Few studies have addressed pollution in subalpine in the Sierra Nevada, although tree species present there may ultimately prove sensitive to certain atmospheric pollutants. One study from subalpine in the European Alps showed increased levels of atmospheric deposition of nitrogen at some locations. Jeffrey and ponderosa pine are susceptible to ozone pollution in the Sierra Nevada, but mostly at lower elevations. However, another study from the European Alps demonstrated the sensitivity of a native subalpine conifer to ozone pollution