Ništix or grizzleybear pricklypear (Opuntia ×columbiana Griffiths (pro sp.) [fragilis ×polyacantha] [Cactaceae]) was grown under solar panels and in full sun. We compared the survival and production of transplanted pads and the morphology of new pads. Survival rate of transplanted pads under the solar panels was much higher (90 ± 2.6%) than in the full sun (17 ± 5.5%), which were subject to decay due to a heavy snow event. The solar panels protected the pads against heavy snow burial, likely contributing to their higher survival rate. Productivity of the transplanted pads under the solar panels was much higher than those in full sun. This finding was measured by the number of new pads produced relative to the number of remaining pads, which was approximately 300% higher under the solar panels. The new pads under the solar panels were etiolated and twice as long as those in full sun. Overall, this preliminary study suggests that O. ×columbiana can be propagated successfully under solar panels, which could have implications for this tribally significant species and for land management.

Bromus tectorum (cheatgrass) is an invasive annual present in much of the western United States (Monaco 2011). The species results in increased fire frequency ([Whisenant 1990][1]) and reduced native-plant diversity ([Daubenmire 1970][2]) and threatens the habitat for sensitive species such as

ABSTRACT:Efforts are underway to return Opuntia columbiana Griffiths (pro sp.) [fragilis × polyacantha] (Ištíš, grizzleybear pricklypear [Cactaceae]) to a mitigation area in the Columbia Basin that is now dominated by invasive species. The relationship between patch size of densely installed pads and survival along with production was examined. This study was done by installing, in separate plots, 1, 3, 6, 18, or 30 pads and replicating this 6 times. Patch size or year had no effect on percent survival, which was 77 ± 5.5% in 2019 and 67 ± 6.1% in 2020. Productivity (the number of new pads/the number of remaining installed pads) decreased with increasing patch size with an estimated maximum of 4 new pads/to the number of remaining installed pads at the 1-pad patch size dropping to 1.2 at the 29-pad patch size. Of the 348 pads installed, 232 remained, producing 574 new pads by 2020. The production of new pads of this First Foods species will be greatest when pads are installed at low density.

In rangeland ecosystems, invasive annual grass replacement of native perennials is associated with higher fire risk. Large bunchgrasses are often seeded to reduce cover of annuals such as Bromus tectorum L. (cheatgrass), but there is limited information about how revegetation reduces fire risk over the long term. We assessed how revegetated community composition influences fire risk at three sites in Columbia National Wildlife Refuge in Grant County, Washington that were revegetated with large bunchgrasses 8−18 years before the study. At each site, five replicates of 10 plots (10 × 10 m) were established. Fire risk was determined as the probability that a plot would completely burn following ignition at a randomly located point in each plot (i.e., if 8 of 10 plots burned, then fire risk was 80%). Preignition, cover of bunchgrasses, cheatgrass, forbs, and surface characteristics were determined for each plot. Fire risk was < 100%. However, fire risk was still relatively high around 73% and did not differ significantly among sites despite differences in cheatgrass and bunchgrass cover, which may have been attributable to other characteristics, such as high total fuels cover (> 80% at all sites) and unvegetated gap cover (soil and soil cryptogams, < 17%). This information can provide guidance for future studies with larger ranges of cover characteristics to develop robust fire risk models, which ultimately will be used to aid rangeland managers who need to specify reduction of fire risk after reestablishing large bunchgrasses in rangelands infested with cheatgrass.

Purshia tridentata (Pursh) DC. (antelope bitterbrush [Rosaceae]) and Psoralidium lance-olatum (Pursh) Rydb. (lemon scurfpea [Fabaceae]) were more likely to survive and increase stem numbers than were herbaceous native perennials in a test to establish native nitrogen-fixing cover crops in a vineyard in the Columbia Basin. Tests were done in silt loam and loamy fine sand fields. All seeds were locally collected. Plants were propagated in a greenhouse in 164 ml (10 in3) Ray Leach Cone-tainer cells. Plants were installed by hand. After 4 y, P. tridentata survival was 53%, independent of soil type. Stems of P. lanceolatum, a rhizomatous species, were 55% of the original number and expanding in the loamy fine sand field. Survival of Astragalus sclerocarpus A. Gray (woodypod milkvetch [Fabaceae]) appeared to stabilize at 25% and A. caricinus (M.E. Jones) Barneby (buckwheat milkvetch) at 20%, both in the silt loam field. Astragalus succumbens Douglas ex Hook. (Columbia milkvetch) and Lupinus leucophyllus Douglas ex Lindl. (velvet lupine [Fabaceae]) failed. Percentage of plants in flower for the herbaceous species decreased by the 4th y while the percentage of plants in flower increased for P. tridentata and stems of P. lanceolatum. Astragalus sclerocarpus and A. succumbens survival was significantly reduced because of increasing interference from the vegetative cover of grasses in the loamy fine sand field. Plants without flowers were significantly smaller than were plants that had flowered. Fifty percent of the herbaceous species experienced herbivory in 2011. There was no herbivory in P. tridentata or P. lanceolatum.

