Stock Dynamics Research Articles

Fishery, systematics and stock dynamics of billfishes landed along the Indian coast

Sailfishes, marlins, spearfishes and swordfishes commonly referred to as billfishes are highlymigratory species, with a worldwide distribution in tropical and subtropical oceans. Thelandings of billfishes along the Indian coast registered an increasing trend with an estimatedlanding of 14,759 t in 2019. Kerala (41%) contributed the maximum followed by Tamil Nadu(28%), Andhra Pradesh (18%), Gujarat (8%) and Maharashtra (2%) to the total billfish landingsduring the last decade. Mechanised gillnetter cum hook and line was the major gear landingbillfishes. The major species landed during 2012-2019 were Istiophorus platypterus (52.2%),Istiompax indica (21.1%), Makaira nigricans (7.3%), Xiphias gladius (17.2%) and Kajikia audax(2.3%). Four of these species could be easily distinguished by COI barcodes but, the stripedmarlin, K. audax showed high sequence similarity with K. albida and cannot be distinguishedby barcodes alone. Control region (889 bp) provided a better phylogenetic signal, consistentwith that of the whole mitochondrial genome topology. The stock status plots of billfishesdepicted that, all the species were in the developing and exploited phase. Growth, mortalityand exploitation rates estimated for four billfishes indicated that the present fishing ratesand biomass levels are at safe levels and there is considerable scope for enhancing theirfishery. Keywords:CO1 barcodes, Exploitation rate, Large pelagics,Life history, Stock status plots

Age estimates derived from hard parts of swordfish Xiphias gladius from the north-western Mediterranean Sea.

Accurate age estimates for fish are critical for properly understanding stock dynamics and health; this is particularly true for larger billfishes. Here we determined the most accurate aging estimation methods for swordfish (Xiphias gladius). We compared age estimates obtained from fin-ray sections, otolith sections, whole otoliths, and vertebrae collected from 87 swordfish off the east coast of Corsica. Age estimates from otolith sections were most consistently estimated across different readers (lowest average percentage error), followed by fin-ray sections, third vertebrae, and whole otoliths. When the age estimates from the otolith sections were compared with the other three age sclerochronological methods, we found the average percentage error to be lowest between the otolith section and fin-ray methods. However, age estimates from fin rays proved most useful for estimating swordfish younger than 6 years, as the fin ray-based age diverged from that of the otolith sections as the swordfish aged. Combining fin ray and otolith section techniques, we estimated the growth parameters of 1-12-year-old females (L∞ = 259.412, k = 0.113, t0 = -2.499) and 1-7-year-old males (L∞ = 175.543, k = 0.202, t0 = -2.239). We found that females grew significantly faster than males after 3 years and remained larger thereafter. Our calculated growth rates for this region of the north-western Mediterranean Sea were lower than those of the Atlantic, Pacific, and eastern Mediterranean Sea swordfish populations, and similar to growth rates recorded for the western Mediterranean Sea populations. Our study provides critical knowledge on biological-related parameters to serve as a guide for preserving the swordfish population in the Mediterranean Sea.

Non-domestic building stock: linking dynamics and spatial distributions

In contrast to domestic buildings, the drivers influencing the stock dynamics (construction subtracted by demolition) of non-domestic buildings (NDB) have not yet been researched on a use-class basis. For the first time, due to elaborated data sets on construction and demolition of NDB in Germany, an in-depth analysis of causal relationships is provided at a subnational level. This paper investigates the cause–effect relationships between influencing variables and stock dynamics of the three quantitatively most relevant use classes of the German NDB stock: office buildings, industrial buildings and warehouses. Influencing variables on the development of the stock were first identified by means of expert interviews. Regions with high construction dynamics were identified. Within these highly dynamic regions, construction activity was correlated with influencing variables. A principal component analysis was used to examine the explanatory power of underlying, use-class-specific components of the variable set. The results show the particular importance of employment-related variables. They combine demographic, economic and wealth-related influences and allow for a distinction to be made in relation to functional non-domestic-use classes. For the first time, this confirms that different use classes of NDB are characterised by different influencing variables, and that these variables recur to uncorrelated overarching drivers. Practice relevance This study identifies the drivers of NDB stock dynamics. These drivers can be used to estimate future changes of the NDB stock on different scales. The linkages to specific use-class drivers allow new understandings of stock dynamics for office, industrial and warehouse buildings at a regional level. This has potential application to circular economy approaches as the results of this research can be applied at city levels. This study can provide a clearer understanding of future construction material volumes and their respective recycling capacities. The same is applicable for research on stock-driven land demand. This study can contribute to the broader discussion on the future development of the non-residential building stock and the resulting environmental impacts due to land use, energy and material consumption or CO2 emissions.

