Savannas Of Southern Africa Research Articles

Repeated clearing as a mechanism for savanna recovery following bush encroachment

Abstract Many savannas are experiencing increased cover of trees and shrubs, resulting in reduced herbaceous productivity, shifts in savanna functional structure and potential reductions in ecotourism. Clearing woody plants has been suggested as an effective management strategy to mitigate these effects and restore these systems to an open state with higher rates of grass production and herbivory. This study investigated the effectiveness of repeated shrub clearing as a tool to mitigate bush encroachment in a semi‐arid savanna in southern Africa. We present data from a 7‐year experiment in the Mthimkhulu Game Reserve bordering Kruger National Park, South Africa. Colophospermum mopane stems and resprouting shoots were basally cut 2–3 times per year (2015–2022) in three pairs of treatment and control plots of 60 × 60 m. We monitored changes in soil moisture, grass biomass and herbivore activity via dung counts. We assessed C. mopane physiological responses to repeated cutting using non‐structural carbohydrates and stable water isotopes to infer changes to energy storage and functional rooting depth, respectively. The cleared treatment had higher soil moisture and grass biomass than the control treatment. Dung counts showed impala and buffalo visited the cleared treatment more frequently than the control treatment. Repeated cutting had limited effects on C. mopane survival in the first 2–3 years after initial clearing, but 80% of individuals were dead after 7 years. Repeatedly cut C. mopane had lower belowground starch concentrations and used water from shallower soil depths than C. mopane in control plots. Synthesis and applications. Repeated cutting increased soil moisture availability and grass biomass, and attracted charismatic grazing herbivores. While more costly than once‐off clearing methods, this practice created more employment opportunities for a neighbouring rural community. Transforming portions of the ecosystem to a grass‐dominated state may increase ecotourism potential through improved game viewing in open systems.

Hungry herbivores and thirsty plants: Browsing wildlife shape savanna tree transpiration independently of water use strategies

Abstract Plant transpiration is a key component of the hydrological cycle that moves water from the soil through plants to the atmosphere and is largely determined by environmental conditions. The challenges of highly variable climatic conditions and water scarcity in the semi‐arid savannas of southern Africa drive trees to exhibit different water use strategies. An additional challenge for savanna trees arises from the browsing of large mammals, and its potential impact on transpiration has largely been overlooked. To assess water use strategies and the impact of browsing on transpiration in three common savanna woody species (Colophospermum mopane, Catophractes alexandri, Senegalia mellifera), we conducted an extensive field experiment in a wildlife reserve in Namibia. We established a browsing gradient ranging from 0% to 100% leaf removal to disentangle complex relationships, and we measured sap flow representing whole‐tree transpiration, stomatal conductance as a proxy for leaf level transpiration, and environmental factors including soil moisture, solar radiation, air temperature and air humidity. We discovered a unimodal relationship between browsing intensity and sap flow, consistent across all species, and peaking at low to moderate browsing levels equivalent to approximately 30% leaf removal. This universal pattern is remarkable since we found water use strategies to differ among species: Colophospermum mopane and C. alexandri exhibit a water‐saving behaviour to reduce water loss under unfavourable conditions while S. mellifera demonstrates water‐spending characteristics. The deviation from a negative linear effect of browsing does not meet the functional expectation when browsing is translated into a simple leaf area reduction. Instead, it can be attributed to stomatal adjustments that partially compensate for transpiratory surface loss. We propose that this conceptual mechanism can be generalised to other woody species and various ecosystems. In addition, common transpiration models relying solely on leaf area indices and abiotic factors can be improved by including a non‐linear relationship to reproduce the effect of browsing accurately. Our findings highlight the role of herbivores in shaping the connection between the Earth's spheres and improve our understanding of ecohydrological and vegetation dynamics in Southern African savannas. Read the free Plain Language Summary for this article on the Journal blog.

