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1.
Decomposition rates of peat and cellulose, and oxygen consumption rates were studied in three minerotrophic peat mires in Sasakami, central Japan. These mires had differences in topography, pedology and hydrology. Two dominant vegetation types in each mire, a Sphagnum palustre–S. cuspidatum community and a Rhynchospora fauriei community, were selected as the decomposition study sites. The objective of this study was to examine how the environmental and vegetational differences in mires correlate with the activity of decomposition. Decomposition rates of peat and the rates of cellulolysis were studied in the field for 6 months. Oxygen consumption rates were measured in the field using a closed chamber equipped with an oxygen electrode. In situ peat decomposition rates showed significant differences among the three mires, whereas in situ cellulolysis rates showed significant differences between communities. Peat mass loss rates positively correlated with the nitrogen and carbon concentration of the peat. Cellulolysis rates positively correlated with the range of water table fluctuation. Oxygen consumption rates showed significant negative correlation with the averaged and minimum water table depth, and positive correlation with the range of water table fluctuation. There was a significant positive correlation between cellulolysis rates and oxygen consumption rates. These are useful parameters for evaluating how the decomposition activity in soil depends on the vegetation types and water conditions.  相似文献   

2.
Carbon dioxide emissions and the mass loss of peat incubated in situ were measured in peat soils in the Australian Alps. The carbon chemistry of incubated peats was characterized using 13C nuclear magnetic resonance (NMR). In situ decomposition decreased as a function of increasing alkyl carbon content of the initial organic matter, providing direct evidence of the oft‐cited link between substrate quality and decomposition rates. More mass loss occurred in the bog peat samples than in the dried peat samples. However, at the peat surface, the amount of CO2 emitted was not significantly different between bog peat and dried peat. Carbon inputs, and therefore the sink or source status, of these peats are yet to be quantified.  相似文献   

3.
Forested peatlands contain large pools of terrestrial carbon. As well as drainage, forest management such as fertilizer application can affect these pools. We studied the effect of wood ash (application rates 0, 5 and 15 t ha?1) on the heterotrophic soil respiration (CO2 efflux), cellulose decomposition, soil nutrients, biomass production and amount of C accumulated in a tree stand on a pine‐dominated drained mire in central Finland. The ash was spread 13 years before the respiration measurements. The annual CO2 efflux was statistically modelled using soil temperature as the driving variable. Wood ash application increased the amounts of mineral nutrients of peat substantially and increased soil pH in the uppermost 10 cm layer by 1.5–2 pH units. In the surface peat, the decomposition rate of cellulose in the ash plots was roughly double that in control plots. Annual CO2 efflux was least on the unfertilized site, 238 g CO2‐C m?2 year?1. The use of wood ash nearly doubled CO2 efflux to 420–475 g CO2‐Cm?2 year?1 on plots fertilized with 5–15 t ha?1 of ash, respectively. Furthermore, ash treatments resulted also in increased stand growth, and during the measurement year, the growing stand on ash plots accumulated carbon 11–12 times faster than the control plot. The difference between peat C emission and amount of C sequestered by trees on the ash plots was 43–58 g C m?2, while on the control plot it was 204 g C m?2. Our conclusion is that adding wood ash as a fertilizer increases more C sequestration in the tree stand than C efflux from the peat.  相似文献   

4.
A field survey was carried out from April to October, 1992 in the Miyatoko Mire in Fukushima Prefecture, Japan, to determine the characteristics of the microbial community and cellulose decomposition rates in the peat soil. A total of 14 study sites were selected, including three types; hummocks (type I), hollows covered with Sphagnum (type II), hollows and streams without Sphagnum (type III). The numbers of fungi (2-1,000×104 CFU g-1) and bacteria (8.5-9,000 ×105 CFU g-1) varied with the sites and sampling dates: seasonal fluctuations were especially high in hummocks. The numbers of cellulolytic fungi (4.7-300×;104 CFU g-1) and cellulolytic bacteria (1.5-9.2×105 CFU g-1) also differed between sites. Cellulolytic fungi were predominant in the Sphagnum peat of type I, while cellulolytic bacteria were predominant in the peat soil of type III. Decomposition rates of cellulose filter paper for the 6 month period ranged from 0.01 to 0.83, and tended to be higher in the peat of type II than type I.  相似文献   

