Assessing the protective effect of vertically heterogeneous canopies against radiative frost: The case of quinoa on the Andean Altiplano

• Published in: Agricultural and forest meteorology Vol. 149; no. 10; pp. 1759 - 1768
• Main Authors: Winkel, T., Lhomme, J.P., Laura, J.P. Nina, Alcón, C. Mamani, del Castillo, C., Rocheteau, A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2009; [Oxford]: Elsevier Science Ltd; Elsevier; Elsevier Masson
• Subjects: Agricultural and forest climatology and meteorology. Irrigation. Drainage; Agronomy. Soil science and plant productions; air temperature; atmospheric circulation; Bioclimatology; Biodiversity and Ecology; Biological and medical sciences; canopy; Canopy thermal stratification; Chenopodium quinoa; cloud cover; cultivars; Ecology, environment; energy balance; Environmental Sciences; field experimentation; frost; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; grain crops; height; landraces; leaf area index; Leaf temperature; leaves; Life Sciences; Night conditions; night temperature; Radiation view factor; relative humidity; simulation models; small grains; spatial variation; wind speed; Bolivia; South America; Andes; America; Bolivia, Altiplano; Night conditions; Leaf temperature; Radiation view factor; Chenopodium quinoa; Canopy thermal stratification; Biometeorology; Vertical; Temperature; Upland area; Night; Radiation; Starch crop; Plant leaf; Cereal crop; Chenopodiaceae; Heterogeneity; Dicotyledones; Angiospermae; Vegetative apparatus; Spermatophyta; Thermal phenomenon; Stratification; Freeze; Canopy(vegetation)
• ISSN: 0168-1923; 1873-2240
• DOI: 10.1016/j.agrformet.2009.06.005

Night radiative frost is a highly limiting factor for agriculture in Andean highlands. Nevertheless, a diversity of crop species have been domesticated there, commonly showing high heterogeneity in plant growth at the field level. The possible protective effect of crop canopy heterogeneity against nocturnal radiative frost is examined using a dual approach, combining a field experiment and a simplified energy balance model at the leaf level. Leaf and air temperatures were registered over an entire quinoa crop cycle in the Andean highlands of Bolivia, comparing two cultivars: Blanca de Yanamuyu, a traditional landrace with high plant height heterogeneity, and Surumi, a more homogeneous selected variety. In both cultivars, inverted air density profiles during calm and clear nights result in air temperature changes up to 3 °C over 0.5 m height, with minimum air temperature concentrated at the upper part of the canopy. In these conditions, leaf temperature gradients of up to 2.6 °C m −1 develop within the canopy of the traditional landrace, with minimum leaf temperature significantly higher ( P < 0.001) in shaded plants of the landrace than in the selected cultivar. A dynamic model of leaf temperature based on canopy parameters and climatic records at screen level adequately simulates leaf temperature differences in the case of a vertically heterogeneous quinoa canopy. A sensitivity analysis of the model reveals that canopy height, leaf area index, and sky cloudiness have the most important influences on the development of the sheltering effect, while air temperature and air humidity play a minor role under typical radiative frost conditions. As for wind speed, its actual influence remains unclear due to experimental and modelling limitations at low wind speeds. The significance of these results is discussed in terms of the trade-off between stress adaptation and biomass productivity.