Plant and Soil最新文献

Aims

Over recent decades, the Chinese government has instigated large-scale vegetation restoration projects across the Loess Plateau to control soil erosion. Yet, this project coupling effect with associative interannual variations and magnitudinous decreases during vegetation species’ developmental stages have rarely been explored. Therefore, we conducted experiments to explore the water budget characteristics under different stand ages of Robinia pseudoacacia.

Methods

We selected five R. pseudoacacia stand ages (i.e., 6 yr, 16 yr, 20 yr, 35 yr, and 45 yr) to investigate their individual interannual water budgets over four consecutive years (2019–2022).

Results

Compared with grassland, the significant soil water amounts were consumed within the deep soil layers (> 200 cm) of all R. pseudoacacia stand ages. The soil water storage (SWS) deficit gradually worsened between 6–20 yr but then improved between 35–45 yr. Also, SWS values of all five R. pseudoacacia stands significantly differed (p < 0.05). Interestingly, as the stands aged, the increasing rate of actual evapotranspiration (AET) largely decreased from 125 mm yr⁻¹ to 29 mm yr⁻¹. The relationship between cumulative precipitation and AET further revealed that the water equilibrium input–output state reached at the stand’s middle age (~ 20 yr), after which the positive water input feedback occurred.

Conclusions

These findings highlight that the water consumption process turning point for R. pseudoacacia occurs at the stand’s middle stage, indicating its role in SWS recovery. Our experimental evidence will benefit both researchers and policymakers, helping them to better regulate water resources and to optimize forest management alternatives.

Background and aims

Plant roots can induced changes in soil nitrogen (N) transformation, which is critical for plant N utilization in N-limited ecosystems. However, the linkage between plant N preference and the rhizosphere effects on soil N transformation is rarely explored.

Methods

We determined the relationship between plant N preference (¹⁵N labeling) and the rhizosphere effects on soil net ammonification/nitrification rates of three dominant shrub species (Artemisia ordosica, Salix psammophila, and Caragana korshinskii) in the Mu Us Desert, as well as root traits, rhizosphere and bulk soil microbiomes, functional genes and enzyme activities.

Results

S. psammophila and C. korshinskii with preference for NO₃⁻ had higher rhizosphere nitrification rates, while A. ordosica with preference for NH₄⁺ had higher rhizosphere ammonification rates. The plant N preference was also positively linked to the rhizosphere effects on soil N transformation, indicating that rhizosphere process provided positive feedback to plant N demands. Furthermore, root exudation rates and morphological traits explained the interspecific variations in rhizosphere effects on net ammonification and nitrification rates, respectively. The rhizosphere nifH gene copies and nitrogenase activity contributed to the increasing rhizosphere effect on ammonification rates, while rhizosphere ammonia-oxidizing archaea gene abundance was responsible for the rhizosphere effect on soil net nitrification rates.

Conclusion

We conclude that the linkage between plant N preference and rhizosphere effects on N transformation is driven by specific rhizosphere physical, physiological and microbial environments. This positive plant-soil feedback may promote species establishment in N-limited soils, which is insightful for understanding plant adaption from a rhizosphere perspective.

Aims

Different legumes are distributed across low phosphorus (P) steppe of Inner Mongolia from west to east, this study aimed to investigate the adaptation strategies of different legumes to soil P availability in steppe regions.

Methods

Three legumes (Caragana microphylla, Melissitus ruthenica and Medicago falcata) were grown in pots with soil P additions ranging from 0 to 300 mg P kg⁻¹ soil. Nitrogen (N) and P uptake, growth, rhizosphere processes, and N fixation were determined at harvest.

Results

C. microphylla and M. falcata exhibited increased biomass in response to P addition, with M. falcata demonstrating a more pronounced effect. M. ruthenica responded positively to P addition at 25 mg P kg⁻¹ soil, but P levels above 50 mg P kg⁻¹ soil significantly suppressed its growth and resulted in lower P utilization efficiency compared to M. falcata and C. microphylla. C. microphylla had higher acid phosphatase activity (APase) than the other species, and highest P absorption rate at P addition below 150 mg P kg⁻¹ soil. Low P enhanced succinate exudation in M. ruthenica but not in the other species. P addition promoted P uptake of M. falcata by increasing root length, area and rhizosphere acidification. Low-P deficiency reduced nodulation and N fixation of three legumes in treatments without P addition.

Conclusions

C. microphylla’s higher P absorption rate and APase activity are main adaptive traits for tolerating and adapting to low-P desert steppe soils. Due to M. ruthenica tolerating low-P with high P utilization efficiency traits, it exhibits a fast relative growth rate. M. falcata thrives in high available P soils with accelerated growth. These findings highlight each species’ distinct strategies for nutrient acquisition and adaptation to varying soil P levels, providing scientific insights for sustainable grassland management.

Backgrounds

Grassland ecosystems consist of different grassland types and provide multiple ecosystem services and functions simultaneously. However, the relative importance of plant community characteristics and soil properties in promoting the ecosystem multifunctionality (EMF) among different grassland types is unclear.