5.
Decomposition rate and composition of the soil arthropod community were studied in a severely and a less-severely burned patch of a Mediterranean Aleppo pine forest burned by a large-scale summer wildfire. Decomposition rates were estimated from the dry mass loss of pure cellulose enclosed in coarse (7 mm) and fine (0.9 mm) mesh bags. The composition of the soil arthropod community was investigated by collecting samples of the burned organic horizon and extracting the animals. The decomposition of cellulose followed the same pattern in both burned patches and mesh bag treatments indicated a similar pattern of decomposer biota activity. Twenty-one arthropod taxa were collected in the less-severely burned patch and sixteen taxa in the severely burned patch; the annual density of their populations was 571.8 and 382.0 ind·m–2, respectively. Season, post-fire age and fire severity were the determinants for the composition of soil arthropod community. Under the conditions studied, the role of soil arthropods in the decomposition process seems to be less critical as decomposition was successfully accomplished despite both the low number and density of soil arthropod taxa.  相似文献   

6.
Tropical acid peat land could be an emission source of greenhouse gases, especially, of methane, because peat soil contains large amount of carbon. When these acid peat lands are utilized for farming, adjustment of the acid condition by adding lime (CaCO3) becomes essential. However, by adding lime to these soils, methane and carbon dioxide production potentials were increased in various acid peat soils. Soluble organic carbon also increased in soils by the lime addition. It was due to that the soil pH rose by liming and the decomposition of organic matter was enhanced under these conditions.  相似文献   

7.
Between 72 and 88% of carbon (C) loss in forest litter decomposition returns to the atmosphere in the form of carbon dioxide. The share of water-soluble organic products does not exceed 3–4%. Between 8% under spruce and 25% under aspen and pine of the total C loss from litter organic matter goes to the formation of humus. Decomposition intensity of the dead organic matter on the soil surface is close to annual litterfall income (except under cedar). The specific rate of decomposition processes among the coniferous litters is minimum for cedar (167 mgC g?1yr?1) and maximum for larch (249 mg C g?1 yr?1). The specific rate of decomposition of organic residues under aspen and birch canopies are 344 and 362 mg C g?1yr?1.  相似文献   

8.
Abundant production of organic matter that decomposes slowly under anaerobic conditions can result in substantial accumulation of soil organic matter in wetlands. Tedious means for estimating production and decomposition of plant material, especially roots, hampers our understanding of organic matter dynamics in such systems. In this paper, I describe a study that amended typical estimates for both production and decomposition of organic matter by measuring net flux of carbon dioxide (CO2) over the peat surface within a conifer swamp, a sedge-dominated marsh, and a bog in the Appalachian Mountain region of West Virginia and western Maryland, USA. The sites are relatively productive, with net primary production (NPP) of 30 to 82.5 mol C m?2 yr?1, but peat deposits are shallow with an average depth of about 1 m. In summer, all three sites showed net CO2 flux from the atmosphere to the peat during the daytime (?20.0 to ?30.5 mmol m?2 d?1), supported by net photosynthesis, which was less than net CO2 flux from the peat into the atmosphere at nighttime (39.2 to 84.5 mmol m?2 d?1), supported by ecosystem respiration. The imbalance between these estimates suggests a net loss of carbon (C) from these ecosystems. The positive net CO2 flux seems to be so high because organic matter decomposition occurs throughout the peat deposit — and as a result concentrations of dissolved inorganic carbon (DIC) in peat pore waters reached 4,000 Μmol L?1 by late November, and concentrations of dissolved organic carbon (DOC) in peat pore waters reached 12,000 Μmol L?1. Comparing different approaches revealed several features of organic matter dynamics: (i) peat accretion in the top 30 cm of the peat deposit results in a C accumulation rate of about 15 mmol m?2 d?1; however, (ii) the entire peat deposit has a negative C balance losing about 20 mmol m?2 d?1.  相似文献   

