Northeast China, with the largest area of forests in China, holds approximately 40% of the national forest carbon stock. Over the past few decades, extensive afforestation and forest restoration efforts have been implemented in this region, yet their impacts on carbon cycling remain unclear. Accurately predicting the future aboveground carbon storage and carbon sequestration potential of the forests in Northeast China is of significance for devising forest management policies. We utilized publicly available forest inventory data to develop a framework which integrated the ecological process model and forest landscape model to simulate the succession process and carbon storage dynamics of Northeast China’s forests over the next 100 years. We employed multisource data (remote sensing data, forest inventory data, and other model outcomes) to validate the simulation results at multiple scales, to enhance the precision of the model simulations. The study aimed to estimate the carbon sequestration potential of forests in Northeast China and quantify the turning point of carbon sequestration. The results showed that: (1) The spatial distribution of forest aboveground carbon storage simulated by the model aligns closely with spatial distribution data derived from remote sensing in literature (Kappa coefficient = 0.81). Furthermore, we validated the model results from a stand age perspective. The proportions of forests in various age classes and the predominant tree species across different age classes correlated with forest inventory data (R²>0.6). (2) Under the current climate conditions, forest aboveground carbon stock in Northeast China would reach its peak at 6.38 Pg C by the year 2060. Compared to the year 2000, there would be a net increase of 4.57 Pg C in aboveground carbon storage and a net increase of 67.46 Mg·hm^-2 in aboveground carbon density. (3) Without considering climate change and forest management policies, the carbon sequestration rate in Northeast China’s forests exhibited a trend of initially increasing and then decreasing. The peak occurs between 2020-2025, reaching 0.108 Pg C·a^-1. The rate is projected to reach zero between 2070-2075 when forests shift from carbon sink to source.

Analyzing the spatial distribution pattern of forest carbon density and exploring the influencing factors can provide a scientific basis for the management of forest carbon sink. Based on forest resources inventory data in 2019, the spatial distribution of carbon density of Cunninghamia lanceolata plantations in Ji’an City of Jiangxi Province was analyzed by geostatistical method, and the influence of site, stand and meteorological factors on carbon density was quantified by structural equation model. The results showed that carbon density of Cunninghamia lanceolata plantations had significant positive spatial autocorrelation. The linear model was the best fitting semivariogram model for carbon density, with the ratio of nugget to sill being 0.81. The carbon density was mainly concentrated in the range of 20.91-51.97 t·hm^-2. The spatial distribution of carbon density was generally higher in the northern and middle region and lower in the southern region, which was not consistent with the geomorphologic characteristics of the study area. The main factors affecting carbon density were average diameter at breast height (DBH), stand density, canopy density, stand age, mean tree height, slope gradient and annual average relative humidity, with their total impact coefficients being 0.650, 0.365, 0.110, 0.090, 0.080, -0.014 and -0.036, respectively. Among them, the average DBH had the greatest direct impact on carbon density, followed by stand density. Stand age, canopy density, annual average relative humidity, and slope gradient had indirect effects on carbon density mainly by affecting the mean height of trees. Carbon density of Cunninghamia lanceolata plantations was most affected by stand factors, followed by site factors, and least affected by the meteorological factors.

To investigate the home-field effects of litter decomposition and the underlying mechanisms at the regional scale, we examined mass loss rate and nitrogen release rate of leaf litter from three dominant tree species of subtropical China (Pinus massoniana, Cunninghamia lanceolata, and Quercus variabilis) under interplanting conditions of different soils at specific temperatures. We collected soil and leaf litter samples in sites of the southern and northern subtropics and carried out a 126-day indoor decomposition experiment under different temperatures. The results showed that: (1) species identity and decomposition time significantly affected the mass loss rate and nitrogen release rate of leaf litter, with Q. variabilis showing the greatest mass loss rate and nitrogen release rate during the 126 days (32.43% and 33.51%), with C. lanceolata having a relatively low mass loss rate (15.35%); (2) Under the same-regional interplanting conditions, Q. variabilis showed home-field disadvantage of nitrogen release only on north subtropical soils (-28.35%), P. massoniana showed both home-field disadvantage of mass loss and nitrogen release on south subtropical soils (-3.20% and -17.65%), and C. lanceolata showed home-field advantage of mass loss on south subtropical soils (2.13%). Under the cross-regional interplanting conditions, Q. variabilis showed home-field disadvantage of mass loss and nitrogen release regardless of the northern and southern subtropics (-57.55% to -3.70%), while P. massoniana and C. lanceolata showed home-field disadvantage of mass loss or nitrogen release in the northern subtropics (-31.76% to -4.40%), and home-field advantage in the southern subtropics (3.78% to 58.43%); (3) The range of home-field advantage (additional decomposition at home, ADH) in leaf litter mass loss and nitrogen release and the frequency of their home-field effect increased under cross-regional interplanting conditions compared to the same-regional interplanting. Staged mass loss was positively correlated with microbial biomass nitrogen, whereas ADH of nitrogen release was negatively correlated with microbial biomass under same-regional interplanting conditions, and ADH of nitrogen release was positively correlated with temperature under cross-regional interplanting conditions. These results suggest that the home-field effects of leaf litter decomposition of the three tree species in the subtropics were affected by a combination of temperature, leaf litter species, decomposition time, and soil microorganisms. In contrast, temperature, in addition to substrate quality, can significantly constrain the home-field effects of leaf litter decomposition under cross-regional interplanting conditions.

To better understand the photosynthetic ecophysiological characteristics of Larix principis-rupprechtii and explore the mechanism of photoinhibition, we measured canopy photosynthetic indicators of Larix principis-rupprechtii plantation under intense irradiation using Li-6400 portable photosynthetic instrument, in Saihanba Mechanical Forest Farm of Hebei Province. We analyzed the main drivers of canopy photoinhibition and the relationships between net photosynthetic rate (P_n) and environmental factors. The results showed that under intense irradiation condition, photoinhibition occurred in the upper and middle layers of canopy. The change trend of stomatal limit values (L_s) was opposite to that of the intercellular CO₂ concentration (C_i). The P_n in the upper and middle canopy was positively correlated with relative humidity (RH) (with the correlation coefficients of 0.720 and 0.934, respectively), but negatively correlated with vapor pressure deficit (VPD) and temperature (T) (with the correlation coefficients of -0.850 and -0.820, respectively). The P_n in the lower canopy was significantly correlated with RH, VPD, and T, but their trends were opposite to upper and middle canopy. Our results indicated that the photoinhibition mainly occurred in the middle and upper canopy, with RH, VPD, and T as the main factors driving P_n. The response patterns of P_n to environmental factors were significantly different among upper, middle and lower canopy. The results lay a foundation for regulating canopy structure, improving the microenvironment, and mitigating canopy photoinhibition.

