川西亚高山不同森林类型土壤呼吸和总硝化速率的季节动态

川西亚高山原始林及其采伐后通过不同恢复措施形成的不同类型森林土壤呼吸和总硝化速率的对比分析及其耦合关系的研究相对匮乏。采用气压过程分离系统(Ba PS)技术研究了川西亚高山岷江冷杉原始林及其砍伐后恢复的粗枝云杉阔叶林、红桦-岷江冷杉天然次生林和粗枝云杉人工林土壤呼吸和总硝化速率的季节动态及其影响因素。结果表明:生长季内平均土壤呼吸速率和总硝化速率分别以粗枝云杉阔叶林和粗枝云杉人工林较高,均以岷江冷杉原始林较低。土壤呼吸和总硝化速率在生长季内具有明显的季节动态,呈以7月份最高的单峰趋势。土壤呼吸和总硝化速率与土壤温度显著相关,而与土壤水分相关性不显著,表明土壤温度是调控呼吸和总硝化作用季节动态的主要因子。土壤呼吸的温度敏感性(Q_(10))介于2.59—4.71,以岷江冷杉原始林最高,表明高海拔的岷江冷杉原始林可能更易受到气候变化的影响。林型间土壤呼吸和总硝化速率主要受凋落物量、p H和有机质的影响。不同林型间土壤呼吸和总硝化速率显著正相关,表明土壤呼吸和总硝化速率存在耦合关系。

Seasonal dynamics of soil respiration and gross nitrification rate of different subalpine forests in western Sichuan

Comparisons of carbon and nitrogen transformation and their coupling relationships among different forest types, including primary and restoration forests after primary forest harvesting in the subalpine region of western Sichuan, are relatively limited. In this study, we measured the seasonal dynamics of soil respiration and gross nitrification rate using the barometric process separation (BaPS) technique and examined their possible effect in Abies faxoniana primary, Picea asperata broadleaved mixed, natural secondary Betula-Abies, and P. asperata plantation forests. The results showed that the average soil respiration and gross nitrification rate during the growing season were the highest in P. asperata broadleaved mixed forest and P. asperata plantation forest, respectively, and were the lowest in A. faxoniana primary forest. The soil respiration and gross nitrification rates varied obviously during the growing season, peaking in July. They were significantly correlated with soil temperature (P < 0.05), but were not significantly correlated with soil water content, indicating that soil temperature, rather than soil water content, is a controlling factor in the regulation of the seasonal dynamics of soil respiration and gross nitrification. Soil respiration temperature sensitivity varied from 2.59 to 4.71 with the highest in the A. faxoniana primary forest, suggesting primary forests at high altitudes may be more vulnerable to climate change. Soil respiration and gross nitrification rates among forest types were mainly influenced by litter mass, pH, and soil organic matter. The soil respiration rate was positively correlated with the gross nitrification rate in different forest types, indicating a coupling relationship between soil respiration and gross nitrification rates.