黄河三角洲贝壳堤湿地优势灌木碳、氮、磷化学计量特征

Foliar C,N,and P stoichiometry of dominant shrubs in the chenier wetland of the Yellow River Delta,China

为探讨黄河三角洲海岸带湿地不同水盐条件下植物叶片化学计量特征的季节动态及植物生长的限制性营养元素,以滨州贝壳堤岛与湿地国家级自然保护区内的柽柳、杠柳、酸枣3种优势灌木为研究对象,于2017—2018年的生长季(5—10月)每月定期采集叶片样品,测定叶片C、N、P含量。结果表明,生长季内3种灌木叶片C含量呈逐渐上升趋势;叶片N、P含量呈先下降后上升趋势,说明3种灌木采用防御性生活史策略适应盐生和干旱生境。3种灌木叶片C平均含量分别为(399.65±2.66)mg/g、(424.32±1.59)mg/g、(437.47±1.08)mg/g,低于全国(455.1 mg/g)及全球(461.6 mg/g)水平,呈现盐生生境下较低的植物碳储存能力。3种灌木叶片N和P平均含量分别为(30.14±0.26)mg/g和(1.81±0.03)mg/g、(23.18±0.38)mg/g和(2.06±0.04)mg/g、(27.36±0.49)mg/g和(2.01±0.03)mg/g,显著高于全国(N∶20.2 mg/g,P:1.46 mg/g)及全球(N∶19.3—20.1 mg/g,P:1.11—1.42 mg/g)水平。叶片C∶N∶P比呈先上升后下降的趋势,叶片P含量对C∶N∶P比变化具有主导作用。3种灌木叶片C∶N∶P质量比分别为246∶17∶1、224∶12∶1、237∶14∶1,说明柽柳的水盐胁迫适应能力高于杠柳和酸枣。从叶片N、P化学计量特征看,生长季内,柽柳生长一定程度上受土壤P限制,杠柳生长受到土壤N限制,酸枣生长则受土壤N、P共同限制,说明3种灌木的生物地球化学生态位发生了分化,避免了对同种资源的竞争,利于物种共生。

During the past decades,the dynamics of water and nutrient availability in soils,induced by rising sea levels under global climate change,have been projected to have profound effects on coastal ecosystems.Stoichiometry is the study of the mass balances of multiple chemical elements in ecosystems,mainly carbon(C),nitrogen(N),and phosphorus(P),and it analyzes the constraints and consequences of these mass balances during the ecological interactions.Understanding the stoichiometry of plants would help to assess the nutrient use strategies under the changed soil conditions.Three shrub species,including Tamarix chinensis,Periploca sepium,and Ziziphus jujuba,were selected to study the stoichiometry during the growth season in the Binzhou chenier island and wetland national nature reserve.The three shrubs were dominant species growing in the national nature reserve.The study was conducted from May to October in 2017 and 2018.We established five 10 m×10 m plots parallel to the coastline for each shrub species.At each plot,ten healthy shrubs were selected from each shrub species to collect the leaf samples.We collected 500g leaves from four compass directions and analyzed the foliar C,N,and P.The results showed a negative correlation between the foliar C concetrations and N,P concetrations.The foliar N concetrations showed a significantly positive correlation with P concetrations.The averages of foliar C concetrations were(399.65±2.66)mg/g for T.chinensis,(424.32±1.59)mg/g for P.sepium,and(437.47±1.08)mg/g for Z.jujuba during the growth season.These were lower than those of the national(455.1 mg/g)and global(461.6 mg/g)levels,and showed a lower carbon storage ability of the shrubs under the water-salt stress habitats.The averages of foliar N,P concetrations were(30.14±0.26)mg/g and(1.81±0.03)mg/g for T.chinensis,(23.18±0.38)mg/g and(2.06±0.04)mg/g for P.sepium,(27.36±0.49)mg/g and(2.01±0.03)mg/g for Z.jujuba.The foliar N and P concetrations of the three shrubs were all higher than the national(N∶20.2 mg/g,P:1.46 mg/g)and global(N∶19.3-20.1 mg/g,P:1.11-1.42 mg/g)levels.The foliar C∶N∶P ratios were 246∶17∶1 for T.chinensis,224∶12∶1 for P.sepium,and 237∶14∶1 for Z.jujube,which demonstrated that T.chinensis had higher adaptability to water-salt stress than P.sepium and Z.jujube.The foliar C∶N∶P ratio was mainly controlled by the foliar P concetrations.The foliar N and P stoichiometry indicated that the growth of T.chinensis was limited by P,P.sepium limited by N,and Z.jujuba limited by both N and P potentially during the growth season,and that niches shift of the three shrubs may partially avoid direct competition for the same resources,thus improving the possibilities of different species coexistence.