Methods

A field study was conducted to investigate the effects of multidimensional plant diversity, plant coverage, and soil properties on EMF in alpine steppe (AS), alpine meadow (AM), and alpine swamp meadow (ASM).

Results

Environmental filtration resulted in a gradual decrease in plant species diversity and Faith’ s phylogenetic diversity (PD) from AS to ASM. Plant species in AM with high functional diversity and mean phylogenetic pairwise distance (MPD). There was no significant difference in EMF among grassland types. Importantly, phylogenetic diversity and plant coverage had a direct positive effect on EMF in AS and AM, respectively. Additionally, soil moisture also played a crucial role in maintaining EMF in AS. Functional richness index (FRic) was positively correlated with EMF, while soil moisture was the key to maintaining EMF in ASM, followed by soil bulk density.

Conclusion

Our research highlighted the importance of plant community characteristics in maintaining the EMF of AS and AM. Additionally, EMF in ASM was mainly regulated by soil properties. We suggest that management measures should be established based on the specific characteristics of each grassland type, which is essential for maintaining ecosystem multifunctionality.

Background and aims

Mulching drip fertigation can effectively increases crop yields. However, with the insufficient recycling rate of mulch films and the continuous accumulation of film residues in the soil, mulch film residues and antibiotic resistance genes (ARGs) coexist in farmland. The impact of biodegradable mulch films on the reduction of soil ARGs remains uncertain.

Methods

This study employed high-throughput sequencing and high-throughput quantitative PCR (HT-qPCR) to examine the effects of three drip fertigation systems (drip fertigation without film (DI), drip fertigation with biodegradable film (DF), and drip fertigation with plastic film (PF) on bacteria and ARGs in farmland soils.

Results

The results indicated that compared with DI, mulched drip irrigation significantly reduced bacterial abundance and diversity (DI > DF > PF) but increased the abundance of ARGs and mobile genetic elements (MGEs) (PF > DF > DI). The ARG network structure in PF was more complex compared to DI and DF, whereas in DF, the ARG network structure was more stable compared to DI and PF. The abundance of MGEs directly influenced the abundance of ARGs, and the MGEs abundance was directly affected by the bacterial Shannon index, which also indirectly affected ARG abundance. Special attention was given to the impact of drip irrigation with different mulch films on ARG dissemination, emphasizing that biodegradable mulch films effectively reduce ecological risks compared to traditional plastic films.

Conclusions

In summary, although DF showed higher bacterial diversity than PF, it also reduced both the diversity and abundance of ARGs, thereby further decreasing soil ARG levels. This study provides new perspectives and scientific evidence for understanding the environmental dissemination mechanisms of ARGs and offers actionable recommendations for sustainable agricultural management, such as reducing mulch residue pollution and optimizing drip fertigation practices.

Graphical Abstract

Background and aims

Microbial necromass carbon (C) significantly contributes to soil organic carbon (SOC) sequestration. However, there is limited information on how biochar amendment affects the accumulation and allocation of microbial necromass C in soil aggregates in paddy soil remains scarce, particularly with regard to changes in microbial life strategies.

Methods

From a 2-year field experiment, topsoil samples with biochar (C15) and without biochar amendment (C0) treatments were collected and fractionated into macroaggregate (2000–250 μm), microaggregate (250–53 μm), and silt–clay (< 53 μm) fractions. We investigated the impact of maize straw-derived biochar amendment on microbial community structure, SOC, and microbial necromass C in paddy soil aggregates.

Results

Biochar amendment significantly increased SOC and microbial biomass C but reduced microbial necromass C concentration. The microbial community shifted towards K-strategists under biochar amendment. Compared with the C0 treatment, total necromass C concentration in the C15 treatment decreased by 14.9% in the bulk soil, primarily due to reductions in fungal and bacterial necromass C concentrations of 14.7% and 16.1%, respectively. The decrease in total necromass C was primarily observed in macroaggregate and microaggregate. Specially, fungal necromass C primarily decreased in macroaggregate, while bacterial necromass C decreased in microaggregate. Biochar amendment did not significantly reduce microbial necromass C in silt–clay fraction, indicating its greater stabilization due to strong binding with soil minerals under biochar amendment, thereby protects it from microbial decomposition.

Conclusions

The results offer new insights into the role of soil aggregates in microbial-mediated SOC sequestration following biochar amendment in paddy soil.

Background and aims

Flooding-driven gravel encroachment is common in arid alluvial fans. However, the effect of gravel encroachment on the plant community structure remains unclear.

Methods

We characterized the relationship between flooding-driven gravel encroachment and plant community structure in an arid alluvial fan in China. Meanwhile, a simulation experiment was conducted to evaluate the soil temperature, water retention, and water-holding capacity of soils mixed with 0%, 20%, 40%, 60, and 80% gravel.

