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1.
To assess the relative influence of edaphoclimatic gradients and stand replacing disturbance on the soil respiration of Oregon forests, we measured annual soil respiration at 36 independent forest plots arranged as three replicates of four age classes in each of three climatically distinct forest types. Annual soil respiration for the year 2001 was computed by combining periodic chamber measurements with continuous soil temperature measurements, which were used along with site-specific temperature response curves to interpolate daily soil respiration between dates of direct measurement. Results indicate significant forest type, age, and type × age interaction effects on annual soil respiration. Average annual soil respiration was 1100–1600, 1500–2100, and 500–900 g C m−2 yr−1 for mesic spruce, montane Douglas-fir, and semi-arid pine forests respectively. Age related trends in annual soil respiration varied between forest types. The variation in annual soil respiration attributable to the climatic differences between forest types was 48%(CV). Once weighted by the age class distribution for each forest type, the variation in annual soil respiration attributable to stand replacing disturbance was 15%(CV). Sensitivity analysis suggests that the regional variation in annual soil respiration is most dependent on summer base rates (i.e. soil respiration normalized to a common temperature) and much less dependent on the site-specific temperature response curves (to which annual rates are relatively insensitive) and soil degree-days (which vary only 10% among plots). 相似文献
2.
Interpreting,measuring, and modeling soil respiration 总被引:32,自引:0,他引:32
This paper reviews the role of soil respiration in determining ecosystem carbon balance, and the conceptual basis for measuring and modeling soil respiration. We developed it to provide background and context for this special issue on soil respiration and to synthesize the presentations and discussions at the workshop. Soil respiration is the largest component of ecosystem respiration. Because autotrophic and heterotrophic activity belowground is controlled by substrate availability, soil respiration is strongly linked to plant metabolism, photosynthesis and litterfall. This link dominates both base rates and short-term fluctuations in soil respiration and suggests many roles for soil respiration as an indicator of ecosystem metabolism. However, the strong links between above and belowground processes complicate using soil respiration to understand changes in ecosystem carbon storage. Root and associated mycorrhizal respiration produce roughly half of soil respiration, with much of the remainder derived from decomposition of recently produced root and leaf litter. Changes in the carbon stored in the soil generally contribute little to soil respiration, but these changes, together with shifts in plant carbon allocation, determine ecosystem carbon storage belowground and its exchange with the atmosphere. Identifying the small signal from changes in large, slow carbon pools in flux dominated by decomposition of recent material and autotrophic and mycorrhizal respiration is a significant challenge. A mechanistic understanding of the belowground carbon cycle and of the response of different components to the environment will aid in identifying this signal. Our workshop identified information needs to help build that understanding: (1) the mechanisms that control the coupling of canopy and belowground processes; (2) the responses of root and heterotrophic respiration to environment; (3) plant carbon allocation patterns, particularly in different forest developmental stages, and in response to treatments (warming, CO2, nitrogen additions); and (4) coupling measurements of soil respiration with aboveground processes and changes in soil carbon. Multi-factor experiments need to be sufficiently long to allow the systems to adjust to the treatments. New technologies will be necessary to reduce uncertainty in estimates of carbon allocation, soil carbon pool sizes, and different responses of roots and microbes to environmental conditions. 相似文献
3.
E. M. Baggs 《Plant and Soil》2006,284(1-2):1-5
Little is known about the respiratory components of CO2 emitted from soils and attaining a reliable quantification of the contribution of root respiration remains one of the major
challenges facing ecosystem research. Resolving this would provide major advances in our ability to predict ecosystem responses
to climate change. The merits and technical and theoretical difficulties associated with different approaches adopted for
partitioning respiration components are discussed here. The way forward is suggested to be the development of non-invasive
regression analysis validated by stable isotope approaches to increase the sensitivity of model functions to include components
of rhizosphere microbial activity, changing root biomass and the dynamics of a wide range of soil C pools.
Section Editor: A. Hodge 相似文献
4.
Hiroshi Koizumi Toshie Nakadai Youzou Usami Mitsumasa Satoh Masae Shiyomi Takehisa Oikawa 《Ecological Research》1991,6(3):227-232
In order to assess the validity of conventional methods for measuring CO2 flux from soil, the relationship between soil microbial respiration and ambient CO2 concentration was studied using an open-flow infra-red gas analyser (IRGA) method. Andosol from an upland field in central
Japan was used as a soil sample. Soil microbial respiration activity was depressed with the increase of CO2 concentration in ventilated air from 0 to 1000 ppmv. At 1000 ppmv, the respiration rate was less than half of that at 0 ppmv.
