Early warning of global change effects on catchment nutrient exports
Abstract
Global change scientists seek sentinels of change. On forested landscapes, first-order catchments serve as sentinels of global stressors and their effects on downstream surface waters. Here, I explored global stressors – including climate warming, hydrological intensification, and recovery from atmospheric acidic deposition – and their effects on nutrient exports in 22-year stream chemistry records from 41 forested first-order catchments in a network of North American long-term monitoring sites. First, I used multivariate autoregressive models to establish relationships between changes in global stressors and changes in catchment nutrient exports. Second, I analyzed the residuals of these relationships to determine if there was evidence of instability in the catchment nutrient exports. I found that changes in global stressors affected the nutrient exports of these catchments but that the global stressors having the largest impacts varied geographically, and that changes in these global stressors were leading to changes in the stability of these nutrient exports.