夏蜡梅及其主要伴生种叶的灰分含量和热值

分别于2006年7月、10月和2007年4月,对全光照、林缘和林下3种光环境下夏蜡梅及群落中35种主要植物叶的灰分含量和去灰分热值进行测定,分析它们在光合作用中对太阳能的固定和积累能力。不同光环境下夏蜡梅叶灰分含量的大小顺序都是全光照＞林缘＞林下,10月3种光环境下夏蜡梅叶灰分含量均高于4月和7月,均差异显著。4月、7月和10月,林下和全光照环境下的叶去灰分热值呈先下降后上升的趋势,而林缘中叶去灰分热值却逐渐下降。群落各层植物的灰分含量大小顺序为草本层＞灌木层＞间层＞乔木层,夏蜡梅灰分含量略低于灌木层灰分含量的平均值;各层次植物平均去灰分热值大小顺序为乔木层＞灌木层＞草本层＞间层,夏蜡梅平均去灰分热值低于间层。多数植物不同季节叶的灰分含量、去灰分热值均以10月最高。

Ash content and caloric value in the leaves of Sinocalycanthus chinensis and its accompanying species

Caloric value, referring to the combustion heat of specific dry mass, was applied to describe energy patterns in ecological processes. Caloric value is a useful tool to study energy transfer and flow efficiency, which can provide information about plant growth, development, and competitive ability. Sinocalycanthus chinensis, the only representative of Sinocalycanthus genus belonging to the family of Calycanthaceae, is an endangered shrub endemic to China. In order to evaluate the potential of S. chinensis and co-occurring species to utilize solar energy, the ash content and caloric value in the leaves of S. chinensis and 35 accompanying species at different habitats (full sunlight, forest understory, forest edge) were analyzed and compared in Spring, Summer, and Fall. The ash content in the leaves of S. chinensis varied among different habitats, and was highest in full sun habitats, intermediate in edge habitats, and lowest in the forest understory. Ash content varied over time, and was significantly higher in October than in April and July. From April to October, the ash-free caloric value in the leaves of S. chinensis at the forest edge decreased gradually, while that under forests and full sunlight decreased first in July, then increased again in October. The dynamics of the ash content and ash-free caloric value in the leaves of S. chinensis indicated that they would be affected by the ecological factors in different seasons and different habitats. The ash content varied among plant species at different strata in the community. The herb strata had the highest ash content, followed by the shrub strata, followed by the vine strata. The tree strata had the lowest ash content. The ash content of S. chinensis was slightly lower than the mean ash content of other shrub taxa. The mean ash-free caloric value in leaves also varied across strata. The tree layer had the highest caloric value, followed by the shrub layer, followed by the herb layer, with the vine layer having the lowest caloric value. The mean ash-free caloric value in the leaves of S. chinensis was lower than that in the leaves of plant species at shrub layer. The ash content and ash-free caloric value of most plant species in the community reached a peak in October. The lower ash content and ash-free caloric value compared with the other shrub taxa might indicate that S. chinensis had low ability to transfer solar energy and turn it into organics, which might contribute to the low competition ability of S. chinensis in the community. The result could provide important information for exploring the endangered mechanisms and the evaluation of the growth and development of plant species in the community dominated by S. chinensis and before establishing the conservation strategies of this species.