Identifying phenological functional types in savanna trees

Savannas are notable for the varied patterns of leaf display in the tree layer. Characterising this variation, and assessing the range of phenological strategies apparent in savanna ecosystems will be helpful for understanding savanna tree life-histories and their response to global change. We recorded leaf phenological metrics on a monthly basis for 28 woody species for one year in a semi-arid savanna at Nylsvley Nature Reserve, South Africa. Using these metrics four plant functional types were described: (1) evergreen species, which retained full canopy throughout the year; (2) semi-evergreen species, which lost a significant amount of canopy during the dry season, but not less than 60%; (3) obligate deciduous species in which the canopy was leafless for about 3 months during the dry season; and (4) rain-stimulated species, in which canopy flushing was driven by rainfall patterns. Of the 28 species, 18% were evergreen, 18% obligate deciduous, 32% semi-evergreen and 32% were rain-stimulated species. These results confirm that phenological strategies are variable in savannas, and highlight that there are numerous cues controlling the timing of leaf out and leaf drop. By defining distinct phenological strategies we can predict which plant functional types will have phenological cues that will be vulnerable to shifting climates.     

降水和氮沉降对内蒙古半干旱草地羊草和大针茅叶片碳交换的影响

本研究对我国北方半干旱草地进行春季增雪、夏季增雨和施氮处理,通过监测羊草（Leymus chinensis）和大针茅（Stipa grandis）的光响应曲线,以期探讨降水和氮沉降对半干旱草地叶片碳交换的影响。结果表明：夏季增雨（100 mm）分别提高了羊草和大针茅最大光合速率,提高了气孔导度和土壤含水量,降低了土壤温度;但春季增雪（25 mm雪水当量）对以上各指标的影响不显著;施氮（10 g· m^-2）显著提高了羊草叶绿素含量,但对以上各指标影响均不显著。本研究表明增水和施氮对关键物种叶片碳交换的作用主要通过影响叶片光合生理特性以及土壤微环境实现。     

Towards the development of a bioeconomic stocking model for the semi‐arid savanna of KwaZulu‐Natal

Abstract

Rainfall variability is a major determinant of system dynamics and profitability of livestock enterprises in arid and semi‐arid environments. Range managers consequently require detailed information on the financial and ecological implications of various stocking strategies in order to formulate viable management systems. Data collected over seven seasons (1986–1993), from a series of extensive grazing trials in the semi‐arid savanna of KwaZulu‐Natal with cattle stocked at three rates (0.17, 0.23 and 0.30 LSU ha^?1) were used to develop a bioeconomic stocking model (LOWBEEF). The model comprised two biological sub‐models (BEEF and GRASS), and an integrated economic component. The BEEF sub‐model related seasonal live mass gain to stocking rate and rainfall. The GRASS sub‐model related residual herbage at the end of summer to summer stocking intensity, range condition (indexed as the sum of proportions of three key forage species, Themeda triandra, Panicum maximum and P. coloratum) and rainfall. The period over which supplementary feeding would be required to maintain cattle mass was related to residual summer herbage mass. The biological sub‐models were linked to an economic component model (ECON) to reflect the influence of various environmental and economic parameters on profitability.     

短期施水对长期干旱铁杆蒿光合作用和叶绿素荧光特征的影响

模拟长期干旱条件下的突然降雨,研究短期施水对长期干旱条件下铁杆蒿(Artemisia sacrorum)光合特性的影响。结果表明,施水后,铁杆蒿的叶水势得到恢复,表观量子效率、羧化速率和最大光合能力明显增加,限制光合作用的气孔因素和非气孔因素得到缓解;铁杆蒿的光化学活性(Fv/Fm)在施水后完全恢复,实际光量子产量(PhiPSII))增加,PSII的还原比例和非化学猝灭(NPQ)降低;不同水分条件下,铁杆蒿叶片的叶绿素荧光光诱导过程存在较大的差异;施水后叶片光合速率(Pn)、气孔导度(gs)和PhiPSII上升速率明显加快,而非化学猝灭(NPQ)启动速度和最大值相对较小。     

