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1.
Mirco Rodeghiero Galina Churkina Cristina Martinez Thomas Scholten Damiano Gianelle Alessandro Cescatti 《Plant and Soil》2013,364(1-2):55-68
Aims
The partitioning of the total soil CO2 efflux into its two main components: respiration from roots (and root-associated organisms) and microbial respiration (by means of soil organic matter (SOM) and litter decomposition), is a major need in soil carbon dynamics studies in order to understand if a soil is a net sink or source of carbon.Methods
The heterotrophic component of the CO2 efflux was estimated for 11 forest sites as the ratio between the carbon stocks of different SOM pools and previously published (Δ14C derived) turnover times. The autotrophic component, including root and root-associated respiration, was calculated by subtracting the heterotrophic component from total soil chamber measured CO2 efflux.Results
Results suggested that, on average, 50.4 % of total soil CO2 efflux was derived from the respiration of the living roots, 42.4 % from decomposition of the litter layers and less than 10 % from decomposition of belowground SOM.Conclusions
The Δ14C method proved to be an efficient tool by which to partition soil CO2 efflux and quantify the contribution of the different components of soil respiration. However the average calculated heterotrophic respiration was statistically lower compared with two previous studies dealing with soil CO2 efflux partitioning (one performed in the same study area; the other a meta-analysis of soil respiration partitioning). These differences were probably due to the heterogeneity of the SOM fraction and to a sub-optimal choice of the litter sampling period. 相似文献2.
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3.
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4.
Merian Skouw Haugwitz Lasse Bergmark Anders Priemé Søren Christensen Claus Beier Anders Michelsen 《Plant and Soil》2014,374(1-2):211-222
Background and aims
Soil microbial responses to global change can affect organic matter turnover and nutrient cycling thereby altering the overall ecosystem functioning. In a large-scale experiment, we investigated the impact of 5 years of climate change and elevated atmospheric CO2 on soil microorganisms and nutrient availability in a temperate heathland.Methods
The future climate was simulated by increased soil temperature (+0.3 °C), extended pre-summer drought (excluding 5–8 % of the annual precipitation) and elevated CO2 (+130 ppm) in a factorial design. Soil organic matter and nutrient pools were analysed and linked to microbial measures by quantitative PCR of bacteria and fungi, chloroform fumigation extraction, and substrate-induced respiration to assess their impact of climate change on nutrient availability.Results
Warming resulted in higher measures of fungi and bacteria, of microbial biomass and of microbial growth potential, however, this did not reduce the availability of nitrogen or phosphorus in the soil. Elevated CO2 did not directly affect the microbial measures or nutrient pools, whereas drought shifted the microbial community towards a higher fungal dominance.Conclusions
Although we were not able to show strong interactive effects of the global change factors, warming and drought changed both nutrient availability and microbial community composition in the heathland soil, which could alter the ecosystem carbon and nutrient flow in the long-term. 相似文献5.
Aims
The aim of this study was to investigate the effects of elevated CO2 concentration and nitrogen addition on soil organic carbon fractions in subtropical forests where the ambient N deposition was high.Methods
Seedlings of typical subtropical forest ecosystems were transplanted in ten open-top chambers and grown under CO2 and nitrogen treatments. The treatments included: 1) elevated CO2 (700?μmol?mol-1); 2) N addition of 100?kg NH4NO3 ha-1?yr-1; 3) combined elevated CO2 and N addition; and 4) control. We measured soil total organic carbon (TOC), particulate organic carbon (POC), readily oxidizable organic carbon (ROC), and microbial biomass carbon (MBC).Results
Results showed that elevated CO2 alone did not significantly affect soil TOC, POC and ROC after 4?years of treatment, but increased soil MBC and soil respiration compared to the control. N addition alone had no significant effect neither on soil TOC, POC and ROC, but decreased MBC and soil respiration over time. However, the elevated CO2 and N addition together significantly increased soil POC and ROC, and had no significant effect on soil MBC.Conclusions
This study indicated that even in N-rich subtropical forest ecosystems, inputs of N are still needed in order to sustain soil C accumulation under elevated CO2. 相似文献6.
