In macroecology, the concept of r‐ and K‐strategy has been widely applied, yet, there have been limited studies on microbial life‐history strategies in temperate grasslands using multiple sequencing approaches. Total phospholipid fatty acid (PLFA) analysis, high‐throughput meta‐genomic sequencing, and GeoChip technologies were used to examine the changes in microbial life‐history traits in a chronosequence of restored grasslands (1, 5, 10, 15, 25, and 30 years since restoration). Grassland restoration increased the relative abundances of Actinobacteria, Proteobacteria, and Bacteroidetes but reduced the relative abundances of Acidobacteria, Planctomycetes, and Chloroflexi. PLFA analysis revealed that grassland restoration reduced the fungi:bacteria and Gram‐positive:Gram‐negative bacteria ratios. Combined with the meta‐genomic data, we found that grassland restoration shifted microorganisms from oligotrophic (K‐) to copiotrophic (r‐) groups, consistent with the increased rRNA operon copy number of the microbial community. Structural equation modeling showed that soil properties positively (p < 0.05) while plant properties negatively (p < 0.05) affected microbial life‐history traits. We built a framework to highlight the importance of plant and soil properties in driving microbial life‐history traits during grassland restoration. Finally, by incorporating meta‐genomic and other microbiological data, this study showed that microbial life‐history traits support the idea that rRNA operon copy number is a trait that reflects resource availability to soil microorganisms.

The large-scale vegetation restoration project on the Loess Plateau increased the ecosystem carbon (C) stocks and affected C budget in arid and semi-arid ecosystems. The specific details affecting the C stocks, their distribution, and dependence on land use and climate were never presented and generalized. We assessed the effects of climate factors and soil properties on ecosystem C stocks through field investigation across the Loess Plateau. The total C stocks in the four ecosystems: forestlands [0.36], shrublands [0.24], grasslands [1.18], and farmlands [1.05] was 2.84 Pg (1 Pg = 10¹⁵ g), among which 30% were stored in topsoil (0–20 cm), 53% in above-ground biomass, and 17% in roots. The total ecosystem C density decreased according to the climate from the southeast (warm dry) to the northwest (cold moist) of the Loess Plateau. The ecosystem C density decreased with increasing temperature (from 5 to 15 °C), but increased with precipitation (from 200 to 700 mm). Variation partitioning analysis and structural equation models indicated that ecosystem C density was more explained by climate compared with soil properties. This supports the theory and empirical findings that large scale pattern of ecosystem C density is predominantly regulated by climate on the Loess Plateau. Our results highlight that grasslands are more predestined to store C compared with the other ecosystems, and the C stored in roots is substantial and should be considered when assessing C stocks and strongly contributes to soil organic matter formation. We suggest that investing in roots can be an effective strategy for meeting part of Loess Plateau C reduction goals to mitigate climate change, which is necessary for validating and parameterizing C models worldwide.