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1.
Christopher J. Kucharik Kristofor R. Brye John M. Norman Jonathan A. Foley Stith T. Gower Larry G. Bundy 《Ecosystems》2001,4(3):237-258
Landmanagement practices such as no-tillage agriculture and tallgrass prairie restoration have been proposed as a possible
means to sequester atmospheric carbon, helping to refurbish soil fertility and replenish organic matter lost as a result of
previous agricultural management practices. However, the relationship between land-use changes and ecosystem structure and
functioning is not yet understood. We studied soil and vegetation properties over a 4-year period (1995–98), and assembled
measurements of microbial biomass, soil organic carbon (SOC) and nitrogen (N), N-mineralization, soil surface carbon dioxide
(CO2) flux, and leached C and N in managed (maize; Zea mays L.) and natural (prairie) ecosystems near the University of Wisconsin Agricultural Research Station at Arlington. Field data
show that different management practices (tillage and fertilization) and ecosystem type (prairie vs maize) have a profound
influence on biogeochemistry and water budgets between sites. These measurements were used in conjunction with a dynamic terrestrial
ecosystem model, called IBIS (the Integrated Biosphere Simulator), to examine the long-term effects of land-use changes on
biogeochemical cycling. Field data and modeling suggest that agricultural land management near Arlington between 1860 and
1950 caused SOC to be depleted by as much as 63% (native SOC approximately 25.1 kg C m−2). Reductions in N-mineralization and microbial biomass were also observed. Although IBIS simulations depict SOC recovery
in no-tillage maize since the 1950s and also in the Arlington prairie since its restoration was initiated in 1976, field data
suggest otherwise for the prairie. This restoration appears to have done little to increase SOC over the past 24 years. Measurements
show that this prairie contained between 28% and 42% less SOC (in the top 1 m) than the no-tillage maize plots and 40%–47%
less than simulated potential SOC for the site in 1999. Because IBIS simulates competition between C3 and C4 grass species,
we hypothesized that current restored prairies, which include many forbs not characterized by the model, could be less capable
of sequestering C than agricultural land planted entirely in monocultural grass in this region. Model output and field measurements
show a potential 0.4 kg C m−2 y−1 difference in prairie net primary production (NPP). This study indicates that high-productivity C4 grasslands (NPP = 0.63
kg C m−2 y−1) and high-yield maize agroecosystems (10 Mg ha−1) have the potential to sequester C at a rate of 74.5 g C m−2 y−1 and 86.3 g C m−2 y−1, respectively, during the next 50 years across southern Wisconsin.
Received 28 December 1999; accepted 11 December 2000. 相似文献
2.
Chengzhang Liao Yiqi Luo Lifen Jiang Xuhui Zhou Xiaowen Wu Changming Fang Jiakuan Chen Bo Li 《Ecosystems》2007,10(8):1351-1361
Whether plant invasion increases ecosystem carbon (C) stocks is controversial largely due to the lack of knowledge about differences
in ecophysiological properties between invasive and native species. We conducted a field experiment in which we measured ecophysiological
properties to explore the response of the ecosystem C stocks to the invasion of Spartina alterniflora (Spartina) in wetlands dominated by native Scirpus mariqueter (Scirpus) and Phragmites australis (Phragmites) in the Yangtze Estuary, China. We measured growing season length, leaf area index (LAI), net photosynthetic rate (Pn), root
biomass, net primary production (NPP), litter quality and litter decomposition, plant and soil C and nitrogen (N) stocks in
ecosystems dominated by the three species. Our results showed that Spartina had a longer growing season, higher LAI, higher Pn, and greater root biomass than Scirpus and Phragmites. Net primary production (NPP) was 2.16 kg C m−2 y−1 in Spartina ecosystems, which was, on average, 1.44 and 0.47 kg C m−2 y−1 greater than that in Scirpus and Phragmites ecosystems, respectively. The litter decomposition rate, particularly the belowground decomposition rate, was lower for Spartina than Scirpus and Phragmites due to the lower litter quality of Spartina. The ecosystem C stock (20.94 kg m−2) for Spartina was greater than that for Scirpus (17.07 kg m−2), Phragmites (19.51 kg m−2) and the mudflats (15.12 kg m−2). Additionally, Spartina ecosystems had a significantly greater N stock (698.8 g m−2) than Scirpus (597.1 g m−2), Phragmites ecosystems (578.2 g m−2) and the mudflats (375.1 g m−2). Our results suggest that Spartina invasion altered ecophysiological processes, resulted in changes in NPP and litter decomposition, and ultimately led to enhanced
ecosystem C and N stocks in the invaded ecosystems in comparison to the ecosystems with native species. 相似文献
3.
