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Douglas C. Andersen

Publications and source records attributed to Douglas C. Andersen.

At least 19 recordsLinked to original sources
USGS2018

Flood effects on soil thermal regimes in contrasting cold‐desert river floodplains (Yampa and Green rivers, Colorado)

Heat transfer theory suggests that floodplain soils in dryland riverine ecosystems can be cooled by hyporheic flows generated during spring floods. I compared soil temperature cycles and associated hydrologic factors on a free‐flowing river to those on a river where flows and surface water temperatures are now regulated. Spring surface water temperatures were comparable on the 2 rivers, as was apparent diffusivity of the soil under mature Populus fremontii in a year when severe drought produced similar soil moisture regimes. Over 9 years of monitoring, mean annual maximum soil temperature was higher on the regulated river than on the free‐flowing river (10 cm depth: 33 vs. 23 °C; 40 cm depth: 30 vs. 20°C, respectively), and sinusoidal models of the annual temperature cycle at each depth indicated higher means and greater amplitudes on the regulated river. The annual maximum soil temperature was inversely related to peak flood discharge on the free‐flowing river but not on the regulated river. Temporal shifts in the lag between diel cycles at 40 and 10 cm depths—an index of soil thermal diffusivity—suggested that the capillary fringe is strongly involved in heat exchange. An increase in the lag during some water table declines suggested that shallow soils may undergo flood‐induced evaporative cooling. Hyporheic recharge can be an ecologically important determinant of growing‐season soil temperatures at plant rooting depth in dryland river floodplains. Reductions in spring flood magnitude due to river regulation, water abstraction, or climate change can increase these temperatures and thereby alter ecosystem structure and functioning.

Colorado↗
USGS2016

Flow regime effects on mature Populus fremontii (Fremont cottonwood) productivity on two contrasting dryland river floodplains

I compared riparian cottonwood ( Populus fremontii ) productivity-discharge relationships in a relictual stand along the highly regulated Green River and in a naturally functioning stand along the unregulated Yampa River in semiarid northwest Colorado. I used multiple regression to model flow effects on annual basal area increment (BAI) from 1982 to 2011, after removing any autocorrelation present. Each BAI series was developed from 20 trees whose mean size (67 cm diameter at breast height [DBH]) was equivalent in the two stands. BAI was larger in the Yampa River stand except in 2 y when defoliating leaf beetles were present there. I found no evidence for a Yampa flood-magnitude threshold above which BAI declined. Flow variables explained ∼45% of residual BAI variability, with most explained by current-year maximum 90-d discharge (Q M90 ) in the Yampa River stand and by a measure of the year-to-year change in Q M90 in the Green River stand. The latter reflects a management-imposed ceiling on flood magnitude—Flaming Gorge Dam power plant capacity—infrequently exceeded during the study period. BAI in the relictual stand began to trend upward in 1992 when flows started to mimic a natural flow regime. Mature Fremont cottonwoods appear to be ecologically resilient. Their productivity along regulated rivers might be optimized using multiyear environmental flow designs.

Southwestern Naturalist↗
USGS2014

Can nitrogen fertilization aid restoration of mature tree productivity in degraded dryland riverine ecosystems?

Restoration of riparian forest productivity lost as a consequence of flow regulation is a common management goal in dryland riverine ecosystems. In the northern hemisphere, dryland river floodplain trees often include one or another species of Populus, which are fast-growing, nutrient-demanding trees. Because the trees are phreatophytic in drylands, and have water needs met in whole or in part by a shallow water table, their productivity may be limited by nitrogen (N) availability, which commonly limits primary productivity in mesic environments. We added 20 g N m −2 in a 2-m radius around the base of mature Populus fremontii along each of a regulated and free-flowing river in semiarid northwest Colorado, USA (total n = 42) in order to test whether growth is constrained by low soil N. Twelve years after fertilization, we collected increment cores from these and matched unfertilized trees and compared radial growth ratios (growth in the 3-year post-fertilization period/growth in the 3-year pre-fertilization period) in paired t tests. We expected a higher mean ratio in the fertilized trees. No effect from fertilization was detected, nor was a trend evident on either river. An alternative test using analysis of covariance (ANCOVA) produced a similar result. Our results underscore the need for additional assessment of which and to what extent factors other than water control dryland riverine productivity. Positive confirmation of adequate soil nutrients at these and other dryland riparian sites would bolster the argument that flow management is necessary and sufficient to maximize productivity and enhance resilience in affected desert riverine forests.

