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1.
Soil microbial activity drives carbon and nutrient cycling in terrestrial ecosystems. Soil microbial biomass is commonly limited by environmental factors and soil carbon availability. We employed plant litter removal, root trenching and stem-girdling treatments to examine the effects of environmental factors, above- and belowground carbon inputs on soil microbial C in a subtropical monsoon forest in southwest China. During the experimental period from July 2006 through April 2007, 2 years after initiation of the treatments, microbial biomass C in the humus layer did not vary with seasonal changes in soil temperature or water content. Mineral soil microbial C decreased throughout the experimental period and varied with soil temperature and water content. Litter removal reduced mineral soil microbial C by 19.0% in the ungirdled plots, but only 4.0% in girdled plots. Root trenching, stem girdling and their interactions influenced microbial C in humus layer. Neither root trenching nor girdling significantly influenced mineral soil microbial C. Mineral soil microbial C correlated with following-month plant litterfall in control plots, but these correlations were not observed in root-trenching plots or girdling plots. Our results suggest that belowground carbon retranslocated from shoots and present in soil organic matter, rather than aboveground fresh plant litter inputs, determines seasonal fluctuation of mineral soil microbial biomass. 相似文献
2.
Yiting He Yong Wang Yi Jiang Guoping Yin Shunping Cao Xiongsheng Liu Renjie Wang Zijian Wu Fengfan Chen 《Soil Use and Management》2023,39(1):92-103
Leaf litter decomposition transfers elements from litter to soils that are essential for regulating nutrient cycles in plantation ecosystems, especially carbon and nitrogen. However, soil carbon and nitrogen dynamics in response to tree litter management remains insufficiently researched. We conducted a one-year field experiment at a fast-growing sweetgum tree plantation to evaluate the effects of leaf litter management on soil available nutrients, respiration rate and nitrogen mineralization rate. Three leaf litter treatments were applied, which were: (1) natural input (control); (2) double input and (3) non-input. It was found that the double input treatment increased soil inorganic nitrogen and microbial biomass nitrogen, but had little effect on microbial biomass carbon, dissolved organic carbon or dissolved organic nitrogen compared with natural input. The non-input treatment caused dissolved organic carbon to decrease compared with natural input. The respiration rate increased in the double input treatment, with a positive priming effect observed. Soil net ammonification, nitrification and mineralization rates also increased in the double input treatment in specific seasons. Meanwhile, positive linear relationships between respiration rate and all nitrogen transformation rates were observed for all treatments. Soil temperature was found to be an important prediction factor for predicting the respiration rate and mineralization as seasonal variations, but not for litter-induced fluctuations. Soil water content and mineral nitrogen were the primary drivers of litter-induced change to the respiration rate, whereas mineral nitrogen and microbial biomass were primary drivers of mineralization change. These results suggest that changes in soil nitrogen mineralization rate are strongly associated with the soil respiratory process, resulting in a potentially strong plant–soil feedback mechanism. 相似文献
3.
Eric Paterson Barry Thornton Andrew J. Midwood Shona M. Osborne Allan Sim Pete Millard 《Soil biology & biochemistry》2008,40(9):2434-2440
Plants link atmospheric and soil carbon pools through CO2 fixation, carbon translocation, respiration and rhizodeposition. Within soil, microbial communities both mediate carbon-sequestration and return to the atmosphere through respiration. The balance of microbial use of plant-derived and soil organic matter (SOM) carbon sources and the influence of plant-derived inputs on microbial activity are key determinants of soil carbon-balance, but are difficult to quantify. In this study we applied continuous 13C-labelling to soil-grown Lolium perenne, imposing atmospheric CO2 concentrations and nutrient additions as experimental treatments. The relative use of plant- and SOM-carbon by microbial communities was quantified by compound-specific 13C-analysis of phospholipid fatty acids (PLFAs). An isotopic mass-balance approach was applied to partition the substrate sources to soil respiration (i.e. plant- and SOM-derived), allowing direct quantification of SOM-mineralisation. Increased CO2 concentration and nutrient amendment each increased plant growth and rhizodeposition, but did not greatly alter microbial substrate use in soil. However, the increased root growth and rhizosphere volume with elevated CO2 and nutrient amendment resulted in increased rates of SOM-mineralisation per experimental unit. As rhizosphere microbial communities utilise both plant- and SOM C-sources, the results demonstrate that plant-induced priming of SOM-mineralisation can be driven by factors increasing plant growth. That the balance of microbial C-use was not affected on a specific basis may suggest that the treatments did not affect soil C-balance in this study. 相似文献
4.
