Plant and Soil最新文献

Background and aims

Although root distributions are assumed to be important for plant growth and coexistence, it remains difficult to quantify how root distributions affect resource uptake and plant landscape abundance.

Methods

In a water- and nitrogen (N)-limited grassland system, Minnesota, USA, we injected water and N tracers to five depths (5–150 cm) during peak growing season. Tracer concentrations in 11 dominant species were measured to describe functional root distributions. Seasonal water and N uptake into these functional root distributions was estimated using depth-specific resource availability. Plant biomass produced from seasonal water and N uptake was estimated using water- and N-use efficiencies. Finally, biomass production was compared to plant landscape abundance.

Results

Differences in functional root distributions resulted in seasonal water uptake between 52 and 67 cm yr⁻¹, and N uptake between 1.0 and 3.1 g m⁻² yr⁻¹ among species. Biomass production caused by water or N uptake was correlated with plant landscape abundance (R² = 0.37, 0.35, for water and N). When combined, biomass production from water and N uptake was better correlated with plant landscape abundance (R² = 0.75).

Conclusion

We show how root systems forage independently for different resources. Consistent with resource availability, water uptake patterns were shallower than N uptake patterns. Root uptake of these two limiting resources affected plant growth and landscape abundance. We provided a quantitative link between functional root distributions, resource uptake, biomass production, and plant landscape abundance. This research represents an important advance from research that describes niche differences among root systems.

Background and aims 

Vascular plants and moss biocrusts are known to coexist in drylands, wherein vascular plant cover is known to be a major influencing factor for biocrusts development. Vascular plants produce litter which may affect moss biocrusts when covering them. However, to which extent the cover of litter may affect the physiology, e.g., photosynthetic activity, of moss biocrusts remains poorly understood.

Methods

We studied the effect of the litter covering on biocrust-forming mosses on the northern Chinese Loess Plateau over four-month period. We used litter from shrubs of Artemisia ordosica and Caragana korshinskii with two levels of litter “thickness”, and monitored moss greenness, and several indicators of moss physiological activity.

Results

Litter covering reduced moss greenness, content of chlorophyll a and b, soluble sugar, and soluble protein, suggesting a reduced photosynthetic and metabolic activity of mosses under litter cover. On the other hand, mosses covered by litter showed higher contents of malondialdehyde, proline, and catalase activity compared to those mosses without any litter cover, suggesting that litter covering increased oxidative stress in mosses and triggered a protective response against oxidative damage. Moreover, we found litter thickness exerted a more significant impact on the physiological indices of mosses than litter type.

Conclusions

Our results demonstrate the detrimental effects of litter covering on the physiological activity of biocrust-forming mosses. The findings provide a mechanistic understanding of the reductions in mosses in ecosystems with high shrub cover, highlighting the importance of litter in mediating the relationships between moss biocrusts and shrub patches.

Background and aims

Soil organic carbon (SOC) content dominates the organic carbon pools in grasslands. Thus, factors that influence and regulate SOC content must be clarified when addressing global climate change.

Methods

We investigated SOC in the top 10 cm of the soil layer from 109 plots of the Mongolian Plateau, including both desert-steppe and steppe landscapes. We then examined the association between SOC with grazing intensity, climatic factors, soil properties, and vegetation diversity indices.

Results

Desert-steppe samples had lower mean SOC than steppe samples (0.3% versus 1.5%). Desert-steppe SOC did not vary with grazing intensity, but steppe SOC did. Instead, desert-steppe SOC decreased and increased, respectively, with higher growing season temperature and soil electrical conductivity; these two variables were the major factors influencing SOC in this grassland type. Besides grazing, outside growing season precipitation and soil pH were the major environmental factors that correlated positively with steppe SOC.

Conclusion

The SOC of steppe grasslands was more sensitive to grazing than SOC of desert-steppe grasslands. Additionally, while climate, grazing, soil, and vegetation all regulated SOC, the most influential variables differed between the two grassland types. These findings enhance our understanding of SOC regulatory mechanisms in different grasslands on the Mongolian Plateau. Such knowledge is crucial for predicting the consequences of environmental change on carbon sequestration.

Background and aims

Land degradation poses a serious threat to soil quality health. Our study aimed to assess soil quality more effectively by establishing a valid and accurate soil quality index (SQI) for four land degraded levels in northeast China.