Disturbed grassland soils are often cited as having the potential to store large amounts of carbon (C). Fertilization of grasslands
can promote soil C storage, but little is known about the generation of recalcitrant pools of soil organic matter (SOM) with
management treatments, which is critical for long-term soil C storage. We used a combination of soil incubations, size fractionation
and acid hydrolysis of SOM, [C], [N], and stable isotopic analyses, and biomass quality indices to examine how fertilization
and haying can impact SOM dynamics in Kansan grassland soils. Fertilized soils possessed 113% of the C possessed by soils
subjected to other treatments, an increase predominantly harbored in the largest size fraction (212–2,000 μm). This fraction
is frequently associated with more labile material. Haying and fertilization/haying, treatments that more accurately mimic
true management techniques, did not induce any increase in soil C. The difference in 15N-enrichment between size fractions was consistent with a decoupling of SOM processing between pools with fertilization, congruent
with gains of SOM in the largest size fraction promoted by fertilization not moving readily into smaller fractions that frequently
harbor more recalcitrant material. Litterfall and root biomass C inputs increased 104% with fertilization over control plots,
and this material possessed lower C:N ratios. Models of incubation mineralization kinetics indicate that fertilized soils
have larger pools of labile organic C. Model estimates of turnover rates of the labile and recalcitrant C pools did not differ
between treatments (65.5 ± 7.2 and 2.9 ± 0.3 μg C d−1, respectively). Although fertilization may promote greater organic inputs into these soils, much of that material is transformed
into relatively labile forms of soil C; these data highlight the challenges of managing grasslands for long-term soil C sequestration. 相似文献
4.
Extracellular Enzyme Activities and Soil Organic Matter Dynamics for Northern Hardwood Forests receiving Simulated Nitrogen Deposition 总被引:5,自引:0,他引:5
Anthropogenic nitrogen enrichment alters decomposition processes that control the flux of carbon (C) and nitrogen (N) from
soil organic matter (SOM) pools. To link N-driven changes in SOM to microbial responses, we measured the potential activity
of several extracellular enzymes involved in SOM degradation at nine experimental sites located in northern Michigan. Each
site has three treatment plots (ambient, +30 and +80 kg N ha−1 y−1). Litter and soil samples were collected on five dates over the third growing season of N treatment. Phenol oxidase, peroxidase
and cellobiohydrolase activities showed significant responses to N additions. In the Acer saccharum–Tilia americana ecosystem, oxidative activity was 38% higher in the litter horizon of high N treatment plots, relative to ambient plots,
while oxidative activity in mineral soil showed little change. In the A. saccharum–Quercus rubra and Q. velutina–Q. alba ecosystems, oxidative activities declined in both litter (15 and 23%, respectively) and soil (29 and 38%, respectively) in
response to high N treatment while cellobiohydrolase activity increased (6 and 39% for litter, 29 and 18% for soil, respectively).
Over 3 years, SOM content in the high N plots has decreased in the Acer–Tilia ecosystem and increased in the two Quercus ecosystems, relative to ambient plots. For all three ecosystems, differences in SOM content in relation to N treatment were
directly related (r2 = 0.92) to an enzyme activity factor that included both oxidative and hydrolytic enzyme responses. 相似文献
5.
Abstract
Sugar maple (Acer saccharum Marsh.)-dominated northern hardwood forests of the Great Lakes Region commonly receive elevated levels of atmospheric nitrate
(NO3−) deposition, which can alter belowground carbon (C) cycling. Past research has demonstrated that chronic experimental NO3− deposition (3 g N m−2 y−1 above ambient) elicits a threefold increase in the leaching loss of dissolved organic carbon (DOC). Here, we used DOC collected
from tension-cup lysimeters to test whether increased DOC export under experimental NO3− deposition originated from forest floor or mineral soil organic matter (SOM). We used DOC radiocarbon dating to quantify
C sources and colorimetric assays to measure DOC aromaticity and soluble polyphenolic content. Our results demonstrated that
DOC exports are primarily derived from new C (<50-years-old) in the forest floor under both ambient and experimental NO3− deposition. Experimental NO3− deposition increased soluble polyphenolic content from 25.03 ± 4.26 to 49.19 ± 4.23 μg phenolic C mg DOC−1, and increased total aromatic content as measured by specific UV absorbance. However, increased aromatic compounds represented
a small fraction (<10%) of the total observed increased DOC leaching. In combination, these findings suggest that experimental
NO3− deposition has altered the production or retention as well as phenolic content of DOC formed in forest floor, however exact
mechanisms are uncertain. Further elucidation of the mechanism(s) controlling enhanced DOC leaching is important for understanding
long-term responses of Great Lakes forests to anthropogenic N deposition and the consequences of those responses for aquatic
ecosystems. 相似文献
6.
