Influence mechanism of calcium on soil organic nitrogen mineralization during calcareous soil evolvement in karst areas
Nitrogen (N) is an essential nutrient element for the normal growth and development of plants,and the major factor affecting the primary productivity of most terrestrial ecosystems. Studying the process of soil organic N mineralization on the basis of regional characteristics is of great significance for formulating reasonable fertilization measures,and optimizing soil environment and global N cycling. Karst is a unique ecological system restricted by N. In order to discuss the influence mechanism of calcium (Ca) in soil organic N mineralization during calcareous soil evolvement in karst areas,the typical black calcareous soil (BLCS),brown calcareous soil (BRCS) and red calcareous soil (RCS) at different soil evolvement stages in the karst areas in Guilin were selected as research objects. The BCR three-step sequential extraction procedure was used to determine Ca contents of different species,and the 15N tracing technology combined with the Markov Chain Monte Carlo (MCMC) algorithm-based numerical optimization model were adopted to investigate the mineralization of labile organic N (MNlab),recalcitrant organic N (MNrec) and organic N (MNorg) to NH+4 in calcareous soil.The results showed as follows:(1) The orders of the contents of Ca species of BLCS and BRCS were both listed as exchangeable Ca (Eca)>acid soluble Ca (ASCa)>residual Ca (Rca)>water soluble Ca (WSCa)>organic compound Ca (OCCa);the order of the contents of Ca species of RCS was:Eca>Rca>ASCa>WSCa>OCCa. The contents of Eca were the highest among the different species of Ca in BLCS,BRCS and RCS in karst areas,repectively accounting for 80％,64％ and 48％ of the total Ca contents of these three calcareous soils,showing that Ca in calcareous soil presents high activity. (2) Mnorg and Mnrec of these three calcareous soils were listed as the following order:BLCS>BRCS>RCS;the order of Mnlab:BLCS<BRCS<RCS. Mnorg was dominated by Mnrec in BLCS,while Mnorg was mainly controlled by Mnlab in both BRCS and RCS,showing that calcareous soil evolvement affected the mineralization process of soil organic N,and the soil inorganic N supply capacity decreased significantly during calcareous soil evolvement in karst areas. (3) Except the insignificant correlation between soil Mnorg,Mnlab and Mnrec,and OCCa and Rca,Mnorg and Mnrec presented significantly positive correlation with the contents of Eca,ASCa and WSCa,respectively,while Mnlab presented significantly negative correlation with these variables,which indicates that high contents of available Ca can promote Mnrec but inhibit Mnlab. As the main species of Ca in calcareous soil,Eca and ASCa were strongly leached during calcareous soil evolvement in karst areas,resulting in the significant decrease of soil Mnrec,which was an important reason for the significant decrease of soil inorganic N supply capacity during calcareous soil evolvement. The study results will help us to clearly understand the characteristics of the distribution and migration of Ca,N mineralization and effect of Ca on N mineralization during calcareous soil evolvement in karst areas,and may provide the basic data for deep understanding of the influence mechanism of N mineralization process in calcareous soil. With the evolvement of calcareous soil,calcareous soil with high degree of evolvement in karst areas,such as BRCS and RCS,may be unfavorable for maintaining soil fertility and natural vegetation restoration due to low inorganic N supply capacity. Therefore,in the process of ecological restoration,for the karst areas with high degree of calcareous soil evolvement such as BRCS and RCS,improving the N content of calcareous soil can promote the effective supply of inorganic N in calcareous soil to create a soil environment conducive to vegetation restoration. This may be an effective strategy for rapid restoration of karst ecosystems.
mineralization ratesoil calcium species15N tracing technologycalcareous soilkarst area
万方数据
维普
