Zululand Coastal Plain Research Articles

A novel approach for providing potable water in rural Sodwana Bay, northern Kwazulu-Natal, South Africa

Many people living in the Sodwana area of South Africa do not have access to potable water. Groundwater is the best source of fresh water for the rural community. Potable water in the Zululand coastal plain, Sodwana, South Africa can be enhanced by: (i) providing detailed information on the aquifer system using geophysics; (ii) providing information on groundwater quality and its efficient use; (iii) providing low-cost/low technology local drillers with light-weight, manoeuvrable rigs with trained teams for drilling of 6-inch diameter boreholes. The electrical resistivity geophysical method was used to study the aquifer system and define viable groundwater zones. The electrical resistivity survey increased the borehole success rate by providing information on the aquifer system suitable for water extraction. A hydrocensus was also conducted for identifying boreholes, quality of drilling and for collecting samples for water quality analysis. The result indicated that the groundwater in the area is of suitable quality. Poor quality drilling and inadequate drilling depth indicated a requirement for improved drilling rigs and suitable training. Providing the rural community with suitable drilling equipment, training and adequate information will help to solve the problem of water scarcity and also create jobs.

Nutrient fluxes in rainfall, throughfall and stemflow in Eucalyptus stands on the Zululand coastal plain, South Africa

Atmospheric deposition was assessed at two sites over a four-year period in post-canopy-closure (mature) Eucalyptus stands in the northern Dukuduku and southern KwaMbonambi commercial plantation forestry areas of Zululand, South Africa. The aim of this study was to determine the magnitude and relevance of nutrient addition with rainfall, throughfall and stemflow to commercial forestry in this region. Canopy cation exchange was used with rainfall and canopy drainage to derive wet, dry and total atmospheric deposition. Nutrient concentrations measured in the rainfall, throughfall and stemflow varied widely throughout the study period, and between sources and sites. Rainfall was slightly acidic at both sides, but became less acidic upon passing through the tree canopies. Canopy exchange and collection of dry deposition resulted in increased cation concentrations under the tree canopy, while the canopy generally absorbed nitrogen (N), from the rainfall, reducing the below canopy concentrations. Atmospheric deposition was shown to be responsible for large quantities of nutrients added to the eucalypt stands at each site. Annualised deposition averaged across all years at each site amounted to N, calcium, magnesium, and potassium (K) fluxes of 11.0, 6.0, 2.7 and 10.2 kg ha−1 y−1 at Dukuduku and 10, 10.6, 7.5 and 18.8 kg ha−1 y−1 at KwaMbonambi, respectively. Organic N fluxes contributed a further 8.1 kg ha−1 y−1 at Dukuduku and 7.1 kg ha−1 y−1 at KwaMbonambi to the total N deposition. Although K deposition values were high, additions of all other nutrients, although also high, were within the ranges reported in local and international research. Over the course of a full rotation, the atmospheric deposition levels recorded at these sites may have potential to supply a large proportion of the nutrients that are lost during stem-wood harvesting. This study adds value to understanding of nutritional sustainability of fast-growing plantation forests, demonstrating the importance of atmospheric deposition as a nutrient addition source to plantation-grown eucalypts along the Zululand coastal plain.

Genetic parameter estimates and parental selection in Eucalyptus longirostrata and Corymbia henryi populations tested in South Africa

Abstract The sub-tropical species, Eucalyptus longirostrata (formerly E. punctata var longirostrata) and Corymbia henryi were investigated as alternative species for growth on the Zululand coastal plain in South Africa. Provenance/progeny trials were established in 2001 at two sites, namely, Nyalazi and Kwambonambi. The seed material purchased from the Commonwealth Scientific and Industrial Research Organization in Australia in 2000 included six provenances of E. longirostrata and five provenances of C. henryi. Six-year diameter at breast height measurements were completed in 2007. Individual narrow-sense heritability coefficients for diameter growth varied from 0.30 to 0.58 for both species, with heritabilities being higher at the drier Nyalazi site. Heritabilities and breeding values were calculated prior to making selections in field. A total of 143 selections were made in the E. longirostrata trials, and 113 in the C. henryi trials during 2008. Predicted gains for the next generation range from 2.8 cm (20%) to 6.1 cm (61%) increase in diameter for E. longirostrata, and 3.4 cm (23%) to 5.4 cm (49%) increase for C. henryi, depending on site and selection scenario. Provenance differences were evident in E. longirostrata at both sites; however, there were no significant differences between the C. henryi provenances of Australian origin. The top families of both species performed better than the hybrid controls at the Nyalazi site, indicating that both E. longirostrata and C. henryi are viable alternative species for successful growth on the drier sites of the Zululand coastal plain.

