共查询到20条相似文献,搜索用时 15 毫秒
1.
T. V. Shushkova G. K. Vasilieva I. T. Ermakova A. A. Leontievsky 《Applied Biochemistry and Microbiology》2009,45(6):599-603
Sorption and microbial destruction of glyphosate, the active agent of the herbicide Ground Bio, in suspensions of sod-podzol
and gray forest soils has been studied. According to the adsorptive values (3560 and 8200 mg/kg, respectively) and the Freundlich
constants (Kf, 15.6 and 18.7, respectively), these soils had a relatively high sorption capacity as related to the herbicide. Sorbed glyphosate
is represented by extractable and bound (non-extractable) fractions. After long-term incubation of sterile suspensions, the
ratio of these fractions reached 2: 1 for sod-podzol soil and 1: 1 for gray forest soil. Inoculation of a native suspension
of sod-podzol soil with cells of a selected strain-degrader Ochrobactum anthropi GPK 3 resulted in a 25.4% decrease in the total glyphosate content (dissolved and extractable), whereas in a noninoculated
suspension, the loss did not exceed 5.5%. The potential for the use of a selected bacterial strain in the glyphosate destruction
processes in soil systems is demonstrated for the first time. 相似文献
2.
Conditions for obtaining the active biomass of Ochrobactrum anthropi GPK 3 and Achromobacter sp. Kg 16, bacteria which are able to degrade the herbicide glyphosate (N-phosphonomethylglycine), were investigated. In
the batch culture, degradation was most effective in the medium with pH 6.0–7.0 and aeration at 10–60% of air saturation supplemented
with glutamate and ammonium chloride as sources of carbon and nitrogen, respectively. Due to the adaptation of the cells and
induction of the relevant enzymatic systems, the inoculum grown in the presence of glyphosate exhibited 1.5–2-fold higher
efficiency of xenobiotic degradation than that grown with other sources of phosphorus (orthophosphate and methylphosphonic
acid). The efficiency of the toxicant decomposition increased with an increase in a specific load of glyphosate, which the
cells were subjected to during the initial stage of growth. The specific load was regulated both by the initial cell concentration
and the concentration of the phosphorus source, and the effect was probably determined by its availability to microorganisms.
Storage of the liquid biopreparation as a paste with stabilizers (ascorbate, thiourea, and glutamate) at room temperature
for 50 days resulted in high level of bacteria viability and a degrading activity approximately equal to that obtained when
the bacteria were maintained on the agar medium containing glyphosate at 4°C with monthly transfers to the fresh culture medium. 相似文献
3.
Bioremediation of glyphosate-contaminated soils 总被引:1,自引:0,他引:1
Inna T. Ermakova Nina I. Kiseleva Tatyana Shushkova Mikhail Zharikov Gennady A. Zharikov Alexey A. Leontievsky 《Applied microbiology and biotechnology》2010,88(2):585-594
Based on the results of laboratory and field experiments, we performed a comprehensive assessment of the bioremediation efficiency
of glyphosate-contaminated soddy-podzol soil. The selected bacterial strains Achromobacter sp. Kg 16 (VKM B-2534D) and Ochrobactrum anthropi GPK 3 (VKM B-2554D) were used for the aerobic degradation of glyphosate. They demonstrated high viability in soil with the
tenfold higher content of glyphosate than the recommended dose for the single in situ treatment of weeds. The strains provided
a two- to threefold higher rate of glyphosate degradation as compared to indigenous soil microbial community. Within 1–2 weeks
after the strain introduction, the glyphosate content of the treated soil decreased and integral toxicity and phytotoxicity
diminished to values of non-contaminated soil. The decrease in the glyphosate content restored soil biological activity, as
is evident from a more than twofold increase in the dehydrogenase activity of indigenous soil microorganisms and their biomass
(1.2-fold and 1.6-fold for saprotrophic bacteria and fungi, respectively). The glyphosate-degrading strains used in this study
are not pathogenic for mammals and do not exhibit integral toxicity and phytotoxicity. Therefore, these strains are suitable
for the efficient, ecologically safe, and rapid bioremediation of glyphosate-contaminated soils. 相似文献
4.
