Cs Everson

Seed dynamics of Themeda triandra in the montane grasslands of South Africa

Seed production, viability, dispersal, predation and seed banks of Themeda triandra were determined to assess the potential of the seeds of this indigenous species in the re-establishment of degraded grassland. Annual seed production of T. triandra increased with length of burning rotation, ranging from 21 seeds m−2 in the annual winter burn to 757 seeds m−2 in the five-year burn. High predation of seeds (70–98%) and low viability (37% in 15-month-old seeds) contributed to the poor representation of T. triandra in the seed bank (<1.2%) when compared to the above-ground vegetation (<29.2%). These attributes, together with its poor dispersal (<1.75 m), indicate that seed dynamics of T. triandra will play a limited role in the restoration of grasslands in degraded areas.

The long-term effects of fire regime on primary production of montane grasslands in South Africa

Natural grasslands deliver essential ecosystem services through plant production, which enhances water supply, nutrient cycling, soil retention and greenhouse gas mitigation. Although the condition of montane grasslands for provision of ecosystem services is maintained by regular annual or biennial burning, controversy exists over the impact of different frequencies and seasons of burning on grassland productivity. The objective of this study was to determine the long-term effects of different burning regimes on primary production and quality of the montane grasslands of the KwaZulu-Natal Drakensberg. There were no significant differences in the mean standing live mass between 30 years of annual winter and biennial spring burning. However, in unburnt areas productivity was 20% lower (118.2 g m−2) than in regularly burnt grassland (144.7–154.5 g m−2). Crude protein did not vary between the annual winter and biennial spring treatments (95–113 kg ha−1), but was significantly lower in unburned areas (45 kg ha−1). However, an infrequent fire in a protected area caused a temporary spike in crude protein (16%) compared with regular burning (5–10%), which can benefit wildlife. We conclude that montane grasslands can be burnt annually or biennially in the dormant season to promote long-term productivity.

Ecological status and uses of juniper species in the cold desert environment of the Lahaul valley, North-western Himalaya, India

The juniper species Juniperus polycarpos C. Koch, J. indica Bertol. and J. communis L. var. saxatilis (Pallas) are important elements of the forest vegetation in Lahaul valley in the north-western Himalaya. Their ability to grow under the barren and xeric conditions of cold deserts makes them particularly suited for afforestation programmes under these ecological conditions. In the Lahaul valley, juniper species are used as subsistence resources and for religious purposes. Excessive removal of juniper wood and leaves by the local population, overgrazing, habitat fragmentation and low regeneration potential are the main obstacles to conservation of juniper forests in this region. The present study was carried out to assess density, basal area and importance value index (IVI) of the local vegetation as well as uses and amounts of juniper wood and leaves removed from the local forests. Pressure on relict juniper forests due to grazing animals and intensive removal of wood and leaves by the local population was found to be greater at an altitude above 3,000 m. The results of the study demonstrated that the different juniper species were adapted to specific altitude ranges. A higher species density was recorded at lower altitude except for J. indica which was only present at high altitude (>3,200 m) on south-facing slopes. Density, basal area and IVI of J. polycarpos were higher at Hinsa (2,700 m) than at Jahlma (3,000 m). The rapid loss of vegetation due to overuse and habitat degradation has made the conservation of juniper forests an important priority in the Lahaul valley. J. polycarpos at lower altitude and J. indica at higher altitude are ecologically the more suitable species for the successful implementation of conservation programmes. The support of rehabilitation programmes by regional authorities is essential for the reestablishment of the local juniper forests.

Modelling annual evapotranspiration in a semi-arid, African savanna: functional convergence theory, MODIS LAI and the Penman–Monteith equation

Accurately measuring evapotranspiration (ET) is essential if we are to derive reasonable estimates of production and water use for semi-arid savannas. Estimates of ET are also important in defining the health of an ecosystem and the quantity of water used by the vegetation when preparing a catchment-scale water balance. We derived ET0 from an automatic weather station 30 km west of Skukuza, Kruger National Park, South Africa using the Penman– Monteith equation, and then used the MODIS LAI to inform the model of canopy phenological dynamics. This result was compared with 173 days of ET measurements from the eddy covariance (ETec) system near Skukuza in 2007 as well as from the ET recorded by a large-aperture scintillometer at the same site in 2005. The model compared favourably with both sets of measured data and, when used independently of the eddy covariance data, ETMODIS predicted an annual ET of 378 mm in 2007 for the semi-arid savanna around the Skukuza flux site.

