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Main conclusion: The keys to alkali-stress resistance of barren-tolerant wild soybean lay in enhanced reutilization of reserves in cotyledons as well as improved antioxidant protection and organic acid accumulation in young roots. Soil alkalization of farmlands is increasingly serious, adversely restricting crop growth and endangering food security. Here, based on integrated analysis of transcriptomics and metabolomics, we systematically investigated changes in cotyledon weight and young root growth in response to alkali stress in two ecotypes of wild soybean after germination to reveal alkali-resistance mechanisms in barren-tolerant wild soybean. Compared with barren-tolerant wild soybean, the dry weight of common wild soybean cotyledons under alkali stress decreased slowly and the length of young roots shortened. In barren-tolerant wild soybean, nitrogen-transport amino acids asparagine and glutamate decreased in cotyledons but increased in young roots, and nitrogen-compound transporter genes and genes involved in asparagine metabolism were significantly up-regulated in both cotyledons and young roots. Moreover, isocitric, succinic, and l-malic acids involved in the glyoxylate cycle significantly accumulated and the malate synthetase gene was up-regulated in barren-tolerant wild soybean cotyledons. In barren-tolerant wild soybean young roots, glutamate and glycine related to glutathione metabolism increased significantly and the glutathione reductase gene was up-regulated. Pyruvic acid and citric acid involved in pyruvate–citrate metabolism increased distinctly and genes encoding pyruvate decarboxylase and citrate synthetase were up-regulated. Integrated analysis showed that the keys to alkali-stress resistance of barren-tolerant wild soybean lay in enhanced protein decomposition, amino acid transport, and lipolysis in cotyledons as well as improved antioxidant protection and organic acid accumulation in young roots. This study provides new ideas for the exploitation and utilization of wild soybean resources. [ABSTRACT FROM AUTHOR]

Main conclusion: The poor-soil-tolerant wild soybean resist phosphorus deficiency by remodeling membrane lipids to reuse phosphorus. The plants synthesize phenolic acids and flavonoids to remove reactive oxygen species and protect membrane stability. Poor soil largely limits plant yields, and the development and utilization of high-quality wild plant resources is an effective approach to resolving this problem. Two ecotypes of wild soybean were used as experimental materials in this experiment. We integrated metabolomics and transcriptomics to determine whether wild soybean (Glycine soja) could resist phosphorus deficiency by remodeling and protecting its membrane system. Under phosphorus-deficient conditions, the plant height and aboveground fresh and dry weight of poor-soil-tolerant wild soybean seedlings were less inhibited than those in common wild soybean. In poor-soil-tolerant wild soybean seedling leaves, the glycerol-3-phosphate content decreased significantly, while caffeic acid, ferulic acid, shikimic acid, phenylalanine, tyrosine, and tryptophan increased significantly. β-Glucosidase and chalcone synthase genes and those that encode SQD2, a crucial enzyme in thiolipid biosynthesis, were specifically up-regulated, whereas the glucosyltransferase UGT74B1 gene was down-regulated. The poor-soil-tolerant wild soybean enhanced glycerolipid metabolism to decompose phospholipids and release phosphorus for reuse to improve resistance to phosphorus deficiency. The plants synthesized thiolipids to replace phospholipids and maintain membrane structure integrity and inhibited glucosinolate biosynthesis to promote phenylpropanoid biosynthesis, leading to the production of phenolic acids and flavonoids that removed reactive oxygen species and protected membrane system stability. The experiments evaluated and provided insight into the innovative utilization of wild soybean germplasm resources. [ABSTRACT FROM AUTHOR]

