Spatial patterns of forest characteristics in the western United States derived from inventories.

In the western United States, forest ecosystems are subject to a variety of forcing mechanisms that drive dynamics, including climate change, land-use/land-cover change, atmospheric pollution, and disturbance. To understand the impacts of these stressors, it is crucial to develop assessments of forest properties to establish baselines, determine the extent of changes, and provide information to ecosystem modeling activities. Here we report on spatial patterns of characteristics of forest ecosystems in the western United States, including area, stand age, forest type, and carbon stocks, and comparisons of these patterns with those from satellite imagery and simulation models. The USDA Forest Service collected ground-based measurements of tree and plot information in recent decades as part of nationwide forest inventories. Using these measurements together with a methodology for estimating carbon stocks for each tree measured, we mapped county-level patterns across the western United States. Because forest ecosystem properties are often significantly different between hardwood and softwood species, we describe patterns of each. The stand age distribution peaked at 60-100 years across the region, with hardwoods typically younger than softwoods. Forest carbon density was highest along the coast region of northern California, Oregon, and Washington and lowest in the arid regions of the Southwest and along the edge of the Great Plains. These results quantify the spatial variability of forest characteristics important for understanding large-scale ecosystem processes and their controlling mechanisms. To illustrate other uses of the inventory-derived forest characteristics, we compared them against examples of independently derived estimates. Forest cover compared well with satellite-derived values when only productive stands were included in the inventory estimates. Forest types derived from satellite observations were similar to our inventory results, though the inventory database suggested more heterogeneity. Carbon stocks from the Century model were in good agreement with inventory results except in the Pacific Northwest and part of the Sierra Nevada, where it appears that harvesting and fire in the 20th century (processes not included in the model runs) reduced measured stand ages and carbon stocks compared to simulations.     

Ladybird mothers mitigate offspring starvation risk by laying trophic eggs

A large proportion of ladybird beetle (Coleoptera: Coccinellidae) eggs are apparently infertile—they do not develop an embryo and are consumed by larvae hatching within the egg batch. The predicted benefits of egg consumption for larvae are empirically well supported. An important question, however, remains: are these eggs a maternal strategy to feed offspring (i.e., trophic eggs) or did egg eating evolve to exploit unavoidably infertile eggs? We investigated the adaptive value of infertile eggs in laboratory experiments with multicoloured Asian ladybirds (Harmonia axyridis). Female H. axyridis were assigned to low and high resource environments for brief intervals; we predicted that tactics to facilitate egg cannibalism, such as infertile egg production and hatching asynchrony, would be adopted in low food environments in which starvation risk for offspring is greater. We conducted two experiments in this manner that provided females with information about resource levels through prey feeding or scent. We also observed female oviposition patterns and tested for infertile egg distributions that departed from random. Females produced 56% more infertile eggs in the low vs. the high food treatment; however, hatching synchrony did not change. We consider a potential confound between information and nutrition state unlikely because ladybirds are well able to tolerate low food for 24 h, the duration of trials, and because females were in good condition when trials began. Results suggest that ladybirds use information from prey encounter to manipulate the proportion of trophic eggs in a manner consistent with the adaptive hypothesis, the first evidence of trophic egg plasticity in a non-eusocial insect.     

Transport and Diffusion of Ozone in the Nocturnal and Morning Planetary Boundary Layer of the Phoenix Valley

The evolution of ozone (O ₃) in the nocturnal and morning-transitional planetary boundary layer (PBL) of the Phoenix valley was measured as a part of the `Phoenix Sunrise Experiment 2001' of the U.S. Department of Energy conducted in June 2001. The goal of the field program was to study the transport, distribution and storage of ozone and its precursors in the urban boundary layer over a diurnal cycle. The ground level O <sub>3</sub> as well as mean meteorological variables and turbulence were measured over the entire period, and vertical profiling (using a tethered balloon) was made during the morning transition period. Approximately half of the observational days showed the usual diurnal cycle of high O <sub>3</sub> during the day and low O <sub>3</sub> at night, with nitrogen oxides (NO <sub>x</sub> = NO <sub>2</sub> + NO) showing an out of phase relationship with O <sub>3</sub>. The rest of the days were signified by an anomalous increase of O <sub>3</sub> in the late evening ( 2200 LST), concomitant with a sudden drop of temperature, an enhancement of wind speed and Reynolds stresses, a positive heat flux and a change of wind direction. NO <sub>x</sub> measurements indicated the simultaneous arrival of an `aged' air mass, which was corroborated by the wind predictions of a mesoscale numerical model. In all, the results indicate that the recirculation of O ₃ rich air masses is responsible for the said high-O ₃ events. Such air masses are produced during the transport of O ₃ precursors by the upslope flow toward mountainous suburbs during the day, and they return back to the city at night via downslope winds (i.e. mountain breeze). The corresponding flow patterns, and hence the high-O ₃ events, are determined by background meteorological conditions. The vertical profiling of O ₃ and flow variables during the morning transition points to a myriad of transport, mixing and chemical processes that determine the fate of tropospheric O ₃. How well such processes are incorporated and resolved in predictive O ₃ models should determine the accuracy of their predictions.     

