Cover Picture and Issue Information

“Each growing season, fierce competition for limited resources takes place in mature deciduous forests. In this month’s cover image, branches and leaves from ashes ( Fraxinus excelsior ), beeches ( Fagus sylvatica ) and sycamores ( Acer pseudoplatanus ) try to outgrow their counterparts for accessing sunlight. A similar battle happens belowground in the rhizosphere (with roots and their associated soil microbes) to access nutrients and water. This picture was taken in mid‐May (2014) at Wytham Woods (Oxford, UK), a 375‐hectare site bequeathed to the University of Oxford in 1943, which has been since one of the most studied woodland ecosystems worldwide. Fine roots release a variety of organic compounds into the surrounding soil, which act as a source of readily‐available energy for soil microbial decomposers (fungi, bacteria). This root ‘exudation’ can speed up their activity, and so the release of nutrients (taken up by roots) and CO 2 (to the atmosphere). Despite their relevance, these effects have remained difficult to quantify in real, field conditions. In the article related to this image, Lopez‐Sangil et al . use a low‐cost device to simulate the effects of increased root exudation rates, minimizing soil disturbance. Their results show significant increases in soil CO 2 efflux following increased root exudation, but the effects were dependent on the presence or absence of aboveground forest litter.” Photo credit: © Luis Lopez‐Sangil