9.
In peatlands the reduced decomposition rate of plant litter is the fundamental mechanism making these peat-accumulating ecosystems effective carbon sinks. A better knowledge of litter decomposition and nutrient cycling is thus crucial to improve our predictions of the effects of anthropogenic perturbation on the capacity of peatlands to continue to behave as carbon sinks. We investigated patterns of plant litter decomposition and nutrient release along a minerotrophic-ombrotrophic gradient in a bog on the south-eastern Alps of Italy. We determined mass loss as well as P, N, K, and C release of seven vascular plant species and four moss species after 1 year in both native and transplanted habitats. Hence, differences in litter decay were supposed to reflect the degree of adaptability of microbial communities to litter quality. Polyphenols/nutrient and C/nutrient quotients appeared as the main parameters accounting for decomposition rates of Sphagnum litter. In particular, litter of minerotrophic Sphagnum species decomposed always faster than litter of ombrotrophic Sphagnum species, both in native and transplanted habitats. Decomposition rates of vascular plant litter in native habitats were always higher than the corresponding mass loss rates of Sphagnum litter. Minerotrophic forbs showed the fastest decomposition both in native and transplanted habitats in accordance with low C/P and C/N litter quotients. On the other hand, C/P quotient seems to play a primary role also in controlling decomposition of graminoids. Decomposition of deciduous and evergreen shrubs was negatively related to their high lignin content. Nitrogen release from Sphagnum litter was primarily controlled by C/N quotient, so that minerotrophic Sphagnum litter released more N than ombrotrophic Sphagnum litter. Overall, we observed slower N release from litter of ombrotrophic vascular plant species compared to minerotrophic vascular plant species. No single chemical parameter could predict the variability associated with different functional groups. The release of K was very high compared to all the other nutrients and rather similar between ombrotrophic and minerotrophic litter types. In Sphagnum litter, a higher C/P quotient was associated with a slower P mineralisation, whereas a faster P release from vascular plant litter seems primarily associated with lower C/P and polyphenols/P quotients.  相似文献   

10.
We examined how hydrology influenced water chemistry, vegetation, nutrient status, aboveground net primary production (ANPP) and litter decomposition rates in two mires on the South-Eastern Alps of Italy. One of the mires had a modest hydraulic gradient and prevalently acted as a recharge system, although there were short phases of vertical flow reversal during dry periods. This mire was, therefore, prevalently fed by rainwater and was covered by bog-like vegetation, mainly hummocks and scrubs with a ground layer rich in Sphagnum mosses. The other mire presented a steeper hydraulic gradient, with the surface being fed by mineral water either by surface runoff or by vertical, upwards directed ground water flow. Compared to the bog-dominated mire, the pore water was less acidic and richer in telluric cations. This mire was covered by fen-like vegetation, prevalently fen meadows. Nitrogen (N) content in the vegetation was very similar in the two mire sites, while phosphorus (P) content was lower in the fen-dominated site. Contrary to our expectations, ANPP did not differ significantly between the two mire sites while litter decomposition rates were significantly lower in the fen-dominated mire, presumably because of P limitation of decomposers. This suggests that the development of ombrogenous mires in this region need not be due to increased accumulation of peat during succession from mineralwater-fed to rainwater-fed conditions.  相似文献   

11.
Summary The development of a microbial community on cellulose (cellophane film and filter paper) buried in waterlogged soil was observed under a microscope. Throughout the decomposition of the cellulose, the biomass, immobilized N, ATP and gas metabolism of the microbial community were examined. As cellulose decomposition progressed, a microbial succession was recognized. This succession was divided into two stages. In the first stage, a few types of cellulolytic microorganisms predominated on the cellulose. Vigorous decomposition of the cellulose was accompanied by a rapid increase in microbial biomass, and H2 was evolved from the microbial community on the cellulose. In the second stage, the rate of cellulose decomposition was slow. The cellulose remaining was thickly covered with various types of microoganisms. The H2 produced was consumed by the microorganisms closely adhering to the remaining cellulose. In addition, non-cellular organic N accumulated on the remaining cellulose. A large part of the microorganisms seemed to be dormant in this stage. The trends in this microbial succession were similar to those found in ecosystem successions.  相似文献   

