Evidence of shift in C4 species range in central Argentina during the late Holocene.

SILVA, L.C.R.; GIORGIS, M.A.; ANAND, M.; ENRICO, L.; PéREZ HARGUINDEGUY, N.; FALCZUK, V.; TIESZEN, L.; CABIDO, M.

PLANT AND SOIL

SPRINGER

Lugar: Berlin; Año: 2011 vol. 349 p. 261 - 279

0032-079X

Aim: Millennial- scale biogeographic changes are well understood in many parts of the world, but little is know about long- term vegetation dynamics in subtropical regions. Here we investigate shifts in C3/C4 plant abundance occurred in central Argentina during the past few millennia. Methods: We determined present day soil organic matter ä 13 C signatures of grasslands, shrublands and woodlands, containing different mixtures of C3 and C4 plants. We measuresd past changes in the relative cover of C3/ C4 plants by comparing ä13 C values in soil profiles with present day ä13 C signatures. We analyzed 14 c activity in soil depths that showed major changes in vegetation. Results: Present day relative cover of C3/C4 plants determines whole ecosystem ä13 C signatures integrated as litter and superficial soil organic matter. Deeper soils show a consistent shift in ä13, indicating a continuous replacement of C4 by C3 plants since 3.870 (+/- 210) YBP: During this period, the relative abundance of C3 plants increased 32 % (average across sites) with significant changes being observed in all studied ecosystems. Conclusions: Our results show that C4 especies were more abundant in the past, but C3 species became dominant during the late Holocene. We identified increases in the relative C3/C4 cover in grasslands, shrublands and woodlands, suggesting a phusiological basis for changes in vegetation, The replacement of C4 by C3 plants coincided with changes in climate towards colder and wetter conditions and could represent a climatically driven shift in the C4 species optimum range.