Apesar de muitos estudos dos diferentes métodos de lotação, a definição de estratégias de manejo eficientes geralmente é embasada em respostas de experimentos realizados com cada método individualmente, e não com ambos impostos sob uma mesma base de comparação. Com o objetivo de fundamentar os argumentos existentes, este estudo avaliou os impactos dos métodos de lotação contínua e intermitente impostos sob duas metas de alturas médias em pastagem de capim Convert HD 364, com avaliações da estrutura e das características morfofisiologicas do dossel, assim como do acúmulo (AF) e taxa de acúmulo (TAF) de forragem durante o verão agrótológico. O delineamento experimental utilizado foi o de blocos completos casualizados, com três repetições, seguindo um arranjo fatorial 2 x 3 entre duas metas de altura média de dossel (20 e 30 cm) e três métodos de lotação: 1) lotação contínua (LC) mimetizada, com taxa de lotação variável; 2) lotação intermitente (i.e., pastejo rotativo) com desfolhação leniente (remoção de ~ 40% da altura de dossel no pré-pastejo) (LIDL); e 3) lotação intermitente (i.e., pastejo rotativo) com desfolhação severa (remoção de ~ 60% da altura de dossel no pré-pastejo) (LIDS), respectivamente impostos por amplitudes de ±10, 25 e 40% entorno das metas de altura média de dossel, totalizando 18 unidades experimentais (piquetes) de 200 m2. Pastos manejados sob LC apresentaram maior AF e TAF (7410 kg MS ha-1 e 87 kg MS ha-1 dia-1, respectivamente). A interceptação de luz pelo dossel foi maior nos pastos sob LC (97%) do que naqueles sob LIDL e LIDS (93,7%) quando comparados nas metas de altura média do dossel (20 e 30 cm). No entanto, em pré-pastejo, os pastos sob LIDL e LIDS apresentaram 99% de interceptação de luz pelo dossel. Alterações com o mesmo padrão de respostas foram registradas para as proporções dos componentes da massa de forragem e índice de área foliar (IAF), com incremento significativo das proporções de lâmina foliar e colmos, assim como do IAF, e redução das proporções de material morto à medida que os pastos eram manejados sob menor intensidade em lotação contínua, ou havia o incremento da altura de pré-pastejo em lotação intermitente. Os métodos de lotação e as respectivas metas de altura não afetaram a taxa de fotossíntese de folhas individuais, mas a maior fotossíntese do dossel (69,35 μmol CO2 m-2 s-1) foi obtida nos pastos manejados sob LIDS com meta de altura média de 30 cm. Os pastos manejados sob LC apresentaram taxas de fotossíntese do dossel constantes (47 μmol CO2 m-2 s-1), o que resultou em maiores TAF e AF dentre os métodos de lotação estudados. / In spite of the great number of studies evaluating plant responses to different stocking methods, the definition of more efficient management strategies is generally based on the results of studies evaluating each stocking method separately. With the purpose of substantiating existing arguments, the present study evaluated the impacts of three stocking methods (1 - mimicked continuous stocking with variable stocking rate - CS; 2 - rotational stocking with lenient defoliation - removal of ~40% of pre-grazing canopy height - RSLD; 3 - rotational stocking with severe defoliation - removal of ~60% of pre-grazing canopy height - RSSD, respectively imposed by ±10, 25 and 40% variations) combined in a factorial arrangement with two mean canopy heights (20 and 30 cm) of Mulato II brachiariagrass, on canopy structure, morphophysiological characteristics, forage accumulation (FA) and forage accumulation rate (FAR) during the summer growing season. The experimental design was a randomized complete block with three replications, totaling 18 experimental units (paddocks) of 200 m2. Paddocks in CS treatments presented greater FA and FAR (7410 kg DM ha-1 and 87 kg DM ha-1 d-1, respectively). Canopy light interception was greater for paddocks in CS (97%) than for those in RSLD and RSSD (93.7%) for the two mean canopy heights. However, at pre-grazing, paddocks under RSLD and RSSD presented 99% of canopy light interception. The same response pattern was observed for forage mass composition and for leaf area index (LAI), with significant increases in the proportions of leaves and stems, as well as in LAI, and decreases in the proportions of dead material, as the grazing intensity decreased in CS, or as the pre-grazing height increased in the rotational stocking treatments. Neither the stocking methods, nor the mean canopy heights affected the photosynthesis rates of individual leaves, but the greatest canopy photosynthesis (69.35 μmol CO2 m-2 s-1) was obtained in paddocks under RSSD with mean canopy heights of 30 cm. Paddocks in CS presented constant canopy photosynthesis rates (47 μmol CO2 m-2 s-1), what lead to the greatest FAR and FA among the investigated stocking methods.