Colorado↗
USGS2014

Effects of soil temperature and depth to ground water on first-year growth of a dryland riparian phreatophyte, Glycyrrhiza lepidota (American licorice)

We investigated the effects of soil temperature and depth to ground water on first-year growth of a facultative floodplain phreatophyte, Glycyrrhiza lepidota , in a 2-×-2 factorial greenhouse experiment. We grew plants in mesocosms subirrigated with water low in dissolved oxygen, mimicking natural systems, and set depth of ground water at 63 or 100 cm and soil temperature at cold (ambient) or warm (≤2.7°C above ambient). We hypothesized the moister (63 cm) and warmer soil would be most favorable and predicted faster growth of shoots and roots and greater nitrogen-fixation (thus, less uptake of mineral nitrogen) under those conditions. Growth in height was significantly faster in the moister treatment but was not affected by soil temperature. Final biomass of shoots and of roots, total biomass of plants, and root:shoot ratio indicated a significant effect only from depth of ground water. Final levels of soil mineral-nitrogen were as predicted, with level of nitrate in the moister treatment more than twice that in the drier treatment. No effect from soil temperature on level of soil-mineral nitrogen was detected. Our results suggest that establishment of G. lepidota requires strict conditions of soil moisture, which may explain the patchy distribution of the species along southwestern dryland rivers.

Southwestern Naturalist↗
USGS2011

Vulnerability of riparian ecosystems to elevated CO 2 and climate change in arid and semiarid western North America

Riparian ecosystems, already greatly altered by water management, land development, and biological invasion, are being further altered by increasing atmospheric CO 2 concentrations ([CO 2 ]) and climate change, particularly in arid and semiarid (dryland) regions. In this literature review, we (1) summarize expected changes in [CO 2 ], climate, hydrology, and water management in dryland western North America, (2) consider likely effects of those changes on riparian ecosystems, and (3) identify critical knowledge gaps. Temperatures in the region are rising and droughts are becoming more frequent and intense. Warmer temperatures in turn are altering river hydrology: advancing the timing of spring snow melt floods, altering flood magnitudes, and reducing summer and base flows. Direct effects of increased [CO 2 ] and climate change on riparian ecosystems may be similar to effects in uplands, including increased heat and water stress, altered phenology and species geographic distributions, and disrupted trophic and symbiotic interactions. Indirect effects due to climate-driven changes in streamflow, however, may exacerbate the direct effects of warming and increase the relative importance of moisture and fluvial disturbance as drivers of riparian ecosystem response to global change. Together, climate change and climate-driven changes in streamflow are likely to reduce abundance of dominant, native, early-successional tree species, favor herbaceous species and both drought-tolerant and late-successional woody species (including many introduced species), reduce habitat quality for many riparian animals, and slow litter decomposition and nutrient cycling. Climate-driven changes in human water demand and associated water management may intensify these effects. On some regulated rivers, however, reservoir releases could be managed to protect riparian ecosystem. Immediate research priorities include determining riparian species' environmental requirements and monitoring riparian ecosystems to allow rapid detection and response to undesirable ecological change.

