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Toward an old-growth concept for grasslands, savannas, and woodlands

  • Avignon Université
  • Instituto de Pesquisas Ambientais - Governo do Estado de São Paulo


We expand the concept of "old growth" to encompass the distinct ecologies and conservation values of the world's ancient grass-dominated biomes. Biologically rich grasslands, savannas, and open-canopy woodlands suffer from an image problem among scientists, policy makers, land managers, and the general public, that fosters alarming rates of ecosystem destruction and degradation. These biomes have for too long been misrepresented as the result of deforestation followed by arrested succession. We now know that grassy biomes originated millions of years ago, long before humans began deforesting. We present a consensus view from diverse geographic regions on the ecological characteristics needed to identify old-growth grasslands and to distinguish them from recently formed anthropogenic vegetation. If widely adopted, the old-growth grassland concept has the potential to improve scientific understanding, conservation policies, and ecosystem management.
154 © The Ecological Society of America
Many of the world’s grasslands are ancient ecosystems
composed of communities that require centuries to
assemble and perennial plants capable of living for
decades to millennia. These ecosystems are being lost to
agriculture, tree plantations, mining, and urban sprawl;
they are also being degraded by invasive species, poorly
managed domestic livestock, altered fire regimes, ele-
vated atmospheric carbon dioxide, and nitrogen deposi-
tion (Parr et al. 2014). Meanwhile, other types of herba-
ceous and grass-dominated vegetation (eg old fields and
derived savannas) are expanding (Veldman and Putz
2011). Confusion over the substantive differences
between natural grassland ecosystems and their novel,
anthropogenic counterparts has contributed to a lack of
concern over the impacts of environmental change on
biodiversity in natural grasslands. This confusion persists
in large part because we currently lack a framework for
conceptualizing the role of long periods of time in the
development of biodiverse grasslands.
To promote the recognition and conservation of nat-
ural grasslands, we extend the concept of “old growth” to
grasslands (Panel 1) and suggest that old growth is not
limited to forests. The ideas we present are drawn from
recent advances in grassland ecology and are motivated
by the threats of human-caused environmental change.
The old-growth grassland concept will help distinguish
ecosystems with high conservation values and unique
ecological attributes from vegetation that forms over
short timescales in response to human land uses. The
concept will also help us evaluate the ecological and eco-
nomic costs associated with the loss or degradation of
grassland ecosystems, and determine the rates at which
such transitions occur. Finally, questions evoked by the
old-growth grassland concept will help identify promising
areas of fundamental ecological research.
We define grasslands broadly as ecosystems in which
graminoids (ie grasses and grass-like plants), forbs, and
shrubs form a relatively continuous “herbaceous layer”
of vegetation. This classification includes grasslands
without trees, as well as savannas and woodlands that
support a range of tree densities (ie “grassy biomes”; Parr
et al. 2014). We emphasize the ecology of the herba-
ceous layer, in recognition that herbaceous species
account for the majority of plant diversity in these sys-
tems and are critical to ecosystem processes. Trees are
important to the ecology of savannas and woodlands (eg
Toward an old-growth concept for
grasslands, savannas, and woodlands
Joseph W Veldman1*, Elise Buisson2, Giselda Durigan3, G Wilson Fernandes4,5, Soizig Le Stradic6,
Gregory Mahy6, Daniel Negreiros4, Gerhard E Overbeck7, Robin G Veldman8, Nicholas P Zaloumis9,
Francis E Putz10, and William J Bond9
We expand the concept of “old growth” to encompass the distinct ecologies and conservation values of the
world’s ancient grass-dominated biomes. Biologically rich grasslands, savannas, and open-canopy woodlands
suffer from an image problem among scientists, policy makers, land managers, and the general public, that fos-
ters alarming rates of ecosystem destruction and degradation. These biomes have for too long been misrepre-
sented as the result of deforestation followed by arrested succession. We now know that grassy biomes originated
millions of years ago, long before humans began deforesting. We present a consensus view from diverse geo-
graphic regions on the ecological characteristics needed to identify old-growth grasslands and to distinguish
them from recently formed anthropogenic vegetation. If widely adopted, the old-growth grassland concept has
the potential to improve scientific understanding, conservation policies, and ecosystem management.
Front Ecol Environ 2015; 13(3): 154–162, doi:10.1890/140270
In a nutshell:
Old-growth grasslands are ancient ecosystems characterized
by high herbaceous species richness, high endemism, and
unique species compositions
Biodiversity in old-growth grasslands is maintained by fre-
quent fires, herbivores, and soil characteristics that limit tree
To survive fires and grazing, many grassland herbs, forbs, and
shrubs have developed specialized underground organs that
enable them to resprout repeatedly; evidence of grassland
plant longevity and ecosystem carbon storage is often below-
Old-growth grasslands are threatened by agricultural conver-
sion, fire exclusion, invasive species, surface mining, poorly
managed livestock, and misinformed afforestation projects
Initiatives to identify, conserve, and restore old-growth grass-
lands are urgently needed
1Department of Ecology, Evolution and Organismal Biology, Iowa State
University, Ames, IA *(; 2IMBE, Avignon
Université, CNRS, IRD, Aix Marseille Université, Avignon, France;
3Laboratório de Ecologia e Hidrologia Florestal, Floresta Estadual de
Assis, Instituto Florestal, Assis, Brazil; continued on p 162
JW Veldman et al.Old-growth grasslands
© The Ecological Society of America
Ratnam et al. 2011), but the vast ecological differences
between trees and herbaceous plants warrant explicit
consideration of these plant communities in concep-
tualizing old-growth grasslands (Kirkman and Mitchell
Grasslands occur across a huge range of environmen-
tal conditions, from the tropics to the Arctic, from sea
level to mountain tops, from arid to humid areas, from
sites with long hydroperiods to well-drained sites, and
from shallow rocky soils to deep clay soils (Brown and
Makings 2014). Given the global diversity of grasslands,
our intention is not to define old growth for any one
place. Instead, we provide an overview of the common
characteristics of old-growth grasslands in hopes of
improving their fates.
nConcept development
Descriptions of old-growth grasslands are scattered
throughout the literature but to our knowledge have not
previously been consolidated into a single framework.
Feller and Brown (2000) argued that an old-growth con-
cept for grasslands, similar to that for forests, was urgently
needed to provide greater protection for natural grasslands
of native species in the western US. Their article has gone
largely unnoticed by ecologists, and “old growth” is still
rarely used in the context of grasslands. Nonetheless, old-
growth themes and descriptions of grasslands with old-
growth characteristics do appear in the ecology and con-
servation literature (eg Noss 2013), as well as in literature
on old-growth “forests” in the US – maintained by fre-
quent fires – that many ecologists would consider to be
savannas (Ratnam et al. 2011). For example, in ecosystems
dominated by ponderosa pine (Pinus ponderosa) and long-
leaf pine (Pinus palustris), frequent fires and high herba-
ceous species diversity characterize old growth (Laughlin
et al. 2004; Kirkman and Mitchell 2006).