Preferential flow, a critical component of soil infiltration, affects water conservation capability of forest plantations, and threatens groundwater quality by facilitating the rapid downward migration of soil pollutants generated by forestry practices. Therefore, understanding the developmental characteristics of preferential flow during the rotation period of plantations can provide a scientific basis for their sustainable management. We investigated preferential flow characteristics during the rotation period of Chinese fir plantations in the Beijiang River Forest Farm in Rongshui, Guangxi, using methylene blue dye tracing. A multi-index evaluation method was employed to assess the relative development degree of preferential flow in Chinese fir plantations of different ages. The results showed that soil dyeing in Chinese fir plantations decreased with increasing soil depth, with the main infiltration area being 0-20 cm. The lateral preferential flow was the dominant infiltration mode of the soil infiltration process, which occurred at the beginning of infiltration. The preferential flow indicators for different aged Chinese fir plantations were in the order of 5-year-old (0.64) > 8-year-old (0.59) > 11-year-old (0.47) > 15-year-old (0.39). Our results indicated that lateral preferential flow predominates in the infiltration process of Chinese fir plantations, and that the degree of preferential flow development decreases with increasing forest age. The findings can provide a theoretical basis for the formulation of scientific forest management measures in Chinese fir plantations, and thereby can promote the sustainable management of plantations.

Mixed afforestation plays an important role in improving soil structure and soil fertility. In this study, we investigated soil stabilization and nutrient contents in Pinus yunnanensis forests with different mixing ratios in central Yunnan. This would provide theoretical supports for optimizing the mixed forestation patterns of Pinus yunnanensis and better evaluation for the ecological benefits of non-commercial forests. Based on the proportion of Pinus yunnanensis in community timber volume, three mixed proportions were selected: 20% of Pinus yunnanensis and 80% of broadleaved species (Y2K8), 50% of Pinus yunnanensis and 50% broadleaved species (Y5K5), and 80% of Pinus yunnanensis and 20% of broadleaved species (Y8K2). 100% Pinus yunnanensis (Y10) was used as the control. Soil aggregate stability was analyzed using screening method, while Nemerow index was used as nutrient index. The correlations between soil aggregate stability and nutrient index were examined. The results showed that soil aggregate stability of the three mixed forests was better than that of the 100% Pinus yunnanensis forest, whose deep soil showed the poorest stability. The sensitivity of the three mixed forests to soil erosion was low, while that of the 100% Pinus yunnanensis forest was at moderate level. The contents of soil organic matter (SOM), total nitrogen (TN), hydrolyzed nitrogen (AN), total phosphorus (TP), and available phosphorus (AP) were the highest in Y2K8 and the lowest in Y10. Soil fertility indices of the four forest types ranged in 0.84-1.53, indicating that soil fertility was at an average level. Specifically, Y2K8 was the highest in soil fertility while Y10 was the lowest. Besides, AP was the limiting factor for soil fertility across all the four forest types. Mixed forestation can improve soil AN content and reduce nutrient supply limitations, and thereby can improve soil fertility. The mean weight diameter (MWD) of aggregate was significantly positively correlated with soil SOM (R=0.85), TN (R=0.88), TP (R=0.75), AN (R=0.68), and AP (R=0.70). The geometric mean diameter (GMD) of aggregate was significantly positively correlated with soil SOM (R=0.83), TN (R=0.88), TP (R=0.75), AN (R=0.68), and AP (R=0.66). Our results indicated that soil aggregate stability and soil fertility of the three mixed forests were better than that of Pinus yunnanensis monoculture, with 20% of Pinus yunnanensis and 80% of broadleaved species being the optimal ratio. It is suggested that the proportion of broad-leaved tree species should be appropriately increased in forest establishment and low-value and low-efficiency forest transformation in central Yunnan, with 20% of Pinus yunnanensis and 80% of broadleaved species as a guide.

We explored the differences in respiration rates of soil aggregates in different soil types in subtropical forests in China and their response to temperature changes, by focusing on neutral limestone soil developed from carbonate rocks and acidic red soil developed from granite cataclasite. The respiration rates of soil aggregates with different sizes (0.106-0.25, 0.25-0.5, and 0.5-2 mm) were measured at different temperatures (5, 15, 25, 35 ℃) after 1, 3, 7, 10, 13, 17, and 21 days of incubation. The cumulative respiration rate, contribution rate of soil respiration, and its temperature sensitivity (Q₁₀) were estimated to examine the differences and main controlling factors at different temperatures and aggregate scales. The results showed that the cumulative respiration rates of the O/A horizon and AB horizon of limestone soil were generally higher than that of red soil. The influencing factors of soil cumulative respiration rate in different temperature ranges were different. Organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), and C/N were the main factors at 15-35 ℃, while pH and C/N were the main factors at 5 ℃. At the aggregate scale, there was no significant difference in the cumulative respiration rates among different aggregate classes of limestone soil and red soil at the same temperature. The Q₁₀ values of different aggregates in limestone soil were higher than those in red soil. There was no significant difference among individual aggregate classes of limestone soil and red soil. The contribution rate of respiration of large aggregates was the largest in the O/A horizon of red soil as well as the O/A horizon and AB horizon of limestone soil, while that in the AB horizon of red soil was the opposite. This study revealed that compared to the acidic red soil, the respiration rate of limestone soil in subtropical forest ecosystems showed more significant positive feedback to future global warming, highlighting the need to emphasize its contribution to global carbon balance.

Combined with the antibiotic inhibition technique, we examined the responses of soil fungal and bacterial N₂O emissions in a laboratory culture experiment. Soil samples were collected from fixed plots with long-term (eight years) nitrogen application and precipitation reduction in a broad-leaved Korean pine forest in Changbai Mountains. Results showed that soil N₂O emissions were 0.79 nmol·g^-1·h^-1 in the control. Nitrogen application, precipitation reduction, and simultaneous precipitation reduction and nitrogen application significantly enhanced soil N₂O emissions, which were 3.55, 1.84 and 1.84 nmol·g^-1·h^-1, respectively. There was a significant interaction between precipitation reduction and nitrogen application. Bacterial N₂O emissions were affected by nitrogen application and precipitation reduction. Nitrogen application promoted bacterial N₂O emissions, thereby promoting total soil N₂O emissions. Fungal N₂O emissions were mainly affected by precipitation reduction. Simultaneous precipitation reduction and nitrogen application promoted fungal N₂O emissions, thereby promoting total soil N₂O emissions. The increase in N₂O emissions caused by precipitation reduction treatment was attributed to the interaction of bacteria and fungi. In the control, precipitation reduction, and nitrogen application treatments, N₂O emissions were mainly contributed by bacteria, with relative contribution rates of 90.3%, 68.2% and 91.1%, respectively. In the nitrogen application and precipitation reduction treatment, N₂O emissions were mainly contributed by fungi, with a contribution rate of 68.5%. Therefore, long-term nitrogen application under drought scenario would alter the main microbial species involved in soil N₂O emission, directly affect the amount of N₂O emissions from soil fungi and bacteria, thereby affecting total soil N₂O emissions, which influence nitrogen cycling in forest ecosystems.

We examined the distribution of soil fauna in four typical vegetation types (trees, shrubs, herbaceous plants, shrubs+herbaceous plants) in the forest-grassland ecotone of the West Tianshan Nature Reserve. Large soil faunas were collected using hand picking method, while small and medium-sized soil faunas were separated using dry funnel method. We analyzed the variations of soil fauna community among different vegetation types. The results showed that the family Isognathidae, suborder Tetranychus, suborder Tetranychus, and suborder Gamasides were the dominant groups of soil faunas across the four vegetation types. The forest habitat had the highest number of soil fauna groups, density, diversity, richness, and evenness index. Soil fauna had the characteristics of surface aggregation in vertical direction across different vegetation types. There were significant positive correlations between soil organic matter, total phosphorus, water content and other environmental factors and soil fauna. RDA analysis showed that ammonium nitrogen, total nitrogen, and available potassium were the major factors affecting community composition of soil fauna.

