Canopy structure as a determining factor in forestry productivity: the case of the wave agroforestry system

Author(s)

Gabriella da Silva Ribeiro

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2022-11-30

Examining board members

Ciro Abbud Righi; Hilton Thadeu Zarate do Couto; Manuela Franco de Carvalho da Silva Pereira

• Advisor: Ciro Abbud Righi

Abstract

Eucalyptus is widely cultivated in homogeneous plantations around the world. However, these plantations still generate environmental and socioeconomic concerns. Increasing the productivity of these plantations to avoid the addition of negative impacts is a challenge. In this sense, adopting different practices, such as agroforestry systems (AFS), can be an alternative. Despite advances in studies on eucalyptus, little is known about their changes in plasticity and production when planted in AFS. There is a need to develop research to evaluate the effects of the environment on eucalyptus trees when planted in different systems. This study aimed to evaluate eucalyptus performance, according to different planting systems - AFS and monoculture - and verify these plants\' responses to different environmental conditions. The experiment was created in 2009 and uses the concept of a three-dimensional structure intermediated by a time scale of planting to create an undulating canopy capable of intercepting more solar radiation (absorptive structure). Eucalyptus trees were planted annually at 3x2m spacing in three treatments: i. Monocrop; ii. Short Wave and; iii. Long Wave. All treatments had eucalyptus with different ages (between ∽10 to ∽4 years). The availability of solar radiation for both the eucalyptus and understory was estimated using mathematical models and photographs of the canopy, respectively. To verify its growth, dendrometric tapes were made and installed. Its crown characteristics, leaf area index, and leaf nitrogen content were evaluated through forest inventories, photographs, and leaf collections, respectively. The accumulation of above-ground biomass was directly determined by the destructive analysis. Based on the results of biomass and inventories, phytometric, hypsometric, and allometric models were developed. The undulating structure of the AFS canopy allowed a greater penetration of radiation to the understory at low solar altitudes (coolest hours of the day) and reduced its penetration when the sun was high (90° - the hottest time of the day). The oldest eucalyptus trees (∽10 years) planted in the waves (Short and Long) were more exposed to solar radiation and, therefore, were the ones that most modified their canopy characteristics, as well as obtaining increases of ∽37% of trunk diameter and ∽120% of canopy volume of those of the same age planted in Monocrop. Such increments allowed these trees to obtain greater growth in basal area and higher values of above-ground biomass and commercial volume. The young trees (∽9 to ∽4 years old) planted in the AFS suffered a reduction in the availability of radiation, given the presence of those old (∽10 years), and, due to this, they maintained their crowns and growth rates similar to those of the control treatment. It is necessary to review the temporal and spatial aspects of the AFS studied to determine the best-growing conditions for all eucalyptus. The development of absorptive structures is a long-term goal and needs further advances to adjust production systems to the natural world. In this way, reducing human activities\' impacts and improving resource use efficiency would be possible. (AU)

• FAPESP's process: 19/20734-5 - The canopy structure as a factor determining forest productivity: the analysis of the waves agroforestry system
• Grantee: Gabriella da Silva Ribeiro
• Support Opportunities: Scholarships in Brazil - Master