Research in global ecology has been concerned with the effect of vegetation removal in semi-arid regions including aspects such as plant succession and desertification and its impact on global change, specifically global warming. In addition, conditions along international borders often are presented as discontinuities in terms of vegetation and soil status. To better document these discontinuities in a semi-arid region, a multi-temporal study along the U.S.-Mexico border was conducted with a series of six Landsat Thematic Mapper (TM) images acquired over the 1992 growing season. Spatial and temporal variations across the border were analyzed with reflectance data. Spatial data was obtained from three different sampling size areas which included: the Parker Canyon grassland; the San Rafael Valley, a grassland combined with riparian areas and croplands; and the regional area along the Arizona-Sonora border including valleys and mountains, and diverse vegetation communities and soil conditions. These areas consisted of about 106 ha, 5,800 ha, and 738,000 ha, respectively, at each side of the border. Temporal data were obtained from the six TM images which were acquired in days of the year 162, 178, 194, 274, 306, and 322. Four remote sensing applications were considered for comparison studies on both sides of the border. These techniques included: (a) band comparisons, (b) albedo, derived from the discrete sensor band information, (c) vegetation indices, and (d) application of a linear mixing model. When comparing both sides of the border, significant differences were observed in most of the remote sensing techniques applied at the Parker Canyon area. Higher differences were found during the wet season with all of the applied techniques with the exception of albedo. The red band and albedo were the most important discriminants during the dry season. At the intermediate size, San Rafael Valley area, U.S.-Mexico differences followed the same pattern as Parker Canyon, but statistically, these differences were deemed insignificant. At the regional area, no differences were observed between the U.S. and Mexican side. The effect of pixel aggregation using the different remote sensing techniques and ground data from field campaigns in 1995 were also analyzed.

The primary goal of my study was to evaluate strategies for promoting local support for wildlife conservation in Masai Mara National Reserve (MMNR) and the adjacent group ranches. This was done by determining the effects of the changing land tenure from communal to individual on the Maasai lives and wildlife, and the role of the revenue sharing program in enhancing support for wildlife conservation. The study used local people's suggestions to recommend strategies for improving revenue sharing. A combination of literature review, questionnaire-based surveys and participant observation methods were used to achieve these goals. The maintenance of a viable ecosystem in Mara has succeeded due to the traditionally benign relationship between the Maasai and wildlife. However, various factors continue to strain this relationship. First, increasing human population and encroachment of agriculture has diminished areas available for livestock and wildlife grazing. Second, the absence of compensation for loss of life and property to wildlife and inadequacy of the revenue sharing has increased people's antagonism towards wildlife. Third, since the local people are excluded from the management of MMNR and wildlife in general, they consider these activities external impositions. Fourth, subdivision of group ranches will severely reduce the land available for livestock and wildlife grazing and eliminate the traditional resource sharing strategy that has sustained the Maasai for centuries. This study also revealed that although the Maasai harbor many negative feelings towards MMNR, they consider it an important asset. Further, they are unwilling to give up pastoralism and expect to continue with communal grazing after subdivision which, is good for wildlife conservation. In view of this, I made the following recommendations: implement a regional land management system with a core wildlife area (the reserve) and a wildlife management-pastoral area surrounding the core, and designated zones for agriculture; support the above system with firm government policies and incentives; redesign the revenue sharing program to cover all the affected people; promote policies that encourage diversified wildlife-based enterprises including consumptive use; transfer much of the wildlife management responsibilities to the local people.

No description available.

In contrast to documented increases in woody plant dominance of former savannas and grasslands of North America, oak (Quercus L.) savannas that form lower treelines in the southwestern United States and northwestern Mexico have been relatively stable over the past millennium. This research identified potential biotic and abiotic constraints on seedling recruitment of Quercus emoryi Torr. (Emory oak) within the context of potential shifts in lower treeline. Field surveys were used to describe seedling distribution at and below lower treeline, and to determine the potential for acorn dispersal from lower treeline into adjacent grassland. Field and greenhouse experiments designed to determine constraints on seedling establishment included reciprocal soil transfers, nutrient amendment studies, provision of artificial shade, and manipulation of seasonal precipitation inputs. Results indicate that rates of Q. emoryi recruitment within grasslands below treeline are relatively low, and are constrained by low rates of seed dispersal coupled with a low probability of seedling emergence. Seedling recruitment rates were directly correlated with quantity of summer precipitation, but were independent of winter precipitation. Results of this and complementary research suggest that lower treeline in southern Arizona is stabilized by self-enhancing feedback mechanisms of overstory shade, seed dispersal, and seedling establishment coupled with strong abiotic constraints beyond the current ecotone. The observed shift in treeline in the last millennium was less likely the result of slow, spatial progression of autogenic safe sites than the result of episodic and infrequent allogenic processes that simulated, or negated the importance of, conspecific, biogenic safe sites. Increases in summer precipitation are one such process that would facilitate (historic or potential future) downslope shifts in lower treeline. This interpretation is consistent with observations that downslope shifts in lower treeline which occurred 700-1700 ybp coincided with a period of particularly high summer precipitation in the region (i.e., the "Medieval Warm" period, 645-1295 ybp).