Thus, it is likely that soil respiration rate is overestimated by the alkali absorption method, because CO2 concentration in the absorption chamber is much lower than the normal level. Metabolic responses to CO2 concentration were different among groups of soil microorganisms. The bacteria actinomycetes group cultivated on agar medium
showed a more sensitive response to the CO2 concentration than the filamentous fungi group. 相似文献
5.
Taiji Kou Jianguo Zhu Zubin Xie Toshihiro Hasegawa Katia Heiduk 《Plant and Soil》2007,299(1-2):237-249
Soil respiration in a cropland is the sum of heterotrophic (mainly microorganisms) and autotrophic (root) respiration. The
contribution of both these types to soil respiration needs to be understood to evaluate the effects of environmental change
on soil carbon cycling and sequestration. In this paper, the effects of free-air CO2 enrichment (FACE) on hetero- and autotrophic respiration in a wheat field were differentiated and evaluated by a novel split-root
growth and gas collection system. Elevated atmospheric pCO2 of approximately 200 μmol mol−1 above the ambient pCO2 significantly increased soil respiration by 15.1 and 14.8% at high nitrogen (HN) and low nitrogen (LN) application rates,
respectively. The effect of elevated atmospheric pCO2 on root respiration was not consistent across the wheat growth stages. Elevated pCO2 significantly increased and decreased root respiration at the booting-heading stage (middle stage) and the late-filling stage
(late stage), respectively, in HN and LN treatments; however, no significant effect was found at the jointing stage (early
stage). Thus, the effect of increased pCO2 on cumulative root respiration for the entire wheat growing season was not significant. Cumulative root respiration accounted
for approximately 25–30% of cumulative soil respiration in the entire wheat growing season. Consequently, cumulative microbial
respiration (soil respiration minus root respiration) increased by 22.5 and 21.1% due to elevated pCO2 in HN and LN, respectively. High nitrogen application significantly increased root respiration at the late stage under both
elevated pCO2 and ambient pCO2; however, no significant effects were found on cumulative soil respiration, root respiration, and microbial respiration.
These findings suggest that heterotrophic respiration, which is influenced by increased substrate supplies from the plant
to the soil, is the key process to determine C emission from agro-ecosystems with regard to future scenarios of enriched pCO2. 相似文献
6.
区分土壤呼吸组分并揭示其与环境因素的相关关系,对于准确评估土壤碳过程及其环境影响机制至关重要。根据底物来源和作用机制的差异,土壤呼吸主要包括根系呼吸、根际微生物呼吸、凋落物分解、自然条件下和激发效应下土壤有机质(SOM)分解。现有土壤呼吸组分拆分方法可以分为基于植物源CO2测定或土壤有机质源CO2测定的差分拆分方法,以及基于土壤呼吸组分同位素信号差异的拆分方法。土壤呼吸组分拆分研究可以解决不同土壤呼吸组分对环境变化的响应机制、植物光合碳输入与地下土壤呼吸组分的交互作用、土壤呼吸组分变化对土壤碳库周转的影响机制等科学问题,但其理论假设、观测技术方法、潜在的误差来源等仍需要继续关注并系统研究。 相似文献
7.
