古尔班通古特沙漠藓结皮光合生理活性与土壤有机碳组分对长期氮添加的响应

Responses of moss crust photosynthetic physiological activity and soil organic carbon fractions to the long-term nitrogen addition in the Gurbantunggut Desert

藓结皮是荒漠生物土壤结皮的重要类型,在荒漠生态系统碳固定与碳排放过程中具有重要作用。研究长期氮添加对藓结皮光合生理活性和土壤有机碳(SOC)组分的影响,有助于理解藓结皮光合生理活性特征与荒漠生态系统土壤碳固存之间的关系及其调控因子。为此,研究依托古尔班通古特沙漠野外长期(13a)氮添加实验,以齿肋赤藓形成的藓结皮为研究对象,选取0(N0)、1.0(N1)、3.0 g N m-2a-1(N3)三种氮处理,阐明长期氮添加对藓结皮光合生理活性和SOC组分的影响。结果表明:(1)相比对照,长期氮添加对结皮层颗粒有机碳(POC)与矿物结合态有机碳(MAOC)含量无显著影响,但显著减少了0—5 cm土层POC和MAOC含量的积累;(2)N1处理显著提高了叶绿素和非结构性碳水化合物(NSC)含量,而N3处理叶绿素a、叶绿素b、总叶绿素及NSC的含量分别显著降低了50.94%、42.49%、46.71%和50.85%;(3)可溶性糖的含量在N1处理下显著增加,N3处理则显著抑制了其积累,脯氨酸的含量随氮浓度呈显著下降的趋势,长期氮添加对可溶性蛋白含量无显著影响;(4)相关性分析表明,长期氮添加、光合生理活性与POC和MAOC含量无显著相关性,酸碱度、微生物量碳氮、电导率、硝态氮和铵态氮皆显著影响POC和MAOC的含量积累。研究揭示了长期氮添加对藓结皮的光合生理活性和SOC组分的影响,且光合生理活性的响应无法有效反映SOC组分变化,为理解荒漠生态系统中氮沉降对生物土壤结皮的影响提供数据支持。

Moss crust is an important type of desert biological soil crust,which plays an important role in the process of carbon fixation and emission in desert ecosystem.Investigating the long-term impact of nitrogen addition on the photosynthetic physiology and soil organic carbon(SOC)components of moss crust will contribute to a better understanding of the relationship between the photosynthetic characteristics of moss crust and soil carbon sequestration in desert ecosystems,and their regulatory factors.In this study,we studied responses of moss crust formed by Syntrichia caninervis based on a 13a field nitrogen addition experiment in the Gurbantunggut Desert.Three nitrogen treatments were chosen:0(N0),1.0(N1),and 3.0 g N m-2 a-1(N3),and the prolonged effects of nitrogen addition on the photosynthetic physiology and SOC components of moss crust were conducted.The results indicated that:(1)Compared with the control,the long-term nitrogen addition had no significant effect on the contents of particulate organic carbon(POC)and mineral-associated organic carbon(MAOC)in the crust layer,but significantly reduced the accumulation of POC and MAOC in the 0—5 cm soil depth.(2)The N1 treatment significantly increased the content of chlorophyll and non-structural carbohydrates(NSC),while the N3 treatment significantly reduced the content of chlorophyll a,chlorophyll b,total chlorophyll,and NSC by 50.94%,42.49%,46.71%,and 50.85%,respectively.(3)The content of soluble sugars significantly increased under the N1 treatment,while the N3 treatment significantly inhibited their accumulation.The content of proline exhibited a significant decreasing trend with nitrogen concentration,while the long-term nitrogen addition had no significant effect on the content of soluble proteins.(4)Correlation analysis revealed no significant correlation between the long-term nitrogen addition,photosynthetic physiological activity,and POC and MAOC content.However,pH,microbial carbon and nitrogen,conductivity,nitrate nitrogen,and ammonium nitrogen significantly influenced the accumulation of POC and MAOC.In summary,this study reveals the impacts of the long-term nitrogen addition on the photosynthetic physiology and SOC components of moss crust.Moreover,it emphasizes that the response of photosynthetic physiological activity cannot effectively reflect the changes in SOC components,providing data support for understanding the influence of nitrogen deposition on biological soil crust in desert ecosystems.