A list of old-growth grassland characteristics based on
observations of and literature about ecosystems in Africa,
Australia, Europe, and the Americas is presented in Panel
1. We acknowledge a bias toward lowland to mid-eleva-
tional, tropical, and temperate ecosystems, and hope that
experts in high-latitude and high-elevation grasslands
will expand on our ideas. These general characteristics
should serve as a guide for developing ecosystem-specific
definitions of old growth.
Fire and herbivores
Recognition of antiquity in old-growth grasslands
requires an appreciation for the roles of fire and herbivores
in grassland plant evolution (Figure 1). Grasslands com-
posed of C3plant species and grazed by ungulates devel-
oped by 20–30 million years ago (MYA; Jacobs et al.
1999). Grasslands composed of C4species, and that
burned frequently, have been prominent in the tropics
Panel 1. Characteristics of many old-growth grasslands, savannas, and woodlands
Ecosystem-level characteristics
Species assemblages that do not occur in
young, secondary grasslands
High herbaceous-layer plant species diversity
High small-scale (eg 1 m2) species richness
Presence of endemic species
Transient seed banks
Persistent bud banks
High ratio of herbaceous species to tree species
High belowground biomass
Little accumulation of litter or duff
Open, discontinuous tree canopies
Factors that maintain biodiversity
Frequent surface fires
Herbivory by native megafauna
Soil disturbance by digging animals
Low-intensity domestic livestock grazing
Shallow soils; nutrient-poor soils
Seasonal water deficits; seasonal flooding
High (toxic) concentrations of soil metals
Land uses incompatible with old growth
Surface mining or quarrying
Tillage agriculture
Plantation forestry
Intensive pasture management (eg use of exotic
forage grasses and fertilizers)
Prolonged high-intensity grazing
Life-history and functional characteristics of
old-growth indicator plant species
Slow growing
Strong resprouting capacity
Low success at establishing from seed
Poor colonization ability
Investment in underground storage organs
Clonal growth
High root:shoot ratio
Fire-enhanced or fire-dependent flowering and fruiting
Fire-tolerant (thick-barked) trees
Causes of degradation
Fire suppression/exclusion
Overgrazing and poorly managed domestic livestock
Declines in native megafaunal herbivores
Woody encroachment
Invasive species
Atmospheric nitrogen deposition
Elevated atmospheric CO2concentrations
Anthropogenic soil disturbances
Land uses potentially compatible with old growth
Low-intensity domestic livestock grazing
Timber or fuelwood extraction
Old-growth grasslands JW Veldman et al.
156 © The Ecological Society of America
and subtropics since 3–8 MYA (Cerling et al. 1997;
Edwards et al. 2010). Millions of years of frequent distur-
bances in grasslands, which intermittently reduced
aboveground biomass, selected for plant morphological
characteristics and life-history strategies that are funda-
mentally different from those of forest species (eg Simon
et al. 2009; Ratnam et al. 2011; Maurin et al. 2014).
Plant longevity in grassland environments requires that
the parts of the plant where growth occurs (ie meristem-
atic tissues, including buds and vascular cambia) are insu-
lated from high temperatures and protected from herbi-
vores, and that photosynthetic tissues can be rapidly
regenerated following disturbances. For most perennial
graminoids and forbs, the principal growth regions are
located near or below the soil surface, where temperatures
remain low during fires (Figure 2). In most savanna trees
(and some herbs; Figure 3), fire-resistant stems with insu-
lated buds permit a substantial portion of a plant’s above-
ground biomass to be retained through fires (Ratnam et
al. 2011). To permit resprouting, many woody plants and
perennial forbs invest in underground organs that store
starch and water (Figure 2; Simon et al. 2009; Maurin et
al. 2014). Clonal growth (eg via rhizomes, stolons, or
tillers) is common, and allows plants to regenerate after
disturbance and to colonize their local area. The preva-
lence of clonal growth likely reflects the many hurdles to
establishment from seed (eg water stress and seed preda-
tion), and apparent life-history trade-offs between persis-
tence and sexual reproduction (Benson and Hartnett
2006; Lamont et al. 2011). In sum, because disturbance
regimes and plant characteristics are dramatically differ-
ent in grasslands than in forests, many signs of antiquity
in old-growth forests (eg large diameter trees, accumu-
lated woody debris; Franklin and Spies 1991) are inap-
plicable to grasslands.
Frequent fires and herbivory are essential to the persis-
tence of most old-growth grasslands, especially where
precipitation and soil nutrient availability are sufficient
to permit forest development (Bond and Keeley 2005).
Fire exclusion or removal of herbivores in these mesic
grasslands can result in rapid transitions from grassland
to forest or shrubland, with associated losses of herba-
ceous plant diversity. Grasslands also occur where tree
growth is limited by shallow soils, low soil moisture
availability, seasonal flooding, or high concentrations of
toxic metals. Because these “edaphic” (influenced by soil
properties) grasslands are less dependent on frequent dis-
turbances than are mesic grasslands, they are often the
only representatives of old growth in severely fire-
excluded landscapes (Noss 2013). Climate-determined
grasslands occur in regions where tree cover is limited by
some aspect of climate, often low precipitation in the
tropics (Staver et al. 2011) or low temperatures at high
latitudes or elevations. While the distinctions between
mesic, edaphic, and climate-determined grasslands are
useful for identifying their primary environmental deter-
minants (ie factors that limit trees), the importance of
fire and herbivory to most old-growth grasslands cannot
be overstated. Across a wide range of climatic and soil
conditions, frequent fires and herbivores limit the abun-
dance of trees and shrubs, promote herbaceous produc-
tivity, consume dead plant material, return nutrients to
Figure 1. Intact disturbance regimes: (a) a surface fire in a Bolivian savanna; (b) megafaunal herbivores in eastern Africa.
(a) (b)
JW Veldman et al.Old-growth grasslands
© The Ecological Society of America
the soil, stimulate reproduc-
tion, and maintain plant
diversity (eg Platt et al. 1988;
Lehmann et al. 2014; Nayak et
al. 2014; Veldman et al. 2014).
Time, degradation, and
How we perceive and concep-
tualize time has an enormous
influence on how we study
and seek to conserve organ-
isms and their environments.
Questions of time are critical;
in a single day, a large tractor
can plow up and convert a
hectare or more of old-growth
grassland into an agricultural
field. If that field is aban-
doned, even if propagule sources are nearby and establish-
ment conditions are favorable, it will require a century or
longer for a comparable grassland to form (Baer et al.
2010; Redhead et al. 2014). Where invasive grass species
are present or biophysical conditions are severely altered,
ecosystems may never return to an old-growth state
(Stromberg and Griffin 1996). Indeed, a number of stud-
ies of severely degraded grasslands conclude that old-
growth indicator species are very slow to re-establish and
that grasslands on former agricultural land are ecologi-
cally distinct from old growth (Stromberg and Griffin
1996; Kirkman et al. 2004; Zaloumis and Bond 2011; Le
Stradic et al. 2014; Redhead et al. 2014). Therefore, we
suggest the term “secondary grassland” be used to describe
young ecosystems on land that historically supported old-
growth grasslands (eg Zaloumis and Bond 2011), and that
old growth be used as the reference to develop definitions
of grassland degradation and to guide restoration
(Laughlin et al. 2004).
nPromoting conservation
Cultural resonance
The old-growth grassland concept is a necessary precursor
to public support for grassland conservation. Similar con-
cepts that draw from both scientific theory and beliefs
about nature have bolstered previous conservation efforts
and achieved lasting relevance; for example, the develop-
ment and promotion of the charismatic, culturally reso-
nant concepts of “biodiversity” and – in the context of
forests – “old growth” continue to serve popular conserva-
tion movements (Takacs 1996; Proctor 2009). The ideals
embodied in these concepts are more than just tools to
guide conservation research and advocacy. For the public,
they evocatively capture the value of certain aspects of
the natural world, including antiquity, diversity, and
beauty, which some may even express in terms of sacred-
ness (Taylor 2010).
