EFFECTS OF SHADE TREE SPATIAL DISTRIBUTION AND SPECIES ON PHOTOSYNTHETIC RATE OF COFFEE TREES

Francisco José Da Silva Neto,Rodrigo Gazaffi,Leila Bonfanti,Anastácia Fontanetti

doi:10.25186/cs.v14i3.1584

Francisco José Da Silva Neto, Rodrigo Gazaffi + Show 2 more

Open Access

https://doi.org/10.25186/cs.v14i3.1584

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Journal: Coffee Science	Publication Date: Sep 25, 2019
Citations: 1	License type: cc-by

Affiliation: Universidade Federal de São Carlos

Abstract

The use of shade trees in coffee fields have been motivated by climatic changes. However, microclimatic conditions in shaded coffee fields differ due to shade tree spatial distribution and species, altering physiological responses of coffee trees. This study aimed to evaluate the effects of shade tree spatial distribution and species on coffee trees photosynthetic rate in two growth seasons, of high (HSD) and low (LSD) sink demand. The experimental design consisted of randomized blocks with three replicates in split-split-plots. Plots were the shade tree species: Anadenanthera falcata, Cassia grandis and Peltophorum dubium. Split plot was formed by five distances between coffee trees and shade tree trunks: coffee trees on planting row of shade trees, distancing one (D1L) and five (D5L) meters from shade trees trunk; coffee trees on inter-rows of shade trees, parallel to D1L and D5L (D1E and D5E); coffee trees distancing 77 meters from shade tree trunks, in a full-sun field (PS). The split-split-plots correspond to coffee tree canopy exposure to the sun: branches facing North or South. Shade trees canopy density and occupation was evaluated with a convex densiometer. Photosynthetic rate (Pn)and photosynthetic active radiation (PAR) were measured with an Infrared Gas Analyzer (IRGA) on two time-frames, between 7.00 and 9.00 solar hours and between 11.00 and 13.00. Shade tree canopy density and occupation was not homogenous during the change of seasons and shift due to spatial distribution, which also changes PAR levels. Shade trees reduce PAR to more suitable values for coffee tree exploitation, especially on D1L and D5L. During HSD, shading did not affect Pn, which was greater in branches facing North. Yet, in LSD, between 11.00 and 13.00, coffee trees shaded with A. falcata showed greater Pn than at PS. Coffee trees shaded with C. grandis at D5L and D1E had greater values of Pn than PS.

Highlights

Coffee trees (Coffea arabica L.) show little photosynthetic capacity when grown under full sun (RONQUIM et al, 2006)
Shade alters coffee tree physiology in a way that photosynthetic active radiation (PAR) becomes more limiting to photosynthesis than stomatal conductance (FRANCK; VAAST, 2009)
It is important to notice that this species showed the smallest height (Table 1) and the most compact crown, according to the classification of Andrade, Salman and Oliveira (2012), corroborating the occupation rate findings. These findings suggest a smaller spacing between trees for this species

Summary

Introduction

Coffee trees (Coffea arabica L.) show little photosynthetic capacity when grown under full sun (RONQUIM et al, 2006). Under this condition, photosynthetic active radiation (PAR) reaches levels of 2,000 μmol m-2s-1 (TAIZ et al, 2017), while the light-saturation point of coffee tree leaves happens between 300 and 700 μmol m-2s-1 (DaMATTA, 2004). Soil and leaf temperature (PEZZOPANE et al, 2011; RICCI et al, 2013), reduce thermal amplitude (FRANCK; VAAST, 2009) and wind velocity, creating more suitable microclimatic conditions to gas exchange among coffee trees (PEZZOPANE et al, 2011). Shade alters coffee tree physiology in a way that PAR becomes more limiting to photosynthesis than stomatal conductance (FRANCK; VAAST, 2009)

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