Seedling Architecture Of Subtropical Evergreen Broad-leaved Forest On Jinyun Mountain

The adaptive strategies of early seedlings play a decisive role in population regeneration.It is of great significance to study the temporal dynamics and responses to heterogeneous habitats of early seedlings adaptation of three common tree species in evergreen broad-leaved forests from the perspective of architecture.This study provide theoretical references for the reasons and mechanism explanation of species coexistence,and it is of great significance for the protection and management of evergreen broad-leaved forests.In this study,we measured twenty key architectural indicators(including six plant overall morphology indicators:height,base,crown area,crown depth,root area and root depth;four stem architectural indicators:stepwise bifurcation ratio_1:2,ratio of branch diameter_2:1,length and angel of the first order branch;four leaf indicators:mean leaf area,specific leaf area,leaf length-width ratio and petiole length;and six root indicators:total root length,fine root length,root surface area,root average diameter,forks and tips)and six biomass indicators to research the seedling architecture of different growth stages?stages one:1-3a;stages two:4-6a;stages three:7-9a?and different canopy conditions?gap,understory?of Castanopsis fargesii,Machilus nanmu and Elaeocarpus japonicas in evergreen broad-leaved forest on Jinyun Mountain,and to analyze the growth adaptation strategies and biomass allocation patterns.The main results are as follows:The temporal patterns and interspecific differences of the seedling architecture of three common tree species mainly reflected in the following three aspects:?1?There were interspecific differences in roots,stems,leaves and overall morphology of the three common tree species over time.The stem and root architectural indicators of C.fargesii and M.nanmu were significantly higher than those of E.japonicas,but the leaf architectural indicators of them were lower than those of E.japonicas.In stage one,plant overall morphology indicators?height,crown depth,root depth?,total length of the first order branch and root average diameter of C.fargesii were significantly higher than those of M.nanmu and E.japonicas.There was no significant difference between the overall morphology of E.japonicus and M.nanmu,while the leaf and root indicators of E.japonicus were significantly higher than those of C.fargesii and M.nanmu.In stage two,the plant overall morphology and stem architectural indicators of M.nanmu were significantly higher than those of C.fargesii and E.japonicas.There was no significant difference between the aboveground overall morphology and stem indicators of E.japonicus and M.nanmu.The crown depth,root depth,leaf length-width ratio and root average diameter of C.fargesii were significantly higher than those of E.japonicas,while the root area,specific leaf area,petiole length and root indicators?except for root average diameter?of C.fargesii were significantly lower than those of E.japonicas.In stage three,C.fargesii seedlings had the minimum branch angel,the maximum total branch length and the big crown,whereas the E.japonicus did the opposite.From stage one to three,the petiole length of E.japonicus was significantly higher than that of C.fargesii and M.nanmu,but the root average diameter of E.japonicus was significantly lower than their.Besides,the root area of C.fargesii in three stages was significantly lower than other species'.?2?The stem mass ratio of three species increased significantly over time,at the decrease of leaf mass ratio.The seedling biomass allocation patterns differed with species.In three stages,the total biomass and leaf mass ratio of C.fargesii and M.nanmu were significantly higher than those of E.japonicus,but the stem mass ratio was significantly lower than E.japonicus.?3?There was a certain coupling relationship between the organs'morphology of seedlings,and the correlation of organs'morphology weakened gradually with time.In stage one,there were significant correlations between various organs'morphology of seedlings,but there was no significant correlation between them in stage three.The adaptation of the seedling architecture of three common tree species to different canopy conditions mainly reflected in the following four aspects:?4?The influence degree of canopy conditions on the architecture varied with species.The height,crown depth,root depth and stem architectural indicators of C.fargesii seedlings differed significantly with canopy conditions,but there were no significant differences among indicators of leaves and roots.The canopy conditions significantly affected the seedling architectural indicators of M.nanmu,and the indicators of M.nanmu seedlings in the gap were significantly higher than those in the understory.For E.japonicas seedlings,the overall morphology?except for height and root area?,stem and partial root?total root length,fine root length and root surface area?architectural indicators differed significantly with canopy conditions.?5?The tolerance of the seedlings of C.fargesii and M.nanmu was stronger than that of E.japonicus.In the gap,there were significant interspecific differences in the overall morphology,stem,leaf?except for mean leaf area?and root?root length,root surface area and root average diameter?indicators.The architectural indicators of M.nanmu were significantly higher than other species'in this study,except for the forks and tips of root.The overall morphology indicators?except for base and root area?,total length of the first branch and root average diameter of C.fargesii were significantly higher than those of E.japonicus,but the total root length was significantly lower than that of E.japonicas.And the other stem and root architectural indicators were not significantly different between C.fargesii and E.japonicus.In the understory,the interspecific differences between leaves and roots of seedlings were consistent with those in the gap.Only the difference of the angle of the first branch in stem indicators was significant among species,and the branch angle of C.fargesii and M.nanmu were significantly higher than that of E.japonicus.?6?There were significantly differences in total biomass and root mass ratio of the seedlings under different canopy conditions.In the gap,the total biomass of C.fargesii and M.nanmu was significantly higher than that of E.japonicus.The leaf mass ratio and main root mass ratio of C.fargesii were significantly higher than those of M.nanmu and E.japonicas,but the stem mass ratio,root mass ratio and root to shoot ratio of C.fargesii were significantly lower than their.The interspecific differences between biomass accumulation and allocation of seedlings were consistent with those in the gap.?7?The coordination between organs was adaptive to different habitat conditions,which depended on the shade tolerance of the species.In the gap,the root morphology of C.fargesii was significantly related to the stem morphology,while the root morphology of M.nanmu and E.japonicus were significantly related to the leaf morphology.In the understory,the root morphology of both C.fargesii and M.nanmu were related to the stem morphology,but there was no relationship among morphology of different organs for E.japonicas.