Masamichi Takahashi Keizo Hirai Pitayakon Limtong Chaveevan Leaungvutivirog Samreong Panuthai Songtam Suksawang 《Soil Science and Plant Nutrition》2013,59(3):452-465
Soil respiration is a carbon flux that is indispensable for determining carbon balance despite variations over time and space in forest ecosystems. In Kanchanaburi, western Thailand, we measured the soil respiration rates at different slope positions—ridge (plot R), upper slope (plot U), and lower slope (plot L)—on a hill in a seasonal tropical forest [mixed deciduous forest (MDF)] to determine the seasonal and spatial variations in soil respiration on the slope. The heterotrophic (organic layer and soil) and autotrophic (root) respiration was differentiated by trenching. Soil respiration rates showed clear seasonal patterns: high and low rates in rainy and dry seasons respectively, at all plots, and tended to decrease up the slope. Soil respiration rates responded significantly to soil water content in the 0–30?cm layer, but the response patterns differed between the lower slope (plot L) and the upper slope (plots R and U): a linear model could be applied to the lower slope but exponential quadratic models to the upper slope. The annual carbon dioxide (CO2) efflux from the forest floor was also associated with the slope position and ranged from 1908?gC?m?2?year?1 in plot L to 1199?gC?m?2?year?1 in plot R. With ascending position from plot L to R, the contribution of autotrophic respiration increased from 19.4 to 36.6% of total soil respiration, while that of the organic layer decreased from 26.2 to 9.4%. Mineral soil contributed to 46.3 to 54.4% of the total soil respiration. Soil water content was the key factor in controlling the soil respiration rate and the contribution of the respiration sources. However, the variable responses of soil respiration to soil water content create a complex distribution of soil respiration at the watershed scale. 相似文献
5.
Mei-Yee CHIN Sharon Yu Ling LAU Frazer MIDOT Mui Sie JEE Mei Lieng LO Faustina E. SANGOK Lulie MELLING 《土壤圈》2023,33(5):683-699
Soil respiration is a vital process in all terrestrial ecosystems, through which the soil releases carbon dioxide (CO2) into the atmosphere at an estimated annual rate of 68-101 Pg carbon, making it the second highest terrestrial contributor to carbon fluxes. Since soil respiration consists of autotrophic and heterotrophic constituents, methods for accurately determining the contribution of each constituent to the total soil respiration are critical for understanding their differential responses to environmental factors and aiding the reduction of CO2 emissions. Owing to its low cost and simplicity, the root exclusion (RE) technique, combined with manual chamber measurements, is frequently used in field studies of soil respiration partitioning. Nevertheless, RE treatments alter the soil environment, leading to potential bias in respiration measurements. This review aims to elucidate the current understanding of RE, i.e., trenching (Tr) and deep collar (DC) insertion techniques, by examining soil respiration partitioning studies performed in several ecosystems. Additionally, we discuss methodological considerations when using RE and the combinations of RE with stable isotopic and modeling approaches. Finally, future research directions for improving the Tr and DC insertion methods in RE are suggested. 相似文献
6.
