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1.
Seasonal changes in the contribution of root respiration to total soil respiration in a cool-temperate deciduous forest 总被引:32,自引:0,他引:32
A trenching method was used to determine the contribution of root respiration to soil respiration. Soil respiration rates in a trenched plot (R
trench) and in a control plot (R
control) were measured from May 2000 to September 2001 by using an open-flow gas exchange system with an infrared gas analyser. The decomposition rate of dead roots (R
D) was estimated by using a root-bag method to correct the soil respiration measured from the trenched plots for the additional decaying root biomass. The soil respiration rates in the control plot increased from May (240–320 mg CO2 m–2 h–1) to August (840–1150 mg CO2 m–2 h–1) and then decreased during autumn (200–650 mg CO2 m–2 h–1). The soil respiration rates in the trenched plot showed a similar pattern of seasonal change, but the rates were lower than in the control plot except during the 2 months following the trenching. Root respiration rate (R
r) and heterotrophic respiration rate (R
h) were estimated from R
control, R
trench, and R
D. We estimated that the contribution of R
r to total soil respiration in the growing season ranged from 27 to 71%. There was a significant relationship between R
h and soil temperature, whereas R
r had no significant correlation with soil temperature. The results suggest that the factors controlling the seasonal change of respiration differ between the two components of soil respiration, R
r and R
h. 相似文献
2.
Duangrat Satakhun Frédéric Gay Naruenat Chairungsee Poonpipope Kasemsap Pisamai Chantuma Sornprach Thanisawanyangkura Philippe Thaler Daniel Epron 《Ecological Research》2013,28(6):969-979
Natural rubber is a valuable source of income in many tropical countries and rubber trees are increasingly planted in tropical areas, where they contribute to land-use changes that impact the global carbon cycle. However, little is known about the carbon balance of these plantations. We studied the soil carbon balance of a 15-year-old rubber plantation in Thailand and we specifically explored the seasonal dynamic of soil CO2 efflux (F S) in relation to seasonal changes in soil water content (W S) and soil temperature (T S), assessed the partitioning of F S between autotrophic (R A) and heterotrophic (R H) sources in a root trenching experiment and estimated the contribution of aboveground and belowground carbon inputs to the soil carbon budget. A multiplicative model combining both T S and W S explained 58 % of the seasonal variation of F S. Annual soil CO2 efflux averaged 1.88 kg C m?2 year?1 between May 2009 and April 2011 and R A and R H accounted for respectively 63 and 37 % of F S, after corrections of F S measured on trenched plots for root decomposition and for difference in soil water content. The 4-year average annual aboveground litterfall was 0.53 kg C m?2 year?1 while a conservative estimate of belowground carbon input into the soil was much lower (0.17 kg C m?2 year?1). Our results highlighted that belowground processes (root and rhizomicrobial respiration and the heterotrophic respiration related to belowground carbon input into the soil) have a larger contribution to soil CO2 efflux (72 %) than aboveground litter decomposition. 相似文献
3.
