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1.
Tree root and soil heterotrophic respiration as revealed by girdling of boreal Scots pine forest: extending observations beyond the first year 总被引:26,自引:0,他引:26
BHUPINDERPAL-SINGH A. NORDGREN M. OTTOSSON LÖFVENIUS M. N. HÖGBERG P. -E. MELLANDER & P. HÖGBERG 《Plant, cell & environment》2003,26(8):1287-1296
Limitations in available techniques to separate autotrophic (root) and soil heterotrophic respiration have hampered the understanding of forest C cycling. The former is here defined as respiration by roots, their associated mycorrhizal fungi and other micro‐organisms in the rhizosphere directly dependent on labile C compounds leaked from roots. In order to separate the autotrophic and heterotrophic components of soil respiration, all Scots pine trees in 900 m2 plots were girdled to instantaneously terminate the supply of current photosynthates from the tree canopy to roots. Högberg et al. (Nature 411, 789–792, 2001) reported that autotrophic activity contributed up to 56% of total soil respiration during the first summer of this experiment. They also found that mobilization of stored starch (and likely also sugars) in roots after girdling caused an increased apparent heterotrophic respiration on girdled plots. Herein a transient increase in the δ13C of soil CO2 efflux after girdling, thought to be due to decomposition of 13C‐enriched ectomycorrhizal mycelium and root starch and sugar reserves, is reported. In the second year after girdling, when starch reserves of girdled tree roots were exhausted, calculated root respiration increased up to 65% of total soil CO2 efflux. It is suggested that this estimate of its contribution to soil respiration is more precise than the previous based on one year of observation. Heterotrophic respiration declined in response to a 20‐day‐long 6 °C decline in soil temperature during the second summer, whereas root respiration did not decline. This did not support the idea that root respiration should be more sensitive to variations in soil temperature. It is suggested that above‐ground photosynthetic activity and allocation patterns of recent photosynthates to roots should be considered in models of responses of forest C balances to global climate change. 相似文献
2.
We assessed the potential of using 14C contents of soil respired CO2 to calculate the contributions of heterotrophic and autotrophic respiration to total soil respiration. The partitioning of these fluxes is of utmost importance to evaluate implications of environmental change on soil carbon cycling and sequestration. At three girdled forest stands in Sweden and Germany, where the tree root (autotrophic) respiration had been eliminated, we measured both flux rates and 14C contents of soil respired CO2 in girdled and control plots in the summers of 2001 or 2002. At all stands, CO2 flux rates were slightly higher in the control plots, whereas the 14C contents of respired CO2 tended to be higher in the girdled plots. This was expected and confirmed that heterotrophically respired CO2 cycles more slowly through the forest ecosystem than autotrophically respired CO2. On the basis of these data, the contributions of hetero‐ and autotrophic respiration to total soil respiration were calculated using two separate approaches (i.e. based on flux rates or 14C). Fractions of heterotrophic respiration ranged from 53% to 87%. Values calculated by both approaches did not differ significantly from each other. Finally, we compared the 14C contents of soil respired CO2 in the girdled plots with the 14C contents of heterotrophically respired CO2 calculated by three different 14C models. None of the models matched the measured data sufficiently. In addition, we suspect that inherent effects of girdling may cause the 14C content of CO2 respired in the girdled plots to be lower than ‘true’ heterotrophically respired CO2 in an undisturbed plot. Nevertheless, we argue that measurements and modeling of 14C can be developed into a valuable tool for separating heterotrophic and autotrophic soil respiration (e.g. when girdling cannot be performed). 相似文献
3.