Faecal nitrogen of browser and mixed feeder game species during different seasons

A practical measure of assessing periods of potential nutritional stress of game species is needed in the management of these species in the Acacia karroo Riparian Thicket of the central Free State. The objectives of the study were to determine N_f concentration of four game species (browsers and mixed feeders) during different seasons, compare N_f with leaf phenology patterns, and assess whether N_f reaches levels at which body condition loss can be expected. A seasonal pattern was observed with the lowest N_f concentrations recorded during late winter, which correlated with the seasonal phenology pattern (leaf carriage) of the winter-deciduous tree species. The N_f concentrations (g N kg?1 dung DM) of giraffe ranged from 18.3 (late winter) to 36.7 (summer) and that of kudu from 13.6 to 33.2. Likewise, the N_f of impala ranged from 16.9 to 28.0 and that of eland from 16.3 to 34.9. Access to evergreen woody species during the late-winter period proved to be essential in avoiding condition loss that corresponds with N_f levels below published critical levels (<16). In the absence of evergreen species, supplementary feeding is essential. Faecal nitrogen proved to be a useful indicator of seasonal trends in the nutritional status of browsing game species.     

Comparison of Seed Bank Estimation Techniques Using Six Weed Species in Two Soil Types

Evaluation of the viable seeds in a soil, otherwise known as the seed pool or seed bank, is a crucial component of many weed dynamic and plant ecology studies. Seed bank estimation is used to predict the possibility of future weed infestations in rangelands as well as the nascent native plant diversity within them. However, there is no standardized method of reporting seed bank evaluation techniques, limiting the ability to compare across studies. After sowing known quantities of cheatgrass, Bromus tectorum (L.); brome fescue, Vulpia bromoides (L., S.F. Gray); pigweed, Amaranthus retroflexus (L.); kochia, Kochia scoparia (L. Schrad.); lambsquarters, Chenopodium album (L.); and field pepperweed, Lepidium campestre (L. R. Br.) into sterile soil, we compared two different watering regimes in two soil types to Petri plate germination of these seeds. Seed bank estimations from the emergence method were lower compared to estimations from the Petri plate germination. Top-and-bottom watering increased absolute abundance, and the rank order of abundance among species changed with watering method. Emergence levels were the same between the two soil types. The higher water availability of the top-and-bottom watering method resulted in greater seedling emergence (26.3% ± 10% SD vs. 9.1% ± 7.5% SD). Lower emergence compared to germination (62.3% ± 24.4%) may indicate that emergence is an important postgermination barrier to seedling establishment. While emergence techniques may not accurately portray the volume of seeds in the soil, they may more accurately predict which plants can become established in field conditions. Our different species abundances between watering methods show that multiple emergence methods may need to be employed to forecast a range of future rangeland conditions from the soil seed bank.     

Soil Moisture Enhancement Techniques Aid Shrub Transplant Success in an Arid Shrubland Restoration

In arid and semi-arid environments, where low and unpredictable rainfall is typical, establishment of perennial vegetation can be enhanced with modest increases in soil moisture. We evaluated methods for promoting shrub transplant establishment. We transplanted approximately 1 000 3-mo-old seedlings in April 2004, 2005, and 2006, using a full-factorial design with combinations of three treatments: addition of mycorrhizae spores to the root zone, addition of a hydrogel to the root zone, and placement of a wood obstruction south of the plant. We planted three shrubs: big sagebrush (Artemisia tridentata Nutt. ssp. tridentate), four wing saltbush (Atriplex canescens [Pursh] Nutt.), and rubber rabbitbrush (Ericameria nauseosa [Pall. ex Pursh] G.L. Nesom & Baird ssp. nauseosa) in a 1.2-ha area. The summer months of 2004 and 2006 were dry, leading to low survivorship (< 1%). With higher rainfall in summer 2005, transplant survivorship was ～18%. For the 2005 transplants, A. tridentata had the highest survivorship after one growing season (31.0%), followed by A. canescens (20.6%) and E. nauseosa (6.9%). Placing a wood obstruction near the plant was significant in the statistical model to describe short-term overall transplant survival and survival of A. tridentata. Placing hydrogel in the root zone also explained short-term overall transplant survival, as well as survival of E. nauseosa. However, by 4.5 yr after transplanting, there was no significant treatment effect on survival. Thus, for transplanting shrub seedlings on arid or semi-arid sites, we recommend some form of resource enhancement technique to increase short-term survival. In this experiment, both the obstruction and hydrogel treatments were effective. We recommend the obstruction treatment since slash is often readily available onsite, has low labor requirements and cost, and it increased transplant survival of A. tridentata, a species of conservation concern; however, other treatments may be appropriate for individual species.     