To clarify the impact of Pinus massoniana forest structure on the bioecological characteristics of Monochamus alternatus adults, we analyzed the relationship between the proportion of P. massoniana and plant diversity with the eclosion quantity, eclosion rate, sex ratio, and body length of M. alternatus adults in forest plots with different proportions of Pinus massoniana and broad-leaved trees. The results showed that the peak of eclosion of M. alternatus occurred from late May to early June. The eclosion curve of M. alternatus adults presented a typical “steamed bread” type, as described by the linear model of y=18.5+21.9x-93x². The proportion of P. massoniana trees in the mixed forest exhibited a significant impact on the number of adults emerged from dead P. massoniana trees (P<0.001). The mean eclosion number of adults per tree increased with increasing proportion of P. massoniana trees. The eclosion rate of M. alternatus adults was not significantly correlated with plant diversity, but positively correlated with the proportion of P. massoniana trees (y=0.216+0.0525x, R²=0.88, P<0.001). There was no difference in the body length of the female adults among the forests with low, medium, and high proportion of P. massoniana trees. Body length of the male in the forests with medium proportion of P. massoniana trees was significantly longer than that in the forests with low and high proportion of P. massoniana trees. Our results indicated that the proportion of P. massoniana trees in the forests had a significant impact on the population dynamics and eclosion rate of M. alternatus. Our findings will help further understand the impact of tree species configuration and structure in mixed forests on the biological characteristics of herbivorous insects, providing important information for the prevention and control of pine wilt disease based on forest manipulation.

Reconstruction of forest fire history is helpful to understand the patterns of forest fire occurrence and their driving mechanisms. Charcoal and pollen records from 37 cm core sediments in Yilong Lake of southern Yunnan provide information for forest fire history as well as vegetational and climatic background over the past 150 years. These data combined with population data were then used to reveal the pattern of forest fire occurrence and its controlling factors. The results showed that the pattern of regional forest fires in the Yilong Lake catchment exhibited an increasing trend over the past 150 years (1886-2013 AD), with its maxima at 2000-2013 AD. The two peaks of local forest fires occurred at 1925-1970 AD and 1995-2013 AD, respectively, but caused by different factors. The high frequency of local forest fires in 1925-1970 AD was largely attributed to dry climatic conditions, while the heavy bombing on Yunnan during the Anti-Japanese War partially contributed to burning charcoals. The high frequency of local forest fires in 1995-2013 AD was primarily attributed to strong human activities (e.g., agricultural production).

We investigated the alleviating effects of nitrogen (N) application (0, 0.46 and 0.92 g per plant) on Rhododendron  ‘Wucai’ng’ under different high temperature stresses (26 ℃/22 ℃, 34 ℃/30 ℃ and 38 ℃/34 ℃), aiming to provide a scientific basis for enhancing plant stress resistance and adaptation to climate change. The results showed that there was a trend of fork-shaped branch structure formed in the roots of seedlings under high temperature stress. At 26 ℃/22 ℃, there was a significant increase in root bifurcation in the N fertilizer treatment of 0.46 g per plant, but a significant decrease in the N fertilizer treatments of 0 and 0.92 g per plant. Under the same level of N fertilizer, there were significant decreases in leaf area, total root length, root surface area, specific root length, specific surface area, and root-shoot ratio, but significant increases in root topology coefficient, soluble protein content, and free amino acid content in plants at 34 ℃/30 ℃ and 38 ℃/34 ℃, compared to that at 26 ℃/22 ℃. There were significant increases in leaf area, specific root length, root-shoot ratio, soluble protein content and free amino acid content of plants under high temperature stress in low N fertilizer treatment (0.46 g·plant^-1), while there were significant decrease in leaf area, specific root length, root-shoot ratio, except for a significant increase in soluble protein content and free amino acids, in the high N fertilizer treatment (0.92 g·plant^-1). The results of principal component analysis and membership function analysis showed that the best performance of seedlings was recorded in the treatments of T3 (26 ℃/22 ℃ and 0.92 g·plant^-1), T2 (26 ℃/22 ℃ and 0.46 g·plant^-1) and T5 (34 ℃/30 ℃ and 0.46 g·plant^-1), with a score of 0.853, 0.599 and 0.550, respectively, exhibiting better overall performance than that in the T1 control treatment (26 ℃/22 ℃ and 0 g·plant^-1). In conclusion, high temperature stress would restrict root growth of seedlings and reduced soluble protein content. Appropriate application of nitrogen fertilization (0.46 g·plant^-1) could alleviate the inhibition in root growth under high temperature and enhance the resistance and adaptation of plants to high temperature. These findings provide theoretical guidance and reference for adopting fertilization in advance in the cultivation of Rhododendron to avoid summer heat damage with high temperature and promoting the application of excellent varieties of Rhododendron in gardens.

The aims of this study were to reveal the diversity and population differences of symbiotic bacteria of weevils (Curculio spp.) from different host sources, to explore the effects of different host plants on symbiotic bacteria of weevils, and to facilitate further research on the roles of symbiotic bacteria in promoting weevil host adaptation. Two species of weevil were examined, Curculio bimaculatus (multiple hosts), which feeds on Lithocarpus polystachyus, Castanopsis tibetana and Castanopsis sclerophylla, and Curculio davidi (specialized host), which feeds only on Castanopsis tibetana. High-throughput sequencing of the 16S rRNA V3-V4 region sequences of the symbiotic bacteria of weevil larvae was performed using Illumina technology. Community alpha and beta diversity based on OTU (operational taxonomic unit) were calculated. After Illumina quality control, a total of 919980 high quality sequences were obtained, which belonged to 914 OTUs in 24 phyla, 53 classes, 129 orders, 219 families and 400 genera. Proteobacteria, Firmicutes, Actinobacteriota were dominant in all four groups of samples. The alpha diversity of symbiotic bacteria differed between the weevils feeding on different plants, but the community structure was similar as indicated by beta diversity index. Wolbachia and Erwinia were not found in both weevils feeding on Castanopsis tibetana, without significant difference in their alpha diversity. Curtobacterium, Streptomyces and Rhodococcu were lacking in Curculio davidi, and the abundance of Sodalis and Rickettsia was very low. The diversity and abundance of symbiotic bacteria were strongly influenced by plant species that the weevils fed on, while the species of the weevils mainly influenced community structure of symbiotic bacteria. This study may provide a reference for further investigation of the role of symbiotic bacteria in driving the differentiation and adaptation of weevils’ hosts.

