Abstract
Examining factors that influence seedling establishment is essential for predicting the impacts of climate change on tree species’ distributions. Seedlings originating from contrasting climates differentially express functional traits related to water and nutrient uptake and drought resistance that reflect their climate of origin and influence their responses to drought. Soil microbes may improve seedling establishment because they can enhance water and nutrient uptake and drought resistance. However, the relative influence of soil microbes on the expression of these functional traits between seedling families or populations from contrasting climates is unknown. To determine if soil microbes may differentially alter functional traits to enhance water and nutrient uptake and drought resistance between dry and wet families, seeds of loblolly pine families from the driest and wettest ends of its geographic range (dry, wet) were planted in sterilized sand (controls) or in sterilized sand inoculated with a soil microbial community (inoculated). Functional traits related to seedling establishment (germination), water and nutrient uptake and C allocation (root:shoot biomass ratio, root exudate concentration, leaf C:N, leaf N isotope composition (δ15N)), and drought resistance (turgor loss point, leaf carbon isotope composition (δ13C)) were measured. Then, plants were exposed to a drought treatment and possible shifts in photosynthetic performance were monitored using chlorophyll fluorescence. Inoculated plants exhibited significantly greater germination than controls regardless of family. The inoculation treatment significantly increased root:shoot biomass ratio in the wet family but not in the dry family, suggesting soil microbes alter functional traits that improve water and nutrient uptake more so in a family originating from a wetter climate than in a family originating from a drier climate. Microbial effects on photosynthetic performance during drought also differed between families, as photosynthetic performance of the dry inoculated group declined fastest. Regardless of treatment, the dry family exhibited a greater root:shoot biomass ratio, root exudate concentration, and leaf δ15N than the wet family. This indicates that the dry family allocated more resources belowground than the wet and the two family may have used different sources of plant available N, which may be related to their contrasting climates of origin and influence their drought resistance. Examination of variation in impacts of soil microbes on seedling physiology improves efforts to enhance seedling establishment and beneficial plant-microbe interactions under climate change.
Highlights
Increased intensity and frequency of heat waves, drought, and wildfire (IPCC, 2018) have led to widespread forest mortality in recent decades (Allen et al, 2010; Hartmann et al, 2018)
We hypothesized that soil microbes would differentially alter functional traits between the dry and wet families where soil microbes would alter functional traits to enhance water and nutrient uptake and drought resistance to a greater extent in a family originating from a wetter climate than in a family originating from a drier climate
The microbial inoculation treatment affected functional traits of both families for the majority of traits we measured (germination, height, YTLP, root exudate concentration, %C, d13 C, photosynthesis (A), and stomatal conductance) but the effect size was only significant for one trait: germination (Figure 1, Supplementary Table 1), where inoculated plants exhibited significantly greater germination than controls regardless of family (ANOVA; P < 0.001; Figures 1 and 2A, Supplementary Table 2)
Summary
Increased intensity and frequency of heat waves, drought, and wildfire (IPCC, 2018) have led to widespread forest mortality in recent decades (Allen et al, 2010; Hartmann et al, 2018). Intraspecific (within-species) variation in the expression of functional traits related to water and nutrient uptake influences seedling establishment and physiological responses to drought (Sultan, 2000; Howe et al, 2003; Kawecki and Ebert, 2004; IsaacRenton et al, 2018; Ramírez‐Valiente et al, 2018; Roches et al, 2018; Chauvin et al, 2019; Roskilly et al, 2019). Intraspecific adaptations to their climate of origin collectively enable a species to survive in diverse climates and span a large geographic range. Seedling populations and families from drier climates can exhibit greater leaf carbon isotope ratios which indicate greater intrinsic water use efficiency and greater stomatal constraints on gas exchange, and lower leaf turgor loss point which can indicate greater drought tolerance (Grossnickle et al, 1996; Cregg and Zhang, 2001; NguyenQueyrens and Bouchet-Lannat, 2003; López et al, 2009; Bartlett et al, 2014; Kerr et al, 2015; Carvalho et al, 2017; Marias et al, 2017)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
