Wet Season Range Research Articles

Multiscale Spatiotemporal Variations of GNSS-Derived Precipitable Water Vapor over Yunnan

The geographical location of Yunnan province is at the upstream area of water vapor transportation from the Bay of Bengal and the South China Sea to inland China. Understanding the spatiotemporal variations of water vapor over this region holds significant importance. We utilized the Global Navigation Satellite System (GNSS) data collected from 12 stations situated in Yunnan, which are part of the Crustal Movement Observation Network of China, to retrieve hourly precipitable water vapor (PWV) data from 2011 to 2022. The retrieved PWV data at Station KMIN were evaluated by the nearby radiosonde data, and the results show that the mean bias and RMS of the differences between the two datasets are 0.08 and 1.78 mm, respectively. Average PWV values at these stations are in the range of 11.77 to 33.53 mm, which decrease from the southwest to the north of Yunnan and are negatively correlated with the stations’ heights and latitudes. Differences between average PWV in the wet season and dry season range from 12 to 27 mm. These differences tend to increase as the average PWV increases. The yearly rates of PWV variations, averaging 0.18 mm/year, are all positive for the stations, indicating a year-by-year increase in water vapor. The amplitudes of the PWV annual cycles are 9.75–20.94 mm. The spatial variation of these amplitudes is similar to that of the average PWV over the region. Generally, monthly average PWV values increase from January to July and decrease from July to December, and the growth rate is less than the decline rate. Average diurnal PWV variations show unimodal PWV distributions over the course of the day at the stations except Station YNRL, where bimodal PWV distribution was observed.

Seasonal patterns of malaria, genital infection, nutritional and iron status in non-pregnant and pregnant adolescents in Burkina Faso: a secondary analysis of trial data

BackgroundAdolescents are considered at high risk of developing iron deficiency. Studies in children indicate that the prevalence of iron deficiency increased with malaria transmission, suggesting malaria seasonally may drive iron deficiency. This paper examines monthly seasonal infection patterns of malaria, abnormal vaginal flora, chorioamnionitis, antibiotic and antimalarial prescriptions, in relation to changes in iron biomarkers and nutritional indices in adolescents living in a rural area of Burkina Faso, in order to assess the requirement for seasonal infection control and nutrition interventions.MethodsData collected between April 2011 and January 2014 were available for an observational seasonal analysis, comprising scheduled visits for 1949 non-pregnant adolescents (≤19 years), (315 of whom subsequently became pregnant), enrolled in a randomised trial of periconceptional iron supplementation. Data from trial arms were combined. Body Iron Stores (BIS) were calculated using an internal regression for ferritin to allow for inflammation. At recruitment 11% had low BIS (< 0 mg/kg). Continuous outcomes were fitted to a mixed-effects linear model with month, age and pregnancy status as fixed effect covariates and woman as a random effect. Dichotomous infection outcomes were fitted with analogous logistic regression models.ResultsSeasonal variation in malaria parasitaemia prevalence ranged between 18 and 70% in non-pregnant adolescents (P < 0.001), peaking at 81% in those who became pregnant. Seasonal variation occurred in antibiotic prescription rates (0.7–1.8 prescriptions/100 weekly visits, P < 0.001) and chorioamnionitis prevalence (range 15–68%, P = 0.026). Mucosal vaginal lactoferrin concentration was lower at the end of the wet season (range 2–22 μg/ml, P < 0.016), when chorioamnionitis was least frequent. BIS fluctuated annually by up to 53.2% per year around the mean BIS (5.1 mg/kg2, range 4.1–6.8 mg/kg), with low BIS (< 0 mg/kg) of 8.7% in the dry and 9.8% in the wet seasons (P = 0.36). Median serum transferrin receptor increased during the wet season (P < 0.001). Higher hepcidin concentration in the wet season corresponded with rising malaria prevalence and use of prescriptions, but with no change in BIS. Mean Body Mass Index and Mid-Upper-Arm-Circumference values peaked mid-dry season (both P < 0.001).ConclusionsOur analysis supports preventive treatment of malaria among adolescents 15–19 years to decrease their disease burden, especially asymptomatic malaria. As BIS were adequate in most adolescents despite seasonal malaria, a requirement for programmatic iron supplementation was not substantiated.