To clarify the species identity and occurrence regularity of main pests and natural enemies in different apple orchards in Zhaotong, we investigated three commonly planting patterns of apple orchards, including natural grass, intercropping soybean, and intercropping alfalfa, by five-point sampling method. The occurrence periods of major pest insects and their natural enemies were divided by the quartile method. The temporal niche index was used to analyze the relationship between the main pest insects and their natural enemies. The results showed that the main pest insects in apple orchards were Aphis citricola, Jacobiasca formosana, and Bactrocera dorsalis, and the main natural enemies were Didea fasciata, Lasiopticus selenitica, Chrysopa sinica, Chrysopa yatsumats, and Harmonia axyridis. Among the three patterns of apple orchards, the longest duration of main occurrence period and earliest occurrence peak of the three pest insect species were recorded in the natural grass orchard. Among the three pest species, A. citricola had the longest duration and earliest occurrence peak during the main occurrence period, with a maximum population density of 124.44 individuals per sticky board on July 19th. D. fasciata had the largest total occurrence number in the three orchards. The population size of natural enemies was the highest in the intercropping alfalfa orchard. The population size of D. fasciata in intercropping alfalfa orchard reached the maximum of 3.22 individuals per sticky board on August 23rd. D. fasciata had following effect on A. citricola, while L. selenitica and C. sinica had following effect on J. formosana. In conclusion, the orchard intercropping with alfalfa is more ecologically stable than orchard with the natural grass, as it is conducive to the reproduction of natural enemies. The main natural enemies in apple orchards have certain natural control abilities to natural insect pests. Our results can provide a reference for the scientific control of insect pests in apple orchards.

Few studies have assessed the effects of different forms of nitrogen combined with low-molecular organic carbon application on plant growth and quality. Residue after evaporation (RAE) is a kind of waste liquid generated during industrial vitamin C (VC) production, which is mainly composed of 2-keto-L-gulonic acid, a low-molecular-weight organic acid. We investigated the effects of urea (amide nitrogen, Urea-N), potassium nitrate (nitrate nitrogen, NO₃^--N), and ammonium chloride (ammonium nitrogen, NH₄⁺-N) combined with RAE on the growth and quality of non-heading Chinese cabbage (Brassica campestris ssp. chinensis). The results showed that the combined application could significantly improve nitrogen uptake efficiency and partial factor productivity of nitrogen fertilizer. RAE promoted the conversion of other forms of nitrogen into the easily absorbed form, NO₃^--N, which was the key to improve nitrogen uptake efficiency. The nitrogen uptake efficiency, contents of VC, soluble protein and nitrate in RAE+NO₃^--N treatment were the highest. The partial factor productivity of nitrogen fertilizer, biomass and soluble sugar accumulation levels under RAE+NH₄⁺-N treatment were the highest, which was closely related to the proportion of photosynthetic pigment components. In addition, the response of soil available P and available K content to RAE and different nitrogen fertilizer combinations was different, which potentially led to the difference of biomass and quality. When RAE was applied in combination with Urea-N or NH₄⁺-N, crop quality could be greatly improved, but there was no significant difference between the two combinations. Comprehensively considering nitrogen uptake efficiency, partial factor productivity of nitrogen fertilizer, crop yield and quality, the combination of RAE and NH₄⁺-N was the best choice.

The niche characteristics and interspecific associations are of great significance for understanding the structure and classification of plant communities, as well as judging community stability and development trends. The Levins (B_L) and Shannon (B_S) niche breadth indices and Pianka’s niche overlap index (O_ik) were estimated for 22 dominant wild herbaceous medicinal plant species in Huguan County, Changzhi City, Shanxi Province. Those indices were used to analyze their niche characteristics. Based on a 2×2 contingency table, methods such as interspecific association coefficient (AC), Jaccard index (JD), Ochiai index (OI), χ² test, Pearson correlation coefficient test were used to analyze the interspecific association of those species. The results showed that: (1) Among the 22 species, Sanguisorba officinalis had highest B_L index at 63.369, followed by Artemisia stechmanniana at 58.276, with Astragalus membranaceus having lowest B_L at 2.489. Sanguisorba officinalis also had highest B_S at 4.290, followed by Adenophora stricta at 4.247, with Astragalus membranaceus having lowest B_S at 1.097. Maximum O_ik was shared between Cirsium arvense var. integrifolium and Chrysanthemum lavandulifolium (0.562), followed by Artemisia stechmanniana and Siphonostegia chinensis (0.534). Minimum overlap was zero, which occurred in 112 species pairs, indicating low overall degree of niche overlap among herbaceous medicinal plant species, less intense interspecies competition, and highly dispersed distributions of herbal medicinal plant species. (2) For AC values, 77 out of the 231 species pairs were positive association pairs, with 11 pairs being strongly positively associated. There were 154 negative association pairs, with 116 of them being strongly negatively associated. The χ² test showed that there were 77 positively associated species pairs, of which 24 were very significantly positively associated; and 154 negatively associated species pairs, of which 7 were very significantly negatively associated. In terms of Pearson correlation coefficients, there were 56 positively associated species pairs, of which 17 were extremely significantly positively associated, and 175 negatively associated species pairs, of which 8 were extremely significantly negatively associated. (3) By considering AC coefficient, JD index, OI index, χ² test and Pearson correlation coefficient, there were more negatively associated species pairs than positively associated species pairs for the 22 medicinal plant species in Huguan County. The number of species pairs with no significant association was more than the number of species pairs with significant association, which indicates low similarity among species pairs of herb medicinal plants thus revealing independent distribution characteristics making them susceptible external disturbances. Overall, Huguan County is rich in wild herbal medicinal plant resources. The species distributed rather randomly, with weak interspecific competition and strong species independence. The community structure can be unstable due to external disturbances. Our results will provide an important basis for understanding the distribution patterns of local medicinal plants, as well as for sustainable use and development.

Low nitrogen availability under salt stress is an important factor limiting crop productivity of coastal saline-alkali soil. Application of biochar and nitrification inhibitors can improve soil nitrogen availability. But there is relatively little research on the application of biochar and nitrification inhibitors in the Yellow River Delta coastal saline-alkali land. A field in situ experiment was conducted to explore the effects of biochar and DCD on nitrogen transformation and nitrogen uptake/utilization of soybean of coastal saline-alkali soil in the Yellow River Delta. There were five treatments: control (no nitrogen application, CK), nitrogen (N), nitrogen + biochar (NB), nitrogen + 2% dicyandiamide DCD (ND), nitrogen + biochar + 2% DCD (NBD). Results showed that: (1) Compared with N application, biochar and DCD decreased soil pH and electrical conductivity (EC), significantly inhibited soil nitrification, regulated the duration and level of soil nitrogen supply, and improved soil nitrogen sequestration by microorganisms in late stage of soybean. (2) The activity of soil nitrogen converting enzymes showed a trend of first increasing and then decreasing during the growing season of soybean. Compared with N treatment, both biochar and DCD additions increased the activity of nitrogen conversion enzymes. The highest activities of protease, urease, nitrate reductase and nitrite reductase were observed under NBD treatment, with an average increase of 33.8%, 28.3%, 26.0% and 18.8%, respectively. (3) Both biochar and DCD promoted nitrogen uptake and utilization of soybean, and increased its biomass and grain yield. The combined application of biochar and DCD had a synergistic effect, with more significant yield improvement. In the Yellow River Delta, combined application of biochar and DCD can improve soil nitrogen availability, and promote nitrogen uptake and utilization by plants, which provide a reference for crop yield improvement and efficient use of nitrogen fertilizer in salinized farmlands.

