Study On Influence Of Granivorous Animals On Seed Fate And Natural Regeneration Of Hadeliodendron Bodinievri

A study on the endangerous plant Hadeliodendron bodinievri including population structure, natural regeneration,seed yields and beating characteristics,seeds predators,pattern of seeds disappearance and seeds dispersals was conducted in Maolan Natural Reserve in Guizhou Province of China in 2006 and 2007.The goals of this study were to explore the influences of seeds predation on natural regeneration of Hadeliodendron bodinievri and analyze the interaction relationship between granivorous animals and seed fates of plants in Karst forest eco-system,and the strategy of plant population's regeneration was considered as well.Based on the results,we concluded that the seeds predation by granivorous animals is a key factor affecting natural regeneration and population recession of Hadeliodendron bodinievri,additionally the seeds fate is determined by the interaction mechanism between seeds predators,Karst micro-habitat and seeds characteristics.Main results and conclusions were listed below:1.The population demograghy of Hadeliodendron bodinievri in study area showed the natural regeneration was poor and age structure had a declining pattern.The clone parental plants taken a large proportions on the populations of Hadeliodendron bodinievri in secondary stands and the seeds output per capsule was low;but the phenomenon of masting was not distinct,and according to the effects of natural regeneration,seeds yield was high relatively which can provide a abundant supply of seeds resource.2.The types of Karst microhabitats of Hadeliodendron bodinievri were complicated with the random distribution pattern,and the pattern of population distributions of Hadeliodendron bodinievri mostly was clustered performing a highly adaption to the Karst microhabitats.Through surveying the parental plants and seedlings,it indicated that the main Karst microhabitats Hadeliodendron bodinievri used included rocky-surface,rocky-ditch,rocky-crack and soil-surface.3.8 species of small rodents including Rhizomys pruinosus,Rattus flavipectus,Beryimys bowersi,R.niviventer,R.losea,Mus musculus,Niviventer fulvescens and Leopoldamys edwardsii were found in study area,which all can be divided into four community types as below:Cropland---Rattus flavipectus & Rattus flavipectus,Shrub--- Niviventer fulvescens& R..niviventer,Forest---Leopoldamys edwardsii & Niviventer fulvescens& R..niviventer,and Shrub-- R..niviventer& Niviventer fulvescens& Leopoldamys edwardsii.Within them,Beryimys bowersi,R.niviventer, Niviventer fulvescens and Leopoldamys edwardsii were the key seed predators of Hadeliodendron bodinievri,and R..niviventer and Leopoldamys edwardsii both were dominant species in stands of study area.The quantity dynamic of population didn't vary with the seeds yields which could indicate that the seed of Hadeliodendron bodinievri just only was the favorite food not the main critical food to the rodents. 4.The squirrels(Sciuridae) and larvas of insects both were the important seed predators in canopy of Hadeliodendron bodinievri,and the species of squirrels included CalIosciurus flavimanus,Tamiops swinhoei and Dremomys rufigenis.Squirrels had the evolutional behaviors of seeds predation that the foraging time could reach to 1.6 h and 179.1 grains per hour with a high selective ability to the seeds and capsules.The insect predators included Dichocricis punctiferalis, Adoxophyes orana,Drosophila sp.and species of Thripidae,the insected rate could reach to 13.9% and 9.5%in early periods and mid periods of fruit falling respectively.5.Ants at least including Polyrhachis Vicina,Odontomachus Haematodus and Dorlus orientalis in study area were the important seed predators to Hadeliodendron bodinievri,generally they ate the elaiosomes of seeds,but still consumed the seeds sometimes.Ants often carried or buried the seeds into shallow soil near the parental plants,but the seeds contributed less to the natural regeneration because of the damage of microbe or animals in the soil and seedling suffered from shadow beneath the parental plant.6.The seed rain of Hadeliodendron bodinievri occurred from last third part of Autumn to first ten-day period and middle ten days of September,and not always consistent annually.The intensity of seed rain was affected by precipitation significantly.The radio of sounds seeds in seed rain was proportional to intensity of seed rain in which there was a significant difference between two study years(Z=-2.204,P=0.028).This results indicated that seeds maybe had more chance to escape from the predator in canopy to enter the seed bank of ground when the seed yield increased.7.The disappearance dynamic of seed bank in ground also affected by the intensity of seed rain, which that the seed predation on ground seed bank intensified as the intensity of seed rain increased. There was a significant difference(F=4.265,df=27,p=0.049) on seeds disappearance rates between two years influenced by intensity of seed rain.So,this results showed that there was a large group of predators which consumed seeds violently to Hadeliodendron bodinievri.8.The experiments of seeds disappearance in seed bank of ground indicated that,seeds had the highest predation risk within 24h from enter the ground(disappearance rate reached to 67%),93% seeds preyed by animals within 48h and only 7%from 48h to 72h.So,it indicated that the seed predation on seed bank of ground was very strong and the seeds would have more chance to survive from predation by animals if the seeds entered the ground as long as possible.9.The types of Karst microhabitats affected the seed predation deeply(χ~2= 12.647,df=5,P =0.027 ),the seed disappearance rate in different Karst microhabitat can be rank as follow:rocky-ditch＞rocky-slot＞soil-surface＞rocky-surface＞rocky-crack＞rocky-cave.The selectivity of microhabitat in the process of seed predation by animals was relevant to cover and access of microhabitats.10.The label-tagged method was used in our study to track the seed dispersal in Karst forest area.The results showed that most of seeds were consumed by post-dispersal predation by granivorous animals,only a few of seeds moved or scattered into the microhabitats of rocky-surface, rocky-ditch and rocky-crack.Through protecting the dispersed seeds and re-visited in next year,we found the seeds moved into this three microhabitats had more chance to germination and seedling if the suitable conditions existed for seeds in the microhabitat.And,these results were accordant with our investigation to microhabitat use of population of Hadeliodendron bodinievri.So,it can be concluded that HadeIiodendron bodinievri must depend on the seeds predators to disperse the seeds at the expensive cost of seeds consumption,and when the seeds moved to somewhere by ganivorous animals,the growth condition of microhabitat would be the first determinant factors to whether the seeds can germinate or recruit into seedling.Finally,through the study,we drew a conclusion that the unsuccessful natural regeneration of Hadeliodendron bodinievri was caused by three factors:enormous seeds lose consumed by seeds predators,complicated Karst microhabitat and physiological characteristics of seed germination. Based on the traits of seed predation and seed dispersal,we believed there was a non-balance dependant evolutionary relationship between Hadeliodendron bodinievri and granivorous animals, and this relationship was a main factor to strategy failure of natural regeneration of Hadeliodendron bodinievri.Furthermore,some management suggestions were mentioned for the conservation of Hadeliodendron bodinievri in our study.