Plant traits and local extinctions in natural grasslands along an urban–rural gradient

Summary 1 The effect that the surrounding landscape matrix has on the loss of species from fragmented patches remains largely unknown. To determine whether there were differences in the persistence of plants inhabiting remnant patches in contrasting landscape types we examined the local extinction of grassland plants along an urban–rural gradient in western Victoria, Australia. 2 Thirty small grassland remnants that had been comprehensively surveyed between 1979 and 1990 were intensively re-surveyed. A total of 289 (26%) of the 1104 plant populations present in the 1980s were not relocated and were presumed to be locally extinct. The proportion of populations lost differed along the gradient, with higher local extinction rates at patches in urban (37%) and peri-urban landscapes (27%) than those in the rural landscape (20%). 3 We calculated the probability of local extinction of species in urban, peri-urban and rural landscapes using Bayesian logistic regression models. Across all plant functional traits examined, species had a consistently higher probability of local extinction in the urban landscape. 4 Species that were geophytes or hemicryptophytes with a flat rosette and species with seeds dispersed by wind or ants had substantially increased risks of extinction in the urban landscape. Low seed mass, the lack of vegetative reproduction and the presence of a soil-stored seed bank increased the probability of local extinction in all landscapes. Regionally rare species had a higher probability of local extinction in rural and peri-urban landscapes but rarity had little influence on extinction risk in urban landscapes. 5 Urbanization has a strong influence on the species composition of urban grasslands and substantially increases the probability of local extinction of plants with particular combinations of functional traits.

[1]  J. Morgan.  Composition and seasonal flux of the soil seed bank of species‐rich Themeda triandra grasslands in relation to burning history , 1998 .

[2]  R. Bagnall.  A study of human impact on an urban forest remnant: Redwood Bush, Tawa, near Wellington, New Zealand , 1979 .

[3]  A. Clements.  Suburban development and resultant changes in the vegetation of the bushland of the northern Sydney region , 2006 .

[4]  C. Raunkiær,et al.  The life forms of plants and statistical plant geography , 1934 .

[5]  M. Mcdonnell,et al.  Factors influencing the loss of an endangered ecosystem in an urbanising landscape: a case study of native grasslands from Melbourne, Australia , 2005 .

[6]  S. Pickett,et al.  Ecosystem Structure and Function along Urban‐Rural Gradients: An Unexploited Opportunity for Ecology , 1990 .

[7]  M. J. Kropff,et al.  Plant strategies and agricultural landscapes: survival in spatially and temporally fragmented habitat , 2002, Landscape Ecology.

[8]  T. Givnish,et al.  Ecological Determinants of Species Loss in Remnant Prairies , 1996, Science.

[9]  R. Buckney,et al.  Invasion of exotic plants in nutrient‐enriched urban bushland , 2002 .

[10]  J. Morgan.  Seedling recruitment patterns over 4 years in an Australian perennial grassland community with different fire histories , 2001 .

[11]  G. Matlack.  Sociological edge effects: Spatial distribution of human impact in suburban forest fragments , 1993 .

[12]  G. Heil,et al.  Reduced colonization capacity in fragmented populations of wind‐dispersed grassland forbs , 2002 .

[13]  J. Morgan,et al.  Effects of time-since-fire on the tussock dynamics of a dominant grass (Themeda triandra) in a temperate Australian grassland , 1999 .

[14]  Y. Haila,et al.  Plants in a boreal city: ecological characteristics of vegetation in Helsinki and its surroundings, southern Finland , 1990 .

[15]  P. Reich,et al.  The Evolution of Plant Functional Variation: Traits, Spectra, and Strategies , 2003, International Journal of Plant Sciences.

[16]  David M. Theobald,et al.  Placing exurban land‐use change in a human modification framework , 2004 .

[17]  Johan Ehrlén,et al.  Habitat configuration, species traits and plant distributions , 2002 .

[18]  P. Groffman,et al.  Soil carbon pools and fluxes in urban ecosystems. , 2002, Environmental pollution.

[19]  R. Bradstock,et al.  An application of plant functional types to fire management in a conservation reserve in southeastern Australia , 2003 .

[20]  S. Pickett,et al.  Litter decomposition and nitrogen mineralization in oak stands along an urban-rural land use gradient , 1997, Urban Ecosystems.

[21]  P. Wade.  Bayesian Methods in Conservation Biology , 2000 .

[22]  J. P. Grime.  Declining plant diversity: empty niches or functional shifts? , 2002 .

[23]  J. Nichols,et al.  OF BUGS AND BIRDS: MARKOV CHAIN MONTE CARLO FOR HIERARCHICAL MODELING IN WILDLIFE RESEARCH , 2002 .

[24]  W. Zipperer,et al.  Urban ecological systems: linking terrestrial ecological, physical, and socioeconomic components of metropolitan areas , 2001 .

[25]  R. O'Neill,et al.  Landscape Ecology Explained@@@Landscape Ecology in Theory and Practice: Pattern and Process , 2001 .

[26]  M. Mcdonnell,et al.  The soil seed bank and its relationship to the aboveground vegetation in deciduous forests in New York City , 1998, Urban Ecosystems.