Sviridov AV Shushkova TV Zelenkova NF Vinokurova NG Morgunov IG Ermakova IT Leontievsky AA 《Applied microbiology and biotechnology》2012,93(2):787-796
Bacterial strains capable of utilizing methylphosphonic acid (MP) or glyphosate (GP) as the sole sources of phosphorus were
isolated from soils contaminated with these organophosphonates. The strains isolated from MP-contaminated soils grew on MP
and failed to grow on GP. One group of the isolates from GP-contaminated soils grew only on MP, while the other one grew on
MP and GP. Strains Achromobacter sp. MPS 12 (VKM B-2694), MP degraders group, and Ochrobactrum anthropi GPK 3 (VKM B-2554D), GP degraders group, demonstrated the best degradative capabilities towards MP and GP, respectively,
and were studied for the distribution of their organophosphonate catabolism systems. In Achromobacter sp. MPS 12, degradation of MP was catalyzed by C–P lyase incapable of degrading GP (C–P lyase I). Adaptation to growth on
GP yielded the strain Achromobacter sp. MPS 12A, which retained its ability to degrade MP via C–P lyase I and was capable of degrading GP with formation of sarcosine,
thus suggesting the involvement of a GP-specific C–P lyase II. O. anthropi GPK 3 also degraded MP via C–P lyase I, but degradation of GP in it was initiated by glyphosate oxidoreductase, which was
followed by product transformation via the phosphonatase pathway. 相似文献
5.
Guomo Zhou Shunyao Zhuang Qiufang Xu Hua Qin Minghung Wong Zhihong Cao 《The Botanical review》2011,77(3):296-303
Area of bamboo forest (Phyllostachys praecox) has rapidly increased in southern China during the last 20 years due to its high economic value. Aims of this study were
to analyse the temporal and spatial variations of soil organic matter (SOM) in heavily winter mulched bamboo stands and to
estimate potential for carbon sequestration. Total of 60 soil profiles with 0–15 years of bamboo plantation were sampled from
three towns in Lin’an County. Results showed that with increased plantation years, SOM decreased slightly at the beginning
(1–5 years), and then rose up steadily. Based on the average of the three locations, the highest SOM content of 75.82 g/kg
was the surface layer (0–10 cm) of the 15 years. As plantation year increased, the variation of SOM in the surface layer (0–10 cm)
was represented by a parabolic shape, and in the second layer (10–20 cm), it was a similar mode, but less vigorous. Soil organic
carbon (SOC) storage significantly increased during 5 to 15 years after it reached full production, and the calculated annual
SOC increment in 0–40 cm soil profile was about 6.3 t C/ha/year. Therefore, extended Phyllostachys praecox forests can be considered as one option for countering CO2 emissions and regional climate change. 相似文献
6.
The role of roots penetrating various undisturbed soil horizons beneath loose layer in water use and shoot growth of maize
was evaluated in greenhouse experiment. 18 undisturbed soil columns 20 cm in diameter and 20 cm in height were taken from
the depths 30–50 cm and 50–70 cm from a Brown Lowland soil, a Pseudogley and a Brown Andosol (3 columns from each depth and
soil). Initial resistance to penetration in undisturbed soil horizons varied from 2.5 to 8.9 MPa while that in the loose layer
was 0.01 MPa. The undisturbed horizons had a major effect on vertical arrangement of roots. Root length density in loose layer
varied from 96 to 126 km m-3 while in adjacent stronger top layers of undisturbed horizons from 1.6 to 20.0 km m-3 with higher values in upper horizons of each soil. For specific root length, the corresponding ranges were 79.4–107.7 m g-1 (on dry basis) and 38.2–63.7 m g-1, respectively. Ratios of root dry weight per unit volume of soil between loose and adjacent undisturbed layers were much
lower than those of root length density indicating that roots in undisturbed horizons were produced with considerably higher
partition of assimilates. Root size in undisturbed horizons relative to total roots was from 1.1 to 38.1% while water use
from the horizons was from 54.1 to 74.0%. Total water use and shoot growth were positively correlated with root length in
undisturbed soil horizons. There was no correlation between shoot growth and water use from the loose layers. 相似文献
7.
