Tree growth and regeneration response to climate and stream fow in a species-rich southwestern riparian forest

We studied the influence of climate variables, stream flow, and topography on regeneration and growth of several riparian tree species ( Acer negundo, Alnus oblongifolia, Fraxinus velutina, Juglans major, Platanus wrightii, Populus fremontii, Salix spp.) at an unregulated perennial stream, West Clear Creek, in central Arizona. A pulse of seedling regeneration occurred for Alnus, Fraxinus, Platanus, Populus , and Salix in 1995 and 1996 following high winter and spring surface flows in 1993 and high spring surface flow in 1995. In contrast, little regeneration occurred for Acer and Juglans under these conditions. Most seedlings occurred at the active channel topographic location, and few seedlings occurred at abandoned channel, gravel-boulder bar, and bench locations. Relationships between environmental variables and annual radial stem growth varied among species and between constrained and unconstrained reaches. High spring or winter surface flows were negatively related to growth of Acer, Alnus, and Platanus , whereas high spring surface flow was positively related to growth of Fraxinus . Positive relationships between precipitation and growth occurred only for Fraxinus and Juglans , suggesting greater use of surface soil water by these species. Annual radial growth was high for Platanus and Alnus, medium for Acer and Fraxinus, and low for Juglans . Overall, the tree species in our study responded individually, rather than collectively, in regeneration and growth to changes in stream flow and climatic variables.     

Variability among five riparian cottonwood ( Populus fremontii Wats.) populations: an examination of size, density, and spatial distribution

Various abiotic and biotic factors are known to affect tree size, including age, genetics, and environment. Knowledge of size variation within natural riparian tree populations has both ecological and restorative importance. We determined tree sizes, basal area densities, and spatial distributions of 5 Populus fremontii Wats. populations within the Rio Grande watershed in New Mexico. At each site 10 randomly spaced plots, perpendicular to the river and extending from the river to the end of the forest, were established. Diameter at breast height (DBH) and distance to the river were determined for 1803 trees within the 5 populations, and stand cover (measured as basal area [BA] per hectare) was determined for each population. Significant variation in tree size and basal area density existed among sites. Mean DBH per site ranged from 11.7 to 58.4 cm and differed significantly ( P P 2 ha -1 . Spatial distribution of trees in relation to the river also differed among sites. Mean distance from the river ranged from 50 to 353 m and differed significantly ( P P. fremontii populations may be influenced by differences in water availability across a site; trees farthest from water sources may experience greater water stress and, therefore, growth limitation. Increasing BA cover with increasing tree size indicated no real thinning of mature trees within a population. Recruitment and establishment of cottonwood seedlings and saplings was evident only at sites with newly formed floodplains. For these 5 populations tree size appeared to be affected by environmental factors.     

Seed production and seedling establishment of a Southwest riparian tree, Arizona walnut ( Juglans major )

A four-year study of five populations has revealed influences on seed production and seedling establishment of the Southwest riparian tree Juglans major . Germination is abundant after production of large seed crops (masts), but masts are produced infrequently. Within years, germination is stimulated by summer rains, enabling seedlings to establish on riparian terraces as well as streambanks. Traits such as capacity for dormancy during summer drought allow some seedlings to survive on terraces, but abundant rainfall is essential for high rates of seedling success. Ranges of moisture tolerance vary among seeds collected from different populations, suggesting that ecotypes may exist between riparian sites with dissimilar moisture regimes. Population-based differences are associated, in part, with differences in seed size.     

The successional status of Cupressus arizonica

Several investigations (size-class analysis, age-determination inquiries, and germination tests) suggest that Cupressus arizonica of southeastern Arizona is a pioneer species. The tree requires disturbance to remove or reduce soil litter, which otherwise inhibits the reproduction of the species. Reduction of light intensity caused by canopy closure appears to be less important than litter accumulation in restricting C. arizonica reproduction. Following disturbance, successful establishment of seedlings may occur over an extended period (50 to 100 years), as litter gradually accumulates. The absence of C. arizonica seedlings in present populations suggest that fire suppression policies on federal lands where C. arizonica occurs have altered fire frequency, and consequently have fostered a short-term reduction in C. arizonica establishment. Only in floodplain environments, where flooding disturbs the soil surface, has much reproduction occurred in recent years. The long-term population pattern of C. arizonica appears stable, due to the great longevity of the species.     

