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1.
Annual variation in soil respiration and its component parts in two structurally contrasting woody savannas in Central Brazil 总被引:1,自引:0,他引:1
Andre Butler Patrick Meir Gustavo Saiz Leandro Maracahipes Beatriz Schwantes Marimon John Grace 《Plant and Soil》2012,352(1-2):129-142
Background and aims
Due to the high spatial and temporal variation in soil CO2 efflux, terrestrial carbon budgets rely on a detailed understanding of the drivers of soil respiration from a diverse range of ecosystems and climate zones. In this study we aim to evaluate the independent influence of vegetation structure and climate on soil CO2 efflux within cerrado ecosystems.Methods
We examine the seasonal and diel variation of soil CO2 efflux, including its autotrophic and heterotrophic components, within two adjacent and structurally contrasting woody savannas in central Brazil.Principle results
We found no significant difference in the annual soil CO2 efflux between the two stands (p?=?0.53) despite a clear disparity in both LAI (p?<?0.01) and leaf litterfall (p?<?0.01). The mean annual loss of carbon from the soil was 17.32(±1.48) Mg C?ha?1 of which approximately 63% was accounted for by autotrophic respiration. The relative contribution of autotrophic respiration varied seasonally between 55% in the wet season to 79% of the total soil CO2 efflux in the dry season. Furthermore, seasonal fluctuations of all the soil respiration components were strongly correlated with soil moisture (R 2?=?0.79–0.90, p?<?0.01).Conclusions
Across these two structurally distinct cerrado stands, seasonal variations in rainfall, was the main driver of soil CO2 efflux and its components. Consequently, soil respiration within these ecosystems is likely to be highly sensitive to any changes in seasonal precipitation patterns. 相似文献2.
C. Uribe R. Inclán D. M. Sánchez M. A. Clavero A. M. Fernández R. Morante A. Cardeña A. Blanco H. Van Miegroet 《Plant and Soil》2013,369(1-2):403-420
Background and Aims
Mediterranean forests are vulnerable to numerous threats including wildfires due to a combination of climatic factors and increased urbanization. In addition, increased temperatures and summer drought lead to increased risk of forest fires as a result of climate change. This may have important consequences for C dynamics and balance in these ecosystems. Soil respiration was measured over 2 successive years in Holm oak (Quercus ilex subsp. ballota; Qi); Pyrenean Oak (Quercus pyrenaica Willd; Qp); and Scots pine (Pinus sylvestris L.; Ps) forest stands located in the area surrounding Madrid (Spain), to assess the long term effects of wildfires on C efflux from the soil, soil properties, and the role of soil temperature and soil moisture in the variation of soil respiration.Methods
Soil respiration, soil temperature, soil moisture, fine root mass, microbial biomass, biological and chemical soil parameters were compared between non burned (NB) and burned sites (B).Results
The annual C losses through soil respiration from NB sites in Qi, Qp and Ps were 790, 1010, 1380 gCm?2?yr?1, respectively, with the B sites emitting 43 %, 22 % and 11 % less in Qi, Qp and Ps respectively. Soil microclimate changed with higher soil temperature and lower soil moisture in B sites after fire. Exchangeable cations and the pH also decreased. The total SOC stocks were not significantly altered, but 6–8 years after wildfires, there was still measurably lower fine root and microbial biomass, while SOC quality changed, indicated by lower the C/N ratio and the labile carbon and a relative increase in refractory SOC forms, which resulted in lower Q10 values.Conclusions
We found long term effects of wildfires on the physical, chemical and biological soil characteristics, which in turn affected soil respiration. The response of soil respiration to temperature was controlled by moisture and changed with ecosystem type, season, and between B and NB sites. Lower post-burn Q10 integrated the loss of roots and microbial biomass, change in SOC quality and a decrease in soil moisture. 相似文献3.