In Finland, over 220,000 ha of arable land has been afforested in recent decades. To meet the goals of forest management on
afforested fields, information on the effects of former agricultural land use on soil fertility is needed. In this study,
we examine the soil fertility of 12 former arable fields afforested either 10 or 60–70 years ago with Norway spruce (Picea abies (L.) Karst.) and adjacent sites that have been forested continuously. Volumetric soil samples were collected from the organic
soil layer and from mineral soil to a depth of 40 cm. Soil samples were analyzed for pH, bulk density, organic matter content
and amounts of nutrients (Kjeldahl N, extractable P, K, Ca, Mg, Zn and B). On afforested fields, amounts of nutrients in the
mineral soil, especially in 10-year-old afforestations, were higher than on continuously forested sites. In the organic layer
plus the 0–40 cm soil layer, the 10-year-old afforestations had 68% more N, 41% more P, 83% more K, 252% more Ca, 6% more
Mg, 61% more Zn and 33% more B than the continuously forested sites at a comparable soil depth. In the 60–70-year-old afforestations,
the differences were significant only for N, Ca and Zn (20% more N, 121% more Ca and 115% more Zn than on the continuously
forested sites). The effects of agriculture on amounts of nutrients were most clearly detected in the former plough layer
(0–20 cm) of the 10-year-old afforestations and in the top layer (0–10 cm) of the older afforestations. Amounts of nutrients
in the organic layer of the afforested sites were lower, but their concentrations were higher than in the continuously forested
sites. On the 10-year-old afforestations, the bulk density of the mineral soil tended to be lower and the organic matter content
higher than on the continuously forested sites. On both young and old afforestations, soil pH was higher than on the continuously
forest sites. According to these results, changes in soil properties caused by agriculture have increased the soil fertility
and therefore probably also the site index. The results also suggest that changes in soil properties due to agricultural land
use are quite long lasting. 相似文献
8.
Vázquez Núñez E García Gaytán A Luna-Guido M Marsch R Dendooven L 《Biodegradation》2009,20(2):191-198
In a previous study, remediation of anthracene from soil was faster in the top 0–2 cm layer than in the lower soil layers.
It was not clear whether this faster decrease was due to biotic or abiotic processes. Anthracene-contaminated soil columns
were covered with black or transparent perforated polyethylene so that aeration occurred but that fluctuations in water content
were minimal and light could reach (LIGHT treatment) or not reach the soil surface (DARK treatment), or left uncovered so
that soil water content fluctuate and light reached the soil surface (OPEN treatment). The amount of anthracene, microbial
biomass C, and microbial activity as reflected by the amount of CO2 produced within 3 days were determined in the 0–2 cm, 2–8 cm, and 8–15 cm layer after 0, 3, 7, 14, and 28 days. In the 0–2 cm
layer of the OPEN treatment, 17% anthracene remained, 48% in the LIGHT treatment and 61% in the DARK treatment after 28 days.
In the 2–8 cm and 8–15 cm layer, treatment had no significant effect on the dissipation of anthracene from soil after 14 and
28 days. It was found that light and fluctuations in water content stimulated the removal of anthracene from the top 0–2 cm
soil layer, but not from the lower soil layers. It can be speculated that covering contaminated soil or pilling it up will
inhibit the dissipation of the contaminant. 相似文献
9.
Sviridov AV Zelenkova NF Vinokurova NG Ermakova IT Leontievsky AA 《Biochemistry. Biokhimii?a》2011,76(6):720-725
We propose a new set of approaches, which allow identifying the primary enzymes of glyphosate (N-phosphonomethyl-glycine)
attack, measuring their activities, and quantitative analysis of glyphosate degradation in vivo and in vitro. Using the developed approach we show that glyphosate degradation can follow different pathways depending on physiological
characteristics of metabolizing strains: in Ochrobactrum anthropi GPK3 the initial cleavage reaction is catalyzed by glyphosate-oxidoreductase with the formation of aminomethylphosphonic
acid and glyoxylate, whereas Achromobacter sp. MPS12 utilize C-P lyase, forming sarcosine. The proposed methodology has several advantages as compared to others described
in the literature. 相似文献
10.