N2O, CH4 and CO2 emissions from seasonal tropical rainforests and a rubber plantation in Southwest China 总被引:2,自引:1,他引:1
Christian Werner Xunhua Zheng Janwei Tang Baohua Xie Chunyan Liu Ralf Kiese Klaus Butterbach-Bahl 《Plant and Soil》2006,289(1-2):335-353
The main focus of this study was to evaluate the effects of soil moisture and temperature on temporal variation of N2O, CO2 and CH4 soil-atmosphere exchange at a primary seasonal tropical rainforest (PF) site in Southwest China and to compare these fluxes with fluxes from a secondary forest (SF) and a rubber plantation (RP) site. Agroforestry systems, such as rubber plantations, are increasingly replacing primary and secondary forest systems in tropical Southwest China and thus effect the N2O emission in these regions on a landscape level. The mean N2O emission at site PF was 6.0 ± 0.1 SE μg N m−2 h−1. Fluxes of N2O increased from <5 μg N m−2 h−1 during dry season conditions to up to 24.5 μg N m−2 h−1 with re-wetting of the soil by the onset of first rainfall events. Comparable fluxes of N2O were measured in the SF and RP sites, where mean N2O emissions were 7.3 ± 0.7 SE μg N m−2 h−1 and 4.1 ± 0.5 SE μg N m−2 h−1, respectively. The dependency of N2O fluxes on soil moisture levels was demonstrated in a watering experiment, however, artificial rainfall only influenced the timing of N2O emission peaks, not the total amount of N2O emitted. For all sites, significant positive correlations existed between N2O emissions and both soil moisture and soil temperature. Mean CH4 uptake rates were highest at the PF site (−29.5 ± 0.3 SE μg C m−2 h−1), slightly lower at the SF site (−25.6 ± 1.3 SE μg C m−2 h−1) and lowest for the RP site (−5.7 ± 0.5 SE μg C m−2 h−1). At all sites, CH4 uptake rates were negatively correlated with soil moisture, which was also reflected in the lower uptake rates measured in the watering experiment. In contrast to N2O emissions, CH4 uptake did not significantly correlate with soil temperature at the SF and RP sites, and only weakly correlated at the PF site. Over the 2 month measurement period, CO2 emissions at the PF site increased significantly from 50 mg C m−2 h−1 up to 100 mg C m−2 h−1 (mean value 68.8 ± 0.8 SE mg C m−2 h−1), whereas CO2 emissions at the SF and RP site where quite stable and varied only slightly around mean values of 38.0 ± 1.8 SE mg C m−2 h−1 (SF) and 34.9 ± 1.1 SE mg C m−2 h−1 (RP). A dependency of soil CO2 emissions on changes in soil water content could be demonstrated for all sites, thus, the watering experiment revealed significantly higher CO2 emissions as compared to control chambers. Correlation of CO2 emissions with soil temperature was significant at the PF site, but weak at the SF and not evident at the RP site. Even though we demonstrated that N and C trace gas fluxes significantly varied on subdaily and daily scales, weekly measurements would be sufficient if only the sink/ source strength of non-managed tropical forest sites needs to be identified. 相似文献
7.
We used sugar maple litter double-labeled with 13C and 15N to quantify fluxes of carbon (C) and nitrogen (N) between litter and soil in a northern hardwood forest and the retention
of litter C and N in soil. Two cohorts of litter were compared, one in which the label was preferentially incorporated into
non-structural tissue and the other structural tissue. Loss of 13C from this litter generally followed dry mass and total C loss whereas loss of 15N (20–30% in 1 year) was accompanied by large increases of total N content of this decaying litter (26–32%). Enrichment of
13C and 15N was detected in soil down to 10–15 cm depth. After 6 months of decay (November–May) 36–43% of the 13C released from the litter was recovered in the soil, with no differences between the structural and non-structural labeled
litter. By October the percentage recovery of litter 13C in soil was much lower (16%). The C released from litter and remaining in soil organic matter (SOM) after 1 year represented
over 30 g C m−2 y−1 of SOM accumulation. Recovery of litter 15N in soil was much higher than for C (over 90%) and in May 15N was mostly in organic horizons whereas by October it was mostly in 0–10 cm mineral soil. A small proportion of this N was
recovered as inorganic N (2–6%). Recovery of 15N in microbial biomass was higher in May (13–15%) than in October (about 5%). The C:N ratio of the SOM and microbial biomass
derived from the labeled litter was much higher for the structural than the non-structural litter and for the forest floor
than mineral SOM, illustrating the interactive role of substrates and microbial activity in regulating the C:N stoichiometry
of forest SOM formation. These results for a forest ecosystem long exposed to chronically high atmospheric N deposition (ca.
10 kg N ha−1 y−1) suggest possible mechanisms of N retention in soil: increased organic N leaching from fresh litter and reduced fungal transport
of N from soil to decaying litter may promote N stabilization in mineral SOM even at a relatively low C:N ratio. 相似文献
8.