The vegetation and wildlife habitats of the Savuti-Mababe-Linyanti ecosystem, northern Botswana

This study classified the vegetation of the Savuti-Mababe-Linyanti ecosystem (SMLE), northern Botswana and developed a detailed map that provides a reliable habitat template of the SMLE for future wildlife habitat use studies. The major vegetation units of the SMLE were determined from satellite imagery and field visits and then mapped using Landsat 8 and RapidEye imagery and maximum likelihood classifier. These units were sampled using 40 m x 20 m (800 m²) plots in which the coverage of all plant species was estimated. Non-metric multidimensional scaling (NMS) demonstrated that plant communities were determined by gradients in soil texture or fertility and wetness. NMS 1 represented a gradient of soil texture with seven woodland communities on sandy soils (sandveld communities and Baikiaea forest) dominated by Baikiaea plurijuga in Baikiaea forest and Terminalia sericea and Philenoptera nelsii in sandveld, with various indicator species differentiating the various sandveld community types. Mopane woodland further from and riparian woodland adjacent to permanent water was common on less sandy alluvial soils. Mineral-rich, heavy clay soils in the sump of a large paleolake system support open grassland and mixed Senegalia/Vachellia (Acacia) savanna, with the mineral-rich soils supporting grasses high in minerals such as phosphorus, calcium, sodium and potassium, and thus this region is a critical wet season range for migratory zebra. Taller, high-quality grasses in the mosaic of sandveld and mopane woodland communities provide critical grazing for taller grass grazers such as buffalo, roan and sable antelope, whereas wetland communities provide reliable green forage during the dry season for a variety of herbivores, including elephant. This study has demonstrated how large-scale environmental gradients determine functional habitat heterogeneity for wildlife.Conservation implications: Our study demonstrated that the functionality of protected areas is determined by large-scale environmental gradients. Thus conservation science must aim to ensure that protected areas cover the full range of key environmental gradients in a region (soil texture and wetness in our study). Our habitat map provides a data base for wildlife habitat use studies in the region.

Wet season range fidelity in a tropical migratory ungulate

1. In migratory populations, the degree of fidelity and dispersal among seasonal ranges is an important population process with consequences for demography, management, sensitivity to habitat change and adaptation to local environmental conditions. 2. Characterizing patterns of range fidelity in ungulates, however, has remained challenging because of the difficulties of following large numbers of marked individuals across multiple migratory cycles and of identifying the appropriate scale of analysis. 3. We examined fidelity to wet season (i.e. breeding) ranges in a recently declining population of wildebeest Connochaetes taurinus Burchell in northern Tanzania across 3 years. We used computer-assisted photographic identification and capture-recapture to characterize return patterns to three wet season ranges that were ecologically discrete and topographically isolated from one another. 4. Among 2557 uniquely identified adult wildebeest, we observed 150 recaptures across consecutive wet seasons. Between the two migratory subpopulations, the probability of remaining faithful to wet season areas ranged between 0·82 and 1·00. Animals from a non-migratory segment of the population (near Lake Manyara National Park) were rarely observed in other wet season ranges, despite proximity to one of the migratory pathways. 5. We found no effect of sex on an individuals' probability of switching wet season ranges. However, the breeding status of females in year i had a strong influence on patterns of range selection in year i + 1, with surviving breeders over three times as likely to switch ranges as non-breeders. 6. Social-group associations between pairs of recaptured animals were random with respect to an individual's wet season range during the previous or forthcoming wet seasons, suggesting that an individual's herd identity during the dry season does not predict wet season range selection. 7. Examining fidelity and dispersal in terrestrial migrations improves our understanding of the constraints that migrants experience when they face rapid habitat changes or fluctuations in environmental conditions.

Inherent density-dependency of wet-season range even at the extreme of nonequilibrium environments

There has been considerable recent progress in integrating equilibrium and nonequilibrium rangeland ecologies on the basis of landscape heterogeneity. This follows from the argument that small key resource areas provide spatial buffer effects that sustain animal populations and are prone to animal–vegetation density-dependency, whereas wet-season ranges are density-independent. Although dryland spatial heterogeneity generally occurs through a combination of heterogeneous precipitation and landscape heterogeneity, the former is rarely considered in the development of such theories. Here, we used a published multi-agent model to examine how both types of heterogeneity interact. We found that a certain level of density-dependency occurred in wet-season range, even under extreme nonequilibrium conditions. During a drought, most of the key resources and part of the wet-season range that was not subject to drought simultaneously exhibited density-dependency, reflecting the impact of rainfall heterogeneity. With decreased key resource area, the density-dependency of the wet-season range after livestock population recovery—a factor included in current theory—decreased dramatically, whereas that during drought—a factor neglected in current theory—did not decrease markedly. Therefore, our results extend current theory by suggesting that the contradiction stemmed from neglecting the spatial buffer effect of heterogeneous precipitation, which is responsible for density-dependency of wet-season ranges during drought.

