Response of chironomids to late Pleistocene and Holocene environmental change in the eastern Bolivian Andes

We present the first palaeolimnological investigation of chironomid larval assemblages from the Bolivian Eastern Cordillera. Taxonomic diagnoses are provided for the 10 chironomid taxa (subfamilies: Chironominae, Orthocladiinae and Tanypodinae) identified in the lake sediments. We compared changes in the chironomid assemblage from two Andean sites with previously reported palynological, charcoal and geochemical data, and highlight the potential of chironomid analysis to provide additional insights into environmental change in this region of high biodiversity over the last 18,000?years. At Lake Challacaba (17°33.257??S, 65°34.024??W; 3,400?m asl), the chironomid and geochemical data indicate periodic desiccation and hypersalinty of the basin c. 4,000?C3,460?cal?year BP. Increased abundance of Chironomus sp. at c. 1,000?cal?year BP suggests a change in human activity, supporting inferences from the pollen and spore records, which indicate elevated pastoral agriculture at this time. The greatest assemblage change in the chironomid record from Laguna Khomer Kocha Upper (17°16.514??S, 65°43.945??W; 4,153?m asl) occurred at c. 6,380?cal?year BP, concomitant with an increase in marsh woodland taxa, wetter conditions and a rising lake level at the end of a Holocene dry event. There is no apparent response in the chironomid assemblage to burning, however, at the onset of this dry event (c. 10,000?cal?year BP), which is the major transformative agent of the terrestrial vegetation. This study shows that chironomid assemblages in the tropical Andes responded to regional and local environmental changes, and in particular, that they were sensitive to adjustments in net moisture balance (water level fluctuations and salinity) and anthropogenic impacts (nutrient input). This suggests that within-lake processes are more important as drivers of chironomid assemblage composition than terrestrial vegetation or fire regime. Nevertheless, the full potential of subfossil chironomid analysis will only be realised once more modern autecological data are available.     

加纳热带自然保护区内反刍动物与非反刍动物对生境斑块利用的变化（英文）

食草动物处理和消耗食物受单位时间内饲料质量和数量有效性的不同影响。异速反应理论被认为是食草动物觅食栖息地选择的重要决定因素,并已经被广泛应用于不同体型的食草动物研究。但其在解释不同消化生理和体型的食草动物如何利用生境斑块方面尚不明确。本研究通过整合河马（河马科,大型非反刍动物）和牛（反刍动物）的觅食关系,揭示了不同消化生理和体型的食草动物对生境斑块的应用。整个雨季和旱季,通过在加纳的Bui国家公园布设的48块100 m×100 m的样方来分析物种密度降低与环境变量之间的显著关系。结果表明,雨季河马和牛更倾向于利用靠近河流的区域,但河马在旱季会选择远离河流的地区觅食。草地的高度也决定了这两个物种对草地的利用,河马选择使用更矮的草地。分析食物的质量可知,食物氮含量对反刍动物（牛）的斑块选择有显著影响。然而,酸性清洁纤维含量则与非反刍动物（河马）呈正相关。在Bui国家公园,草地高度和食物质量对斑块使用的高季节性影响主要是由河马和牛的消化生理和体型不同所决定。     

Trust,Trustworthiness, and Motivation in the Natural Resource Management Context

Trust is critical for natural resource management (NRM). In recognition of this, a noteworthy body of literature has investigated the construct but is, as yet, still developing. The current research proposes and tests an increasingly complete model that integrates the major advances in not only the NRM literature but in the social psychological literature addressing trust more generally as well. To that end, the current analyses were conducted with a large sample of Michigan hunters (n?=?23,954). The results suggest that, as hypothesized, the theoretical model is a statistically defensible account of trust in this context and suggest that both trustworthiness and motivation have important roles to play in driving cooperation intention and behavior. Thus, the current work suggests that although it is important for NRM institutions to attend to their trustworthiness, they should not ignore the motivation that arises from benefits they provide.     

Approximate axial alignment times for spinning bodies

Using a different approximate scheme for each of two separate body shapes, we compute for torque-free rotating quasi-rigid bodies the rate of damping of the nutation angle due to internal energy dissipation. The first method calculates the alignment rate as well as the free precession period of a Maxwell body; it modifies, and thereby makes clearer, a similar calculation by Gerstenkorn (1967b). The second method deals with an elongated body and models it by symmetrically placing masses along a massless rod, where all energy dissipation occurs through the hysteresis loss of the strain energy stored during the precession motion. For both cases, the damping time is proportional to the material strength of the body and to its damping properties, and inversely proportional to the square of the body's radius and the cube of the rotation frequency.The results agree well with those of another approximate solution (Burns and Safronov, 1973) and numerically check that solution for the alignment times of asteroids. They show that essentially all observed asteroids align quite rapidly and thus explain why asteroids are observed in pure spin despite numerous misaligning collisions.     