Soil organic carbon (SOC) models have been widely used to predict SOC change with changing environmental and management conditions,
but the accuracy of the prediction is often open to question. Objectives were (i) to quantify the amounts of C derived from
maize in soil particle size fractions and at various depths in a long-term field experiment using 13C/12C analysis, (ii) to model changes in the organic C, and (iii) to compare measured and modelled pools of C. Maize was cultivated
for 24 years on a silty Luvisol which resulted in a stock of 1.9 kg maize-derived C m−2 (36% of the total organic C) in the Ap horizon. The storage of maize-derived C in particle size fractions of the Ap horizon
decreased in the order clay (0.65 kg C m−2) > fine and medium silt (0.43) > coarse silt (0.33) > fine sand (0.13) > medium sand (0.12) > coarse sand (0.06) and the
turnover times of C3-derived C ranged from 26 (fine sand) to 77 years (clay). The turnover times increased with increasing soil depth. We used
the Rothamsted Carbon Model to model the C dynamics and tested two model approaches: model A did not have any adjustable parameters,
but included the Falloon equation for the estimation of the amount of inert organic matter (IOM) and independent estimations
of C inputs into the soil. The model predicted well the changes in C3-derived C with time but overestimated the changes in maize-derived C 1.6-fold. In model B, the amounts of IOM and C inputs
were optimized to match the measured C3- and C4-derived SOC stocks after 24 years of continuous maize. This model described the experimental data well, but the modelled
annual maize C inputs (0.41 kg C m−2 a−1) were less than the independently estimated total input of maize litter C (0.63 kg C m−2 a−1) and even less than the annual straw C incorporated into the soil (0.46 kg C m−2 a−1). These results indicated that the prediction of the Rothamsted Carbon Model with independent parameterization served only
as an approximation for this site. The total amount of organic C associated with the fraction 0–63 μm agreed well with the sum of the pools ‘microbial biomass’, ‘humified-organic matter’ and IOM of the model B. However, the
amount of maize-derived C in this fraction (3.4 g kg−1) agreed only satisfactorily with the sum of maize-derived C in the pools ‘microbial biomass’ and ‘humified organic matter’
(2.6 g kg−1). 相似文献
9.
Modelling soil C sequestration in spruce forest ecosystems along a Swedish transect based on current conditions 总被引:1,自引:1,他引:0
The change of current pools of soil C in Norway spruce ecosystems in Sweden were studied using a process-based model (CoupModel).
Simulations were conducted for four sites representing different regions covering most of the forested area in Sweden and
representing annual mean temperatures from 0.7°C to 7.1°C. The development of both tree layer and field layer (understory)
was simulated during a 100-year period using data on standing stock volumes from the Swedish Forest Inventory to calibrate
tree growth using different assumptions regarding N supply to the plants. The model successfully described the general patterns
of forest stand dynamics along the Swedish climatic transect, with decreasing tree growth rates and increasing field layer
biomass from south to north. However, the current tree growth pattern for the northern parts of Sweden could not be explained
without organic N uptake and/or enhanced mineralisation rates compared to the southern parts. Depending on the assumption
made regarding N supply to the tree, different soil C sequestration rates were obtained. The approach to supply trees with
both mineralised N and organic N, keeping the soil C:N ratio constant during the simulation period was found to be the most
realistic alternative. With this approach the soils in the northern region of Sweden lost 5 g C m−2 year−1, the soils in the central region lost 2 g C m−2 year−1, and the soils in the two southern regions sequestered 9 and 23 g C m−2 year−1, respectively. In addition to climatic effects, the feedback between C and N turnover plays an important role that needs
to be more clearly understood to improve estimates of C sequestration in boreal forest ecosystems. 相似文献
10.
Carbon isotopic composition of soils subjected to C3–C4 vegetation change can be used to estimate C turnover in bulk soil and in soil organic matter (SOM) pools with fast and intermediate
turnover rates. We hypothesized that the biological availability of SOM pools is inversely proportional to their thermal stability,
so that thermogravimetry can be used to separate SOM pools with contrasting turnover rates. Soil samples from a field plot
cultivated for 10.5 years with the perennial C4 plant Miscanthus×gigantheus were analyzed by thermogravimetry coupled with differential scanning calorimetry (DSC). Three SOM fractions were distinguished
according to the differential weight losses and exothermic or endothermic reactions measured by DSC. The δ13C and δ15N values of these three fractions obtained by gradual soil heating were measured by IRMS. The weight losses up to 190 °C mainly
reflected water evaporation because no significant C and N losses were detected and δ13C and δ15N values of the residual SOM remained unchanged. The δ13C values (−16.4‰) of SOM fraction decomposed between 190 and 390 °C (containing 79% of total soil C) were slightly closer
to that of the Miscanthus plant tissues (δ13C = −11.8‰) compared to the δ13C values (−16.8‰) of SOM fraction decomposed above 390 °C containing the residual 21% of SOM. Thus, the C turnover in the
thermally labile fraction was faster than that in thermally stable fractions, but the differences were not very strong. Therefore,
in this first study combining TG-DSC with isotopic analysis, we conclude that the thermal stability of SOM was not very strongly
related to biological availability of SOM fractions. In contrast to δ13C, the δ15N values strongly differed between SOM fractions, suggesting that N turnover in the soil was different from C turnover. More
detailed fractionation of SOM by thermal analysis with subsequent isotopic analysis may improve the resolution for δ13C. 相似文献
11.
