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1.
The influence of ants on soil and water losses from an orange orchard in eastern Spain 总被引:2,自引:0,他引:2
Herbicide applications have greatly reduced plant cover, and increased soil erosion on a new orange orchard planted on valley slopes in eastern Spain. This has increased the importance of soil fauna, such as ants, in regulating soil erosion processes. Ants increase water infiltration rates by forming soil macropores during nest construction, but new soil brought to the surface by ant activity could increase the sediments available for erosion. Simulated rainfall experiments were conducted on 20 paired plots (20 with ant activity and 20 controls) to study the impact of ants on surface water flow and sediment movement in an intensively managed orange orchard near Valencia, Spain. Simulated rainfall was applied to each plot at a rate of 55 mm/h on a 0.25 m2 area for 1 h. We found a reduction of soil bulk density, an increase in soil organic matter, and an increase in macropore flow in ant‐affected soils, as compared to soil without ant activity. These ant‐induced soil changes increased water infiltration rates and runoff discharge. However, the fresh, unconsolidated soil brought to the surface during nest construction resulted in greater soil loss on two plots than their ant‐free controls. Ants can be an important factor in soil erosion processes when surface vegetation is removed by intensive herbicide use. 相似文献
2.
Soil carbon storage, litterfall and CO2 efflux in fertilized and unfertilized larch (Larix leptolepis) plantations 总被引:1,自引:0,他引:1
Choonsig Kim 《Ecological Research》2008,23(4):757-763
This study evaluated the effects of forest fertilization on the forest carbon (C) dynamics in a 36-year-old larch (Larix leptolepis) plantation in Korea. Above- and below-ground C storage, litterfall, root decomposition and soil CO2 efflux rates after fertilization were measured for 2 years. Fertilizers were applied to the forest floor at rates of 112 kg
N ha−1 year−1, 75 kg P ha−1 year−1 and 37 kg K ha−1 year−1 for 2 years (May 2002, 2003). There was no significant difference in the above-ground C storage between fertilized (41.20 Mg C
ha−1) and unfertilized (42.25 Mg C ha−1) plots, and the C increment was similar between the fertilized (1.65 Mg C ha−1 year−1) and unfertilized (1.52 Mg C ha−1 year−1) plots. There was no significant difference in the soil C storage between the fertilized and unfertilized plots at each soil
depth (0–15, 15–30 and 30–50 cm). The organic C inputs due to litterfall ranged from 1.57 Mg C ha−1 year−1 for fertilized to 1.68 Mg C ha−1 year−1 for unfertilized plots. There was no significant difference in the needle litter decomposition rates between the fertilized
and unfertilized plots, while the decomposition of roots with 1–2 mm diameters increased significantly with the fertilization
relative to the unfertilized plots. The mean annual soil CO2 efflux rates for the 2 years were similar between the fertilized (0.38 g CO2 m−2 h−1) and unfertilized (0.40 g CO2 m−2 h−1) plots, which corresponded with the similar fluctuation in the organic carbon (litterfall, needle and root decomposition)
and soil environmental parameters (soil temperature and soil water content). These results indicate that little effect on
the C dynamics of the larch plantation could be attributed to the 2-year short-term fertilization trials and/or the soil fertility
in the mature coniferous plantation used in this study. 相似文献
3.
Patch Configuration Non-linearly Affects Sediment Loss across Scales in a Grazed Catchment in North-east Australia 总被引:1,自引:0,他引:1
John A. Ludwig Rebecca Bartley Aaron A. Hawdon Brett N. Abbott David McJannet 《Ecosystems》2007,10(5):839-845
Abstract
A principle of the cross-scale interaction (CSI) framework is that disturbance-induced landscape changes resulting in coarser-grained
spatial structure may non-linearly amplify transfer processes across scales. We studied suspended sediment losses at two spatial
scales (0.24 m2 plots and ca. 0.25 ha hillslopes of about 140 m in length) in a semiarid savanna landscape to determine whether the spatial
structure of grassy and bare soil areas introduced a non-linear amplification of sediment loss. Sediment loss rates from 0.24 m2 bare plots averaged 1.527 t ha−1 y−1, which was 23 times the loss rate from nearby grassy plots (0.066 t ha−1 y−1). These rates were then extrapolated linearly to two hillslopes separated by only 200 m and having similar total grass cover,
slope and soil type but differing in the spatial structure of bare soil patches. The coarse-grained hillslope had a large
bare patch on its lower slope, whereas the fine-grained hillslope had no bare soil patches when quantified at a 4 m grid-cell
resolution. Measured sediment loss from the fine-grained hillslope averaged 0.050 t ha−1 y−1, whereas the average sediment loss from the coarse-grained hillslope was 2.133 t ha−1 y−1. By linearly extrapolating from the plot scale, the expected sediment loss for the fine-grained hillslope was 0.066 t ha−1 y−1, which is similar to that observed. The expected sediment loss for the coarse-grained hillslope was 0.855 t ha−1 y−1, where linear extrapolation assumed a 46:54 ratio of bare to grassy plots and that the spatial arrangement of plots does
not affect sediment loss processes. For the coarse-grained hillslope observed sediment loss is 2.5 times greater than that
expected by linear extrapolation from the plot scale. This result indicates a cross-scale interaction related to spatial configuration
of patches. We suggest that there were non-linearities in hillslope ecohydrological transfer processes (runoff, erosion) across
scales due to a specific patch configuration that greatly amplified sediment loss because the pattern failed to slow runoff
and retain sediment before it entered a creek. This example supports the CSI framework and indicates the importance of considering
the effect of spatial structure when predicting system dynamics at different scales. 相似文献
4.
