The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan)
植物资源(光、氮、水分)利用效率是反映生态功能适应气候变化的关键指示,然而鲜有研究综合考虑植物资源利用效率间的相对变化及其调控机制。选取宁夏盐池毛乌素沙地优势物种油蒿(Artemisia ordosica)为研究对象,于2017-2019年生长季对油蒿光合生理参数和环境因子进行原位监测,实验室测定叶片比叶面积(SLA)和叶氮含量(LNC),分析叶片光利用效率(LUE)、水分利用效率(WUE)、氮利用效率(NUE)的相对变化特征及其生物和非生物影响因子,探讨油蒿叶片资源利用效率对环境的响应。结果显示:油蒿LUE和NUE的季节变化趋势基本一致,两者呈正相关(R2=0.17;P<0.01),且皆与WUE季节变化不同,无显著关系(P>0.05),WUE波动幅度最高(CV=48%),NUE最低(CV=39%);研究期间LUE、WUE和NUE月均值基本在夏季出现高峰值,分别为0.12 mol/mol,104.02 μmol/mol和11.49 μmol g-1 s-1。土壤含水量(SWC)>0.09 m3/m3,叶片资源利用效率不受其影响,而SWC<0.09 m3/m3,WUE和SWC关系为二次函数;SWC调节土壤氮含量(Nsoil)和光合有效辐射(PAR)对叶片资源利用效率的影响。叶片资源利用效率与LNC无显著相关性;SLA与LUE显著负相关(P<0.01),与NUE显著正相关(P<0.01),与WUE相关性不显著(P>0.05)。LUE主要受SLA和Nsoil影响,NUE主要受SLA和SWC影响,SWC和Nsoil还可通过SLA和LNC间接影响LUE和NUE。结果表明水分和土壤氮含量是限制油蒿叶片资源利用效率的主要非生物因子,比叶面积则是调控其资源利用效率的关键生物因子,是深入探究荒漠植物群落对环境响应策略的重要补充。
Resource (light, nitrogen and water) use efficiency of a plant is a key indicator of ecological function acclimation to climate change and extremes. Its resource use efficiency has been widely used as the indicator to understand plant acclimation processes to unfavorable environmental conditions. However, comprehensive understanding of relative changes and its regulatory mechanism of resource use efficiencies (RUEs) including light use efficiency (LUE), water use efficiency (WUE) and nitrogen use efficiency (NUE) remain limited. Artemisia ordosica, the dominant species in the Mu Us Desert, was selected as the research object in this study. The study was based on season-long in-situ measurements of its leaf photosynthesis and abiotic factors from 2017 to 2019. Measurements of specific leaf area (SLA) and leaf nitrogen concentration (LNC) were made in the laboratory. The study aimed to examine the relative changes in leaf-level RUEs (i.e., LUE, WUE and NUE) and their biophysical controls in A. ordosica, which to understand the responses of A. ordosica' RUEs to environment at leaf level. As a result, seasonal patterns of LUE and NUE were convergent, being positively correlated (R2=0.17; P<0.01). By contrast, WUE fluctuated largely and had no relationship with LUE and NUE (P>0.05). Among the leaf-level RUEs, the seasonal variation was largest in WUE (CV=48%) and the lowest in NUE (CV=39%). Monthly mean leaf-level RUEs >generally peaked in summer, reaching a maximum of 0.12 mol/mol, 104.02 μmol/mol and 11.49 μmol g-1 s-1 for LUE, WUE, and NUE during the study period, respectively. The variation in leaf-level RUEs was not affected by soil water content (SWC) when SWC > 0.09 m3/m3. However, WUE was quadratically related to SWC when SWC < 0.09 m3/m3. SWC was observed to modify the influence of incident photosynthetically active radiation (PAR) and soil total nitrogen (Nsoil) on leaf-level RUEs. There was no significant correlation between leaf-level RUEs and LNC. The SLA was negatively related to LUE (P<0.01), positively related to NUE (P<0.01) and not related to WUE. The LUE is mainly affected by SLA and Nsoil, while NUE was mainly affected by SLA and SWC. The SWC and Nsoil also affected LUE and NUE through SLA and LNC indirectly. Our results indicate that water and soil total nitrogen are the main abiotic stresses limiting leaf-level resource use efficiencies and specific leaf area is the key biotic factor to regulate leaf-level resource use efficiencies in A. ordosica. Our findings are important addition to the understandings of acclimation strategies of desert plants to climate change and climatic extremes.