Effects of goat pastoralism on ecosystem carbon storage in semiarid thicket,Eastern Cape,South Africa

Abstract Intensive pastoralism with goats transforms semiarid thicket in the Eastern Cape, South Africa from a dense vegetation of tall shrubs to an open landscape dominated by ephemeral grasses and forbs. Approx. 800 000 ha of thicket (which prior to the introduction of goats had a closed canopy and a Portulacaria afra Jacq. component) have been transformed in this manner. Ecosystem C storage in intact thicket and loss of C due to transformation were quantified. Carbon storage in intact thicket was surprisingly high for a semiarid region, with an average of 76 t C ha^?1 in living biomass and surface litter and 133 t C ha^?1 in soils to a depth of 30 cm. Exceptional C accumulation in thicket may be a result of P. afra dominance. This succulent shrub switches between C₃ and CAM photosynthesis, produces large quantities of leaf litter (approx. 450 g m^?2 year^?1) and shades the soil densely. Transformed thicket had approx. 35% less soil C to a depth of 10 cm and approx. 75% less biomass C than intact thicket. Restoration of transformed thicket landscapes could consequently recoup more than 80 t C ha^?1.     

Rate of Carbon Sequestration at Two Thicket Restoration Sites in the Eastern Cape, South Africa

Ecosystem carbon storage in intact thicket in the Eastern Cape, South Africa exceeds 20 kg/m², which is an unusually large amount for a semiarid ecosystem. Heavy browsing by goats transforms the thicket into an open savanna and can result in carbon losses greater than 8.5 kg/m². Restoration of thicket using cuttings of the dominant succulent shrub Portulacaria afra could return biodiversity to the transformed landscape, earn carbon credits on international markets, reduce soil erosion, increase wildlife carrying capacity, improve water infiltration and retention, and provide employment to rural communities. Carbon storage in two thicket restoration sites was investigated to determine potential rates of carbon sequestration. At the farm Krompoort, near Kirkwood, 11 kg C/m² was sequestered over 27 years (average rate of 0.42 ± 0.08 kg C m^?2 yr^?1). In the Andries Vosloo Kudu Nature Reserve, near Grahamstown, approximately 2.5 kg C/m² was sequestered over 20 years (0.12 ± 0.03 kg C m^?2 yr^?1). Slower sequestration in the Kudu Reserve was ascribed to browsing by black rhinoceros and other herbivores, a shallower soil and greater stone volumes. Planting density and P. afra genotype appeared to affect sequestration at Krompoort. Closely‐packed P. afra planting may create a positive feedback through increased infiltration of rainwater. The rate of sequestration at Krompoort is comparable to many temperate and tropical forests. Potential earnings through carbon credits are likely to rival forest‐planting schemes, but costs are likely to be less due to the ease of planting cuttings, as opposed to propagating forest saplings.     

Aspect and slope as determinants of vegetation composition and soil properties in coastal forest backdunes of Eastern Cape,South Africa

Coastal sand dune ecosystems are subjected to many stress and disturbance factors that are particularly high in the foredunes compared to the backdunes. Although a few studies have been conducted on eastern coastline sand dunes of South Africa, none have examined the relationship between aspect and slope on vegetation composition and soil properties of coastal forest backdunes. Vegetation and soil sampling were conducted in 11 transects, each with four plots measuring 10 × 10 m, located on the seaward and landward sides and on middle and lower slopes of backdunes of Bathurst coastal forest. A total of 39 species were identified, of which 23 were trees and shrubs, thirteen were forbs and three were grasses. The data show that both aspect and slope had limited influence on vegetation community assemblage and soil properties, but had significant effects on individual species distribution. There was a grass‐dominated community on the middle slope and a tree‐ and shrub‐ dominated community on the lower slope. These two plant communities act as the required coastal forest ecosystem engineer driving variability in soil properties between the slopes, the most prominent being high soil nutrients and moisture in the lower slopes compared to the middle slopes.     

