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Converting monocultures to mixed plantations has been emphasized to improve ecosystem productivity and services. However, the impact of tree species identity on phosphorus (P) bioavailability in acidic soils in subtropical China, where P is relatively scarce, is not fully understood. This study explored the changes in soil biologically‐based P fractions and the effect of mineral and microbial properties on P transformation after mixing five broadleaved trees (Bretschneidera sinensis, Manglietia conifera, Cercidiphyllum japonicum, Michelia maudiae and Camellia oleifera) individually with coniferous trees (Pinus massoniana). The results showed that most mixed plantations significantly increased pH and citric acid and decreased exchangeable Fe3+ and Al3+ and the activation of Fe and Al oxides compared with monospecific plantations, which significantly reduced P precipitation and adsorption. Mixed planting significantly increased phosphatase activity and altered the community composition of P‐mobilizing bacteria carrying phoD and pqqC genes, which contributed to organic P mineralization and inorganic P (Pi) desorption. Mixed planting increased microbial biomass and the relative rate of microbial biomass P turnover. Labile organic P (Enzyme‐P) was a potentially significant source of soluble Pi (CaCl2‐P) among the biologically‐based P fractions, plus microbial biomass P. Overall, introducing broadleaved species, especially in species (e.g. Cercidiphyllum japonicum, Michelia maudiae and Camellia oleifera) with relatively high litter quality and belowground secretions (e.g. citric acid, phosphatase), significantly increased the solubilization of recalcitrant Pi (HCl‐P), desorption of chemisorbed Pi (Citrate‐P) and accumulation and mineralization of Enzyme‐P, thereby increasing the available P pools. Redundancy analysis demonstrated that P fractions were mainly driven by phosphatases, exchangeable cations, floor fresh litter lignin/N and citric acid. Altogether, we highlight the importance of choosing tree species mixtures that have synergistic or complementary effects when constructing mixed plantations in order to alleviate soil P limitations. [ABSTRACT FROM AUTHOR]

Chub mackerel (Scomber japonicus) is a commercially important fish species which are widely distributed in the North Pacific. Based on the fishery data from China's high-sea light-purse seine fishing from 2014 to 2020 and the marine environment factors, a mixed linear model considering the actual spatiotemporal stratification of the catch per unit effort (CPUE) was established to analyze the fixed and random effects of marine environmental factors on the CPUE of chub mackerel and to investigate the relationship between the abundance of chub mackerel resources in the Northwest Pacific and two marine environmental factors: sea surface temperature (SST) and chlorophyll-a concentration (CHL). The results showed that SST had a significant fixed effect on the CPUE. In contrast, the natural logarithm of chlorophyll (logCHL) had no fixed effect on the CPUE. Based on the monthly analysis, random fluctuations were observed in the impact of logCHL on the CPUE. LogCHL and CPUE show a positive correlation during spawning and wintering periods and a negative correlation during the feeding period. The study showed that when fishery sampling data exhibit spatiotemporal stratification, linear mixed models can effectively incorporate both the fixed and random effects of environmental factors on the CPUE of chub mackerel. Linear mixed models can play an important role in analyzing the fluctuations in resource abundance and the mechanisms governing the formation of fishing grounds for chub mackerel in the Northwest Pacific. [ABSTRACT FROM AUTHOR]

Understanding the spatial distribution of fishing activity and suitable fishing areas is important for improving sustainable fisheries management and protecting vulnerable fish stocks. To identify climate-related habitat changes and variations in the distribution of fishing activity for squid-jigging vessels in the Northwest Pacific Ocean, two types (weighted arithmetic mean method, weighted-AMM; weighted geometric mean method, weighted-GMM) of habitat suitability index (HSI) models were developed in this study with marine environmental data at different depths. The boosted regression tree (BRT) model was adopted to access the monthly important environmental variables and the relative influence of the corresponding variables. The results showed that the weighted-AMM has better prediction performance than the weighted-GMM. The suitable fishing areas showed significant seasonal changes in both spatial location and coverage area. The hotspot map showed that the suitable fishing area for squid-jigging vessels was located in the scope of 42 ∘ N∼44 ∘ N, 155 ∘ E∼170 ∘ E throughout the year during 2012∼2019, which suggests that high squid-jigging fishing pressure should be given more attention in fishery management. The HSI model also had good prediction performance for the fishery data of Chinese companies, except for June and July. Additionally, fishing efforts could be used as alternative data for fishery research. The study has also suggested that fishery data are restricted by spatial and temporal distribution and fishing experience, which probably biases the results of the research. [ABSTRACT FROM AUTHOR]

