Evaluation of Tree Species of Plantation in Southwest Guangxi

The results of investigation and economic benefits analysis on increments,forest soil and vegetation of plantations with multiple tree species and under various management patterns showed that the increments of fast-growing broadleaved tree species such as Mytilaria laosensis,Castanopsis hystrix,Betula alnoides,etc.were higher that of coniferous species.Mytilaria laosensis had the highest annual average dbh and height increments,which were 1.67 cm,1.29 m respectively,60.6% and 61.2% higher compared with Pinus massoniana,70.4% and 57.3% higher compared with Cunninghamia lanceolata.Betula alnoides had the highest annual average stock volume increment(20.44 m3·hm-2),which was near double compared with that of Cunninghamia lanceolata.The economic benefits of broadleaved forest were obviously higher than that thet of coniferous forest,while that of mixed forest was higher than that of pure coniferous forest.There existed obvious of extreme obvious difference in economic benefits among tree species.Betula alnoides had the highest benefits with the annual average value of 21 459.7 RMB yuan per hectare,ten times that of Cunninghamia lanceolata.The study on soil physical and chemical properties showed that after afforestation,the soil bulk density,water-holding capacity and water permeability improved,the soil organic matter content raised and aluminum-enrichment ability was promoted.For other soil nutrients,there existed significant difference among tree species,but overall,the broadleaved forest was better than coniferous forest in improving soil physical and chemical properties.