Decrease In Biological Productivity Research Articles

Palaeosedimentary Environment and Formation Mechanism of High-Quality Xujiahe Source Rocks, Sichuan Basin, South China

AbstractTriassic Xujiahe source rocks, the main gas source of shallow tight gas, are the most typical continental coal-bearing source rocks in the Sichuan Basin, South China. However, the organic matter enrichment section cannot be identified easily, leading to limited progress in the exploration of coal-bearing tight gas. This paper reveals the main controlling factors of the organic matter enrichment, reconstructs the evolution process of the Xujiahe palaeosedimentary environment, proposes a dynamic enrichment mechanism of the organic matter, and determines the organic matter enrichment section of the high-quality coal-bearing source rocks by geochemical characteristics of the source rocks, major elements, and trace elements. The results show that the Xujiahe sedimentary environment can be divided into a fluctuating stage of transitional sedimentation, stable stage of transitional sedimentation, fluctuating stage of continental sedimentation, and stable stage of continental sedimentation. The Xujiahe source rocks were featured with high-quality coal-bearing source rocks with high total organic carbon and maturity and good parent material in the stable stage of transitional sedimentation and fluctuating stage of continental sedimentation, in which the water was connected with the Palaeo-Tethys Ocean with abundant terrestrial organisms. The water was shallow in the fluctuating stage of transitional sedimentation with a low sedimentation rate, leading to poor organic matter enrichment. The Palaeo-Tethys Ocean withdrew westward from the Yangtze plate in the late period of the fluctuating stage of continental sedimentation, leading to the absence of algae and dinosteranes and a decrease in biological productivity in the stable stage of continental sedimentation. Therefore, high terrestrial inputs and biological productivity and high sedimentation rate were conducive to the organic matter preservation in the coal-bearing source rocks.

Ecotoxicological sensing of the arctic seas

The results of ecotoxicological monitoring - studies of the resistance of marine phytoplankton communities of the Arctic seas to some pollutants are presented. The influence of pollutants on primary productivity was assessed as the most sensitive biological process. It is shown that the method of ecotoxicological sounding makes it possible to identify areas most susceptible to chronic pollution, leading to a decrease in biological productivity.

Эколого-физиологические особенности реакции сосны обыкновенной на уровень плодородия почвы как показатель адаптации к условиям среды

Comprehensive ecological and physiological studies (on the organism level) of plant response of Scots pine to changes in soil fertility were carried out in order to obtain quantitative parameters of the leaf apparatus and root system functioning and nature of their interrelation. Biological productivity was calculated according to V.M. Lebedev and E.V. Lebedev (2006), net productivity of photosynthesis – according to A.A. Nichiporovich (1955), and mineral productivity – according to V.M. Lebedev (1998). The response of 2–3-year-old scots pine plants was studied for fertilization with 30, 60, 120 and 240 kg/ha of nitrogen against the fertilizer application rate of Р60К60 under the conditions of a microfield experiment on gray forest soil. An increase in the level of nitrogen nutrition led to a change in the ecological and physiological parameters of the root system and leaf apparatus functioning: the ratio between root and photosynthetic potential, nitrogen absorption by the unit of the active surface of roots per day, net productivity of photosynthesis, and biological productivity of plants. The nitrogen status slightly affected the net productivity of photosynthesis, however drove up an increase in biological productivity by 1.2–1.5 times. An increase in the nitrogen status led to a change in the ratio between the values of root and photosynthetic potentials in favor of the leaf apparatus. A high positive correlation (0.931–0.992) between the photosynthetic potential and increase in dry mass; and a high negative correlation (–(0.843–0.963)) between the ratio of root potential to photosynthetic potential and nitrogen uptake were established. The maximum of pine biological productivity was observed at a nitrogen rate of 120 kg/ha. A further increase of the nitrogen status led to a decrease in biological productivity and was found to be toxic. The response of pine to a decrease in soil fertility (due to its slow response) was determined as a result of a retrospective comprehensive ecological and physiological analysis of tabular phytomass data compiled by V.A. Usol’tsev (2002) for tree stands growing in the European and Asian parts of Russia in the age range from 10–20 to 150–300 years. The natural decrease in soil fertility of pine stands with the age from 25 to 100 years in all the regions caused a decrease in nitrogen uptake by 18.5–84.5 times, and net productivity of photosynthesis by 3.4–18.0 times. The correlation between plant age, nitrogen uptake, and net productivity of photosynthesis ranged from –0.714 to –0.870 and –0.894 to –0.991, respectively. The decrease in the activity of photosynthetic apparatus and root system adversely affected the biological productivity, which fell from 2.8 to 4.0 times depending on the region. The relationship between biological productivity and age was high negative (correlation coefficient ranged from –0.572 to –0.783). The relationship between mineral productivity with biological productivity and net productivity of photosynthesis in all cases was high positive from 0.907 to 0.994 and from 0.757 to 0.932, respectively. Starting from the age of 25, the plants adapted to a decrease in soil fertility by increasing the ratio of root to photosynthetic potential, which grew from 4.8 to 12.5 times during ontogenesis depending on the region. This nonspecific reaction is confirmed by the high positive correlation (from 0.947 to 0.997) of the ratio of root to photosynthetic potential with the tree age.For citation: Lebedev V.M., Lebedev E.V. Ecological and Physiological Features of the Scots Pine Reaction to the Soil Fertility Level as an Indicator of Adaptation to Environmental Conditions. Lesnoy Zhurnal [Russian Forestry Journal], 2019, no. 6, pp. 92–103. DOI: 10.17238/ issn0536-1036.2019.6.92

