Hail deeply affects the growth of rubber trees in Xishuangbanna

Water use efficiency (WUE) is one of the most important indicators of the strength of the carbon-water coupling for ecosystems and plants. Annual patterns of WUE among different types of forests have been widely reported. However, the annual carbon-water coupling pattern of rubber trees has never been explored at the plant and ecosystem level. The responses of the carbon-water coupling to cold stress and hail events remain unknown.

In a study published in Crops and industrial products, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences attempted to reveal the adaptation strategy of rubber trees to cold stress and hail from the point of view of WUE. They compared the WUEs of rubber plantations by considering different scales (plant and ecosystem) and methods (turbulent covariance and isotopic techniques).

Researchers continuously measured the sap flow density, diameter at breast height (DHH), and carbon and water flow of rubber plantations in Xishuangbanna in southwest China from 2012 to 2016.

They observed high correlations in annual WUE models of rubber plantations between plant and ecosystem scales. These models were characterized by a single peak curve after the cold stress period from March to December and by the maximum values ​​of WUE occurring between July and September.

The WUE of tropical rubber trees was greatly overestimated during the period of cold stress as leaves discolored with high levels of anthocyanins would soon fall off and may reduce photosynthetic activity.

Compared to the effects of cold stress on rubber tree WUE, the hail event severely disrupted the annual WUE model by weakening the carbon-water coupling process, as well as disrupting the relationship between the rate ratio. DBH growth rate and sap flow density in the following annual life cycle of rubber trees.

The results reveal that rubber trees may have potentially adapted to the adverse climatic conditions of Xishuangbanna in the northern margin of the tropics.

“However, we noted significant vulnerability and uncertainty for rubber tree responses to frequent extreme weather events, as this could profoundly affect rubber tree growth,” said Lin Youxing of XTBG.