Growth and desiccation of Themeda triandra and Sporobolus fimbriatus in relation to diminishing moisture availability

Abstract

Water was withheld from individual plants of Themeda triandra and Sporobolus fimbriatus growing in pots in a greenhouse. Leaf extension growth, followed by successive degrees of tiller desiccation, were monitored on a daily basis and related to diminishing moisture availability. Leaf extension growth ceased after about 40 % soil water depletion in both species on the sandy clay loam used in the trial. Thereafter, leaves and growing points senesced progressively with increasing evaporative demand, despite a relatively small drop in soil moisture content. The tentative conclusion is that active leaf growth in semi‐arid grassveld takes place in short sporadic spells subsequent to each effective rainfall event. It seems, for example, that after a rain of 50 mm in midsummer, the duration of active leaf growth could be no more than a week.     

Long-Term Effects of Fire,Livestock Herbivory Removal,and Weather Variability in Texas Semiarid Savanna

We examined how the occurrence and structure of grasses and woody plants changed after 12 yr of a fire season manipulation and removal of livestock herbivores. Applying high intensity fires in the summer preserved the structural integrity of this semiarid live oak (Quercus virginiana Mill.) savanna while decreasing or eliminating numerous problematic plants in the understory and overstory, such as prickly pear cactus (Opuntia spp.), sacahuista (Nolina texana S. Watson), Ashe juniper (Juniperus ashei J. Buchholz), Pinchot's juniper (J. pinchotii Sudw.), and honey mesquite (Prosopis glandulosa Torr.). In the less intense repeat winter burning treatments, undesirable woody plants were generally maintained at pretreatment levels in the overstory but all woody plants except Ashe juniper increased in the understory. Alternatively, areas excluded from fire in the control treatment rapidly transitioned from a grass-tree codominated savanna environment to one that is heavily dominated by woody plants. In the grass community, the most frequently occurring grass species in the winter burn treatment differed from summer burn and control treatments, whereas the summer burn treatment was not different from the control. Of the herbaceous plants, only little bluestem (Schizachyrium scoparium &lsqb;Michx.] Nash) responded to fire treatments. Little bluestem increased in the winter burn treatment, remained fairly constant in the summer burn treatment, and decreased in the control. Other grasses varied largely as a function of annual weather variability, the removal of livestock, and legacy effects resulting from pre-existing variability. These findings suggest that fire can reduce or eliminate woody plant species that threaten the stability of live oak savannas while having little long-term effect on grasses desired by rangeland managers.     

Texas Wintergrass and Buffalograss Response to Seasonal Fires and Clipping

There is increased interest in the use of summer-season fires to limit woody plant encroachment into grasslands, but effects of these fires on grasses are poorly understood. We quantified effects of repeated winter fires, repeated summer fires, and clipping (to simulate grazing) on aboveground total yield, live yield, and percentage of live tissue of C₃ Texas wintergrass (Nassella leucotricha [Trin. & Rupr.] Pohl.), and C₄ buffalograss (Buchloë dactyloides [Nutt.] Engelm.) in 2 experiments. Monospecific patches of each species were exposed to 1 of 3 fire treatments (no-fire, 2 winter fires in 3 years, or 2 summer fires in 3 years) and 1 of 2 clip treatments (no clip or clip once each spring). Experiment 1 evaluated effects of fire without grazing or clipping on late-growing season (late-season) yields. Late-season total yield of both species recovered from winter and summer fires within 1 or 2 growing seasons post-fire. By 3 years post-fire, Texas wintergrass late-season total yield was 2 times greater in the summer fire treatment than the winter fire or no-fire treatments, and buffalograss late-season total yield was 3 times greater in summer and winter fire treatments than in the no-fire treatment. Experiment 2 evaluated combined effects of fire and clipping the previous spring on spring-season yields. Clipping alone or with fire (summer or winter) reduced Texas wintergrass yields on more sample dates than occurred with buffalograss. By 3 years post-fire, buffalograss spring total yield was greater in all fire and fire + clip treatments than in the clip only or untreated controls. Results suggest: 1) both species were tolerant of summer fire, 2) fire in either season with or without clipping stimulated buffalograss production, and 3) buffalograss was more tolerant than Texas wintergrass to the combined effects of clipping + fire (either season).     

