Particulate dispersion from sources within a forest

Particulate dispersion from sources within a 10- to 13-m tall pine forest was studied experimentally at Brookhaven National Laboratory using stained ragweed pollen and other tracers ranging from 14 to 58 m in size. Forty-seven continuous point source releases lasting from 22 to 55 min were made at heights from 1.75 to 14.0 m from locations having a long fetch through the forest. In most experiments, differently colored ragweed pollen were emitted simultaneously from three locations. In other tests, several particle types were released from a single point. The sampling network consisted of 119 rotoslide samplers at heights from 0.5 to 21.0 m at 57 positions within and at the edge of the forest. Deposition to the ground was sampled by greased microscope slides at each position. Meteorological measurements were taken in and near the forest.Data were classified by particle characteristics, source height and meteorological parameters. Concentration patterns were illustrated on scale diagrams of the sampling grid. Changes in centerline and crosswind integrated concentrations, plume width and height, mass flux, deposition and deposition velocity were studied as a function of distance, particle size and wind speed. Results were compared to those obtained from similar releases over open terrain.In the forest, vertical predominates over lateral dispersion and considerable interchange occurs through the canopy. Flow is channelled somewhat by vegetation density differences but is generally in the direction of the mean wind above the forest. No systematic turning of the wind with height was observed. Most particles are lost to the foliage rather than to the ground and large particles are lost more rapidly than smaller ones. Rate of change in mass flux is similar to that over open terrain and is greater with light than with stronger wind speeds.This research was carried out under the auspices of the New York State Museum and Science Service and the U.S. Atomic Energy Commission (now Energy Research and Development Administration) and was partially supported by Research Grant No. R-800677 from the Division of Meteorology, U.S. Environmental Protection Agency.     

Nyctiphanes australis (Euphausiacea) and an upwelling plume in western Cook Strait,New Zealand

Quantitative data are presented on the distribution of adult and larval stages of the euphausiid Nyctiphanes australis G. O. Sars, in western Cook Strait, New Zealand, an area influenced by an upwelling plume. The behaviour of N. australis in the Kahurangi Point region at different stages of its life history appears to ensure its maintenance, in general, over the continental shelf on an upwelling coast. Population structure at the source of the upwelling near Kahurangi Point differed from that in regions “down stream” from the plume. Nyctiphanes australis was most abundant at the “downstream” eastern end of the upwelling plume, and the evidence suggesting that the dense populations there may be resident is discussed. Possible reasons for low densities of furcilia II and III stages in the eastern plume region are considered.     

Dielectric constants of crystalline and amorphous spodumene,anorthite and diopside and the oxide additivity rule

The dielectric constants and dissipation factors of LiAlSi₂O₆, CaAl₂Si₂O₈ and CaMgSi₂O₆ in both the crystalline (α-spodumene, anorthite, and diopside) and amorphous forms were determined at 1 MHz using a two-terminal method and empirically determined edge corrections. The results are: spodumene κ′ ₁₁=7.30 tan δ= 0.0007 κ′₂₂=8.463 tan δ= 0.0002 κ′₃₃ =11.12 tan δ= 0.0007 anorthite κ′ _a ^*=5.47 tan δ= 0.0009 κ′_b ^*=8.76 tan δ= 0.0010 κ′_c ^*=7.19 tan δ= 0.0013 diopside κ′₁₁=9.69 tan δ= 0.0016 κ′₂₂ = 7.31 tan δ= 0.0007 κ′₃₃=7.29 tan δ= 0.00019 LiAlSi₂O₆ κ′=8.07 tan δ= 0.047 amorphous CaAl₂Si₂O₈ κ′=7.50 tan δ= 0.0024 amorphous CaMgSi₂O₆ κ′=8.89 tan δ= 0.0021 amorphous The dielectric properties of a spodumene glass, progressively crystallized at different conditions, were also determined. As the crystallization temperature was increased from 720 to 920° C, κ′ increased from 6.22 to 6.44. The dissipation factor, tan δ, remained constant at 0.020. Similarly, as the crystallization time at 750° C increased from 0.5 hr to 6.0 hr, κ′ increased from 6.28 to 6.35. The deviations of the measured dielectric polarizabilities as determined from the Clausius-Mosotti equation from those calculated from the sum of oxide polarizabilities according to α _D(mineral, glass) = σ α _D(oxides) are +7.4% for α-spodumene, +1.2% for diopside, and +28.0, +19.6 and +15.9% for amorphous spodumene, anorthitie and diopside compositions, respectively. Positive deviations in α-spodumene and anorthite are consistent with lower than normal apparent cation bond valence sums and are believed to be evidence for loosely bonded “rattling” Li and Ca ions. Diopside, with Ca and Mg ions having normal bond valence sums, exhibits no abnormal deviation from additivity. Larger positive deviations in amorphous SiO₂, LiAlSi₂O₆, CaAl₂Si₂O₈ and CaMgSi₂O₆ are postulated to arise from a combination of loosely bonded cations and disordered O⁼ ions where the oxygen dielectric polarizability increased from its normal value of 2.0 ų in well-behaved oxides to 2.2–3.0 Å₃ in the amorphous phases.     

Two species of benthopelagic calanoid copepods of the genus Neoscolecithrix Canu, 1896 s.s. from New Zealand and the segregation of Cenognatha n. gen.

