摘要
通过测定中国亚热带5个不同林龄(3、8、14、21、46a)杉木人工林不同序级细根氮稳定同位素(δ^(15)N)组成,研究它们对土壤净氮矿化、硝化速率的指示并将其与叶片δ^(15)N值对土壤氮循环速率的指示作用进行对比,从而探索研究植物同位素对土壤氮循环状况的指示作用。结果显示,不同林龄杉木人工林细根δ^(15)N值间具有极显著差异,3年生幼林与46年生老林显著高于其他林分。不同序级细根δ^(15)N值间的差异未达到显著水平,但具有随着序级增大δ^(15)N值逐渐降低的趋势。细根δ^(15)N值与土壤净氮矿化和净硝化速率间均具有极显著相关性,并有随着细根序级减小相关性逐渐增加的趋势,而叶片δ^(15)N值与土壤氮循环速率间则不具有显著相关性。研究结果表明,相较叶片来说,细根氮稳定同位素组成能更好地指示土壤氮循环速率,且序级越小的细根指示作用越强;细根δ^(15)N值反映出尽管中国亚热带地区氮沉降现象严重,氮素可能仍是处于速生期杉木人工林生长的限制因素。
Nitrogen（N） is an essential nutrient to plants. However, increasing N deposition into forest ecosystems due to will result in N saturation. The aims of this study were to （1） measure the composition of stable nitrogen isotope （δ^15N） in fine roots in Cunninghamia lanceolata plantations at different ages and of various root orders, （2） examine whether the stable isotopes （δ^15N） of fine roots in different orders were representative of the relative rates of soil net nitrogen （N）mineralization/nitrification across stands at different ages, and （3） determine whether fine root δ^15N could be used as a better indicator of the rate of soil N cycling than foliar δ^15N. We analyzed the δ^15N of fine roots and leaves in C. lanceolata plantations at 3, 8, 14, 21, and 46 years of age in subtropical China and carried out a 28-day laboratory incubation to analyze soil potential net N mineralization and nitrification rates. The results showed that there were significant differences in the δ^15N values of fine roots between different forest ages, the δ^15N was higher in 3- and 46-year-old plantations than those at other ages. While there were no significant differences between δ^15N values of fine roots in different root orders, the δ^15N values of fine roots tended to be lower with the increased orders of root. The δ^15N values of fine roots at all ages were significantly correlated with the potential net N mineralization and net nitrification rates, and the correlation coefficients between these parameters seemed to decrease with increasing root orders ; however, this correlation was not significant between foliar δ^15N at different ages and the soil N cycling rates. In conclusion, the result imply that fine root δ^15N could be a better indicator of the relative rate of N cycling than the δ^15N value of leaves, and first order roots were the best indicator. Moreover, fine root δ^15N values suggested that N may still be a factor limiting the growth of the C. lanceolata plantations at th
出处
《生态学报》
CAS
CSCD
北大核心
2016年第8期2185-2191,共7页
Acta Ecologica Sinica
基金
国家973计划和重大科学研究计划项目(2014CB954002)
国家自然科学基金项目(41371269)
教育部新世纪优秀人才支持计划(DB-168)
关键词
年龄序列
杉木
细根
氮循环速率
稳定同位素
Chrono sequence
Cunninghamia lanceolata
fine roots
N cycling rate
stable isotope
