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1.
Long-term black carbon dynamics in cultivated soil 总被引:7,自引:0,他引:7
Binh Thanh Nguyen Johannes Lehmann James Kinyangi Ron Smernik Susan J. Riha Mark H. Engelhard 《Biogeochemistry》2009,92(1-2):163-176
Black carbon (BC) is a quantitatively important C pool in the global C cycle due to its relative recalcitrance compared with other C pools. However, mechanisms of BC oxidation and accompanying molecular changes are largely unknown. In this study, the long-term dynamics in quality and quantity of BC were investigated in cultivated soil using X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) techniques. BC particles and changes in BC stocks were obtained from soil collected in fields that were cleared from forest by fire at 8 different times in the past (2, 3, 5, 20, 30, 50, 80 and 100 years before sampling) in western Kenya. BC contents rapidly decreased from 12.7 to 3.8 mg C g?1 soil during the first 30 years following deposition, after which they slowly decreased to a steady state at 3.5 mg C g?1 soil. BC-derived C losses from the top 0.1 m over 100 years were estimated at 6,000 kg C ha?1. The initial rapid changes in BC stocks resulted in a mean residence time of only around 8.3 years, which was likely a function of both decomposition as well as transport processes. The molecular properties of BC changed more rapidly on surfaces than in the interior of BC particles and more rapidly during the first 30 years than during the following 70 years. The Oc/C ratios (Oc is O bound to C) and carbonyl groups (C=O) increased over the first 10 and 30 years by 133 and 192%, respectively, indicating oxidation was an important process controlling BC quality. Al, Si, polysaccharides, and to a lesser extent Fe were found on BC particle surfaces within the first few years after BC deposition to soil. The protection by physical and chemical stabilization was apparently sufficient to not only minimize decomposition below detection between 30 and 100 years after deposition, but also physical export by erosion and vertical transport below 0.1 m. 相似文献
2.
To identify the controls on dissolved organic carbon (DOC) production, we incubated soils from 18 sites, a mixture of 52 forest
floor and peats and 41 upper mineral soil samples, at three temperatures (3, 10, and 22°C) for over a year and measured DOC
concentration in the leachate and carbon dioxide (CO2) production from the samples. Concentrations of DOC in the leachate were in the range encountered in field soils (<2 to >50 mg l−1). There was a decline in DOC production during the incubation, with initial rates averaging 0.03–0.06 mg DOC g−1 soil C day−1, falling to averages of 0.01 mg g−1 soil C day−1; the rate of decline was not strongly related to temperature. Cumulative DOC production rates over the 395 days ranged from
less than 0.01 to 0.12 mg g−1 soil C day−1 (0.5–47.6 mg g−1 soil C), with an average of 0.021 mg g−1 soil C day−1 (8.2 mg g−1 soil C). DOC production rate was weakly related to temperature, equivalent to Q10 values of 0.9 to 1.2 for mineral samples and 1.2 to 1.9 for organic samples. Rates of DOC production in the organic samples
were correlated with cellulose (positively) and lignin (negatively) proportion in the organic matter, whereas in the mineral
samples C and nitrogen (N) provided positive correlations. The partitioning of C released into CO2–C and DOC showed a quotient (CO2–C:DOC) that varied widely among the samples, from 1 to 146. The regression coefficient of CO2–C:DOC production (log10 transformed) ranged from 0.3 to 0.7, all significantly less than 1. At high rates of DOC production, a smaller proportion
of CO2 is produced. The CO2–C:DOC quotient was dependent on incubation temperature: in the organic soil samples, the CO2–C:DOC quotient rose from an average of 6 at 3 to 16 at 22°C and in the mineral samples the rise was from 7 to 27. The CO2–C:DOC quotient was related to soil pH in the organic samples and C and N forms in the mineral samples. 相似文献
3.