Despite the extensive literature on the effect of afforestation of former arable land on soil properties, we still do not
fully understand whether the changes proceed in the same direction and at the same rate or how long it takes to achieve a
state of soil equilibrium typical of a natural forest ecosystem. Therefore, as part of a comparative study of post-arable
sandy soils (Distric Arenosols) afforested with Scots pine (Pinus silvestris L.) with respect to arable soils and soils of continuous coniferous forests, a range and direction of the changes in some of
their physical and sorptive properties were determined. The studies were carried out in SE Poland, 51°30′–51°37′N, 22°20′–22°35′E.
Ten paired sites of the afforested soils (five with 14- to 17-year-old stands and five with 32- to 36-year-old stands) with
adjacent cultivated fields and five sites of continuous forests with present stands of ca. 150 years were selected. For the
physical properties, undisturbed soil cores were sampled from the upper part of each horizon while in the case of A horizon
of the afforested soils, from two layers: 0–5 cm and 10–15 cm. For the remaining analyses, soil was taken from the whole thickness
of the master horizons and in the case of A horizon of the afforested soils, from three layers: 0–5, 5–10 and 10–20 cm. The
following properties were analysed: texture, bulk density (BD), total porosity (TP), water content at potential of −0.098,
−9.81 and −49.03 kPa, hydrolytic acidity (Ha), base exchangeable cations: Ca2+, Mg2+, K+, Na+, total exchangeable bases (TEB), cation exchange capacity (CEC) and base saturation (BS). Afforestation caused a decrease
in BD, an increase in TP and had no affect on water properties when compared with the cultivated soils. The changes referred
to the A horizon, particularly to its 0–5 cm layer, and were related to the stand age. The CEC gradually rose in the former
plough layer, beginning from the uppermost part, but during the first two decades its increase in the 0–5 cm layer was offset
by a decline in the deeper layers. No substantial increase in CEC, in the whole A horizon, was recorded until three to four
decades of afforestation. Afforestation also invoked an increase in Ha, a drop in TEB, particularly Ca2+, Mg2+ and K+, and reduction in BS. No differences between soils for all the studied properties for B and C horizons were observed. It
was noted that more than 30 years after afforestation, the TEB and BS as well as Ca2+, Mg2+ and K+ content differed substantially, but in most cases not significantly, from their values in the cultivated soils and reached
a level more similar to the soils of continuous coniferous forests. With respect to the water properties, Ha and CEC of the
afforested soils still resembled arable soils, whereas regarding the TP and BD, they were somewhere in the middle. This implies
that to understand changes in the soil properties resulting from afforestation and to predict future trends, long-term research
is needed. 相似文献
11.
Elzbieta Krolak Jerzy Kwapulinski Agnieszka Fischer 《Radiation and environmental biophysics》2010,49(2):229-237
The vertical 137Cs profile of forest and wasteland soils was analyzed in the south of the Podlasie Lowland area (Eastern Poland) about 20 years
after the Chernobyl accident. In addition, the concentration of 40K in soils of the investigated area was measured. Below the litter layer (mean thickness 3 cm), the soil samples were collected
up to a depth of 12 cm and then divided into three layers: 0–3, 3–7, 7–12 cm. The behavior of 137Cs and 40K isotopes in soils was analyzed depending on the depth from which the soil samples were collected, as well as on the content
of organic carbon, pH of soil and its granulometric composition. It was established that the density of 137Cs in the litter layer equals 2.17 kBq m−2; it is the highest in layer 0–3 cm where it equals 3.44 kBq m−2, and it decreases with the depth to the value of 0.76 kBq m−2 in layer 7–12 cm. No similar pattern was observed in wasteland soils. The concentrations of 40K in forest and wasteland soils did not change significantly with depth. 相似文献
12.
