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1.
The effect of elevated carbon dioxide (CO2) concentration on symbiotic nitrogen fixation in soybean under open-air conditions has not been reported. Two soybean cultivars (Glycine max (L.) Merr. cv. Zhonghuang 13 and cv. Zhonghuang 35) were grown to maturity under ambient (415?±?16?μmol?mol?1) and elevated (550?±?17?μmol?mol?1) [CO2] at the free-air carbon dioxide enrichment experimental facility in northern China. Elevated [CO2] increased above- and below-ground biomass by 16–18% and 11–20%, respectively, but had no significant effect on the tissue C/N ratio at maturity. Elevated [CO2] increased the percentage of N derived from the atmosphere (%Ndfa, estimated by natural abundance) from 59% to 79% for Zhonghuang 13, and the amount of N fixed from 166 to 275?kg N ha?1, but had no significant effect on either parameter for Zhonghuang 35. These results suggest that variation in N2 fixation ability in response to elevated [CO2] should be used as key trait for selecting cultivars for future climate with respect to meeting the higher N demand driven by a carbon-rich atmosphere.  相似文献   

2.
Climate change, as a result of increase in the concentration of greenhouse gases, influences growth and productivity of leguminous crops. A study was carried out to analyse the impacts of elevated carbon dioxide (CO2) and cyanobacterial inoculation on growth, N2 fixation and N availability and uptake in cowpea crop, under different doses of phosphorus. Cowpea crop was grown under ambient (400 µmol mol?1) and elevated (550 ± 20 µmol mol?1) CO2 levels using Free-Air Carbon dioxide Enrichment facility. Elevated CO2 level increased chlorophyll content in leaves, improved nodulation and nitrogen fixation by the crop. Increase in P dose up to 16 mg kg?1 soil enhanced nodule development and N2 fixation under high CO2 condition. Cyanobacterial inoculation increased nodule weight, leghaemoglobin content in nodules and total nitrogenase activity. Although nitrogen concentration in cowpea seeds decreased in high CO2 treatment, higher N uptake was recorded. Under elevated CO2 condition, cyanobacterial inoculation and higher P doses led to enhanced root growth and N2 fixation and availability of soil nitrogen. The study illustrated the synergistic effect of high CO2 and cyanobacterial inoculation in enhancing crop growth and availability of soil N, mediated by biological N2 fixation in cowpea under different levels of P.  相似文献   

3.
Global climate change affects the availability of soil nutrients, thereby influencing crop productivity. This study examined the effects of elevated [CO2] and temperature on the availability of soil N and P in a paddy field in the Taihu Lake region, China. Winter wheat (Triticum aestivum L.) was planted at two levels of atmospheric [CO2] (375 μmol L–1 ambient; 575 μmol L–1 elevated) and two temperature levels (ambient; ambient + 2°C). The results were as follows: Compared to ambient, the interaction effects of elevated [CO2] and temperature significantly decreased soil NH$ _4^+ $ ‐N contents by 20.3%, 20.6%, and 18.7% in the jointing, heading, and ripening stages (p < 0.05), respectively, while soil NO3–‐N content had no clear variation trend under different [CO2] and temperature conditions. Elevated [CO2] significantly increased soil available P content by 14.3% in the jointing stage, and elevated temperature significantly decreased soil available P content by 18.8% in the jointing stage. Compared with ambient [CO2], elevated [CO2] significantly increased wheat biomass in jointing and heading stages (p < 0.05). The positive effect of elevated [CO2] on wheat biomass was more significant at ambient temperature (AT) than at elevated temperature (ET) in the middle and late plant growth stages. These results explained that the availability of soil N and P varied under elevated [CO2] and temperature conditions. The application of N and P should be adjusted to meet the need of wheat plants after the wintering stage.  相似文献   