Conservation partnerships are working throughout the United States to address natural resource problems in watersheds. These projects have levels of complexity that challenge successful accomplishments. This study investigates what constitutes success in watershed partnerships and what measures may define success. Characteristics are identified from a literature search to create a success model. Characteristics of three partnerships led by the U. S. D. A. Natural Resources Conservation Service, Conservation Districts, and Resource Conservation and Development councils are compared to the model. Analyses address frequencies of occurrence of characteristics and differences between public and private responses. The results do not support the success model. Eight common characteristics of success are found in the case studies. Six of these characteristics are of a qualitative nature indicating a need to include qualitative measures with quantitative measures of success. The development of an effective guide for successful conservation partnerships is based on the eight characteristics.

Sap flow, leaf gas exchange, and micrometeorological parameters were evaluated during 1997 in riparian forest at perennial and ephemeral stream sites on the San Pedro River in southeastern Arizona, USA. At the perennial stream site, measurements of sapwood area based transpiration and sapwood area/canopy area of clusters of Populus fremontii and Salix goodingii were used to estimate transpiration across the stand. Stand structural heterogeneity resulted in as much as 30% variation in mean transpiration across the stand. Transpiration of cottonwood was more dependent upon vapor pressure deficit at the ephemeral stream site which had an open, less dense canopy compared to that at the perennial stream site. This may be due to differences in advection properties and canopy feedback processes between sites. Conversely, transpiration in willow was less dependent upon vapor pressure at the ephemeral stream site than that at the perennial stream site. This may be due to water stress associated with deeper depth to groundwater.

Yellow bluestem (Bothriochloa ischaemum (L.) Keng.) cultivars are used in conservation plantings in New Mexico, Texas and Oklahoma. The recommended cultivar in southern Arizona is Ganada. However, a population from Saudi Arabia P.I. 237110, may be better adapted to the Sonoran Desert environment. This study was conducted to determine why P.I. 237110 may be better adapted to this environment than Ganada. Morphological and physiological characteristics of P.I. 237110 and Ganada were compared in five experiments. Evaluations revealed significant differences in combined stomate densities on both leaf surfaces, leaf surface area, and water use efficiency but not in apparent photosynthesis or dark respiration. Combined average stomate density was significantly lower for P.I. 237110 than Ganada (107 vs. 136 stomates mm⁻²). P.I. 237110 had a significantly higher leaf surface area (40.5 cm²) than Ganada (25.3 cm²). Apparent photosynthetic rates were not significantly different between the populations (Ganada: 12 mumol m⁻² s-1 and P.I. 237110: 10 mumol m⁻² s⁻¹). Dark respiration rates for Ganada were not significantly different (1.4 mumol m⁻² s⁻¹) from those of P.I. 237110 (1.9 mumol m⁻² s⁻¹). P.I. 237110 required 88.9 g of water per 1 g of dry matter than Ganada which required 52.3 g of water.

