Samuel R. Rushforth

Effects of long-term grazing on cryptogam crust cover in Navajo National Monument, Arizona.

The effects of long-term grazing (40 years) on cryptogamic crusts of Navajo National Monument were investigated. Both vascular and nonvascular communities were heavily impacted with the cryptogamic community showing the greatest reduction in cover. Lichens and mosses were the most damaged, while the algae were much more tolerant. Individual cryptogamspeeies were affected in similar patterns with all identifuble species showing reduced cover. Vascuhr plant species were also affected with grassesshowing the greatest reduction under grazing pressure. Throughout desert systems of western North America there is scant ground cover and often extensive open areas between the plants. In such open areas, soils are exposed to powerful erosive impacts. When soils are unprotected, erosion can be extensive and soil losses can be great. Of primary importance in the protection of desert soils are communities of nonvascular cryptogamic plants that grow upon or immediately beneath the soil surface. When well established and undisturbed such plants form a crust which plays an important role in soil stabilization (Fletcher and Martin 1948; Kleiner and Harper 1972, 1977; Loope and Gifford 1972; Anderson et al. 1982a, 1982b). Algae are the primary components of these crusts but they are often accompanied by lichens and mosses (Anderson and Rushforth 1977, Kleiner and Harper 1972). Algae are the most effective in binding the soil particles (Anantani and Marathe 1974, Anderson and Rushforth 1976). Where cryptogam crusts are well developed the soil surface is almost always highly stable. Research has been done on several aspects of the biology of soil crusts and cryptogamic communities. Ecological relationships have been studied by Anderson et al. (1982a) and Anderson et al. (1982b). Species composition and taxonomic relationships of crusts were studied by Anderson and Rushforth (1976). The role of such crusts in nitrogen fixation was studied by Rychert and Skujins (1974) and their effects on infiltrationand sedimentation by Loope and Gifford (1972). However, much is yet to be learned about the role of these crusts in desert ecosystems. The Navajo National Monument boundary (fenceline) provided an excellent opportunity to evaluate the effects of grazing on the cryptogamic soil crusts of the pinyon-juniper zone in northeastern Arizona. The objective of this study was to evaluate the effects of long-term grazing (40 years) on the cryptogamic soil cover of the pinyon-juniper zone in northern Arizona (Navajo National Monument).

Algal communities associated with different alpine stream types

We investigated major physical-chemical characteristics and benthic algae of different alpine lotic systems comprising streams and lake outlets of rhithral and kryal origin over an annual cycle. We also evaluated the structure of the algal communities and its relation to environmental characteristics for the different stream types. Algal communities were generally dominated by diatoms, Cyanophyta, and Hydrurus foetidus (Chrysophyceae). Community structure was similar among alpine streams and lake outlets, but more algal taxa occurred in lake outlets (rhithral and kryal) than in kryal streams. Although algae were identified mainly to genera, distinct patterns in community structure were evident. A major environmental determinant of the algal community among stream types was the presence of a glacier and resulting seasonal differences in flow, temperature, and turbidity. An upstream lake was a secondary determinant in buffering seasonal fluctuations in environmental conditions thus leading to greater stability. Algal communities, consequently, were more diverse and less seasonally variable at lake outlets. The diatom genera Amphora, Denticula, Fragilaria, Gomphonema, Nitzschia, and Synedra and the blue-green algae Oscillatoria and Phormidium were characteristic of lake outlets, whereas Chamaesiphon (blue-green) and Hydrurus foetidus were indicative of kryal sites.

Effects of Burning on the Algal Communities of a High Desert Soil near Wallsburg, Utah.

