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Abstract. Andosols are among the most carbon-rich soils, with an average of 254 Mg ha−1 organic carbon (OC) in the upper 100 cm. A current theory proposes an upper limit for OC stocks independent of increasing carbon input, because of finite binding capacities of the soil mineral phase. We tested the possible limits in OC stocks for Andosols with already large OC concentrations and stocks (212 g kg−1 in the first horizon, 301 Mg ha−1 in the upper 100 cm). The soils received large inputs of 1800 Mg OC ha−1 as sawdust within a time period of 20 years. Adjacent soils without sawdust application served as controls. We determined total OC stocks as well as the storage forms of organic matter (OM) of five horizons down to 100 cm depth. Storage forms considered were pyrogenic carbon, OM of < 1.6 g cm−3 density and with little to no interaction with the mineral phase, and strongly mineral-bonded OM forming particles of densities between 1.6 and 2.0 g cm−3 or > 2.0 g cm−3. The two fractions > 1.6 g cm−3 were also analysed for aluminium-organic matter complexes (Al–OM complexes) and imogolite-type phases using ammonium-oxalate–oxalic-acid extraction and X-ray diffraction (XRD). Pyrogenic organic carbon represented only up to 5 wt % of OC, and thus contributed little to soil OM. In the two topsoil horizons, the fraction between 1.6 and 2.0 g cm−3 had 65–86 wt % of bulk soil OC and was dominated by Al–OM complexes. In deeper horizons, the fraction > 2.0 g cm−3 contained 80–97 wt % of the bulk soil's total OC and was characterized by a mixture of Al–OM complexes and imogolite-type phases, with proportions of imogolite-type phases increasing with depth. In response to the sawdust application, only the OC stock at 25–50 cm depth increased significantly (α=0.05, 1-β=0.8). The increase was entirely due to increased OC in the two fractions > 1.6 g cm−3. However, there was no significant increase in the total OC stocks within the upper 100 cm. The results suggest that long-term large OC inputs cannot be taken up by the obviously OC-saturated topsoil but induce downward migration and gradually increasing storage of OC in subsurface soil layers. The small additional OC accumulation despite the extremely large OC input over 20 years, however, shows that long time periods of high input are needed to promote the downward movement and deep soil storage of OC.

Mera, Santa Clara and Pastaza municipalities are located in the Ecuadorian Amazon region. The objective of the study was to identify plant species used in traditional medicine by small farmers of these localities, and to classify these plants according to locality, farmer ethnicity and purposes of use. It was also investigated whether the use of medicinal plants differs between the ethnic groups. Data were collected by applying a questionnaire and personal interview with 213 farmers belonging to two ethnicities (Kichwa and mestizo), and to different municipalities (Mera, Santa Clara and Pastaza). Generated data were analyzed using contingency tables and frequency and the most representative species were determined by proportion analysis comparison. A total of 34 families and 52 species of medicinal plants were identified. The most used species was Ilex guayusa which was cited 48 times. Santa Clara municipality and Kichwa farmers used the highest number of species. These species belonged to the Lamiaceae and Solanacease family, and the plants were used for treating stomach pain, cold and inflammations. There were significant differences (Chi square test p < 0.05) between localities and ethnicities (Kichwa and mestizo). There were differences in the use of medicinal plant species among members of the Kichwa ethnicity and mestizo farmers, depending on locality, being Ilex guayusa the most used species.KEYWORDS: ethnic group, Kichwa, Mera, Santa Clara Uso de plantas medicinais por populações rurais da província de Pastaza, na Amazônia equatoriana RESUMO A pesquisa foi desenvolvida em três municípios da Província de Pastaza, (Mera, Santa Clara e Pastaza), na Amazônia equatoriana. O objetivo do estudo foi identificar espécies vegetais utilizadas na medicina tradicional pelos agricultores nestas localidades e classificar as espécies segundo a localidade, etnia do produtor e as aflições nas que eram utilizadas. Alem disso, na pesquisa analisaram-se as diferença de uso das plantas entre as etnias Kichwa e Mestiça. A metodologia do trabalho consistiu na aplicação de questionários e entrevistas pessoais com 213 agricultores das diferentes etnias. Utilizaram-se as tabelas de contingência por freqüência de uso com os dados gerados, para determinar as espécies mais representativas e em cada grupo realizou-se comparação por análise de proporções. Os principais resultados mostraram a existência de 52 espécies de plantas medicinais pertencente a 34 famílias. A espécie mais utilizada foi Ilex guayusa com 48 registros. Os produtores Kichwa do município Santa Clara registraram o maior número de espécies pertencente às famílias Lamiaceae e Solanacease e as plantas foram utilizadas para tratamento de dor de estômago, gripe e inflamações. A prova de "chi quadrado" mostrou diferenças (p < 0,05) entre os municípios e as etnias. Conclui-se que existe diferença no uso de plantas medicinais entre as localidades e os grupos étnicos estudados. A espécie Ilex guayusa foi a planta medicinal mais usada pelos agricultores independentemen...

Slash-and-burn shifting cultivation is common in indigenous societies in the Amazon basin. The large land use of this farming practice is of increasing concern because most indigenous communities are faced with population growth and territory losses. Our study aims to evaluate the feasibility of transforming shifting cultivation into a permanent cropping system by application of Terra Preta practice. For this purpose, an overview of the nutrient cycles of the agroecosystem of an indigenous family in Sarayaku, located in the eastern lowlands of the Ecuadorian Amazon, is provided. Household nutrient input and output data were collected and complemented with information from literature. The balances of nitrogen, phosphorus, and potassium were calculated in five different scenarios: (I) recycling of household waste; (II) recycling of household waste and urine; (III) recycling of household waste, urine, and feces. Whereas the first three scenarios include an external wood source, IV and V additionally integrate a tree plantation. In scenario IV the tree plantation is fertilized only with feces, while in V also with household waste. Even after consideration of nutrient losses, scenarios II to V show potential to accumulate nutrients at the farmland. These results indicate the feasibility of closing nutrient cycles with the purpose to generate permanent farmland by combining knowledge of Terra Preta practice and the way of life of indigenous communities. In a described step by step manner this new agricultural system could be implemented and improve greatly resilience and sustainability of land use in the Amazon.

Distribution data on Achatina fulica Bowdich were obtained from pest control agencies and from a survey of potential localities randomly distributed in all provinces of Ecuador. Among the total of 1,236 localities, 1,065 (86.2%) held populations of the species. The snail was found to spread much faster than predicted and was present in areas not previously suspected to be under the risk of invasion. The most endangered and infested areas were the coastal and Amazonian regions of the country. According to the pest control reports from government agencies, A. fulica most often affected plantations of cocoa (24.8% of localities), plantain (11.8%) and banana (11.2%), but was also known to forage on 56 other species of cultivated plants. The survey of likely habitats in random localities showed a high infestation rate; urban and ruderal sites turned out to be important but largely neglected dispersal hotspots for the species. Regular observations on two populations in the city of Puyo (Pastaza province, Amazonia) showed that the growth rate and population density were high: reaching adult size took on average four weeks.