Two species of benthopelagic calanoid Copepoda, Neoscolecithrix cf. magna (Grice, 1972) and N. ornata n. sp., are described from the upper slope off North Cape, New Zealand. Neoscolecithrix ornata is distinguished from other species of Neoscolecithrix Canu, 1896 s.s. that have a female leg 5 terminal segment with 4 spines (2 terminal and 1 on each border) principally by the transverse row of long, fine spines on the female genital double somite; and by the more squat terminal segment of leg 5 (length/width ratio about 3.7). This is the second time Neoscolecithrix has been recorded from New Zealand. A new genus, Cenognatha n. gen., is distinguished from Neoscolecithrix principally because: rostrum short (bearing 2 filaments); mandibu‐lar gnathobase masticatory margin with slender dorsal spinulose seta; maxilla endite 1 with 5 well‐developed setae, endite 3 without brush‐like sensory seta, endopod usually with 3 long worm‐like sensory setae and 5 brush‐like setae; posterodistal border of basis of legs 1–3 without spines; distal segment of female leg 5 and its basis subequal in length; male leg 5 of similar lengths on both sides (styliform on right), endopod present at least on 1 side, 1‐segmented and spine‐like on right.     

Effects of climate change and urban development on the distribution and conservation of vegetation in a Mediterranean type ecosystem

Climate and land-use changes are projected to threaten biodiversity over this century. However, few studies have considered the spatial and temporal overlap of these threats to evaluate how ongoing land-use change could affect species ranges projected to shift outside conservation areas. We evaluated climate change and urban development effects on vegetation distribution in the Southwest ecoregion, California Floristic Province, USA. We also evaluated how well a conservation network protects suitable habitat for rare plant species under these change projections and identified primary sources of uncertainty. We used consensus-based maps from three species distribution models (SDMs) to project current and future suitable habitat for 19 species representing different functional types (defined by fire-response – obligate seeders, resprouting shrubs – and life forms – herbs, subshrubs), and range sizes (large/common, small/rare). We used one spatially explicit urban growth projection; two climate models, emission scenarios, and probability thresholds applied to SDMs; and high-resolution (90 m) environmental data. We projected that suitable habitat could disappear for 4 species and decrease for 15 by 2080. Averaged centroids of suitable habitat (all species) were projected to shift tens (up to hundreds) of kilometers. Herbs showed a small-projected response to climate change, while obligate seeders could suffer the greatest losses. Several rare species could lose suitable habitat inside conservation areas while increasing area outside. We concluded that (i) climate change is more important than urban development for vegetation habitat loss in this ecoregion through 2080 due to diminishing amounts of undeveloped private land in this region; (ii) the existing conservation plan, while extensive, may be inadequate to protect plant diversity under projected patterns of climate change and urban development, (iii) regional assessments of the dynamics of the drivers of biodiversity change based on high-resolution environmental data and consensus predictive mapping, such as this study, are necessary to identify the species expected to be the most vulnerable and to meaningfully inform regional-scale conservation.     

Modeling the mudslide aftermath of the 2007 Southern California Wildfires

An investigation is made of the influence of fire-caused deforestation on precipitation-triggered, shallow landslide susceptibilities in southern California, using a scalable and extensible geo-fluid model (SEGMENT), that accounts for soil mechanics, root distribution, and relevant hydrologic processes. SEGMENT is applicable to variable regional topography, soil thickness profiles, and vegetation coverage. In this study, for southern California following the 2007 wildfires, three experiments were performed with rainfall recurrence periods chosen to be 2, 10, and 25 years. These intervals correspond to 24-h storm rainfall totals of 17, 25.4, and 33 mm. The model generated landslide stability maps that identified three areas of high instability. These unstable regions are located in the San Fernando Valley, the San Gabriel Mountains, and the Santa Monica Mountains. In each case, the vegetation cover had been severely burned during the preceding 2007 wildfires. The model results showed that burning from wildfires is a major destabilizing factor for southern California. Burn sites are more prone to landslides than vegetated slopes because the soil more readily exceeds its critical moisture content. Severe droughts in a future warming climate are expected to increase the likelihood of more frequent and intense wild fires. Higher temperatures combined with decreased total rainfalls facilitate more intense landslides, including devastating mudslides, following heavy precipitation. Finally, the model is designed to assist in developing timely mitigation measures for post-fire, storm-triggered landslides.     

Land surface hydrology in a General Circulation Model N-global and regional fields needed for validation

Treatments of land surface processes in General Circulation Models are presently limited by the realism of the simulations of precipitation and surface radiation. We explore this thesis by examination of some of the climatological fields of a 6-year model simulation, using the Community Climate Model version 1 of the National Center for Atmospheric Research with addition of a diurnal cycle and coupled to a detailed treatment of land surface processes referred to as the Biosphere-Atmosphere Transfer Scheme. We examine July climatological surface fields over North America and note an excess of surface solar radiation over Eastern United States. Comparison with satellite derived cloud forcing suggests that the model underestimates the reduction of solar radiation by clouds over Eastern United States and in high latitudes, and so probably largely explaining the excess surface radiation. We consider the annual cycle of model hydrological fields (soil moisture, runoff, precipitation, evapotranspiration, net radiation) averaged over a box covering the central part of the United States (roughtly the Mississippi basin). The seasonal cycle of evapotranspiration over this box appears to be dominated by the variation of surface solar radiation and less related to that of precipitation.