Carvalho, Paulo Cesar de FaccioPires, Gabriela CastroOliveira, Rafael Loverdede Souza, Juliana Mendes Andrade...
10页
查看更多>>摘要：In sustainable tropical agriculture, grass-legume intercropping can increase productivity, enhance the nutritional quality of the crop and affect soil microbiological activity, leading to higher yields in succession crops. This study evaluated the impact of grass-legume intercropping, during the pasture phase of integrated crop-livestock systems under no-tillage (ICLS-NT), on soil microbiota, pasture quality, and soybean productivity in the Brazilian Cerrado. We evaluated the effect of intercropping on total soil contents of organic carbon and nitrogen, soil microbial activity, animal and soybean productivity (2017 and 2018 crop seasons), and pasture production and quality. The experiment consisted of twelve treatments under grass-legume intercropping in the pasture phase of ICLS-NT. The grasses Urochloa ruziziensis 'Kennedy', U. brizantha 'Paiagu ' as', Panicum maximum 'Tamani' and U. brizantha 'Piata similar to' were grown in monoculture and intercropped with cowpea (Vigna unguiculata) 'Tumucumaque' or pigeon pea (Cajanus cajan) 'Mandarin'. A randomized block design, with three repetitions, was used in a split-plot arrangement, considering the grasses as plots and the legumes as subplots. The results showed that ICLS-NT improved the activity of soil microbial biomass when compared to monoculture systems. Grass-legume intercropping during the pasture phase, mainly with cowpea (Vigna unguiculata), increased soybean productivity, and grass dry matter. Total organic carbon (TOC), carbon management index (CMI%), microbial biomass carbon (MBC), soil basal respiration (BR), and metabolic quotient (Qmic) are the most sensitive markers when it comes to the effects of intercropping on soil microbiological activity and soybean productivity in ICLS-NT. Identifying the best grass-legume combinations allows the establishment of more productive crop-livestock integration systems under no-tillage better adapted to the bio-edaphoclimatic conditions of the Brazilian Cerrado.
查看更多>>摘要：Tardigrades are ubiquitous microfauna that act as consumers and predators in soil food webs. Several studies have suggested that tardigrades have great potential to control nematode populations. However, the regulatory function of tardigrades depends on many factors, including their feeding preferences. Yet, tardigrade feeding preferences remain largely unresolved. Therefore, in our experiment, nine predatory tardigrade species were tested for their preferences for three types of microfauna prey (nematodes, rotifers and tardigrades) under controlled laboratory conditions. We also tested whether tardigrade prey preferences can be predicted by selected functional traits (body length and buccal tube dimensions), because such traits are known to be a powerful tool in determining ecological links between organisms. We observed overall avoidance of tardigrades as prey along with preference for nematode prey. The difference in the total consumed number of the three types of prey were attributable to predator species identity, whereas proportional differences in the three types of prey in the diet were attributable to buccal tube length. Buccal tube width, buccal tube width to length ratio and body length lacked the predictive power for feeding preferences of predatory tardigrades. Our results showed that buccal tube length is more informative of tardigrade prey preference than predator species identity and can be used to predict tardigrade feeding preferences. The knowledge of tardigrade feeding preferences is crucial for understanding the role of tardigrades in soil food web.
Salomao, Renato PortelaPires, Diego de AlcantraBaccaro, Fabricio BeggiatoSchietti, Juliana...
9页
查看更多>>摘要：The high biodiversity of the Amazon region is related to variation in soil physical properties and water-table depths. Dung beetles are efficient bioindicators that feed and breed on the soil surface and below ground, affecting soil properties and being affected by them. Here, we investigate the influence of soil physical characteristics (proportions of sand, silt, clay) and water-table depth on dung beetle assemblages and functional groups in a forest in central Amazonia. We sampled beetles in 29 transects with different soil physical properties and water-table maximum levels, and analyzed beetle species richness, abundance and species composition for the total assemblage and for each functional group (rollers, tunnellers, dwellers). Dung beetle abundance increased with soil clay content (GLMM; p = 0.009) whereas dweller (GLMM; p = 0.017) and tunneller species richness increased with clay and silt contents (GLMM; p = 0.018). Sites with deeper water table had greater roller-beetle abundance (GLMM; p = 0.049). Dung beetle assemblage composition was strongly influenced by clay content. Our results suggest that soil texture and water-table levels determine dung beetle distributions, both for the whole assemblages and for each functional group separately. These findings highlight the role of soil structure in determining dung beetle assemblages.