Annual variation in soil respiration and its components in a coppice oak forest in Central Italy 总被引:30,自引:0,他引:30
Ana Rey Emiliano Pegoraro Vanessa Tedeschi† Ilaria De Parri† Paul G. Jarvis Riccardo Valentini† 《Global Change Biology》2002,8(9):851-866
In order to investigate the annual variation of soil respiration and its components in relation to seasonal changes in soil temperature and soil moisture in a Mediterranean mixed oak forest ecosystem, we set up a series of experimental treatments in May 1999 where litter (no litter), roots (no roots, by trenching) or both were excluded from plots of 4 m2. Subsequently, we measured soil respiration, soil temperature and soil moisture in each plot over a year after the forest was coppiced. The treatments did not significantly affect soil temperature or soil moisture measured over 0–10 cm depth. Soil respiration varied markedly during the year with high rates in spring and autumn and low rates in summer, coinciding with summer drought, and in winter, with the lowest temperatures. Very high respiration rates, however, were observed during the summer immediately after rainfall events. The mean annual rate of soil respiration was 2.9 µ mol m?2 s?1, ranging from 1.35 to 7.03 µmol m?2 s?1. Soil respiration was highly correlated with temperature during winter and during spring and autumn whenever volumetric soil water content was above 20%. Below this threshold value, there was no correlation between soil respiration and soil temperature, but soil moisture was a good predictor of soil respiration. A simple empirical model that predicted soil respiration during the year, using both soil temperature and soil moisture accounted for more than 91% of the observed annual variation in soil respiration. All the components of soil respiration followed a similar seasonal trend and were affected by summer drought. The Q10 value for soil respiration was 2.32, which is in agreement with other studies in forest ecosystems. However, we found a Q10 value for root respiration of 2.20, which is lower than recent values reported for forest sites. The fact that the seasonal variation in root growth with temperature in Mediterranean ecosystems differs from that in temperate regions may explain this difference. In temperate regions, increases in size of root populations during the growing season, coinciding with high temperatures, may yield higher apparent Q10 values than in Mediterranean regions where root growth is suppressed by summer drought. The decomposition of organic matter and belowground litter were the major components of soil respiration, accounting for almost 55% of the total soil respiration flux. This proportion is higher than has been reported for mature boreal and temperate forest and is probably the result of a short‐term C loss following recent logging at the site. The relationship proposed for soil respiration with soil temperature and soil moisture is useful for understanding and predicting potential changes in Mediterranean forest ecosystems in response to forest management and climate change. 相似文献
4.
Cristina Castanha Biao Zhu Caitlin E. Hicks Pries Katerina Georgiou Margaret S. Torn 《Biogeochemistry》2018,137(1-2):267-279
The breakdown and decomposition of plant inputs are critical for nutrient cycling, soil development, and climate-ecosystem feedbacks, but uncertainties persist in how the rates and products of litter decomposition are affected by soil temperature, rhizosphere, and depth of input. We investigated the effects of soil warming (+ 4 °C), rhizosphere, and depth of litter placement on the decomposition of Avena fatua (wild oat grass) root litter in a Mediterranean grassland ecosystem. Field lysimeters were subjected to three environmental treatments (heating, control, and plant removal) and three 13C-labeled root litter addition treatments (to A horizon, to B horizon, and no-addition disturbance control) for each of two harvest time points. We buried root litter in February 2014 and measured loss of 13C in CO2 from the soil surface and in leachate as dissolved organic carbon (DOC) over two growing seasons. At the end of each growing season we recovered the 13C remaining in the soil. Loss of root litter C occurred almost entirely via heterotrophic respiration, with an estimated < 2% lost as DOC during the initial decay period. The added roots were broken down and incorporated into bulk soil material very quickly; only ~ 30% of added root was visible after 6 months. In the first growing season, decomposition occurred faster in the B than in the A horizon, the latter having greater moisture limitation. Subsequently, there was almost no further decomposition in the B horizon. After two growing seasons, less than 20% of the added root litter C remained in the A or B horizons of all environmental treatments. Heating did not stimulate decomposition, likely because it exacerbated the moisture limitation. However, while plots without plants dried down more slowly than plots with plants, their decomposition rate was not significantly greater, possibly due to the lack of rhizosphere processes such as priming. We conclude that in this Mediterranean grassland ecosystem, soil moisture, which is affected by season, depth, heating, and rhizosphere, plays a dominant role in mediating the effect of those factors on root litter decomposition, which after two seasons did not differ by depth or by treatment. 相似文献
5.
This study aims to assess the effects of corrections for disturbances such as an increased amount of dead roots and an increase
in volumetric soil water content on the calculation of soil CO2 efflux partitioning. Soil CO2 efflux, soil temperature and superficial soil water content were monitored in two young beech sites (H1 and H2) during a
trenching experiment. Trenching induced a significant input of dead root mass that participated in soil CO2 efflux and reduced the soil dissolved organic carbon content, while it increased superficial soil water content within the
trenched plot. Annual soil CO2 efflux in control plots was 528 g C m−2 year−1 at H1 and 527 g C m−2 year−1 at H2. The annual soil CO2 efflux in trenched plots was 353 g C m−2 year−1 at H1 and 425 g C m−2 year−1 at H2. By taking into account annual CO2 efflux from decaying trenched roots, the autotrophic contribution to total soil CO2 efflux reached 69% at H1 and 54% at H2. The partitioning calculation was highly sensitive to the initial root mass estimated
within the trenched plots. Uncertainties in the remaining root mass, the fraction of root C that is incorporated into soil
organic matter during root decomposition, and the root decomposition rate constant had a limited impact on the partitioning
calculation. Corrections for differences in superficial soil water content had a significant impact on annual respired CO2 despite a limited effect on partitioning. 相似文献
6.
