Abstract
To measure intraspecific and interspecific interaction coefficients among tree species is the key to explore the underlying mechanisms for species coexistence and biodiversity maintenance in forests. Through the response surface experimental design, we established a long-term field experiment by planting 27,300 seedlings of four tree species (Erythrophleum fordii, Pinus massoniana, Castanopsis fissa, and Castanopsis carlesii) in 504 plots in different species combinations (six pairwise combinations of four species), abundance proportions (five abundance proportions of two species, i.e. A: B = 1:0, 3:1, 1:1, 1:3, 0:1), and stand densities (25, 36, 64, and 100 seedlings per plot). In this initial report, we aimed to quantify the relative importance of biotic and abiotic factors on seedling survival at the early stage of growth, which is a critical period for seedling establishment. We found that plot-level seedling survival rate was determined by species combination and their abundance proportion rather than stand density. At the individual level, individual survival probability was mainly explained by species identity, initial seedling size, and soil conditions rather than neighborhood competition. Our study highlights that the seedling intrinsic properties may be the key factors in determining seedling survival rate, while neighborhood effects were not yet prominent at the seedling life stage.
Highlights
Forests are one of the most important ecosystems in maintaining global biodiversity and determine ecosystem functioning and services (Lang et al, 2012; Wang et al, 2012)
The plot-level survival rates were significantly affected by species combination and abundance proportion as well as their interactions, but not affected by stand density or its interaction with species combination and abundance proportion (Table 1)
We found that species combination and abundance proportion played an important role in seedling survival in our experiment (Table 1)
Summary
Forests are one of the most important ecosystems in maintaining global biodiversity and determine ecosystem functioning and services (Lang et al, 2012; Wang et al, 2012). The tree seedling survival is known to be affected by its own intrinsic properties (e.g. its species identity and size, Wang et al, 2012) and its local conditions including biotic (e.g. neighbors, Comita and Hubbell, 2009) and abiotic factors (e.g. soil properties, Bai et al, 2012; Pu et al, 2017). Besides the intrinsic properties of tree species, many studies have found that focal seedling survival was strongly influenced by neighborhood individuals, including the number, diversity, size, and identity of neighbors (Comita and Hubbell, 2009; Chen et al, 2010; Zhu et al, 2015). Other soil properties including soil organic carbon and soil moisture had a significant positive effect on seedling survival (Pu et al, 2017), while topographic variables (e.g. elevation, slope, and aspect) did not (Wang et al, 2012)
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