查看更多>>摘要：Coastal marshes play a notable role in sequestering carbon in plants and soil; however, coastal ecosystems are vulnerable to global change in terms of sea-level rise and saltwater intrusion. The effects of independent and interactive hydrological treatments of waterlogging and elevated salinity on soil CO2 effluxes in Spartina alterniflora marshes were investigated based on a mesocosm approach. This study highlighted the importance of respective soil respirations during inundation (nondrainage, Rs.ND) and reaeration (drainage, Rs.D) in the marshes soils. We found that waterlogging treatments heavily suppressed Rs.ND but increased the Rs.D, regardless of salinity levels. Light salinity enhanced soil respiration, whereas high salinity inhibited soil CO2 efflux, regardless of the water table level. Waterlogging strengthened the negative effects of salinity on Rs.ND and offset the negative effects on Rs.D. The variations in soil respiration under the hydrological treatments can be mainly attributed to changes in root biomass; indigenous soil microbial biomass; and activities of sucrase, cellulase and dehydrogenase, as well as ionic concentrations and oxidation-reduction potential. The temperature sensitivity (Q10 value) of soil respiration (only for Rs.D) after drainage showed a notable decline under the conditions of waterlogging and high salinity. The effect degree of coupled hydrological treatments on soil respiration and Q10 values was similar to a single waterlogging factor before drainage and more strongly than a single factor after drainage. We suggest that the soil CO2 efflux under water flooding and reaeration, inundation duration, and salinity levels need to be considered to understand the impacts of future hydrological changes on coastal marshes.
查看更多>>摘要：Diazotrophs and arbuscular mycorrhizal fungi (AMF) are important functional microbes that provide and transport nutrients to plants. Diazotroph and AMF diversity and community composition were investigated in karst mature forests (MFs) and non-karst forests, as well as in croplands (CRs) as a reference. Diazotroph diversity and community composition significantly shifted in MFs between karst and non-karst soils, with a higher diazotroph richness and Shannon index in karst MFs than in non-karst soils. Similar levels of AMF diversity and community composition were observed between karst and non-karst CRs and MFs. According to the cooccurrence network analysis results, the pairs of correlation links within the diazotroph and AMF groups were higher in karst MFs than in non-karst MFs, whereas this interaction was lower in karst CRs than in non-karst CRs. The diazotroph genera Bradyrhizobium and Anabaena and the AMF genera Glomus and Rhizophagus were mostly correlated with other species in both karst and non-karst soils. Diazotrophs and AMF communities were mainly affected available nutrients (e.g., nitrogen and phosphorus) and environmental factors (e.g., temperature and precipitation), respectively. Soil calcium content was an important factor that affected the distributions of diazotrophs and AMF between karst and non-karst soils. Overall, our study suggested that the increased interactions between diazotrophs and AMF in karst forests, as compared with those in non-karst soil, led to the stability of the diazotrophs and AMF co-occurrence patterns for maintaining nutrients that are effectively absorbed and utilized. Thus, strengthening the cooperative relationships between diazotrophs and AMF are important and necessary in calcareous soils during natural vegetation restoration.
查看更多>>摘要：Plants promote the mineralization of soil organic phosphorus by secreting phosphatase into the rhizosphere, in addition they promote the growth of bacteria which also release phosphatase to the rhizosphere. Sugars are the main component of root exudates and a key driver of soil microbial activity. In this study, we added different concentrations of a range of sugars found in root exudates to the soil during maize growth to investigate whether sugars could stimulate alkaline phosphatase activity. Sugars increased alkaline phosphatase activity in soil, while different sugars increased this activity to different extents. Small concentration of sugars did not stimulate alkaline phosphatase activity in the rhizosphere, change the bacterial community structure or select phosphatase producing species such as Saccharimonadales. However, alkaline phosphatase activity was enhanced by larger concentration of added sugars, which increased indigenous soil Saccharimonadales abundance. Notwithstanding this, Saccharimonadales were rare in the microbial taxa at the order level and their relative abundance was only 2.1%-4.9% at different sugar concentration levels. Our results suggest that addition of sugars selected for indigenous soil Saccharimonadales, enhancing alkaline phosphatase activity in the rhizosphere. These rare microbial taxa may be a key species in soil phosphorus cycling.
查看更多>>摘要：Grassland degradation is widespread globally, yet limited information is available on the effects and mechanisms of grassland degradation regarding the response of soil organic carbon (SOC) to temperature change. This is especially true for alpine regions, which can have high SOC storage and are extreme vulnerability to global warming. Here, we studied the temperature sensitivity of SOC decomposition (Q(10), proportional change in decomposition rate for a 10 degrees C difference in temperature) in both the topsoil (0-10 cm depth) and subsoil (20-30 cm) along an alpine meadow degradation gradient on the Qinghai-Tibetan plateau (QTP). Q(10) values were increased in response to alpine meadow degradation (severely degraded (2.42) > moderately degraded (2.20) > non-degraded (2.11)) and were higher in subsoil (2.34) than in topsoil (2.14) as a whole. Soil carbon quantity and quality and extracellular enzyme activities all decreased significantly with increasing degradation levels and soil depths. Among all the factors considered (soil texture; soil pH; carbon quantity, availability, and quality; and enzyme activities), Q(10) values were found to be primarily mediated by carbon quality and enzyme activities. This result supported the "carbon-quality temperature" hypothesis in degraded alpine grassland, and that considering soil carbon quality and enzyme activity could improve predictions of the feedbacks between soil carbon and global warming under grassland degradation. Our findings suggest that alpine meadow degradation will further increase the losses of SOC in a warming climate, making the ecosystem more vulnerable to climate change.
