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971.
不同密度柚木人工林林下植被及土壤理化性质的研究 总被引:5,自引:0,他引:5
研究不同密度柚木人工林对林下植被及土壤理化性质的影响,为柚木人工林营建与可持续经营提供理论依据。以广东揭阳14~16年生不同林分密度(650、900、1 050、1 200和1 450 株·hm-2)柚木人工林为研究对象,通过样方调查植被的种名、株数、高度及盖度等,并采集0~20和20~40 cm土样进行理化性质分析,对林下植被物种多样性指数及其土壤理化性质进行主成分分析评价,来评价不同林分密度下柚木人工林的立地质量。结果表明:随着林分密度增加,柚木人工林林下植被盖度整体表现出降低趋势,草本优势物种由阳生性到中生性,逐渐向阴生性的过渡,林下植被Shannon-Wiener指数、Simpson优势度指数、丰富度指数和均匀度指数表现出先增加后减少的趋势;相同密度下,表层土土壤理化性质优于下层土,随着林分密度增大,土壤理化性质整体呈现出先改善后退化的变化过程,不同林分密度间柚木人工林土壤毛管孔隙度、非毛管孔隙度、速效K、速效P、全P、交换性酸和交换性Al等指标差异性显著(P<0.05);基于林下植被物种多样性和土壤理化性质主成分分析,不同林分密度柚木人工林物种多样性和土壤理化性质综合得分由大到小依次是:1 050 株·hm-2(4.82)、900 株·hm-2(1.58)、650 株·hm-2(-1.30)、1 200 株·hm-2(-1.81)、1 450 株·hm-2(-3.29)。因此,说明适宜的林分密度(1 050 株·hm-2)有利于保持较好的林下植被物种多样性和土壤理化性质,在柚木人工林经营的过程中,可以根据实际情况合理调整林分的密度。 相似文献
972.
南药立体经营模式土壤质量综合评价 总被引:1,自引:0,他引:1
为筛选优化的南药立体经营模式,本试验选用适宜南方种植的4种药用植物,采用随机区组设计,在已有的杉木林下,构建4种林药立体经营模式,分别是杉木(Cunninghamia lanceolata)+梅叶冬青(Ilex asprella)+艾纳香模式(Blumea balsamifera)(简称SMA)、杉木+梅叶冬青+广金钱草(Desmodium styracifolium)模式(简称SMG),杉木+梅叶冬青+草珊瑚(Sarcandra glabra)模式(简称SMC),杉木+梅叶冬青模式(SM)),以杉木纯林(简称CK)为对照,分析不同模式内0~20和20~40 cm土层土壤理化性质和土壤酶活性变化,并运用主成分分析法综合评价模式对林地土壤质量的影响。结果表明(1)与对照(纯林)相比,4种林药模式下的土壤容重均显著下降,且随土层深度的增加而增加。0~20 cm土层各模式土壤容重降幅分别为:模式SMA13.4%、模式SMG 14.1%、模式SMC 20.8%和模式SM 22.3%、;20~40 cm土层的土壤容重各处理降幅为7.0%~15.5%。各模式土壤质量含水量、田间持水量、毛管持水量、毛管孔隙度和总孔隙度均显著提高(P<0.05),且随土层深度的增加而减小,0~20 cm土层,均是以模式SM最大,分别比对照提高54.9%、100.1%、88.6%、44.9%和36.8%;20~40 cm土层,均以模式SMG最大,分别是对照的61.5%、67.6%、69.7%、43.4%和44.0%。(2)0~20 cm土层pH呈下降趋势,降幅0.7%~6.2%,20~40 cm土层中各处理pH差异较大,但均未达到显著水平。除全钾外,其余土壤养分含量各模式均随着土层深度的增加而降低。0~20 cm土层中,有机质、全氮、全磷、速效氮磷钾、交换性钙和镁以及阳离子交换量均以模式SMC含量最高,分别比对照提高79.7%、69.5%、30.3%、91.4%、279.4%、166.1%、91.6%、677.0%和70.3%。全钾含量以模式SMG最高,比对照增加了26.9%。(3)各处理土壤酶活性均随着土层深度的增加而降低。在0~20 cm土层中,与对照相比,各模式土壤的脲酶、蔗糖酶、多酚氧化酶和酸性磷酸活性差异显著(P<0.05),其中脲酶和多酚氧化酶活性以模式SMC活性最高,分别是对照的1.7倍和1.6倍,蔗糖酶活性各模式皆低于对照,降幅59.3%~69.4%;酸性磷酸酶活性模式SMA最高,比对照提高78.7%。20~40 cm土层中,各模式及对照间仅酸性磷酸酶活性差异达到显著水平。(4)南药立体经营模式对土壤质量影响的综合排序为,模式SMC(2.811)>模式SMG(1.293)>模式SMA(0.111)>模式SM(-1.544)>CK(-2.671)。 相似文献
973.