Kristell Hergoualc’h Dede T. Hendry Daniel Murdiyarso Louis Vincent Verchot 《Biogeochemistry》2017,135(3):203-220
Heterotrophic respiration is a major component of the soil C balance however we critically lack understanding of its variation upon conversion of peat swamp forests in tropical areas. Our research focused on a primary peat swamp forest and two oil palm plantations aged 1 (OP2012) and 6 years (OP2007). Total and heterotrophic soil respiration were monitored over 13 months in paired control and trenched plots. Spatial variability was taken into account by differentiating hummocks from hollows in the forest; close to palm from far from palm positions in the plantations. Annual total soil respiration was the highest in the oldest plantation (13.8 ± 0.3 Mg C ha?1 year?1) followed by the forest and youngest plantation (12.9 ± 0.3 and 11.7 ± 0.4 Mg C ha?1 year?1, respectively). In contrast, the contribution of heterotrophic to total respiration and annual heterotrophic respiration were lower in the forest (55.1 ± 2.8%; 7.1 ± 0.4 Mg C ha?1 year?1) than in the plantations (82.5 ± 5.8 and 61.0 ± 2.3%; 9.6 ± 0.8 and 8.4 ± 0.3 Mg C ha?1 year?1 in the OP2012 and OP2007, respectively). The use of total soil respiration rates measured far from palms as an indicator of heterotrophic respiration, as proposed in the literature, overestimates peat and litter mineralization by around 21%. Preliminary budget estimates suggest that over the monitoring period, the peat was a net C source in all land uses; C loss in the plantations was more than twice the loss observed in the forest. 相似文献
7.
Differential controls by climate and substrate over the heterotrophic and rhizospheric components of soil respiration 总被引:11,自引:0,他引:11
Laura E. Scott-Denton Todd N. Rosenstiel Russell K. Monson 《Global Change Biology》2006,12(2):205-216
The partitioning of soil respiration rates into the component processes of rhizospheric respiration (because of live roots and those microorganisms that subsist on root exudations) and heterotrophic respiration (because of decomposer microorganisms that subsist on the oxidation of soil organic matter) is difficult to accomplish through experimental observation. In order to minimize disturbance to the soil and maximize preservation of the natural relationships among roots, rhizospheric microorganisms, and decomposers, we conducted a girdling experiment in a subalpine forest dominated by lodgepole pine trees. In two separate years, we girdled trees in small forest plots (5–7 m in diameter) and trenched around the plots to sever invading roots in order to experimentally stop the transport of photosynthate from needles to roots, and eliminate rhizospheric respiration. Soil respiration rates in plots with trees girdled over 1 year prior to measurement were higher than those in plots with trees girdled 2–3 months prior to measurement. These results suggest that any stimulation of respiration because of the experimental artifact of fine root death and addition of labile carbon to the pool of decomposer substrates is slow, and occurs beyond the first growing season after girdling. Compared with control plots with nongirdled trees, soil respiration rates in plots with girdled trees were reduced by 31–44% at the mid‐summer respiratory maximum. An extreme drought during one of the 2 years used for observations caused greater reductions in the heterotrophic component of soil respiration compared with the rhizospheric component. In control plots, we observed a pulse in K2SO4‐extractable carbon during the spring snowmelt period, which was absent in plots with girdled trees. In control plots, soil microbial biomass increased from spring to summer, coincident with a seasonal increase in the rhizospheric component of soil respiration. In plots with girdled trees, the seasonal increase in microbial biomass was lower than in control plots. These results suggest that the observed seasonal increase in rhizospheric respiration rate in control plots was because of an increase in rhizospheric microbial biomass following ‘soil priming’ by a spring‐time pulse in dissolved organic carbon. Winter‐time, beneath‐snow microbial biomass was relatively high in control plots. Soil sucrose concentrations were approximately eight times higher during winter than during spring or summer, possibly being derived from the mechanical damage of shallow roots that use sucrose as protection against low‐temperature extremes. The winter‐time sucrose pulse was not observed in plots with girdled trees. The results of this study demonstrate that (1) the rhizospheric component of soil respiration rate at this site is significant in magnitude, (2) the heterotrophic component of soil respiration rate is more susceptible to seasonal drought than the rhizospheric component, and (3) the trees in this ecosystem exert a major control over soil carbon dynamics by ‘priming’ the soil with sugar exudates during the late‐spring snowmelt period and releasing high concentrations of sucrose to the soil during winter. 相似文献
8.