O melhor entendimento sobre os aspectos metabólicos, nutricionais e produtivos das gramíneas forrageiras quanto ao uso do nitrogênio é necessário para aumentar a eficiência de uso do nutriente e para a sustentabilidade da produção pecuária. Com isso, objetivou-se analisar alguns cultivares de gramíneas forrageiras utilizados em pastagens no Brasil, quanto a: I) modificações morfológicas e produtivas da parte aérea e das raízes; II) formas de partição do nitrogênio absorvido para melhorar a eficiência de uso do nitrogênio e III) forma de assimilação do nitrogênio absorvido, sendo avaliados pelas variáveis: produção de massa seca, números de folhas e perfilhos, área foliar, concentração e conteúdos de nitrogênio total, nitrato e amônio, eficiência de uso do nitrogênio, atividades das enzimas nitrato redutase e glutamina sintetase e concentração de aminoácidos livres totais na parte aérea e nas raízes dessas gramíneas, quando submetidas a alta e baixa dose de nitrogênio. Na baixa dose de nitrogênio os cultivares Marandu, Xaraés, Piatã, Basilisk e Mombaça mantiveram o número de perfilhos constante e diminuíram o número de folhas e a área foliar, enquanto o cultivar Tanzânia manteve o número de perfilhos e área foliar constantes e reduziu o número de folhas e os cultivares Aruana e Massai aumentaram o número de perfilhos e de folhas e reduziram a área foliar. A baixa dose de nitrogênio resultou em proporções da massa seca da parte aérea e das raízes distintas entre os cultivares quando comparada à alta dose de nitrogênio, favorecendo o crescimento das raízes. Os cultivares estudados modificaram a partição de nitrogênio, nitrato e amônio da parte aérea e raízes, quando em alto e baixo suprimento de nitrogênio. Essas diferenças refletiram na mais alta eficiência de uso do nitrogênio pelos cultivares Mombaça e Tanzânia. A assimilação do nitrato ocorreu principalmente na parte aérea desses capins. Os cultivares Mombaça e Aruana apresentaram elevadas atividades da enzima nitrato redutase nas folhas diagnósticas. A atividade da enzima glutamina sintetase nas folhas diagnósticas foi mais elevada nos cultivares de Panicum. A concentração de amônio nas raízes foi mais alta nos cultivares Piatã e Xaraés, na baixa dose de nitrogênio, e nos capins Aruana e Mombaça, na dose alta de nitrogênio. A concentração de aminoácidos totais nas folhas diagnósticas foi mais elevada nos cultivares de Panicum, quando submetidos à alta dose de nitrogênio, enquanto nas raízes foi maior nos cultivares de Brachiaria, nas duas doses de nitrogênio. / A better understanding of the metabolic, nutritional and production aspects of nitrogen use by grasses are needed to increase nutrient use efficiency and livestock production sustainability. Thus, this study aimed to analyze some forage grasses cultivars used in Brazilian pastures, for: i) morphological and production changes in shoots and roots; II) absorbed nitrogen partition to improve nitrogen use efficiency and III) nitrogen assimilation, evaluated by the variables: dry matter production, number of leaves and tillers, leaf area, concentration and content of total nitrogen, nitrate and ammonium, nitrogen use efficiency, nitrate reductase and glutamine synthetase activities and free amino acids concentration in shoots and roots of these grasses, when supplied with high and low nitrogen rates. At low nitrogen rate, Marandu, Xaraés, Piatã, Basilisk and Mombaça cultivars kept the number of tillers constant and decreased the number of leaves and leaf area, while Tanzânia cultivar kept the number of tillers and leaf area constant and reduced the number of leaves, and Aruana and Massai cultivars increased the number of tillers and leaves and reduced leaf area. The low nitrogen rate resulted in different shoots to roots proportions among cultivars when compared to the higher nitrogen rate, which favored roots growth. The cultivars changed the partition of nitrogen, nitrate and ammonium between roots and shoots, in both nitrogen rates. These differences reflect the higher nitrogen use efficiency by Mombaça and Tanzânia cultivars. The nitrate assimilation occurred mainly in the shoots of these grasses. Mombaça and Aruana cultivars showed high nitrate reductase activity in diagnostic leaves. The glutamine synthetase activity in diagnostic leaves was higher in Panicum cultivars. Ammonium concentration in the roots was high in Piatã and Xaraés, at low nitrogen rate, and Aruana and Mombaça grasses, at high nitrogen rate. The total amino acids concentration in diagnostic leaves was higher in Panicum cultivars than in Brachiaria cultivars, when high nitrogen rate was supplied, whereas Brachiaria cultivars had this concentration high in the roots, at the two nitrogen rates.