Old growth forest soils are large C reservoirs, but the impacts of tree-fall gaps on soil C in these forests are not well
understood. The effects of forest gaps on soil C dynamics in old growth northern hardwood–hemlock forests in the upper Great
Lakes region, USA, were assessed from measurements of litter and soil C stocks, surface C efflux, and soil microbial indices
over two consecutive growing seasons. Forest floor C was significantly less in gaps (19.0 Mg C ha−1) compared to gap-edges (39.5 Mg C ha−1) and the closed forest (38.0 Mg C ha−1). Labile soil C (coarse particulate organic matter, cPOM) was significantly less in gaps and edges (11.1 and 11.2 Mg C ha−1) compared to forest plots (15.3 Mg C ha−1). In situ surface C efflux was significantly greater in gaps (12.0 Mg C ha−1 y−1) compared to edges and the closed forest (9.2 and 8.9 Mg C ha−1 y−1). Microbial biomass N (MBN) was significantly greater in edges (0.14 Mg N ha−1) than in the contiguous forest (0.09 Mg N ha−1). The metabolic quotient (qCO2) was significantly greater in the forest (0.0031 mg CO2 h−1 g−1/mg MBC g−1) relative to gaps or edges (0.0014 mg CO2 h−1 g−1/mg MBC g−1). A case is made for gaps as alleviators of old growth forest soil C saturation. Relative to the undisturbed closed forest,
gaps have significantly less labile C, significantly greater in situ surface C efflux, and significantly lower decreased qCO2 values. 相似文献
5.
Ants are among the most important elements in many ecosystems and known as famous ecosystem engineers. By changing physical and chemical properties of soil, ants may provide suitable habitats for other species. Based on previous observations, we hypothesized that Persian goitered gazelles (Gazella subgutturosa subgutturosa) exhibit a preference for utilizing sites close to seed harvester ant (Messor spp.) nests. We tested our hypothesis by (1) mapping the occurrence of harvester ant nests and aggregated gazelle pellet groups along 31 strip transects, (2) monitoring pellet group accumulation bimonthly at 56 pairs of permanent plots established on ant nests and at adjacent control sites for a complete year, and (3) comparing vegetation and soil parameters between ant nest sites used by gazelles and paired control plots without ant nests. Although the area of Messor spp. nest sites covered only about 0.29% of the sampled transects, 84% of the gazelle pellet group aggregation sites were positioned upon ant nests, suggesting that gazelles actively selected Messor spp. nest sites. Pair-wise comparisons between ant nest plots and paired control plots also confirmed higher use of ant nest sites by gazelles compared to sites without ant nests in all time periods. Percent soil organic matter, percent cover of gravel, and annual herb vegetation significantly differed between ant nest and paired control plots in all the vegetation communities. We suggest that the alterations brought about by harvester ants on soil and vegetation make these sites attractive to gazelles. Gazelle territoriality behaviour and use of ant nests as bedding sites may be the reasons for selection of ant nest sites by gazelles. 相似文献
6.