A recently burned area near Wallsburg, Wasatch County, Utah, was sampled to determine if differences existed between the soil algal flora of a burned area and that of an adjacent ecologically similar unburned area. Soil samples were cultured and analyzed to determine presence and relative frequency of living algae. The frequency of visible algal patches present after eight days of culturing was much higher in the unburned soil samples than in the burned samples. Percent relative frequencies and absolute densities of diatoms were also determined. Diatom floras of the two areas were very similar. However, the absolute densities of diatoms were significantly greater in the unburned samples. The major effect of the burn was to decrease algal biomass, although the flora remained remarkably similar. Edaphic algal communities have been studied throughout the years in many parts of the world. Landmark studies include those of Bischoff and Bold (1963), Bristol-Roach (1926, 1927), Fritsch and John (1942), Moore and Carter (1926), Moore and Karrer (1919), Lowe and Moyse (1935) and Shields and Durrell (1964). Novichkova-Ivanova (1968) reviewed soil algal studies conducted in the U.S.S.R. Algal soil communities in arid regions of the world have received attention from several workers (Ali and Sandhu 1972; Anantani and Marathe 1947a, 1974b; Cameron 1964; Chantanachat and Bold 1962; Deason and Bold 1960; Durrell 1959; Fletcher and Martin 1948; Forest and Weston 1966). Edaphic diatom communities have likewise been studied (Bristol 1920; Hayek and Hulbary 1956; Lund 1945, 1946; Petersen 1915, 1935; Reimer 1970). All of these studies deal with communities found in mesic soils and diatom studies of arid regions of the world are rare. The populations of playas and dry lakes of western North American have been studied by St. Clair and Rushforth (1978) and Van Landingham (1966). However, though such sites experience long periods of dryness and high temperature, they are occasionally flooded and thus differ from true desert soils. Anderson and Rushforth (1976) examined desert soils crusts throughout Utah and discussed the taxonomy and distribution of the diatoms as well as other cryptogamic crust components. In a more recent study conducted in Navajo National Monument, Kayenta County, Arizona (Johansen et al. in press) we found that uncrusted soils, though poor in green and blue-green algae, support a viable and occasionally rather diverse diatom community. We had several objectives in mind at the outset of the present study. First, we wanted to learn more about algal communities in arid soils of western North America. Second, we wanted to determine absolute densities of diatoms in these soils. And third, we wished to discover if differences existed between the algal populations of recently burned soils and those of adjacent unburned soils. This could be of particular interest since burning is a commonly used technique for the management of some rangeland ecosystems of western North America. Authors are with the Department of Botany and Range Science, Brigham Young University, Provo, Utah 84602. Site Description The site of the present study was aproximately 5 km northwest of Wallsburg, Wasatch County, Utah. This region of Utah is subject to periodic burning from unplanned range fires. The last fire occurred in the summer of 1976. It was ignited by lightning and burned about 1,210 hectares over a 2-day period. Sampling sites were selected in an area near U.S. Highway 189 overlooking Deer Creek Reservoir. Soils of the study site are sandy with varying amounts of silt. They are ultimately derived from the Oquirrh Formation, which has locally prominent intercalated limestone and sandstone beds with minor shales and siltstones. Average annual precipitation is approximately 30 cm. Precipitation occurs primarily as winter snow and summer thunderstorms, although gentle spring rains are not uncommon. Vegetation of the study area is primarily comprised of shrubs and grasses. Sagebrush (Artemisia tridentata) and serviceberry (Amelanchier alnifolia) are the most abundant shrubs and are dominant in the unburned regions. Cheatgrass (Bromus tectorum) and several wheatgrasses (Agropyron species) are the most abundant grass species and are found primarily in the burned area. Shrubs in the study area provide winter browse for mule deer while domestic grazers more commonly utilize the grasses. Visible soil cryptogamic communities are rare throughout the study area and the absence of such communities is likely due to grazing (Anderson et al. 1982, Loope and Gifford 1972). However, even though crusts are absent, algae probably still bind soil particles and thus function to protect against erosion (Durrell and Shields 1961). Materials and Methods Fifteen paired stands were established at 30-m intervals along a 400-m section of the fireline. Each paired stand consisted of 2-m square