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1.
(Jpn. J. Soil Sci.Plant Nutr., 77, 299–306, 2006)

The effects of Collembola (Folsomia candida Willem) on nutrient cycling, microbial biomass, and soil respiration were studied using intact soil microcosms. Intact soil microcosms (dia. 10·6 cm and depth 15 cm) were taken from pine forest soil, and were divided into four treatments · the unmanipulated control and three Collembolan manipulations in which microcosms were defaunated by deep-freezing, and then F. candida were introduced at three densities (0, 50, 100 per microcosm). The microcosms were incubated on forest floor with a roof. At 3- to 4-week intervals the microcosms were irrigated with deionized water for analyses of nutrients (Na+, K+, NH4+, Ca2+, Mg2+, Cl?, NO3?, SO42?) in the leachate. Soil respiration was measured using an infrared gas analyser. After 13 and 34 weeks of exposure, microcosms were destructively sampled. Collembola did not significantly affect microbial biomass C, N, and P nor soil respiration. Because the experiment was started in winter, nutrient leaching increased from spring to summer with increasing microbial activity. At the end of the experiment, leached nitrate from microcosms was significantly different between the 0 and 50 Collembolan treatments. Total established Collembolan biomass was under 4% of the soil microbial biomass in the microcosms, while manipulation of Collembola affected soil nitrogen dynamics at high microbial and collembolan activity.  相似文献   

2.
Organic matter and abiotic conditions seem to influence distribution patterns of Enchytraeidae. In this study effects of changes in management practices on population dynamics of enchytraeids were determined. At two sites (in Athens and Griffin, GA) parts of a fescue (FE) field were converted into conventional tillage (CT) and no-tillage (NT) plots and changes in densities and depth distribution of enchytraeids were followed for 3 years. A site at Watkinsville, containing various soil textures and characterised by very low organic carbon content, which was converted into no-tillage 4 years earlier, was also sampled. Significant reductions in enchytraeid densities, after conversion of fescue into CT, were only found at Griffin. The management practices affected the vertical distribution of enchytraeids. In fescue and NT more enchytraeids were found in the 0–5cm than in the 5–15cm layer. In conventional tillage fields enchytraeids were more evenly distributed over the profile or more abundant in the 5–15cm layer. Management also affected the timing of population dynamics in the different plots. At two sample dates high abundances were found in CT plots only, not in any of the other plots. Enchytraeids were larger at Athens than at Griffin and Watkinsville and contained more soil particles in their gut. At Athens enchytraeids will presumably contribute more to the development of soil structure than at the other sites. We conclude that management affects vertical enchytraeid distributions in soil and changes the timing of population dynamics. Received: 7 January 1996  相似文献   

3.
Organic upland soils store large amounts of humified organic matter. The mechanisms controlling the leaching of this C pool are not completely understood. To examine the effects of temperature and microbial cycling on C leaching, we incubated five unvegetated soil cores from a Podzol O horizon (from NE Scotland), over a simulated natural temperature cycle for 1 year, whilst maintaining a constant soil moisture content. Soil cores were leached with artificial rain (177 mm each, monthly) and the leachates analysed for dissolved organic carbon (DOC) and their specific C‐normalized UV absorbance determined (SUVA, 285 nm). Monthly values of respiration of the incubated soils were determined as CO2 efflux. To examine the effects of vegetation C inputs and soil moisture, in addition to temperature, we sampled O horizon pore waters in situ and collected five additional field soil cores every month. The field cores were leached under controlled laboratory conditions. Hysteresis in the monthly amount of DOC leached from field cores resulted in greater DOC on the rising, than falling temperature phases. This hysteresis suggested that photosynthetic C stimulated greater DOC losses in early summer, whereas limitations in the availability of soil moisture in late summer suppressed microbial decomposition and DOC loss. Greater DOC concentrations of in‐situ pore waters than for any core leachates were attributed to the effects of soil drying and physico‐chemical processes in the field. Variation in the respiration rates for the incubated soils was related to temperature, and respiration provided a greater pathway of C loss (44 g C m−2 year−1) than DOC (7.2 g C m−2 year−1). Changes in SUVA over spring and summer observed in all experimental systems were related to the period of increased temperature. During this time, DOC became less aromatic, which suggests that lower molecular weight labile compounds were not completely mineralized. The ultimate DOC source appears to be the incomplete microbial decomposition of recalcitrant humified C. In warmer periods, any labile C that is not respired is leached, but in autumn either labile C production ceases, or it is sequestered in soil biomass.  相似文献   