To explore the source and spatiotemporal distribution of organic matter and its influencing factors in the Pearl River Estuary and adjacent sea areas, we collected suspended particulate organic matters (SPOM) in June (summer) and December (winter) in 2015, and analyzed δ¹³C and δ¹⁵N of SPOM. The results showed that the distributions of SPOM in the Pearl River Delta region had obvious seasonal differences (P<0.01). The coupling effect of the Pearl River diluted water and outer seawater played an important role in controlling the temporal and spatial distribution of SPOM. In summer, the Pearl River Estuary and its adjacent waters were mainly affected by the Pearl River diluted water, brachish mixed water, and outer seawater. The SPOM of the inner sea area was characterized by higher organic matter content, lower δ¹³C value and higher δ¹⁵N value, indicating that organic matter was mainly affected by the terrigenous matter carried by the Pearl River runoff, freshwater algae and anthropogenic discharge. In winter, the δ¹³C and δ¹⁵N distributions of SPOM were consistent with the thermohaline distribution, showing higher δ¹⁵N and lower δ¹³C, indicating that the freshwater algae carried by the Pearl River runoff may be the important source of organic matter in this region. On the whole, the contribution of phytoplankton to organic matter increased gradually from the inner part of the Pearl River estuary to the outer part of the sea.

Fatty acids are sensitive to environmental changes, and have been considered as ecological bioindicators to environmental alterations. It is critical to decipher the traits of lipid remodeling in perennial macroalgae with seasons, which could contribute to understanding how the intertidal macroalgae respond to environmental stresses. We investigated three common macroalgae, including Mazzaella japonica (Rhodophyta), Neorhodomela munita (Rhodophyta) and Ulva lactuca (Chlorophyta), which were distributed in the rocky intertidal zone of the Heishi Reef, Dalian, China. The changes in composition and content of fatty acids in the three macroalgae were compared during February (winter), July (summer), October (fall) 2022, and February (winter) 2023. The fatty acid unsaturation and the content ratio of ω-3/ω-6 fatty acids were further analyzed, while the potential fatty acid biomarkers in each macroalga in response to seasonal variations were uncovered. The results showed that total fatty acid contents and their seasonal fluctuation degrees in the three macroalgae were ranked as M. japonica < N. munita < U. lactuca during February 2022 and February 2023. The content of the total fatty acids in U. lactuca collected on February 2023 was 2.3 and 1.7-fold of that in M. japonica and N. munita, respectively. The total fatty acid contents in all the three macroalgae were high in winter and low in summer, with fatty acid compositions varying with seasons. The relative amounts of the saturated C16:0 and the major ω-6 fatty acids increased significantly in the high temperature season (July), and decreased notably in the low temperature season. The relative abundances of the major ω-3 fatty acids exhibited an opposite variation trend. The fatty acid biomarkers differed from each other in distinct phyla of macroalgae in response to seasonal changes. The saturated C16:0 together with the polyunsaturated C20:4n6 and C20:5n3 was characterized as the potential bioindicators in M. japonica and N. munita (Rhodophyta). Differently, the saturated C16:0 together with the polyunsaturated C16:4n3, C18:3n3 and C18:4n3 was identified as the potential biomarkers in U. lactuca (Chlorophyta). These results provided valuable insights into further understanding the lipid remodeling of intertidal macroalgae in response to seasonal variations, and would facilitate the exploration and utilization of high-quality seaweed resources.

To investigate the characteristics of benthic diatom communities and changes in water quality in Jiulingshan National Nature Reserve during summer, a survey was conducted at 56 sampling sites in the stream waters of the Baofeng Station (BF), Daqishan Station (DQ), Zaodu Station (ZD), and Qingshan Station (QS) in July and August 2022. Physicochemical parameters of the water and the composition of benthic diatom communities were assessed. Diversity and diatom indices were used to assess water quality. A total of 77 species from 25 genera of benthic diatoms were identified at the four stations. A total of 13 genera were identified as dominant ones, with 9, 6, 4, and 6 dominant genera being observed at the BF, DQ, ZD, and QS stations, respectively. The main dominant genera included Navicula, Gomphonema, and Cocconeis. The total abundance of benthic diatoms in BF, DQ, ZD, and QS stations ranged from 0.03×10⁵ to 20.27×10⁵, 0.05×10⁵ to 7.96×10⁵, 0 to 14.65×10⁵, and 0 to 12.85×10⁵ ind·cm^-2, respectively. The biomass of benthic diatoms in these stations ranged from 0.02 to 8.11, 0.01 to 3.44, 0 to 5.86, and 0 to 5.14 mg·cm^-2, respectively. The total abundance and biomass of benthic diatoms were lower in DQ than in other stations, and the highest at the BF station. The Margalef, Pielou, and Shannon indices were higher at the QS station. Based on the results of diversity index and generic index of diatom (GI), water quality in Jiulingshan National Nature Reserve was generally classified as clean-moderately polluted. The water quality at QS was the best and that at BF was the worst. Multiple linear regression analysis showed that total phosphorus, total nitrogen, ammonium nitrogen, and altitude had strong impacts on benthic diatom communities. Our results provide valuable information for the conservation and maintenance of aquatic ecological environment in Jiulingshan National Nature Reserve.

To clarify fish community structure and diversity in Lake Gaobaoshaobo and the effects of environmental factors on fish community, we conducted fish resource surveys in four consecutive seasons (April, June, September, and December 2022) in three lake regions of Lake Gaobaoshaobo: Lake Gaoyou, Lake Baoying, and Lake Shaobo. A total of 48 fish species (which belonged to 12 families and 36 orders) were collected, among which Cypriniformes accounted for 70.8% of the total species captured. There were nine dominant species, including Coilia ectenes taihuensis, Carassius auratus, Aristichthys nobilis, Culter dabryi, and Hypophthalmichthys molitrix. How-ever, there were differences in the composition and dominance of dominant species among the lake areas. The predominant species in Lake Gaoyou and Lake Shaobo was Coilia ectenes taihuensis, and was Aristichthys nobilis in Lake Baoying. From the perspective of fish diversity, the Margalef species richness, Shannon index, and Pielou index of the fish community of Lake Gaobaoshaobo were 1.80-2.20, 1.36-1.68, and 0.61-0.74, respectively. The quantitative analysis results of Random Forests showed that the degree of water pollution and zooplankton biomass were the main factors leading to the differences in the fish diversity indices of Lake Gaobaoshaobo. In comparison with historical data, the number of fish species in Lake Gaobaoshaobo has declined and the composition of fish resources has changed, but the trend of fish miniaturization has slightly eased. The implementation of fishery management, water quality, and bio-food resources were the potential major factors for the changes of fishery resources in Lake Gaobaoshaobo.

Pseudocrossocheilus tridentris, from the Labeoninae subfamily, is an indigenous fish species in China. In this study, 206 individuals of P. tridentris were collected during the spring, summer, and autumn of 2019 from Mabie River, a primary tributary of the Nanpanjiang River. We examined the sex ratios, gonad development, gonadosomatic index, size at sexual maturity, egg size, and fecundity of the species. The results showed that the ratio of male to female was close to 1∶1 (P>0.05). Matured females were consistently observed throughout the survey period. The majority (over 80%) reached sexual maturity from April to June, exhibiting a significantly higher gonadosomatic index compared to other sampling months (P<0.05). Logistic regression analysis revealed the sizes at first sexual maturity (SL₅₀) for females and males was 136.5 mm and 134.3 mm, respectively. The mean absolute fecundity and relative fecundity of P. tridentris was 1039 eggs per female and 18 eggs per gram, respectively. Absolute fecundity was positively correlated with body length and net weight. The frequency distributions of egg diameter for stages III, IV, and V showed unimodal patterns, suggesting a single-batch spawning strategy. P. tridentris is characterized as a typical opportunist, displaying sexual maturity at a small body size, relatively low absolute fecundity, and a single-batch spawning strategy. The results could provide foundational data for the conservation of P. tridentris and artificial reproduction efforts.

