Biomass And Understory Plant Diversity Of A Cyclobalanopsis Gracilis And Chinese Fir(Cunninghamia Lanceolata) Mixed Forest Plantation

Sample plot survey and trunk analysis were utilized to study the growth amount,growth process,tree layer biomass,understory vegetation diversity and understory vegetation biomass of the pure Cunninghamia lanceolata forest and adjacent mixed forest(Cunninghamia lanceolata and Cyclobalanopsis gracilis)in Xinkou Forest Farm,Xinkou City,for the purpose of revealing the differences between the pure Cunninghamia lanceolata forest and adjacent mixed forest in terms of the growth law and the stand structure and exploring the influencing mechanism of different afforestation models on the understory vegetation diversity and biomass.The results show that:(1)There is a significant difference in species composition,height,and coverage of understory vegetation between the pure Cunninghamia lanceolata forest and mixed forest.In mixed forest,there are 24 understory vegetations,including 15 species of shrubs and 9 species of herbs.The main shrubs are Schima superba,Maesa japonica,Ficus hirta,Callicarpa macrophylla.The average height of the shrub layer is 130 cm and the average coverage is 63%.The main herbs are Woodwardia japonica,Alpinia chinensis,Adiantum capillus-veneris,and Allantodia metteniana.The average height of the herb layer is 35cm,and the average coverage is 55%.In the pure Cunninghamia lanceolata forest,there are 12 species of understory vegetations,including 4 species of shrubs and 8 species of herbs,and the main shrubs are Maesa japonica,Ficus hirt,Stemona tuberosa and Tarenna millissima.The average height of the shrub layer is 40 cm and the average coverage is 3.5%.The main herbs are Cibotium barometz,Selaginella doederleinii,Angioopteris fokiensis and Adiantum capillus-veneris.The average height of the shrub layer is 150 cm and the average coverage is 97%.(2)There is a significant difference in Margalef index and Shannon-Wiener index of the shrub layer and the herb layer between the pure Cunninghamia lanceolata forest and adjacent mixed forest.In mixed forest,the Margalef index of the shrub layer is 2.43,the Shannon-Wiener index is 2.15,the Margalef index of the herb layer was 1.09,and the Shannon-Wiener index is 1.73.In the pure Cunninghamia lanceolata forest,the Margalef index of the shrub layer is 0.76 and the Shannon-Wiener index is 0.88,the Margalef index is 0.78 and the Shannon-Wiener index is 1.52.The Margalef index and Shannon-Wiener index of the mixed forest re higher than those of pure Cunninghamia lanceolata forest.(3)There is no significant difference in total biomass(242.094t.hm-2 and 238.652t.hm'2)and tree layer biomass(240.43t.hm-2 and 237.43t.hm-2)between the pure Cunninghamia lanceolata forest and adjacent mixed forest.However,there is a significant difference in shrub layer biomass and herb layer biomass between the pure Cunninghamia lanceolata forest and adjacent mixed forest.The shrub layer:the mixed forest(1.138t.hm'2)>pure Cunninghamia lanceolata forest(0.112t.hm-2);herb layer:the mixed forest(0.526t.hm'2)<pure Cunninghamia lanceolata forest(1.11 Afforestation of Chinese Fir Forest).In the mixed forest,the understory vegetation biomass mainly consists of shrub layer.In pure Cunninghamia lanceolata forest,the understory vegetation biomass mainly consists of herb layer.(4)The correlations under different afforestation models show that there is a significant positive correlation between the shrub layer biomass and the total understory vegetation biomass,the diversity index of the shrub layer and the total understory vegetation biomass,while there is a significant negative correlation between the herb layer biomass and the total understory vegetation biomass,the shrub layer biomass and the herb layer biomass.