Nocturnal increases in water potential (ψ) and water content (θ) in the upper soil profile are often attributed to root water efflux, a process termed hydraulic redistribution
(HR). However, unsaturated liquid or vapor flux of water between soil layers independent of roots also contributes to the
daily recovery in θ (Δθ), confounding efforts to determine the actual magnitude of HR. We estimated liquid (J
l) and vapor (J
v) soil water fluxes and their impacts on quantifying HR in a seasonally dry ponderosa pine (Pinus ponderosa) forest by applying existing datasets of ψ, θ and temperature (T) to soil water transport equations. As soil drying progressed, unsaturated hydraulic conductivity declined rapidly such that
J
l was irrelevant (<2E−05 mm h−1 at 0–60 cm depths) to total water flux by early August. Vapor flux was estimated to be the highest in upper soil (0–15 cm),
driven by large T fluctuations, and confounded the role of HR, if any, in nocturnal θ dynamics. Within the 15–35 cm layer, J
v contributed up to 40% of hourly increases in nocturnal soil moisture. While both HR and net soil water flux between adjacent
layers contribute to θ in the 15–65 cm soil layer, HR was the dominant process and accounted for at least 80% of the daily
recovery in θ. The absolute magnitude of HR is not easily quantified, yet total diurnal fluctuations in upper soil water content
can be quantified and modeled, and remain highly applicable for establishing the magnitude and temporal dynamics of total
ecosystem water flux. 相似文献
13.
We used sugar maple litter double-labeled with 13C and 15N to quantify fluxes of carbon (C) and nitrogen (N) between litter and soil in a northern hardwood forest and the retention
of litter C and N in soil. Two cohorts of litter were compared, one in which the label was preferentially incorporated into
non-structural tissue and the other structural tissue. Loss of 13C from this litter generally followed dry mass and total C loss whereas loss of 15N (20–30% in 1 year) was accompanied by large increases of total N content of this decaying litter (26–32%). Enrichment of
13C and 15N was detected in soil down to 10–15 cm depth. After 6 months of decay (November–May) 36–43% of the 13C released from the litter was recovered in the soil, with no differences between the structural and non-structural labeled
litter. By October the percentage recovery of litter 13C in soil was much lower (16%). The C released from litter and remaining in soil organic matter (SOM) after 1 year represented
over 30 g C m−2 y−1 of SOM accumulation. Recovery of litter 15N in soil was much higher than for C (over 90%) and in May 15N was mostly in organic horizons whereas by October it was mostly in 0–10 cm mineral soil. A small proportion of this N was
recovered as inorganic N (2–6%). Recovery of 15N in microbial biomass was higher in May (13–15%) than in October (about 5%). The C:N ratio of the SOM and microbial biomass
derived from the labeled litter was much higher for the structural than the non-structural litter and for the forest floor
than mineral SOM, illustrating the interactive role of substrates and microbial activity in regulating the C:N stoichiometry
of forest SOM formation. These results for a forest ecosystem long exposed to chronically high atmospheric N deposition (ca.
10 kg N ha−1 y−1) suggest possible mechanisms of N retention in soil: increased organic N leaching from fresh litter and reduced fungal transport
of N from soil to decaying litter may promote N stabilization in mineral SOM even at a relatively low C:N ratio. 相似文献
14.
Fallows improve soil fertility and allow sustainable agriculture. Soil fertility was assessed under different types of fallow
through pH, nutrient concentrations and particulate organic matter (POM) quantity and quality. The two year-fallows were under
Chromolaena odorata, Calliandra calothyrsus and Pueraria phaseoloides on a Typic Kandiudult. Soils were sampled from 0–10 cm and 10–20 cm depth. The weight of POM was 2 mg g−1 of soil under Calliandra, 3.9 mg g−1 under Chromolaena and 3.7 mg g−1 under Pueraria in the 0–10 cm layer. The tPOM-C (proportion of C in the total POM) and tPOM-N (proportion of N in total POM) were 26.1%
and 14.5% under Calliandra, 39.6% and 18.8% under Chromolaena and 37.0% and 16.7% under Pueraria. However, despite the improvement of soil fertility under Pueraria as compared to planted Calliandra, the effect of Pueraria on nutrient concentration and POM status remained similar to that of Chromolaena. Calliandra increased soil acidity and allowed a deterioration of nutrient concentration (Ca, K), ECEC and an impoverishment of POM status. 相似文献
15.