PBDEs in the San Francisco Bay Area: measurements in harbor seal blubber and human breast adipose tissue

To explore the levels of polybrominated diphenyl ethers (PBDEs) in California, samples from 11 archived harbor seals (Phoca vitulina Richardsi) from the San Francisco Bay and breast adipose tissue samples from 23 women were analyzed. The levels of PBDEs in human tissue samples were in the low ng/g fat range, with PBDEs 47, 153, 154, 99, and 100 as the major congeners. Average sigma PBDEs (86 ng/g fat) in these California women are the highest human levels reported to date. An inverse relationship between concentration of PBDEs and age of these women was apparent. The levels of PBDEs measured in harbor seal blubber were in the low ng/g to low microg/g fat range, with the same major congeners as those measured in the human tissues. PBDE 47 was the highest among all congeners measured in both human tissue and seal blubber samples. The concentrations of PBDEs in harbor seals in the San Francisco Bay have increased dramatically over the past decade, with current levels among the highest reported for this species.     

Modeling and spatially distributing forest net primary production at the regional scale

Forest, agricultural, rangeland, wetland, and urban landscapes have different rates of carbon sequestration and total carbon sequestration potential under alternative management options. Changes in the proportion and spatial distribution of land use could enhance or degrade that area's ability to sequester carbon in terrestrial ecosystems. As the ecosystems within a landscape change due to natural or anthropogenic processes, they may go from being a carbon sink to a carbon source or vice versa. Satellite image analysis has been tested for timely and accurate measurement of spatially explicit land use change and is well suited for use in inventory and monitoring of terrestrial carbon. The coupling of Landsat Thematic Mapper (TM) data with a physiologically based forest productivity model (PnET-II) and historic climatic data provides an opportunity to enhance field plot-based forest inventory and monitoring methodologies. We use periodic forest inventory data from the U.S. Department of Agriculture (USDA) Forest Service's Forest Inventory and Analysis (FIA) Program to obtain estimates of forest area and type and to generate estimates of carbon storage for evergreen, deciduous, and mixed-forest classes. The area information is used in an accuracy assessment of remotely sensed forest cover at the regional scale. The map display of modeled net primary production (NPP) shows a range of forest carbon storage potentials and their spatial relationship to other landscape features across the southern United States. This methodology addresses the potential for measuring and projecting forest carbon sequestration in the terrestrial biosphere of the southern United States.     

Photographic and acoustic tracking observations of the behaviour of the grenadier Coryphaenoides (Nematonurus) armatus the eel Synaphobranchus bathybius,and other abyssal demersal fish in the North Atlantic Ocean

Using an autonomous free-fall vehicle (AU-DOS), observations were made of demersal fish attracted to baits and baited acoustic transmitters at two stations in the North Atlantic Ocean. A comparison was made between Station PAP (48°50N; 16°30W), 4800 m deep on the Porcupine Abyssal Plain which is relatively eutrophic, and Station MAP (31°N; 20°W), 4900 m deep on the Madeira Abyssal Plain, which is oligotrophic. Experiments were conducted during summer, in 1989 and 1990. Four species of fish were observed at Station MAP, the grenadier, Coryphaenoides (Nematonurus) armatus, the eel, Synaphobranchus bathybius, and the ophidiids Spectrunculus grandis, and Barathrites sp. At Station PAP, C. (N.) armatus and H. (S.) bathybius were attracted to bait on all deployments and only two other individuals of different species, probably ophidiids, were seen. The mean first grenadier arrival time was 30 and 138 min at Stations PAP and MAP, respectively. Mean first eel arrival time was 29 and 151 min at Stations PAP and MAP, respectively. Estimated population densities of fish were 167 grenadiers km^-2 and 180 synaphobranchid eels km^-2 at Station PAP and 8 grenadiers km^-2 and 7 eels km^-2 at Station MAP. Only the grenadier C. (N.) armatus definitely ingested transmitters, and this species dominated fish activity around the baits. Mean time of departure of grenadiers with transmitters in their stomachs across an acoustic horizon at 1000 m range was 371 and 488 min at Stations PAP and MAP, respectively. Grenadiers had a longer mean staying time at the food source at the more oligotrophic Station MAP (364 min) than at Station PAP (141 min). This corresponds with predictions of optimal foraging theory.     