Diffusive fractionation complicates isotopic partitioning of autotrophic and heterotrophic sources of soil respiration 总被引:1,自引:0,他引:1
ANDREW B. MOYES SARAH J. GAINES ROLF T. W. SIEGWOLF DAVID R. BOWLING 《Plant, cell & environment》2010,33(11):1804-1819
Carbon isotope ratios (δ13C) of heterotrophic and rhizospheric sources of soil respiration under deciduous trees were evaluated over two growing seasons. Fluxes and δ13C of soil respiratory CO2 on trenched and untrenched plots were calculated from closed chambers, profiles of soil CO2 mole fraction and δ13C and continuous open chambers. δ13C of respired CO2 and bulk carbon were measured from excised leaves and roots and sieved soil cores. Large diel variations (>5‰) in δ13C of soil respiration were observed when diel flux variability was large relative to average daily fluxes, independent of trenching. Soil gas transport modelling supported the conclusion that diel surface flux δ13C variation was driven by non‐steady state gas transport effects. Active roots were associated with high summertime soil respiration rates and around 1‰ enrichment in the daily average δ13C of the soil surface CO2 flux. Seasonal δ13C variability of about 4‰ (most enriched in summer) was observed on all plots and attributed to the heterotrophic CO2 source. 相似文献
9.
The aim of this study was to determine how roots and their ectomycorrhizal symbionts affect the fluxes of nitrous oxide (N2O) from nutrient-rich drained organic forest soils. Specifically, the relative impacts of roots and mycorrhizal mycelia on N2O fluxes were investigated using two different trenching treatments, excluding (a) roots or (b) roots and mycorrhizal mycelia, from the soil. N2O fluxes were measured at the soil surface, for 1 year before and 2.5 years after trenching, within the two trenching treatments and on untreated controls. While the exclusion of roots alone did not affect N2O emissions, the simultaneous exclusion of roots and mycorrhizal mycelia doubled N2O emissions, compared to the control plots. Two probable explanations for the increased fluxes were identified: (1) a decreased uptake of nitrogen (N) from the soil, through the mycorrhizal fungi, which increased N availability for the N2O-producing microorganisms, and (2) a decreased uptake of water from the soil, through the mycorrhiza, which increased the soil water content and thus the N2O emissions from denitrification. If the trenching reduced any potential stimulation of N cycling, through rhizodeposition, this mechanism did not outweigh the effects of a discontinued mycorrhizal N and/or water uptake on N2O fluxes. The results of the study emphasise the importance of ectomycorrhiza in regulating N2O emissions from forested organic soils. 相似文献
10.
Tree root and soil heterotrophic respiration as revealed by girdling of boreal Scots pine forest: extending observations beyond the first year 总被引:26,自引:0,他引:26
BHUPINDERPAL-SINGH A. NORDGREN M. OTTOSSON LÖFVENIUS M. N. HÖGBERG P. -E. MELLANDER & P. HÖGBERG 《Plant, cell & environment》2003,26(8):1287-1296
Limitations in available techniques to separate autotrophic (root) and soil heterotrophic respiration have hampered the understanding of forest C cycling. The former is here defined as respiration by roots, their associated mycorrhizal fungi and other micro‐organisms in the rhizosphere directly dependent on labile C compounds leaked from roots. In order to separate the autotrophic and heterotrophic components of soil respiration, all Scots pine trees in 900 m2 plots were girdled to instantaneously terminate the supply of current photosynthates from the tree canopy to roots. Högberg et al. (Nature 411, 789–792, 2001) reported that autotrophic activity contributed up to 56% of total soil respiration during the first summer of this experiment. They also found that mobilization of stored starch (and likely also sugars) in roots after girdling caused an increased apparent heterotrophic respiration on girdled plots. Herein a transient increase in the δ13C of soil CO2 efflux after girdling, thought to be due to decomposition of 13C‐enriched ectomycorrhizal mycelium and root starch and sugar reserves, is reported. In the second year after girdling, when starch reserves of girdled tree roots were exhausted, calculated root respiration increased up to 65% of total soil CO2 efflux. It is suggested that this estimate of its contribution to soil respiration is more precise than the previous based on one year of observation. Heterotrophic respiration declined in response to a 20‐day‐long 6 °C decline in soil temperature during the second summer, whereas root respiration did not decline. This did not support the idea that root respiration should be more sensitive to variations in soil temperature. It is suggested that above‐ground photosynthetic activity and allocation patterns of recent photosynthates to roots should be considered in models of responses of forest C balances to global climate change. 相似文献
11.