The eutrophication of reservoir has become a significant research focus globally. However, the response of eutrophication to variations in the concentrations and structure of biogenic elements remains inadequately understood. We conducted experiments in Hongfeng Lake (HFH), Hongjiadu (HJD), Dongfengdu (DFD) and Wujiangdu (WJD) reservoirs in the upper reaches of Wujiang River Basin. Water physicochemical indices, phytoplankton, and dissolved concentrations of biogenic elements such as carbon (C), nitrogen (N), phosphorus (P) and silicon (Si) in both inflow rivers and reservoir waters were monitored for 12 months. We analyzed the temporal and spatial variations of biogenic elements in the reservoirs and their influence on water eutrophication. The results showed that annual mean phytoplankton abundance followed an order: HFH (30.27×10⁶ cells·L^-1) > WJD (6.13×10⁶ cells·L^-1) > DFD (2.56×10⁶ cells·L^-1) > HJD (2.13×10⁶ cells·L^-1). Both DFD and HJD were primarily dominated by diatom phylum, which comprised more than 53.32% of total abundance. In contrast, HFH and WJD were predominantly composed of cyanobacterial phylum, with relative abundances of 93.36% and 68.63%, respectively. Reservoirs exhibited a retention effect on biogenic elements due to phytoplankton absorption and fixation. The mean retention fluxes of biogenic elements in the reservoirs were as follows: DIN at 0.13 mmol·m^-3·month^-1, DIP at 6.17 μmol·m^-3·month^-1, DSi at 0.82 mmol·m^-3·month^-1, and DIC at 14.51 mmol·m^-3·month^-1. Moreover, the mean DIN/DIP ratio was less than 16, confirming that all reservoirs were DIP-limited. Among these, the HFH and WJD reservoirs were co-limited by both DIP and DSi, as indicated by a DSi/DIP ratio less than 20. Results of the multiple regression analysis showed strong correlations (R² values of 0.14 and 0.25) between eutrophication potential indices (N-ICEP and C-ICEP) and both biogenic elements and environmental factors, suggesting that DSi-limited reservoirs experienced a heightened level of eutrophication driven by DIN and DIC. Cyanobacteria emerged as dominant species, while high DIC concentration promoted long-term maintenance of cyanobacteria dominated community. Consequently, eutrophication in reservoirs is not solely governed by the concentrations of biogenic elements but also significantly influenced by their imbalances. These findings provide theoretical insights for future strategies aiming to mitigate eutrophication through monitoring the changes in biogenic element ratios.

To evaluate the effectiveness of air pollution control policies in Tianjin, we collected PM_2.5 samples over six consecutive winters from 2017 to 2022 and measured the concentration of water-soluble inorganic ions (SO₄^2-, NO₃^-, NH₄⁺, Cl^-, K⁺, Ca²⁺, Na⁺, Mg²⁺). The results revealed a marked decline in the mass concentrations of SO₄^2-, NO₃^- and NH₄⁺ in PM_2.5 from 2017 to 2022, with reductions of 83.9%, 46.2%, and 55.2%, respectively. However, the proportion of NO₃^- within water-soluble inorganic ions (WSIIs) has been rising annually, with the dominant form of secondary inorganic ions (SO₄^2-, NO₃^- and NH₄⁺) transitioning from (NH₄)₂SO₄ to NH₄NO₃. The ratios of NO₃^-/SO₄^2-, NO₃^-/Cl^- and NO₃^-/K⁺ have been increasing annually as well, indicating that compared to stationary sources such as coal combustion and biomass burning, the influence of mobile sources such as motor vehicle exhaust on air quality in Tianjin was increasing. Backward trajectory analyses showed that the PM_2.5 in Tianjin was mainly influenced by air masses from the northwest, the southern part of Tianjin, and the central Hebei, without interannual differences in potential source areas. Furthermore, compared to short-distance air masses around Tianjin, SO₄^2- carried by longdistance air masses from the northwest showed a significant decrease. The reductions in NO₃^- and NH₄⁺ concentrations were relatively modest. Notably, NO₃^- and NH₄⁺ levels associated with short-distance air masses displayed an increasing trend in 2020, indicating the need to strengthen vehicle exhaust emissions control in Tianjin and the surrounding areas.

Rural areas have experienced significant changes in land use/land cover (LULC) during urbanization, resulting in alterations of the surface thermal environment. However, the relationship between rural land surface temperature (LST) and landscape patterns at different scales of analysis remains poorly elucidated. This study scrutinizes rural regions of the Fuchun River Basin by employing correlation analysis, spatial autocorrelation analysis, and geographically weighted correlation coefficient analysis. The investigation aimed to discern the impacts of land-use landscape patterns on LST during the summers of 1990 and 2020 across multiple scales of analysis (300, 600, 900, 1200, 1500, 1800, 2100 m, and township levels). The results showed that: (1) From 1990 to 2020, cultivated land and forest land were the predominant land use types. There was a substantial reduction in cultivated land area over 30 years, primarily due to the conversion to industrial land, urban construction land, and rural residential land. (2) Zones with moderate and severe temperature increases concentrated in urban construction land, rural residential land, and industrial land clusters along both banks of the Fuchun River. Furthermore, the distinctiveness of LST changes diminished as the scale of analysis units increased. (3) The degree of correlation between changes in landscape pattern indices and LST among various land types follows the order: urban construction land > industrial land > cultivated land > water bodies > rural residential land > forest land, exhibiting different trends with an increase in the scale of analysis. The percent of landscape (PLAND) index exerted the strongest impact on LST. The rise in local LST could be attributed to decreased area of cultivated land and increased area of urban construction land and industrial land. The increase of rural residential land had a relatively mild impact on LST. The change in forest land was not significant, but it alleviated the surface thermal environment. (4) There was a clear spatial autocorrelation and spatial spillover effect between landscape pattern index of urban construction land and industrial land and LST. These findings contribute to understanding the impact of LULC changes on LST in rural areas. Moreover, the findings furnish a theoretical foundation for mitigating the adverse effects of urbanization on rural environments.