Background and aims
Across the world, about 264 million ha forest plantations are monospecific. This practice has been found to cause site productivity and soil fertility decline in the regions where forests have been harvested several times. To mitigate these problems, mixed-species plantations, especially with broadleaved and coniferous species, are preferred. Understanding the effects of introducing broadleaved tree in monospecific coniferous plantation on ecosystem carbon (C) storage and soil organic C (SOC) stability is critical to improve our understanding of forest C sequestration and C cycle.Methods
Plots were established in subtropical plantations with a randomized block design to examine the influence of introducing Michelia macclurei trees into pure Cunninghamia lanceolata plantation on biomass C storage, SOC storage of total, labile, and recalcitrant fractions (0–40 cm depth), and SOC stability.Results
Introducing M. macclurei trees increased biomass C by 17.9 % and 14.2 % compared with monospecific C. lanceolata and M. macclurei plantations, respectively. Storage of different SOC fractions was not significantly different between monospecific C. lanceolata and mixed plantations. SOC stability in bulk soils was not affected, although it differed in 10–20 cm and 20–40 cm soil depth among three plantations.Conclusions
Mixed species plantations can increase C sequestration, and in the subtropical forest ecosystem examined this was mainly attributed to an increase in biomass C. 相似文献4.
改变碳输入对亚热带人工林土壤微生物生物量和群落组成的影响 总被引:3,自引:0,他引:3
通过在亚热带杉木(Cunninghamia lanceolata)和米老排(Mytilaria laosensis)人工林中设置互换凋落物、去除凋落物、去除凋落物+去除根系和对照处理来分析改变地上、地下碳输入对人工林土壤微生物生物量和群落组成的影响。结果显示,改变地上、地下碳输入对土壤微生物生物量碳、氮的影响因树种而异。在米老排林中,土壤微生物生物量不受碳源的限制。而在杉木林中,加入米老排凋落物、去除凋落物和去除凋落物+去除根系3种处理中土壤微生物生物量碳、氮具有明显增加的趋势。磷脂脂肪酸分析结果显示,杉木林中,添加高质量的米老排凋落物后,革兰氏阳性细菌、阴性细菌、丛枝菌根真菌、放线菌和真菌群落生物量分别显著增加了24%、24%、53%、25%、28%,革兰氏阴性细菌和丛枝菌根真菌的相对丰度均有显著增加。与对照相比,杉木林中去除凋落物后革兰氏阳性细菌、阴性细菌、丛枝菌根真菌、放线菌和真菌群落生物量分别显著增加了22%、29%、44%、25%、52%,真菌与细菌比值显著增加了21%。但是,去除凋落物+去除根系处理对两个树种人工林土壤微生物群落组成均无显著影响。米老排和杉木林土壤微生物生物量碳、氮的季节变化格局不同,土壤养分有效性可能是驱动土壤微生物生物量季节变化的主要因子。未来研究需要关注凋落物和根系在不同树种人工林中对土壤微生物群落的相对贡献。 相似文献
5.
Root respiration of barley in a semiarid Mediterranean agroecosystem: field and modelling approaches 总被引:1,自引:0,他引:1
Francisco Joaquín Morell A. P. Whitmore J. álvaro-Fuentes J. Lampurlanés C. Cantero-Martínez 《Plant and Soil》2012,351(1-2):135-147
Aims
Root respiration is a major contributor to soil CO2 flux, and its response to management practices needs to be evaluated. The aim was to determine the effect of management practices (tillage systems and nitrogen fertilization levels) on root respiration and to develop a model able to simulate root respiration and its components.Methods
The study was carried out during two contrasting growing seasons (2007–2008 and 2008–2009). Root respiration, including root tissue respiration (R ts ) and rhizomicrobial respiration of exudates (R rz ), was estimated as the difference between the soil CO2 flux of cropped and bare soil (the so-called root exclusion technique). Additionally a novel sub-model of R ts , was used to simulate root respiration based on root growth and specific root respiration rates.Results
Root respiration was reduced under no-tillage. The model agreed well with the patterns and the amounts of the observed values of root respiration, although prior calibration was needed.Conclusions
Root respiration was reduced by the long-term adoption of no-tillage, but was increased by N fertilizer. The root exclusion technique and the model were useful means to estimate root respiration on cropland under semiarid Mediterranean conditions. Additionally the model successfully separated out the theoretical contributions of R ts and R rz to root respiration. 相似文献6.