Fertilization of boreal forest reduces both autotrophic and heterotrophic soil respiration 总被引:10,自引:0,他引:10
The boreal forest is expected to experience the greatest warming of all forest biomes, raising concerns that some of the large quantities of soil carbon in these systems may be added to the atmosphere as CO2. However, nitrogen deposition or fertilization has the potential to increase boreal forest production and retard the decomposition of soil organic matter, hence increasing both tree stand and soil C storage. The major contributors to soil‐surface CO2 effluxes are autotrophic and heterotrophic respiration. To evaluate the effect of nutrient additions on the relative contributions from autotrophic and heterotrophic respiration, a large‐scale girdling experiment was performed in a long‐term nutrient optimization experiment in a 40‐year‐old stand of Norway spruce in northern Sweden. Trees on three nonfertilized plots and three fertilized plots were girdled in early summer 2002, and three nonfertilized and three fertilized plots were used as control plots. Each plot was 0.1 ha and contained around 230 trees. Soil‐surface CO2 fluxes, soil moisture, and soil temperature were monitored in both girdled and nongirdled plots. In late July, the time of the seasonal maximum in soil‐surface CO2 efflux, the total soil‐CO2 efflux in nongirdled plots was 40% lower in the fertilized than in the nonfertilized plots, while the efflux in girdled fertilized and nonfertilized plots was 50% and 60% lower, respectively, than in the corresponding nongirdled controls. We attribute these reductions to losses of the autotrophic component of the total soil‐surface CO2 efflux. The estimates of autotrophic respiration are conservative as root starch reserves were depleted more rapidly in roots of girdled than in nongirdled trees. Thus, heterotrophic activity was overestimated. Calculated on a unit area basis, both the heterotrophic and autotrophic soil respiration was significantly lower in fertilized plots, which is especially noteworthy given that aboveground production was around three times higher in fertilized than in nonfertilized plots. 相似文献
12.
Wenting Feng Douglas A. Schaefer Jianzhou Li Jianhui Chen Zhili Feng Xiaoming Zou 《Biogeochemistry》2009,92(1-2):119-128
Soil mono- and disaccharides (SS) and total free amino acids (AA) can influence soil microbial activities, whether they are derived from decomposition of organic materials or from plant root exudates. To quantify the relative importance of aboveground plant litter input and belowground inputs of root exudates and root debris on SS and AA, we conducted litter removal, root trenching and tree girdling experiments in a subtropical moist forest of southwest China. We found that concentrations of SS and AA had pronounced seasonal fluctuations. Litter removal markedly reduced SS concentrations, but it had no effect on AA concentrations. Concentrations of SS were significantly correlated with litterfall that had occurred 2 months earlier in the control plots, but that correlation was not observed in the litter removal plots. Multiple-linear regressions of soil respiration and soil temperature on AA concentrations were significant in both control and litter removal plots, but not in the root trenching or tree girdling plots. These results suggest that SS levels are likely to be regulated by aboveground plant litter input, and concentrations of AA are affected by microbial activity that fluctuates with soil temperature and belowground carbon input. 相似文献
13.
