Treesearch

Simulated grazing techniques were used to investigate livestock impacts on structural characteristics of streambanks. The treatments consisted of no grazing, moderate early summer grazing, moderate mid summer grazing, and heavy season-long grazing. The heavy season-long treatment resulted in a 11.5 cm depression of the streambank surface, while the moderate treatments depressed the streambank surface about 3 cm. There were no differences between no grazing and moderate grazing treatments on bank angle, bank retreat, or stream width. The heavy season-long treatment produced significant...

A grazing study was conducted on a cold, mountain meadow riparian system in central Idaho in response to cattle grazing-salmonid fisheries conflicts. Six pastures were established along a 3rd order, 2 to 3 m wide stream to study the effects on fisheries habitat of no grazing, light grazing (20 to 25% use), and medium grazing (35 to 50%) during late June. Most measurements of streamside variables moved closer to those beneficial for salmonid fisheries when pastures were grazed to a 10 cm stubble height; virtually all measurements improved when pastures were grazed to 14 cm stubble height,...

Effects of complete removal of mesquite overstory, complete removal of mesquite overstory with control of post-treatment sprouts, and retention of the mesquite overstory as a control on herbage production are described. Mulching treatments included applications of a chip mulch, a commercial compost, lopped-and-scattered mesquite branchwood, and an untreated control. Preliminary results of this study provide an insight on the changes in herbage production as a result of mesquite overstory control and the addition of mulches.

The mesquite woodland distributed in approximately 200,000 ha in Llanos de Angostura, and Pozo del Carmen, San Luis Potosi, represents a main source of firewood, construction material, honey, and forage for the rural people that inhabit part of the lowlands of the hydrological region RH26 and RH37. Firewood collection in this region averages 142 m3 /week. Most of this wood is used by brick makers to fuel the kilns, and for domestic purposes (i.e., cooking and heating). Mesquite pod yields fluctuate by year. A three-year study, sampling pod production in two native stands located in Llanos...

Important components of Southwest forest ecosystem are subalpine and montane grassland communities, Grassland communities provide habitat diversity for wildlife, forage for domestic livestock and wildlife, and contribute to the visual quality of an area. The objectives of this research were to determine if: 1) vegetation attributes and soil-surface cover variables of interest have changed, or if they have maintained equilibrium relative to conditions in 1913 through 1915; and 2) a correlation exists between the ecological diversity-stability hypothesis (Huston 1979, Pimm 1984, McNaughton...

Less than 10% of the annual precipitation in the Southwestern United States is recovered for use by people; most of the precipitation is lost by evapotranspiration. A large portion of the precipitation that is recovered originates on watersheds in montane forests. Even here, 80% to 90% of the precipitation is currently unavailable to downstream users. The possibility of increasing the amount of recoverable precipitation in this region is greater for snow than rain. A 50-year review of snow hydrology in the Southwestern United States is presented to indicate the possibilities for increasing...

The discipline of dendrochronology, that is, development and use of time series of annual growth rings of trees, is a set of techniques by which the annual growth layers of trees may be assigned to definite calendar years. The history of changes in the trees’ environment may be reconstructed using various properties of tree rings. In this paper we will discuss how tree- ring measurement series can be used to reconstruct past river flow, precipitation, and forest fires over time spans of several centuries and occasionally over millennia. With an understanding of these variables, land and...

The introduction of exotic grasses in native rangelands to increase the production of forage has been a good alternative for the cattle industry in North America. Different studies have demonstrated that buffelgrass (Cenchrus ciliaris L.), a plant introduced from Africa, increases the annual green forage production approximately three times in comparison to production in areas with native species in rangelands of Sonora, Mexico. However, soil erosion processes caused by natural circumstances and/or natural resources mismanagement can decrease productivity of buffelgrass pastures. Soil...

A study was conducted to investigate the causes of and rock characteristics at three landslide sites in the Tesngwen Reservoir watershed of southern Taiwan. Research methods used included the petrographic microscope, X-ray diffraction (XRD), scanning electron microscope (SEM), inductively coupled plasma spectroscope (ICP), constant head permeameter in triaxial apparatus, surface extensometer, and seismic exploration by wave-refraction processes. Chemical analyses of the rock indicated a higher Na than K content at all three landslide sites; iron normally occurs as Fe3+. The relationships...

Plant and soil processes within a natural ecosystem interact with surface hydrology through their influence on surface roughness, soil structure, and evaporation, and through their relation with soil biota. In the Southwest, decreases in perennial grass cover and erosion on uplands and stream channels can initiate a decline in watershed condition. Agronomic literature has recognized the role of the vesiculararbuscular mycorrhizae (VAM) in maintaining soil structure and aggregate stability, seeing beyond the plant nutritional relationship of the host and endophyte. Results confirm the role...