Shade trees and tree pruning alter throughfall and microclimate in cocoa (Theobroma cacao L.) production systems

Abstract

& Key message Shade trees in agroforestry systems protect the understory cocoa from climate extremes. Shade tree pruning manages microclimatic conditions in favor of cocoa production while tree diversity is maintained. Adaptation of pruning has to consider seasonal changes in temperature and precipitation to protect the understory cocoa. & Context Structural characteristics of tree stands such as species diversity, tree density, and stratification can affect throughfall and microclimate. Pruning changes the canopy and may therefore modulate internal conditions. & Aims The aim of this study is to assess the environmental growing conditions of cocoa trees. & Methods We monitored canopy openness and the impact of stand structure on throughfall and microclimate in three cocoa production systems (monoculture, agroforestry, and successional agroforestry) and a natural regrowth in a long-term trial in Bolivia from 2013 to 2015. We further focused on the effect of annual shade tree and cocoa pruning on these variables to evaluate the potential impact of this activity. & Results Agroforestry systems buffered extreme climate events like temperature fluctuations compared to monocultures but reduced light and throughfall drastically. Spatial variability of throughfall and transmitted light were low under a high and closed shade tree canopy. Shade tree pruning resulted in higher canopy openness, light transmittance, and throughfall, while the buffer function of the agroforestry systems concerning temperature and humidity fluctuations was reduced. & Conclusion Differences between cocoa production systems regarding throughfall and microclimate were overlain by pruning activities. Cocoa agroforestry systems are temporal dynamic systems. Pruning timing and intensity is pivotal for balancing light and water availability under seasonally varying environmental conditions to conserve micro-environments for cocoa production with less exposure to unfavorable climate.

Effect of canopy management in the water status of cacao ( Theobroma cacao ) and the microclimate within the crop area

“…The crops under open canopy recorded higher photosynthetically active radiation, air temperature, soil temperature, vapor pressure deficit and relative humidity in both seasons of the year. The results are similar to those reported in cacao agroforestry systems in Brazil, where the decrease in tree cover increases the incidence of radiation, temperature and vapor pressure deficit (Niether et al 2018), while in crops with a 2.2 % canopy opening, i.e., greater canopy coverage, a decrease in air temperature and soil temperature is reported compared to crops with a 7.7 % canopy opening (Pinheiro et al 2013). Nevertheless, canopy management did not affect water availability in the soil, since the water potential at a depth of 10 cm presented no differences between canopy conditions in the two seasons of the year; this behavior is contrary to that reported in agroforestry systems with greater canopy coverage which recorded less water loss, above all in the first layers of soil (Lin 2007).…”

“…In light of this, cacao crops can be found with degrees of canopy opening from closed to open canopy, depending on the management by each producer (Carr & Lockwood 2011). The intensity of canopy management is responsible for the microclimate inside the crop area, therefore, the microclimate in an open canopy system is expected to contrast significantly with one in a closed canopy system (Babic et al 2015, Niether et al 2018.…”

The physiological responses of cacao to the environment and the implications for climate change resilience. A review

“…Overhead shade, typically provided by companion crops such as plantain, is required for early establishment of seedlings in the field as these are particularly sensitive to high light levels (Alvim 1977;Owusu 1978). Niether et al (2018) measured light transmission through the canopy of various cacao-growing systems in Alto Beni in Bolivia. Above the canopy, under clear skies, light levels of between 1580 and 2028 μmol m −2 s −1 were recorded depending on the time of year.…”

The effect of short-term vs. long-term soil moisture stress on the physiological response of three cocoa (Theobroma cacao L.) cultivars

“…challenge for cocoa plantations, already common in lowlands and areas with heavy rainfall (Bertolde et al 2010). The adaptation strategies of the cocoa production systems to reduce the impact of climate change have been widely discussed (Tscharntke et al 2011;Vaast and Somarriba 2014), e.g., agroforestry systems that buffer climatic extremes and, therefore, protect the understory cocoa (Niether et al 2018) and improve soil water infiltration (Tscharntke et al 2011). Other efforts have focused on the identification and development of drought-tolerant cocoa cultivars (Apshara et al 2013;Bae et al 2008).…”