Heterotrophic Soil Respiration in Relation to Environmental Factors and Microbial Biomass in Two Wet Tropical Forests 总被引:2,自引:0,他引:2
We examined the correlation between fungal and bacterial biomass, abiotic factors such as soil moisture, carbon in the light
soil fraction and soil nitrogen to a depth of 0–25 cm and heterotrophic soil respiration using a trenching technique – in
a secondary forest (Myrcia splendens, Miconia prasina and Casearia arborea) and a pine (Pinus caribeae) plantation in the Luquillo Experimental Forest in Puerto Rico. Soil respiration was significantly reduced where roots were
excluded for 7 years in both the secondary forest and the pine plantation. Microbial biomass was also significantly reduced
in the root exclusion plots. In root exclusion treatment, total fungal biomass was on average 31 and 65% lower than the control
plots in the pine plantation and the secondary forest, respectively, but the total bacterial biomass was 24 and 8.3% lower
than the control plots in the pine plantation and the secondary forest, respectively. Heterotrophic soil respiration was positively
correlated with fungal biomass (R2=0.63, R2=0.39), bacterial biomass (R2=0.16, R2=0.45), soil moisture (R2=0.41, R2=0.56), carbon in light fraction (R2=0.45, R2=0.39) and total nitrogen (R2=0.69, R2=0.67) in the pine plantation and the secondary forest, respectively. The regression analysis suggested that fungal biomass
might have a greater influence on heterotrophic soil respiration in the pine plantation, while the bacterial biomass might
have a greater influence in the secondary forest. Heterotrophic soil respiration was more sensitive to total N than to carbon
in the light fraction, and soil moisture was a major factor influencing heterotrophic soil respiration in these forests where
temperature is high and relatively invariable. 相似文献
14.
Werner L. Kutsch Tryggve Persson Marion Schrumpf Fernando E. Moyano Martina Mund Stefan Andersson Ernst-Detlef Schulze 《Biogeochemistry》2010,100(1-3):167-183
Three different approaches were used to calculate heterotrophic soil respiration (Rh) and soil carbon dynamics in an old-growth deciduous forest in central Germany. A root and mycorrhiza exclosure experiment in the field separated auto- and heterotrophic soil respiration. It was compared to modeled heterotrophic respiration resulting from two different approaches: a modular component model of soil respiration calculated autotrophic and heterotrophic soil respiration with litter, climate and canopy photosynthesis as input variables. It was calibrated by independent soil respiration measurements in the field. A second model was calibrated by incubation of soil samples from different soil layers in the laboratory. In this case, the annual sum of Rh was calculated by an empirical model including response curves to temperature and a soil moisture. The three approaches showed good accordance during spring and summer and when the annual sums of Rh calculated by the two models were compared. Average Rh for the years 2002–2006 were 436 g C m?2 year?1 (field model) and 417 g C m?2 year?1 (lab-model), respectively. Differences between the approaches revealed specific limitations of each method. The average carbon balance of the Hainich forest soil was estimated to be between 1 and 35 g C m?2 year?1 depending on the model used and the averaging period. A comparison with nighttime data from eddy covariance (EC) showed that EC data were lower than modelled soil respiration in many situations. We conclude that better filter methods for EC nighttime data have to be developed. 相似文献
15.
Samuel Olajuyigbe Brian Tobin Michael Hawkins Maarten Nieuwenhuis 《Plant and Soil》2012,360(1-2):77-91
Background and aims
The decomposition of roots is an important process in the loss of carbon (C) and the mineralization of nitrogen (N) in forest ecosystems. The early stage decomposition rate of Sitka spruce (Picea sitchensis (Bong.) Carr.) roots was determined using trenched plots and decomposition bags.Methods
Stumps of known age were trenched and quadrants (50?cm by 50?cm) excavated from randomly selected stumps every 6?months over 4?years, while the mass loss from buried roots in decomposition bags, divided among four diameter categories (ranging from fine roots <2?mm to large roots >50?mm), was monitored for 27?months. The C and N concentrations of excavated samples at different time points were analysed.Results
The change in total root necromass per quadrant showed a higher decomposition rate-constant (k) of 0.24?±?0.068?year?1 than the k-value of roots in decomposition bags (0.07?±?0.005?year?1). The C concentration (47.24?±?0.609?%) did not significantly change with decomposition. There was a significant increase in the C:N ratio of roots in all diameter categories (fine: 48.92?%, small: 38.53?%, medium 11.71?%, large: 76.25?%) after 4?years of decomposition, driven by N loss. Root diameter accounted for 78?% of the variation in the N concentration of roots as decomposition progressed.Conclusion
Though the trenched plot approach offered an alternative to the more common decomposition bag method for estimating root decomposition, high spatial variation and sampling difficulties may lead to an overestimation of the mass loss from trenched roots, thus, the decomposition bag method gives a more reliable decomposition rate-constant. 相似文献16.