Altitudinal changes in carbon storage of temperate forests on Mt Changbai, Northeast China 总被引:8,自引:0,他引:8
Biao Zhu Xiangping Wang Jingyun Fang Shilong Piao Haihua Shen Shuqing Zhao Changhui Peng 《Journal of plant research》2010,123(4):439-452
A number of studies have investigated regional and continental scale patterns of carbon (C) stocks in forest ecosystems; however,
the altitudinal changes in C storage in different components (vegetation, detritus, and soil) of forest ecosystems remain
poorly understood. In this study, we measured C stocks of vegetation, detritus, and soil of 22 forest plots along an altitudinal
gradient of 700–2,000 m to quantify altitudinal changes in carbon storage of major forest ecosystems (Pinus koraiensis and broadleaf mixed forest, 700–1,100 m; Picea and Abies forest, 1,100–1,800 m; and Betula ermanii forest, 1,800–2,000 m) on Mt Changbai, Northeast China. Total ecosystem C density (carbon stock per hectare) averaged 237 t C ha−1 (ranging from 112 to 338 t C ha−1) across all the forest stands, of which 153 t C ha−1 (52–245 t C ha−1) was stored in vegetation biomass, 14 t C ha−1 (2.2–48 t C ha−1) in forest detritus (including standing dead trees, fallen trees, and floor material), and 70 t C ha−1 (35–113 t C ha−1) in soil organic matter (1-m depth). Among all the forest types, the lowest vegetation and total C density but the highest
soil organic carbon (SOC) density occurred in Betula ermanii forest, whereas the highest detritus C density was observed in Picea and Abies forest. The C density of the three ecosystem components showed distinct altitudinal patterns: with increasing altitude, vegetation
C density decreased significantly, detritus C density first increased and then decreased, and SOC density exhibited increasing
but insignificant trends. The allocation of total ecosystem C to each component exhibited similar but more significant trends
along the altitudinal gradient. Our results suggest that carbon storage and partitioning among different components in temperate
forests on Mt Changbai vary greatly with forest type and altitude. 相似文献
4.
Permafrost soils are a significant global store of carbon (C) with the potential to become a large C source to the atmosphere.
Climate change is causing permafrost to thaw, which can affect primary production and decomposition, therefore affecting ecosystem
C balance. To understand future responses of permafrost soils to climate change, we inventoried current soil C stocks, investigated
∆14C, C:N, δ13C, and δ15N depth profiles, modeled soil C accumulation rates, and calculated decadal net ecosystem production (NEP) in subarctic tundra
soils undergoing minimal, moderate, and extensive permafrost thaw near Eight Mile Lake (EML) in Healy, Alaska. We modeled
decadal and millennial soil C inputs, decomposition constants, and C accumulation rates by plotting cumulative C inventories
against C ages based on radiocarbon dating of surface and deep soils, respectively. Soil C stocks at EML were substantial,
over 50 kg C m−2 in the top meter, and did not differ much among sites. Carbon to nitrogen ratio, δ13C, and δ15N depth profiles indicated most of the decomposition occurred within the organic soil horizon and practically ceased in deeper,
frozen horizons. The average C accumulation rate for EML surface soils was 25.8 g C m−2 y−1 and the rate for the deep soil accumulation was 2.3 g C m−2 y−1, indicating these systems have been C sinks throughout the Holocene. Decadal net ecosystem production averaged 14.4 g C m−2 y−1. However, the shape of decadal C accumulation curves, combined with recent annual NEP measurements, indicates soil C accumulation
has halted and the ecosystem may be becoming a C source. Thus, the net impact of climate warming on tundra ecosystem C balance
includes not only becoming a C source but also the loss of C uptake capacity these systems have provided over the past ten
thousand years. 相似文献
5.
Plant and soil carbon accumulation following fire in Mediterranean woodlands in Spain 总被引:1,自引:0,他引:1
We measured plant and soil carbon (C) storage following canopy-replacing wildfires in woodlands of northeastern Spain that
include an understory of shrubs dominated by Quercus coccifera and an overstory of Pinus halepensis trees. Established plant succession models predict rapid shrub recovery in these ecosystems, and we build on this model by
contrasting shrub succession with long-term C storage in soils, trees, and the whole ecosystem. We used chronosequence and
repeated sampling approaches to detect change over time. Aboveground plant C increased from <100 to ~3,000 g C m−2 over 30 years following fire, which is substantially less than the 5,942 ± 487 g C m−2 (mean ±1 standard error) in unburned sites. As expected, shrubs accumulated C rapidly, but the capacity for C storage in
shrubs was <600 g C m−2. Pines were the largest plant C pool in sites >20 years post fire, and accounted for all of the difference in plant C between
older burned sites and unburned sites. In contrast, soil C was initially higher in burned sites (~4,500 g C m−2) than in unburned sites (3,264 ± 261 g C m−2) but burned site C declined to unburned levels within 10 years after fire. Combining these results with prior research suggests
two states for C storage. When pine regeneration is successful, ~9,200 g C m−2 accumulate in woodlands but when tree regeneration fails (due to microclimatic stress or short fire return intervals), ecosystem
C storage of ~4,000 g C m−2 will occur in the resulting shrublands. 相似文献
6.
