Crown architecture affects tree growth through the control of leaf area and its display. Yet the linkages between crown structure, leaf traits, and productivity of elite selections of forest trees and responses to intensive silviculture are not fully understood. It was hypothesized that trees with crown and leaf traits governing efficient light capture and photosynthesis at the canopy scale would be the most productive. To this end, families of loblolly (Pinus taeda) and slash pine (Pinus elliottii) were grown at three experimental sites in the West Gulf Coastal Plain of Texas and Louisiana under two silvicultural treatments, including repeated fertilization with control of competing vegetation (HI), and a control (C) consisting of fertilization at planting. Families and species differed in crown traits and aboveground productivity, and genotype differences increased throughout the first 5 years of stand development. Crown shape was important for light interception and growth initially, but at the onset of canopy closure, crown size, stand leaf area and its distribution within crowns affected canopy light interception and tree growth. Among all families and treatments, aboveground biomass productivity was positively related to absorbed photosynthetically active radiation (APAR) and canopy photosynthesis. Light-use efficiency (ε) varied from 0.41 to 0.56 g MJ-1 among families and was lowest in slash pine. Variability in aboveground biomass growth was related more to stand leaf area and APAR than to differences in light-use efficiency in these young stands. Leaf physiological, chemical and morphological attributes changed within crowns in accordance with developing light availability gradients. Physiological attributes, such as net photosynthesis, were better predictors of family performance when integrated at the canopy level than leaf level in the examined pine species. Crown size, light absorption, and aboveground growth generally ranked higher in the HI treatment than in the control, although the effects of the intensive silvicultural treatments did not differ statistically. Family performance was independent of treatment. Crown and canopy attributes, such as high leaf area index and large crowns with low leaf area density per crown volume, may be useful in the selection of highly productive genotypes of loblolly and slash pine under intensive silviculture.

Crown architecture affects tree growth through the control of leaf area and its display. Yet the linkages between crown structure, leaf traits, and productivity of elite selections of forest trees and responses to intensive silviculture are not fully understood. It was hypothesized that trees with crown and leaf traits governing efficient light capture and photosynthesis at the canopy scale would be the most productive. To this end, families of loblolly (Pinus taeda) and slash pine (Pinus elliottii) were grown at three experimental sites in the West Gulf Coastal Plain of Texas and Louisiana under two silvicultural treatments, including repeated fertilization with control of competing vegetation (HI), and a control (C) consisting of fertilization at planting. Families and species differed in crown traits and aboveground productivity, and genotype differences increased throughout the first 5 years of stand development. Crown shape was important for light interception and growth initially, but at the onset of canopy closure, crown size, stand leaf area and its distribution within crowns affected canopy light interception and tree growth. Among all families and treatments, aboveground biomass productivity was positively related to absorbed photosynthetically active radiation (APAR) and canopy photosynthesis. Light-use efficiency (ε) varied from 0.41 to 0.56 g MJ-1 among families and was lowest in slash pine. Variability in aboveground biomass growth was related more to stand leaf area and APAR than to differences in light-use efficiency in these young stands. Leaf physiological, chemical and morphological attributes changed within crowns in accordance with developing light availability gradients. Physiological attributes, such as net photosynthesis, were better predictors of family performance when integrated at the canopy level than leaf level in the examined pine species. Crown size, light absorption, and aboveground growth generally ranked higher in the HI treatment than in the control, although the effects of the intensive silvicultural treatments did not differ statistically. Family performance was independent of treatment. Crown and canopy attributes, such as high leaf area index and large crowns with low leaf area density per crown volume, may be useful in the selection of highly productive genotypes of loblolly and slash pine under intensive silviculture.

No description available.