Num ecossistema de pastagem a interceptação da luz incidente é o passo inicial de uma seqüência de eventos que resulta na produção de forragem. Vários são os fatores que interferem no processo de interceptação da luz e, dentre eles, os mais expressivos são aqueles relacionados com o índice de área foliar, com as características estruturais e com o arranjo espacial de componentes do dossel forrageiro. O presente experimento teve como objetivo estudar a estrutura do dossel, a interceptação luminosa e o acúmulo de forragem em pastos de Brachiaria brizantha cv. Marandu submetidos a lotação contínua por bovinos de corte. O experimento foi conduzido no Departamento de Zootecnia da USP/ESALQ. Os tratamentos corresponderam a quatro alturas de dossel (10, 20, 30 e 40 cm) mantidas constantes por meio de lotação contínua e taxa de lotação variável. O delineamento experimental foi o de blocos completos casualizados com quatro repetições. As variáveis estudadas foram: índice de área foliar (IAF), ângulo foliar, interceptação de luz, composição botânica/morfológica da forragem, distribuição vertical dos componentes do dossel forrageiro e acúmulo de forragem. A composição da massa de forragem dos pastos não apresentou grande variação entre tratamentos, principalmente no que diz respeito à porcentagem de hastes (27%) e de folhas (21%). A quantidade absoluta e a porcentagem de material morto em relação aos outros componentes morfológicos do dossel aumentaram do verão (30%) até o início da primavera (61%). Quanto maior a altura do dossel, maior foi o deslocamento dos componentes morfológicos ao longo de seu perfil vertical durante o ano. Reduções acentuadas nos valores de IAF dos pastos mantidos a 20 (5,2 para 1,6), 30 (7,0 para 1,5) e 40 cm (7,5 para 2,1) do verão ao início da primavera, respectivamente, não foram acompanhadas por reduções em interceptação luminosa, que se manteve consistentemente acima de 98%. O componente material morto interferiu de foma significativa na interceptação de luz, além de ter apresentado um padrão "dinâmico" de posicionamento no perfil vertical do dossel ao longo do ano. Essa variação na estrutura vertical do dossel foi tão maior quanto mais altos foram mantidos os pastos, e seu efeito sobre os padrões de interceptação luminosa provocou grandes variações na produção de forragem ao longo do ano. De toda a forragem produzida, 65 e praticamente 100% foi acumulada durante o final da primavera e verão nos pastos mantidos a 10 e 40 cm, respectivamente. A produção total de forragem não diferiu entre os pastos mantidos a 10, 20 e 30 cm (aproximadamente 24 ton.ha-1.ano-1), sugerindo haver grande flexibilidade de manejo para essa espécie forrageira. As modificações no sentido vertical e horizontal na estrutura do dossel forrageiro tiveram impacto maior sobre a distribuição estacional do que propriamente sobre a produção total de forragem. / In a pastoral ecossystem the interception of incident radiation is the first step of a sequence of events that results in herbage production. Several are the factors interfering on the light interception process including sward leaf area index, structure and architecture. The objective of this experiment was to study sward struture, light interception and herbage acummulation of Brachiaria brizantha cv. Marandu pastures submitted to continuous stocking by beef cattle. The experiment was carried out at Departamento de Zootecnia, USP/ESALQ. Treatments correspondended to four sward heights (10, 20, 30 and 40 cm) kept constant through continuous stocking and variable stocking rate, allocated to experimental units according to a complete randomized block design with four replications. The response variables evaluated were sward leaf area index (LAI), foliage angle, light interception, botanical and morphological composition and hebarge production. There was no significant change in hebarge mass composition with stems representing 27% and leaves 21% of the sward. Quantity and proportion of dead material relative to the other sward morphological components increased from Summer (30%) to early Spring (61%). The taller the swards, the larger was the shift in the position of the morphological components across the vertical sward profile throughout the year. Significant reductions in LAI values for the 20 cm (5,2 to 1,6), 30 cm (7,0 to 1,5) and 40 cm swards (7,5 to 2,1) from Summer to early Spring were not followed by reduction in light interception, which remained above 98% consistent by through out the year around. The dead material component played an important role on sward light interception, and its placement across the vertical sward profile exhibited a "dynamic" pattern of variation. This variation was more evident in taller swards and affected sward light interception, resulting in varying seasonalities of herbage production. From the total herbage yield, 65 and 100% was produced during late Spring and Summer on the 10 and 40 cm swards, respectively. There was no difference in total herbage production among swards maintained at 10, 20 and 30 cm (24 ton.ha-1.year-1), sugesting that there is a large flexibilitty in grazing management for Brachiaria brizantha cv. Marandu. Modifications in both vertical and horizontal structure of the sward were more effective in changing the seasonal pattern of herbage production than determining herbage yield.