Bouma Tjeerd J. Nielsen Kai L. Eissenstat David M. Lynch Jonathan P. 《Plant and Soil》1997,195(2):221-232
Little information is available on the variability of the dynamics of the actual and observed root respiration rate in relation to abiotic factors. In this study, we describe I) interactions between soil CO2 concentration, temperature, soil water content and root respiration, and II) the effect of short-term fluctuations of these three environmental factors on the relation between actual and observed root respiration rates. We designed an automated, open, gas-exchange system that allows continuous measurements on 12 chambers with intact roots in soil. By using three distinct chamber designs with each a different path for the air flow, we were able to measure root respiration over a 50-fold range of soil CO2 concentrations (400 to 25000 ppm) and to separate the effect of irrigation on observed vs. actual root respiration rate. All respiration measurements were made on one-year-old citrus seedlings in sterilized sandy soil with minimal organic material.Root respiration was strongly affected by diurnal fluctuations in temperature (Q10 = 2), which agrees well with the literature. In contrast to earlier findings for Douglas-fir (Qi et al., 1994), root respiration rates of citrus were not affected by soil CO2 concentrations (400 to 25000 ppm CO2; pH around 6). Soil CO2 was strongly affected by soil water content but not by respiration measurements, unless the air flow for root respiration measurements was directed through the soil. The latter method of measuring root respiration reduced soil CO2 concentration to that of incoming air. Irrigation caused a temporary reduction in CO2 diffusion, decreasing the observed respiration rates obtained by techniques that depended on diffusion. This apparent drop in respiration rate did not occur if the air flow was directed through the soil. Our dynamic data are used to indicate the optimal method of measuring root respiration in soil, in relation to the objectives and limitations of the experimental conditions. 相似文献
8.
Succession-driven changes in soil respiration following fire in black spruce stands of interior Alaska 总被引:1,自引:0,他引:1
Boreal forests are highly susceptible to wildfire, and post-fire changes in soil temperature and moisture have the potential
to transform large areas of the landscape from a net sink to a net source of carbon (C). Understanding the ecological controls
that regulate these disturbance effects is critical to developing models of ecosystem response to changes in fire frequency
and severity. This paper combines laboratory and field measurements along a chronosequence of burned black spruce stands into
regression analyses and models that assess relationships between moss succession, soil microclimate, decomposition, and C
source-sink dynamics. Results indicate that post-fire changes in temperature and substrate quality increased decomposition
in humic materials by a factor of 3.0 to 4.0 in the first 7 years after fire. Bryophyte species exhibited a distinct successional
pattern in the first five decades after fire that corresponded to decreased soil temperature and increased C accumulation
in organic soils. Potential rates of C exchange in mosses were greatest in early successional species and declined as the
stand matured. Residual sources of CO2 (those not attributed to moss respiration or humic decomposition) increased as a function of stand age, reflecting increased
contributions from roots as the stand recovered from disturbance. Together, the field measurements, laboratory experiments,
and models provide strong evidence that interactions between moss and plant succession, soil temperature, and soil moisture
largely regulate C source-sink dynamics from black spruce systems in the first century following fire disturbance. 相似文献
9.
Examination of the method for measuring soil respiration in cultivated land: Effect of carbon dioxide concentration on soil respiration 总被引:6,自引:1,他引:6
Toshie Nakadai Hiroshi Koizumi Youzou Usami Mitsumasa Satoh Takehisa Oikawa 《Ecological Research》1993,8(1):65-71
An acceleration of soil respiration with decreasing CO2 concentration was suggested in the field measurements. The result supporrs that obtained in laboratory experiments in our
previous study. The CO2 concentrations in a chamber of the alkali absorption method (the AA-method) were about 150–250 parts/106 lower than that in the atmosphere (about 350 parts/106), while those observed in the open-flow IRGA method (the OF-method) were nearly equal to the soil surface CO2 levels. The AA-method at such low CO2 levels in the chamber appears to overestimate the soil respiration. Our results showed that the rates obtained by the AA-method
were about twice as large as those by the OF-method in field and laboratory measurements. This finding has important consequences
with respect to the validity of the existing data obtained by the AA-method and the estimation of changes in the terrestrial
carbon flow with elevated CO2 相似文献
10.
Alexander Knohl Astrid R. B. Søe Werner L. Kutsch Mathias Göckede Nina Buchmann 《Plant and Soil》2008,302(1-2):189-202
Respiration has been proposed to be the main determinant of the carbon balance in European forests and is thus essential for
our understanding of the carbon cycle. However, the choice of experimental design strongly affects estimates of annual respiration
and of the contribution of soil respiration to total ecosystem respiration. In a detailed study of ecosystem and soil respiration
fluxes in an old unmanaged deciduous forest in Central Germany over 3 years (2000–2002), we combined soil chamber and eddy
covariance measurements to obtain a comprehensive picture of respiration in this forest. The closed portable chambers offered
to investigate spatial variability of soil respiration and its controls while the eddy covariance system offered continuous
measurements of ecosystem respiration. Over the year, both fluxes were mainly correlated with temperature. However, when soil
moisture sank below 23 vol.% in the upper 6 cm, water limitations also became apparent. The temporal resolution of the eddy
covariance system revealed that relatively high respiration rates occurred during budbreak due to increased metabolic activity
and after leaf fall because of increased decomposition. Spatial variability in soil respiration rates was large and correlated
with fine root biomass (r
2 = 0.56) resulting in estimates of annual efflux varying across plots from 730 to 1,258 (mean 898) g C m−2 year−1. Power function calculations showed that achieving a precision in the soil respiration estimate of 20% of the full population
mean at a confidence level of 95%, requires about eight sampling locations. Our results can be used as guidelines to improve
the representativeness of soil respiration measurements by nested sampling designs, being applied in long-term and large-scale
carbon sequestration projects such as FLUXNET and CarboEurope. 相似文献
11.