Background and Aims
Below-ground translocated carbon (C) released as rhizodeposits is an important driver for microbial mobilization of nitrogen (N) for plants. We investigated how a limited substrate supply due to reduced photoassimilation alters the allocation of recently assimilated C in plant and soil pools under legume and non-legume species.Methods
A non-legume (Lolium perenne) and a legume (Medicago sativa) were labelled with 15N before the plants were clipped or shaded, and labelled twice with 13CO2 thereafter. Ten days after clipping and shading, the 15N and 13C in shoots, roots, soil, dissolved organic nitrogen (DON) and carbon (DOC) and in microbial biomass, as well as the 13C in soil CO2 were analyzed.Results
After clipping, about 50 % more 13C was allocated to regrowing shoots, resulting in a lower translocation to roots compared to the unclipped control. Clipping also reduced the total soil CO2 efflux under both species and the 13C recovery of soil CO2 under L. perenne. The 15N recovery increased in the shoots of M. sativa after clipping, because storage compounds were remobilized from the roots and/or the N uptake from the soil increased. After shading, the assimilated 13C was preferentially retained in the shoots of both species. This caused a decreased 13C recovery in the roots of M. sativa. Similarly, the total soil CO2 efflux under M. sativa decreased more than 50 % after shading. The 15N recovery in plant and soil pools showed that shading has no effect on the N uptake and N remobilization for L. perenne, but, the 15N recovery increased in the shoot of M. sativa.Conclusions
The experiment showed that the dominating effect on C and N allocation after clipping is the need of C and N for shoot regrowth, whereas the dominating effect after shading is the reduced substrate supply for growth and respiration. Only slight differences could be observed between L. perenne and M. sativa in the C and N distribution after clipping or shading. 相似文献7.
不同杉木林分类型土壤团聚体生态化学计量特征 总被引:1,自引:0,他引:1
在野外调查的基础上,选择成土母质相同、坡向坡度相似、海拔基本一致的杉木-米老排、杉木-火力楠和杉木纯林3种杉木人工林采集土壤样品,通过干筛法分离2 mm、2~0.25 mm和0.25 mm 3个团聚体组分,研究其土壤团聚体有机碳、全氮、全磷的含量及其生态化学计量特征,以阐明不同杉木林分类型土壤团聚体碳氮磷生态化学计量特征的指示意义。结果表明:(1)0~10 cm和10~20 cm土层有机碳、全氮和全磷含量的变异系数分别为21.37%、21.00%、21.46%和20.35%、16.51%、17.82%;全氮的变异系数低于有机碳和全磷,但三者含量呈极显著正相关关系。(2)有机碳和全氮含量集中分布于小粒径团聚体(0.25 mm)中,全磷含量在各粒径团聚体中分布较为均匀;在不同林分类型中土壤有机碳、全氮和全磷含量均表现为杉木-火力楠杉木-米老排杉木纯林;在0~10 cm和10~20 cm土层的C/N、C/P和N/P的变异系数分别为14.09%、19.75%、22.24%和19.56%、21.28%、24.49%;土壤C/N的变异性较低,土壤C/P和N/P均在大粒径团聚体(0.25 mm)中较高,土壤C/N、C/P和N/P对土壤有机碳储量具有良好的指示作用。研究表明,在杉木与火力楠混交林中,缺乏磷元素,建议及时补充P元素,避免土壤持续利用受到磷的限制。 相似文献
8.
Aims
There is evidence that increased N inputs to boreal forests, via atmospheric deposition or intentional fertilization, may impact negatively on ectomycorrhizal (ECM) fungi leading to a reduced flux of plant-derived carbon (C) back to the atmosphere via ECM. Our aim was to investigate the impact of N fertilization of a Pinus sylvestris (L.) forest stand on the return of recently photoassimilated C via the ECM component of soil respiration.Methods
We used an in situ, large-scale, 13C-CO2 isotopic pulse labelling approach and monitored the 13C label return using soil gas efflux chambers placed over three different types of soil collar to distinguish between heterotrophic (RH), autotrophic (RA; partitioned further into contributions from ECM hyphae and total RA) and total (RS) soil respiration.Results
The impact of N fertilization was to significantly reduce RA, particularly respiration via extramatrical ECM hyphae. ECM hyphal flux in control plots showed substantial spatial variability, resulting in mean flux estimates exceeding estimates of total RA, while ECM contributions to RA in N treated plots were estimated at around 30%.Conclusion
Significant impacts on soil C cycling may be caused by reduced plant C allocation to ECM fungi in response to increased N inputs to boreal forests; ecosystem models so far lack this detail. 相似文献9.