Performance of simple irrigation scheduling calendars based on average weather data for annual ryegrass

Poor irrigation management in pastures can lead to yield and quality reduction as well as loss of income through extra pumping and leaching of nitrate fertiliser. A number of irrigation scheduling techniques of varying levels of sophistication have been developed over the years to address limited irrigation water availability and maximise productivity. Despite this, the adoption of irrigation scheduling tools by farmers remains low. The objective of this study was to assess the use of simple irrigation scheduling calendars based on average weather data to improve irrigation management in ryegrass. The calibrated Soil Water Balance (SWB) model was used to generate simple irrigation calendars and assess effectiveness for different scenarios by mechanistically simulating water dynamics and pasture growth. Scheduling irrigation using the calendars gave similar irrigation applications, water losses and yields compared to a more scientific real-time scheduling (in response to soil water depletion by the crop). While site-specific irrigation scheduling calendars can easily be generated by consultants and irrigators, even simpler monthly estimates of average daily water use can also be useful. Application of calendars by farmers is encouraged to improve water and nutrient use efficiency of irrigated pastures, if real-time irrigation scheduling is not employed.

Availability and Use of Willow Species in Representative Cold Desert Areas of Northwestern Himalaya, India

Willow species (Salix fragilis L. and S. alba L.) are important elements of cold desert agroforestry systems in the Lahaul valley, northwestern Himalaya. Their ability to grow through shoot-cuttings plantations under extreme and xeric climatic conditions of cold deserts, makes them ecologically suited and socially accepted for forestry programmes. Willow species in cold deserts may combat desertification and can thrive well in these areas as compared to any other species. Salix fragilis L. and S. alba L. are under cultivation in the Lahaul valley. However, S. fragilis is widely cultivated under the agroforestry and plantation forestry systems. In the Lahaul valley, willow species are used as subsistence resources and for socio-religious purposes. The present study was carried out to examine the vegetation analysis, density, diversity and distribution of willow species, present status and potential willow plantation sites and uses. The results of present study revealed that a higher species density was recorded at middle altitude villages (Jahlma-3,000 m asl and Hinsa-2,700 m asl), except, a higher density of S. fragilis was at Khoksar (3,200 m asl) in plantation forestry on south-facing slopes. In forests, S. fragilis was planted mainly along the water channels, resulted a low density. The shrubby willow species occurred naturally in the entire Lahaul valley up to an altitude of 3,850 m asl. 81% of households felt the scarcity of willow trees, whereas, 19% of households were satisfied with the willow trees they owned. The majority of willow species were planted in middle altitudes on privately owned irrigated lands. It was rated most potential prospective willow planting site by the farmers. Small size of land-holdings was one of the main constraints for establishing a large number of willow plantations. Commercial aspects of willow species need to be investigated to encourage the farmers to plant more willows further.

Inula racemosa Hook. f: A potential medicinal crop in the cold desert agro-ecosystem of North Western Himalaya, India

Inula racemosa Hook. f. (Manu), a critically endangered medicinal herb, was studied in terms of its uses and cultivation practices and problems in the cold desert environment of the Lahaul valley in the North Western Himalaya. The roots of I. racemosa are used in traditional medicine, but are also of great economic importance due to the large demand by the pharmaceutical industry. Energy and monetary efficiencies of I. racemosa were characterized by output/input ratios of 0.69 and 5.91, respectively. A survey was conducted to establish reasons for the decline in the cultivation of I. racemosa. The lengthy cultivation cycle, prevalence of small land holdings and continuously fluctuating market prices were the main constraints stated by the interviewed farmers. The results of this study highlight the need for technical support, the establishment of value-addition centres and farmers’ federations as well as mechanisms to strengthen and stabilize the existing market in order to promote the cultivation of this endangered medicinal herb.

