William John Bond

William John Bond
University of Cape Town | UCT · Department of Biological Sciences

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489
Publications
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Publications

Publications (489)
Article
Modeling fire spread as an infection process is intuitive: An ignition lights a patch of fuel, which infects its neighbor, and so on. Infection models produce nonlinear thresholds, whereby fire spreads only when fuel connectivity and infection probability are sufficiently high. These thresholds are fundamental both to managing fire and to theoretic...
Article
Ecology and evolutionary biology have focused on how organisms fit the environment. Less attention has been given to the idea that organisms can also modify their environment, and that these modifications can feed back to the organism, thus providing a key factor for their persistence and evolution. There are at least three independent lines of evi...
Article
Full-text available
Recent findings point to plant root traits as potentially important for shaping the boundaries of biomes and for maintaining the plant communities within. We examined two hypotheses: 1) Thin-rooted plant strategies might be favored in biomes with low soil resources; and 2) these strategies may act, along with fire, to maintain the sharp boundary be...
Article
Full-text available
1. Fires in savannas limit tree cover, thereby promoting flammable grass accumulation and fuelling further frequent fires. Meanwhile, forests and thickets form dense canopies that reduce C4‐grass fuel loads and creating a humid microclimate, thereby excluding fires under typical climatic conditions. However, extreme fires occasionally burn into the...
Article
We introduce the concept of Biome Awareness Disparity (BAD)-defined as a failure to appreciate the significance of all biomes in conservation and restoration policy-and quantify disparities in (i) attention and interest, (ii) action, and (iii) knowledge amongst biomes in tropical restoration science, practice, and policy. By analysing 50,000 tweet...
Article
Fire is commonly identified as strong driver of alternative stable states such as adjacent open‐ versus closed‐canopy vegetation types. The absence of open‐canopy species from closed‐canopy understoreys, where light availability is low and dynamic, however, suggests shade tolerance is an integral determinant of such vegetation boundaries. While the...
Preprint
Full-text available
Typically, savannas experience frequent fires, which limit tree cover and promote flammable grass accumulation, whereas forests form dense canopies that exclude fires by reducing C4-grass fuel loads and creating a humid microclimate. However, extreme fires occasionally burn into forests. Although these are known to kill forest trees and can make re...
Article
Full-text available
Grassland ecosystems supporting wildlife and livestock populations have undergone significant transformation in the last millennium. Climate, herbivory, fire, and people are identified as important drivers of ecosystems dynamics; however, grassland resilience has been rarely explored in landscapes with mixed grazing histories. Here we analyse ecosy...
Article
Full-text available
Plant functional traits provide a valuable tool to improve our understanding of ecological processes at a range of scales. Previous handbooks on plant functional traits have highlighted the importance of standardising measurements of traits to improve our understanding of ecological and evolutionary processes. In open ecosystems (i.e. grasslands, s...
Article
Full-text available
The cool season rainfall at our study site should favour C3 rather than C4 grasses. There are, however, several locations where C4 grasses have become dominant, suggesting that rainfall seasonality is not a constraint on distribution. Here, we explored the limitations on C4 grass distribution in a fynbos shrubland. Using δ13C values of SOM, we dete...
Article
Earth’s ecosystems, upon which all life depends, are in a severe state of degradation. The upcoming UN Decade of Ecosystem Restoration aims to “prevent, halt and reverse the degradation of ecosystems on every continent and in every ocean.” These Voices articulate why and what action is urgently needed.
Article
Full-text available
Plant functional traits provide a valuable tool to improve our understanding of ecological processes at a range of scales. Previous handbooks on plant functional traits have highlighted the importance of standardising measurements of traits to improve our understanding of ecological and evolutionary processes. In open ecosystems (i.e. grasslands, s...
Article
1. Global change is expected to increase savanna woody encroachment as well as fire spreading into forest. Forest‐savanna ecotones are the frontier of these processes and can thus either mitigate or enhance the effects of global change. However, the ecology of the forest‐savanna ecotone is poorly understood. In this study, we determined whether a d...
Article
In savannas, ruminant herbivores can have divergent impacts on tree recruitment and subsequent woody cover. Whereas heavy grazing by cattle results in woody thickening, intensive grazing by wildlife instead tends to be associated with lower woody cover. To disentangle why woody cover is low in areas heavily grazed by wildlife, we investigated (a) w...
Article
Full-text available
Despite growing recognition of the conservation value of grassy biomes, our understanding of how to restore biodiverse tropical and subtropical grassy biomes (grasslands and savannas; TGB) remains limited. Several tools have recently been identified for TGB restoration including prescribed fires, appropriate management of livestock and wild herbivo...