Forb,Insect, and Soil Response to Burning and Mowing Wyoming Big Sagebrush in Greater Sage-Grouse Breeding Habitat

Wyoming big sagebrush (Artemisia tridentata wyomingensis A. t. Nutt. ssp. wyomingensis Beetle and Young) communities provide structure and forbs and insects needed by greater sage-grouse (Centrocercus urophasianus) for growth and survival. We evaluated forb, insect, and soil responses at six mowed and 19 prescribed burned sites compared to 25, paired and untreated reference sites. Sites were classified by treatment type, soil type, season, and decade of treatment (sites burned during 1990–1999 and sites burned or mowed during 2000–2006). Our objective was to evaluate differences in ten habitat attributes known to influence sage-grouse nesting and brood rearing to compare responses among treatment scenarios. Contrary to desired outcomes, treating Wyoming big sagebrush through prescribed burning or mowing may not stimulate cover or increase nutrition in food forbs, or increase insect abundance or indicators of soil quality compared with reference sites. In some cases, prescribed burning showed positive results compared with mowing such as greater forb crude protein content (%), ant (Hymenoptera; no./trap), beetle (Coleoptera/no./trap), and grasshopper abundance (Orthoptera; no./sweep), and total (%) soil carbon and nitrogen, but of these attributes, only grasshopper abundance was enhanced at burned sites compared with reference sites in 2008. Mowing did not promote a statistically significant increase in sage-grouse nesting or early brood-rearing habitat attributes such as cover or nutritional quality of food forbs, or counts of ants, beetles, or grasshoppers compared with reference sites.     

Transitioning from unstable to stable colony growth in the desert leafcutter ant Acromyrmex versicolor

Like organisms, cohesive social groups such as insect colonies grow from a few individuals to large and complex integrated systems. Growth is driven by the interplay between intrinsic growth rates and environmental factors, particularly nutritional input. Ecologically inspired population growth models assume that this relationship remains constant until maturity, but more recent models suggest that it should be less stable at small colony sizes. To test this empirically, we monitored worker population growth and fungal development in the desert leafcutter ant, Acromyrmex versicolor, over the first 6 months of colony development. As a multitrophic, symbiotic system, leafcutter colonies must balance efforts to manage both fungus production and the growth of the ants consuming it. Both ants and fungus populations grew exponentially, but the shape of this relationship transitioned at a size threshold of 89?±?9 workers. Above this size, colony mortality plummeted and colonies shifted from hypometric to hypermetric growth, with a distinct stabilization of the relationship between the worker population and fungus. Our findings suggest that developing colonies undergo key changes in organizational structure and stability as they grow, with a resulting positive transition in efficiency and robustness.     

<Emphasis Type="Italic">Octopus insularis</Emphasis> (Octopodidae), evidences of a specialized predator and a time-minimizing hunter

Shallow-water octopuses have been reported as major predators of motile species in benthonic marine communities, capturing their prey by different foraging techniques. This study assessed for the first time the feeding ecology, foraging behavior, and defensive strategy during foraging, including the use of body patterns, to construct a general octopus foraging strategy in a shallow water-reef system. Octopus insularis was studied in situ using visual observations and video recordings. The diet included at least 55 species of crustaceans (70%), bivalves (17.5%), and gastropods (12.5%); however, only four species accounted for half of the occurrences: the small crabs Pitho sp. (26.8%) and Mithrax forceps (23.9%), the bivalve Lima lima (5.3%), and the gastropod Pisania pusio (4.9%). Poke and crawl were most frequent foraging behaviors observed in the video recordings. The foraging behaviors were associated with environmental variables and octopus body size. The sequences of foraging behavior showed characteristics of a tactile saltatory searching predator, as well as a visual opportunist. Body patterns showed a relationship with foraging behavior, habitat variables, and octopus body size. Mottle was the most frequent pattern, especially during poke and crawl, in shallower depths. Dorsal light–ventral blue green was more frequent during swimming at mid-water, and Blotch was the normal pattern during web-over by large animals. The large proportion of two species of small crabs in den remains, the intense search for food during short hunting trips, and the intense use of cryptic body patterns during foraging trips, suggest that this species is a ‘time-minimizing’ forager instead of a ‘rate-maximizer’.     

Feeding biology of <Emphasis Type="Italic">Ophiura sarsii</Emphasis> Lütken, 1855 on Banquereau bank and the effects of fishing

Ophiura sarsii was collected in May/June from Banquereau Bank off Nova Scotia, Canada as part of the benthic fauna analyzed in a 2 year clam dredging-impact experiment. In total, 529 O. sarsii specimens were analyzed; 174 (33%) had stomach contents while the rest were empty. Ophiura sarsii is a trophic generalist feeding on at least 31 taxa (52% identified to species) drawn from four phyla: Arthropoda (81.8%), Annelida (13.2%), Mollusca (3%), and Cnidaria (1.5%). However, the diet was largely restricted to two amphipod families (Ampeliscidae and Lysianassidae), accounting for 54–70% of stomach contents at any one sampling period. This diet provides indirect evidence for carnivory. Limited spatial and temporal heterogeneity in the proportion of animals feeding showed no consistent pattern. Where diet composition differed (ANOSIM) it was attributed to the proportion of lysianassid and ampeliscid amphipods consumed. Dredging introduced new dietary items, although diet composition was not significantly altered.