Premium
Expansion of Juniperus virginiana L. in the Great Plains: Changes in soil organic carbon dynamics
Author(s) -
Smith Dixie L.,
Johnson Loretta C.
Publication year - 2003
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2002gb001990
Subject(s) - juniper , soil carbon , soil water , environmental science , grassland , cycling , soil organic matter , soil horizon , carbon cycle , agronomy , soil science , forestry , ecology , ecosystem , geography , biology
Woody encroachment by Juniperus virginiana into Great Plains grasslands allowed us to answer: Does changing the type of plant input to soils alter soil organic carbon (SOC) distribution or soil carbon (C) storage? The answer is critical because woody encroachment may alter C cycling over millions of hectares in the Great Plains and Midwest. We predicted that (1) forest SOC would become concentrated in shallow soil layers compared to SOC distribution in grassland, (2) woody expansion would increase soil C storage, and (3) forest C would be apparent in the larger soil organic matter fractions. Using δ 13 C signatures of SOC, 1/5 of the C from 0 to 25 cm in juniper forest soils was derived from C 3 juniper trees. Forest C 3 input occurred primarily in shallow surface layers: Forest soils developed over former C 4 prairie contained 42% C 3 ‐SOC from 0 to 2.5 cm depth, and decreased to 6% at 25 cm. Isotopic analysis of SOC size fractions revealed that at 0–2.5 cm, the forest soil fraction >212 μm was −25.7‰. The fraction <2 μm had a 13 C isotope ratio of −17.0‰ at the same depth, reflecting the predominance of residual prairie C in the smallest fraction. In spite of fast dynamics of soil C turnover, there was no net change in SOC amounts over 40–60 years (cumulative mineral and organic SOC in forest, 8782 g C/m 2 ± 810; in grassland, 7699 ± 1004). Thus as junipers expand into mesic areas of the Great Plains, juniper forests will provide little additional soil C storage.