Zhi-Shan Zhang Xin-Rong Li Robert S. Nowak Pan Wu Yan-Hong Gao Yang Zhao Lei Huang Yi-Gang Hu Rong-Liang Jia 《Plant and Soil》2013,367(1-2):449-463
Aims
Explore how soil CO2 efflux and its components change after moving sand dunes are stabilized with shrubs, and how abiotic factors affect those components at different scales.Methods
Soil CO2 efflux from a sand-stabilized area was compared to that from moving sand dunes in the Tengger Desert. To partition rhizosphere respiration (RR) from soil basal respiration (RB), a root-isolation plot was established.Results
Compared to moving sand dunes, total soil respiration (RT) in the sand-stabilized area increased 3.2 fold to 0.28?±?0.08 μmol CO2 m-2?s-1, two thirds of which was from RB. Shrub patchiness produced spatial variation in soil respiration, whereas temporal dynamics of soil respiration were affected mainly by soil water content. Shallow soil water content (0–20 cm) influenced RT and RB, whereas deep soil water content (30–210 cm) influenced RR and the ratio RR/RT. During most of the year when soil water content was below field capacity, diurnal changes in soil respiration were partially decoupled from soil temperature but could be modeled using soil temperature and photosynthetic active radiation.Conclusions
Sand-dune stabilization increased soil respiration, and increased RB from biological soil crust and altered soil properties such as increased soil organic matter contributed more than increased RR from increased shrubs. 相似文献10.
Chuansheng Wu Yiping Zhang Xingliang Xu Liqing Sha Guangyong You Yuhong Liu Youneng Xie 《Plant and Soil》2014,381(1-2):215-224
Aims
The aims were to identify the effects of interactions between litter decomposition and rhizosphere activity on soil respiration and on the temperature sensitivity of soil respiration in a subtropical forest in SW China.Methods
Four treatments were established: control (CK), litter removal (NL), trenching (NR) and trenching together with litter removal (NRNL). Soil CO2 efflux, soil temperature, and soil water content were measured once a month over two years. Soil respiration was divided into four components: the decomposition of basic soil organic matter (SOM), litter respiration, root respiration, and the interaction effect between litter decomposition and rhizosphere activity. A two-factor regression equation was used to correct the value of soil CO2 efflux.Results
We found a significant effect of the interaction between litter decomposition and rhizosphere activity (R INT) on total soil respiration, and R INT exhibited significant seasonal variation, accounting for 26 and 31 % of total soil respiration in the dry and rainy seasons, respectively. However, we found no significant interaction effect on the temperature sensitivity of soil respiration. The temperature sensitivity was significantly increased by trenching compared with the control, but was unchanged by litter removal.Conclusions
Though the interaction between litter decomposition and rhizosphere activity had no effects on temperature sensitivity, it had a significant positive effect on soil respiration. Our results not only showed strong influence of rhizosphere activity on temperature sensitivity, but provided a viable way to identify the contribution of SOM to soil respiration, which could help researchers gain insights on the carbon cycle. 相似文献11.
Alessandra Lagomarsino Martin Lukac Douglas L. Godbold Sara Marinari Paolo De Angelis 《Plant and Soil》2013,362(1-2):93-106
Background and aims
The response of soil respiration (SR) to elevated CO2 is driven by a number of processes and feedbacks. This work aims to i) detect the effect of elevated CO2 on soil respiration during the second rotation of a short rotation forest, at two levels of N availability; and ii) identify the main drivers behind any changes in soil respiration.Methods
A poplar plantation (POP-EUROFACE) was grown for two rotations of 3 years under elevated CO2 maintained by a FACE (Free Air CO2 Enrichment) technique. Root biomass, litter production and soil respiration were followed for two consecutive years after coppice.Results
In the plantation, the stimulation of fine root and litter production under elevated CO2 observed at the beginning of the rotation declined over time. Soil respiration (SR) was continuously stimulated by elevated CO2, with a much larger enhancement during the growing (up to 111 %) than in the dormant season (40 %). The SR increase at first appeared to be due to the increase in fine root biomass, but at the end of the 2nd rotation was supported by litter decomposition and the availability of labile C. Soil respiration increase under elevated CO2 was not affected by N availability.Conclusions
The stimulation of SR by elevated CO2 was sustained by the decomposition of above and belowground litter and by the greater availability of easily decomposable substrates into the soil. In the final year as elevated CO2 did not increase C allocation to roots, the higher SR suggests greater C losses from the soil, thus reducing the potential for C accumulation. 相似文献12.