Technical Report
Full-text available
Translation of the original article "Myth-busting tropical grassy biome restoration” published in Restoration Ecology Tradução do artigo original “Myth-busting tropical grassy biome restoration” publicado na Restoration Ecology que pode ser acessado aqui (https://onlinelibrary.wiley.com/doi/abs/10.1111/rec.13202?af=R). Em caso de citação, deve-se...
Article
Full-text available
Process‐based vegetation models attempt to represent the wide range of trait variation in biomes by grouping ecologically similar species into plant functional types (PFTs). This approach has been successful in representing many aspects of plant physiology and biophysics but struggles to capture biogeographic history and ecological dynamics that de...
Article
Full-text available
Ideas on hominin evolution have long invoked the emergence from forests into open habitats as generating selection for traits such as bipedalism and dietary shifts. Though controversial, the savanna hypothesis continues to motivate research into the palaeo-environments of Africa. Reconstruction of these ancient environments has depended heavily on...
Article
Full-text available
The historical focus in research and policy on forest restoration and temperate ecosystems has created misunderstandings for the restoration of tropical and subtropical old-growth grassy biomes (TOGGB). Such misconceptions have detrimental consequences for biodiversity, ecosystem services and human livelihoods in woodlands, savannas and grasslands...
Article
Plants are the largest biomass component of most terrestrial ecosystems, and litter decomposition is considered the dominant process by which nutrients return to plants. We show that in terrestrial ecosystems, there are three major pathways by which plant biomass is degraded into forms that release nutrients again available to plants: microbial dec...
Article
Full-text available
Forest edges that border savanna are dynamic features of tropical landscapes. Although the role of fire in determining edge dynamics has been relatively well explored, the role of mega-herbivores, specifically elephants, has not received as much attention. We investigated the role of forest elephants in shaping forest edges of the forest–savanna mo...
Article
Full-text available
The ecological niche of a species describes the variation in population growth rates along environmental gradients that drives geographic range dynamics. Niches are thus central for understanding and forecasting species’ geographic distributions. However, theory predicts that migration limitation, source–sink dynamics, and time-lagged local extinct...
Article
There is growing interest in the application of alternative stable state (ASS) theory to explain major vegetation patterns of the world. Here, we introduce the theory as applied to the puzzle of nonforested (open) biomes growing in climates that are warm and wet enough to support forests (alternative biome states, ABSs). Long thought to be the prod...
Article
Full-text available
Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research sp...
Preprint
Full-text available
Process-based vegetation models attempt to represent the wide range of trait variation in biomes by grouping ecologically similar species into plant functional types (PFTs). This approach has been successful in representing many aspects of plant physiology and biophysics, but struggles to capture biogeographic history and ecological dynamics that d...
Article
Drought studies are often opportunistic and post hoc, where a drought fortuitously occurs during a research project that was not specifically designed to study the drought, but where researchers capitalised on the opportunity. These studies often lack focus on formulating and studying ‘drought specific’ research questions. By learning from observat...
Article
Full-text available
During the last decades, climate and land use changes led to an increased prevalence of megafires in Mediterranean-type climate regions (MCRs). Here, we argue that current wildfire management policies in MCRs are destined to fail. Focused on fire suppression, these policies largely ignore ongoing climate warming and landscape-scale buildup of fuels...
Article
Large specialized fruit (megafaunal fruit) have evolved alongside megaherbivores to take advantage of their unparalleled seed dispersal service. Megaherbivores were widespread and abundant in the Pleistocene but due to multiple extinction events have been extirpated from all continents except Africa and small pockets of South East Asia. In Africa,...
Article
Full-text available
Bastin et al .’s estimate (Reports, 5 July 2019, p. 76) that tree planting for climate change mitigation could sequester 205 gigatonnes of carbon is approximately five times too large. Their analysis inflated soil organic carbon gains, failed to safeguard against warming from trees at high latitudes and elevations, and considered afforestation of s...
Article
Bastin et al.’s estimate (Reports, 5 July 2019, p. 76) that tree planting for climate change mitigation could sequester 205 gigatonnes of carbon is approximately five times too large. Their analysis inflated soil organic carbon gains, failed to safeguard against warming from trees at high latitudes and elevations, and considered afforestation of sa...
Article
Full-text available
Does complex topography facilitate the establishment and persistence of fire‐sensitive (forest) vegetation in a fire‐prone landscape? We test the prediction that fire‐sensitive vegetation will establish and persist in areas where the fire return interval is lower due to a topographic hindrance on fire spread. Hluhluwe–iMfolozi Park, KwaZulu Natal,...
Article
Despite growing recognition of the conservation values of grassy biomes, our understanding of how to maintain and restore biodiverse tropical grasslands (including savannas and open‐canopy grassy woodlands) remains limited. To incorporate grasslands into large‐scale restoration efforts, we synthesised existing ecological knowledge of tropical grass...
