Can salvage logging affect seed dispersal by birds into burned forests?

Abstract

The recovery of vegetation in Mediterranean ecosystems after wildfire is mostly a result of direct regeneration, since the same species existing before the fire regenerate on-site by seeding or resprouting. However, the possibility of plant colonization by dispersal of seeds from unburned areas remains poorly studied. We addressed the role of the frugivorous, bird-dependent seed dispersal (seed rain) of fleshy-fruited plants in a burned and managed forest in the second winter after a fire, before on-site fruit production had begun. We also assessed the effect on seed rain of different microhabitats resulting from salvage logging (erosion barriers, standing snags, open areas), as well as the microhabitats of unlogged patches and an unburned control forest, taking account of the importance of perches as seed rain sites. We found considerable seed rain by birds in the burned area. Seeds, mostly from Olive trees Olea europaea and Evergreen pistaches Pistacia lentiscus, belonged to plants fruiting only in surrounding unburned areas. Seed rain was heterogeneous, and depended on microhabitat, with the highest seed density in the unburned control forest but closely followed by the wood piles of erosion barriers. In contrast, very low densities were found under perches of standing snags. Furthermore, frugivorous bird richness seemed to be higher in the erosion barriers than elsewhere. Our results highlight the importance of this specific post-fire management in bird-dependent seed rain and also may suggest a consequent heterogeneous distribution of fleshy-fruited plants in burned and managed areas. However, there needs to be more study of the establishment success of dispersed seeds before an accurate assessment can be made of the role of bird-mediated seed dispersal in post-fire regeneration.

Deadwood anisotropic facilitation on seedling establishment after a stand-replacing wildfire in Aosta Valley (NW Italy)

“…Furthermore salvage harvesting can produce ground disturbance affecting vegetation development (Macdonald, 2007). The presence of patches of standing dead trees could moreover favour tree recruitment by providing perching sites for frugivore birds, potentially improving species richness in the regeneration layer (McClanahan and Wolfe, 1993;Rost et al, 2009;Castro et al, 2009). Ground cover conditions contributed to patterns of seedling occurrence.…”

Post‐fire salvage logging alters a key plant‐animal interaction for forest regeneration

“…Different post-fire treatments altered jay behavior in terms of seed dispersal, which subsequently altered the spatial pattern of seedling recruitment. Recent studies are showing that salvage logging alters other interactions as well, such as herbivory (increasing its impact after log removal; Relva et al 2009), ungulatewolf interaction (Hebblewhite et al 2009), or seed dispersal by frugivorous birds (Rost et al 2009(Rost et al , 2010. All this supports that salvage logging may interfere with a wide array of species interactions, adding to the growing body of evidence that shows its potential impact at the ecosystem level.…”

“…By contrast, salvage logging reduced the natural recruitment of new oaks, as it created a habitat not used by the main seed disperser (Castro et al 2010a). Furthermore, it is likely that the conditions of our experimental salvage logging even produced an over-estimation of the role of jays in the salvage logging treatment, as the permanence of trunk piles could have increased the use of this habitat for caching (see Rost et al 2009Rost et al , 2010 for a similar pattern for frugivorous, bird-dependent seed dispersal). In addition, seedling recruitment in the salvaged areas is largely dependent on the presence of live trees that survived the fire (either isolated or in small clusters), as those trees were highly attractive to jays.…”

“…It is well known that animal species are affected by intermediate to severe disturbances that modify habitat structure and complexity (e.g., Cody 1985), including the removal of dead trees (e.g., Hutto 2006, Relva et al 2009, Castro et al 2010a. The degree to which post-fire salvage logging changes the habitat could then be of great importance for key plant-animal interactions, as is the case with seed dispersal (Rost et al 2009, Castro et al 2010a, Rost et al 2010. This can affect the resilience of the ecosystem in terms of the time needed for natural regeneration after fire.…”

Building wood debris piles benefits avian seed dispersers in burned and logged Mediterranean pine forests

“…Previous studies have reported that bird-dependent seed rain strongly relies on habitat structures that act as dispersal foci, such as isolated trees that act as perches (Guevara & Laborde, 1993;Pausas et al 2006, Herrera & García 2009). After logging, wood debris piles and barriers built in a burned pine forest can also act as dispersal foci (Rost et al 2009). Thus, the variability of postfire treatments after logging, which leads to the presence of different microhabitats on a small scale, may have important implications for bird-dependent seed rain, depending on the differential use that seed dispersers make of the resulting microhabitats.…”