Patricia A. Werner

Australian National University | ANU · Fenner School of Environment & Society

Savannas are the major biome in tropical regions of the globe, defined as sparsely wooded regions with a continuous herbaceous layer of mainly C4 grasses where rainfall is distinctly seasonal. Fire is a common feature of most savannas. The largest protected areas of savannas are found in sparsely populated monsoonal northcentral Australia with stro...

1. In mesic savannas worldwide, trees experience frequent fires, almost all set by humans. Management fires are set to reduce or enhance tree cover. Success depends greatly on responses of sub-adult trees to such fires. To date, the number of successive years that sub-adult trees can resprout nor the number of years that they must resist being t...

Understanding the responses of rare species to altered fire disturbance regimes is an ongoing challenge for ecologists. We asked: are there associations between fire regimes and plant rarity across different vegetation communities? We combined 62 years of fire history records with vegetation surveys of 86 sites across three different dry sclerophyl...

In mesic savannas worldwide, trees experience frequent fires, almost all set by humans. Management fires are set to reduce or enhance tree cover. Success depends greatly on responses of sub‐adult trees to such fires. To date, the number of successive years that sub‐adult trees can resprout nor the number of years that they must resist being top‐kil...

The impact of feral Asian water buffalo (Bubalus bubalis) and season of fire on growth and survival of mature trees was monitored over 8 years in the eucalypt savannas of Kakadu National Park. Permanently marked plots were paired on either side of a 25-km-long buffalo-proof fence at three locations on an elevational gradient, from ridge-top to the...

The 100-year history of the Ecological Society of America spans most of the major advances in the field of ecology, from the "niche" of Grinnell and others, to Lotka and Volterra's models of predation and competition based on the logistic growth equation, to the concept of competitive exclusion developed from experimental ecology, to genetics and e...

the Genetics of Colonizing Species was written after an early symposium that brought together ecologists, taxonomists, and geneticists to summarize knowledge about colonizing species and to exchange ideas about the kinds of evolutionary changes that occur when organisms are introduced into new territories. Twenty-seven authors from nine countries p...

Fire is a major disturbance driving the dynamics of the world's savannas. Almost all fires are set by humans who are increasingly altering fire timing and frequency on every continent. The world's largest protected areas of savannas are found in monsoonal northern Australia. These include relatively intact, tall, open forests where traditional indi...

Rainfall, fire and competition are emphasized as determinants of the density and basal area of woody vegetation in savanna. The semi-arid savannas of Australia have substantial multi-year rainfall deficits and insufficient grass fuel to carry annual fire in contrast to the mesic savannas in more northern regions. This study investigates the influen...

Three decades of field data on the effects of fire on individual eucalypt trees of the humid wooded savanna in north-central Australia are integrated into a stage-based matrix population model. The model explicitly considers how fire season and understory influence parameters of growth, survival, and recruitment for eight different life-history sta...

The western subspecies of the Purple-crowned Fairy-wren (Malurus coronatus coronatus) is listed as vulnerable under Commonwealth and Northern Territory legislation. Declines in numbers are presumed to be due to loss and degradation of riparian habitats upon which it depends. In the Northern Territory portion of its range, the species nests, and mai...

In 1961, HG Andrewartha (Australian) defined ecology as the scientific study of the distribution and abundance of organisms and analyzed these in light of landscape-scale abiotic factors (eg, soils, water) with less importance given to the biotic interactions. In the 1970s, Charles Krebs (North American, NA) defined ecology as the scientific intera...

Australia's native biota has evolved in the absence of large ungulates such as those found on other continents. Over the past 2 centuries, however, seven large ungulate grazers and browsers were introduced into the tropical monsoon region. The Asian water buffalo (Bubalus bubalis) was the most successful; by the late 1970s, populations had reached...

Savanna trees often display significant hollows due to the combined action of fire and termites (N’Dri et al., J Trop Ecol 27:269–278, 2011). Observations have shown that internal cavities caused by termites in tree stems often result in external hollows under annual fire regimes, and it is quite possible that such hollows/fire interaction may incr...

Tree populations in mesic (>650 mm precipitation/yr) savannas of the world have strong demographic bottlenecks to the transition of subadult trees to the canopy layer. Although such bottlenecks are a major determinant of savanna physiognomy, the factors that allow subadults to traverse the bottleneck are little studied. In a landscape-scale field e...