Polar stratification: A critical view from the Southern Ocean

Oceanic stratification represents an effective mechanism to reduce vertical mixing of the water column, thereby locking up carbon dioxide (CO 2) in the deep sea and preventing air–sea exchange of CO 2. It has been proposed that enhanced stratification of the upper water column in polar oceans during late Cenozoic cooling episodes limited the upwelling of CO 2-rich deep waters and thus CO 2-release to the atmosphere, resulting in a net global drawdown of atmospheric CO 2. Increased stratification in the Subarctic Northwest Pacific, during both the onset of Northern Hemisphere glaciation at 2.73 Ma and late Quaternary glacial periods, has been recently linked to enhanced ocean stratification south of the Antarctic Polar Front (APF) in the Pacific and Atlantic sectors of the Southern Ocean. Increased stratification of Southern Ocean surface waters was mainly deduced from a reduction of biological production during these cooling episodes, manifested by the decrease of geochemical proxies for productivity, such as biogenic opal and barium, in the marine sediment records. However, the records chosen from the Southern Ocean do not provide evidence for a more stratified upper water column, rather the observed decrease in biological productivity is likely to have resulted from an expansion of annual sea-ice coverage. The sediment records suggest that south of the APF in the Pacific and Atlantic sectors of the Southern Ocean, extensive sea ice may have contributed to the global CO 2-drawdown during glacial periods, with hypothetical glacial increase of stratification in today's permanent open-ocean zone merely being an “add on“ caused by this expansion.

A multiproxy reconstruction of biological productivity and oceanography in the eastern equatorial Pacific for the past 30,000 years

Surface ocean biological productivity was reconstructed for oxygen isotope stages 1 and 2 in 5 cores from the eastern equatorial Pacific using a newly developed proxy based on assemblages of benthic foraminifera. Along the equator and in the South Equatorial Current there was a drop in productivity during the early to mid-Holocene, a peak during the later stages of the glacial-interglacial transition, and full glacial values lower than those of the present. There was a decrease in biological productivity (new production) on the order of 25% along the equator during the last full glacial. The west to east productivity gradient in the east equatorial Pacific was maintained in glacial times, but was reduced compared to the present. In contrast, values to the south and north of the equatorial belt of high productivity may have increased modestly during the glacial. The equatorial decrease in surface ocean biological productivity during the Ice Age was tested using multispecies benthic foraminiferal carbon isotope data and carbonate preservation indices. These tests support the faunal interpretations. The paleoproductivity results presented here conflict with those based on the record of organic carbon in deep sea sediments. The nature of this conflict and reasons for it are examined. Finally, the results here may be compatible with geochemical reconstructions of surface water nutrient concentrations, nutrient utilization, paleo-pH estimates and CO 2 efflux in the eastern equatorial Pacific. However, the nutrient reconstructions are not supported by planktonic foraminiferal multispecies carbon isotope values, and an alternative model of glacial age circulation and plankton communities may be needed to account for all the data.