Establishment, growth, and early survival of woody riparian apecies at a Colorado gravel pit

Presence of a wetted edge during the period of seedfall was an effective predictor of suitable establishment (defined as germination and survival to the 1st autumn) locations for Populus deltoides subsp. monilifera, Salix amygdaloides, S. exigua, and Tamarix ramosissima seedlings during 3 successive years of a gravel pit revegetation project in Fort Collins, Colorado. At locations predicted to be suitable for establishment, position within the pit (possibly reflecting additional moisture provided by seepage) was a significant factor in determining whether establishment actually occurred. Cover of herbaceous species, which became established at the same time as, or after, woody seedlings, was positively related to probability of establishment for 8 of 11 species-year combinations, probably reflecting more favorable moisture conditions at certain locations. Herbaceous cover also was positively related to seedling height at the end of the 1st summer of growth for 9 of 11 species-year combinations. Neither establishment nor 1st-summer growth was consistently related to overall decline in the water table as estimated by the drop in surface-water level during the growing season. Flooding in the 1st spring after establishment was negatively related to subsequent survival for 5 of 8 species-year combinations. The 4 species established at different elevations in the pit, depending on location of the wetted edge during the period of seedfall, and there was no evidence that differential mortality subsequently altered their distribution along the elevation gradient. However, the primary objective in this study was to restore native woody species, and we attempted to maintain conditions conducive to meeting this objective. Differential postestablishment mortality may be more important in structuring the riparian community in more rigorous riverine environments.     

A 4000-year record of woodland vegetation from Wind River Canyon, central Wyoming

Plant macrofossil analyses of 16 radiocarbon-dated woodrat middens spanning the past 4000 years from the Wind River Canyon region in central Wyoming provide information concerning late Holocene development of juniper woodlands. The study sites are currently dominated by Juniperus osteosperma , with J. scopulorum present locally. Woodlands in the region were dominated by J. scopulorum from ca 4000 yr BP until at least 2800 yr BP. Juniperus osteosperma invaded and expanded before 2000 yr BP. This expansion fits a regional pattern of J. osteosperma colonization and expansion in north central Wyoming during a relatively dry period between 2800 and 1000 yr BP. At the time the Wind River Canyon region was colonized by J. osteosperma , the species had populations 50-100 km to both the north and south. Long-distance seed dispersal was required for establishment in the study area. Genetic studies are necessary to identify source populations and regions.     

Spatial relationships among young Cercogarpus ledifolius (curlleaf mountain mahogany)

This study analyzed spatial location patterns Cercocarpus ledifolius Nutt. (cutleaf mountain mahogany) plants, classified as current-year seedling, established seedling, juvenile, and immature individuals, at a central Nevada study site. Most current-year seedlings were located in mahogany stands in which large, mature individuals had the greatest abundance. These stands had greater litter cover and a thicker layer of litter than areas with few current-year seedlings. Most established young Cercocarpus were located in adjacent Artemisia tridentata spp. vaseyana (mountain big sagebrush) communities, or in frequent canopy gaps between relatively few large, mature Cercocarpus . We discuss potential roles of plant litter, root growth characteristics, nurse plants, and herbivory in the establishment and renewal of Cercocarpus communities.     

Experimental manipulations of precipitation seasonality: effects on oak ( Quercus ) seedling demography and physiology

Predicted changes in regional precipitation patterns and soil moisture caused by anthropogenic trace gas emissions may affect the distribution and abundance of woody plants in arid and semiarid regions. To test the response of woody plants to potential changes in precipitation regimes, we manipulated summer and winter precipitation on plots that contained seedlings of Quercus emoryi Torr. (Emory oak), the dominant tree in oak savannas of the southwestern United States. Throughout the growing season, we monitored seedling survival and physiology (predawn leaf water potential, midday instantaneous gas exchange, and leaf carbon isotope discrimination). Seedling survival and physiological performance differed little between treatments, which embodied 50% changes to quantities of summer and winter precipitation, and encompassed a continuum of precipitation from 359 mm · year -1 to 846 mm · year -1 . However, survival and physiological performance of seedlings were negatively impacted by seasonal environmental conditions common to all treatments, especially during the annual pre-'monsoon' drought. Seedling predawn leaf water potentials, net CO 2 assimilation, and stomatal conductance indicate that growing conditions for Q. emoryi seedlings at this site are generally restricted to periods with adequate soil moisture (i.e., April and August). Results contrast with an assumption implicit to the ""two-layer"" soil water resource partitioning hypothesis that woody plants in all life history stages are more dependent upon winter than summer precipitation. In fact, summer precipitation appears more important than winter precipitation for Q. emoryi seedling recruitment and growth.     