4.
Yield responsiveness to elevated CO2 concentration [CO2] was previously found to be greater when nitrogen (N) was supplied in adequate amounts; however, it remains unclear whether genotypic differences in N2-fixing capacity affect yield responsiveness in soybean. We tested the hypothesis that yield responsiveness to elevated [CO2] in soybean is greater in a genotype with a higher capacity for N2 fixation. We used three near-isogenic genotypes with contrasting nodulation capacities: super-nodulating, normally nodulating and non-nodulating genotypes. Plants were subjected to two levels of [CO2] (ambient or elevated: ambient + 200 μmol mol−1) and two temperature regimes (low or high: low + ca. 4-5 °C) using temperature gradient chambers. The super-nodulating genotype exhibited a higher N content in leaves, regardless of [CO2] and temperature. Photosynthetic rates were enhanced by CO2 enrichment at earlier growth stages, but not at later growth stages, regardless of genotype. This photosynthetic acclimation was reflected in biomass production in all the genotypes examined. Yield responsiveness to elevated [CO2] was greater in the nodulating genotypes than in the non-nodulating genotype, but the genotypic differences were obscured between the normally nodulating and super-nodulating genotype, thus our hypothesis was not fully verified.  相似文献   

5.
The rise in atmospheric carbon dioxide (CO2) concentration is predicted to have positive effects on agro‐ecosystem productivity. However, an area which requires further study centers on nutrient dynamics of crops grown under elevated CO2 in the field. In 1989 and 1990, cotton [Gossypium hirsutum (L.) ‘Deltapine 77'] was grown under two CO2 levels [370 umol mol‐1=ambient and 550 μmol mor‐1=free‐air CO2 enrichment (FACE)]. At physiological maturity, nutrient concentration and content of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) were determined for whole plant and individual plant organs. While the effects of added CO2 on whole plant nutrient concentrations and contents were consistent, some differences among plant organs were observed between years. FACE often decreased tissue nutrient concentration, but increased total nutrient accumulation. Results indicate that under elevated CO2, field grown cotton was more nutrient efficient in terms of nutrient retrieval from the soil and nutrient utilization in the plant. This implies more efficient fertilizer utilization, better economic return for fertilizer expenditures, and reduced environmental impact from agricultural fertilization practices in the future.  相似文献   

6.
We evaluated the possibility of elevated CO2 concentration ([CO2]) to reduce the negative effect of drought on growth and physiological parameters of cassava (Manihot esculenta Crantz). Plants were grown with 390 ppm or 750 ppm of CO2, under well-watered or under water deficit conditions. The study was conducted in a climate-controlled greenhouse using 14 L pots, for 100 days. For any value of fraction of transpirable soil water (FTSW) the carbon assimilation was always higher for plants grown under elevated [CO2]. Still, elevated [CO2] reduced the negative effect of drought on transpiration, water use efficiency, all growth measures and harvest index. Elevated [CO2] increased the dry matter of tuber roots (DMTR) of well-watered plants by 17.4%. The DMTR of plants grown under water deficit were 124.4 g and 58.9 g, respectively, for plants under elevated and ambient CO2, an increase of 112%. Thus, the CO2 effect was relatively stronger to the production of tuberous roots when cassava were subjected to water-deficit. Our results suggest that cassava tuber production might be resilient to changes in precipitation that will accompany higher atmospheric CO2 and reinforce cassava as a specie that can significantly contribute to mitigate hunger in a changing climate environment.  相似文献   

