毛乌素沙地樟子松林植物-土壤生态化学计量特征演变关系

Evolutionary Relationship of Ecological Stoichiometric Characteristics Between Soil and Plant of Pinus sylvestris Forest in Mu Us Sandy Land

[目的]探究沙漠化土地植被恢复过程的植物与土壤碳(C)、氮(N)、磷(P)化学计量特征的演变关系,可以深入认知樟子松固沙林植被恢复的机制。[方法]以榆林毛乌素沙地的半固定沙地为对照,分析了恢复25~56 a樟子松林下的物种多样性、樟子松植物组织(叶片、枯落物、细根)与土壤的C,N,P含量及其化学计量动态变化特征与交互作用。[结果](1)樟子松植物组织C,N,P平均含量表现为:叶片>枯落物>细根,碳氮磷化学计量比为:枯落物>细根>叶片。(2)与半固定沙地相比,植被恢复后樟子松植物组织和土壤中的C,N,P含量显著变化。从恢复25 a到56 a,枯落物和土壤C含量分别显著增加了14.9%和61.5%,N含量分别显著增加了55.0%和52.4%。(3)随着恢复年限增加,枯落物和细根的C∶N以及叶片和细根C∶P,N∶P均显著降低,叶片C∶N及枯落物C∶P,N∶P显著增加。(4)枯落物与土壤C含量,细根与土壤N,P含量及植物组织与土壤间C∶P均呈显著正相关关系。(5)植被恢复年限通过影响枯落物生物量和林下植被根量间接影响土壤C,N,P含量,且总效应最大。[结论]榆林沙区樟子松林植被恢复土壤C含量的增加与枯落物的输入密切相关,土壤N,P含量的增加主要与细根养分密切相关,C∶P是影响樟子松林地植物-土壤间养分交互的关键化学计量比。

[Objective]Explore the evolving relationship between the chemical stoichiometry of carbon(C),nitrogen(N),and phosphorus(P)in plants and soil during the process of vegetation restoration on desertified land,and gain a deeper understanding of the vegetation restoration mechanism of Pinus sylvestris fixed sand forest.[Methods]This study compared the semi-fixed sand land in the Mu Us sandy land in Yulin as a control,and the species diversity,as well as the dynamic changes and interactive effects of C,N,and P contents and its stoichiometry in the vegetation(leaves,litter,fine roots)and soil was analyzed under 25~56-year-old Pinus sylvestris var.mongolica plantation during the restoration process.[Results](1)The average content of C,N,and P in the plant tissues of Pinus sylvestris is expressed as follows:leaves>litter>fine roots.The stoichiometric ratio among C,N and P was as follows:litter>fine roots>leaves.(2)Compared with the semi-fixed sand land,significant changes in the content of carbon(C),nitrogen(N),and phosphorus(P)were observed in the plant tissues and soil of Pinus sylvestris after vegetation restoration.From the 25 yeas to the 56 yeas of restoration,the content of C in litter and soil significantly increased by 14.9%and 61.5%,respectively,while N content increased significantly by 55.0%and 52.4%,respectively.(3)As the restoration time increases,the C∶N ratios of litter and fine roots,as well as the C∶P and N∶P in leaf and fine root,all showed significant decreases.Meanwhile,the leaf C∶N ratio and the litter C∶P and N∶P ratios exhibited significant increases.(4)There was a significant positive correlation between the C content in litter and soil,the content of N and P in fine roots and soil,and the C∶P ratios between plant tissues and soil.(5)The restoration time of vegetation has the greatest total effect on the content of C,N and P in the soil by indirectly affecting the biomass of litter and the root mass of undergrowth vegetation.[Conclusion]The increase in soil C content during vegetation restoration in the Pinus sylvestris forest of Yulin sandy area was closely related to the input of litter.The increase in soil N and P content was mainly related to the nutrient uptake of fine roots.The C∶P ratio is a key stoichiometric ratio that affected the nutrient exchange between plants and soil in Pinus sylvestris forests.