Powers Correlation Analysis of Returns with a Non-stationary Zero-Process

Abstract The higher order dynamics of individual stocks is investigated. We show that classical powers correlation analysis can lead to a spurious assessment of the volatility persistence or long memory volatility effects, if the zero return probability is non-constant over time. In other words, classical tools are not able to distinguish between long-run volatility effects, such as IGARCH, and the case where the zero returns are not evenly distributed over time. As a remedy, new diagnostic tools are proposed that are robust to changes in the zero return probability. Since a time-varying zero return probability could potentially be accompanied by a non-constant unconditional variance, we also develop powers correlation analysis that is robust in such a case. In addition, the diagnostic tools we propose offer a rigorous analysis of the short-run volatility effects, while the use of the classical powers correlations lead to doubtful conclusions. Monte Carlo experiments, and the study of the absolute value correlation of daily returns taken from the Chilean financial market and the 1-min returns of Facebook stocks, suggest that the volatility effects are only short-run in many cases.

Memahami Dinamika Harga Saham melalui Kinerja Keuangan dan Skala Perusahaan, Dengan Peran Kebijakan Dividen sebagai Variabel Pengendali pada Perusahaan Industri Dasar dan Kimia di Indonesia

The dynamics of stock prices is a very important aspect of the capital market. The price of a company's stock is influenced by many factors, including the company's financial performance and the size of the company. In addition, dividend policy is also considered as an important variable in controlling stock prices. However, there is not yet a strong consensus about the extent of the role of dividend policy in moderating the relationship between financial performance and company scale and stock prices. This study aims to understand in depth the dynamics of stock prices through analysis of financial performance and company scale, with particular emphasis on the role of dividend policy as a controlling variable. We aim to identify the extent to which financial performance and firm size affect stock prices, and to what extent dividend policy can moderate this relationship. This study uses a quantitative approach with regression analysis as the main method. Historical data on financial performance, company scale, dividend policy and company stock price will be analyzed for the relevant period. In addition, descriptive statistical analysis and significance test will be used to examine the relationship between these variables. The results of the study show that simultaneously financial performance, company scale, and dividend policy have an effect on stock prices with a contribution value of 72% is a significant finding. It provides a solid understanding of the complexity of the factors that influence stock prices in Chemical and Basic Industry companies in Indonesia. In addition, the finding that dividend policy can act as a moderating factor in increasing stock prices also has important implications. This indicates that company management has an effective tool in managing market perceptions of their stock prices through dividend policy. When used wisely, dividend policy can be a strategic instrument to increase the value of the company in the eyes of investors.

