Susanne Schwinning

• PhD
• Professor at Texas State University

Aims Invasive species often have higher relative growth rates (RGR) than their native counterparts. Nutrient use efficiency, total leaf area and specific leaf area (SLA) are traits that may confer RGR differences between natives and invasives, but trait differences are less prominent when the invasive species belongs to the same plant functional ty...

QuestionCan the timing of cutting or burning be used to selectively damage an invasive C4 grass species while limiting collateral damage to dominant native C4 grass species in a grassland community?LocationA medium to short grass prairie in central Texas, US.Methods We conducted six cut and burn trials between June 2011 and January 2012 during an e...

In contrast with the fundamental ecological expectation that similarity induces competition and loss of species, temporal dynamics allows similar species to co-occur. In fact, the coexistence of similar species contributes significantly to species diversity and could affect ecosystem response to climate change. However, because temporal processes t...

Increases in fire frequency are disrupting many ecological communities not historically subjected to fire. In the southwestern United States, the blackbrush (Coleogyne ramosissima) community is among the most threatened, often replaced by invasive annual grasses after fire. This long-lived shrub is vulnerable because it recruits sporadically, parti...

Woody plant encroachment into grasslands has occurred worldwide, but it is unclear why some tree and shrub species have been markedly more successful than others. For example, Prosopis velutina has proliferated in many grasslands of the Sonoran Desert in North America over the past century, while other shrub species with similar growth form and lif...

Native plant communities persist by quashing the establishment of new arrivals but disturbance and changes in the resource regime can tip the competitive balance in favor of the newcomers. Although invasive traits are well characterized, their success inside mature communities is rarely tested. In this experiment, we evaluated the ability of one of...

Purpose Allelopathy is a plant interaction in which a donor species releases chemicals that suppress the development of receptor species. Allelopathy has been suggested as one explanation for catastrophic loss of native biodiversity in some invaded biomes; however, experimental tests of this hypothesis have had inconsistent results. Here, we examin...

Common garden experiments are indoor or outdoor plantings of species or populations collected from multiple distinct geographic locations, grown together under shared conditions. These experiments examine a range of questions for theory and application using a variety of methods for analysis. The eight papers of this special feature comprise a cros...

Widely distributed species are often locally adapted to climate gradients across their ranges. But little is known about the patterns of intraspecific adaptation in desert shrubs. We examined the questions of local adaptation in multiple populations of two common shrub species of the winter‐wet Mojave Desert in North America in a multiple common ga...

Background The paper by Korboulewsky and co-authors in this issue of Plant and Soil address some of the central questions of critical zone ecohydrology: how do plants interact with rocks that exclude roots but hold plant-available water?ScopeI compare plant water uptake from stony soils and fractured bedrock in the critical zone, suggesting that th...

This chapter provides an overview of the variety of methods available that scientists have developed to explore the natural and material world. Each method is accompanied by discussion of a rich set of procedures that extend beyond just experiments that many believe to be the way that science works. This limited view of scientific research is frequ...

Aims(1) To develop a 3D root distribution model for piñon-juniper woodland using only tree species, sizes and locations as input. (2) To interpret a two-year time series of soil moisture relative to root distributions.Methods The study was conducted in a piñon (Pinus edulis (Englem.)) -juniper (Juniperus monosperma (Englem.) Sarg.) woodland in New...

Hot drought is a climate phenomenon that has received much attention lately for its potential to disrupt forest function worldwide. A sharp increase in tree mortality associated with this climate pattern is often cast as a disturbance, in which high temperature is responsible for causing exceptional rates of mortality across species. The alternativ...

Hot drought is a climate phenomenon that has received much attention lately for its potential to disrupt forest function worldwide. A sharp increase in tree mortality associated with this climate pattern is often cast as a disturbance, in which high temperature is responsible for causing exceptional rates of mortality across species. The alternativ...

Plant water use is an important component in the function of Earth's critical zone and this can be examined by decomposing isotope composition of xylem water into contributions from precipitation stored in shallow soil layers and deeper groundwater. The usual procedure for estimating the proportional use of groundwater by plants is to sample the is...