Canopy tree populations in mesic savannas are often bimodal with few saplings but many smaller individuals of indeterminate age that repeatedly suffer topkill and regenerate from underground tissues. Little is known about growth rates or mechanisms that allow subadult trees to reach the canopy. The wooded savannas of northern Australia have high fr...

Tree populations in mesic (>650 mm ppt yr–1) savannas of the world have strong demographic bottlenecks to the transition of sub-adults to the canopy layer. Such bottlenecks are a major determinant of savanna physiognomy, yet factors that allow sub-adults to traverse the bottleneck are little studied. A conceptual framework was developed, linking la...

Australia’s native biota has evolved in the absence of large ungulates such as those found on other continents (Mulvaney and Kamminga 1999; Janis 2008). Over the past two centuries, however, large ungulate grazers and browsers have been introduced into Australia with varying degrees of success (Ridpath 1991 and references therein). Those introduced...

Trees in tropical and sub-tropical savannas develop hollow cores, or pipes, caused by termite activity. It is commonly accepted that such tree hollows an adaptive trait whereby trees benefit by the release of nutrients, yet remarkably little has been documented about their effect on tree growth or survival. In the natural mesic savanna of Kakadu Na...

The pattern of oak (Quercus velutina L. and Quercus alba L.) seedling establishment in relation to ground-cover vegetation was examined over a 5-year period in a 30-year Michigan old field. Three types of vegetation cover were identified: primary patches were areas of bare ground or those covered by moss, lichen, or a moss–lichen matrix over minera...

A seed trap for terrestrial plants having dry seeds or fruits is described which holds seeds upon contact and whose trapped seeds are protected to a high degree from loss due to invertebrate predation or wind action. The trap makes use of "Tanglefoot," a sticky non-drying material and is easily constructed, operated, and maintained at minimal cost....

In northern Australian savannas, canopy tree species often have juvenile tree banks that are composed mainly of small individuals of indeterminate age that have resprouted repeatedly after fire. Little is known about their demography. We report the initial responses (mortality, topkill and resprouting type) of 3133 marked juvenile eucalypts to set...

Climate change acts as a new and complex stressor on all levels of biodiversity from genes to ecosystems. It interacts with a large number of historical and existing stressors such as habitat loss and invasive species. The Australian government, through its Natural Resource Management Ministerial Council, commissioned an independent expert advisory...

As in all parts of the globe, rapid climate change in Australia will have significant negative impacts on biodiversity. It also will interact with pre-existing stressors such as native vegetation clearing, altered natural disturbance regimes and invasive species – all of which already have major negative effects on biota in Australia. Strategies to...

As in all parts of the globe, rapid climate change in Australia will have significant negative impacts on biodiversity. It also will interact with pre-existing stressors such as native vegetation clearing, altered natural disturbance regimes and invasive species-all of which already have major negative effects on biota in Australia. Strategies to r...

Bowman et al. (Journal of Biogeography, 2008, 35, 1976–1988) aimed to explain observed increases in woody cover on floodplains and savannas of Kakadu National Park using estimates of buffalo (Bubalus bubalis) density as a causal variable. They found that buffalo were a minor model variable and concluded that buffalo are ‘not a major driver of flood...

Climate change acts as a new and complex stressor on all levels of biodiversity from genes to ecosystems, interacting with a large number of historical and existing stressors. We have conducted an assessment of the vulnerability of Australia’s biodiversity to climate change that includes current status and trends, as well as several adaptation tool...

This article was submitted without an abstract, please refer to the full-text PDF file.

This article was submitted without an abstract, please refer to the full-text PDF file.

Most trees in the eucalypt savannas of Australia have hollow cores, or pipes, caused by termite activity, yet little is known about their effect on tree growth or survival. Five hundred and forty-one trees with known growth and survival histories were cored to determine pipe diameters in wooded savanna of Kakadu National Park, north Australia. Gene...

Savannas are the major biome of tropical regions, spanning 30% of the Earth's land surface. Tree:grass ratios of savannas are inherently unstable and can be shifted easily by changes in fire, grazing, or climate. We synthesize the history and ecological impacts of the rapid expansion and eradication of an exotic large herbivore, the Asian water buf...

