The Northern tamarisk beetle (Diorhabda carinulata) was introduced to the Colorado River Basin in 2004 as a biological control agent for the invasive shrub: tamarisk (Tamarix spp.). Since 2004, D. carinulata has colonized much of the Colorado River Basin, defoliating tamarisk and adapting to local abiotic cues as it has spread across the landscape. I studied the interplay of abiotic cues, tamarisk defoliation, and the population dynamics of D. carinulata along portions of the Colorado, Dolores, and San Juan rivers from 2007-2012. My results suggest that the timing and location of tamarisk defoliation can be predicted based on the abiotic cues of a location (specifically temperature and day length) and the spatial distribution of D. carinulata across the landscape. In contrast, I also found that the spatial distribution of D. carinulata was often a result of D. carinulata abandoning areas where it had defoliated tamarisk at high intensities. I found that larval abundances from the first new generation of D. carinulata produced in a year were positively linearly correlated with defoliation intensities one month later. Comparatively, generations of larvae produced later in the season were correlated with defoliation intensity along a bell curve, in which the number of D. carinulata declined in areas>50% defoliated. The timing of defoliation during the active season was correlated with the arrival of each new generation of larvae. I found the number of generations of D. carinulata produced in a year varied based on spring temperatures and fall day lengths. The timing of when spring temperatures rose above 15°C dictated when D. carinulata could begin reproductive activity, and this in turn resulted in how early in the year tamarisk could become defoliated. Day length cues governing overwintering in D. carinulata appear to have shortened by>30 min. compared to populations of D. carinulata first released in North America in 2001, resulting in longer duration of activity into the fall. We found the range of D. carinulata could grow as much as 62.8±5.6 km in a year along a linear riparian system, and populations of D. carinulata could defoliate between 24±11.2 and 116±11.2 km of river corridor tamarisk in a year.

abstract: Mycorrhizal fungi form symbiotic relationships with plant roots, increasing nutrient and water availability to plants and improving soil stability. Mechanical disturbance of soil has been found to reduce mycorrhizal inoculum in soils, but findings have been inconsistent. To examine the impact of restoration practices on riparian mycorrhizal inoculum potential, soil samples were collected at the Tres Rios Ecosystem Restoration and Flood Control Project located at the confluence of the Salt, Gila, and Agua Fria rivers in central Arizona. The project involved the mechanical removal of invasive Tamarix spp.( tamarisk, salt cedar) and grading prior to revegetation. Soil samples were collected from three stages of restoration: pre-restoration, soil banks with chipped vegetation, and in areas that had been graded in preparation for revegetation. Bioassay plants were grown in the soil samples and roots analyzed for arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) infection percentages. Vegetations measurements were also taken for woody vegetation at the site. The mean number of AM and EM fungal propagules did not differ between the three treatment area, but inoculum levels did differ between AM and EM fungi with AM fungal propagules detected at moderate levels and EM fungi at very low levels. These differences may have been related to availability of host plants since AM fungi form associations with a variety of desert riparian forbs and grasses and EM fungi only form associations with Populus spp. and Salix spp. which were present at the site but at low density and canopy cover. Prior studies have also found that EM fungi may be more affected by tamarisk invasions than AM fungi. Our results were similar to other restoration projects for AM fungi suggesting that it may not be necessary to add AM fungi to soil prior to planting native vegetation because of the moderate presence of AM fungi even in soils dominated by tamarisk and exposed to soil disturbance during the restoration process. In contrast when planting trees that form EM associations, it may be beneficial to augment soil with EM fungi collected from riparian areas or to pre-inoculate plants prior to planting. / Dissertation/Thesis / M.S. Applied Biological Sciences 2012

Four closely related species of leaf beetles (Diorhabda spp.; Coleoptera:Chrysomelidae) have been introduced into the western United States as biocontrol agents for the invasive Eurasian shrub tamarisk (Tamarix spp.; Violales:Tamaricaceae). These beetles have since continued to spread and establish throughout the western United States. Another exotic insect, the tamarisk leafhopper (Opsius stactogalus, Fieber;Hemiptera: Cicadellidae), had previously become established in these areas and now shares tamarisk as a host plant with the beetles. To assess more carefully the potential for interactions between leafhoppers and beetles, field censuses and cage studies were conducted to determine the phenologies and potential interactions of O. stactogolus and D. carinulata when attacking Tamarix ramosissima (Ledebour) in western Colorado. The leafhopper underwent development through at least three generations per season, whereas the beetle was shown to develop through two generations per season. Variation in leafhopper abundance was associated with the extent and type of foliar damage to tamarisk trees. Individual trees with greatest D. carinulata abundances and subsequent defoliation had significantly reduced O. stactogalus abundances thereafter. Abundance of O. stactogalus was also shown to vary significantly among tamarisk plants in cage settings where leafhoppers were given the choice of potted tamarisk plants with ~50% damage to foliage from D. carinulata versus undamaged plants. In contrast, D. carinulata abundance was not shown to differ strongly in response to O. stactogalus damage in the field or in cage experiments. Field results across sites, however, showed similar trends of reduced beetle abundance on plants more heavily attacked by leafhoppers, and larval growth tests suggested slight reductions in larval pupation and adult emergence of D. carinulata when grown on O. stactogalus-damaged tamarisk. It is not clear if slight tendencies in D. carinulata abundance along with much stronger responses in O. stactogalus abundance were the result of limited plant material, rather than an induced plant defense. It is clear, however, that these specialist herbivores are interacting in an asymmetric competitive fashion while feeding on the same host plant.

