Chongzhe Zhang

Atmospheric carbon dioxide enrichment (eCO ₂ ) stimulates crop growth, and the fertilization effect can translate into sustained plant performance through soil biota‐mediated plant–soil feedbacks (PSFs). However, how cultivar‐specific responses to eCO ₂ shape soil biotic legacies and determine the direction of PSFs remains poorly understood. Here, we combined a long‐term rice free‐air CO ₂ enrichment (FACE) with a greenhouse PSF experiment to test whether weakly and strongly CO ₂ ‐responsive cultivars develop contrasting PSFs, using soil inocula collected from FACE plots with contrasting CO ₂ treatments and rice cultivars. The results showed that eCO ₂ amplified cultivar‐specific PSFs, as reflected by negative PSFs in the strongly responsive cultivar and positive PSFs in the weakly responsive cultivar. Specifically, the strongly responsive cultivar exhibited a 20% reduction in biomass when grown with its own eCO ₂ ‐conditioned soil, which was associated with increased herbivorous nematode abundance (35%). Moreover, soil biota‐mediated feedbacks altered cultivar‐specific growth–defence allocation under eCO ₂ . The strongly responsive cultivar showed a growth–defence trade‐off, with increased phenolic concentrations occurring at the expense of biomass production, whereas the weakly responsive cultivar exhibited a synergistic enhancement of both biomass (21.4%) and phenolic concentrations (33.9%). Synthesis . Our study suggests that sustaining crop performance under future CO ₂ scenarios requires cultivars that coordinate growth, defence and beneficial soil biotic interactions. Integrating cultivar selection with soil biota management therefore offers a promising strategy for sustaining crop production, soil health and agroecosystem resilience under future global change.

Summary: Within the growth–survival trade‐off framework, embolism resistance is considered a contributor to survival, yet whether greater embolism resistance inherently limits growth remains unclear. We investigated this relationship among 22 Eucalyptus species spanning wide precipitation and temperature gradients, grown under controlled conditions for 6–10 months. We quantified embolism resistance (drought‐induced stem P ₅₀ ), growth, and wood anatomy. Our experimental results reveal a clear trade‐off between embolism resistance and growth rate, consistently supported by both cross‐species and phylogenetic (correlated‐divergence) analyses. Faster growing species exhibited less negative P ₅₀ and higher vessel lumen fraction, driven by wider vessels, enhancing hydraulic conductivity. Conversely, slower growing species had more negative P ₅₀ , characterised by thicker vessel walls and a greater density of narrower vessels, reducing hydraulic conductivity. P ₅₀ and growth rate were significantly related to climate‐of‐origin, with species from drier or colder regions exhibiting greater embolism resistance and slower growth. Furthermore, we conducted a global vote‐counting review of 34 studies, showing weak but context‐dependent support for the growth rate–P ₅₀ trade‐off, with no evidence of concurrent faster growth and greater embolism resistance. These findings advance understanding of growth rate–embolism resistance trade‐offs, reveal climatic adaptation mechanisms in woody species, and inform predictions of plant persistence under climate change.

Societal Impact Statement: Earth is currently experiencing a mass extinction crisis, predominantly driven by anthropogenic activities, with land use change causing widespread loss and degradation of native ecosystems and indigenous species. There is an urgent need to halt this trend and restore degraded habitat to preserve biodiversity and protect threatened plants and animals. Restoration focuses largely on the vegetation aboveground, with limited attention to soil biology and function, despite soil biodiversity underpinning ecosystem function. We illustrate how soil biological and functional attributes can be implemented to improve restoration outcomes and, under favourable conditions, enhance habitat suitability for threatened plant species. Summary: Anthropogenic activities, including land clearing for agriculture and infrastructure, have resulted in considerable loss of native ecosystems and their unique species. Remnant vegetation is often highly fragmented and degraded, and is under continued pressure from multiple global change drivers. Hence, there is an urgent need to improve remnant vegetation and restore habitat to compensate for these losses. Ecological restoration, however, generally focuses on recovering vegetation structure and composition, with limited attention given to soil biological and functional attributes, which are often considered solely as barriers to restoration. This is problematic given that ecosystems' structure and function, and therefore their capacity to be self‐sustaining, are underpinned by the strong linkages among plants, soils and the soil biota. Moreover, soil is a biological hotspot, with more than half of Earth's biodiversity being soil‐borne. Here, we illustrate how soil biological and functional attributes can be used to guide restoration interventions, enhance restoration outcomes and complement vegetation‐focused metrics for more comprehensive assessments of ecosystem condition and recovery. Importantly, soil biology can be managed to improve restoration outcomes and, under favourable conditions, enhance habitat suitability for threatened plant species. Future ecological restoration projects would thus benefit from explicitly considering soil biological and functional attributes.

Summary: Aboveground and belowground attributes of terrestrial ecosystems interact to shape carbon (C) cycling. However, plants and soil organisms are usually studied separately, leading to a knowledge gap regarding their coordinated contributions to ecosystem C cycling. We explored whether integrated consideration of plant and nematode traits better explained soil organic C (SOC) dynamics than plant or nematode traits considered separately. Our study system was a space‐for‐time natural restoration chronosequence following agricultural abandonment in a subtropical region, with pioneer, early, mid and climax stages. We identified an integrated fast–slow trait spectrum encompassing plants and nematodes, demonstrating coordinated shifts from fast strategies in the pioneer stage to slow strategies in the climax stage, corresponding to enhanced SOC dynamics. Joint consideration of plant and nematode traits explained more variation in SOC than by either group alone. Structural equation modeling revealed that the integrated fast–slow trait spectrum influenced SOC through its regulation of microbial traits, including microbial C use efficiency and microbial biomass. Our findings confirm the pivotal role of plant‐nematode trait coordination in modulating ecosystem C cycling and highlight the value of incorporating belowground traits into biogeochemical cycling under global change scenarios.