Carbon Sequestration Dynamics in Urban-Adjacent Forests: A 50-Year Analysis

Achieving carbon neutrality is crucial for urban ecosystems. Forests growing near cities largely determine the state of the environment in urban areas. The aim of the present research is to assess the carbon productivity dynamics in forests near Krasnoyarsk (a large industrial center) over a 50-year period in terms of carbon sequestration and conservation. The study was based on forest inventory conducted in Karaul'noe Forestry in 1972, 1982, and 2002 and forest inventory covering six forest compartments in 2022. The forest covers 3980 ha and consists of 52 forest compartments. The analysis was based on the assessment of carbon productivity dynamics and followed four levels of principles: forestry, structure, forest compartment, and forest stand. The research was based on forest fund dynamics, analyzing methods, long-term forest inventory, assessing carbon stock, and growing stock dynamics. Pine is the dominant forest-forming species that absorbs the most carbon in the study area. Pine is long-lived, covers a vast area, and has the highest carbon sequestration potential. At the forest structure level, the predominant carbon pools are mid-late successional and late successional stands dominated by pine, birch, and aspen. Forest compartment-level analysis revealed three trends in carbon sequestration: carbon balance, a decrease in carbon sequestration, and an increase in carbon sequestration. Notably, the prevailing trend is determined by changes in carbon sequestration by dominant forest-forming species (pine). Forest stand-level analysis showed that stands have become more and more uneven-aged. About 65% of total carbon stock is concentrated in mid successional, mid-late successional and late-successional stands, and 35% in young stands. The carbon sequestration rate decreases in forests with age. However, pine forests increase biological productivity and continue to successfully sequester carbon. Deciduous forests have lost their carbon sequestration potential, and the area they occupy is currently decreasing in the study area. The development of the young generation in pine stands suggests that the carbon sequestration potential in forests growing near the city will not decrease and may even increase due to climate change. Doi: 10.28991/CEJ-2023-09-09-08 Full Text: PDF

Long-term dynamics of aboveground carbon stocks in managed loblolly pine plantations in the southeast United States

Intensively managed pine plantations in the southeastern US could not only meet the increasing demand for traditional wood products and biomass for energy, but also play a critical role in meeting US greenhouse gas emission reduction goals through additional carbon (C) sequestration. Adapting forest management to help mitigate climate change requires better understanding of long-term effects of silvicultural treatments on forest production and C sequestration. With two long-term culture-by-density research experiments for loblolly pine plantations across the southern US, we assessed the impacts of site quality, cultural intensity (operational and intensive), and planting density (741, 1483, 2224, 2965, 3706 and 4448 trees ha−1) on dynamics of aboveground net primary production in C (ANPPC), aboveground live tree C stocks (AGC), and cumulative C lost to tree mortality and other litter production (CLC), and total gross C capture (TGC). Cultural intensity significantly affected ANPPC and AGC before age 15 years, and CLC and TGC during the whole study period; while planting density significantly affected ANPPC before age 15 years, CLC after age 6 years, and AGC and TGC over time. Site quality significantly affected AGC at early and late ages, CLC at mid-rotation, and TGC at early ages. After age 20 years, higher quality sites still resulted in higher AGC than lower quality sites, while higher-planting densities might no longer promote aboveground live tree C stock. Intensive management practices that promote growth along with C accumulation in young stands do not necessarily result in higher C stocks in older stands. There exist a maximum C sequestration rate and a maximum C storage in loblolly pine plantations. Continuing carbon capture in the extended rotation or deferred harvest forests is in no way guaranteed to continuously increase carbon stocks. To develop effective climate-smart forest management recommendations, long-term dynamics of carbon capture, release, and storage, especially in managed forest plantations, need more research.

Joint dynamics of stock returns and cash flows: A time‐varying present‐value framework

AbstractThis paper proposes a novel time‐varying present‐value model to analyze the joint dynamics of stock returns and cash flows periodically. We use a nonparametric time‐varying vector autoregressive model to examine the economic implications of the time‐varying present‐value model. By conducting several nonparametric tests, we reject the stability of multivariate forecasting models and the null that stock returns and cash flows are simultaneously unpredictable in any given period. Additional bootstrap analyses show that under the null of unpredictable returns, dividend growth is highly predictable. Finally, the proposed time‐varying present‐value framework holds robustly for both the dividend–price ratio and the earnings–price ratio.