Karst regions, which account for about 15% of the terrestrial surface area, are characterized by specific hydrogeological structure that different from most non-karst regions. Thus, many research methods that are used in non-karst regions cannot be directly used in karst regions. This issue is especially relevant to research on plant water sources....

Invasive plant species often dominate native species in competition, augmenting other potential advantages such as release from natural enemies. Resource pre-emption may be a particularly important mechanism for establishing dominance over competitors of the same functional type. We hypothesized that competitive success of an exotic grass against n...

Woody vegetation in grasslands and savannas has increased worldwide over the past 100–200 years. This phenomenon of “woody plant encroachment” (WPE) has been documented to occur at different times but at comparable rates in rangelands of the Americas, Australia, and southern Africa. The objectives of this chapter are to review (1) the process of WP...

Brush removal is widely practiced as a tool for increasing groundwater recharge, but its efficacy depends greatly on the way in which the removed species interact with the hydrological system relative to the vegetation replacing it. We examined the effects of Ashe juniper removal in the recharge zone of the Edwards Aquifer, Texas, USA, a karst aqui...

Background and aims We quantified spatial variability in water storage and plant access to water in the rocky soils of a karst savanna dominated by Ashe juniper (Juniperus ashei) and honey mesquite (Prosopis glandulosa). Methods In a 25×25 m grid with 5-m node spacing, water content and bulk density profiles were measured to a depth of 1.6 m by a c...

Woody plants are encroaching into grasslands and savannas of the karst Edwards Plateau, but their impacts on climate and hydrology are unclear because of high variability in soil depth and uncertainties about the contribution of water in fractured limestone to the water available to trees. Water use is controlled by available energy (AE) and its pa...

In contrast with the fundamental ecological expectation that similarity induces competition and loss of species, temporal dynamics allows similar species to co-occur. In fact, the coexistence of similar species contributes significantly to species diversity and could affect ecosystem response to climate change. However, because temporal processes t...

The epikarst is a permeable boundary between surface and subsurface environments and can be conceptualized as the vadose critical zone of epigenic karst systems which have not developed under insoluble cover. From a hydrologic perspective, this boundary is often thought of as being permeable in one direction only (down), but connectivity between th...

We review plant competition in water‐limited environments with focus on temporal niche dynamics and examine implications for diversity–productivity relationships and the response of ecosystem productivity to changes in water availability. The main theses under examination are that (i) plant functional types ( PFT s) have distinct resource pulse use...

Two explanations exist for the evolutionary origin of grouping in primary consumers: reduction of individual prédation risk and resource-mediated aggregation. While several studies have assessed relationships between aggregation and prédation risk, few studies have examined the circumstances under which resource-mediated aggregation can lead to sta...

Background In this issue, Estrada-Medina and coworkers described the diversity of materials in the rhizosphere of the Yucatán karst, México, and quantified the distribution of roots across karst features. Scope This commentary explores the implications of their work for below-ground competition and the dynamics of plant-available water on seasonal...

An important component of the hydrological niche involves the partitioning of water sources, but in landscapes characterized by shallow soils over fractured bedrock, root growth is highly constrained. We conducted a study to determine how physical constraints in the root zone affected the water use of three tree species that commonly coexist on the...

Background/Question/Methods Small washes and channels create a complex hydrological network across desert bajadas but represent only a small proportion of the bajada’s spatial area. Nonetheless, these channels may be the most important geomorphic feature influencing local vegetation properties and processes. We examined the functional influence o...

Background/Question/Methods Native perennial grasses are widely considered alternatives to corn for biofuel production. However, there is concern that nitrogen fertilization of perennial grasses makes them just as vulnerable to noxious weeds. One of the most problematic weeds in grasslands is the C4 perennial grass Johnsongrass (Sorghum halepense...

Background/Question/Methods Targeted invasive species control is difficult when the invasive and native species belong to the same plant functional type due to their overlap in resource use and seasonal growth periods. In addition, management attempting to target an invasive species that has a higher rate of increase than native components can in...

Background/Question/Methods Regional warming trends are expected to alter species ranges, shifting species assemblages upward and northward. Models primarily use temperature and precipitation to predict future vegetation distributions with little consideration of edaphic factors. In the Mojave Desert, shrub dominance changes along an elevational g...