Surface barrier technology is used to isolate radioactive waste and to reduce or eliminate recharge water to the waste zone for 1000 years or longer. However, the design and evaluation of such a barrier is challenging because of the extremely long design life. After establishing a set of design and performance objectives, a package of design solutions was developed for 1000-year surface barriers over nuclear waste sites. The Prototype Hanford Barrier (PHB) was then constructed in 1994 in the field over an . existing waste site as a demonstration. The barrier was tested to evaluate surface-barrier design and performance at the field scale under conditions of enhanced and natural precipitation and of no vegetation. The monitoring data demonstrate that the barrier satisfied nearly all objectives in the past two decades. The PHB far exceeded the Resource Conservation and Recovery Act criteria, functioned in Han ford's semiarid climate, limited drainage to well below the 0.5 mm yr(-1) performance criterion, limited runoff, and minimized erosion and bio-intrusion. Given the two-decade record of successful performance and consideration of the processes and mechanisms that could affect barrier stability and hydrology in the future, the results suggest the PHB is very likely to perform for its 1000-year design life. This conclusion is based on two assumptions: (1) the exposed subgrade receives protection against erosion and (2) institutional controls prevent inadvertent human activity at the barrier. The PHB design can serve as the basis for site-specific barriers over waste sites containing underground nuclear waste, uranium mine tailings, and hazardous mine waste. (C) 2016 Elsevier B.V. All rights reserved.

Engineered surface barriers are recognized as a remedial alternative to the removal, treatment and disposal of near-surface contaminants at a variety of waste sites within the DOE complex. One issue impacting their acceptance by stakeholders the use of limited data to predict long-term performance. In 1994, a 2-ha multi-component barrier was constructed over an existing waste disposal site at Hanford using natural materials. Monitoring has been almost continuous for the last 15 yrs and has focused on barrier stability, vegetative cover, plant and animal intrusion, and the components of the water balance, including precipitation, runoff, storage, drainage, and percolation. The total precipitation received from October 1994 through August 2008 was 3311 mm on the northern half (formerly irrigated), and 2638 mm on the southern, non-irrigated half. Water storage in the fine-soil layer shows a cyclic pattern, increasing in the winter and decreasing in the spring and summer to a lower limit of around 100 mm, regardless of precipitation, in response to evapotranspiration. Topographic surveys show the barrier and side slopes to be stable and the pea-gravel admix has proven effective in minimizing erosion through the creation of a desert pavement during deflationary periods. Three runoff events have been observed but the 600-mm design storage capacity has never been exceeded. Total percolation ranged from near zero amounts under the soil-covered plots to over 600 mm under the side slopes. The asphaltic concrete prevented any of this water from reaching the buried waste thereby eliminating the driving force for the contaminant remobilization. Plant surveys show a relatively high coverage of native plants still persists after the initial revegetation although the number of species decreased from 35 in 1994 to 10 in 2009. Ample evidence of insect and small mammal use suggests that the barrier is behaving like a recovering ecosystem. In September 2008, the north half of the barrier was burned to remove vegetation and study the effects of fire on barrier performance. The most immediate effects has been on water storage patterns with the bare surface showing a slower accumulation of water, a smaller peak storage and a delayed release relative to the unburned side due to evaporation . Nonetheless the residual storage at the end of the year was similar for the burned and unburned sides.

Monitoring is an essential component of engineered barrier system design and operation. A composite capacitive cover, including a capillary break and an evapotranspiration (ET) barrier at the Hanford Site, is generating data that can be used to help resolve these issues. The prototype Hanford barrier was constructed over the 216-B-57 Crib in 1994 to evaluate surface-barrier constructability, construction costs, and physical and hydrologic performance at the field scale. The barrier has been routinely monitored between November 1994 and September 1998 as part of a Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) treatability test of barrier performance for the 200 BP 1 Operable Unit. Since FY 1998, monitoring has focused on a more limited set of key water balance, stability, and biotic parameters. In FY 2009, data collection was focused on: (1) water-balance monitoring, consisting of precipitation, runoff, soil moisture storage, and drainage measurements with evapotranspiration calculated by difference; (2) stability monitoring, consisting of asphalt-layer-settlement, basalt-side-slope-stability, and surface-elevation measurements; (3) vegetation dynamics; and (4) animal use. September 2009 marked 15 years since the start of monitoring and the collection of performance data. This report describes the results of monitoring activities during the period October 1, 2008, through September 30, 2009, and summarizes the 15 years of performance data collected from September 1994 through September 2009.

