| In this paper, the semi-natural forest in the core area of Chongqing is taken as the research object through the typical sample method, involving 4 sample plots and 35 formations. Some community indexes like species composition, age structure and diversity index are analyzed, the characteristics of regeneration seedlings and soil seed banks are discussed, in order to find some local plant communities with high-quality landscape quality and good growth and regeneration to be applied in urban forest construction and ecological restoration. The main results are as follows:(1)The semi-natural forest in the core district of Chongqing are mainly distributed in the foot of Gele and Tongluo maintain, central ridgeline and urban park. The area of semi-natural forest is 1213.65 hm2, and it’s 14.83% of all green space in study area.The semi-natural plant communities in 4 areas can be divided into 2 vegetation type groups(coniferous forest vegetation type group and broad-leaved forest vegetation type group), 5 vegetation types(evergreen needle-leaved forest, coniferous and broadleaved mixed forest, evergreen broad-leaved forest, deciduous broad leaved forest and evergreen and deciduous broadleaved mixed forest) and 35 formations according to Chinese vegetation classification system. Among them, the broad-leaved forests are most distributed and the coniferous forests are least distributed.(2)Diversity Characteristic of Different Communities35 formations in 4 sample plots record 150 species, belonging to 132 genera and 74 families. Among them, there are 68 families, 124 genera and 141 species of seed plants, including 42 species of trees, 25 species of shrubs and 74 species of herbs, in which there are 5 species of bamboos.The species richness indexes of the formation types vary between 10 and 20 with the average of 14. The species richness indexes of deciduous broad-leaved forest and evergreen and deciduous broad-leaved mixed forest are higher. The species richness in 4 plots are ordered as: Zhaomushan Forest Park > Geleshan Forest Park > Hongensi Forest Park >Tuwan District, the order of different vegetation types are: natural forest >seminatural forest > artificial forest.For the tree layer, the Shannon-wiener diversity index ranges from 0.7 to 1.3 with the average of 1.023; the Simpson diversity index ranges from 0.6 to 0.8 with the average of 0.628; the evenness index(Pielou) ranges from 0.7 to 0.9 with the average of 0.797. For the shrub layer, the Shannon-wiener diversity index ranges from 0.5 to 1.5 with the average of 1.11; the Simpson diversity index ranges from 0.5 to 0.8 with the average of 0.661; the evenness index(Pielou) ranges from 0.75 to 0.95 with the average of 0.82. For the herb layer, the Shannon-wiener diversity index ranges from 0.9 to 1.9 with the average of 1.448; the Simpson diversity index ranges from 0.55 to 0.85 with the average of 0.723; the evenness index(Pielou) ranges from 0.75 to 0.95 with the average of 0.824. The diversity index of the herb layer is the largest. It is followed by that of the shrub layer and the tree layer.(3)Growth Form and Age Structure Characteristics of Different Community TypesAmong semi-natural plant communities in the core area of Chongqing, phanerophytes are the most distributed. The proportions of different life forms are ordered as follows: phanerophyte(48.23%) > annual plants(18.44%) > hemicryptophyte(17.02%) > geophyte(9.22%) > surface plants(7.09%).In terms of the height level distribution, tree seedlings and shrubs with the height of less than 2m are most distributed. The trees are mainly in 5-12 meters in height, accounting for 30.8%. The woody plants of each sample plot have good ability to update, which is stable in Tuwan district and Geleshan forest park while evolutionary in Zhaomushan forest park and Hongensi forest park.. From the DBH distribution of trees, most trees is smaller than 30 cm, accounting for 93.5%. The largest proportion of DBH level is 11.5-20 cm, accounting for 34.6%. The biomass of different plots are ordered as follows: Geleshan Forest Park(100.03 t/hm2) > Tuwan District(90.01 t/hm2) > Zhaomushan Forest Park(83.18 t/hm2)>Hongensi Forest Park(80.61 t/hm2), the order of the basal area is the same as the biomass.(4)Regeneration and Succession of CommunityAmong 35 formations in the survey area, 10 tree species have good regeneration, like Cinnamomumcamphora(Linn.) Presl, Firmianasimplex(L.) W. Wight, Broussonetia papyrifera(Linn.) L’Hert. ex Vent. etc; 14 tree species have medium regeneration, like Schima superba Gardn. et Champ., Quercus acutissima Carruth., etc; 17 tree species have poor regeneration, like Pinus. massoniana Lamb., Erythrina variegata Linn., etc. 5 tree species have poor regeneration, they are Pinus. massoniana Lamb., Cupressus Cupressus funebris Endl., Ficus virens Aiton, Erythrina variegata Linn, Eucalyptus robusta Smith. The communities with camphor and Koelreuteria paniculata Laxm as the dominant species are stable. Those with Pinus massoniana, Erythrina variegata, eucalyptus and Ficus lacor as the dominant species have weak regeneration ability and poor stability.(5)Soil Seed Bank CharacteristicsThe species of the soil seed banks of communities in different sample plots are mostly herbs, followed by trees and shrubs. The density difference of the soil seed bank varies greatly in different soil layers(p<0.05). Most seeds are concentrated in the upper soil with the thickness of 0 to 5 cm. The density of the soil seed bank is larger in winter than that in summer. The average densities of the soil seed banks of the sample plots are ordered as follows: Hongensi Forest Park > Tuwan District > Geleshan Forest Park > Zhaomushan Forest Park, varying from 745±88 to 1502±178 grain/㎡. The similarity coefficients between the seed bank and the ground plants are ordered as: Hongensi Forest Park(0.419) > Tuwan District(0.413) > Geleshan Forest Park(0.289) > Zhaomushan Forest Park(0.227). |
PDF Full Text Request