Responses of foliar carbohydrates and nutrient status of two distinctive cypress species to shading and nitrogen addition

Externally environmental stresses (e.g., low light environment and nutrient shortage) could limit plant growth and recruitment, even causing a species to be rare or endangered. In the present study, we aimed to elucidate whether shading environment formed in the natural forests limited growth of an endangered cypress species, Thuja sutchuenensis, by artificial shading level associated with nitrogen treatment, by compared with a widely distributed species from the same family, Platycladus orientalis. Our results showed that though leaf non-structural carbohydrates decreased with increasing shading level, T.sutchuenensis kept stable or even slight increasing relative growth rate toward lower light environments, which was opposite to the shade-intolerant species, P. orientalis. Our results did not provide evidence for a congruent suite of traits associated with rarity in T.sutchuenensis, but proved it as a shade-tolerant species and had to some extent practical significance for resource management for the targeted species. Keywords: Shading, Non-structrual carbohydrates, Nitrogen, Thuja sutchuenensis, Platycladus orientali