Spatially-distributed water consumption was modeled over a segment of the Lower Colorado River, which contains irrigated agricultural and Tamarisk-dominated riparian ecosystems. For the irrigation scheme, distributed evapotranspiration data were analyzed in conjunction with point measurements of precipitation and surface flow in order to close daily and annual water balance. The annual closure error was less than 1% of the total water diversion to the area. In addition, it was found that the soil water storage component of the water balance cannot be neglected if the analysis is performed over time frames shorter than annual (e.g. growing season). Water consumption was highly uniform within agricultural fields, and all the full-cover fields were transpiring close to their potential rates. Mapping several new and existing drainage performance indicators showed that neither soil salinization nor water-logging would be of concern in this irrigation scheme. However, the quality of high-volume return flow must be studied, especially since the degraded water quality of the western US rivers is believed to act in favor of the invasive riparian species in outcompeting native species. Over the Tamarisk forest, the remotely-sensed evapotranspiration estimates were higher than the results of an independent groundwater-based method during spring and winter months. This was chiefly due to the fixed satellite overpass time, which happened at low sun elevation angles in spring and winter and resulted in a significant presence of shadows in the satellite scene and consequently a lower surface temperature estimate, which resulted in a higher evapotranspiration estimate using the SEBAL model. A modification based on the same satellite imagery was proposed and found to be successful in correcting for this error. Both water use and crop coefficients of Tamarisk estimated by the two independent methods implemented in this study were significantly lower than the current approximations that are used by the US Bureau of Reclamation in managing the Lower Colorado River. Studying the poorlyunderstood stream-aquifer-phreatophyte relationship revealed that diurnal and seasonal groundwater fluctuations were strongly coupled with the changes in river stage at close distances to the river and with the Tamarisk water extraction at further distances from the river. The direction of the groundwater flow was always from the river toward the riparian forest. Thus the improved Tamarisk ET estimates along with a better understanding of the coupling between the river and the riparian aquifer will allow the Bureau of Reclamation to re-asses their reservoir release methodology and improve efficiency and water savings.

Extensive research exists regarding invasive alien plant species including impacts to native ecosystems and efficacy of control methods on public lands and river corridors. Many studies have identified the need for more research regarding the social implications of invasive alien species management. More specifically, additional research is needed regarding the impacts of invasive alien plant management on the Colorado Plateau to river-based recreation experiences. It is important for public land management agencies like the National Park Service to understand recreation-based stakeholders’ knowledge, norms, and preferences toward managing prevalent alien plants like tamarisk. For this study, 330 river users were questioned about their knowledge of tamarisk and preferences for tamarisk management on the Green and Colorado River corridors of the Colorado Plateau. Results show that a majority of river users want tamarisk to be removed. The tamarisk control methods investigated in this thesis were also evaluated by respondents as acceptable. The methods evaluated to be the most acceptable were the cut-stump method and the use of tamarisk leaf beetle, while prescribed fire and the use of a machine to mulch tamarisk were found to be less acceptable. The use of chainsaws to perform the cut-stump method was found to be acceptable in both the Green and Colorado River corridors. This thesis concludes with a summary of findings and implications for land managers and future research.

The Dolores River in Utah and the Virgin River in Nevada are ecosystems under pressure from increased groundwater withdrawal due to growing human populations, climate change and introduced species such as Tamarix spp. (tamarisk). Tamarisk is reputed to take excessive water from its environment. Controlling tamarisk is of concern in the western United States where plants grow quickly in already fragile and diminishing riparian areas. For this reason, biologic control beetles Chrysomelidae: Diorhabda carinulata were released to weaken the tamarisk population, thus reducing its water use. The studies for this dissertation were conducted between 2010 and 2011. We quantified tamarisk water use over multiple cycles of annual defoliation using sap flow measurements, leaf area index (LAI), well data, allometry and satellite imagery from EOS-1 Moderate Resolution Imaging Spectrometer (MODIS) sensor. Study objectives for the Virgin River were to measure evapotranspiration (ET) before beetles ever arrived and to examine the effects on tamarisk ET in the year after beetle arrival. This site showed plant ET from sap flow averaged about 4.3 mm m⁻² leaf day⁻¹ in 2010. In 2011, ET from sap flow averaged 6.4 mm m⁻² leaf area day⁻¹ pre beetle arrival, but dropped to 3-4 mm m⁻² leaf area day⁻¹ after beetle arrival. Stand level ET measured by MODIS was 2.2 mm d⁻¹ in 2010 and approximately 1.5 mm day⁻¹ when beetle arrival was measured in 2011. Significant visual change was apparent as the trees senesced. Results showed the first year of beetle arrival resulted in reduced ET but did not result in significant water savings. We also compared the reaction of the newly defoliated (in 2011) Virgin River site to the long-term defoliated (since 2007) Dolores River site to explore if all beetle invasions were created equal. This paper views the two sites as fairly extreme examples of tamarisk stand reaction to the beetle. While no mortality was reported at the Dolores River site, the site is much older, less photosynthetically active and covers far less ground when compared to the younger tamarisk monoculture on the Virgin River. Pre-beetle arrival Normalized Difference Vegetation Index (NDVI) values were higher on the Virgin River than on the Dolores River. Beetle arrival at each site was captured with Landsat NDVI and a reduced NDVI signal (13% drop in NDVI at Dolores River, 5% drop at Virgin River) was seen after beetle arrival.

