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ResumenLa deforestación es una de las principales causas de pérdida de biodiversidad en todo el mundo. Las hormigas son clave como ingenieras del ecosistema, por lo tanto, la pérdida de la diversidad de hormigas puede indicar la pérdida de funciones cruciales de los ecosistemas. El objetivo de este estudio fue evaluar la riqueza de hormigas del suelo y estimar si los niveles superiores (Subfamilia y Género) pueden ser usados como sustitutos para estimar la riqueza de especies en diferentes estados de sucesión del bosque (bosque primario, bosque secundario y sistema agroforestal) en la Amazonía Oriental. Fueron muestreadas 65 parcelas en el estado de Maranhão y Pará entre 2011 y 2014. El esquema de muestreo siguió el procedimiento de Biología de Suelos Tropicales y Fertilidad (TSBF). Primero caracterizamos los tipos de vegetación de acuerdo con su edad y luego se estimó la riqueza de especies. Para evaluar si los taxones superiores pueden utilizarse como sustitutos utilizamos funciones lineales y exponenciales y correlación de Pearson. En total, se identificaron 180 especies distribuidas en 60 géneros. Los resultados mostraron que la riqueza fue superior en el bosque secundario intermedio (88) y avanzado (76) y fue menor en el sistema agroforestal (38) y bosque ribereño primario (35). El género fue el mejor sustituto para estimar la riqueza de especies de hormigas a través de los diferentes tipos de sucesión vegetal, explicando entre el 72-97 % (P < 0.001) de la variabilidad total de especies. Nuestros resultados confirman que el uso del nivel de género es un excelente sustituto para estimar la riqueza de especies de hormigas en la región y tanto los bosques en regeneración y sistemas agroforestales pueden contribuir en la conservación de la comunidad de hormigas en la Amazonía Oriental. Abstract:Deforestation in Amazon forests is one of the main causes for biodiversity loss worldwide. Ants are key into the ecosystem because act like engineers; hence, the loss of ants’ biodiversity may be a guide to measure the loss of essential functions into the ecosystems. The aim of this study was to evaluate soil ant’s richness and to estimate whether higher taxa levels (Subfamily and Genus) can be used as surrogates of species richness in different vegetation types (fallows, old-growth forests and agroforestry systems) in Eastern Amazon. The samples were taken in 65 areas in the Maranhão and Pará States in the period 2011-2014. The sampling scheme followed the procedure of Tropical Soil Biology and Fertility (TSBF). Initially, the vegetation types were characterized according to their age and estimated species richness. Linear and exponential functions were applied to evaluate if higher taxa can be used as surrogates and correlated with the Pearson coefficient. In total, 180 species distributed in 60 genera were identified. The results showed that ant species richness was higher in intermediate fallows (88) and old secondary forest (76), and was lower in agroforestry systems (38) and mature riparian forest (35). The genus level was the best surrogate to estimate the ant’s species richness across the different vegetation types, and explained 72-97 % (P < 0.001) of the total species variability. The results confirmed that the genus level is an excellent surrogate to estimate the ant’s species richness in the region and that both fallows and agroforestry systems may contribute in the conservation of Eastern Amazon ant community. Rev. Biol. Trop. 65 (1): 279-291. Epub 2017 March 01.

In the Peruvian Amazon, a significant amount of the agricultural landscape is cultivated with cocoa (Theobroma cacao) mostly grown under the shade of Musacea and timber trees. There, deforestation and its control are one of the main environmental issues for the Peruvian government and further, for the international community. In these landscapes, farmers who want to establish new plantations have the choice between tropical forest and degraded lands. Most of the latest are abandoned pastures or annual crops with mostly red ferralitic soils heavily unsaturated. As a response to the loss of fertility, farmers have currently two alternatives: entering illegally into the natural forest or practicing shifting cultivation on a long term basis that can reach more than 15 years. In this last case, the fallow lands, locally called “Purma”, are named under three categories according to the height of the pioneer vegetation: (i) low (10 years). Our study has been conducted with former coca farmers moved 20 years ago by the Peruvian government to the Ucayali department to produce cocoa. There, we compared soil quality, cadmium content and plant biomass including fine roots at 0-20 and 20-50 cm depth, among three land uses: (i) 31 agroforestry cocoa plantations at different ages, (ii) 24 low, 24 medium and 22 high “purmas”, and finally (iii) 22 forest patches as a control. Our results provide an interesting basis to discuss the ability of cocoa-based agroforestry systems to maintain and even restore soil fertility in degraded landscape at the Amazonian forest margin. The evolution of Cadmium content depending on land use and fallow period gives interesting indications for further investigations.

National audience; Soil quality is a concept often considered as non-objective because no absolute reference to an optimal quality can be identified. This is a consequence of the extreme variability of soils and the difficulty to link soil attributes to sustainability. Consequently some authors claim that soil quality cannot be measured but only management practices should be compared to determine which one enhanced some particular soil attribute at stake. Most studies on soil quality use clear factors or typologies to select the indicators that best explain the differences between soils. Our strategy was different : i) we defined an “objective” data set of soil quality indicators, based on literature. This first step was achieved by selecting “objective” non biotic soil indicators from recent reviews. The most actualized set of indicators available was selected out of 53 publications that provided 95 indicators. These indicators were listed, pooled when closely related and classified according to their frequency, reducing their number to 86; ii) we compared this set to the 25 soil attributes available from 36 cocoa-based AFS sampled in the Bribri indigenous reserve of Talamanca (Costa Rica), in order to select a minimum “objective” data set (MDS); and iii) we assessed correlations between soil macrofauna functional groups and the MDS. We selected 36 cocoa fields maximizing diversity based on landscape topography and fragmentation, on-plot vegetation and management intensity. Plots of 50x20m were installed at the centre of each field. Soil and litter were sampled separately on 5 locations in each plot. Macrofauna was hand-sorted immediately after sampling. Functional groups were sorted, identified and counted in laboratory. Soil was sampled within 2m from the macrofauna sampling point at depths of 0-10 and 10-20 cm and analyzed for: Bulk Density (BD), Water Content, Texture, pH, P, K, Mn, Cu, Zn, Fe, Acidity, Total C and N. WFPS, Porosity, CEC and Sum of Bases were calculated. The MDS was: BD, pH, Sum of Bases and C, and explained 62.5% of the variability of the other 21 indicators. The MDS separated cocoa plots into five soil quality groups. Forest fragments entered the first two groups indicating that cocoa AFS can conserve forest soil quality. Twelve macrofauna functional groups explained 71% of the MDS thus confirming the importance of macrofauna in soil formation and conservation. This suggests that a small number of selected indicators could be retained for monitoring purposes in Talamanca cocoa AFS.