[Nitrogen and phosphorus contents and resorption efficiency of thirty broadleaved woody plants in Yangjifeng, Jiangxi, China.] / æ±Ÿè¥¿é˜³é™ å³°30ç§é˜”å¶æ ‘å¶ç‰‡æ°®ç£·å«é‡åŠå†å¸æ”¶æ•ˆçŽ‡.

Nutrient resorption is an important strategy of nutrient conservation, which reflecting the ability of plants to conserve and utilize nutrients and adapt to environment. To explore the relationship between nutrient content and nutrient resorption of broadleaved woody species of different life forms (i.e., evergreen vs. deciduous), we sampled 30 broadleaved woody species in subtropical region of China located in Yangjifeng National Nature Reserve, Jiangxi Province. The nitrogen (N) and phosphorus (P) concentrations in green and senescent leaves of each species were measured to calculate nutrient resorption efficiency. Furthermore, we analyzed the relationship of leaf nutrient concentration and resorption efficiency for the different life forms. The results showed that N and P concentrations in green leaves were significantly higher in deciduous trees than those in evergreen trees. The P concentrations of senescent leaves in deciduous woody species was significantly higher than that in evergreen woody species. There was no significant difference of N concentration in senescent leaves between evergreen and deciduous species. Nitrogen resorption efficiency (NRE) and phosphorus resorption efficiency (PRE) of the 30 broadleaved woody species were 49.6% and 50.9%, respectively. There were no significant differences between the NRE and PRE of evergreen and deciduous species. NRE and PRE negatively correlated with N and P concentrations in senescent leaves, respectively. Additionally, evergreen and deciduous species showed similar relationships between nutrient resorption efficiency and nutrient concentration in senescent leaves. The sca-ling exponent of allometric relationship between NRE and PRE was 1.18 across all the species. The nutrient resorption efficiency of all the species were affected by the nutrient status of the senesced leaves. Plants examined in this study generally re-absorbed P from senescing leaves than N.

[Effects of the current-year shoot stem configuration on leaf biomass in different canopy heights of woody plants in evergreen broad-leaved forest in Jiangxi Province, China.] / æ±Ÿè¥¿å¸¸ç»¿é˜”å¶æž—æœ¨æœ¬æ¤ç‰©ä¸åŒå† å±‚é«˜åº¦å½“å¹´ç”Ÿå°æžèŒŽæž„åž‹å¯¹å¶ç”Ÿç‰©é‡çš„å½±å“.

To investigate the effects of stem configuration on leaf biomass allocation in different organs of the current-year shoots at different canopy heights, relationships of biomass in different organs (i.e., leaves, stems, and twigs) and stem configuration (i.e., stem diameter, length, width/length, stem volume and stem density) were analyzed using the data of 69 woody species from the Yangjifeng Natural Reserve, Jiangxi Provence. Standardized major axis (SMA) was used to explore the regression between biomass and stem configuration. The results showed that there was no significant difference in leaf biomass, stem biomass, twig biomass, stem diameter, stem length, stem width/length and stem volume of current year shoots from upper and lower canopy heights and life forms (i.e., evergreen and deciduous woody plants). Stem density differed significantly in the current year shoots at different heights for both evergreen and deciduous woody species. There were isometric relationships among leaf, stem and total biomass of shoots in different canopy heights and in different life forms. Leaf biomass scaled allometrically with stem diameter and volume, with the scaling exponents being not different significantly among different canopy heights. With respect to the stem configuration of the twigs, stem length, stem width/length and stem density contributed less than 24% to the leaf biomass variation in the current-year shoots. On the contrary, stem diameter and volume had greater effects on leaf biomass of the current-year shoots than stem length, stem width/length and stem density. Canopy heights did not significantly affect the allometric scaling relationships between the stem configuration and leaf biomass of the current-year shoots.

[Allometry between twig size and leaf size of typical bamboo species along an altitudinal gradient]. / ä¸åŒæµ·æ‹”å ¸åž‹ç«¹ç§æžå¶å¤§å°å¼‚é€Ÿç”Ÿé•¿å ³ç³».

To investigate the trade-off between the twig size and leaf size, we measured the total leaf mass, stem mass, individual leaf mass and leafing intensity of typical bamboo’s (Phyllostachys edulis, Indocalamus tessellatus, Oligostachyum oedogonatume, Yushania hirticaulis and Yushania wuyishanensis) twigs at different altitudes in Wuyi Mountain. The results showed that the exponents of the scaling between total leaf mass and stem mass on twigs significantly decreased with increasing altitude for all the five bamboo species. The common scaling exponents of total leaf mass vs. stem mass for P. edulis, I. tessellatus and O. oedogonatum were 0.94, 0.85 and 0.84, respectively. A common slope of 0.79 was observed in total leaf mass vs. stem mass in Y. hirticaulis and Y. wuyishanensis. There was significant negative correlation between individual leaf mass and leafing intensity among bamboo species, except Y. wuyishanensis. A common slope of -1.12 existed between individual leaf mass and leafing intensity for five bamboo species. In conclusion, bamboos at low altitudes tended to support more leaf biomass while preferring to invest more to stem biomass at high altitudes. Although the stem mass investment of different bamboo’s twig increased with altitude, the leafing intensity strategies based on stem mass were determined by the leaf size construction rather than altitude.

Effects of light on the growth and clonal reproduction of Ligularia virgaurea.

Ligularia virgaurea is a perennial herb that is widely distributed in the alpine meadow on the eastern Qinghai-Tibet plateau. We investigated the patterns of growth and reproduction of L. virgaurea under two contrasting levels of light conditions for two continuous growing seasons. Our results showed that the light effects on the maximum relative growth rate, the shoot weight ratio and the root weight ratio differed between the two growing seasons. L. virgaurea reproduced initially through rhizome in the second growing season, rather than sexual reproduction. The proportion of genets with clonal reproduction decreased under shaded conditions. A minimum genet size should be attained for clonal reproduction to begin under the shaded conditions. There was a positive linear relationship between clonal reproduction and genet size. Light level affected the allocation of total biomass to clonal structures, with less allocation under the full natural irradiance than under the shaded conditions. There seemed to be a trade-off between vegetative growth and clonal reproduction under the full natural irradiance, in terms of smaller relative growth rates of genets with clonal reproduction than those without clonal reproduction. L. virgaurea emphasized clonal reproduction under the full natural irradiance, while the plant emphasized vegetative growth under the shaded conditions.