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Zhao X.,CAS Institute of Botany | Zhao X.,University of Chinese Academy of Sciences | Lai L.,CAS Institute of Botany | Zhu L.,CAS Institute of Botany | And 9 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica

Fine roots comprise plant roots with a diameter less than 2 mm and are important for plant growth and development, the soil carbon pool, and the global carbon cycle. In this research, sequential soil coring and ingrowth bag methods were used to investigate the fine root dynamics and turnover (formation, senescence, death and decomposition) of two Reaumuria soongarica communities with different physiognomy characteristics from May to October 2010 (representing the whole growing season) in the Sangong River basin. The fine root distribution, selected soil properties (such as moisture content, pH, and electrical conductivity), community structure, fine root decomposition rate, and fine root turnover of two R. soongarica communities were measured. Stepwise regression analysis was used to reveal the relationship between fine root dynamics and soil characteristics. The soil bulk density, soil water content, pH and electrical conductivity were significantly different between the two communities. The fine root biomass of the two communities showed the same trends in seasonal change and vertical distribution; for example, the fine root biomass increased gradually from May to August, and reached the maximum in August, then declined gradually from September to October. The monthly average fine root biomass of Community 1 and Community 2 was 51.55 g/ m2 and 133.93 g/ m2, respectively. The live fine-root biomass and dead fine-root biomass were 69.68% and 30.32% of total fine-root biomass in Community 1, and 72.61% and 27.39% of total fine-root biomass in the Community 2, respectively. The fine root biomass of the two communities increased initially then decreased gradually as soil depth increased. The fine root biomass was highest in the 10—20 cm soil layer, comprising 46.48% and 29. 15% of the total fine root biomass in Community 1 and Community 2, respectively. The fine decomposition rate showed a sharp decline to a minimum but thereafter increased steadily in both two commun annual fine root decomposition rate was 34.82% and 42.91% in Community 1 and Community 2, respectively. 50% decomposition and 95% decomposition, periods of 630 days and 2933 days, respectively, for Community 1 and 467 days and 2238 days, respectively, for Community 2 were needed. Fine root net productivity of Community 1 and Community 2 was 50.67 g/ m2 and 178.15 g/ m2, respectively, and the fine root annual turnover rate in the two communities was 1.41 times/ a and 1.69 times/ a, respectively. The stepwise regression analysis showed that fine root dynamics were significantly influenced by soil factors such as soil moisture content, pH and electrical conductivity. Fine root growth was restricted by low soil moisture content, high soil pH, and high soil electrical conductivity, and therefore the two R. soongarica communities showed low fine root biomass and a low fine root turnover rate compared with most forest and grassland ecosystems. Nevertheless, carbon and nutrient release into the soil by fine root turnover is still an important component the carbon and nutrient budget and is of importance for monitoring climatic change in an arid region. © 2014, Science Press. All rights Reserved. Source

Wang J.J.,CAS Institute of Botany | Wang J.J.,University of Chinese Academy of Sciences | Wang Y.J.,CAS Institute of Botany | Lai L.M.,CAS Institute of Botany | And 7 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica

Production and decomposition of plant litter is one of the most important processes in terrestrial ecosystems. This process could be affected by climate, which elucidates that the spatial patterns and environmental regimes, which regulate the process, are essential to understand the mechanism of ecosystem functioning in both local and broad scales. However, the pattern of the process in large scales along environmental gradients in mid-and eastern China was poorly understood. The aim of the present work was to quantify litter production and its decomposition rate in forest ecosystems from subtropical to temperate zones with a view to gaining further insights into the recycling of above-ground organic matter. Data from 72 plots in six major forest types in China was used to clarify litter production and decomposition in six forest ecosystems and their relations with environmental factors in different climatic zones including Huzhong in Heilongjiang province, Mt. Changbai in Jilin province, Mt. Dongling in Beijing municipality, Mt. Gutian in Zhejinag province, Shennongjia in Hubei province, and Dujiangyan in Sichuan province. The storage of litter fall was in the sequence of: Shennongjia>Dujiangyan> Mt. gutian>Mt. Dongling>Mt. Changbai>Huzhong. The annual litter production for Shennongjia, Dujiangyan, Mt. gutian, Mt. Dongling, Mt. Changbai, Huzhong were averaged at 910. 98, 830. 18, 574. 06, 396. 19, 374. 64, and 249. 29 gm-2 a-1, respectively. Annual litter fall production was highly significant in relation to forest type and positively related to mean annual temperature, but was not significantly related to mean annual precipitation. There were two litter fall peaks in the subtropical forests in a year, one in spring (from April to May) and the other in autumn (October and November), while there was just on peak in the cold temperate, temperate and warm temperate forests, which occurred in autumn (from September to October). The litter decomposition rate (k) was consistent with litter fall production, and the k value decreased with increasing latitude. The annual litter decomposition rate (k) for Shennongjia, Dujiangyan, Mt. gutian, Mt. Dongling, Mt. Changbai, Huzhong were averaged at 0. 13, 0. 26, 0. 36, 0. 79, 0. 92, and 0. 8, respectively. A simple regression model was capable of explaining the majority of climatic effects on litter production and the decomposition rates of various litter types tested in different environments over geographical regions. In conclusion, mean annual temperature is the most important environment variable affecting litter decomposition rate, followed by mean annual precipitation. Source

Ji W.-P.,Shanxi University | Wang J.-J.,CAS Institute of Botany | Wang J.-J.,University of Chinese Academy of Sciences | Zhao X.-C.,CAS Institute of Botany | And 7 more authors.
Chinese Journal of Ecology