Drought release and post-drought changes in herbaceous composition and diversity in two land uses subjected to selective bush control in a semi-arid Kalahari savanna

Land degradation due to bush encroachment and drought threatens the well-being of land users and forage production in the semi-arid savannas of southern Africa. This study aimed to analyse how herbaceous vegetation in the Kalahari savanna can recover from drought, and how this is affected by previously implemented bush control measures. We compared plant species composition and diversity of the herbaceous layer across a drought-release (2021) and post-drought (2022) year within two land use types (game and livestock) in bush-encroached and controlled areas, respectively. Diversity decreased significantly during the post-drought year. Annual species dominated in the drought-release year, which were replaced by perennial forbs and dwarf shrubs in the post-drought year. Selective bush control enhanced herbaceous species abundance and richness due to decreased competition. The species richness was higher in the game ranch compared to the cattle farm during the drought-release year. Herbaceous abundance, however, increased on the cattle farm. The management strategies, feeding behaviour and animal movement may have contributed to these differences in these two contrasting land use types. This study showed that herbaceous plant communities can recover rapidly after a drought period and in areas where bush control was applied.

Alien invasive Leucaena leucocephala successfully acquires nutrients by investing in below-ground biomass compared to native Vachellia nilotica in nutrient-amended soils in South Africa.

Soils in grasslands and savannas of southern Africa are acidic and nutrient-poor. Legume plants, such as Vachellia nilotica and alien invasive Leucaena leucocephala, are a major component of the vegetation there. Vachellia nilotica can establish in drought-prone environments, and is invasive in high rainfall areas. Leucaena leucocephala is an emerging invasive in South Africa and is ranked among the world’s 100 most invasive alien species. Alien plants can invade native habitats through their adaptability to low-resource soils, and thus can out-compete and displace native vegetation. We investigated the effects of phosphorus (P) deficiency and soil acidity on legume–microbe symbiosis, nitrogen (N) nutrition and carbon (C) growth costs of these two legumes in grassland soils. We used as inoculum and growth substrate soils collected from a long-term (>65 years) nutrient and lime-addition trial, the Veld Fertilizer Trial (VFT), located at Ukulinga Research Farm near Pietermaritzburg in South Africa. We used soils from three VFT treatments: soils fertilized with superphosphate (336 kg ha−1) applied once per year (+P), soils fertilized with superphosphate (336 kg ha−1) applied once per year with dolomitic lime (2250 kg ha−1) applied once every 5 years (P+L) and soils with no superphosphate and no dolomitic lime applications (Control). Seeds of V. nilotica and L. leucocephala were germinated and grown independently in these soils in green house conditions and harvested after 125 days for measurement of growth, legume–microbe symbiosis, N nutrition and C growth costs. Results showed that the two legumes had different growth adaptations. Vachellia nilotica grown in control soils and +P soils nodulated with various Burkholderia spp., while L. leucocephala did not nodulate in all soil treatments. Both legumes utilized for growth both atmospheric- and soil-derived N across all treatments thereby decreasing C growth costs. Vachellia nilotica grown in +P soils accumulated the most biomass and N nutrition. Leucaena leucocephala maximized specific N assimilation rates by investing in below-ground biomass accumulation in control soils. This shows that L. leucocephala possesses traits that are successful in acquiring nutrients by investing in below-ground biomass and relying on utilization of N from both the soil and the atmosphere.

The Future of Food: Domestication and Commercialization of Indigenous Food Crops in Africa over the Third Decade (2012–2021)

