Tree‐ring stable isotopes show different ecophysiological strategies in native and invasive woody species of a semiarid riparian ecosystem in the Great Plains of the United States

Abstract

Persistent shifts in riparian vegetation associated with the invasion of introducedElaeagnus angustifolia and native nonriparian Juniperus virginiana have been reported in the U.S. Great Plains, with significant impacts on ecosystem services. In Nebraska, these species have been expanding into the native Populus deltoides riparian forests along the Republican River. Using dendrochronological data and stable isotope ratios, we examined the annual growth and acclimation strategies of these three species to climatic and streamflow variability. We hypothesized that the ability of invasive species to grow under a wide range of environmental conditions favour vegetation shifts at the expense of native species. Streamflow was the strongest predictor for performance. When accompanied with above-average annual precipitation, streamflow resulted in peak tree-ring widths in P. deltoides. J. virginiana showed less sensitivity, and E. angustifolia showed no response. δ 18 O values did not differ among species, which indicates that all species compete for the same water source. δ 13 C ratios and WUEi were higher in J. virginiana than in P. deltoides and E. angustifolia and increased in all species over time. E. angustifolia and P. deltoides exhibit a strong stomatal control and response to relative humidity relative to J. virginiana, which showed anisohydric stomatal behaviour. Our results show that once established, J. virginiana and E. angustifolia thrive in the understory of P. deltoides using different adaptive and acclimation strategies. Based on current water flow management, which prevents highflood pulses through the riparian zone, these species will continue to establish and spread throughout the Republican River watershed.

Analysing the influence of a large flood on eastern redcedar (Juniperus virginiana) distribution along the Missouri River using remote‐sensing techniques

“…River floodplains are among the world's most altered ecosystems due to flow regulation, dam construction, levee building, land use change, and agricultural practices (Awada et al, 2019; Friedman, Osterkamp, Scott, & Auble, 1998; Whited, Bettes, & Paris, 2007). Dams substantially alter downstream hydrologic processes and river dynamics.…”

“…Alterations to flood timing, frequency, and magnitude and changes in water tables in the former floodplain may also enhance the risk of invasion of the riparian habitats by non‐native or upland plant species (Awada et al, 2019; Greene & Knox, 2014; Pattison, Vallejo‐Marín, & Willby, 2019; Richardson et al, 2007). As an example, floodplains along flow‐regulated rivers in western North America have been invaded by Russian‐olive ( Elaeagnus angustifolia ), tamarisk ( Tamarix spp .…”

“…As an example, floodplains along flow‐regulated rivers in western North America have been invaded by Russian‐olive ( Elaeagnus angustifolia ), tamarisk ( Tamarix spp . ), and Siberian elm ( Ulmus pumila ), which are non‐native invasive tree species (Awada et al, 2019; Friedman et al, 1998; Lesica & Miles, 2004; Perry, Reynolds, & Shafroth, 2018; Sher & Marshall, 2003). Further, drought‐resistant eastern redcedar ( Juniperus virginiana ), which is a native upland species, established along the flow‐regulated Republican River, Nebraska, USA (Awada et al, 2019).…”

Flooding with shallow water promotes the invasiveness of Mikania micrantha

“…The effect of soil moisture on invasive plants has received widespread attention, especially in the context of global climate change (Awada et al, 2019;Saptiningsih, Dewi, Santosa, & Purwestri, 2018). The effect of soil moisture on invasive plants has received widespread attention, especially in the context of global climate change (Awada et al, 2019;Saptiningsih, Dewi, Santosa, & Purwestri, 2018).…”

“…Soil moisture is a key environmental factor for plant growth and development. The effect of soil moisture on invasive plants has received widespread attention, especially in the context of global climate change (Awada et al, 2019;Saptiningsih, Dewi, Santosa, & Purwestri, 2018). Different invasive plants showed different responses to soil water conditions; for example, the invasive species Centaurea diffusa Lam.…”