Development of ground vegetation biomass and nutrient pools in a clear-cut disc-plowed boreal forest
Marjo Palviainen Leena Finér Ari Laurén Hannu Mannerkoski Sirpa Piirainen Michael Starr 《Plant and Soil》2007,297(1-2):43-52
Nutrient leaching from forest substrate after clear-cutting and subsequent soil preparation is strongly influenced by the
capacity of ground vegetation to sequester the released nutrients. We studied the rates and patterns of biomass and nutrient
accumulation in ground vegetation growing on ridges, in furrows and on undisturbed surfaces for 2–5 years after disc-plowing
in eastern Finland. The biomass of mosses on ridges remained significantly lower than that in furrows and on undisturbed surfaces.
Field layer biomass on ridges and in furrows was significantly lower than on undisturbed surfaces throughout the study period.
Field layer biomass increased more on ridges than in furrows. Root biomass on ridges and undisturbed surfaces was considerably
higher than in furrows. Five years after disc-plowing, total biomass and nutrient pools for ridges (biomass 4,975 kg ha−1, N 40 kg ha−1, P 5 kg ha−1, K 20 kg ha−1 and Ca 18 kg ha−1) and undisturbed surfaces (biomass 5,613 kg ha−1, N 43 kg ha−1, P 5 kg ha−1, K 22 kg ha−1 and Ca 18 kg ha−1) were similar, but considerably lower for furrows (biomass 1,807 kg ha−1, N 16 kg ha−1, P 2 kg ha−1, K 10 kg ha−1 and Ca 6 kg ha−1). Ridges covered 25% of the area, furrows 30 and 45% was undisturbed surfaces. Taking into account the proportion of each
type of surface, values for the whole prepared clear-cut area were 4,312, 34, 4, 18 and 14 kg ha−1 for biomass, N, P, K and Ca, respectively. Biomass and nutrient pools had not returned to uncut forest levels at the end
of the 5-year study period. The results indicate that mosses and field layer vegetation respond differently to soil preparation,
that the development of biomass on ridges, in furrows and on undisturbed surfaces proceeds at different rates, and that the
biomass and nutrient uptake of ground vegetation remains below pre-site preparation levels for several years. However, ridges,
which are known to be the most susceptible to leaching, revegetate rapidly.
Responsible Editor: Tibor Kalapos. 相似文献
7.
The effects of a slow-release N-enriched rock powder on soil chemistry, on the development of the soil vegetation (field layer
vegetation), on the nutritional status of pine seedlings (Pinus sylvestris L.), and on decomposition rates of cellulose in
lignite-poor mine spoils were studied. In the initial phase after afforestation fertilization caused a significant increase
in NO3
−-N concentrations in the soil solution of the top-soil (0–60 cm). Subsequently, NO3
−-N concentrations of all N fertilized treatments decreased with the exception of the highest N application area (500 kg N
ha−1). This decrease of NO3
−-N concentrations was related to the establishment of a field layer vegetation, which developed according to the amount of
N applied. In the above-ground phytomass of the field layer vegetation a maximum N accumulation amount of 22 kg ha−1 was measured. Cellulose decomposition increased with higher N application rates. In the second year after N-fertilization,
the pine needles indicated insufficient supply for almost all nutrients except for N. The deficiency symptoms were most pronounced
at the plots that had received the highest amounts of nitrogen. This phenomenon appears to be related to the competition by
the field layer vegetation.
This revised version was published online in June 2006 with corrections to the Cover Date.
This revised version was published online in June 2006 with corrections to the Cover Date.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
8.
Jirko Holst Chunyan Liu Nicolas Brüggemann Klaus Butterbach-Bahl Xunhua Zheng Yuesi Wang Shenghui Han Zhisheng Yao Jin Yue Xingguo Han 《Ecosystems》2007,10(4):623-634
Gross rates of N mineralization and nitrification, and soil–atmosphere fluxes of N2O, NO and NO2 were measured at differently grazed and ungrazed steppe grassland sites in the Xilin river catchment, Inner Mongolia, P. R.
China, during the 2004 and 2005 growing season. The experimental sites were a plot ungrazed since 1979 (UG79), a plot ungrazed
since 1999 (UG99), a plot moderately grazed in winter (WG), and an overgrazed plot (OG), all in close vicinity to each other.
