A note of caution concerning the relationship between cumulated intercepted solar radiation and crop growth

Demetriades-Shah, T. H.; Fuchs, M.; Kanemasu, E. T.; Flitcroft, Ian D.

doi:10.1016/0168-1923(92)90061-8

Cited by 97 publications

(27 citation statements)

References 11 publications

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“…Since photosynthesis is a quantum-dependent process, it is intuitively obvious (although disputed by Demetriades-Shah et al 1992; see the replies by Arkenbauer et al 1994, Kiniry 1994, Monteith 1994 that there is likely to be some relationship between the solar energy incident on the canopy of a plant community, and dry matter production. This has been explicitly recognised, and extensively exploited, in numerous models of crop and forest growth (see next section), based on PAR absorption by canopies and leaf photosynthetic characteristics.…”

Section: Evolution Of the E Modelmentioning

confidence: 97%

Energy Conversion and Use in Forests: An Analysis of Forest Production in Terms of Radiation Utilisation Efficiency (ɛ)

Landsberg

Prince

Jarvis

et al. 1997

The Use of Remote Sensing in the Modeling of Forest Productivity

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The linear relationship between the photosynthetically active solar radiation (PAR) absorbed by forest canopies (APAR) and the production of dry mass by forests provides a simple, robust model with only one parameter for the estimation of forest production. The slope of the relationship is normally denoted E. The E model has been developed from plant production studies and is soundly based physiologically. It has also evolved from remote sensing studies. Although the relationship between APAR and canopy photosynthesis may be highly variable over short periods, it remains constant over longer periods, such as months or seasons.The effectiveness with which canopies convert energy into dry mass depends on environmental conditions such as temperature, water status and nutrition. Values of E derived experimentally, in terms of net primary production (NPP) and APAR, range from 2.8 g Mr 2 for agricultural crops to a low value of 0.2 g Mr 2 for tropical rainforests. Values for other forests tend to lie in the range of 1-2 g Mr 2 .Modifying factors with values between 0 and 1, dependent upon the availability of water in the soil, atmospheric vapour pressure deficits or nutrition, are used to account for the effects of these variables on E. If the modifiers are applied to E, the result is an estimate of potential E. Analysis of experimental results, therefore, should lead to the identification of optimum, unconstrained values of E, which may vary considerably less than the current experimental values.Since the proportion of incident energy absorbed by a plant canopy depends on the leaf area index (L*) of the canopy, good estimates of L* provide a sound basis for estimating APAR. Strong statistical relationships exist between reflectance ratios in the infrared, near-infrared and visible spectra, monitored from space, and L*, but these vary with vegetation type and surface conditions. More important are recent developments showing that the fraction of incoming energy absorbed by a canopy can be calculated directly from canopy reflectance properties measured from space. These allow direct application of the E model. As our knowledge of the factors causing variation in radiation utilisation by canopies improves, along with our capacity to The Use of Remote Sensing in the Modeling of Forest Productivityestimate environmental conditions and their modifying effects on radiation utilisation, it should be possible to use the £ model with remotely sensed data to estimate forest productivity over large areas.

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Section: Evolution Of the E Modelmentioning

confidence: 97%

Energy Conversion and Use in Forests: An Analysis of Forest Production in Terms of Radiation Utilisation Efficiency (ɛ)

Landsberg

Prince

Jarvis

et al. 1997

The Use of Remote Sensing in the Modeling of Forest Productivity

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“…However, Haverkort & Harris (1986) found that the RUE for potato tuber dry matter varied from 0.64 to 1.42 g MJ -1 for a single cultivar. Kiniry et al (1989), Stockle & Kiniry (1990) and Demetriades-Shah et al (1992) all explained that these large variations in RUE indicate that daily growth cannot be fully explained by intercepted radiation alone and that other soil and atmospheric factors must be considered.…”

