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The sensitivity of soil organic carbon (SOC) decomposition in seasonally frozen soils, such as alpine ecosystems, to climate warming is a major uncertainty in global carbon cycling. Here we measure soil CO2 emission during four years (2018-2021) from the whole-soil warming experiment (4 °C for the top 1 m) in an alpine grassland ecosystem. We find that whole-soil warming stimulates total and SOC-derived CO2 efflux by 26% and 37%, respectively, but has a minor effect on root-derived CO2 efflux. Moreover, experimental warming only promotes total soil CO2 efflux by 7-8% on average in the meta-analysis across all grasslands or alpine grasslands globally (none of these experiments were whole-soil warming). We show that whole-soil warming has a much stronger effect on soil carbon emission in the alpine grassland ecosystem than what was reported in previous warming experiments, most of which only heat surface soils.

Global climate warming could affect the methane (CH4) and nitrous oxide (N2O) fluxes between soils and the atmosphere, but how CH4 and N2O fluxes respond to whole‐soil warming is unclear. Here, we for the first time investigated the effects of whole‐soil warming on CH4 and N2O fluxes in an alpine grassland ecosystem on the Tibetan Plateau, and also studied the effects of experimental warming on CH4 and N2O fluxes across terrestrial ecosystems through a global‐scale meta‐analysis. The whole‐soil warming (0–100 cm, +4°C) significantly elevated soil N2O emission by 101%, but had a minor effect on soil CH4 uptake. However, the meta‐analysis revealed that experimental warming did not significantly alter CH4 and N2O fluxes, and it may be that most field warming experiments could only heat the surface soils. Moreover, the warming‐induced higher plant litter and available N in soils may be the main reason for the higher N2O emission under whole‐soil warming in the alpine grassland. We need to pay more attention to the long‐term response of greenhouse gases (including CH4 and N2O fluxes) from different soil depths to whole‐soil warming over year‐round, which could help us more accurately assess and predict the ecosystem‐climate feedback under realistic warming scenarios in the future. [ABSTRACT FROM AUTHOR]

Summary: The adoption of diverse resource acquisition strategies is critical for plant growth and species coexistence. Root phosphatase is of particular importance in the acquisition of soil phosphorus (P), yet it is often overlooked in studies of root trait syndromes.Here, we evaluated the role of root phosphatase activity (RPA) within the root economics space and the order‐based variation of RPA, as well as the correlations between RPA and a suite of leaf traits and soil properties over a range of evergreen tree species in a subtropical forest.Root phosphatase activity exhibited a high degree of inter‐specific variation. We found that there were two leading dimensions of the multidimensional root economics space, the root diameter–specific root length axis (collaboration trait gradient) and the root tissue density–root nitrogen concentration axis (classical trait gradient), and RPA aligned with the former. Root phosphatase activity is used as a 'do it yourself' strategy of soil P acquisition, and was found to be inversely correlated with mycorrhizal colonization, which suggests a trade‐off in plant P acquisition strategies. Compared with soil and foliar nutrient status, root traits mattered most for the large inter‐specific changes in RPA. Furthermore, RPA generally decreased from first‐ to third‐order roots.Taken together, such diverse P‐acquisition strategies are conducive to plant coexistence within local forest communities. The use of easily measurable root traits and their tight correlations with RPA could be a feasible and promising approach to estimating species‐specific RPA values, which would be helpful for better understanding plant P acquisition and soil P cycling. See also the Commentary on this article by Yaffar et al., 234: 773–775. [ABSTRACT FROM AUTHOR]

The alpine meadow ecosystem on the Qinghai–Tibetan Plateau (QTP) is very sensitive to warming and plays a key role in regulating global carbon (C) cycling. However, how warming affects the soil organic carbon (SOC) pool and related C inputs and outputs in alpine meadow ecosystems on the QTP remains unclear. Here, we combined two field experiments and a meta‐analysis on field experiments to synthesize the responses of the SOC pool and related C cycling processes to warming in alpine meadow ecosystems on the QTP. We found that the SOC content of surface soil (0–10 cm) showed a minor response to warming, but plant respiration was accelerated by warming. In addition, the warming effect on SOC was not correlated with experimental and environmental variables, such as the method, magnitude and duration of warming, initial SOC content, mean annual temperature, and mean annual precipitation. We conclude that the surface SOC content is resistant to climate warming in alpine meadow ecosystems on the QTP. [ABSTRACT FROM AUTHOR]

