Yan Lu

Continuous maize cropping is often associated with yield decline and soil degradation, yet the temporal responses of rhizosphere bacterial communities to prolonged monocropping remain incompletely understood. Here, we used a continuous maize cropping chronosequence representing 0, 1, 2, 3, 6, 7, and 8 years of cropping to evaluate soil physicochemical properties, maize yield, rhizosphere bacterial community composition, and BugBase-predicted phenotypes using 16S rRNA gene amplicon sequencing. Available potassium declined progressively with cropping duration, whereas alkali-hydrolyzable nitrogen (AN) increased and available phosphorus (AP) changed nonlinearly. Soil pH declined in the later stages of the chronosequence. Maize yield declined progressively with prolonged cropping, with reduction of 46–55% in the 6–8 years treatments relative to earlier within-plot peaks. Bacterial alpha diversity changed nonlinearly, with Shannon diversity peaking at C3, declining at C6, and partially recovering at C7–C8. Because years 4 and 5 were not sampled, the exact shape of the transition between C3 and C6 remains unknown. Community composition also shifted with cropping duration, including a relative decline in Proteobacteria and enrichment of Actinobacteria in the longer-duration treatments. At the genus level, Arthrobacter increased in the later stages of the chronosequence. Redundancy analysis indicated broad associations between community composition and soil variables, although the phylum-level model was only marginally significant. BugBase-predicted phenotypes also varied across treatments, but these functional inferences should be interpreted cautiously because they were derived from 16S-based predictions. Overall, our findings support nonlinear changes in rhizosphere bacterial communities along the continuous maize cropping chronosequence and suggest an unresolved transition between C3 and C6, followed by partial stabilization at later stages. However, due to the missing data for years 4–5 and the inherent limitations of the chronosequence design, the existence and timing of a proposed mid-term transition remain tentative. These findings highlight the need for complete annual sampling to resolve successional trajectories.

This study investigated how fertilization regimes and ridge furrow planting patterns influence the soil nutrient conditions and microbial taxonomic composition and function in the rhizosphere of spring maize in Northeast China. Three treatments were compared: CK (compound fertilizer, small ridge), KF (formula fertilization, small ridge), and BMP (formula fertilization, large double-row ridge). High-throughput sequencing was used to characterize the soil bacterial and fungal community composition and diversity. The results showed that the combination of formula fertilizer and wide-ridge cultivation synergistically improved soil physicochemical properties and significantly increased maize yield (p < 0.05). Compared with CK, both BMP and KF significantly improved the composition and diversity of microbial communities. Notably, the BMP treatment increased the relative abundances of Ascomycota and Basidiomycota—key decomposers of soil organic matter, lignin, and cellulose—which suggested enhanced nutrient cycling potential under this integrated management practice. Among the three treatments, BMP (N:P₂O₅:K₂O = 1:2:1, 130 cm wide-ridge double-row planting) achieved the highest maize yield (859 ± 14 kg ha⁻¹), representing an 11.0% increase over conventional practices (CK, 774 ± 13 kg ha⁻¹). We propose that integrating optimized fertilization with ridge configuration is an effective strategy for improving soil quality, microbial functionality, and crop productivity in Northeast China’s black soil region.