Zhao Liang Xu Shixiao Li Yingnian Tang Yanhong Zhao Xinquan Gu Song Du Mingyuan Yu Guirui 《Frontiers of Biology in China》2007,2(3):324-332
Carbon dioxide fluxes of Kobresia humilis and Potentilla fruticosa shrub meadows, two typical ecosystems in the Qinghai-Tibet Plateau, were measured by eddy covariance technology and the data
collected in August 2003 were employed to analyze the relations between carbon dioxide fluxes and environmental factors of
the ecosystems. August is the time when the two ecosystems reach their peak leaf area indexes and stay stable, and also the
period when the net carbon absorptions of Kobresia humilis and Potentilla fruticosa shrub meadows reach 56.2 g C·m−2 and 32.6 g C·m−2, with their highest daily carbon dioxide absorptions standing at 12.7 μmol·m−2·s−1 and 9.3 μmol·m−2·s−1, and their highest carbon discharges at 5.1 μmol·m−2·s−1 and 5.7 μmol·m−2·s−1, respectively. At the same photosynthetic photo flux densities (PPFD), the carbon dioxide-uptake rate of the Kobresia humilis meadow is higher than that of the Potentilla fruticosa shrub meadow; where the PPFD are higher than 1,200 μmol·m−2·s−1. The carbon dioxide uptake rates of the two ecosystems declined as air temperature increased, but the carbon dioxide uptake
rate of the Kobresia humilis meadow decreased more quickly (−0.086) than that of the Potentilla fruticosa shrub meadow (−0.016). Soil moistures exert influence on the soil respirations and this varies with the vegetation type.
The daily carbon dioxide absorptions of the ecosystems increase with increased diurnal temperature differences and higher
diurnal temperature differences result in higher carbon dioxide exchanges. There exists a negative correlation between the
vegetation albedos and the carbon dioxide fluxes.
Translated from Acta Bot Boreal—Occident Sin, 2006, 26(1): 133–142 [译自: 西北植物学报] 相似文献
12.
It is unclear how changing atmospheric composition will influence the plant–soil interactions that determine soil organic
matter (SOM) levels in fertile agricultural soils. Positive effects of CO2 fertilization on plant productivity and residue returns should increase SOM stocks unless mineralization or biomass removal
rates increase in proportion to offset gains. Our objectives were to quantify changes in SOM stocks and labile fractions in
prime farmland supporting a conventionally managed corn–soybean system and the seasonal dynamics of labile C and N in soybean
in plots exposed to elevated [CO2] (550 ppm) under free-air concentration enrichment (FACE) conditions. Changes in SOM stocks including reduced C/N ratios
and labile N stocks suggest that SOM declined slightly and became more decomposed in all plots after 3 years. Plant available
N (>273 mg N kg−1) and other nutrients (Bray P, 22–50 ppm; extractable K, 157–237 ppm; Ca, 2,378–2,730 ppm; Mg, 245–317 ppm) were in the high
to medium range. Exposure to elevated [CO2] failed to increase particulate organic matter C (POM-C) and increased POM-N concentrations slightly in the surface depth
despite known increases (≈30%) in root biomass. This, and elevated CO2 efflux rates indicate accelerated decay rates in fumigated plots (2001: elevated [CO2]: 10.5 ± 1.2 μmol CO2 m−2 s−1 vs. ambient: 8.9 ± 1.0 μmol CO2 m−2 s−1). There were no treatment-based differences in the within-season dynamics of SOM. Soil POM-C and POM-N contents were slightly
greater in the surface depth of elevated than ambient plots. Most studies attribute limited ability of fumigated soils to
accumulate SOM to N limitation and/or limited plant response to CO2 fertilization. In this study, SOM turnover appears to be accelerated under elevated [CO2] even though soil moisture and nutrients are non-limiting and plant productivity is consistently increased. Accelerated SOM
turnover rates may have long-term implications for soil’s productive potential and calls for deeper investigation into C and
N dynamics in highly-productive row crop systems. 相似文献
13.
Toshiyuki Ohtsuka Wenhong Mo Takami Satomura Motoko Inatomi Hiroshi Koizumi 《Ecosystems》2007,10(2):324-334
Biometric based carbon flux measurements were conducted over 5 years (1999–2003) in a temperate deciduous broad-leaved forest
of the AsiaFlux network to estimate net ecosystem production (NEP). Biometric based NEP, as measured by the balance between
net primary production (including NPP of canopy trees and of forest floor dwarf bamboo) and heterotrophic respiration (RH),
clarified the contribution of various biological processes to the ecosystem carbon budget, and also showed where and how the
forest is storing C. The mean NPP of the trees was 5.4 ± 1.07 t C ha−1 y−1, including biomass increment (0.3 ± 0.82 t C ha−1 y−1), tree mortality (1.0 ± 0.61 t C ha−1 y−1), aboveground detritus production (2.3 ± 0.39 t C ha−1 y−1) and belowground fine root production (1.8 ± 0.31 t C ha−1 y−1). Annual biomass increment was rather small because of high tree mortality during the 5 years. Total NPP at the site was
6.5 ± 1.07 t C ha−1 y−1, including the NPP of the forest floor community (1.1 ± 0.06 t C ha−1 y−1). The soil surface CO2 efflux (RS) was averaged across the 5 years of record using open-flow chambers. The mean estimated annual RS amounted to
7.1 ± 0.44 t C ha−1, and the decomposition of soil organic matter (SOM) was estimated at 3.9 ± 0.24 t C ha−1. RH was estimated at 4.4 ± 0.32 t C ha−1 y−1, which included decomposition of coarse woody debris. Biometric NEP in the forest was estimated at 2.1 ± 1.15 t C ha−1 y−1, which agreed well with the eddy-covariance based net ecosystem exchange (NEE). The contribution of woody increment (Δbiomass + mortality)
of the canopy trees to NEP was rather small, and thus the SOM pool played an important role in carbon storage in the temperate
forest. These results suggested that the dense forest floor of dwarf bamboo might have a critical role in soil carbon sequestration
in temperate East Asian deciduous forests. 相似文献
14.