4.
In this study the fate of naphthalene, fluorene and pyrene were investigated in the presence and absence of enchytraeid worms. Microcosms were used, which enabled the full fate of 14C-labelled PAHs to be followed. Between 60 and 70% of naphthalene was either mineralised or volatilised, whereas over 90% of the fluorene and pyrene was retained within the soil. Mineralisation and volatilisation of naphthalene was lower in the presence of enchytraeid worms. The hypothesis that microbial mineralisation of naphthalene was limited by enchytraeids because they reduce nutrient availability, and hence limit microbial carbon turnover in these nutrient poor soils, was tested. Ammonia concentrations increased and phosphorus concentrations decreased in all microcosms over the 56 d experimental period. The soil nutrient chemistry was only altered slightly by enchytraeid worms, and did not appear to be the cause of retardation of naphthalene mineralisation. The results suggest that microbial availability and volatilisation of naphthalene is altered as it passes through enchytraeid worms due to organic material encapsulation.  相似文献   

5.
Traditional models of soil organic matter decomposition predict that soil carbon pools with high chemical stability and large physical structure are more resistant against degradation than chemically labile and fine-grained material. We investigated whether soil fauna, by its direct and indirect effects on carbon turnover, would reinforce or counteract this general trend.The effects of four major faunal groups on carbon pools of differing recalcitrance were studied in an extensive microcosm experiment. Ninty-six microcosms were inoculated with nematodes, enchytraeids, collembola, and lumbricids in three densities, including combinations of groups. Bare agricultural soil and soil covered with maize litter were used as substrates. The microcosms were kept under constant conditions at 12 °C and 50% water holding capacity for 60 days. At the end of the experiment, soil particles were separated into size classes (<63 μm, 63-250 μm, >250 μm) and carbon pools were separated into solubility fractions (K2SO4-soluble, pyrophosphate-soluble, insoluble), by means of ultrasonic dispersion and subsequent stepwise solubilisation.Both in bare soil and in soil with litter, the carbon pools with the highest chemical stability (insoluble) and the larger particle sizes (>63 μm) were degraded more intensively than all other pools in the presence of lumbricids. The pools of intermediate chemical stability (pyrophosphate-soluble) underwent simultaneous degradation and neoformation brought about by different animal groups. The chemically most labile pool (K2SO4-soluble) remained largely unaffected by the fauna. Fixation of carbon in microbial biomass was increased by nematodes in bare soil and by enchytraeids in soil with litter. The results illustrate in detail how, under the influence of soil fauna, soil carbon pools are decomposed in a cascade-like process where carbon is transferred from the stable to the more labile pools, while simultaneously a proportion is fixed in microbial biomass and another part is lost as CO2. Thereby, the relationship between a substrate's persistence and its chemical stability and physical size is substantially modified. We summarize the mechanisms that most likely are responsible for the different effects of the investigated faunal groups.  相似文献   

