Through litter decomposition enormous amounts of carbon is emitted to the atmosphere. Numerous large-scale decomposition experiments have been conducted focusing on this fundamental soil process in order to understand the controls on the terrestrial carbon transfer to the atmosphere. However, previous studies were mostly based on site-specific litter and methodologies, adding major uncertainty to syntheses, comparisons and meta-analyses across different experiments and sites. In the TeaComposition initiative, the potential litter decomposition is investigated by using standardized substrates (Rooibos and Green tea) for comparison of litter mass loss at 336 sites (ranging from -9 to +26 °C MAT and from 60 to 3113 mm MAP) across different ecosystems. In this study we tested the effect of climate (temperature and moisture), litter type and land-use on early stage decomposition (3 months) across nine biomes. We show that litter quality was the predominant controlling factor in early stage litter decomposition, which explained about 65% of the variability in litter decomposition at a global scale. The effect of climate, on the other hand, was not litter specific and explained <0.5% of the variation for Green tea and 5% for Rooibos tea, and was of significance only under unfavorable decomposition conditions (i.e. xeric versus mesic environments). When the data were aggregated at the biome scale, climate played a significant role on decomposition of both litter types (explaining 64% of the variation for Green tea and 72% for Rooibos tea). No significant effect of land-use on early stage litter decomposition was noted within the temperate biome. Our results indicate that multiple drivers are affecting early stage litter mass loss with litter quality being dominant. In order to be able to quantify the relative importance of the different drivers over time, long-term studies combined with experimental trials are needed.

A metagenomic cosmid library was prepared in Escherichia coli from DNA extracted from the contents of rabbit cecum and screened for cellulase activities. Eleven independent clones expressing cellulase activities (four endo-beta-1,4-glucanases and seven beta-glucosidases) were isolated. Subcloning and sequencing analysis of these clones identified 11 cellulase genes; the encoded products of which shared less than 50% identities and 70% similarities to cellulases in the databases. All four endo-beta-1,4-glucanases and all seven beta-glucosidases, respectively, belonged to glycosyl hydrolase family 5 (GHF 5) and family 3 (GHF 3) and formed two separate branches in the phylogenetic tree. Ten of the 11 cloned cellulases exhibited highest activities at pH 5.5 approximately 7.0 and 40 approximately 55 degrees C, a condition similar to that in the rabbit cecum. All the four endo-beta-1,4-glucanases could hydrolyze a wide range of beta-1,4-, beta-1,4/beta-1,3- or beta-1,3/beta-1,6-linked polysaccharides. One endo-beta-1, 4-glucanase gene, umcel5G, was overexpressed in E. coli, and the purified recombinant enzyme was characterized in detail. The enzymes cloned in this work represented at least some of the cellulases operating efficiently in the rabbit cecum. This work provides the first snapshot on the cellulases produced by bacteria in rabbit cecum.

Afforestation of marginal agricultural land has been considered to be an effective measure to sequester atmospheric CO 2 . In this study, we adopted the volume-and mass-based methods to investigate the changes in soil organic C and total N stocks in 100 cm depth following afforestation of marginal agricultural land using a chronosequence of poplar (Populus euramericana cv. "N3016") stands in a semiarid region of Liaoning Province, Northeast China. Our results showed that soil organic C and total N concentrations in 45-60 cm layer increased gradually following afforestation of agricultural land, whereas in 60-100 cm layer, they declined initially, and then increased with stand development. Based on volume-and mass-based methods, such land-use change caused initial declines in soil organic C and total N stocks, and then increases between the stand ages of 10 and 20. Forest soils recovered to the initial soil organic C and N stocks found in agricultural land at age 15. However, the volume-based method would underestimate the absolute organic C and N stocks compared with the mass-based methods. Our results suggest that afforestation of marginal agricultural land has the potential to sequester atmospheric CO 2 in soils in semiarid regions. Stand age, soil sampling depth and the methods used to quantify organic C and N stocks should be considered for accurate assessments of changes in soil organic C and N stocks.

We compared soil moisture content, pH, total organic carbon (C org ), total nitrogen (TN), total phosphorus (TP) and inorganic N (NH 4concentrations, soil potential C and N mineralization rates, soil microbial biomass C (C mic ), soil metabolic quotient (qCO 2 ), soil microbial quotient (C mic /C org ) and soil enzyme (urease and invertase) activities in semiarid sandy soils under three types of land cover: grassland, Mongolian pine (Pinus sylvestris var. mongolica) plantation, and elm (Ulmus punila)-grass savanna in southeastern Keerqin, in northeast China. Soil C org , TN and TP concentrations (0-10, 10-20, 20-40 and 40-60 cm) were lower while soil C/N and C/P ratios were higher in the plantation than in grassland and savanna. The effects of land cover change on NH 4 + -N and NO 3 − -N concentrations, soil potential nitrification and C mineralization rates in the surface soil (0-10 cm) were dependent on sampling season; but soil potential N mineralization rates were not affected by land cover type and sampling season. The effects of land cover change on C mic and qCO 2 of surface soil were not significant; but C mic /C org were significantly affected by land cover change and sampling season. We also found that land cover change, sampling season and land cover type× sampling season interaction significantly influenced soil enzyme (urease and invertase) activities. Usually soil enzyme activities were lower in the pine plantations than in grassland and savanna. Our results suggest that land cover change markedly influenced soil chemical and biological properties in sandy soils in the semiarid region, and these effects vary with sampling season.