@article {96101, title = {Negative effects of nitrogen override positive effects of phosphorus on grassland legumes worldwide.}, journal = {Proc Natl Acad Sci U S A}, volume = {118}, year = {2021}, month = {2021 Jul 13}, abstract = {

Anthropogenic nutrient enrichment is driving global biodiversity decline and modifying ecosystem functions. Theory suggests that plant functional types that fix atmospheric nitrogen have a competitive advantage in nitrogen-poor soils, but lose this advantage with increasing nitrogen supply. By contrast, the addition of phosphorus, potassium, and other nutrients may benefit such species in low-nutrient environments by enhancing their nitrogen-fixing capacity. We present a global-scale experiment confirming these predictions for nitrogen-fixing legumes (Fabaceae) across 45 grasslands on six continents. Nitrogen addition reduced legume cover, richness, and biomass, particularly in nitrogen-poor soils, while cover of non-nitrogen-fixing plants increased. The addition of phosphorous, potassium, and other nutrients enhanced legume abundance, but did not mitigate the negative effects of nitrogen addition. Increasing nitrogen supply thus has the potential to decrease the diversity and abundance of grassland legumes worldwide regardless of the availability of other nutrients, with consequences for biodiversity, food webs, ecosystem resilience, and genetic improvement of protein-rich agricultural plant species.

}, issn = {1091-6490}, doi = {10.1073/pnas.2023718118}, author = {Tognetti, Pedro M and Prober, Suzanne M and B{\'a}ez, Selene and Chaneton, Enrique J and Firn, Jennifer and Risch, Anita C and Schuetz, Martin and Simonsen, Anna K and Yahdjian, Laura and Borer, Elizabeth T and Seabloom, Eric W and Arnillas, Carlos Alberto and Bakker, Jonathan D and Brown, Cynthia S and Cadotte, Marc W and Caldeira, Maria C and Daleo, Pedro and Dwyer, John M and Fay, Philip A and Gherardi, Laureano A and Hagenah, Nicole and Hautier, Yann and Komatsu, Kimberly J and McCulley, Rebecca L and Price, Jodi N and Standish, Rachel J and Stevens, Carly J and Wragg, Peter D and Sankaran, Mahesh} } @article {103399, title = {Opposing community assembly patterns for dominant and jonnondominant plant species in herbaceous ecosystems globally}, journal = {ECOLOGY AND EVOLUTION }, year = {2021}, month = {11/02021}, abstract = {

Biotic and abiotic factors interact with dominant plants-the locally most frequent or with the largest coverage-and nondominant plants differently, partially because dominant plants modify the environment where nondominant plants grow. For instance, if dominant plants compete strongly, they will deplete most resources, forcing nondominant plants into a narrower niche space. Conversely, if dominant plants are constrained by the environment, they might not exhaust available resources but instead may ameliorate environmental stressors that usually limit nondominants. Hence, the nature of interactions among nondominant species could be modified by dominant species. Furthermore, these differences could translate into a disparity in the phylogenetic relatedness among dominants compared to the relatedness among nondominants. By estimating phylogenetic dispersion in 78 grasslands across five continents, we found that dominant species were clustered (e.g., co-dominant grasses), suggesting dominant species are likely organized by environmental filtering, and that nondominant species were either randomly assembled or overdispersed. Traits showed similar trends for those sites (\<50\%) with sufficient trait data. Furthermore, several lineages scattered in the phylogeny had more nondominant species than expected at random, suggesting that traits common in nondominants are phylogenetically conserved and have evolved multiple times. We also explored environmental drivers of the dominant/nondominant disparity. We found different assembly patterns for dominants and nondominants, consistent with asymmetries in assembly mechanisms. Among the different postulated mechanisms, our results suggest two complementary hypotheses seldom explored: (1) Nondominant species include lineages adapted to thrive in the environment generated by dominant species. (2) Even when dominant species reduce resources to nondominant ones, dominant species could have a stronger positive effect on some nondominants by ameliorating environmental stressors affecting them, than by depleting resources and increasing the environmental stress to those nondominants. These results show that the dominant/nondominant asymmetry has ecological and evolutionary consequences fundamental to understand plant communities.

