Search

Trees of the genus Inga are used in agroforestry systems with cocoa and coffee because of their ecosystem services. In agroforestry systems, the canopy closure and the morphological characteristics of the shade trees are crucial for the growth of the cocoa. This study aims to show that species from the genus Inga are not similar, though in many places only one common name describes the whole genus (e.g. “pacay” in Bolivia), but that they show specific traits that affect the canopy. The objective was to evaluate the function of genus Inga trees, specifically the I. ingoides, I.marginata and I. spectabilis species, regarding the quality of shade for the development of Theobroma cacao. The study area is located in Sara Ana, in the municipality of Alto Beni, in northeastern department of La Paz, at an altitude of 430 meters above sea level, in the Subandean Amazonian forest ecoregion. To this end, we compared both the percentage of shade of Inga spp. between two cocoa Agroforestry Systems - conventional and organic - as well as the morphometric characters. The evaluation of the shade effectiveness with the functional species in cocoa Agroforestry Systems with the genus Inga, showed a similar proportion of canopy closure in conventional plots and in organic plots. The I. ingoides species has an average of 73% closed canopy, I. spectabilis a closed canopy of 59% and I. marginata 84% closed canopy. The morphometric analysis of I. ingoides showed a linear positive increase in diameter at breast height (DBH) with plant height. Similarly, the canopy increased linearly with height, and a positive relationship was also recorded between canopy and DBH. In the case of I. marginata, no statistically significant relationship was observed between the morphometric characters. I. spectabilis only showed a linear increase in DBH as the total height increased. The three Inga species showed interspecies specific differences according to their shading characteristics that affect their applicability in agroforestry systems with cocoa: producers have to consider climatic situations (sun-shine hours per day) and their ability to manage a certain species before species selection and planting.

Cocoa (Theobroma cacao L.) grows naturally as an understory tree in tropical forests and produces well under shaded and non-shaded conditions. It is cultivated by small scale farmers in South America under various conditions, ranging from monocultures to different kinds of agroforestry systems. While in monocultures it is exposed to direct sunlight, one or various tree species shade the cocoa in agroforestry systems. Also organic cocoa cultivation is becoming more and more popular due to premium prices and increasing ecological consciousness. In Alto Beni, Bolivia, the Research Institute of Organic Agriculture (FiBL) and local partners have established a long-term field trial to compare cocoa production systems. The bi-factorial randomised block design includes management and biodiversity factors combined to the following five cocoa treatments: monoculture and agroforestry systems both under organic and conventional management, and successional agroforestry system (high plant species diversity) under organic management and for further comparison fallow plots of same age as the cocoa plots. Research is done in all fields of agronomic, economic and environmental interest. This study focuses on the comparison of the canopy openness of the different cocoa production systems and fallow plots. Knowledge about the canopy openness enables the estimation of light entering the production system, especially on the cocoa layer (photosynthesis relevant) and also on the soil as canopy openness influences the microclimate in the plantation. Another aspect of the canopy is the impact on the throughfall within the plot. Over the time, variations in the canopy structure indicate the production of biomass, of nutrient enrichment by throughfall (rain-wash and nutrient leaf leaching in the canopy) and may indicate pruning necessities when the plant cover above the cocoa exceeds critical values. To estimate the canopy openness, in the years 2012 and 2013 hemispherical photography was taken with fisheye lenses in the different cocoa production systems and in the fallow plots. The photos were analysed with the programme Gap Light Analyser. First results of canopy openness between the cocoa systems will be shown and discussed for leave area index and potential microclimate differences.