If old-growth grasslands are to be conserved, they need
to be conceptualized in a culturally resonant manner
because their biodiversity is not always evident to the
untrained eye. Even if ecologists recognize their value,
most lay observers are not yet accustomed to seeking
Figure 2. (a) Storage taproots and rhizomes of a grassland forb (Cryptosepalum maraviense) in
central Africa; (b) root tubers of a shrub (Campomanesia adamantium) in a Brazilian savanna; (c)
basal rosette and bulb of a grassland herb (Ledebouria stenophylla) from southern Africa; (d) storage
taproot (~1.1 m deep) of a savanna forb (Eriogonum tomentosum) in the southeastern US.
A Willem
(b) (c)
Old-growth grasslands JW Veldman et al.
158 © The Ecological Society of America
“Nature” – much less appreciating antiquity – in grass-
lands, where signs of old growth and associated conserva-
tion values are subtle, if not subterranean. Recognition of
grassland conservation values is further complicated by
the dependence of grasslands on disturbances that some
consider “unnatural” or “undesirable” but that must be
maintained, often through active management (Panel 2).
Given this cultural context, we suggest that the old-
growth concept can help scientists and the public to rec-
ognize the value of grasslands and to advocate for their
Carbon, conservation, and old growth
There is growing recognition that natural grasslands
composed of native species are at risk from policies
designed to sequester carbon (C) to mitigate climate
change (Putz and Redford 2010; Parr et al. 2014). In
particular, C payment schemes under development by
the United Nations Framework Convention on
Climate Change (UNFCCC) and the program for
Reducing Emissions from Deforestation and Forest
Degradation (REDD+), as well as the definitions of
“forest” used by the United Nations Food and
Agriculture Organization, put grasslands at risk from
afforestation projects and agricultural conversion.
Grasslands are a target for C sequestration projects
because fire suppression and tree planting are straight-
forward means of dramatically increasing aboveground
biomass, at least in the short term (Canadell and
Raupach 2008). We are also concerned that a lack of
international policies recognizing natural grasslands
and including mechanisms to slow their loss will incen-
tivize the conversion of old-growth grasslands to agri-
cultural uses.
The old-growth grassland concept addresses these con-
servation concerns in several ways. First, by emphasizing
the long periods of time required for species-diverse
grasslands of native species to assemble, this concept will
raise awareness of the long-term biodiversity costs associ-
ated with a narrow focus on C and forests. Second, by
emphasizing the roles of time and disturbances in grass-
land formation, the old-growth concept requires that we
consider the permanence of sequestered C in climate
mitigation projects. With C stored in belowground plant
organs, accumulated soil organic matter, and the wood of
fire-tolerant savanna trees (eg Miranda et al. 2014), old-
growth grasslands may securely store C for long periods
of time in fire- and drought-prone landscapes. Third,
advancement of the concept depends on ecologists
developing ecosystem-specific definitions of old growth.
Once established, these definitions should help reconcile
conflicts between global agreements on C and biodiver-
sity conservation priorities at the national level (Sasaki
and Putz 2009).
Figure 3. (a) Persistent charred stem of a graminoid (Bulbostylis paradoxa) and (b) old stems of Vellozia variabilis in highland
grasslands in Brazil.
(a) (b)
Panel 2. The cattle conundrum
A challenge to conceptualizing old-growth grasslands is deter-
mining their compatibility with livestock grazing (Nayak et al.
2014). The idea of domestic livestock in an old-growth ecosys-
tem may seem counterintuitive given the role of cattle ranching
as a global driver of ecosystem degradation. Indeed, poor range-
land management (eg high stocking densities, sowing exotic
grasses) can irreparably change natural grasslands (Feller and
Brown 2000). Nevertheless, livestock grazing at appropriate
densities and intervals appears to be compatible with, or even
beneficial to, grassland biodiversity in some systems. This is the
case in southern Brazil, where cattle exclusion leads to forest
succession and declines in old-growth grassland plant diversity
(Overbeck et al. 2007). Cattle may also provide opportunities to
maintain or restore grasslands that would otherwise be con-
verted to mechanized agriculture or other land uses (Miller et
al. 2012). In grasslands highly suited to agriculture, livestock
grazing is perhaps the only land use that provides economic
returns while maintaining many old-growth grassland character-
istics. In sum, livestock represent both perils and opportunities
for grassland conservation. We need to determine where live-
stock are compatible with biodiversity and use the old-growth
concept to move beyond production-focused grassland man-
agement (Feller and Brown 2000).
JW Veldman et al.Old-growth grasslands
© The Ecological Society of America
nFuture ecological research
There is a great deal that we do not know about grassland
plant longevity, the time required for old-growth commu-
nities to assemble, and the rates at which other old-
growth attributes develop (eg soil C storage). The old-
growth concept challenges us to investigate basic
questions about grassland natural history, potentially
improving our ability to answer fundamental ecological
questions (Panel 3).
The few estimates of grassland plant longevity that are
available are based on anecdotal accounts of plant size,
longitudinal studies of individual plants, and modeling of
clonal plant demographics and growth. Accounts from
Brazilian grasslands, for example, suggest that Vellozia spp
require 100 years to reach reproductive maturity and can
live for over 500 years (Alves and Kolbek 1994).
Longitudinal studies provide reliable age estimates, but
are limited in their time and spatial scales. On the basis of
39 years of observations in a grassland in central North
America, Lauenroth and Adler (2008) found that forbs
are typically short-lived ( 18 years) and that most grasses
can live for at least 20 years, with individuals of two
species known to be 39 years old. Previously, Lauenroth
et al. (1994) used demographic data to estimate that blue
grama (Bouteloua gracilis), a C4bunchgrass, can live for
450 years. Indeed, clonal species (including bunch-
grasses) are likely to be the oldest grassland plants, with
the potential to live for decades to millennia (de Witte
and Stöcklin 2010). A variety of modeling techniques
have been used to estimate the ages of both genets
(colonies of genetically identical individuals) and ramets
(individual clones). For example, matrix modeling of pale
pitcher plants (Sarracenia alata) in wet savannas of the
southern US suggests that ramets typically live 59 years
(Brewer 2001), and genets can presumably be much older.
Takahashi et al. (2011) combined molecular genetics and
modeling approaches to estimate that genets of the fire-
adapted saw palmetto, Serenoa repens, which is endemic
to the southeastern US, may live for 10 000 years. In sum,
the maximum ages of old-growth grassland plants may
range widely, depending on growth form, disturbance
regimes, and historical climate stability (Panel 4). More
research is needed on the ages and demographics of long-
lived grassland plants, but short-lived species deserve
consideration as well.
