Increasing nitrogen depositions can reduce lichen viability and limit winter food for an endangered Chinese monkey

Increasing economic growth and industrial development in China is starting to impact even remote areas such as the Shennongjia nature reserve, where nitrogen pollution is becoming a major environmental threat. The epiphytic lichen flora is particularly rich in this area and is one of the components of this habitat most sensitive to nitrogen pollution. Since lichens represent an important food resource for the endangered monkey species Rhinopithecus roxellana, a reduction in lichen availability would have harmful consequences for the conservation of its habitat in the Shennongjia Mountains. To investigate the effects of increased nitrogen availability on the local lichen communities, so far scarcely considered, we conducted a one-year field experiment measuring growth, survival, and phosphomonoesterase activity of the widespread species Usnea luridorufa in response to nitrogen (up to 50 kg N ha−1 year−1 deposition) and phosphorus supply. Growth and survival of thalli and propagules of U. luridorufa decreased when treated with N deposition >12.05 kg N ha−1 year−1 and >2.14 kg N ha−1 year−1, respectively. The important role of phosphorus availability in relation to nitrogen supply was demonstrated by the increase in phosphomonoesterase activity with increasing nitrogen availability until a nitrogen toxicity threshold was reached. However, the high concentration of phosphorus in rainwater showed that phosphorus is not a limiting nutrient in the area. The results make a contribution to the knowledge of the negative effects of increased N deposition in the Shennongjia forest ecosystem.