Seasonal abundance and life cycle of Archaeomysis articulata (Crustacea: Mysidacea) on a sandy beach of western Hokkaido,Japan

Abundance and life cycle of the sandy beach mysid Archaeomysis articulata Hanamura were investigated based on seasonal collections over 2 years in the surf-swept intertidal zone of an open sandy beach in Ishikari Bay, western Hokkaido, Japan. The number of mysids in the intertidal zone increased from winter to spring, reaching its maximum in summer to autumn (average >2500 ind. m^-2), and decreased considerably towards the end of the year. The abundance was maintained at a minimal level (<200 ind. m^-2) throughout the winter. The breeding season was March to November, during which the liberation of young was most intensive from late April to mid-October. Three alternate generations, including overwintering, spring and summer generations, were suggested from field observations. Archaeomysis articulata is primarily iteroparous; only a restricted number of breeding females could produce more than two broods. The life span was estimated to be 7–9 months for the overwintering generation and 2.5–3.5 months for the spring–summer generations. The sex ratio fluctuated at samplings, with a tendency toward female dominance (overall mean=54%). The number of embryos carried by a single female ranged from 16 to 94, tending to increase with increasing size of females. The size of egg-like embryos varied seasonally from 0.45 to 0.54mm, being largest in spring and smallest in summer, with no correlation to the length of females; water temperature is considered an important factor in regulating the size of eggs. The embryonic development time was estimated to be 1.5 months for the spring generation (water temperature 5–10°C), and much shorter than this for the summer and overwintering generations. The mortality rate during embryonic development was estimated to be 7–18%.     

Exceptional fish yield in a mid-elevation Utah trout reservoir: effects of angling regulations

We used creel surveys to evaluate how a change from a 6-mon to a year-round fishing season affected the sport fish harvest in East Canyon Reservoir (Utah), a 277-ha mesoeutrophic system. Under the year-round season, fishing effort was 840 angler-h . ha -1. yr -1 , and 360 trout ha -1 were captured. Catch rates were proportional to estimated trout densities in the reservoir, ranging from 1.06 during the winter ice fishery, to 0.18 fish angler -1. h -1 in July. Ninety-nine percent of fish harvested were rainbow trout ( Oncorhynchus myskiss ). Thirty-two percent of the 300,000 75-mm fingerling trout stocked annually were captured by anglers within 2.5 yr, but return rates varied with the strain and/or size of trout stocked. Annual fish yield was 102 kg/ha, among the highest yet reported for a temperate zone, lacustrine system. Extending fishing from a 6-mon season to year-round increased the number of fish captured and provided almost twice as many hours of recreational fishing in the reservoir. The harvest period was changed from traditional spring-summer months to primarily a winter-spring fishery because relatively few trout survived for more than 6 mon after reaching harvestable size. Although salmonid production in East Canyon Reservoir is very high, the fishery is in a precarious state because high primary productivity driven, in part, by cultural cutrophication, makes water quality suboptimal during midsummer.     