Prescribed burning is a popular method for the control of invasive species; however, research is lacking on the application of fire in a species-specific manner. We assess whether heat sensitivity differences among seeds of Texas grassland species can be used to target invasive species in prescribed burns. We conducted heat treatments on the invasi...

The extensive network of small washes and channels that pervades most desert bajadas usually represents only a small proportion of the bajada's spatial area and are usually devoid of vegetation. However, these channels may be the most important geomorphic feature influencing vegetation properties and processes in arid lands. To evaluate the functio...

In response to rare high-intensity or long duration rainstorms, runoff in desert ephemeral channels can redistribute water through landscapes and potentially serve as a resource subsidy. We are using transect studies, mapping, monitoring and manipulation experiments to investigate the ecohydrologic relations of these pervasive features with vegetat...

The spread of non‐indigenous, C4 grasses threatens global conservation of savannas and subtropical grasslands. Identifying control methods to selectively target these invasives has proven difficult. Here, we tested the hypothesis that the effectiveness of prescribed burns for control is determined, in part, by the phenology of the target species at...

Background/Question/Methods Much of earth’s land area is characterized by shallow soil over weathered bedrock. It is important to develop good estimates of water flux and water storage in these regions, since they often contribute disproportionally to regional water yield. Additionally, they may show quantitatively and qualitatively different res...

Effects of watering amount and frequency on root biomass accumulation and taproot elongation were examined 16–17days post-germination in seedlings of Larrea tridentata, a dominant shrub in North American hot deserts. Two experimental variables manipulated in a full factorial design greenhouse study were (i) number of “triggering” days: consecutive...

Drainage channels are among the most conspicuous surficial features of deserts, but little quantitative analysis of their influence on plant distributions is available. We analysed the effects of desert stream channels (‘washes’) on Larrea tridentata and Ambrosia dumosa density and cover on an alluvial piedmont in the Mojave Desert, based on a spat...

Study of the soil-vegetation-atmosphere system has been overwhelmingly dominated by systems with deep soils, yet large portions of the world are characterized by shallow soils underlain by fractured bedrock. In these systems, fractured bedrock may provide significant water storage, but we know little about the function of fractured bedrock as a wat...

Background/Question/Methods Over the past century, central Texas experienced rapid encroachment of Ashe juniper (Juniperus ashei) into grasslands and savannahs. The high year-round water use of this species is assumed to reduce aquifer recharge, although direct evidence that juniper clearing leads to increases in water yield is lacking. An explana...

Background/Question/Methods While much is known about the water use and hydrological adaptations of trees in deep soils, we are only beginning to examine adaptations to non-soil substrates, such as the fractured bedrock structure of the epikarst, the top layer of the vadose zone in karst systems. This substrate is spatially much more constraining...

Large portions of the world are characterized by shallow soil underlain by weathered bedrock or cemented soil horizons. The implications of this substrate condition for ecohydrological processes have not been systematically explored, but misrepresentation in models could have profound consequences for climate prediction and global vegetation modell...

Ephemeral stream channels are widespread features throughout desert landscapes, particularly on alluvial fans. These channels range in width from a few tens of centimeters to many meters. Runoff in these channels can redistribute water from upper portions of the landscape in response to rare high-intensity or long duration rainstorms. Visual observ...

Woody encroachment into karst grasslands and savannas is presumed to reduce water availability and aquifer recharge, in part, because deep roots extract large quantities of water from perennial sources within the fractured bedrock underlying shallow soils. If true, energy balance partitioning and transpiration in woody ecosystems should be decouple...

While some studies aim to generalise the attributes of woody encroachers, examining their functional differences across biogeographic regions may also be instructive. Most of Texas is encroached by Prosopis glandulosa, but on the eastern Edwards Plateau, a limestone plateau with thin soils, P. glandulosa is rare and Juniperus ashei is dominant. We...

Changes in Earth's surface temperatures caused by anthropogenic emissions of greenhouse gases are expected to affect global and regional precipitation regimes. Interactions between changing precipitation regimes and other aspects of global change are likely to affect natural and managed terrestrial ecosystems as well as human society. Although much...

"The Colorado Plateau is located in the interior, dry end of two moisture trajectories coming from opposite directions, which have made this region a target for unusual climate fluctuations. A multi-decadal drought event some 850 years ago may have eliminated maize cultivation by the first human settlers of the Colorado Plateau, the Fremont and Ana...