Short-lived grasses and forbs, in combination with
long-lived perennials, can be indicators of old growth,
particularly in grasslands of the arid tropics and temperate
steppes (Coiffait-Gombault et al. 2012). Annual, bien-
nial, and short-lived perennial species are often among
the early colonists of sites disturbed by digging animals
(Platt 1975) or locally intense grazing (Mack and
Thompson 1982) and are thus an important part of
dynamic, old-growth grasslands. But where abundant,
annuals can indicate severe degradation associated with
altered disturbance regimes, biological invasions, and
declines in native perennial populations (Mack and
Thompson 1982; Feller and Brown 2000). Whether as
indicators of old growth or as signs of degradation it will
be important to determine the role of short-lived plants
in ecosystem-specific definitions of old-growth grasslands.
Although plant community composition is an indicator
of grassland maturity (Panel 1; Figure 4), we lack firm
estimates of the time required for species-diverse grass-
lands that include rare and endemic species to form. Our
best estimates are based on studies of secondary grasslands
following abandonment of agriculture, plantation
forestry, and surface mining (Kirkman et al. 2004;
Zaloumis and Bond 2011; Le Stradic et al. 2014; Redhead
et al. 2014). These studies clearly demonstrate that old-
growth grassland communities require many decades, and
probably several centuries, to assemble. Rates of grassland
formation are likely influenced by interactions between a
Figure 4. Unique plant communities: (a) a highland grassland
in Brazil; (b) post-fire flowering and a charred, fire-tolerant tree
in a savanna of the southeastern US.
(a) (b)
Old-growth grasslands JW Veldman et al.
160 © The Ecological Society of America
host of factors, including soil biophysical characteristics.
At grassland restoration sites on former agricultural land
in central North America, soil microbial communities are
estimated to require 30–60 years, and soil C and nitrogen
140 years, to recover to levels found in old-growth grass-
lands (Bach et al. 2010; Baer et al. 2010). In these studies,
soil recovery varied with soil texture, suggesting that rates
of grassland soil development can be quite different, even
within the same ecosystem. Additional studies are needed
to improve our understanding of the role of time in the
development of old-growth grassland soils, as well as the
assembly of plant and animal communities.
Having presented the ecological basis and conservation
motivations for the old-growth grassland concept, we sug-
gest that much work remains. Ecologists should establish
ecosystem-specific definitions of old growth and work to
identify and map these grasslands at local, regional, and
continental scales. Land managers should learn to recog-
nize old-growth characteristics and prioritize the mainte-
nance of disturbance regimes through prescribed fire,
wildfire, native herbivores, and, in certain cases, domes-
tic livestock. Conservation advocacy groups should seek
legal protection for old-growth grasslands and support
educational outreach to raise awareness of these imper-
iled biomes.
Policies designed to promote afforestation for any of a
variety of reasons, including climate-change mitiga-
tion, should explicitly acknowledge the conservation
values of old-growth grasslands. Specifically, these poli-
cies should recognize destruction of natural grasslands
for agriculture to be a form of “agricultural conversion”
with negative environmental consequences similar to
those that occur from deforestation. Likewise, policies
that promote fire suppression or planting exotic forage
grasses should be re-evaluated in regions that support
old-growth grasslands; non-native invasive species
should be recognized as a serious threat to old-growth
grassland biodiversity and a major hurdle to restoration.
Finally, financial mechanisms (eg payments for ecosys-
tem services) should be developed that promote the
protection and maintenance of biodiverse ancient
Panel 3. Relevance of old-growth grasslands to ecology
Adler et al. (2011) assessed the relationship between productivity
and species richness in a global dataset of herbaceous plant com-
munities; the majority of their study sites were grasslands of vari-
ous forms and origins, and these were grouped together for their
analyses. Although the authors did not specifically distinguish old-
growth grasslands from others, they did describe a subset of sites
as “anthropogenic”. They concluded that there was no consistent
pattern in the data, and thus productivity alone was a poor predic-
tor of species richness.
We reclassified the sites used by Adler et al. (2011) into two
groups (Figure 5): (1) those likely to be old-growth grasslands (ie
sites with no known history of cultivation, intact disturbance
regimes, and native plant communities; n= 13), and (2) secondary
grasslands and derived savannas (ie previously cultivated sites and
those classified by Adler et al. [2011] as anthropogenic; n= 16);
sites with insufficient information remained unclassified (n= 19).
We found a strong positive linear relationship between productiv-
ity and diversity for old-growth sites (r2= 0.40, P= 0.02), and no
apparent relationship for secondary grasslands and derived savan-
nas. We suggest that this is one example of how distinguishing old-
growth grasslands from other ecosystem states may lead to funda-
mental insights.
Panel 4. Latitudinal trends in old-growth grasslands
There are likely to be profound differences between grasslands
in regions that were transformed during Pleistocene glaciations
(2.6–0.12 MYA) and grasslands of tropical and subtropical
regions with relatively stable climates (Kirkman et al. 2014).
Post-glacial grasslands (eg in temperate North America, Europe,
and Asia) have assembled during the past 12 000 years through
dispersal from refugia where grasslands persisted during glacia-
tions. In contrast, many tropical and subtropical grasslands have
existed for >2 million years in more or less the same locations.
These trends in paleoclimatic stability have likely resulted in lat-
itudinal trends in grassland plant life-history characteristics. In
particular, we hypothesize that in post-glacial grasslands, peren-
nial plants are shorter-lived (ie years to decades; Lauenroth and
Adler 2008) and have higher dispersal and colonization poten-
tials than in climate-stable grasslands, where perennial plants
can be extremely long-lived (centuries to millennia; Alves and
Kolbek 1994; Takahashi et al. 2011) and are usually poor colo-
nizers. In looking for old-growth grasslands, we should expect
that, as in old-growth forests (Outcalt 1997; Devall 1998), the
time required for these grasslands to form – and the ages of
old-growth plants – may vary by at least an order of magnitude,
from ~100 years (Redhead et al. 2014) to perhaps >1000 years.
In many cases, these differences may be attributable to latitudi-
nal trends in climate stability.
Figure 5. The productivity–diversity relationship in old-
growth grasslands compared to secondary grasslands and
derived savannas. Modified from Adler et al. (2011).
Mean richness (species m–2)
0 200 400 600 800
Mean live biomass (g m–2)
Old-growth grassland
Secondary grassland
and derived savanna
JW Veldman et al.Old-growth grasslands
© The Ecological Society of America
grasslands. It is our hope that if our proposed concept is
widely adopted by ecologists, policy makers and others
will follow suit, thereby improving the prospects for
conservation of the world’s old-growth grasslands,
savannas, and woodlands.
We thank A Willem for Figure 2a and the Nutrient
Network for the data used in Figure 5.
