【摘要】 有机碳和氮素含量低、结构性差等土壤退化特征,是干热河谷土壤退化的普遍现象,漫长旱季与集中雨季使干热河谷干湿交替格局不同于其他区域。通过监测不同干湿交替模式下培养土壤的呼吸、水溶性有机碳(DOC)和水溶性氮(DN)动态,评估干湿交替特征对干热河谷土壤有机碳和氮库退化的影响。结果显示,风干土壤再湿润对土壤呼吸具有激发效应,可使呼吸强度增加1.52~7.13倍;随着干湿交替次数的增加,激发效应随之衰减,经过多次干湿交替后(当周期为3d,则干湿交替5次)降至某一稳定水平,干湿交替周期越长(周期长于12d),土壤再湿润后导致的土壤呼吸激发效应的衰减越不明显。土壤DOC和DN含量同样受再湿润激发,但DOC和DN激发效应滞后于土壤呼吸,干湿交替多次后土壤DOC和DN随之降低并稳定低于最初水平,而随着干湿交替周期延长,DOC和DN在每个干湿交替末期含量变化不明显。这暗示干湿交替尽管可激发土壤DOC和DN释放,但是这种激发效应随干湿交替次数和周期延长而降低,因此对土壤碳氮动态的影响有限,干湿交替格局可能不是干旱河谷土壤有机碳和氮素退化的主要原因。更多还原

【Abstract】 Soil quality degradation,characterized by lower organic carbon,soil nitrogen content,and poor soil structure,was very common in the dry-hot valley of the Hengduan Mountains.Pattern of drying-rewetting cycle in the dry-hot valley was different from other regions due to its long dry season and monsoon.In this study,microbial respiration,dissolved organic carbon（DOC）,and water dissolved nitrogen（DN）were monitored in dry-hot valley soil under different drying and rewetting cycle to assess the impacts of the special dry-rewetting pattern on the degradation of soil carbon and nitrogen.The results showed that rewetting of air-dried soil caused a large pulse in soil CO₂ efflux from 1.52 to 7.13 times,and the burst effect（Birch effect）of respiration of rewetting decreased with the number and frequency increase of drying and rewetting cycles.The release of soil DOC and DN were also stimulated by rewetting,and the enhancement of DOC and DN release were triggered lagged behind the soil CO₂ burst in a rewetting-drying cycle.Similarly,Birch effect of rewetting on DOC and DN release also deceased with the number and frequency increase of drying and rewetting cycles.These results indicated that Birch effect of soil rewetting did not seem to be the main contributing factor in soil degradation of organic carbon and nitrogen in the dry-hot valleys owing to pulses of soil CO₂,DOC and DN release,reduction with increase of the number and frequency of dry-wetting cycles.更多还原