Nitrogen availability mediates soil organic carbon cycling in response to phosphorus supply: A global meta-analysis

Soil organic carbon (SOC) is the largest carbon (C) pool in terrestrial ecosystems, and plays an important role in mitigating climate change. With increasing nitrogen (N) loading, phosphorus (P) becomes more limiting for plants and soil microbes, and consequently has a strong impact on ecosystem C sequestration. However, the response of SOC to altered P supply and its mechanisms have not been systematically investigated at the global scale. We conducted a meta-analysis of 536 paired observations from 232 published experiments to explore the dynamics of SOC stock in response to experimental P additions. We found that P additions significantly increased SOC stock across the globe, but the P addition effect on SOC strongly depended on soil N availability. This was confirmed by larger effect sizes in ecosystems dominated by N-fixing species compared with those dominated by non-N-fixing species, under high N availability (soil C:N ratio ≤16) compared with low N availability (soil C:N ratio >16), and under N + P additions compared with P additions alone. Under high N availability, P additions significantly increased aboveground biomass and litterfall, but had no significant effect on soil microbial biomass and oxidase activity. Under low N availability, P additions not only increased aboveground biomass and litterfall but also increased soil microbial biomass and oxidase activity. However, the increases in aboveground biomass and litterfall did not induce a corresponding accumulation of C in the soil, possibly because P additions promoted microbial CO2 release that offset the increasing plant C inputs. The reactive N input reduced P-addition-induced C loss from the soil to increase SOC sequestration, and the P addition effect on SOC was largely enhanced with increasing experimental duration, partly due to N retention in the soil after P additions. Collectively, the findings suggest that future changes in global exogenous P loads will have divergent impacts on SOC sequestration, depending on soil N availability.

Soil organic carbon stock change following perennialization: a meta-analysis

Perennial crops replacing annual crops are drawing global attention because they harbor potential for sustainable biomass production and climate change mitigation through soil carbon sequestration. At present, it remains unclear how long perennial crops can sequester carbon in the soil and how soil carbon stock dynamics are influenced by climate, soil, and plant properties across the globe. This study presents a meta-analysis synthesizing 51 publications (351 observations at 77 sites) distributed over different pedo-climatic conditions to scrutinize the effect of perennialization on organic carbon accumulation in soil compared with two annual benchmark systems (i.e., monoculture and crop rotation). Results showed that perennial crops significantly increased soil organic carbon stock by 16.6% and 23.1% at 0–30 cm depth compared with monoculture and crop rotation, respectively. Shortly after establishment (< 5 years), perennial crops revealed a negative impact on soil organic carbon stock; however, long duration (> 10 years) of perennialization had a significant positive effect on soil organic carbon stock by 30% and 36.4% at 0–30 cm depth compared with monoculture and crop rotation, respectively. Compared with both annual systems, perennial crops significantly increased soil organic carbon stock regardless of their functional photosynthetic types (C3, C4, or C3-C4 intermediates) and vegetation type (woody or herbaceous). Among other factors, pH had a significant impact on soil organic carbon; however, the effect of soil textures showed no significant impact, possibly due to a lack of observations from each textural class and mixed pedoclimatic effects. Results also showed that time effect of perennialization revealed a sigmoidal increase of soil organic carbon stock until about 20 years; thereafter, the soil carbon stocks advanced towards a steady-state level. In conclusion, perennial crops increased soil organic carbon stock compared with annual systems; however, the time since conversion from annual to perennial system decisively impacted soil organic carbon stock changes.

THE EFFECT OF TAX BURDEN, FOREIGN OWNERSHIP, INTANGIBLE ASSETS AND BONUS MECHANISM ON TRANSFER PRICING

In Indonesia, a country with a significant mining industry and a dynamic stock exchange, transfer pricing decisions among mining companies have become a subject of interest. These decisions involve determining the prices at which related entities within the same multinational corporation trade with each other. The complexity arises from the potential discrepancies between market prices and the prices set for intra-company transactions. This study aims to investigate the impact of Tax Burden, Foreign Ownership, Intangible Assets, and Bonus Mechanism on Transfer Pricing Decisions among Indonesian mining firms listed on the Stock Exchange from 2017 to 2021. Using purposive sampling, six mining companies were selected as the research sample. Employing Panel Data Regression Analysis via Eviews 9 software at a 5% significance level, the study finds that collectively, the independent variables significantly influence companies' choices for transfer pricing, as indicated by the F-test (F-statistic value = 13.07910, F-table value = 2.759). Regarding individual variables, Tax Burden lacks significant influence (p-value = 0.3819), while Foreign Ownership negatively impacts transfer pricing decisions (p-value = 0.002, t-statistic = -3.503829). Intangible Assets (p-value = 0.8969) and Bonus Mechanism (p-value = 0.6290) also do not significantly influence transfer pricing. The study concludes that investors should cautiously analyze company policies due to varied motivations for transfer pricing, and recommends government review of policies to curb detrimental transfer pricing practices. The limited number of multinational mining companies and scarce information on their transfer pricing practices are study limitations.