Effects of soil water content on soil respiration in forests and cattle pastures of eastern Amazonia 总被引:78,自引:0,他引:78
Eric A. Davidson Louis V. Verchot J. Henrique Cattânio Ilse L. Ackerman J.E.M. Carvalho 《Biogeochemistry》2000,48(1):53-69
The effect of soil water content on efflux of CO2 from soils has been described by linear, logarithmic, quadratic, and parabolic functions of soil water expressed as matric potential, gravimetric and volumetric water content, water holding capacity, water-filled pore space, precipitation indices, and depth to water table. The effects of temperature and water content are often statistically confounded. The objectives of this study are: (1) to analyze seasonal variation in soil water content and soil respiration in the eastern Amazon Basin where seasonal temperature variation is minor; and (2) to examine differences in soil CO2 emissions among primary forests, secondary forests, active cattle pastures, and degraded cattle pastures. Rates of soil respiration decreased from wet to dry seasons in all land uses. Grasses in the active cattle pasture were productive in the wet season and senescent in the dry season, resulting in the largest seasonal amplitude of CO2 emissions, whereas deep-rooted forests maintained substantial soil respiration during the dry season. Annual emissions were 2.0, 1.8, 1.5, and 1.0 kg C m-2 yr-1 for primary forest, secondary forest, active pasture, and degraded pasture, respectively. Emissions of CO2 were correlated with the logarithm of matric potential and with the cube of volumetric water content, which are mechanistically appropriate functions for relating soil respiration at below-optimal water contents. The parameterization of these empirical functions was not consistent with those for a temperate forest. Relating rates of soil respiration to water and temperature measurements made at some arbitrarily chosen depth of the surface horizons is simplistic. Further progress in defining temperature and moisture functions may require measurements of temperature, water content and CO2 production for each soil horizon. 相似文献
12.
杉木人工林不同深度土壤CO2通量 总被引:3,自引:0,他引:3
土壤CO2通量具有明显的时间和空间变异性。土壤温度和含水量是影响土壤CO2通量的重要因素,同时,不同深度的土壤CO2通量对温度和含水量变化的响应差异较大,因此,研究土壤CO2通量和影响因素随土壤深度的变化,对于准确评估土壤碳排放具有重要意义。选择福建三明杉木人工林(Cunninghamia lanceolata)作为研究对象,利用非散射红外CO2浓度探头和Li-8100开路式土壤碳通量系统,并使用Fick扩散法计算了0-60cm深度土壤CO2的通量,结果表明:(1)5种扩散模型计算的表层(5cm)CO2通量与Li-8100测量结果均具有显著相关性(P<0.01),Moldrup气体扩散模型计算结果较好。(2)土壤CO2浓度随深度的增加而升高,但60cm深度以下土壤CO2浓度开始降低;不同深度土壤CO2浓度的日变化均呈现单峰型;0-60cm土壤CO2通量日通量均值变化范围为0.54-2.17μmol m-2 s-1;(3)指数拟合分析显示,5、10cm和60cm深度处土壤CO2通量与温度具有显著相关性,Q10值分别为1.35、2.01和4.95。不同深度土壤含水量与CO2通量的相关性不显著。 相似文献
13.