Adler PB, Seabloom EW, Borer ET, et al. 2011. Productivity is a
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4Ecologia Evolutiva e Biodiversidade, Universidade Federal de Minas
Gerais, Belo Horizonte, Brazil; 5Department of Biology, Stanford
University, Stanford, CA; 6Gembloux Agro-Bio tech, Biodiversity and
Landscape Unit, University of Liege, Gembloux, Belgium;
7Department of Botany, Universidade Federal do Rio Grande do Sul,
Porto Alegre, Brazil; 8Department of Philosophy and Religious Studies,
Iowa State University, Ames, IA; 9Department of Biological Sciences,
University of Cape Town and South African Environmental
Observation Network, NRF, Rondebosch, South Africa;
10Department of Biology, University of Florida, Gainesville, FL
... Grassy ecosystems occur in all Brazilian biomes as defined by the Brazilian Institute of Geography and Statistics (IBGE, 2019; see Box 1 for Brazil's grassy ecosystems in a global biome classification). Brazil's grassy ecosystems harbor a wealth of shade-intolerant plants, typically (but not always) with high dominance of perennial grasses and a relatively continuous layer of herbaceous plants, including many forbs and subshrubs (see also Veldman et al., 2015;Bond, 2019;Buisson et al., 2019). The characteristic species of grassy ecosystems evolved under, and are maintained by, frequent fires (e.g., Simon et al., 2009), megafaunal herbivores (e.g., Dantas and Pausas, 2020;Lopes et al., 2020), edaphic factors (e.g., Silveira et al., 2016) and climatic constraints (e.g., Behling et al., 2004), or a combination of these factors that limit tree growth. ...
... However, recent work suggests that the distribution of grassy ecosystems is only partially governed by current climate (e.g., Bond, 2019;Pausas and Bond, 2019;Dantas and Pausas, 2020). Past or present fire, grazing, waterlogging and edaphic constraints have also been underlined as critical factors for the existence of grassy ecosystems (e.g., Veldman et al., 2015;Bond, 2019). In recognition that some climatic regimes allow for the existence of forest-grassland mosaics, Whittaker (1975) defined an 'Ecosystem Uncertainty Climate Zone' that spans over large parts of the globe (Bond, 2005). ...
... Furthermore, a distinction between primary (i.e., old-growth grassland sensu Veldman et al., 2015) versus secondary grassland would more clearly highlight conservation value and restoration need. Primary grasslands are grasslands that were never replaced by other land uses ...
In Brazil, the country with the highest plant species richness in the world, biodiverse savannas and grasslands – i.e., grassy ecosystems, which occupy 27% of the country – have historically been neglected in conservation and scientific treatments. Reasons for this neglect include misconceptions about the characteristics and dynamics of these ecosystems, as well as inconsistent or regionally restricted terminology that impeded a more adequate communication about Brazil's savannas and grasslands, both within the country and internationally. Toward improved communication and recognition of Brazil’s diversity of ecosystems, we present the key drivers that control the main types of grassy ecosystems across Brazil (including in regions of the country where forests dominate). In doing so, we synthesize the main features of each grassy ecosystem in terms of physiognomy and ecological dynamics (e.g., relationships with herbivores and fire). We propose a terminology both for major grassland regions and for regionally relevant vegetation physiognomies. We also discuss terms associated with human land management and restoration of grassy ecosystems. Finally, we suggest key research needs to advance our understanding of the ecology and conservation values of Brazil’s grassy ecosystems. We expect that a common and shared terminology and understanding, as proposed here, will stimulate more integrative research that will be fundamental to developing improved conservation and restoration strategies.
... In recent years, research on the importance of savanna ecosystems has shown that while major conservation and restoration efforts have focused on forested ecosystems, savannas in some parts of the world have remained understudied and their biodiversity value relatively unknown or undervalued (Veldman et al. 2015a). In many cases, savannas are misunderstood as degraded or deforested ecosystems (Fairhead and Leach 1996), and were at the centre of many colonial era debates about savanna origins, if they were anthropogenic or natural (Pellegrin and Le Testu 1938;Mangenot 1955;Keay 1959;Aubréville 1962;Swift 1996) and how savanna fire policy should favour forest growth (Collin 1951;Perriguey 1951). ...
... These biomes often have species compositions that are influenced by anthropogenic and natural fire (Maurin et al. 2014;Solofondranohatra et al. 2020;Demichelis et al. 2021). These old-growth savannas, defined as "ancient ecosystems characterized by high herbaceous species richness, high endemism, and unique species compositions" (Veldman et al. 2015a) can be distinguished by the presence of endemic species, geoxylic suffrutices that form underground forests, and/or forbs with underground storage organs or flowering stimulated by fire (Veldman et al. 2015a;Bond and Zaloumis 2016). Geoxylic suffrutices are species with underground, woody stems, owing their structure to regular fires which kill the leaves but not the stems, creating underground forests (White 1976;Maurin et al. 2014). ...
... These biomes often have species compositions that are influenced by anthropogenic and natural fire (Maurin et al. 2014;Solofondranohatra et al. 2020;Demichelis et al. 2021). These old-growth savannas, defined as "ancient ecosystems characterized by high herbaceous species richness, high endemism, and unique species compositions" (Veldman et al. 2015a) can be distinguished by the presence of endemic species, geoxylic suffrutices that form underground forests, and/or forbs with underground storage organs or flowering stimulated by fire (Veldman et al. 2015a;Bond and Zaloumis 2016). Geoxylic suffrutices are species with underground, woody stems, owing their structure to regular fires which kill the leaves but not the stems, creating underground forests (White 1976;Maurin et al. 2014). ...
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Background and aims – Old-growth savannas in Africa are impacted by fire, have endemic and geoxylic suffrutices, and are understudied. This paper explores the Parc National des Plateaux Batéké (PNPB) in Gabon and the impact of fire on its flora to understand if it is an old-growth savanna. It presents 1) a vascular plant checklist, including endemic species and geoxylic suffrutices and 2) an analysis of the impact of fire on the savanna herbaceous flora, followed by recommendations for fire management to promote plant diversity. Material and methods – 1,914 botanical collections from 2001–2019 collected by the authors and others were extracted from two herbaria databases in 2021 to create the checklist. The impact of fire was explored through a three season plot-based inventory of plant species (notably forbs and geoxylic suffrutices) in five annually, dry-season burned study areas located at 600 m in elevation. A two-factor ANOVA was conducted across two burn treatments and three season treatments. Key results – The area has a vascular flora of 615 taxa. Seven species are endemic to the Plateaux Batéké forest-savanna mosaic. Seventeen species are fire-dependent geoxylic suffrutices, attesting to the ancient origins of these savannas. Burning promotes fire-dependent species. Conclusion – The PNPB aims to create a culturally-adapted fire management plan. The combination of customary fire and fire-adapted species in the savanna creates a unique ancient forest-savanna mosaic in Central Africa that merits protection while recognising the role that the Batéké-Alima people have in shaping and governing this landscape.
... Tropical savannas are increasingly being recognised for their significant environmental, economic and cultural importance. This fireprone ecosystem is mostly formed by species of C4 grasses, herbs, shrubs and sub-shrubs, forming a continuous herbaceous layer in the vegetation together with sparse trees (Parr et al., 2014;Veldman et al., 2015). Despite the recent science and media attention to the savannas, they are threatened all around the world by land conversion, biological invasions and fire suppression (Durigan and Ratter, 2006;Parr et al., 2014). ...