Gross rates of N mineralization and nitrification determined at in situ soil moisture and soil temperature conditions were
in a range of 0.5–4.1 mg N kg−1 soil dry weight day−1. In 2005, gross N turnover rates were significantly higher at the UG79 plot than at the UG99 plot, which in turn had significantly
higher gross N turnover rates than the WG and OG plots. The WG and the OG plot were not significantly different in gross ammonification
and in gross nitrification rates. Site differences in SOC content, bulk density and texture could explain only less than 15%
of the observed site differences in gross N turnover rates. N2O and NO
x
flux rates were very low during both growing seasons. No significant differences in N trace gas fluxes were found between
plots. Mean values of N2O fluxes varied between 0.39 and 1.60 μg N2O-N m−2 h−1, equivalent to 0.03–0.14 kg N2O-N ha−1 y−1, and were considerably lower than previously reported for the same region. NO
x
flux rates ranged between 0.16 and 0.48 μg NO
x
-N m−2 h−1, equivalent to 0.01–0.04 kg NO
x
-N ha−1 y−1, respectively. N2O fluxes were significantly correlated with soil temperature and soil moisture. The correlations, however, explained only
less than 20% of the flux variance. 相似文献
9.
Response of soil respiration to simulated N deposition in a disturbed and a rehabilitated tropical forest in southern China 总被引:3,自引:1,他引:2
Jiangming Mo Wei Zhang Weixing Zhu Yunting Fang Dejun Li Ping Zhao 《Plant and Soil》2007,296(1-2):125-135
Responses of soil respiration (CO2 emission) to simulated N deposition were studied in a disturbed (reforested forest with previous understory and litter harvesting)
and a rehabilitated (reforested forest with no understory and litter harvesting) tropical forest in southern China from October
2005 to September 2006. The objectives of the study were to test the following hypotheses: (1) soil respiration is higher
in rehabilitated forest than in disturbed forest; (2) soil respiration in both rehabilitated and disturbed tropical forests
is stimulated by N additions; and (3) soil respiration is more sensitive to N addition in disturbed forest than in rehabilitated
forest due to relatively low soil nutrient status in the former, resulting from different previous human disturbance. Static
chamber and gas chromatography techniques were employed to quantify the soil respiration, following different N treatments
(Control, no N addition; Low-N, 5 g N m−2 year−1; Medium-N, 10 g N m−2 year−1), which had been applied continuously for 26 months before the respiration measurement. Results showed that soil respiration
exhibited a strong seasonal pattern, with the highest rates observed in the hot and wet growing season (April–September) and
the lowest rates in winter (December–February) in both rehabilitated and disturbed forests. Soil respiration rates exhibited
significant positive exponential relationship with soil temperature and significant positive linear relationship with soil
moisture. Soil respiration was also significantly higher in the rehabilitated forest than in the disturbed forest. Annual
mean soil respiration rate in the rehabilitated forest was 20% lower in low-N plots (71 ± 4 mg CO2-C m−2 h−1) and 10% lower in medium-N plots (80 ± 4 mg CO2-C m−2 h−1) than in the control plots (89 ± 5 mg CO2-C m−2 h−1), and the differences between the control and low-N or medium-N treatments were statistically significant. In disturbed forest,
annual mean soil respiration rate was 5% lower in low-N plots (63 ± 3 mg CO2-C m−2 h−1) and 8% lower in medium-N plots (61 ± 3 mg CO2-C m−2 h−1) than in the control plots (66 ± 4 mg CO2-C m−2 h−1), but the differences among treatments were not significant. The depressed effects of experimental N deposition occurred
mostly in the hot and wet growing season. Our results suggest that response of soil respiration to elevated N deposition in
the reforested tropical forests may vary depending on the status of human disturbance.
Responsible Editor: Hans Lambers. 相似文献
10.
Late-successional forests in the upper Great Lakes region are susceptible to nitrogen (N) saturation and subsequent nitrate
(NO3−) leaching loss. Endemic wind disturbances (i.e., treefall gaps) alter tree uptake and soil N dynamics; and, gaps are particular
susceptible to NO3− leaching loss. Inorganic N was measured throughout two snow-free periods in throughfall, forest floor leachates, and mineral
soil leachates in gaps (300–2,000 m2, 6–9 years old), gap-edges, and closed forest plots in late-successional northern hardwood, hemlock, and northern hardwood–hemlock
stands. Differences in forest water inorganic N among gaps, edges, and closed forest plots were consistent across these cover
types: NO3− inputs in throughfall were significantly greater in undisturbed forest plots compared with gaps and edges; forest floor leachate
NO3− was significantly greater in gaps compared to edges and closed forest plots; and soil leachate NO3− was significantly greater in gaps compared to the closed forest. Significant differences in forest water ammonium and pH
were not detected. Compared to suspected N-saturated forests with high soil NO3− leaching, undisturbed forest plots in these late-successional forests are not losing NO3− (net annual gain of 2.8 kg ha−1) and are likely not N-saturated. Net annual NO3− losses were observed in gaps (1.3 kg ha−1) and gap-edges (0.2 kg ha−1), but we suspect these N leaching losses are a result of decreased plant uptake and increased soil N mineralization associated
with disturbance, and not N-saturation. 相似文献
11.