Frequent fire is a feature of the mesic Australian savannas, yet little is known about its effect on tree growth rates. Growth data are critical for the development of demographic models to understand the consequences of different land management regimes. We used generalized linear mixed effects models and information-theoretic multi-model inferenc...

Tree populations in the wooded savannas of northern Australia lack a well developed seed bank, but instead rely on a persistent ground layer of suppressed juvenile plants < 1m of indeterminate ages. The feral Asian water buffalo has been implicated as a factor in inhibiting the movement of juvenile trees to sapling stage. In a 6-year field study in...

Cited By (since 1996):29, Export Date: 26 November 2013, Source: Scopus

Abstract The impact of feral Asian water buffalo (Bubalus bubalis) and season of fire on growth and survival of mature trees was monitored over 8 years in the eucalypt savannas of Kakadu National Park. Permanently marked plots were paired on either side of a 25-km-long buffalo-proof fence at three locations on an elevational gradient, from ridge-to...

The biomass of component parts of individuals of three dominant canopy tree species in the northern savannas of Australia was determined from field populations in World Heritage Kakadu National Park. Forty individual trees of Eucalyptus tetrodonta F. Muell., E. miniata Cunn. ex Schauer and E. papuana F.Muell., representing a range in size from 4 to...

Oral rabies vaccine-laden baits, with a tetracycline biomarker, were distributed in Pinellas County (Florida, USA) by helicopter drop and from cars from January to April 1997. A total of 130,320 baits was distributed throughout the county, yielding an average bait density of 185 baits per km2. Bait ingestion was estimated by microscopic detection o...

The reduced frequency of fire in southeastern pine savannas of the USA over the past 6 decades has caused increases in woody species cover and decreases in herbaceous species cover. In an experimental field study we examined the response of Lilium catesbaei to fire and roller-chopping (common management tools) in saw-palmetto-dominated dry prairie...

Rabies is enzootic in raccoons (Procyon lotor) in the eastern United States. Oral vaccination of free-ranging raccoons against rabies has the potential to control the disease in a principal reservoir and reduce the risk of rabies exposure among domestic animals and humans. Free-ranging animal contact with baits containing a vaccinia virus recombina...

This research demonstrates that frequently used vegetation indices not be applied comprehensively across subtropical, semi-arid and arid zones, Zonal, species specific band combinations are considered more sensitive to changing conditions. In three areas within a subtropical to arid climatic gradient, ground radiometer readings were undertaken to e...

A survey of the distribution and abundance of invasive alien plant species in Kakadu National Park in Australia's tropical Northern Territory was undertaken to provide a basis for management. Some 5·8% (89 species) of the vascular flora of Kakadu were considered invasive aliens. The majority of these species were either rare in distribution or wide...

This is the fifth volume in a series of publications on the ecology of tropical savannas, sponsored by the UNESCO Man & the Biosphere Programme. It comprises 23 research papers presented at a symposium, in Darwin, 1988. These are divided into four sections: overviews of Australasian savannas; abiotic and biotic ecological determinants of savannas;...

Intercontinental comparisons can provide insights to scientists trying to understand the functioning of their own savanna lands. This article presents conclusions drawn from twenty-three articles published in a double volume issue of the Journal of Biogeography (17). Topics include the relative roles of herbivory and fire, of vertebrate vs. inverte...

The main task of rangeland restoration seems to be one of repair, or reassembly, of damaged landscapes and biota, but in fact, managers and scientists must assemble entirely new communities of plants and animals. The goals of particular restoration projects vary greatly, although they often contain the same set of potentially incompatible qualities...

Time of flowering of transplants was consistent among replicates of individual clones across the soil moisture gradient and regardless of the size of the transplants themselves, or the height of surrounding vegetation. Further, the flowering times of the transplants were significantly positively correlated with the flowering times of the original p...

Achenes of five goldenrod species (Solidago canadensis, S. graminifolia, S. juncea, S. nemoralis and S. speciosa) were collected from two old-field sites in southern Michigan to compare seed biomass and resource allocation within the fruit. The taxa differed from one another on the basis of total achene biomass as well as absolute biomass of embryo...

Competitive effect and response were inversely correlated. The inverse correlation led to a hierarchy of competitive ability, with Ambrosia artemisiifolia being the competitive dominant, followed by Agropyron repens, Plantago lanceolata, and finally the competitive subordinates Chenopodium album, Lepidium campestre (used in Year 1), and Trifolium r...