quadrats, one in the burned area and one in the unburned area, each placed 30 m away from and perpendicular to the fireline. The slope and exposure of both members of each stand pair were required to be approximately the same. A 15-20 g soil sample, 2 cm deep, was taken randomly within each quadrat. Frequencies of visible cryptogams were recorded. Upon returning to the laboratory 10 g of each soil sample were moistened in 10 ml of deionized water in sterilized petri dishes. After 4 days an additional 10 ml of water were added. After 8 days under continuous light, the samples were examined. Frequency of visible algal patches was determined by placing a petri dish lid which had been marked into quarters over the culture and recording the number of quarters containing algae. A subsample from each quarter was mounted on a microscope slide, the algal patches being sampled when present. Frequency of living algal species was determined by observing 20 microscope fields and recording the number of times each species was seen. Permanent diatom slides were prepared by boiling the remaining 10 g of soil from each sample in concentrated nitric acid. After 598 JOURNAL OF RANGE MANAGEMENT 35(5), September 1982 This content downloaded from 207.46.13.75 on Sat, 03 Sep 2016 04:59:19 UTC All use subject to http://about.jstor.org/terms rinsing, diatoms were mounted in Naphrax diatom mountant. Through the use of quantitative dilutions, all diatom slides contained the equivalent of 2 mg of soil. Diatoms were identified and quantified by studying transects across the slide until at least 50 frustules had been observed. In most cases the completion of the transect made it necessary to count more than 50 diatoms and consequently a total of more than 2000 frustules was counted during this study. Using the Spearman rank correlation coefficient (Siegel 1956), the frequencies of diatoms along each transect were compared with frequency of the same species along other transects taken at that sample location to determine uniformity among subsamples. By using this test, we found that our sampling methods were adequate to describe qualitatively the diatom communities. The Spearman rank correlation coefficient (Siegel 1956) was also used to determine the similarity of living algal floras of samples from burned and unburned areas. Similarity of the diatom floras was calculated using Ruzickas (1958) similarity index. Shannon-Wiener diversity indices (Krebs 1978) were calculated for each diatom sample. Results and Discussion A total of 27 algal taxa were observed during this study. Nineteen of these were diatoms (Bacillariophyta), 7 were bluegreen algae (Cyanophyta), I was a green alga (Chlorophyta), and I was a Euglena (Euglenophyta). Fourteen taxa were observed as living specimens in the fresh mounts. Algal biomass in both burned and unburned soils was dominated by blue-green algae, primarily Microcoleus vaginatus. This alga and Phormidium tenue were the chief components of the algal patches observed after moistening. Hantzschia amphioxys was the most abundant diatom. It occurred together with other diatoms in the matrix of the blue-green algal patches as well as in the soil between patches. Percent frequencies of the algae observed in the fresh mounts are given in Table 1. The diatom community was dominated by Hantzschia amphioxys, Navicula mutica var. cohnii and Pinnularia borealis, in that order. Navicula mutica and Stauroneis kriegeri were also important. These taxa are characteristic of arid soils throughout Utah and Arizona (Anderson and Rushforth 1976, Johansen et al. in press). Average percent relative densities as well as importance values equal to frequency times absolute density (Warner and Harper 1972) are presented in Table 2. Statistical analyses of the data proved fruitful. Frequencies of algal patches in the samples from the unburned and burned areas were compared using a two-tailed t-test. They were significantly different at the a = .05 level. The unburned area had higher Table 1. Percent relative frequencies of the algae observed in fresh mounts made from soil collected from burned and unburned soils. Species Unburned Burned Cyanophyta Chroococcus rufescens (Kuetz.) Naegeli .7 .6 Chroococcus turgidus (Kuetz.) Naegeli .2 Microcoleus vaginatus (Vauch.) Gomont 50.1 34.7 Oscillatoria angusta Koppe .9 1.3 Oscillatoria boryana Bory .6 Phormidium tenue (Menegh.) Gomont 10.2 4.5 Chlorophyta Unknown coccoid green algae 4.6 Euglenophyta Euglena gracilis Klebs 2.9 Bacillariophyta Achnanthes species .2 .3 Hantzschia amphioxys (Ehr.) Grunow 28.0 49.7 Navicula mutica Kuetzing 2.2 1.3 Navicula mutica var. cohnii (Hilse) Grunow .2 Pinnularia borealis Ehrenberg 1.1 1.6 Stauroneis kriegeri Patrick .9 2.9 Table 2. Average percent relative densities and importance values of diatoms encountered in the study: UB = Unburned; B = Burned Area. Average percent Importance relative dens. values

