2. Predictive modelling of the potential future distribution of Vachellia nilotica
within the KwaZulu-Natal province of South Africa
Janet Taylor1,2*, Nico Smit2 and Debbie Jewitt3,4
ABSTRACT
Many regions of South Africa are prone to woody plant thickening. This can have an ecologically detrimental effect on the open savannas and grasslands. KwaZulu-Natal, a province on the east coast of South Africa, is currently experiencing an increase in both the density and distribution of Vachellia nilotica. This research aims to gain better insight into the potential distribution of this plant and to determine some of the main environmental conditions that promote its thickening. Using the Maxent programme to determine the potential distribution, a map was developed to illustrate the possible extent of V. nilotica within KwaZulu-Natal. It is estimated that a possible 800 968 ha (8.5%) of the province has a greater than 50% distribution probability, whereas in 26.9% of the province there is 25%–50% probability of V. nilotica inhabiting these areas. Using Maxent, it was determined that geology and altitude were key
determinants for V. nilotica habitat selection. This model-based map will be particularly useful for conservation and rangeland planning for future management and control of the plant through being able to predict which areas of the province are more likely to be high potential regions for the thickening of V. nilotica.
Keywords: bush thickening, KwaZulu-Natal, Maxent, species distribution model, Vachellia nilotica
Identifying phenological functional types in savanna trees
Nthambeleni D Masia1,2,3, Nicola Stevens4 and Sally Archibald1,2
ABSTRCAT
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.
Keywords: deciduous, evergreen, leaf phenology, plant functional types, semi-arid
Effects of seasonal variation, group size and sex on the activity budget and
diet composition of the addax antelope
Hicham Seri1*, Mohsen Chammem1, Luis MM Ferreira2 , Marwa Kechnebou1, Touhami Khorchani1 and Severiano R
Silva3
ABSTRACT
Behaviour and diet composition are critical elements in conservation biology within the scope of reintroduction programs. Here we focused on addax (Addax nasomaculatus), a Critically Endangered antelope species, in the Jbil National Park, Tunisia. In this study, we advanced the hypothesis that season, day period, sex and social structure have an effect on the activity budgets and diet composition of addax. Three groups were selected (large group, adult pair and solitary male). Resting, moving, grazing, vigilance and other behaviours were recorded during two seasons (dry and wet) and in the morning and the afternoon. In addition, faecal samples were collected. The results indicate that season and day period were the main factors affecting the activity budgets. The resting behaviour increased from the wet to the dry season, and from morning to afternoon. The grazing and moving behaviours increased during the wet season and decreased from morning to afternoon. Addax select a mixed diet composed of perennial and herbaceous plant species notably during the wet season. In addition, we observed that addax modify their behaviour according to the season and forage availability. This represents an adaptive strategy to survive in a desert climate with a stochastic low-resource environment and depending on ambient climatic conditions.
Keywords: activity budgets, addax antelope, faecal microhistological analysis, Jbil National Park, seasonal variations
Seasonal changes in pasture biomass and grazing behaviour of cattle in
the Guinea Savanna agroecological zone of Ghana
Maxwell Akapali1, Terry Ansah1*, Ibn Iddriss Abdul-Rahman1, Benjamin Alenyorege1 and Bernard N Baatuuwie2
ABSTRACT
Spatial and temporal availability of pasture vegetation and cattle grazing behaviour in three seasons (intermediate season [IM], peak season [PS] and dry season [DS]) in the Guinea Savanna agroecological zone of Ghana was examined. The frequency of occurrence of three species groups (grass, legume and forbs) and biomass yield was estimated in 1 m² plots. The grazing behaviour of 18 cows from six herds was monitored over three days per animal. Season affected the prevalence of species groups with grasses being most dominant in all seasons. Most grazing lands were heavily grazed in IM and DS but moderately grazed in PS. Whilst harvested rice fields represented the most frequently grazed land in DS, fallowed hard pans were used in PS and IM. Biomass yield was highest in DS owing to the contribution of crop residues from harvested farmlands. Carrying capacity was linked to biomass production and averaged 0.55 in DS, 0.38 in PR and 0.21 in IM. Animals spent less time outside the kraal in PS than IM and DS. Walking time was higher in DS than in IM and PS. Less than 20% of the time on pasture was spent on resting, watering and social interaction across seasons.
Keywords: carrying capacity, grazing behaviour, rangeland, savanna, tropical livestock unit
Tiller population dynamics in eight cultivars of elephant grass during
undisturbed growth
José A Rueda1 , Eusebio Ortega-Jiménez2* , Javier F Enríquez-Quiroz3 , Rogelio E Palacios-Torres1 and
Sergio Ramírez-Ordoñes1
ABSTRACT
The aim of the study was to assess tiller population dynamics of aerial and basal tillers in eight cultivars of Pennisetum purpureum (Schumach.), syn. Cenchrus purpureus (Schumach.) Morrone, in a warm humid climate in Veracruz, Mexico. This is a pioneer study on tiller population dynamics in elephant grass under conditions of undisturbed growth. The tiller population assays included data from 14 days after cutting until 154 and 182 days after cutting for the dry and wet seasons, respectively. On each sampling date, a distinctive ring was placed on every new tiller, and rings were removed from dead tillers. Tiller density, mortality and appearance were determined. In wet seasons, copious tillering occurred on initial regrowth (by day 42, mostly aerial tillers, with a ratio of 2:1 to 4:1 for aerial to basal tiller appearance), and on day 98 (a higher proportion of basal tillers, with an aerial to basal tiller ratio of 1.5:1). Aerial tillers showed a higher overall mortality rate than basal tillers (29.0 vs 14.4). Younger basal tillers showed higher mortality than older tillers. Higher tiller density occurred during the dry season, where it increased gradually until day 70 and then declined. The cultivars ‘Cameroon’, ‘CT115’ and ‘OM22’ showed remarkably high tillering ability. The findings indicate that harvesting a forage bank is possible from day 70 during a dry season.