Global Change Biology↗
USGS2003

Flood flows, leaf breakdown, and plant-available nitrogen on a dryland river floodplain

We tested the hypothesis that decomposition in flood-inundated patches of riparian tree leaf litter results in higher plant-available nitrogen in underlying, nutrient-poor alluvium. We used leafpacks ( n = 56) containing cottonwood ( Populus deltoides ssp. wislizenii ) leaf litter to mimic natural accumulations of leaves in an experiment conducted on the Yampa River floodplain in semi-arid northwestern Colorado, USA. One-half of the leafpacks were set on the sandy alluvial surface, and one-half were buried 5 cm below the surface. The presence of NO 3 − and NH 4 + presumed to result from a leafpack's submergence during the predictable spring flood pulse was assessed using an ion-exchange resin bag (IER) placed beneath each leafpack and at control locations. Leafpacks and IERs were collected one week after flood peak (71 days total exposure) at half the stations; the remainder were collected three weeks later (93 days exposure). A multi-peaked spring flood with above-average maximum discharge inundated leafpacks for total time periods ranging from 133 to 577 hours. Litter lost from 43 to 68 percent of its initial organic matter (OM) content. Organic matter loss increased with total time inundated and total time of exposure on the floodplain. Burial retarded OM loss if the total time inundated was relatively long, and substrate texture (sand vs. silt) affected OM loss in a complex manner through interactions with total time inundated and total time of exposure. No pulse of N attributable to leaf breakdown was detected in the IERs, and leafpack litter showed no net change in the mass of nitrogen present. Patterns of leafpack and IER nitrogen levels suggested that litter removed N from floodwater and thereby reduced N availability in underlying sediment. Immobilization of floodwater-N by litter and N mineralization outside the flood period may be important components of N flux in semi-arid and arid floodplain environments.

Colorado↗
USGS1999

Factors controlling the establishment of Fremont cottonwood seedlings on the Upper Green River, USA

Declines in cottonwood ( Populus spp.) recruitment along alluvial reaches of large rivers in arid regions of the western United States have been attributed to modified flow regimes, lack of suitable substrate, insufficient seed rain, and increased interspecific competition. We evaluated whether and how these factors were operating during 1993–1996 to influence demographics of Fremont cottonwood ( P. deltoides Marshall subsp. wislizenii (Watson) Eckenwalder) along reaches of the Green and Yampa Rivers near their confluence in northwestern Colorado. We examined seedling establishment, defined as survival through three growing seasons, at three alluvial reaches that differed primarily in the level of flow regulation: a site on the unregulated Yampa, an upper Green River site regulated by Flaming Gorge Dam, and a lower Green River site below the Green–Yampa confluence. Seed rain was abundant in all sites, and led to large numbers of germinants (first-year seedlings) appearing each year at all sites. The regulated flow in the upper Green River reach restricted germination to islands and cut banks that were later inundated or eroded; no seedlings survived there. Mortality at the lower Green River site was due largely to desiccation or substrate erosion; 23% of 1993 germinants survived their first growing season, but at most 2% survived through their second. At the Yampa River site, germinants appeared on vegetated and unvegetated surfaces up to 2.5 m above base flow stage, but survived to autumn only on bare surfaces at least 1.25 m above base flow stage, and where at least 10 of the upper 40 cm of the alluvium was fine-textured. Our studies of rooting depths and the stable isotopic composition of xylem water showed that seedlings in the most favorable locations for establishment at the Yampa site do not become phreatophytic until their third or fourth growing season. Further, the results of experimental field studies examining effects of shade and competition supported the hypothesis that insufficient soil moisture, possibly in combination with insufficient light, restricts establishment to unvegetated sites. Collectively, the demographic and experimental studies suggest that, in arid regions, soil water availability is at least as important as light level in limiting establishment of Fremont cottonwood seedlings. We hypothesize that in cases where arid land rivers experience large spring stage changes, recruitment is further constrained within bare areas to those sites that contain sufficient fine-textured alluvium, saturated during the spring flood, to provide the flood-derived soil moisture normally necessary for late-summer seedling survival.

Upper Green River↗
USGS1994

Are cicadas (Diceroprocta apache) both a "keystone" and a "critical-link" species in lower Colorado River riparian communities?