As climate change continues to reshape ecosystems worldwide, understanding its impact on species distribution becomes crucial for effective conservation and management. In this study, we predicted the potential distribution area of an important native grass species in China, Elymus nutans Griseb., with an optimized MaxEnt modeling approach. Main aims of this study were: (1) exploring the distribution of Elymus nutans in different climate scenarios; (2) identifying the essential environmental factors influencing its geographical range and suitable habitats; (3) assessing the contraction, expansion, and stability of Elymus nutans’ range under future climate scenarios, and tracking the shift in its centroid under various climate scenarios. The results show that the potential distribution area of Elymus nutans is approximately 337×10⁴ km², accounting for 35.1% of the total national area. This species is primarily distributed in the western and northeastern China, including western Sichuan Province, most of Qinghai Province and Xizang Autonomous Region, the southwestern part of Gansu Province, the northwestern part of Xinjiang Autonomous Region, and the eastern part of Inner Mongolia Autonomous Region. There is also a significant distribution in the northern part of Shanxi Province, Jilin Province, and Heilongjiang Province. The entire potential distribution area of Elymus nutans exhibits a rising trend under future climatic scenario. The main environmental factors limiting the distribution of Elymus nutans include three temperature-related factors: annual mean temperature (-4.2 to 5.0 ℃), maximum temperature of the warmest month (12.3-21.4 ℃), and isothermality (36.4%-52.8%); one precipitation-related factor: precipitation of the driest month (0.6-5.9 mm); one topographical factor: elevation (2830-4839 m); and a human activity factor: anthropogenic disturbance index (1.3-20.6). Under future climate change scenarios, the highly suitable area of Elymus nutans will expand greatly, while the expansion area will remain relatively stable under various emission scenarios. The moderately suitable area of Elymus nutans would not change greatly. The area of lowly suitable zones exhibits different change patterns across different periods, decreasing first and then increasing from 2021 to 2040, but increasing first and then decreasing from 2041 to 2060. Additionally, its centroid will follow a southwestward shift first and a northeastward migration after that. Our results suggest that climate change drives the distribution of Elymus nutans. By elucidating the distribution patterns and the underlying drivers, this study can enhance our ability to protect and utilize Elymus nutans more effectively. Our finding serves as a valuable theoretical basis for endeavors such as ecological restoration, the selection of seed field locations, forage cultivation, and resource conservation.

The trade-offs among reproductive traits reflect the ecological strategies of resource acquisition and allocation in plant reproduction, which affects the germination, growth and competitiveness of offsprings. Plants play a crucial role in both productivity and ecological functions in grasslands. The studies on the ecological strategies of reproductive traits in grassland plants have found that there are trade-offs between vegetative growth and reproduction, reproductive mode, and floral traits. In contrast, less attention has been paid on the trade-offs among reproductive traits. Here, we review the progress of research on trade-offs among reproductive traits in grassland plants from the perspectives of sexual and asexual reproduction, floral traits, seed size and number, and tradeoffs between the underground bud bank and soil seed bank. Few studies have focused on trade-off relationships at the level of individual plants and inflorescences within populations. We revealed how reproductive trade-offs shape plant reproductive strategies and the mechanisms of survival adaptability. Furthermore, by delving into the critical role of trade-off mechanisms in plant growth, population dynamics, and ecosystem diversity, we elucidated their theoretical significance in understanding plant growth, reproduction, and stress responses under the background of global change. This review would provide diverse perspectives for future research on the trade-offs of plant reproductive traits in grasslands.

Estuarine wetland vegetation has high primary productivity and plays a significant role in climate change mitigation. As an important component of wetland ecological processes, hydrological connectivity has a profound impact on ecosystem stability of estuarine wetland. Clarifying the response mechanism of estuarine salt marsh wetland vegetation carbon sink capacity to changes in hydrological connectivity is a hot research topic. We reviewed the research on estuarine wetlands in China in terms of the assessment methods of vegetation carbon stock, the current status of carbon stock research and the quantification methods of hydrological connectivity, and compared the advantages and disadvantages of various methods. We sorted out the influence of hydrological connectivity on vegetation carbon sink capacity of estuarine wetlands at three scales: individual, community, and landscape, and clarified the specific mechanism characteristics. Future research on the response of vegetation carbon sink capacity to hydrological connectivity in estuarine salt marsh wetlands should focus on multi-scale simultaneous observations and the construction of multi-source data fusion analysis assessment methods, the mechanism of hydrological connectivity blocking and vegetation carbon sink function stability in estuarine salt marsh wetlands under multiple stresses, and vegetation carbon sink enhancement and conservation technology based on hydrological connectivity modification of estuarine salt marsh wetlands.

China is short of soil resources for arable lands. There is a significant overlap between heavy metal soil pollution in arable lands and the primary grain-producing regions, which seriously affects the quality of agricultural products, threatens human health and ecological safety, and becomes challenges for the remediation of polluted cropland soils. The applications of silicon fertilizer could supplement plant nutrition and mitigate the toxic effects of heavy metals. Nano-silicon fertilizer has received great attention due to its advantages of large specific surface area, multiple micro-pores, high utilization efficiency, strong adsorption capacity for pollutants, and enhancement of plant resistance. These advantages demonstrate great potential for the remediation of polluted croplands. In this review, we explored the differences in physical and chemical properties between various types of silicon fertilizers (traditional silicon fertilizers and nano-silicon fertilizers), the action mechanisms of different types of silicon fertilizers on the bioavailability of heavy metals in soil, the absorption and translocation of heavy metals in crops, and the physiological regulation mechanisms of alleviating heavy metal toxicity. The utilization of nanosilicon fertilizer exhibits promising prospects in the remediation of heavy metal pollution in croplands. The current research challenges include the optimal dose and size of nano-silicon fertilizer for agricultural applications, and the molecular mechanism by which nano-silicon fertilizer alleviates heavy metal toxicity. These issues need to be solved in the future to advance the effective utilization of nano-fertilizers in addressing agricultural pollution and promoting sustainable green development, thereby ensuring optimal soil health and food security.

Due to the rapid development of industry and agriculture, a large number of environmental pollutants have been released into the environment, resulting in adverse effects such as the damage to animal organs and increasing incidence of disease. Baicalein is mainly extracted from the roots of Scutellaria baicalensis. Baicalein is a flavonoid that can play a therapeutic and restorative role in organisms through various pathways. Moreover, it can alleviate the toxic effects of pollutants. In this paper, we outlined the pharmacological functions of baicalein, such as anti-oxidative stress, anti-inflammation, anti-viral pathogens and regulation of apoptosis. The detoxification effects and mechanisms of baicalein on the intestine, heart, liver, kidney, lung, and the nervous system of animals after pollutant exposure were introduced. As a potential detoxifying and therapeutic agent, baicalein has strong detoxification effects with few side effects. Baicalein has important potential value and broad application prospects in repairing organ damage or chronic diseases caused by environmental pollutants.

Millipedes (Diplopoda) are a common name for animals in the Myriapoda group of Arthropoda, which are one of the earliest groups of terrestrial animals on the Earth. Most millipede species have chemical defense glands that secrete chemicals such as phenols, quinones, and hydrogen cyanide. These substances could exhibit potent repellent, anti-feeding activities and contact toxicity against natural predators, and display significant antiinflammatory and anticancer effects, making them valuable for research and development. However, distinct types and derivatives of chemical defense compounds have evolved in different millipede species due to varying natural selection pressures during natural evolution. This has greatly increased the variety of chemical defense compounds in millipedes. We review the types and functions of compounds found in millipedes, and discuss the future research directions, aiming to provide a reference for studying millipede chemical defense and system evolution, as well as natural product chemicals.

The invasion of exotic fishes possesses a serious threat to local ecosystems and has received attention for ecologists and natural resource conservationists. In 1978, Coptodon zillii was firstly introduced into China for aquacultural purposes. Due to its strong ecological adaptability, it has already invaded into many natural water systems in south of the Yangtze River, with a tendency to expand to the north. However, domestic researches on the invasion of Coptodon zilli commenced relatively late, and had primarily focused on fundamental aspects. It is critically needed to summarize its invasion biology and hence put forward feasible prevention and control methods. Here, we give an overview of the origin, distribution, biological characteristics, pathways of introduction, invasion status, potential hazards and prevention and control strategies of Coptodon zillii, and analyze the problems and challenges of invasion mechanism research and management. We proposed four main aspects for the future development of invasion biology research: (1) comprehensively collecting background data of the invasion of Coptodon zillii; (2) elucidating the patterns and mechanisms of life history plasticity and ecological niche changes of Coptodon zillii, analyzing the population dispersal patterns, and establishing models and scenarios to predict the future trend of the invasion; (3) utilizing the emerging multi-omics technology to screen the key genes for environmental adaptation, and analyzing the molecular genetic basis of its rapid adaptation; (4) based on the elucidation of the invasion mechanism, gradually establishing an integrated prevention and control system to provide new ideas for prevention and control of Coptodon zillii.