Aims
Fungi play a central role in litter decomposition, a key process controlling the terrestrial carbon cycle and nutrient availability for plants and microorganisms. Climate change and elevated CO2 affect soil fungi, but the relative importance of the global change variables for litter decomposition is still uncertain. The main objective was therefore to assess the short-term litter decomposition and associated fungal community in a global change manipulated temperate heath ecosystem.Methods
The heath had been exposed to 6 years of warming, elevated atmospheric CO2 and an extended pre-summer drought. Litterbags with litter from heather (Calluna vulgaris) and wavy-hair grass (Deschampsia flexuosa) were incubated in the litter layer for 6 months, where after we analyzed the litter-associated fungal community, litter loss, CO2 respiration, and total content of carbon, nitrogen and phosphorus.Results
Elevated temperature tended to increase litter decomposition rates, whereas elevated CO2 had no effect on the process. The pre-summer drought treatment had a positive impact on litter decomposition, CO2 respiration and fungal abundance in the litterbags, although we observed no major changes in fungal community composition.Conclusions
The drought treatment during pre-summer had a legacy effect on litter decomposition as decomposition rates were positively affected later in the year. The community structure of litter-decomposing fungi was not affected by the drought treatment. Hence, the legacy effect was not mediated by a change in the fungal community structure.7.
Background and purpose
Rapid increases in atmospheric carbon dioxide concentration ([CO2]) may increase crop residue production and carbon: nitrogen (C:N) ratio. Whether the incorporation of residues produced under elevated [CO2] will limit soil N availability and fertilizer N recovery in the plant is unknown. This study investigated the interaction between crop residue incorporation and elevated [CO2] on the growth, grain yield and the recovery of 15N-labeled fertilizer by wheat (Triticum aestivum L. cv. Yitpi) under controlled environmental conditions.Methods
Residue for ambient and elevated [CO2] treatments, obtained from wheat grown previously under ambient and elevated [CO2], respectively, was incorporated into two soils (from a cereal-legume rotation and a cereal-fallow rotation) 1 month before the sowing of wheat. At the early vegetative stage 15N-labeled granular urea (10.22 atom%) was applied at 50 kg?N ha?1 and the wheat grown to maturity.Results
When residue was not incorporated into the soil, elevated [CO2] increased wheat shoot (16 %) and root biomass (41 %), grain yield (19 %), total N uptake (4 %) and grain N removal (8 %). However, the positive [CO2] fertilization effect on these parameters was absent in the soil amended with residue. In the absence of residue, elevated [CO2] increased fertilizer N recovery in the plant (7 %), but when residue was incorporated elevated [CO2] decreased fertilizer N recovery.Conclusions
A higher fertilizer application rate will be required under future elevated [CO2] atmospheres to replenish the extra N removed in grains from cropping systems if no residue is incorporated, or to facilitate the [CO2] fertilization effect on grain yield by overcoming N immobilization resulting from residue amendment. 相似文献8.
Changes in water content of two agricultural soils does not alter labile P and C pools 总被引:1,自引:0,他引:1
Clayton R. Butterly Ann M. McNeill Jeff A. Baldock Petra Marschner 《Plant and Soil》2011,348(1-2):185-201
Aims
An incubation study was conducted to investigate how changes in soil water content affect labile phosphorus and carbon pools, mineralisation patterns and microbial community composition.Methods
Two soils from different climatic histories were subjected to four long-term (15 weeks) soil water regimes (constant field capacity (m); 3 dry-rewet (DRW) cycles evenly spaced (intermittent, int); 3 DRW cycles with a shorter interval after a long dry period (false break, fb); constantly air-dry (d)) (incubation period 1). In the subsequent incubation period 2, a set of cores from each treatment were subjected to one DRW cycle (air-dry for 7 day; field capacity for 14 day) or maintained at field capacity.Results
Long-term soil water regime altered soil respiration with the largest CO2 pulse occurring in soil with the longest dry period. However, changing the distribution of the 3 DRW events within incubation period 1 (int/fb) did not alter cumulative CO2. In addition, DRW during incubation period 2 did not affect cumulative CO2 in either treatment (m, int, fb, d) (except for Hamilton int). Our results show that carbon and phosphorus availability and the size and community composition of the microbial biomass were largely unaffected by fluctuating soil water content.Conclusions
Changes in soil water content altered respiration, phosphatase activity and microbial C:P ratio and indicate physiological and/or functional changes in the microbial community. However, it appeared that these would have little impact on plant P availability. 相似文献9.
