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Soil C and N changes with afforestation of grasslands across gradients of precipitation and plantation age
Author(s) -
Berthrong Sean T.,
Piñeiro Gervasio,
Jobbágy Esteban G.,
Jackson Robert B.
Publication year - 2012
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.1890/10-2210.1
Subject(s) - afforestation , environmental science , biomass (ecology) , soil carbon , precipitation , grassland , agronomy , agroforestry , soil organic matter , carbon sequestration , soil water , ecology , forestry , carbon dioxide , soil science , geography , biology , meteorology
Afforestation, the conversion of unforested lands to forests, is a tool for sequestering anthropogenic carbon dioxide into plant biomass. However, in addition to altering biomass, afforestation can have substantial effects on soil organic carbon (SOC) pools, some of which have much longer turnover times than plant biomass. An increasing body of evidence suggests that the effect of afforestation on SOC may depend on mean annual precipitation (MAP). The goal of this study was to test how labile and bulk pools of SOC and total soil nitrogen (TN) change with afforestation across a rainfall gradient of 600–1500 mm in the Rio de la Plata grasslands of Argentina and Uruguay. The sites were all former grasslands planted with Eucalyptus spp. Overall, we found that afforestation increased (up to 1012 kg C·ha −1 ·yr −1 ) or decreased (as much as 1294 kg C·ha −1 ·yr −1 ) SOC pools in this region and that these changes were significantly related to MAP. Drier sites gained, and wetter sites lost, SOC and TN ( r 2 = 0.59, P = 0.003; and r 2 = 0.57, P = 0.004, respectively). Labile C and N in microbial biomass and extractable soil pools followed similar patterns to bulk SOC and TN. Interestingly, drier sites gained more SOC and TN as plantations aged, while losses reversed as plantations aged in wet sites, suggesting that plantation age in addition to precipitation is a critical driver of changes in soil organic matter with afforestation. This new evidence implies that longer intervals between harvests for plantations could improve SOC storage, ameliorating the negative trends found in humid sites. Our results suggest that the value of afforestation as a carbon sequestration tool should be considered in the context of precipitation and age of the forest stand.