Livestock Browsing,Not Water Limitations,Contributes to Recruitment Failure of Dobera glabra in Semiarid Ethiopia

The study used nursery and field experiments to investigate why recruitment of Dobera glabra (Forssk) Poir., a native food source for both humans and livestock, often fails in the semiarid rangelands of Afar, Ethiopia. We hypothesized that soil water limitations and browsing by livestock would be the primary mechanisms accounting for the failure of natural regeneration. We used three sets of experiments—1) seedling performance in response to shade and watering in a nursery, 2) field regeneration with and without browsing, and 3) regeneration beneath trees with and without browsing—to examine regeneration success. Seedlings were established in plots from seeds sown directly into the soil for nursery and field experiments, but natural germination occurred beneath trees. Survival and relative growth rates (RGR) were used to monitor seedling performance. Seedlings that received neither shade nor watering treatments had lower seedling survival (53 ± 15%) as compared with other treatment combinations. Highest seedling survival was recorded under shade and 1 d watering s wk^-1 treatment combinations (92 ± 1%). However, shade treatments had a minimal increase on seedling RGR. Water limitation is not a crucial limiting factor for D. glabra recruitment, as 53% of the seedlings survived without both shade and supplemental water for 1 yr. Field experiments, however, demonstrated that browsing greatly reduced seedling survival (below 15%) and suppressed growth of surviving seedlings, suggesting that browsing is the major factor preventing natural recruitment. Natural recruitment of D. glabra is unlikely with the existing continuous and intensive grazing/browsing in Afar rangelands, where the mobility of pastoralists is restricted. We suggest that planting nursery-raised seedlings in home gardens of settled pastoralists and establishment of grazing reserves in some key range sites that contain D. glabra could help offset the recruitment failure of native food species D. glabra in Afar rangelands.     

Early Decomposition of Ashe Juniper (Juniperus ashei) Wood in Open and Shaded Habitat

Grasslands of the Edwards Plateau of central Texas have been extensively altered through woody species encroachment, particularly as a result of increasing abundance of the invasive native shrub, Ashe juniper (Juniperus ashei). Over the last several decades there has been widespread mechanical removal of the species. The wood is often left in place to decompose, either mulched or not. Where the wood is left to decompose might have some bearing on its rate of decomposition. This study was conducted to determine the rates of Ashe juniper wood decomposition as a function of open vs. shaded habitat and the potential effect of wood decomposition on nutrient inputs into this system. Wood decomposition in this arid ecosystem might be expected to occur more rapidly in shaded habitat where the moisture and temperature regimes would be more favorable for wood-decomposing fungi. On the other hand, during times of low rainfall we might expect wood to decompose more rapidly when exposed to high levels of ultraviolet radiation. In our experiment, we found no difference between open and shaded treatments. Wood biomass loss occurred rapidly over the first 3–4 mo of the study and slowed for the remaining 2 yr. Wood carbon (C) increased only slightly (7.3%), but nitrogen (N) increased significantly (176%). As a consequence of changes in wood nitrogen, C∶N decreased through time. Results of this study suggest that the wood decomposition process in open and shaded habitats in this arid ecosystem during a time of low rainfall do not differ. Our findings also suggest that land managers aiming to establish native species following felling of Ashe juniper should do so in the first year when nutrient release from decomposing wood is the highest.     

