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Nitrogen availability in the rhizosphere relies on root‐microorganism interactions, where root exudates trigger soil organic matter (SOM) decomposition through the rhizosphere priming effect (RPE). Though microbial necromass contribute significantly to organically bound soil nitrogen (N), the role of RPEs in regulating necromass recycling and plant nitrogen acquisition has received limited attention. We used 15N natural abundance as a proxy for necromass‐N since necromass is enriched in 15N compared to other soil‐N forms. We combined studies using the same experimental design for continuous 13CO2 labelling of various plant species and the same soil type, but considering top‐ and subsoil. RPE were quantified as difference in SOM‐decomposition between planted and unplanted soils. Results showed higher plant N uptake as RPEs increased. The positive relationship between 15N‐enrichment of shoots and roots and RPEs indicated an enhanced necromass‐N turnover by RPE. Moreover, our data revealed that RPEs were saturated with increasing carbon (C) input via rhizodeposition in topsoil. In subsoil, RPEs increased linearly within a small range of C input indicating a strong effect of root‐released C on decomposition rates in deeper soil horizons. Overall, this study confirmed the functional importance of rhizosphere C input for plant N acquisition through enhanced necromass turnover by RPEs. Summary statement: Interactions between roots and microorganisms in the rhizosphere enhance nitrogen availability through the rhizosphere priming effect (RPE). Our study confirmed that increasing RPEs promote higher plant nitrogen uptake and indicate enhanced turnover of necromass‐nitrogen through rhizosphere priming. [ABSTRACT FROM AUTHOR]

A holistic understanding of plant strategies to acquire soil resources is pivotal in achieving sustainable food security. However, we lack knowledge about variety‐specific root and rhizosphere traits for resource acquisition, their plasticity and adaptation to drought. We conducted a greenhouse experiment to phenotype root and rhizosphere traits (mean root diameter [Root D], specific root length [SRL], root tissue density, root nitrogen content, specific rhizosheath mass [SRM], arbuscular mycorrhizal fungi [AMF] colonization) of 16 landraces and 22 modern cultivars of temperate maize (Zea mays L.). Our results demonstrate that landraces and modern cultivars diverge in their root and rhizosphere traits. Although landraces follow a 'do‐it‐yourself' strategy with high SRLs, modern cultivars exhibit an 'outsourcing' strategy with increased mean Root Ds and a tendency towards increased root colonization by AMF. We further identified that SRM indicates an 'outsourcing' strategy. Additionally, landraces were more drought‐responsive compared to modern cultivars based on multitrait response indices. We suggest that breeding leads to distinct resource acquisition strategies between temperate maize varieties. Future breeding efforts should increasingly target root and rhizosphere economics, with SRM serving as a valuable proxy for identifying varieties employing an outsourcing resource acquisition strategy. Summary statement: This study provides novel insights into the diversity of soil resource acquisition strategies within a single plant species. By comparing landraces and modern cultivars of maize and considering plant‐soil‐microbe interactions, we reveal functional differences in root and rhizosphere economics and trait plasticity that shed light on their ecological role and breeding relevance. [ABSTRACT FROM AUTHOR]

Summary: Biophysicochemical rhizosheath properties play a vital role in plant drought adaptation. However, their integration into the framework of plant drought response is hampered by incomplete mechanistic understanding of their drought responsiveness and unknown linkage to intraspecific plant–soil drought reactions.Thirty‐eight Zea mays varieties were grown under well‐watered and drought conditions to assess the drought responsiveness of rhizosheath properties, such as soil aggregation, rhizosheath mass, net‐rhizodeposition, and soil organic carbon distribution. Additionally, explanatory traits, including functional plant trait adaptations and changes in soil enzyme activities, were measured.Drought restricted soil structure formation in the rhizosheath and shifted plant–carbon from litter‐derived organic matter in macroaggregates to microbially processed compounds in microaggregates. Variety‐specific functional trait modifications determined variations in rhizosheath drought responsiveness. Drought responses of the plant–soil system ranged among varieties from maintaining plant–microbial interactions in the rhizosheath through accumulation of rhizodeposits, to preserving rhizosheath soil structure while increasing soil exploration through enhanced root elongation.Drought‐induced alterations at the root–soil interface may hold crucial implications for ecosystem resilience in a changing climate. Our findings highlight that rhizosheath soil properties are an intrinsic component of plant drought response, emphasizing the need for a holistic concept of plant–soil systems in future research on plant drought adaptation. [ABSTRACT FROM AUTHOR]

