A model for simulating photosynthesis in plant communities

Duncan, W. G.; Loomis, R. S.; Williams, William A.; Hanau, R.

doi:10.3733/hilg.v38n04p181

Cited by 389 publications

(205 citation statements)

References 22 publications

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“…Minimum values of specific leaf mass were observed at moderated depth in the haulm, which agrees with Gutschick & Wiegel (1988). Increased absorption of photosynthetically active radiation at high depth in the haulm (due to reduced leaf shading and leaf-angle distribution, with more erected leaves at the top and more horizontal leaves toward the bottom) increases light penetration (Duncan et al, 1967) and helps explain such variation in specific leaf mass for different leaf number and treatment.…”

Section: Leaf Growth and Partitioningsupporting

confidence: 68%

Potato crop growth as affected by nitrogen and plant density

Oliveira

2000

Pesq. agropec. bras.

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-Growth and development variables and dry matter characteristics were studied for cultivar Snowden of potato (Solanum tuberosum L.) to evaluate nitrogen and plant density influence. Disregarding ending of season plant stress, the average number of actives haulms per plant was five and it was not affected by plant spacing. However, seasonal and final number of active haulms per plant were increased at 200 kg/ha of nitrogen. Maximum stem elongation was reached quickly with double density and had the tendency to keep constant at the highest and lowest nitrogen levels after 70 days after planting. Specific stem mass defined as mass per unit stem length was established as an indirect measure of stem thickness and load capacity. Specific leaf mass position in plant was higher at upper stem leaves, increased as plant density increased and did not vary markedly over time throughout the season. The rate of leaf appearance increased drastically due to more branching caused by high nitrogen level, and increased above ground dry matter per plant. Canopy growth and development influenced main tuber yield components. The number of active tubers per haulm decreased after 60 days after planting showing that tuberization is reversible. Tuber growth functions were established allowing the estimate of dry biomass partitioning coefficients for each plant organ.Index terms: Snowden cultivar, plant nutrition, canopy, leaf area, tubers, stems, dry matter, plant population. CRESCIMENTO DA BATATEIRA INFLUENCIADO POR NITROGÊNIO E DENSIDADE DE PLANTIORESUMO -Foram estudadas variáveis de crescimento e desenvolvimento e características da matéria seca da batata (Solanum tuberosum L.), cultivar Snowden, com o objetivo de avaliar a influência do nitrogênio e da densidade de plantio. Desconsiderando o estresse da planta ao final da estação, o número médio de hastes ativas por planta foi de cinco, e não foi afetado pelo espaçamento entre plantas. Entretanto, o número médio estacional e final de hastes ativas por planta foi aumentado com 200 kg/ha de nitrogênio. O comprimento máximo do caule foi atingido rapidamente quando se dobrou a densidade de plantio, e apresentou a tendência de ficar constante nos níveis mais alto e mais baixo de nitrogênio, 70 dias após o plantio. A massa de caule específica, definida como massa por unidade de comprimento de caule, foi estabelecida como uma estimativa da espessura e capacidade de suporte do caule. A massa de folha específica, por posição na planta, foi maior nas folhas mais altas do caule, aumentou com a densidade de plantio, e não variou acentuadamente com o tempo durante o ciclo da cultura. A taxa de surgimento de folhas aumentou acentuadamente, em virtude da maior formação de ramos, causada pelo alto nível de nitrogênio, aumentando a matéria seca acima do solo, por planta. O crescimento e desenvolvimento da parte aérea da planta influenciou os componentes de produção dos tubérculos. O número de tubérculos ativos por haste diminuiu depois de 60 dias após o plantio, o que mostra que a tuberizaçã...

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Section: Leaf Growth and Partitioningsupporting

confidence: 68%

Potato crop growth as affected by nitrogen and plant density

Oliveira

2000

Pesq. agropec. bras.

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“…As such, modelling should become an important resource-saving tool to guide the choice of breeding and agronomic management investment. Crop models have simulated the effect of crop management and climate on yield (Duncan et al, 1967;de Wit et al, 1970;de Wit, 1978;Kumar et al, 2009;Kim et al, 2010). Later, crop models were redesigned into farming systems models that could consider more broadly the effects of the management system including the carryover effects of rotations, planting density and intercropping.…”

Section: Crop Growth Simulation and Modelling Approachesmentioning

confidence: 99%

Accelerating genetic gains in legumes for the development of prosperous smallholder agriculture: integrating genomics, phenotyping, systems modelling and agronomy