Knowledge of how seed production is regulated by components of seed yield can provide insight into what determines fitness in natural populations. This study examines patterns and sources of variation and interaction among components of seed yield within and among 10 populations of a perennial weed. Much of the variation in total yield among indivi...

Kakadu National Park large, diverse and ecologically intact. It is both representative and unique. It is representative of the ecosystems of a vast area of northern Australia, and is unique in that it incorporates within one drainage basin all the major habitat types of the Top End. Species have not been lost from the area, unlike most areas of the...

The Park is large, diverse and ecologically intact. It is representative of the ecosystems of a vast area of N Australia, and is unique in that it incorporates within one drainage basin all the major habitat types of the Top End. Species have not been lost from the area, unlike most areas of the Australian continent. Environmental damage caused by...

Summer-flowering old-field annuals do not extend into the often adjacent disturbed woodland areas because the old-field annuals do not allocate enough biomass to reproduction at the low light levels typical of the disturbed woodland environment, to produce enough seeds to allow for population replacement. Summer-flowering woodland annuals do not co...

Seasonal patterns of leaf water potential and stomatal conductances were determined for two species of goldenrods (Solidago juncea, a dry site species, and S canadensis, a wet site species) in greenhouse experiments Both seedlings and genetically-identical clonal transplants grown across broad gradients of soil moisture-holding capacity were used T...

We investigated the effects of size of opening in the vegetation and litter cover on seedling establishment of two species of goldenrods (Solidago spp.) in an abandoned field in southwestern Michigan, U.S.A. Seeds of S. canadensis and S. juncea were sown into clipped plots, ranging from 0 cm (control, unclipped) to 100 cm in diameter, with and with...

Argues that, in sessile plants at least, competitive interactions are not usually species-specific and that there exists a large degree of equivalence of the effect of species of similar growth form on the ability of any particular species to establish within a community. This null hypothesis of equivalence of competitive effects is based on 3 char...

One of the underlying assumptions of both theoretical and empirical community ecology is that the processes determining community composition and abundance of species are interactions specific to particular pairs of species. However, we argue that, in sessile plants at least, competitive interactions are not usually species-specific and that there...

Four co-occurring species of goldenrod bloom at different times with varying degrees of overlap; in order of peak flowering they are Solidago juncea, S. graminifolia, S. canadensis, and S. nemoralis. All four species are self-incompatible and require an insect vector for successful seed-set. First, the relationship between flowering time and seed-s...

Water use patterns and the seasonal progression of functional leaf area were determined for Solidago canadensis L. var. scabra and S. juncea Ait., two species of cooccurring goldenrods which differ in their competitive ability and distribution along soil moisture gradients. Field measurements of diurnal trends in stomatal conductances and leaf wate...

Individual plants of Arctium minus (Hill) Bernh. (common burdock), a "biennial," were marked and followed for 3 years in an old-field population in southwestern Michigan. In addition, growth and survival of A. minus individuals derived from seed sown in cleared plots and natural vegetation were monitored for 2 years. Seedling emergence and survival...

The @'biennial@' plant series Verbascum thapsus, Oenothera biennis, Daucas carota, and Tragopogon dubius are all found in abandoned agricultural fields, but they differ in their time of first appearance, peak abundance, and length of time populations persist. In experimental field studies these species showed differences in their abilities to colon...

Trees invading 10-year and 16-year-old abandoned fields in Michigan were aged to determine year of establishment. Vegetation cover was mapped to develop correlates between tree establishment patterns and vegetation type. Few trees established in the 1st 5 years after the fields were abandoned from cropping. Most (74%) of the 947 individual trees we...

A field study of resource allocation in Potentilla recta is used to illustrate problems in both intra- and interspecific comparisons of reproductive effort in plants. Resource allocation was compared in three populations of P. recta from habitats differing in successional maturity. In the first year of study average reproductive effort declined sig...

Solidago canadensis L. is a native rhizomatous perennial which is characteristic of abandoned farmland. infrequently grazed pasture. waste areas. and tall-grass prairies in North America. original research and information from other studies are incorporated into a summary of the biology of this species complex. The review uses the taxonomic treatme...