Results

The percentages of gravel in the soils of five representative plant communities, Stipa breviflora, Stipa tianschanica, Convolvulus tragacanthoides, Ephedra rhytidosperma, and Salsola laricifolia was 34.71%, 38.68%, 61.71%, 64.30%, and 65.95%, respectively. A further simulation experiment revealed that soil temperature increased, yet soil water retention and water-holding capacity decreased as the gravel percentage increased. The density, coverage, biomass, and importance value of perennial herbs decreased, whereas those of shrubs increased with increasing gravel percentage in the soils. Thus, gravel encroachment led to an alteration from perennial herb-dominant communities to shrub-dominant communities owing to soil moisture deterioration. Although this study also found that shrubs create a beneficial living environment for herbs under their canopy, the niche overlap between perennial herbs and shrubs in shrub-dominant communities was significantly promoted. Consequently, gravel encroachment resulted in lower community stability in shrub-dominant communities.

Conclusion

Flooding-driven gravel encroachment has reshaped the plant community structure and reduced the community stability of this arid alluvial fan. Moreover, the shrub-dominant communities may difficult recover to perennial herb-dominant communities in arid alluvial fans with flooding become more intense.

Background and aims

Root traits of tree species are of great importance for selection of trees in dry zone agroforestry systems. Climate models predict increased frequency and severity of drought in the Sahel but our understanding on the strategies of root growth of tree species under drought is limited. To increase our knowledge of species differences in rooting patterns we investigated root growth of nine dryland tree species in West Africa during one year when exposed to drought stress.

Methods

Seedlings were planted in 2 m tubes inserted into the soil and subjected to irrigation and drought (no irrigation during the dry season). After 4, 8 and 12 months, we assessed root growth and root biomass, supplemented with assessments of water potential, leaf phenology, and above-ground growth.

Results

Tree species showed significant differences in rooting profile. Drought induced deeper root growth, especially in deciduous species. Adansonia digitata, Sterculia setigera and Anacardium occidentale had shallow roots when irrigated. Acacia senegal, Acacia nilotica and Faidherbia albida had deeper root growth and showed clear differences in leaf water potential between treatments while A. digitata and S. setigera appeared to be water conserving under drought.

Conclusions

Our results link root growth with phenology, physiology and above-ground growth and provide an attempt to group dryzone tree species in functional types based on their root growth.

Background and aims

Microplastics affect plant growth and change abiotic and biotic soil properties, such as soil structure and soil-community composition. However, how microplastics affect plant-soil interactions, such as plant-soil feedbacks (PSFs), is still poorly understood. Here, we tested how artificial particles affect heterospecific PSFs, depending on an intact or depleted soil community.

Methods

We conducted a two-phase-greenhouse experiment using Centaurea jacea to condition soil containing an intact or initially depleted (by sterilization) soil community in the first phase. Subsequently, we grew individuals of Crepis biennis and Eragrostis minor in all combinations of soil conditioning (presence or absence of C. jacea in the first phase), soil-community status, and different material treatments including no added particles, glass particles, or three microplastics individually and mixed. Effects of soil community, material treatment and their interaction on PSFs were assessed based on plant biomass and root-morphology traits.

Results

Particles in general, microplastics and glass, strengthened PSFs based on plant biomass. PSFs tended to be negative with the intact but positive with the initially depleted soil community. Overall, particle-addition effects on PSFs were stronger in the initially depleted community, indicating interactive effects of artificial particles in the soil and soil biota. Interactive particle and soil-community effects generally depended on material type and concentration.

Conclusion

Our findings indicate that artificial particles can affect heterospecific PSFs and that these effects are likely to be partly mediated by the initial soil community. Further, they highlight the need for studies assessing potential ecological implications of microplastics on plant-soil interactions.

Aims

Pseudomonas chlororaphis PCL1606 (PcPCL1606), displays strong antagonistic and biological control abilities against several soil-borne fungal pathogens mainly due to the production of the antifungal molecule 2-hexyl, 5-propyl resorcinol (HPR). HPR governs other beneficial phenotypes, suggesting its additional regulatory activity. Published transcriptomic data identifying HPR-regulated genes involved in the interaction of PcPCL1606 with the avocado rhizosphere were used as a target database to identify putative genes involved in avocado roots colonization.

Methods

The induction of several consecutive genes that showed homology with genes encoding a putative type IV Flp/Tad (tight adherence) pilus but with a few differences from the Tad type A and B was observed. To study the role of this tad-like gene cluster in the biology of PcPCL1606, a chromosomal deletion mutant was constructed. The molecular characterization of the tad-like gene cluster and different in vitro and in vivo phenotypes related to colonization were addressed in the mutant strain respect to PcPCL1606.

Results

The tad-like gene cluster was composed of five independent transcriptional units. Furthermore, the tad-like deletion mutant was impaired in early attachment, early biofilm formation, bacterial autoggregation and in root competitiveness in avocado plants and biocontrol activity against R. necatrix.

Conclusions

These results expand our understanding about the role of HPR as a putative signalling molecule. This study revealed the importance of a putative novel type of a Tad system of PcPCL1606 in the avocado roots colonization, confirming that initial attachment to roots is a fundamental mechanism for the PcPCL1606 rhizospheric performance.