Cluster planting facilitates survival but not growth in early development of restored tropical forest

Abstract

Interspecific interactions are considered to be important structuring forces in early successional vegetation. Whereas competition seems to prevail in less severe environments, facilitation tends to increase in importance in harsh environments. Hence, facilitation is expected to play an important role in degraded tropical areas with high irradiance, heat loads, and evapotranspiration, where conditions are far from optimum for most forest species. We planned a restoration project on the southeastern Brazilian coastal plain to compare growth and survival of tree seedlings planted at two densities (isolated or aggregated) in a factorial experiment with nutrient addition. We monitored survival, height, ground level diameter, and crown projection of 4132 saplings from 19 species that ranged along a successional gradient, over an 18-month period. We used mixed-effect models to analyze the relationship between species performance and treatments, and Akaike's information criterion (AIC) to select the models. The best model showed higher survival in aggregated plantations (indicating facilitation) for non-pioneer (slower growing) species. In contrast, we found lower diameter growth in aggregated plantation (indicating competition). Fertilizer addition did not affect survival in clusters, but, surprisingly, it had a negative effect on isolated plants of both pioneer and non-pioneer species. Fertilizer addition had a positive effect on diameter and crown projection growth in aggregated plantations (reducing competition), especially for pioneer species. Thus, whether facilitation or competition was the predominant interaction depended on the effect analyzed. As establishment of non-pioneer species in disturbed sites can be challenging, restoration designs could take advantage of higher survival rates in clusters and use resource addition to ameliorate growth and decrease competition for limited resources. Zusammenfassung

The role of nurse successional stages on species‐specific facilitation in drylands: Nurse traits and facilitation skills

“…Nurse successional stage, therefore, could partially explain species-specific interactions. Our results also corroborate three process that are frequently reported in the literature: (1) Facilitation is a widespread process in harsh environments (Flores & Jurado, 2003;He, Bertness, & Altieri, 2013;Soliveres & Maestre, 2014); (2) Species-specific interaction outcomes are common for semiarid biomes (Landero & Valiente-Banuet, 2010;Paterno et al, 2016;Wright, Schnitzer, & Reich, 2014); and (3) Nurse positive effects are stronger on survival than growth, a general pattern found in different ecosystem types (Bertoncello, Oliveira, Hool, & Martini, 2016;Ganade & Brown, 2002;Gómez-Aparicio, 2009).…”

“…Our results emphasize that the Brazilian Caatinga is a harsh environment where drought is a strong force shaping plant recruitment. Despite generally positive nurse effects on survival (Bertoncello et al., ; He et al., ), drought was still the strongest force limiting regeneration (Jankju, ). It is important to understand that wet seasons can be very erratic in Caatinga, and seedlings have to reach a certain root size, and a minimum amount of storage to be able to keep themselves alive through dry periods until the next rain arrives.…”

Litterfall Production as a Function of Planting Seedlings System in a Two Years Forest Restoration Area in the Coastal - Plain of Caraguatatuba, São Paulo, Brazil

“…However, the planting of cluster seedlings have higher costs, as it makes it difficult to mechanize the implantation, management and monitoring of the area. On the other hand, a recent work carried out in the same study area showed lower mortality of non-pioneer species in cluster than row planting system (Bertoncello et al, 2016), which suggests that the effects of planting techniques differ among ecological process, so that the recommendation of restoration techniques should not be based on a single ecological process. Also, the combined use of different planting techniques can maximize the recovery of several ecological processes in the restoration of degraded areas.…”

“…The planting of native seedlings was carried out between February and April 2012, with 15,693 seedlings of 54 tree species, including pioneer and non-pioneer species (Bertoncello et al, 2016). Seeds were previously collected in forest fragments in the SP Coastal-plain.…”

Facilitation and competition in coastal dunes: meta-analysis of determinants of plant interactions

“…Net outcome of interaction also depends on the choice of performance estimator (Foster 2002, Franks 2003, Gómez-Aparicio 2009, Bertoncello et al 2016).…”