Carbon cycling and sequestration opportunities in temperate grasslands

Abstract

Temperate grasslands account for c. 20% of the land area in Europe. Carbon accumulation in grassland ecosystems occurs mostly below ground and changes in soil organic carbon stocks may result from land use changes (e.g. conversion of arable land to grassland) and grassland management. Grasslands also contribute to the biosphere±atmosphere exchange of non-CO 2 radiatively active trace gases, with¯uxes intimately linked to management practices. In this article, we discuss the current knowledge on carbon cycling and carbon sequestration opportunities in temperate grasslands. First, from a simple two-parameter exponential model ®tted to literature data, we assess soil organic carbon¯uxes resulting from land use change (e.g. between arable and grassland) and from grassland management. Second, we discuss carbon¯uxes within the context of farming systems, including crop±grass rotations and farm manure applications. Third, using a grassland ecosystem model (PaSim), we provide estimates of the greenhouse gas balance, in CO 2 equivalents, of pastures for a range of stocking rates and of N fertilizer applications. Finally, we consider carbon sequestration opportunities for France resulting from the restoration of grasslands and from the de-intensi®cation of intensive livestock breeding systems. We emphasize major uncertainties concerning the magnitude and non-linearity of soil carbon stock changes in agricultural grasslands as well as the emissions of N 2 O from soil and of CH 4 from grazing livestock.

Winter cover crops as green manure in a temperate region: the effect on nitrogen budget and yield of silage maize

“…a sink) in soils under grassland and forest (from 0-100 million tonnes of carbon per year) than under arable land (from 10-40 million tonnes of carbon per year) (Schils et al, 2008). Soil carbon losses occur when grasslands, forest lands or native ecosystems are converted to croplands, and carbon stocks increase, albeit much more slowly, when the reverse takes place (Soussana et al, 2004). There is evidence that some soil cultivation methods on arable land can halt the decrease of SOC and even can lead to an increase.…”

Dynamics of the land use, land use change, and forestry sink in the European Union: the impacts of energy and climate targets for 2030

“…Although forest harvest has increased steadily, improved forest management and establishment of new forests have outweighed this, resulting in a continued net sink (Ciais et al 2008). Grasslands in the EU countries also form a carbon sink, especially those that have been recently converted from cropland (Soussana et al 2004). Emissions from deforestation and cropland soils do reduce the total carbon sequestered by forests and grassland; however, deforestation rates in EU countries are relatively stable at a low level (UNFCCC).…”

Exploiting Soil-Management Strategies for Climate Mitigation in the European Union: Maximizing “Win–Win” Solutions across Policy Regimes

“…Studies show that a complete conversion of arable land to permanent grass is estimated to increase soil carbon by 0.5 t/ yr -1 /ha -1 (IPCC 2000, Conant et al 2001, whereas temporary http://www.ecologyandsociety.org/vol16/iss4/art22/ grass may increase soil carbon by 0.35 t/yr -1 /ha -1 (Soussana et al 2004). The water requirements for permanent grass and temporary grass are lower than for most other arable crops; for example, cereals and maize require 10% more water than grass (Food and Agriculture Organization 1991).…”