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Title: Cacao agroforestry management systems effects on soil fungi diversity in the Peruvian Amazon

Author
item AREVALO-GARDINI, ENRIQUE - Tropical Crop Institute (ICT)
item CANTO, JULIO - La Molina National Agrarian University
item ALEGRE, JULIOQ - La Molina National Agrarian University
item LOLI, OSCA - La Molina National Agrarian University
item JULCA, ALBERTO - La Molina National Agrarian University
item Baligar, Virupax

Submitted to: Ecological Indicators
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2020
Publication Date: 4/18/2020
Citation: Arevalo-Gardini, E., Canto, J., Alegre, J., Loli, O., Julca, A., Baligar, V.C. 2020. Cacao agroforestry management systems effects on soil fungi diversity in the Peruvian Amazon. Ecological Indicators. https://doi.org/10.1016/j.ecolind.2020.106404.
DOI: https://doi.org/10.1016/j.ecolind.2020.106404

Interpretive Summary: The maintenance of soil quality is essential in sustainable cacao agroforestry systems that are managed for the production of high yielding cacao. Diversity of soil microbial community is an important indicator of soil quality and the diversity of fungal communities is a key factor in determining the soil quality. Management practices have a significant impact on the composition and activity of soil fungi. Changes in the composition or activity of the soil fungi community could have an immediate or a long term effect on the operation of the agroecosystem. In this paper we report the impact of two long-term agroforestry systems (improved natural agroforestry system (INAS) and improved traditional agroforestry system (ITAS) on the diversity and functionality of various groups of fungi that makeup the soil community in the Peruvian Amazon. Differential changes in physical, chemical and biological properties of the soil were observed and correlated to the different agroforestry systems and cacao genotypes used. Such changes in soil properties affected significantly the fungal diversity parameters (abundance, richness, Shannon-Wiener, Simpson), and functional groups such as potential biocontrol (BCF), potential plant pathogenic (PPF), facultative (PSF) and saprophytes (SF). This information will be of useful to researchers and extension workers who are developing agroforesty management systems that improve the soil biological quality indicators. These improvement will ultimately help resource limited cacao growers to achieve higher sustainable cacao production.

Technical Abstract: In the Peruvian Amazon, an agroforestry system of cacao (Theobroma cacao L.) management provides a productive use of the land, preserves the best conditions for physical, chemical and biological properties of tropical soils, and plays an important role in improving fertility of degraded tropical soils and cacao production. The aim of this study was to evaluate the impact of two long term agroforestry systems of management of cacao genotypes on soil fungal diversity in an area originally inhabited by 30 years old native secondary forest. The two agroforestry systems adapted were: improved natural agroforestry system (INAS) where trees without economic value were selectively removed to provide 50% shade and improved traditional agroforestry system (ITAS) where all native trees were cut and burnt in the location. In both systems, new economically valuable trees were planted to provide shade for cacao. For evaluation of the soil fungi diversity with time due to the imposed cacao management systems we consider parameters of total population or abundance, richness, Shannon-Wiener and Simpson index. , In these management systems, plots of 10 cacao genotypes (ICS95, UF613, CCN51, ICT1112, ICT1026, ICT2162, ICT2171, ICT2142, H35, U30) and one plot with a spontaneous cacao hybrid were selected for fungal evaluations. In each plot soil samples were taken at 0-20, 20-40 and 40-60 cm depths at the installation of the management systems (2004), and then followed at two years intervals until 2010. Total population or abundance, richness, Shannon-Wiener and Simpson index varied significantly during the years of assessment in the different soil depths and under the systems assessed. The fungal communities showed significant changes due to soil disturbance influenced by the installation of agroforestry system INAS and ITAS, and mainly after the burning of native secondary forest in ITAS. The levels of abundance, richness, Shannon-Wiener and Simpson index of soil under cacao genotypes showed a marked difference in both systems. Overall higher soil organic matter (SOM) and nutrient status in the ITAS than INAS might have played major role in the observed soil fungal diversity parameters. In both the systems of management, differential changes in physical and chemical properties of soil under different cacao genotypes might be a contributing factor in observed differences in fungi diversity parameters (abundance, richness, Shannon-Wiener, Simpson), and functional groups such as potential biocontrol (BCF), potential plant pathogenic (PPF), facultative (PSF) and saprophytes (SF).