不同密度樟子松人工林土壤碳氮磷化学计量特征

以科尔沁沙地不同密度(490、750、1550、1930、2560株·hm^-2)樟子松人工林(栽植于1980年)为研究对象,分析林分密度对土壤碳、氮、磷浓度及其计量比的影响,研究林分密度与土壤养分状况的关系。结果表明:随着樟子松林密度增加,各土层(0~10、10~20和20~40 cm)土壤有机碳、全氮、全磷浓度和C∶N呈先增加后降低趋势,而土壤有效磷浓度呈先降低后增加趋势。土壤有机碳浓度在490株·hm^-2密度小于其他密度,而有效磷浓度大于其他密度;土壤C∶P和N∶P在2560株·hm^-2密度显著大于其他密度。各密度樟子松林土壤有机碳、全氮、全磷和有效磷浓度在0~10 cm土层显著大于10~20和20~40cm土层,樟子松人工林土壤养分具有表聚性。通过典范对应分析发现,密度对樟子松林土壤养分影响的主要因子是土壤有机碳、全氮和全磷,且密度为1550株·hm^-2时土壤有机碳、全氮、全磷和碱解氮浓度较高,而C∶P和N∶P较低。因此,当樟子松人工林密度为1550株·hm^-2时,土壤养分浓度较高,林木生长较好,为最佳经营密度。

Soil carbon,nitrogen and phosphorus stoichiometry of Pinus sylvestris var.mongolica plantations with different densities.

To understand the relationship between tree density and soil nutrient status,we analyzed the concentrations and stoichiometry of soil carbon,nitrogen and phosphorus in Pinus sylvestris var.mongolica plantations planted in 1980 with different densities(490,750,1550,1930 and 2560 trees·hm^-2)in Horqin sandy land.The results showed that with the increases of tree density,the concentrations of soil organic carbon,total nitrogen,total phosphorus and C∶N increased and then decreased,while soil available phosphorus concentration decreased and then increased at 0-10,10-20 and 20-40 cm soil layers.Lower soil organic carbon concentration and higher available phosphorus concentration were found in the stand density of 490 trees·hm^-2 than others.Soil C∶P and N∶P at the density of 2560 trees·hm^-2 were significantly higher than that of other densities.The concentrations of soil organic carbon,total nitrogen,total phosphorus and available phosphorus were significantly higher at the depths of 0-10 cm than those at10-20 and 20-40 cm of P.sylvestris var.mongolica plantations with different densities,suggesting that soil nutrients had surface accumulation characteristics.According to the canonical correspondence analysis,the most important soil nutrient factors affected by stand density were soil organic carbon,total nitrogen and total phosphorus.Higher soil organic carbon,total nitrogen,totalphosphorus and available nitrogen concentrations and lower soil C∶P and N∶P were found at the stand density of 1550 trees·hm^-2.Therefore,1550 trees·hm^-2 was an optimal density for P.sylvestris var.mongolica plantations with higher soil nutrient concentrations and better growth.