The ecohydrology of karst has not received much attention, despite the disproportionally large contribution of karst aquifers to freshwater supplies. Karst savannas, like many savannas elsewhere, are encroached by woody plants, with possibly negative consequences on aquifer recharge. However, the role of savanna tree species in hydrological process...

Background/Question/Methods Over the past century, tree-grass ratios have shifted markedly in favor of woody plants in many grasslands and savannas. Although shrub and tree proliferation has been widely documented, patterns of change and causal mechanisms are poorly understood. Ability to establish amid grass competition varies widely among speci...

The ecohydrology of karst has not received much attention, despite the disproportionally large effect that karst ecosystems might have on the availability of global freshwater quantity and quality. Theoretical considerations suggest that the ecohydrology of woody plants in karst, specifically where soil cover is thin and trees take root in the epik...

Historically, ecosystems in the southwestern United States derived much of their nitrogen (N) from N-fixation in biological soil crusts. Today, these regions have highly reduced crust cover, and atmospheric deposition may be the dominant source of N. This study investigates the effects of increased nitrogen deposition on nitrogen uptake, photosynth...

We investigated the effects of winter and summer drought on a shrub/grass community of the Colorado Plateau in western North America, a winter-cold, summer-hot desert that receives both winter and summer precipitation. Summer, winter and yearlong drought treatments were imposed for 2 consecutive years using rainout shelters. We chose three perennia...

We investigated the effects of winter and summer drought on plants of the Colorado Plateau in western North America. This winter-cold, summer-hot desert region receives both winter and summer precipitation. Droughts were imposed for two consecutive years using rainout shelters. Here, we examine drought effects on the hydrologic interactions between...

The amount and spatial distribution of deep drainage (downward movement of water across the bottom of the root zone) and groundwater recharge affect the quantity and quality of increasingly limited groundwater in arid and semiarid regions. We synthesize research from the fields of ecology and hydrology to address the issue of deep drainage in arid...

In the arid and semiarid regions of North America, discrete precipitation pulses are important triggers for biological activity. The timing and magnitude of these pulses may differentially affect the activity of plants and microbes, combining to influence the C balance of desert ecosystems. Here, we evaluate how a "pulse" of water influences physio...

Arid environments are characterized by limited and variable rainfall that supplies resources in pulses. Resource pulsing is a special form of environmental variation, and the general theory of coexistence in variable environments suggests specific mechanisms by which rainfall variability might contribute to the maintenance of high species diversity...

In arid/semi-arid ecosystems, biological resources, such as water, soil nutrients, and plant biomass, typically go through periods of high and low abundance. Short periods of high resource abundance are usually triggered by rainfall events, which, despite of the overall scarcity of rain, can saturate the resource demand of some biological processes...

Water availability limits plant growth and production in almost all terrestrial ecosystems. However, biomes differ substantially in sensitivity of aboveground net primary production (ANPP) to between-year variation in precipitation. Average rain-use efficiency (RUE; ANPP/precipitation) also varies between biomes, supposedly because of differences i...

The amount and spatial distribution of deep drainage (downward movement of 6 water through the bottom of the root zone) and groundwater recharge affect water supply 7 and quality in the rapidly growing, semiarid USA. We synthesize research from the fields 8 of ecology and hydrology to address the issue of deep drainage in semiarid regions. We 9 sta...

We conducted experiments to examine the quantitative relationships between rainfall event size and rainwater uptake and use by four common native plant species of the Colorado Plateau, including two perennial grasses, Hilaria jamesii (C(4)) and Oryzopsis hymenoides (C(3)), and two shrubs, Ceratoides lanata (C(3)), and Gutierrezia sarothrae (C(3))....

In desert ecosystems a large proportion of water and nitrogen is supplied in rain-induced pulses. It has been suggested that competitive interactions among desert plants would be most intense during these pulse periods of high resource availability. We tested this hypothesis with three cold desert shrub species of the Colorado Plateau (Gutierrezia...