<p> It is difficult to assess rangeland management practices at a hillslope scale because of the spatial and temporal variability of ecohydrological processes across a landscape. The Conservation Effects Assessment Project (CEAP) aims to provide a cost-effective method for quantifying benefits of conservation practices on rangelands. This study uses the Rangeland Hydrology and Erosion Model (RHEM) to develop a framework to assess rangeland management practices by quantifying sediment yield and runoff. Kaler Ranch, located in Eastern Arizona, was used as a study site because of their recently implemented rangeland conservation practices. Vegetation parameters were developed based on field data collected across the ranch and used to represent various rangeland management scenarios in RHEM. Peak flow and sediment yield rates were determined for each scenario using RHEM and were used as metrics to evaluate rangeland condition. RHEM provided an adequate method to evaluate the relative differences between upland rangeland management scenarios; however, it was less effective at evaluating changes in management practices within a riparian area.</p>

<p> The vegetation associations in the Eastern San Cristobal Valley of Barry M. Goldwater Range-East (BMGR) were mapped using a combination of field surveys (relev&eacute;s) and interpretation of aerial imagery in order to contribute to ongoing mapping efforts of Barry M. Goldwater Range -East. Throughout the San Cristobal Valley, 149 relev&eacute; samples were collected to characterize the vegetation associations. Seventeen vegetation associations were identified and mapped, including a new <i>Larrea tridentata/Ambrosia dumosa/Grusonia kunzei</i> (Creosote bush-White bursage-Devil's cholla) association. Accuracy assessment of the map was conducted using a contingency table finding the map to be 82% accurate.</p><p> Route proliferation in the San Cristobal Valley of Barry M. Goldwater Range-East (BMGR) was also mapped and measured using remotely sensed imagery in geographic information systems and modeled with geographical variables in a multivariate regression. Throughout the San Cristobal Valley study site, 6,878 km of unauthorized routes were identified. Geographic explanatory variables distance from slopes greater than 34% (b = -3.252e-5, <i>p</i> &lt; 0.001) and the most influential variable distance from unauthorized routes (b = -0.006568, <i>p</i> &lt; 0.001) were tested for significance and influence in predicting unauthorized route density. The resulting model, built from the two significant geographic variables in a multivariate regression, was able to explain 57% of the variability in the data. The results from this study have shown that through the use of GIS and remote sensing, unauthorized route density can be predicted by geographic variables which can then be used to make future route management decisions.</p>

<p> The United States increasingly calls upon elite teams of Special Operations Forces, like the Navy SEALs, to respond to the evolving asymmetric threats posed by terrorists and extremists. These teams must have the capacity to adapt as a collective unit in the most dynamic circumstance. This research explored the nature of collective adaptation by these exceptional action teams using a qualitative case study methodology and a lens of complexity theory. Specifically, data gathered from official documents and interviews with retired Navy SEALs expanded the understanding of dynamic instability as it relates to team adaptation in uncertain environments. A greater understanding of this phenomenon contributed to the scholarly literature by identifying and describing the critical factors used by teams to promote adaptive capacity through the appropriate usage of structure and innovative flexibility in a dynamically changing situation. The study produced the following conclusions: 1. Individuals in an action team mentally reference a combination of general simple rules and situation-specific simple rules when they adapt in an uncertain environment. &bull; Varying application of different types of simple rules correspond with different levels of environmental uncertainty. &bull; Simple rules provide the basis for a shared cognitive structure that enables greater collective adaptation. 2. Previous experience plays an important role in the adaptive capacity of an action team. &bull; Experience provides an individual with context to determine how simple rules can and should be applied. &bull; Experience strengthens the relationship (trust and familiarity) between team members which allows them to adapt more quickly and effectively as a collective. 3. Relationships between team members, grounded in previous experience and a shared culture, play an important role in the adaptive capacity of an action team. &bull; Trust between team members gives each individual the freedom and permission to take initiative and adapt as necessary. &bull; Familiarity between team members enables the action team to collectively adapt more quickly and effectively because they can predict how another teammate will react given a specific set of parameters without the need for extensive communication. 4. The ability of individual team members to control emotions, slow and simplify reactions, and focus communication promotes more effective adaptation by an action team in an uncertain environment. &bull; Individual decision-making is enhanced when individuals are able to control their reactions and react calmly in the midst of an uncertain environment. &bull; As environmental uncertainty increases, individuals who react by slowing down and simplifying their actions are capable of more effective adaptation. &bull; In an uncertain environment, action teams that focus communication, reduce potential distractions for team members. This reduced, but effective communication is possible because of trust and familiarity between team members. 5. An action team's ability to adapt is dependent upon its dynamic instability (the interplay between morphostatic and morphogenetic factors). &bull; Morphostatic factors that promote structure include simple rules, selection of team members, familiarity between team members, and perpetuation of a structured culture that regulates behavior. &bull; Morphogenetic factors that promote flexibility include previous experience, distributed leadership, trust between team members, and perpetuation of a permissive culture that encourages innovation.</p>