Plant and Soil最新文献

Background and aims

Nitrogen enrichment often increases plant aboveground biomass but reduces biodiversity. The mechanisms through which increased nitrogen can lead to the loss of plant species are still highly controversial. Furthermore, atmospheric nitrogen increases gradually over years, while our current understanding of the effects of nitrogen deposition largely relies on step nitrogen addition experiments.

Methods

In this study, we conducted a step versus gradual nitrogen addition field experiment in a semiarid grassland during 3-years, focusing on the potential mechanisms underlying species loss.

Results

Our findings revealed that both gradual and step nitrogen addition significantly increased plant aboveground biomass by 150% and 221%, respectively. However, step nitrogen addition resulted in a significant reduction in plant species richness by 18%, while gradual nitrogen addition did not significantly alter species richness. Our structure equation model indicated that reduction in soil water crucially regulated the extent of species loss under step versus gradual nitrogen additions. The regulation of soil water on plant diversity was further supported by our meta-analysis of water and nitrogen addition experiments conducted across arid and semiarid grasslands worldwide.

Conclusion

Collectively, soil water content is the dominant regulator of plant species loss after nitrogen enrichment in water-limiting grasslands. Our findings suggested that 3-years total nitrogen amount rather than the nitrogen input in the final year of experiment determined decline of plant diveristy, i.e., nitrogen addition had a legacy effect on grassland community.

Background and Aims

Polygonatum, a classic source of food and traditional medicine, possess great potential and applicability in combating chronic and hidden hunger. To study the relationship between the selected Polygonatum -associated microbiome and the fitness of the host plants.

Methods

The microbial communities were investigated using a high-throughput sequencing method. Their association with the soil chemical properties and Polygonatum adaptation ability were elucidated.

Results

P. kingianum var. grandifolium (PG) was more adaptive than P. kingianum (PK) or P. sibiricum (PS) due to the highest rhizome fresh weight (RFW) and polysaccharide content (PSC) (P < 0.05). RFW and PSC reached the highest when the pH was 7.48 – 7.95 and showed a significant reduction with the soil acidification. The diversity, community structure, and composition of the rhizospheric microbiota were more significantly affected by Polygonatum than those of the endosphere. The microbial diversity and richness in the rhizosphere soils of PG were higher. Specific microorganisms were related to both the yield and quality of Polygonatum and the soil chemical properties; the highest for PG was associated with the beneficial microorganisms such as, Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium and Talaromyces in the rhizospheric soil while the low yield and poor quality of PK and PS were linked with the pathogenic microorganisms such as Pseudomonas, Fusarium, Neocosmospora, and Tausonia.

Conclusion

The adaptability of the Polygonatum genotypes was closely related to the soil pH, which may connect with the growth of either beneficial or pathogenic microorganisms in the rhizosphere, thereby affecting the growth and quality of Polygonatum.

Graphical Abstract

Background and aims

Biological soil crusts (biocrusts) play a vital role in desert ecosystems. The sand-dune slope position crucially affects biocrust growth and development. This paper investigates the effect of slope position on nonstructural carbohydrates (NSCs) in biocrusts in the Gurbantunggut Desert.

Methods

Samples were collected from the eastern and western slopes and the bottom of the slope. Biocrust coverage, soil physicochemical properties, and NSCs were assessed.

Results

The NSCs were more affected by the slope position in the lichen crusts than the algae crusts. The contents of NSCs and their components in the lichen crust were the highest at the bottom of the slope, while those of the algae crust were the highest at the eastern slope. In the algae crusts, soluble sugar, starch, and NSCs were positively correlated with the electrical conductivity, soil organic carbon, and ammonium nitrogen. In the lichen crusts, they were significantly positively correlated with the soil water content, electrical conductivity, total nitrogen, total phosphorus, and ammonium nitrogen. The structural equation model revealed that the most important factors affecting the NSCs were the changes in the soil nutrients caused for the algae crusts and the soil moisture and temperature for the lichen crusts.

Conclusions

The slope position indirectly influenced the NSC variations in the biocrusts through the soil physicochemical properties, but the key factors affecting the NSC in the different types of biocrusts were different. In conclusion, biocrusts adapt to environmental discrepancies arising from slope position by modulating the NSC content and distribution pattern.

Background and aims

Intercropping with legumes is beneficial for crop nitrogen (N) uptake, but the mechanism behind efficient N uptake in intercropping is not well understood. Therefore, this study aimed to measure the effect of crop diversity on N uptake in intercrop and to assess the mechanisms contributing to diversity effects.