12.
北方泥炭地甲烷排放研究: 综述   总被引：7，自引：0，他引：7  
D. Y. F. LAI 《土壤圈》2009,19(4):409-421
Northern peatlands store a large amount of carbon and play a significant role in the global carbon cycle. Owing to the presence of waterlogged and anaerobic conditions, peatlands are typically a source of methane (CH4), a very potent greenhouse gas. This paper reviews the key mechanisms of peatland CH4 production, consumption and transport and the major environmental and biotic controls on peatland CH4 emissions. The advantages and disadvantages of micrometeorological and chamber methods in measuring CH4 fluxes from northern peatlands are also discussed. The magnitude of CH4 flux varies considerably among peatland types (bogs and fens) and microtopographic locations (hummocks and hollows). Some anthropogenic activities including forestry, peat harvesting and industrial emission of sulphur dioxide can cause a reduction in CH4 release from northern peatlands. Further research should be conducted to investigate the in fluence of plant growth forms on CH4 flux from northern peatlands, determine the water table threshold at which plant production in peatlands enhances CH4 release, and quantify peatland CH4 exchange at plant community level with a higher temporal resolution using automatic chambers.  相似文献   

13.
Soil temperature is a major factor affecting organic matter decomposition and thus, global warming may accelerate decomposition processes. However, it remains unclear whether the effects will be similar in climatically different regions. The effects of soil temperatures of 5, 10 and 15 °C on the decomposition of Scots pine (Pinus sylvestris L.) needles were assessed in a 1-year (360 days) growth chamber experiment. Intact peat cores from two climatically different peatland sites (southern and northern Finland) were used as the incubation environments. Needles were incubated in litter bags beneath the living moss layer, and mass loss and nitrogen (N) concentration were determined at 60-day intervals. The rate of mass loss from the needles over time was clearly lower in the 5 °C treatment than at the higher temperatures. Mass loss was strongly related to the accumulated soil temperature sum. In temperatures higher than 5 °C, mass losses were higher in the northern peat. Also, the limit value of decomposition (asymptotic maximum mass loss) was slightly higher in the northern peat (92%), than in the southern peat (87%). The N concentration increased up to a mass loss of 50–60%, whereupon it decreased, while the amount of N (as a percentage of the original amount) remained unchanged until a mass loss of 50–60%, whereupon it decreased linearly. It seems that increasing soil temperatures may result in slightly higher rates of needle litter mass loss and consequent N release in northern peat than in southern peat. The faster decomposition in higher temperatures in the northern peat, together with the slightly higher maximum mass loss value, imply that with climatic warming, susceptibility of boreal peatlands for becoming sources of carbon to the atmosphere may increase towards north.  相似文献   

14.
Data on the input of plant falloff and organic matter decomposition on the surface of the peaty podzolic-gleyic humus-illuvial (Gleyic Podzol) soil under a mature blueberry pine forest in the middle taiga are presented. The fractional composition of the falloff was determined, and constants of decomposition for its components were calculated. The carbon flux to the atmosphere due to the mineralization of plant residues is estimated at 251 g/m2. A close positive correlation (r = 0.71; P < 0.05) was found between the carbon dioxide emission measured using a gas analyzer and the soil temperature at the depth of 10 cm. The CO2 emission for a growing period calculated from the data on its dependence on soil temperature in different years varied from 243 to 313 g C/m2 and was related to weather conditions.  相似文献   

15.
Partitioning soil respiration (SR) into its components, heterotrophic and rhizospheric respiration, is an important step for understanding and modelling carbon (C) cycling in organic soils. However, no partitioning studies on afforested organic soil croplands exist. We separated soil respiration originating from the decomposition of peat (SRP), and aboveground litter (SRL) and root respiration (SRR) in six afforested organic soil croplands in Finland with varying tree species and stand ages using the trenching method. Across the sites temporal variation in SR was primarily related to changes in soil surface temperature (?5 cm), which explained 71–96% of variation in SR rates. Decomposition of peat and litter was not related to changes in water table level, whereas a minor increase in root respiration was observed with the increase in water table depth. Temperature sensitivity of SR varied between the different respiration components: SRP was less sensitive to changes in soil surface temperature than SRL or SRR. Factors explaining spatial variation in SR differed between different respiration components. Annual SRP correlated positively with peat ash content while that of SRL was found to correlate positively with the amount of litter on the forest floor, separately for each tree species. Root respiration correlated positively with the biomass of ground vegetation. From the total soil respiration peat decomposition comprised a major share of 42%; the proportion of autotrophic respiration being 41% and aboveground litter 17%. Afforestation lowered peat decomposition rates. Nevertheless the effect of agricultural history can be seen in peat properties for decades and due to high peat decomposition rates these soils still loose carbon to the atmosphere.  相似文献   