Albedo heterogeneity on the surface of (1943) Anteros

We have investigated the effect of rotation on the polarization of scattered light for the near-Earth asteroid (1943) Anteros using the Dual Beam Imaging Polarimeter on the University of Hawaii’s 2.2 m telescope. Anteros is an L-type asteroid that has not been previously observed polarimetrically. We find weak but significant variations in the polarization of Anteros as a function of rotation, indicating albedo changes across the surface. Specifically, we find that Anteros has a background albedo of p_v = 0.18 ± 0.02 with a dark spot of p_v < 0.09 covering <2% of the surface.     

Mid Campanian‐Lower Maastrichtian magnetostratigraphy of the James Ross Basin,Antarctica: Chronostratigraphical implications

The James Ross Basin, in the northern Antarctic Peninsula, exposes which is probably the world thickest and most complete Late Cretaceous sedimentary succession of southern high latitudes. Despite its very good exposures and varied and abundant fossil fauna, precise chronological determination of its infill is still lacking. We report results from a magnetostratigraphic study on shelfal sedimentary rocks of the Marambio Group, southeastern James Ross Basin, Antarctica. The succession studied covers a ~1,200 m‐thick stratigraphic interval within the Hamilton Point, Sanctuary Cliffs and Karlsen Cliffs Members of the Snow Hill Island Formation, the Haslum Crag Formation, and the lower López de Bertodano Formation. The basic chronological reference framework is given by ammonite assemblages, which indicate a Late Campanian – Early Maastrichtian age for the studied units. Magnetostratigraphic samples were obtained from five partial sections located on James Ross and Snow Hill islands, the results from which agree partially with this previous biostratigraphical framework. Seven geomagnetic polarity reversals are identified in this work, allowing to identify the Chron C32/C33 boundary in Ammonite Assemblage 8‐1, confirming the Late Campanian age of the Hamilton Point Member. However, the identification of the Chron C32/C31 boundary in Ammonite Assemblage 8‐2 assigns the base of the Sanctuary Cliffs Member to the early Maastrichtian, which differs from the Late Campanian age previously assigned by ammonite biostratigraphy. This magnetostratigraphy spans ~14 Ma of sedimentary succession and together with previous partial magnetostratigraphies on Early‐Mid Campanian and Middle Maastrichtian to Danian columns permits a complete and continuous record of the Late Cretaceous distal deposits of the James Ross Basin. This provides the required chronological resolution to solve the intra‐basin and global correlation problems of the Late Cretaceous in the Southern Hemisphere in general and in the Weddellian province in particular, given by endemism and diachronic extinctions on invertebrate fossils, including ammonites. The new chronostratigraphic scheme allowed us to calculate sediment accumulation rates for almost the entire Late Cretaceous infill of the distal James Ross Basin (the Marambio Group), showing a monotonous accumulation for more than 8 Myr during the upper Campanian and a dramatic increase during the early Maastrichtian, controlled by tectonic and/or eustatic causes.     

Voyager photometry of Iapetus

Voyager images of Iapetus ranging in phase angle from 8 to 90° were used to define the satellite's photometric properties and construct an albedo map of its surface. The images confirm that the albedo distribution has a roughly hemispheric asymmetry, as had been inferred from earlier analyses of the disk-integrated lightcurve. On the darker leading hemisphere albedo contours are roughly elliptical in shape and centered at the apex of orbital motion, flattened at the poles and elongated along the equator. The reflectance within the darker material is lowest (0.02–0.03) at the apex, and increases with increasing distance from the apex. The albedo pattern on the brighter trailing hemisphere is more complex. Reflectance increases gradually with increasing distance from the interface with the darker material, and reaches a maximum near the poles. Reflectances of 0.3–0.4 in the brighter material are common, and the highest values probably reach 0.6. The transition in reflectance contours between the two materials is gradual rather than sharp, and albedo histograms of images centered on the visually perceived boundary are weakly bimodal. The dark material on Iapetus is reddish, the bright material somewhat less so.     

