Landscape history, time lags and drivers of change : urban natural grassland remnants in Potchefstroom, South Africa

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du Toit , M J , Kotze , D J & Cilliers , S S 2016 , ' Landscape history, time lags and drivers of change : urban natural grassland remnants in Potchefstroom, South Africa ' , Landscape Ecology , vol. 31 , no. 9 , pp. 2133-2150 . https://doi.org/10.1007/s10980-016-0386-6

Title: Landscape history, time lags and drivers of change : urban natural grassland remnants in Potchefstroom, South Africa
Author: du Toit, Marie J.; Kotze, D. Johan; Cilliers, Sarel S.
Contributor: University of Helsinki, Environmental Sciences
Date: 2016-11
Language: eng
Number of pages: 18
Belongs to series: Landscape Ecology
ISSN: 0921-2973
URI: http://hdl.handle.net/10138/224140
Abstract: The history of the landscape directly affects biotic assemblages, resulting in time lags in species response to disturbances. In highly fragmented environments, this phenomenon often causes extinction debts. However, few studies have been carried out in urban settings. To determine if there are time lags in the response of temperate natural grasslands to urbanization. Does it differ for indigenous species and for species indicative of disturbance and between woody and open grasslands? Do these time lags change over time? What are the potential landscape factors driving these changes? What are the corresponding vegetation changes? In 1995 and 2012 vegetation sampling was carried out in 43 urban grassland sites. We calculated six urbanization and landscape measures in a 500 m buffer area surrounding each site for 1938, 1961, 1970, 1994, 1999, 2006, and 2010. We used generalized linear models and model selection to determine which time period best predicted the contemporary species richness patterns. Woody grasslands showed time lags of 20-40 years. Contemporary open grassland communities were, generally, associated with more contemporary landscapes. Altitude and road network density of natural areas were the most frequent predictors of species richness. The importance of the predictors changed between the different models. Species richness, specifically, indigenous herbaceous species, declined from 1995 to 2012. The history of urbanization affects contemporary urban vegetation assemblages. This indicates potential extinction debts, which have important consequences for biodiversity conservation planning and sustainable future scenarios.
Subject: Urban ecology
Urban landscape measures
Temperate grasslands
Indigenous species
Exotic species
Disturbance indicator species
Extinction debt
EXOTIC PLANT INVASIONS
NORTH-WEST PROVINCE
PAST LAND-USE
EXTINCTION DEBT
MUNICIPAL AREA
RURAL GRADIENT
HABITAT FRAGMENTATION
SPECIES RICHNESS
LOCAL EXTINCTION
VEGETATION
1172 Environmental sciences
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