Climate Change 1995 is a scientific assessment that was generated by more than 1 000 contributors from over 50 nations. It was jointly co-ordinated through two international agencies; the World Meteorological Organization and the United Nations Environment Programme. The assessment was completed by the Intergovernmental Panel on Climate Change (IPCC) with a primary aim of reviewing the current state of knowledge concerning the impacts of climate change on physical and ecological systems, human health, and socioeconomic factors. The second aim was to review the available information on the technical and economic feasibility of the potential mitigation and adaptation strategies.

Climate Change 1995

Soils act as sources and sinks for greenhouse gases (GHG) such as carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O). Since both storage and emission capacities may be large, precise quantifications are needed to obtain reliable global budgets that are necessary for land-use management (agriculture, forestry), global change and for climate research. This paper discusses exclusively the soil emission-related processes and their influencing parameters. It reviews soil emission studies involving the most important land-cover types and climate zones and introduces important measuring systems for soil emissions. It addresses current shortcomings and the obvious bias towards northern hemispheric data. When using a conservative average of 300 mg CO 2 e m −2  h −1 (based on our literature review), this leads to global annual net soil emissions of ≥350 Pg CO 2 e (CO 2 e = CO 2 equivalents = total effect of all GHG normalized to CO 2 ). This corresponds to roughly 21% of the global soil C and N pools. For comparison, 33.4 Pg CO 2 are being emitted annually by fossil fuel combustion and the cement industry.

Greenhouse gas emissions from soils—A review

The impact on nitrogen ([N][1]) and phosphorus ([P][2]) cycles of human activity is a growing concern and has several causes and consequences ([MacDonald et al., 2011][3]; [Penuelas et al., 2012][4]; [Sardans et al., 2012b][5]). Carbon ([C][6]) inputs by human CO2 emissions and [N][1] inputs from

The Role of Plants in the Effects of Global Change on Nutrient Availability and Stoichiometry in the Plant-Soil System

For decomposing foliar litter in forest systems the pattern for accumulated mass loss vs time varies among litter species and environments. Thus, decomposition may be complete (100% accumulated mass loss) or the rate may cease and proceed at such a low rate that a limit value for decomposition may be estimated. Such limit values have been found to range from 42% accumulated mass loss to 100%, resulting in stable fractions of 58 and 0%, respectively. To support a discussion about pattern we need causal relationships and I have used a conceptual model with three decomposition stages as a reference and discuss that in relation to two nutrients that influence the degradation of lignin and lignified tissue. Whereas a high nitrogen (N) concentration may have a stimulating effect on degradation of holocellulose in the early stage the same high N concentration may retard the degradation of lignified tissue in the late stage and the higher the N concentration the stronger the retardation. Through the enzyme manganese peroxidase (MnP), manganese (Mn) stimulates lignin degradation and thus the lignified fraction of litter. A high level of Mn appears to support a further degradation of the lignified tissue and thus results in a high limit value, whereas a high N has been related to a low value. The aim behind this review is to: (i) identify specific factors that may influence the pattern of accumulated mass loss and thus the type of regression model that describes the data; and (ii) present a possible climate influence on decomposition pattern. To this purpose we need to discuss a possible variation in pattern following the variation in concentrations of the two nutrients N and Mn. Concentrations of N and Mn in newly shed litter are both influenced by site climate, with N increasing and Mn decreasing with increasing mean annual temperature (MAT) and increasing annual actual evapotranspiration (AET). Thus, climate becomes at least an indirect regulating factor for decomposition pattern. Two main regression models are used to describe the patterns, namely the single exponential and a function separating a readily decomposed and a stable fraction, by estimating a limit value (asymptotic function). For the discussion on decomposition pattern a model parameter was used, namely estimated limit values with a so far observed range in variation from 42 to 100%. The stabilized litter fraction defined by the limit value may be used for estimating the accumulation rate of stable carbon (C) in soil.

Honglei Zhuang

Papers

Comparison of greenhouse gas emissions from rice paddy fields under different nitrogen fertilization loads in Chongming Island, Eastern China

Variation in leaf nitrogen and phosphorus stoichiometry in Picea abies across Europe: An analysis based on local observations