以安徽省滁州市红琊山林场麻栎人工林为研究对象,测定了4种施肥处理(0、0.15、0.30和0.45kg·株-1)林分碳密度,并采用开沟隔离法对不同处理林分休眠期土壤呼吸组分进行测定。结果表明:4种施肥处理林分总碳密度分别为73.68、84.49、87.20和91.70t·hm-2。与对照相比,各施肥处理麻栎树干碳密度、树枝碳密度和枯落物碳密度均有极显著提高(P<0.01)。不同处理林分的土壤总呼吸速率和异养呼吸速率随着施肥量增加呈递增趋势,施肥量为0.45kg·株-1样地土壤总呼吸速率和异养呼吸速率较对照样地分别增加了48.9%和38.6%。不同施肥样地土壤异养呼吸对土壤总呼吸的贡献率远大于根系呼吸,施肥量为0、0.15、0.30和0.45kg·株-1时分别是根系呼吸的5.0、3.8、3.4和3.2倍。土壤呼吸受生物因子和非生物因子共同调控,在所选取的4个指标中(土壤含水量、土壤C/N、根生物量和枯落物有机碳含量),土壤含水量和枯落物有机碳含量与土壤总呼吸及土壤异养呼吸速率均有显著相关性(P<0.05)。 相似文献
17.
Effects of experimental drought on soil respiration and radiocarbon efflux from a temperate forest soil 总被引:6,自引:0,他引:6
WERNER BORKEN ‡ KATHLEEN SAVAGE ERIC A. DAVIDSON SUSAN E. TRUMBORE† 《Global Change Biology》2006,12(2):177-193
Soil moisture affects microbial decay of SOM and rhizosphere respiration (RR) in temperate forest soils, but isolating the response of soil respiration (SR) to summer drought and subsequent wetting is difficult because moisture changes are often confounded with temperature variation. We distinguished between temperature and moisture effects by simulation of prolonged soil droughts in a mixed deciduous forest at the Harvard Forest, Massachusetts. Roofs constructed over triplicate 5 × 5 m2 plots excluded throughfall water during the summers of 2001 (168 mm) and 2002 (344 mm), while adjacent control plots received ambient throughfall and the same natural temperature regime. In 2003, throughfall was not excluded to assess the response of SR under natural weather conditions after two prolonged summer droughts. Throughfall exclusion significantly decreased mean SR rate by 53 mg C m?2 h?1 over 84 days in 2001, and by 68 mg C m?2 h?1 over 126 days in 2002, representing 10–30% of annual SR in this forest and 35–75% of annual net ecosystem exchange (NEE) of C. The differences in SR were best explained by differences in gravimetric water content in the Oi horizon (r2=0.69) and the Oe/Oa horizon (r2=0.60). Volumetric water content of the A horizon was not significantly affected by throughfall exclusion. The radiocarbon signature of soil CO2 efflux and of CO2 respired during incubations of O horizon, A horizon and living roots allowed partitioning of SR into contributions from young C substrate (including RR) and from decomposition of older SOM. RR (root respiration and microbial respiration of young substrates in the rhizosphere) made up 43–71% of the total C respired in the control plots and 41–80% in the exclusion plots, and tended to increase with drought. An exception to this trend was an interesting increase in CO2 efflux of radiocarbon‐rich substrates during a period of abundant growth of mushrooms. Our results suggest that prolonged summer droughts decrease primarily heterotrophic respiration in the O horizon, which could cause increases in the storage of soil organic carbon in this forest. However, the C stored during two summers of simulated drought was only partly released as increased respiration during the following summer of natural throughfall. We do not know if this soil C sink during drought is transient or long lasting. In any case, differential decomposition of the O horizon caused by interannual variation of precipitation probably contributes significantly to observed interannual variation of NEE in temperate forests. 相似文献
18.
