Treesearch

Large floods in northwestern California in the past two decades have mobilized extensive areas of valley floors, removed streamside trees, and widened channels. Channel cross sections were surveyed to illustrate an hypothesis on the linkage between sediment transport, colonization of channel margins by trees, and streambank recovery. Riparian trees, e.g., white alder (Alnus rhombifolia), colonize the water's edge at low flow to receive adequate moisture during the dry season. Such stands can endure annual high flows only after the flood-enhanced sediment load declines and the width of the...

A hierarchical perspective of relationships between valley floor landforms, riparian plant communities, and aquatic ecosystems has been developed, based on studies of two fifth-order basins in the Cascade Mountains of Oregon. Retention of dissolved nitrogen and leaves were approximately 2-3 times greater in unconstrained reaches than in constrained reaches. Both valley floor landforms and riparian plant communities influenced the abundance of primary producers. Abundances of cutthroat and rainbow trout in unconstrained reaches were approximately twice those observed in constrained valley...

Wildfires have affected the landscape since the dawn of time and will continue to do so for the foreseeable future. Policies and practices in response to fire have varied, however, contingent upon a complex mix of values and attitudes overlaid by the technical acumen available to both "fight" the fire and reclaim the land afterwards.

Removal of stream channel shading during timber harvest operations may raise the stream temperature and adversely affect desirable aquatic populations. Field work in California at one clearcut and one mature fir site demonstrated diurnal water temperature cycles and provided data to evaluate two stream temperature prediction techniques. Larger diurnal temperature fluctuations were observed in the water flowing through the clearcut than in the undisturbed area above the clearcut site. The mature fir forest also had a large diurnal water temperature variation. A 5.6°C temperature rise was...

Twelve low radius of curvature bends, half of which were rivetted, were studied in the Butte Basin reach of Sacramento River, California, to determine whether bank revetment deleteriously affected salmonid habitat. At low discharge (128.6 cubic meters/s) it was demonstrated that revetment does not cause channel narrowing or deepening, nor does it prevent re-entrainment of gravels on point bars. Point bar sediments in rivetted bends are not coarser than those in non-rivetted bends. Point bar morphology is stage-dependent, and therefore, point bars are both sources and sinks for spawning-size...

Air pollution may affect forest ecosystems by altering nutrient cycling rates. The objective of this study was to compare decomposition rates of L-layer litter of ponderosa pine (Pinus ponderosa Laws.) and Jeffrey pine (Pinus jeffreyi Grev. & Balf,) collected from across an air-pollution gradient in the San Bernardino Mountains in southern California. Litter from the more polluted western areas decomposed at a significantly (P = 0.01) faster rate than litter from plots in areas exposed to moderate or low pollution levels. The Shannon diversity index values for litter fungi were 1.41, 1.84,...