Effects of wildfire ash on water chemistry and biota in South‐Western U.S.A. streams

Abstract

SUMMARY 1. We monitored streams within the Gila River drainage in south‐western New Mexico, U.S.A., over a 5‐year period, to investigate the influence of ash input on water quality and stream biota following forest wildfires. 2. Nutrients [ammonium, nitrate, soluble reactive phosphate (SRP)], potassium and alkalinity were most affected by fires; all were increased in stream water following ash input. Concentrations of each returned to prefire conditions within 4 months. Ammonium and nitrate also increased in stream water as a result of atmospheric fallout (e.g. smoke) from fires outside the catchment. 3. Periphyton biomass was not affected significantly by wildfires, although there was a shift in diatom assemblage to smaller more adnate taxa. Cocconeis placentula was frequently the dominant postfire species. 4. The influence of wildfires on macroinvertebrates ranged from minimal to dramatic reductions in density depending upon the duration of ash flows and the characteristics of the ash material that entered each system. Macroinvertebrate densities returned to prefire conditions within 1 year. 5. An in‐situ ashing experiment was conducted on a first‐order stream in the Gila River drainage to monitor on‐site physiochemical and biotic responses during and after fire ash addition, for comparison with ash delivery from real wildfires on monitored streams. Physical–chemical parameters and algae and macroinvertebrates were monitored in an ashed and upstream reference reach for 13 months. Results generally substantiated findings from monitored streams. 6. Concentrations of major ions and nutrients, as well as turbidity, conductivity and pH, increased immediately in stream water below the point of ashing, while dissolved oxygen decreased. Changes in water chemistry were short‐lived (=24 h) except for SRP. The concentration of SRP in stream water was significantly higher in the ashed reach than the control reach for at least 1 month after ash input. 7. Periphyton biomass and diatom assemblages were not significantly altered in the ashing study, whereas macroinvertebrate density was measurably lower in the ashed reach for nearly a year. Macroinvertebrate drift was over 10‐fold greater in the ashed reach compared with the reference reach during ashing. Dissimilarity between macroinvertebrate communities in the reference and ashed reaches was significantly greater than variation within reaches for nearly a year.

Changing Water Quality in the Middle Mahakam Lakes: Water Quality Trends in a Context of Rapid Deforestation, Mining and Palm Oil Plantation Development in Indonesia’s Middle Mahakam Wetlands

“…Forest fires also result in an increase in nutrient availability entering the water system through run-off and deposition. Earl and Blinn (2003) reported an increase in nitrates, phosphates and alkalinity after ash from forest fires entered USA streams, again consistent with our results for all three lakes. The increased input of nutrients and ash particles is likely to explain the high levels of chemical oxygen demand and total dissolved solids in 1998 (both indicators for eutrophication) and the low levels of dissolved oxygen and transparency.…”

“…According to Hope et al (2005) and Chokkalingam et al (2005), 72-85 % of the swamp forest was affected by these fires. Large-scale fires can have a detrimental effect on water quality (Gumiri 2000;Earl and Blinn 2003). According to Anderson and Bowen (2000), Page et al (2002) and Suyanto et al (2004), the major driving forces behind the fires are plantation developments, by the government and companies, and large-scale transmigration.…”

The Stream Biome Gradient Concept: factors controlling lotic systems across broad biogeographic scales

“…Fire maintains grasslands but probably has more modest effects on nutrient content in grassland streams than in forest or desert streams. Post-fire ash flows in dry areas can drastically increase nutrients (Earl and Blinn 2003) and, ultimately, can cause great harm to existing biota. Forest fires generally increase nutrient loads (e.g., Minshall et al 1989, Bayley et al 1992.…”

Effect of Atmospheric Deposition and Weathering on Trace Element Concentrations in Glacial Meltwater at Grand Teton National Park, Wyoming, U.S.A.

“…Anthropogenic aerosols, wildfire ash, and mineral dust are important sources of nutrients and trace metals to otherwise pristine and protected alpine catchments in the Western United States (Earl and Blinn, 2003;Aarons et al, 2016). Dust contributes substantial loading of soluble salts, metals, and metalloids to snowpack (Turk et al, 2001;Clow et al, 2002;Ingersoll et al, 2008;Lawrence et al, 2010;Rhoades et al, 2010;Carling et al, 2012).…”