Tree-girdling to separate root and heterotrophic respiration in two Eucalyptus stands in Brazil 总被引:4,自引:0,他引:4
The release of carbon as CO2 from belowground processes accounts for about 70% of total ecosystem respiration. Insights about factors controlling soil CO2 efflux are constrained by the challenge of apportioning sources of CO2 between autotrophic tree roots (and mycorrhizal fungi) and heterotrophic microorganisms. In some temperate conifer forests, the reduction in soil CO2 efflux after girdling (phloem removal) has been used to separate these sources. Girdling stops the flow of carbohydrates to the belowground portion of the ecosystem, which should slow respiration by roots and mycorrhizae while heterotrophic respiration should remain constant or be enhanced by the decomposition of newly dead roots. Therefore, the reduction in CO2 efflux after girdling should be a conservative estimate of the belowground flux of C from trees. We tested this approach in two tropical Eucalyptus plantations. Tree canopies remained intact for more than 3 months after girdling, showing no reduction in light interception. The reduction in soil CO2 efflux averaged 16–24% for the 3-month period after girdling. The reduction in CO2 efflux was similar for plots with one half of the trees girdled and those with all of the trees girdled. Girdling did not reduce live fine root biomass for at least 5 months after treatment, indicating that large reserves of carbohydrates in the root systems of Eucalyptus trees maintained the roots and root respiration. Our results suggest that the girdling approach is unlikely to provide useful insights into the contribution of tree roots and heterotrophs to soil CO2 efflux in this type of forest ecosystem. 相似文献
4.
Differential controls by climate and substrate over the heterotrophic and rhizospheric components of soil respiration 总被引:11,自引:0,他引:11
Laura E. Scott-Denton Todd N. Rosenstiel Russell K. Monson 《Global Change Biology》2006,12(2):205-216
The partitioning of soil respiration rates into the component processes of rhizospheric respiration (because of live roots and those microorganisms that subsist on root exudations) and heterotrophic respiration (because of decomposer microorganisms that subsist on the oxidation of soil organic matter) is difficult to accomplish through experimental observation. In order to minimize disturbance to the soil and maximize preservation of the natural relationships among roots, rhizospheric microorganisms, and decomposers, we conducted a girdling experiment in a subalpine forest dominated by lodgepole pine trees. In two separate years, we girdled trees in small forest plots (5–7 m in diameter) and trenched around the plots to sever invading roots in order to experimentally stop the transport of photosynthate from needles to roots, and eliminate rhizospheric respiration. Soil respiration rates in plots with trees girdled over 1 year prior to measurement were higher than those in plots with trees girdled 2–3 months prior to measurement. These results suggest that any stimulation of respiration because of the experimental artifact of fine root death and addition of labile carbon to the pool of decomposer substrates is slow, and occurs beyond the first growing season after girdling. Compared with control plots with nongirdled trees, soil respiration rates in plots with girdled trees were reduced by 31–44% at the mid‐summer respiratory maximum. An extreme drought during one of the 2 years used for observations caused greater reductions in the heterotrophic component of soil respiration compared with the rhizospheric component. In control plots, we observed a pulse in K2SO4‐extractable carbon during the spring snowmelt period, which was absent in plots with girdled trees. In control plots, soil microbial biomass increased from spring to summer, coincident with a seasonal increase in the rhizospheric component of soil respiration. In plots with girdled trees, the seasonal increase in microbial biomass was lower than in control plots. These results suggest that the observed seasonal increase in rhizospheric respiration rate in control plots was because of an increase in rhizospheric microbial biomass following ‘soil priming’ by a spring‐time pulse in dissolved organic carbon. Winter‐time, beneath‐snow microbial biomass was relatively high in control plots. Soil sucrose concentrations were approximately eight times higher during winter than during spring or summer, possibly being derived from the mechanical damage of shallow roots that use sucrose as protection against low‐temperature extremes. The winter‐time sucrose pulse was not observed in plots with girdled trees. The results of this study demonstrate that (1) the rhizospheric component of soil respiration rate at this site is significant in magnitude, (2) the heterotrophic component of soil respiration rate is more susceptible to seasonal drought than the rhizospheric component, and (3) the trees in this ecosystem exert a major control over soil carbon dynamics by ‘priming’ the soil with sugar exudates during the late‐spring snowmelt period and releasing high concentrations of sucrose to the soil during winter. 相似文献
5.
