Brazil's riparian forests are continuously threatened by conversion into agricultural areas, causing not only degradation and loss of vegetation but also negative changes in soil properties and ecosystem services. In order to select vegetation and soil variables that are affected by degradation and to evaluate whether forest structure can be used as a proxy for soil ecosystem services, two watersheds in eastern Amazon were chosen as a study area in which four degradation levels were identified (very high, high, moderate and low), based on forest canopy openness and height. Vegetation structural characteristics, water infiltration rates, and soil properties were evaluated in 24, 1,000 m 2 permanent plots. Results indicated that forest degradation significantly reduced soil carbon, phosphorus, cation exchange capacity, silt proportion, total porosity, and water content as well as water infiltration rate. Vegetation structure was a good proxy for monitoring soil ecosystem services (i.e. regulation of water flow, erosion control and life-supporting). Tree height and basal area, as well as herb biomass, were identified as the best vegetation indicators for changes in soil properties that underlie ecosystem services. Application of this strategy may facilitate the monitoring and modeling of riparian forest ecosystem services across broader spatial scales, to help guide efficient restoration efforts and conservation policies.

* Autor correspondente: guilirous@yahoo.ca RESUMOAs florestas ripárias provêem serviços ecossistêmicos essenciais à humanidade, mas estão sendo degradadas em um ritmo acelerado na Amazônia. Esse estudo teve como objetivo quantificar os estoques de carbono acima e abaixo do solo de florestas ripárias com quatro níveis de degradação (muito alta, alta, média e baixa) em duas microbacias (Rio Pepital e Rio Grande) em Alcântara (Maranhão), na Amazônia Oriental. Foram instaladas 24 parcelas permanentes de 1.000 m 2 , onde a vegetação (árvores, arbustos, herbáceas, lianas e palmeiras), a necromasa (serapilheira, árvores mortas, galhos) e o solo (0-20 cm e raízes) foram amostrados. A biomassa foi estimada mediante modelos alométricos (vegetação com DAP > 1 cm e árvores mortas) e de forma destrutiva (herbáceas, serapilheira, galhos finos, raízes). O estoque total de carbono nas florestas ripárias mais conservadas variou entre 88 e 202 Mg(C) ha -1. A degradação reduziu significativamente o estoque de carbono em todos os compartimentos (até 97% na biomassa viva acima do solo, até 91% de necromassa e até 47% no solo). Nas áreas conservadas, a biomassa viva acima do solo tem a maior participação no estoque total de carbono (> 70%), principalmente devido às árvores de grande porte. O estoque de carbono nos diferentes compartimentos estão fortemente relacionados entre si e também com a abertura do dossel. A incorporação desses resultados em modelos regionais de carbono pode auxiliar na implementação e revisão do Código Florestal Brasileiro, em particular na restauração das florestas ripárias onde a agricultura está consolidada. PALAVRAS-CHAVE: Maranhão, mata ciliar, conservação florestal, serviços ecossistêmicos, sucessão ecológica. Impact of degradation on carbon stock of riparian forests in the eastern Amazon, Brazil ABSTRACTRiparian forests provide essential ecosystem services to humanity, but are being degraded at an accelerated rate in the Amazon. This study aimed to quantify carbon stocks above and below ground in riparian forests with four levels of degradation (very high, high, medium and low) in two watersheds (Pepital Rio and Rio Grande) in Alcântara, Eastern Amazon. Twenty-four permanent plots of 1,000 m 2 were installed, and vegetation (trees, shrubs, herbs, lianas and palms), necromass (litter, dead trees, branches) and soil (0-20 cm and roots) were sampled. The biomass was estimated using allometric models (vegetation with dbh> 1 cm and dead trees) and destructively (herbaceous, litterfall, branches, roots). The total carbon stock in the most conserved riparian forests ranged between 88 and 202 Mg(C) ha -1. Degradation significantly reduced carbon stock in all compartments (up to 97% in above-ground biomass, up to 91% of necromass, and up to 47% in soils). In conserved areas, the aboveground biomass is the largest compartment of the total carbon stock (> 70%), mainly due to large trees. The carbon stock in the different compartments are strongly correlated with each other and with the canopy opening. The incorpor...