Soil carbon storage, litterfall and CO2 efflux in fertilized and unfertilized larch (Larix leptolepis) plantations 总被引:1,自引:0,他引:1
Choonsig Kim 《Ecological Research》2008,23(4):757-763
This study evaluated the effects of forest fertilization on the forest carbon (C) dynamics in a 36-year-old larch (Larix leptolepis) plantation in Korea. Above- and below-ground C storage, litterfall, root decomposition and soil CO2 efflux rates after fertilization were measured for 2 years. Fertilizers were applied to the forest floor at rates of 112 kg
N ha−1 year−1, 75 kg P ha−1 year−1 and 37 kg K ha−1 year−1 for 2 years (May 2002, 2003). There was no significant difference in the above-ground C storage between fertilized (41.20 Mg C
ha−1) and unfertilized (42.25 Mg C ha−1) plots, and the C increment was similar between the fertilized (1.65 Mg C ha−1 year−1) and unfertilized (1.52 Mg C ha−1 year−1) plots. There was no significant difference in the soil C storage between the fertilized and unfertilized plots at each soil
depth (0–15, 15–30 and 30–50 cm). The organic C inputs due to litterfall ranged from 1.57 Mg C ha−1 year−1 for fertilized to 1.68 Mg C ha−1 year−1 for unfertilized plots. There was no significant difference in the needle litter decomposition rates between the fertilized
and unfertilized plots, while the decomposition of roots with 1–2 mm diameters increased significantly with the fertilization
relative to the unfertilized plots. The mean annual soil CO2 efflux rates for the 2 years were similar between the fertilized (0.38 g CO2 m−2 h−1) and unfertilized (0.40 g CO2 m−2 h−1) plots, which corresponded with the similar fluctuation in the organic carbon (litterfall, needle and root decomposition)
and soil environmental parameters (soil temperature and soil water content). These results indicate that little effect on
the C dynamics of the larch plantation could be attributed to the 2-year short-term fertilization trials and/or the soil fertility
in the mature coniferous plantation used in this study. 相似文献
7.
Jana Woelfel Rhena Schumann Florian Peine Anita Flohr Aleksandra Kruss Jaroslaw Tegowski Philippe Blondel Christian Wiencke Ulf Karsten 《Polar Biology》2010,33(9):1239-1253
During summer 2007, Arctic microphytobenthic potential primary production was measured at several stations around the coastline
of Kongsfjorden (Svalbard, Norway) at ≤5 m water depth and at two stations at five different water depths (5, 10, 15, 20,
30 m). Oxygen planar optode sensor spots were used ex situ to determine oxygen exchange in the overlying water of intact sediment
cores under controlled light (ca. 100 μmol photons m−2 s−1) and temperature (2–4°C) conditions. Patches of microalgae (mainly diatoms) covering sandy sediments at water depths down
to 30 m showed high biomass of up to 317 mg chl a m−2. In spite of increasing water depth, no significant trend in “photoautotrophic active biomass” (chl a, ratio living/dead cells, cell sizes) and, thus, in primary production was measured at both stations. All sites from ≤5 to
30 m water depth exhibited variable rates of net production from −19 to +40 mg O2 m−2 h−1 (−168 to +360 mg C m−2 day−1) and gross production of about 2–62 mg O2 m−2 h−1 (17–554 mg C m−2 day−1), which is comparable to other polar as well as temperate regions. No relation between photoautotrophic biomass and gross/net
production values was found. Microphytobenthos demonstrated significant rates of primary production that is comparable to
pelagic production of Kongsfjorden and, hence, emphasised the importance as C source for the zoobenthos. 相似文献
8.