A comparison of soil moisture relations between standing and clearfelled plots with burnt and unburnt harvest residue treatments of a clonal <i>eucalypt</i> plantation on the Zululand Coastal Plain, South Africa

The effects of clearfelling and subsequent residue retention or burning on water and nutrient balances needs to be understood and quantified on forest sites that are sensitive to loss, so that the long-term sustainable productivity of such sites can be maintained and promoted. An experimental site was established in a clonal eucalypt compartment on the Zululand Coastal Plain, to compare changes in water fluxes through the mature undisturbed eucalypt stand with those after felling and re-planting, under 2 conditions: burning, and retention of the harvesting residues. The study was located in an area of high rainfall and high stand productivity, with sandy soils and low soil carbon and nutrient status; chosen so that the effects of intensive demands on water and nutrient fluxes on a potentially sensitive site could be investigated. This paper presents only the hydrological component of the study. Data collection included weekly determination of rainfall, throughfall, stemflow and soil moisture fluxes from the surface to a depth of 1 m. Drainage rates through the profile were established using time domain reflectometry probes while water drainage volumes were assessed using shallow plate lysimeters. Despite slow growth in the unfelled crop during the monitoring period (attributed to a pest infestation), soil moisture depletion remained rapid and drainage below 1 m remained low. Soil moisture was recharged within a few months after clearfelling, but became rapidly depleted as the canopy of new crop developed and approached canopy closure. A decreased wetting-front velocity and a marginally higher field capacity were proposed as evidence of pore clogging that appeared to occur during the inter-rotation period. The soil profile under the unburnt residue maintained a marginally higher soil moisture status and lower drainage than the soil profile under the burnt residue. Although soil moisture and drainage in the burnt and unburnt residue treatments became similar to the unfelled crop from canopy closure onwards, rainfall additions to soil moisture were depleted faster under the new crop during the first few months after canopy closure. Small differences in soil moisture status between the burnt and unburnt residue treatments presented here may not be sufficient to influence residue manage ment decisions. The length of the inter-rotation period and practice of residue burning may, however, need consideration where soil carbon and nutrient loss or displacement may negatively affect the sustainability of the site.

Wood and fibre productivity potential of promising new eucalypt species for coastal Zululand, South Africa

Summary In South Africa pressure is increasing to improve the quantity and quality of eucalypt wood being produced from the existing forestry land base, and to identify species that would enable profitable forestry on land currently considered marginal. In a series of site x species interaction trials established on the Zululand coastal plain during 1992, alternative eucalypt species were compared with a number of commercial eucalypt species and clones at three sites. At rotation age of 7 y, the wood and fibre productivity of the five most promising new species, namely Corymbia henryi, C. citriodora ssp. citriodora. Eucalyptus longirostrata, E. pilularis and E. tereticornis, was assessed at two of the sites. On the basis of merchantable wood production, E. longirostrata Monto provenance showed excellent potential for high productivity (wet) sites on the Zululand coastal plain, and C. citriodora ssp. citriodora and C. henryi excellent potential for marginal (moderately dry) sites. On the basis of fibre production, E. longirostrata Monto and C. henryi showed excellent potential for high productivity sites, and C. citriodora ssp. citriodora and C. henryi excellent potential for marginal sites. Eucalyptus longirostrata could be a good partner for E. grandis and E. urophylla for the production of hybrids better adapted to the range of environmental conditions in coastal Zululand than either of the latter two species. In such hybrid combinations, the high basic wood density of E. longirostrata could be of advantage to the local hardwood woodchip export industry.