[27]  M. Carreiro,et al.  Forest leaf litter quantity and seedling occurrence along an urban-rural gradient , 1998, Urban Ecosystems.

[28]  John A. Wiens,et al.  Landscape mosaics and ecological theory , 1995 .

[29]  D. Lindenmayer,et al.  Conserving Forest Biodiversity: A Comprehensive, Multiscaled Approach , 2002 .

[30]  R. Tremont.  Life-History Attributes of Plants in Grazed and Ungrazed Grasslands on the Northern Tablelands of New South Wales , 1994 .

[31]  J. Morgan.  Ecological Studies of the Endangered Rutidosis leptorrhynchoides. II. Patterns of Seedling Emergence and Survival in a Native Grassland , 1995 .

[32]  P. Klinkhamer,et al.  Declining plant species richness of grassland ditch banks—a problem of colonisation or extinction? , 2003 .

[33]  Ian J. Wright,et al.  Differences in seedling growth behaviour among species: trait correlations across species, and trait shifts along nutrient compared to rainfall gradients , 1999 .

[34]  S. Pickett,et al.  The Application of the Ecological Gradient Paradigm to the Study of Urban Effects , 1993 .

[35]  Neville Nicholls,et al.  commentary and analysis: The Insignificance of Significance Testing , 2001 .

[36]  I. Noble,et al.  The Use of Vital Attributes to Predict Successional Changes in Plant Communities Subject to Recurrent Disturbances , 1980 .

[37]  Marc Kéry,et al.  Extinction Rate Estimates for Plant Populations in Revisitation Studies: Importance of Detectability , 2004 .

[38]  J. Majer,et al.  The effects of urbanization on the ant fauna of the Swan Coastal Plain near Perth, Western Australia , 1986 .

[39]  M. Fischer,et al.  Plants with longer-lived seeds have lower local extinction rates in grassland remnants 1950–1985 , 1999, Oecologia.

[40]  I. Lunt.  A Protocol for Integrated Management, Monitoring, and Enhancement of Degraded Themeda triandra Grasslands based on Plantings of Indicator Species , 2003 .

[41]  R. Duncan,et al.  DETERMINANTS OF PLANT EXTINCTION AND RARITY 145 YEARS AFTER EUROPEAN SETTLEMENT OF AUCKLAND, NEW ZEALAND , 2000 .

[42]  S. Lavorel,et al.  Plant life-history attributes: their relationship to disturbance response in herbaceous vegetation. , 1995 .

[43]  William F. Fagan,et al.  Ground arthropod community structure in a heterogeneous urban environment , 2001 .

[44]  O. Eriksson,et al.  Abundance, distribution and life histories of grassland plants: a comparative study of 81 species , 1998 .

[45]  Douglas T. Bolger,et al.  EFFECTS OF FRAGMENTATION AND INVASION ON NATIVE ANT COMMUNITIES IN COASTAL SOUTHERN CALIFORNIA , 1998 .

[46]  Sandra Lavorel,et al.  Plant response to disturbance in a Mediterranean grassland: How many functional groups? , 1999 .

[47]  Sandra Lavorel,et al.  Disturbance response in vegetation – towards a global perspective on functional traits , 1999 .

[48]  S. Godefroid,et al.  Distribution pattern of the flora in a peri-urban forest: an effect of the city–forest ecotone , 2003 .

[49]  S. Pickett,et al.  Soil Characteristics of Oak Stands along an Urban‐Rural Land‐Use Gradient , 1995 .

[50]  S. McIntyre,et al.  Natural grassy vegetation and native forbs in temperate Australia: structure, dynamics and life histories. , 1994 .

[51]  W. Turechek,et al.  Short- and long-term effects of site factors on net N-mineralization and nitrification rates along an urban-rural gradient , 2001, Urban Ecosystems.

[52]  Raquel Montes Diez,et al.  Bayesian methods in plant conservation biology , 2003 .

[53]  I. Lunt.  The soil seed bank of a long-grazed Themeda triandra grassland in Victoria. , 1990 .

[54]  M. Westoby,et al.  Leaf-size divergence along rainfall and soil-nutrient gradients: Is the method of size reduction common among clades? , 2003 .

[55]  Y. Touyama,et al.  The Argentine ant, Linepithema humile, in Japan: Assessment of impact on species diversity of ant communities in urban environments , 2003 .

[56]  J. Morgan.  Comparative Germination Responses of 28 Temperate Grassland Species , 1998 .

[57]  M. Fischer,et al.  Local Extinctions of Plants in Remnants of Extensively Used Calcareous Grasslands 1950 –1985 , 1997 .

[58]  J. Majer,et al.  Influence of Argentine and coastal brown ant (Hymenoptera: Formicidae) invasions on ant communities in Perth gardens, Western Australia , 2000, Urban Ecosystems.

[59]  J. Morgan.  Importance of Canopy Gaps for Recruitment of some Forbs in Themeda triandra-dominated Grasslands in South-eastern Australia , 1998 .

[60]  Douglas H. Johnson.  The Insignificance of Statistical Significance Testing , 1999 .