Rojaspotter5679

At large scale, they were no correlated in both moderately and seriously disturbed stands. The results suggested that abundance of trees with small diameter in the forests was negatively with disturbance intensity, which led to the lower degree of intraspecific aggregation at small scale. Meanwhile, appropriate levels of disturbance would benefit the collaborative use of environmental resources for trees. Our results revealed the impacts of disturbance density on forest community structure and could provide theoretical basis for forest management.We investigated the effects of warming on soil nitrogen cycling process in alpine scrub ecosystem, with an in-situ simulated warming experiment at Sibiraea angustata alpine scrubland on the eastern Qinghai-Tibet Plateau, China. We examined the responses of soil nitrogen transformation rate to warming in three critical periods (the early, late, and non-growing seasons). The results showed that warming increased soil temperature by 1.2 ℃, but decreased soil moisture by 2.5%. The soil net nitrogen mineralization rates (i.e., ammonification and nitrification) in the growing season were significantly higher than those in the non-growing season. learn more The rates of soil net nitrogen fixation in the non-growing season were significantly higher than that in the growing season. Soil nitrification was the major process of soil nitrogen transformation in the early growing season, while soil ammonification was the major one in the late growing season and non-growing season. The effects of experimental warming on soil nitrogen transformation differed among those three periods. Experimental warming significantly increased soil net ammonification, nitrification, nitrogen mine-ralization and fixation in the early growing season, and enhanced soil net nitrification and nitrogen mineralization in the non-growing season. However, warming significantly decreased soil net nitrification, nitrogen mineralization and fixation in the late growing season and soil net ammonification in the non-growing season. Moreover, warming did not affect soil net nitrogen fixation rates in the non-growing season and soil net nitrification rates in the late growing season. Future climate warming would significantly change soil nitrogen transformation by accelerating soil nitrogen cycling in the alpine scrub ecosystem on the eastern Qinghai-Tibet Plateau.Engraulis japonicus, an important fishery resource, is a key species in ecosystem trophodynamics studies. In this study, we examined stomach content of E. japonicusby stable isotope analyses, with samples collected from the East China Sea in 2008-2009 and 2020. The aim of this study was to demonstrate their diet composition, diel and ontogenetic changes in feeding habits and trophic level. Results of the stomach content analysis showed that E. japonicus mainly fed on planktonic crustaceans and small fish. The main prey species were Euphausia pacifica [index of relative importance (IRI)=87.6%; frequency(F)=57.6%], Paracalanus parvus (IRI=3.2%, F=15.3%), and Themisto gracilipes (IRI=2.1%, F=13.1%). Results of the stable isotope analysis showed that Copepoda were the main food source of E. japonicus, followed by Euphausiacea, and the contribution rate of Amphipoda was the least, which was less than 1%. There was significant diel change in diet composition. Feeding intensity was higher in the daytime than at night, with the highest in the dusk and the lowest at midnight. Ontogenetic change in feeding habit occurred when fork length reached 90 mm, over which the fish fed both zooplankton and small fishes. The δ13C of E. japonicus was between -21.66‰ and -18.14‰, with an average of (-19.92±0.86)‰. The δ15N of E. japonicus ranged from 4.07‰ to 10.78‰, with an average of (8.14±2.48)‰. link2 Both δ13C and δ15N values were positively correlated with fork length. Trophic level of the fish was 3.4 with stomach content analysis and 2.7 with stable isotope analysis. The results would provide important reference for understanding nutritional status of pelagic small fish, and offer some basic data to establish ecopath model.To analyze the feeding habits and trophic level of jellyfish (Rhopilema esculentum), Chinese shrimp (Fenneropenaeus chinesis), grass shrimp (Penaeus monodon), and clam (Ruditapes philippinarum), and the food web structure in marine aquaculture pond, we measured the δ13C and δ15N values of the four species and different feed from May to September in 2017. The average proportional contribution of different feed to the four species were analyzed using the IsoSource linear mixture model. The results showed that zooplankton was the main food source to jellyfish, Engraulis japonicus was the main food source to the two shrimp species, and the phytoplankton, benthic diatoms and dejecta of the two shrimp species were the main food source to the clam. The trophic level of the clam ranged from 2.64 to 2.95, with a mean value of 2.84. The trophic level of jellyfish ranged from 2.78 to 3.27, with a mean value of 3.06. the grass shrimp ranged from 3.03 to 3.54, with a mean value of 3.25. The trophic level of Chinese shrimp ranged from 3.76 to 4.40, with a mean value of 3.95. Results of comprehensive analysis showed that the clam was the primary consumer, jellyfish was the secondary consumer, and shrimps were the predators. Jellyfish filtered the dejecta of the two kinds of prawns and improved water quality of the polyculture pond to a certain extent.A method for geographical discrimination of Portunus trituberculatus was explored to provide technical support for the protection of geographical indication products and for tracing the origin of seafood. P. trituberculatus were collected from three major production areas, including the Yellow Sea, the Bohai Sea, and the East