}, doi = {10.1002/ece3.8266}, author = {Arnillas, Carlos Alberto and Borer, Elizabeth and Seabloom, Eric and Alberti, Juan and B{\'a}ez, Selene and Bakker, Jonathon and Boughton, Elizabeth and Buckley, Yvonne and Bugalho, Miguel Nuno and Donohue, Ian and Dwyer, John and Eskelinen, Anu and Firn, Jennifer and Gridzak, Riley and Hagenah, Nicole and Hautier, Yann and Helm, Aveliina and Jentsch, Anke and Knops, Johannes M. H. and Komatsu, Kimberly J. and Laanisto, Lauri and Laungani, Ramesh and McCulley, Rebecca and Moore, Joslin and Morgan, John and Peri, Pablo Luis and Power, Sally A. and Price, Jodi and Sankaran, Mahesh and Schamp, Brandon and Speziale, Karina and Standish, Rachel and Virtanen, Risto and Cadotte, Marc W.} } @article {105155, title = {Opposing community assembly patterns for dominant and nondominant plant species in herbaceous ecosystems globally.}, journal = {Ecol Evol}, volume = {11}, year = {2021}, month = {2021 Dec}, pages = {17744-17761}, abstract = {

Biotic and abiotic factors interact with dominant plants-the locally most frequent or with the largest coverage-and nondominant plants differently, partially because dominant plants modify the environment where nondominant plants grow. For instance, if dominant plants compete strongly, they will deplete most resources, forcing nondominant plants into a narrower niche space. Conversely, if dominant plants are constrained by the environment, they might not exhaust available resources but instead may ameliorate environmental stressors that usually limit nondominants. Hence, the nature of interactions among nondominant species could be modified by dominant species. Furthermore, these differences could translate into a disparity in the phylogenetic relatedness among dominants compared to the relatedness among nondominants. By estimating phylogenetic dispersion in 78\ grasslands across five continents, we found that dominant species were clustered (e.g., co-dominant grasses), suggesting dominant species are likely organized by environmental filtering, and that nondominant species were either randomly assembled or overdispersed. Traits showed similar trends for those sites (\<50\%) with sufficient trait data. Furthermore, several lineages scattered in the phylogeny had more nondominant species than expected at random, suggesting that traits common in nondominants are phylogenetically conserved and have evolved multiple times. We also explored environmental drivers of the dominant/nondominant disparity. We found different assembly patterns for dominants and nondominants, consistent with asymmetries in assembly mechanisms. Among the different postulated mechanisms, our results suggest two complementary hypotheses seldom explored: (1) Nondominant species include lineages adapted to thrive in the environment generated by dominant species. (2) Even when dominant species reduce resources to nondominant ones, dominant species could have a stronger positive effect on some nondominants by ameliorating environmental stressors affecting them, than by depleting resources and increasing the environmental stress to those nondominants. These results show that the dominant/nondominant asymmetry has ecological and evolutionary consequences fundamental to understand plant communities.

}, issn = {2045-7758}, doi = {10.1002/ece3.8266}, author = {Arnillas, Carlos Alberto and Borer, Elizabeth T and Seabloom, Eric W and Alberti, Juan and B{\'a}ez, Selene and Bakker, Jonathan D and Boughton, Elizabeth H and Buckley, Yvonne M and Bugalho, Miguel Nuno and Donohue, Ian and Dwyer, John and Firn, Jennifer and Gridzak, Riley and Hagenah, Nicole and Hautier, Yann and Helm, Aveliina and Jentsch, Anke and Knops, Johannes M H and Komatsu, Kimberly J and Laanisto, Lauri and Laungani, Ramesh and McCulley, Rebecca and Moore, Joslin L and Morgan, John W and Peri, Pablo Luis and Power, Sally A and Price, Jodi and Sankaran, Mahesh and Schamp, Brandon and Speziale, Karina and Standish, Rachel and Virtanen, Risto and Cadotte, Marc W} }