Soybean inclusion reduces soil organic matter mineralization despite increasing its temperature sensitivity.

Legume-based cropping increased the diversity of residues and rhizodeposition input into the soil, thus affecting soil organic matter (SOM) stabilization. Despite this, a comprehensive understanding of the mechanisms governing SOM mineralization and its temperature sensitivity across bulk soil and aggregate scales concerning legume inclusion remains incomplete. Here, a 6-year field experiment was conducted to investigate the effects of three cropping systems (i.e., winter wheat/summer maize, winter wheat/summer maize-soybean, and nature fallow) on SOM mineralization, its temperature sensitivity, and the main drivers in both topsoil (0-20 cm) and subsoil (20-40 cm). Soybean inclusion decreased the SOM mineralization by 17%-24%, while concurrently increasing the majority of soil biochemical properties, such as carbon (C) acquisition enzyme activities (5%-22%) and microbial biomass C (5%-9%), within the topsoil regardless of temperature. This is attributed to the increased substrate availability (e.g., dissolved organic C) facilitating microbial utilization, thus devoting less energy to mining nutrients under diversified cropping. In addition, SOM mineralization was lower within macroaggregates (∼12%), largely driven by substrate availability irrespective of aggregate sizes. In contrast, diversified cropping amplified the Q10 of SOM mineralization in mesoaggregates (+6%) and microaggregates (+5%) rather than in macroaggregates. This underscores the pivotal role of mesoaggregates and microaggregates in dominating the Q10 of SOM mineralization under soybean-based cropping. In conclusion, legume-based cropping diminishes soil organic matter mineralization despite increasing its temperature sensitivity, which proposes a potential strategy for C-neutral agriculture and climate warming mitigation.

Drivers of seedling establishment success in dryland restoration efforts.

Restoration of degraded drylands is urgently needed to mitigate climate change, reverse desertification and secure livelihoods for the two billion people who live in these areas. Bold global targets have been set for dryland restoration to restore millions of hectares of degraded land. These targets have been questioned as overly ambitious, but without a global evaluation of successes and failures it is impossible to gauge feasibility. Here we examine restoration seeding outcomes across 174 sites on six continents, encompassing 594,065 observations of 671 plant species. Our findings suggest reasons for optimism. Seeding had a positive impact on species presence: in almost a third of all treatments, 100% of species seeded were growing at first monitoring. However, dryland restoration is risky: 17% of projects failed, with no establishment of any seeded species, and consistent declines were found in seeded species as projects matured. Across projects, higher seeding rates and larger seed sizes resulted in a greater probability of recruitment, with further influences on species success including site aridity, taxonomic identity and species life form. Our findings suggest that investigations examining these predictive factors will yield more effective and informed restoration decision-making.