Plantas cultivadas em ambientes com média e alta disponibilidade de cádmio apresentam menor produção de folhas e perfilhos devido à maior quantidade de cádmio absorvido, resultando em menor produção de biomassa. O fornecimento de enxofre às plantas pode minimizar os efeitos negativos causados pelo cádmio, uma vez que esse nutriente participa de compostos que atuam no sistema antioxidante, conferindo maior tolerância aos metais pesados. Objetivou-se avaliar as modificações ocorridas: i) nos aspectos morfológicos, morfogênicos e produtivos; ii) no estado nutricional e iii) na resposta do sistema antioxidante do capim-tanzânia (Panicum maximum) cultivado com combinações de doses de enxofre (0,1; 1,0; 1,9; 2,8 e 3,7 mmol L-1) e de cádmio (0,0; 0,5; 1,0; 1,5 e 2,0 mmol L-1) em solução nutritiva. O experimento foi desenvolvido em casa de vegetação, utilizando o esquema fatorial 5² fracionado, em blocos ao acaso, com seis repetições. O primeiro corte do capimtanzânia foi realizado 40 dias após o transplantio das mudas para os vasos e o segundo corte 18 dias após o primeiro. Para a taxa de mortalidade de perfilhos, valor SPAD, concentração de cádmio e a atividade da APX (segundo corte) do capim-tanzânia foi significativa a interação doses de enxofre x doses de cádmio, de forma que o suprimento de enxofre atenuou a taxa de mortalidade, diminuiu a quantidade de cádmio absorvida, aumentou o valor SPAD e a atividade da APX. O teor de água, número de perfilhos, taxa de aparecimento de perfilhos, número de folhas, área foliar, taxa de aparecimento foliar, razão de área foliar, produção de massa seca da parte aérea e das raízes, valor SPAD, concentração de potássio, teor de GSH e a atividade da CAT foram menores com o fornecimento de cádmio na solução nutritiva. De forma contrária, as concentrações de nitrogênio, fósforo, zinco e cádmio, o fator de transporte do cádmio, os teores de GSSG e glutationa, e a atividade da APX aumentaram. O fornecimento de enxofre aumentou a concentração de enxofre na parte aérea do capimtanzânia. Os efeitos causados pelo cádmio são mais acentuados durante a rebrotação, principalmente, em condições de alta disponibilidade do metal pesado. As enzimas CAT e GR apresentaram mais isoformas na parte aérea do que nas raízes do capim-tanzânia, sugerindo que esse tecido é mais eficaz no combate aos danos oxidativos causados pelas altas concentrações de cádmio. O suprimento de enxofre ao capim-tanzânia cultivado em ambientes com alta disponibilidade de cádmio é indicado para aumentar a tolerância da gramínea ao metal pesado. / Plants grown at medium and high cadmium availability has produced low number of leaves and tillers due to the great amount of cadmium absorbed, resulting in lower biomass production. Sulfur supply to plants may mitigate negative effects caused by cadmium, since compounds containing sulfur participate of the antioxidative plant system, resulting in greater tolerance to heavy metals. This study evaluated changes in: i) morphological, morphogenesis and productive aspects, ii) nutritional status, and iii) response of the antioxidative system of Tanzania guineagrass (Panicum maximum) grown under combined sulfur rates (0.1; 1.0, 1.9, 2.8 and 3.7 mmol L-1) and cadmium rates (0.0, 0.5, 1.0, 1.5 and 2.0 mmol L-1) in nutrient solution. The experiment was conducted in greenhouse, by using a fractionated factorial 5², in randomized block design, with six replications. The first harvest of Tanzania guineagrass was performed at 40 days after seedlings transplanting to the pots, and the second at 18 days after the first harvest. Mortality rate of tillers, SPAD value, cadmium concentration and APX activity (second harvest) of Tanzania guineagrass had statistically significant sulfur rates x cadmium rates interaction, since that sulfur supply mitigate the mortality rate, decreased the amount of cadmium absorbed and increased SPAD value and the APX activity. The water content, number of tillers, tiller emergence rate, number of leaf, leaf area, leaf emergence rate, ratio of leaf area, dry mass of shoots and roots, SPAD value, potassium concentration, GSH content and CAT activity decreased with the cadmium supply in the nutrient solution. Contrary to that, nitrogen, phosphorus, zinc and cadmium concentrations were increased as well as the transporting factor of cadmium, GSSG and glutathione contents and APX activity. Sulfur supply increased sulfur concentration in shoots of Tanzania guineagrass and the effects of cadmium were more pronounced during the plant regrowth period, especially under high availability of the heavy metal. Isoforms of CAT and GR showed higher abundance in shoots compared to roots, suggesting higher effectiveness of such tissue in avoiding oxidative damage caused by high concentrations of cadmium. Thus, sulfur supply to the Tanzania guineagrass grown in environment with high cadmium availability is indicated to increase tolerance to this heavy metal.