区分森林土壤呼吸组分是了解生态系统碳循环的重要环节。该文以福建省三明市格氏栲自然保护区米槠(Castanopsis carlesii)人工林和邻近的杉木(Cunninghamia lanceolata)人工林为研究对象, 于2012年8月至2013年7月, 采用LI-8100开路式土壤碳通量系统, 通过挖壕沟方法, 测定了土壤呼吸及异养呼吸的速率, 同时测定了5 cm深处的土壤温度和0-12 cm深处的土壤含水量。利用指数模型和双因素模型, 分析土壤呼吸及其组分与土壤温度和土壤含水量的关系, 同时计算了土壤呼吸各组分在土壤呼吸中所占的比例, 并分析了不同森林类型对土壤呼吸及其组分的影响。结果表明: 米槠人工林和杉木人工林土壤呼吸及其组分的季节变化显著, 均呈单峰型曲线, 与5 cm深处的土壤温度呈极显著正相关关系。土壤温度可以分别解释米槠人工林土壤呼吸、自养呼吸和异养呼吸变化的70.3%、73.4%和58.2%, 可以解释杉木人工林土壤呼吸、自养呼吸和异养呼吸变化的77.9%、65.7%和79.2%。土壤呼吸及其组分与土壤含水量没有相关关系。米槠和杉木人工林自养呼吸的年通量分别为4.00和2.18 t C·hm-2·a-1, 占土壤呼吸年通量的32.5%和24.1%; 异养呼吸年通量分别为8.32和6.88 t C·hm-2·a-1, 分别占土壤呼吸年通量的67.5%和75.9%, 米槠人工林土壤呼吸及其组分的年通量都大于杉木人工林。 相似文献
6.
ANDREAS HEINEMEYER IAIN P. HARTLEY† SAM P. EVANS‡ JOSÉ A. CARREIRA DE LA FUENTE§ PHIL INESON 《Global Change Biology》2007,13(8):1786-1797
Forests play a critical role in the global carbon cycle, being considered an important and continuing carbon sink. However, the response of carbon sequestration in forests to global climate change remains a major uncertainty, with a particularly poor understanding of the origins and environmental responses of soil CO2 efflux. For example, despite their large biomass, the contribution of ectomycorrhizal (EM) fungi to forest soil CO2 efflux and responses to changes in environmental drivers has, to date, not been quantified in the field. Their activity is often simplistically included in the ‘autotrophic’ root respiration term. We set up a multiplexed continuous soil respiration measurement system in a young Lodgepole pine forest, using a mycorrhizal mesh collar design, to monitor the three main soil CO2 efflux components: root, extraradical mycorrhizal hyphal, and soil heterotrophic respiration. Mycorrhizal hyphal respiration increased during the first month after collar insertion and thereafter remained remarkably stable. During autumn the soil CO2 flux components could be divided into ∼60% soil heterotrophic, ∼25% EM hyphal, and ∼15% root fluxes. Thus the extraradical EM mycelium can contribute substantially more to soil CO2 flux than do roots. While EM hyphal respiration responded strongly to reductions in soil moisture and appeared to be highly dependent on assimilate supply, it did not responded directly to changes in soil temperature. It was mainly the soil heterotrophic flux component that caused the commonly observed exponential relationship with temperature. Our results strongly suggest that accurate modelling of soil respiration, particularly in forest ecosystems, needs to explicitly consider the mycorrhizal mycelium and its dynamic response to specific environmental factors. Moreover, we propose that in forest ecosystems the mycorrhizal CO2 flux component represents an overflow ‘CO2 tap’ through which surplus plant carbon may be returned directly to the atmosphere, thus limiting expected carbon sequestration from trees under elevated CO2. 相似文献
7.
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
8.
