In the states of Tabasco and Chiapas, Mexico there is a lack of long-term harvest scheduling models that consider the effects of the harvest activities on the surrounding areas. Additionally, these problems are combinatorial in nature, which makes them hard to solve. Consequently, only harvest scheduling for small areas can be solved to optimality using traditional approaches such as integer programming (IP). In this study, a genetic algorithms (GA) model was used to generate multiple viable solutions for long-term spatially constrained problems on large areas with a great number of management units. This model enables consideration of regeneration and reharvest in forest planning. The flexibility of the model allows it to handle a different set of time periods, database sizes, different species and diverse tree growth models. The data set employed corresponds to a eucalyptus plantation with a cutting cycle seven years and a planning horizon of 10 rotation periods. Total plantation area is 300,000 ha, divided in 5,388 harvest units. IP was used as a standard to validate the efficiency and accuracy of the GA method. The GA performance with different combinations of genetic operators was tested. Scheduled volume flow for simulated communities was computed. Additionally, three different volume assignment scenarios (low, medium and high) were compared to estimate the effect of volume assignment on the spatial optimization output. The significant findings of this research are: (1) a long-term spatially constrained robust solution was found through the use of genetic algorithms for a large area with more harvest units than those reported elsewhere, (2) the solution allowed re-harvest in the same planning horizon, (3) most of the genetic algorithms runs performed better than the integer programming, and (4) on average the volume scheduled for every simulated community was comparable for the two methods used in the work. In both cases, the percentages of the potential volume ranged between 7 and 29%.

The management of bighorn sheep in Mexico is not based on empirical data. We conducted phone interviews and a literature review to determine published information on desert bighorn sheep in Mexico. Most information on bighorn sheep was published prior to 1983 and focused on population size and structure. We concluded that desert bighorn sheep in Mexico are in need of further research. To provide better management to bighorn sheep, research needs to focus on basic life history strategies (e.g., minimum viable population size, diet, habitat relationships, movements, predation, diseases, and metapopulation dynamics). Bighorn sheep in Mexico have been scarcely studied. We conducted a habitat use study in Rancho el Plomito, Sonora, Mexico from April 1997 to December 1998 and the data were used to determine causes of sexual segregation. Vegetation associations were not used according to their availability. Segregated females formed larger groups, were closer to escape terrain and occupied more rugged areas than males. Sexual segregation exhibited by desert bighorn sheep in Rancho el Plomito may result from different energetic and reproductive strategies for males and females. Females tend to optimize conditions suitable for rearing offspring and males maximize body condition. Bighorn sheep in Mexico are important game animals and are confined to scattered populations (Villa 1.959). Little research has been conducted on desert bighorn sheep and consequently the species is listed in appendix II of CITES (i.e., vulnerable) (Valdez 1997). Tarangb and Krausman (1997) emphasized food selection as a fundamental research topic for the species in Mexico. We conducted a study of diet composition in Sonora, Mexico from April 1997 to December 1998. We identified 41 plant species consumed by desert bighorn sheep. The mean annual diet was composed of browse, forbs, succulents, and grasses. Composition of forage categories in diets of males and females was similar. The coefficient of overlap (Morisita 1959) of diets of male and female bighorns for seasons indicated significant overlap. Sexual segregation of desert bighorn sheep in Sonora, Mexico was not related to forage selection (i.e., botanical composition, forage quality), and suggested that other factors (i.e., physiographic characteristics) were responsible for this segregation.

From April 1988 to August 1988 and from March 1989 to August 1989 I studied habitat utilization of the endangered Sonoran pronghorn (Antilocapra americana sonoriensis) on the Cabeza Prieta National Wildlife Refuge and the Organ Pipe Cactus National Monument in southwestern Arizona. Pronghorn groups were small (x = 2.5) and dispersed widely throughout the study area. I never saw Sonoran pronghorns drinking water. Cacti were the major diet components in the dry seasons. Forbs were the major diet component in the wet season. Cover, plants, and vertical obstruction was generally greater in occupied areas than in unoccupied areas. Plants in occupied areas were higher in protein than plants in unoccupied areas. The percentage of indigestible material (e.g., cellulose) in plants from occupied areas was generally less than in unoccupied areas. My data represent the characteristics of vegetation in areas used by Sonoran pronghorn. They could be applied in an intensive habitat management program to improve the quality of pronghorn habitat.