974.
Soil Properties and their Spatial Pattern in a Degraded Sandy Grassland under Post-grazing Restoration, Inner Mongolia, Northern China 总被引:10,自引:0,他引:10
In this study, we use classical and geostatistical methods to identify characteristics of some selected soil properties including
soil particle size distribution, soil organic carbon, total nitrogen, pH and electrical conductivity and their spatial variation
in a 5-year recovery degraded sandy grassland after two different grazing intensity disturbance: post-heavy-grazing restoration
grassland (HGR) and post-moderately grazing restoration grassland (MGR), respectively, in Horqin steppe, Inner Mongolia, northern
China. The objective was to examine effect of grazing intensity on spatial heterogeneity of soil properties. One hundred soil
samples were taken from the soil layer 0–15 cm in depth of a grid of 10 m×10 m under each treatment. The results showed that
soil fine fractions (very fine sand, 0.1–0.05 mm and silt + clay, <0.05 mm), soil organic carbon and total nitrogen concentrations
were significant lower and their coefficients of variation significant higher under the HGR than under the MGR. Geostatistical
analysis of soil heterogeneity revealed that soil particle size fractions, organic carbon and total nitrogen showed different
degree of spatial dependence with exponential or spherical semivariograms on the scale measured under HGR and MGR. The spatial
structured variance account for a large proportion of the sample variance in HGR plot ranging from 88% to 97% for soil particle
fractions, organic C and total N, however, except for organic C (88.8%), the structured variance only account for 50% of the
sample variance for soil particle fractions and total N in the MGR plot. The ranges of spatial autocorrelation for coarse-fine
sand, very fine sand, silt + clay, organic C and total N were 13.7 m, 15.8 m, 15.2 m, 22.2 m and 21.9 m in HGR plot, respectively,
and was smaller than in MGR plot with the corresponding distance of 350 m, 144.6 m, 45.7 m, 27.3 m and 30.3 m, respectively.
This suggested that overgrazing resulted in an increase in soil heterogeneity. Soil organic C and total N were associated
closely with soil particle fractions, and the kriging-interpolated maps showed that the spatial distribution of soil organic
C and total N corresponded to the distribution patterns of soil particle fractions, indicating that high degree of spatial
heterogeneity in soil properties was linked to the distribution of vegetative and bare sand patches. The results suggested
that the degree of soil heterogeneity at field scale can be used as an index for indicating the extent of grassland desertification.
Also, the changes in soil heterogeneity may in turn influence vegetative succession and restoration process of degraded sandy
grassland ecosystem. 相似文献
975.
Understanding the interactions between terrestrial and aquatic ecosystems remains an important research focus in ecology.
In arid landscapes, catchments are drained by a channel continuum that represents a potentially important driver of ecological
pattern and process in the surrounding terrestrial environment. To better understand the role of drainage networks in arid
landscapes, we determined how stream size influences the structure and productivity of riparian vegetation, and the accumulation
of organic matter (OM) in soils beneath plants in an upper Sonoran Desert basin. Canopy volume of velvet mesquite (Prosopis velutina), as well as overall plant cover, increased along lateral upland–riparian gradients, and among riparian zones adjacent to
increasingly larger streams. Foliar δ13C signatures for P. velutina suggested that landscape patterns in vegetation structure reflect increases in water availability along this arid stream
continuum. Leaf litter and annual grass biomass production both increased with canopy volume, and total aboveground litter
production ranged from 137 g m−2 y−1 in upland habitat to 446 g m−2 y−1 in the riparian zone of the perennial stream. OM accumulation in soils beneath P. velutina increased with canopy volume across a broad range of drainage sizes; however, in the riparian zone of larger streams, flooding
further modified patterns of OM storage. Drainage networks represent important determinants of vegetation structure and function
in upper Sonoran Desert basins, and the extent to which streams act as sources of plant-available water and/or agents of fluvial
disturbance has implications for material storage in arid soils. 相似文献
976.