Altitudinal changes in carbon storage of temperate forests on Mt Changbai, Northeast China 总被引:8,自引:0,他引:8
Biao Zhu Xiangping Wang Jingyun Fang Shilong Piao Haihua Shen Shuqing Zhao Changhui Peng 《Journal of plant research》2010,123(4):439-452
A number of studies have investigated regional and continental scale patterns of carbon (C) stocks in forest ecosystems; however,
the altitudinal changes in C storage in different components (vegetation, detritus, and soil) of forest ecosystems remain
poorly understood. In this study, we measured C stocks of vegetation, detritus, and soil of 22 forest plots along an altitudinal
gradient of 700–2,000 m to quantify altitudinal changes in carbon storage of major forest ecosystems (Pinus koraiensis and broadleaf mixed forest, 700–1,100 m; Picea and Abies forest, 1,100–1,800 m; and Betula ermanii forest, 1,800–2,000 m) on Mt Changbai, Northeast China. Total ecosystem C density (carbon stock per hectare) averaged 237 t C ha−1 (ranging from 112 to 338 t C ha−1) across all the forest stands, of which 153 t C ha−1 (52–245 t C ha−1) was stored in vegetation biomass, 14 t C ha−1 (2.2–48 t C ha−1) in forest detritus (including standing dead trees, fallen trees, and floor material), and 70 t C ha−1 (35–113 t C ha−1) in soil organic matter (1-m depth). Among all the forest types, the lowest vegetation and total C density but the highest
soil organic carbon (SOC) density occurred in Betula ermanii forest, whereas the highest detritus C density was observed in Picea and Abies forest. The C density of the three ecosystem components showed distinct altitudinal patterns: with increasing altitude, vegetation
C density decreased significantly, detritus C density first increased and then decreased, and SOC density exhibited increasing
but insignificant trends. The allocation of total ecosystem C to each component exhibited similar but more significant trends
along the altitudinal gradient. Our results suggest that carbon storage and partitioning among different components in temperate
forests on Mt Changbai vary greatly with forest type and altitude. 相似文献
12.
The influence of subterranean termites on the hydrological characteristics of a Chihuahuan desert ecosystem 总被引:4,自引:0,他引:4
Summary Rainfall simulation at an average intensity of 124 mm·h-1 was used to compare infiltration and run off on arid areas where subterranean termites had been eliminated four years prior to the initiation of the study (termite free) with adjacent areas populated by subterranean termites (termites present). Infiltration rates on termite free plots with less than 5% perennial plant cover were significantly lower 51.3±6.8 mm·h-1 than rates on comparable termites present plots 88.4±5.6 mm·h-1. On plots centered on Larrea tridentata shrubs, there were no differences in infiltration rates with or without termites. Plots with shrub cover had the highest infiltration rates 101±6 mm·h-1. Highest run-off volumes were recorded from termite free <5% grass cover plots and the lowest from plots with shrubs. There were no differences in suspended sediment concentrations from termites present and termite free plots. Average bed load concentration was more than three times greater from termite free, <5% cover plots than from termites present, <5% cover plots.The reduction in infiltration, high run-off volumes and high bedloads from termite free areas without shrub cover is related to increased soil bulk density resulting from the collapse of subterranean galleries of the termites that provide avenues of bulk flow into the soil. Subterranean termites affect the hydrology of Chihuahuan desert systems by enhancing water infiltration and retention of top soil. The presence of a shrub canopy and litter layer cancels any effect of subterranean termites on hydrological parameters. Since approximately 2/3 of the area is not under shrub canopies, subterranean termites are considered to be essential for the maintenance of the soil water characteristics that support the present vegetation. 相似文献
13.
