• Energy Research

Earthworm distribution in global soils Earthworms are key components of soil ecological communities, performing vital functions in decomposition and nutrient cycling through ecosystems. Using data from more than 7000 sites, Phillips et al. developed global maps of the distribution of earthworm diversity, abundance, and biomass (see the Perspective by Fierer). The patterns differ from those typically found in aboveground taxa; there are peaks of diversity and abundance in the mid-latitude regions and peaks of biomass in the tropics. Climate variables strongly influence these patterns, and changes are likely to have cascading effects on other soil organisms and wider ecosystem functions. Science , this issue p. 480 ; see also p. 425

Significance Last Glacial millennial-timescale warming phases well-recorded in Greenland ice cores are relevant across the Northern Hemisphere. However, dating limitations in loess deposits inhibited characterizing their impact on the European Great Plain. Here, the radiocarbon dating of a large set of earthworm calcite granule samples from the Nussloch reference loess sequence (Rhine Valley, Germany) led to a straightforward chronological distinction of all soil horizons. Resulting correlations with Greenland interstadials between 50 and 20 ka also revealed more complex climate dynamics than interpreted from Greenland δ 18 O records. This study is a fundamental contribution to understanding links between mid- and high-latitude climate changes and their spatial and temporal impact on paleoenvironments and prehistoric population settlement in Europe.

Although nitrogen (N) availability is a major determinant of ecosystem properties, little is known about the ecological importance of plants' preference for ammonium versus nitrate (β) for ecosystem functioning and the structure of communities. We modeled this preference for two contrasting ecosystems and showed that β significantly affects ecosystem properties such as biomass, productivity, and N losses. A particular intermediate value of β maximizes the primary productivity and minimizes mineral N losses. In addition, contrasting β values between two plant types allow their coexistence, and the ability of one type to control nitrification modifies the patterns of coexistence with the other. We also show that species replacement dynamics do not lead to the minimization of the total mineral N pool nor the maximization of plant productivity, and consequently do not respect Tilman's R* rule. Our results strongly suggest in the two contrasted ecosystems that β has important consequences for ecosystem functioning and plant community structure.