Home range size, spatial distribution and habitat use of elephants in two enclosed game reserves in the Eastern Cape Province, South Africa

We studied space use and habitat selection by elephants in two enclosed reserves in the Eastern Cape Province (South Africa) that conserve components of the regionally important and poorly conserved Thicket Biome. Home ranges of bulls and herds occupied most of the reserves, and core areas were significantly smaller and centred on permanent water. There was no significant difference in home range size of bulls and herds and both were significantly smaller in winter than summer. Components of the Thicket Biome occurred in the home ranges and core areas of all elephants where it was either used according to its abundance or avoided. However, this should not be interpreted as indicating that elephants will not affect plants of the Thicket Biome since change will be cumulative and monitoring should be ongoing to ensure the conservation of this regionally important Biome.     

Continued decline in tree euphorbias (Euphorbia tetragona and E. triangularis) on the Great Fish River Reserve,Eastern Cape,South Africa

A dramatic decline averaging 43% over a 4‐year period has occurred in tree Euphorbia (Euphorbia tetragona and Euphorbia triangularis) populations on the Great Fish River Reserve, South Africa. These changes are evident from data gathered by general vegetation monitoring methods as well as from a focused study of four tree Euphorbia populations. The decline from 2003 to 2007 was more marked for E. triangularis than for E. tetragona and was accompanied by a general absence of seedlings and a reduced presence of younger age classes of both species, decreasing the proportion of younger trees in the populations. The role of megaherbivores, specifically the black rhinoceros, in these changes is well established. However, the impact of baboon activity, leading to damage to tree crowns and upper branches, is also substantial, especially on E. triangularis populations. Damaged crowns were recorded significantly more often for E. triangularis than for E. tetragona, and the damage frequency increased with decreasing tree height. Thus, our work provides the first evidence that these two closely related Euphorbia species may be affected differently by herbivory.     

Mapping Restoration Opportunity for Collaborating with Land Managers in a Carbon Credit‐Funded Restoration Program in the Makana Municipality,Eastern Cape,South Africa

Spatial prioritization techniques are commonly used in conservation planning, but are relatively new for planning restoration programs. Typically, ecological data, and more recently data on economic costs and vulnerability of sites, are used. However, the effectiveness of restoration action ultimately relies on a combination of the appropriate ecological restoration techniques and the human and social dynamics of social‐ecological systems. Surveys were conducted with 29 land managers within the Makana Municipality of the Eastern Cape, South Africa, to identify a range of human and social factors hypothesized to define the potential effectiveness of restoration action. Land managers with similar characteristics were grouped using a cluster analysis, and the groups ranked and mapped in geographical information system (GIS) to provide a spatial representation of restoration opportunity. The total number of questions were reduced by 35.6%, a step toward developing a rapid assessment approach for assessing land managers' potential participation in restoration initiatives. Identifying and incorporating human and social factors that directly influence restoration prioritization should promote efficient and effective implementation of restoration actions by the Working for Woodlands programme, who are looking to funding landscape‐scale restoration through carbon trading.     

土壤活性有机质及其与土壤质量的关系

活性有机质是土壤的重要组成部分 ,主要包括溶解性有机碳、微生物生物量、轻组有机质。它在土壤中具有重要作用 :(1)可以表征土壤物质循环特征、评价土壤质量 ,可以作为土壤潜在生产力以及由土壤管理措施引起土壤有机质变化的早期指标 ;(2 )在养分周转中起重要作用 ,是植物的养分库 ,可以提供植物所需要的养分如氮、磷、硫等 ;(3)能稳定土壤结构 ,对维持团粒结构稳定性有重要作用。从土壤养分、土壤物理、化学性质方面讨论了活性有机质与土壤质量的关系。土壤中的溶解性有机碳、微生物生物量碳氮含量与土壤有机碳、全氮和碱解氮等物质的含量呈正相关。活性有机质受土壤质地、含水量、温度等因素影响 ,与土壤酸碱度、阳离子交换量等也有关。土壤微生物生物量碳和微生物量 C/有机碳比与土壤粘粒、粉粒含量呈正相关、与砂粒含量呈负相关     