In desert ecosystems a large proportion of water and nitrogen is supplied in rain-induced pulses. It has been suggested that competitive interactions among desert plants would be most intense during these pulse periods of high resource availability. We tested this hypothesis with three cold desert shrub species of the Colorado Plateau (Gutierrezia...

We contrasted the seasonal use of simulated large rain events (24 mm) by three native species of the arid Colorado Plateau: the perennial grass Hilaria jamesii and two shrubs Artemesia filifolia and Coleogyne ramosissima. Deuterium-enriched water was used to distinguish shallow "pulse" water from water in deeper soil layers that were unaffected by...

In arid land communities of the Colorado Plateau soil resources for plant uptake are typically available only during short pulses immediately following precipitation events. Using the stable isotopes 15N and 2H as tracers, we investigated the capacity of siz desert perennials with different rooting habits to utilise pulses of water and nitrogen dur...

On the Colorado Plateau, near Canyonlands National Park, precipitation averages 215mm per year, evenly distributed between the cold fall/winter season and the warm spring/summer season. Warm season rain events cause brief pulses of soil moisture in the shallow soil(0-20cm), while winter precipitation tends to accumulate and infiltrate into greater...

We introduce a hydraulic soil‐plant model with water uptake from two soil layers; one a pulse‐dominated shallow soil layer, the other a deeper soil layer with continuous, but generally less than saturated soil moisture. Water uptake is linked to photosynthetic carbon assimilation through a photosynthesis model for C 3 plants. A genetic algorithm is...

This modeling study explores the relationships between seasonal precipitation patterns, physiological and morphological plant adaptations and plant functional diversity in arid and semi-arid ecosystems. At the basis of the study is a hydraulic soil-plant model that simulates photosynthetic carbon gain under water-limited conditions. Soil in the mod...

Recent studies have provided detail of the mechanisms by which plants and animals interact, but attempts to apply this knowledge to understand function at the scale of whole fields or grazed ecosystems can be fraught with difficulties. Faced with a plethora of detail, and yet demands to make models more comprehensive, modellers face pressure to rev...

This chapter considers biting (defoliation) as a source of heterogeneity in the grazed sward, with consequent effects on grass growth and animal intake. Three contrasting methods of spatially exploiting the sward (sequential grazing, random grazing and selective grazing) and models of the impact of these methods on bite-sized patches of sward are d...

Since Noy-Meir’s (1975) analysis, much progress has been made in refining understanding of the grazing process in temperate grassland. Particularly, advances have been made in understanding grazing at the bite scale (Illius & Gordon 1987; Spalinger & Hobbs 1992; Parsons et al. 1994). Domestic ruminants remove a relatively fixed proportion (some 40–...

When plants are competing, larger individuals often obtain a disproportionate share of the contested resources and suppress the growth of their smaller neighbors, a phenomenon called size-asymmetric competition. We review what is known about the mechanisms that give rise to and modify the degree of size asymmetry in competition among plants, and at...

It is widely assumed that grass-legume associations offer a way to sustainable, low input land use, with reduced environmental impact. However, a combination of both ecological and physiological principles may be needed to understand the sustainability of species balances. 2 To increase understanding of grass-legume dynamics, we developed a model t...

Cited By (since 1996):56, Export Date: 9 December 2013, Source: Scopus

An analysis is introduced, based on the decomposition of relative growth rates, to examine the mode of competition (i.e. whether competition is symmetric or asymmetric), the size-dependence of growth, and their interdependence. In particular, the basis for two commonly held views is examined: (1) that the type of resource limitation determines the...

The value of white clover as a component of New Zealand pastures is undeniable, but it is also widely recognised that clover has limitations as a pasture plant and that these can lead to inefficiencies in the performance of grass/clover associations. This paper identifies some of the limitations to optimising the contribution of clover in complex s...

Asymmetric competition is a form of resource division among plants, in which large plants greatly suppress the growth of smaller neighbors. In annual plants, small size differences between seedlings at the onset of competition are magnified into large differences in seed-set by asymmetric competition. We formulate a novel neighborhood model, which...

Simulated the habitat selection behavior in a 3 population predator-prey system with a mid-level predator that is also prey. There were 2 habitats, one of which was a relative refuge from predation. Individuals moved to wherever they could improve their fitness, as if subject to the rules of the ideal-free distribution, but the 3 populations could...