The effects of dissolved heavy metals on attached diatoms in the Uintah Basin of Utah, U.S.A.

The relationships of diatom species to dissolved heavy metals in the streams of the Uintah Basin of Utah were studied through four seasons of 1977–1978. Niche center gradient analysis, cluster analysis and correlation analysis were performed.Achnanthes minutissima, Cyclotella meneghiniana, Cymbella minuta, Gomphonema parvulum, Navicula secreta var.apiculata, Nitzschia frustulum, Nitzschia frustulum var.perminuta, Nitzschia frustulum var.perpusilla, Nitzschia palea, andSynedra ulna appear to be indicator species of high or low heavy metal concentrations. Several other species also showed meaningful relationships to high or low heavy metal concentrations.

Algal response to a thermal effluent: study of a power station on the Provo River, Utah, USA

The effect of a thermal effluent on the attached algae of the Provo River, Utah, USA, was studied from 1975 to 1977. Data for macroscopic and microscopic algae were collected and analyzed. Diatoms, Cladophora glomerata, and Hydrurus foetidus dominated the flora. The thermal effluent significantly affected the algal flora in a section of river 100 to 135 meters long immediately below the discharge point. Cladophora growth was increased and Hydrurus was absent in this area. In addition, diatom production was often higher and diversity lower than in the rest of the river. Community structure was unique from all other adjacent areas. Small temperature increases which occured as effluent and river waters mixed farther downstream were apparently not as important to the algal flora as other environmental factors.

DIATOM ASSEMBLAGES OF STREAMS INFLUENCED BY WILDFIRE1

The Greater Yellowstone Area ecosystem experienced major wildfires in 1988, resulting in a substantial number of catchments being burned. We studied diatom assemblage structure at 14 sites over 5 years in catchments ranging from 0 to over 90% burned. Coefficients of variation for selected physical measures provided a good assessment of the degree of disturbance experienced by the various sites and correlated highly with percentage of catchment burned. Principal components analysis quantitatively estimated the degree of temporal change in diatom assemblages at a site. The more extensively burned catchments showed the greatest amount of structural change in diatom taxa among years. Navicula permitis Hust. and Nitzschia inconspicua Grun. were predominant in the heavily disturbed systems, whereas Achnanthes minutissima Kuetz., A. lanceolata (Breb.) Grun., Rhoicosphenia curvata (Kuetz.) Grun. ex Rabh., and Diatoma hiemale var. mesodon (Ehr.) Grun. were common in less disturbed streams. The results demonstrate that recovery trajectories of lotic diatom assemblages following major landscape‐scale disturbances are a function of disturbance intensity resulting from differences in catchment characteristics.

Seasonal Colonization Dynamics of Macroinvertebrates in an Idaho Stream

Field experiments were conducted to examine effects of macroinvertebrate removal frequency on community development on bricks with similar food resource levels (chlorophyll a levels and diatom composition). The experiments were conducted during summer and fall to examine effects of seasonal differences in animal abundances. For each experiment macroinvertebrates were removed from groups of bricks at intervals of 3, 9, or 27 days or were not removed for 54 days. Insect removal frequency had no significant effect on macroinvertebrate abundance in summer when overall animal abundance and richness were low. During fall, when overall abundance was 3× greater, there were significantly fewer animals on bricks with a 3-day removal interval. Baetis tricaudatus represented 65% of all invertebrates in summer, but declined in relative abundance to about 25% in fall. In contrast, the Chironomidae increased from 6% of the assemblage in summer to comprise over 30% in fall, suggesting that differences in the composition of dispersal modes influenced the patterns of colonization observed. We suggest that an algal resource is important in the colonization dynamics of macroinvertebrates by acting as a food source and/or habitat templet. Our experiments illustrate that macroinvertebrate colonization and community development on rocks is influenced by seasonal changes in animal density and composition.

Diatom species composition along a thermal gradient in the Portneuf River, Idaho, USA

Glass microscope slides were placed to span a range of temperatures in and around a warm spring in the Portneuf River, Idaho in the winter of 1987. Diatoms were allowed to colonize these slides for 8 weeks. Analysis of slides revealed that maximum species diversity and species richness were reached between 25° and 30 °C. Analysis also showed that certain diatom taxa were stenothermal, showing distinct preferences for various temperatures while others were eurythermal.

Algal communities of springs and streams in the Mt. St. Helens region, Washington, U.S.A. following the may 1980 eruption

Mt. St. Helens, a volcanic peak in the Cascade Range in southern Washington erupted violently on May 18, 1980, causing enormous damage to both terrestrial and aquatic ecosystems. The initial explosion evaporated, scoured or buried all springs and streams in the blast impact area. Ash fall and erosion from defoliated hillsides subsequently filled most of the lotic habitats with organic debris and volcanic ash. Recolonization of springs and streams by algae occurred quickly in areas where erosion through the ash progressed down to bedrock. Within 15 months or less of the eruption, algal communities were established throughout the blast impact area. However, as a result of the initial and continued disturbance these communities remained in an early successional stage. Floral assemblages were highly variable except that they were composed mostly of diatoms, with Achnanthes minutissima dominating most lotic sites. Springs showed the most rapid development toward stable floras.

Biotic Adjustments to Changing Salinities in the Great Salt Lake, Utah, USA

The salinity of the Great Salt Lake, Utah has changed greatly over the past 23 years. The north arm of the lake has increased in salinity and decreased in overall biological diversity, whereas the south arm has decreased in salinity and increased markedly in biological diversity.