Zhang, S.; Tang, F.; Fan, W.; Yang, S.; Zhu, W.; Zhang, H., and Cui, X., 2023. Analysis of hauling net hours for Gazami crab (Portunus trituberculatus) gillnets based on the Beidou vessel monitoring system (BDVMS). Journal of Coastal Research, 39(4), 663–674. Charlotte (North Carolina), ISSN 0749-0208. Gillnets are among the most widely used fishing gear in the world, and there are nearly 97 thousand gillnetters in China's offshore. With the decline of resource fisheries, the fishing quota has remained a topic of concern for the world's fishing nations. At the beginning of 2017, the Ministry of Agriculture and Rural Affairs of the People's Republic of China implemented the total management of marine fishery resources and began to launch the quota fishing experiment. The vessel monitoring system (VMS) provides a new data source for fisheries research. It is a new attempt to estimate fishing yield from VMS. Refined fishing intensity can be obtained through calculation of hauling time or net length. In China, the shipboard Beidou satellite navigation system terminal was installed on well-equipped fishing vessels. It sends vessel identification and location information at three minute intervals and with 10 m spatial resolution. In this paper, the speed threshold was used to consider the hauling duration of the net. The hauling nets' hours were calculated to estimate the catch rate with the hours. The speed thresholds of the 56 vessels were from 1.7 to 2.4 m/s. The hauling duration in hour of the vessels were distributed throughout eight fishing grounds in 2017. Hauling duration was divided into 0.01° × 0.01° grids based on coordinate locations. The average hauling duration of the nets was 1.7 h, and the maximum value was 41.5 h. There were approximately 514 thousand net hauling points, and the catch weight of the swimming crab (Portunus trituberculatus) was calculated to be approximately 4.7 million kg in 2017 based on the hauling duration data. [ABSTRACT FROM AUTHOR]

A previous survey reported that swimming crabs Portunus trituberculatus (Miers, 1976) in the East China Sea may have a low risk of sperm limitation under the current nonselective fishing practices. In this study, the possible mechanism of avoiding sperm limitation was investigated in a mating season (from July to November 2007) from a male perspective. Males reached 50% gonadal maturity at a carapace length of 99.4 mm and the reproductive measures (vas deferens weights, sperm number, and sperm concentration retained in the vasa deferentia) did not differ significantly throughout the mating season. As shown for other decapods, the quantity of seminal material in the vasa deferentia increased significantly with male size, without a concomitant change in sperm concentration. The proportion of stored sperm transferred at a single mating was calculated, and the results showed that males exhibited low sperm transfer at each mating, regardless of size. These findings indicate that the current fishery practices for P. trituberculatus may have little impact on the quantity of sperm stored by males throughout the mating season. This would guarantee that males of all sizes retain the capacity to mate throughout the breeding season, and, moreover, provide sufficient sperm to fertilize eggs spawned by their mates and reduce the risk of sperm limitation under the current fishing practices in the East China Sea. KEY WORDS: Portunus trituberculatus, sperm storage, nonselective fishery, East China Sea, sperm limitation, INTRODUCTION Sperm limitation occurs when the sperm supply of males is insufficient to fertilize the total number of potential eggs of females. Many studies on exploited wild decapods have revealed [...]

