极端干旱区绿洲植物叶功能性状及其对土壤水盐因子的响应

Leaf functional traits of oasis plants in extremely arid areas and its response to soil water and salt factors

【目的】极端干旱区绿洲是全球变化的敏感区域,特别是由于水资源短缺及水文过程的改变,绿洲土壤环境因此产生了强烈异质性。植物如何适应高度土壤异质性是绿洲植物多样性维持的关键性科学问题。而探究植物叶片这一对土壤异质性敏感器官的功能性状及其对土壤水盐因子的响应,有利于揭示全球变化背景下绿洲植物适应的根本策略。【方法】本研究以额济纳这一典型荒漠绿洲的常见植物叶片为研究对象,选择25种植物的8种叶功能性状,包括叶片厚度(LT)、叶干物质含量(LDMC)、比叶面积(SLA)、叶碳含量(LCC)、叶氮含量(LNC)、叶磷含量(LPC)、叶片碳氮比(C/N)、叶片氮磷比(N/P),分析了功能性状之间的相关性及其在群落水平上的特征,并探讨了叶功能性状对不同土壤水盐环境的响应。【结果】(1)在不同土壤水盐环境中,各个叶功能性状具有不同程度的变异幅度,其中SLA最大,LCC最小。(2)部分功能性状之间表现出显著的协同或权衡变化趋势。LT与SLA、LDMC与SLA、LPC与LDMC、LNC与C/N、LPC与N/P呈极显著负相关(P <0.01);LCC与LT、LNC与LCC、C/N与N/P呈显著负相关(P <0.05)。LDMC与C/N、SLA与LPC、LCC与C/N、N/P与LCC、LNC与N/P呈极显著正相关(P <0.01);LDMC与LCC、SLA与LNC呈显著正相关(P <0.05)。(3)叶功能性状对土壤水盐因子的响应具有显著的差异。在低水低盐环境中,叶片通过提高LDMC、LNC、N/P,降低LPC、C/N来适应干旱胁迫为主的土壤环境。在低水高盐环境中,叶片通过降低LDMC、C/N、N/P,提高LNC、LPC来适应盐胁迫为主的土壤环境。在(相对)高水高盐环境中,叶片主要通过降低LNC、N/P,提高C/N来适应盐胁迫相对较低、水分含量相对充足的土壤环境。【结论】在额济纳绿洲区域内,植物群落叶功能性状通过一定程度的变异和某种协同-权衡的功能组合形式适应极端干旱的环境,并对土壤水盐因子的响应具有一定程度的差异,其中盐分含量对该环境下的群落叶功能性状的影响更为关键。本研究为进一步探究极端干旱区绿洲植物对土壤水盐因子的适应机制研究提供了科学依据。

[Objective] Extremely arid oasis is a sensitive area of global change, especially water shortage and changes in hydrological processes had led to strong heterogeneity in the oasis soil environment. How plants adapt to high soil heterogeneity is a key scientific issue in the maintenance of oasis plant diversity. So investigating plant leaves, the most sensitive organ traits and their response to soil water and salt factors is helpful to reveal the fundamental strategies of plant adaptation under environmental heterogeneity conditions. [Method] In this study, the common plant leaves of Ejina, a typical desert oasis, were selected as research objects, and eight leaf functional traits of 25 plants were selected, including leaf thickness(LT),leaf dry matter content(LDMC), specific leaf area(SLA), leaf carbon content(LCC), leaf nitrogen content(LNC), leaf phosphorus content(LPC), leaf carbon to nitrogen ratio(C/N) and leaf nitrogen to phosphorus ratio(N/P). The correlations between functional traits and their characteristics at the community level were analyzed. And the response of leaf functional traits to different soil water and salt environments was discussed. [Result] Results showed that:(1) each leaf functional trait had varying degrees of variation,among which SLA had the highest coefficient of variation and LCC had the smallest coefficient of variation.(2) There was a significant synergy or trade-off between some functional traits. LT and SLA, LDMC and SLA, LPC and LDMC, LNC and C/N, LPC and N/P were significantly negatively correlated(P < 0.01), and there was a significant negative correlation between LCC and LT, LNC and LCC, C/N and N/P(P < 0.05).LDMC and C/N, SLA and LPC, LCC and C/N, N/P and LCC, LNC and N/P were significantly positively correlated(P < 0.01), and there was a significantly positive correlation with LDMC and LCC, SLA and LNC(P < 0.05).(3) Leaf functional traits had a certain degree of difference in response to soil water and salt factors. In the low-water and low-salt environment, the leaves were adapted to drought-stressed soil environment by increasing LDMC, LNC, N/P, and lowering LPC and C/N. In the low-water and high-salt environment, the leaves improved LNC and LPC to reduce the soil environment dominated by salt stress by reducing LDMC, C/N and N/P. In the(relative) high-water and high-salt environment, the leaves were mainly adapted to the soil environment with relatively low salt stress and relatively sufficient water content by reducing LNC, N/P and increasing C/N. [Conclusion] In the Ejina Oasis Region, the leaf functional traits of plant community adapted to the extreme arid environment through a certain degree of variation and a synergistic-balanced functional combination. The response to soil water and salt factors also had a certain degree of difference. Among them, the effect of salt content on the leaf functional traits of the plant community was more critical. This study provides a scientific basis for further research on the adaptation mechanism of oasis plants in extreme arid regions to soil water and salt factors.