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Soil Organic Matter Fractions under Managed Pine Plantations of the Southeastern USA
Author(s) -
Echeverría Marietta E.,
Markewitz Daniel,
Morris Lawrence A.,
Hendrick Ronald L.
Publication year - 2004
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/sssaj2004.9500
Subject(s) - soil water , mineralization (soil science) , organic matter , soil organic matter , zoology , chemistry , agronomy , environmental science , environmental chemistry , soil science , biology , organic chemistry
Herbicide application in plantation forests may affect soil productive capacity through its effect on the quantity and characteristics of soil C. We examined changes in surface soil (<10 cm) soil organic matter (SOM) fractions in 12‐ to 18‐yr‐old pine stands from the Lower Coastal Plain and Piedmont of the southeastern USA that were receiving complete competition control treatments ( n = 13 paired plots). Light (LF) (<1.6 g cm −3 ), medium (MF) (1.6–2.0 g cm −3 ), and heavy (HF) fraction (2.0 g cm −3 ) SOM were isolated by density separation and the HF was hydrolyzed isolating a hydrolyzable (H‐HF) and residual fraction (R‐HF). Herbicide treated surface soils had lower whole soil C (12.8 g kg −1 ) and N (0.51 g kg −1 ) compared with untreated controls, 16.1 g C kg −1 and 0.63 g N kg −1 Across all sites, the greatest decreases in soil C and N occurred in the LF and MF fractions. The majority of C and N in Lower Coastal Plain surface soils (∼90% sand) is partitioned in the LF + MF, while in the Piedmont soils (∼60% sand) it is in the H‐HF. Decreases in these SOM fractions were only slightly greater than decreases in whole soil SOM. Additionally, there was a significant decrease of 27, 41, and 31% in net N mineralization (7‐d anaerobic incubation) due to treatment in a Piedmont site for whole soil (WS), WS + L/MF, and WS + HF, respectively. For the Lower Coastal Plain site, there was an 18% decrease in the WS + L/MF mixture only. Complete competition control in both the Piedmont and Coastal Plain clearly decreased SOM quantity. Decreases in SOM quality as indicated by decreased net N mineralization potential were also evident. The results suggest herbicide treatments may decrease the productive capacity of surface soils.