Dynamics of codfish stocks in the North Atlantic region

Purpose: to investigate the features of the long-term dynamics of codfish stocks in the North Atlantic region as a basis for predicting their state and sustainable fishing (exploitation). Materials: data on spawning stock biomass, abundance of recruitment at age 0 to 3 years, survival indices at early ontogenesis stage for 11 Atlantic cod stocks, 6 Atlantic haddock stocks, and 4 saithe stocks for the period 1946–2020 Methods: a comparative analysis of the above time series based on their statistical processing. Novelty: For the first time, a 50–60-year cycle which characterizes the long-term variations of the Atlantic Multidecadal Oscillation index, were revealed in the long-term fluctuations of the Northeast Arctic cod recruitment. This assumes a relationship in the long-term variations of two parameters under consideration. Results: The significant interannual variability of all characteristics was identified for each of the 21 commercial fish stocks under consideration. Statistically significant positive correlations were found between changes in recruitment abundance of Atlantic cod in the Northwest Atlantic and Atlantic cod, Atlantic haddock, and saithe in the areas of Greenland, Iceland, North and Baltic Seas. Changes in the recruitment abundance of Labrador cod and Northeast Arctic cod in the Barents Sea are opposite. Practical significance: the results of this work can be used to improve the methods of the medium-range and long-range forecasts of codfish catches in the North Atlantic region.

Distribution of catches of aquatic biological resources in the Russian waters of the Bering Sea by areas, dates and fishing gear

The purpose of the work: revealing the features of the distribution of the catches of aquatic biological resources by area, timing and fishing gear in the course of modern fishery in the Russian waters of the Bering Sea. Methods used: the catches of marine fish and invertebrates were considered based on operational information on the fishery according to the data of daily ship reports of the sectoral monitoring system. The ratio of the catch of the main species of aquatic biological resources and by-catch objects in 10 fishing gear was analyzed according to the data of 50 marine and 28 coastal expeditions. Novelty: elements of novelty are generalized materials on the spatial and bathymetric distribution of the catch of the main fishing objects for the fishing industry in the western part of the Bering Sea for the period 2003–2021. The distribution of catches of aquatic organisms is given by types of vessels used in the fishery, depths and terms of fishing, as well as various fishing gear. Data on the ratio in commercial catches of both individual fish species and some species in the combined groups of «flounders», «rockfishes», «sculpins», «skates» and «grenadiers» are presented. Practical significance: the results of this study can be used in forecasting the dynamics of stocks of aquatic biological resources, creating a system of interlocked quotas and formulating recommendations for the transition of specialized fisheries to multi-species fisheries.

Analysis of Soil Carbon Stock Dynamics by Machine Learning—Polish Case Study

A simplified differential equation for the dynamics of soil organic carbon (SOC) that describes the rate of SOC change (dSOC/dt) was constructed using the LASSO regression—a regularized linear regression machine learning method. This method selects the best predefined explanatory variables and empirically evaluates the relevant parameters of the equation. The result, converted into a formula for the long-term equilibrium level of soil carbon, indicates the existence of carbon sequestration potential in the studied regions of Poland. In particular, the model predicts high SOC content in regions with a high Topographic Wetness Index (TWI), such as river valleys or areas with high cattle density, as expected.