I analyzed 1,182 gray wolf (Canis lupus) scats, representing summer diet in 1988-1990, collected from 9 packs in northwest Alaska. Using a linear regression model, I determined the biomass of prey species consumed using relative estimated bulk and frequency of occurrence of prey types in scats. There were no significant differences (P < 0.05) between methods in percent biomass of prey consumed and ranking of prey types. Caribou (Rangifer tarandus), moose (Alces alces), microtines, and birds composed 47.0, 21.9, 10.6, and 13.8%, of prey items, respectively. Ungulates composed 90.1%, birds 6.7%, and microtines 0.5% of biomass consumed. Ungulates composed 3.4%, birds 50.4%, and microtines 38.5% of numbers of individuals consumed. Significant (P < 0.05) observer bias was found in the detection and frequency of prey types in the analysis of 1,052 scats by multiple observers.

I evaluated different approaches for monitoring of amphibians, reptiles, and mammals in national parks based on data from Tonto National Monument, Arizona, and 3 criteria: statistical power, cost, and ability to meet monitoring goals. Detecting a declining trend in abundance (18% over 10 years) with 80% power would require approximately 65 person-days of annual sampling for the 2 most common rodents, and 110 person-days for the 2 most common lizards. Detecting this trend in species richness of terrestrial vertebrates (reptiles, amphibians, and mammals) would require only 30 person-days annually. Monitoring abundances of vertebrates is often recommended for parks, but my study suggests that this approach is too expensive for most parks, and results may be inadequate for achieving agency goals of monitoring biological diversity. I advocate use of species richness in monitoring, and provide field and analytical methods for estimating this parameter.

I evaluated water use by female Coues white-tailed deer (Odocoileus virginianus couesi) and calculated their diurnal ranges relative to available water in southeastern Arizona during hot-dry and hot-wet summer seasons. Developed water sources were scarce in 1988 and abundant during 1989. Freestanding water was not the only determinant of diurnal seasonal ranges. Not all diurnal seasonal ranges contained permanent water, but a water source density of 1/km² was sufficient during the 1989 hot-dry season and ephemeral water was common in hot-wet seasons. Deer visited developed water sources regularly during hot-dry seasons and infrequently 14 days after the summer rains began. Large amounts of preformed water were available in hot-wet season diets, but permanent or ephemeral water was necessary to meet total water requirements. Visits of cattle to troughs did not preclude deer use because of different activity patterns between the 2 species. Wildlife managers should provide free-standing water in Coues white-tailed deer ranges during hot-dry seasons and in the early part of hot-wet seasons. If winter precipitation is substantially below normal, available free-standing water in summer is especially critical.

The Central Arizona Project (CAP) canal system restricts movements of mammals across Avra Valley, Arizona. The Wildlife Mitigation Corridor (WMC) was established to provide access for animals over the Tucson Aqueduct of the CAP, and allow movement across Avra Valley. To determine if animals used the WMC more or less than other canal crossings (i.e., bridges), we recorded tracks of desert mule deer (Odocoileus hemionus crooki), collared peccary (Pecari tajacu), and coyote (Canis latrans) in and out of the WMC from August 1996 through July 1997. We also monitored two water catchments adjacent to crossings within the WMC with cameras to determine if catchments were used by wildlife. Deer and collared peccaries used crossings in the WMC more than those outside of the WMC. There was no significant difference between use of crossings by coyotes. Coyotes used all crossings throughout the year regardless of the availability of water sources.

There is increasing interest in the use of prescribed fire to reduce fuel loadings and other management objectives in ecosystems of the Madrean Province. Fuel loadings were measured on the same pine-oak ecosystem occurring on five different sites with a range of different fire frequencies. To determine the effects of fire frequencies on fuel loading. Study sites located in Mexico were characterized by a high fire frequency. Study sites in the United States were characterized by low and intermediate fire frequencies. Heavy fuel loadings on sites with high fire frequencies were below the recommended amounts for coarse woody debris. Sites with intermediate fire frequencies were within recommended amounts of coarse woody debris while sites with low fire frequencies were above recommended amounts for coarse woody debris. There was no difference in fine fuel loading among sites with 2, 5, 9, and 13 fires since 1900. Total fuel loading was inversely related to fire frequency. The effects of intermediate fire frequencies can be used to assess ecosystem function and meet multiple use management objectives.

To determine the factors affecting the distribution and abundance of submersed aquatic vegetation (SAV) within Topock Marsh, I measured 4 factors: (1) light availability (water depth and turbidity); (2) substrate type (grain size and organic content); (3) sediment nutrient availability; and (4) exposure to wave action. Multiple regression indicated that turbidity negatively affected the distribution and abundance of SAV in Topock Marsh during 1996 and 1997. Principal components analysis of sediment data in combination with a manipulative experiment indicated substrate type and sediment nutrients may influence SAV. Young shoots of Najas marina L. grew taller and had more branches when grown in sediments that had a smaller grain size and relatively higher amounts of NH4-N and soluble K. If the main objective of the refuge is to provide waterfowl foraging habitat, careful manipulation of water levels may be necessary to adequately promote the growth of SAV in Topock Marsh.

No description available.