China Sea. The variations of carbon and nitrogen stable isotope values of origins and the correlation of stable isotope ratios in different tissues were analyzed. The results showed that there were significant differences in carbon and nitrogen stable isotope ratio among different origins. Significant isotope fractionation effects were observed among different tissues. The discriminant model was developed and the origin discriminant analysis was performed by the stable isotope ratios of different tissues in P. trituberculatus. The correct rate of origin diffe-rentiationf using carbon and nitrogen stable isotopes in muscle and gills (>95%) was significantly higher than that of hepatopancreas and gonad, indicating that stable isotope ratios of muscle and gills could effectively differentiate P. trituberculatus in different sea areas. This study filled the gap of stable isotope tracing technology for P. trituberculatus.Stable carbon and nitrogen isotope ratios (δ13C and δ15N, respectively) of multiple tissues with different turnover rates can provide trophic information at different timescales, and thus play an important role in tracing the changes of feeding, habitat utilization and trophic niche of consumers. The δ13C and δ15N contents of muscle, liver and blood of blue sharks (Prionace glauca), longfin mako sharks (Isurus paucus), crocodile sharks (Pseudocarcharias kamoharai) and shortfin mako sharks (I. oxyrinchus) from tropical Atlantic were measured, and the trophic niche was evalua-ted. The results showed that I. oxyrinchus, P. kamoharai, and P. glauca had similar δ15N values, higher than that of I. paucus. Feeding segregation was found between P. glauca and other species, showing unique trophic niche. The largest trophic niche width was observed in I. oxyrinchus, indicating the high diversity of prey and (or) feeding habitats. High trophic niche overlap was found in P. kamoharai and I. oxyrinchus, implying their potential competition for resources. There was no correlation between the differences among tissues in the δ13C or δ15N values and the body size of I. oxyrinchus, P. kamoharai and P. glauca, indicating no recent diet shifts for those species. I. paucus showed significant correlation between δ15N differences in liver, blood and muscle with the shark fork length, indicating its short-term diet shift. The similarity of δ13C and δ15N values and the higher metabolic rates of liver and blood were found in all four shark species, implying the similar incorporation rates of both tissues, which were considered as the short-term indicator of diet.To explore the effects of zinc levels on the synthesis and translocation of photosynthetic products from leaves to fruits, and to lay a theoretical foundation for improving fruit quality through zinc supplementation during the critical period of apple fruit development, a field experiment was carried out with a eight-year old 'Hanfu'/GM256/Malus baccata Borkh apple. We used the 13C tracer method to examine the effects of different zinc levels (ZnSO4·H2O 0, 0.1%, 0.2%, 0.3%, 0.4%, expressed by CK, Zn1, Zn2, Zn3, Zn4, respectively) on translocation of photosynthate to fruit during the stage of fruit expanding. The results showed that, with increasing zinc concentration, Rubisco enzyme activity, net photosynthetic rate, sorbitol and sucrose content, sorbitol 6-phosphate dehydrogenase, and sucrose phosphate synthase enzyme activities of leaves first increased and then decreased, with the highest values being observed in Zn3 treatment. Zn3 treatment significantly increased the 13C assimilation capability of leaves. Compared with other treatments, the 13C of self-retention (labeled leaves and labeled branches) was lowest in Zn3 treatment (61.2%) and the output of 13C photoassimilates was highest in Zn3 treatment (38.8%). 13C absorption of apple fruit showed a trend of Zn3 ＞ Zn2 ＞ Zn4 ＞ Zn1 ＞ CK. In summary, foliar zinc application under appropriate concentration (0.3% ZnSO4·H2O) enhanced photosynthesis, increased the assimilation capability of leaves, and promoted the directional transportation of photosynthate to fruit.Losses of organic matter in agricultural watersheds result in eutrophication and land degra-dation, which not only threaten water quality and food security, but also lead to environmental problems such as the greenhouse gases emission. We used 13C, 15N and C/N as fingerprint markers to trace the sources of sedimentary organic matter at the outlet in the Nanyue small watershed. We analyzed the spatial distribution in watershed sedimentary organic matter and soils of typical land use types, including forest, paddy field, and vegetable fields. The Bayesian stable isotope mixing model was used to quantitatively estimate the contribution of different sources. The results showed that there was significant spatial variation of δ13C. The δ13C of sediment organic matter (-22.6‰±0.53‰) and forest soil (-23.13‰±1.71‰) was significantly higher than that of paddy soil (-25.24‰±1.4‰). The differences of δ15N among the sources were not significant, with sediment having the maximum (4.37±0.83)‰ and forest soil having the minimum (2.38±1.97)‰. Forest soil had the highest C/N of 16.66±7.18, while paddy soil had the lowest C/N of 11.95±0.92. link3 The results of the Bayesian stable isotope mixture model showed that the contribution rates of forest land, paddy fields and vegetable fields to the organic matter deposited at the outlet in the watershed were 19.6%, 15.7%, and 64.7%, respectively. Paddy filed and vegetable field had a combined contribution rate of 80.4%. It was concluded that, soils of agricultural land were the main sources of organic matter deposited in the Nanyue small watershed, and that nutrient loss in the watershed would be effectively controlled by optimizing farmland management.