京都大学 / 0048 / 新制・課程博士 / 博士(地球環境学) / 甲第22101号 / 地環博第187号 / 新制||地環||37(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 舟川 晋也, 教授 西前 出, 准教授 真常 仁志 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

The processes and interactions that determine the width of a river channel remain a fundamental area of investigation in geomorphology. An increasing appreciation of the capacity of riparian vegetation to alter fluvial processes, and thus influence channel form, has highlighted the need to include vegetation in these analyses. However, a disconnect exists between the small spatial and temporal scales over which the linkages among flow patterns, sediment, and plants are evaluated and the larger spatial and temporal scales in which river systems operate. In this dissertation, I strove to identify some of the key mechanisms by which vegetation affects channel width. I worked to reconcile the issue of scale by developing a novel tool that resolves patch-scale (sub-meter) patterns of hydraulic roughness over the reach scale. While the approach can be generalized to evaluate any vegetated floodplain, the multi-scalar model was specifically applied to stands dominated by the non-native riparian shrub, tamarisk, that invaded the riparian corridor of southwestern US rivers during the past century. I focused my analyses on the lower Yampa River in western Colorado. Tamarisk colonized the Yampa in the absence of other environmental perturbations. As a result, adjustments to channel form may be linked to an altered vegetation community. From a careful geomorphic and vegetation reconstruction of the Yampa, I determined that tamarisk was the driving force in channel narrowing. Application of the multi-scalar model of vegetation resistance to the Yampa enabled me to reconstruct the changing hydraulic conditions as tamarisk established and the channel narrowed over time. This hydraulic reconstruction furthered our understanding of the interactions among vegetation recruitment patterns, the increased hydraulic resistance, and the changing flow and sediment transport field. Positive feedbacks between vegetation and geomorphic change created additional areas within the channel where tamarisk could establish, and thus accelerated the rate of channel narrowing. However, these feedbacks also changed the importance of common and large floods for vegetation establishment and sediment transport. Application of this process-based understanding to future flow regimes will help managers anticipate locations along the channel that are susceptible to vegetation encroachment and changes to channel width.

The invasive species Saltcedar is affecting water and land resources throughout the western states of America. Because of great water use capabilities and other ecosystem detriments, Saltcedar has been targeted for treatment. For successful management of Saltcedar, individual landowners need to be aware of the costs and benefits of treating Saltcedar. Eleven of the most commonly reported treatment methods were evaluated for firm level economic feasibility. Evaluated on the basis of treatment cost, treatment effectiveness, Saltcedar water-use, and re-vegetation water-use, a production plan of ten years was created for each treatment method. Some treatment methods required re-treatment and were evaluated with re-treatments most commonly found in the literature. Of the treatment methods evaluated, five treatment methods were determined to be most feasible. Landowner valuation of environmental changes in the ecosystem brought on by Saltcedar is very important in the decision of which treatment method to implement. Personal valuation, over a period of ten years, will often determine which treatment methods are most cost efficient.

From the Proceedings of the 1976 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 29-May 1, 1976, Tucson, Arizona / Energy budget evaluations of evapotranspiration from saltcedar were carried out on the flood plain of the Rio Grande River, near Bernardo, New Mexico. The site was adjacent to the Bureau of Reclamation's lysimeter study of water use by saltcedar. The energy budget for the cloudless day of June 14, 1975, revealed that energy gains from net radiation totaled 432 cal/cm² , while energy losses (in cal/cm2 ), were 14 to stored energy, 31 to convection, and 387 to evapotranspiration (ET). The energy loss to ET is equivalent to the latent energy contained in about 6.5 mm of water. The energy budget values are reasonable for a phreatophyte community in a semi-arid environment. The latent energy loss compares favorably with 401 cal/cm² measured by three lysimeters, although there were discrepancies in timing and amounts of loss among the individual lysimeters. The mean canopy diffusion resistance was 1.90 sec/cm over a 10-hour daytime period on June 14. The mean resistance was combined with vapor pressure deficit to predict lysimeter ET on three subsequent days. The agreement was within 12 percent, which suggests that diffusion resistance may be useful for simple ET predictions.