6.
【目的】通过研究黄淮平原潮土区两年不同轮耕模式下土壤微生物量碳氮、酶活性的差异和变化特征,为该地区选择适宜的耕作制度提供理论依据。【方法】2016-2018年采用裂区设计进行田间小麦–玉米轮作系统下的轮耕试验。主处理为小麦季旋耕(RT)和深耕(DT),3个副处理为玉米季免耕(NT)、行间深松(SBR)、行内深松(SIR),共6个处理。2017、2018年玉米收获后,每10 cm一个层次,测定了0-50 cm土层土壤有机质、全氮、速效养分、微生物量碳(SMBC)、微生物量氮(SMBN)和脲酶、蔗糖酶、中性磷酸酶活性。【结果】各处理土壤有机质、全氮、速效养分、SMBC、SMBN及酶活性均随土层深度的增加而降低,40-50cm土层不受耕作方式的影响。小麦季深耕和玉米季深松对表层土壤有机质和全氮影响不明显,但显著提高了深层土壤有机质和全氮含量。小麦季旋耕显著增加了玉米季0-10 cm土层中速效养分含量,而小麦季深耕条件下的DT-SBR和DT-SIR处理则显著增加了20-40 cm土层中的速效养分含量。在0-20 cm土层,小麦季旋耕条件下的RT-NT、RT-SBR和RT-SIR处理的SMBC明显高于小麦季深耕条件下的DT-NT、DT-SBR和DT-SIR处理,但在20-40 cm土层,SMBC和SMBN均表现为小麦季深耕处理显著高于旋耕处理,且以DT-SIR处理SMBC (67.99 mg/kg)和SMBN (45.96 mg/kg)最高。小麦季深耕处理提高了深层(30-40 cm)土壤微生物量氮/全氮值,但降低了表层(0-20 cm)土壤中的微生物熵。玉米季深松处理(RT-SBR、RT-SIR、DT-SBR和DT-SIR)较免耕处理(RT-NT和DT-NT)均提高了土壤酶活性,其中,在0-20 cm土层,RT-SBR和RT-SIR处理土壤脲酶活、蔗糖酶和中性磷酸酶活性较高;而DT-SBR和DT-SIR处理则提高了深层(20-40 cm)土壤中这三种酶的活性。【结论】在本试验期内,小麦季旋耕–玉米季深松处理(RT-SBR和RT-SIR)能明显提高0-10 cm土壤速效养分含量、0-20 cm土壤微生物量碳含量,而小麦季深耕–玉米季深松处理(DT-SBR和DT-SIR)则提升了20-40 cm土层土壤有机质、全氮、速效养分、微生物量碳和氮含量;小麦季深耕处理提高了深层(30-40 cm)微生物量氮/全氮比,但降低了表层(0-20 cm)土壤微生物熵。  相似文献   

7.
Grassland field plots were compared to two sizes of excised microcosms (15 and 30 cm diameter) and 30-cm diameter homogenized microcosms to assess the effects of As on soil-plant nutrient dynamics. The goal of this experiment was to determine the feasibility of using microcosms for screening chemicals which are potentially toxic to terrestrial ecosystems. All experimental units were treated with As, at rates of 0, 0.5, and 5.0 mg cm?2, by superficial application of dissolved Na2AsO4. Calcium, PO4-P, NO3-N, dissolved organic carbon (DOC), and NH4-N were determined in soil leachate and soil extracts. Greater loss of PO4-P, NO3-N, NH4-N, and DOC occurred via soil leachate from microcosms treated with the greatest level of As relative to untreated microcosms. Field plots were unaffected by As treatment. Excised microcosms were found to be more representative of field plots in reflecting microbial dynamics than were homogenized microcosms. Thus excised microcosms were recommended for testing potentially hazardous chemicals.  相似文献   

