Seed bank strategies in Patagonian semiarid grasslands in relation to their management and conservation

BERTILLER, M.B; ALOIA, D

BIODIVERSITY AND CONSERVATION

SPRINGER

Lugar: Berlin; Año: 1997 vol. 6 p. 639 - 650

0960-3115

We addressed the following questions: (a) May di€erent seed bank functional types (SBFT), de®nedon the basis of singularities of their persistence in soil, be identi®ed in the Festuca pallescensgrasslands? (b) Do di€erent above-ground vegetation states modify the expression of SBFTsingularities? (c) Is the potential for vegetation recovery from the soil seed bank associated with thecharacteristics of their SBFT? To address these questions we examined the sizes of immediately andnon-immediately-germinable seed banks (IGSB and NIGSB, respectively) in four di€erent vegetation states of the steppe of F. pallescens resulting from the combined e€ects of topography andgrazing. The results show that four lifeforms (perennial grasses, perennial graminoid non-grasses,annual dicots and annual grasses) display three characteristic SBFT. These are: (1) a transient typeconstituted by perennial grasses (SBFT1), (2) an intermediate type represented by annuals (SBFT2),and (3) a persistent type characteristic of one perennial graminoid non-grass (SBFT3). Other lifeforms (perennial dicots and biennials) could not be assigned to any of these types or characterizedinto a de®nite one. Seed bank functional types do not change among vegetation states in terms of therelative proportions of IGSB and NIGSB, although di€erences in the absolute and the relative size ofeach SBFT could be found. Species with persistent or mixed persistent/non-persistent seed banktypes (SBFT2, SBFT3, etc.) colonize habitats disturbed by grazing with more success than those withnon-persistent seed banks (SBFT1). Species with persistent seed banks are over-represented in thesoil seed bank in relation to their contribution to above-ground cover. Management strategies forconservation in these grasslands could conveniently be targeted to increase the seed rain of perennialgrasses as well as to the creation of suitable micro-environmental conditions to enhance theirestablishment.