid Gley Soils, Allophanic Brown Soils, and Orthic or Pan Podzols. The major influence on the nature of soils is site hydrology which is determined by macroscale features of landforms (slope, relief, drainage density), mesoscale effects related to position on landforms, and microscale influences determined by microtopography and individual tree effects. Much of the soil variability arises at microscales so that it is not possible to map areas of uniform soils at practical map scales. The distribution of soil variability across spatial scales, in relation to the intensity of forest management, dictates that it is most appropriate to map soil complexes with boundaries coinciding with landforms. Disturbance of canopy trees is an important agent in forest dynamics. The frequency of forest disturbance in the production area of Saltwater Forest varies in a systematic way among landforms in accord with changes in abundance of different soils. The frequency of forest turnover is highest on landforms with the greatest abundance of extremely poorly-drained Organic Soils. As the abundance of better-drained soils increases the frequency of forest turnover declines. Changes in turnover frequency are reflected in the mean size and density of canopy trees (Dacrydium cupressinum) among landforms. Terrace and ablation moraine landforms with the greatest abundance of extremely poorly-drained soils have on average the smallest trees growing most densely. The steep lateral moraines, characterised by well drained soils, have fewer, larger trees. The changes manifested at the landform scale are an integration of processes operating over much shorter range as a result of short-range soil variability. The systematic changes in forest structure and turnover frequency among landforms and soils have important implications for sustainable forest management.

An injection technique, in which undisturbed soil cores are labelled with ³²P to study dissolution of phosphate fertilisers in the soil, was evaluated in field and glasshouse trials. When ³²P was injected between 0-150 mm depths of the undisturbed soil columns and fertilisers applied at the surface, the amounts of fertiliser P dissolved, as measured by the increases in the exchangeable P pools, were overestimated. Three possible reasons were suggested: (i) the interaction between surface-applied fertiliser, ³²P injected through the whole soil column, and the vertical decline in root density, (ii) the decline of specific activity in the exchangeable P pool due to losses of ³²P to nonexchangeable P pools and continuous addition of P from fertiliser dissolution, and (iii) non-uniform distribution of ³²P vis-a-vis ³¹P phosphate. The injection technique may be employed to assess the effectiveness of phosphate fertilisers by introducing a concept, the fertiliser equivalent (FE). The FE is a measure of the amounts of soil exchangeable P that the fertilisers are equivalent to in supplying P to plants, when applied at the specific location. Soluble single superphosphate (SSP) applied at the surface of undisturbed grassland soil cores (Tekapo fine sandy loam), was much more effective than surface-applied unground North Carolina phosphate rock (NCPR) and 30% acidulated NCPR with phosphoric acid (NCPAPR) within the 56 day period of plant growth. An isotopic dilution method, based on tracer kinetic theory, was developed to study the rates of dissolution (F in) and retention (F out) of phosphate fertilisers in the soil in growth chamber experiments. The estimation of F in and F out required labelling of the soils with carrier-free ³²P and determination of the corresponding values of the specific activities of the exchangeable P pools, SA₁ and SA₂, and the sizes of the exchangeable P pools, Q₁ and Q₂, at times t₁ and t₂. Most of the phosphate in the monocalcium phosphate (MCP) solution entered the exchangeable P pool immediately after addition to the soils (Tekapo fine sandy loam and Craigieburn silt loam), and there was little further phosphate input. With increasing periods of incubation, the phosphate was quickly transformed to less rapidly exchangeable forms. In the soils treated with ground North Carolina phosphate rock (<150 µm, NCPR) or partially acidulated (30%) NCPR with phosphoric acid (NCPAPR), the initial exchangeable P pools were not as large as those in the soils treated with MCP, but were maintained at relatively stable concentrations for extended periods, due to the continuous dissolution of PR materials and to lower rates of pretention. An increase in P-retention caused a slight rise in the rate of PR dissolution, but also a rise in the rate of P-retention by the soil. The rate of dissolution was higher at a lower application rate in relative terms, but smaller in absolute terms. The trends in the changes of plant-available P in the soils, measured by the water extractable P, Bray I P and Olsen P, correspond to those predicted by the F in and F out values. The average rates of dissolution between 1-50 and 50-111 days estimated by the F in, however, were higher than those estimated by extractions with 0.5 M NaOH followed by 1 M HCl, and with 0.5 M BaCl₂/TEA. This is partly because the Fin values reflect a plant growth effect on PR dissolution. The relative agronomic effectiveness of NCPR and NCPAPR with respect to MCP was higher after 50 and 111 days of incubation than after 1 day. The F in values were included in all the two-variable models constructed by stepwise regression to describe the relationship between plant P uptake and soil measurements. The amounts of variation in plant P uptake accounted for by the regression model was significantly improved by including F in in the model. This indicates the importance of fertiliser dissolution rates in affecting soil P supply, when phosphate fertilisers differing in solubility are applied.