Precipitation variability does not affect soil respiration and nitrogen dynamics in the understorey of a Mediterranean oak woodland 总被引:1,自引:0,他引:1
Marjan Jongen Xavier Lecomte Stephan Unger David Fangueiro João Santos Pereira 《Plant and Soil》2013,372(1-2):235-251
Background and aims
Future climate scenarios for the Mediterranean imply increasing precipitation variability. This study presents a large-scale water manipulation experiment simulating changes in precipitation variability, aiming at a better understanding of the effects of rainfall patterns on soil C and N cycling and understorey productivity in a Mediterranean oak woodland.Methods
We used rain-out shelters to achieve (1) a normal dry period (7 days), and (2) a dry period increased three-fold (21 days), without altering total annual precipitation inputs.Results
The temporal patterns of soil respiration (R s) and soil inorganic N were not affected by treatment. However, water infiltration and N leaching increased with large infrequent watering events. R s and soil NH4 +-N correlated with soil temperature, with soil NO3 ?-N being influenced by leaching.Conclusions
The lack of significant treatment effects on either R s or soil inorganic N can be explained by (1) minor differences in plant productivity between the treatments, suggesting equal plant N demand, and (2) the absence of moisture dependence of R s and soil NH4 +-N. Increased N leaching with large infrequent precipitation events may have longer-term consequences for ecosystem functioning. Our results contribute to an improved understanding of possible climate change effects on key ecosystem processes in Mediterranean ecosystems. 相似文献13.
Carbon allocation in Larrea tridentata plant-soil systems as affected by elevated soil moisture and N availability 总被引:1,自引:0,他引:1
Paul S. J. Verburg Sheila E. Kapitzke Bryan A. Stevenson Marion Bisiaux 《Plant and Soil》2014,378(1-2):227-238
Background and Aims
Global change will likely express itself in southwestern United States arid lands through changes in amounts and timing of precipitation in response to elevated CO2 concentrations. In addition, increased nitrogen (N) deposition may occur due to increased urban development. This study addressed the effects of water and N availability on C allocation in arid land soil-plant systems.Methods
Columns filled with Mojave Desert topsoil containing Larrea tridentata seedlings with two treatment levels each of N and soil moisture were labeled by exposure to 13C-enriched CO2.Results
Increased soil moisture increased plant biomass, total 13C uptake, 13C levels in leaves, soil organic matter, and soil respiration, decreased relative C allocation to stems but increased allocation to soil organic matter. Increased soil N availability increased N uptake but decreased C allocation to soil respiration presumably due to decreased substrate supply for microbes. There was no detectable label in carbonate C, suggesting that this pool does not significantly contribute to ecosystem C fluxes.Conclusions
Our study indicates that increased water availability causes increased C uptake with increased C allocation to soil organic matter in Larrea tridentata-dominated communities while increased N deposition will have a minimal impact on C sequestration. 相似文献14.
Yingchun Liao M. Luke McCormack Houbao Fan Huimin Wang Jianping Wu Jie Tu Wenfei Liu Dali Guo 《Plant and Soil》2014,381(1-2):225-234
Background and aims
Growth and distribution of fine roots closely depend on soil resource availability and affect soil C distribution in return. Understanding of relationships between fine root distribution and soil C can help to predict the contribution of fine root turnover to soil C accumulation.Methods
A study was conducted in a subtropical Cunninghamia lanceolata plantation to assess the fine root mass density (FRMD), fine root C density (FRCD) of different fine root groups as well as their relations with soil C.Results
The FRMD and FRCD of short-lived roots, dead roots and herb roots peaked in the 0–10 cm soil layer and decreased with soil depth, while FRMD, FRCD of long-lived roots peaked in the 10–20 cm soil layer. Soil C was positively related to FRMD and FRCD of total fine roots (across all three soil layers), dead roots (0–10 cm) and herb roots (10–20 cm) as well as FRCD of short-lived roots (20–40 cm) (P <0.05).Conclusions
Soil C was mainly affected by herb roots in upper soil layers and by woody plant roots in deeper soil layers. 相似文献15.
