Changes in Abiotic Factors Drive Non-native Plants Colonization in Subtropical Mangroves

Abstract

The colonization and spread of non-native species are recognized as a critical driver of environmental change in mangrove ecosystems. However, environmental factors that favor non-native plant colonization in mangroves are still poorly understood. To fill this gap, we investigated the effect of selected abiotic factors controlling non-native plant species colonization in mangroves in Southeastern Brazil. We selected 18 plots in mangrove forests under different levels of anthropogenic N inputs, both colonized and non-colonized by non-native plants in the Estuarine-Lagoon Complex of Cananeia-Iguape, southeastern Brazil. We measured interstitial salinity, sediment nitrate and ammonium concentrations, and sediment physicochemical properties. We found that interstitial salinity at 10 cm depth followed by nitrate concentrations in sediment were the main factors associated with the occurrence of non-native species in the studied mangroves. Low salinity and increased N availability in sediment allowed for the success of non-native plants into mangrove forests, also resulting in high amount of dead mangrove trunks. Aiming to conserve and restore such areas, the restoration of abiotic conditions is the first step in the management of non-native species in this region.