Diverse belowground resource strategies underlie plant species coexistence and spatial distribution in three grasslands along a precipitation gradient

Abstract

Functional traits and their variation mediate plant species coexistence and spatial distribution. Yet, how patterns of variation in belowground traits influence resource acquisition across species and plant communities remains obscure. To characterize diverse belowground strategies in relation to species coexistence and abundance, we assessed four key belowground traits - root diameter, root branching intensity, first-order root length and mycorrhizal colonization - in 27 coexisting species from three grassland communities along a precipitation gradient. Species with thinner roots had higher root branching intensity, but shorter first-order root length and consistently low mycorrhizal colonization, whereas species with thicker roots enhanced their capacity for resource acquisition by producing longer first-order roots and maintaining high mycorrhizal colonization. Plant species observed across multiple sites consistently decreased root branching and/or mycorrhizal colonization, but increased lateral root length with decreasing precipitation. Additionally, the degree of intraspecific trait variation was positively correlated with species abundance across the gradient, indicating that high intraspecific trait variation belowground may facilitate greater fitness and chances of survival across multiple habitats. These results suggest that a small set of critical belowground traits can effectively define diverse resource acquisition strategies in different environments and may forecast species survival and range shifts under climate change.

The response of root traits to precipitation change of herbaceous species in temperate steppes

“…These results are in agreement with previous studies reporting multifarious trait‐based adaptive strategies among species (Larson & Funk, ; Li, Liu, McCormack, Ma, & Guo, ; Tobner, Paquette, & Messier, ). The species‐specific and trait‐dependent response of plant roots to changing precipitation may enable different species occupy different trait space and niches, thus ensuring full utilization of resources and coexistence under changing climate conditions (Freschet, Bellingham, Lyver, Bonner, & Wardle, ; Laughlin & Messier, ; Li et al, ). Our results for the response of root traits at species level may provide important information on plants’ response in the community under future climate change.…”

Global meta‐analysis reveals different patterns of root tip adjustments by angiosperm and gymnosperm trees in response to environmental gradients

“…Previous studies have also revealed that local environmental conditions, in particular soil nutrients, temperature, and precipitation can influence specific root tip traits including abundance, density, and colonization by mycorrhizal fungi (Helmisaari et al., ; Kjøller et al., ; Leppälammi‐Kujansuu et al., ). Furthermore, trade‐offs with mycorrhizal fungi may mediate plant responses to soil resource availability (Chen et al., ; Li, Liu, McCormack, Ma, & Guo, ; Liu et al., ). Together, these adjustments in patterns of resource allocation across the root system are likely vital strategies for tree species to acclimate to different environmental conditions (Leppälammi‐Kujansuu et al., ; Svistoonoff et al., ; Zadworny et al., ).…”

Linking reliance on deep soil water to resource economy strategies and abundance among coexisting understorey shrub species in subtropical pine plantations

“…Our results support the assumption that species having low trait variation around optimal trait values are able to easily dominate the local environment (Umaña et al ., ). However, at a regional scale with larger environmental heterogeneity, species relative abundance was reported to be positively related to intraspecific variation in root branching intensity and mycorrhizal colonization but not related to first‐order root diameter (Li et al ., ). Considering that first‐order root diameter is a phylogenetically conserved root trait (Kong et al ., ), whereas deep water reliance showed highly plastic responses to the environment (Fig.…”

“…; Snyder & Williams, ), we might expect an important role of deep water utilization in adapting to water resource gradients at regional scales. Although a recent study suggests that species traits are not necessarily near ‘optimum’ in habitats where they occur frequently and abundantly (Mitchell et al ., ), our results further showed that common species tended to have neither very high nor very low deep water reliance in the dry season, complementing a growing body of evidence that rare species tended to occupy the periphery of the community traits space (Shipley et al ., ; Umaña et al ., ; Li et al ., ) when species occurred in locations facing strong stabilizing selection for particular traits (Muscarella & Uriarte, ).…”

“…All statistical processing was conducted in SPSS (2010, v.19.0; S pss Inc., Chicago, IL, USA). Species importance values were calculated as the sum of the relative coverage, relative density and relative occurrence frequency divided by 3 (Li et al ., ). To evaluate the relative position of each shrub species with respect to the deep water source proportion at the community level, we calculated the community weighted mean (CWM) of the deep water source proportion:( a i , relative importance value of species i ; t i , median of deep water source proportion of species i ).…”