Arizona Chaparral Research Articles

Direct effects of prescribed fire on available nitrogen and phosphorus in an Arizona chaparral watershed

The effect of prescribed fire on soil nutrients in Arizona chaparral is limited even though prescribed fire is used extensively as a management tool. Concentrations of exchangeable NH4 +‐N and NO3 ‐‐N and extractable P were studied under two Arizona chaparral shrubs growing on a Lithic Ustorthent soil before and after a prescribed fire. The results show exchangeable NH4 +‐N increased from 5.19 to 48.74 mg kg‐1 and extractable P increased from 5.38 to 14.55 mg kg‐1 in the surface horizon. NH4 +‐N increased from 5.39 to 71.62 mg kg‐1 under Cercocarpus betuloides and from 5.23 to 36.10 mg kg‐1 under Quercus turbinella, while extractable P increased from 5.80 to 22.62 mg kg‐1 under C. betuloides and from 5.46 to 14.58 mg kg‐1 under Q. turbinella. The difference in soil nutrient status between species after prescribed fire is due to the amount of litter accumulated and the nutrient concentration difference in the litter and standing biomass of these two species. The majority of N and P is lost owing to volatil...

Nitrogen Mineralization in Soils of a Chaparral Watershed in Arizona

This study was undertaken to extend our knowledge of nutrient availability in soils of the Arizona chaparral. Our objective was to determine the effect of shrub species and topographic aspect on N mineralization of soils from a watershed in central Arizona and to relate N mineralization to other soil properties. Soil for an incubation study was collected from the 0- to 2- and 2- to 10-cm soil layers beneath the canopy of 32 randomly selected shrubs, eight each of birchleaf mountain mahogany (Cercocarpus betuloides Nutt. ex. Torr. & A. Gray) and shrub live oak (Quercus turbinella Greene) from both north and south aspects. Neither cumulative N mineralization (Nm) nor potentially mineralizable N (No) was influenced by shrub species or aspect. Aspect significantly influenced NH4 released in the 2- to 10-cm layer, with greater amounts released in soils from north and south aspects. Both Nm and No were markedly higher in the 0- to 2-cm soil layer than in the 2- to 10-cm layer; NO3 was the dominant form of mineralized N. Nitrogen-mineralized in both soil layers correlated highly with soil C, N, P, and N/P and C/P ratios. Phosphorus supply (Pav) differed markedly between the two soil layers (3.8 and 0.7% of total P, respectively) and was related to Nm. The association of Pav with N, however, leaves the real effect of Pav on Nm in doubt.

Aspect and Species Influences on Nitrogen and Phosphorus Availability in Arizona Chaparral Soils

AbstractBiota and topography are among the most important factors affecting nutrient status of wildland soils. Knowledge of these relations has a fundamental bearing on management of chaparral ecosystems. This study was conducted to determine the effect of shrub species and topographic aspect on availability of soil N and P in Arizona chaparral soils. Soil was collected under the canopy of 32 randomly selected shrubs, eight each of birchleaf mountain mahogany (Cercocarpus betuloides Nutt.) and shrub live oak (Quercus turbinella Greene) from both north and south aspects. A pot culture technique, using barley (Hordeum vulgare L. var. gustoe) and mountain mahogany (C. montanus Torr.) as test plants, was used to estimate availability of soil N. and P. Both test plants showed that shrub species and aspect influenced nutrient availability. Availability of P was very low, while that of N was quite high. Lower availability of P in soils from southerly aspects was associated with low amounts of total soil P, probably the result of long‐standing differential erosion between north and south aspects, aggravated by fire. High N availability was probably associated with inputs of N via symbiosis between actinomycetes and mountain mahogany. Higher fertility of soils from oak systems is associated with lower lignin content of litter from these shrubs.