Carbon stock dynamics in a disturbed tropical forest ecosystem of Central India: Strategies for achieving carbon neutrality

Anthropogenic land use changes in the vicinity of forest catchments are explicitly responsible for the deforestation and degradation of tropical forest thereby altering the carbon (C) balance under rising atmospheric carbon dioxide (CO2). Thus, strategic mitigation measures are required to achieve climate neutrality by 2030. It becomes imperative to understand the impact of land cover conversion on the functioning of tropical forests and to determine the carbon dynamics. The present study examined the land cover changes (LUC) in dry tropical ecosystem of Central India during the last two decades and assessed its influence on the forest biomass, litter crop, and C stocks. Geospatial techniques coupled with ground measurements were employed in the study. The total biomass, vegetative C stocks and soil C were estimated as 64 to 338.3 Mg ha−1, 26.4 to 131.1 Mg C/ha and 24.6 to 50.2 Mg C/ha respectively. In the past decades (2000–2020), about 1851.8 ha of forest constituting 15.1% of the total area under study was lost (mainly to Agriculture) under open mixed forest, moderately mixed forest and mixed teak forest. The study demonstrated that forests of the studied region behave as a potential C source, which accounted for a net loss of 59 gigagram carbon (Gg C) equivalent to 216 Gg CO2eq. Besides, discussed three viable scenarios of restoration to offset C emissions and to achieve C neutral landscape by 2030. The conservation and restoration of 26–85% degraded forests (open mixed forest and moderately mixed dense forests), use of agroforestry on 1/5th of existing agricultural lands, or implementation of regenerative agricultural practices in 30% of the area will compensate for net losses, while attaining C neutrality. Further, the finding of this study helps to understand the climatic extremes as per the commitments of Paris Agreement, 2015 and Glasgow Pact, 2021.

The Barents and Norwegian Seas beaked redfish (Sebastes mentella): stock assessment and fishery management

An analytical review of the stock assessment and fishery regulation of the Barents and Norwegian Seas beaked redfish is presented. Model estimates of stock dynamics are characterized by uncertainty associated with incomplete coverage of the beaked redfish distribution in surveys, age determination problems, and assumptions made in the model. The regulation of fishing mortality is based on the precautionary approach, and the main management aim is achievement of the maximum sustainable yield. Technical measures include limiting the minimum mesh size in the trawl, establishing a minimum fish length for fishery, temporal fishery closures and limiting by-catch in multi-species fisheries. The unregulated fishery of the Norwegian-Barents Sea beaked redfish in the 1970s was one of the reasons for the decline in its stock and appearance of poor recruitment, which led to the ban on its targeted fishing in the Norwegian Economic Zone and in the fish protection area of the Svalbard. In 2014, the fishing was reopened. At present, the stock of beaked redfish of the Norwegian-Barents Sea population is in a safe state and further growth of the catch is expected.

Dynamics of stocks of Japanese icefish Salangichthys microdon and the possibility of it forecasting in the Primorsky Krai (Japan Sea)

Japanese icefish Salangichthys microdon is a commercial but little studied species in the Far Eastern waters of Russia. The intraseasonal and interannual dynamics of estimates of the abundance of noodle fish in estuaries is characterized by sharp fluctuations: the values of the minimum and maximum estimates differ by more than 100 times. The instant total mortality rate of fish noodles is 2,06, and the total annual mortality rate is 0,87.

Macrofauna and Organic Matter in Postagrogenic Sandy Soils at the NW Smolensk Region (Russia)