The ranging patterns of elephants in Marsabit protected area, Kenya: the use of satellite‐linked GPS collars

AbstractWe investigated the ranging patterns of elephants in the Marsabit protected area, north eastern Kenya, to ascertain the range of bachelor and female family herds in different seasons, and to identify corridor and noncorridor areas. Data were acquired for five bachelor and four female family herds equipped with satellite‐linked geographical positioning system collars, and monitored from December 2005 to December 2007. Distinct dry (about 260 km2) and wet seasons (about 910 km2) ranges were observed, with connecting corridors (north‐eastern corridor: about 90 km long, about 2‐7 km wide; southern corridors: about 10‐20 km long, about 2‐3 km wide). The dry season range corresponded with Marsabit evergreen forest, while the wet season range matched with dry deciduous lowland shrubs. The ranging elephants moved at speed of about 0.2‐20 kmh−1. Bachelor herds moved faster than female family herds. Elephants moved fast during the intermediate and wet seasons than during the dry season. The speed of ranging elephants was over 1 kmh−1 in the corridor areas and about 0.2 to less than 1 kmh−1 in the non‐corridor areas. Expansion of settlements towards corridor areas needs to be controlled to avoid future blocking of connectivity between wet and dry season elephant ranges.

Seasonal home range of Swayne\'s Hartebeest (&lt;i&gt;Alcelaphus buselaphus swaynei&lt;/i&gt;) in Senkele Swayne\'s Hartebeest Sanctuary

The home range of the endangered Ethiopian endemic hartebeest, Swayne\'s hartebeest, Alcelaphus buselaphus swaynei, was studied in Senkele Swayne\'s Hartebeest Sanctuary (SSHS). The size of the sanctuary has been diminishing since 1974, resulting in the shrinking of the area available for the hartebeests. Even in the current available habitat, the animals still preserved their behaviour of ranging in wider area during the wet season and smaller area during the dry season. However, when the human settlers migrate from the sanctuary and the bordering area during the dry season, the hartebeests occupy a range which is larger than their wet season range in the sanctuary. As their dry season home range increased in absence of the settlers, their movement was observed to have increased becoming equivalent to that of the wet season. Key words/phrases: Alcelaphus buselaphus swaynei, home range, human interference, movement, Senkele Swayne\'s Hartebeest Sanctuary SINET: Ethiopian Journal of Science Vol. 27 (2) 2004: 121–126

Seasonal influence of rainfall and crops on home range expansion by bull elephants

'Knowledge of distribution and movement patterns in relation to their environment is essential if elephants are to be effectively managed because crop raiding is spatial and temporal in nature.' This study attempted to obtain estimates of the home ranges of elephants in Sengwa Wildlife Research Area, to establish seasonal crossing patterns into surrounding communal agricultural lands, and to examine the the concept of wet season range expansion. 7 adult and 3 subadult bulls were radio tracked during a two year period. 'Range sizes and crossing patterns out of the protected area were compared by season.' Results suggest that the concept of range expansion at the end of the wet season is correlated with the movement of elephants into agricultural lands. Knowing how and when crop raiding elephants move into subsistence agricultural areas that surround many of the protected areas is considered essential to identifying the reason why elephants and people come into conflict.

Impact of land‐use changes on the wildebeest migration in the northern part of the Serengeti–Mara ecosystem