Background and aims
Positive relationships between temperature and soil respiration rate are widely observed, but it remains unclear if the relationships are due to increases in soil organic matter mineralisation (R om ), or in root and rhizosphere respiration (R roots ), or increases in both. This study aims to determine the relative sensitivity of R om and R roots to temperature in soils with differing properties.Methods
Taking advantage of the difference in stable carbon isotopic composition provided by C3 and C4 plants, we partitioned soil respiration into R om and R roots for two soils with contrasting clay mineralogy, pH and carbon content over a 24 °C temperature range (from 12 to 36 °C).Results
The Chromosol (dominated by illite, with near neutral pH and low organic carbon content) showed an increase in the proportion of R om with temperature, indicating an increase in the decomposition of soil organic carbon. In contrast, the Ferrosol (dominated by hematite and goethite, with acidic pH and high organic carbon) showed no change in the proportion of R om with warming, and a negative priming effect at the highest temperature.Conclusions
The observed positive priming effect for the Chromosol and a negative priming effect for the Ferrosol are consistent with contrasting mineralogy, reflecting the relatively weaker bond strength between soil carbon and illites in the Chromosol compared to the Ferrosol. 相似文献16.
Potential effects of warming on soil respiration and carbon sequestration in a subtropical forest 总被引:1,自引:0,他引:1
Aims
Subtropical ecosystems are receiving unprecedented changes in temperature as a consequence of anthropogenic activities, which potentially affects soil respiration (R s) and carbon (C) sequestration. Due to the large amounts of C store and cycle in subtropical forests, investigations about how R s and C sequestration respond to warming will be critical for our understanding of future global-scale climate and biogeochemical cycling.Methods
In this study, we transferred soil samples and plant seedlings collected from a mixed forest to the growth chambers in two sites (300 m and 30 m a.s.l.), which induced an artificial warming of ca. 1 °C between the two corresponding forest mesocosms. We tested whether the modification of abiotic factors induced by the downward translocation could alter R s and soil C sequestration. We also investigated the effects on the biotic factors by including root biomass and soil microbial biomass.Results
Our results showed that R s was greater in the warm site than in the control site, which were related to the higher aboveground biomass, litterfall and root biomass. R s showed a significantly positive exponential relationship with soil temperature. The downward translocation tended to decrease soil C sequestration, which was attributed to the decreased C use efficiency of soil microorganisms and increased root growth under downward translocation.Conclusion
R s responded strongly to downward translocation, suggesting that climate warming exacerbated R s and tended to reduce soil C sequestration. The ability of subtropical forests to act as CO2 sink may be reduced under climate warming.17.
Background and Aims
The reclamation of natural salt marshes for agricultural use is expected to profoundly influence the effects of predicted global warming on the carbon balance of coastal areas globally. This study was undertaken to understand the potential for soil respiration changes in a disturbed coastal ecosystem under future atmospheric warmingMethods
An in situ simulated warming experiment was conducted in a reclaimed salt marsh on Chongming Island in the Yangtze Estuary, China. Open-top chambers (OTCs) were applied to simulate air-warming conditions.Results
Based on the 2-year study, we found the following: (1) Averaged across the entire study period, the OTCs significantly increased the mean air temperature by 1.53?±?0.17 °C. (2) The air warming resulted in no significant stimulation of the mean soil respiration averaged across the entire study period. Warming had no significant effect on soil respiration in the growing season, but it markedly reduced soil respiration by 16 % in the non-growing season. (3) Air warming had no significant effect on the mean soil temperature or volumetric moisture at a 5 cm depth, but it increased the mean soil porewater salinity by 119 % averaged across the entire study period. (4) Air warming had no significant effect on total organic carbon, total nitrogen or the molar C/molar N ratio of the soil in the uppermost 10 cm layer during the 2 years of soil respiration measurement. The warming treatment also had no significant effect on aboveground biomass or fine root (<2 mm) density during the second year of soil respiration measurement. (5) Soil temperature accounted for 81.0 % and 79.0 % of the temporal variations of soil respiration in the control (CON) and elevated temperature (ET) plots, respectively. No significant correlation between soil volumetric moisture and soil respiration was observed in either CON or ET. Soil porewater salinity was positively correlated with soil respiration in CON, but such a positive correlation was not found in ET. No change of the temperature sensitivity of soil respiration (Q 10 value) was observed.Conclusions
Based on above results, we speculate that soil porewater salinity was the key factor controlling the effects of air warming on soil respiration in the reclaimed salt marsh. Our results suggest that an air warming of approximately 1.5 °C over the next few decades may not lead to a higher soil respiration in reclaimed salt marshes. 相似文献18.