Mirco Rodeghiero Galina Churkina Cristina Martinez Thomas Scholten Damiano Gianelle Alessandro Cescatti 《Plant and Soil》2013,364(1-2):55-68
Aims
The partitioning of the total soil CO2 efflux into its two main components: respiration from roots (and root-associated organisms) and microbial respiration (by means of soil organic matter (SOM) and litter decomposition), is a major need in soil carbon dynamics studies in order to understand if a soil is a net sink or source of carbon.Methods
The heterotrophic component of the CO2 efflux was estimated for 11 forest sites as the ratio between the carbon stocks of different SOM pools and previously published (Δ14C derived) turnover times. The autotrophic component, including root and root-associated respiration, was calculated by subtracting the heterotrophic component from total soil chamber measured CO2 efflux.Results
Results suggested that, on average, 50.4 % of total soil CO2 efflux was derived from the respiration of the living roots, 42.4 % from decomposition of the litter layers and less than 10 % from decomposition of belowground SOM.Conclusions
The Δ14C method proved to be an efficient tool by which to partition soil CO2 efflux and quantify the contribution of the different components of soil respiration. However the average calculated heterotrophic respiration was statistically lower compared with two previous studies dealing with soil CO2 efflux partitioning (one performed in the same study area; the other a meta-analysis of soil respiration partitioning). These differences were probably due to the heterogeneity of the SOM fraction and to a sub-optimal choice of the litter sampling period. 相似文献9.
The goal of this study was to evaluate the contribution of oak trees (Quercus spp.) and their associated mycorrhizal fungi to total community soil respiration in a deciduous forest (Black Rock Forest) and
to explore the partitioning of autotrophic and heterotrophic respiration. Trees on twelve 75 × 75-m plots were girdled according
to four treatments: girdling all the oaks on the plot (OG), girdling half of the oak trees on a plot (O50), girdling all non-oaks
on a plot (NO), and a control (C). In addition, one circular plot (diameter 50 m) was created where all trees were girdled
(ALL). Soil respiration was measured before and after tree girdling. A conservative estimate of the total autotrophic contribution
is approximately 50%, as indicated by results on the ALL and OG plots. Rapid declines in carbon dioxide (CO2) flux from both the ALL and OG plots, 37 and 33%, respectively, were observed within 2 weeks following the treatment, demonstrating
a fast turnover of recently fixed carbon. Responses from the NO and O50 treatments were statistically similar to the control.
A non-proportional decline in respiration rates along the gradient of change in live aboveground biomass complicated partitioning
of the overall rate of soil respiration and indicates that belowground carbon flux is not linearly related to aboveground
disturbance. Our findings suggest that in this system there is a threshold disturbance level between 35 and 74% of live aboveground
biomass loss, beyond which belowground dynamics change dramatically. 相似文献
10.
Carbon losses due to soil warming: Do autotrophic and heterotrophic soil respiration respond equally? 总被引:1,自引:0,他引:1
ANDREAS SCHINDLBACHER SOPHIE ZECHMEISTER-BOLTENSTERN ROBERT JANDL 《Global Change Biology》2009,15(4):901-913
Global warming has the potential to increase soil respiration (RS), one of the major fluxes in the global carbon (C) cycle. RS consists of an autotrophic (RA) and a heterotrophic (RH) component. We combined a soil warming experiment with a trenching experiment to assess how RS, RA, and RH are affected. The experiment was conducted in a mature forest dominated by Norway spruce. The site is located in the Austrian Alps on dolomitic bedrock. We warmed the soil of undisturbed and trenched plots by means of heating cables 4 °C above ambient during the snow‐free seasons of 2005 and 2006. Soil warming increased the CO2 efflux from control plots (RS) by ∼45% during 2005 and ∼47% during 2006. The CO2 efflux from trenched plots (RH) increased by ∼39% during 2005 and ∼45% during 2006. Similar responses of RS and RH indicated that the autotrophic and heterotrophic components of RS responded equally to the temperature increase. Thirty‐five to forty percent or 1 t C ha−1 yr−1 of the overall annual increase in RS (2.8 t C ha−1 yr−1) was autotrophic. The remaining, heterotrophic part of soil respiration (1.8 t C ha−1 yr−1), represented the warming‐induced C loss from the soil. The autotrophic component showed a distinct seasonal pattern. Contribution of RA to RS was highest during summer. Seasonally derived Q10 values reflected this pattern and were correspondingly high (5.3–9.3). The autotrophic CO2 efflux increase due to the 4 °C warming implied a Q10 of 2.9. Hence, seasonally derived Q10 of RA did not solely reflect the seasonal soil temperature development. 相似文献
11.
