氮添加及林下植被去除对沙地樟子松人工林土壤呼吸组分的影响

Effects of nitrogen addition and understory removal on soil respiratory components in a sandy Pinus sylvestris var. mongolica plantation

土壤呼吸是森林生态系统碳循环的关键环节,主要由土壤微生物呼吸和根系呼吸组成,二者对于氮添加及林下植被去除的响应可能不同。本研究以科尔沁沙地樟子松(Pinus sylvestris var. mongolica)人工林为对象,探讨了氮添加(N+)和林下植被去除(U-)对一个生长季土壤呼吸及其组分的影响。结果表明:在沙地樟子松人工林中,土壤微生物呼吸是土壤呼吸的主要贡献者,其贡献率达85.53%;根系呼吸的贡献率相对较小,仅有14.47%;生长季内,土壤呼吸速率平均值为1.59(CK)、1.73(N+)、1.66(U-)、1.89(N+U-)μmol C·m-2·s-1,氮添加促进了生长季初期、末期的土壤呼吸,林下植被去除提高了生长季旺盛期土壤呼吸,而氮添加+林下植被去除同时作用下,整个生长季内土壤呼吸速率显著增强,且高于氮添加与林下植被去除的单独作用,说明氮添加+林下植被去除对于促进土壤呼吸存在叠加效应;土壤微生物呼吸速率为1.36(CK)、1.45(N+)、1.44(U-)、1.52(N+U-)μmol C·m-2·s-1,各种处理对土壤微生物呼吸均无显著影响;氮添加与林下植被去除均降低了土壤微生物呼吸的温度敏感性;各处理下根系呼吸R10变化幅度大于微生物呼吸,说明根系呼吸对各处理的响应要比土壤微生物呼吸更加敏感;受土壤含水量的影响,土壤呼吸与土壤温度表现不一样的变化规律,表明土壤含水量为该地区樟子松人工林土壤呼吸的重要调控因素。本研究为理解沙地樟子松人工林碳循环过程及其模型构建提供基础数据和科学依据。

Soil respiration is a key component in the carbon cycle of forest ecosystems,which can be divided into soil microbial respiration and root respiration.Effects of nitrogen addition and understory removal on soil microbial respiration and root respiration would be different.In this study,we investigated the effects of nitrogen addition(N+)and understory removal(U-)on soil respiration and its components in a Pinus sylvestris var.mongolica plantation in Horqin Sandy Land during the growing season of 2018.The results showed that soil microbial respiration was the main contributor to soil respiration in this ecosystem,with a contribution rate of 85.53%.The contribution rate of root respiration was smaller,being 14.47%.During the growing season,the average values of soil respiration were 1.59(CK),1.73(N+),1.66(U-),and 1.89(N+U-)μmol C·m-2·s-1.Nitrogen addition had a positive effect on soil respiration during the early and late stages of the growing season,while understory removal showed a positive effect during vigorous growth season.Under the effects of nitrogen addition+vegetation removal,soil respiration rate increased significantly,indicating that nitrogen addition+vegetation removal had synergistic effects on soil respiration.Soil microbial respiration rates were 1.36(CK),1.45(N+),1.44(U-)and 1.52(N+U-)μmol C·m-2·s-1,without variation among different treatments.Both nitrogen addition and understory removal reduced the temperature sensitivity of soil microbial respiration.The R10 of root respiration changed more greatly than that of the microbial respiration under each treatment,indicating that root respiration responded more sensitive to each treatment than soil microbial respiration.Under the influence of soil water content,soil respiration and soil temperature showed different changes,indicating that soil water content is the limiting factor for soil respiration in Pinus sylvestris var.mongolica plantation in Horqin Sandy Land.Our results help understand carbon cycling and its modeling of sandy Pinus sylvestris var.mongolica plantation.