Guizhou Province is located in the largest continuous karst area in the world. The karst landform accounts for 73.8% of the province's land area where 88% of its rural population live. The exposed area of carbonate rocks developed in karst reaches 130,000 km2, accounting for 73% of land area in this province. Soil erosion leads to the exposure of carbonate rocks on the surface, aggravates the process of karst rocky desertification, and causes a series of ecological and environmental problems, all of which seriously affect the development of local economy and people's life. The research on the comprehensive prevention and control of karst rocky desertification has become a scientific problem that needs to be solved urgently. In addition, bedrock and vegetation play a prominent role in soil development and formation. In different soil development stages, bedrock and vegetation types have an important impact on the soil physical and chemical properties. However, the current research on karst soils mainly focuses on the soil properties of limestone-formed soils. There is still a lack of research on the characteristics of soil developed by carbonate rock and the effects of their interactions on soil in karst areas from the perspective of vegetation-soil-bedrock system. Taking the soil developed by carbonate rock (limestone, calcareous dolomite and dolomite) as the research object, this study aims to explore the distribution characteristics and influencing factors of the soil developed by carbonate rock under different vegetation conditions in karst areas, and analyze the effects of different vegetation types, bedrock types and soil layers on soil properties. The study area is located in Huaxi district, Guiyang City, Guizhou Province. It has a subtropical monsoon climate with an average annual temperature of 14.9 °C and an average annual precipitation of 1,229 mm. Three representative plots in Huaxi district were selected, including Huaxi Reservoir, Huaxi TV Tower, and the area near the southern Guizhou University, and a total of 60 soil samples were collected from these three sample plots of different carbonate rock types. The main tree species in the study area are Cupressus funebris, Quercus, and Myrsine Africana, and grass species are Stipa bungeana and Cynodon dactylon. The soil physicochemical properties were determined by potentiometric method, Kjeldahl method, alkaline hydrolysis diffusion method, molybdenum antimony anti-colorimetric method (sodium bicarbonate extraction), and potassium dichromate oxidation with an external heating method. The particle size distribution of soil was determined by the hydrometer method. In SPSS24 software, Shapiro-Wilk test was used to test the normality of the data. Mann-Whitney U test and Kruskal-Wallis H test (multiple comparison, Bonferroni method) were used to test the difference of soil properties with different sampling depths, vegetation types and bedrock types. Scheirer-Ray-Hare test was used to determine whether vegetation type, bedrock type, soil layer, and their interactions had a significant effect on soil particles and fertility. Permutation multivariate analysis of variance (PERMANOVA) was used to analyze whether there were significant differences between two or three groups of data. Non-metric multi-dimensional (NMDS) was used to analyze the particle and fertility indexes of the soil developed by different bedrock types in the 0-20 and 20-40 cm soil layers. Redundancy analysis (RDA) was used to analyze the effects of vegetation type, bedrock type, and soil layer on changes in soil properties. These analyses were performed in the R version 4.0.3. The bedrock and vegetation types are the main factors affecting the development of carbonate rocks into soil, followed by soil layers. In 0-20 and 20-40 cm soil layers, the fertility and particles of the soil developed by limestone, limy dolomite and dolomite are significantly different. However, between the 0-20 and 20-40 cm soil layers, there is no significant difference in the nature of the soil developed from the same bedrock except the differences between gravel content (SLC) and fine particle ratio (<0.002 mm) of limestone-developed soil and the differences between available phosphorus (AP) and organic matter (SOM) content of dolomite-developed soil. In the 0-40 cm soil layer, the bedrock type significantly affects the distribution of soil pH, AP, SLC, AN, total nitrogen (TN), SOM, and 0.2-0.25 mm and 0.002-0.02 mm particles. Vegetation type significantly affects the pH value, AP, TN content of limestone-developed soil, pH, SLC, coarse particles (0.25-2 mm) and fine particles of dolomite-developed soil, and available nitrogen (AN), SOM, coarse and fine particles of soil developed by limestone dolomite. The soil layer significantly affects the distribution of SLC, coarse and fine particles in limestone-developed soil and AP in dolomite-developed soil. At present, the soil under the abandoned grassland slope and grass cover and the limestone-developed soil in the study area are likely being damaged by erosion. Therefore, according to the lithology of the parent rock, moderately changing the planting structure of vegetation on soil has a positive effect on improving soil nutrients and soil particle composition, and enhancing soil erosion resistance. Besides, the interaction of bedrock-vegetation-soil system and human activities should be comprehensively considered in the prevention and control of soil erosion in karst areas. [ABSTRACT FROM AUTHOR]

Image fusion of satellite sensors can generate a high-resolution multi-spectral image from inputs of a high spatial resolution panchromatic image and a low spatial resolution multi-spectral image for feature extraction and target recognition, such as enclosure seines and floating rafts. However, there is currently no clear and definite method of image fusion for different aquaculture areas distribution extraction from high-resolution satellite images. This study uses three types of high-resolution remote sensing images, GF-1 (Gaofen-1), GF-2 (Gaofen-2), and WV-2 (WorldView-2), covering the raft and enclosure seines aquacultures in the Xiangshan Bay, China, to evaluate panchromatic and multispectral image fusion techniques to determine which is the best. This study applied PCA (principal component analysis), GS (Gram-Schmidt), and NNDiffuse (nearest neighbor diffusion) algorithms to panchromatic and multispectral images fusion of GF-1, GF-2, and WV-2. Two quantitative methods are used to evaluate the fusion effect. The first used seven statistical parameters, including gray mean value, standard deviation, information entropy, average gradient, correlation coefficient, deviation index, and spectral distortion. The second is the CQmax index. Comparing the evaluation results by these seven common statistical indicators with the results of the image fusion evaluation by index CQmax, the results prove that the CQmax index can be applied to the evaluation of image fusion effects in different aquaculture areas. For the floating raft cultured area, the conclusion is consentaneous; NNDiffuse was also optimal for GF-1 and GF-2 data, and PCA was optimal for WV-2 data. For the enclosure seines culture area, the conclusion of quantitative evaluations is not consistent and it shows that there is no definite good method that can be applied to all areas; therefore, careful evaluation and selection of the best applicable image fusion method are required according to the study area and sensor images. [ABSTRACT FROM AUTHOR]