Impacts of long-term application of organic fertilizers on soil quality parameters in reclaimed loess soils of the Rhineland lignite mining area

On the basis of long-term field experiments, the impact is demonstrated of the periodic application of organic fertilizers on the accumulation of organic matter and the development of the micro-pollutant content of reclaimed loess soils of the Rhineland lignite mining area under agricultural use. The oldest of these experiments (‘Berrenrath Humus Accumulation Experiment’) was begun in 1969. The results show that the regular input of organic matter (e.g. manure, waste compost, sewage sludge) favors the accumulation of soil organic matter (SOM). However, the type of organic material applied seems to be less important to the long-term accumulation process than the application rate. This is also true for composted and uncomposted manure, if the decay of organic matter during the composting process is taken into account. Nevertheless, the application of similar amounts of organic C in the form of manure resulted in a higher accumulation of SOM in a nitrogen-reduced farming system. Depending on the treatment, accumulation rates were between 0.02 and 0.08% SOM per year with values decreasing with time. From these results, it is estimated that reclaimed soils will take much longer to reach the former SOM level than was previously assumed. However, it is important to determine which SOM level is adequate for different soil functions (e.g. production function, filter and buffer function, transformation function), and whether the young SOM of reclaimed soils has the same properties as older SOM in undisturbed topsoils. As was expected, long-term fertilization with sewage sludge and waste compost led to an accumulation of some micro-pollutants in the topsoils treated. Nevertheless, the observed concentrations are quite low compared to background levels in topsoils of rural regions in North Rhine-Westphalia. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Nest boxes for Cape Parrots Poicephalus robustus in the Hogsback area,Eastern Cape,South Africa

Breeding propensity of tree-cavity nesting bird species are often limited by a shortage of natural nesting sites. Artificial nests can be used to provide alternative nest sites. Cape Parrots Poicephalus robustus are nationally endangered and nest in existing tree-cavities in high-altitude fragmented Afromontane forests in South Africa, assumed to be in short supply due to historic and current logging practices. To increase nest site availability, 179 wooden bird boxes and 28 bee boxes (to ‘pull’ bees) were erected during 2011–2012 in Hogsback, Eastern Cape. In 2016, no bird boxes were occupied by Cape Parrots. A total of 43% were used by other species, 51% were unused and 6% could not be inspected due to tree instability and inaccessibility. Two bird boxes were inspected by two pairs of Cape Parrots, but were never occupied. Occupancy of boxes by birds was not associated with nest, tree or habitat characteristics. However, occupancy of boxes by bees was associated with habitat type and tree species. Future conservation efforts will include locating natural Cape Parrot nesting sites and reforestation efforts to ensure the long-term availability of natural nesting sites.     

Activity patterns of springhares from the Eastern Cape Province, South Africa

The activity patterns of springhares Pedetes capensis ( Rodentia: Pedetidae ) from the Eastern Cape Province, South Africa, were investigated by counting the number of springhares active above ground at regular intervals throughout the night at different times of the year and under different weather conditions and phases of the moon. A combination of time of year, time of night and level of illumination best explained springhare activity, accounting for 43% of the variation in springhare numbers. Springhare activity generally reached its peak soon after dark, thereafter remaining fairly constant throughout most of the night and only decreasing in the 2–4-h period before sunrise. On those nights when the moon either rose or set during the night, this pattern was modified by the level of illumination. Springhares responded to moonlight by reducing above-ground activity, shifting activity to dark, moonless periods of the night, and by reducing their use of open space. Except for extremes, other weather conditions had no significant effect on springhare activity.     

