Intra-annual variation in soil C, N and nutrients pools after prescribed fire in a Mississippi longleaf pine (Pinus palustris Mill.) plantation

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Abstract

Prescribed fire is an essential tool that is widely used for longleaf pine (Pinus palustris Mill.) stand management; periodic burning serves to reduce competition from woody shrubs and fire-intolerant trees and enhance herbaceous diversity. Low-intensity, prescribed burning is thought to have minimal long-term impact on soil chemistry in southern pine forests, although few studies report the intra-annual variation in soil chemistry after burning. We monitored changes in C, N, oxidation resistant C (CR), pH and elemental nutrients in the forest floor and soil (0-5, 5-10 cm depths) before and after burning (1, 3, 6, 12 months) in a mature longleaf pine plantation at the Harrison Experimental Forest, near Saucier, Mississippi. Prescribed fire consumed much of the forest floor (11.3 Mg ha-1; -69%), increased soil pH and caused a pulse of C, N and elemental nutrients to flow to the near surface soils. In the initial one to three months post-burn coinciding with the start of the growing season, retention of nutrients by soil peaked. Most of the N (93%), Ca (88%), K (96%) and Mg (101%), roughly half of the P (48%) and Mn (52%) and 25% of the C lost from the forest floor were detected in the soil and apparently not lost to volatilization. By month 12, soil C and N pools were not different at depths of 0-5 cm but declined significantly below pre-burn levels at depths of 5-10 cm, C -36% (p = 0.003), contrary to other examples in southern pine ecosystems. In the upper 5 cm of soil, only Cu (-49%) remained significantly lower than pre-burn contents by month 12, at depths of 5–10 cm, Cu (-76%), Fe (-22%), K (-51%), Mg (-57%), Mn (-82%) and P (-52%) remain lower at month 12 than pre-burn contents. Burning did not increase soil CR content, conversely significant declines in CR occurred. It appears that recovery of soil C and N pools post-burn will require more time on this site than other southern pine forests.

  • Citation: Butnor, John R.; Johnsen, Kurt H.; Maier, Christopher A.; Nelson, C. Dana. 2020. Intra-annual variation in soil C, N and nutrients pools after prescribed fire in a Mississippi longleaf pine (Pinus palustris Mill.) plantation. Forests. 11(2): 181-. https://doi.org/10.3390/f11020181.
  • Keywords: forest soils, prescribed fire, carbon, nitrogen, phosphorus, potassium, calcium, priming, Harrison Experimental Forest, longleaf pine
  • Posted Date: February 11, 2020
  • Modified Date: November 12, 2020

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