Keywords: density dynamics, king grass, tiller appearance rate, tiller mortality rate, tropical grasses
Silages in the form of diet based on spineless cactus and buffelgrass
Alberto Jefferson da Silva Macêdo1* , Edson Mauro Santos2 , Gherman Garcia Leal de Araújo3, Ricardo Loiola
Edvan4 , Juliana Silva de Oliveira2, Alexandre Fernandes Perazzo5 , Wilma Cristina Cavalcante dos Santos Sá2
and Danillo Marte Pereira2
ABSTRCAT
This study was conducted to evaluate the fermentation pattern and the in situ dry matter degradability of silages in the form of diet. Five diets were formulated based on spineless cactus (Opuntia fícus-indica cv. ‘Gigante’) and buffelgrass (Cenchrus ciliaris). The experimental design was completely randomised, with five treatments and three replicates in which the diets differed in the proportion of buffelgrass (0%, 15%, 25%, 30% and 35%, on a fresh matter basis). There was significant difference (p < 0.05) in the chemical composition of the diets, with all dry matter contents being within the ideal range. Ammonia-nitrogen content was not affected (p > 0.05). There were significant differences (p < 0.05) in dry matter recovery across diets, which ranged from 96.28% to 99.93%. The pH values decreased as the time of opening (days) was extended. Organic acid contents differed across all diets; however, overall, all diets showed satisfactory lactic acid contents. As the proportion of buffelgrass in the diets was increased, the degradability of dry matter decreased. Based on fermentation profile, losses and chemical composition the diet with higher proportion of spineless cactus can be recommended for silage production.
Keywords: cactus, ensiling, fermentation, foraging, semi-arid zones
Degradability of amino acids in selected legume forages using the in situ
nylon-bag technique
Simbarashe Katsande1*, Joseph J Baloyi1, Florence V Nherera-Chokuda2, Nobbert T Ngongoni3, Jacob Gusha4, Gift
Matope4 and Plaxedis I Zvinorova4
ABSTRACT
This study was conducted to determine the amino acid profiles and rumen degradability of amino acids of three cultivated forage legumes – velvet bean (Mucuna pruriens), cowpea (Vigna unguiculata) and silverleaf desmodium (Desmodium uncinatum) – using the in situ nylon-bag technique. Two Friesian cows fitted with 10-cm-diameter rumen cannulae on a complete dairy feed ration (19% crude-protein dairy meal and maize silage) were used. Silverleaf desmodium had significantly (p < 0.05) higher concentration of amino acids compared with cowpea and velvet bean. Aspartic acid showed the highest (p < 0.05) concentration in all legumes and cysteine showed the
lowest concentration. Legume forage of cowpea showed the highest (p < 0.05) level of degradability of amino acid followed by silverleaf desmodium and then velvet bean. Readily and slowly degradable components in all amino acids were highest (p < 0.05) in cowpea followed by silverleaf desmodium and then velvet bean. Moreover, silverleaf and cowpea showed higher (p < 0.05) levels of effective degradability of amino acids (at outflow rates p = 0.02, 0.04 and 0.06 h−1) than velvet bean. Total amino acid disappearance was the least in velvet bean, which suggests that it can be used to supply bypass protein to the duodenum of the ruminant animal.
Keywords: amino acids, forage legumes, rumen degradability
Essential oil composition of Pentzia incana (Asteraceae), an important
natural pasture plant in the Karoo region of South Africa
Isabel M Hulley1, Nicholas J Sadgrove1, Patricia M Tilney1, Gulmira Özek2 , Suleyman Yur3, Temel Özek2,3 , Kemal
Hüsnü Can Başer4 and Ben-Erik van Wyk1*
ABSTRCAT
Pentzia incana is one of the most important of all natural pasture plants in the dry interior (Karoo) region of South Africa. This highly aromatic shrub is thought to be responsible for the distinctive flavour of Karoo lamb (a registered geographical indication), yet the essential oil is here characterised for the first time. Leafy twigs are traditionally chewed for relief of stomach ache. Essential oil is associated with numerous small, multicellular glands. Gas chromatography and gas chromatography/mass spectrometry analysis of 17 essential oil samples from five populations showed considerable variation in both yield (0.12% to 0.88% dry weight) and composition. Of
interest was the presence of one major biosynthetic group comprising yomogi alcohol (to 38.9%), artemisia alcohol (to 26.1%), artemisia ketone (to 35.0%) and artemisyl acetate (to 9.4%). High levels of fragranol (26.9%) and fragranyl acetate (27.1%) were observed only in a single specimen. Other main compounds were 1,8-cineole (to 16.7%), santolina alcohol (to 11.3%), camphor (to 47.9%), linalyl acetate (to 17.4%) and bicyclogermacrene (to 11.8%). Six of the 10 major compounds were isolated and their identities confirmed by nuclear magnetic resonance. The volatile compounds may possibly be linked to the medicinal use of P. incana, as well as the flavour profile of Karoo lamb.
Keywords: deciduous, evergreen, leaf phenology, plant functional types, semi-arid
