The World's grasslands are under severe threat from on-going degradation, yet they are largely ignored in sustainable development agendas. This degradation is undermining the capacity of grasslands to support biodiversity, ecosystem services, and human wellbeing. In this Perspective, we examine the current state of grasslands worldwide and explore the extent and dominant drivers of global grassland degradation. We identify actions that are critical to the development of socio-ecological solutions to combat degradation and promote restoration of global grasslands. Specifically, we argue that progress can be made by: increasing recognition of grasslands in global policy, developing standardised indicators of grassland degradation, using scientific innovation for effective restoration at regional and landscape scales, and enhancing knowledge transfer and data sharing on restoration experiences. The integration of these strategies into sustainability policy should help to halt grassland degradation and enhance restoration success, and protect the socio-economic, cultural and ecological benefits that grasslands provide.Grasslands, comprising open grassland, grassy shrublands and savannah, cover about 40% of the Earth's surface and some 69% of the world's agricultural land area 1-3 . Not only do they serve as an important global reservoir of biodiversity, including many iconic and endemic species, but also, they provide a wide range of material and non-material benefits to humans and our quality of life. These benefits include a wide range of ecosystem services, such as food production, water supply and regulation, carbon storage and climate mitigation, pollination, and a host of cultural services 1-3 . Despite its importance, grassland degradation is widespread and accelerating in many parts of the world 4-6 with as much as 49% of grassland area worldwide having been degraded to some extent 5,7,8 .Grassland degradation poses an enormous threat to the hundreds of millions of people who rely on grasslands worldwide for food, fuel, fibre and medicinal products, as well as their multiple cultural values 9,10 . In terms of livestock production, the global cost of grassland degradation has been estimated at $6.8 billion 11 , with the impact on human welfare being particularly severe in regions where most the population is below the poverty line Grassland degradation also creates major environmental problems, given that grasslands play a critical role in biodiversity conservation, climate and water regulation, and global biogeochemical cycles 2,4 . For example, the conversion of tropical grassy biomes to arable cropland poses a significant threat to biodiversity given that they have a vertebrate species richness comparable to forests 12 , while the recent expansion of croplands in United States has caused widespread conversion of prairie grasslands, with considerable cost to wildlife 6 . Moreover, the conversion of grasslands to arable cropland and disturbance through overgrazing, fire and invasive species can lead to signif...

A method for collecting an isotopically representative sample of CO2 from an air stream using a zeolite molecular sieve is described. A robust sampling system was designed and developed for use in the field that includes reusable molecular sieve cartridges, a lightweight pump, and a portable infrared gas analyzer (IRGA). The system was tested using international isotopic standards (13C and 14C). Results showed that CO2 could be trapped and recovered for both δ13C and 14C analysis by isotope ratio mass spectrometry (IRMS) and accelerator mass spectrometry (AMS), respectively, without any contamination, fractionation, or memory effect. The system was primarily designed for use in carbon isotope studies of ecosystem respiration, with potential for use in other applications that require CO2 collection from air.

There is an emerging consensus that microbial necromass carbon is the primary constituent of stable soil carbon, yet the controls on the stabilization process are unknown. Prior to stabilization, microbial necromass may be recycled by the microbial community. We propose that the efficiency of this recycling is a critical determinant of soil carbon stabilization rates. Here we explore the controls on necromass recycling efficiency in 27 UK grassland soils using stable isotope tracing and indicator species analysis. We found that recycling efficiency was unaffected by land management. Instead, recycling efficiency increased with microbial growth rate on necromass, and was highest in soils with low historical precipitation. We identified bacterial and fungal indicators of necromass recycling efficiency, which could be used to clarify soil carbon stabilization mechanisms. We conclude that environmental and microbial controls have a strong influence on necromass recycling, and suggest that this, in turn, influences soil carbon stabilization.

SummaryMore than 200 years ago, von Humboldt reported decreases in tropical plant species richness with increasing elevation and decreasing temperature. Surprisingly, co-ordinated patterns in plant, bacterial and fungal diversity on tropical mountains are yet to be observed, despite the central role of soil microorganisms in terrestrial biogeochemistry. We studied an Andean transect traversing 3.5 km in elevation to test whether the species diversity and composition of tropical forest plants, soil bacteria and fungi can follow similar biogeographical patterns with shared environmental drivers. We found co-ordinated changes with elevation in all three groups: species richness declined as elevation increased, and the compositional-dissimilarity of communities increased with increased separation in elevation, although changes in plant diversity were larger than in bacteria and fungi. Temperature was the dominant driver of these diversity gradients, with weak influences of edaphic properties, including soil pH. The gradients in microbial diversity were strongly correlated with the activities of enzymes involved in organic matter cycling, and were accompanied by a transition in microbial traits towards slower-growing, oligotrophic taxa at higher elevations. We provide the first evidence of co-ordinated temperature-driven patterns in the diversity and distribution of three major biotic groups in tropical ecosystems: soil bacteria, fungi and plants. These findings suggest that, across landscape scales of relatively constant soil pH, inter-related patterns of plant and microbial communities with shared environmental drivers can occur, with large implications for tropical forest communities under future climate change.

ABSTRACT. As part of a study investigating the carbon balance of a blanket bog, we made an assessment of the spatial variation of radiocarbon concentrations in the surface layers of a small area of peatland in the north of England. The peat depth at which bomb-14 C content was the highest varied considerably between cores sampled from across the site. At several sampling locations, 14 C levels >100% Modern were confined to the surface 8 cm, whereas bomb 14 C was evident at 1 site, located only meters away, to a depth of at least 12-16 cm. Using the layer where 14 C levels first exceeded 100% Modern as a chronological reference layer, we estimated the carbon accumulation rate over the last 50 yr for the surface peat at each site (range ∼20 to ∼125 g C m 2 yr -1 ). Our results show that although carbon accumulation over the last 50 yr was similar across the site, variation in the depth to which bomb 14 C was evident implied considerable variation in the vertical peat growth rate.