Risk factors of porcine cysticercosis in the Eastern Cape Province, South Africa

There is a high prevalence of Taenia solium taeniosis/cysticercosis in humans and pigs in the Eastern Cape Province (ECP) of South Africa. The objective of this study was to identify risk factors of porcine cysticercosis in select districts of the ECP. Data were collected in 2003 by interviewing 217 pig producers from the area. Blood samples were collected from 261 of their pigs, which were tested using two enzyme-linked immunosorbent assays (ELISA) for the presence of antibodies to cysticercosis. Frequencies of both owner- and pig-level characteristics were determined. For pig-level analysis, all bivariable and multivariable associations were determined using the surveylogistic procedure of the SAS/STAT? software to accommodate for the intraclass correlation that exists for clusters of pigs within one owner and for clusters of owners within a district. All tests for significance were performed at the α?=?0.05 level, and adjusted odds ratios (aOR) and 95% confidence intervals (CI) were determined. Among the respondents, 48% of their households lacked a latrine, 98% slaughtered pigs at home, and 99% indicated that meat inspection services were not available. On bivariable analysis, there was a significant association between porcine infection and district (p?=?0.003), breed (p?=?0.041) and the absence of a latrine (p?=?0.006). On multivariable analysis, the absence of a latrine was the only variable significantly associated with porcine infection (aOR?=?1.89; 95% CI?=?1.07, 3.35) (p?=?0.028). The increased odds of porcine infection with households lacking a latrine contributes to our understanding of the transmission of this parasite in the ECP. Determining and addressing the risk factors for T. solium infection can potentially lower the very high prevalence in humans and pigs in this endemic area.     

子午岭植被演替过程中土壤剖面有机质与持水性能变化

研究表明,自然植被正向演替对土壤剖面有机质积累有显著促进作用,表现为：由弃耕地、草地、灌木、乔灌群聚到乔木的植被演替过程中,0-25cm土层有机质含量逐步增加,且演替初期的增加速度较快,而后增加速度相对变缓。植被演替过程中土壤有机质含量变化的主要原因在于植物凋落物归还量的变化。在同一时间测定的土壤剖面水分含量以及0-5cm土层田间持水量、容重、总孔度等与土壤持水性能相关的指标都与有机质含量呈极显著或显著相关,表明随剖面有机质的积累,土壤持水性能得到改善。     

Diatoms as water quality indicators in the upper reaches of the Great Fish River,Eastern Cape,South Africa

This study focused on the spring-fed upper reaches of the economically important Great Fish River with the aim of determining if diatoms could be used for biomonitoring in semi-arid conditions in southern Africa. Five sites were monitored monthly from 2010 to 2012. Of the 269 diatom taxa belonging to 51 genera identified, the dominant taxa were mostly those considered to be pollution-tolerant: Amphora pediculus, Craticula buderi, Fragilaria biceps, Nitzschia frustulum, Nitzschia paleacea, Planothidium lanceolatum and Rhopalodia gibba. A number of diatom-based numerical indices were used to infer water quality, including the generic diatom index, the specific pollution sensitivity index, the biological diatom index, and percentage pollution-tolerant valves, which forms part of the UK trophic diatom index. All index scores showed the Great Fish River to be impacted, and showed significant correlations of diatom species abundance with pH, NO₃-N, electrical conductivity, NH4-N and CaCO_3. Analysis revealed EC and NO3-N as the main environmental drivers affecting diatom community composition, followed by pH and PO4-P. The percentage of diatom deformities at all sites was high, at 3.5%. Diatom indices showed the river to be impacted by decades of agricultural activity, which was confirmed by chemical water analysis. Thus diatom indices can be used for biomonitoring in semi-arid areas.     

