Research Of Biomass And Mineral Nutrients Charcacteristics In Pinus Massoniana Needle And Broad-leaved Forest

In southern China, there is a large area of natural forest and plantation, for the reasonthat the subject to the long-term human disturbance and destruction and the long-term ofafforestation, the original vegetation began to reverse succession to the formation ofsecondary forest and large area of pure plantation. The long-term management of the pureplantation will result in degradation of the forest ecosystems, such as species diversitydecreasing, instability in the community structure, soil fertility declination and poorwater-holding function. Mixed-species stands are generally believed to be superior tomonocultures in improving the stability, stress resistance, and complexity of theecosystems. Thus the interest in the ecology and management of mixed-species stands hasincreased in recent decades. A large number of studies have been focused on Masson pineforest management, but very few concerned with multiple mixed stand patterns on one site.In this study, biomass, primary productivity, and mineral nutrient status of the Massonpine-liquidambar, Masson pine-light betula stands in Jixi, southern Anhui wereinvestigated to determine the effects of the mixture and forest age on the growth andmineral nutrient of conifer-broadleaved mixture and to provide the foundation ofsilviculture and management of mixed-species plantations.The results showed that the total biomasses were32.32,39.69and59.37t·hm^-2forpure Masson pine stands of10-,15-and20-year-old,34.42,56.37and65.09t·hm^-2forMasson pine-liquidambar mixed stands of10-,15-and20-year-old,63.07,73.82and77.09t·hm^-2for Masson pine-light skin birch mixed stands of10-,15-and20-year-old,respectively. As to the vertical stratification of biomass, the largest proportion is in thearbor layer reaching68.9%⁸4%, undergrowth come to the second, and forest floor theleast. The biomass allocation showed that stem covered69.8%⁸0.1%of the total,branches10%¹4.8%and foliar6.3%¹0.1%. In the pure stands, the largest proportion ofbiomass was in the stems, foliage involved the smallest proportion. Compared with thesame age of pure stands, the aboveground, root and forest floor biomass were significantlyincreased in the mixed stands. However, the ratio of the L layer to the total forest floorbiomass was low in the mixed stands. This suggests that the litter decomposed rapidly inthe mixed stands. In addition, the undergrowth biomass has a high correlation with thecanopy closure. The concentrations of five macro-elements in the arbor trees of the mixed standsdecreased in the order: N> Ca> K> Mg> P, but the sequenc varied somewhat in the purestands （N> K> Ca> Mg> P）. In the forest floor, the concentrations of the elmentsshowed the similar patterns in all stands, i.e. N> Ca> Mg> K> P. In the undergrowth, theregularity of concentrations of the five elements is not obvious, while the concentration ofP and Mg keep the order of Mg>P and both were lower than the concentrations of N, K andCa. The N, P and Ca have the lowest concentrations in the pure pine stand and the arbortrees of the mixed stands. In the undergrowth and forest floor, the concentrations becomehigher. For P and K, the concentraions varied in the different forests, but the average wereordered as: the undergrowth layer> arbor layer> forest floor.Nutrient concentrations in the different tree species and organs varied notably. Theconcentrations of N, Ca and Mg were higher in the broad-leaved species than in theconifers. However, there is not obvious differences for K and P. The nutrients in the leavesand roots were usually high. Amongst the several organs, the trunk was the lowest fornutrient. Ca concentrations were highest in the bark. The nutrient concentrations had littercorrelation with the tree age.The soil nutrient was different between the pure and the mixed stands in addition toK. the order of the soil nutrient concentrations for all stand was as0-10cm>10-30cm>30-50cm. The concentrations of Ca, NH₄⁺-N and Available P were higher in mixed standsthan in pure stands. The concentrations of NH₄⁺-N and Available P incerased with forestage in the mixed forest.The results from the study showed that the mixed stands can increase stand biomassabviously and can significantly improve the soil nutrient. Masson pine-light birch mixedmode demonstrated an excellent effects on the biomass production and the soilnutrient improvement. Based on its ecomomic, ecological and social benefits the Massonpine-light birch mixed mode is worth of extention in the subtropic regions.