Work has been initiated to restore native vegetation on the soil and base gravel layers that were once underneath constructed facilities at the Umatilla Chemical Depot (UMCD) in eastern Oregon. Propagules were collected from native plant species found around the UMCD. Germination success ranged from 0% to 75% for the species tested. Ten species were successfully propagated in sufficient numbers to use in an out planting study to monitor species survival. After three growing seasons, survival ranged from 100% for Opuntia polycantha (pricklypear) to 5.6% for Lupinus sericeus (silky lupine) with average survival over all species at 50%. Further testing is needed to determine what species are best adapted to local environmental conditions.

During 2010, the U.S. Department of Energy (DOE), Richland Operations Office removed a number of facilities and debris from the Fitzner/Eberhardt Arid Lands Ecology Reserve (ALE), which is part of the Hanford Reach National Monument (HRNM). Revegetation of disturbed sites is necessary to stabilize the soil, reduce invasion of these areas by exotic weeds, and to accelerate re-establishment of native plant communities. Seven revegetation units were identified on ALE based on soils and potential native plant communities at the site. Native seed mixes and plant material were identified for each area based on the desired plant community. Revegetation of locations affected by decommissioning of buildings and debris removal was undertaken during the winter and early spring of 2010 and 2011, respectively. This report describes both the details of planting and seeding for each of the units, describes the sampling design for monitoring, and summarizes the data collected during the first year of monitoring. In general, the revegetation efforts were successful in establishing native bunchgrasses and shrubs on most of the sites within the 7 revegetation units. Invasion of the revegetation areas by exotic annual species was minimal for most sites, but was above initial criteria in 3 areas: the Hodges Well subunit of Unit 2, and Units 6 and 7.

A critical unknown for long-term engineered barrier performance is the effect of wild fire during a post-institutional control environment where routine maintenance may be limited or non-existent. In September 2008, a controlled burn was conducted on one half of a vegetated, multilayered capillary barrier emplaced over a Hanford waste site. The effects on barrier performance have been monitored and documented over the past year. Soil physical, chemical, and hydrologic properties; plant floristics and density; and animal-use were characterized before and after the fire with the unburned half of the barrier serving as a control. Temperatures during the controlled burn ranged from 250 o C 1.5 cm below the surface to over 700 o C, 1 m above the surface. Significant decreases in hydraulic conductivity and surface-soil wettability were observed immediately after the fire. Post-fire concentrations of major soil nutrients, pH, and electrical conductivity remain elevated. Dense stands of sagebrush were destroyed from the fire allowing many more species to emerge, thereby increasing species diversity. Seed sources contributing to this species diversification were from either the existing seedbank and/or wind-blown sources. There were significant differences in the rate of accumulation and loss of soil moisture on the burned and unburned sections. On the burned section, water storage was higher during the fall; it increased more slowly with the onset of winter precipitation (owing to higher evaporation); and it decreased more slowly in the spring (owing to lower evapotranspiration). There were significant differences in storage between the burned and unburned sections by end of October 2009 although barrier effectiveness has not been compromised.

A critical unknown for long-term engineered barrier performance is the effect of wild fire during a post-institutional control environment where routine maintenance may be limited or non-existent. In September 2008, a controlled burn was conducted on one half of a vegetated, multilayered capillary barrier emplaced over a Hanford waste site. The effects on barrier performance have been monitored and documented over the past year. Soil physical, chemical, and hydrologic properties; plant floristics and density; and animal-use were characterized before and after the fire with the unburned half of the barrier serving as a control. Temperatures during the controlled burn ranged from 250 oC at 1.5 cm below the surface to over 700 oC at 1 m above the surface. Significant decreases in hydraulic conductivity and surface-soil wettability were observed immediately after the fire due primarily to hydrophobic conditions created by the fire. Major soil nutrients, pH, and electrical conductivity remain elevated post-fire. Up until June 2009, post-burn soil moisture content in the 0-1 m depth interval was significantly lower on the burned section than the unburned section and is attributed to differences in surface evaporation. Higher soil moisture contents in the 1-2 m interval on the burned section are attributed more » to insignificant water uptake owing to the absence of deep-rooted shrubs. Moisture profiles reversed after June to show lower water contents throughout the profile on the unburned section. Dense stands of sagebrush were destroyed from the fire allowing many more species to emerge thereby increasing species diversity. Seed sources contributing to this species diversification were from either the existing seedbank and/or wind-blown sources. Measurements are ongoing and the results are expected to help close a knowledge gap about barrier recovery after major disturbances. « less