AimThe study tests the hypothesis that land‐use changes in Narok District have had an impact on the wildebeest population [Connochaetes taurinus mearnsi (Burchell)] in the northern part of the Serengeti–Mara ecosystem.LocationThe Serengeti–Mara ecosystem is a vast area of rangelands, straddling the Tanzanian–Kenyan border in East Africa. The area is home to some 1.3 million wildebeest, of which some 30,000 animals currently reside in the Kenyan part of the ecosystem.MethodsWe analysed the temporal changes in the wildebeest population in the Kenyan part of the Serengeti–Mara ecosystem and their relationship with possible driving forces of change, such as rainfall, normalized difference vegetation index (NDVI), livestock numbers and land‐cover changes. Changes in the spatial distribution of wildebeest for three periods were compared with spatial changes in livestock distribution and land cover. The analyses were repeated for the Tanzanian part of the ecosystem and results compared. We thus tested the relative importance of land‐use changes among the different potential driving forces of change in the wildebeest populations.ResultsThe wildebeest population in the Kenyan part of the Serengeti–Mara ecosystem declined drastically over the past 20 years and is currently fluctuating around an estimated population of 31,300 animals, which is about 25% of the population size at the end of the 1970s. The wildebeest population in the Kenyan part of the Serengeti–Mara ecosystem has, over the last decades, been controlled by food supply during the dry and the wet seasons. Expansion of large‐scale mechanized wheat farming in the Loita Plains since the early 1980s has drastically reduced the wildebeest wet season range, forcing the wildebeest population to use the dryer rangelands in the south‐eastern part of the Loita eco‐unit, or to move to the Mara eco‐unit, where competition with cattle is higher. The expansion of the farming area has not influenced the size of the total cattle population in the Kenyan part of the study area, nor its spatial distribution. The much larger migratory wildebeest population of the Serengeti, in Tanzania, has not been affected by a downward trend from the late 1970s and is regulated by food supply in the dry season (Mduma et al., 1999). Around the Serengeti, in Tanzania, land‐use changes are much less widespread, occur at a lower rate and affect a much smaller area compared with the Kenyan part of the ecosystem. Moreover, land‐use changes around the Serengeti have taken place away from the main migration routes of wildebeest.ConclusionsOver the last decades, the decline in the Kenyan wildebeest population did not seem to affect the much larger Serengeti wildebeest population. However, if more land were to be converted to large scale farming closer to the Masai Mara National Reserve, the dry season range for both the Kenyan and the Serengeti population would be reduced. This might have serious consequences for both populations and therefore for the entire Serengeti–Mara ecosystem.

ON THE RELEVANCE OF NONEQUILIBRIUM CONCEPTS TO ARID AND SEMIARID GRAZING SYSTEMS

The dynamics of arid and semiarid grazing systems are prone to the effects of highly variable rainfall, with droughts causing frequent episodic mortality in herbivore populations. This has led to the suggestion that they are nonequilibrium systems, in which animal impacts on plants are strongly attenuated or absent. We examine the utility and appropriateness of nonequilibrium concepts for understanding ecosystem processes in African rangeland, attempt to distinguish disequilibrium from nonequilibrium, and argue that such concepts do not justify the view that herbivory has little impact in climatically variable systems. We present evidence for an alternative view of African rangeland function. We argue that, despite the apparent lack of equilibrium, animal numbers are regulated in a density-dependent manner by the limited forage available in key resource areas, which are utilized in the dry season. This model asserts that strong equilibrial forces exist over a limited part of the system, with the animal population being virtually uncoupled from resources elsewhere in the system. Spatially and temporally, the whole system is heterogeneous in the strength of the forces tending to equilibrium, these diminishing with distance from watering and key resource areas and during the wet season. We argue that wet-season range is more heavily utilized by animal populations sustained by key resource areas than would apply in the absence of key resources, and that uncoupling of the animal population from vegetation carries an increased risk of degradation. Droughts may impose intense and localized defoliation on vegetation, and this may result in altered species composition, reduced rain-use efficiency, soil erosion, and loss of productive potential. Rather than ignoring degradation, policy-makers and ecologists should seek to identify the characteristics of grazing systems that predispose some systems toward degradation, while others appear to be resistant. Development policies should focus on the spatial heterogeneity in susceptibility to grazing impacts and on preserving the productive capacity of key resource areas.

White rhinoceros range size in the south‐western Kruger National Park

White rhinoceros range size was ascertained telemetrically in the south‐western Kruger National Park. The mean annual range size of territorial males was 9.86 km2 compared to 22.83 km2 for adult females. White rhinoceros females' summer wet season range was larger (21.44 km2) than the winter dry season range (11.64 km2). It is argued that abundant field‐water during the wet season enables animals to range further from permanent water supplies and to utilize larger foraging areas. White rhinoceros have core areas in their individual ranges that usually are situated along riverbanks in the preferred grazing regions. These core areas also include some favourite resting spots on high‐lying areas. White rhinoceros range sizes in the south‐western Kruger National Park were similar to those of other reserves with comparable white rhinoceros densities. In the Umfolozi Game Reserve, which has a higher white rhinoceros density than the Kruger National Park, the individual ranges are much smaller.

