毛乌素沙地油蒿叶建成成本及相关叶性状沿降水梯度的变化

干旱区植物在如何提高水分利用效率与降低叶建成成本之间可能存在一种权衡。我们假设: 与湿润区植物相比, 干旱区植物能通过调节叶功能性状之间的关系(如通过提高单位面积叶氮含量(N_area)), 实现在相同的叶建成成本下具有更高的水分利用效率。为了验证这一假设, 该研究以毛乌素沙地的广布物种油蒿(Artemisia ordosica)为研究对象, 分析了油蒿叶建成成本沿降水梯度的变化规律及其与比叶面积(SLA)、单位质量叶氮含量(N_mass)、N_area和叶碳稳定同位素比率(δ ¹³C)的关系。结果表明: 油蒿单位质量叶建成成本(CC_m)在不同降水条件下差异不显著, 而单位面积叶建成成本(CC_a)在不同降水条件下虽有显著差异, 但并未随降水减少而明显增加。油蒿CC_m与SLA无显著相关性, 与叶δ ¹³C值呈显著正相关关系。油蒿叶建成成本与N_area呈显著正相关关系, 但这种关系格局在低降水量(264 mm)区与高降水量(310-370 mm)区之间存在策略位移现象——即在相同叶建成成本下, 低降水量区植物比高降水量区植物具有更高的N_area。以上结果表明, 尽管高水分利用效率与高叶建成成本相关, 但与高降水量区植物相比, 低降水量区植物具有较高的N_area并没有导致其叶建成成本增加。

Variations of leaf construction cost and leaf traits within the species of Artemisia ordosica along a precipitation gradient in the Mau Us sandy land

Aims There would be a trade-off between enhancing water use efficiency and decreasing leaf construction cost in arid plants. We hypothesized that plants in lower precipitation areas could have higher water use efficiency at a given leaf construction cost compared to plants in higher precipitation areas by altering relationships between leaf functional traits (i.e. increasing area-based leaf nitrogen concentration, N_area).Methods Artemisia ordosica is a widespread species in the Mau Us sandy land. Variations of leaf construction cost of A. ordosica along a precipitation gradient and its relationships to other leaf traits such as specific leaf area (SLA), mass-based leaf nitrogen concentration (N_mass), N_area and leaf stable carbon isotopes ratio (δ ¹³C) value were analyzed.Important findings There were no significant differences in mass-based leaf construction cost (CC_m) among different precipitation areas. Although area-based leaf construction cost (CC_a) showed significant differences among different precipitation areas, they did not increase significantly with decreasing precipitation. The relationship between CC_m and SLA was not significant while CC_m positively correlated with leaf δ ¹³C value. There was a strategy shift in the positive relationship of leaf construction cost to N_area between plant-groups in the lowest precipitation (264 mm) areas and other higher precipitation (310-370 mm) areas, i.e. plants from low precipitation areas have higher N_area at a given leaf construction cost. Our results indicated that although high water use efficiency was accompanied by high leaf construction cost, the high N_area for plants from lower precipitation areas did not increase their leaf construction cost.