Apache cicada (Homoptera: Cicadidae: Diceroprocta apache Davis) densities were estimated to be 10 individuals/m 2 within a closed-canopy stand of Fremont cottonwood ( Populus fremontii ) and Goodding willow ( Salix gooddingii ) in a revegetated site adjacent to the Colorado River near Parker, Arizona. Coupled with data drawn from the literature, I estimate that up to 1.3 cm (13 1/m 2 ) of water may be added to the upper soil layers annually through the feeding activities of cicada nymphs. This is equivalent to 12% of the annual precipitation received in the study area. Apache cicadas may have significant effects on ecosystem functioning via effects on water transport and thus act as a critical-link species in this southwest desert riverine ecosystem. Cicadas emerged later within the cottonwood-willow stand than in relatively open saltcedar-mesquite stands; this difference in temporal dynamics would affect their availability to several insectivorous bird species and may help explain the birds' recent declines. Resource managers in this region should be sensitive to the multiple and strong effects that Apache cicadas may have on ecosystem structure and functioning.

Southwestern Naturalist↗
USGS1994

An assessment of riparian environmental quality by using butterflies and disturbance susceptibility scores

The butterfly community at a revegetated riparian site on the lower Colorado River near Parker, Arizona, was compared to that found in a reference riparian site. Data indicated that the herbaceous plant community, which was lacking at the revegetated site, was important to several butterfly taxa. An index using butterfly sensitivity to habitat change (species classified into risk groups) and number of taxa was developed to monitor revegetation projects and to determine restoration effectiveness.

Southwestern Naturalist↗
USGS1990

Search path of a fossorial herbivore, Geomys bursarius , foraging in structurally complex plant communities

The influence of habitat patchiness and unpalatable plants on the search path of the plains pocket gopher ( Geomys bursarius ) was examined in outdoor enclosures. Separate experiments were used to evaluate how individual animals explored (by tunnel excavation) enclosures free of plants except for one or more dense patches of a palatable plant ( Daucus carota ), a dense patch of an unpalatable species ( Pastinaca sativa ) containing a few palatable plants ( D. carota ), or a relatively sparse mixture of palatable ( D. carota ) and unpalatable ( Raphanus sativus ) species. Only two of eight individuals tested showed the predicted pattern of concentrating search effort in patches of palatable plants. The maintenance of relatively high levels of effort in less profitable sites may reflect the security afforded food resources by the solitary social system and fossorial lifestyle of G. bursarius . Unpalatable plants repelled animals under some conditions, but search paths in the sparsely planted mixed-species treatment suggest animals can use visual or other cues to orient excavations. Evidence supporting area-restricted search was weak. More information about the use of visual cues by G. bursarius and the influence of experience on individual search mode is needed for refining current models of foraging behavior in this species.

Journal of Mammalogy↗
USGS1988

Tunnel-construction methods and foraging path of a fossorial herbivore, Geomys bursarius

The fossorial rodent Geomys bursarius excavates tunnels to find and gain access to belowground plant parts. This is a study of how the foraging path of this animal, as denoted by feeding-tunnel systems constructed within experimental gardens, reflects both adaptive behavior and constraints associated with the fossorial lifestyle. The principal method of tunnel construction involves the end-to-end linking of short, linear segments whose directionalities are bimodal, but symmetrically distributed about 0°. The sequence of construction of left- and right-directed segments is random, and segments tend to be equal in length. The resulting tunnel advances, zigzag-fashion, along a single heading. This linearity, and the tendency for branches to be orthogonal to the originating tunnel, are consistent with the search path predicted for a "harvesting animal" (Pyke, 1978) from optimal-foraging theory. A suite of physical and physiological constraints on the burrowing process, however, may be responsible for this geometric pattern. That is, by excavating in the most energy-efficient manner, G. bursarius automatically creates the basic components to an optimal-search path. The general search pattern was not influenced by habitat quality (plant density). Branch origins are located more often than expected at plants, demonstrating area-restricted search, a tactic commonly noted in aboveground foragers. The potential trade-offs between construction methods that minimize energy cost and those that minimize vulnerability to predators are discussed.