On the assessment of root and soil respiration for soils of different textures: interactions with soil moisture contents and soil CO2 concentrations 总被引:10,自引:0,他引:10
Estimates of root and soil respiration are becoming increasingly important in agricultural and ecological research, but there
is little understanding how soil texture and water content may affect these estimates. We examined the effects of soil texture
on (i) estimated rates of root and soil respiration and (ii) soil CO2 concentrations, during cycles of soil wetting and drying in the citrus rootstock, Volkamer lemon (Citrus volkameriana Tan. and Pasq.). Plants were grown in soil columns filled with three different soil mixtures varying in their sand, silt
and clay content. Root and soil respiration rates, soil water content, plant water uptake and soil CO2 concentrations were measured and dynamic relationships among these variables were developed for each soil texture treatment.
We found that although the different soil textures differed in their plant-soil water relations characteristics, plant growth
was only slightly affected. Root and soil respiration rates were similar under most soil moisture conditions for soils varying
widely in percentages of sand, silt and clay. Only following irrigation did CO2 efflux from the soil surface vary among soils. That is, efflux of CO2 from the soil surface was much more restricted after watering (therefore rendering any respiration measurements inaccurate)
in finer textured soils than in sandy soils because of reduced porosity in the finer textured soils. Accordingly, CO2 reached and maintained the highest concentrations in finer textured soils (> 40 mmol CO2 mol−1). This study revealed that changes in soil moisture can affect interpretations of root and soil measurements based on CO2 efflux, particularly in fine textured soils. The implications of the present findings for field soil CO2 flux measurements are discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
Separating root and soil microbial contributions to soil respiration: A review of methods and observations 总被引:119,自引:12,他引:119
Forest soil respiration is the sum of heterotrophic (microbes, soil fauna) and autotrophic (root) respiration. The contribution of each group needs to be understood to evaluate implications of environmental change on soil carbon cycling and sequestration. Three primary methods have been used to distinguish hetero- versus autotrophic soil respiration including: integration of components contributing to in situ forest soil CO2 efflux (i.e., litter, roots, soil), comparison of soils with and without root exclusion, and application of stable or radioactive isotope methods. Each approach has advantages and disadvantages, but isotope based methods provide quantitative answers with the least amount of disturbance to the soil and roots. Published data from all methods indicate that root/rhizosphere respiration can account for as little as 10 percent to greater than 90 percent of total in situ soil respiration depending on vegetation type and season of the year. Studies which have integrated percent root contribution to total soil respiration throughout an entire year or growing season show mean values of 45.8 and 60.4 percent for forest and nonforest vegetation, respectively. Such average annual values must be extrapolated with caution, however, because the root contribution to total soil respiration is commonly higher during the growing season and lower during the dormant periods of the year. 相似文献
15.
Global atmospheric carbon dioxide concentration ([CO2]) is increasing rapidly. The Intergovernmental Panel on Climate Change estimated that atmospheric [CO2] has risen from approximately 280 μmol mol?1 in pre-industrial times to approximately 381 μmol mol?1 at present and will reach 550 μmol mol?1 by 2050. In the absence of strict emission controls, atmospheric [CO2] is likely to reach 730–1020 μmol mol?1 by 2100. Rising atmospheric [CO2] is the primary driver of global warming, but as the principal substrate for photosynthesis it also directly affects the yield and quality of crops. Food quality is receiving much more attentions recently, however, compared with grain yield, our understanding in the response of grain quality to elevated [CO2] is very limited. Rice (Oryza sativa L.) is one of the most important crops in the world and the first staple food in Asia, providing nutrition to a large proportion of the world’s population. Elevated [CO2] leads to numerous physiological changes in rice crops, such as changes in the photosynthesis and assimilate translocation, nutrient uptake and translocation, water relation, and altered gene expression and enzyme activity. These altered processes are very likely to affect the chemical and physical characteristics of rice grains. In this review, we first describe main characteristics of rice grain quality, and then summarize findings in literature related to the impact of elevated [CO2] on grain quality falling into four categories: processing quality, appearance, cooking and eating quality, and nutritional quality, as well as the possible mechanisms responsible for the observed impacts. Elevated [CO2] caused serious deterioration of processing suitability, in particular, head rice percentage was significantly decreased. In most cases, elevated [CO2] increased chalkiness of rice grains. The evaluation of physicochemical characteristics together with starch Rapid Visco Analyser (RVA) properties indicated no change or small changes in cooking and eating quality under elevated [CO2], and these changes could not be detected by sensory taste panel evaluation. Elevated [CO2] significantly decreased nitrogen or protein concentration in rice grains, while in most cases other macro- and micro-nutrients showed no change or decrease in concentration. In addition, the responses of rice quality to elevated [CO2] might be modified by varieties, applied fertilizer rates or gas fumigation methodologies. The available information in the literature indicates a clear tendency of quality deterioration and thus lower commercial value for rice grains grown under a projected high CO2 environment. Understanding the factors causing quality deterioration in rice and the related biological mechanisms might be the utmost important scientific theme in future research. Here we also discuss the necessity of formulating adaptation strategies for rice production in future atmospheric environments, nevertheless, the increase in yield, the improvement in quality and stress resistance of rice should be combined and integrated into the adaptation approaches. Compared with enclosure studies, the field experiments using Free-Air CO2 Enrichment (FACE) system provide sufficient experimental space and the most realistic mimic of a future high CO2 atmosphere, and give scientists perhaps the best opportunity to achieve multiple goals. 相似文献
16.