Background and aims: Soil microorganisms play key roles in soil nutrient turnover and plant community composition; however, the soil microbial community composition and species diversity are often influenced by nutrient enrichment which may affect how soil microbes influence nutrient cycles and the plant community structure. The resistance of soil fungal and bacterial communities to nitrogen (N) and phosphorus (P) additions and whether the responses of the soil microbes and the plant community are simultaneous in a N-limited temperate meadow ecosystem are still unclear. Methods: We carried out a 7-year experiment with N and P additions in a temperate meadow. The community structures of soil bacteria and fungi were examined based on high-throughput sequencing targeting the 16S rRNA and ITS genes, respectively. Results: Nitrogen addition did not influence the community composition or species richness of bacteria, but it did alter the soil fungal community composition and increased fungal operational taxonomic unit (OTU) richness. Phosphorus addition significantly altered the soil fungal and bacterial community compositions, decreased the richness of bacterial OTUs, and increased the OTU richness of fungi. Proteobacteria (38.5%) and Acidobacteria (22.3%) were the most dominant bacteria. Ascomycota were the dominant fungi (42.6%) across all samples. The enrichment of available P in the soil due to P addition reduced the bacterial β-diversity, while the β-diversity of soil fungi was mainly influenced by the concentrations of soil N and P, as well as soil moisture. Conclusions: The sensitivity of soil fungi and bacteria to P addition was stronger than that of N addition, and the response of the soil microbes to N and P additions was more sensitive than that of the plant community. Our results highlight the unequal sensitivity of the soil fungal and bacterial community composition and structure to N and P additions, thereby causing changes in above and belowground community composition and structures in the studied temperate meadow ecosystem. [ABSTRACT FROM AUTHOR]

Studying the responses of phytoliths to warming is a new approach to interpret how grassland ecosystems respond to global change. We used an infrared radiator to simulate warming on Phragmites communis in the Songnen Grassland, China - three warming treatments and a control were used to study the relationships between phytolith size and temperature. Warming changed the size of different types of phytoliths. During June-October, the average size of saddle phytoliths decreased and that of hair cell phytoliths and silicified stomata increased with warming. The responses of phytolith size to warming differed among months. With warming, the size of saddle phytoliths, hair cell phytoliths and silicified stomata increased in July and September, but decreased in October. Overall, the results demonstrate that P. communis phytoliths were sensitive to warming. This study provides experimental evidence for phytoliths as reliable proxy indicators for reconstruction of paleo-environments. [ABSTRACT FROM AUTHOR]

Phragmites communis phytoliths were extracted from the xerophytic habitat of 12 sampling sites in northeast (NE) China during June-October in 2011 and 2012. The changes of P. communis phytolith concentrations in different temperature zones and growth stages were used to reveal the ecological environmental significance of P. communis phytoliths. The purpose of the study is to provide a scientific reference for quantitative reconstruction of paleoenvironment and studies of phytolith formation. The main phytolith types extracted from the 12 sampling sites and different growth stages were identical; however, the phytolith concentrations differed markedly. In NE China, from the temperate to the warm temperate zone, as temperature increased, the saddle phytoliths, bulliform phytoliths and the silicified stomata concentrations all increased, whereas the lanceolate phytolith concentration decreased. Moreover, in the humid, semi-humid and semi-arid areas, there were different responses of P. communis phytolith concentrations to temperature. Consequently, the spatial results showed that P. communis phytolith concentrations in NE China were closely related to temperature, which enabled inference of the change in temperature from phytolith concentration; however, they were also somewhat affected by humidity. During June-October, the temporal variation results of P. communis phytolith concentrations revealed that there were high lanceolate and bulliform phytolith concentrations in September or October; whereas the saddle phytolith concentration was high in July or August, and the maximum concentration for silicified stomata was in July. These findings may improve the understanding of phytolith formation, and provide useful information to further interpret phytolith assemblages in sediments. [ABSTRACT FROM AUTHOR]

Background and Aims: Gaining a better understanding of the legacy effects of logging and forest restoration on soil microbial communities could improve our ability to conserve biodiversity and promote ecosystem sustainability. Herein, we investigated how soil microbial community is linked to natural, restored, and planted forests and the legacies of historical forest. Methods: Soil microbial biomass and composition were measured in four forest types (i.e., primary forest, once-clearcut forest, twice-logged forest, and plantation forest) and related to physico-chemical soil properties and forest community structure data by using analysis of covariance. Results: Fungal, bacterial, and total microbial biomass measured by phospholipid fatty acid profiles were significantly lower in the two secondary forests and the plantation than in the primary forest. The conversion of vegetation and soil regimes due to forest logging altered microbial communities. Conclusions: Our findings elucidate the correlation of plant communities and soil characteristics to soil microbial communities in the context of subtropical forest management. Naturally restored and planted forests may affect soil microorganisms largely by directly modifying the soil labile C and N fractions of organic matter. [ABSTRACT FROM AUTHOR]