Aims
In this study we quantified the annual soil CO2 efflux (annual SCE) of a short rotation coppice plantation in its establishment phase. We aimed to examine the effect of former (agricultural) land use type, inter-row spacing and genotype.Methods
Annual SCE was quantified during the second growth year of the establishment rotation in a large scale poplar plantation in Flanders. Automated chambers were distributed over the two former land use types, the two different inter-row spacings and under two poplar genotypes. Additional measurements of C, N, P, K, Mg, Ca and Na concentrations of the soil, pH, bulk density, fine root biomass, microbial biomass C, soil mineralization rate, distance to trees and tree diameters were performed at the end of the second growth year.Results
Total carbon loss from soil CO2 efflux was valued at 589 g m?2 yr?1. Annual SCE was higher in former pasture as compared to cropland, higher in the narrow than in the wider inter-row spacings, but no effect of genotype was found.Conclusions
Spatial differences in site characteristics are of great importance for understanding the effect of ecosystem management and land use change on soil respiration processes and need to be taken into account in modeling efforts of the carbon balance. 相似文献10.
Litter species traits, but not richness, contribute to carbon and nitrogen dynamics in an alpine meadow on the Tibetan Plateau 总被引:2,自引:0,他引:2
Jing Jiang Yikang Li Mozhu Wang Caiping Zhou Guangmin Cao Peili Shi Minghua Song 《Plant and Soil》2013,373(1-2):931-941
Aims
Litter, as afterlife of plants, plays an important role in driving belowground decomposition processes. Here we tested effects of litter species identity and diversity on carbon (C) and nitrogen (N) dynamics during litter decomposition in N-limited alpine meadow soil from the Qinghai–Tibet Plateau.Methods
We incubated litters of four meadow species, a sedge (“S”, Kobresia humilis), a grass (“G”, Elymus nutans), a herb (“H”, Saussurea superba), and a legume (“L”, Oxytropis falcata), in monoculture and in mixture with meadow soil. CO2 release was measured 21 times during the incubation, and soil available N and microbial biomass C and N were measured before and after the experiment.Results
The organic C decay rate did not differ much among soils amended with monocultures or mixtures of litter, except in the H, S, L, and S+H treatments, which had much higher decay rates. Potential decomposable C pools were lowest in the control, highest in the L treatment, and intermediate in the S treatment. Mineralized N was completely immobilized by soil microbes in all treatments except the control, S+L, and S+G+L treatments. Litter mixtures had both additive and non-additive effects on CO2-C emission (mainly antagonistic effects), net N mineralization (mainly synergistic), and microbial biomass C and N (both). Overall, these parameters were not significantly correlated with litter species richness. Similarly, microbial C or N was not significantly correlated with litter N content or C/N. However, cumulative CO2-C emission and net N mineralization were positively correlated with litter N content and negatively correlated with litter C/N.Conclusions
Litter N content and C/N rather than litter species richness drove the release of CO2-C and net available N in this ecosystem. The antagonistic effects of litter mixtures contributed to a modest release of CO2-C, but their synergistic effects enhanced net available N. We suggest that in alpine meadow communities, balancing species with high and low N contents will benefit soil carbon sequestration and plant competition for available N with soil microbes. 相似文献11.
Interactions between leaf litter and soil organic matter on carbon and nitrogen mineralization in six forest litter-soil systems 总被引:2,自引:0,他引:2
Background and aims
Leaf litter decomposes on the surface of soil in natural systems and element transfers between litter and soil are commonly found. However, how litter and soil organic matter (SOM) interact to influence decomposition rate and nitrogen (N) release remains unclear.Methods
Leaf litter and mineral soil of top 0–5 cm from six forests were incubated separately, or together with litter on soil surface at 25 °C for 346 days. Litter N remaining and soil respiration rate were repeatedly measured during incubation. Litter carbon (C) and mass losses and mineral N concentrations in litter and soil were measured at the end of incubation.Results
Net N transfer from soil to litter was found in all litters when incubated with soil. Litter incubated with soil lost more C than litter incubated alone after 346 days. For litters with initial C: N ratios lower than 52, net Nmin after 346 days was 100 % higher when incubated with soil than when incubated alone. Litter net Nmin rate was negatively related to initial C: N ratio when incubated with soil but not when incubated alone. Soil respiration rate and net Nmin rate did not differ between soil incubated with litter and soil incubated alone.Conclusions
We conclude that soils may enhance litter decomposition rate by net N transfer from soil to litter. Our results together with studies on litter mixture decomposition suggest that net N transfer between decomposing organic matter with different N status may be common and may significantly influence decomposition and N release. The low net Nmin rate during litter decomposition along with the small size of litter N pool compared to soil N pool suggest that SOM rather than decomposing litter is the major contributor to plant mineral N supply. 相似文献12.