Owing to the substantial spatiotemporal variability and intricacy in the hydrodynamic and water quality responses to water diversion, the determination of impact on the aquatic environment has been predominantly qualitative. The quantitative assessment of the impact of anthropogenic activities (water diversion) on the aquatic environment has the potential to enhance the accuracy of a comprehensive benefit evaluation. The present study utilised hydrological data, encompassing flow rate (Q) and water quality index (WQI) in the lakes Taohu and Gehu basin (TGHs), from two typical water resource allocations in the Taihu basin. The study revealed how hydrodynamics and water quality in response to water diversion. Furthermore, it introduced the concept of “water diversion impact value” to quantify the impacts of water diversion on the aquatic environment. The results indicated when the overall water diversion effect showed enhancement in water quality, the WQI impact value was positive alongside a negative Q impact value (); Conversely, when water diversion improved hydrodynamic conditions, the WQI impact value was negative accompanied by a larger positive Q impact value (). Principal component analysis (PCA) further validated these results, demonstrating that prolonged and stable diversion was positively correlated with WQI, while short and fluctuating diversion was positively correlated with Q, thereby supporting the method of evaluating the effects of water diversion using impact values. In addition, the TGHs was divided into three distinct components: namely mainstream areas, tributary areas, and lake areas, in accordance with the respective hydrological compartment. The present study set out to explore the response mechanisms of three distinct hydrological compartments to water diversion. The findings revealed that the impact extremes predominantly occurred in the mainstream areas, exhibited minimal occurrence in lake areas, and manifested within the range between the two in tributary areas. The diversion impact value has been shown to be a reliable metric for evaluating the effects of water diversion, thereby providing substantial theoretical underpinnings for the enhancement of aquatic environments.

Nutrient enrichment facilitates algal outbreaks in eutrophic shallow lakes. To further understand the influence of various inorganic nutrient forms on cyanobacterial blooms, a nitrate (NO₃), ammonium (NH₄), and orthophosphate (PO₄) amendment experiment was conducted in a large shallow lake of China (Lake Taihu) during summer. The results showed that the photosynthetic performance of phytoplankton responded more positively to phosphorus (P) than nitrogen (N), and NH₄ addition stimulated higher algal photosynthetic activities in P‐enriched waters. Individual inorganic N or PO₄ addition significantly activated cyanobacteria and green algae. Meanwhile, the N plus P amendment promoted higher biomass of the planktonic microbial community, and the dual addition of NH₄ + PO₄ yielded the highest chlorophyll a concentration. NH₄ additions provisionally promoted higher green algae than cyanobacteria biomass in the beginning, while cyanobacteria dominated again with increasing NH₄:PO₄ ratios. These results revealed that increasing ammonium would enhance the increase in phytoplankton biomass in advance and prolong the duration of algal blooms. Hence, based on the control of P loading, the reduction in external inorganic N focusing on ammonium sources (such as ammonia N fertilizer) at the watershed scale would help to alleviate eutrophication and cyanobacterial blooms over the long term in Lake Taihu.Practitioner points: Ammonium addition stimulated higher algal photosynthetic activities in P‐enriched waters. Individual inorganic N or PO₄ addition significantly activated cyanobacteria and green algae. The dual addition of NH₄ + PO₄ yielded the highest chlorophyll a concentration. Increasing NH₄ would enhance the increase in phytoplankton biomass in advance and prolong the duration of cyanobacterial blooms.

As a typical waterway modification, the spur dike narrows the water cross section, which increases the flow velocity and flushes the riverbed. Meanwhile, it also protects ecological diversity and improves river habitat. Different types of spur dikes could greatly impact the interaction between flow structure and local geomorphology, which in turn affects the evolution of river aquatic habitats. Four different types of spur dikes—including rock-fill, permeable, w-shaped rock-fill, and w-shaped permeable—were evaluated using flume experiments for spur dike hydrodynamics and fish aggregation effects. Based on Shannon’s entropy, an index for calculating water flow diversity is proposed. Additionally, the impact of the different spur dikes on water flow diversity and the relationship between water flow diversity and fish aggregation effects were studied. The water flow diversity index around the spur dike varied from 1.13 to 2.96. The average aggregation rate of test fish around the spur dike was 5% to 28%, and the attraction effect increased with increasing water flow diversity. Furthermore, we plotted the relationship between water flow diversity index and average fish aggregation rate. A fish hydroacoustic study conducted on the Laohutan fish-bone dike in the Dongliu reach of downstream Yangtze River showed that the fish aggregation effect of the permeable spur dike was greater than the rock-fill spur dike. These research results could provide theoretical support for habitat heterogeneity research and ecologically optimal design of spur dikes.