The impact of atmospheric CO2 concentration enrichment on rice quality – A research review 下载免费PDF全文
Global atmospheric carbon dioxide concentration ([CO2]) is increasing rapidly. The Intergovernmental Panel on Climate Change estimated that atmospheric [CO2] has risen from approximately 280 μmol mol?1 in pre-industrial times to approximately 381 μmol mol?1 at present and will reach 550 μmol mol?1 by 2050. In the absence of strict emission controls, atmospheric [CO2] is likely to reach 730–1020 μmol mol?1 by 2100. Rising atmospheric [CO2] is the primary driver of global warming, but as the principal substrate for photosynthesis it also directly affects the yield and quality of crops. Food quality is receiving much more attentions recently, however, compared with grain yield, our understanding in the response of grain quality to elevated [CO2] is very limited. Rice (Oryza sativa L.) is one of the most important crops in the world and the first staple food in Asia, providing nutrition to a large proportion of the world’s population. Elevated [CO2] leads to numerous physiological changes in rice crops, such as changes in the photosynthesis and assimilate translocation, nutrient uptake and translocation, water relation, and altered gene expression and enzyme activity. These altered processes are very likely to affect the chemical and physical characteristics of rice grains. In this review, we first describe main characteristics of rice grain quality, and then summarize findings in literature related to the impact of elevated [CO2] on grain quality falling into four categories: processing quality, appearance, cooking and eating quality, and nutritional quality, as well as the possible mechanisms responsible for the observed impacts. Elevated [CO2] caused serious deterioration of processing suitability, in particular, head rice percentage was significantly decreased. In most cases, elevated [CO2] increased chalkiness of rice grains. The evaluation of physicochemical characteristics together with starch Rapid Visco Analyser (RVA) properties indicated no change or small changes in cooking and eating quality under elevated [CO2], and these changes could not be detected by sensory taste panel evaluation. Elevated [CO2] significantly decreased nitrogen or protein concentration in rice grains, while in most cases other macro- and micro-nutrients showed no change or decrease in concentration. In addition, the responses of rice quality to elevated [CO2] might be modified by varieties, applied fertilizer rates or gas fumigation methodologies. The available information in the literature indicates a clear tendency of quality deterioration and thus lower commercial value for rice grains grown under a projected high CO2 environment. Understanding the factors causing quality deterioration in rice and the related biological mechanisms might be the utmost important scientific theme in future research. Here we also discuss the necessity of formulating adaptation strategies for rice production in future atmospheric environments, nevertheless, the increase in yield, the improvement in quality and stress resistance of rice should be combined and integrated into the adaptation approaches. Compared with enclosure studies, the field experiments using Free-Air CO2 Enrichment (FACE) system provide sufficient experimental space and the most realistic mimic of a future high CO2 atmosphere, and give scientists perhaps the best opportunity to achieve multiple goals. 相似文献
17.
Evaluation of soil respiration and soil CO2 concentration in a lowland moist forest in Panama 总被引:2,自引:0,他引:2
T. A. Kursar 《Plant and Soil》1989,113(1):21-29
Soil gas exchange was investigated in a lowland moist forest in Panama. Soil water table level and soil redox potentials indicate that the soils are not waterlogged. Substantial microspatial variation exists for soil respiration and soil CO2 concentration. During the rainy season, soil CO2 at 40 cm below the surface accumulates to 2.3%–4.6% and is correlated with rainfall during the previous two weeks. Temporal changes in soil CO2 are rapid, large and share similar trends between sampling points. Possible effects of soil CO2 changes on plant growth or phenology are discussed. 相似文献
18.
