The relationship between species richness and biomass changes from boreal to subtropical forests in China

Abstract

Diversity‐manipulation experiments suggest a positive effect of biodiversity on ecosystem properties (EPs), but variable relationships between species richness and EPs have been reported in natural communities. An explanation for this discrepancy is that observed richness–EPs relationships in natural communities change with environment and species functional identities. But how the relationships change along broad‐scale climatic gradients has rarely been examined. In this paper, we sampled 848 plots of 20 × 30 m2 from boreal to tropical forests across China. We examined plot biomass with respect to environmental factors, tree species richness and functional group identity (FGI, i.e. evergreen vs deciduous, and coniferous vs broadleaf). Variation partitioning was used to evaluate the relative effects of the three classes of factors. We found that, most of the ‘effects’ (percentage of variation explained) of richness and FGI on forest biomass were shared with environmental factors, but species richness and FGI still revealed significant effects in addition to environment for plots across China. Richness and FGI explained biomass mainly through their shared effects instead of independent effects, suggesting that the positive biodiversity effect is closely associated with a sampling effect. The relative effects of richness, FGI and environment varied latitudinally: the independent effects of environment and richness decreased from boreal to subtropical forests, whereas the total effect of FGI increased. We also found that the slope of richness–biomass relationship decreased monotonically from boreal to subtropical forests, possibly because of decreasing complementarity and increasing competition with increasing productivity. Our results suggest that while species richness does have significant effects on forest biomass it is less important than environmental gradients and other biotic factors in shaping large‐scale biomass patterns. We suggest that understanding how and why the diversity–EPs relationships change along climatic gradient would be helpful for a better understanding of real biodiversity effects in natural communities.

Aboveground Biomass and Carbon in a South African Mistbelt Forest and the Relationships with Tree Species Diversity and Forest Structures

“…More specifically, it was found that species richness was significantly and positively correlated with AGC. Indeed, it is a well-known pattern, especially at the global scale, that carbon stocks increase with increasing diversity [27,29,65]. The positive relationships between tree species diversity and carbon stocks in this study supports the idea that diversity-carbon patterns are also identifiable even at smaller spatial scales.…”

Climate modulates the effects of tree diversity on forest productivity

“…; He, Bertness & Altieri ; Prior & Bowman ), and evidence suggests that positive relationships between diversity and productivity are in fact more common where environmental conditions are most limiting (Paquette & Messier ; Wu et al . ; Toïgo et al . ).…”

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

“…That could be related to the lower soil nutrient availability in conifer stands indicated by lower soil C:N ratio (Cools et al, 2014;Dawud et al, 2017), and thus to the need to allocate more biomass in fine roots in nutrient poor conditions (Finér et al, 2007;Helmisaari et al, 2007). In addition to diversity and identity effects other stand characteristics, soil properties and climatic conditions affect fine root productivity and these relationships have been studied in European forests (Finér et al, 2007;Helmisaari et al, 2007;Lehtonen et al, 2016) and other geographic areas (Finér et al, 2011;Wu et al, 2015). Fine root biomass has been shown to increase with stand basal area, age and soil C:N ratio in European forests (Finér et al, 2007;Helmisaari et al, 2007;Lehtonen et al, 2016), but the relationship between fine root biomass and mean annual temperature and precipitation has not been significant (Finér et al, 2007).…”

“…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.…”