O melhor entendimento sobre os aspectos metabólicos, nutricionais e produtivos das gramíneas forrageiras quanto ao uso do nitrogênio é necessário para aumentar a eficiência de uso do nutriente e para a sustentabilidade da produção pecuária. Com isso, objetivou-se analisar alguns cultivares de gramíneas forrageiras utilizados em pastagens no Brasil, quanto a: I) modificações morfológicas e produtivas da parte aérea e das raízes; II) formas de partição do nitrogênio absorvido para melhorar a eficiência de uso do nitrogênio e III) forma de assimilação do nitrogênio absorvido, sendo avaliados pelas variáveis: produção de massa seca, números de folhas e perfilhos, área foliar, concentração e conteúdos de nitrogênio total, nitrato e amônio, eficiência de uso do nitrogênio, atividades das enzimas nitrato redutase e glutamina sintetase e concentração de aminoácidos livres totais na parte aérea e nas raízes dessas gramíneas, quando submetidas a alta e baixa dose de nitrogênio. Na baixa dose de nitrogênio os cultivares Marandu, Xaraés, Piatã, Basilisk e Mombaça mantiveram o número de perfilhos constante e diminuíram o número de folhas e a área foliar, enquanto o cultivar Tanzânia manteve o número de perfilhos e área foliar constantes e reduziu o número de folhas e os cultivares Aruana e Massai aumentaram o número de perfilhos e de folhas e reduziram a área foliar. A baixa dose de nitrogênio resultou em proporções da massa seca da parte aérea e das raízes distintas entre os cultivares quando comparada à alta dose de nitrogênio, favorecendo o crescimento das raízes. Os cultivares estudados modificaram a partição de nitrogênio, nitrato e amônio da parte aérea e raízes, quando em alto e baixo suprimento de nitrogênio. Essas diferenças refletiram na mais alta eficiência de uso do nitrogênio pelos cultivares Mombaça e Tanzânia. A assimilação do nitrato ocorreu principalmente na parte aérea desses capins. Os cultivares Mombaça e Aruana apresentaram elevadas atividades da enzima nitrato redutase nas folhas diagnósticas. A atividade da enzima glutamina sintetase nas folhas diagnósticas foi mais elevada nos cultivares de Panicum. A concentração de amônio nas raízes foi mais alta nos cultivares Piatã e Xaraés, na baixa dose de nitrogênio, e nos capins Aruana e Mombaça, na dose alta de nitrogênio. A concentração de aminoácidos totais nas folhas diagnósticas foi mais elevada nos cultivares de Panicum, quando submetidos à alta dose de nitrogênio, enquanto nas raízes foi maior nos cultivares de Brachiaria, nas duas doses de nitrogênio. / A better understanding of the metabolic, nutritional and production aspects of nitrogen use by grasses are needed to increase nutrient use efficiency and livestock production sustainability. Thus, this study aimed to analyze some forage grasses cultivars used in Brazilian pastures, for: i) morphological and production changes in shoots and roots; II) absorbed nitrogen partition to improve nitrogen use efficiency and III) nitrogen assimilation, evaluated by the variables: dry matter production, number of leaves and tillers, leaf area, concentration and content of total nitrogen, nitrate and ammonium, nitrogen use efficiency, nitrate reductase and glutamine synthetase activities and free amino acids concentration in shoots and roots of these grasses, when supplied with high and low nitrogen rates. At low nitrogen rate, Marandu, Xaraés, Piatã, Basilisk and Mombaça cultivars kept the number of tillers constant and decreased the number of leaves and leaf area, while Tanzânia cultivar kept the number of tillers and leaf area constant and reduced the number of leaves, and Aruana and Massai cultivars increased the number of tillers and leaves and reduced leaf area. The low nitrogen rate resulted in different shoots to roots proportions among cultivars when compared to the higher nitrogen rate, which favored roots growth. The cultivars changed the partition of nitrogen, nitrate and ammonium between roots and shoots, in both nitrogen rates. These differences reflect the higher nitrogen use efficiency by Mombaça