石灰土演替过程中颗粒态有机质和矿物结合态有机质的微生物群落特征

碳酸盐岩经风化作用并在地形、植被、气候、时间及生物等因素的影响下逐渐演替出黑色石灰土、棕色石灰土、黄色石灰土和红色石灰土。【目的】研究不同演替阶段石灰土颗粒态有机质(particulate organic matter, POM)和矿物结合态有机质(mineral-associated organic matter, MAOM)的微生物群落特征,为岩溶土壤有机质稳定机制研究提供理论依据。【方法】以广西弄岗国家级自然保护区的黑色石灰土、棕色石灰土、黄色石灰土和红色石灰土为研究对象,运用湿筛法将土壤有机质(soil organic matter, SOM)分为POM和MAOM,分析其理化性质以及微生物群落特征。【结果】石灰土演替过程中POM和MAOM的有机碳、总氮、交换性钙含量均呈下降趋势,且MAOM的C/N均大于POM,POM的C/P均大于MAOM。细菌α多样性在黑色石灰土POM和MAOM中最高,且四类石灰土MAOM的真菌多样性比POM要高。Acidobacteria、Proteobacteria、Ascomycota均为石灰土演替过程中POM和MAOM的优势菌门。总磷是影响石灰土演替过...     

Landscape dysfunction and reduced spatial heterogeneity in soil resources and fertility in semi‐arid succulent thicket,South Africa

Abstract Succulent thicket in the Eastern Cape of South Africa is one of many rangeland ecosystems in the world that displays evidence of unsustainable grazing pressure. Widespread transformation of succulent thicket has resulted in the replacement of the typical two‐phase perennial vegetation patches with a structurally simple field layer of ephemeral and weakly perennial grasses and forbs. We hypothesized that (i) transformation of succulent thicket leads to a switch from a spatially heterogeneous landscape to a homogenous and relatively infertile state; and (ii) that this loss of fertility is associated with a breakdown in the processes that conserve resources and promote water use efficiency. We tested these hypotheses at five fenceline contrast sites in Sundays River Thicket, an arid form of succulent thicket. We compared soil fertility (organic carbon, available nitrogen and phosphorus), texture, matric potential, and surface microtopography in the two main microhabitats on either side of the fencelines using a nested anova. Our results show that intact Sundays River thicket has a distinct spatial pattern of soil fertility where nutrients and organic carbon are concentrated under the patches of perennial shrubs, compared with under canopy trees. Transformation results in a significant homogenization of this pattern and an overall reduction in the fertility of the landscape. The proportion of the landscape surface that promotes infiltration due to a distinct litter layer decreases from 60% to 0.6%. Soil moisture retention (matric potential) also decreases with transformation. We interpret these patterns within the framework of semi‐arid landscape functionality.     

Different responses of soil respiration to environmental factors across forest stages in a Southeast Asian forest

Soil respiration (SR) in forests contributes significant carbon dioxide emissions from terrestrial ecosystems and is highly sensitive to environmental changes, including soil temperature, soil moisture, microbial community, surface litter, and vegetation type. Indeed, a small change in SR may have large impacts on the global carbon balance, further influencing feedbacks to climate change. Thus, detailed characterization of SR responses to changes in environmental conditions is needed to accurately estimate carbon dioxide emissions from forest ecosystems. However, data for such analyses are still limited, especially in tropical forests of Southeast Asia where various stages of forest succession exist due to previous land‐use changes. In this study, we measured SR and some environmental factors including soil temperature (ST), soil moisture (SM), and organic matter content (OM) in three successional tropical forests in both wet and dry periods. We also analyzed the relationships between SR and these environmental variables. Results showed that SR was higher in the wet period and in older forests. Although no response of SR to ST was found in younger forest stages, SR of the old‐growth forest significantly responded to ST, plausibly due to the nonuniform forest structure, including gaps, that resulted in a wide range of ST. Across forest stages, SM was the limiting factor for SR in the wet period, whereas SR significantly varied with OM in the dry period. Overall, our results indicated that the responses of SR to environmental factors varied temporally and across forest succession. Nevertheless, these findings are still preliminary and call for detailed investigations on SR and its variations with environmental factors in Southeast Asian tropical forests where patches of successional stages dominate.     

