Seed Characteristics And Population Regeneration Dynamics Of Different Ornamental Rhododendron Species In Baili Rhododendron Scenic Spot

In order to investigate the seed characteristics and population regeneration status of different ornamental Rhododendron plants in Baili Dujuan scenic spot of Guizhou,In this paper,seeds of Rhododendron delavayi,Rhododendron irroratum,Rhododendron agastum,and Rhododendron decorum were collected from Baili Rhododendron scenic spot in northwest Guizhou and four plant communities were chosed as the research object,using field community investigation,control experiment and indoor analysis method,studied the species composition and population dynamic,the morphology of fruits and seeds,dynamic of seeds rain,and the influence of litter cover on seed germination,seedling growth in the four Rhododendron plant communities.The main results showed as follows:(1)A total of 76 plant species were found in the study communities,belonging to60 genera and 36 families.There were 49 plant species in R.delavayi community,belonging to 39 genera and 27 families.There were 33 species of plants in the R.irroratum community,belonging to 22 families and 29 genera.There are 26 plant species in R.agastum community,belonging to 22 genera and 19 families.There are21 species of plants in the R.decorum community,belonging to 19 genera and 13 families.The diameter class structure of the four Rhododendron communities increased,and the number of plants decreased gradually with the increase of diameter class,showing strong potential regeneration ability.The seed productivity of different Rhododendron plants in the community was as follows: R.agastum > R.decorum > R.delavayi > R.irroratum.(2)The fruits of the four ornamental Rhododendrons were cylindrical capsules.There were villi,glands and other appendages on the surface of the fruits.The pericarp all were yellow-green,and closed before maturing.After maturity,the fruit could dehisce naturally,then the skins were black brown,ribbed,with evident glandular.The fruit size was as follows: R.decorum > R.delavayi > R.agastum > R.irroratum.The seeds of the four Rhododendrons were reddish-brown in color,with slightly different shades and different seed shapes.The seeds were winged,and the location of the seed wing was different.The seed size was as follows: R.decorum > R.irroratum > R.delavayi > R.agastum.(3)The seed rain and litter production of the four ornamental Rhododendrons were significantly different in different months,and the seed rain and litter production reached the maximum in May.The spatial pattern of seed rain was uniform,and the annual seed production was as follows: R.delavayi > R.agastum > R.irroratum > R.decorum.(4)The germination rate of seeds of R.irroratum was the highest,while R.agastum was the lowest.The germination potential of R.agastum was the highest,while that of R.irroratum was the lowest.White R.decorum had the highest germination index,while R.agastum had the lowest.R.decorum had the longest bud length and root length,while R.irroratum had the shortest.Seeds control experiment showed,seeds germination index of the four ornamental Rhododendron plants were higher underside of the litter than the seeds above on the litter,the leaf number of plants seedlings,plant height and base diameter were characterized as: R.agastum > R.decorum > R.irroratum > R.delavayi,the seeding of four ornamental Rhododendrons died after germination when the seeds were placed above the litter.A large amount of litter blocked the contact between Rhododendron seeds and soil and inhibited seeds germination.Seeds germination and seedlings survival of Rhododendrons could be promoted by litter cover treatment.