Journal of Mammalogy↗
USGS1987

Geomys bursars burrowing patterns: influence of season and food patch structure

The relationship between belowground food resources and the pattern and pace of soil excavation by Geomys bursarius, the plains pocket gopher, was assessed during spring and autumn using replicated 18 x 18 m enclosures containing uniform arrays of food plants (Daucus carota) at spacings assumed to result in burrowing being energetically profitable (25 and 50 cm) or unprofitable (100 cm and empty). Soil excavation rate, measured in terms of either daily additions to tunnel length or volume, or the maximum volume excavated during a 3—d interval, varied greatly among individuals. No significant effect due to season or density of belowground plant biomass was detected when burrowing was profitable. Individuals readily initiated aboveground travel in unprofitable treatments. Soil bulk density was negatively related and animal body mass positively related to excavation rate. Individuals deposited from 41 to 87% of excavated soil on the ground surface; the remainder was used to backfill previously created tunnels or chambers. Plant size, but not plant spacing, affected the ratio of the volumes deposited aboveground and belowground. There was no evidence that animals in enclosures disturbed soil in a manner quantitatively or qualitatively different from free—ranging adults. The large proportions and absolute quantities (up to 30 L/d) of soil involved suggest that backfilling may affect ecosystem structure and functioning as much as surface mound—building.

Ecology↗
USGS1987

Below-ground herbivory in natural communities: a review emphasizing fossorial animals

Roots, bulbs, corms, and other below-ground organs are almost universally present in communities containing vascular plants. A large and taxonomically diverse group of herbivores uses these below-ground plant parts as its sole or primary source of food. Important within this group are plant-parasitic nematodes and several fossorial taxa that affect plants through their soil-disturbing activities as well as by consuming plant tissue. The fossorial taxa are probably best exemplified by fossorial rodents, which are distributed on all continents except Australia. All other fossorial herbivores are insects. The impact of below-groud herbivory on individual plant fitness will depend upon the extent to which, and under what circumstances, the consumption of plant tissue disrupts one or more of the six functions of below-ground plant parts. Below-ground herbivory is probably more often chronic than acute. Indirect evidence suggests that plants have responded evolutionarily to herbivory by enhancing the functional capacities of below-ground organs, thus developing a degree of tolerance, and by producing compounds that serve as feeding deterrents. Many plant species respond to the removal of root tissues by increasing the growth rate of the remaining roots and initiating new roots. Soil movement and mixing by fossorial rodents infleuce the environment of other below-ground herbivores as well as that of plants and plant propagules. The relationships among the various groups of below-ground herbivores, and between below-ground herbivores and plants, are at best poorly known, yet they appear to have major roles in determining the structure and regulating the functioning of natural communities.

The Quarterly Review of Biology↗
USGS1986

An assessment of ground-nest depredation in a catastrophically disturbed region, Mount St. Helens, Washington

The explosive eruption of the Mount St. Helens volcano on 18 May 1980 severely affected a large ar- ray of plant and animal populations (Edwards and Schwartz 1981, MacMahon 1982, Wissmar et al. 1982) over a vast area (>600 kM2) (Fig. 1). Volcanic eruptions are relatively common agents of large-scale biotic disturbance, yet few studies have addressed either short- or long-term effects on avian populations (see Hayward et al. 1982 for entry on pre-1980 literature). We present data gathered during 1980- 1984 on relative abundances of birds in disturbed areas near Mount St. Helens. These data indicate that a ground-nesting species was numerically dominant in the early posteruption avifauna. We also test the null hypothesis that predation rates on ground nests were unaltered by the eruption. We assumed that the breeding abundance of ground-nesting species is affected significantly by nesting success in previous years (Duebbert and Lokemoen 1980) and speculated whether dramatic changes in ground-nest predation rate might have occurred as a result of the eruption.