Future Spruce Budworm Outbreak May Create a Carbon Source in Eastern Canadian Forests 总被引:2,自引:0,他引:2
Caren C. Dymond Eric T. Neilson Graham Stinson Kevin Porter David A. MacLean David R. Gray Michel Campagna Werner A. Kurz 《Ecosystems》2010,13(6):917-931
Spruce budworm (Choristoneura fumiferana Clem.) is an important and recurrent disturbance throughout spruce (Picea sp.) and balsam fir (Abies balsamea L.) dominated forests of North America. Forest carbon (C) dynamics in these ecosystems are affected during insect outbreaks
because millions of square kilometers of forest suffer growth loss and mortality. We tested the hypothesis that a spruce budworm
outbreak similar to those in the past could switch a forest from a C sink to a source in the near future. We used a model
of ecosystem C to integrate past spruce budworm impact sequences with current forest management data on 106,000 km2 of forest in eastern Québec. Spruce budworm-caused mortality decreased stand-level merchantable C stocks by 11–90% and decreased
ecosystem C stocks by 2–10% by the end of the simulation. For the first 13 years (2011–2024), adding spruce budworm significantly
reduced ecosystem C stock change for the landscape from a sink (4.6 ± 2.7 g C m−2 y−1 in 2018) to a source (−16.8 ± 3.0 g C m−2 y−1 in 2018). This result was mostly due to reduced net primary production. The ecosystem stock change was reduced on average
by 2 Tg C y−1 for the entire simulated area. This study provides the first estimate that spruce budworm can significantly affect the C
sink or source status of a large landscape. These results indicate that reducing spruce budworm impacts on timber may also
provide an opportunity to mitigate a C source. 相似文献
9.
Matteo Campioli Anders Michelsen Andreas Demey Annemie Vermeulen Roeland Samson Raoul Lemeur 《Ecosystems》2009,12(5):760-776
Mesic–dry tundras are widespread in the Arctic but detailed assessments of net primary production (NPP) and ecosystem carbon
(C) stocks are lacking. We addressed this lack of knowledge by determining the seasonal dynamics of aboveground vascular NPP,
annual NPP, and whole-ecosystem C stocks in five mesic–dry tundras in Northern Sweden with contrasting microtopography, altitude,
and dominant species. Those measurements were paralleled by the stock assessments of nitrogen (N), the limiting nutrient.
The vascular production was determined by harvest or in situ growing units, whereas the nonvascular production was obtained
from average species growth rates, previously assessed at the sites. Results showed that aboveground vascular NPP (15–270 g m−2), annual NPP (214–282 g m−2 or 102–137 g C m−2) and vegetation biomass (330–2450 g m−2) varied greatly among communities. Vegetation dominated by Empetrum hermaphroditum is more productive than Cassiope tetragona vegetation. Although the large majority of the apical NPP occurred in early-mid season (85%), production of stems and evergreen
leaves proceeded until about 2 weeks before senescence. Most of the vascular vegetation was belowground (80%), whereas most
of the vegetation production occurred aboveground (85%). Ecosystem C and N stocks were 2100–8200 g C m−2 and 80–330 g N m−2, respectively, stored mainly in the soil turf and in the fine organic soil. Such stocks are comparable to the C and N stocks
of moister tundra types, such as tussock tundra.
Author Contributions Matteo Campioli, Anders Michelsen, Roeland Samson, Raoul Lemeur—conceived and designed study, Matteo Campioli, Anders Michelsen,
Andreas Demey, Annemie Vermeulen—performed research, Matteo Campioli—analyzed data, and Matteo Campioli—wrote the paper. 相似文献
10.
11.