Early in 1962 the Forest Research Institute of the New Zealand Forest Service became aware that stands of second crop Pinus radiata (D. Don) on some areas of the Moutere Gravel formation were showing slow growth and had a chlorotic appearance (Fig. 1.1). The second crop followed clear felling of mature P. radiata trees and were aged from 0 to 15 years (stone and Will, 1965). It was felt that the apparent reduced growth of the second generation had much in common with similar productivity decline reported especially in European forestry literature. Stone and Will (1965) postulated that the immediate cause o£ the decline was a deficiency of nitrogen highlighted by the low levels of nitrogen in the leaves of the second crop trees, especially those growing on ridge sites. Numerous field trials have been laid out but many of the trials were poorly designed and consequently could not provide statistically sound results. However, some indication of nutrient deficiencies which occur on the Moutere Gravels were obtained. Even before these trials were laid down nutrient deficiencies had been highlighted by early attempts at farming. It was the partial failure of these crops that initially led to the planting of exotic pines, in the belief that these trees thrived on a limited supply of nutrients. The first crop of pines generally fulfilled expectations but nutrient deficiencies started to appear in extensive areas of the second crop. Accordingly, the Forest Research Institute made available three scholarships to study different aspects of the problem. Work was started on a study of the soil sequence across the Moutere Gravels to determine if there was a general decline in fertility of tho soil with the age of the soil and the environmental factors, such as climate which differs in the high inland areas and the low seaside areas of the Moutere Gravels, rather than a particular decline in fertility induced by the first crop of P. radiata. In another study the major weed species Ulex europaeus and Cytisus scoparius was studied to see if its value as a nitrogen fixer would outweigh its disadvantages as a silvicultural weed. Thirdly, a study of the microbial ecology of the soils was undertaken. Whyte (1966) reported that the second rotation trees started to increase their growth rate after approximately five years to a level paralleling the estimated growth rate of the first crop. It was postulated that the residues (needles, roots and branches) remaining after clear felling could cause an increase in microbial numbers and activity with a consequent immobilization of mineral nutrients which were not initially very plentiful. For this reason an area in Tasman Forest was selected in which mature trees and regeneration up to nine years old were found together to study microbial activity and numbers, energy dissipation and nitrogen dynamics to determine if immobilization of nutrients was causing the apparent declines.

The present work is a contribution to description and understanding of the distribution and movement of water in swelling soils. In order to investigate the moisture distribution in swelling soils a detailed knowledge of volume change properties, flow characteristics and total potential of water in the soil is essential. Therefore, a possible volume change mechanism is first described by dividing the swelling soils into four categories and volume change of a swelling soil is measured under different overburden pressures. The measured and calculated (from volume change data) overburden potential components are used to check the validity of the derivation of a load factor, ∝. Moisture diffusivity in swelling soil under different overburden pressures is measured using Gardner's (1956) outflow method. Behaviour of equilibrium moisture profiles in swelling soils is theoretically explained, solving the differential equation by considering the physical variation of individual soil properties with moisture content and overburden pressure. Using the measured volume change data and moisture potentials under various overburden pressures, the behaviour of possible moisture profiles are described at equilibrium and under steady vertical flows in swelling soils. It is shown that high overburden pressures lead to soil water behaviour quite different from any previously reported.

Thesis (Ph. D.)--Uniformed Services University of the Health Sciences, 2005. / Typescript (photocopy).

