| Amygdalus davidiana is one of the main tree species of vegetation resuming,drought afforestation and ornamental value in National Nature Reserve of Liupan Mountains.In this paper,seed dispersal,seed dormancy and breaking methods,factors influencing on seed germination and seedling gwoth relative to population regeneration of A.davidiana and their relationships were investigated,based on surveying the fruiting rate,seedling bank and age composition in A.davidiana forest of Liupan Mountains.Also,the effects of mechanical damage on the re-sprouting ability of A.davidiana seedling were investigated.The results would provide scientific basis for the natural or artificial regeneration and ecosystem management of A.davidiana population.The main results were as follows:1.It was the non-mast seeding of A.davidiana population in our experiment;Slope and canopy habitat affect the growth and survival of A.davidiana seedlings by affecting the heterogeneity of light and soil moisture.Both fruiting amount and fruiting rate of A.davidiana plant were low in 2016,3.44 /plant and 0.24% in average respectively at habitat of lower slope;Habitat(canopy gap,CP/under canopy,UC)had significant influence on density of A.davidiana seedling bank(P<0.01)and seedling density in both CP and UC habitats maximized in lower slope(LS).A significant difference was found between CP and UC habitat in top slope(TS)(P<0.01),while no significant difference was detected between different habitats of other slope position and among different slope positions.The groups of 2-3-year-old and 4-5-year-old seedlings were superior numerically,but less for groups of one-year-old and six-year-old and older seedlings.2.Soil coverage was favorable for the survival of the A.davidiana seeds;The synergistic effect of characteristics of seed and removed and hoarded by rodents could promote seed dispersal.The highest retention rates of A.davidiana seeds covered by soil were observed under the treatments of 1 seeds /m2,4 seeds /m2 and 9 seeds /m2 density(83.33%,41.67% and 47.22% respectively).Hoarding rate of A.davidiana seeds after removal by rodents treated by litter elimination maximized under the relative low density of 1 seeds /m2 and 4 seeds /m2(16.67% and 18.75% respectively).There were no significant difference in the predation and hoarding distance of A.davidiana seeds after removal by rodents among different treatments of coverage and seed density(P>0.05),while the predation distance after removal by rodents was longer than hoarding distance.In general,both the distance of predation and hoarding after removal by rodents were litter coverage > litter elimination > soil coverage.The removal distance of seeds treated by litter elimination mainly distributed in groups of 1-3 m,3-5 m,5-10 m distance,those of seeds treated by litter coverage mainly in groups of 3-5 m and 5-10 m and by soil coverage mainly in groups of <1 m,1-3 m,3-5 m.3.Low temperature stratification could effectively break the dormancy of and facilitated germination of A.davidiana seeds and promoting its germination.The optimal stratification period of A.davidiana seeds was 35 d.Germination parameters decreased slightly with the the duration of stratification period.The germination percentages of both large and small A.davidiana seeds decreased with the decrease of light intensity.The germination parameters of large seeds were higher than those of the small seeds at the sowing depths of either 0.5 cm or 1 cm(P<0.05),while the relative deep sowing depths were no favorable to the germination of A.davidiana seeds.4.Light and moisture were important environmental factors that affect the growth and survival of A.davidiana seedlings.The minimum of shoot height(9.9 cm)of A.davidiana seedlings was observed in the highest light(55.4% natural sunlight,NS)and that both shoot height and leaf area per plant increased and then declined with the decreasing of light intensity.Basal stem diameter,leaf number,taproot length,lateral root number,total dry mass,and root-shoot ratio of A.davidiana seedlings all maximized under the treatment of either 55.4% NS or 18.9% NS,and with the decreasing of light intensity,all these parameters continuously or fluctuately declined.The specific root length,specific shoot length and specific leaf area all increased with the induce of light intensity and their maximum were observed in either 5.5% NS or 2.2% NS.In general,light facilitate the growth and mass accumulation of A.davidiana seedlings.Great morphological plasticity was detected in seedlings grown under different light intensity,indicating the higher adaptatiion of A.davidiana seedlings to light environment of their natural distribution area;Under the combined effect of light and drought stress,the A.davidiana seedlings were adapted to the environment by reducing seedling height,leaf area per plant and increasing their root/shoot ratio,while adequate light and water conditions were beneficial to the accumulation of biomass of A.davidiana seedlings.The dry mass of A.davidiana seedlings watering 500 ml water every 3 d and 7 d were significantly higher than those of the other treatments under 55.4% NS(P<0.05).5.Different slope habitats could effect the growth and survival of A.davidiana seedlings.The results show: The survival rate of A.davidiana seedling grown in different slope position of A.davidiana forest presented as: LS > middle slope(MS)> TS.Shoot height,basal stem diameter,taproot length,leaf number,leaf area per plant and total dry mass all maximized at LS and minimized at MS,and leaf number of seedlings gradually declined from LS to TS.The minimum of root-shoot ratio of A.davidiana seedlings was observed at LS(0.36)while there was no significant difference among different slope position.The specific leaf area of seedlings maximized at LS(241.3 cm2·g-1).Seedlings grown at TS(200.1 cm2·g-1)had the lowest specific leaf area and was significantly higher than those of seedlings grown at both MS and LS(P<0.01).LS habitat was more favorable for growth of A.davidiana seedlings than MS and TS.6.Sprouting was a regeneration pattern of A.davidiana population in Liupan Mountains.Seedlings of A.davidiana could re-sprout after treatment of mechanical damage to resist the environmental disturbance,indicating the important role of re-sprouting in population regeneration of A.davidiana.Maximums of sprout number,sprout length and basal stem diameter of sprout all detected in seedlings sstubbled 10 cm and were all higher sigficantly than those of control seedlings(P<0.05). |
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