Response of soil properties and maize yield to simulated erosion by artificial topsoil removal 总被引:3,自引:0,他引:3
The study was aimed at identifying the soil properties responsible for maize yield decline on eroded soils and at quantifying
their relationship with yield. Topsoil was artificially removed to incremental depths of 0, 5, 10, 15 and 20 cm to simulate
various degrees of erosion. Maize growth and yield were monitored on the plots and soil physical and chemical properties were
determined after two years (4 seasons) of cultivation. Soil pH was significantly higher on the control plot and decreased
with increased depth of topsoil removal. Bulk density (BD) increased with depth of topsoil removal from a mean value of 1.38 g cm−3 under control to 1.55 g cm−3 at 20 cm depth of removal, while cone index of penetrometer resistance (CI) correspondingly increased from 1.09 g cm−2 to 1.37 g cm−2. Maize yield significantly decreased in the first year from 3.2 t ha−1 on the control plot to 0.12 t ha−1 where 20 cm of topsoil was removed and correspondingly from 1.85 to 0.09 t ha−1 in the second year of cropping. Maize yield decreased exponentially with increase in depth of topsoil removal (r
2=0.99, P<0.01) with an average of 55% yield loss on the removal of just 5 cm topsoil. Soil organic carbon (SOC), BD, CI, field capacity
(FC), pH and exchangeable Mg2+ were significantly correlated to maize yield parameters. However, factor analysis showed that the combination of SOC and
exchangeable Mg2+ with soil physical properties (BD, FC, CI and depth of topsoil removal) explained 99% of variation in maize grain yield.
The need for conservation farm practices is recommended on the soil to prevent soil degradation.
Section Editor: L. Wade 相似文献
14.
Prunings of Calliandra calothyrsus, Grevillea robusta, Leucaena diversifolia and farm yard manure were applied each cropping season at 3 and 6 t dry matter ha−1 to an Oxisol in Burundi. The field plots also received basal applications of nitrogen (N), phosphorus (P) and potassium (K).
Application of the tree prunings or farm yard manure decreased the concentration of monomeric inorganic aluminium (Al) in
soil solution from 2.92 mg Al dm−3 in the control plots to 0.75 mg Al dm−3 in the plots receiving 6 t ha−1
Calliandra prunings. The other organic materials also decreased the concentration of monomeric inorganic aluminium in the soil solution.
The lowered Al concentration led to a corresponding decrease in the percentage Al saturation of the 0–10 cm soil layer from
80% to 68%. Grain yields of maize and beans were strongly inversely related to the percentage Al saturation of the soil. This
confirms that soil acidity was the main constraint to maize and beans production. The yield improvement was mainly attributed
to the ameliorating effects of the organic matter application on Al toxicity. The nutrient content had less effect presumably
because of fertilizer use. In the best treatments, the yield of maize increased from 0.9 to 2.2 t ha−1 and the corresponding beans yield increased from 0.2 to 1.2 t ha−1. A C Borstlap Section editor 相似文献
15.
Christian Brümmer Nicolas Brüggemann Klaus Butterbach-Bahl Ulrike Falk Jörg Szarzynski Konrad Vielhauer Reiner Wassmann Hans Papen 《Ecosystems》2008,11(4):582-600
In a combined field and laboratory study in the southwest of Burkina Faso, we quantified soil-atmosphere N2O and NO exchange. N2O emissions were measured during two field campaigns throughout the growing seasons 2005 and 2006 at five different experimental
sites, that is, a natural savanna site and four agricultural sites planted with sorghum (n = 2), cotton and peanut. The agricultural fields were not irrigated and not fertilized. Although N2O exchange mostly fluctuated between −2 and 8 μg N2O–N m−2 h−1, peak N2O emissions of 10–35 μg N2O–N m−2 h−1 during the second half of June 2005, and up to 150 μg N2O–N m−2 h−1 at the onset of the rainy season 2006, were observed at the native savanna site, whereas the effect of the first rain event
on N2O emissions at the crop sites was low or even not detectable. Additionally, a fertilizer experiment was conducted at a sorghum
field that was divided into three plots receiving different amounts of N fertilizer (plot A: 140 kg N ha−1; plot B: 52.5 kg N ha−1; plot C: control). During the first 3 weeks after fertilization, only a minor increase in N2O emissions at the two fertilized plots was detected. After 24 days, however, N2O emission rates increased exponentially at plot A up to a mean of 80 μg N2O–N m−2 h−1, whereas daily mean values at plot B reached only 19 μg N2O–N m−2 h−1, whereas N2O flux rates at plot C remained unchanged. The calculated annual N2O emission of the nature reserve site amounted to 0.52 kg N2O–N ha−1 a−1 in 2005 and to 0.67 kg N2O–N ha−1 a−1 in 2006, whereas the calculated average annual N2O release of the crop sites was only 0.19 kg N2O–N ha−1 a−1 and 0.20 kg N2O–N ha−1 a−1 in 2005 and 2006, respectively. In a laboratory study, potential N2O and NO formation under different soil moisture regimes were determined. Single wetting of dry soil to medium soil water
content with subsequent drying caused the highest increase in N2O and NO emissions with maximum fluxes occurring 1 day after wetting. The stimulating effect lasted for 3–4 days. A weaker
stimulation of N2O and NO fluxes was detected during daily wetting of soil to medium water content, whereas no significant stimulating effect
of single or daily wetting to high soil water content (>67% WHCmax) was observed. This study demonstrates that the impact of land-use change in West African savanna on N trace gas emissions
is smaller—with the caveat that there could have been potentially higher N2O and NO emissions during the initial conversion—than the effect of timing and distribution of rainfall and of the likely
increase in nitrogen fertilization in the future. 相似文献
16.