Influence of Spanish Goats on Vegetation and Soils in Arizona Chaparral

The key to managing Arizona chaparral depends on creating and maintaining brush-free or savanna-like habitats. Brush control using fire, chemicals, and mechanical methods has been tested previously; but limited information is available on goats. This study evaluated the effect of 4 goat-stocking levels in a short duration grazing system and mechanical brush crushing on chaparral shrubs, herbaceous vegetation, litter, and soils. After 4-1/2 years, percent total shrub cover was lower (P<0.05) on paddocks stocked at 1.4, 2.4, and 4.2 Spanish goats/ha (35, 39, and 38%, respectively) compared to unstocked controls (51%). Crushing brush increased the effectiveness of goats; mean total shrub cover was lower (P<0.05) on paddocks where brush was crushed vs not crushed (33 and 50%, respectively). Shrubs least preferred by goats were not affected, while preferred browse was impacted at all stocking levels. Goat stocking and brush treatments did not affect perennial herbs, while annuals were generally increased by soil disturbance. Less litter (P<0.05) accumulated under shrubs subjected to heavy stocking levels compared to unbrowsed paddocks. Concentrations of N and P in the soil were also affected (P<0.05) under desert ceanothus (Ceanothus greggii Gray) where the soil bulk density was also increased (P<0.05). While goats can reduce total shrub cover, problems may result. Perennial herbaceous vegetation did not respond. Shrubs preferred by goats were also preferred by native deer. Reduced forage diversity and nutritional stress could result if these species were eliminated from the stand. Also, trampling disturbance by goats affected nitrogen accumulation in the litter and soil, but more importantly heavy browsing may eliminate nitrogen-fixing shrubs.

Prescribed fire in Arizona chaparral: Effects on stream water quality

Prescribed fire in Arizona chaparral can be used to obtain temporary improvements in forage supplies and a mosaic of uneven-aged stands of chaparral to reduce risks of widespread wildfires. A paired-watershed study demonstrated that prescribed fire had a negligible effect on the ionic composition of streamflow from a chaparral watershed that had been converted by means of a herbicide to grasses, forbs, and scattered shrubs. Before the prescribed fire, nitrate concentrations from the converted watershed were about 10 × greater than those from the control watershed because of nitrate release associated with the conversion process. The fire did not cause further increases in nitrate concentration. Concentrations of sulfrte, bicarbonate, and chloride anions and of calcium, magnesium, sodium, and potassium cations were not affected by the fire. Electrical conductivity and pH also were not influenced. Seasonal fluctuations in ionic concentrations coincided with seasonal variations in rainfall and streamflow. Nitrate concentrations increased during periods of high streamflow, but other anions and all cations decreased during periods of high flow. Electrical conductivity and pH remained relatively constant during the study.

Effects of Fall Burning of Chaparral Woodland on Soil Residues of Picloram

Residue of picloram (4-amino-3,5,6-trichloropicolinic acid) aerially sprayed onto a central Arizona chaparral stand was markedly reduced in the surface 7.6 cm of soil from a fall burn conducted 5 weeks later. Brush control was also reduced.

Some Aspects of Black Bear Ecology in the Arizona Chaparral

A study ofthe black bear (Ursus americanus) on a 100-km2 study area in the chaparral vegetation type of Arizona was initiated in 1973. During the subsequent 3.5-year period, 44 individual bears were captured and minimum density of 1 bear per 2 km2 was estimated. Twenty-eight bears were radio-instrumented and more than 1,100 locations were recorded. The radio-locations indicated that subadult males have a home range averaging 42 km2, adult males 29 km2, adult females 18 km2, and subadult females 13 km2. There is considerable overlap of home ranges among adult males. A lesser degree of overlap was observed for adult females. Twenty-four dens were located. Most den sites were at elevations between 1,300 and 1,500 m. Some bears den by 1 November, the majority by 15 November. Emergence from dens begins about 15 March and all bears, except females with cubs, leave their dens by 15 April. Females with cubs remain at den sites approximately 30 days longer. Until recently, Arizona black bears were of little interest to either hunters or wildlife biologists. The majority of bears taken in the state were shot incidental to the hunting of other big game. Few sportsmen hunted specifically for bears. Campers and picnickers also encountered bears on occasion, and livestock operators suffered varying degrees of livestock loss each year from bears. As Arizona's population has increased, campers, picnickers, and summer home residents have increas- ingly encountered bears. Also, more hunters began to

Soil Wettability and Fire in Arizona Chaparral

Soils on typical Arizona chaparral sites showed water repellence both before and after fire. Both field and laboratory fires caused major changes in the water repellency of four natural soil layers. Relatively cool fires caused water repellence in the surface layer, while hot fires produced repellence at a greater depth. Under hot fires, however, the surface layer was rendered completely wettable. By measuring the wetting angle of soil layers from progressively hotter fires, it was possible to pinpoint temperatures where water-repellent layers are first formed and then destroyed. Organic matter decreased at the progressively higher temperatures. Volatilization and subsequent loss to the atmosphere are believed an important part of this loss of organic matter. The volatilized material causing water repellence is almost completely lost above 270C. Below this temperature, sufficient material is trapped and condensed on exchange sites to produce water repellence.