Precipitable water in the Sahel measured using sun photometry

A sunphotometer network in Mali and Niger was established in 1984 to measure the temporal and spatial variability of aerosols and water vapor. A new technique developed by Reagan was applied to the master calibration instrument based on a Mauna Loa Langley calibration data set. Measurements obtained with the calibrated instrument for 14 days in July 1987 at Goddard Space Flight Center (Greenbelt, MD), retrieved the vertical column precipitable water ( P W) to within an average of 0.28 cm of the radiosonde measured values under a 2–5 cm P W range and a large range of aerosol optical thicknesses. The calibration was transferred to the sunphotometers in the Sahel via inter-calibration. Precipitable water retrieved for the Sahelian sites show close agreement with the sparse radiosonde data available and is consistent with published data. The spatial variability of the precipitable water was found to be significantly lower than the aerosol optical depth spatial variability, and there is no correlation between the magnitude of precipitable water and aerosol optical depth. The network shows a dry season monthly average P W value of 1–2 cm and a wet season range of 3.5–4.5 cm.

Rumen Digestive Capability of Zebu Steers in Wet and Dry Seasons

Most authors have suggested that the rumen’s capability to digest foodstuff is itiuenced by the conditions resulting from microbial populations which are regulated by composition of the diets. Presumably the greatest ecological diierences within the rumens of cattle grazing tropical semiarid range phmts would be during wet and dry seasons. Rumen dry matter digestion indexes were determined by the nylon bag technique during wet and dry seasons for 4 different plant materials at the National Range Research Station near Kiboko, Kenya. The rumen digestive capbility of 3 Zebu steers was not different between wet and dry seasons when these rumen fistulates selected their own foods from natural range vegetation. Much confusion exists relative to the conditions within the rumen which allow normal digestion to occur. One assumption is that different kinds of diets may cause different rumen dry matter digestion (RDMD) rates. Most researchers using the nylon bag technique (Van Dyne 1962) have offered the rumen tistulates an assigned diet (Weakley et al. 1983) in order to minimize any variation between animals and/ or dates that could be suspected to have been caused by diets. At the National Range Research Station (NRRS) near Kiboko, Kenya, rumen fistulated animals during nylon bag digestion trials select their own diets while grazing range vegetation (Hansen et al. 1984). The general decline in nutritive value of forages with age is most obvious at the NRRS proceeding from “wet seasons” to “dry seasons.” I have assumed in this study that the greatest diet difference would occur when rumen fistulates graze wet and dry season range vegetation. The purpose of this paper is to present RDMD values obtained by the nylon bag technique at different times during wet and dry seasons of 1984. An objective was to rumen digest the same 4 plant Author was range management specialist, Winrock International, Kenya National Range Research Station, P.O. Box 12, Makindu, Kenya. Author’s current address is Winrock International, Rte. 3, Morrilton, Arkansas 72110. Research was funded by a USAID grant to the Government of Kenya and published with approval of the Director of Research for the Ministry of Agriculture and Livestock Development. Manuscript accepted 25 July 1985. JOURNAL OF RANGE MANAGEMENT 39(2), March 1986 materials in all of the trials and to compare the results to determine if the trials were different. General observations of results obtained during 1983 led me to hypothesize that there was no significant difference between RDMD indexes for wet and dry season trials.

The ecology of the Kafue lechwe population of Zambia before the operation of hydro‐electric dams on the Kafue River

SummaryAerial surveys from 1970 onwards suggest a stable Kafue lechwe population of 94 000±9% on the Kafue Flats. The present distribution shows a contraction in dry and wet season range in comparison with 1953/54.Sex ratios of populations on both the North and South banks of the Kafue river do not differ significantly from unity. North bank males have a higher survival rate than South bank males. Survival curves for males and females on the South bank show the same pattern. For both the 1971 and 1972 breeding seasons 73% of South bank females older than 1½ years are expected to have bred successfully. The peaks of conceptions for both seasons are from mid‐December to mid‐March, suggesting a main lambing period from mid‐July until mid‐October. Present sex ratio, age structure, reproductive status and the reproductive cycle have been compared with 1961/62 data.Variation in physical condition, based on monthly measurements of the kidney fat percentage, dressing‐out percentage and live weight, although influenced by the physiological demands of rut and pregnancy, is correlated with the availability of flood‐plain grazing. The lowest values of condition parameters are found during the period of maximum flood, after the end of the rains (April/May), until the receding flood makes flood‐plain grazing available, usually in early June. A high level of tuberculosis, lungworm infection and many other pathogens amongst the South bank population are reported. Animals from the North bank are thought to be in better physical condition.The Kafue Gorge dam, completed in 1971, and the Iteshi‐teshi dam, at present under construction, will prolong the high flood period in wet years and prevent most flooding in dry years, both of these effects will reduce the carrying capacity of the flood plain for lechwe and a large reduction of the size of the population is expected to result from the operation of the dams.