Short-term effects of fire on soil and plant nutrients in palmetto flatwoods

Abstract

Fire may have different effects on the relative availability of nitrogen (N) and phosphorus (P) because N volatilization occurs at lower temperatures than P volatilization, and fire-mediated changes in soil nutrient availability may affect foliar nutrient concentrations. We assessed the short-term effects of fire on soil and plant nutrients and 15 N isotopic signatures in a palmetto flatwoods ecosystem in central Florida. Fire caused a short-term increase in extractable ammonium (NH 4 + ) and phosphate (PO 4 3-). The increase in PO 4 3-was greater than the increase in NH 4 + , resulting in a decrease in the soil extractable N: P ratio shortly after fire. Similarly, foliar %P of the palmetto Serenoa repens (W. Bartram) Small increased more than foliar %N, resulting in a decrease in foliar N:P ratios shortly after fire. Soil δ 15 N and the difference between foliar and soil δ 15 N did not vary with time since fire; however, foliar δ 15 N of S. repens decreased after fire. Foliar %N of Quercus geminata Small and ericaceous shrubs was positively correlated with soil extractable inorganic N, while foliar %P of S. repens was positively correlated with soil extractable PO 4 3-. Variation in foliar δ 15 N after fire and the positive relationship between soil and foliar nutrients suggest that both increased soil nutrient availability and reallocation of nutrients from below-to aboveground can be important for plant nutrient status after fire in palmetto flatwoods.

Contributions of microbial activity and ash deposition to post-fire nitrogen availability in a pine savanna

“…5). Although a global meta-analysis found that post-fire soil NO − 3 concentrations peak 10 months after NH + 4 concentrations (Wan et al, 2001), studies in southeastern US ecosystems found no change in soil NO − 3 up to 30 days (pine savanna; Boring et al, 2004), 320 days (pine forest; Lavoie et al, 2010) and 500 days (shrubland; Schafer and Mack, 2010) following fire. Across the full growing season, we measured NH + 4 pool sizes of burned sites that were nearly 5 times that of unburned sites.…”

“…Fire may stimulate microbial turnover of organic matter if additions of C or N from ash deposition or root exudation (southern shrubland; Schafer and Mack, 2010) enhance microbial activity. Soil surface blackening after fire may increase soil temperature and stimulate immediate and prolonged N transformations after fire (Booth et al, 2005;Ojima et al, 1994).…”

“…These nutrients can be lost through volatilization, or redistributed as ash in low-intensity fires. Despite the ecosystem-level nutrient losses associated with fires, short-term pulses of increased N availability in the soil are also observed following prescribed forest fires across vegetation types (Certini, 2005;Schafer and Mack, 2010;Smithwick et al, 2005;Wan et al, 2001), including in longleaf pine (Pinus palustris Mill.) savannas (Boring et al, 2004).…”

Role of season and interval of prescribed burning on ponderosa pine growth in relation to soil inorganic N and P and moisture

“…Fire induced pH changes may last for over 3 years after burning (Ulery et al, 1993), nearly long enough to begin accumulating available P in the 5-year-interval treatments. Schafer and Mack (2010) found that the effects of burning on available P were longer lasting than available N suggesting that the effects of burning on available P may accumulate when sites are reburned if the burning interval is short enough.…”

Effect of slight vegetation degradation on soil properties in Brachypodium pinnatum grasslands

“…While considerable knowledge has accumulated about plant-soil relationships, these mostly encompass single-species studies (Morales-Sillero et al 2009;Schafer and Mack 2010). Less is known about vegetation-soil interactions and about how vegetation status, including degradation is reflected in soils.…”