The Cerrado, the most biodiverse savanna, has been losing its natural areas through conversion to agricultural land. In the Santa Barbara Ecological Station (SBES), more than 136.4 ha of open Cerrado vegetation were converted into pine plantations in the 1960s-1970s. Nonetheless, nowadays techniques such as clear-cutting pine trees and burning of the remaining material have been used to recover the native vegetation in those areas. In one of these recovering areas, some native species have resprouted, particularly Psidium grandifolium, which naturally occurs in open Cerrado vegetation. Here, we aimed to elucidate which attributes ensured the resilience of this species after decades of afforestation. To do so, we compare the belowground systems, bud banks, chemical contents of roots and vessel characteristics of P. grandifolium occurring in a natural open Cerrado area and an area under regeneration after the clear-cutting of pine and later burning at SBES. In both study areas, plants showed xylopodium whose upper parts consisted of a thin cauline axis joined to a lignified tuberous root with fusiform morphology. In the natural area, the xylopodia were orientated vertically on the ground, while in the regenerating area, there was a curvature in the cauline axis, changing the xylopodia orientation to a horizontal position. The belowground bud bank was three times greater in the area under regeneration. Roots presented significant differences in the concentrations of total soluble carbohydrates and flavonoids between study areas. Our results also demonstrated that plants with thickened bud-bearing belowground systems held great resilience capacity, even when the structures were damaged by soil management before pine planting. Individuals of P. grandifolium managed to remain dormant in the plantations for decades until the conditions for resprouting were adequate. This work showed a series of plastic responses that Cerrado species present when submitted to afforestation and different growing conditions.
Referring to the manifold studies and the long-term experiences of the restoration of near-natural ecosystems and traditional land-use types, respectively, examples from all over the world are outlined. Additionally to rewilding as a progressive approach to nature conservation, letting nature take care of itself and enabling natural processes, particularly the restoration of heathland, agricultural grassland, savannas, agroforestry systems, silvopastoral systems, coppice forests, lakes, peatland, coastal mangroves, terraced and irrigation land-use systems is addressed. The unique features of these ecosystems and land-use systems, respectively, which are or could be embedded in traditional and multifunctional cultural landscapes encompass high biodiversity, agrobiodiversity, and agrodiversity, respectively, as well as the provision of manifold ecosystem and landscape services.
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Aims and background Underground storage organs (USOs) have long featured prominently in human diets. They are reliable year-round resources, especially valuable in seasonal climates. We review a significant but scattered literature and oral recounts of USOs utilised by Noongar people of the Southwest Australian Floristic Region (SWAFR). USOs are important to First Nations cultures in other geophyte-rich regions with Mediterranean climate, with specialist knowledge employed, and productive parts of the landscape targeted for harvest, with likely ecological interactions and consequences. Methods We have gathered Noongar knowledge of USOs in the SWAFR to better understand the ecological role of Noongar-USO relationships that have existed for millennia. Results We estimate that 418 USO taxa across 25 families have Noongar names and/or uses. Additionally, three USO taxa in the SWAFR weed flora are consumed by Noongar people. We found parallels in employment of specific knowledge and targeted ecological disturbance with First Nations’ practice in other geophyte-rich floristic regions. We found that only in 20% of cases could we identify the original source of recorded USO knowledge to an acknowledged Noongar person. Conclusion This review identified that traditional Noongar access to USOs is taxonomically and geographically extensive, employing specific knowledge and technology to target and maintain resource rich locations. However, we also found a general practice of ‘extractive’ documentation of Noongar plant knowledge. We identify negative implications of such practice for Noongar people and SWAFR conservation outcomes and assert ways to avoid this going forward, reviving Noongar agency to care for traditional Country.
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Monitoring of vegetation on the herbaceous layer in a Cerrado sensu stricto in Planaltina (DF) was carried out eight times from 1988 to 1994 and in 2012, in two areas of 1.25 ha (Area 1, Area 2). Using the interception method on line, two transections of 100 m in length were defined, which were subdivided in sample units measuring one meter, totaling 200 units per area. In Area 1, prescribed burnings were applied in 1988, 1990 and in 1992. Area 2 was protected until July 1994, however an accidental fire hit the whole area in August the same year. Species of different habits up to a meter high were recorded in both areas. A number ranging between 92 and 134 species was observed from 1988 to 1994, and 115 species were recorded in 2012 in Area 1. Also, a number between 97 and 129 species was observed from 1988 to 1994, and 106 species were recorded in 2012 in Area 2. The results indicated the recovery and resiliency of the community after biennal burnnings. Biennal prescribed fires did not change the richness and diversity, but the community structure. The suppression of fire for 18 years did not promoted differences in the richness, but in the community diversity and structure. The exclusion of fire for 18 years also did not favored the floristic similarity between the two areas.
Subtropical humid grazing lands represent a large global land use and are important for livestock production, as well as supplying multiple ecosystem services. Patch-burn grazing (PBG) management is applied in temperate grazing lands to enhance environmental and economic sustainability; however, this management system has not been widely tested in subtropical humid grazing lands. The objective of this study was to determine how PBG affected forage resources, in comparison with the business-as-usual full-burn (FB) management in both intensively managed pastures (IMP) and seminative (SN) pastures in subtropical humid grazinglands. We hypothesized that PBG management would create patch contrasts in forage quantity and nutritive value in both IMP and SN pastures, with a greater effect in SN pastures. A randomized block design experiment was established in 2017 with 16 pastures (16 ha each), 8 each in IMP and SN at Archbold Biological Station's Buck Island Ranch in Florida. PBG management employed on IMP and SN resulted in creation of patch contrast in forage nutritive value and biomass metrics, and recent fire increased forage nutritive value. Residual standing biomass was significantly lower in burned patches of each year, creating heterogeneity within both pasture types under PBG. PBG increased digestible forage production in SN but not IMP pastures. These results suggest that PBG may be a useful management tool for enhancing forage nutritive value and creating patch contrast in both SN and IMP, but PBG does not necessarily increase production relative to FB management. The annual increase in tissue quality and digestible forage production in a PBG system as opposed to once every 3 yr in an FB system is an important consideration for ranchers. Economic impacts of PBG and FB management in the two different pasture types are discussed, and we compare and contrast results from subtropical humid grazing lands with continental temperate grazing lands.
Occupancy models have been underused in multispecies plant studies. We evaluated the effectiveness of occupancy models to document impacts of management on grassland plant species populations in a pilot study. The study was designed to answer three questions: (1) From a list of 44 plant species, how many will have sufficient frequency to be analyzed? (2) Within a single site, which factor (sampling year or unit) influences occupancy and detection of each plant species? (3) How does the number of plots and visits affect the number of species with sufficient frequency for analysis? In 2012 and 2013, occupancy and detection probabilities of 44 plant species were assessed using permanently marked plots on two different grassland sites. Within each site, a fire and grazing managed unit and a burn‐only control unit were used to test the efficacy of occupancy modeling for multiple plant species and study design. Four of the 44 species had sufficiently high known presence (π) on both sites and years to be analyzed. There was little evidence to support that occupancy was different between years, despite very different weather patterns. There was support that occupancy was different in the burned and grazed unit compared with the control for Rhus copallinum L. Detection was highest (≥0.8) for R. copallinum, while the other species analyzed varied. In 2012, eight species had sufficient π for analysis. In 2013, 12 species had sufficient π for analysis. Occupancy models can be useful for investigating multiple plant species; however, a priori investigation of species' distribution is necessary to ensure species can be analyzed. Detection of plants was never 1, and therefore, detection should continue to be incorporated in plant population models, regardless of modeling technique.