Ants are arthropods providing crucial ecosystem services such as soil structuring, nutrient cycling, seed dispersal and pest predation. Thus, their abundance and diversity need to be considered in approaches to improve sustainability of land use such as Mediterranean viticulture. In our study, we tested whether (1) inter-row vegetation and the absence of tillage increase the species richness and/or functional diversity of ants in vineyards and (2) ground cover vegetation drives ant species composition. We included 23 Mediterranean organic vineyards in our analyses and distinguished three types of inter-row management: all inter-rows tilled, half of the inter-rows tilled, and all inter-rows are untilled and covered by vegetation. The occurrence of ant species was analysed in six pitfall traps per vineyard. Around each trap, the floristic composition of inter-row vegetation was analysed in 2 × 2 m² plots. We found that inter-row tillage significantly affected ant species richness, being higher in partially than in fully tilled vineyards whereas untilled vineyards were not different from the other tillage types. Grass cover and the perennial/annual rate were positively correlated with ant species richness. Ant functional diversity and the frequency of most predatory ants were not correlated neither with plant functional groups nor with tillage type. In conclusion, ant communities benefit from inter-row vegetation and/or absence of soil disturbance but partial inter-row tillage of vineyards may be tolerated and even benefit several species. In particular, grasses and perennial plant species favour ants in our system and need to be considered in inter-row sowing. 相似文献
17.
Summary Balance sheets were computed for total nitrogen and phosphorus in plough layer (0–15 cm) of a Typic Ustochrept soil under
continuous multiple cropping for seven years (1971–72 to 1977–78) with a fixed rotation of pearl millet (Pennisetum typhoideum L.) wheat (Triticum aestivum L.) (Vigna sinensis Savi.) The treatments considered of soil test-based rates of N, P and K, applied both singly and in combinations together with
farm yard manure, sulphur and zinc superimposed over optimum rates (100%) of NPK. Heavy, losses of N (762–899 kg ha−1) occurred in the plots which received high rates of Nviz. 150% of recommended NPK and 100% NPK plus FYM. Application of N alone accelerated N losses whereas addition of P, PK, PKS
to N minimised such losses. Enrichment of P (66 to 198 kg ha−1) occurred in all phosphate-treated plots. A marginal net decrease (29–54 kg ha−1) in P levels was observed in control and N alone treatments. 相似文献
18.
Changes in the Above- and Below-ground Biomass and Nutrient Pools of Ground Vegetation After Clear-cutting of a Mixed Boreal Forest 总被引:3,自引:0,他引:3
Marjo Palviainen Leena Finér Hannu Mannerkoski Sirpa Piirainen Michael Starr 《Plant and Soil》2005,275(1-2):157-167
Ground vegetation may act as a sink for nutrients after clear-cutting and thus decrease leaching losses. Biomass and nutrient
(N, P, K, Ca) pools of ground vegetation (mosses, roots and above-ground parts of field layer) were determined one year before
and five years after clear-cutting of a Norway spruce (Picea abies (L.) H. Karst.) dominated boreal mixed forest stand in
eastern Finland (63°51′ N, 28°58′ E). Before clear-cutting the average biomass of ground vegetation was 5307 kg ha−1, with nutrient contents of 46.9 kg N ha−11, 4.1 kg P ha−11, 16.2 kg K ha−11 and 13.9 kg Ca ha−11. The biomass and nutrient pools decreased after clear-cutting being lowest in the second year, the biomass decreasing by
46–65% in the cut plots. The nutrient pools decreased as follows: N 54–72%, P 36–68%, K 51–71% and Ca 57–74%. The decrease
in ground vegetation nutrient uptake, and the observed reduced depth of rooting may decrease nutrient retention after clear-cutting
and decomposing dead ground vegetation is a potential source of leached nutrients. These negative effects of clear-cutting
on the nutrient binding capacity of ground vegetation was short-lived since the total biomass and nutrient pools returned
to pre-cutting levels or were even greater by the end of the 5-year study period. 相似文献
19.
