The article discusses the concept of nutrient co-limitation in primary producer communities, emphasizing the interactions between nitrogen (N) and phosphorus (P) as limiting resources. It reviews 641 studies across freshwater, marine, and terrestrial systems, showing that more than half of the studies exhibited synergistic responses to N and P addition. The study supports strict definitions of co-limitation in 28% of the studies, where community biomass responded only to combined N and P addition or to both N and P when added separately. The findings highlight the importance of N and P interactions in regulating primary producer community biomass and suggest the need for future studies to address the mechanisms behind different types of co-limitation. The article also explores various definitions of co-limitation, including simultaneous co-limitation, independent co-limitation, and serial limitation. It notes that while simultaneous co-limitation is a strict definition, serial limitation and super-additive responses are more general and may overlap with strict co-limitation definitions. The study uses a meta-analytic approach to test the prevalence of empirical evidence for alternative definitions of co-limitation in primary producer community biomass responses to N and P addition. The results show that the type of nutrient limitation observed in studies depends on experimental covariates such as experiment duration, latitude, and total N and P levels. The study found that nutrient limitation responses varied across systems, with similar distributions of log-ratio responses to N, P, and N + P addition in freshwater, marine, and terrestrial systems. The results suggest that nutrient limitation is not system-specific and that the relative responses to N and P are similar across systems. The study also found that negative responses to nutrient addition were surprisingly common, with 15% of studies showing some type of negative response. These negative responses may be due to toxicity effects or unbalanced nutrient supply ratios. The study concludes that co-limitation is a common phenomenon in aquatic and terrestrial systems, and that nutrient interactions are more frequent than previously thought. The findings support the idea that co-limitation occurs frequently across a variety of ecosystems, with biological and theoretical basis. The study also highlights the need for further research to better understand the mechanisms behind nutrient co-limitation and its implications for ecosystem functioning.The article discusses the concept of nutrient co-limitation in primary producer communities, emphasizing the interactions between nitrogen (N) and phosphorus (P) as limiting resources. It reviews 641 studies across freshwater, marine, and terrestrial systems, showing that more than half of the studies exhibited synergistic responses to N and P addition. The study supports strict definitions of co-limitation in 28% of the studies, where community biomass responded only to combined N and P addition or to both N and P when added separately. The findings highlight the importance of N and P interactions in regulating primary producer community biomass and suggest the need for future studies to address the mechanisms behind different types of co-limitation. The article also explores various definitions of co-limitation, including simultaneous co-limitation, independent co-limitation, and serial limitation. It notes that while simultaneous co-limitation is a strict definition, serial limitation and super-additive responses are more general and may overlap with strict co-limitation definitions. The study uses a meta-analytic approach to test the prevalence of empirical evidence for alternative definitions of co-limitation in primary producer community biomass responses to N and P addition. The results show that the type of nutrient limitation observed in studies depends on experimental covariates such as experiment duration, latitude, and total N and P levels. The study found that nutrient limitation responses varied across systems, with similar distributions of log-ratio responses to N, P, and N + P addition in freshwater, marine, and terrestrial systems. The results suggest that nutrient limitation is not system-specific and that the relative responses to N and P are similar across systems. The study also found that negative responses to nutrient addition were surprisingly common, with 15% of studies showing some type of negative response. These negative responses may be due to toxicity effects or unbalanced nutrient supply ratios. The study concludes that co-limitation is a common phenomenon in aquatic and terrestrial systems, and that nutrient interactions are more frequent than previously thought. The findings support the idea that co-limitation occurs frequently across a variety of ecosystems, with biological and theoretical basis. The study also highlights the need for further research to better understand the mechanisms behind nutrient co-limitation and its implications for ecosystem functioning.