【农业对陆地植物生产力的影响】W. Kolby Smith1* Cory C. Cleveland2 Sasha C. Reed3 Steven W. Running1. Agricultural conversion without external water and nutrient inputs reduces terrestrial vegetation productivity. Geophysical Research Letters
Abstract
Driven by global population and standard of living increases humanity co-opts a growing share of the planet's natural resources resulting in many well-known environmental trade-offs. In this study we explored the impact of agriculture on a resource fundamental to life on Earth: terrestrial vegetation growth (net primary production; NPP). We demonstrate that agricultural conversion has reduced terrestrial NPP by ~7.0%. Increases in NPP due to agricultural conversion were observed only in areas receiving external inputs (i.e. irrigation and-or fertilization). NPP reductions were found for ~88% of agricultural lands with the largest reductions observed in areas formerly occupied by tropical forests and savannas (~71% and ~66% reductions respectively). Without policies that explicitly consider the impact of agricultural conversion on primary production future demand-driven increases in agricultural output will likely continue to drive net declines in global terrestrial productivity with potential detrimental consequences for net ecosystem carbon storage and subsequent climate warming.
【腐殖质的氧化还原循环】Laura Klüpfel Annette Piepenbrock Andreas Kappler & Michael Sander. Humic substances as fully regenerable electron acceptors in recurrently anoxic environments. Nature Geoscience 7 195–200 (2014) doi:10.1038-ngeo2084
Abstract
Humic substances form through the degradation of microbial and plant precursors and make up a significant fraction of natural organic matter in terrestrial and aquatic environments1. Humic substances are redox-active2