Methods

The minimum data set (MDS) and different scoring techniques (linear and nonlinear scoring) were selected through network analysis (NA) and principal component analysis (PCA). As potential SQI indicators, 11 physical, 12 chemical and 6 biological indicators were measured at 0 – 20 cm depth.

Results

Our results showed that the soil properties were degraded and SQI decreased significantly with increasing land degradation. In addition, maize yield was positively related to SQI. The number of MDS generated by NA was much lower than that generated by PCA but increased the contributions of the indicators. For validating the accuracy and sensitivity of SQI, we found SQI-NA had greater correlations with maize yields and higher sensitivity indexes than SQI-PCA, implying that NA performs better in terms of accuracy and sensitivity to variation in soil quality under land degradation. So NA not only screens fewer metrics but also is more efficient in differentiating among SQIs. In addition, the SQIs calculated using the nonlinear integral through NA (NA-NL) had larger sensitivity index and F values than the other SQIs and were thus better able to discriminate under land degradation.

Conclusion

We conclude that NA-NL was recommended as a sensitive and effective approach for assessing SQIs at different land degradation levels.

Aims

Ecological restoration of mine tailing ponds plays a crucial role in managing heavy metal pollution and enhancing biodiversity. This study aimed to investigate the ecological restoration potential of pioneer plants under high manganese metal pollution, as well as the microbial community composition and functional characteristics of their rhizosphere soil.

Methods

Sampling and analysis were conducted on seven plants of Neyraudia reynaudiana (LL), Pueraria montana (GT), Bidens pilosa (GZC), Buddleja asiatica (BBF), Pogonatherum crinitum (JSC), Crotalaria albida (XND), Thysanolaena maxima (ZYL) and their rhizosphere soil in Daxin manganese tailing ponds of Guangxi Province.

Results

Pioneer plants improved the physicochemical properties of rhizosphere soil, and increase soil enzyme activity and the abundance and diversity of microbial communities, and reduce soil available metal content. The BTF values of GZC, GT, BBF, and XND are close to or greater than 1 for Mn, Cd and Cu, indicating their strong ability to absorb and transfer heavy metals from underground to above-ground. Proteobacteria, Actinobacteria, and Bacteroidetes are the bacterial communities with the dominant abundance, showing a significant positive correlation with the BTF value and promoting the absorption of heavy metals by plants. FAPROTAX function prediction revealed that chemoheterotrophy, aerobic chemoheterotrophy, and chloroplasts were the main metabolic modes.

Conclusions

GZC, GT, BBF, and XND can be utilized as habitat improvement plants in the preliminary ecological restoration of manganese tailing ponds. Rhizosphere soil microorganisms of pioneer plants respond to heavy metal pollution by regulating community structure and influencing metabolic function.

Graphical abstract

Aims

HDS sediment is a type of solid waste produced when the high-concentration mud method (HDS) is adopted to treat acid wastewater from copper mines. It can rationally utilize sediment resources by using phytoremediation, which plays a role in the ecological restoration of mines.

Methods

To reveal the effect of different phytoremediation on the heavy metal, enrichment capacity and microbial diversity of the HDS sediments of copper mines, in this experiment, the HDS sediments of a copper mine without phytoremediation were selected as the control group, while the sediments of black locust (Robinia pseudoacacia), slash pine (Pinus elliottii Engelmann) and Chinese white poplar (Populus tomentosa Carr.) were used as test groups to analyze the physical and chemical properties, heavy metal pollution and bioaccumulation capacity of HDS sediments under three phytoremediation.

Results

The results show that different phytoremediation can reduce the sediment's conductivity and adjust the sediment’s pH value to the range suitable for plant growth. The BCF_Shoot and BTF values of Chinese white poplar to Cd and Zn and slash pine to Pb were both greater than 1.

Conclusions

As discovered from the bioconcentration coefficient and biotransport coefficient results, Chinese white poplar is a Cd-enriched and Zn-enriched plant, while slash pine is a Pb-enriched plant.

Background and aims

The Kiwifruit Vine Decline Syndrome (KVDS) is a disease that is currently a challenge for kiwifruit production in Italy, and it is spreading in new production areas. However, the causal agent of this syndrome has not been clearly identified, and we still know little about the overall effects of KVDS on the interactions between the host plant and its microbiome.

Methods

In this study, we combined metabarcoding and targeted isolation (leaf baiting) to characterize the changes in the rhizosphere and root microbiomes associated with symptoms of KVDS.