The Effects of Permafrost Thaw on Soil Hydrologic, Thermal, and Carbon Dynamics in an Alaskan Peatland 总被引:1,自引:0,他引:1
Jonathan A. O’Donnell M. Torre Jorgenson Jennifer W. Harden A. David McGuire Mikhail Z. Kanevskiy Kimberly P. Wickland 《Ecosystems》2012,15(2):213-229
Recent warming at high-latitudes has accelerated permafrost thaw in northern peatlands, and thaw can have profound effects
on local hydrology and ecosystem carbon balance. To assess the impact of permafrost thaw on soil organic carbon (OC) dynamics,
we measured soil hydrologic and thermal dynamics and soil OC stocks across a collapse-scar bog chronosequence in interior
Alaska. We observed dramatic changes in the distribution of soil water associated with thawing of ice-rich frozen peat. The
impoundment of warm water in collapse-scar bogs initiated talik formation and the lateral expansion of bogs over time. On
average, Permafrost Plateaus stored 137 ± 37 kg C m−2, whereas OC storage in Young Bogs and Old Bogs averaged 84 ± 13 kg C m−2. Based on our reconstructions, the accumulation of OC in near-surface bog peat continued for nearly 1,000 years following
permafrost thaw, at which point accumulation rates slowed. Rapid decomposition of thawed forest peat reduced deep OC stocks
by nearly half during the first 100 years following thaw. Using a simple mass-balance model, we show that accumulation rates
at the bog surface were not sufficient to balance deep OC losses, resulting in a net loss of OC from the entire peat column.
An uncertainty analysis also revealed that the magnitude and timing of soil OC loss from thawed forest peat depends substantially
on variation in OC input rates to bog peat and variation in decay constants for shallow and deep OC stocks. These findings
suggest that permafrost thaw and the subsequent release of OC from thawed peat will likely reduce the strength of northern
permafrost-affected peatlands as a carbon dioxide sink, and consequently, will likely accelerate rates of atmospheric warming. 相似文献
12.
Impact of long-term nitrogen addition on carbon stocks in trees and soils in northern Europe 总被引:4,自引:2,他引:2
The aim of this study was to quantify the effects of fertiliser N on C stocks in trees (stems, stumps, branches, needles,
and coarse roots) and soils (organic layer +0–10 cm mineral soil) by analysing data from 15 long-term (14–30 years) experiments
in Picea abies and Pinus sylvestris stands in Sweden and Finland. Low application rates (30–50 kg N ha−1 year−1) were always more efficient per unit of N than high application rates (50–200 kg N ha−1 year−1). Addition of a cumulative amount of N of 600–1800 kg N ha−1 resulted in a mean increase in tree and soil C stock of 25 and 11 kg (C sequestered) kg−1 (N added) (“N-use efficiency”), respectively. The corresponding estimates for NPK addition were 38 and 11 kg (C) kg−1 (N). N-use efficiency for C sequestration in trees strongly depended on soil N status and increased from close to zero at
C/N 25 in the humus layer up to 40 kg (C) kg−1 (N) at C/N 35 and decreased again to about 20 kg (C) kg−1 (N) at C/N 50 when N only was added. In contrast, addition of NPK resulted in high (40–50 kg (C) kg−1 (N)) N-use efficiency also at N-rich (C/N 25) sites. The great difference in N-use efficiency between addition of NPK and
N at N-rich sites reflects a limitation of P and K for tree growth at these sites. N-use efficiency for soil organic carbon
(SOC) sequestration was, on average, 3–4 times lower than for tree C sequestration. However, SOC sequestration was about twice
as high at P. abies as at P. sylvestris sites and averaged 13 and 7 kg (C) kg−1 (N), respectively. The strong relation between N-use efficiency and humus C/N ratio was used to evaluate the impact of N
deposition on C sequestration. The data imply that the 10 kg N ha−1 year−1 higher deposition in southern Sweden than in northern Sweden for a whole century should have resulted in 2.0 ± 1.0 (95% confidence
interval) kg m−2 more tree C and 1.3 ± 0.5 kg m−2 more SOC at P. abies sites in the south than in the north for a 100-year period. These estimates are consistent with differences between south
and north in tree C and SOC found by other studies, and 70–80% of the difference in SOC can be explained by different N deposition. 相似文献
13.
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
14.
Sempere F Martínez-Soria V Palau J Penya-Roja JM San-Valero P Gabaldón C 《Bioprocess and biosystems engineering》2011,34(7):859-867
The removal of styrene-polluted air emissions by biotrickling filtration was performed to evaluate the influence of using
nitrate and urea as a nitrogen source in the nutrient solution supplied to two bioreactors run in parallel under the same
operational conditions for 3 months. The use of urea resulted in less biomass content along the packed bed and better performance
of the process, with a maximum elimination capacity (EC) of 57.6 g C m−3 h−1 (removal efficiency (RE) of 88.3% and empty bed residence time (EBRT) of 60 s), which was around 54% higher than when using
nitrate. EBRTs of 60, 30 and 15 s were evaluated with a urea-based nutrient supply. By decreasing the EBRT from 60 to 30 s
the styrene concentration that could be treated with REs above 80% was almost the half, from 1,100 to 600 mg C m−3, resulting in ECs of 52.8 g C m−3 h−1. Working at 15 s was not possible to obtain REs higher than 40% with a maximum EC of 28.5 g C m−3 h−1. 相似文献
15.