Effects of wildfire and postfire floods on stonefly detritivores of the Pajarito Plateau, New Mexico

Wildfires alter the quantity and quality of allochthonous detritus in streams by burning riparian vegetation and through flushing during postfire floods. As such, fire disturbance may negatively affect detritivorous insects that consume coarse organic matter. We assessed how 2 crown fires impacted stonefly detritivores in streams of the Pajarito Plateau, New Mexico. We documented stonefly populations before and after the fires and postfire floods, and compared recovery trajectories among unburned, lightly burned, and severely burned reaches. We also conducted experiments to assess burned detritus as a food resource for Pteronarcella badia Hagen. Specifically, we characterized microbial conditioning, nutrient content, and breakdown rates of burned and unburned deciduous leaves and pine needles. We compared colonization of P. badia in field-placed leaf packs and growth of P. badia in a microcosm experiment on burned and unburned treatments. Detritivorous stoneflies in Plateau streams survived wildfire, but were extirpated from burned reaches after severe postfire floods in both Capulin and Guaje canyon. In Guaje Canyon, Amphinemura banksi Baumann and Gaufin was more resilient to flood disturbance than P. badia and recolonized soon after floods abated, whereas recolonization of A. banksi was delayed in Capulin Canyon. Experiments revealed that detritus quality did not explain slow recovery; despite reduced microbial conditioning and decomposition rates, P. badia colonized and grew well on burned detritus. Instead, postfire floods removed shredder stoneflies and their detrital resources; and traits such as body size, voltinism, and dispersal likely interacted with the postfire landscape to shape recovery trajectories in burned streams. Los incendios cambian la cantidad y calidad de la materia org&aacute;nica al&oacute;ctona en los r&iacute;os mediante la quema de la vegetaci&oacute;n ribere&ntilde;a; adem&aacute;s, las inundaciones despu&eacute;s de los incendios se llevan materia org&aacute;nica r&iacute;o abajo. Como tal, la perturbaci&oacute;n por incendio puede afectar negativamente a los insectos detrit&iacute;voros que consumen la materia org&aacute;nica gruesa. Evaluamos c&oacute;mo 2 fuegos de copas afectaron a los plec&oacute;pteros detrit&iacute;voros en arroyos del Altiplano Pajarito, NM. Documentamos las poblaciones de plec&oacute;pteros antes y despu&eacute;s de los incendios e inundaciones y comparamos las trayectorias de recuperaci&oacute;n entre &aacute;reas no quemadas, levemente quemadas y gravemente quemadas. Tambi&eacute;n llevamos a cabo experimentos para evaluar los detritos quemado como fuente alimenticia para Pteronarcella badia Hagen. Espec&iacute;ficamente, caracterizamos el acondicionamiento microbiano, el contenido de nutrientes y las tasas de descomposici&oacute;n de hojas caducifolias y hojas de pino quemadas y no quemadas. Comparamos la colonizaci&oacute;n de P. badia en paquetes de hojas colocadas en el campo, y su crecimiento en un experimento de microcosmos, en detrito quemado y no quemado. Los plec&oacute;pteros detrit&iacute;voros en los arroyos del Altiplano sobrevivieron a los incendios pero fueron extirpados de las &aacute;reas quemadas despu&eacute;s de inundaciones severas que siguieron a incendios en los ca&ntilde;ones Capulin y Guaje. En Guaje, Amphinemura banksi Baumann y Gaufin fue m&aacute;s resistente a la perturbaci&oacute;n por inundaci&oacute;n que P. badia y recoloniz&oacute; poco despu&eacute;s de que la inundaci&oacute;n cedi&oacute;, mientras que la recolonizaci&oacute;n de A. banksi tard&oacute; m&aacute;s en Capulin. Los experimentos revelaron que la calidad de los detritos no explican esta lenta recuperaci&oacute;n; a pesar del menor acondicionamiento microbiano y las tasas de descomposici&oacute;n m&aacute;s bajas, P. badia coloniz&oacute; y creci&oacute; bien en detritos quemados. Es probable que las inundaciones despu&eacute;s de los incendios se hayan llevado a los plec&oacute;pteros y a los detritos que consumen, y que los rasgos tales como el tama&ntilde;o del cuerpo, el voltinismo, y la dispersi&oacute;n hayan interactuado con el paisaje despu&eacute;s del incendio para determinar las trayectorias de recuperaci&oacute;n en arroyos quemados.     