7.
Both plant species and CO2 concentration can potentially affect rhizodeposition and consequently soil microbial activity and community composition. However, the effect differs based on plant developmental stage. We focused on the effect of three plant species (forbs, grasses, and N2‐fixers) at an early stage of development on root C deposition and fate, soil organic matter (SOM) mineralization and soil microbial community composition at ambient (aCO2) and elevated (eCO2) CO2 levels. Plants were grown from seed, under continuous 13C‐labelling atmospheres (400 and 800 µmol mol?1 CO2), in grassland soil for three weeks. At the end of the growth period, soil respiration, dissolved organic C (DOC) and phospholipid fatty acid (PLFA) profiles were quantified and isotopically partitioned into root‐ and soil‐derived components. Root‐derived DOC (0.53 ± 0.34 and 0.26 ± 0.29 µg mL soil solution?1) and soil‐derived CO2 (6.14 ± 0.55 and 5.04 ± 0.44 µg CO2‐C h?1) were on average two times and 22% higher at eCO2 than at aCO2, respectively. Plant species differed in exudate production at aCO2 (0.11 ± 0.11, 0.10 ± 0.18, and 0.58 ± 0.58 µg mL soil solution?1 for Plantago, Festuca, and Lotus, respectively) but not at eCO2 (0.20 ± 0.28, 0.66 ± 0.32, and 0.75 ± 0.15 µg mL soil solution?1 for Plantago, Festuca, and Lotus, respectively). However, no differences among plant species or CO2 levels were apparent when DOC was expressed per gram of roots. Relative abundance of PLFAs did not differ between the two CO2 levels. A higher abundance of actinobacteria and G‐positive bacteria occurred in unplanted (8.07 ± 0.48 and 24.36 ± 1.18 mol%) and Festuca‐affected (7.63 ± 0.31 and 23.62 ± 0.69 mol%) soil than in Plantago‐ (7.04 ± 0.36 and 23.41 ± 1.13 mol%) and Lotus‐affected (7.24 ± 0.17 and 23.13 ± 0.52 mol%) soil. In conclusion, the differences in root exudate production and soil respiration are mainly caused by differences in root biomass at an early stage of development. However, plant species evidently produce root exudates of varying quality affecting associated microbial community composition.  相似文献   

8.
There are no reports on the effects of elevated carbon dioxide [CO2] on the fluxes of N2O, CO2 and CH4 from semi-arid wheat cropping systems. These three soil gas fluxes were measured using closed chambers under ambient (420 ± 18 μmol mol−1) and elevated (565 ± 37 μmol mol−1) at the Free-Air Carbon dioxide Enrichment experimental facility in northern China. Measurements were made over five weeks on a wheat crop (Triticum aestivum L. cv. Zhongmai 175). Elevated [CO2] increased N2O and CO2 emission from soil by 60% and 15%, respectively, but had no significant effect on CH4 flux. There was no significant interaction between [CO2] and N application rate on these gas fluxes, probably because soil N was not limiting. At least 22% increase in C storage is required to offset the observed increase in greenhouse gas emissions under elevated [CO2].  相似文献   

9.
The response of wheat to elevated carbon dioxide concentration (e[CO2]) is likely to be dependent on nitrogen supply. To investigate the underlying mechanism of growth response to e[CO2], two wheat cultivars were grown under different carbon dioxide concentration [CO2] in a chamber experimental facility. The changes in leaf photosynthesis, C and N concentration, and biomass were investigated under different [CO2] and N supply. The result showed an increase in photosynthesis under e[CO2] at all N level except the one with the lowest N supply. Furthermore, a significant decrease in gs and Tr for both the cultivars was also observed under e[CO2] at all N levels. A considerable increase in WUEi was observed for both the cultivars under e[CO2] at all N levels except for the lowest concentration one. Therefore, the study shows that a stimulation of plant growth under e[CO2] to be marginal at higher N supply.  相似文献   

10.
This study was conducted to improve our understanding of how earthworms and microorganisms interact in the decomposition of litter of low quality (high C : N ratio) grown under elevated atmospheric [CO2]. A microcosm approach was used to investigate the influence of endogeic earthworm (Aporrectodea caliginosa Savigny) activity on the decomposition of senescent Charlock mustard (Sinapis arvensis L.) litter produced under ambient and elevated [CO2]. Earthworms and microorganisms were exposed to litter which had changed in quality (C : N ratio) while growing under elevated [CO2]. After 50 d of incubation in microcosms, C mineralization (CO2 production) in the treatment with elevated‐[CO2] litter was significantly lower in comparison to the ambient‐[CO2] litter treatment. The input of Charlock mustard litter into the soil generally induced N immobilization and reduced N2O‐emission rates from soil. Earthworm activity enhanced CO2 production, but there was no relationship to litter quality. Although earthworm biomass was not affected by the lower quality of the elevated‐[CO2] litter, soil microbial biomass (Cmic, Nmic) was significantly decreased. Earthworms reduced Cmic and fungal biomass, the latter only in treatments without litter. Our study clearly showed that A. caliginosa used the litter grown under different [CO2] independent of its quality and that their effect on the litter‐decomposition process was also independent of litter quality. Soil microorganisms were shown to negatively react to small changes in Charlock mustard litter quality; therefore we expect that microbially mediated C and N cycling may change under future atmospheric [CO2].  相似文献   