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13.
Zhuping Jin Zhiqing Wang Qingxia Ma Limin Sun Liping Zhang Zhiqiang Liu Danmei Liu Xuefeng Hao Yanxi Pei 《Plant and Soil》2017,418(1-2):141-151
Background and aims
Changes in net primary productivity in response to climate change are likely to affect litter inputs to forest soil. However, feedbacks between changes in litter input and soil carbon dynamics remain poorly understood in tropical and subtropical forests. This study aims to test whether the effects of litter manipulation on soil respiration differ between natural and plantation forests.Methods
Soil respiration, soil properties, fine root biomass and enzyme activity were measured in adjacent plots with doubling vs. eliminating litter input in both natural and plantation forests of Castanopsis carlesii in southern China.Results
After only 3 years of litter manipulation, the magnitude of change in soil respiration was greater in response to a doubling of the litter input (+24%) than to the elimination of litter input (?15%) in the natural forest, possibly due to a positive priming effect on decomposition of soil organic carbon (SOC). The quick and intense priming effect was corroborated by elevated enzyme activities for five of the six enzymes analyzed. In contrast, the response to litter removal (?31%) was greater than the response to litter addition (1%; not significant) in the plantation forest. The lack of positive priming in the plantation forest may be related to its lower soil fertility, which could not meet the demand of soil microbes, and to its high clay content, which protected SOC from microbial attack. The positive priming effect in the natural forest but not plantation forest of C. carlesii is also consistent with the significant declines in total soil carbon observed following litter addition in the natural forest but not the plantation forest.Conclusions
Increases in aboveground litter production may trigger priming effects and subsequently transfer more soil carbon to atmospheric CO2 in the natural forest but not in the plantation forest with low fertility. Changes in litter inputs resulting from global change drivers may have different impacts on natural and plantation forests.14.
Background and aims
The knowledge of individual tree species impacts on soil respiration based on rigorous experimental designs is limited, but is crucial to help guide selection of species for reforestation and carbon (C) management purposes.Methods
We assessed monthly soil respiration and its components, litterfall input, fine root production and mortality under 19-year-old native coniferous Cunninghamia lanceolata and broadleaved Mytilaria laosensis plantations in sub-tropical China.Results
Total soil respiration from October 2011 to March 2013 was significantly lower under the C. lanceolata than the M. laosensis plantation. The difference in respiration rates derived from fine roots and the litter layer explained much of the variation of total soil respiration between the two tree species. We used an exponential equation and base temperature (10 °C) to normalize soil respiration rate and its components (R10) and determined the correlation between R10 and soil moisture. Although soil moisture had a positive relationship with R10 derived from roots or litter under both C. lanceolata and M. laosensis forests, these positive correlations were masked by negative relationships between soil moisture and R10 derived from root-free soil, which resulted in a neutral correlation between total R10 and soil moisture under C. lanceolata forests. Monthly litterfall input was associated with variation in concurrent total soil respiration rate under the M. laosensis plantation and respiration rate lagging 3 months behind under the C. lanceolata plantation, which may suggest that litterfall input from M. laosensis can more rapidly produce C substrates for microbial respiration than litterfall from C. lanceolata.Conclusions
This study highlighted that tree species-induced variation in the quality and quantity of fine roots and litterfall can impact not only the soil respiration rate but also the seasonal variation model of forest soil respiration. 相似文献15.
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16.
The influence of 3-years of warming and N-deposition on ecosystem dynamics is small compared to past land use in subalpine meadows 总被引:1,自引:0,他引:1
Richard A. Gill 《Plant and Soil》2014,374(1-2):197-210
Background and aims
Drivers of ecosystem dynamics that are under human influence range from local, land-management decisions to global processes such as warming temperatures and N deposition. The goal of this study was to understand how multiple, potentially interacting factors influence net primary production, N mineralization, and water and soil CO2 fluxes.Methods
Here I report on a three-year experiment that manipulated air temperature using ITEX passive warming cones and N deposition in a mountain meadow ecosystems that were historically grazed or protected from grazing.Results
The strongest and most consistent effect was due to the legacy of grazing, with previously grazed sites having lower primary production, lower soil respiration rates, lower soil moisture, and lower soil C and N stocks than historically ungrazed sites. Warming increased soil respiration, but the effect was transient, and decreased over the 3-year study. Nitrogen addition increased primary production in the second and third year of the experiment but had no significant effect on soil respiration. The effect of historical grazing on primary production was approximately double the effect of N addition. Temperature and N deposition rarely interacted except for increasing N availability during the warm, wet growing season of 2004.Conclusions
These findings indicate that the legacies of land use, with their influence on plant community composition and hydrologic processes, are locally more important than short-term step changes in temperature and nutrient availability. 相似文献17.