Factors associated with wetwood intensity of Populus fremontii (Fremont cottonwood) in Arizona

Wetwood is a condition of Populus fremontii and other tree species characterized by staining and water soaking in the heartwood, bleeding from wounds and stem junctions, and leaf and branch dieback. A field survey indicated that wetwood symptoms were present in populations of Populus fremontii at all 17 riparian sites survived in Arizona. However, incidence and severity of bleeding systems varied within and among sites. Within sites, incidence and severity increased with tree size. In the smallest size class of trees (1-32 cm dbh), incidence (% of trees with wetwood bleeding symptoms) ranged among sites from 14% to 83%, and mean severity ranged from 1.1 to 2.6 (on a 5-point scale). Closer host spacing (i.e., greater density), more homogenous stand composition, finer substrate texture, and channel instability all were significantly correlated with increased expression of wetwood symptoms. Bleeding symptoms also were significantly correlated with canopy effects. As the severity of bleeding symptoms increased, so did canopy decline independent of changes in host density.     

Distribution of Brechmorhoga clubskimmers (Odonata: Libellulidae) in the Grand Canyon region, southwestern USA

We examined the distribution of Brechmorhoga mendax and B. pertinax (Libellulidae) in northern Arizona and southern Nevada. Brechmorhoga mendax occurs widely throughout the Southwest and in Arizona up to the Mogollon Rim, and up the Colorado River from the west to at least River Mile 132 (downstream from Lees Ferry, Arizona) at elevations of 110-1460 m. In Grand Canyon it occurs along small to large tributaries and on the mainstream at elevations below 650 m. The only previously reported locality for B. pertinax in the United States is in southeastern Arizona, where it was presumed to be accidental. We report B. pertinax along 5 small, perennial tributaries emanating from Redwall Formation aquifer springs on the south side of central Grand Canyon. Those springs habitats may be threatened by regional groundwater depletion. Brechmorhoga pertinax appears to be somewhat more stenotolerant in its habitat requirements than B. mendax , a finding in keeping with these differences in range. The presence of isolated populations of B. pertinax in Grand Canyon is an example of a Neotropical influence on the fauna and indicates biogeographic corridor and refuge functions of this large, deep canyon.     

Productivity, food habits, and associated variables of Barn Owls utilizing nest boxes in north central Utah

Productivity and food habits of the Barn Owl ( Tyto alba ) utilizing nest boxes in Juab, Utah, and Salt Lake counties, Utah, During 1979-1984 were examined. Average clutch size was 5.8 eggs for the 6-yr period; mean number fledged was 3.9 young per successful nest. While severe weather during the 1981-82 winter did not result in significant decrease in productivity during the 1982 breeding season, it may have resulted in a significant overproduction of female young. Barn Owls in north central Utah fed almost exclusively on mammalian species, particularly Microtus spp. Difference in clutch size between areas and years may be a response to availability as well as abundance of prey.     

Drosophila pseudoobscura (Diptera: Drosophilidae) of the Great Basin IV: a release experiment at Bryce Canyon

Some populations of Drosophila pseudoobscura in the Great Basin have very little genetic variation for third chromosome inversion gene arrangements. These populations are essentially monomorphic for the Arrowhead gene arrangement. At Bryce Canyon, Utah, individuals with other gene arrangements (Standard, Pikes Peak, and Treeline) were released and their frequencies monitored. One generation after release, the released arrangements had increased in frequency from 0.7% to almost 10%. After overwintering, the arrangement frequencies were not statistically different from the prerelease samples. The samples did demonstrate a low-level retention of the released Pikes Peak arrangement. The decline in the released arrangements was probably the result of large population size at Bryce Canyon and the bottleneck effects of overwintering. The results do not seem consistent with a model of the released arrangements having a lowered fitness.     

Along‐ and across‐shore components of the spatial distribution of the clam Tivela mactroides (Born, 1778) (Bivalvia,Veneridae)