CLAUDIA I. CZIMCZIK SUSAN E. TRUMBORE MARIAH S. CARBONE GREGORY C. WINSTON 《Global Change Biology》2006,12(6):957-971
Radiocarbon signatures (Δ14C) of carbon dioxide (CO2) provide a measure of the age of C being decomposed by microbes or respired by living plants. Over a 2‐year period, we measured Δ14C of soil respiration and soil CO2 in boreal forest sites in Canada, which varied primarily in the amount of time since the last stand‐replacing fire. Comparing bulk respiration Δ14C with Δ14C of CO2 evolved in incubations of heterotrophic (decomposing organic horizons) and autotrophic (root and moss) components allowed us to estimate the relative contributions of O horizon decomposition vs. plant sources. Although soil respiration fluxes did not vary greatly, differences in Δ14C of respired CO2 indicated marked variation in respiration sources in space and time. The 14C signature of respired CO2 respired from O horizon decomposition depended on the age of C substrates. These varied with time since fire, but consistently had Δ14C greater (averaging ~120‰) than autotrophic respiration. The Δ14C of autotrophically respired CO2 in young stands equaled those expected for recent photosynthetic products (70‰ in 2003, 64‰ in 2004). CO2 respired by black spruce roots in stands >40 years old had Δ14C up to 30‰ higher than recent photosynthates, indicating a significant contribution of C stored at least several years in plants. Decomposition of O horizon organic matter made up 20% or less of soil respiration in the younger (<40 years since fire) stands, increasing to ~50% in mature stands. This is a minimum for total heterotrophic contribution, since mineral soil CO2 had Δ14C close to or less than those we have assigned to autotrophic respiration. Decomposition of old organic matter in mineral soils clearly contributed to soil respiration in younger stands in 2003, a very dry year, when Δ14C of soil respiration in younger successional stands dropped below those of the atmospheric CO2. 相似文献
12.
Nicolas Chemidlin Prévost-Bouré Jérome Ngao Daniel Berveiller Damien Bonal Claire Damesin Eric Dufrêne Jean-Christophe Lata Valérie Le Dantec Bernard Longdoz Stéphane Ponton Kamel Soudani Daniel Epron 《Plant and Soil》2009,319(1-2):1-13
Disentangling the autotrophic and heterotrophic components of soil CO2 efflux is critical to understanding the role of soil system in terrestrial carbon (C) cycling. In this study, we combined a stable C-isotope natural abundance approach with the trenched plot method to determine if root exclusion significantly affected the isotopic composition (δ13C) of soil CO2 efflux (RS). This study was performed in different forest ecosystems: a tropical rainforest and two temperate broadleaved forests, where trenched plots had previously been installed. At each site, RS and its δ13C (δ13CRs) tended to be lower in trenched plots than in control plots. Contrary to RS, δ13CRs differences were not significant. This observation is consistent with the small differences in δ13C measured on organic matter from root, litter and soil. The lack of an effect on δ13CRs by root exclusion could be from the small difference in δ13C between autotrophic and heterotrophic soil respirations, but further investigations are needed because of potential artefacts associated with the root exclusion technique. 相似文献
13.