Soil Carbon, Nitrogen and Phosphorus Dynamics as Affected by Solarization Alone or Combined with Organic Amendment 总被引:1,自引:0,他引:1
Antonio Gelsomino Luigi Badalucco Loretta Landi Giovanni Cacco 《Plant and Soil》2006,279(1-2):307-325
Soil solarization, alone or combined with organic amendment, is an increasingly attractive approach for managing soil-borne
plant pathogens in agricultural soils. Even though it consists in a relatively mild heating treatment, the increased soil
temperature may strongly affect soil microbial processes and nutrients dynamics. This study aimed to investigate the impact
of solarization, either with or without addition of farmyard manure, in soil dynamics of various C, N and P pools. Changes
in total C, N and P contents and in some functionally-related labile pools (soil microbial biomass C and N, K2SO4-extractable C and N, basal respiration, KCl-exchangeable ammonium and nitrate, and water-soluble P) were followed across
a 72-day field soil solarization experiment carried out during a summer period on a clay loam soil in Southern Italy. Soil
physico-chemical properties (temperature, moisture content and pH) were also monitored. The average soil temperature at 8-cm
depth in solarized soils approached 55 °C as compared to 35 °C found in nonsolarized soil. Two-way ANOVA (solarization×organic
amendment) showed that both factors significantly affected most of the above variables, being the highest influence exerted
by the organic amendment. With no manure addition, solarization did not significantly affect soil total C, N and P pools.
Whereas soil pH, microbial biomass and, at a greater extent, K2SO4-extractable N and KCl-exchangeable ammonium were greatly affected. An increased release of water-soluble P was also found
in solarized soils. Yet, solarization altered the quality of soluble organic residues released in soil as it lowered the C-to-N
ratio of both soil microbial biomass and K2SO4-extractable organic substrates. Additionally, in solarized soils the metabolic quotient (qCO2) significantly increased while the microbial biomass C-to-total organic C ratio (microbial quotient) decreased over the whole
time course. We argued that soil solarization promoted the mineralization of readily decomposable pools of the native soil
organic matter (e.g. the microbial biomass) thus rendering larger, at least over a short-term, the available fraction of some
soil mineral nutrients, namely N and P forms. However, over a longer prospective solarization may lead to an over-exploitation
of labile organic resources in agricultural soils. Manure addition greatly increased the levels of both total and labile C,
N and P pools. Thus, addition of organic amendments could represent an important strategy to protect agricultural lands from
excessive soil resources exploitation and to maintain soil fertility while enhancing pest control. 相似文献
977.
N. Kljun T. A. Black T. J. Griffis A. G. Barr D. Gaumont-Guay K. Morgenstern J. H. McCaughey Z. Nesic 《Ecosystems》2006,9(7):1128-1144
In 2001–03, continuous eddy covariance measurements of carbon dioxide (CO2) flux were made above mature boreal aspen, black spruce, and jack pine forests in Saskatchewan, Canada, prior to and during
a 3−year drought. During the 1st drought year, ecosystem respiration (R) was reduced at the aspen site due to the drying of surface soil layers. Gross ecosystem photosynthesis (GEP) increased as
a result of a warm spring and a slow decrease of deep soil moisture. These conditions resulted in the highest annual net ecosystem
productivity (NEP) in the 9 years of flux measurements at this site. During 2002 and 2003, a reduction of 6% and 34% in NEP,
respectively, compared to 2000 was observed as the result of reductions in both R and GEP, indicating a conservative response to the drought. Although the drought affected most of western Canada, there was
considerable spatial variability in summer rainfall over the 100−km extent of the study area; summer rainfalls in 2001 and
2002 at the two conifer sites minimized the impact of the drought. In 2003, however, precipitation was similarly low at all
three sites. Due to low topographic position and consequent poor drainage at the black spruce site and the coarse soil with
low water-holding capacity at the jack pine site almost no reduction in R, GEP, and NEP was observed at these two sites. This study shows that the impact of drought on carbon sequestration by boreal
forest ecosystems strongly depends on rainfall distribution, soil characteristics, topography, and the presence of vegetation
that is well adapted to these conditions. 相似文献
978.