Biology of Larks (Aves: Alaudidae) in the Central Namib Desert

1. The biology of six species of larks in the Namib Desert near Walvis Bay, South West Africa, was studied in 1964, 1965 and 1966.

2. All species reproduced following rainfall in summer and autumn months, with the appearance of green grass and abundant insects on which the birds fed.

3. The primarily insectivorous species, Certhilauda albofasciata, shows no seasonality in moulting and testicular development, and reproduces whenever local rainfall results in favourable feeding and nesting circumstances, while the primarily granivorous Spizoeorys starki and Eremopterix verticalis have markedly seasonal testicular and moulting cycles timed so that reproduction occurs only during the late summer and autumn months. Ammomanes grayi is intermediate in food habits and in timing of moulting and reproduction, and C. albescens and Mirafra naevia may also be intermediate in this respect.

4. S. starki and E. verticalis are the only larks that normally drink, but flocks of both species were observed that were independent of drinking water.

5. Larks avoid heat stress during daytime by keeping to the shade of stones, tufts of vegetation and mouths of rodent burrows; and nests are nearly always placed on the shady side of a stone' or tuft of grass.

6. It is suggested that larks may be successful desert occupants because they have not become highly specialized and therefore can tolerate rapidly and severely changing environ-mental conditions associated with drought and irregular rainfall.     

Distribution,biology and flower relationships of fideliid bees of southern Africa (Hymenoptera,Apoidea, Fideliidae)

Fideliids are ground-nesting bees, covered in a dense pale straw to brown pile, with pollen being carried on an abdominal scopa. Fidelia paradoxa, F. villosa and F. kobrowi are restricted to flowers of the Mesembryanthemaceae, and Parafidella major and two new Parafidelia species to Grielum and Neuradopsls (Roseaceae). Parafidelia ornata collects pollen mainly from Tribulus and Tribulocarpus and P. pallidula only from Sisyndite (Zygophyllaceae). Parafidelia friesei visits flowers of Sesamum (Pedaliaceae) and Fidelia braunsiana is confined to Berkheya (Asteraceae). The rainfall pattern divides the species into early summer bees (7 species) of the winter rainfall and autumn bees (4 species) of the summer rainfall areas. Two of the above species have populations in both regions. The winter rainfall bees have a south-western distribution with Graaff-Reinet the eastern limit but the summer rainfall species occur further north, with the eastern Botswana border their eastern limit and Keimoes on the Orange River their southern limit.     

Community Stability Was Maintained by Divergent Mechanisms in Arid Desert Ecosystem

More attention has been paid to the effects of diversity and dominance on community temporal stability rather than spatial stability in the main biome globally. Moreover, the maintenance mechanisms underlying the stability patterns of plant communities dominated by different plants in the Gobi Desert remain unknown. This article addresses the maintenance mechanism of plant community stability dominated by different plants in the Gobi Desert northwest of China. Four communities dominated by Sympegma regelii, Reaumuria songarica, Nitraria sphaerocarpa, and Gymnocarpos przewalskii, respectively, were selected in the national nature reserve, and a total of 240 quadrats, 20 × 20 m each, were established in the four communities. The correlations among species richness, species evenness, species diversity, community stability, and the biomass of dominant species were analyzed by linear regression model and structural equation model. The dominant species determined positively and directly the stability of the N. sphaerocarpa community, while diversity acted negatively in the maintenance of G. przewalskii community stability. However, species richness contributed mainly and positively to the maintenance of stability in the S. regelii community. Direct and negative effect of species richness and positive function of diversity were found in the maintenance of stability in the R. songarica community. Taken together, community stability is maintained by the divergent mechanisms in arid environment, which depends on the dominant species and diversity. The study could provide reference for the management of communities in the arid desert regions.     