DANIEL EPRON YANN NOUVELLON†‡ PHILIPPE DELEPORTE†‡ SUSPENS IFO† GUY KAZOTTI† ARMEL THONGO M'BOU† WELCOME MOUVONDY† LAURENT SAINT ANDRE‡ OLIVIER ROUPSARD‡ CHRISTOPHE JOURDAN‡ OLIVIER HAMEL‡ 《Global Change Biology》2006,12(6):1021-1031
Soil CO2 efflux was measured in clear‐cut and intact plots in order to quantify the impact of harvest on soil respiration in an intensively managed Eucalyptus plantation, and to evaluate the increase in heterotrophic component of soil respiration because of the decomposition of harvest residues. Soil CO2 effluxes showed a pronounced seasonal trend, which was well related to the pattern of precipitation and soil water content and were always significantly lower in the clear‐cut plots than in the intact plots. On an annual basis, soil respiration represented 1.57 and 0.91 kgC m?2 yr?1 in intact and clear‐cut plots, respectively. During the first year following harvest, residues have lost 0.79 kgC m?2 yr?1. Our estimate of heterotrophic respiration was calculated assuming that it was similar to soil respiration in the clear‐cut area except that the decomposition of residues did not occur, and it was further corrected for differences in soil water content between intact and clear‐cut plots and for the cessation of leaf and fine root turnover in clear cut. Heterotrophic respiration in clear‐cut plots was estimated at 1.18 kgC m?2 yr?1 whereas it was only 0.65 kgC m?2 yr?1 in intact plots (41% of soil respiration). Assumptions and uncertainties with these calculations are discussed. 相似文献
14.
Nitrogen (N) added through atmospheric deposition or as fertilizer to boreal and temperate forests reduces both soil decomposer activity (heterotrophic respiration) and the activity of roots and mycorrhizal fungi (autotrophic respiration). However, these negative effects have been found in studies that applied relatively high levels of N, whereas the responses to ambient atmospheric N deposition rates are still not clear. Here, we compared an unfertilized control boreal forest with a fertilized forest (100 kg N ha?1 yr?1) and a forest subject to N‐deposition rates comparable to those in Central Europe (20 kg N ha?1 yr?1) to investigate the effects of N addition rate on different components of forest floor respiration and the production of ectomycorrhizal fungal sporocarps. Soil collars were used to partition heterotrophic (Rh) and autotrophic (Ra) respiration, which was further separated into respiration by tree roots (Rtr) and mycorrhizal hyphae (Rm). Total forest floor respiration was twice as high in the low N plot compared to the control, whereas there were no differences between the control and high N plot. There were no differences in Rh respiration among plots. The enhanced forest floor respiration in the low N plot was, therefore, the result of increased Ra respiration, with an increase in Rtr respiration, and a doubling of Rm respiration. The latter was corroborated by a slightly greater ectomycorrhizal (EM) fungal sporocarp production in the low N plot as compared to the control plot. In contrast, EM fungal sporocarp production was nearly eliminated, and Rm respiration severely reduced, in the high N plot, which resulted in significantly lower Ra respiration. We thus found a nonlinear response of the Ra components to N addition rate, which calls for further studies of the quantitative relations among N addition rate, plant photosynthesis and carbon allocation, and the function of EM fungi. 相似文献
15.
Aims
There is evidence that increased N inputs to boreal forests, via atmospheric deposition or intentional fertilization, may impact negatively on ectomycorrhizal (ECM) fungi leading to a reduced flux of plant-derived carbon (C) back to the atmosphere via ECM. Our aim was to investigate the impact of N fertilization of a Pinus sylvestris (L.) forest stand on the return of recently photoassimilated C via the ECM component of soil respiration.Methods
We used an in situ, large-scale, 13C-CO2 isotopic pulse labelling approach and monitored the 13C label return using soil gas efflux chambers placed over three different types of soil collar to distinguish between heterotrophic (RH), autotrophic (RA; partitioned further into contributions from ECM hyphae and total RA) and total (RS) soil respiration.Results
The impact of N fertilization was to significantly reduce RA, particularly respiration via extramatrical ECM hyphae. ECM hyphal flux in control plots showed substantial spatial variability, resulting in mean flux estimates exceeding estimates of total RA, while ECM contributions to RA in N treated plots were estimated at around 30%.Conclusion
Significant impacts on soil C cycling may be caused by reduced plant C allocation to ECM fungi in response to increased N inputs to boreal forests; ecosystem models so far lack this detail. 相似文献16.
