ANC and Stream Temperature Predictions

<p>This dataset contains stream water acid neutralizing capacity (ANC) and temperature predictions for southern Appalachian Mountain streams.</p

Downstream Warming and Headwater Acidity May Diminish Coldwater Habitat in Southern Appalachian Mountain Streams

<div><p>Stream-dwelling species in the U.S. southern Appalachian Mountains region are particularly vulnerable to climate change and acidification. The objectives of this study were to quantify the spatial extent of contemporary suitable habitat for acid- and thermally sensitive aquatic species and to forecast future habitat loss resulting from expected temperature increases on national forest lands in the southern Appalachian Mountain region. The goal of this study was to help watershed managers identify and assess stream reaches that are potentially vulnerable to warming, acidification, or both. To our knowledge, these results represent the first regional assessment of aquatic habitat suitability with respect to the combined effects of stream water temperature and acid-base status in the United States. Statistical models were developed to predict July mean daily maximum water temperatures and air-water temperature relations to determine potential changes in future stream water temperatures. The length of stream considered suitable habitat for acid- and thermally sensitive species, based on temperature and acid neutralizing capacity thresholds of 20°C and 50 μeq/L, was variable throughout the national forests considered. Stream length displaying temperature above 20°C was generally more than five times greater than the length predicted to have acid neutralizing capacity below 50 μeq/L. It was uncommon for these two stressors to occur within the same stream segment. Results suggested that species’ distributional shifts to colder, higher elevation habitats under a warming climate can be constrained by acidification of headwater streams. The approach used in this study can be applied to evaluate climate change impacts to stream water resources in other regions.</p></div

Landscape characteristics used for statistical modeling.

<p>All variables were calculated as watershed average or percentage, with the exception of drainage density and watershed area.</p><p>Landscape characteristics used for statistical modeling.</p

Coefficients and descriptive statistics associated with the multiple linear regression model¹ for continuous estimates of the strength of maximum daily stream temperature (MDST) and maximum daily air temperature (MDAT) correlations.

<p>¹ This model was only applied to reaches for which MDST was considered to have high sensitivity to increases in MDAT based on the logistic regression model (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0134757#pone.0134757.t003" target="_blank">Table 3</a>).</p><p>Coefficients and descriptive statistics associated with the multiple linear regression model<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0134757#t004fn001" target="_blank">¹</a> for continuous estimates of the strength of maximum daily stream temperature (MDST) and maximum daily air temperature (MDAT) correlations.</p

Streams located in the Pisgah Ranger District of the Pisgah National Forest, which comprises 2.8% of the stream length in the study region, having predicted ANC < 50 μeq/L (red), temperature > 20°C (orange), or suitable habitat with respect to both ANC and temperature (blue).

<p>Modeled habitat suitability results are shown for a) ambient July mean maximum daily air temperature (MDAT), and future increases in July mean MDAT of b) 2°C, and c) 4°C. The suitable stream habitat under contemporary July MDAT that is located in the west-central portion of the ranger district is predominantly located in the Shining Rock Wilderness.</p

Map showing national forest proclamation boundaries within the study region and locations of observed stream water temperature sites.

<p>Map showing national forest proclamation boundaries within the study region and locations of observed stream water temperature sites.</p

Coefficients and descriptive statistics associated with the multiple linear regression model for predicting July mean daily maximum stream water temperature (JMMST).

<p>Coefficients and descriptive statistics associated with the multiple linear regression model for predicting July mean daily maximum stream water temperature (JMMST).</p

Distribution of observed a) July mean daily maximum stream water temperature (JMMST; n = 201) and b) slope of the relationship between daily maximum air and water temperature from June 1, 2012 to August 31, 2012 (n = 191).

<p>Distribution of observed a) July mean daily maximum stream water temperature (JMMST; n = 201) and b) slope of the relationship between daily maximum air and water temperature from June 1, 2012 to August 31, 2012 (n = 191).</p

Locations of suitable and unsuitable stream habitat throughout the study region, based on broadly applicable thresholds for acid- and thermally sensitive species.

<p>Suitable stream habitat is shown in blue. Streams with ANC < 50 μeq/L and/or temperature > 20°C are considered unsuitable and are shown in gray. Modeled habitat suitability results are shown for a) current July mean daily maximum air temperature (MDAT), and future increases of b) 2°C and c) 4°C.</p

Coefficients and descriptive statistics associated with the logistic regression model for predicting maximum daily stream water temperature (MDST) sensitivity (high/low) to changes in maximum daily air temperature (MDAT).

<p>Coefficients and descriptive statistics associated with the logistic regression model for predicting maximum daily stream water temperature (MDST) sensitivity (high/low) to changes in maximum daily air temperature (MDAT).</p