• High microbial activity in topsoil causes apparent PE shortly after substrate addition. • The input of C from fertilizers induces apparent PE at the 10–30 cm depth. • The release and decomposition of mineral-bound organic C shortly after substrate addition contributes to positive PE. • Negative PE in topsoil during later incubation stages is linked to reduced microbial biomass and substrate depletion. • In subsoil, positive PE and net C loss was caused by microbial N mining. Fertilization is crucial for increasing crop productivity and it alters soil microbial biomass and activities. These alterations exert implications for soil carbon (C) stocks, primarily through the priming effect (PE). Here, we investigated the mechanisms underlying PE and their impact on soil C stocks in paddy soils subjected to long-term (31 years) fertilization. Soils from four depths within the upper 40 cm layer, subjected to four fertilization types (no fertilizer, mineral fertilizer, mineral + straw, mineral + chicken manure), were incubated for 60 days with or without 13C-labeled glucose. Following substrate addition, an increase in isotopically unlabeled CO 2 efflux may stem from accelerated microbial turnover (apparent PE) or modified soil organic matter (SOM) mineralization (real PE). By analyzing microbial biomass (MBC), CO 2 and dissolved organic C (DOC) dynamics, we explored the partitioning of C from glucose into three pools. Following glucose addition (day 2), the SOM-derived MBC decreased by 4.7 % at 0–10 cm in unfertilized and by 6.3 % in mineral-fertilized soils. SOM-derived MBC also decreased in soils fertilized with straw- and chicken manure at 0–20 and 0–30 cm. Hence, the apparent PE closely correlated with fertilization types. At day 2, the SOM-derived DOC increased with the increase in extractable Fe2+ content, indicating high contribution of the released mineral-bound organic C in the DOC pool. Microbial decomposition of SOM-derived DOC and loss of unlabeled C through apparent PE increased the release of unlabeled CO 2 , resulting in a positive but low PE. After 60 days of incubation, the addition of glucose to the subsoils (30–40 cm) caused a net loss of C (positive PE) of 6.6–19 mg kg−1. In contrast, negative PEs were observed in the topsoil, indicating a decrease in microbial activity and C turnover. These findings suggested that fertilization regimes, whether involving long-term extra C input or not, can alter microbial biomass and turnover rates. Moreover, the C turnover mechanisms in paddy soils are complex, including apparent PE, release of mineral-bound organic C, and negative PE. Collectively, these processes can consequently change soil C stocks. [ABSTRACT FROM AUTHOR]

• Intact plant-soil mesocosms are translocated along an elevational gradient ranging from 1260 m to 350 m a.s.l. • Translocated microorganisms increased their active fraction, enzymatic activity and changed enzyme systems. • Warming in combination with decreased precipitation leads to shifts in microbial life strategies to K -strategists. • Microorganisms are C limited along the translocation from higher to lower elevations. • Climate change with warmer temperatures and periodically less precipitation will modify the microbial C and N demand. Soil microorganisms are the major players controlling the soil carbon (C) and nutrient cycling, however the extent to which the functional properties of soil microorganisms will alter with climate change in mountain grasslands is still unclear. To simulate future climatic conditions (higher temperature and less precipitation), intact plant-soil mesocosms of three mountain grassland sites, Esterberg (1260 m a.s.l.), Graswang (860 m a.s.l.), and Fendt 550 m a.s.l.), were translocated to the lowest elevation Bayreuth (350 m a.s.l.). After two years of translocation to warmer and drier environments, specific growth rates of soil microorganisms were 25 % slower than those at higher elevations. This indicated a shift towards to slow-growing K -strategists with increasing temperature and decreasing soil moisture, presumably attributed to the depletion of available C for microorganisms. Simultaneously, higher activity and faster substrate turnover time of C-acquiring enzymes in the warmer and drier soils implied a stronger C rather nutrient limitation. This was supported by the increased vector length, which was induced by decreased dissolved organic compounds at lower elevation. In contrast, microorganisms were limited by nitrogen (N) at higher elevation because of the stronger competition for N between plants and microorganisms. In short, translocated microorganisms increased their active fraction, enzymatic activity and altered enzyme systems but decreased specific growth rates. This indicated that soil microbial community adjusted to the changing climate resulting in faster substrate turnover, and in turn caused 15 % reduction in soil C content from Esterberg to Bayreuth. We therefore conclude that climate warming in combination with decreased precipitation increases microbial activity, leads to shifts in microbial life strategies and induces alterations in microbial nutrient limitation, i.e. shift from N- to C and P co-limitation with translocation to lower elevation sites. This in turn, is likely to result in C losses of mountain grassland soils under future climate change, which will amplify negative impacts on global warming. [ABSTRACT FROM AUTHOR]