岩溶区和碎屑岩区林地和农田土壤氮矿化过程对比研究

Comparative study on nitrogen mineralization of soil in woodland and cropland in karst and clasolite regions

通过^(15)N标记法和MCMC氮素转化模型,研究了岩溶区(石灰性土壤)和碎屑岩区(红壤)林地和农田土壤易分解有机氮矿化(M_易)、难分解有机氮矿化(M_难)和总有机氮矿化(M_总)速率。结果发现,土壤矿化速率受土壤类型和土地利用方式的显著影响。林地石灰性土壤M_总(3.71mg N/kg)显著低于林地红壤(5.57mg N/kg),石灰性土壤M_(Nlab)(1.81mg N/kg)与M_(Nrec)(1.90mg N/kg)相近,而红壤M_易(4.60mg N/kg)显著高于M_难(0.96mg N/kg)。林地变为农田后,石灰性土壤M_总显著提高,而红壤显著降低。与林地相比,岩溶区农田土壤M_易提高了72.5%,而M_难下降了33.7%。碎屑岩区农田土壤M_易和M_难分别降低至2.47和0.46mg N/kg。岩溶区土壤CaO和MgO含量与M_易呈显著负相关,而与M_难呈显著正相关,表明岩溶区土壤钙镁含量是影响氮矿化速率的重要因素。

In this study, the ^15N tracing technique and N transformation model were used to investigate the mineralization of labile organic nitrogen （as N） （MNrec）, recalcitrant organic N （MNlab） and organic N （MNorg） to NH4^＋ in calcareous and red soils of woodland and cropland in karst and clasolite regions, respectively. The results show that soil N mineralization rates are significantly affected by soil types and land uses. MNorg in calcareous soil （3.71 mg N/kg/d） of woodland is considerably lower than that of red soil （5.57 mg N/kg/ d）. there is no significant difference between MNlab （1. 81 mg N/kg/d） and MNrec （1.90 mg N/kg/d） observed in calcareous soil of woodland. However, the MNlab （4. 60 mg N/kg/d） is much higher than MNrec（0. 96 mg N/kg/d） in red soil of woodland. After converting woodland into cropland, the MNorg level significantly in- creases to 4.21 mg N/kg/d in calcareous soil, but it decreases to 2.93 mg N/kg/d in red soil. In contrast to woodland, MNlab increases by approximately 72.5% and MNrec decreases by approximately 33.7% in calcare- ous soil of cropland, respectively. CaO and MgO concentrations in calcareous soils are related positively with MNlab, but negatively with MNrec, suggesting that soil CaO and MgO are the important factors affecting N min- eralization rates in karst regions.