Effects of soil frost on soil respiration and its radiocarbon signature in a Norway spruce forest soil 总被引:3,自引:0,他引:3
Apart from a general increase of mean annual air temperature, climate models predict a regional increase of the frequency and intensity of soil frost with possibly strong effects on C cycling of soils. In this study, we induced mild soil frost (up to −5 °C in a depth of 5 cm below surface) in a Norway spruce forest soil by removing the natural snow cover in the winter of 2005/2006. Soil frost lasted from January to April 2006 and was detected down to 15 cm depth. Soil frost effectively reduced soil respiration in the snow removal plots in comparison to undisturbed control plots. On an annual basis 6.2 t C ha−1 a−1 were emitted in the control plots compared with 5.1 t C ha−1 a−1 in the snow removal plots. Only 14% of this difference was attributed to reduced soil respiration during the soil frost period itself, whereas 63% of this difference originated from differences during the summer of 2006. Radiocarbon (Δ14C) signature of CO2 revealed a considerable reduction of heterotrophic respiration on the snow removal plots, only partly compensated for by a slight increase of rhizosphere respiration. Similar CO2 concentrations in the uppermost mineral horizons of both treatments indicate that differences between the treatments originated from the organic horizons. Extremely low water contents between June and October of 2006 may have inhibited the recovery of the heterotrophic organisms from the frost period, thereby enhancing the differences between the control and snow removal plots. We conclude that soil frost triggered a change in the composition of the microbial community, leading to an increased sensitivity of heterotrophic respiration to summer drought. A CO2 pulse during thawing, such as described for arable soils several times throughout the literature, with the potential to partly compensate for reduced soil respiration during soil frost, appears to be lacking for this soil. Our results from this experiment indicate that soil frost reduces C emission from forest soils, whereas mild winters may enhance C losses from forest soils. 相似文献
19.
Soil acidification and N saturation are considered to affect the decomposition of soil organic matter as well as growth and mortality of fine roots in many forest soils. Here we report from a field experiment where ‘clean rain’ has been applied to the soil for about 10 years under a roofed plot of a 71‐year‐old Norway spruce plantation at Solling, Central Germany. Reduced amounts of protons (?78%), sulphate (?53%), ammonium (?86%), and nitrate (?49%) were sprayed on the soil surface of the clean rain plot between 1992 and 2001. In an adjacent roofed control plot, throughfall was collected and immediately re‐sprinkled below the roof construction without any chemical manipulation. One year before the clean rain treatment started, live and dead fine root masses (≤2 mm) were determined from undisturbed soil cores down to 40 cm mineral soil depth. Total live fine root mass was significantly lower in the clean rain plot than in the control plot. After the first sampling, the soil holes were refilled with quartz sand and repeatedly sampled in June 1992, June 1996, and October 2001. There were no differences in live and dead fine root masses between the plots in 1992 and 1996. In 2001, both live and dead fine root masses of the clean rain plot were about twice as high as in the control plot, indicating that fine root growth recovered in the mineral soil following 10 years of clean rain treatment. Moreover, the clean rain treatment significantly reduced the total N concentrations of live fine roots and 1‐year‐old needles. Our results suggest that the reduced N input promoted fine root growth to compensate N deficiency. Reduced Al concentration in soil solution may have contributed to the recovery of fine root growth, however, the toxicity of Al species is largely unknown. Mean annual soil respiration rate was 24% higher in the period from 2000 to 2001, indicating that the clean rain treatment increased respiration of roots and heterotrophic microorganisms within the rhizosphere. Laboratory incubation of samples from the organic horizon and the top mineral soil revealed no differences between the plots in the decay rate of soil organic matter. Our results suggest that strong reductions in atmospheric N deposition from about 30 to 10 kg N ha?1 yr?1 and decreasing acid stress can have beneficial effects on growth of fine roots in the mineral soil within a decade. We conclude that biological recovery under reduced atmospheric loads can affect the nutrient and carbon budget of spruce soils in the long run. 相似文献
20.
Chuansheng Wu Yiping Zhang Xingliang Xu Liqing Sha Guangyong You Yuhong Liu Youneng Xie 《Plant and Soil》2014,381(1-2):215-224