| With the rapidly development of Eucalyptus plantation, a lot of economic benefit have been brought to the society. However, a great deal of ecological problems have been emerged because of irrationally management practices, Which caused more and more vehement dispute in the academe. The focus of the argument are:(1)The problem of biodiversity of the understory plants in eucalyptus plantation; (2)The problem of decline of soil fertility. (3) Allelopathic effects of Eucalyptus plantations. In this paper, three sort of plots were set, including Eucalyptus urophylla×E.Grandis plantation with different ages and Cupressus sempervirens open forest. The changes of community compositions and soil physical-chemical proprieties we researched through wild investigations and indoor analysis, in order to elucidate the influence of Eucalyptus plantation on understory species diversity, soil fertility and allelopathic effects.The results of the study on soil physical proprieties showed as follows:(1)at 0～20cm soil layer, Soil water content had no significant differences except which in Eucalyptus urophylla×E.Grandis plantation and Cupressus sempervirens open forest, at the 20～40cm soil layer Soil water content had not significant differences in the forests. And at 0～20cm layer, the soil water content was greater than 20～40cm, which reached a significant level. (2) at 0～20cm and 20～40cm soil layer, soil bulk density was showed as 2 years Eucalyptus plantation> the Cupressus sempervirens open forest> 1 year Eucalyptus plantation> 0.5 year of Eucalyptus plantation. Between 0.5 year old Eucalyptus plantation and 1 year old,2 years old Eucalyptus and Cupressus sempei-virens open forest, the soil bulk density had significant differences. The other three had no significant difference. The soil bulk density at 0～20cm was less than at 20～40cm, and reached a significant level.The results of the study on soil chemical proprieties showed as follows:(1) At 0～20cm and 20～40cm soil layer, the soil pH value showed a significant descent trend. and the soil pH at 0～20cm was less than at 20～40cm, which reached a significant level. (2) At 0～20cm and 20～40cm. soil organic matter, total N, P content showed an increasing trend. Soil organic matter, total N and total P content at 0～20cm was more than at 20～40cm soil layer, which achieved a significant level. (3) Available N, the total K, available K content at 0～20cm were greater than at 20～40cm, which achieved a significant level. (4) At 0～20cm and 20～40cm soil layer, Available P content showed a significant descent trend, and Available P content at 0～20cm was more than at 20～40cm, which reached a significant level.The results of study on community compositions showed as follow:(1) Since the Cupressus sempervirens open forest was replaced by the Eucalyptus urophylla×E.Grandis plantation, human interference and burning site preparation led to disappearence of the shrub layer. (2) The dominant species of herb layer changes:the composition of herb layer under the Cupressus sempervirens open forest are the Centella asiatica (L.) Urban, Imperata koenigii (Retz.) Beauv and Artemisia apiacea as the main species.0.5 year Eucalyptus plantation is based on Cynodon dactylon (L.) Pers, Paspalum thunbergii Kunth ex Steud and Imperata koenigii (Retz.) Beauv as the dominant species.1 year Eucalyptus plantation was based on Imperata koenigii (Retz.) Beauv, Cynodon dactylon (L.) Pers, Conyza Canadensis (L.) Crong, Oplismeums compositus (L.) Beauv, and Pinellia ternate (Thunb.) Breit as the dominant species, and 2 years old Eucalyptus plantation was based on Duchesnea indica (Andr.) Focke, Oplismeums compositus (L.) Beauv, Pinellia ternate (Thunb.) Breit and Oxalis coniculata L as the dominant species. (3) The results of study on diversity index and species richness showed that the species diversity ofunderstory had increased.The experimental results indicated that:(1) With the water extracts of roots of Eucalyptus urophyllaxE.Grandis, the allelopathic effect was not significant for Giycine max (L)Merrill and Phaseolus vulgaris L., but germination percentage, seedling growth of lolium multiflorum Lam. were inhibited significantly. (2)The rhizosphere soil leachate of Eucalyptus urophylla×E.Grandis grandis was not significantly inhibited the seed gemrination and seedling growth of Lolium multiflorum Lam., Giycine max (L)Merrill and Phaseolus vulgaris L.Under field conditions, the allelopathic effect of Eucalyptus urophylla×E.Grandis plantation did not have significant influences on the germination percentage of lolium multiflorum Lam., Giycine max (L)Merrill, Phaseolus vulgaris L. and Phaseolus vulgaris L., the same to root growth of Giycine max (L)Merrill. However,2 years Eucalyptus urophylla×E.Grandis had remarkably inhibited the stem growth of Phaseolus vulgaris L.and Lolium multiflorum Lam. when the root elongation of Giycine max (L)Merrill and Phaseolus vulgaris L.presented a downward trend as the inhibitory effects strengthening with increase of the age,except Lolium multiflorum Lam..The results of cultivation experiment shows that:(1)The soil water content of Eucalyptus plantation and Cupressus sempervirens open forest had decreased to some extent after planting. (2) The soil pH value, total K,P content were not obvious changed in all treatments at harvest compared to those before transplanting. (3)After transplanting, the soil organic matter content had increased, and the lolium multiflorum Lam. made the largest increase. (4)The total N and available P content had increased significantly after planting, the performance of increasing was Giycine max (L)Merrill>Phaseolus vulgaris L.>lolium multiflorum Lam... |
PDF Full Text Request