11.
Cultivars of Triticum aestivum, T. durum, and Secale cereale were grown at low (2 μM) and sufficient (500 μM) phosphorus (P) under ambient carbon dioxide (380 μmol mol?1; aCO2) and elevated CO2 (700 μmol mol?1, eCO2) to study responses of cereal species in terms of growth and P utilization efficiency (PUE) under P x CO2 interaction. Dry matter accumulation increased under eCO2 with sufficient P. Nevertheless, dry matter accumulated at eCO2 with low-P was similar to that obtained at aCO2 with sufficient P. Leaf area was 43% higher under eCO2 with sufficient P. Significant increase in lateral root density, length and surface area were noted at low-P under eCO2. Phosphorus use efficience (PUE) increased by 59% in response to eCO2­ in low-P plants. Thus, eCO2 can partly compensate effect of low-P supply because of improved utilization efficiency. Among cereals, durum wheat was more suitable in terms of PUE under high CO2 and limiting P supply.  相似文献   

12.
Abstract

Plant responses to elevated CO2 are governed by temperature, and at low temperatures the beneficial effects of CO2 may be lost. To document the responses of winter cereals grown under cold conditions at northern latitudes, autumn growth of winter wheat exposed to ambient and elevated levels of temperature (+2.5°C), CO2 (+150 µmol mol?1), and shade (?30%) was studied in open-top chambers under low light and at low temperatures. Throughout the experiment, temperature dominated plant responses, while the effects of CO2 were marginal, except for a positive effect on root biomass. Increased temperature resulted in increased leaf area, total biomass, total root biomass, total stem biomass, and number of tillers, but also a lower content of total sugars and a weaker tolerance to frost. The loss of frost tolerance was related to the larger size of plants grown at elevated temperature. The 30% light reduction under shading did not affect the growth, sugar content, or frost tolerance of winter wheat. At the low temperatures found at high latitudes during autumn, the atmospheric CO2 increase is unlikely to enhance autumn growth of winter wheat to any significant extent, while a temperature increase may have important and major effects on its development and growth.  相似文献   

13.
ABSTRACT

Elevated concentrations of carbon dioxide (e[CO2]) affect plant growth and physiological characteristics, including metal accumulation, and the activity of anti-oxidant enzymes. These effects were investigated in cadmium (Cd) tolerant wheat (Triticum aestivum L.) and sorghum (Sorghum bicolor (L.) Moench.) cultivars. Plants were grown at the ambient and elevated CO2 levels, with four concentrations of Cd (0, 10, 20 and 40 mg kg?1) added to the soil. After 60 days, subsamples were tested for chlorophylls and carotenoids, protein, enzyme activities and morphological characteristics.

Results showed that e[CO2] increased plant height, leaf area, and the dry weight of shoots and roots (P < 0.01). In addition, it decreased the Cd concentration in the shoots and roots of wheat, and increased the same concentrations for sorghum. With increasing Cd, the activities of the anti-oxidants, SOD and GSH-px increased in wheat. The differences in enzyme activity parallel the changes in Cd concentration in the plants of both species.  相似文献   

