| In the forest ecosystem,hoarding animals usually carry and scatter hoard plant seeds to other places far away from the parent trees to meet their own needs when feeding the seeds.The scatter hoarding behaviors of small rodents contribute to promoting seed dispersal service,seed germination and subsequent seedling establishment,which drives the process of plant natural regeneration.Acorns are larger and depend entirely on small rodents for seed dispersal to achieving regeneration and succession for oak forests.However,the studies on seed dispersal for oak tree species have focused on the effects of biotic factors(i.e.,the interaction of animal and plant)on it,and the differences in animal predation and hoarding behaviors with environmental factors and how the process of seed dispersal occurs are still unclear.This study focused on the interaction between seed-eating animals and seeds for Quercus wutaishansea Forest in the northern Taihang Mountains and for Quercus variabilis Forest in the southern Taihang Mountains to explore the effect of the environmental factors(i.e.,altitude,slope position,forest gap and treeline)on the regeneration and seed dispersal pattern for oak trees,reveal the internal relationship between rodent-mediated seed dispersal and environmental factors,and illustrate the seed dispersal process with the influence of environmental factors and its response mechanism to oak forest regeneration.The study aimed to further enrich the theory of interaction between of animal and plant,and provide scientific basis for vegetation regeneration,recovery and management in the forest ecosystem.The results are as follows:(1)Apodemus peninsulae,Sciurotamias davidianus,Tamiops swinhoei and A.sagrarius were main rodents in the northern Taihang Mountains,which they feed and hoard seeds.And we first found that the large amount of T.swinhoei population foraged,and Sciurus vulgaris ate and dispersal seeds as captured by infrared camera,but the live traps did not capture them.A.peninsulae,S.davidianus and Niviventer confucianus were main rodents in the southern Taihang Mountains,and Arctonyx collaris fed a large number of seeds as repeatedly captured by infrared camera during the experiment.The community structure and composition of rodent varied with the increase of altitudes,and the rodent abundance increased in the beginning and then decreased with the increase of altitudes,i.e.,the rodent abundance was the highest at the middle and lower altitudes of 1020?1160 m and 1170?1320 m.(2)Altitude significantly affected rodent-mediated seed dispersal.The seed removal rate decreased with the increase of altitude in the whole.The seed removal rate was higher in the middle and lower altitudes(i.e.,1020?1160 m and 1170?1320 m)than higher altitudes(1490?1600 m and 1610?1770m)and it has showed higher dispersal advantage.And it may be related to the higher composition and abundance of rodents in the middle and lower altitudes,which indicated that seed dispersal rate varied along the altitude gradient,showing a similar trend with rodent abundance.The seeds released in the seed stations usually were eaten,and 52.2%,44.4%,61.1% of the released seeds were eaten in situ or eaten after removal with the altitudes of 1020?1160 m,1700?1320 m and 1330?1480 m,respectively,showing a high predation pressure.Only seven seeds(1.1%)were scatter hoarded at the lower altitudes of 1020?1160 m,which may be related to higher predation percentage and the seed poor year in this study.Slope position had no significant effect on the seed dispersal rate,however,the rodents tended to remove the seeds in the lower slope position upward,i.e.,the direction of upward dispersal.(3)Forest stands and gap size played the important roles in influencing seed removal by predators or dispersers.The seed removal rate was significantly higher in CCF(closed canopy forest)than in gap.There were significant differences in predation and hoarding strategies of rodents in different habitats,and acorns were usually eaten after being removed from the closed canopy forest and forest edges.By contrast,the acorns in the forest gap stands were more likely to be scatter hoarded.However,the proportions of scatter-hoarded acorns did not increase significantly as the gap size increased.The scatter hoarding proportion and times of acorns,and the dispersal distance in the small gap forest were higher than those in other forest stands,thus,small gap forest are preferred for the scatter hoarding of acorns by rodents.(4)The animals did not remove and disperse the seeds from treeline ecotone in Dongling Mountain in the northern Taihang Mountains,which indicated that it lacked service system of rodent-mediated seed dispersal.The results preliminarily explained that oak treeline regeneration in northern Taihang Mountains may be limited by seed dispersal,and the lack of seed dispersal service may explain part of the relatively stable positions for treeline.(5)The number of seed banks increased significantly with the increase of altitude.The lower number of seed banks at lower and middle altitude may be due to the higher percentage of seed predation.However,the seedling amount increased with the altitudes of 1020?1600 m,and then decreased with altitudes of 1600?1770 m,which maybe related to low temperature limit.The number of seed banks varied with the change of slope position,showing a similar trend with seedlings number,and they were the highest in the middle and upper slope positions,which maybe the reason of local microhabitat.(6)The effects of environmental topographical factors(e.g.,altitude and slope position)on the composition and number of rodent communities and ability of rodent-mediated seed dispersal may be extremely complex.The combined effect of forest gaps,treeline and environmental factors such as altitude and slope position,may play the key role in the composition,quantity and seed dispersal ability of rodent communities on a larger spatial scale.Thus,the pattern of rodent-mediated seed dispersal may be greatly influenced by community structure and hoarding behaviors of animals with the combined effect of environmental factors,and it is likely to participate in formation of the regeneration pattern of seed bank,seed germination and seedling establishment for oak forests. |
PDF Full Text Request