Section: Introductionmentioning

confidence: 94%

Estimating potato leaf area index for specific cultivars

Brown

Dixon

1997

Potato Res

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SummaryThe growth and duration of crop leaf area determines the amount of solar radiation intercepted by the canopy and therefore influences the extent of photosynthesis, evaporation, transpiration and final dry matter yield. The objective of this study was to develop cultivar specific relationships to estimate the daily leaf area index (LAI) for the potato crop (Solanum tuberosum L.) that included the effects of available soil water. The model is divided into three LAI growth stages, the durations of which are partially related to potato heat units (PJ-IU). The LAI in the first stage is estimated from a cultivar specific leaf area-based radiation use efficiency index with a soil water reduction factor. The second stage involves the maintenance of a constant LAI with the duration related to both PHU and a soil water index that can accelerate senescence. The final stage includes a decrease in the LAI from a maximum to zero in response to a cultivar specific PHU accumulation.Model simulations compared favourably with independent LAI measurements obtained with a LI-COR plant canopy analyzer over two seasons.

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“…As a first step in this study, we developed simple, objective methods to quantify understorey L ( L u ) from its biomass and nitrogen content, for eucalypt forest in south western Australia. We reasoned that as plants increase in size they will also increase in leaf area (Demetriades‐Shah et al. 1992), hence, biomass should be a primary predictor of L u .…”

Section: Introductionmentioning

confidence: 99%

A new model for predicting understorey leaf area from biomass in eucalypt forest to test the ecohydrological equilibrium theory

Macfarlane

Lardner

Patterson

et al. 2010

Methods in Ecology and Evolution

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Summary1. Ecohydrological equilibrium theory predicts that vegetation leaf area approaches a maximum dictated by climate and available soil moisture, and that changes in the overstorey and understorey layers compensate such that combined leaf area is maintained. Thus, rapid recovery of understorey following overstorey thinning and burning can diminish catchment water yield increases expected as a result of reductions in evapotranspiration losses. However, the understorey layer is rarely considered in management decisions, in part because methods to estimate understorey leaf area are poorly developed. Improved methods are needed to advance our understanding of ecological and hydrological processes involving forest understorey. 2. We developed models for accurately estimating leaf area of the biodiverse understorey layer of eucalypt forests. Models based on biomass as the independent variable were simpler and more general than models based on above-ground nitrogen or N ⁄ C ratios which were sensitive to the relative proportions of N 2 -fixing plants. We applied our model to compare understorey leaf area with overstorey leaf area in regrowth eucalypt forest, and to derive estimates of leaf area for the world's forests. 3. In thinned and prescribed burnt forest, understorey leaf area was inversely proportional to overstorey leaf area such that combined stand leaf area after only 4AE5 years was unaffected by treatment. This represents the first reported confirmation of the ecohydrological equilibrium theory that is described in terms of the leaf area of the two layers. In contrast, understorey leaf area did not respond to thinning in plots with no follow-up burning. We conclude that more attention should be paid to strategies for managing understorey recovery when manipulating regrowth eucalypt forests for increased catchment water yields. 4. Synthesis and applications. Recovery in vegetation leaf area after thinning in eucalypt forest can be rapid due to the response of the understorey layer. We show that understorey leaf area can completely compensate for reductions in overstorey leaf area, consistent with ecohydrological equilibrium theory, within 5 years of disturbance if thinning is followed by prescribed burning. Applying our model to published biomass data for the world's forests, we also show that forest understorey can have a leaf area comparable with some forest overstorey. Without this new model, these increases in biological understanding would be much more difficult to obtain. By simplifying the estimation of understorey leaf area, the new model will enable researchers to progress rapidly towards greater understanding of understorey and overstorey interactions in natural and disturbed forest ecosystems.

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A note of caution concerning the relationship between cumulated intercepted solar radiation and crop growth

Cited by 97 publications

References 11 publications

Energy Conversion and Use in Forests: An Analysis of Forest Production in Terms of Radiation Utilisation Efficiency (ɛ)

Energy Conversion and Use in Forests: An Analysis of Forest Production in Terms of Radiation Utilisation Efficiency (ɛ)

Estimating potato leaf area index for specific cultivars

A new model for predicting understorey leaf area from biomass in eucalypt forest to test the ecohydrological equilibrium theory

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