Seasonal dynamics of fine root biomass, root length density, specific root length, and soil resource availability in a Larix gmelinii plantation 总被引:1,自引:0,他引:1
Cheng Yunhuan Han Youzhi Wang Qingcheng Wang Zhengquan 《Frontiers of Biology in China》2006,1(3):310-317
Fine root turnover is a major pathway for carbon and nutrient cycling in terrestrial ecosystems and is most likely sensitive
to many global change factors. Despite the importance of fine root turnover in plant C allocation and nutrient cycling dynamics
and the tremendous research efforts in the past, our understanding of it remains limited. This is because the dynamics processes
associated with soil resources availability are still poorly understood. Soil moisture, temperature, and available nitrogen
are the most important soil characteristics that impact fine root growth and mortality at both the individual root branch
and at the ecosystem level. In temperate forest ecosystems, seasonal changes of soil resource availability will alter the
pattern of carbon allocation to belowground. Therefore, fine root biomass, root length density (RLD) and specific root length
(SRL) vary during the growing season. Studying seasonal changes of fine root biomass, RLD, and SRL associated with soil resource
availability will help us understand the mechanistic controls of carbon to fine root longevity and turnover. The objective
of this study was to understand whether seasonal variations of fine root biomass, RLD and SRL were associated with soil resource
availability, such as moisture, temperature, and nitrogen, and to understand how these soil components impact fine root dynamics
in Larix gmelinii plantation. We used a soil coring method to obtain fine root samples (⩽2 mm in diameter) every month from May to October
in 2002 from a 17-year-old L. gmelinii plantation in Maoershan Experiment Station, Northeast Forestry University, China. Seventy-two soil cores (inside diameter
60 mm; depth intervals: 0–10 cm, 10–20 cm, 20–30 cm) were sampled randomly from three replicates 25 m × 30 m plots to estimate
fine root biomass (live and dead), and calculate RLD and SRL. Soil moisture, temperature, and nitrogen (ammonia and nitrates)
at three depth intervals were also analyzed in these plots. Results showed that the average standing fine root biomass (live
and dead) was 189.1 g·m−2·a−1, 50% (95.4 g·m−2·a−1) in the surface soil layer (0–10 cm), 33% (61.5 g·m−2·a−1), 17% (32.2 g·m−2·a−1) in the middle (10–20 cm) and deep layer (20–30cm), respectively. Live and dead fine root biomass was the highest from May
to July and in September, but lower in August and October. The live fine root biomass decreased and dead biomass increased
during the growing season. Mean RLD (7,411.56 m·m−3·a−1) and SRL (10.83 m·g−1·a−1) in the surface layer were higher than RLD (1 474.68 m·m−3·a−1) and SRL (8.56 m·g−1·a−1) in the deep soil layer. RLD and SRL in May were the highest (10 621.45 m·m−3 and 14.83m·g−1) compared with those in the other months, and RLD was the lowest in September (2 198.20 m·m−3) and SRL in October (3.77 m·g−1). Seasonal dynamics of fine root biomass, RLD, and SRL showed a close relationship with changes in soil moisture, temperature,
and nitrogen availability. To a lesser extent, the temperature could be determined by regression analysis. Fine roots in the
upper soil layer have a function of absorbing moisture and nutrients, while the main function of deeper soil may be moisture
uptake rather than nutrient acquisition. Therefore, carbon allocation to roots in the upper soil layer and deeper soil layer
was different. Multiple regression analysis showed that variation in soil resource availability could explain 71–73% of the
seasonal variation of RLD and SRL and 58% of the variation in fine root biomass. These results suggested a greater metabolic
activity of fine roots living in soil with higher resource availability, which resulted in an increased allocation of carbohydrate
to these roots, but a lower allocation of carbohydrate to those in soil with lower resource availability.
