Seasonality and nutrient addition affect seasonal temporal beta-diversity in grasslands.

GARBOWSKI M; FAY, PHILIP A.; HAUTIER, YANN; LAURA YAHDJIAN; HARPOLE, W. STANLEY

Montreal

Congreso; 2022 ESA & CSEE Joint Meeting.; 2022

Ecological Society of America

Background/Question/MethodsTemporal niche segregation, or the temporal separation of resource use by species,promotes coexistence in many ecological communities. Evidence suggests that seasonalfluctuations in precipitation and temperature (i.e., seasonality) may be particularly importantdrivers of seasonal dynamics in herbaceous plant communities in which species with distinctresource-use strategies often dominate in different seasons. However, in these systems,nutrient enrichment may promote the dominance of species with specific resource-usestrategies for longer periods of time and disrupt within-season community dynamics. Giventhe importance of temporal niche segregation to species coexistence in grasslands,elucidating how seasonality and fertilization affect seasonal community composition isessential to our understanding of how biodiversity is maintained in these valuable systems.We used early-season and late-season compositional data collected from 10 grassland sitesaround the world that are part of the Nutrient Network, a globally replicated nutrientenrichment experiment to: (1) assess the relationships between precipitation andtemperature seasonality and seasonal beta-diversity, (2) examined the effects of fertilizationon seasonal beta-diversity, and (3) assess whether species from specific functional groups(i.e., graminoid, forb, legume) or with specific characteristics (e.g., C3 vs. C4) drive changesin seasonal beta-diversity among seasons and fertilization treatments.Results/ConclusionsUniversity of New MexicoChristiane RoscheriDiv, GermanyPedro TognettiUniversidad de Buenos Aires, ArgentinaPeter A. WilfahrtUniversity of Minnesota, United StatesLara YahdjianUniversity of Buenos Aires, ArgentinaStanley HarpoleiDivLeipzig, GermanyTOCRPTPWLYSHUsing deviations from a null model of beta-diversity (i.e., Bray-Curtis dissimilarity) as ourresponse, we found a significant negative relationship between precipitation seasonality andseasonal beta-diversity across study sites. This result is contrary to other studies and mayarise from differences in results when observed beta-diversity vs. null models of betadiversity are used to assess community dissimilarity. Nutrient enrichment had a smallpositive effect on seasonal temporal beta-diversity. Compositional differences were driven byunique shifts of species from specific functional groups or with specific characteristics amongseasons and treatments. For example, nutrient enrichment resulted in higher cover ofannuals and C3 grasses but lower cover of C4 grasses both early and late in the season.However, annual cover varied between early and late sampling dates in fertilized plots butnot control plots, whereas C4 grass cover varied between early and late sampling dates incontrol plots but not fertilized plots. Our results demonstrate that nutrient enrichment candisrupt within-season plant community dynamics by altering the overall dominance ofspecific species across and within growing seasons. These findings advance ourunderstanding of how biodiversity is maintained in grassland systems which are threatenedby global change drivers such as nutrient enrichment.