Effects Of Gaps And Their Characteristics On The Regeneration Of Pinus Massoniana

Pinus massoniana is one of the coniferous tree species with the widest distribution and the richest resources in the humid subtropical region of Eastern China.It plays an important role in the national economy and plays an obvious role in maintaining the ecological balance.However,the long-term adoption of a single tree species pure forest management model can easily lead to the decline of forest land fertility,forest productivity,species diversity and ecological function.As a smal-scale forest disturbance,forest gaps can solve the above problems to a certain extent.However,in the field survey,it was found that Pinus massoniana seedlings were seldom seen under the forest and in the gap.Therefore,this study took Pinus massoniana as the experimental object to study the effects of gap plant and ground cover characteristics on Pinus massoniana regeneration,and to provide theoretical basis and technical guidance for artificial assisted Pinus massoniana forest regeneration and sustainable development.The main conclusions are as follows:(1)Study on Gap Plant Diversity and Seed Bank of Pinus massonianaThe traditional sampling method is used to investigate plant diversity and counting statistics;the sampling method is used to collect soil samples from seed bank,and the data of seed bank were investigated by screen sorting and laboratory greenhouse cultivation,so as to study plant diversity and seed bank in forest gaps.It is found that plant diversity in forest gaps is becoming more and more abundant and rare plant species were decreasing.There are many plant species and genera in forest gaps,a total of 1275 plants are found,belonging to 52 families and 88 species,the number of shrubs and dwarf trees is the largest,totaling 23 families and 42 species.Rosaceae plants are the largest,but no seeds of Pinus massoniana are found.It is easy to form single dominant species or constructive species in small gaps.The area and age class of forest gaps had significant or extremely significant effects on plant diversity.The plant diversity index in different gaps is small gaps > medium gaps > large gaps.The plant diversity indices of different age classes were late gaps > middle age gaps > young gaps.There were 531 seeds,belonging to 74 species in 50 families,with the largest number of herbaceous plants,totaling 350 seeds in 28 species in 17 families.The species of shrubs and trees were the most abundant,with 125 seeds in 33 species in 21 families,showing a trend of uniform increase with age.(2)Alelopathy of Common Plants in Pinus massoniana Gap on the Germination of Pinus massoniana SeedsThe alelopathic effect of root and leaf extracts of common plant Pteridium aquilinum?Carex capilliformis?Parthenocissus tricuspidata?Rubus saxatilis L.? Camellia oleifera Abel.in the Pinus massoniana forest gaps on seed germination of Pinus massoniana was studied,to find the cause of fewer new seedlings in the window of Pinus massoniana forest.It was found that there was no uniform rule for the effects of herbal and vine extracts on the germination rate,radicle length and germination rate of Pinus massoniana seeds,and there were few alelopathic effects of low or low or high promotion.However,all plant extracts inhibited the germination rate of Pinus massoniana seeds,and the effect of Camellia oleifera Abel.on the germination of Pinus massoniana seeds was reduced by 24.60% compared with the control.Therefore,the regeneration seedlings of Pinus massoniana rarely seen in forest gaps were closely related to the Allelopathy of common herbs and lianas in forest gaps.The effects of plant extracts on radicle length and germination rate of Pinus massoniana seeds were complex,but all of them had significant inhibitory effects,the effect of Camellia oleifera Abel.on the germination of Pinus massoniana seeds was reduced by 24.60% compared with the control,and the promotion effect was not significant.The extract of Camellia oleifera Abel.,a woody plant often used as intercropping with Pinus massoniana,inhibited the germination rate,radicle length and germination index of Pinus massoniana seeds at high,middle and low concentrations,and 3 were significant differences between the 3 indexes and the control at high concentrations,the germination rate,radicle length and germination index of Pinus massoniana seeds decreased by 61.29%,16.36% and 68.19% respectively compared with the control..(3)Effects of Litter Coverage and Thickness in Gap on Seed RegenerationThe number of regenerated Pinus massoniana Seedlings in different litter coverage and thickness samples of forest gaps was investigated by sampling method.After the initial experimental results were obtained,a simulation experiment was carried out in the experimental nursery with a seedling pot to confirm the effect of litter on the germination of Pinus massoniana seeds.Field investigation and nursery experiments have proved that the ground cover and litter can significantly inhibit the natural regeneration of Pinus massoniana.One-year-old Pinus massoniana seedlings reach 44.67 /?,two-year-old seedlings 12 /?,while no Pinus massoniana seedlings are found in herbaceous litter layer.After the litter coverage reached 100%,the effects of litter with different thickness on the germination and regeneration of Pinus massoniana seeds did not conform to the homogeneity test of variance,but there was no significant difference between the experimental group and the control group without litter coverage,when the litter thickness was more than 1 cm,the number of seedlings in the plot was less than 5.70%-80% litter coverage promoted the germination and regeneration of Pinus massoniana seeds at the early stage of the experiment,but the effect was not significant.The number of remaining seedlings was significantly lower than that of uncovered control group,but after low temperature stress,the number of regenerated seedlings without purple phenomenon was 5.33% higher than that of the control group which indicated that a certain amount of litter coverage was conducive to the germination and regeneration of Pinus massoniana seeds under the conditions of subsequent insecticidal work.