Methods

The N uptake on equivalent area basis was determined during 2012 to 2014 using a long-term experiment established in 2009 including faba bean/maize intercropping and corresponding monocultures. Complementarity effects (CE) and selection effects (SE) were calculated to assess N complementarity/facilitation and dominant species effects.

Results

Faba bean/maize intercropping had 17.6% greater system N uptake than weighted means of two monocultures. The fertilizer-N rate required to achieve the maximum total N uptake was 300 kg N ha^–1 without inoculation and was 225 kg N ha^–1 with inoculation. Similar results were observed for biological N fixation of faba bean. Enhanced N uptake from intercropping compared with monoculture was strongly and positively correlated with the CE, but not correlated with the SE. In addition, N fixation accounted for approximately 20% of the positive CE in faba bean/maize intercropping.

Conclusions

N complementarity and/or facilitation drove the increased N uptake in faba bean/maize intercropping. The results highlight the role of applying microbial inoculants to increase crop N uptake while reducing reliance on fertilizer N especially in newly reclaimed desert soils, and may also be useful for guiding the design of intercropping systems with complementary traits for efficient N use.

Background and aims

Inland sand dunes constitute Natura 2000 habitat that has become a priority to ensure biodiversity protection and habitat heterogeneity at the landscape scale; however, without proper management, spontaneous succession leads to overgrowing of trees and thus to habitat degradation. Understanding succession processes, relationships between biotic and abiotic components, and their changes over time after restoration, is the key to proper planning of future restoration activities. The aim was to determine the changes of biological soil crust (BSC), vascular plants and physicochemical parameters of BSC, below-crust, rhizosphere, and bare substrate types at different stages of succession in inland dunes of the Błędowska Desert (Poland). We also analyzed the interplay between these factors to further understand the mechanism of BSC development and recognize driving factors causing changes in the soil environment.

Results

Our results showed that BSCs contributed to increased organic C, total N, nutrients in soil, and acidification with the succession. The content of inorganic N forms was significantly higher in bare soil compared to below-crust soil. Rhizosphere soil was enriched in organic matter and nutrients, which improves soil conditions within plant patches. Moreover, below-crust soil pH, total N content and water holding capacity drive the patterns of BSC morphological groups and species composition of lichens, bryophytes, and vascular plants.

Conclusion

Our study shows that spatial structure of the inland dune ecosystem is a mosaic of BSCs and plants that contribute to the spatial heterogeneity of key soil properties. We concluded that it is necessary to consider the matter of BSC in restoration treatments.

Background and aims

Soil quality is critical to maintaining the sustainability of vegetation reclamation. However, its variation and crucial driving factors along long-term reclamation chronosequences in metallic mine wastelands require further exploration.

Methods

This study determined the variation in soil quality and its dominant drivers across a 49-year vegetation reclamation chronosequence in a vanadium titanomagnetite tailings reservoir using the minimum data set-soil quality index (MDS-SQI) method by analysing multiple soil physical, chemical, and biological properties and plant biomass.

Results

The results revealed that phosphatase (AP), soil organic carbon (SOC), heavy metal pollution (PLI), clay, and total phosphorous were retained as indicators of the MDS. The SQI values increased significantly during the first 13 years after reclamation (p < 0.01), owing to the elevated AP activities and SOC contents. They then maintained a stable and high level within the following reclamation age, which was attributable to the sluggishly increased AP activities and SOC contents and constantly increased PLI values. The aboveground plant biomass primarily drove the reclamation-age dependence of the SQI by impacting soil (microbial) nutrient turnover.

Conclusions

Our study highlights the necessity of incorporating changes in soil heavy metal pollution into post-reclamation soil quality monitoring in metallic mine wastelands. Moreover, the results imply that aboveground plant biomass can indicate the response of soil quality to long-term vegetation reclamation at sites with a single vegetation composition.

Background

Soil water dynamics and its response to precipitation are affected by soil properties and vegetation characteristics. Changes in forest age will significantly affect soil properties and vegetation characteristics. Therefore, exploring the contribution of rainfall to soil water (CRSW) in forests with different ages is helpful to understand the recharge mechanism of precipitation to soil water in forests with different ages.

Methods

We calculated the CRSW by using stable hydrogen isotope combined with binary linear mixed model. Furthermore, we used structural equation modeling (SEM) to quantify the relative importance of vegetation factors (leaf area index, litter and fine root biomass) and soil properties (bulk density, porosity and field capacity, pre-rain soil water content) to CRSW.

Results

Following small rainfall events (7.4 mm, 19.6 mm), there was no difference in CRSW among forests with different ages, while the CRSW of rainfall events above 20 mm (23.3 mm, 30.1 mm, 47.3 mm) was significantly different among them. When heavy rainfall events (30.1 and 47.3 mm) occurred, the CRSW of the old-growth forest (> 150 years) was the largest. SEM analysis showed that plant factors significantly affected CRSW after 23.3 mm and 30.1 mm rainfall events. After the 47.3 mm rainfall event, soil properties were the most important factors affecting CRSW.