Fine root plays a key role in the water and nutrient uptake by plants. To accurately understand the fine root production, turnover, and decomposition is crucial for studying the carbon budget in terrestrial ecosystem. Taking the Alhagi sparsifolia community, a typical plant community in arid area of Xinjiang, as test object, and by using soil core sampling and fine root litterbags, this paper studied the fine root amount, its spatiotemporal variation, and decomposition and turnover patterns in the growth period (from May to October, 2010) of the A. sparsifolia. The monthly average fine root biomass of the community was 93.10 g · m-2, of which, live and dead ones accounted for 72.72% and 27.28%, respectively. The fine root biomass showed an obvious seasonal variation trend, i. e., increased from May, peaked in late August, and declined gradually from September to October. 72.22% of live roots and 76.66% of dead ones were distributed in 0-30 cm soil layer, 13.82% of live roots and 13.39% of dead ones were distributed in 30-40 cm soil layer, and a little proportion of live roots were in the soil layers below 40 cm. The annual decomposition rate of fine roots was 64.52%, and it took 228 days and 916 days to decompose 50% and 95% of the total fine roots, respectively. The annual net production of fine roots was 118.81 g · m-2 · a-1, and the annual turnover rate of fine roots was 1.75 cycles ·a-1. All the results showed that the fine root production of the A. sparsifolia community varied significantly with season and soil depth, and, due to the lower decomposition rate but higher turnover rate, the fine roots of A. sparsifolia community had great significance in the distribution pattern of underground carbon cycling in arid area ecosystem. Source

Wang Y.-J.,CAS Institute of Botany | Wang Y.-J.,University of Chinese Academy of Sciences | Zhao X.-C.,CAS Institute of Botany | Zhao X.-C.,University of Chinese Academy of Sciences | And 10 more authors.
Journal of Ecology and Rural Environment

Fine root plays a significant role in plant community performance of functions, soil carbon pool and global carbon recycling. Observation was done of biomass, decomposition and turnover of the fine roots of Haloxylon ammodendron communities in the Sanjiang River Valley throughout the whole growing season from May to October in 2010, using soil column method and litter bag method. Results show that fine root biomass of the H ammodendron communities varied significantly with seasons. It increased gradually in the period from May to August, peaked in August, and then declined gradually in September and October, and its monthly average reached 183.76 g · m-2, of which live fine root accounted for 72.59% and dead one for 27.41%. And its distribution varied with soil depth, showing a trend of increasing first and then declining, with a major portion distributed in >10-30 cm soil layer, accounting for 51.36% of the live fine root and 51.81% of the dead one. The annual decomposition rate of the fine root was 58.76%. It took 279 and 1 302 days for the decomposition rate to reach 50% and 95%, respectively. The net productivity of the fine root was 110.73 g · m-2 · a-1, and its annual turnover rate was 1.25 times · a-1. In conclusion, the fine root production of H. ammodendron communities varied significantly with season and soil depth. These findings suggest that the fine roots of H. ammodendron communities are of great significance for underground carbon recycling in the arid area. Source

Zhu L.,CAS Institute of Botany | Zhu L.,University of Chinese Academy of Sciences | Ding J.,CAS Institute of Botany | Wang J.,CAS Institute of Botany | And 9 more authors.
Chinese Journal of Applied and Environmental Biology

With industrial production and application of oil, oil pollution has become a worldwide and serious environmental problem. Ecological effects of oil pollution on soil, plant individuals, plant community and ecosystem are summed up systematically in this paper. There are many toxicants such as BTEX (benzene, toluene, ethylbenzene, and xylene) and PAHs (polycyclic aromatic hydrocarbons) in oils and petrochemicals. These oil pollutants transfer into the soil-plant system and affect the quality of underground water. Thus, oil pollution affects not only soil-plant system (including its composition, structure, function and service), but also human health through food chain. Oil pollution affects soil water condition, porosity and other physical properties; as well as soil carbon, nutrient and other chemical properties. It influences the composition and diversity of soil microbial community, soil enzymes and other biological properties. In most cases, oils pose oxidative stress to plants. Cell membranes are damaged by penetration of hydrocarbon molecules, leading to the leakage of cell contents. Oils usually reduce photosynthesis rates by destroying chloroplast membranes. Oil pollution often inhibits plant germination, growth, flowering and fruiting. However, low dose of oils may promote the growth of some plants. The effects of oil pollution on plant individuals can be classified into four categories: Promoting, no effect, sublethal and lethal. Correspondingly, plant responds in three ways (adaptation, tolerance and death). Thus, there are three basic patterns in which oil pollution affects plant community and finally reduces its biomass, species diversity and vegetation cover. The combination of the changes of plant community and the alternation of soil environment reduces the productivity, stability and health of ecosystem. Finally, functions and services of ecosystem are decreased by oil pollution. Oil pollutants can be biologically remediated and degraded by microorganisms, plants and mycorrhizae. These biological processes can be enhanced by nutrient addition and aeration. Vegetation indices, red edge effect and other remote sensing technologies are potential methods to monitor ecological effects of oil pollution. Overall, indices of different hierarchical levels in the soil-plant system respond to oil pollutants acutely or chronically. Linking these responses with ecological effects of oil pollution is one of the important and difficult issues in future researches. Therefore, multi-scaled and systematic researches should be carried out, and these researches should integrate indoor controlled experiments, outdoor controlled experiments and field investigations. With these researches, the system of hierarchical indices for ecological effects of oil pollution should be established to quantify the relationships between oil pollutants and indices of ecological effects. Then the ecological effects of oil pollution could be mechanically interpreted with simulations of some models, and the effects of oil pollution on soil-plant system could be comprehensively understood. These efforts will provide theoretical foundation and practical guidelines for ecological risk assessment, remediation and control of oil pollution. Source

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