Deposited in plant cells and their intercellular space, phytoliths, a special form of silica, could be used to determine information on plant structure and physiology especially their size and content. With the hypothesis that phytolith in plant would change under variable climate and environment, the dominant plant species in Songnen grassland, guinea grass ( Leymus chinensis), was treated by an open-top chamber (OTC) to elevate CO concentration, infrared heaters, and artificial nitrogen (N) addition for three years from 2006-2008. Phytoliths were extracted by wet-ashing method and analyzed by variance analysis and so on. We found that the responses to elevated CO are complicated, and warming is positive while N addition is negative to the deposition of phytoliths in L. chinensis leaves. Especially, warming could reduce the negative impact of N addition on phytolith in L. chinensis. The short cell's taxonomic in graminea is significant because of no disappearance with simulated environmental changes. The phytolith originated in the long cell and plant intercellular space are more sensitive to elevated CO concentration, warming, and N addition, and could become some new indicators for environmental changes. In conclusion, different phytolith types have various responses to simulated warming, N addition and elevated CO concentration. [ABSTRACT FROM AUTHOR]

Measuring the response of terrestrial ecosystems to elevated CO2 concentrations is very important for understanding the effects of global change. In this study, OTC (open top chambers) were used to simulate elevated CO2 concentrations in the Songnen Grassland. As well, phytoliths in Leymus chinensis were extracted to study the relationships between phytoliths and CO2 concentration. The results show the rondel is abundant in Leymus chinensis, while the trapeziform polylobate is rare. When phytolith production is increased, the rondel phytoliths grow bigger and the proportions of the different phytolith types changes under high CO2 concentration. These types include elongate hollow, acicular hair cell, square and laminate and are only observed in samples grown under high CO2 concentrations. All this evidence demonstrates that phytoliths in Leymus chinensis are sensitive to CO2 concentration, and indicate that phytolith analysis may have potential use in the study of global change, identifying different ecotypes of Leymus chinensis and for the reconstruction of paleoatmospheric CO2 concentrations. [ABSTRACT FROM AUTHOR]

In this study, the linear regression between soil respiration rate and root biomass was adopted to estimate the contribution of root respiration to total soil respiration in Puccinellia tenuiflora dominated community of a semi-arid meadow steppe in northeast China. The soil respiration rate reached the maximum value 2.45 µmol·m-2·s-1 in late June and the minimum value 0.39 µmol·m-2·s-1 in late September. Soil temperature is the major environmental factor controlling the seasonal variation of soil respiration. The root biomass ranged from 0.54 to 0.97 kg·m-2, showing insignificant seasonal variation. Microbial biomass C reached the maximum value 0.50 g·m-2 in mid August, presenting the least within-site variation. The pattern of seasonal change in root respiration rate was different from that in microbial respiration. Root respiration rate ranged from 0.19 µmol·m-2·s-1 in May, to the maximum value 1.39 µmol·m-2·s-1 in late June, then down to 0.28 µmol·m-2·s-1 in late September; whereas, microbial respiration rate ranged from 0.61 µmol·m-2·s-1 in May, to the maximum value 1.27 µmol·m-2·s-1 in July, then down to 0.11 µmol·m-2·s-1 in late September. There was a significant exponential correlation between microbial respiration rate and soil temperature, whereas not so for root respiration rate. We estimated that the contribution of root respiration to total soil respiration ranged within 24% - 57% in spring and summer, and increased to 73% in autumn. [ABSTRACT FROM AUTHOR]

