Regeneration Characteristics Of Kmeria Septentrionalis And The Role Of Frugivorous Animals On Its Seed Dispersal In The Karst Habitat

Kmeria septentrionalis is an endemic species in China,belongs to the family of Magnoliaceae,which only distributed in the karst habitat in northwestern of Guangxi,southeast of Yunnan and southern of Guizhou.Because of narrow distribution,poor natural regeneration,it has been listed as category I state key protected plants in China.Research the natural regeneration characteristics and the role of frugivorous animals in its seed dispersal of K.septentrionalis in karst habitat was of great significance to understand the population endangered mechanisms and formulate effective population protection strategies.Data on the regeneration characteristics and the environmental influence factors of K.septentrionalis,foraging and dispersal of birds to its seeds,feeding and removal of its seeds by rodents,content of the secondary metabolite ocimene in its seeds and it effect on the foraging behavior of rodents were collected between September to October,in 2018 and 2019 in Guangxi Mulun National Nature Reserve.The results as follows:1)The natural regeneration population of K.septentrionalis was slowly increasing,and the survival curve was close to Deevy-?I type.The number of seedlings in the mother forest was the largest,and the number of seedlings of diameter class II was the most.There are significant differences in the number of seedlings among different height classes in different habitat,and the number of seedlings decreased with the increase of height class,and the population structure was inverted “J” type.The spatial distribution of regeneration population in different habitat showed an aggregate distribution pattern,this may be the result of the biological characteristics of seeds,activity pattern of seed dispersers,and the heterogeneity of karst habitat.Canopy density,soil moisture and rock exposure rate were the main factors influenced the spatial distribution of the regeneration population of K.septentrionalis.2)Birds play an important role in the natural regeneration of K.septentrionalis.The mother trees could attracted 21 frugivorous bird species to foraging its seeds,among them 11 bird species were confirmed as seed dispersers.Hemixos castanonotus,Yuhina castaniceps and Perirocotus flammeus were the mainly seed dispersers.There was a significant positive correlation between the bird morphological characteristics and the number of seeds removed,indicating that the larger size of birds the more seeds were removed from the mother trees.62 1-year regeneration seedlings were found in the active area of birds,which indicates that the foraging of birds have dispersal effectiveness for K.septentrionalis seeds.There was some difference in the dispersal effectiveness of different birds to the seeds of K.septentrionalis,and there was a high concordance between the dispersal distance of H.castanonotus and seedling recruitment distance than that of P.flammeus and Y.castaniceps.Compared with the complete seeds,the cumulative germination rate of seeds treated by the digestive tract of birds was significantly higher,and the average germination time of these seeds was significantly shorter than that of the complete seeds.The digestive tract of birds accelerated the separation of pulp and seeds,which was helpful to improve the germination rate and germination time of K.septentrionalis seeds.3)Rodents could remove and stored the seeds of K.septentrionalis.Rattus norvegicus,Leopoldamys edwardsi and R.flavipectus were the mainly rodents that feed and removed its seed.Among the labeled seeds,73.5% were mildewed in situ,17.67% were removed and stored by rodents,and 8.83% were eaten by rodents in situ,and the average removed distance of labeled seeds was 1.72±0.14 m.The seed removal rate was significantly different among different microhabitats,and the average seed removal rate in three stone microhabitats was obviously higher than that of the soil surface.The seed removal rate was significantly different among different seed types,and exposed seeds had a highest average removal rate in all microhabitats,while that of fresh seeds was the lowest.Leaf litter coverage only increased the survival time but not the survival rate of K.septentrionalis seeds.Seed removal rate was significantly affected by both microhabitat and seed types,and leaf litter effected the seed survival rate of K.septentrionalis.The role of rodents in the regeneration of K.septentrionalis was the result of the interaction of rodent removal behavior,karst microhabitat and the biological characteristics of K.septentrionalis seeds.4)The content of the ocimene in K.septentrionalis seeds gradually decreases with the increase of the storage time.The intake and feeding behavior of rodents to artificial seeds were significantly inhibited with the increase of the concentration of ocimene.The intake,feeding number and single feeding time decreased with the increase of the concentration of ocimene,while the time interval between the first feeding and the second feeding,and the time interval between put it to first feeding increased with the increase of the concentr ation of ocimene.The intake of rodents to artificial seeds was only affected by the concentration of ocimene.The body size,feeding experience,tolerance level and detoxification ability may be the main reasons for the differences of feeding behavior of different rodents.Our results show that the foraging of birds to the seeds of K.septentrionalis could promote its population regeneration,but the high-intensity predatory of seeds by the rodents will cause a large number of seed lose,resulting in the reduction of seed resources for regeneration in the later period.In addition,due to the effected of karst microhabitat conditions and the biological characteristics of K.septentrionalis seeds,even the seeds of K.septentrionalis were removed and stored by rodents it also difficult to germinate,and these may be the main reason for the poor natural regeneration of this endangered plant.