Feeding value of hays of tropical forage legumes in pigs: Vigna unguiculata,Psophocarpus scandens,Pueraria phaseoloides and Stylosanthes guianensis

The effects of four tropical forage legume hays (Vigna unguiculata, Psophocarpus scandens, Pueraria phaseoloides and Stylosanthes guianensis) on voluntary feed intake (VFI) and their nutritive value were studied in growing pigs using a corn-soybean meal-based diet containing varying proportions of forage legume hays (0, 10, 20 and 40 % or 0, 12.5 and 25 % for VFI and nutritive value determination, respectively). There was no difference in VFI between species (P?>?0.20), but a linear response to forage inclusion level (P?V. unguiculata, where the response was quadratic (P?=?0.01). All four forage species linearly decreased the total tract apparent digestibility (TTAD) from 0.76 to 0.61, 0.80 to 0.68, 0.54 to 0.40 and 0.58 to 0.31 except for S. guianensis (0.44) for DM, N, NDF and N retention, respectively. Differences in digestibility (P?S. guianensis, in which N retention remained quite high (0.44) at the highest inclusion level (25 %). P. phaseoloides hay should be avoided in pigs as it combines the lowest VFI with the lowest nutrient digestibility.     

Successional Transitions and Management of a Phosphorus-Limited Shrubland Ecosystem

The decline of traditional pastoral systems has highlighted the problem of managing shrub encroachment on successional shrublands in the Mediterranean region, especially in marginal habitats. A long-term study of the response of ecosystem dynamics to phosphate amelioration and shrub control was initiated in 1988 on an area of phosphorus deficient terra rossa, dominated by dwarf shrubs that had been burnt in the summer of that year. The treatments were imposed in a replicated factorial design once at the beginning of the study. The area was previously grazed yearlong by goats, but during the experiment beef cattle grazed the area during the summer of each year. Without herbicide control, shrub cover reached its preburn level within 5 years, but with shrub control after 17 years, it had not yet reached the preburn level. The average shrub cover over the whole experimental period was 41.9%–49.1% without herbicide and 13.5%–24.4% with (P < 0.0001, SE of the difference = 3.99). The effect of phosphate application on shrub cover was not significant, but cover of herbaceous vegetation increased (P < 0.0016, SE of difference = 5.03). A “state and transition” scheme was constructed that defines the interventions necessary to buffer any one of the states against the pressures of successional processes. Vegetation states were defined by the dominance of either herbaceous vegetation or one of two spiny shrub species, Prickly burnet (Sarcopoterium spinosum, Rosaceae) and Calicotome villosa (Fabaceae). The timing and scale of the interventions depend largely on landscape management objectives and on available economic and logistic resources. We conclude that appropriate management of grazing, periodic control of the shrub component, and occasional soil nutrient amelioration can lead to the development of attractive open woodland with a productive herbaceous understory that provides a wider range of ecological services than a landscape dominated by the undisturbed successional shrub thickets.     

Long-Term Response Patterns of Tallgrass Prairie to Frequent Summer Burning

Knowledge of how tallgrass prairie vegetation responds to fire in the late growing season is relatively sparse and is based upon studies that are either spatially or temporally limited. To gain a more robust perspective of vegetation response to summer burning and to determine if repeated summer fire can drive vegetational changes in native tallgrass prairie, we evaluated species cover and richness over a 14-yr period on different topographic positions from ungrazed watersheds that were burned biennially in the growing season. We found that annual forbs were the primary beneficiaries of summer burning, but their fluctuations varied inconsistently among years. Concomitantly, species richness and diversity increased significantly with summer burning but remained stable through time with annual spring burning. After 14 yr, species richness was 28% higher in prairie that was burned in the summer than in prairie burned in the spring. Canopy cover of big bluestem (Andropogon gerardii Vitman) and Indiangrass (Sorghastrum nutans [L.] Nash) increased significantly over time with both summer and spring burning, whereas heath aster (Symphyotrichum ericoides [L.] Nesom), aromatic aster (Symphyotrichum oblongifolium [Nutt.] Nesom), and sedges (Carex spp.) increased in response to only summer burning. Kentucky bluegrass (Poa pratensis L.) cover declined in both spring-burned and summer-burned watersheds. Repeated burning in either spring or summer did not reduce the cover or frequency of any woody species. Most perennial species were neutral in their reaction to summer fire, but a few species responded with large and inconsistent temporal fluctuations that overwhelmed any clear patterns of change. Although summer burning did not preferentially encourage spring-flowering forbs or suppress dominance of the warm-season grasses, it is a potentially useful tool to increase community heterogeneity in ungrazed prairie.     