Washington↗
USGS1985

Nutritional ecology of a fossorial herbivore: protein N and energy value of winter caches made by the northern pocket gopher, Thomomys talpoides

Northern pocket gophers ( Thomomys talpoides ) are fossorial herbivores that excavate belowground plant parts for food. In subalpine areas during autumn and winter, pocket gophers hoard plant parts in caches placed in or under snow. We examined the size and composition of 17 nival caches and tested the hypotheses that (i) cached food can provide complete energy and protein N sustenance during typical periods when burrowing is precluded by soil conditions, and (ii) cached food is a random sample of items encountered by burrowing gophers during tunnel excavation. Our data indicate that caches provide substantially more energy than protein in terms of a pocket gopher's daily maintenance requirements. Nevertheless, quantities stored are sufficient to allow individuals to endure commonly encountered adverse environmental conditions without entering negative energy or protein balance. Analysis of stomach contents and a comparison of cache composition to availability of plant species suggests that gophers consume high-protein items as they are encountered, and store low-protein items in caches.

Canadian Journal of Zoology↗
USGS1985

The effects of catastrophic ecosystem disturbance: the residual mammals at Mount St. Helens

Individuals that survive the direct effects of community- or ecosystem-level disturbances, i.e., "residuals", can have major roles in determining the rate and pathway of subsequent secondary succession. The explosive eruption of the Mount St. Helens volcano on 19 May 1980 resulted in severe damage to a cast array of animal and plant populations (Edwards and Schwartz, 1981; MacMahon, 1982; Hayward et al., 1982). We apply the term "catastrophic" to this event because of its intensity and the large area (>600 km 2 ) over which successional processes were initiated. We present here the results of surveys for mammals, particularly small mammals (excluding bats), conducted in the Mount St. Helens region during the 40 months following the eruption. Our purpose was to elucidate any patterns in species representation that might exist along a gradient of disturbance "intensity", and thus document which species could potentially influence early plant successional patterns there. We infer whether individuals captured were more likely to have been residuals (or their descendants), or immigrants from areas less affected by the eruption, from consideration of the time span between the eruption and the capture date, the trapping location, and life history data. We also make inferences concerning the animal-environment relationships that led to our survey results, and thereby address the question of the likelihood of other types of disturbance, either natural or anthropogenic, producing similar results. Data concerning survival of Thomomys talpoides , the northern pocket gopher, have been presented elsewhere (Andersen, 1982). Initial results from our studies of the relationships among residual small mammals and plant population dynamics are detailed in MacMahon and Warner (1984), Allen et al. (1984) and Andersen and MacMahon (in press).

Washington↗
USGS1985

Snowpack and variation in reproductive ecology of a montane ground-nesting passerine, Junco hyemalis

Effects of snow depth and rate of snowmelt on reproduction of a montane ground-nesting passerine were examined in a 5-year study of Dark-eyed Juncos Junco hyemalis in northern Utah, USA. Distribution of clucth sizes differed significantly among years. Although most clutches contained four eggs, 3-egg clutches, due primarily to second nestings, were more common during a year of early snowmelt and 5-egg clutches were most common during two years of late snowmelt. Average clutch size was lowest in an early snowmelt year and average clutch size and date at which meadows became snow-free were significantly positively correlated. Average hatching date of 4-egg clutches was also significantly positively correlated with date at which meadows became snow-free demonstrating that most birds tracked the pattern of snowmelt. Early snowmelt may allow more pairs to attempt second nesting, but late-lying snow causes breeding to be delayed, allowing time for only one nesting attempt. During this delay, female juncos continue to feed and some may gain enough reserves to produce larger clutches, accounting for the increase in average clutch size in years of late snowmelt. Three female juncos examined in June 1982, a period of late snowmelt, had significantly more lipid reserves than did six males collected at the same time, suggesting that females are not physiologically stressed while awaiting snowmelt. By tracking snowmelt patterns, juncos synchronize production of young with peak summer insect abundance and potentially decrease risk of predation. Snow depth and rate of snowmelt are thus proximate environmental factors that may influence the reproductive ecology of ground-nesting passerines.

Utah↗