Water uptake by saltcedar (Tamarix ramosissima) in a desert riparian forest: responses to intra‐annual water table fluctuation

Abstract

There is considerable interest in naturalizing flow regime on managed rivers to slow the spread of saltcedar (Tamarix ramosissima) invasion in southwestern USA or to preserve riparian forests dominated by saltcedar and other species in northwestern China. However, little is known about the responses of established saltcedar in water sources to frequent intra‐annual fluctuation of water table resulting from this new, more dynamic flow regime. This study investigates how saltcedar at a riparian site in the middle reaches of the Heihe River, northwest China, responds in water sources use to intra‐annual water table fluctuations. Stable oxygen isotope was employed to determine accurate depth at which saltcedar obtains its water supply, and soil moisture monitoring was used to determine sources of plant‐available soil water. We found that the primary zone of water uptake by saltcedar were stable at 25–60 cm depth, but the water sources used by saltcedar switched between groundwater and soil moisture with the water table fluctuations. Saltcedar derived its water from groundwater when water table was at depth less than 60 cm but switched to soil moisture at 25–60 cm depth when water table declined. It is supposed that the well‐developed clay layer at 60–80 cm depth constrained lateral roots of saltcedar to the soil layers above 60 cm, while the fine‐textured soils at this site, which were periodically resaturated by rising groundwater before the stored soil moisture had become depleted, provided an important water reservoir for saltcedar when groundwater dropped below the primary zone of fine roots. The root distribution of saltcedar may also be related to local groundwater history. The quick decline in water table in the early 1980s when the riparian saltcedar had established may strand its roots in the shallow unsaturated zone. We suggested that raising the water table periodically instead of maintaining it invariably above the rooting depth could sustain desired facultative phreatophytes while maximizing water deliveries. Copyright © 2015 John Wiley & Sons, Ltd.

Responses of two desert riparian species to fluctuating groundwater depths in hyperarid areas of Northwest China

“…For instance, many riparian species can alternate between extracting water from groundwater and soil water sources in response to changes in GWD (Andrews, Flanagan, Sharp, & Cai, 2012;Chen, Chen, Xu, & Li, 2016;Lamontagne, Cook, O'Grady, & Eamus, 2005;Rossatto, de Carvalho Ramos Silva, Villalobos-Vega, Sternberg, & Franco, 2012;Snyder, 2000;Sun, Long, & Ma, 2016). For instance, many riparian species can alternate between extracting water from groundwater and soil water sources in response to changes in GWD (Andrews, Flanagan, Sharp, & Cai, 2012;Chen, Chen, Xu, & Li, 2016;Lamontagne, Cook, O'Grady, & Eamus, 2005;Rossatto, de Carvalho Ramos Silva, Villalobos-Vega, Sternberg, & Franco, 2012;Snyder, 2000;Sun, Long, & Ma, 2016).…”

Flood water legacy as a persistent source for riparian vegetation during prolonged drought: an isotopic study of Arundo donax on the Rio Grande

“…Perhaps woody phreatophytes are periodically dependent on shallow moisture and likewise utilize flood water legacies. For example, Tamarix ramosissima has been shown to switch between shallow moisture and groundwater sources in response to water table fluctuations (Sun et al ., In Press).…”

“…Furthermore, as soil moisture varies inter-annually and seasonally, plants may switch between soil moisture and groundwater sources (e.g. McCole and Stern, 2007;Nippert et al, 2010;Snyder et al, 1998;Sun et al, In Press).…”

Using Isotopic and Geochemical Tracers to Determine the Contribution of Glacier‐Snow Meltwater to Streamflow in a Partly Glacierized Alpine‐Gorge Catchment in Northeastern Qinghai‐Tibet Plateau

“…Our speculation is also supported by the δ 18 O values in meltwater samples, which were relatively negative in the early warm season, more positive in the middle warm season, and most negative in the late warm season in 2012. The depleted 18 O in meltwater samples in the early and late warm seasons demonstrated that the meltwater might originate from the glacier storages generated in a colder environment (Sun et al, ; C. Wang et al, ). We suggest that the major sources of meltwater in the early warm season were seasonal snow cover that accumulated mainly in winter (~191 mm in total water equivalent) and relatively small snowfall events that occurred just during this period (~72 mm in total water equivalent).…”