Conclusions

Under the background of frequent extreme precipitation events, old-growth forests (> 150 years) exhibit stronger storage capacity for large-scale rainfall events. Therefore, the effects of forest age on soil water interception and storage should be fully considered in the forest management and protection.

Background and aims

Drought has a substantial adverse impact on maize growth during the jointing stage. Nitrogen (N) is an essential nutrient that fosters the growth and yield of maize. However, the underlying mechanisms behind the connection between N and drought tolerance require elucidation.

Methods

In this study, we explored the effects of drought and N application on maize during the jointing stage using soil column cultivation. The investigation includes phenotypic analyses, measurements of physiological indexes, microstructural observations, and proteomics analyses.

Results

The impacts of N on maize plants under drought stress were as follows: (1) The supply of N enhanced the root water uptake capacity by reducing the biosynthesis of lignin in the root endodermis and increasing the proportion of deep nodal roots; (2) N reduced the inhibition of photosynthate assimilation caused by drought, resulting in increased leaf area, chlorophyll content, biomass and higher levels of growth-promoting hormones; (3) N improved drought tolerance in maize plants, probably caused by N strengthening the root antioxidant system and thus maintaining reactive oxygen species (ROS) homeostasis.

Conclusions

The physiological mechanisms of N in alleviating drought in maize at the jointing stage, as explored in this study, provide a theoretical foundation and potential strategies for dryland maize cultivation or the selection and design of new drought-tolerant maize lines.

Background and aims

Despite plant-soil interactions being able to influence the functional characteristics of vegetation, it remains unclear whether and how the effects of different coastal reclamation patterns on plant-soil interactions would change vegetation allocation strategies and biodiversity.

Methods

This study evaluated the vegetation characteristics, soil quality, and plant-soil interactions in three different types of wetlands: a natural coastal wetland (NCW), a reclaimed wetland with sea embankments on a native wetland (SEW), and a reclaimed wetland formed through land reclamation from the sea (LRW).

Results

The findings indicated that different reclamation patterns significantly impacted the ecological characteristics of Spartina alterniflora and Phragmites australis communities in coastal wetlands (P < 0.05), while Suaeda salsa communities were insensitive to reclamation. Reclamation activities improved the integrated soil quality index by 5% in SEW and 27% in LRW. Notably, enhancing soil quality may boost above ground biomass allocation while reducing biodiversity. Additionally, plant-soil interactions in reclaimed wetlands showed light incoordination, with the higher coordination degree potentially promoting root allocation and biodiversity.

Conclusion

Coastal reclamation impacts plant-soil interactions, varying by reclamation patterns and community types. In the future restoration and management of reclaimed wetlands, zoned management should be implemented according to different types of plant communities, with appropriate thinning and replanting of native species based on the plants growth status to promote species diversity. Moreover, management practices such as improving soil aeration and inoculating beneficial microbial formulations are recommended to enhance coordinated plant-soil interactions.

Graphical abstract

Background and aim

Soil bacterial and fungal communities play different but mutually interrelated roles in releasing enzymes that catalyze organic matter decomposition. In Malaysian Borneo, decreasing litter inputs caused by forest degradation lead to reductions in soil organic carbon (SOC) and C/N ratio. Enzyme activities also decrease with forest degradation. However, it is unclear if/how changes in microbial community compositions affect soil enzymes, despite their importance in ecosystem processes. We investigated how reduced SOC substrate affects microbial community compositions and further influences enzyme activities during forest degradation.

Methods

We used 16S and ITS amplicon sequencing and ergosterol extraction to derive microbial absolute and relative abundances. A principal coordinate analysis was performed on absolute abundances to analyze patterns of bacterial and fungal community compositions. Structural equation modeling (SEM) was conducted to investigate how SOC affects enzyme activities via microbial community compositions.

Results

Fungal community composition shifted more distinctly than bacterial community composition along the forest degradation gradient. SEM suggested that reduced SOC influenced bacterial and fungal community compositions, while fungal community composition affected activities of acid phosphatase, β-glucosidase, and leucine aminopeptidase.

Conclusion

Changes in fungal community composition may be due to different responses of fungal phyla to changing quality of bulk soil organic matter with decreasing litter input during forest degradation. Variations in fungal community composition subsequently induced changes in enzyme activities. By contrast, bacterial community composition did not change because labile organic matter of bacterial substrates was available throughout degradation course, particularly such matter being supplied as fungal decomposition by-products.