Beach clam fisheries often provide an alternate income for traditional fishermen, but this activity is highly vulnerable to urbanization of coastal areas. Tivela mactroides is a beach clam commonly harvested in the Caribbean (Venezuela) and on the south‐eastern Brazilian coast. Only localized records on its spatial structure in size and abundance are available to support management of this clam. The present study showed that the spatial distribution in abundance and size of T. mactroides in Caraguatatuba Bay, state of São Paulo, Brazil, has both along‐ and across‐shore (intertidal and subtidal) components. The nature of this distribution should be taken into account in the design of further population or monitoring studies concerning this species. Clam density varied along‐shore, with a tendency towards higher numbers of individuals in the stations near the northern side of river mouths of this bay. Lower densities were related to the occurrence of sea‐stars and sand‐dollars. The intertidal and subtidal across‐shore distribution of clam abundance and size varied between and within areas (southern and northern). The individuals from the southern area were concentrated at intermediate tidal levels (0.2–0.6 m in relation to mean low water), whereas in the northern area the clams were more homogeneously distributed. The uppermost limit of their distribution was 0.8 m (southern) and 0.4 m (northern), and an upwards tendency towards increased size was more evident in the northern area. In the subtidal, abundance and individual size tended to increase from the deepest (4.5 m) to the shallowest (0.5 m) levels only in the southern area. Individual clams in the northern area tended to be smaller and more abundant than in the southern area. The species had an ontogenic distribution: small‐sized individuals were recorded only in the subtidal. Possible causes for these patterns and for the differences between areas (human exploitation, organic pollution, beach morphodynamics, differential recruitment, and adult–larvae interactions) are discussed, and specific studies are suggested to evaluate formally the proposed hypotheses.     

Survival rates of translocated and native Mountain Quail in Oregon

We estimated survival rates for 232 radio-tagged native ( n = 157) and translocated ( n = 75) Mountain Quail ( Oreortyx pictus ) from 1997 to 1999 in Hells Canyon National Recreation Area (HCNRA) in northeastern Oregon and in the Cascade Mountain Range (CMR) of southwestern Oregon. For the combined areas the estimated survival rate during 150-day intervals was 0.42 ± 0.04. Estimated survival was 0.41 ± 0.04 for Mountain Quail in HCNRA and 0.34 ± 0.34 for quail in CMR. There were no differences in survival functions for native quail in HCNRA and CMR ( P = 0.91), for translocated and native quail in HCNRA ( P = 0.93), for native quail in CMR and translocated quail in HCNRA ( P = 0.97), or for birds released in the fall and birds released in the winter ( P = 0.57). Male and female survival functions were significantly different ( X 2 1 = 4.61, P = 0.02). The estimated risk ratio for males was 0.66 that of females. Translocated wild Mountain Quail appeared to have survival rates similar to native quail. Mountain Quail experienced mortalities of > 50% over a 150-day interval in both the conifer forests of the western Cascade Mountain Range and the semiarid habitats of northeastern Oregon. With the ability to rapidly expand their populations and exploit marginal habitats, Mountain Quail are excellent candidates for reintroduction programs, and translocated wild Mountain Quail could be used to supplement declining populations.     

Bald eagle winter survey in the Snake River Canyon, Wyoming

A 5-year winter bald eagle survey was conducted along 22 km of the Snake River Canyon in northwestern Wyoming. Surveys were done on 94 days requiring 1,414 hrs and 1,888 km driving. In all, 220 (85 percent adults) bald eagles were seen. Seventy-seven percent of all eagles were perching, 15 percent were flying, 4 percent were feeding on road-killed mule deer, and 4 percent were flying low over water. Perching sites were identified as 32 percent cottonwoods, 30 percent spruce, 17 percent Douglas-fir, and 22 percent other. Eagles were somewhat clumped in distribution.     

Responses of pink shrimp Farfantepenaeus brasiliensis (Latreille, 1817) (Penaeoidea) to physico-chemical parameters in a marine protected area: changes in abundance and distribution after 20 years

ABSTRACT

This study analysed the influence of temperature, salinity and sediment texture on the distribution of pink shrimp juveniles (Farfantepenaeus brasiliensis) over a 20-year period. The shrimps were sampled monthly in Fortaleza Bay, north coast of São Paulo, Brazil, in November 1988–October 1989 (period 1) and then 20 years later in November 2008–October 2009 (period 2). In period 1 we captured 80 juveniles whereas in period 2 we captured 226. The abundance and distribution of F. brasiliensis seemed to be modulated by temperature and sediment texture, along with the fishing activity. The management strategies established between the samplings might have been responsible for the higher abundance of juveniles seen during period 2. The strategies included the limitation of fishing effort, regulation of fishing equipment and the establishment of environmental protection areas and temporary fishing ban.