Eastern Mississippi delta: late Wisconsin unconformity, overlying transgressive facies, sea level and subsidence

Analysis of 92 engineering core logs located in the Balize sector of the eastern Mississippi delta focuses on the late Wisconsin unconformity and lithofacies of strata lying immediately below and above this stratigraphic horizon. This major sequence boundary is a key feature used to correlate strata across shelf and slope to the basin. Observations emphasize lithofacies distributions of the latest Pleistocene sediments underlying the unconformity, the late Pleistocene to early Holocene transgressive facies, and the immediately overlying deltaic deposits. Maps and a cross-section compiled with this information highlight the critical relation between lithofacies distributions and late Wisconsin sea-level oscillations. Core analysis reveals that the transgressive facies comprises distinct environments of deposition, offshore to onshore. Findings identify criteria to determine the approximate position of the shoreline at the late Wisconsin maximum sea-level lowstand and at the extent of early Holocene maximum marine inundation in the Balize complex. Mapping of lithologies along the late Wisconsin unconformity serves to improve correlation of sediment facies with changes in acoustic response along high-resolution seismic profiles. An estimate of long-term averaged land subsidence suggests lowering of at least 1 mm/year near the shelfedge during the past 18 000 years. This mapping also refines sea-level response models for the Mississippi delta, including criteria to locate key paleogeographic features such as shelfedges and maximum flooding surfaces in other Recent marine deltas and in older, stacked deltaic sequences.     

Hillslope sediment production after wildfire and post-fire forest management in northern California

High severity wildfires impact hillslope processes, including infiltration, runoff, erosion, and sediment delivery to streams. Wildfire effects on these processes can impair vegetation recovery, producing impacts on headwater and downstream water supplies. To promote forest regeneration and maintain forest and aquatic ecosystem functions, land managers often undertake active post-fire land management (e.g., salvage logging, sub-soiling, re-vegetation). The primary objective of our study was to quantify and compare sediment yields eroded from (a) burned, (b) burned and salvage logged, and (c) burned, salvage logged, and sub-soiled plots following the 2015 Valley Fire in the northern California Coast Range. We distributed 25 sediment fences (~75 m² contributing area) across four hillslopes burned at high severity and representative of the three management types. We collected eroded sediment from the fences after precipitation events for 5 years. We also quantified precipitation, canopy cover, ground cover, and soil properties to characterize the processes driving erosion across the three management types. Interestingly, during the second year after the fire, sediment yields were greater in the burned-only plots compared with both the salvage logged and sub-soiled plots. By the third year, there were no differences in sediment yields among the three management types. Sediment yields decreased over the 5 years of the study, which may have occurred due to site recovery or exhaustion of mobile sediment. As expected, sediment yields were positively related to precipitation depth, bulk density, and exposed bare soil, and negatively related to the presence of wood cover on the soil surface. Unexpectedly, we observed greater sediment yields on the burned-only plots with greater canopy closure, which we attributed to increased throughfall drop size and kinetic energy related to the residual canopy. While these results will aid post-fire management decisions in areas with Mediterranean climates prone to low intensity, long duration rainstorms, additional research is needed on the comparative effects of post-fire land management approaches to improve our understanding of the mechanisms driving post-fire erosion and sediment delivery.     

The zonal distribution of hydrogen in the Jovian atmosphere

The Voyager ultraviolet spectrometer disclosed strong longitude variation in the midlatitude Lyman alpha brightness of Jupiter. Minimum brightness of 16 and 14.4 kR were observed from Voyagers 1 and 2, respectively, with the intensity rising to peaks of 21 and 19.6 kR at a longitude near 110°. Observations of Jovian Lyman alpha, made with the International Ultraviolet Explorer (IUE) beginning in December 1978, and continuing through January 1982, also show a region of persistently enhanced but variable flux near a longitude, λ, of 100°; however, IUE measured brightnesses are consistently lower than those of Voyager. Although the Lyman alpha flux from the “normal” region of the plant between λ 200 and 300° remained nearly constant during the period of the IUE observations, that from the “perturbed” region centered on λ 110° varied by ±25% from the mean. The sources of Lyman alpha flux include resonance scattering of solar and interplanetary Lyman alpha, and excitation by charged particle precipitation. That portion of the dayside flux due to charged particle excitation has been variously estimated at between 2.3 and 7 kR. About 1 kR of the dayside flux is due to resonance scattering of the sky background. It is assumed that H and an absorber (CH₄) are distributed above the homopause according to the local height distribution of temperature. The daytime equation of radiative transfer is solved to determine the longitudinal distribution of freely scattering atomic hydrogen that would account for the observed flux. This daytime solution shows that if the hydrogen bulge is the result of localized heating and a consequent increase in scale height, the temperature in the perturbed region must be about 100°K warmer than that in the normal region. The nightside Lyman alpha brightness exhibits a longitude variation very similar to that on the dayside. The H distribution derived from the dayside solution is used with the nightside flux to estimate the longitude variation of particle precipitation on the nightside.