and Tanzânia cultivars. The nitrate assimilation occurred mainly in the shoots of these grasses. Mombaça and Aruana cultivars showed high nitrate reductase activity in diagnostic leaves. The glutamine synthetase activity in diagnostic leaves was higher in Panicum cultivars. Ammonium concentration in the roots was high in Piatã and Xaraés, at low nitrogen rate, and Aruana and Mombaça grasses, at high nitrogen rate. The total amino acids concentration in diagnostic leaves was higher in Panicum cultivars than in Brachiaria cultivars, when high nitrogen rate was supplied, whereas Brachiaria cultivars had this concentration high in the roots, at the two nitrogen rates.

The influence of rootstock and canopy density on grape berry composition was investigated over the summer of 2003-2004 on a commercial vineyard at Waipara, North Canterbury. This experiment was designed to investigate the influence of rootstock and canopy density on the acid composition, potassium (K) content and final pH of harvested fruit (Pinot Noir AM 10/5 Lincoln Selection). The trial block consisted of eight rootstocks laid out to an 8 x 8 latin square, each plot consisting of five vines of the same rootstock. Two canopy treatments were overlaid the block (down whole rows, assigned randomly, four rows to each treatment); one treatment allowed to grow naturally, in the other treatment the canopy was thinned removing double burst shoots and laterals. The bunch numbers were adjusted in the Unthinned canopy treatment (UCT) to match the Thinned canopy treatment (TCT). Information was gathered to assess: the canopy size and density (Pinot Quadrat Leaf Layer and Percent Gaps and canopy porosity), the plant yield (and berry size, berries per cluster, cluster weight, clusters per plant), plant K levels at flowering and veraison (from petioles and leaf blades) and berry composition at harvest (soluble solids (as brix), K, titratable acidity (TA), tartaric acid concentration, malic acid concentration and pH). The trial area was non-irrigated on clay loam soils and viticultural management was to best commercial practice. It was found that although rootstock influenced the levels of K in the plant and in the juice at harvest, the level of K in the juice did not influence pH in this experiment (range of rootstock juice K: 808 ppm to 928 ppm, l.s.d. = 75 ppm). The level of tartaric acid concentration in the juice was found to be the dominant influence on the level of pH in this experiment (rootstock pH range: 3.21 to 3.39, l.s.d. = 0.05). The juice concentration of tartaric acid was influenced by both rootstock (rootstock range 4.0 to 4.7 g/L, l.s.d = 0.4) and canopy density (UCT = 4.1, TCT = 4.7, l.s.d. = 0.4), decreased shading positively increasing the level of tartaric acid. The malic acid concentration in the juice was positively influenced by increasing canopy density (UCT = 4.7 g/L, TCT = 4.1 g/L, l.s.d = 0.4) and this played a minor role in the determination of pH in this experiment; an influence of rootstock on the level of malic acid concentration was found. The malic acid concentration strongly influenced the determination of TA (UCT = 11.0 g/L, TCT = 10.2 g/L, l.s.d = 0.5); tartaric acid concentration had a minor influence on the recorded TA. Attempts to characterise the influence of rootstock on malic acid, tartaric acid and pH were inconclusive. Rootstock was found to influence the canopy variables measured in this experiment and the recorded average plant yield. Crosses of Vitis rupestris were found to exhibit the most canopy vigour and those derived from Vitis berlandieri and Vitis riparia the least. The Canopy treatment did not show an influence over yield but the rootstock was found to influence plant yield, through the numbers of berries set in a cluster and the final harvest cluster weight. The influence of rootstock on pH may be described by the influence it exerts on canopy growth and yield but this was thought unlikely. Further research is required to describe the nature of the rootstock influence on K, malic acid, tartaric acid and pH.