14.
The effect of medium-term (5 years) application of organic and inorganic sources of nutrients (as mineral or inorganic fertilizers) on soil organic carbon (SOC), SOC stock, carbon (C) build-up rate, microbial and enzyme activities in flooded rice soils was tested in west coast of India. Compared to the application of vermicompost, glyricidia (Glyricidia maculate) (fresh) and eupatorium (Chromolaena adenophorum) (fresh) and dhaincha (Sesbania rostrata) (fresh), the application of farmyard manure (FYM) and combined application of paddy straw (dry) and water hyacinth (PsWh) (fresh) improved the SOC content significantly (p < 0.05). The lowest (p < 0.05) SOC content (0.81%) was observed in untreated control. The highest (p < 0.05) SOC stock (23.7 Mg C ha?1) was observed in FYM-treated plots followed by recommended dose of mineral fertilizer (RDF) (23.2 Mg C ha?1) and it was lowest (16.5 Mg C ha?1) in untreated control. Soil microbial biomass carbon (Cmb) (246 µg g?1 soil) and Cmb/SOC (1.92%) were highest (p < 0.05) in FYM-treated plot. The highest (p < 0.05) value of metabolic quotient (qCO2) was recorded under RDF (19.7 µg CO2-C g?1 Cmb h?1) and untreated control (19.6 µg CO2-C g?1 Cmb h?1). Application of organic and inorganic sources of nutrients impacted soil enzyme activities significantly (p < 0.05) with FYM causing highest dehydrogenase (20.5 µg TPF g?1 day?1), phosphatase (659 µg PNP g?1 h?1) and urease (0.29 µg urea g?1 h?1) activities. Application of organic source of nutrients especially FYM improved the microbial and enzyme activities in flooded and transplanted rice soils. Although the grain yield was higher with the application of RDF, but the use of FYM as an organic agricultural practice is more useful when efforts are intended to conserve more SOC and improved microbial activity.  相似文献   

15.
Rising carbon dioxide (CO2) concentration causes fertilization effects resulting in enhanced crop biomass and yields and thus likely enhances nutrient demand of plants. Hence, this field study was carried out to investigate the effects of elevated CO2 and N on biomass yield, nutrient partitioning, and uptake of major nutrients by soybean (Glycine max L.) using open‐top chambers (OTCs) of 4 m × 4 m size. Soybean was grown in OTCs under two CO2 [ambient and elevated (535 ± 36.9 mg L?1)] and four N levels during July to October 2016. The four N levels were N0, N50, N100, and N150 referring to 0, 50, 100, and 150% recommended dose of N. Both CO2 and N significantly affected biomass and grain yield, though the interaction was non‐significant. CO2 enrichment produced 30–65% higher biomass and 26–59% higher grain yield under various N levels. As compared to the optimum N application (N100), the CO2‐mediated increment in biomass yield decreased with either lower or higher N application, with the response being lowest at N150. As compared to ambient concentration, elevated CO2 resulted in significant reduction of seed P concentration at all N application levels but at N150, an opposite trend was observed. The decrease in seed P was maximum at N0 and N50 (7–9%) and by 3% at N100, whereas there was a gain of 7.5% at N150. The seed N and K concentrations were not affected either by CO2 or N application. Total N, P, and K uptake at harvest were significantly affected by CO2 and N, but not by CO2 × N interaction. Elevated CO2 resulted higher uptake of N by 18–61%, P by 23–62%, and K by 22–62% under various N treatments.  相似文献   

16.

Purpose

In recent years, climate change, particularly rising carbon dioxide (CO2) concentration and global warming, has attracted much attention around the world. Forest ecosystems still play a crucial role in global carbon (C) fixation. Quantifying forest aboveground biomass (AGB) and its temporal variations is essential for understanding external impacts (e.g., urbanization, environmental change) as well as assessing the potential of forest ecosystems assimilating the atmospheric CO2.

Materials and methods

In this study, we established regression models for AGB estimation in the Miyun Reservoir region, based on relationships between Landsat-derived variables and ground truth AGB values, which were obtained from both plot measurements and estimations using Light Detection and Ranging (LiDAR) dataset. The models were applied to calibrated Landsat images acquired in 1990, 2000, and 2010 to track the forest AGB temporal variations and the corresponding spatial distributions for each period. The AGB estimations using LiDAR showed high consistency with values based on the plot measurements, while the established models presented an acceptable accuracy.