查看更多>>摘要：Soil methanotrophs can modulate net methane (CH4) emissions in rice paddy fields, but their growth and development depend, to a great extent, upon the soil nutrient status. In this study, a pot experiment was conducted to explore how deficiencies in soil phosphorus (P) or potassium (K) affect the methanotrophic abundance (based on pmoA q-PCR), community composition (based on MiSeq high-throughput sequencing) and CH4 oxidation potential using historically severe P and K deficient paddy soils, respectively. The results showed that P deficiency induced a significant decrease in methanotrophic abundance and potential activity in both rhizosphere and bulk soils. Additionally, P deficiency also caused clear shifts in the methanotrophic community composition within the rhizosphere, where the relative abundance of type II methanotrophs (e.g., Methylocystis and Methylosinus) increased while type I (e.g., Methylomonas, Methylobacter and Unclassified_typeIb) decreased. In contrast, K deficiency did not significantly affect the methanotrophic potential activity and community composition in both rhizosphere and bulk soils. More interestingly, P or K deficiency, particularly P deficiency, narrowed the differences in the abundance and community composition between rhizosphere and bulk soils, implying that P and K deficiencies could attenuate the rhizosphere effects on methanotrophic communities by limiting rice plant growth. Collectively, our results indicated that soil P deficiency, would inhibit soil CH4 oxidation directly or indirectly through restricting rice plant growth, while K deficiency have slight effects on the activity and community composition of soil methanotrophs.
查看更多>>摘要：Arbuscular mycorrhizal fungi (AMF) promote the P uptake of host plants not only by themselves but also by regulating P mobilizing bacterial (PMB) community in the plant-AMF-PMB holobiont. However, the differences in PMB community between two important niches (rhizosphere vs. hyphosphere) as regulated by AMF are scarcely revealed. With stylo (Stylosanthes guianensis) and bahiagrass (Paspalum notatum) inoculated with AMF Rhizophagus irregularis DAOM 197198 in compartmented rhizoboxes, the objective of this study was to compare PMB community, phosphatase activity and P status in rhizosphere and hyphosphere. The abundances of PMB functional genes (phoD, phoC, gcd, pqqC) were also quantified. Mycorrhizal inoculation greatly increased plant biomass, and enhanced the phosphatase activity in both the rhizosphere and the hyphosphere. The abundances of phoC and pqqC in the rhizosphere were significantly increased by AMF, but those in the hyphosphere were not affected. Sequencing of phoD and pqqC indicated that PMB community in the rhizosphere differed very much from that in the hyphosphere. AMF greatly altered PMB community structure in both the rhizosphere and the hyphosphere, and enriched different PMB taxa in these two niches. Taken together, these data reveal that AMF regulate PMB community in the rhizosphere more greatly than that in the hyphosphere and PMB are mainly shaped by roots rather than AMF in this study. Our results highlight the importance of regulating and utilizing the PMB community not only in the rhizosphere but also in the hyphosphere.
Chen, XiaohuiIqbal, ArshadMunir, Muhammad ZeeshanZheng, Chaoyuan...
12页
查看更多>>摘要：Arbuscular mycorrhizal fungi (AMF) are key attributes for the grassland ecosystems and their occurrence varies with increasing atmospheric nitrogen (N) deposition. The increasing N-deposition inevitably reduces the species richness and changes the community composition in a variety of grassland systems throughout the world. Despite the significant impacts of N-deposition on grassland AMF communities, only limited studies have explicitly examined the N-deposition effects on AMF linked with dominant plant species of grassland. Therefore, the current study investigated the effect of N-addition (e.g., 0, 7.06, 14.14, and 21.19 mg.kg(-1)) on AMF diversity and community composition linked with two dominant plant species of Inner Mongolia, i.e., Leymus chinensis (L. chinensis), Cleistogene squarrosa (C. squarrosa). The results showed that 65 AMF phylotypes were identified with the most dominant belonging to Glomeraceae (54), and its relative abundance increased with increasing N-addition in both plant species. The increasing N-addition resulted in a significant increase in AMF colonization (maximum 81% at N3), but species richness and diversity were not affected in C. squarrosa. In contrast, L. chinensis showed significantly reduced AMF colonization (minimum 38% at N3) and diversity with increasing N-addition, while species richness was not affected. N-addition did not alter AMF community composition in C. squarrosa, while for L. chinensis, significant differences were recorded. These findings imply that the sensitivity of AMF to N-addition is closely dependent on their host plant species. These findings also provide critical bases for the N-evoked differential response of AMF communities associated with dominant species of temperate grassland system, e.g., L. chinensis and C. squarrosa.
NSTL
Elsevier