The impact of black wattle encroachment of indigenous grasslands on soil carbon,Eastern Cape,South Africa

Black wattle (Acacia mearnsii, De Wild.) is a fast growing tree species introduced into South Africa in the nineteenth century for commercial purposes. While being an important source of timber and firewood for local communities, black wattle is an aggressive invasive species and has pervasive adverse environmental impacts in South Africa. Little is known about the effects of black wattle encroachment on soil carbon, therefore the aim of this study was to investigate the impact of black wattle encroachment of natural grassland on soil carbon stocks and dynamics. Focussing on two sites in the Eastern Cape, South Africa, the study analysed carbon stocks in soil and litter on a chronosequence of black wattle stands of varying ages (up to >50 years) and compared these with adjacent native grassland. The study found that woody encroachment of grassland at one site had an insignificant effect on soil and litter carbon stocks. The second site showed a clear decline in combined soil and litter carbon stocks following wattle encroachment. The lowest stock was in the oldest wattle stand, meaning that carbon stocks are still declining after 50 years of encroachment. The results from the two sites demonstrate the importance of considering changes in soil carbon when evaluating ecosystem effects of invasive species.     

Soil and vegetation recovery following alien tree clearing in the Eastern Cape Province of South Africa

The impact of alien tree clearing on soil and vegetation recovery remains largely understudied. This study focused on changes in soil and vegetation properties following Acacia removal. The aim was to quantify the long‐term consequences of alien clearing. Paired cleared (old – 15 years; medium – 11 years; recent – 6 years) and uncleared sites were selected along the Palmiet catchment in Eastern Cape Province, South Africa. Various soil physico‐chemical properties (soil moisture, pH, P, N, C, K, Na, Ca, Mg and soil repellency) and vegetation diversity measures were studied on 10 m × 10 m plots. Results indicate that measured soil nutrients are significantly (P < 0.05) lower in cleared than in uncleared sites. However, comparisons among cleared sites alone indicate that soil properties are recovering with older cleared sites having higher (P < 0.05) nutrients than recent cleared sites. Soils in uncleared sites are more repellent than soil in cleared sites. Vegetation recovery in cleared sites was taking place with older cleared sites having higher native species diversity than recently cleared site. We conclude that the removal of alien plants could have caused a reduction in soil nutrients. However, as native vegetation recovers on cleared sites, soil nutrients are gradually improving.     

Secondary succession in Acacia nilotica (L.) savanna in the Hluhluwe Game Reserve,South Africa

Analysis of aerial photographs indicates that woody plant biomass has rapidly increased in Hluhluwe Game Reserve over the last 40 years. Open Acacia nilotica savanna is being replaced by broadleaf species, especially Euclea spp. We were interested in whether this secondary successional shift was due to high numbers of seedlings establishing and growing to maturity under acacias (facilitation) or due to the release of already established, but suppressed individuals (gullivers) of the resprouting broadleaf species. We examined the recruitment patterns and size-class distributions (height, basal diameter) of important species in this savanna.Densities of euclea seedlings (<0.6 cm basal diameter) under Acacia nilotica were low (median of 0 and mean of 0.06 m²) below adult canopies and effectively zero in adjacent interspaces. No differences in numbers of other broadleaf species were found between open sites and under Acacia nilotica sites. Few large eucleas or other broadleaf species occurred under Acacia nilotica. Few Acacia nilotica recruits were found either under adults or in the open whereas Acacia karroo recruits were more common.The overall size class distribution for eucleas was dominated by individuals in the intermediate size class, suggesting that recruitment is not the dominant demographic process. We propose that the escape of intermediate sized eucleas from the fire trap has caused the increase in woody plants.Analysis of a time sequence of aerial photographs shows that invasion occurred rapidly between 1954 and 1975. A common feature for sites where woody plant invasion has taken place, was the presence of barriers to fire (especially roads). We suggest that the recent and rapid increase in woody vegetation is due to a decrease in the frequency of intense fires, rather than the recent absence of megaherbivores which allowed Acacia nilotica establishment. Few intense fires allow suppressed tree or shrub individuals, ('gullivers'), to escape the grass/fire layer and thereby become tall and fire-resistant. This release may explain the rapid rate of invasion by inherently slow growing broad-leaf species.