摘要:高盐环境与土壤贫瘠成为限制滨海湿地植被生长的主要因素，盐分稀释（salt-dilution）与盐分抵御（salt-exclusion）为盐生植物普遍的两种适生策略，这些策略影响植物水分与养分利用效率的权衡过程。以江苏盐城滨海湿地常见稀盐盐生植物、拒盐盐生植物为研究对象，通过探讨滨海湿地不同盐生植物叶片δ¹³C（水分利用效率的直接反映参数），与主要养分元素（N、P、K）及化学计量特征的关系，以揭示不同盐生植物养分利用策略及养分利用效率与水分利用效率之间的权衡关系。研究结果表明：滨海湿地盐生植物叶片N/P为15.3，较全球陆生植物平均值低，表现出N、P共同限制特征。两种盐生植物叶片δ¹³C与N、P含量显著正相关，表明盐生植物采取N、P光合相关型策略适应不良环境。拒盐盐生植物叶片δ¹³C与K⁺正相关，采取K⁺渗透调节相关型策略，以减小细胞渗透势、增加水分吸收，减轻植物体内盐分毒害。两种不同耐盐型植物δ¹³C与C/N成反比，表明植物采取扩大水分利用效率以代偿减小的N利用率策略。稀盐盐生植物δ¹³C与C/P成反比，且叶片P含量较高，表明植物可以提高P利用率以增大低水分利用率环境下的C合成和生物量。研究可为滨海湿地生态系统恢复与重建提供理论依据。



Abstract:Plant growth is often limited by high salt concentration and nutrient deficiency in soil of coastal wetlands. Salt-dilution and salt-exclusion are two common strategies by which halophytes adapt to salty environment, and both strategies can affect plant trade-off of water and nutrient use efficiency. In order to understand plant nutrient strategies and trade-offs between water and nutrient use efficiency in different halophytes, we investigated two common halophytes including salt-dilution and salt-exclusion halophyte in Yancheng, Jiangsu, China. We also analyzed the relationship between foliar δ¹³C, which is a direct measure for water use efficiency (WUE), and main nutrition elements stoichiometry such as nitrogen (N), phosphorus (P), potassium (K) in different halophytes. The results showed that the foliar N/P ratio of halophytes was 15.3, which was lower than the average value of the global terrestrial plants, indicating a co-limitation by N and P for halophyte growth in coastal wetlands. For two types of halophytes, δ¹³C showed significantly positive correlations with foliar N and P. These correlations indicated that plants in poor environment may be profit N-related and P-related photosynthetic capacity strategies. In addition, salt-exclusion halophyte showed the positive correlations between δ¹³C and K⁺, suggesting a K⁺-related osmotic adjustment strategy for taking up sufficient water while containing salt toxicity in plants. Furthermore, both types of halophytes showed a negative correlation between δ¹³C and C/N. These results suggested that both salt-dilution and salt-exclusion halophytes were adapted to salty soil through a high WUE at the expense of decreased nitrogen use efficiency in the coastal wetlands of eastern China. A negative correlation between δ¹³C and C/P and the enhanced foliar phosphorus concentration were observed in salt-dilution halophyte, which suggested that these plants could improve C sequestration and biomass production by increasing P use efficiency in the habitat with low water availability. Our study can contribute to providing a baseline information for the restoration and conservation of coastal wetlands.





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