Nutrient Intake of Deer in Arizona Chaparral and Desert Habitats

Chemical analyses and in vitro digestibility of hand-harvested forages comprising seasonal diets of desert mule deer (Odocoileus hemionus crooki) and Coues white-tailed deer (O. sirginsnus couesi) were combined with diet-composition data, to estimate qualitative nutrient intake. Despite differences in habitat and composition of diet, the two deer species have similar intakes of protein, phosphorus, calcium, and fiber. Digestibility is somewhat more variable. Phosphorus appears inadequate in early winter, although selection by deer for higher-quality plants and plant parts may coampensate for this factor. Browse and fruits of woody plants exceed herbaceous forages in percentage of annual composition of diet, but the latter contribute disproportionately more phosphorus. Other nutrients tested appeared to be adequate, but quantitative intake was not measured. Deer populations on chaparral and semidesert ranges in central Arizona, seldom high in density, have declined sharply in recent years. The decline on the Three Bar experimental area in central Arizona was tentatively attribluted to hunter harvests in excess of low yearling recruitnent ( Smith et al. 1969)) although the basic problem here, and generally in Arizona, aplpeared to be extremely high fawn mortality. Nutritional deficiencies have long been suspected for adversely influencing fawn survival and population levels (Hanson and McCulloch 195S, Swank 1956 ) . However, studies of forage quality have been restricteld to proximate analyses of important browse species ( Swank 1958, Reynolds 1967 ) . Levels of phosphorus and protein in most browse species appear inadequate except during periods of active growth. McCulloch ( l963, 1967 ) has shown that deer depend upon browse and fruits of woody plants for a major proportion of 1 Rocky Mountain Forest and Range Experiment Station, Forest Service, U. S. Department of Agriculture. Central headquarters is maintained in cooperation with Colorado State University at Fort Collins. 2 Present address: Tonto National Forest, Federal Building, Phoenix. yearlong diets, but, they also consume significant quantities of herbaceous forages when these are available in late winter, spring, and fall. These forages vere believed,to supplement nutrients belosv minimum requirements in dormant browse. The problem of estimating Ithe quality of the diet is partially resolved by combining the nutritive value of individual forages, a function of chemical composition and digestibility, with the intake of forage ( Barnes 1965). Recently developed in vitro techniques for obtaining coefficients of digestibility (Tilley and Terry 1963) offer a relatively inexpensive and fast alternative to laborious in vivo methods. Tilley and Terry report generally high correlations betveen in vitro and in vivo estimates of digestibility. The present study was conducted by the Rocky Mountain Forest and Range Expleriment Station in cooperation with Arizona State University. Seasonal quality of the diet was estimated to reveal possible deficiencies in nutrients that could account for poor reproductive performance of deer in central Arizona. H. A. Pelarson, Project Leader for range research at the Southern Forest and Range Experiment Station, pro-

Survival of Quercus turbinella and Q. emoryi Seedlings in an Arizona Chaparral Community

Survival of Quercus turbinella and Q. emoryi Seedlings in an Arizona Chaparral Community

Chemical Constituents and Deer Use of Some Crown Sprouts in Arizona Chaparral

Chemical Constituents and Deer Use of Some Crown Sprouts in Arizona Chaparral

Factors Affecting the Distribution of Shrub Live Oak (Quercus Turbinella Greene)

The disjunct distribution, reproduction, and rooting habits of Quercus turbinella in the Arizona chaparral were studied on quartz diorite, sedimentary, and volcanic substrata. The oak was less dense on the sediments and volcanics that on quartz diorite. Lower densities on the bedded sediments resulted from restricted root penetration which prevented access to deep soil moisture; on the volcanic substratum heavy clay soils gave an overall poorer moisture regime than soils developed from the quartz diorite. Shrubs growing on the less favorable sedimentary and volcanic substrata probably were more susceptible to damage by drought and fire, and low mobility and low seedling production tended on eliminate the species from these areas. It is suggested that the Q. turbinella islands within large areas of grassland are relicts rather than evidence of invasion.

Control of Arizona Chaparral with 2,4,5-T and Silvex

Control of Arizona Chaparral with 2,4,5-T and Silvex

The Mule Deer in Arizona Chaparral

The Mule Deer in Arizona Chaparral

Density of Wood Rat Houses in Arizona Chaparral

Density of Wood Rat Houses in Arizona Chaparral