Engineered surface barriers are recognized as a remedial alternative to the removal, treatment and disposal of near- surface contaminants at a variety of waste sites within the DOE complex. One outstanding issue that has impacted stakeholder acceptance of this technology is the limited amount of performance data and the uncertainty in using them to predict long-term performance. In 1994, a 2-ha multi-component barrier was constructed over an existing waste disposal site using natural materials. The 4.5-m thick barrier includes a 1-m thick silt loam surface layer with 15% pea gravel to control erosion as well as a capillary break, an asphaltic concrete layer at the base, and two protective side-slope configurations. The cover was designed to meet a 0.5 mm/yr drainage criterion and is instrumented to monitor stability as well water balance components. A treatability test conducted from 1994-1998 included irrigation at a rate of 480 mm/yr including a simulated 1000-yr return storm each March, in which 68 mm of water was applied over an 8 hr period. Monitoring has been almost continuous for the last 15 yrs and has focused on barrier stability, vegetative cover, evidence of plant and animal intrusion, and the main components of the water balance, including precipitation, runoff, storage, drainage, and deep percolation. The total precipitation received from October 1994 through August 2008 was 3311 mm on the northern half (formerly irrigated), and 2638 mm on the southern, non-irrigated half. Water storage in the fine-soil layer shows a cyclic pattern, increasing in the winter and decreasing in the spring and summer to a lower limit of around 100 mm, regardless of precipitation, in response to evapotranspiration. The functional portion of the barrier and its side slopes are structurally stable. Over the 15 years, only three runoff events have been observed but the 600-mm design storage capacity has never been exceeded. Total percolation ranged from near zero amounts under the soil-covered plots to over 600 mm under the side slopes but an asphalt layer prevented any of this water from reaching the buried waste. A relatively high ground cover of native plants still persists after the initial revegetation although the number of species decreased from 35 in 1994 to 15 in 2009. The vegetative cover, in addition to the silt-loam-gravel admix, proved effective in minimizing erosion but a recent removal of vegetation from the north half resulted in significant soil movement. There is ample evidence of insect and small mammal use suggesting that the barrier is beginning to function like a recovering ecosystem. These data have proven useful in the development of more rigorous methods for evaluating long-term performance and quantifying associated risk and uncertainty using numerical models.

A critical unknown in use of barrier technology for long-term waste isolation is performance after a major disturbance especially when institutional controls are intact, but there are no resources to implement corrective actions. The objective of this study was to quantify the effects of wild fire on alterations the function of an engineered barrier. A controlled burn September 26, 2008 was used to remove all the vegetation from the north side of the barrier. Flame heights exceeded 9 m and temperatures ranged from 250 oC at 1.5 cm below the surface to over 700 oC at 1 m above the surface. Post-fire analysis of soil properties show significant decreases in wettability, hydraulic conductivity, air entry pressure, organic matter, and porosity relative to pre-fire conditions whereas dry bulk density increased. Decreases in hydraulic conductivity and wettabilty immediately after the fire are implicated in a surface runoff event that occurred in January 2009, the first in 13 years. There was a significant increase in macro-nutrients, pH, and electrical conductivity. After one year, hydrophobicity has returned to pre-burn levels with only 16% of samples still showing signs of decreased wettability. Over the same period, hydraulic conductivity and air entry pressure returned to pre-burn levels at one third of the locations but remained identical to values recorded immediately after the fire at the other two thirds. Soil nutrients, pH, and electrical conductivity remain elevated after 1 year. Species composition on the burned surface changed markedly from prior years and relative to the unburned surface and two analog sites. An increase in the proportion of annuals and biennials is characteristic of burned surfaces that have become dominated by ruderal species. Greenhouse seedling emergence tests conducted to assess the seed bank of pre- and post-burn soils and of two analog sites at the McGee Ranch show no difference in the number of species emerging from soils collected before and after the fire. However, there were fewer species emerging from the seed bank on the side slopes and more species emerging from two analog sites. Leaf area index measures confirmed the substantial differences in plant communities after fire. Xylem pressure potential were considerably higher on the burned half of the barrier in September 2009 suggesting that not all the water in the soil profile will be removed before the fall rains begin. The results of this study are expected to contribute to a better understanding of barrier performance after major disturbances in a post-institutional control environment. Such an understanding is needed to enhance stakeholder acceptance regarding the long-term efficacy of engineered barriers. This study will also support improvements in the design of evapotranspiration (ET) and hybrid (ET + capacitive) barriers and the performance monitoring systems.