Varshney

Thudi

Pandey

et al. 2018

Journal of Experimental Botany

102

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Grain legumes form an important component of the human diet, provide feed for livestock, and replenish soil fertility through biological nitrogen fixation. Globally, the demand for food legumes is increasing as they complement cereals in protein requirements and possess a high percentage of digestible protein. Climate change has enhanced the frequency and intensity of drought stress, posing serious production constraints, especially in rainfed regions where most legumes are produced. Genetic improvement of legumes, like other crops, is mostly based on pedigree and performance-based selection over the past half century. To achieve faster genetic gains in legumes in rainfed conditions, this review proposes the integration of modern genomics approaches, high throughput phenomics, and simulation modelling in support of crop improvement that leads to improved varieties that perform with appropriate agronomy. Selection intensity, generation interval, and improved operational efficiencies in breeding are expected to further enhance the genetic gain in experimental plots. Improved seed access to farmers, combined with appropriate agronomic packages in farmers' fields, will deliver higher genetic gains. Enhanced genetic gains, including not only productivity but also nutritional and market traits, will increase the profitability of farming and the availability of affordable nutritious food especially in developing countries.

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“…However, the nonlinear response of leaf carbon assimilation to light interception can create appreciable bias when scaling up canopy carbon assimilation using the big-leaf approach. To avoid the bias with the big-leaf scaling up scheme, multilayer models were developed where the plant canopy was divided into a number of parallel horizontal layers [Duncan et al, 1967;Baldocchi, 1993;Raupach and Finnigan, 1988]. More recent multilayer models consider the transfer of momentum, heat, water vapor, and CO 2 between the biosphere and the atmosphere and resolve all the way-way interactions between leaves and their immediate microclimate using higher order turbulent transport theories [Juang et al, 2008].…”

Section: Discussionmentioning

confidence: 99%

Energy, water, and carbon fluxes in a loblolly pine stand: Results from uniform and gappy canopy models with comparisons to eddy flux data

et al. 2009

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[1] This study investigates the impacts of canopy structure specification on modeling net radiation (R n ), latent heat flux (LE) and net photosynthesis (A n ) by coupling two contrasting radiation transfer models with a two-leaf photosynthesis model for a maturing loblolly pine stand near Durham, North Carolina, USA. The first radiation transfer model is based on a uniform canopy representation (UCR) that assumes leaves are randomly distributed within the canopy, and the second radiation transfer model is based on a gappy canopy representation (GCR) in which leaves are clumped into individual crowns, thereby forming gaps between the crowns. To isolate the effects of canopy structure on model results, we used identical model parameters taken from the literature for both models. Canopy structure has great impact on energy distribution between the canopy and the forest floor. Comparing the model results, UCR produced lower R n , higher LE and higher A n than GCR. UCR intercepted more shortwave radiation inside the canopy, thus producing less radiation absorption on the forest floor and in turn lower R n . There is a higher degree of nonlinearity between A n estimated by UCR and by GCR than for LE. Most of the difference for LE and A n between UCR and GCR occurred around noon, when gaps between crowns can be seen from the direction of the incident sunbeam. Comparing with eddy-covariance measurements in the same loblolly pine stand from May to September 2001, based on several measures GCR provided more accurate estimates for R n , LE and A n than UCR. The improvements when using GCR were much clearer when comparing the daytime trend of LE and A n for the growing season. Sensitivity analysis showed that UCR produces higher LE and A n estimates than GCR for canopy cover ranging from 0.2 to 0.8. There is a high degree of nonlinearity in the relationship between UCR estimates for A n and those of GCR, particularly when canopy cover is low, and suggests that simple scaling of UCR parameters cannot compensate for differences between the two models. LE from UCR and GCR is also nonlinearly related when canopy cover is low, but the nonlinearity quickly disappears as canopy cover increases, such that LE from UCR and GCR are linearly related and the relationship becomes stronger as canopy cover increases. These results suggest the uniform canopy assumption can lead to underestimation of R n , and overestimation of LE and A n . Given the potential in mapping regional scale forest canopy structure with high spatial resolution optical and Lidar remote sensing plotforms, it is possible to use GCR for up-scaling ecosystem processes from flux tower measurements to heterogeneous landscapes, provided the heterogeneity is not too extreme to modify the flow dynamics.

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A model for simulating photosynthesis in plant communities

Cited by 389 publications

References 22 publications

Potato crop growth as affected by nitrogen and plant density

Potato crop growth as affected by nitrogen and plant density

Accelerating genetic gains in legumes for the development of prosperous smallholder agriculture: integrating genomics, phenotyping, systems modelling and agronomy

Energy, water, and carbon fluxes in a loblolly pine stand: Results from uniform and gappy canopy models with comparisons to eddy flux data

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