Evapotranspiration from mine-affected riparian sites along the Vaal River in central South Africa

Abstract Long-term gold mining within the Witwatersrand Basin Goldfields has led to the creation of over 200 tailings storage facilities (TSFs) releasing acid mine drainage. Plumes of contaminated shallow groundwater occur downslope of these TSFs. One such area lies adjacent to the Vaal River east of the town of Orkney. Natural vegetation in the riparian soils comprises a mixture of grasslands, reeds and woodlands dominated by Vachellia karroo. The Mine Woodlands Project initiated by Witwatersrand University and AngloGold Ashanti is exploring the use of engineered woodlands for hydraulic control of plumes and immobilization of contaminants to protect the wider hydrological resource. To estimate the net increase in evapotranspiration (ET) resulting from various remedial woodlands, ET from existing vegetation types requires quantification. Growing season patterns of ET were measured and modelled in riparian grassland and two V. karroo woodland sites close to the Vaal River. Two independent estimates of annual ET from these woodland sites (674 and 787 mm) were similar to that from grassland (697 mm) and much less than the 1100–1200 mm reported from some forms of engineered evergreen woodlands established in the vicinity. We conclude that the Vachellia woodlands have low potential for hydraulic control of contaminant plumes.

Tree legumes-temperate grass agroforestry system effects on inorganic soil nitrogen as ecosystem services provision for smallholder farming systems in South Africa

ABSTRACT Nitrogen is an essential macro-nutrient for plant growth and is indispensable for high agricultural food productivity and quality. Shortage of good quality forage under the dry winter season and low soil fertility conditions are the major constraints in rural farming systems in the Moist Tall Grassveld of the Upper Thukela, South Africa. The effect of legumes on inorganic soil nitrogen was assessed in an agroforestry trial (Leucaena leucocephala (Lam.) De Wit, Acacia karroo Hayne, Dactylis glomerata L., Festuca arundinacea Schreb.), by soil sampling method. In the agroforestry trial, total inorganic soil nitrogen accumulation was significantly greater under intercropping than under sole crop treatments and, irrespective of the treatments, significantly more nitrate than ammonium nitrogen was measured. The study demonstrated that intercropping grasses with tree legumes could provide important ecosystem services of nitrogen supply in the soil. The results suggested that introducing legume intercrops might constitute a relevant cropping strategy to improve the soil fertility status with regard to nitrogen while at the same time providing forage in smallholder farming systems in South Africa’s Moist Tall Grassveld regions.

Intercropping maize (Zea mays L.) with lablab (Lablab purpureus L.) for sustainable fodder production and quality in smallholder rural farming systems in South Africa

ABSTRACT An on-farm field experiment was conducted in South Africa’s rural Moist Tall Grassveld region which is characterized by overgrazing and a reduced grazing capacity. The grassland is sour veld and only provides palatable material during the 6-month growing season. The experiment was conducted to assess the effect of intercropping maize with lablab on maize fodder, grain yield, and quality, social and economic aspects. The results indicated superiority of intercropping over sole cropping, with intercropping treatments showing consistent superiority across 4 years of the experiment. Maize grain and fodder yields were positively influenced by intercropping with lablab. The maize fodder and total fodder yields were higher in intercropped than in sole maize plots. The maize grain DM yield of the first harvest in maize-only treatment was not significantly higher than in M + L treatment. Intercropping significantly increased crude protein of maize leaves and reduced the leaves’ fiber content. Crude protein contents were lower and fiber contents higher in maize stalks and leaves than in lablab. The field trial demonstrated that diverse plant communities in the form of intercropping provide sustainable production, positive environmental, and social impacts through reduced agrochemicals and are economically viable through cost avoidance and savings. The results of this study suggest that including lablab in traditional maize cropping systems can be beneficial when entanglement of maize is avoided by delayed under sowing of lablab.