This research examined the mechanisms by which temperature, water availability and nitrogen (N) affect the dry matter (DM) yield potential of cocksfoot (Dactylis glomerata L.) dominant pastures. The experiment was a split plot design with main plots of fully irrigated (I) or dryland (D), sub-plots of N fertiliser at 800 kg N/ha in 2003/04; and 1600 kg N/ha in 2004/05 (+N) or 0 kg N/ha (-N). The potential environmental yield of an established 8 year old cocksfoot dominant pasture was 21.9 t DM/ha/y from I+N pastures compared with 9.8 t DM/ha by I-N pastures and 15.1 t DM/ha/y by D+N pastures. The lowest yields were from dryland pastures with no N which produced 7.5 t DM/ha/y in 2003/03 and 5.0 t DM/ha/y in 2004/05. The effect of seasonal temperatures on the DM production, when periods of water stress were excluded, was quantified using thermal time accumulated above a base temperature of 3°C as 7.0 kg DM/°Cd/ha for N fertilised pastures and 3.3 kg DM/°Cd/ha for pastures with no N. The 2.5 t DM/ha difference in yields of D-N pastures in 2003/04 and 2004/05 was the result of the duration, extent and timing of the water stress period. In both years the critical limiting deficit (DL) was calculated as 78 mm from the soil moisture deficit in the 0-0.8 m soil layers. Beyond DL yield decreased at a rate of 1.45%/mm in +N and –N pastures, relative to fully irrigated control pastures. Yields of D+N and D-N pastures were similar during periods of water stress with 0.4±0.1 t/DM/ha produced during the rotation ending 30/12/2003. This was less than from either the I-N (1.2 t DM/ha) or I+N (3.5 t DM/ha) pastures due to the reduction in the amount of photosynthetically active radiation intercepted by the canopies of the dryland pastures. However, in the rotation ending 2/5/2004, after autumn rain alleviated drought conditions, yield of the D+N pasture was 2.1 t DM/ha compared with 1.7 t DM/ha by I+N pastures. The effect of N on yield was described using a nutrition index which showed that as DM yield increased N% in the herbage declined. This is a function of the ratio between metabolic and structural N requirements rather than caused by ontogeny alone. Specific leaf N was determined at two harvests and appeared constant at a given point in time (1.0-1.6 g N/m² leaf). In contrast, specific pseudostem N increased from 0.8-1.0 g N/m² pseudostem at an NNI of 0.4 in –N pastures to 2.6-3.0 g N/m² pseudostem at an NNI of 1.2 in the +N pastures. Differences between the yields of +N and –N pastures were caused by differences in radiation use efficiency (RUE) as determined by the linear relationship (R²=0.76) between RUE and the nitrogen nutrition index (NNI). In this thesis, empirical relationships for the effects of temperature, water availability and N were derived and the physiological mechanisms which underlie these descriptions were identified. These relationships provide clear and simple explanations of the effects of environmental variables on the productivity of cocksfoot based pastures which will enhance understanding of the benefits and limitations of cocksfoot, particularly in dryland farming systems.

The effects of crop load and berry exposure on the composition of Marlborough Sauvignon blanc grapes and wine from the Brancott vineyard, Blenheim, were explored. Commercially grown, 2-cane and 4-cane Sauvignon blanc vines were used with a row orientation of north-south. Two exposure treatments were imposed in the following manner: complete leaf removal was undertaken in the fruit zone and 50% shade cloth was erected to give a uniform shading treatment to half the trial vines. Weekly thirty-berry and whole bunch samples were taken from each of the 32 plots with the exception of the veraison period when two samples per week were taken. Vine vigour was assessed using pruning and leaf area per vine data. Harvest occurred on different dates for 2-cane and 4-cane pruned vines so that fruit attained from both treatments had similar °Brix. Fruit was processed at the Lincoln University winery. Must analysis and wine analysis were undertaken. As expected, 4-cane vines had almost double the yield of 2-cane vines. Higher crop load significantly reduced leaf area per shoot and shoot thickness. Lower leaf area to fruit ratio for 4-cane berries resulted in delayed onset of veraison and slowed the rate of sugar accumulation. Crop load, which limited leaf area to fruit ratio, appeared to be the dominant factor in determining timing of grape physiological ripeness as expressed by °Brix over other factors such as fruit exposure. Malic acid, tartaric acid, IPMP (iso-propylmethoxypyrazine) and IBMP (iso-butyl-methoxypyrazine) were lower at equivalent °Brix in 4-cane compared with 2-cane berries. Significantly higher concentrations of quercetin were found in exposed compared to shaded berries. Must analysis showed a significant influence of crop load on berry titratable acidity and pH, reflecting berry ripening results. Exposure significantly increased the concentrations of nitrogenous compounds in 4-cane must yet showed no influence on 2-cane must. After wine processing lower malic acid concentrations in wines made from 100% exposed fruit became evident in lower wine titratable acidity but showed no influence on wine pH. Bentonite addition to wines had a small but statistically significant influence on wine by reducing pH, titratable acidity and alcohol. Bound sulphur concentrations were significantly higher in 4-cane versus 2-cane wines. At harvest, methoxypyrazine levels in grapes and wines were very low; IBMP concentrations where significantly lower than those normally found in Sauvignon blanc wines from Marlborough. This was attributed to the absence of basal leaves from the shoots of ripening berries. The results suggest that leaf area to fruit ratio is a powerful determinant of grape and wine quality.

