The role of soil nitrogen and phosphorus in the distribution of Leucobryum juniperoideum in the Tianmu Mountain National Nature Reserve, Zhejiang, China

Leucobryum juniperoideum (Brid.) Müll.Hal., a common moss in eastern China, grows in three typical habitats in the Tianmu Mountain National Nature Reserve, Zhejiang, China. This study aims to reveal the role of soil nitrogen and phosphorus in the distribution of Leucobryum juniperoideum by investigating soil conditions in the Tianmu Mountain National Nature Reserve. Epigeic populations of this bryophyte were found only in areas with a Moso bamboo forest, while the epixylous populations always occurred in areas with Chinese fir forest and Chinese cedar forest, and the epilithic populations occurred in all three habitat types. Analyses showed that nitrogen (N) and phosphorus (P) concentrations in the soils of Chinese fir forests and Chinese cedar forests were remarkably higher than those of Moso bamboo forests. In the laboratory, experiments showed that the growth of L. juniperoideum was remarkably reduced by N additions of 0.1 mol/L over a period of six months, while growth was increased by P additions of up to 0.1 mol/L over six months. In addition, physiological responses to N indicated that the mosses were sensitive to N additions, but not to additions of P. Also, high concentrations of N (200 mg/L) can significantly reduce the germination rates and can delay the development of early germination stages and stable germination stages for 2 to 4 days. Phosphorus additions did not affect the germination rate, but did cause delays in the development of germination stages. The combination of N and P caused remarkable declines in the germination rate and delayed the germinating time. Taken together, our results demonstrate that soil N is the primary determinant in limiting the distribution of L. juniperoideum populations.