The effect of harvesting operations, slash management and fertilisation on the growth of aEucalyptusclonal hybrid on a sandy soil in Zululand, South Africa

Harvesting operations during clearfelling and extraction of timber from commercial plantations result in many processes that may affect long-term site productivity such as soil compaction and residue manipulation. The objective of this work was to evaluate the effects of various harvesting operations and fertiliser applications on soil physical properties and the subsequent growth of a Eucalyptus clonal hybrid ( Eucalyptus grandis x camaldulensis ) on the sandy soils of the Zululand coastal plain in northern KwaZulu- Natal. Increases in bulk density and penetrometer soil strength and decreases in aeration porosity were recorded on plots where a wheeled harvester had been used and on extraction roads, but these were not of a sufficient magnitude to limit tree growth. Available water capacity increased on the compacted plots. At six years of age there were no significant differences in stand volume between the plots harvested by different methods or between fertiliser treatments, nor was there any interaction between the treatments. However, a significant response to fertilisation was evident after one year. In contrast to the other treatments, trees in plots subjected to the wheeled harvesting operation did not respond to fertilisation, suggesting that an early release of nutrients occurred, caused by the breakdown and incorporation of slash in the topsoil. Key Words: Harvesting impacts; soil compaction; Zululand; soil physical properties; Eucalyptus grandis x camaldulensis; long-term site productivity Southern African Forestry Journal No.203 2005: 15-26

Site and stand analysis for growth prediction ofEucalyptus grandison the Zululand coastal plain

Synopsis The integration of site information with that of tree growth is of special importance in Zululand, where sustainable supply of timber is essential for local processing and export commitments. Site prediction growth models need to be based on easily attainable input variables that are suitable for operational implementation by planners and for deployment of advanced silvicultural technology. Recently concluded growth studies based on permanent sampling plots established across Eucalyptus grandis plantations yielded useful information for revising the current knowledge on site-growth relationships in the region. The Chapman-Richards model was used to define the height growth curves over a range of sites. Standspecific site indices were calculated for trees of five years of age and regressed against a range of site variables. The multiple regression analysis showed that a large portion ofthe variation (r2=O,63) in the site index could be explained by topsoil organic carbon and clay content in the subsoil. The soil data in the routine survey format and modelled climatic data in a grid pattern did not contribute significantly to the models. It is clear that the variables capturing the nutrient status ofthe soil and the soil's ability to store and make water available to the trees are the most important ones on the Zululand coastal plain when site prediction growth modelling is performed. Future research on site productivity modelling should include site variables specifically designed for that purpose and should further be enhanced with studies including their influence on wood quality.

The effects of remedial fertilizer treatments on growth and pulp properties ofEucalyptus grandisstands established on infertile soils of the Zululand coastal plain

Synopsis Remedial fertilizer applications were applied to nutrient-poor stands of Eucalyptus grandis growing on infertile (ex-agricultural) land of the Zululand coastal plain. Two nitrogen-rich fertilizer mixtures were applied in one year-old stands at rates ranging from zero to 160 kg N ha-1. Foliar nitrogen levels increased highly significantly at the higher levels of fertilization. Ahighly significant response to height, diameter and basal area growth was observed within 6 months of treatment initiation which was sustained until clear felling (8.3 years). A comparison ofthe unfertilized control with the optimum treatment i.e. a single fertilizer dose equivalent to 80 kg N ha-1) yielded the following results: Utilizable wood volume increased from 136.7 to 264.3 m 3 ha-1, The wood density showed a weakly significant increase from 448 to 472 kg m-3. The pulpability factor (defined as the pulp yield / kappa number) decreased significantly from 2.63 to 2.32. The net effect of fertilization on pulping proper...