Temperate grasslands are the most endangered and least protected biome in the world. Few significant parcels remain and strategies for ongoing protection are critical for conservation efforts worldwide. In southwestern Saskatchewan, three contiguous blocks of native grassland, known as the Prairie Pastures Conservation Area, are federally managed by Environment and Climate Change Canada. Previously, the 800‐km2space was managed by the Department of Agriculture as public rangeland in the Prairie Farm Rehabilitation Agency (PFRA). We interviewed 11 individuals, including NGO representatives and pasture patrons, familiar with the PFRA at a native prairie/grassland conference to enhance our understanding of the importance of the agency and the lands in the province to them, as well as to Canada and globally. Themes that emerged included benefits of historic PFRA management, reservations about privatization of pasturelands, and worries about mismanagement. We take these themes and build them into our recommendations for what Environment and Climate Change Canada should do with the Prairie Pastures Conservation Area going forward: enhance Indigenous collaboration, establish a conservation network, and increase public use and awareness. Globally, grassland ecosystems are extremely endangered with few significant parcels remaining and are critical to conserving native species at risk. The Prairie Pastures Conservation Area in southern Saskatchewan has some of the largest remaining blocks of native grasslands under Canadian federal control. This area should be managed to enhance Indigenous collaboration, establish a conservation network, and increase public access to native grassland ecosystems. Globally, grassland ecosystems are extremely endangered with few significant parcels remaining and are critical to conserving native species at risk. The Prairie Pastures Conservation Area in southern Saskatchewan has some of the largest remaining blocks of native grasslands under Canadian federal control. This area should be managed to enhance Indigenous collaboration, establish a conservation network, and increase public access to native grassland ecosystems. Les prairies tempérées sont probablement le biome le plus menacé et le moins protégé au monde. Il reste peu de parcelles de taille significative et les stratégies de protection continue sont essentielles à l'échelle internationale. Dans le sud‐ouest de la Saskatchewan, trois blocs contigus de prairies naturelles, connus sous le nom d'aire de conservation des pâturages des Prairies, sont gérés par Environnement et Changement climatique Canada. Auparavant, cet espace de 800 km2était administré par le ministère de l'Agriculture en tant que pâturages publics par le biais de l'Agence du rétablissement agricole des Prairies (ARAP). Lors d'une conférence sur les prairies naturelles et les pâturages, nous avons interviewé 11 personnes, dont des représentants d'ONG et des propriétaires de pâturages, qui connaissent bien l'ARAP, afin de mieux comprendre l'importance de l'Agence et des terres de la province pour ceux‐ci, ainsi que pour le Canada et le monde entier. Parmi les thèmes qui sont ressortis des entrevues, mentionnons les avantages de la gestion historique de l'ARAP, les réserves à l'égard de la privatisation des pâturages et les inquiétudes envers la perspective d'une mauvaise gestion. Nous reprenons ces thèmes et les intégrons à nos recommandations sur ce qu'Environnement et Changement climatique Canada devrait faire à l'avenir avec l'aire de conservation des pâturages des Prairies, c'est‐à‐dire renforcer la collaboration avec les Autochtones, établir un réseau de conservation et accroître l'utilisation et la sensibilisation du public.
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Approximately one-third of the Earth's vegetative cover comprises savannas, grasslands, and other grass-dominated ecosystems. Paleobotanical, paleofaunal, and stable carbon isotope records suggest five major phases in the origin of grass-dominated ecosystems: (1) the late Maastrichtian (or Paleocene) origin of Poaceae; (2) the opening of Paleocene and Eocene forested environments in the early to middle Tertiary; (3) an increase in the abundance of C3 grasses during the middle Tertiary; (4) the origin of C4 grasses in the middle Miocene; and (5) the spread of C4 grass-dominated ecosystems at the expense of C3 vegetation in the late Miocene. Grasses are known from all continents except Antarctica between the early Paleocene and middle Eocene. Herbivore morphology indicative of grazing, and therefore suggestive of grass-dominated ecosystems, appears in South America by the Eocene-Oligocene boundary, prior to the occurrence of grazing morphology elsewhere, and persists throughout the Cenozoic. Clear vertebrate and paleobotanical evidence of widespread grass-dominated ecosystems in northern continents does not occur until the early to middle Miocene. C4 grasses are present from approximately 15 Ma and undergo a dramatic expansion in the lower latitudes of North America, South America, East Africa, and Pakistan between 9 and 4 Ma. The expansion may have taken place in a shorter interval in some regions. C4 grasses are characteristic of seasonal, arid, and warm environments and are more tolerant of lower atmospheric CO2 (< 400 ppmv) than C3 plants. C4 grass distribution, therefore, is climatically controlled. The late Miocene spread of C4 grasses possibly involved a decrease in atmospheric CO2 and heralded the establishment of modern seasonality and rainfall patterns.
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In the shortgrass steppe region of North America there is a controversy about the ability of the dominant species to recruit from seedlings. The prevailing view is that Bouteloua gracilis is incapable of recruitment from seedlings in areas receiving mean), emphasizes the importance of the intraseasonal distribution of precipitation. The sensitivity of recruitment to soil water availability suggests that climate change, particularly changes that increase or decrease the amount or the effectiveness of soil water, could have important effects on the future of populations of B. gracilis.
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QuestionHuman-altered disturbance regimes and agricultural land uses are broadly associated with reduced plant species diversity in terrestrial ecosystems. In this study, we seek to understand how fire frequency and agricultural land-use history influence savanna understorey plant diversity through complex relationships (i.e. indirect effects) among multiple biophysical variables.LocationFort Bragg, NC, US, Savannah River Site, SC, US and Fort Stewart, GA, US.Methods We use structural equation modelling (SEM) to evaluate the relationships among six groups of predictor variables and their influence on local-scale species richness in pine savannas at 256 sites from three locations in the southeastern USA. In the model, fire frequency and agricultural history are hypothesized to control richness through a combination of direct effects, and indirect effects mediated by resource availability, tree abundance, understorey plant abundance and the O horizon (litter and duff depth).ResultsFrequent fires promote richness by limiting tree abundance, which increases understorey abundance and reduces the O horizon. Frequent fires also limit the O horizon independent of tree abundance. Of the total positive effect of fire on richness, 70% is attributable to reductions in the O horizon and 30% to reduced tree abundance. Agricultural history has a negative effect on richness through a positive correlation with tree abundance, which decreases understorey abundance and increases the O horizon. Agricultural history has a modest negative effect on richness by reducing resource availability as well as a strong direct negative effect (38% of the total effect) that is unrelated to other modelled variables.Conclusions Through a multivariate framework and large-scale data set, this study unites and tests our understanding of the factors that control plant species diversity in a fire-dependent ecosystem. We show that the effects of fire frequency and agricultural history on richness are largely mediated through other ecosystem attributes, including vegetation structure (i.e. tree and understorey abundance), resource availability and the O horizon. Persistent, negative effects of agricultural history demonstrate the slow rates of savanna plant community recovery on post-agricultural land and highlight the conservation value of frequently burned savanna remnants.