Ecosystem respiration in a heterogeneous temperate peatland and its sensitivity to peat temperature and water table depth 总被引:1,自引:0,他引:1
Radosław Juszczak Elyn Humphreys Manuel Acosta Maria Michalak-Galczewska Dariusz Kayzer Janusz Olejnik 《Plant and Soil》2013,366(1-2):505-520
Background and aims
Ecosystem respiration (R eco ) is controlled by thermal and hydrologic regimes, but their relative importance in defining the CO2 emissions in peatlands seems to be site specific. The aim of the paper is to investigate the sensitivity of R eco to variations in temperature and water table depth (WTD) in a wet, geogenous temperate peatland with a wide variety of vegetation community groups.Methods
The CO2 fluxes were measured using chambers. Measurements were made at four microsites with different vegetation communities and peat moisture and temperature conditions every 3 to 4 weeks during the period 2008–2009, 2 years with contrasting WTD patterns. Models were used to examine the relative response of each microsite to variations in peat temperature and WTD and used to estimate annual total R eco .Results
Temporal variations in R eco were strongly related to peat temperature at the 5 cm depth. However, two of the microsites did not show any significant change in this relationship while two others showed contrasting responses including an increase and decrease in temperature sensitivity with deeper WTD. Average R eco varied among the microsites and tended to be greatest for those with greatest leaf area which also positively correlated with deeper WTD, ash content and degree of peat decomposition at 20 cm. A combined temperature and WTD model explained up to 94 % of the temporal variation in daily average R eco and was used to show that on an annual basis, R eco was between 5 and 18 % greater in the warmer year with deeper WTD.Conclusion
Microsite-specific responses were related to differences in vegetation and peat characteristics among microsites. R eco may have remained insensitive to WTD variations at one microsite due to the dominance of autotrophic respiration from abundant sedge biomass. At a Sphagnum-dominated microsite, a lack of response may have been due to relatively small variations in WTD that did not greatly influence microbial respiration or due to offsets between decreasing and increasing respiration rates in near-surface and deeper peat. The microsite with the most recalcitrant peat had reduced R eco sensitivity to temperature under more aerobic conditions while another microsite showed the opposite response, perhaps due to less nutrient availability during the wet year. Ultimately, micro-site specific models with both soil temperature and WTD as explanatory variables described temporal variations in R eco and highlighted the significant spatial variations in respiration rates that may occur within a single wetland. 相似文献19.
杉木林改造成乡土阔叶林对林下植物物种组成和多样性的影响 总被引:1,自引:0,他引:1
把杉木林改造成乡土阔叶林,不仅能提供高价值木材,而且能够提升生态系统服务功能,是我国目前改造退化针叶林最常见的经营模式之一,但这些改变对其林下植物物种组成和多样性的影响及机制我们尚知之甚少。以南亚热带杉木林采伐迹地上重新种植的杉木林、红锥林和米老排林为研究对象,调查研究其灌木层和草本层植物物种组成和多样性,结果表明:(1)和杉木林相比,改造后的红锥林和米老排林灌木层的植物物种丰富度和多样性均呈极显著降低(P<0.01),但其草本层植物只有物种丰富度极显著降低(P<0.01),多样性均无显著变化(P>0.05);(2)主成分分析(PCA)表明改造后的林分灌木层和草本层的植物物种组成发生明显的变化,冗余分析(RDA)确定导致林分灌木层植物物种组成发生变化的主要原因是杉木林改造成红锥林和米老排林后的冠层透光率、土壤碳氮比、土壤含水量和凋落物碳氮比的显著变化,而冠层透光率和土壤碳氮比的显著变化是导致其林下草本层植物物种组成发生明显变异的主要因子;(3)方差分解结果显示微地形、乔木特性和土壤理化性质的独立效应对灌木层和草本层植物物种组成的影响高于它们的交互效应。该研究为科学经营管理人工林和提高人工林生态系统多功能性提供科学依据。 相似文献
20.
Jiaojiao Zhang Yongfu Li Scott X. Chang Peikun Jiang Guomo Zhou Juan Liu Jiasen Wu Zhenming Shen 《Plant and Soil》2014,376(1-2):363-375