Samples of foraged fruits from a former industrial site have been analyzed for potentially toxic elements (PTEs) (i.e., As, Cd, Cr, Cu, Ni, Pb, and Zn). The foraged fruit (blackberries, rosehips, and sloes) was gathered over two seasons along with samples of soil from the same sampling areas. All samples were acid digested, using a microwave oven, and then analyzed by inductively coupled plasma mass spectroscopy (ICP-MS). The concentration levels of the selected elements in foraged samples varied between not detectable limits and 24.6 μg/g (Zn). The soil-to-plant transfer factor was assessed for the PTEs. In all cases, the transfer values obtained were less than 1.00, indicating that the majority of the PTEs remains in the soil and that the uptake of PTEs from soil to plant at this site is not significant. 相似文献
979.
Allocation of carbon in a mature eucalypt forest and some effects of soil phosphorus availability 总被引:4,自引:0,他引:4
Pools and annual fluxes of carbon (C) were estimated for a mature Eucalyptus pauciflora (snowgum) forest with and without phosphorus (P) fertilizer addition to determine the effect of soil P availability on allocation of C in the stand. Aboveground biomass was estimated from allometric equations relating stem and branch diameters of individual trees to their biomass. Biomass production was calculated from annual increments in tree diameters and measurements of litterfall. Maintenance and construction respiration were calculated for each component using equations given by Ryan (1991a). Total belowground C flux was estimated from measurements of annual soil CO2 efflux less the C content of annual litterfall (assuming forest floor and soil C were at approximate steady state for the year that soil CO2 efflux was measured). The total C content of the standing biomass of the unfertilized stand was 138 t ha-1, with approximately 80% aboveground and 20% belowground. Forest floor C was 8.5 t ha-1. Soil C content (0–1 m) was 369 t ha-1 representing 70% of the total C pool in the ecosystem. Total gross annual C flux aboveground (biomass increment plus litterfall plus respiration) was 11.9 t ha-1 and gross flux belowground (coarse root increment plus fine root production plus root respiration) was 5.1 t ha-1. Total annual soil efflux was 7.1 t ha-1, of which 2.5 t ha-1 (35%) was contributed by litter decomposition.The short-term effect of changing the availability of P compared with C on allocation to aboveground versus belowground processes was estimated by comparing fertilized and unfertilized stands during the year after treatment. In the P-fertilized stand annual wood biomass increment increased by 30%, there was no evidence of change in canopy biomass, and belowground C allocation decreased by 19% relative to the unfertilized stand. Total annual C flux was 16.97 and 16.75 t ha-1 yr-1 and the ratio of below- to aboveground C allocation was 0.43 and 0.35 in the unfertilized and P-fertilized stands, respectively. Therefore, the major response of the forest stand to increased soil P availability appeared to be a shift in C allocation; with little change in total productivity. These results emphasise that both growth rate and allocation need to be estimated to predict changes in fluxes and storage of C in forests that may occur in response to disturbance or climate change. 相似文献
980.
With four soils differing in K supplying power and with four rice cultivars (Oryza sativa L.) differing in K uptake kinetic parameters, the relationship between K fertilizer application and soil redox status in rhizosphere and; the distribution of ferrous iron and other toxic substances on the root surface and in the rhizosphere; and the effect of K supply on uptake of reduced iron by rice plants have been studied.The results show that K application on K-deficient soils reduced the content of active reducing substances and ferrous iron in the soil, raised the soil redox potential in the rhizosphere, increased the Eh value of rice roots and lowered the content of iron in the rice plants. These effects of K varied with different rice cultivars. When no K fertilizer was applied, active reducing substances and ferrous iron in rhizosphere soils were decreased more by the rice cultivars absorbing K strongly (e.g. Shanyou 64) than by cultivars absorbing K weakly (e.g. Zhongguo 91). Therefore, the diminution of the toxic substances by K application in the weakly K-absorbing cultivars was more significant.The observation of a rhizobox separated by a nylon screen showed that appreciably more iron oxides, compared with the control, were deposited at or adjacent to the root surfaces of the rice plant supplied with K fertilizer, fully demonstrating the relationship between K nutrition and the total oxidizing power of rice plants. According to the distribution of active reducing substances and ferrous iron, the oxidizing range of the rice root extended in K application treatment a few centimeters away from the root plane. K application to rice affected the soil redox status in rhizosphere in many ways. The main effect was an increase of the oxidizing power of the rice root. As a result, the value of soil Eh was increased, the contents of active reducing substances and ferrous iron were lowered, as well as the number of oxygen consuming microorganisms. 相似文献