This paper follows the transition from ethnobotany to a deeper scientific understanding of the food and medicinal properties of African agroforestry tree products as inputs into the start of domestication activities. It progresses on to the integration of these indigenous trees as new crops within diversified farming systems for multiple social, economic and environmental benefits. From its advent in the 1990s, the domestication of indigenous food and non-food tree species has become a global programme with a strong African focus. This review of progress in the third decade is restricted to progress in Africa, where multi-disciplinary research on over 59 species has been reported in 759 research papers in 318 science publications by scientists from over 833 research teams in 70 countries around the world (532 in Africa). The review spans 23 research topics presenting the recent research literature for tree species of high priority across the continent, as well as that in each of the four main ecological regions: the humid zone of West and Central Africa; the Sahel and North Africa; the East African highlands and drylands; and the woody savannas of Southern Africa. The main areas of growth have been the nutritional/medicinal value of non-timber forest products; the evaluation of the state of natural resources and their importance to local people; and the characterization of useful traits. However, the testing of putative cultivars; the implementation of participatory principles; the protection of traditional knowledge and intellectual property rights; and the selection of elite trees and ideotypes remain under-researched. To the probable detriment of the upscaling and impact in tropical agriculture, there has been, at the international level, a move away from decentralized, community-based tree domestication towards a laboratory-based, centralized approach. However, the rapid uptake of research by university departments and national agricultural research centres in Africa indicates a recognition of the importance of the indigenous crops for both the livelihoods of rural communities and the revitalization and enhanced outputs from agriculture in Africa, especially in West Africa. Thus, on a continental scale, there has been an uptake of research with policy relevance for the integration of indigenous trees in agroecosystems and their importance for the attainment of the UN Sustainable Development Goals. To progress this in the fourth decade, there will need to be a dedicated Centre in Africa to test and develop cultivars of indigenous crops. Finally, this review underpins a holistic approach to mitigating climate change, as well as other big global issues such as hunger, poverty and loss of wildlife habitat by reaping the benefits, or ‘profits’, from investment in the five forms of Capital, described as ‘land maxing’. However, policy and decision makers are not yet recognizing the potential for holistic and transformational adoption of these new indigenous food crop opportunities for African agriculture. Is ‘political will’ the missing sixth capital for sustainable development?

Effect of fire on the palatability of plants in an African woodland savanna: varying impacts depending on plant functional groups.

Fire and herbivores are two important drivers of changes in vegetation composition, quality and dynamics and both are highly related to each other. Herbivores are known to respond to fire both in terms of foraging decisions and distribution. However, little is known about the actual changes in plant chemistry following a fire event and how long these changes will last. We investigated the effect of fire on two different plant functional groups (grasses and woody species) in a woodland savanna of southern Africa. We studied chemical compounds known to be important for palatability of five perennial grass and seven woody species (trees and shrubs) common in the woodland savanna and known to be utilized by herbivores. We wanted to know if plant chemistry differs between a recently burned site (burned 2 years ago) and a control site, burned 16 years ago, and if grasses and woody species show similar relative differences between sites (i.e., the plants’ response to fire). We found a clear difference in chemical composition patterns between the plant functional groups, with an almost homogenous response to fire among woody species, but higher variability in response among grass species. Furthermore, we found that woody species maintained a higher nutritional value even 2 years after burning, whereas grasses did not show clear differences among the two investigated sites. Hence, few years after burning, woody plants might still serve as an attraction for herbivores, especially browsers, in contrast to grasses. The knowledge about these differences between the two functional groups in response to fire is beneficial for the development of management strategies for large herbivores whether domestic or wild.

Historical diversification and biogeography of the endemic southern African dung beetle genus, Epirinus (Scarabaeidae: Scarabaeinae)

Abstract The role of the geological uplift and climatic changes during the late Cenozoic on the species diversification of southern African dung beetles is not fully understood. Therefore, we use a divergence-time-estimated phylogeny, macroevolutionary analyses and ecological niche modelling under different climatic scenarios to investigate diversification of the endemic southern African genus, Epirinus. We predict the ancestral range and vegetation type occupied by Epirinus and how late Cenozoic climatic fluctuations and resulting vegetation changes affected speciation and extinction of Epirinus species. Our results suggest that the genus originated in forest with radiation into three geographical centres: (a) north-east escarpment forest and highland grassland; (b) south-east forest; and (c) south-west lowlands to north-east uplands in open vegetation. Reduced speciation rates in the mid-Miocene and increased extinction rates during the drier and cooler Plio-Pleistocene coincide with the replacement of forest by grassland or savanna in southern Africa. The drier climate in southern Africa may have driven extensive contraction of shaded vegetation, forcing an adaptation of forest inhabitants to upland grassland environments, or driving Epirinus species to extinction. Our study supports hypothesis of climatically driven diversification of Epirinus whereas ecological niche modelling across different geological periods suggest that the south-east and, to a lesser extent, the west coast of South Africa as stable areas.