Short rotation forests can serve as sources of renewable energy and possibly for soil C storage. However, the high frequency of management practices and the fertilisation could reduce C storage into the soil, by increasing CO2 emissions and annulling the potential of C sequestration. The objectives of this work were to evaluate the impacts of coppicing and fertilisation on total soil CO2 efflux, soil heterotrophic processes and consequent changes of soil C storage in a short rotation poplar plantation. Field soil CO2 efflux, heterotrophic soil CO2 efflux and soil organic C were compared before and after coppicing. Temporal dynamics of fine root biomass and water-soluble carbon after coppicing were also analysed. Coppicing increased total soil CO2 efflux by more than 50%, while heterotrophic soil CO2 efflux remained unchanged. Nevertheless, an increase in total organic carbon was observed as a result of above and belowground litter inputs, as well as root re-growth and exudation. This trend was more evident in fertilised soils due to lower heterotrophic and autotrophic soil CO2 effluxes. Fertilisation can reduce the increase of CO2 emissions after coppicing. Although soil organic C storage increased, the accumulation of labile fractions may trigger microbial respiration in the following years. 相似文献
17.
DAVID GAUMONT-GUAY T. ANDREW BLACK† HARRY MCCAUGHEY‡ ALAN G. BARR§ PRAVEENA KRISHNAN¶ RACHHPAL S. JASSAL† ZORAN NESIC† 《Global Change Biology》2009,15(5):1302-1319
Similar nonsteady‐state automated chamber systems were used to measure and partition soil CO2 efflux in contrasting deciduous (trembling aspen) and coniferous (black spruce and jack pine) stands located within 100 km of each other near the southern edge of the Boreal forest in Canada. The stands were exposed to similar climate forcing in 2003, including marked seasonal variations in soil water availability, which provided a unique opportunity to investigate the influence of climate and stand characteristics on soil CO2 efflux and to quantify its contribution to the net ecosystem CO2 exchange (NEE) as measured with the eddy‐covariance technique. Partitioning of soil CO2 efflux between soil respiration (including forest‐floor vegetation) and forest‐floor photosynthesis showed that short‐ and long‐term temporal variations of soil CO2 efflux were related to the influence of (1) soil temperature and water content on soil respiration and (2) below‐canopy light availability, plant water status and forest‐floor plant species composition on forest‐floor photosynthesis. Overall, the three stands were weak to moderate sinks for CO2 in 2003 (NEE of ?103, ?80 and ?28 g C m?2 yr?1 for aspen, black spruce and jack pine, respectively). Forest‐floor respiration accounted for 86%, 73% and 75% of annual ecosystem respiration, in the three respective stands, while forest‐floor photosynthesis contributed to 11% and 14% of annual gross ecosystem photosynthesis in the black spruce and jack pine stands, respectively. The results emphasize the need to perform concomitant measurements of NEE and soil CO2 efflux at longer time scales in different ecosystems in order to better understand the impacts of future interannual climate variability and vegetation dynamics associated with climate change on each component of the carbon balance. 相似文献
18.
I. INGLIMA G. ALBERTI† T. BERTOLINI‡ F. P. VACCARI§ B. GIOLI§ F. MIGLIETTA§ M. F. COTRUFO A. PERESSOTTI† 《Global Change Biology》2009,15(5):1289-1301
In regions characterized by arid seasons, such as the Mediterranean basin, soil moisture is a major driver of ecosystem CO2 efflux during periods of drought stress. Here, a rain event can induce a disproportional respiratory pulse, releasing an amount of CO2 to the atmosphere that may significantly contribute to the annual ecosystem carbon balance. The mechanisms behind this pulse are unclear, and it is still unknown whether it is due to the stimulation of autotrophic, heterotrophic and/or inorganic CO2 fluxes. On the Mediterranean island of Pianosa, eddy flux measurements showed respiratory pulses after rain events following prolonged drought periods, which occurred in the summer of 2003 and 2006. To investigate the mechanisms of this observed enhanced respiration fluxes and partition of the soil CO2 sources, two water manipulation experiments were performed. The first was designed to estimate the effect of soil rewetting on soil CO2 efflux, in the different ecosystem types existing on the island (i.e. woodland, ex‐agricultural and Mediterranean shrubland). The second was a soil CO2 partitioning experiment to investigate the relative contribution of inorganic and organic CO2 sources to soil respiration, under dry and wet soil conditions. Our results suggest that the pulse in the CO2 efflux is primarily due to the enhancement of heterotrophic respiration, likely caused by the degradation of easily decomposable substrates, accumulated in soils during the dry period. In fact, the vegetation at the site was senescent and did not play any significant role in CO2 exchange, as suggested by the absence of diurnal CO2 uptake in eddy covariance measurements. In addition, soil rewetting did not significantly enhance inorganic CO2 efflux. 相似文献
19.