Results and discussion

The AGB density in the Miyun Reservoir experienced an overall increase since 1990 and was averaged at 52.20 and 32.12 t ha?1, for stand forest and shrub in 2010, respectively. Total AGB in 2010 was estimated to be 4.5 × 107 t, which increased by 8% when compared with the level in 1990. Our results are in the similar range of AGB density reported by other studies carried out in Northern China. Ecological programs including Three-North Shelter Forest Project and Returning Farming to Forest promoted the forest expansion and development during this period, while local farming activities exerted certain negative effects on the surrounding forest systems.

Conclusions

Absolute AGB density values indicated that regions with less external interventions present more consistent biomass accumulation. However, the coarse spatial resolution and 10-year interval of the datasets limited detailed analysis of impacts from urbanization of Beijing City. Future studies incorporating sophisticated ecosystem research methods are expected to uncover the mechanisms and key drivers for the observed variations in the AGB in the Miyun Reservoir region of Beijing, China.
  相似文献   

17.
To estimate the effect of elevated [CO2] on nitrogen (N) and phosphorus (P) dynamics and productivity in summer maize, a field experiment was conducted in open-top chambers (OTCs) at different [CO2] (550 μmol/mol, T1; 750 μmol/mol, T2 and a control, CK) in Nanjing in Jiangsu Province, China. The results showed that maize total N and P accumulation were 13.23–66.56% higher in the elevated [CO2] treatments than in the CK plots during the jointing, anthesis and maturity stages. There was only a significant difference in total N accumulation between the T2 treatment and CK at maturity (P < 0.05). However, rising [CO2] decreased the N and P concentrations in each biomass fraction. Elevated [CO2] increased the amounts of N and P translocation, resulting in the contribution of translocated N to grain N. Similarly, rising [CO2] increased N and P translocation efficiencies, N or P harvest index, and N or P utilization efficiency based on grain yield and N or P utilization efficiencies based on biomass in both growing seasons. In addition, elevated [CO2] significantly increased aboveground biomass at three stages, including 4.73–12.34% at maturity. The grain yields of summer maize increased by 21.28% and 29.07% in the two elevated [CO2] plots. Furthermore, spike numbers, kernels per spike and 100-grain weight were increased by elevated [CO2] treatments. Kernels per spike and grain yield showed obvious differences between elevated [CO2] treatments and CK (p < 0.05).  相似文献   

18.
Background, Aims, and Scope  The genetic structure and the functionality of soil microbes are both important when studying the role of soil in the C cycle in elevated CO2 scenarios. The aim of this work was to investigate the genetic composition of the fungal community by means of PCR-DGGE and the functional diversity of soil micro-organisms in general with MicroResp-based community level physiological profiling (CLPP) in a poplar plantation (POPFACE) grown under elevated [CO2] with and without nitrogen fertilization. Materials and Methods  The POPFACE experimental plantation and FACE facility are located in central Italy, Tuscania (VT). Clones of Populus alba, Populus nigra and Populus x euramericana were grown, from 1999 to 2004, in six 314 m2 plots treated either with atmospheric (control) or enriched (550 μmol mol−1) CO2 with FACE (Free Air CO2 Enrichment) technology in each growing season. Each plot is divided into six triangular sectors, with two sectors per poplar genotype: three species × two nitrogen levels. After removal of the litter layer one soil core per genotype (10 cm wide, 20 cm depth) was taken inside each of the three sectors in each plot, for a total of 36 soil cores (3 replicates × 2 [CO2] × 2 fertilization × 3 species) in October 2004 and in July 2005. DNA was extracted with a bead beating procedure. 18S rDNA gene fragments were amplified with PCR using fungal primers (FR1 GC and FF390). Analysis of CLPP was performed using the MicroResp method. Carbon substrates were selected depending on their ecological relevance to soil and their solubility in water. In particular rhizospheric C sources (carboxylic acids and carbohydrates) were chosen considering the importance of root inputs for microbial metabolism. Results  The fertilization treatment differentiated the fungal community composition regardless of elevated [CO2] or the poplar species; moreover the number of fungal species was lower in fertilized soil. The effect of elevated [CO2] on the fungal community composition was evident only as interaction with the fertilization treatment as, in N-sufficient soils, the elevated [CO2] selected a different microbial community. For CLPP, the differ ent poplar species were the main factors of variation. The FACE treatment, on average, resulted in lower C utilization rates in un-fertilized soils and higher in fertilized soils. Discussion  Fungal biomass and fungal composition depend on different factors: from previous studies we know that the greater quantity and the higher C/N ratio of organic inputs under elevated [CO2] influenced positively the fungal biomass both in fertilized and in un-fertilized soil, whereas nitrogen availability resulted to be the main determinant of fungal community composition in this work. Whole active microbial community was directly influenced by the soil nutrient availability and the poplar species. Under elevated CO2 the competition for N with plants strongly affected the microbial communities, which were not able to benefit from added rhizospheric substrates. Under Nsufficient conditions, the increase of microbial activity due to [CO2] enrichment was related to a more active microbial community, favoured by the current availability of C and N. Conclusions  Different factors influenced the microbial community at different levels: poplar species and root exudates affected the functional properties of the microbial community, while the fungal specific composition (as seen with DGGE) remained unaffected. On the other hand, factors such as N and C availability had a strong impact on the community functionality and composition. Fungal community structure reflected the availability of N in soils and the effect of elevated [CO2] on community structure and function was evident only in N-sufficient soils. The simultaneous availability of C and N was therefore the main driving force for microbial structure and function in this plantation. Recommendations and Perspectives  Using the soil instead of soil extracts for CLPP determination provides a direct measurement of substrate catabolism by microbial communities and reflects activity rather than growth because more immediate responses to substrates are measured. Further applications of this approach could include selective inhibition of different microbial functional groups to investigate specific CLPPs. To combine the structural analysis and the catabolic responses of specific microbial communities (i.e. fungi or bacteria) could provide new outlooks on the role of microbes on SOM decomposition. ESS-Submission Editor: Dr. Kirk Semple (k.semple@lancaster.ac.uk)  相似文献   

