Inclusion of Native and Alien Species in Temperate Nature Reserves: an Historical Study from Central Europe

Abstract

Abstract: We studied the establishment and inclusion of native and alien plant species in nature reserves in the Czech Republic. Our aim was to answer the following questions: Do young and old nature reserves contain the same proportion of invasive plant species? Does the time of their introduction affect their representation in these reserves? We obtained recent lists of vascular plant species for 302 reserves established since 1838 and designated the species as native or alien. We divided the latter category into archaeophytes and neophytes, introduced before and after 1500, respectively. The increase in the number of reserves and species was evaluated by inclusion curves. For inclusion curves describing an increase in the number of reserves, the estimated time of 50% inclusion indicated when half the reserves of a particular type were established. For inclusion curves describing an increase in the number of species, the estimated time of 50% inclusion indicated when half the species of a particular category ( native species, all aliens, archaeophytes, neophytes ), reported from the country, were included in the nature reserves. The forest and dry‐grassland reserves were established earlier than those in wetlands and peat bogs, whereas humid‐grassland reserves tended to be the most recently established. Half the native species were included significantly earlier ( after 25 years ) than half of alien species ( 86 years ), and half the neophytes were included later ( 143 years ) than half the archaeophytes ( 31 years ). Early reserves harbor a significantly lower number of alien species than those established later. These reserves include a higher proportion of the Czech Republic's native species and archaeophytes than of its neophytes. There was no difference in the relative rates of inclusion of native species, archaeophytes, and neophytes. However, the fact that the same inclusion rate applies to neophytes, a group with an increasing species pool, as to archaeophytes and native species, which both have constant species pools, suggests that natural vegetation in nature reserves is an effective barrier against the establishment of alien species. On a historical time scale, the early establishment of nature reserves in a given country decreases the probability that the reserve will be invaded by alien plants.