Spatial and temporal variability of canopy cover and understory light in a Cerrado of Southern Brazil

Brazilian Journal of Biology

Jp. Lemos-filho²  Cfa. Barros¹  Gpm. Dantas¹  Lg. Dias¹  Rs. Mendes¹ 

[1] ,Universidade Federal de Minas Gerais Instituto de Ciências Biológicas Departamento de BotânicaBelo Horizonte MG ,Brazil

关键词: leaf area index;    Lambert-Beer ratio;    photosynthesis;    seedling growth;    tropical savanna;    índice de área foliar;    razão Lambert-beer;    fotossíntese;    crescimento de plântulas;    savana tropical;   

DOI  :  10.1590/S1519-69842010000100005

来源: SciELO

【 摘 要 】

Canopy cover has significant effects on the understory environment, including upon light availability for seedling growth. The aim of the present study was to verify spatial heterogeneity and seasonal changes in the canopy cover of a dense Cerrado area, and their relationship to understory photosynthetic active radiation availability. Leaf area index (LAI) values in the rainy season varied from 0.9 to 4.83, with 40% of the values ranging from 4.0 to 5.0, while in the dry season LAI varied from 0.74 to 3.3, with 53% of the values oscilating from 2.0 to 3.0. Understory light (Qi ) and the Lambert-Beer ratio (Qi/Qo) were taken around noon on sunny days (between 11:00 AM and 1:00 PM). They were also statistically different (p < 0.01) between the dry and wet seasons, with 72% of sampled points in the rainy season presenting photosynthetic photon flux density (PPFD) values lower than 250 μmol.m-2/s around noon, whereas in the dry season, most PPFD values varied from 1500 to 1817 μmol.m-2/s , thus providing high light availability for understory plants. In most of the studied sites, understory plants did not even receive enough light for 50% of their photosynthetic capacity in the wet season. In contrast during the dry season, Qi/Qo values of 0.8 to 1.0 were observed in more than 50% of the points, thereby allowing for photosynthetic light saturation. Thus, light variability around noon was higher during the dry season than in the wet season, its heterogeneity being related to spatial complexity in the canopy cover.

【 授权许可】

CC BY   
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