19.
Elevated atmospheric CO2 concentration ([CO2]) may change litter chemistry which affects litter decomposability. This study investigated respiration and microbial biomass of soils amended with litter of Pinus densiflora (a coniferous species; pine) and Quercus variabilis (a deciduous species; oak) that were grown under different atmospheric [CO2] and thus had different chemistry. Elevated [CO2] increased lignin/N through increased lignin concentration and decreased N concentration. The CO2 emission from the soils amended with litter produced under the same [CO2] regime was greater for oak than pine litter, confirming that broadleaf litter with lower lignin decomposes faster than needle leaf litter. Within each species, however, soils amended with high lignin/N litter grown under elevated [CO2] emitted more CO2 than those with low lignin/N litter grown under ambient [CO2]. Such contrasting effects of lignin/N on inter- and intra-species variations in litter decomposition should be ascribed to the effects of other litter chemistry variables including nonstructural carbohydrate, calcium and manganese as well as inhibitory effect of N on lignin decomposition. The microbial biomass was also higher in the soils amended with high lignin/N litter than those with low lignin/N litter probably due to low substrate use efficiency of lignin by microbes. Our study suggests that elevated [CO2] increases lignin/N for both species, but increased lignin/N does not always reduce soil respiration and microbial biomass. Further study investigating a variety of tree species is required for more comprehensive understanding of inter- and intra-species variations of litter decomposition under elevated [CO2].  相似文献   

20.
The association between the responses of microbial activity and residue decomposition to elevated atmospheric [CO2] under field conditions in Australian cropping systems is unknown. We measured soil CO2 emission and decomposition of wheat and field pea residues in a wheat cropping system in the field using the Australian Grains Free-Air CO2 Enrichment (AGFACE) facility in Horsham, Victoria. Elevated [CO2] (550 μmol mol−1) increased soil CO2 emission by 41%, but did not affect the percentage of the original mass or C remaining for either type of residue throughout the experimental period. Our findings suggest that the rates of residue decomposition and residue C mineralization in this semi-arid wheat cropping system were not affected by elevated [CO2] despite higher microbial activity. This has major implication for the C sequestration potential of semi-arid cropping systems under future CO2 climates.  相似文献   

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