Permissible Value for Vanadium in Allitic Udic Ferrisols Based on Physiological Responses of Green Chinese Cabbage and Soil Microbes 总被引:2,自引:0,他引:2
Greenhouse experiments were conducted to study the permissible value of vanadium (V) based on the growth and physiological
responses of green Chinese cabbage (Brassica chinensis L.), and effects of V on microbial biomass carbon (MBC) and enzyme activities in allitic udic ferrisols were also studied.
The results showed that biomass of cabbage grown on soil treated with 133 mg V kg−1 significantly decreased by 25.1% compared with the control (P < 0.05). Vanadium concentrations in leaves and roots increased with increasing soil V concentration. Contents of vitamin
C (Vc) increased by 10.3%, while that of soluble sugar in leaves significantly decreased by 54.0% when soil V concentration
was 133 mg kg−1, respectively. The uptake of essential nutrient elements by cabbage was disturbed when soil V concentration exceeded 253 mg kg−1. Soil MBC was significantly stimulated by 15.5%, while dehydrogenase activity significantly decreased by 62.8% and urease
activity slightly changed at treatment of 133 mg V kg−1 as compared with the control, respectively. Therefore, the permissible value of V in allitic udic ferrisols is proposed as
130 mg kg−1. 相似文献
16.
Modification of fire regimes in tropical savannas can have significant impacts on the global carbon (C) cycle, and therefore,
on the climate system. In Australian tropical savannas, there has been recent, large-scale implementation of fire management
that aims to decrease Kyoto-compliant non-CO2 greenhouse gas emissions by reducing late dry season intense fires through strategic early dry season burning. However, there
is no accounting for changes to soil C stocks resulting from changes to savanna fire management, although impacts on these
pools may be considerable. We present a hypothesis that soil C storage is greatest under low intensity fires with an intermediate
fire return interval. Simulations using the CENTURY Soil Organic Matter Model confirmed this hypothesis with greatest soil
C storage under a fire regime of one low intensity fire every 5 years. Key areas of uncertainty for CENTURY model simulations
include fine root dynamics, charcoal production and nitrogen (N) cycling, and better understanding of these processes could
improve model predictions. Soil C stocks measured in the field after 5 years of annual, 3 year and unburned fire treatments
were not significantly different (range 41–58 t ha−1), but further CENTURY modelling suggests that changes in fire management will take up to 100 years to have a detectable impact
(+4 t ha−1) on soil C stocks. However, implementation of fire management that reduces fire frequency and intensity within the large
area of intact savanna landscapes in northern Australia could result in emissions savings of 0.17 t CO2-e ha−1 y−1, four times greater than reductions of non-CO2 emissions. 相似文献
17.
Forests soils should be neither sinks nor sources of carbon in a long-term perspective. From a Swedish perspective the time
since the last glaciation has probably not been long enough to reach a steady state, although changes are currently very slow.
In a shorter perspective, climatic and management changes over the past 100 years have probably created imbalances between
litter input to soils and organic carbon mineralisation. Using extant data on forest inventories, we applied models to analyse
possible changes in the carbon stocks of Swedish forest soils. The models use tree stocks to provide estimates of tree litter
production, which are fed to models of litter decomposition and from which carbon stocks are calculated. National soil carbon
stocks were estimated to have increased by 3 Tg yr−1 or 12–13 g m−2 yr−1 in the period 1926–2000 and this increase will continue because soil stocks are far from equilibrium with current litter
inputs. The figure obtained is likely to be an underestimation because wet sites store more carbon than predicted here and
the inhibitory effect of nitrogen deposition on soil carbon mineralisation was neglected. Knowledge about site history prior
to the calculation period determines the accuracy of current soil carbon stocks estimates, although changes can be more accurately
estimated.
This article has previously been published in issue 82/3, under DOI . 相似文献
18.
