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It has been suggested that rock climbing in some national parks may reduce the nesting success of some bird species, including birds of prey, but little research exists to substantiate such claims. A new study of rock climbing and bird communities at Joshua Tree National Park, CA, is presented. The study finds no differences in numbers of bird taxa among different climbing categories but only the more common bird species were found at climbed cliffs. Birds' use of unclimbed cliffs was greater than for climbed cliffs, while more birds were seen flying at climbed cliffs.

(1) Along the Niagara Escarpment in Ontario, Canada, a stunted forest of old-growth Thuja occidentalis occurs on cliff faces, but is replaced by a deciduous forest dominated by Acer saccharum within 5 m of the cliff edge on the upper plateau. (2) The stem frequencies of all seedling and sapling size-classes of Thuja decreased with distance from the cliff, but for Acer the smallest size classes displayed the greatest increase in stem frequency away from the cliff edge. (3) Seed input did not change significantly across the cliff-edge--deciduous-forest continuum for either species. (4) Recruitment patterns of the two species differed significantly across the gradient. Seed emergence of Thuja was limited by litter in the deciduous forest but not at the cliff edge. Herbivory restricted recruitment of Acer more at the cliff edge than in the deciduous forest. (5) The maintenance of the spatial pattern appears to be due to an array of interacting factors which change across the environmental gradient and over time.

Vegetation differences between pristine cliffs and cliffs subjected to rock-climbing were found to be the result not of climbing disturbance but to climber choice of cliffs with less vegetation. Implications for rock-climbing development and conservation management are discussed.

The functional dependence of bedrock conversion to soil on the overlying soil depth (the soil production function) has been widely recognized as essential to understanding landscape evolution, but was quantified only recently. Here we report soil production rates for the first time at the base of a retreating escarpment, on the soil-mantled hilly slopes in the upper Bega Valley, southeastern Australia. Concentrations of [sup.10]Be and [sup.26]Al in bedrock from the base of the soil column show that soil production rates decline exponentially with increasing soil depth. These data define a soil production function with a maximum soil production rate of 53 m/m.y. under no soil mantle and a minimum of 7 m/m.y. under 100 cm of soil, thus constraining landscape evolution rates subsequent to escarpment retreat. The form of this function is supported by an inverse linear relationship between topographic curvature and soil depth that also suggests that simple creep does not adequately characterize the hillslope processes. Spatial variation of soil production shows a landscape out of dynamic equilibrium, possibly in response to the propagation of the escarpment through the field area within the past few million years. In addition, we present a method that tests the assumption of locally constant soil depth and lowering rates using concentrations of [sup.10]Be and [sup.26]Al on the surfaces of emergent tors. Keywords: erosion, cosmogenic nuclides, landscape evolution, geomorphology, tors.

The lower part of the Campanian Castlegate Formation, one of the best known fluvial sheet sands of the Western Interior seaway, combines with an overlying finer grained unit (middle member of the Castlegate Formation) to form an unconformity-bounded, third-order stratigraphic sequence (~3 m.y. duration). This sequence contains a mappable muddy zone along the western Book Cliffs of Utah now mapped as contiguous with the open-marine parts of the succession (Buck Tongue, Sego Sandstone, Anchor Mine Tongue) to the east. The correlation within the middle Castlegate has been refined and the nature of the link between tidally influenced fluvial strata in the west and marine strata in the east has been remapped. Five high-frequency stratigraphic sequences (all within the upper part of the larger third-order sequence), forming a thickness to 160 m, have been mapped in the Price area southeastward into the time-equivalent marine succession near Green River. Individual sequences (probably [is less than] 0.5 m.y. duration), reflecting transgressive to regressive estuary infilling, have an internal architecture in which fluvial and tidally influenced distributary-channel belts pass up into muddy central-basin sedimentary units, to bayhead-delta deposits, and in some places up to more fluvial channel belts. The key to the mapping of individual sequences is recognition of the muddy, brackish-water interval, developed during maximum transgression of the time-equivalent shoreline. The two most proximal marine-influenced sequences (2 and 3) are probably broadly time-equivalent with the Buck and Anchor Mine Tongues to the east. The analysis here, contrary to recent suggestions, shows that the marine sequences in the eastern Book Cliffs can be traced far into the time-equivalent, western fluvio-estuarine succession. Keywords: Castlegate, Book Cliffs, nonmarine, sequence stratigraphy.