Long-Term Effects of a Summer Fire on Desert Grassland Plant Demographics in New Mexico

Plant demographic responses to an experimental summer fire were monitored for 12 yr on the Sevilleta National Wildlife Refuge, New Mexico, to determine recovery rates of burned plants and evaluate fire effectiveness in preventing shrub invasion of desert grasslands. Fourteen common species of grasses, shrubs, yucca, and cacti were measured for mortality, resprouting, regrowth, herbivory, and reproduction. After the first postfire growing season, black grama (Bouteloua eriopoda [Torr.] Torr.) declined 80% in size, whereas blue grama (Bouteloua gracilis [Willd. ex Kunth] Lag. ex Griffiths) exhibited no decline. Linear regression indicated that B. eriopoda needed 11 yr to recover. Spike dropseed (Sporobolus contractus A.S. Hitchc.) and purple three-awn (Aristida purpurea Nutt.) showed postfire declines in plant sizes, requiring 4- and > 5-yr recovery times, respectively. Sand muhly (Muhlenbergia arenicola Buckl.) exhibited no fire impact. Snakeweed (Gutierrezia sarothrae [Pursh] Britt. & Rusby) sustained 61% fire mortality and reduction in regrowth canopy size. Creosotebush (Larrea tridentata [Sesse & Moc. ex DC.] Coville) had 12% mortality, but survivors recovered over 12 yr. Fourwing saltbush (Atriplex canescens [Pursh] Nutt.) sustained 62% mortality, but recovered plant size in 5–6 yr. Winterfat (Krascheninnikovia lanata [Pursh] A. D. J. Meeuse & Smit) suffered 7% mortality, but required 9+ yr to recover. Pale desert-thorn (Lycium pallidum Miers) survived fire, recovering prefire canopy size in 3 yr. Torrey joint-fir (Ephedra torreyana Watson) exhibited < 1% mortality, and recovered in 2–3 yr. Soapweed yucca (Yucca glauca Nutt.) had < 2% mortality, recovered plant sizes in 2 yr, and increased numbers of rosettes 17%. Chollas (Opuntia imbricata [Haw.] DC. and Opuntia clavata Engelm.) suffered high mortality rates and required > 12 yr recovery times. Results demonstrated that summer fire may counter some shrub and cacti invasion in central New Mexico, but once shrubs mature, fire is less effective in removing woody plants to restore southwestern grasslands.     

Chukar Watering Patterns and Water Site Selection

We evaluated chukar (Alectoris chukar) watering patterns as well as habitat variables influencing water site selection in western Utah. Motion-sensing cameras and chukar dropping counts were primary techniques to evaluate watering patterns. We took vegetative and other habitat measurements at each water source (n = 43) to discriminate use from nonuse sites using logistic regression. Chukars watered during daylight hours with a modal hour from 1200 hours to 1300 hours daylight savings time. Annual patterns suggest limited use of water sources from November to May with first observed visits occurring in June and last observed visits in October. Shrub canopy cover was the only variable to discriminate between site types (P &spilt; 0.01). Cross validation showed a predictive success rate of 84%. Significant differences were found between use and nonuse sites in terms of security cover (P &spilt; 0.01), but not total cover (P &spigt; 0.05). Chukars seem to have a loose shrub canopy threshold near 11% that is likely due to predation risk. Water sources meeting this threshold received use, whereas those not meeting this threshold did not. Increasing shrub canopy cover above 11% did not translate into increased water source use. Managers might want to consider annual patterns when setting hunt season timing and structure as well as judging sites for new water developments based on shrub canopy cover. More generally, these results suggest a behavioral constraint on the use of water sources as a function of predation risk—we should expect other species to demonstrate similar behavioral constraints. These constraints must be considered in any effort to determine benefits or impacts of water developments.