【冬季气候变化对草原土壤C、N循环的影响】Jorge Durán Alexandra Rodríguez Jennifer L. Morse Peter M. Groffman. Winter climate change effects on soil C and N cycles in urban grasslands. Global Change BiologyVolume 19Issue 9 pages 2826–2837 September 2013

Abstract

Despite growing recognition of the role that cities have in global biogeochemical cycles urban systems are among the least understood of all ecosystems. Urban grasslands are expanding rapidly along with urbanization which is expected to increase at unprecedented rates in upcoming decades. The large and increasing area of urban grasslands and their impact on water and air quality justify the need for a better understanding of their biogeochemical cycles. There is also great uncertainty about the effect that climate change especially changes in winter snow cover will have on nutrient cycles in urban grasslands. We aimed to evaluate how reduced snow accumulation directly affects winter soil frost dynamics and indirectly greenhouse gas fluxes and the processing of carbon (C) and nitrogen (N) during the subsequent growing season in northern urban grasslands. Both artificial and natural snow reduction increased winter soil frost affecting winter microbial C and N processing accelerating C and N cycles and increasing soil : atmosphere greenhouse gas exchange during the subsequent growing season. With lower snow accumulations that are predicted with climate change we found decreases in N retention in these ecosystems and increases in N₂O and CO₂ flux to the atmosphere significantly increasing the global warming potential of urban grasslands. Our results suggest that the environmental impacts of these rapidly expanding ecosystems are likely to increase as climate change brings milder winters and more extensive soil frost.

【土地利用变化与CO2排放】Atul K. Jain^1* Prasanth Meiyappan¹ Yang Song¹ Joanna I. House². CO₂emissions from land-use change affected more by nitrogen cycle than by the choice of land-cover data. Global Change BiologyVolume 19Issue 9 pages 2893–2906 September 2013

Abstract

The high uncertainty in land-based CO₂ fluxes estimates is thought to be mainly due to uncertainty in not only quantifying historical changes among forests croplands and grassland but also due to different processes included in calculation methods. Inclusion of a nitrogen (N) cycle in models is fairly recent and strongly affects carbon (C) fluxes. In this study for the first time we use a model with C and N dynamics with three distinct historical reconstructions of land-use and land-use change (LULUC) to quantify LULUC emissions and uncer