Recovery of Aboveground Plant Biomass and Productivity After Fire in Mesic and Dry Black Spruce Forests of Interior Alaska 总被引:1,自引:0,他引:1
Michelle C. Mack Kathleen K. Treseder Kristen L. Manies Jennifer W. Harden Edward A. G. Schuur Jason G. Vogel James T. Randerson F. Stuart Chapin III 《Ecosystems》2008,11(2):209-225
Plant biomass accumulation and productivity are important determinants of ecosystem carbon (C) balance during post-fire succession.
In boreal black spruce (Picea mariana) forests near Delta Junction, Alaska, we quantified aboveground plant biomass and net primary productivity (ANPP) for 4 years
after a 1999 wildfire in a well-drained (dry) site, and also across a dry and a moderately well-drained (mesic) chronosequence
of sites that varied in time since fire (2 to ∼116 years). Four years after fire, total biomass at the 1999 burn site had
increased exponentially to 160 ± 21 g m−2 (mean ± 1SE) and vascular ANPP had recovered to 138 ± 32 g m−2 y−1, which was not different than that of a nearby unburned stand (160 ± 48 g m−2 y−1) that had similar pre-fire stand structure and understory composition. Production in the young site was dominated by re-sprouting
graminoids, whereas production in the unburned site was dominated by black spruce. On the dry and mesic chronosequences, total
biomass pools, including overstory and understory vascular and non-vascular plants, and lichens, increased logarithmically
(dry) or linearly (mesic) with increasing site age, reaching a maximum of 2469 ± 180 (dry) and 4008 ± 233 g m−2 (mesic) in mature stands. Biomass differences were primarily due to higher tree density in the mesic sites because mass per
tree was similar between sites. ANPP of vascular and non-vascular plants increased linearly over time in the mesic chronosequence
to 335 ± 68 g m−2 y−1 in the mature site, but in the dry chronosequence it peaked at 410 ± 43 g m−2 y−1 in a 15-year-old stand dominated by deciduous trees and shrubs. Key factors regulating biomass accumulation and production
in these ecosystems appear to be the abundance and composition of re-sprouting species early in succession, the abundance
of deciduous trees and shrubs in intermediate aged stands, and the density of black spruce across all stand ages. A better
understanding of the controls over these factors will help predict how changes in climate and fire regime will affect the
carbon balance of Interior Alaska.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
15.
Headwater streams are key sites of nutrient and organic matter processing and retention, but little is known about temporal
variability in gross primary production (GPP) and ecosystem respiration (ER) rates as a result of the short duration of most
metabolism measurements in lotic ecosystems. We examined temporal variability and controls on ecosystem metabolism by measuring
daily rates continuously for 2 years in Walker Branch, a first-order deciduous forest stream. Four important scales of temporal
variability in ecosystem metabolism rates were identified: (1) seasonal, (2) day-to-day, (3) episodic (storm-related), and
(4) inter-annual. Seasonal patterns were largely controlled by the leaf phenology and productivity of the deciduous riparian
forest. Walker Branch was strongly net heterotrophic throughout the year with the exception of the open-canopy spring when
GPP and ER rates were co-equal. Day-to-day variability in weather conditions influenced light reaching the streambed, resulting
in high day-to-day variability in GPP particularly during spring (daily light levels explained 84% of the variance in daily
GPP in April). Episodic storms depressed GPP for several days in spring, but increased GPP in autumn by removing leaves shading
the streambed. Storms depressed ER initially, but then stimulated ER to 2–3 times pre-storm levels for several days. Walker
Branch was strongly net heterotrophic in both years of the study, with annual GPP being similar (488 and 519 g O2 m−2 y−1 or 183 and 195 g C m−2 y−1) but annual ER being higher in 2004 than 2005 (−1,645 vs. −1,292 g O2 m−2 y−1 or −617 and −485 g C m−2 y−1). Inter-annual variability in ecosystem metabolism (assessed by comparing 2004 and 2005 rates with previous measurements)
was the result of the storm frequency and timing and the size of the spring macroalgal bloom. Changes in local climate can
have substantial impacts on stream ecosystem metabolism rates and ultimately influence the carbon source and sink properties
of these important ecosystems. 相似文献
16.