Mapping floristic communities in Southern Africa savannas, Mozambique

Abstract The present study was carried out in Limpopo National Park (LNP) with the objective to map floristic communities that occur inside the park. Three (3) Landsat 8 satellite images were obtained by Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS) tools and were pre-processed and classified, culminating in six (6) types of land use and cover. The floristic survey consisted of stratified sampling in three (3) main LNP landscapes types, namely landscape of limestone soils, landscape of rhyolite shallow soils and landscape of deep sandy soils. The final map presents 13 floristic communities identified by the names of greatest value of ecological importance (IVI) species. The community of Terminalia sericea / Combretum apiculatum / Guibourtia conjugata / Colophospermum mopane presented a larger occurrence area. Colophospermum mopane was the most representative species among the mapped communities, mostly occurring in association with other species. The overall accuracy was 74% and the Kappa index was 68%, thus giving a good rating. The mapping also showed that human occupied areas are larger than some floristic communities areas, so we suggest that these smaller communities, should be given priority actions for their conservation, especially those without human occupation.

Automated training sample definition for seasonal burned area mapping

Monitoring of environmental change can benefit from the increasing availability of multitemporal satellite imagery, and efficient and effective analysis tools are needed to generate relevant spatio-temporal land cover datasets. We present a data driven approach for automatic training sample selection to support supervised spatio-temporal mapping of seasonally burned areas in the semi-arid savannas of Southern Africa. Our approach leveraged the distinctive spectral-temporal trajectories associated with areas on the landscape burned at different times or areas remaining unburned over time. Using fuzzy c-means clustering, we extracted distinctive trajectories from the multitemporal mid-infrared burn index (MIRBI) data derived from Landsat data and characterized them based on empirically developed labeling rules. The selected training trajectories captured both the burn condition (burned or unburned) and if burned, the timeframe of the burn event. We assessed the approach by training a Random Forests model using over 2500 automatically selected training data and validated the model against ground truth for years 2009 and 2014. Based on over 1000 validation points in each year, we obtained overall accuracies above 90% showing reliable and consistent training data were supplied by our automatic training sample selection approach. The method provides a data driven and automatic approach which can reduce the time-consuming and expensive training task, enabling quicker generation of relevant burned area information that can support fire monitoring programs and climate change research.

Plant endemism in Griqualand West, South Africa

Griqualand West, a region in the semi-arid Northern Cape and North-West provinces of South Africa, has been variously suggested to contain a number of range-restricted plant species, and was proposed to be a local centre of plant endemism. The Griqualand West Centre (GWC), hitherto demarcated by geological features and limited floristic data, is hereby investigated to determine the true levels of endemism and its extent of occurrence. Findings suggest that at least 23 plant species have their natural distribution ranges restricted to the Griqualand West region. These endemics represent 1.4% of the region's flora. Although this is a lower than the predicted level of endemism, it matches the trends of endemicity found in other centres in semi-arid savanna of southern Africa. Many of the GWC endemics show indications of holo-endemism owing to their apparent preference for the Ca- and Mg-rich substrates of the Ghaap Plateau. When the total distributions of all GWC endemic species are considered, then the resulting boundary of the GWC is more extensive than the substantial area already proposed previously (>40,000 km2). This study therefore proposes the concept of ‘core area’ in which distant outlier populations of endemic species (>100 km outside the main distribution range with no suitable habitat in between) are discarded during the demarcation of the centre's boundary. It is proposed that this concept is best applied when assessing extensive areas with few endemic species. A more refined GWC core area will allow for more effective conservation and future research efforts by focussing attention on those areas where high numbers of endemic plant species co-occur. Within the GWC core area, specific regions, such as the increasingly densely populated Kimberley region, the banded ironstone hill ranges, and the unique environment that is the Ghaap Plateau, are highlighted as areas of conservation importance.

Colophospermum Mopane Leaf Production and Phenology in Southern Africa's Savanna Ecosystem - A Review

Colophospermum mopane, commonly known as mopane, is a dominant tree or shrub in the mopane woodland. It is widely distributed in the low-lying areas of southern Africa's savanna. Despite its wide distribution, ability to survive water stress conditions, and value as a source of browse for herbivores, especially during the dry season, there is limited knowledge on mopane leaf production and phenology as well as its implications to browsers.

