Abstract
t is generally acknowledged that land-use structure and its changes influences levels of invasion by alien plants across the landscape. In this study, we asked how land-use changes over the last 180 years influenced spatial patterns of alien plant invasions in the Czech Republic.
We hypothesize that (i) dynamically changing landscapes with a high level of disturbances host more alien or invasive species than those with long-term habitat continuity, and (ii) land-use changes resulting in more degraded landscape (e.g. increase in built-up areas or arable land) are associated with increased invasion levels. To test these hypotheses, we used plant distribution data from the Pladias database.
This dataset contains species occurrence records in 2370 grid cells (~ 6 x 5,5 km) of floristic mapping covering the area of the Czech Republic. Environmental data (e.g. mean annual temperature, annual precipitation) and historical land-use data (indices of land-use change) were used as explanatory variables of invasion levels, which were defined as the proportion of alien species among the total flora in each grid cell.
Alien plants were considered either as one group or divided according to (i) the most advanced stage they have reached in the invasion process (naturalized and invasive species) or (ii) the residence time status (archaeophytes and neophytes). Historical land-use data were extracted from digitized topographical maps for the following periods: 1836-1852 (2nd Austrian Military Survey), 1876-1880 (3rd Austrian Military Survey), 1952-1955, 1988-1995, and 2002-2006.
These data allowed us to quantify individual land-use changes (e.g. afforestation or expansion of built-up areas) in each grid cell and between each period. The proportions of neophytes, naturalized and invasive species in the grid cells were best explained by the mean annual temperature followed by an increase in built-up area and a decrease in forest area.
A weaker correlation was found with changes in the proportion of grasslands and arable land. The proportion of archaeophytes was best explained by a decrease in forest area, similar to neophytes, but also by an increase in the area of arable land.
Our results corroborate the second hypothesis that the extension of human-made land-use types increases invasion levels. However, the correlations between the overall landscape change and the levels of invasion were very weak.