Results

Our results suggest that KVDS has little impact on the bacterial, fungal, and oomycete communities associated with soil and roots, and we detected weak signatures of potential dysbiosis. On the other hand, we found a consistent association of the oomycete Phytopythium vexans with samples from plants symptomatic to KVDS, which matches the nucleotide sequences of the isolates obtained through baiting and, partially, the isolates from previous studies.

Conclusion

While our results support the idea that P. vexans might be the major candidate agent of KVDS, there are still several unanswered questions that need to be addressed before being able to provide effective solutions to this emerging challenge in kiwifruit production.

Background and aims

Understanding the variation of root hydraulic conductance (L_p) is critical for the simulation of the soil–plant-atmosphere continuum (SPAC), but its monitoring remains challenging. In this study, we introduce a new non-destructive method for characterizing L_p dynamics in woody species through the combination of simultaneous determinations of sap flow and xylem water potential. Recent studies indicate that modern microtensiometers provide robust estimates of xylem water potential, but it is unknown whether they allow tracking rapid changes in water potential without significant time lags, which may have implications for the proposed methodology.

Methods

The impulse response of microtensiometers was measured in the lab, developing a procedure for correcting sensor data by deconvolution. Then, microtensiometers and compensation heat pulse sensors were used to evaluate the variations in L_p in two well-watered olive trees during the summer of 2022 in Cordoba, Spain.

Results

Correcting microtensiometer outputs was critical to analyze our field data as strong stomatal oscillations occurred, with microtensiometers damping xylem water potential variations. By contrast, our results suggest that correction procedures may not be required for many practical applications like irrigation scheduling. The daytime values of L_p were close to those obtained in previous studies, while nighttime values were extremely low. Therefore, a proportionality between L_p and sap flow rate was observed, which agrees with previous studies, although it does not prove a causal relationship.

Conclusions

The methods proposed here could be applied to studying the temporal dynamics of root hydraulic conductance in other tree species.

Background and aims

Both soil properties and plant traits shape the diversity, composition and functions of plant-associated soil microbial communities. However, the relative influence of these factors is poorly understood, as are interactive effects between factors and the degree to which their influence varies among climate zones.

Methods

To address this gap, we compared the diversity and composition of soil microbial communities associated with co-occurring C₃ and C₄ grasses from arid and mesic environments, and plant traits influencing them.

Results

Climate emerged as the main determinant of plant traits and microbial community properties. Within each climatic region, above- and below-ground traits and soil properties differentially affected microbial community composition, and their relative influence varied among communities. In both mesic and arid environments aboveground traits related to quantity and quality of leaf litter (e.g., specific leaf area, leaf C content) and nutrient availability were the most influential variables for community composition. However, in arid regions, belowground traits (i.e., root tissue density and specific root area) significantly contributed to structure the eukaryotic community, supporting the role of roots as important driver of eukaryotic differentiation in constrained environments. Further, the presence of C₄ plants in the arid region resulted in higher relative abundance of ciliate protists and higher recruitment of potentially beneficial microbial community members from green algae mediated by drought adaptation traits (e.g. decreased abundance of fine roots).

Conclusions

Overall, our study revealed a differential response of microbial communities to environmental conditions, suggesting that soil microbial community composition is influenced by trade-offs between host adaptive traits across distinct climatic regions.

Background and aims

Increased atmospheric nitrogen (N) deposition and climate warming can both exert strong, cumulative effects on N losses from ecosystems. However, given their potential interactions with interannual variability in environmental conditions or other factors, it is uncertain how effectively the comparison of short- vs. long-term results from N addition and warming field experiments can reveal these cumulative effects. Our aim was to compare the short-term versus long-term effects of N addition and warming on aboveground and belowground N retention while controlling for interannual variation in other factors.

Methods

We added ¹⁵N tracer to N addition and warming plots in a northern temperate grass-dominated old field in early spring, then assessed the amount of the added ¹⁵N recovered aboveground and belowground at the peak of the growing season. We controlled for interannual variation in background environmental conditions by comparing new N addition and warming plots (3 years old) to those of an existing field experiment (16 years old).

Results

Both N addition and warming significantly increased aboveground and belowground ¹⁵N tracer retention. However, there were no significant interactions between either of the treatments and plot age for ¹⁵N tracer retention, nor for plant production. The lack of interactions with plot age corresponded with the continued dominance of two non-native grass species in the plots.

Conclusion

Our results highlight the potentially important role of dominant species that resist replacement in buffering against the effects of global change on cumulative, long-term changes in ecosystem N retention.