Pools and fluxes of carbon in three Norway spruce ecosystems along a climatic gradient in Sweden 总被引:1,自引:0,他引:1
Dan Berggren Kleja Magnus Svensson Hooshang Majdi Per-Erik Jansson Ola Langvall Bo Bergkvist Maj-Britt Johansson Per Weslien Laimi Truus Anders Lindroth Göran I. Ågren 《Biogeochemistry》2008,89(1):7-25
This paper presents an integrated analysis of organic carbon (C) pools in soils and vegetation, within-ecosystem fluxes and
net ecosystem exchange (NEE) in three 40-year old Norway spruce stands along a north-south climatic gradient in Sweden, measured
2001–2004. A process-orientated ecosystem model (CoupModel), previously parameterised on a regional dataset, was used for
the analysis. Pools of soil organic carbon (SOC) and tree growth rates were highest at the southernmost site (1.6 and 2.0-fold,
respectively). Tree litter production (litterfall and root litter) was also highest in the south, with about half coming from
fine roots (<1 mm) at all sites. However, when the litter input from the forest floor vegetation was included, the difference
in total litter input rate between the sites almost disappeared (190–233 g C m−2 year−1). We propose that a higher N deposition and N availability in the south result in a slower turnover of soil organic matter
than in the north. This effect seems to overshadow the effect of temperature. At the southern site, 19% of the total litter
input to the O horizon was leached to the mineral soil as dissolved organic carbon, while at the two northern sites the corresponding
figure was approx. 9%. The CoupModel accurately described general C cycling behaviour in these ecosystems, reproducing the
differences between north and south. The simulated changes in SOC pools during the measurement period were small, ranging
from −8 g C m−2 year−1 in the north to +9 g C m−2 year−1 in the south. In contrast, NEE and tree growth measurements at the northernmost site suggest that the soil lost about 90 g C m−2 year−1.
An erratum to this article can be found at 相似文献
17.
To determine the sources and sinks of atmospherically deposited Pb at a forested watershed (Plastic Lake) in central Ontario,
Canada, Pb pools and fluxes through upland, wetland and lake compartments were measured during 2002/2003 and compared with
previous measurements taken between 1989 and 1991. In 2002/2003, annual bulk deposition of Pb was 0.49 mg m−2 compared with 1.90–1.30 mg m−2 in 1989–1991. Annual Pb concentrations in stream water draining the upland part of the catchment were very low (0.04 μg l−1) and were approximately half those measured in 1989–1991 (0.11–0.08 μg l−1). Leaching losses in stream water were small and mass balance estimates indicate almost complete retention (>95%) of atmospherically
deposited Pb in upland soils. In contrast, annual Pb concentrations in stream water draining a wetland were between 0.38 and
0.77 μg l−1, with the highest concentration occurring in 2002/2003 and mass balance calculations indicate that the wetland is a net source
of Pb in all measured years. Lead concentrations in the lake outflow were low and the average Pb concentration measured in
2002/2003 (0.09 μg l−1) was approximately half the value recorded in 1989–1991 (0.19 μg l−1 both years). Annual mass balance estimates indicate that the lake retained between 2.47 mg m−2 (1989/1990) and 1.42 mg m−2 (2002/2003) and that in 2002/2003 68% of the Pb input to the lake is derived from the terrestrial catchment. These estimates
are higher than sediment core records, which indicate around 18 mg m−2 Pb was retained in sediment during the 1990s. Nevertheless, Pb concentrations decrease with sediment depth and 206Pb/207Pb concentrations increase with depth, a pattern also observed in mineral soils that reflects the substantial contribution
of anthropogenic Pb to the watershed. Lead isotope data from soil and sediment indicate a recent anthropogenic Pb signal (206Pb/207Pb ∼ 1.185) in upper soils and sediments and an older anthropogenic signal (206Pb/207Pb ∼ 1.20) in deeper soil and sediment. Lead isotope data in sediment and vegetation indicate that practically all the Pb
cycled in the forest at Plastic Lake is anthropogenic in origin. 相似文献
18.
CO2 applied for Free-Air CO2 Enrichment (FACE) experiments is strongly depleted in 13C and thus provides an opportunity to study C turnover in soil organic matter (SOM) based on its δ
13C value. Simultaneous use of 15N labeled fertilizers allows N turnover to be studied. Various SOM fractionation approaches (fractionation by density, particle
size, chemical extractability etc.) have been applied to estimate C and N turnover rates in SOM pools. The thermal stability
of SOM coupled with C and N isotopic analyses has never been studied in experiments with FACE. We tested the hypothesis that
the mean residence time (MRT) of SOM pools is inversely proportional to its thermal stability. Soil samples from FACE plots
under ambient (380 ppm) and elevated CO2 (540 ppm; for 3 years) treatments were analyzed by thermogravimetry coupled with differential scanning calorimetry (TG-DSC).
