Desiccation and post-dispersal infestation of acorns of Quercus schottkyana, a dominant evergreen oak in SW China

The Asian evergreen broad-leaved forests in Southwestern China are among the most diverse in the world. Quercus schottkyana is a dominant oak in these forests but its seedlings are noticeably uncommon. Quercus schottkyana has desiccation-sensitive acorns despite being widespread in regions with a distinct 5- to 6-month dry season shortly following acorn drop. Here we investigated the effects of desiccation and post-dispersal predation by rodents and bark beetles [Coccotrypes sp. (Coleoptera: Curculionidae)] on acorns of Q. schottkyana. Most acorns of Q. schottkyana lie on the soil surface after dispersal, but some acorns (1.5 %) were buried. For the sound acorns (acorns not infested by weevils) that lay on the soil surface during the dry season, moisture content decreased to 34.6 % in the cotyledons and 42.3 % in the axes and viability decreased significantly from 81 to 32 %. Surface acorns were also subject to high infestation by bark beetles which emerge towards the end of the dry season and cause high mortality of acorns that survived the dry season. Burial effectively retained moisture and viability of acorns during the dry season. However, approximately 75 % of buried sound acorns were subsequently damaged by bark beetles. We show that desiccation and post-dispersal infestation by Coccotrypes sp. killed about 98 % of sound acorns on the soil surface before germination could begin in June but about 20 % of buried sound acorns germinated. However, because most acorns of Q. schottkyana lie on the soil surface and there is limited burial, regeneration of this species from acorns is problematic.