Quantification of methane emissions from Chinese rice fields (Zhejiang Province) as influenced by fertilizer treatment 总被引:7,自引:0,他引:7
Reiner Wassmann Helmut Schütz Hans Papen Heinz Rennenberg Wolfgang Seiler Dai Aiguo Shen Renxing Shangguan Xingjian Wang Mingxing 《Biogeochemistry》1993,20(2):83-101
Methane emissions from rice paddies were quantified by using an automatic field system stationed in Zhejiang Province, one
of the centres for rice cultivation in China. The data set showed pronouned interannual variations over 5 consecutive vegetation
periods; by computing average values of all experimental plots the annual emissions were 177 g CH4 m−2 yr−1 in 1987, 50 g CH4 m−2 yr−1 in 1988, and 187 g CH4 m−2 yr−1 in 1989.
The field preparations encompassed 4 different treatments: (1) no fertilizers, (2) mineral fertilizer (KCl, K2SO4), (3) organic manure (rape seeed cake, animal manure), (4) mineral fertilizer plus organic manure. The methane emission rates
of the different fertilizer treatments did not show significant differences. The mean emission rates, calculated over the
entire observation period of 5 seasons, were 30.4 mg CH4 m−2 h−1 (non-fertilized plot) and 28.3 mg CH4 m−2 h−1 (mineral fertilizers). These values indicate a high level of methane production even without additional input of organic
material into the rice-soils. In the other plots, the organic fertilizers were added once per vegetation period at app. 1
t fresh weight per ha, a relatively low application rate by agronomical standards. The mean emission rates were 35.1 mg CH4 m−2 h−1 when manure was applied as sole fertilizer and 27.5 mg CH4 m−2 h−1 when applied jointly with potassium fertilizers.
Based on the results of this study we estimate a range of 18–28 Tg CH4 yr−1 as the total methane emission from Chinese rice fields. However, more field data from representative sites in China are needed
to reduce the uncertainties in this estimate. 相似文献
20.
Tree species and wood ash application in plantations of short-rotation woody crops (SRWC) may have important effects on the
soil productive capacity through their influence on soil organic matter (SOM) and exchangeable cations. An experiment was
conducted to assess changes in soil C and N contents and pH within the 0–50 cm depth, and exchangeable cation (Ca2+, Mg2+, K+, and Na+) and extractable acidity concentrations within the 0–10 cm depth. The effects of different species (European larch [Larix decidua P. Mill.], aspen [Populus tremula L. × Populus tremuloides Michx.], and four poplar [Populus spp.] clones) and wood ash applications (0, 9, and 18 Mg ha−1) on soil properties were evaluated, using a common garden experiment (N = 70 stands) over 7 years of management in Michigan’s Upper Peninsula. Soils were of the Onaway series (fine-loamy, mixed,
active, frigid Inceptic Hapludalfs). The NM-6 poplar clone had the greatest soil C and N contents in almost all ash treatment
levels. Soil C contents were 7.5, 19.4, and 10.7 Mg C ha−1 greater under the NM-6 poplar than under larch in the ash-free, medium-, and high-level plots, respectively. Within the surface
layer, ash application increased soil C and N contents (P < 0.05) through the addition of about 0.7 Mg C ha−1 and 3 kg N ha−1 with the 9 Mg ha−1 ash application (twofold greater C and N amounts were added with the 18 Mg ha−1 application). During a decadal time scale, tree species had no effects—except for K+—on the concentrations of the exchangeable cations, pH, and extractable acidity. In contrast, ash application increased soil
pH and the concentration of Ca2+ (P < 0.05), from 5.2 ± 0.4 cmolc kg−1 (ash-free plots) to 8.6 ± 0.4 cmolc kg−1 (high-level ash plots), and tended to increase the concentration of Mg2+ (P < 0.1), while extractable acidity was reduced (P < 0.05) from 5.6 ± 0.2 cmolc kg−1 (ash-free plots) to 3.7 ± 0.2 cmolc kg−1 (high-level plots). Wood ash application, within certain limits, not only had a beneficial effect on soil properties important
to the long-term productivity of fast-growing plantations but also enhanced long-term soil C sequestration. 相似文献