Abstract
BackgroundForest productivity has a pivotal role in human well-being. Vegetation quantity, niche complementarity, mass-ratio, and soil resources are alternative/complementary ecological mechanisms driving productivity. One challenge in current forest management depends on identifying and manipulating these mechanisms to enhance productivity. This study assessed the extent to which these mechanisms control above-ground biomass productivity (AGBP) of a Chilean mediterranean-type matorral. AGBP measured as tree above-ground biomass changes over a 7-years period, was estimated for twelve 25 m × 25 m plots across a wide range of matorral compositions and structures. Variables related to canopy structure, species and functional diversity, species and functional dominance, soil texture, soil water and soil nitrogen content were measured as surrogates of the four mechanisms proposed. Linear regression models were used to test the hypotheses. A multimodel inference based on the Akaike’s information criterion was used to select the best models explaining AGBP and for identifying the relative importance of each mechanism.ResultsVegetation quantity (tree density) and mass-ratio (relative biomass of Cryptocarya alba, a conservative species) were the strongest drivers increasing AGBP, while niche complementarity (richness species) and soil resources (sand, %) had a smaller effect either decreasing or increasing AGBP, respectively. This study provides the first assessment of alternative mechanisms driving AGBP in mediterranean forests of Chile. There is strong evidence suggesting that the vegetation quantity and mass-ratio mechanisms are key drivers of AGBP, such as in other tropical and temperate forests. However, in contrast with other studies from mediterranean-type forests, our results show a negative effect of species diversity and a small effect of soil resources on AGBP.ConclusionAGBP in the Chilean matorral depends mainly on the vegetation quantity and mass-ratio mechanisms. The findings of this study have implications for matorral restoration and management for the production of timber and non-timber products and carbon sequestration.
Highlights
Forest productivity has a pivotal role in human well-being
The values of aboveground biomass productivity (AGBP) were positive in almost all the plots, but in two plots dominated by Q. saponaria and L. caustica the growth was nil
The analysis of simple pairwise regression suggested that AGBP significantly increased with increasing vegetation quantity (Fig. 3a–c), species and functional dominance (Fig. 3d–g) and some soil attributes related to resources availability (Fig. 3h–j)
Summary
Forest productivity has a pivotal role in human well-being. Vegetation quantity, niche complementarity, mass-ratio, and soil resources are alternative/complementary ecological mechanisms driving productivity. At small-scales and under natural conditions AGBP is driven by vegetation quantity, species diversity, particular dominant species and soil resources availability through four so far controversial hypothesis, recently compared (Lohbeck et al 2015; Finegan et al 2015; Prado-Junior et al 2016; Kamruzzaman et al 2017; van der Sande et al 2017a), and namely: a) The hypothesis of vegetation quantity proposes that the amount of vegetation is the main driver of changes in the rates of different ecosystem processes (Lohbeck et al 2015) Consistent with this hypothesis, some studies show that greater aboveground biomass, tree density, basal area and leaf area increase AGBP (Paquette and Messier 2011; Reich 2012; Prado-Junior et al 2016). Other studies show neutral or negative effects of these variables on AGBP (Finegan et al 2015; Prado-Junior et al 2016; van der Sande et al 2017a)
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