16.
Agroforestry can increase the sequestration of carbon (C) in soils of tropical agroecosystems through increased litter and tree pruning inputs. Decomposition of these inputs is a key process in the formation of soil organic matter and in nutrient cycling. Our objectives were to study decay of tree pruning mulch and effects on soil C and N in a shaded coffee agroecosystem in Hawaii. Chipped tree pruning residues (mulch) were added to coffee plots shaded with the Leucaena hybrid KX2 over three years. We measured mulch decomposition and nitrogen loss over one year and changes in soil carbon and nitrogen (N) over two years. Mass loss of mulch was 80% over one year and followed first-order decay dynamics. There was significant loss from all major biochemical components. Net N loss from the mulch was positive throughout the entire period. The C:N and lignin:N ratios of the mulch declined significantly over the decomposition period. Mulch additions significantly increased soil C and N in the top 20 cm by 10.8 and 2.12 Mg ha−1, respectively. In the no-mulch treatment, there was no significant change in soil C or N concentration, but a decline in soil bulk density led to a significant decline in total soil C. Leucaena mulch can provide an important source of organic C and N to coffee agroecosystems and can help sequester C lost as plant biomass during shade tree management.  相似文献   

17.
The dynamics of the carbon dioxide emissions from the surface of a gleyic iron-illuvial sandy peat podzolic soil under a mature bilberry-sphagnum pine forest were studied during the growing seasons of 2008–2010. The maximum rates of the CO2 emission were observed in late July-early August, and the minimum rates were in October. In the hot summer of 2010, an additional maximum was observed in June. A close positive correlation existed between the intensity of the CO2 emission and the soil temperature (r = 0.71, α = 0.05), whereas no significant correlation was found between the CO2 emission and the soil water content. The coefficient of multiple correlation between the rate of the CO2 emission and the hydrothermic soil characteristics reached 0.57 (at α = 0.05). The total CO2 emission from the soil surface during the growing season was estimated at 68–100 g of C m?2.  相似文献   

18.
Tropical acid peat land could be an emission source of greenhouse gases, especially, of methane, because peat soil contains large amount of carbon. When these acid peat lands are utilized for farming, adjustment of the acid condition by adding lime (CaCO3) becomes essential. However, by adding lime to these soils, methane and carbon dioxide production potentials were increased in various acid peat soils. Soluble organic carbon also increased in soils by the lime addition. It was due to that the soil pH rose by liming and the decomposition of organic matter was enhanced under these conditions.  相似文献   

19.
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20.

Purpose

The carbon sink function of peatlands is primarily driven by a higher production than decomposition of the litter Sphagnum mosses. The observed increase of vascular plants in peatlands could alter the decomposition rate and the carbon (C) cycle through a litter mixing effect, which is still poorly studied. Here, we examine the litter mixing effect of a peat moss (Sphagnum fallax) and two vascular plants (Pinus uncinata and Eriophorum vaginatum) in the field and laboratory-based experiment.

Materials and methods

During the laboratory incubation, mass loss, CO2 production, and dissolved organic carbon concentration were periodically monitored during 51 days. The collected data were then processed in a C dynamics model. The calculated enzymatic activity was correlated to the measured β-glucosidase activity in the litter. In the field experiment, mass loss and CO2 production from litter bags were annually measured for 3 years.

Results and discussion

Both laboratory and field experiments clearly show that the litter mixture, i.e., Sphagnum-Pinus-Eriophorum, had a synergistic effect on decomposition by enhancing the mass loss. Such enhanced mass loss increased the water extractable C and CO2 production in the litter mixture during the laboratory experiment. The synergistic effect was mainly controlled by the Sphagnum-Eriophorum mixture that significantly enhanced both mass loss and CO2 production. Although the β-glucosidase activity is often considered as a major driver of decomposition, mixing the litters did not cause any increase of the activity of this exo-enzyme in the laboratory experiment suggesting that other enzymes can play an important role in the observed effect.

Conclusions

Mixing litters of graminoid and Sphagnum species led to a synergistic effect on litter decomposition. In a context of vegetation dynamics in response to environmental change, such a mixing effect could alter the C dynamics at a larger scale. Identifying the key mechanisms responsible for the synergistic effect on litter decomposition, with a specific focus on the enzymatic activities, is crucial to better predict the capacity of peatlands to act as C sinks.
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