Costanza Zavalloni Sara Vicca Manu Büscher Ivan E. de la Providencia Hervé Dupré de Boulois Stéphane Declerck Ivan Nijs Reinhart Ceulemans 《Plant and Soil》2012,359(1-2):121-136
Aims
In view of the projected increase in global air temperature and CO2 concentration, the effects of climatic changes on biomass production, CO2 fluxes and arbuscular mycorrhizal fungi (AMF) colonization in newly established grassland communities were investigated. We hypothesized that above- and below-ground biomass, gross primary productivity (GPP), AMF root colonization and nutrient acquisition would increase in response to the future climate conditions. Furthermore, we expected that increased below-ground C allocation would enhance soil respiration (Rsoil).Methods
Grassland communities were grown either at ambient temperatures with 375?ppm CO2 (Amb) or at ambient temperatures +3°C with 620?ppm CO2 (T+CO2).Results
Total biomass production and GPP were stimulated under T+CO2. Above-ground biomass was increased under T+CO2 while belowground biomass was similar under both climates. The significant increase in root colonization intensity under T+CO2, and therefore the better contact between roots and AMF, probably determined the higher above-ground P and N content. Rsoil was not significantly affected by the future climate conditions, only showing a tendency to increase under future climate at the end of the season.Conclusions
Newly established grasslands benefited from the exposure to elevated CO2 and temperature in terms of total biomass production; higher root AMF colonization may partly provide the nutrients required to sustain this growth response. 相似文献18.
Aims
Soil respiration in forest plantations can be greatly affected by management practices such as irrigation. In northwest China, soil water is usually a limiting factor for the development of forest plantations. This study aims to examine the effects of irrigation intensity on soil respiration from three poplar clone plantations in this arid area.Methods
The experiment included three poplar clones subjected to three irrigation intensities (without, low and high). Soil respiration was measured using a Li-6400-09 chamber during the growing season in 2007.Results
Mean soil respiration rates were 2.92, 4.74 and 3.49 μmol m?2 s?1 for control, low and high irrigation treatments, respectively. Soil respiration decreased once soil water content was below a lower (14.8 %) or above an upper (26.2 %) threshold. When soil water content ranged from 14.8 % to 26.2 %, soil respiration increased and correlated with soil temperature. Fine root also played a role in the significant differences in soil CO2 efflux among the three treatments. Furthermore, the three poplar hybrid clones responded differently to irrigation regarding fine root production and soil CO2 efflux.Conclusions
Irrigation intensity had a strong impact on soil respiration of the three poplar clone plantations, which was mainly because fine root biomass and microbial activities were greatly influenced by soil water conditions. Our results suggest that irrigation management is a main factor controlling soil carbon dynamics in forest plantation in arid regions. 相似文献19.
Christian Brandstätter Katharina Keiblinger Wolfgang Wanek Sophie Zechmeister-Boltenstern 《Plant and Soil》2013,371(1-2):139-154
Aims
Litter decomposition and subsequent nutrient release play a major role in forest carbon and nutrient cycling. To elucidate how soluble or bulk nutrient ratios affect the decomposition process of beech (Fagus sylvatica L.) litter, we conducted a microcosm experiment over an 8 week period. Specifically, we investigated leaf-litter from four Austrian forested sites, which varied in elemental composition (C:N:P ratio). Our aim was to gain a mechanistic understanding of early decomposition processes and to determine microbial community changes.Methods
We measured initial litter chemistry, microbial activity in terms of respiration (CO2), litter mass loss, microbial biomass C and N (Cmic and Nmic), non purgeable organic carbon (NPOC), total dissolved nitrogen (TDN), NH4 +, NO3 - and microbial community composition (phospholipid fatty acids – PLFAs).Results
At the beginning of the experiment microbial biomass increased and pools of inorganic nitrogen (N) decreased, followed by an increase in fungal PLFAs. Sites higher in NPOC:TDN (C:N of non purgeable organic C and total dissolved N), K and Mn showed higher respiration.Conclusions
The C:N ratio of the dissolved pool, rather than the quantity of N, was the major driver of decomposition rates. We saw dynamic changes in the microbial community from the beginning through the termination of the experiment. 相似文献20.