A lepidopteran (Imbrasia belina) might influence tree-grass balance of Colophospermum mopane savanna

Traditional explanations of tree-grass coexistence in African savannas are based on competition between these growth forms or demographic bottlenecks of trees maintained by fire or mammalian browsers. Perturbation of their “balance” may result in an alternate system state of woody encroachment. Invertebrate herbivory has never been offered as an explanation. We developed a consumer-resource model which illustrated that annual irruptions of a lepidopteran (Imbrasia belina), known as mopane worm, can determine the tree-grass balance of semi-arid Colophospermum mopane savanna in southern Africa. Model performance was sensitive to the abundance, hence mortality, of mopane worms, owing to their complete defoliation of tree leaf biomass resulting in altered competitive relations between trees and grasses. Invertebrate herbivores have been recognized in other systems as agents for effecting a state change of host tree populations; this modeling study offers a first indication of such a role for the well-researched tree-grass relations of African savannas.

Temperature fluctuations inside savanna termite mounds: Do size and plant shade matter?

Mound building termites are key ecosystem engineers of subtropical savanna regions. Mounds allow termites to maintain suitable conditions for termite reproduction and food cultivation ('fungus gardens'). We studied how the internal mound temperature of Macrotermes natalensis, a dominant mound-building termite of the subtropical savanna of southern Africa, responds to a number of environmental variables. We used general additive mixed models (GAMM) to determine how external temperature, mound size (volume) and the amount of vegetation shade affects mound internal temperature over a 24-h period. Internal mound temperature varied daily following changes of the external temperature, although the range of variation was much smaller. Active termite mounds maintained a higher internal temperature than inactive ones, and mound activity reinforced the positive effect of mound size and moderated the negative effect of vegetation shade on internal temperatures. In turn, external temperature fluctuations equally affected active and inactive mounds. Large mounds maintained near optimal internal temperatures compared to smaller sized mounds. We therefore conclude that termite mound size is a stronger determinant of internal mound temperature stability compared to plant shade cover.

Community structure of bats in the savannas of southern Africa: Influence of scale and human land use

Community structure of bats in the savannas of southern Africa: Influence of scale and human land use

Response of Land Surface Phenology to Variation in Tree Cover during Green-Up and Senescence Periods in the Semi-Arid Savanna of Southern Africa

Understanding the spatio-temporal dynamics of land surface phenology is important to understanding changes in landscape ecological processes of semi-arid savannas in Southern Africa. The aim of the study was to determine the influence of variation in tree cover percentage on land surface phenological response in the semi-arid savanna of Southern Africa. Various land surface phenological metrics for the green-up and senescing periods of the vegetation were retrieved from leaf index area (LAI) seasonal time series (2001 to 2015) maps for a study region in South Africa. Tree cover (%) data for 100 randomly selected polygons grouped into three tree cover classes, low (<20%, n = 44), medium (20–40%, n = 22) and high (>40%, n = 34), were used to determine the influence of varying tree cover (%) on the phenological metrics by means of the t-test. The differences in the means between tree cover classes were statistically significant (t-test p < 0.05) for the senescence period metrics but not for the green-up period metrics. The categorical data results were supported by regression results involving tree cover and the various phenological metrics, where tree cover (%) explained 40% of the variance in day of the year at end of growing season compared to 3% for the start of the growing season. An analysis of the impact of rainfall on the land surface phenological metrics showed that rainfall influences the green-up period metrics but not the senescence period metrics. Quantifying the contribution of tree cover to the day of the year at end of growing season could be important in the assessment of the spatial variability of a savanna ecological process such as the risk of fire spread with time.

