Underground deserts below fertility islands? – Woody species desiccate lower soil layers in sandy drylands

Abstract

4Woody plants in water-limited ecosystems affect their environment on multiple scales: 5 locally, natural stands can create islands of fertility for herb layer communities compared to 6 open habitats, but afforestation has been shown to negatively affect regional water balance 7 and productivity. Despite these contrasting observations, no coherent multiscale framework 8 has been developed for the environmental effects of woody plants in water-limited 9 ecosystems. To link local and regional effects of woody species in a spatially explicit model, 10 we simultaneously measured site conditions (microclimate, nutrient availability and topsoil 11 moisture) and conditions of regional relevance (deeper soil moisture), in forests with different 12 canopy types (long, intermediate and short annual lifetime) and adjacent grasslands in sandy 13 drylands. All types of forests ameliorated site conditions compared to adjacent grasslands, 14 although natural stands did so more effectively than managed ones. At the same time, all 15 forests desiccated deeper soil layers during the vegetation period, and the longer the canopy 16 lifetime, the more severe the desiccation in summer and more delayed the recharge after the 17 active period of the canopy. We conclude that the site-scale environmental amelioration 18 brought about by woody species is bound to co-occur with the desiccation of deeper soil 19layers, leading to deficient ground water recharge. This means that the cost of creating islands 20 of fertility for sensitive herb layer organisms is an inevitable negative impact on regional 21 water balance. The canopy type or management intensity of the forests affects the magnitude 22 but not the direction of these effects. The outlined framework of the effects of woody species 23 should be considered for the conservation, restoration, or profit-oriented use of forests as well 24 2 as in forest-based carbon sequestration and soil erosion control projects in water-limited 25 ecosystems. 26 27

Underground deserts below fertility islands? Woody species desiccate lower soil layers in sandy drylands

“…Data available from the Dryad Digital Repository: <https://doi.org/10.5061/dryad.59zw3r248> (Tölgyesi et al ).…”

Urgent need for updating the slogan of global climate actions from “tree planting” to “restore native vegetation”

“…Grasslands lack large and obvious above-ground carbon stores such as massive tree trunks and their microclimate is generally more hostile (i.e. warmer and drier) compared to that of forests (Tölgyesi et al 2020), hindering their appreciation as efficient climate solutions by the general public and policy makers. However, grasslands may sometimes represent larger and more stable carbon sinks belowground than forests below-and aboveground combined (Dass et al 2018).…”

Book Review - László Erdős: Green Heroes. From Buddha to Leonardo DiCaprio. Springer. e-book: ISBN 978-3-03031806-2, 21,39 €. Hardcover: ISBN 978-3-030-318055

“…Land managers may need to favour grasslands instead of forests in such regions, despite that this may, at first sight, contradict the global trends of afforestation to mitigate climate change. For further details please check our recent paper in Ecography (Tölgyesi et al 2020). "What kind of story can start with Buddha and conclude with Leonardo DiCaprio?…”