Based on differential weight losses (TG) and energy release or consumption (DSC), five SOM pools were distinguished. Soil
samples were heated up to the respective temperature and the remaining soil was analyzed for δ
13C and δ
15N by IRMS. Energy consumption and mass losses in the temperature range 20–200°C were mainly connected with water volatilization.
The maximum weight losses occurred from 200–310°C. This pool contained the largest amount of carbon: 61% of the total soil
organic carbon in soil under ambient treatment and 63% in soil under elevated CO2, respectively. δ
13C values of SOM pools under elevated CO2 treatment showed an increase from −34.3‰ of the pool decomposed between 20–200°C to −18.1‰ above 480°C. The incorporation
of new C and N into SOM pools was not inversely proportional to its thermal stability. SOM pools that decomposed between 20–200
and 200–310°C contained 2 and 3% of the new C, with a MRT of 149 and 92 years, respectively. The pool decomposed between 310–400°C
contained the largest proportion of new C (22%), with a MRT of 12 years. The amount of fertilizer-derived N after 2 years
of application in ambient and elevated CO2 treatments was not significantly different in SOM pools decomposed up to 480°C having MRT of about 60 years. In contrast,
the pool decomposed above 480°C contained only 0.5% of new N, with a MRT of more than 400 years in soils under both treatments.
Thus, the separation of SOM based on its thermal stability was not sufficient to reveal pools with contrasting turnover rates
of C and N.
Responsible Editor: Bernard Nicolardot. 相似文献
19.
Mycorrhizal Hyphal Turnover as a Dominant Process for Carbon Input into Soil Organic Matter 总被引:1,自引:0,他引:1
Douglas L. Godbold Marcel R. Hoosbeek Martin Lukac M. Francesca Cotrufo Ivan A. Janssens Reinhart Ceulemans Andrea Polle Eef J. Velthorst Giuseppe Scarascia-Mugnozza Paolo De Angelis Franco Miglietta Alessandro Peressotti 《Plant and Soil》2006,281(1-2):15-24
The atmospheric concentration of CO2 is predicted to reach double current levels by 2075. Detritus from aboveground and belowground plant parts constitutes the
primary source of C for soil organic matter (SOM), and accumulation of SOM in forests may provide a significant mechanism
to mitigate increasing atmospheric CO2 concentrations. In a poplar (three species) plantation exposed to ambient (380 ppm) and elevated (580 ppm) atmospheric CO2 concentrations using a Free Air Carbon Dioxide Enrichment (FACE) system, the relative importance of leaf litter decomposition,
fine root and fungal turnover for C incorporation into SOM was investigated. A technique using cores of soil in which a C4 crop has been grown (δ13C −18.1‰) inserted into the plantation and detritus from C3 trees (δ13C −27 to −30‰) was used to distinguish between old (native soil) and new (tree derived) soil C. In-growth cores using a fine
mesh (39 μm) to prevent in-growth of roots, but allow in-growth of fungal hyphae were used to assess contribution of fine
roots and the mycorrhizal external mycelium to soil C during a period of three growing seasons (1999–2001). Across all species
and treatments, the mycorrhizal external mycelium was the dominant pathway (62%) through which carbon entered the SOM pool,
exceeding the input via leaf litter and fine root turnover. The input via the mycorrhizal external mycelium was not influenced
by elevated CO2, but elevated atmospheric CO2 enhanced soil C inputs via fine root turnover. The turnover of the mycorrhizal external mycelium may be a fundamental mechanism
for the transfer of root-derived C to SOM. 相似文献
20.
Hongxing Zhang Xiaoping Zhou Fei Lu Junzhu Pang Zongwei Feng Wenzhao Liu Zhiyun Ouyang Xiaoke Wang 《Ecological Research》2011,26(4):735-743
An automated chamber system was employed to measure the soil CO2 efflux (SCE) in situ for 2 years in a conventional wheat field of the Loess Plateau, China under semi-arid conditions. The
annual mean SCE values were 2.44 ± 2.52 μmol m−2 s−1 in 2006 and 2.37 ± 2.33 μmol m−2 s−1 in 2007. Distinct seasonality in the SCE was observed, with significant differences occurring among four periods divided
by harvesting, tillage and sowing. In the period from tillage to sowing, the mean SCE values were 2.82 and 2.69 times the
annual mean values in 2006 and 2007, respectively, and SCE accounted for 39% and 48% of the annual total within 14% and 18%
of the days of the years. Although there were significant exponential correlations between the SCE and soil temperature, and
significant linear correlations between the SCE and soil moisture for measurements conducted in the periods before tillage
and after sowing each year, the SCE from tillage to sowing was significantly beyond the correlation curves. These findings
indicated that seasonal variation in the SCE in a conventional field was controlled not only by soil temperature and moisture,
but also by tillage practice. The confounding effects of climate and practice on SCE should be considered when developing
ways to mitigate soil carbon loss in conventional cropland in semi-arid regions. 相似文献