Spatiotemporal patterns and drivers of landscape change in a semi-arid, southern African savanna: a satellite imaging and intensity analysis

Abstract Background The savannas of southern Africa are a highly variable and globally important biome that supports rapidly expanding human populations. They also have one of the greatest concentrations of wildlife on the continent. Savannas occupy a fifth of the earth's land surface, yet despite their ecological and economic significance, little is understood about the complex couplings and feedbacks that drive long-term spatiotemporal patterns of change. Here, we aimed to describe land-cover change in Chobe District, Botswana, and address questions about the complex drivers of patterns of land cover change, with a particular focus on climate, fire, herbivory, and anthropogenic disturbance. Methods We used Landsat Thematic Mapper (TM), Enhanced Thematic Mapper Plus (ETM+), and Operational Land Imager (OLI) satellite imagery from 1990 to 2013 to explore land-cover change across the 21 000 km 2 Chobe District. Net and gross land cover change were assessed for the Chobe National Park, six protected forest reserves, areas surrounding towns and villages, and the riparian corridor of the Chobe River. We also used intensity analysis methods developed by Aldwaik and Pontius to compare observed changes to a hypothetical uniform change to examine how the size and intensity of land cover losses and gains vary between time periods and across different land-cover classes. Findings Patterns of land-cover change in the Chobe District were not strictly linear in nature, a characteristic noted for other dryland systems, with gross land-cover change and intensity analysis showing extensive, active bidirectional exchange between woodland, shrubland, and grassland. Changes in land cover over the study period were characterised by a loss of woodlands, accompanied by an expansion of shrubland. Woodland losses were greatest along the Chobe River, which provides a large proportion of the drinking water, and other essential resources, for human and wildlife populations. Interpretation The multi-decadal monitoring of land-cover changes in southern Africa using remote-sensing provides essential information for societies to manage ecosystem resources locally, so that they might increase resilience to future climate change. Our identification of spatial and temporal patterns of land-cover changes supports the need to develop an early warning framework to identify existing and emergent threats to forest resources and services, and reduce potential adverse effects on the livelihoods and health of local communities. Funding Forest Conservation Botswana (FCB); National Science Foundation.

Utilization of the SAVANNA model to analyze future patterns of vegetation cover in Kruger National Park under changing climate

Within southern Africa's savanna ecosystems, woody and herbaceous species have differing growth characteristics that allow a tenuous co-existance. The high dependence of humans on the landscape, through agricultural production, tourism, and natural resource extraction makes understanding savanna vegetation dynamics essential. Studies analyzing resilience of savannas suggest potential state changes in vegetation structure from continuous grasslands with sporadic woody cover to less biologically productive landscapes. One of the biggest questions in this landscape is the impact of climate change. The spatially explicit SAVANNA model is used to analyze the impact of climate change on vegetation cover across Kruger National Park’s (KNP) main land system classifications (Satara, Skukuza, Letaba, and Phalaborwa). Manipulating climate inputs and management regimes allowed us to analyze the resilience of savanna vegetation under multiple Intergovernmental Panel on Climate Change (IPCC) scenarios. Trends in future climate indicate an increase in temperatures greater than 1.0°Celsius and a slight decrease in precipitation by 2080. Model results indicate a long-term decrease in multiple size classes of vegetation across all the four land systems. However, the model runs show differing response to climate change between the woody and herbaceous cover types. Spatial trends across the park follow closely with the north-south climate gradient. The most spatially distinct land system was Skukuza, which exhibited some of the highest initial net primary production (NPP) values and also the greatest decreases in NPP into the future. While this region is projected to lose large proportions of its herbaceous and shrub vegetation it is projected to increase in tree green leaf, mostly related to increasing fine leaf vegetation (Acacia sp.). The northern land systems were already dominated by mopane, but under all model scenarios mopane will increase in Letaba and Phalaborwa. This mopane increase will offset the loss of herbaceous and shrub vegetation, resulting in little to no decrease in NPP across time for these land systems. This work illustrates that landscape resilience is not only impacted by the severity of changing climate but the degree to which we manage such systems.