Establishing a scientific, objective, and highly operational compensation mechanism for fisheries ecological damage will contribute to the sustainable development of marine fishery. Here, we summarized the research advances of compensation mechanism of ecological damage to marine fishery from three perspectives, namely sources, receptors, and quantitative methods. We systematically formulated the effects of human activities, such as reclamation, marine construction projects, marine oil spills, and illegal fishing, on biological and non-biological receptors in the marine ecosystems. Moreover, we analyzed the applicability and limitations of models based on different principles in quantifying ecological damage in the fishery. Based on the complexity and dynamics of fishery ecosystems, we pointed out the problems in the compensation system of fishery ecological damage, such as differentiations in quantification, compensation accounting and implementation effect, and the subsequent discontinuity of restoration measures. We further proposed development directions of the compensation system of marine fishery ecological damage. This review will help promote the construction process of marine ecological civilization in China, and provide sound reference for the further studies on fishery ecological damage compensation.

Dissolved organic matter (DOM) in water plays an important role in biogeochemical cycles in aquatic environment, which affects water environment quality in watershed. Reservoirs are recharged by rivers and make a significant contribution to the supplement of drinking water, particularly Northern China. Therefore, the quality of reservoir water would be impacted by river pollution. In this study, UV-vis spectroscopy and three-dimensional fluorescence techniques were used to analyze the dynamics and sources of DOM in river water during both high and low flow seasons in Yuqiao Reservoir, a project of Diverting Luanhe River to Tianjin, and its inflow rivers. The results showed that newly produced humic substances were the primary components of river DOM during high flow season, with mixed internal and external inputs. Precipitation and river input had significant impacts on humic-like DOM during high flow season. The molecular weight of humus DOM was regulated by photodegradation during river transport. The abundance of proteins-like DOM was higher during low flow season, which corresponded to the low humification levels. The fluorescence index (FI) was below 1.9, indicating mixed contribution from internal and external sources of DOM during low flow season. Endogenous sources were typically regulated by metabolic accumulation of DOM under limited hydrodynamic conditions. However, due to severe point source pollution, high-molecular-weight proteins primarily originated from sewage inputs, resulting in a large accumulation of macromolecular DOM in the water column during low flow season. The humification index (HIX) and FI of the reservoir were lower than those of the inflow rivers, and the abundance of aromatic protein components was increased, which was obviously different from that of the inflow rivers of the same period. There was a strong correlation between the optical parameters, which was consistent with seasonal variations of river DOM. These observations suggest that DOM optical characteristics can effectively reflect its sources and fate in rivers. In the context of water resource protection in China, future consideration should be given to hydrological regulation on aquatic DOM sources.

Wetland water allocation based on market mechanism is an institutional innovation for the insurance of ecological water demands. A water rights trading model was constructed based on interval two-stage stochastic bi-level uncertainty programming method. We quantitatively analyzed the effect of natural wetlands’ participation on water resource system of Dagu River Basin. The results showed that the trading mechanism of natural wetlands participation reduces the environmental capacity of river sections and limits the amount of pollutant discharge and actual water consumption of industries. Under such mechanism, natural wetlands become the main buyer of water rights by purchasing water rights to meet their water demands, thereby enhancing market vitality. In contrast, the trading amount among social production users would decrease, and the planting industries would become the main seller of the social production users. This mechanism considers the ecological benefit of natural wetlands. The system benefit increases with increasing vegetation coverage. Based on the multi-criteria analysis, a vegetation coverage rate of 75% under the trading mechanism with natural wetlands participation has the best performance for water rights trading. Our results can provide a theoretical basis for natural wetlands to participate in water rights trading as main market players, providing a decision support for the coordinated optimal allocation of water resources in ecology and production use.

The water retention functions in the source region of the Yellow River play a vital role in water resource security and ecological protection in the lower reaches of the Yellow River. The research on the spatiotemporal variations of water retention functions and their influencing factors in the source region of the Yellow River is conducive to the ecological protection and high-quality development of the basin. Based on the meteorological and hydrological data of the source region of the Yellow River from 1957 to 2016, we estimated the change trend and mutation time of meteorological and hydrological factors by Mann-Kendall test and Pettitt mutation analysis method, and examined the contribution of climate change and human activities to runoff variation using hydrological simulation attribution method. Further, we applied the WEP-L model to estimate the spatial and temporal variations of the amount of water retention and various water retention functions in the source region of the Yellow River, and comprehensively analyzed the influence of different factors on the water retention functions. The results showed that temperature significantly increased from 1957 to 2016. According to the mutation time of the runoff, the runoff sequence was divided into the base period (1956-1989) and the change period (1990-2016). The contribution of climate change and human activities (land use change) to the decrease of runoff during the change period was 32% and 68%, respectively. The amount of water retention showed a non-significant increasing trend from 1957 to 2016, with a rate of 0.36 mm·a^-1. The amount of water retention in the northern and western regions increased during the change period, while it decreased in the southern and southeastern parts of the study area. Among the functions of water retention, the functions of maintaining vegetation water use, replenishing basic flows, and reducing floods showed an increasing trend over the years, but the function of replenishing basic flows weakened in the southeast region during the change period. Precipitation was the main factor affecting the variation of water retention functions, while temperature indirectly affected the water retention functions by changing the underlying surface conditions.

As a major type of terrestrial ecosystems, forests are an important foundation for high-quality development in the Yellow River Basin, China. The assessment of forest ecological quality in the Yellow River Basin will help to elucidate the current situation and development trend, and provide a scientific basis for ecological protection and management. In this study, the forest ecological quality evaluation index system was established based on the DPSIR model with analytic hierarchy process, with which forest ecological quality in the Yellow River Basin from 2000 to 2020 was evaluated and the spatiotemporal changes and correlation were analyzed. The major findings are as follows: (1) forest ecological quality in the Yellow River Basin showed spatial variation, with lower values in the west than in the east and lower values in the north than in the south. (2) In terms of spatial change, forest ecological quality improved overall in the Yellow River Basin, but degraded locally. During the first 15 years of the studied period, the forest ecological quality in the western part of the basin initially improved and then degraded, while the northern regions of the basin exhibited degradation followed by improvement. The forest ecological quality markedly improved during 2015-2020. In the middle and lower reaches of the Yellow River Basin, including some regions of Henan and Shanxi provinces, the forest ecological quality decreased significantly from 2000 to 2005, and gradually improved in the following 15 years. The forest ecological quality in the counties of Shandong Province slowly improved. The forest ecological quality in the southern region of Aba Prefecture of Sichuan Province, the Qinling Mountains, and the counties near Liangshan Mountain in Yan’an, remained stable and at the excellent level. (3) Forest ecological quality in the Yellow River Basin showed marked spatial agglomeration of similar values in the past 20 years, and the spatial agglomeration was weakened overall.