Root respiration is a critical physiological trait involved in root resource acquisition strategies, yet it is less represented in root trait syndrome. Here we compiled a large dataset of root respiration associated with root chemical and morphological traits from 245 plant species. Our results demonstrated that root respiration correlated positively with root nitrogen concentration (RNC) and negatively with root tissue density (RTD) across and within woody and non‐woody species. However, the relationships between root respiration and specific root length (SRL) and root diameter (RD) were weak or even insignificant. Such root respiration–traits relationships were not completely in line with predictions by the root economics spectrum (RES). Furthermore, the principal component analysis showed that root trait syndrome was multidimensional. Root respiration was associated more strongly with the RNC‐RTD axis (the classical RES) than with the orthogonal SRL‐RD axis for woody species, but not for non‐woody species. Collectively, the linkages of root physiological, chemical, and morphological traits provide a better understanding of root trait covariation and root resource acquisition strategies. [ABSTRACT FROM AUTHOR]

Summary: Root exudation stimulates microbial decomposition and enhances nutrient availability to plants. It remains difficult to measure and predict this carbon flux in natural conditions, especially for mature woody plants. Based on a known conceptual framework of root functional traits coordination, we proposed that root functional traits may predict root exudation.We measured root exudation and other seven root morphological/chemical/physiological traits for 18 coexisting woody species in a deciduous‐evergreen mixed forest in subtropical China.Root exudation, respiration, diameter and nitrogen (N) concentration all exhibited significant phylogenetic signals. We found that root exudation positively correlated with competitive traits (root respiration, N concentration) and negatively with a conservative trait (root tissue density). Furthermore, these relationships were independent of phylogenetic signals. A principal component analysis showed that root exudation and morphological traits loaded on two perpendicular axes.Root exudation is a competitive trait in a multidimensional fine‐root functional coordination. The metabolic dimension on which root exudation loaded was relatively independent of the morphological dimension, indicating that increasing nutrient availability by root exudation might be a complementary strategy for plant nutrient acquisition. The positive relationship between root exudation and root respiration and N concentration is a promising approach for the future prediction of root exudation. [ABSTRACT FROM AUTHOR]

Soil CO 2 efflux varies significantly in time and space in terrestrial ecosystems, obtaining a detailed understanding of what controls the dynamics of soil respiration (SR) can improve the estimation accuracy of forest carbon budgets. We examined the effects of forest conversion (from primary forest to both secondary forest and coniferous plantations) on the temporal dynamics of SR and its components (heterotrophic = R H , and autotrophic = R A ), at both seasonal and inter-annual time scales within four adjacent forest stands in north-eastern China. Trenching method was used to partition R H and R A. The results showed that R H was the primary contributor to the overall magnitude and variability of SR, which showed similar seasonal and inter-annual variation, while R A displayed higher temporal variation compared to SR and R H . Generally, the between-year seasonal variation of SR and R H varied significantly in both secondary forest and plantations. The secondary forest exhibited a relatively higher seasonal change in R A compared to that in primary forest and coniferous plantations, while there was no significant disparity in the seasonal and inter-annual variation of SR and R H among forest stands. Soil temperature was the primary factor driving the temporal dynamics of R H and accounted for 63–91% and 22–64% of seasonal and inter-annual variations, respectively. However, R A was less controlled by soil temperature. This study implies that forest conversion magnifies the responses of R H to the minor variations in the between-year seasonal patterns of soil temperature and increases the seasonal variability of R A . [ABSTRACT FROM AUTHOR]

Global climate warming could affect the methane (CH 4 ) and nitrous oxide (N 2 O) fluxes between soils and the atmosphere, but how CH 4 and N 2 O fluxes respond to whole-soil warming is unclear. Here, we for the first time investigated the effects of whole-soil warming on CH 4 and N 2 O fluxes in an alpine grassland ecosystem on the Tibetan Plateau, and also studied the effects of experimental warming on CH 4 and N 2 O fluxes across terrestrial ecosystems through a global-scale meta-analysis. The whole-soil warming (0-100 cm, +4°C) significantly elevated soil N 2 O emission by 101%, but had a minor effect on soil CH 4 uptake. However, the meta-analysis revealed that experimental warming did not significantly alter CH 4 and N 2 O fluxes, and it may be that most field warming experiments could only heat the surface soils. Moreover, the warming-induced higher plant litter and available N in soils may be the main reason for the higher N 2 O emission under whole-soil warming in the alpine grassland. We need to pay more attention to the long-term response of greenhouse gases (including CH 4 and N 2 O fluxes) from different soil depths to whole-soil warming over year-round, which could help us more accurately assess and predict the ecosystem-climate feedback under realistic warming scenarios in the future., (© 2023 John Wiley & Sons Ltd.)