Carex disperma Dewey versus Carex loliacea L. (Cyperaceae): distribution dynamics and conservation status in Poland.
<em>Carex disperma</em> Dewey reaches its south-eastern range limit in north-eastern Poland. It has often been confused with <em>Carex loliacea</em> L. In this paper the diagnostic features of both species are presented. A total of about 47 reliable localities of <em>C. disperma</em> were recorded within the present borders of Poland. Less than one-third of them have only been confirmed recently. They are aggregated in large forest complexes in north-eastern Poland (Romincka, Białowieża, Borki, Augustów and Knyszyn Forests). A list of localities of <em>C. disperma</em> based on herbarium records, credible literature data and the author's own data is provided, as well as maps of distribution of both <em>C. disperma</em> and <em>C. loliacea</em> in Poland. The existence of <em>C. disperma</em> × <em>C. loliacea</em> hybrid was not confirmed. Considering the number of localities, dynamics and population sizes of both species it is clear that <em>C. disperma</em> is a species with higher conservation value than <em>C. loliacea</em>. Unlike <em>C. disperma</em>, the latter species is not threatened with extinction in Poland. The resources of <em>C. disperma</em> are very limited and the species needs conservation measures such as creating sufficiently large nature reserves where appropriate hydrological conditions can be maintained.