Article
Extensive tree planting is widely promoted for reducing atmospheric CO2. In Africa, 1 million km2, mostly of grassy biomes, have been targeted for 'restoration' by 2030. The target is based on the erroneous assumption that these biomes are deforested and degraded. We discuss the pros and cons of exporting fossil fuel emission problems to Africa.
Chapter
This chapter summarizes some of the points of contention related to understanding the distribution and determinants of savanna ecosystems worldwide, and describes some resolution where possible. It provides comparisons across continents and between temperate and tropical savannas, hoping to isolate some general patterns and rules that persist despi...
Chapter
This chapter describes the savannas of Sahul – the continent formed by the joining of Australia and New Guinea during the Pleistocene. This geographic focus allows the functioning of these savannas to be considered prior to the extinction of many species of mega‐ and meso‐fauna that were known to exist in Pleistocene Australia and New Guinea. The c...
Chapter
This book is about the light side of ecology, the non-forested open ecosystems of the world. More than a quarter of the world’s land area is dominated by open, non-forested ecosystems in climates which can support closed forests. They are particularly common in the tropics, making up grasslands and savannas, but also occur in other climate zones. O...
Chapter
Boundaries between open and closed ecosystems often coincide with soil differences of greater or lesser degree. It has long been argued that these soil differences explain the striking differences in vegetation structure. But the nature of the vegetation itself feeds back on soil properties so that it is far from trivial to determine whether soil d...
Chapter
What is the future of open ecosystems, the ancient savannas, grasslands, shrublands, and woodlands that are the central topic of this book? Their trajectories under current and future climate change are difficult to project since their dominant growth forms are only indirectly determined by climate. Rising CO 2 is changing the balance so as to favo...
Book
This book explores the geography, ecology, and antiquity of ‘open ecosystems’, which include grasslands, savannas, and shrublands. They occur in climates that can support closed forest ecosystems and often form mosaics with forest patches. With the aid of remote sensing, it is now clear that open ecosystems are a global phenomenon and occur over va...
Chapter
If open ecosystems were of recent anthropogenic origin, linked to human activity in the last millennia, they should support an impoverished biota assembled in large part from forest-dwelling species. Yet several of the world’s biodiversity hotspots are open ecosystems, rich in species and rich in endemics. This chapter introduces the diversity of o...
Chapter
Can fire account for the widespread occurrence of open ecosystems? This chapter explores fire as a major consumer shaping vegetation in diverse regions worldwide. The concept of fire regime helps explain the diverse influences of fire on vegetation structure. Fire regimes select compatible growth forms from the species pool. These, in turn, create...
Chapter
Explanations for vegetation change in the past, including the ‘deep past’ (many millions of years ago) are deeply rooted in the idea that climate determines major vegetation patterns. But other factors have also changed, including large fluctuations in atmospheric CO 2 , influencing plant growth, and atmospheric oxygen, altering fire activity. Vert...
Chapter
Climate has long been considered the prime factor determining the distribution of major vegetation based on climate–vegetation correlations. These correlations underlie the common assumption that there is a single stable vegetation state for a given climate. Thus tropical forests are characteristic of climates that are warm and wet, deserts where c...
Chapter
Climate sets the potential biomass of trees and physiologists have made considerable progress in understanding and predicting that potential and applying it in global vegetation models. The problem is in understanding and predicting tree cover where it is far from the climate potential. Vast areas of non-forested vegetation occur where climates are...
Chapter
Can herbivores account for the widespread occurrence of open ecosystems? Some suggest that Pleistocene megafauna did so, and large mammal herbivory is still important in some regions today. Exclosure studies have been widely used to test herbivore impacts on trees, but global patterns of the ‘brown world’ are not readily seen from satellites. Areas...
Article
en South Africa experienced a severe multiyear drought from 2014 to 2016. Here, we explore the response of a South African savannah ecosystem to this drought focusing on tree and grass dynamics. We used open long‐term monitoring plots established in 2000 and distributed across broad rainfall gradients in the Hluhluwe‐iMfolozi Park in KwaZulu‐Natal....
Article
•Phenotypic plasticity facilitates species persistence across resource gradients but may be limited in low resource environments requiring resource conservation. We investigated the trade‐off between trait plasticity and resource conservatism across a biome boundary characterized by high turnover in nutrient and light availability, and whether this...
Preprint
Full-text available
Global change impacts on the Earth System are typically evaluated using biome classifications based on trees and forests. However, during the Cenozoic, many terrestrial biomes were transformed through the displacement of trees and shrubs by grasses. While grasses comprise 3% of vascular plant species, they are responsible for more than 25% of terre...
Article
Global change impacts on the Earth System are typically evaluated using biome classifications based on trees and forests. However, during the Cenozoic, many terrestrial biomes were transformed through the displacement of trees and shrubs by grasses. While grasses comprise 3% of vascular plant species, they are responsible for more than 25% of terre...
