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Planting native riparian trees can help recover wildlife and fish habitat on a local scale, when full recovery of natural processes that sustain riparian ecosystems is infeasible. To help improve planting success, we determined which environmental factors and management practices most influenced survival of planted Populus fremontii (Fremont cottonwood) in a field experiment on the San Rafael River, Utah, U.S.A. We planted 474 approximately 2‐m‐tall trees and tracked survival for 1.25 years. We used logistic regression to evaluate whether tree height, elevation above the river channel, distance to existing cottonwood or Salix exigua (coyote willow), soil conductivity, soil texture, planting depth, planting method (mechanical auger vs. hand‐digging), and provision of natural and commercial supplements affected survival probability. Survival probability decreased with elevation above the river channel bottom and was greater in auger‐dug than hand‐dug holes. Survival probability was lower in soils with the highest salinity levels and was lower in sandy soils than soils with silt and clay. Survival may be improved by planting well above the channel to avoid flooding impacts but within 2 m above the channel in auger‐dug holes to ensure access to soil moisture. Testing soil salinity and texture in areas with suitable elevation could also help improve survival. Approximately 35% of trees survived to the end of the study period, indicating that planting can help recover riparian habitat locally, especially if survival is improved in future planting efforts. However, full recovery of desired riparian habitat throughout the floodplain will require natural flows. [ABSTRACT FROM AUTHOR]

The article investigates the processes of Eurasian shrub, Tamarix, invasion,Populus deltoides decline, and floodplain development along the lower Green River in Utah. The study has played significant role in assessing ecological, hydrologic, and geomorphic changes. The researchers determined the ages of several Tamarix and Populus species, studied hydrologic and geomorphic processes which controlled species domination, distinguished spatial relationships of sprouting areas within floodplain, and mapped woody riparian vegetation cohorts along three segments of the lower Green River. Their findings revealed that Tamarix invasion was caused by large annual floods, while Populus floodplain invasion was limited.

Summary 1 The structure and functioning of riverine ecosystems is dependent upon regional setting and the interplay of hydrologic regime and geomorphologic processes. We used a retrospective analysis to study recruitment along broad, alluvial valley segments (parks) and canyon segments of the unregulated Yampa River and the regulated Green River in the upper Colorado River basin, USA. We precisely aged 811 individuals of Populus deltoides ssp. wislizenii (native) and Tamarix ramosissima (exotic) from 182 wooded patches and determined the elevation and character of the germination surface for each. We used logistic regression to relate recruitment events (presence or absence of cohort) to five flow and two weather parameters. 2 Woody plant establishment occurred via multiple pathways at patch, reach and segment scales. Recruitment occurred through establishment on (1) vertically accreting bars in the unregulated alluvial valley, (2) high alluvial floodplain surfaces during rare large flood events, (3) vertically accreting channel margin deposits in canyon pools and eddies, (4) vertically accreting intermittent/abandoned channels, (5) low elevation gravel bars and debris fans in canyons during multi-year droughts, and (6) bars and channels formed prior to flow regulation on the dammed river during controlled flood events. 3 The Yampa River's peak flow was rarely included in models estimating the likelihood that recruitment would occur in any year. Flow variability and the interannual pattern of flows, rather than individual large floods, control most establishment. 4 Regulation of the Green River flow since 1962 has had different effects on woody vegetation recruitment in canyons and valleys. The current regime mimics drought in a canyon setting, accelerating Tamarix invasion whereas in valleys the ongoing geomorphic adjustment of the channel, combined with reduced flow variability, has nearly eliminated Populus establishment. 5 A single year's flow or a... [ABSTRACT FROM AUTHOR]

The significance of xylem function and metabolic scaling theory begins from the idea that water transport is strongly coupled to growth rate. At the same time, coordination of water transport and growth seemingly should differ between plant functional types. We evaluated the relationships between water transport, growth and species stature in six species of co-occurring trees and shrubs. Within species, a strong proportionality between plant hydraulic conductance (K), sap flow (Q) and shoot biomass growth (G) was generally supported. Across species, however, trees grew more for a given K or Q than shrubs, indicating greater growth-based water-use efficiency (WUE) in trees. Trees also showed slower decline in relative growth rate (RGR) than shrubs, equivalent to a steeper G by mass (M) scaling exponent in trees (0.77-0.98). The K and Q by M scaling exponents were common across all species (0.80, 0.82), suggesting that the steeper G scaling in trees reflects a size-dependent increase in their growth-based WUE. The common K and Q by M exponents were statistically consistent with the 0.75 of ideal scaling theory. A model based upon xylem anatomy and branching architecture consistently predicted the observed K by M scaling exponents but only when deviations from ideal symmetric branching were incorporated., (© 2014 John Wiley & Sons Ltd.)