The Biomass And Diversity Of Understory Vegetation Of Masson Pine Mixedwoods In Zongyang Area

In order to understand the effect of tree species composition on growing development of understory vegetation in Masson pine mixedwood, 5 kinds of 20 years old Masson pine and broad-leaved mixedwoods were analysed in Dashan Village, Zongyang County , Anhui Province based on the proportion of Masson pine. The project researched the instructure, species diversity and biomass of understory vegetation of different Masson pine forests. Meanwhile the soil physicochemical properties also were analysed. The results showed as follows:(1) There were 34 plant species in shrub layer in the 15 sample plots. The plants belong to 23 families and 30 genus. Fagaceae and Leguminosae were dominant families within them. 14 species were found in all 5 kinds of mixedwoods, they were Quercus acutissima, Quercus glandulifera var.brevipetiolata, Quercus dentata, Castanea seguinii, Albizia kalkora, Albizzia julibrissin, etc. Quercus acutissima, Quercus glandulifera var.brevipetiolata, Quercus dentata, Liquidambar formosana and Euscaphis japonica were dominant species in shrub layer. There were only 6 species in herb layer. They belong to 5 families and 6 genus. Cyperus rotundus,Imperata cylindrica were common species, and Adiantum capillus-veneris, Phaenosperma globosa, Lophatherum gracile, Dicranopteris linearis were relatively rare. Richness in shrub layer increased from the 0 to 60% of Masson pine proportion in the forests, decreased from 60% to100% Masson pine. At 40-60% stands, there was hightest richness. But richness in herb layer had nearly no change and it was lower compared with the shrub. With the increase of the proportion of Masson pine, height of shrub layer fluctuated and height of herb declined slowly. And with the increase of the proportion of Masson pine, coverage of shrub layer tended to decline and coverage of herb layer did not change significantly.(2) The differences of species diversity indices of the shrub were significant with the different stand composition proportion in the shrub layer as well as the herb layer. The differences order of the Margalef index and Shannon-Wiener index in shrub layer were as follows: 40-60%>60-80%>20-40%>0-20%>80-100%. With the increase of the proportion of Masson pine, evenness index tended to decline lightly. The maximum of herb layer Margalef index appeared in 40-60% stands, and the minimum appeared in 20-40% stands. The maximum of herb layer Shannon-Wiener index appeared in 60-80% stands, and the minimum appeared in 20-40% stands and 80-100% stands. Evenness index of herb layer fluctuated with the increase of the proportion of Masson pine. The hightest and lowest value appeared at 80-100% stands and 20-40% stands respectively.(3) The total biomass of the understory vegetation first increased gradually and then decreased gradually with the increase of the proportion of Masson pine. Shrub layer biomass contributed 80-95%, and the differences order of it were as follows: 40-60%>20-40%>0-20%>80-100%>60-80%. The branch or root biomass took the majority of the shrub layer biomass and the leaves took the minority. The herb layer biomass took the minority of the total biomass of the understory vegetation and the differences order of it were as follows: 60-80%>40-60%>20-40%>80-100%>0-20%. And the biomass of the aboveground part in the herb layer was more than the underground.(4) Composition proportion had a strong effect on the soil physical and chemical properties. With the increase of the proportion of Masson pine, bulk density gradually increased in the same soil layer, while water content and total porosity decreased. With the increase of the proportion of Masson pine, the soil nutrient, such as total N, total P, total K, available P and available K tended to decrease. Composition proportion also had a strong effect on illuminance, temperature and relative humidity in woods. With the increase of the proportion of broad-leaved trees, illuminance, temperature tended to increase, but relative humidity tended to decrease.(5) The correlation analysis among the biomass, species diversity of the shrub or herb layer and soil physicochemical properties showed that there were certain correlations among them. The total biomass of understory vegetation had a positive relation with shrub biomass, shrub Margalef index, shrub species diversity respctively. Herb layer biomass had a positive relation with herb layer species diversity, but had a negative correlation. There was a significantly negative relation between shrub layer biomass and herb layer biomass.Soil bulk density had a negative relation with total biomass of the understoy vegetation, shrub layer biomass, herb layer biomass respectively. And total biomass had a significantly negative relation with soil bulk density, but had a significantly positive relation with soil total porosity. However, soil total porosity was the opposite compared to soil bulk density.Shrub layer Margalef index was related with soil water content, pH, organic matter, total N, total P, total K, available P, available K respectively, as well as Shrub layer Shannon-Wiener index, Herb layer Margalef index, Herb layer Shannon-Wiener index, but had no significant relation among them.