Abstract:

To better understand whether and how nitrogen addition impacts the epiphytic lichens in the Shennongjia Nature Reserve (China).

Five dominant epiphytic lichen species, including Usnea longissima, U. luridorufa, Ramalina calicaris var. japonica, U. dasopoga and U. betulina, were selected as materials, and then field and laboratory nitrogen addition experiments were performed. The phosphomonoesterase (PME) activity and nitrogen (N) and phosphorus (P) content of these lichens were measured, and then the effects of nitrogen addition on thallus nutrient balance and PME activity were discussed.

Our results showed that with an increased N deposition from 0.6 to 50 kg N ha?1 a?1, the thallus N content of the five lichen species increased significantly, suggesting that those lichens had strong ability to take up and accumulate N, and an universality of N intolerance in epiphytic lichens. Meanwhile, the P content of five lichens increased slower than N content among N treatments, indicating the supply of P was deteriorated when the supply of N increased. The N addition also led to the N:P ratios of five lichens increased from about 10 to 20, and reached a maximum at 50 kg N ha?1 a?1, and the PME activity of the five lichen species was upregulated by the N addition, indicated that the balance between N and P was deteriorated in these lichens. We concluded that increases in N deposition will lead to nutrient imbalance in lichens and that nitrogen enrichment will change these five lichen species from being N limited to being P limited. Our research will be of value in the conservation of lichen diversity in the Shennongjia Nature Reserve (China).

Key words: nitrogen deposition, lichens, N:P ratios, Shennongjia, phosphomonoesterase activity