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Soil Aggregation and Organic Matter Mineralization in Forests and Grasslands: Plant Species Effects
Author(s) -
Scott Neal A.
Publication year - 1998
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1998.03615995006200040032x
Subject(s) - panicum virgatum , mineralization (soil science) , agronomy , botany , soil water , chemistry , biology , ecology , bioenergy , renewable energy
Plant‐soil feedbacks can alter N cycling rates in terrestrial ecosystems, but the mechanistic relationship between species characteristics, soil properties, and N dynamics is unclear. Plant species may affect patterns of soil aggregation, which can affect soil C and net N mineralization. This mechanism was examined in two common garden experiments: one containing five tree species (European larch [ Larix decidua Miller], red oak [ Quercus rubra L.], red pine [ Pinus resinosa Ait.], white pine [ Pinus strobus L.], and Norway spruce [ Picea abies (L.) Karst]) and one containing six grass species (big bluestem [ Andropogon gerardi Vitm.], indiangrass [ Sorghastrum nutans (L.) Nash], prairie sandreed [ Calamovilfa longifolia (Hook) Scrib.], switchgrass [ Panicum virgatum L.], little bluestem [ Schizachyrium scoparium (Michx.) Nash.], and sideoats grama [ Bouteloua curtipendula (Michx.) Torr.]). The grass monocultures are burned annually. Soils were wet sieved into four size classes (>2000, 250‐2000, 53‐250, and <53 µm). Unsieved soil was incubated aerobically for 30 and 387 d to examine C and net N mineralization. For tree species, aggregate weighted mean diameter (WMD) differed between species ( P = 0.01), and correlated positively with fungal biomass ( r = 0.56). Large macroaggregate (>2000 µm) C concentration ranged from 15 to 26 g kg ‐1 , and was lowest for Norway spruce and red oak ( P = 0.07). Aggregate WMD correlated weakly (and negatively) with potentially mineralizable N ( r = −0.57) and in situ net N mineralization ( r = −0.67), but positively (again weakly) with potentially mineralizable C ( r = 0.49). Grass species had no effect on aggregate‐size distribution or organic matter concentration in spite of twofold differences in root biomass and threefold differences in N cycling rates. Species‐induced changes in soil aggregation explained little of the variation in whole‐soil C and N cycling rates, and are therefore unlikely to be an important mechanism explaining species effects on ecosystem processes.