Alternative eucalypt species for Zululand: Seven year results of site: species interaction trials in the region

Abstract The ICFR initiated a search for alternative eucalypt species for the Zululand Coastal Plain region during 1992 by establishing a series ofsite: species interaction trials in the area. Sixteen pure species (seedlings), one E. grandis intra-specific clone and five inter-specific hybrid (E. grandis x either camaldulensis or urophylla) commercial clones were planted at three sites ranging in climatic condition from warm and wet in the south to hot and dry in the north. Final measurements, assessments and wood-sampling for pulping properties was carried out during 1999. These results together with relevant recommendations are discussed in this paper. On a growth, disease-resistance and pulpwood-quality basis, the top performing pure species at the southern (highly productive) site at Terranera were E. longirostrata and E. pilularis, and on the drier, more marginal sites at Teza and False Bay, E. henryi, E. citriodora, E. longirostrata and E. tereticornis gave impressive results.

Holocene and recent peat growth rates on the Zululand coastal plain

Five Holocene to late Pleistocene peatlands (mires), those at Majiji, Manzengweya, Nhlangu, Mgobezeleni and Mfabeni on the Zululand Coastal Plain, South Africa, have been investigated as part of a comprehensive programme to delineate its peat resources. These peatlands, part of the Natal Mire Complex, have been radiocarbon dated to determine their stratigraphic position within the Holocene to late Neogene Maputaland Group. The proximity of exotic tree species in nearby commercial plantations provides a unique opportunity to determine recent accumulation rates i.e. within the last 3 decades. Pinus and Casuarina spp. pollen provide a proxy indicator whose introduction to the study area is well constrained. In all five cases the generation rates are similar and are in the region of 1–2 cm y −1. These rates are an order of magnitude less than previous estimates and indicate that the extraction of peat from these wetlands would be unsustainable.

Research note: Calibrating a disc pasture meter to estimate grass fuel loads on the Zululand coastal plain

Abstract A disc meter was calibrated to estimate fuel load on the Zululand coastal plain. The regression model was valid for fuel load estimates within a disc height of 1–58 cm. The mean calibrated disc height was 11.8 cm. Estimated fuel load at mean disc height, with standard error (SE), was 4 593±113 kg ha−1. Using this equation to estimate fuel load at the calibrated mean, the precision of the estimates varied depending on the number of disc readings. As sample size increased there was at first a rapid reduction in the SE and hence in the 95% confidence limits (CL) of the predicted fuel load. There was little reduction in the CL with increasing sample size for more than 100 observations. To achieve a CL±10% of 5 000 kg ha−1, 100 samples are needed. With fuel loads of less than 4 000 kg ha−1, more than 160 samples are required to achieve the same precision. Sampling with more than 100 readings is not, however, recommended owing to the poor reward (precision) per unit of sampling effort.

The influence of temperature on the life-cycle and distribution of Biomphalaria pfeifferi (Krauss, 1948) in South-Eastern Africa

An annual life-cycle of three over-lapping generations was found for Biomphalaria pfeifferi in a perennial stream on the eastern Transvaal escarpment. The 2nd of these generations appeared during the hottest months of the year—late January and February. This generation sequence was confirmed in a completely different environment, a permanent pond in a climatically different area, the coastal peneplain of north-eastern Zululand though the density of the 2nd generation here was much reduced. The species is moreover absent from certain types of shallow, permanent waterbody (pans) on this plain. In these habitats the thermal regime rose above those in other types during spring and early summer—the maturation period of the 1st generation. A negative partial-correlation, significant at a 1% level, was found between decreasing fecundity of the 1st generation and increasing periods of above-optimal temperatures (> 27°C) during its maturation period. This temperature effect accounts for the species' absence from pans in the area and the critical duration of these above-optimal temperatures appears to lie between mean weekly levels of 120 and 179 deg.h. > 27°C. The discontinuous distribution of B. pfeifferi in the Lake Sibaya area of the Zululand coastal plain corresponds to an ecological succession amongst waterbodies associated with the lake's fluctuating water level. The separation of sheltered bays from the lake was followed by further lowering of their levels and a spread of emergent vegetation. This is believed to have contributed to an increasingly high thermal regime, especially during spring when temperatures rise rapidly. The pans from which B. pfeifferi is absent constitute the present end point of this succession.