Aims Within-community variation accounts for a remarkable proportion of the variation in leaf functional traits.Plant height may be used to explain within-community variances of leaf traits because different microenvironments,especially light intensity,may occur at different heights.This study determines whether or not leaf nitrogen(N)and phosphorus(P)contents as well as leaf mass per area(LMA)are interspecifically correlated with the adult height of forest woody species.We also discuss these relationships with respect to community structure and functions of the ecosystem.Methods A total of 136 dicotyledonous woody species from 6 natural forests(3 evergreen and 3 deciduous ones)in East China(18°44′–45°25′N,108°50′–128°05′E)were investigated.For each of the 157 species–site combinations,6 traits were measured:plant adult height relative to the forest canopy(H_(R)),leaf N and P contents per unit area(N_(area) and P_(area)),N and P contents per unit dry mass(N_(mass) and P_(mass))and LMA.The total variances of each leaf trait across sites were partitioned in a hierarchical manner.The relationships between leaf traits and H_(R) within forest communities were then analyzed using both standardized major axis regression and Felsenstein’s phylogenetic independent contrasts.Relationships between evergreen and deciduous forests were compared by linear mixed models.Important Findings H_(R) is a robust predictor of leaf N_(area),P_(area) and LMA,explaining 36.7%,39.4%and 12.0%of their total variations across forests,respectively.Leaf N_(area),P_(area) and LMA increased with H_(R) in all of the studied forests,with slopes that were steeper in evergreen forests than in deciduous ones.Leaf N_(mass) and P_(mass) showed no significant relationship with H_(R) generally.The increase in leaf N_(area),P_(area) and LMA with H_(R) across species is assumed to maximize community photosynthesis and may favor species with larger H_(R).
于2009年3月底至4月上旬在江西新岗山亚热带森林生物多样性监测样地A对皆伐后生长起来的草本植物进行了种类鉴定和盖度调查。应用Canoco for windows 4.5软件对所获得的79个物种的盖度数据和4个环境因子数据进行了典范对应分析(CCA),并作出了物种分布与环境因子关系的二维排序图。结果表明,所选取的环境因子对草本植物分布均有影响,且影响大小依次为:海拔>年太阳总辐射值>坡向>坡度。CCA为量化环境因子和皆伐后草本植物分布的关系提供了一种很好的方法。皆伐后初期草本植物中的多年生种类相对于一年生或二年生种类而言对皆伐后的森林更新有更大影响。
Aims Evaluation of the interaction intensity between Masson pine(Pinus massoniana)and broadleaved trees will facilitate selecting tree combinations suitable for reforestation in abandoned sites in subtropical areas.Methods Pinus massoniana and seven broadleaved trees species were grown either in monoculture or in two-species mixture.Biomass of tree species was measured and inter-specific interactions were estimated using log response ratio.Test of homogeneity of variances was performed to compare the stability of biomass in the monoculture of the broadleaved trees with that in the mixture.Important Findings Our results showed that the direction and intensity of interactions between P.massoniana and the broadleaved trees varied from year to year and the identity of the broadleaved species.Facilitative interactions were found between Camellia oleifera,Rhus chinensis and P.massoniana.Pinus massoniana had competitive effects on Lithocarpus glaber,Cyclobalanopsis glauca and Elaeocarpus japonicus.Significantly negative relations were found between biomass of P.massoniana and the broadleaved trees in the third year of the experiment,and the compensatory effects between P.massoniana and the broadleaved trees may be involved in stability maintenance in the multi-species forests in the subtropical area.The results of homogeneity test of variances also showed that the biomass per pot in the mixture had significantly lower variances than that in the monoculture,suggesting that total biomass is more stable in the mixture than the monoculture.
Coarse roots play a critical role in forest ecosystems and both abiotic and biotic factors affect their spatial distribution.To some extent,coarse root density may reflect the quantity of root biomass and biotic competition in forests.However,using traditional methods(e.g.,excavation)to study coarse roots is challenging,because those methods are time-consuming and laborious.Furthermore,these destructive methods cannot be repeated in the same forests.Therefore,the discovery of non-destructive methods for root studies will be very significant.In this study,we used a ground-penetrating radar technique to detect the coarse root density of three habitats(ridge,slope and valley)and the dominant tree species(Castanopsis eyrei and Schima superba)in a subtropical forest.We found that(i)the mean of coarse root density for these three habitats was 88.04roots m–2,with roots being mainly distributed at depths of 0–40 cm.Coarse root densities were lower in deeper soils and in areas far from the trunk.(ii)Coarse root densities differed significantly among the three habitats studied here with slope habitat having the lowest coarse root density.Compared with S.superba,C.eyrei had more roots distributed in deeper soils.Furthermore,coarse roots with a diameter>3 cm occurred more frequently in the valleys,compared with root densities in ridge and slope habitats,and most coarse roots occurred at soil depths of 20–40 cm.(iii)The coarse root density correlated negatively with tree species richness at soil depths of 40–60 cm.The abundances of the dominant species,such as C.eyrei,Cyclobalanopsis glauca,Pinus massoniana,had significant impacts on coarse root density.(iv)The soil depth of 0–40 cm was the"basic distribution layer"for coarse roots since the majority of coarse roots were found in this soil layer with an average root density of 84.18 roots m–2,which had no significant linear relationships with topography,tree species richness,rarefied tree species richness and tree density.Significant relationships between coarse r
YAN HuiDONG XinLiangFENG GangZHANG ShouRenMUCCIARDI Anthony