Indirect partitioning of soil respiration in a series of evergreen forest ecosystems 总被引:1,自引:0,他引:1
A simple estimation of heterotrophic respiration can be obtained analytically as the y-intercept of the linear regression between soil-surface CO2 efflux and root biomass. In the present study, a development of this indirect methodology is presented by taking into consideration
both the temporal variation and the spatial heterogeneity of heterotrophic respiration. For this purpose, soil CO2 efflux, soil carbon content and main stand characteristics were estimated in seven evergreen forest ecosystems along an elevation
gradient ranging from 250 to 1740 m. For each site and for each sampling date the measured soil CO2 efflux (R
S) was predicted with the model R
S = a × S
C + b × R
D ± ε, where S
C is soil carbon content per unit area to a depth of 30 cm and R
D is the root density of the 2–5 mm root class. Regressions with statistically significant a and b coefficients allowed the indirect separation of the two components of soil CO2 efflux. Considering that the different sampling dates were characterized by different soil temperature, it was possible to
investigate the temporal and thermal dependency of autotrophic and heterotrophic respiration. It was estimated that annual
autotrophic respiration accounts for 16–58% of total soil CO2 efflux in the seven different evergreen ecosystems. In addition, our observations show a decrease of annual autotrophic respiration
at increasing availability of soil nitrogen.
Section Editor: A. Hodge 相似文献
19.
土壤呼吸是陆地碳循环中仅次于全球总初级生产力的第二大碳通量途径, 揭示土壤呼吸的时空格局对整个陆地碳循环具有重要意义。该文在中国东部亚热带季风气候区, 按纬度梯度由南向北选取深圳梧桐山、杨东山十二度水保护区、宁波天童山3个区域作为研究对象, 于2009年8月至2010年10月测定了不同季节各个区域内代表性植被类型的土壤呼吸速率及地下5 cm处土壤温度, 旨在初步了解中国东部亚热带森林地区土壤呼吸的时空格局及其影响因素。结果显示: 3个区域的土壤呼吸速率均存在显著的季节变化, 其变幅为2.64-6.24 μmol CO2·m -2·s-1, 总体趋势和地下5 cm处土壤温度的季节变化一致, 均为夏季最高冬季最低; 土壤温度的变化可以解释不同样地土壤呼吸季节变化的58.3%-90.2%; 各样地全年的Q10值从1.56到3.27; 通过离样地最近的气象站点的日平均气温与试验样地地下5 cm处土壤温度之间的线性正相关关系推算出日土壤温度的变化, 利用土壤呼吸速率和地下5 cm处土壤温度之间的指数关系, 估算出各样地全年的土壤CO2通量为1 077-2 058 g C·m-2·a-1, 在全球所有生态系统类型中处于较高水平。 相似文献
20.
The [CO2] in the xylem of tree stems is typically two to three orders of magnitude greater than atmospheric [CO2]. In this study, xylem [CO2] was experimentally manipulated in saplings of sycamore (Platanus occidentalis L.) and sweetgum (Liquidambar styraciflua L.) by allowing shoots severed from their root systems to absorb water containing [CO2] ranging from 0.04% to 14%. The effect of xylem [CO2] on CO2 efflux to the atmosphere from uninjured and mechanically injured, i.e., wounded, stems was examined. In both wounded and unwounded stems, and in both species, CO2 efflux was directly proportional to xylem [CO2], and increased 5-fold across the range of xylem [CO2] produced by the [CO2] treatment. Xylem [CO2] explained 76–77% of the variation in pre-wound efflux. After wounding, CO2 efflux increased substantially but remained directly proportional to internal stem [CO2]. These experiments substantiated our previous finding that stem CO2 efflux was directly related to internal xylem [CO2] and expanded our observations to two new species. We conclude that CO2 transported in the xylem may confound measurements of respiration based on CO2 efflux to the atmosphere. This study also provided evidence that the rapid increase in CO2 efflux observed after tissues are excised or injured is likely the result of the rapid diffusion of CO2 from the xylem, rather than an actual increase in the rate of respiration of wounded tissues. 相似文献