Utilizing Multiple Lines of Evidence to Determine Landscape Degradation within Protected Area Landscapes: A Case Study of Chobe National Park, Botswana from 1982 to 2011

The savannas of Southern Africa are an important dryland ecosystem as they cover up to 54% of the landscape and support a rich variety of biodiversity. This paper evaluates landscape change in savanna vegetation along Chobe Riverfront within Chobe National Park Botswana, from 1982 to 2011 to understand what change may be occurring in land cover. Classifying land cover in savanna environments is challenging because the vegetation spectral signatures are similar across distinct vegetation covers. With vegetation species and even structural groups having similar signatures in multispectral imagery difficulties exist in making discrete classifications in such landscapes. To address this issue, a Random Forest classification algorithm was applied to predict land-cover classes. Additionally, time series vegetation indices were used to support the findings of the discrete land cover classification. Results indicate that a landscape level vegetation shift has occurred across the Chobe Riverfront, with results highlighting a shift in land cover towards more woody vegetation. This represents a degradation of vegetation cover within this savanna landscape environment, largely due to an increasing number of elephants and other herbivores utilizing the Riverfront. The forested area along roads at a further distance from the River has also had a loss of percent cover. The continuous analysis during 1982–2011, utilizing monthly AVHRR (Advanced Very High Resolution Radiometer) NDVI (Normalized Difference Vegetation Index) values, also verifies this change in amount of vegetation is a continuous and ongoing process in this region. This study provides land use planners and managers with a more reliable, efficient and relatively inexpensive tool for analyzing land-cover change across these highly sensitive regions, and highlights the usefulness of a Random Forest classification in conjunction with time series analysis for monitoring savanna landscapes.

No two are the same: Assessing variability in broad-leaved savanna tree phenology, with watering, from 2012 to 2014 at Nylsvley, South Africa

Ecologists and modellers are yet to fully understand and design accurate models simulating the unpredictable green-up of savanna ecosystems, possibly due to the lack of long-term, phenological monitoring of this biome. In this study, we observed the percentage of leaf age class (new, fully expanded and mature) phenology of two dominant, broad-leaved savanna trees at a weekly scale over the green-up period (August–November) and a monthly scale during the rest of the growing season (December–May) between August 2012 and May 2015 at the Nylsvley Nature Reserve, South Africa. We used an irrigation experiment, commencing in the dry season, to determine whether the simulation of a 20mm rainfall event for several weeks prior to the start of rainfall, could influence the leaf phenology of Burkea africana and Terminalia sericea. Each observed season experienced different environmental conditions from early onset average rainfall (2012), to late-onset high (2013) or low rainfall (2014). Irrigation of T. sericea in 2012 increased green-up rates and in combination with a late season fire during September 2013, resulted in a delayed green-up of the watered trees. Early-greening of B. africana was only observed during the 2014 season. Terminalia sericea showed faster maturation rates than B. africana which indicates the use of a facultative-greening strategy, while B. africana had faster green-up rates after the fire when competition for available nutrients was low. This study has demonstrated that using fine-scale phenological measurements can provide a clearer picture of how trees are greening up in the early stages of the green-up period and showcases the seasonal variability in savanna tree phenology. Investment into long-term phenological monitoring across southern Africa's savannas is needed if we intend to understand cues and predict phenology accurately in the future.

Comparison of global inventories of CO2 emissions from biomass burning during 2002–2011 derived from multiple satellite products

This study compared five widely used globally gridded biomass burning emissions inventories for the 2002–2011 period (Global Fire Emissions Database 3 (GFED3), Global Fire Emissions Database 4 (GFED4), Global Fire Assimilation System 1.0 (GFAS1.0), Fire INventory from NCAR 1.0 (FINN1.0) and Global Inventory for Chemistry-Climate studies-GFED4 (G-G)). Average annual CO2 emissions range from 6521.3 to 9661.5 Tg year−1 for five inventories, with extensive amounts in Africa, South America and Southeast Asia. Coefficient of Variation for Southern America, Northern and Southern Africa are 30%, 39% and 48%. Globally, the majority of CO2 emissions are released from savanna burnings, followed by forest and cropland burnings. The largest differences among the five inventories are mainly attributable to the overestimation of CO2 emissions by FINN1.0 in Southeast Asia savanna and cropland burning, and underestimation in Southern Africa savanna and Amazon forest burning. The overestimation in Africa by G-G also contributes to the differences.