Seed limitation during early forest succession in a rural landscape onChiloé Island,Chile: implications for temperate forest restoration

Abstract

Summary1. Re-establishment of native forest species in rural landscapes may be conditioned by the proximity of seed sources, the post-disturbance composition of successional patches and the seed dispersal patterns of frugivores. Knowledge of seed dispersal rates into early seral communities, and how these are influenced by the structural and compositional characteristics of these communities is still quite poor. 2. We used an observational approach to quantify the seed rain and seed limitation (SL) (proportion of sites to which seeds were not dispersed) of woody species during two growing seasons in three early successional shrublands with contrasting species composition and attractiveness to frugivores on Chiloe´Island, Chile. We compared species immigration based on dispersal types (bird-vs. wind dispersed) and life-form (shrubs vs. trees). Concomitantly, we used an experimental approach to test whether artificial perches would relieve SL and enhance seed dispersal and seedling establishment of fleshy-fruited species. 3. Most seeds collected were of pioneer shrubs already present in the early successional sites. Few (5%) were from trees appearing only in the surrounding second-growth forest. Density of seeds from fleshy-fruited trees and shrubs was seven times higher in the seral community most attractive to frugivores, whereas density of seeds from wind-dispersed trees was similar among communities. Artificial perches significantly increased the density and species richness of seeds from fleshy-fruited trees in all communities, but the magnitude of the facilitation effect depended on the ecological context of each seral community. Seed rain enhancement was higher in the community less attractive to frugivores. Seedling recruitment, however, remained low even under perches, indicating that additional constraints act during seed germination and/or seedling survival and growth. 4. Synthesis and applications. Forest succession in this rural landscape may be delayed or arrested by extremely low seed rain, despite the proximity (<100 m) of seed sources in older forest patches. Although artificial perches significantly enhance inputs of birddispersed tree seeds into shrublands, especially where fleshy-fruited pioneer species are absent from the seral community, they do not overcome other site-related barriers to establishment, as the lack of shaded places and limited soil drainage. Thus, in some ecological contexts, multiple approaches, such as direct seeding or planting, and the use of nurse plants, may be required to enhance seed rain and seedling establishment of fleshy-fruited species.

Distinguishing the importance between habitat specialization and dispersal limitation on species turnover

“…Our inference was further confirmed by the significant association between GeoD and turnover deviation (Table 1), whereas GeoD was always used as a proxy for dispersal limitation (Kristiansen et al 2012;Tuomisto et al 2012). Moreover, the importance of dispersal limitation has also been extensively proved in the temperate forests using different methods, such as seed addition experiments (Tuomisto et al 2003;Bustamante-S anchez and Armesto 2012;Myers et al 2013). In conclusion, identifying the relative influence of dispersal limitation is of particular importance for our understanding the community assembly, for which dispersal may be the first step for community assembly (Egler 1954).…”

“…Moreover, the importance of dispersal limitation has also been extensively proved in the temperate forests using different methods, such as seed addition experiments (Tuomisto et al. ; Bustamante‐Sánchez and Armesto ; Myers et al. ).…”

Changes in the fruiting landscape relax restrictions on endozoochorous tree dispersal into deforested lands

“…However, even in these cases, seed deposition is restricted to the area beneath the canopy of remnant trees, resulting in a pattern of cover‐nucleated seed rain similar to that found in forest areas (Duncan & Chapman ; Carrière et al. ; Bustamante‐Sánchez & Armesto ).…”

“…Debussche & Lepart ; Holl et al. ; Duncan & Chapman ; Bustamante‐Sánchez & Armesto ). Seed arrival in deforested lands depends mostly on two landscape features, namely, the distance from seed sources to recovering sites and the quantity of surrounding seed sources, usually represented by the amount and spatial configuration of cover of remnant forest (Kunstler et al.…”

Artificial Perches and Solarization for Forest Restoration: Assessment of Their Value

“…The recruitment of seed dispersed beneath artificial perches is, however, often reduced compared to the seed rain attracted [3, 9–10-]. Recruitment of these seedlings may be prevented by adverse micro-climatic conditions, low soil nutrient availability, low seed viability, seed predation [11],or competition from other plants, especially non-native and invasive species [3, 6, 11].…”