Modes of functional biodiversity control on tree productivity across the European continent

Abstract

Aim The relative contribution of community functional diversity and composition to ecosystem functioning is a critical question in ecology in order to enable better predictions of how ecosystems may respond to a changing climate.However, there is little consensus about which modes of functional biodiversity are most important for tree growth at large spatial scales. Here we assessed the relative importance of climate, functional diversity and functional identity (i.e. the communitymeanvalues of four key functional traits) for tree growth across the European continent, spanning the northern boreal to the southern Mediterranean forests. Location Finland, Germany, Sweden, Spain and Wallonia (Belgium). Methods Using data from five European national forest inventories we applied a hierarchical linear model to estimate the sensitivity of tree growth to changes in climate, functional diversity and functional identity along a latitudinal gradient. Results Functional diversity was weakly related to tree growth in the temperate and boreal regions and more strongly in the Mediterranean region. In the temperate region, where climate was the most important predictor, functional diversity and identity had a similar importance for tree growth. Functional identity was strongest at the latitudinal extremes of the continent, largely driven by strong changes in the importance of maximum height along the latitudinal gradient. Main conclusions Functional diversity is an important driver of tree growth in the Mediterranean region, providing evidence that niche complementarity may be more important for tree growth in water-limited forests. The strong influence of functional identity at the latitudinal extremes indicates the importance of a particular trait composition for tree growth in harsh climates. Furthermore, we speculate that this functional identity signal may reflect a trait-based differentiation of successional stages rather than abiotic filtering due to water or energy limitation

How do trees respond to species mixing in experimental compared to observational studies?

“…Our results confirmed our hypothesis of a general positive effect of tree species mixing on species growth across the three research approaches, although this effect was nonsignificant in the experiments. Our findings are also in line with studies that investigated the same inventory dataset and found positive effect of tree diversity on the productivity of the whole tree community(Ruiz-Benito et al, 2014;Ratcliffe et al, 2016;Ruiz-Benito et al, 2017), although we investigated the effects on individual species and manipulated the inventory dataset to make it compatible to the exploratories. In the exploratory and inventory dataset, tree species showed, on average, an increase of 27% and 20% in growth in mixed as compared to monospecific stands.…”

Conifer proportion explains fine root biomass more than tree species diversity and site factors in major European forest types

“…Reported relationships were positive (Schmid, 2002;Meinen et al, 2009a;Brassard et al, 2011, Brassard et al, 2013Laclau et al, 2013;Bu et al, 2017;Ma and Chen, 2017;Sun et al, 2017), insignificant (Hendricks and Bianchi, 1995;Schmid and Kazda, 2002;Bauhus et al, 2000;Meinen et al, 2009b, Meinen et al, 2009cJacob et al, 2010, Jacob et al, 2013Brassard et al, 2013;Lei et al, 2012b;Domisch et al, 2015;Ma and Chen, 2017) or negative (Bolte and Villanueva, 2006). The more numerous studies between tree species diversity and above-ground biomass and biomass production of trees show more consistent positive diversity effects (Zhang et al, 2012;Gamfeldt et al, 2013;Vilà et al, 2013;Ratcliffe et al, 2015;Toïgo et al, 2015;Wu et al, 2015;Jucker et al, 2016;Liang et al, 2016;Pretsch and Schütze, 2016), suggesting that tree species diversity effects on above-ground biomass or productivity are not necessarily mirrored by tree fine root productivity (Bauhus et al, 2000;Chen and Klinka, 2003;Brassard et al, 2011;Lei et al, 2012a). There are no comprehensive studies explaining the inconsistent responses of fine root biomass or productivity to tree species diversity.…”

“…There are no comprehensive studies explaining the inconsistent responses of fine root biomass or productivity to tree species diversity. The varying above-ground biomass and productivity responses have been related to different climatic conditions and site productivity (Paquette and Messier, 2011;Jucker et al, 2014a, Jucker et al, 2016Potter and Woodall, 2014;Ratcliffe et al, 2015;Toïgo et al, 2015;Wu et al, 2015), suggesting that responses are positive under cold or dry climatic conditions and at low site productivity. Thus, systematic studies covering a wide range of mature forest ecosystems and tree species and their combinations are still needed to understand below-ground productivity responses to tree species diversity, identity, stand characteristics and soil properties.…”

Essential Annotation Schema for Ecology (EASE)—A framework supporting the efficient data annotation and faceted navigation in ecology

“…Data reuse allows to extend the scope of studies in order to cover wider temporal and spatial scales which are relevant to human societies and which help to generalize theory across environmental contexts. For example, meta-analyses reusing data from scattered experiments have allowed to develop the theory of multifunctionality in biodiversity/ecosystem functioning research [5], and extended functional biodiversity research from plots to continents [6] and the parameterization of global climate models [7]. Although the reuse of data is important for research in ecology it can be challenging to find suitable data which qualifies for the reuse in a specific context and which comes with context data necessary for an integration into meta-analyses.…”