Made available in DSpace on 2016-06-02T19:31:38Z (GMT). No. of bitstreams: 1 1456.pdf: 806888 bytes, checksum: c1a017c0d739e9db5205b7784a9e4a47 (MD5) Previous issue date: 2007-06-06 / Universidade Federal de Sao Carlos / Young plants of Coffea arabica grafted over C. canephora were submitted to six watering cycles (WC) during 35 days. Each WC was accomplished until net photosynthesis (PN) close to zero or leaf water potential (&#936;) close to -2.0 MPa in Acauã (AC), Mundo- Novo (MN), and Obatã (OB) cultivars. After 2 WC (about 10 days) gs dropped from 0.15 to 0.01 mol m-2 s-1 in all cultivars changing the pattern of leaf gas exchange in subsequent WC. From 3 to 6 WC the cultivars showed high oscillations of water use efficiency or substomatal CO2 concentration (Ci) besides negative PN at the end of WC. After 3 WC, gs increased faster than PN after watering and Ci increased indicating some damage in photosynthetic machinery. It happened strongly in OB, which showed progressive reduction of PN after 3 WC and the lowest values of &#936; (-2.0 MPa) at the end of 6 WC. The survivorships for cultivars were 80% till 3 WC and 70% after 6 WC. The gas exchange pattern alteration could indicate the potential hardening of AC, MN and OB cultivars. After field plantation of hardened and control (without perivous hardening) Mundo-Novo and Obatã cultivars, with 180-days-old, it was observed significant (p<0.05) greater accumulation of leaf, stem and root biomass in hardened in control plants. Stem diameter, height and the number of leaf and branch were also higher (p<0.05) in previous hardened individuals. Greater differences in crown structure and biomass between control and hardened plants were observed mainly after the first period of low water availability (210 days under field conditions). The higher leaf number and leaf area in more branched crowns could carbon assimilation and grain production. For practical proposes, 3 WC before growing under field conditions are sufficient for changing consistently the leaf gas exchange pattern in 3 cultivars studied, keeping photosynthetic machinery free of damage and high survivorship. Previous hardening proportioned less interrupted vegetative development after transplantation under field conditions in both cultivars. / Plantas jovens de Coffea arabica enxertadas sobre C. canephora foram submetidas a 6 ciclos de suspensão de rega (CR) durante 35 dias. Cada CR foi acompanhado até que a fotossíntese líquida (PN) fosse próxima de zero ou até que o potencial hídrico foliar (&#936;) fosse próximo de -2.0 MPa nos cultivares Acauã (AC), Mundo-Novo (MN) e Obatã (OB). Após 2 CR (cerca de 10 dias) os valores médios de condutância estomática (gs) diminuíram de 0,15 para 0,01 mol m-2 s-1 em todos os cultivares, mudando o padrão de trocas gasosas nos subseqüentes CR. De 3 a 6 CR os cultivares apresentaram maiores oscilações da eficiência do uso da água e da concentração substomática de CO2, além de valores negativos de PN ao final dos CR. Após 3 CR ocorreu um aumento proporcionalmente maior em gs do que em PN após rega, com um aumento correspondente de Ci, indicando possíveis danos no aparato fotossintético. Este evento ocorreu de forma mais clara em OB, o qual demonstrou redução progressiva de PN após 3 CR e os menores valores de &#936; (-2,0 MPa) ao final de 6 CR. A sobrevivência dos cultivares foi de 80% em 3 CR e 70% em 6 CR. As alterações dos padrões de trocas gasosas nos cultivares AC, MN e OB podem indicar que os exemplares foram potencialmente rustificados. Após o plantio de MN e OB rustificados e controle (sem prévia rustificação) em campo, com 180 dias de idade, foi observado no tratamento rustificado valores significativamente (p<0,05) maiores do acúmulo de biomassa e do número de componentes estruturais da copa. A rustificação prévia proporcionou maior acumulo de biomassa de folhas, de caule e de raízes que nas plantas controle em ambos os cultivares. O diâmetro do caule, a altura, o número de folhas e o número de ramos também foram significativamente maiores (p<0,05) nos indivíduos previamente rustificados. As maiores diferenças da estrutura da copa e da biomassa acumulada entre plantas controle e rustificadas foram encontradas principalmente após o primeiro período de rezudida disponibilidade hídrica (210 dias em condições de campo). O maior número de folhas e a maior área foliar em copas mais ramificadas podem proporcionar um aumento da assimilação de carbono por planta e maior produção de grãos nas plantas rustificadas. Em termos práticos, 3 CR antes do crescimento em campo são suficientes para mudar consistentemente o padrão de trocas gasosas foliares nos 3 cultivares estudados, mantendo o aparato fotossintético livre de danos e proporcionando maior sobrevivência. A prática de rustificação prévia antes do plantio deve ser adotada nos cultivares estudados, pois o custo é reduzido e o desenvolvimento vegetativo inicial é fortemente favorecido após o transplante sob condições de campo.