POSITIVE EFFECTS OF LEGUMES ON SOIL ORGANIC CARBON STORAGE DISAPPEAR AT
HIGH LEGUME PROPORTION ACROSS A WIDE RANGE OF ENVIRONMENTAL CONDITIONS
IN GRASSLANDS IN THE PYRENEES
Abstract
Soil is the largest terrestrial carbon pool, making it crucial for
climate change mitigation. To disentangle the relationships of plant
guild diversity with soil organic carbon (SOC) storage at broad spatial
scales, we applied diversity-interaction models to a regional grassland
database. The questions were if: 1) positive effects of plant guild
diversity on SOC at broad spatial scales are similar to experiments; 2)
the enhancement of SOC by legumes is constant in natural grasslands; and
3) the effects of legumes on SOC depend on interactions with other
guilds. SOC increased with legume proportion up to 15-20%, then
decreased, across broad spatial scales. Additionally, legume effects
were enhanced when grasses were dominant, which could be related to the
strong capacity of grasses for capturing nitrogen; grass carbon
exudates; the balance symbiotic/non-symbiotic nitrogen. Our findings can
facilitate the elaboration of regional and local strategies to
ameliorate the soil capacity to absorb carbon.