Copepods are considered to be the main component of the Arctic marine zooplankton. We examined the copepod distribution and
diversity off Franz Josef Land (northern Barents Sea) in August 2006 and 2007. A total of 18 and 14 copepod taxa were identified
from the sampling layers (100–0 m or bottom–0 m) in 2006 and in 2007, respectively. There were no significant differences
in the total copepod abundance between the years (means ± SE: 118,503 ± 24,115 individuals m−2 in 2006 vs. 113,932 ± 28,564 individuals m−2 in 2007). However, the copepod biomass in 2006 (4,518 ± 1,091 mg C m−2) exceeded clearly the value in 2007 (1,253 ± 217 mg C m−2). The copepod community showed low species richness and diversity in both years (Simpson index D: 0.34 and 0.38, respectively).
Biomass of the large and small copepod species strongly decreased from 2006 to 2007. The total abundance of copepods was negatively
correlated with water temperature in 2006 and positively correlated with salinity in 2007. The patchiness in copepod distribution
was associated with local hydrography and temperature conditions. 相似文献
19.
Soil Inorganic N Leaching in Edges of Different Forest Types Subject to High N Deposition Loads 总被引:2,自引:0,他引:2
Karen Wuyts An De Schrijver Jeroen Staelens Lotte Van Nevel Sandy Adriaenssens Kris Verheyen 《Ecosystems》2011,14(5):818-834
We report on soil leaching of dissolved inorganic nitrogen (DIN) along transects across exposed edges of four coniferous and
four deciduous forest stands. In a 64-m edge zone, DIN leaching below the main rooting zone was enhanced relative to the interior
(at 128 m from the edge) by 21 and 14 kg N ha−1 y−1 in the coniferous and deciduous forest stands, respectively. However, the patterns of DIN leaching did not univocally reflect
those of DIN throughfall deposition. DIN leaching in the first 20 m of the edges was lower than at 32–64 m from the edge (17
vs. 36 kg N ha−1 y−1 and 15 vs. 24 kg N ha−1 y−1 in the coniferous and deciduous forests, respectively). Nitrogen stocks in the mineral topsoil (0–30 cm) were, on average,
943 kg N ha−1 higher at the outer edges than in the interior, indicating that N retention in the soil is probably one of the processes
involved in the relatively low DIN leaching in the outer edges. We suggest that a complex of edge effects on biogeochemical
processes occurs at the forest edges as a result of the interaction between microclimate, tree dynamics (growth and litterfall),
and atmospheric deposition of N and base cations. 相似文献
20.
Janine Bolliger Frank Hagedorn Jens Leifeld Jürgen Böhl Stephan Zimmermann Reto Soliva Felix Kienast 《Ecosystems》2008,11(6):895-907
We assessed how consequences of future land-use change may affect size and spatial shifts of C stocks under three potential
trends in policy—(a) business-as-usual: continuation of land-use trends observed during the past 15 years; (b) extensification:
full extensification of open-land; and (c) liberalization: full reforestation potential. The build-up times for the three
scenarios are estimated at 30, 80 and 100 years, respectively. Potential C-stock change rates are derived from the literature.
Whereas the business-as-usual scenario would cause marginal changes of 0.5%, liberalization would provoke a 13% increase in
C stocks (+62 MtC). Gains of 24% would be expected for forests (+95 MtC), whereas open-land C stock would decrease 27% (−33 MtC).
Extensification would lead to a C stock decrease of 3% (−12 MtC). Whereas forest C is expected to increase 12% (+36.5 MtC)
at high elevations, stocks of open-land C would decline 38.5% (−48.5 MtC). Most affected are unfavorable grasslands, which
increase in area (+59%) but contribute only 14.5% to the C stocks. C sinks would amount to 0.6 MtC y−1 assuming a build-up time of 100 years for the liberalization scenario. C stocks on the current forest area are increasing
by 1 MtC y−1. The maximal total C sink of 1.6 MtC might thus suffice to compensate for agricultural greenhouse gases (2004: 1.4 Mt CO2–C equivalents), but corresponds only to 11–13% of the anthropogenic greenhouse gas emission in Switzerland. Thus, even the
largest of the expected terrestrial C stocks under liberalization will be small in comparison with current emissions of anthropogenic
greenhouse gases. 相似文献