Päivi Mäkiranta Kari Minkkinen Jyrki Hytönen Jukka Laine 《Soil biology & biochemistry》2008,40(7):1592-1600
Partitioning soil respiration (SR) into its components, heterotrophic and rhizospheric respiration, is an important step for understanding and modelling carbon (C) cycling in organic soils. However, no partitioning studies on afforested organic soil croplands exist. We separated soil respiration originating from the decomposition of peat (SRP), and aboveground litter (SRL) and root respiration (SRR) in six afforested organic soil croplands in Finland with varying tree species and stand ages using the trenching method. Across the sites temporal variation in SR was primarily related to changes in soil surface temperature (?5 cm), which explained 71–96% of variation in SR rates. Decomposition of peat and litter was not related to changes in water table level, whereas a minor increase in root respiration was observed with the increase in water table depth. Temperature sensitivity of SR varied between the different respiration components: SRP was less sensitive to changes in soil surface temperature than SRL or SRR. Factors explaining spatial variation in SR differed between different respiration components. Annual SRP correlated positively with peat ash content while that of SRL was found to correlate positively with the amount of litter on the forest floor, separately for each tree species. Root respiration correlated positively with the biomass of ground vegetation. From the total soil respiration peat decomposition comprised a major share of 42%; the proportion of autotrophic respiration being 41% and aboveground litter 17%. Afforestation lowered peat decomposition rates. Nevertheless the effect of agricultural history can be seen in peat properties for decades and due to high peat decomposition rates these soils still loose carbon to the atmosphere. 相似文献
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Changes in above-ground litterfall can influence below-ground biogeochemical processes in forests. In order to examine how above-ground litter inputs affect soil carbon (C), nitrogen (N) and phosphorus (P) in a temperate deciduous forest, we studied a 14-year-old small-scale litter manipulation experiment that included control, litter exclusion, and doubled litter addition at a mature Fagus sylvatica L. site. Total organic C (TOC), total N (TN) and total P (TP), total organic P (TOP), bioavailable inorganic P (Pi), microbial C, N and P, soil respiration and fine root biomass were analyzed in the A and in two B horizons. Our results showed that litter manipulation had no significant effect on TOC in the mineral soil. Litter addition increased the bioavailable Pi in the A horizon but had no significant effect on N in the mineral soil. Litter exclusion decreased TN and TP in the B horizon to a depth of 10 cm. In the A horizon of the litter exclusion treatment, TP, TOP and bioavailable Pi were increased, which is most likely due to the higher root biomass in this treatment. The high fine root biomass seems to have counteracted the effects of the excluded aboveground litter. In conclusion, our study indicates that aboveground litter is not an important source for C in the mineral soil and that P recycling from root litter might be more important than from above-ground litter. 相似文献
9.
In a Quercetum petraeae–cerris forest in northeastern Hungary, we examined effects of litter input alterations on the quantity and quality soil carbon stocks and soil CO2 emissions. Treatments at the Síkfőkút DIRT (Detritus Input and Removal Treatments) experimental site include adding (by doubling) of either leaf litter (DL) or wood (DW) (including branches, twigs, bark), and removing all aboveground litter (NL), all root inputs by trenching (NR), or removing all litter inputs (NI). Within 4 years we saw a significant decrease in soil carbon (C) concentrations in the upper 15 cm for root exclusion plots. Decreases in C for the litter exclusion treatments appeared later, and were smaller than declines in root exclusion plots, highlighting the role of root detritus in the formation of soil organic matter in this forest. By year 8 of the experiment, surface soil C concentrations were lower than Control plots by 32% in NI, 23% in NR and 19% in NL. Increases in soil C in litter addition treatments were less than C losses from litter exclusion treatments, with surface C increasing by 12% in DL and 6% in DW. Detritus additions and removals had significant effects on soil microclimate, with decreases in seasonal variations in soil temperature (between summer and winter) in Double Litter plots but enhanced seasonal variation in detritus exclusion plots. Carbon dioxide (CO2) emissions were most influenced by detritus input quantity and soil organic matter concentration when soils were warm and moist. Clearly changes in detritus inputs from altered forest productivity, as well as altered litter impacts on soil microclimate, must be included in models of soil carbon fluxes and pools with expected future changes in climate. 相似文献
10.
干湿交替对土壤呼吸和土壤有机碳矿化的影响述评 总被引:2,自引:0,他引:2
土壤干湿交替循环对土壤呼吸的“激发效应”被证实在干旱、半干旱和地中海气候区普遍存在。土壤干湿交替被认为是影响土壤呼吸的重要因素。土壤物理、化学、生物性状会在干湿交替过程中发生一系列变化,引发土壤CO2排放量显著激增而引起“Birch效应”。随着未来气候变化下极端降水天气事件发生频率的增加,降雨强度和频率的改变将导致部分地区的土壤经受更广泛和频繁的干湿交替作用,加剧土壤干湿循环,影响土壤呼吸。重点论述了干湿交替对土壤碳素循环各个关键过程(尤其是土壤呼吸和SOC矿化)的影响效应,归纳总结了干湿交替对土壤碳素循环的影响机制,从土壤团聚体、根系呼吸、微生物呼吸等方面阐述了干湿交替对土壤呼吸和土壤有机碳(SOC)矿化激发效应的影响及其机理。综合生理学说与物理学说观点,认为干湿交替主要通过土壤结构、SOC的分解速率、土壤微生物群落的结构与稳定性等的改变来影响土壤呼吸和SOC矿化过程。目前,关于干湿交替对土壤碳素循环关键过程影响的研究结果还不尽一致,其影响机制尚不明晰,研究方法也还有一些不足之处。简要指出了目前研究过程中存在的一些不足,并对未来研究中值得深入研究的科学问题进行了探讨与展望。 相似文献