Tracking leaf area index and coefficient of light extinction over the harvesting cycle of black wattle

Abstract

The amount of photosynthetic radiation intercepted by a crop is a function of the incident solar radiation on the plants, the leaf area index (L _AI), and the light extinction coefficient (k). We quantified L _AI and k in stands of black wattle (Acacia mearnsii De Wild.) over a 7-year growth cycle at two locations in the state of Rio Grande do Sul, Brazil. Our study was conducted in commercial stands in agroecological regions with high densities of black wattle plantations. L _AI was calculated as the ratio between the leaf area of a tree and its planting space, and k was derived from Beer’s law. L _AI depends on the planting site and stand age. Between the two sites, the L _AI was similar over time, the amount of variation differed. Values of k depended only on stand age, with the highest average observed for stands up to 5 years old. The trend of k during the plantation cycle was inversely proportional to L _AI and was correlated with L _AI, leaf area, leaf dry mass, canopy volume, height, branches dry mass, total dry mass, and crown diameter.

Keywords

Leaf area / Light attenuation / Tree canopy / Biomass / Photosynthetic radiation intercepted

References

[1] Almeida AC, Soares JV. Comparação entre uso de água em plantações de Eucalyptus grandis e floresta ombrófila densa (mata atlântica) na costa leste do Brasil. Rev Árvore, 2003, 27(2): 159-170.

[2] Brown RH, Blaser RE. Leaf area index in pasture growth. Herb Abstr, 1968, 38(1): 1-9.

[3] Callegari-Jaques SM. Bioestatística – Princípios e Aplicações, 2003, Porto Alegre: ArtMed 207

[4] Campbell GS. Extinction coefficients for radiation in plant canopies calculated using an ellipsoidal inclination angle distribution. Agric Meteorol, 1986, 36: 317-321.

[5] Larcher W. Ecofisiologia Vegetal, 2000, São Carlos: Rima Artes e Textos 531

[6] Linhares CA, Ponzoni FJ, Shimabukuro YE. Relação entre volume de madeira e índice de área foliar em um povoamento de Pinus spp.: estudo de caso. Rev Árvore, 2000, 24: 47-54.

[7] Longdoz B, Aubinet M, François LM. Model of forest carbon sequestration incorporating aerial wood radiative budget. Agric Meteorol, 2004, 125: 83-104.

[8] Mochiutti S. 2007. Produtividade e sustentabilidade de plantações de acácia-negra (Acacia mearnsii De Wild.) no Rio Grande do Sul. PhD Dissertation on Forest Science. Federal University of Paraná. 270 pp

[9] Monteith JL, Unsworth MH. Principles of environmental physics, 1990 2 London: Edward Arnold 291

[10] Rhodes I. Relationship between canopy structure and productivity in herbage grasses and its implication for plant breeding. Herb Abstr, 1973, 43: 129-133.

[11] Varlet-Grancher C, Gosse G, Chartier M, Sinoquet H, Bonhomme R, Allirand JM. Mise au point: rayonnement solaire absorbé ou intercepté par un couvert végétal. Agronomie, 1989, 9: 419-439.

[12] Watson DJ. Comparative physiological studies on growth of field crops. I. Variation in net assimilation rate and leaf area between species and varieties, and within and between years. Ann Bot, 1947, 11: 41-76.

[13] Watson DJ. The dependence of net assimilation on leaf area index. Ann Bot, 1958, 22(85): 37-54.

[14] Xavier AC, Soares JV, Almeida AC. Variação do índice de área foliar em clones de eucalipto ao longo de seu ciclo de crescimento. Rev Árvore, 2002, 26(4): 421-427.