Natural reforestation on the abandoned arable lands is one of the characteristic processes that triggers the transformation of soils, accompanied by the change in the abundance, biomass, and taxonomic structure of the soil macrofauna. The assessment of the restoration potential of the soil properties and soil macrofauna to the natural state, the duration of this period, the dynamics of soil organic carbon stocks, and the role of macrofauna in this process at different stages of post-agrogenic successions is relevant for prediction of changes in ecosystem components and their role in the storage of organic carbon under various land use scenarios. The work is based on the data on organic carbon reserves, morphological properties of soils, abundance, biomass and taxonomic structure of the soil macrofauna of arable lands, primary forests and 5 stages of pine forest restoration (fallow meadows and pine forests of different ages) at the Smolenskoye Poozerye National Park (Smolensk region). It was revealed that in the soils of the 85–100-year-old pine forests, signs of plowing are preserved in the form of the smooth lower boundary of the humus horizon. At the same time, signs of soil regradation appear already at the meadow stage and are expressed in the formation of a thin humus horizon penetrated by roots, which transforms further at the next stages. In the litter and mineral part of the soil, the carbon stocks change non-monotonically with a maximum at the meadow stage and a minimum in 70–80-year-old forests. By the age of 80, the stock of organic carbon in the mineral part of soils is almost restored to the background values. The composition of soil macrofauna changes drastically during the transition from meadow to forest communities. At the initial stages (in agrocenoses and fallow meadows), the fauna of mineral soil horizons predominates: endogeic earthworms and larvae of lamellar beetles. Further, the fauna of organic horizons is restored, among which there is a high proportion of saprophages – epigeic and epi-endogeic earthworms, which contribute to the differentiation of litter. The biomass of saprophages has a negative correlation with the carbon reserves in the mineral part of forest soils, the thickness and reserves of organic carbon in the litter, and a positive correlation with the share of the easily decomposable litter fraction.

Sustainable stingray stock (Dasyatis sp.) in Malacca Strait, Serdang Bedagai Regency

Sustainable stingray stock catches and increasing the potential that these fish populations may become overfished this may have a negative impact on the size of fish stocks. In order to estimate stock models and prospective resources of stingrays in the seas of the Malacca Strait, the descriptive technique was utilized to collect secondary data. The necessary to conduct stock dynamics research that examines the exploitation rate of stingrays. Based on the Schaefer model, obtained the value of sustainable potential (MSY) for Stingray resources (Dasyatis sp.) at Tanjung Beringin fishing port of 37,24625 tons/year and the optimum effort value of 148,6119 trips/ years. The percentage of stingray resource utilization rate which landed in Tanjung Beringin TPI during the last 5 years has an average value of 0,925% and an effort level of 1,234%. TAC is 29,797 tons/year, shows that fishing can still be increased to get more optimal results. The value of the allowable catch must be below the MSY value which is 80%. The average allowable catch of stingray (Dasyatis sp.) is 80% of the MSY. This means that fishermen’s catches can still be optimized, but must not exceed MSY limit.

Decomposition and nutrient dynamics of stumps and coarse roots of Eucalyptus plantations in southern China

Key messagePrimary remains of Eucalyptus (E. urophylla × E. grandis) plantations following clear-cutting are the stumps and coarse roots. A chrono-sequence approach revealed that the biomass of coarse roots is higher than that of stumps, while they have a smaller rate of biomass loss than stumps. This implies that coarse roots serve as long-term stock for nutrients (carbon, nitrogen, and phosphorus).ContextA significant quantity of stumps and coarse roots persist in the forest floor following the clear-cutting of Eucalyptus plantations in China. The decomposition of these stumps and coarse roots is a crucial aspect of the nutrient stocks in plantation ecosystems.AimsWe described the stock and decomposition dynamics of stumps and coarse roots on Eucalyptus plantations, as well as the nutrient loss rate associated with them.MethodsWe used a chrono-sequence of 0–6-year-old clear-cutting stands of Eucalyptus plantations in southern China. The biomass and nutrient stocks of these samples were assessed at different times of decomposition.ResultsThe highest biomass of stump-root system was 33.8 Mg·ha−1, with nutrient stocks were 16.3 Mg·ha−1, and 63.0 kg·ha−1, and 6710.9 g·ha−1, for C, N, and P. The coarse roots accounted for 81–96% of the biomass of the stump-root system. The loss rate of biomass and nutrients from stumps was higher than that of coarse roots. This suggests that the decomposition of coarse roots could serve as a long-term source of nutrients, thereby improving the nutrient status of the plantations.ConclusionStumps and coarse roots serve as significant nutrient stocks that decay at varying rates. The loss of nutrients must be considered while analyzing the decomposition dynamics following clear-cutting in Eucalyptus plantations.