Journal Article

Fire frequency drives decadal changes in soil carbon and nitrogen and ecosystem productivity

Pellegrini, Adam F. A., Anderegg, William R. L., Reich, Peter B., Nieradzik, Lars P., Staver, A. Carla, Randerson, James T., Scharenbroch, Bryant C., Jackson, Robert B., Jumpponen, Ari, Ahlström, Anders, Hobbie, Sarah E.

2018

Overview

A meta-analysis and field data show that frequent fires in savannas and broadleaf forests decrease soil carbon and nitrogen over many decades; modelling shows that nitrogen loss drives carbon loss by reducing net primary productivity. Soil degradation fuelled by fire The patterns of naturally occurring fires have been altered, both spatially and temporally, as a result of climate and land-use changes. The long-term effects of fire frequency on soil carbon and nutrient storage and the resulting potential limitations on plant productivity remain poorly understood. On the basis of a meta-analysis and an independent dataset of additional field sites, this paper finds that frequent burning leads to soil carbon and nitrogen losses that emerge over decadal timescales. Furthermore, the authors use a model to suggest that the decadal losses of soil nitrogen as a result of more frequent burning could decrease the amount of carbon sequestered by net primary productivity. Fire frequency is changing globally and is projected to affect the global carbon cycle and climate 1 , 2 , 3 . However, uncertainty about how ecosystems respond to decadal changes in fire frequency makes it difficult to predict the effects of altered fire regimes on the carbon cycle; for instance, we do not fully understand the long-term effects of fire on soil carbon and nutrient storage, or whether fire-driven nutrient losses limit plant productivity 4 , 5 . Here we analyse data from 48 sites in savanna grasslands, broadleaf forests and needleleaf forests spanning up to 65 years, during which time the frequency of fires was altered at each site. We find that frequently burned plots experienced a decline in surface soil carbon and nitrogen that was non-saturating through time, having 36 per cent (±13 per cent) less carbon and 38 per cent (±16 per cent) less nitrogen after 64 years than plots that were protected from fire. Fire-driven carbon and nitrogen losses were substantial in savanna grasslands and broadleaf forests, but not in temperate and boreal needleleaf forests. We also observe comparable soil carbon and nitrogen losses in an independent field dataset and in dynamic model simulations of global vegetation. The model study predicts that the long-term losses of soil nitrogen that result from more frequent burning may in turn decrease the carbon that is sequestered by net primary productivity by about 20 per cent of the total carbon that is emitted from burning biomass over the same period. Furthermore, we estimate that the effects of changes in fire frequency on ecosystem carbon storage may be 30 per cent too low if they do not include multidecadal changes in soil carbon, especially in drier savanna grasslands. Future changes in fire frequency may shift ecosystem carbon storage by changing soil carbon pools and nitrogen limitations on plant growth, altering the carbon sink capacity of frequently burning savanna grasslands and broadleaf forests.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 631/158/1144 / 631/158/2465 / 631/158/47/4112 / 631/158/47/4113 / 704/47/4113 / Agricultural productivity / Biologi / Biological Sciences / Biomass / Biomass burning / Carbon / Carbon content / Carbon cycle / Carbon sequestration / Carbon sinks / Climate Science / Dynamic models / Earth and Related Environmental Sciences / Ecology (including Biodiversity Conservation) / Ecosystems / Ekologi / Environmental aspects / Environmental impact analysis / Fire effects / Fires / Forest fires / Forests / Geovetenskap och relaterad miljövetenskap / Grasslands / Humanities and Social Sciences / Klimatvetenskap / letter / Long-term effects / Mathematical models / Meta-analysis / Methods / multidisciplinary / Natural Sciences / Naturvetenskap / Nitrogen / Nitrogen content / Nutrient loss / Nutrients / Plant growth / Prescribed fire / Savannahs / Science / Soil nutrients / Soil surfaces / Soils / Vegetation