__________
Translated from Acta Phytoecologica Sinica, 2005, 29(3): 403–410 [译自: 植物生态学报, 2005, 29(3): 403–410] 相似文献
16.
The side effects of glyphosate on the soil microflora were monitored by applying a range of glyphosate concentrations (0,
2, 20, and 200 μg g−1 herbicide) to incubated soil samples, and following changes in various microbial groups over 27 days. Bacterial propagule
numbers were temporarily enhanced by 20 μg g−1 and 200 μg g−1 glyphosate, while actinomycete and fungal propagule numbers were unaffected by glyphosate. The frequency of three fungal
species on organic particles in soil was temporarily enhanced by 200 μg g−1 glyphosate, while one was inhibited. One species was temporily enhanced on mineral particles. However, many of these fungi
were inhibited by 200 μg g−1 glyphosate in pure culture. There was little agreement between species responses to glyphosate in incubated soil samples
and in pure culture. 相似文献
17.
Akira Oyafuso Moriya Ota Masato Ishimine Norio Arakaki 《Applied Entomology and Zoology》2011,46(2):171-176
To determine the depth of soil at which mated females of the white grub beetle Dasylepida ishigakiensis Niijima et Kinoshita oviposited and their larval offspring stayed in the soil in different seasons, 847 mated female and
male adults were released into a caged sugarcane field on Miyako Island. We then excavated this field systematically to collect
adults and their larval offspring in the soil once or twice per month from 24 April 2002 to 31 March 2003. Dead females were
found between 10 and 50 cm deep in the soil (N = 91), but most frequently in the layer 30–40 cm deep (N = 42; 46.2%). They were recovered more frequently in the soil at the plant foot (N = 73; 80.2%) than in the furrows (N = 18; 19.8%). On the other hand, no male carcass was discovered either in the soil or on the ground surface. The number of
larvae discovered in the soil per row was large on 30 April (N = 52.5) and on 5 June (N = 58.3), when they were at the first instar. It decreased rapidly thereafter until 21 August (N = 9.5), when they molted to the second instar, and remained at similar levels through to the following 31 March (N = 8.0), during which they were mostly at the third instar. The larvae were found at various soil depths ranging from 0 to
70 cm, but the majority were found between 10 and 30 cm deep. The last sampling on 31 March indicated that mature larvae moved
to a deeper layer for estivation. These results suggested that physical control through rotary tillage before they move to
the deeper layer may be effective. 相似文献
18.
The fate of sheep urine sulphate in the soil and its plant uptake was monitored using 35S-labelled sulphate-S in undisturbed pasture microplots in two glasshouse experiments. The extent of macropore flow of simulated
urine immediately following a sheep urination was also investigated at 5 pasture sites in the field.
Immediately following urination to pasture microplots in the glasshouse, the amounts of urinederived 35S recovered in the 0–2.5, 2.5–7.5, 7.5–15 and 15–30 cm soil layers were 38, 28, 18 and 9%, respectively. In the field study
on 5 contrasting soils, a similar pattern was found with 55–70, 20–35 and 13–20% of simulated urine being recovered in the
0–5, 5–10 and 10–15 cm soil layers, respectively. There was insignificant loss below 15 cm. If urine had moved via simple
displacement in these soils the wetting front would have reached only 2.0–2.5 cm in depth suggesting that significant downward
movement of urine via macropore flow occurs after urination.