Forgotten Grasslands of the South" is a literary and scientific case study of some of the biologically richest and most endangered ecosystems in North America. Eminent ecologist Reed Noss tells the story of how southern grasslands arose and persisted over time and addresses questions that are fundamental for conserving these vital yet poorly understood ecosystems. The author examines: the natural history of southern grasslandstheir origin and history (geologic, vegetation, and human)biological hotspots and endangered ecosystemsphysical determinants of grassland distribution, including ecology, soils, landform, and hydrology fire, herbivores, and ecological interactions.The final chapter presents a general conservation strategy for southern grasslands, including prioritization, protection, restoration, and management. Also included are examples of ongoing restoration projects, along with a prognosis for the future. In addition to offering fascinating new information about these little-studied ecosystems, Noss demonstrates how natural history is central to the practice of conservation. Natural history has been on a declining trajectory for decades, as theory and experimentation have dominated the field of ecology. Ecologists are coming to realize that these divergent approaches are in fact complementary, and that pursuing them together can bring greater knowledge and understanding of how the natural world works and how we can best conserve it. "Forgotten Grasslands of the South" explores the overarching importance of ecological processes in maintaining healthy ecosystems, and is the first book of its kind to apply natural history, in a modern, comprehensive sense, to the conservation of biodiversity across a broad region. It sets a new standard for scientific literature and is essential reading not only for those who study and work to conserve the grasslands of the South but also for everyone who is fascinated by the natural world.
Scientists have called repeatedly for a broader conservation agenda that emphasizes not only protected areas but also the landscapes in which those areas are embedded. We describe key advances in the science and practice of engaging private landowners in biodiversity conservation and propose a conceptual model for integrating conservation management on reserves and privately owned lands. The overall goal of our model is to blur the distinction between land management on reserves and the surrounding landscapes in a way that fosters widespread implementation of conservation practices. Reserves assume a new role as natural laboratories where alternative land-use practices, designed to achieve conservation objectives, can be explored. We articulate the details of the model using a case study from the North American tallgrass prairie ecoregion.
Grasslands at the Hastings Natural History Reservation (HNHR) and in adjacent Santa Lucia coastal range of Monterey County, California were sampled from 1971 to 1991. Grasslands on HNHR showed two distinct and stable associations: stands with and without historical cultivation ($\approx 1865-1937$). Relict stands dominated by native, perennial grasses (e.g., Nassella pulchra, Poa secunda) are limited to uncultivated, steeper stands, often where soils have more clay. Abandoned agricultural fields have stable compositions dominated by Avena fatua, Bromus mollis, B. diandrus, Erodium spp., Hypochaeris glabra, Vulpia spp., Eremocarpus setigerus, and Amsinckia spp. Patterns in species composition were associated with gradients in soil texture, gopher abundance, and slope. Gophers provide a significant and continuous source of soil disturbance and may slow successional processes in old fields. Where gophers are excluded, aboveground biomass accumulates. Germination and establishment of native perennial grasses (compared to introduced, annual grasses) are reduced on gopher tailings in old fields. Species composition patterns reflecting past cultivation on both grazed and ungrazed stands are apparent. Relict (uncultivated) stands of native grasses persist under many historical levels of grazing. Effects of grazing are often only seen on old fields, and not on relict grasslands. Compared to stands where grazing was removed in 1937, stands currently or recently grazed by cattle show higher soil nitrogen, but reductions in cover of gopher tailings, species diversity, soil phosphate, and sulphate.
Ecological characteristics of old-growth Douglas-fir forests are examined in terms of compositional, functional, and structural features. Old-growth forests typically include dis-tinctive animal and plant species-that is, organisms that are most abundant in such forests. Functional behavior of old-growth forests differs from functional behavior under other forest conditions. Productivity is typically high, but most energy is used to maintain the large mass of living material; growth and mortality are in approximate balance over long periods. Nutrient and sediment yields from old-growth forests are typically very low. Old-growth forests also differ from younger forests in their effects on hydrologic cycles in areas where cloud or fog precipitation, rain-on-snow events, or both are important. The structural characteristics of old-growth forests are the basis for most of their unique com-positional and functional attributes. Specifically, important structural components are large individual old trees-whether live, dead and standing (snags), or dead and fallen (logs)-in both terrestrial and associated aquatic environ-ments. Old-growth forests also have stand attributes that are very different from younger and, especially, from managed forests. The distinctive communities of microbes, inverte-brates, higher plants, and animals that occur in old-growth forests are integrally related to the collective structural attributes.
The origin of fire-adapted lineages is a long-standing question in ecology. Although phylogeny can provide a significant contribution to the ongoing debate, its use has been precluded by the lack of comprehensive DNA data. Here, we focus on the ‘underground trees’ (=geoxyles) of southern Africa, one of the most distinctive growth forms characteristic of fire-prone savannas. We placed geoxyles within the most comprehensive dated phylogeny for the regional flora comprising over 1400 woody species. Using this phylogeny, we tested whether African geoxyles evolved concomitantly with those of the South American cerrado and used their phylogenetic position to date the appearance of humid savannas.� We found multiple independent origins of the geoxyle life-form mostly from the Pliocene, a period consistent with the origin of cerrado, with the majority of divergences occurring within the last 2 million yr. When contrasted with their tree relatives, geoxyles occur in regions characterized by higher rainfall and greater fire frequency. Our results indicate that the geoxylic growth form may have evolved in response to the interactive effects of frequent fires and high precipitation. As such, geoxyles may be regarded as markers of fire-maintained savannas occurring in climates suitable for forests.
Scientists have called repeatedly for a broader conservation agenda that emphasizes not only protected areas but also the landscapes in which those areas are embedded. We describe key advances in the science and practice of engaging private landowners in biodiversity conservation and propose a conceptual model for integrating conservation management on reserves and privately owned lands. The overall goal of our model is to blur the distinction between land management on reserves and the surrounding landscapes in a way that fosters widespread implementation of conservation practices. Reserves assume a new role as natural laboratories where alternative land-use practices, designed to achieve conservation objectives, can be explored. We articulate the details of the model using a case study from the North American tallgrass prairie ecoregion.
Tropical grassy biomes (TGBs) are globally extensive, provide critical ecosystem services, and influence the earth-atmosphere system. Yet, globally applied biome definitions ignore vegetation characteristics that are critical to their functioning and evolutionary history. Hence, TGB identification is inconsistent and misinterprets the ecological processes governing vegetation structure, with cascading negative consequences for biodiversity. Here, we discuss threats linked to the definition of TGB, the Clean Development Mechanism (CDM) and Reducing Emissions from Deforestation and Forest Degradation schemes (REDD+), and enhanced atmospheric CO2, which may facilitate future state shifts. TGB degradation is insidious and less visible than in forested biomes. With human reliance on TGBs and their propensity for woody change, ecology and evolutionary history are fundamental to not only the identification of TGBs, but also their management for future persistence.