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null (Ed.)Soil nitrogen (N) availability is of critical importance to the productivity of terrestrial ecosystems worldwide. Plant diversity continues to decline globally due to habitat conversion and degradation, but its influence on soil N remains uncertain. By conducting a global meta-analysis of 1,650 paired observations of soil N in plant species mixtures and monocultures from 149 studies, we show that, on average across observations, soil total N is 6.1% higher in species mixtures. This mixture effect on total N becomes more positive with the number of species in mixtures and with stand age. The mixture effects on net N mineralization rate and inorganic N concentrations shift from negative in young stands to positive in older stands with greater positive effects in more-diverse mixtures. These effects of mixtures were consistent among cropland, forest and grassland ecosystems and held across climate zones. Our results suggest that plant diversity conservation not only enhances the productivity of current vegetation but also increases soil N retention that will sustain the productivity of future vegetation.more » « less
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Summary Despite widespread anthropogenic nutrient enrichment, it remains unclear how nutrient enrichment influences plant–arbuscular mycorrhizal fungi (AMF) symbiosis and ecosystem multifunctionality at the global scale.
Here, we conducted a meta‐analysis to examine the worldwide effects of nutrient enrichment on AMF and plant diversity and ecosystem multifunctionality using data of field experiments from 136 papers.
Our analyses showed that nutrient addition simultaneously decreased AMF diversity and abundance belowground and plant diversity aboveground at the global scale. The decreases in AMF diversity and abundance associated with nutrient addition were more pronounced with increasing experimental duration, mean annual temperature (MAT) and mean annual precipitation (MAP). Nutrient addition‐induced changes in soil pH and available phosphorus (P) predominantly regulated the responses of AMF diversity and abundance. Furthermore, AMF diversity correlated with ecosystem multifunctionality under nutrient addition worldwide.
Our findings identify the negative effects of nutrient enrichment on AMF and plant diversity and suggest that AMF diversity is closely linked with ecosystem function. This study offers an important advancement in our understanding of plant–AMF interactions and their likely responses to ongoing global change.
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One of the most fundamental questions in ecology is how many species inhabit the Earth. However, due to massive logistical and financial challenges and taxonomic difficulties connected to the species concept definition, the global numbers of species, including those of important and well-studied life forms such as trees, still remain largely unknown. Here, based on global ground-sourced data, we estimate the total tree species richness at global, continental, and biome levels. Our results indicate that there are ∼73,000 tree species globally, among which ∼9,000 tree species are yet to be discovered. Roughly 40% of undiscovered tree species are in South America. Moreover, almost one-third of all tree species to be discovered may be rare, with very low populations and limited spatial distribution (likely in remote tropical lowlands and mountains). These findings highlight the vulnerability of global forest biodiversity to anthropogenic changes in land use and climate, which disproportionately threaten rare species and thus, global tree richness.more » « less
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Abstract Ecosystem stability is essential to its sustainable functions and services to humanity. Although climate warming is projected to vary from 1 to 5°C by the end of 21st century, how the temporal stability of plant community biomass production responds to different warming scenarios remains unclear.
To fill this knowledge gap, we conducted a 6‐year field experiment with three levels of warming treatments (control, +1.5°C, +2.5°C) by using infrared radiators, in an alpine meadow on the Qinghai–Tibet Plateau.
We found that low‐level warming (+1.5°C), compared to the control, did not significantly change the temporal stability of plant community biomass production and its underlying causes, including species diversity, compensatory dynamics, mean–variance scaling, biomass temporal stability of plant population (the average of temporal stability of species biomass production of all species in the community) or dominant species. However, high‐level warming (+2.5°C) significantly reduced them. Species diversity was not a significant predictor of temporal stability of plant community biomass production in this species‐rich ecosystem, regardless of the magnitude of warming, while co‐existing species compensatory dynamics and the biomass temporal stability of dominant species determined the response of temporal stability of plant community biomass production to warming.
Synthesis . Our results suggest that the responses of plant community biomass temporal stability and its underlying mechanisms to climate warming depend on warming magnitudes. The findings highlight the various responses of ecosystem functions and services to different warming scenarios and imply that ecosystem will fail to maintain and provide stable biomass‐related services for humanity under high‐level climate warming.