Arctium minus (Hill) Bernh. , common burdock, and A. lappa L. , great burdock, are introduced weeds of abandoned fields, roadsides, pastures and streambanks. The species are naturalized throughout much of southern Canada, especially in the eastern piovinces, and the U.S.A. A summary of the biology of these two ruderal species is presented as part o...

A method is developed for determining the exact value of the intrinsic rate of increase of populations which have heterogeneous life histories. The method works whenever the life history can be represented by a finite set of "reproductive paths" taken by individual members of the population. The finite rate of increase is found as the largest real...

Ecological approaches are used to address the question of how similar plant species manage to coexist in a common habitat. Because plants are sessile and generally require similar classes of resources from their environments (eg, light, nutrients, pollinators), competition is basically for space. This paper discusses individual plant characteristic...

Verbascum thapsus L., common mullein, and V. blattarla L., moth mullein, are introduced weeds of pasture, abandoned fields, and roadsides occurring in widelj'-spaced, but dense patches in Southem Ontario, Quebec, the Maritime Provinces, British Columbia and throughout the U.S.A. Original research and information from other studies are incorporated...

A transient behavior analysis of the population dynamics of an herbaceous plant species (teasel, Dipsacus sylvestris Huds.) was developed to contrast with the long-term limiting response analysis of an earlier study. Following the arrival of a cohort of seeds at a site, there is typically an immediate increase in the rate of growth of rosette cover...

Mathematical models are developed to examine the population-level response of an herbaceous plant species (teasel, Dipsacus sylvestris Huds.) which was experimentally introduced into several habitats and monitored for 5 yr. Models based on morphological stages (size) rather than chronological age give more satisfactory results. Populations growth r...

In order to gain understanding of the relationships of life history characteristics to colonization success, species cohabitation, and species replacement, a known number of seeds (fruits, achenes) of teasel, a "biennial' plant species, Dipsacus sylvestris Huds. were experimentally introduced into 52 permanent plots within each of 8 contiguous aban...

Agropyron repens (L.) Beauv., quack grass, is an introduced perennial grass found in all provinces of Canada and the Northwest Territories. In most agricultural areas it is a serious weed of cultivated crops; alternately it can be used as pasture or hay. A surnmary of the biology of quack grass is presented as part of a series of the biology of Can...

An integrative approach to the study of secondary succession involves considerations of plant life-history characteristics, species coexistence, and species replacements. Competition is of primary concern as an ecological factor influencing proximal changes in species composition and as an evolutionary factor in the selection of life-history charac...

Original research and information from other studies are incorporated into a summary of the biology of weedy species of Potentilla found in Canada: P. recta L. (sulphur cinquefoil, an introduced perennial), P. norvegica L. (rough cinquefoil, an annual, biennial, or rarely perennial), and P. argentea L. (silvery cinquefoil, a perennial). Les auteurs...

Field and greenhouse studies were conducted to examine the role of plant litter in the germination of teasel (Dipsacus sylvestris Huds.) seed The field study revealed that litter (mainly quack grass, Agropyron repens) inhibits germination. When litter was removed just prior to sowing, 32.0% of the seeds germinated, compared to, 0.8% when litter rem...

In field populations of the biennial plant (Dipsacus fullonum L.) the probability that an individual will die, remain vegetative, or flower during a particular growing season is highly correlated with the size of its vegetative rosette at the end of the growing season of the preceding year. Further, a rosette forms a flowering stalk only after atta...

Dipsacus sylvestris Huds., wild teasel, is an introduced weed of pastures, abandoned fields and roadsides occurring in widely-spaced but very dense patches in southern Ontario, Quebec, northeastern U.S.A., and northwestern U.S.A. Original research and information from other studies are incorporated into a summary of the biology of this fugitive pla...

This article reports on an academic program which aimed to foster the integration of ecologists and engineers/mathematicians which was established at Michigan State University in the early 1970s when systems modelling was first applied to ecological/environmental problems. The authors are an ecologist and systems scientist, respectively; many pract...

We propose that plants possessing the C4-dicarboxylic acid pathway of photosynthetic carbon fixation are generally inferior food sources for herbivores, and are often avoided by them, relative to plants possessing only the C3-Calvin cycle pathway. As initial support of this hypothesis, we present data from the literature, dealing primarily with ins...

Thesis (Ph. D.)--Michigan State University, 1972. Includes bibliographical references (leaves 128-140). Photocopy of typescript. Ann Arbor: