Relationships between aboveground and belowground trait responses of a dominant plant species to alterations in watertable depth
2018
Mao, Wei | Felton, Andrew J. | Ma, Yunhua | Zhang, Tonghui | Sun, Zhibin | Zhao, Xueyong | Smith, Melinda D.
Drought impacts to plant growth can be indicated by changes in key functional traits. However, previous research has focused on aboveground trait responses to precipitation deficits, with less emphasis on concomitant belowground impacts and deep soil drought from groundwater depletion. We assessed changes in a suite of aboveground and belowground traits of a dominant plant, Phragmites communis, in response to an experimental gradient of underground watertable depth. Our study occurred within the northeastern Inner Mongolia region, where changes to groundwater tables have been pervasive in recent years. In general, the results indicate that both aboveground and belowground traits responded positively, yet eventually negatively, to continual increases in watertable depth, indicative of reduced access to soil moisture as watertable depths increased. Key adjustments include changes to the ratio of coarse roots to fine roots, and the distribution of fine roots within the soil profile. These changes in belowground traits had strong correlations with changes in aboveground traits. In particular, specific root length of fine roots was positively correlated with leaf area, height, and aboveground biomass, whereas root biomass was linked to leaf area, specific root length of coarse roots, and root length density. Fine and coarse root production also had positive and negative relationships with aboveground biomass, respectively, suggestive of biomass allocation tradeoffs. We suggest that biomass production responses of this species to changes in watertable depths may largely be driven by interactions between the distribution of fine and coarse roots in the soil profile and changes to leaf area.
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