In a 15-day period following urine application to a pasture soil there was a rapid rate of incorporation of 35S into organic forms, while between 15 and 64 days the rate of incorporation declined. After 7 days, 27% of added 35S had been incorporated into organic forms with 19% being C-bonded S and 8% Hl-reducible S. This rapid incorporation was attributed
to the large and active microbial biomass present in the rhizosphere. Since urine application depressed pasture growth, due
to ‘urine burn’, less than 10% of applied 35S was absorbed by pasture plants over a 64-day period. A second experiment using microplots of contrasting soil types, confirmed
that the majority of the 35S incorporated into the organic form was present as C-bonded S. Results showed that of the 35S remaining in the 0–2.5 cm layer 35 days after application, 20–40% was present as sulphate, 10–20% as Hl-reducible S and
50–60% as C-bonded S. Plant uptake of S accounted for only 7–12% of applied 35S over the 35-day period. 相似文献
19.
Eva Ritter 《Plant and Soil》2007,295(1-2):239-251
Afforestation has become an important tool for soil protection and land reclamation in Iceland. Nevertheless, the harsh climate
and degraded soils are growth-limiting for trees, and little is know about changes in soil nutrients in maturing forests planted
on the volcanic soils. In the present chronosequence study, changes in C, N and total P in soil (0–10 and 10–20 cm depth)
and C and N in foliar tissue were investigated in stands of native Downy birch (Betula pubescens Enrh.) and the in Iceland introduced Siberian larch (Larix sibirica Ledeb.). The forest stands were between 14 and 97 years old and were established on heath land that had been treeless for
centuries. Soils were Andosols derived from basaltic material and rhyolitic volcanic ash. A significant effect of tree species
was only found for the N content in foliar tissue. Foliar N concentrations were significantly higher and foliar C/N ratios
significantly lower in larch needles than in birch leaves. There was no effect of stand age. Changes in soil C and the soil
nutrient status with time after afforestation were little significant. Soil C concentrations in 0–10 cm depth in forest stands
older than 30 years were significantly higher than in heath land and forest stands younger than 30 years. This was attributed
to a slow accumulation of organic matter. Soil N concentrations and soil Ptot were not affected by stand age. Nutrient pools in the two soil layers were calculated for an average weight of soil material
(400 Mg soil ha−1 in 0–10 cm depth and 600 Mg soil ha−1 in 10–20 cm depth, respectively). Soil nutrient pools did not change significantly with time. Soil C pools were in average
23.6 Mg ha−1 in the upper soil layer and 16.9 Mg ha−1 in the lower soil layer. The highest annual increase in soil C under forest compared to heath land was 0.23 Mg C ha−1 year−1 in 0–10 cm depth calculated for the 53-year-old larch stand. Soil N pools were in average 1.0 Mg N ha−1 in both soil layers and did not decrease with time despite a low N deposition and the uptake and accumulation of N in biomass
of the growing trees. Soil Ptot pools were in average 220 and 320 kg P ha−1 in the upper and lower soil layer, respectively. It was assumed that mycorrhizal fungi present in the stands had an influence
on the availability of N and P to the trees.
Responsible Editor: Hans Lambers. 相似文献
20.
Soil erodibility (K factor) is an important index for measuring soil susceptibility to water erosion, and an essential parameter that is needed
for the prediction of soil erosion. Field investigation and laboratory analysis were conducted to study the changes of soil
characteristics during long-term vegetation restoration in the hilly gullied loess area. The soil erodibility K values were calculated using the EPIC model and the physico-chemical properties as well as microbial characteristics were
evaluated along a chronosequence of natural vegetation recovery (0–50 years) in abandoned land in the Zhifanggou Watershed
of Ansai County, northwestern Shaanxi Province, China. The results showed that natural vegetation recovery following abandonment
resulted in improvement of the soil properties and structure and these improving effects were closely related to the date
of abandonment. Specifically, the K value of the surface layer (0–20 cm) was significantly reduced with time, while the total organic carbon, total nitrogen
and soil microbial biomass C, microbial N and microbial P and the water-stable aggregate increased quickly. During the first
10 years of abandonment, these changes occurred relatively quickly due to a significant increase in soil organic matter, after
which they gradually fluctuated for approximately 20 years, reaching their uttermost or minimum levels finally. However, these
values differed greatly under Platycladus orientalis forest, which suggests that soil rehabilitation is a long-term task that requires several generations to complete. 相似文献