Preprint
Full-text available
The ecological niche of a species describes the variation in population growth rates along environmental gradients that drives geographic range dynamics. Niches are thus central for understanding species geographic distributions and forecasting biodiversity responses to environmental change. However, theory predicts that migration limitation, sourc...
Article
Full-text available
Large specialized fruit (megafaunal fruit) have evolved alongside megaherbivores to take advantage of their unparalleled seed dispersal service. Megaherbivores were widespread and abundant in the Pleistocene but due to multiple extinction events have been extirpated from all continents except Africa and small pockets of South East Asia. In Africa,...
Article
Full-text available
Plant growth forms likely respond differently to disturbances such as trampling. We investigated the trampling effect of 1 600 sheep encamped at night in temporary enclosures (kraals, corrals or pens), which were relocated weekly. To examine trampling effects and regeneration rates of the various growth forms we compared vegeta- tion composition, c...
Article
1.Alexander von Humboldt is a key figure in the history of ecology and biogeography who contributed to shape what is today ecology, as well as the environmentalist movement. His observation that the world's vegetation varies systematically with climate was one of his many contributions to science. 2.Here we question to what extent Humboldt's view b...
Article
Full-text available
Forest-savanna mosaics are maintained by fire-mediated positive feedbacks; whereby forest is fire suppressive and savanna is fire promoting. Forest-savanna transitions therefore represent the interface of opposing fire regimes. Within the transition there is a threshold point at which tree canopy cover becomes sufficiently dense to shade out grasse...
Article
The idea of alternate stable states (ASS) has been used to explain the juxtaposition of distinct vegetation types within the same climate regime. ASS may explain the co‐existence of relatively inflammable closed‐canopy Afrotemperate Forest patches (“Forest”) within fire‐prone open‐canopy Fynbos in the Cape Floristic Region (CFR) on sandstone‐derive...
Article
Full-text available
Plant species range shifts are predicted to occur in response to climate change. The predictions are often based on the assumption that climate is the primary factor limiting the distribution of species. However the distribution of grassy biomes in Africa cannot be predicted by climate alone, instead interactions between vegetation, climate and dis...
Article
There is theoretical, empirical and modeled evidence that atmospheric enrichment of carbon dioxide (CO2) is driving the conversion of open savannas to woodlands (i.e., woody thickening or bush encroachment). This study measured the impacts of available CO2 and water limitation on seedling growth and physiology to determine how these two environment...
Article
Tropical savannas have a ground cover dominated by C4 grasses, with fire and herbivory constraining woody cover below a rainfall‐based potential. The savanna biome covers 50% of the African continent, encompassing diverse ecosystems that include densely wooded Miombo woodlands and Serengeti grasslands with scattered trees. African savannas provide...
Article
Full-text available
Roughly 3% of the Earth’s land surface burns annually, representing a critical exchange of energy and matter between the land and atmosphere via combustion. Fires range from slow smouldering peat fires, to low-intensity surface fires, to intense crown fires, depending on vegetation structure, fuel moisture, prevailing climate, and weather condition...
Article
Full-text available
The extirpation of native wildlife species and widespread establishment of livestock farming has dramatically distorted large mammal herbivore communities across the globe. Ecological theory suggests that these shifts in the form and the intensity of herbivory have had substantial impacts on a range of ecosystem processes, but for most ecosystems i...
Article
Full-text available
Bastin et al. (Reports, 12 May 2017, p. 635) infer forest as more globally extensive than previously estimated using tree cover data. However, their forest definition does not reflect ecosystem function or biotic composition. These structural and climatic definitions inflate forest estimates across the tropics and undermine conservation goals, lead...
Article
In the Anthropocene, alien species are no longer the only category of biological organism establishing and rapidly spreading beyond historical boundaries. We review evidence showing that invasions by native species are a global phenomenon and present case studies from Southern Africa, and elsewhere, that reveal how climate-mediated expansions of na...
Poster
Full-text available
Large mammalian herbivores (LMH) are one of the major drivers of directional vegetation change in grass dominated terrestrial ecosystems. Areas where LMHs aggregate are often associated with switches from tallgrasses to shortgrasses and this is followed by changes in soil properties. However, the relationship between LMHs and vegetation is complica...
Article
Owing to the late Pleistocene extinctions, the megafauna of Europe, Australia and the Americas disappeared, and with them the dispersal service they offered megafaunal fruit. The African savanna elephant, the largest remaining megaherbivore, offers valuable insights into the seed dispersal services provided by extinct megafauna in prehistoric times...
Conference Paper
Climatic and seasonal pulses in rainfall regulate the availability of grazing in key resource areas (KRAs) that are important for maintaining herbivore and human populations. KRAs have been extensively studied in contemporary ecological and sociological studies because of their ecological resilience and role in providing forage for herbivores and f...