Aims: The interactions between aboveground and belowground biota are crucial for determining plant community composition and the response of ecosystem stability to climate change, but how warming and drought further impact plant performance and plant competition during plant-soil feedback (PSF) remains unclear.We investigated the impact of soil community compositions and root traits on the PSF and plant competition. We used two types of plants: Leymus chinensis (perennial and dominant), and Kalimeris integrifolia (annual and subordinate) subjected to warming and drought in both monoculture and competitive conditions. Soil bacterial and fungal community compositions, aboveground biomass, and plant root functional traits were assessed.We found that in most cases, L. chinensis remained the dominant position in interspecific competition due to its stronger root system and other aspects. However, K. integrifolia exhibited higher competitiveness after plant-soil feedback, particularly in soil that had been conditioned by K. integrifolia. Our path analysis results indicate that warming had an impact on the PSF and plant competitiveness by negatively influencing the soil bacterial community composition and positively influencing the soil fungal community composition rather than affecting plant root traits. Drought did not affect the PSF and plant competitiveness via affecting soil microbial community and plant root traits.Our findings indicated that soil microbial communities may have a greater impact on the PSF under climate change. Our study also highlights the mechanisms by which climate change alters the PSF and the structure of plant communities by altering the interactions between plant and soil microorganisms.Methods: The interactions between aboveground and belowground biota are crucial for determining plant community composition and the response of ecosystem stability to climate change, but how warming and drought further impact plant performance and plant competition during plant-soil feedback (PSF) remains unclear.We investigated the impact of soil community compositions and root traits on the PSF and plant competition. We used two types of plants: Leymus chinensis (perennial and dominant), and Kalimeris integrifolia (annual and subordinate) subjected to warming and drought in both monoculture and competitive conditions. Soil bacterial and fungal community compositions, aboveground biomass, and plant root functional traits were assessed.We found that in most cases, L. chinensis remained the dominant position in interspecific competition due to its stronger root system and other aspects. However, K. integrifolia exhibited higher competitiveness after plant-soil feedback, particularly in soil that had been conditioned by K. integrifolia. Our path analysis results indicate that warming had an impact on the PSF and plant competitiveness by negatively influencing the soil bacterial community composition and positively influencing the soil fungal community composition rather than affecting plant root traits. Drought did not affect the PSF and plant competitiveness via affecting soil microbial community and plant root traits.Our findings indicated that soil microbial communities may have a greater impact on the PSF under climate change. Our study also highlights the mechanisms by which climate change alters the PSF and the structure of plant communities by altering the interactions between plant and soil microorganisms.Results: The interactions between aboveground and belowground biota are crucial for determining plant community composition and the response of ecosystem stability to climate change, but how warming and drought further impact plant performance and plant competition during plant-soil feedback (PSF) remains unclear.We investigated the impact of soil community compositions and root traits on the PSF and plant competition. We used two types of plants: Leymus chinensis (perennial and dominant), and Kalimeris integrifolia (annual and subordinate) subjected to warming and drought in both monoculture and competitive conditions. Soil bacterial and fungal community compositions, aboveground biomass, and plant root functional traits were assessed.We found that in most cases, L. chinensis remained the dominant position in interspecific competition due to its stronger root system and other aspects. However, K. integrifolia exhibited higher competitiveness after plant-soil feedback, particularly in soil that had been conditioned by K. integrifolia. Our path analysis results indicate that warming had an impact on the PSF and plant competitiveness by negatively influencing the soil bacterial community composition and positively influencing the soil fungal community composition rather than affecting plant root traits. Drought did not affect the PSF and plant competitiveness via affecting soil microbial community and plant root traits.Our findings indicated that soil microbial communities may have a greater impact on the PSF under climate change. Our study also highlights the mechanisms by which climate change alters the PSF and the structure of plant communities by altering the interactions between plant and soil microorganisms.Conclusions: The interactions between aboveground and belowground biota are crucial for determining plant community composition and the response of ecosystem stability to climate change, but how warming and drought further impact plant performance and plant competition during plant-soil feedback (PSF) remains unclear.We investigated the impact of soil community compositions and root traits on the PSF and plant competition. We used two types of plants: Leymus chinensis (perennial and dominant), and Kalimeris integrifolia (annual and subordinate) subjected to warming and drought in both monoculture and competitive conditions. Soil bacterial and fungal community compositions, aboveground biomass, and plant root functional traits were assessed.We found that in most cases, L. chinensis remained the dominant position in interspecific competition due to its stronger root system and other aspects. However, K. integrifolia exhibited higher competitiveness after plant-soil feedback, particularly in soil that had been conditioned by K. integrifolia. Our path analysis results indicate that warming had an impact on the PSF and plant competitiveness by negatively influencing the soil bacterial community composition and positively influencing the soil fungal community composition rather than affecting plant root traits. Drought did not affect the PSF and plant competitiveness via affecting soil microbial community and plant root traits.Our findings indicated that soil microbial communities may have a greater impact on the PSF under climate change. Our study also highlights the mechanisms by which climate change alters the PSF and the structure of plant communities by altering the interactions between plant and soil microorganisms. [ABSTRACT FROM AUTHOR]