F. Yang’s scientific contributions

Understanding the seasonal variation in root biomass (root diameter less than or equal to 5 mm) of Pinus hwangshanensis would provide a theoretical basis for the sustainable development of P. hwangshanensis forestry in China. In the natural habitat of P. hwangshanensis, five investigation sites along an elevational gradient from 1000 m to 2000 masl (meters above sea level) were established at 200 m intervals. The root biomass of P. hwangshanensis, along with the diameter at breast height (DBH) and plant height (H), were measured seasonally at each elevational site. We found that the average annual biomass of small roots (d ≤ 2 mm) and medium roots (2 mm < d ≤ 5 mm) was 158.76 g/m² and 4.68 g/m² respectively. The fine-root biomass and medium-root biomass of P. hwangshanensis changed significantly along the elevational gradient. The fine-root biomass of P. hwangshanensis did not change from season to season. At each site, however, the medium-root biomass varied significantly across seasons, with higher biomass observed in winter than in all other seasons (P < 0.05). In summary, the fine-root biomass and medium-root biomass of P. hwangshanensis varied significantly along the elevational gradient; the biomass of fine and medium roots showed divergent seasonal variations, suggesting that different seasonal growth mechanisms occurred between the two root types.

Taking Pinus taiwanensis Hayata at altitudes of 1 200, 1 600, and 2 000 m in Wuyishan National Nature Reserve of Jiangxi Province as research object, total nitrogen and total phosphorus contents and their ratio in leaf, stem and fine root in June and September were compared, respectively, and Pearson correlation analysis and allometric relationship analysis were conducted. The results show that compared with June, in September, total nitrogen content in leaf and fine root, and total phosphorus content in fine root of P. taiwanensis increase, while total nitrogen content in stem and total phosphorus content in leaf decrease significantly. On the view of mean, total nitrogen content in leaf is the highest and the lowest in fine root, total phosphorus content in stem is the highest and the lowest in fine root. With increasing of altitude, total nitrogen content in leaf increases gradually, total phosphorus content in leaf and total nitrogen and total phosphorus contents in stem appear the trend of “decreasing -increasing”, while total nitrogen content in fine root appears the trend of " increasing-decreasing”, and total phosphorus content in fine root increases gradually. The result of Pearson correlation analysis shows that there is an extremely significantly negative correlation of total nitrogen content in fine root with total phosphorus content in leaf, and significantly negative correlations with total nitrogen and total phosphorus contents in stem. There are extremely significantly positive correlations of total nitrogen content in stem with total nitrogen content in leaf and total phosphorus content in stem and leaf, total nitrogen content in leaf with total phosphorus content in stem and leaf, total nitrogen content in fine root with its total phosphorus content, and total phosphorus content in stem with that in leaf. The results of analysis on allometric exponent between nitrogen and phosphorus show that in June, with increasing of altitude, allometric exponents between nitrogen and phosphorus in leaf and fine root decrease gradually, while that in stem increases gradually; in September, allometric exponent between nitrogen and phosphorus in leaf at altitude of 1 600 m is the smallest, while that in stem and fine root at altitude of 1 600 m is the largest. On the whole, allometric relationships between nitrogen and phosphorus in different organs of P. taiwanensis in different months and altitudes all reach the significant or extremely significant level. Besides, allometric exponents between nitrogen and phosphorus in leaf, stem, and fine root of P. taiwanensis are high with values of 0. 79, 0. 83 and 0. 78, respectively. It is suggested that there are obvious differences in allocation of nitrogen and phosphorus in different organs of P. taiwanensis in different months and altitudes. © 2017, Editorial Office, Journal of Plant Resources and Environment. All rights reserved.