In recent decades, changes in land use and land cover (LULC) arising from socio-economic development, coupled with climate change, have severely undermined and compromised the environmental sustainability of the upper part of Dong Nai (UPDN) river basin. Assessing the long-term impacts of climate change and changes in LULC on hydrological conditions and water balance in the UPDN river basin is essential for sustainable watershed management. In the present study, Landsat images and SWAT (Soil and Water Assessment Tool) model were used to assess water balance changes due to changes of climate and LULC at three different intervals: 1994, 2004, and 2014. The results of Landsat images classification indicated that forest land was the main LULC type in the basin. In 1994 the forest cover was 706,803 ha (72.68% of the total landmass). In 2004 the forest area dropped to 520,359 ha (53.51%). In 2014 the forest area dropped further to 485,908 ha (49.97%). The change in LULC has caused changes in the annual and peak water flows. The analysis of the results revealed that the effect of historical climate variations on water yield was greater than the LULC change. With the scenario of LULC 2014, the consumption of irrigation water was the highest and mainly in the dry season. The findings can provide useful information for decision-makers in planning and formulating policies for sustainable watershed management and climate change adaptation. / Trong những thập niên gần đây, sự thay đổi về sử dụng đất và thực phủ (LULC) do những hoạt động phát triển kinh tế - xã hội cùng với biến đổi khí hậu đã đặt ra những thách thức cho sự bền vững về môi trường ở lưu vực thượng nguồn sông Đồng Nai (UPDN). Đánh giá các tác động lâu dài của biến đổi khí hậu và những thay đổi trong LULC đến điều kiện thủy văn và cân bằng nước là việc cần thiết cho quản lý bền vững nguồn nước. Trong nghiên cứu này, các ảnh vệ tinh Landsat, công cụ đánh giá đất và nước (SWAT) được sử dụng để đánh giá sự thay đổi cân bằng nước do sự thay đổi khí hậu và LULC tại ba thời điểm khác nhau 1994, 2004 và 2014. Kết quả phân loại các ảnh Landsat cho thấy rừng là loại thực phủ chính trong lưu vực. Diện tích rừng của năm 1994 là 706.803 ha (72,68%). Diện tích rừng của năm 2004 đã giảm xuống còn 520.359 ha (53,1%) và đến năm 2014 chỉ còn 485.908ha (49,97%). Thay đổi sử dụng đất và thực phủ đã làm thay đổi chế độ thủy văn và dòng chảy đỉnh. Phân tích kết quả đã xác định rằng những sự thay đổi về điều kiện khí hậu trong quá khứ có ảnh hưởng đến lượng nước lớn hơn so với thay đổi về thực phủ. Với kịch bản LULC năm 2014, nhu cầu sử dụng nước tưới cho cây trồng là lớn nhất và chủ yếu trong mùa khô. Những kết quả đạt được trong nghiên cứu này sẽ cung cấp thông tin hữu ích cho các nhà hoạch định trong lập kế hoạch và ban hành chính sách cho quản lý lưu vực bền vững, thích ứng với biến đổi khí hậu.

<p>Current watershed-scale, nonpoint source (NPS) pollution models do not represent the processes and impacts of agricultural best management practices (BMP) on water quality with sufficient detail. To begin addressing this gap, a novel process-based, watershed-scale, water quality model (WEPP-WQ) was developed based on the Water Erosion Prediction Project (WEPP) and the Soil and Water Assessment Tool (SWAT) models. The proposed model was validated at both hillslope and watershed scales for runoff, sediment, and both soluble and particulate forms of nitrogen and phosphorus. WEPP-WQ is now one of only two models which simulates BMP impacts on water quality in ‘high’ detail, and it is the only one not based on USLE sediment predictions. Model validations indicated that particulate nutrient predictions were better than soluble nutrient predictions for both nitrogen and phosphorus. Predictions of uniform conditions outperformed nonuniform conditions, and calibrated model simulations performed better than uncalibrated model simulations. Applications of these kinds of models in real-world, historical simulations are often limited by a lack of field-scale agricultural management inputs. Therefore, a prototype tool was developed to derive management inputs for hydrologic models from remotely sensed imagery at field-scale resolution. At present, only predictions of crop, cover crop, and tillage practice inference are supported and were validated at annual and average annual time intervals based on data availability for the various management endpoints. Extraction model training and validation were substantially limited by relatively small field areas in the observed management dataset. Both of these efforts contribute to computational modeling research and applications pertaining to agricultural systems and their impacts on the environment.</p>