In the paper by Grant and Jung (2005) discussing salamanders in Shenandoah National Park, low ANC is thought to be adding to stream acidification. What does ANC stand for?

ANC stands for: Acid Neutralizing Capacity

Explanation:

Before I go further to explain what ANC is, we have to understand what Acidification is.

Acidification in aquatic ecosystems is the lowering of the pH (hydrogen ion concentration) of the aquatic ecosystem below the normal range, which supports the survival of fishes and other aquatic organisms. Most aquatic organisms and fishes thrive in aquatic environments at pH ranges of 6.5 to 8.5. Acidification occurs mainly by acid rains and runoffs from mines(mostly supplying the nitrate and sulfate compounds that cause acidification ), they also occur due by natural means like the existence of acidifying organic substances in the water, and the presence of acidifying vegetation.

Some of the detrimental effects of an aquatic environment that is acidified is that; there may be calcium deficiencies in the aquatic organisms which will affect the formation of bones and exoskeletons, and make the eggs of these organisms brittle.

Acid Neutralizing Capacity is defined as the measure of the extent to which a water body can reduce the effect (neutralize) of a strong acid. A sufficiently high value of the ANC means that there is a high chance of the pH of the water body staying within its optimum range, while a low ANC, means that the pH can become easily acidic and hence will be directly or indirectly toxic to the living organisms in the water. The ANC of water bodies depend on physical characteristics such as; geology, size, hydrology and soils.

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.