Annual variation in soil respiration and its component parts in two structurally contrasting woody savannas in Central Brazil 总被引:1,自引:0,他引:1
Andre Butler Patrick Meir Gustavo Saiz Leandro Maracahipes Beatriz Schwantes Marimon John Grace 《Plant and Soil》2012,352(1-2):129-142
Background and aims
Due to the high spatial and temporal variation in soil CO2 efflux, terrestrial carbon budgets rely on a detailed understanding of the drivers of soil respiration from a diverse range of ecosystems and climate zones. In this study we aim to evaluate the independent influence of vegetation structure and climate on soil CO2 efflux within cerrado ecosystems.Methods
We examine the seasonal and diel variation of soil CO2 efflux, including its autotrophic and heterotrophic components, within two adjacent and structurally contrasting woody savannas in central Brazil.Principle results
We found no significant difference in the annual soil CO2 efflux between the two stands (p?=?0.53) despite a clear disparity in both LAI (p?<?0.01) and leaf litterfall (p?<?0.01). The mean annual loss of carbon from the soil was 17.32(±1.48) Mg C?ha?1 of which approximately 63% was accounted for by autotrophic respiration. The relative contribution of autotrophic respiration varied seasonally between 55% in the wet season to 79% of the total soil CO2 efflux in the dry season. Furthermore, seasonal fluctuations of all the soil respiration components were strongly correlated with soil moisture (R 2?=?0.79–0.90, p?<?0.01).Conclusions
Across these two structurally distinct cerrado stands, seasonal variations in rainfall, was the main driver of soil CO2 efflux and its components. Consequently, soil respiration within these ecosystems is likely to be highly sensitive to any changes in seasonal precipitation patterns. 相似文献20.
CO2 efflux from subterranean nests of ant communities in a seasonal tropical forest,Thailand
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Sasitorn Hasin Mizue Ohashi Akinori Yamada Yoshiaki Hashimoto Wattanachai Tasen Tomonori Kume Seiki Yamane 《Ecology and evolution》2014,4(20):3929-3939
Many ant species construct subterranean nests. The presence of their nests may explain soil respiration “hot spots”, an important factor in the high CO2 efflux from tropical forests. However, no studies have directly measured CO2 efflux from ant nests. We established 61 experimental plots containing 13 subterranean ant species to evaluate the CO2 efflux from subterranean ant nests in a tropical seasonal forest, Thailand. We examined differences in nest CO2 efflux among ant species. We determined the effects of environmental factors on nest CO2 efflux and calculated an index of nest structure. The mean CO2 efflux from nests was significantly higher than those from the surrounding soil in the wet and dry seasons. The CO2 efflux was species‐specific, showing significant differences among the 13 ant species. The soil moisture content significantly affected nest CO2 efflux, but there was no clear relationship between nest CO2 efflux and nest soil temperature. The diameter of the nest entrance hole affected CO2 efflux. However, there was no significant difference in CO2 efflux rates between single‐hole and multiple‐hole nests. Our results suggest that in a tropical forest ecosystem the increase in CO2 efflux from subterranean ant nests is caused by species‐specific activity of ants, the nest soil environment, and nest structure. 相似文献