Ecosystem carbon loss with woody plant invasion of grasslands

RB JACKSON; JL BANNER; EG JOBBÁGY; WT POCKMAN; DH WALL

NATURE

Nature Publishing Group

Lugar: London; Año: 2002 vol. 418 p. 623 - 626

0028-0836

The invasion of woody vegetation into deserts, grasslands andsavannas is generally thought to lead to an increase in the amountof carbon stored in those ecosystems. For this reason, shrub andforest expansion (for example, into grasslands) is also suggestedto be a substantial, if uncertain, component of the terrestrialcarbon sink1–14. Here we investigate woody plant invasion along aprecipitation gradient (200 to 1,100mmyr21) by comparingcarbon and nitrogen budgets and soil d13C profiles between sixpairs of adjacent grasslands, in which one of each pair wasinvaded by woody species 30 to 100 years ago. We found a clearnegative relationship between precipitation and changes in soilorganic carbon and nitrogen content when grasslands wereinvaded by woody vegetation, with drier sites gaining, and wettersites losing, soil organic carbon. Losses of soil organic carbon atthe wetter sites were substantial enough to offset increases inplant biomass carbon, suggesting that current land-based assessmentsmay overestimate carbon sinks. Assessments relying oncarbon stored from woody plant invasions to balance emissionsmay therefore be incorrect.