The vegetative and reproductive development of balansa clover (Trifolium michelianum Savi.) were quantified in relation to the environmental drivers of each phenophase in field and controlled environments. In a grazed experiment over 6 years, balansa clover sown with cocksfoot (Dactylis glomerata) contributed 1.6 t DM/ha/year, or ~20% of the total DM production. However, grazing management for increased seed production during flowering in the establishment year strongly influenced balansa clover regeneration. The earliest closed plot (September) averaged between 2.2 and 4.3 t DM/ha/year of balansa clover across all six years. In an incubator, balansa clover required 29°Cd for germination with an optimum temperature of 14°C and a maximum of 40°C. The base temperature for germination was 0°C. A field experiment determined that 38°Cd were required for emergence with an optimum soil temperature (Topt) of 8.5°C. The time from emergence until the first leaf appeared, the phyllochron and timing of axillary leaf appearance were compared with perennial ryegrass (Lolium perenne) and white clover (Trifolium repens L.). The rate of each was found to increase linearly with temperature. The balansa clover cultivar ‘Frontier’ required 97°Cd from sowing for the first leaf to appear, had a phyllochron of 47°Cd and secondary leaves appeared after 490°Cd. For each vegetative stage, the base temperature was 2.5°C. The timing of flower appearance depended on the quantity and direction of change of the photoperiod at emergence. A balansa clover plant, cv. ‘Bolta’, which emerged on 1 December into an increasing photoperiod of 15.6 hours flowered after 574°Cd (Tbase = 2.5°Cd) or 58 days after emergence. In contrast, if the plant emerged on 16 January into a similar but decreasing photoperiod it took 1503°Cd or 227 days to flower. This length of time became progressively shorter until remaining constant after the shortest day. In contrast, ‘Frontier’ took a constant 390 and 690 °Cd in increasing and decreasing photoperiods, respectively. The time which an individual inflorescence took from pollination until seeds were physiologically mature was 250 °Cd for both ‘Bolta’ and ‘Frontier’. The re-establishment of balansa clover each year relied on a large seed set (>1000 kg/ha) in the establishment year. The continued survival of balansa clover would then depend on a similar seeding event within a 4-5 year period to maintain the seed bank. Management considerations for balansa clover persistence and survival are discussed.

Linking environmental variation to population dynamics is necessary to understand and predict how the environment influences species abundances and distributions. I used demographic, environmental and trait data of forest herbs to study effects of spatial variation in environmental factors on populations as well as environmental change in terms of effects of forest succession on field layer plants. The results show that abundances of field layer species during forest succession are correlated with their functional traits; species with high specific leaf area increased more in abundance. I also found that soil nutrients affect vegetative and flowering phenology of the forest herb Actaea spicata. The effect of nutrients shows that a wider range of environmental factors than usually assumed can influence plant phenology. Moreover, local environmental factors affected also the demography of A. spicata through effects on vital rates. An abiotic factor, soil potassium affecting individual growth rate, was more important for population growth rate than seed predation, the most conspicuous biotic interaction in this system. Density independent changes in soil potassium during forest succession, and to a lesser extent plant population size dependent seed predation, were predicted to alter population growth rate, and thereby the abundance, of A. spicata over time. Because these environmental factors had effects on population projections, they can potentially influence the occupancy pattern of this species along successional gradients. I conclude that including deterministic, as opposed to stochastic, environmental change in demographic models enables assessments of the effects of processes such as succession, altered land-use, and climate change on population dynamics. Models explicitly incorporating environmental factors are useful for studying population dynamics in a realistic context, and to guide management of threatened species in changing environments.