8.
A field experiment was conducted in an irrigated olive orchard to determine the effects of an orchard management system consisting of increased carbon input management on spatial distribution (tree inter-row/in-row, soil depth 0–10/10–20 cm) of nitrogen and carbon in the soil as well as on some microbial properties in relation to water availability. The experiment consisted of 12 blocks (each with 4 trees covering 200 m2 of land), uniform olive tree canopy size and natural vegetation, used as replications (three per treatment) in a split plot design for the following four treatments: a) spreading of olive mill compost on the soil without soil tillage, b) spreading of chopped pruning residue on the soil without soil tillage, c) combination of b + c, and d) control which received no organic materials and soil was kept free of weeds with frequent tillage and herbicide sprays. Increased soil organic matter content (SOM) (up to +80%), NO3 N (up to +194%), and NH4 N (up to +37%) by carbon inputs were observed in soil layer 0–10 cm. Irrigation enhanced SOM, NH4 N, and electrical conductivity (EC) while it favored NO3 N increase by carbon inputs. All microbial properties (Soil Basal Microbial Respiration, Soil Microbial Biomass Carbon, and Metabolic quotient) were significantly higher at 0–10 cm in comparison to 10–20 cm depth. This study suggests good agricultural management practices for optimized soil organic carbon (SOC) storage adapted to the typical Mediterranean agroecosystems.  相似文献   

9.
以长期定位试验点的紫色水稻土为研究对象，研究了耕作制度对紫色水稻土活性有机质和碳库管理指数的影响。结果表明：稻田长期垄作免耕0～10cm土层有机质含量比常规平作高，10～60cm土层有机质含量则比常规平作低；表明稻田长期垄作免耕土壤有机质具有表层富集现象；水旱轮作各土层有机质含量均比常规平作低。垄作免耕各土层活性有机质含量普遍增加，水旱轮作表层（0～10cm）活性有机质含量减少，其余土层变化不大。对活性有机质组分含量的研究表明：与常规平作相比，垄作免耕增加了土壤表层活性有机质各个组分的含量，在其余土层增加了低活性有机质含量，而减少了高活性有机质含量；水旱轮作增加了各土层低活性有机质含量而减少了中活性和高活性有机质含量。垄作免耕所有土层的碳库管理指数都在100以上，水旱轮作除表层（0～10cm）小于100以外，其余土层都在100以上。由此可见，农业管理措施对土壤有机质、活性有机质及碳库管理指数有较大影响。  相似文献   

10.
Long-term effect of mungbean inclusion in lowland rice-wheat and upland maize-wheat systems on soil carbon (C) pools, particulate organic C (POC), and C-stabilization was envisaged in organic, inorganic and without nutrient management practices. In both lowland and upland systems, mungbean inclusion increased very-labile C (Cfrac1) and labile C (Cfrac2) in surface soil (0–0.2 m). Mungbean inclusion in cereal-cereal cropping systems improved POC, being higher in lowland (107.4%). Lowland rice-based system had higher passive C-pool (11.1 Mg C ha?1) over upland maize-based system (6.6 Mg C ha?1) indicating that rice ecology facilitates the stabilization of passive C-pool, which has longer persistence in soil. Organic nutrient management (farmyard manure + full crop residue + biofertilizers) increased Cfrac1 and carbon management index (CMI) over inorganic treatment. In surface soil, higher CMI values were evident in mungbean included cropping systems in both lowland and upland conditions. Mungbean inclusion increased grain yield of cereal crops, and yield improvement followed the order of maize (23.7–31.3%) > rice (16.9–27.0%) > wheat (lowland 7.0–10.7%; upland 5.4–16.6%). Thus, the inclusion of summer mungbean in cereal-cereal cropping systems could be a long-term strategy to enrich soil organic C and to ensure sustainability of cereal-cereal cropping systems.  相似文献   

11.
[目的]研究以玉米秸秆为主要原料制备的不同类型有机物料对东北黑土土壤肥力和玉米产量的影响,为黑土地保护和秸秆资源高效利用提供理论依据.[方法]田间定位试验连续进行了5年.试验设不施肥对照(CK)、单施化肥(NPK)、化肥配施秸秆(NPK+ST)、化肥配施生物炭(NPK+BR)以及化肥配施堆肥(NPK+CP)5个处理,各...  相似文献   

12.
The number and biomass of the microbial community in the upper humus horizon (0–20 cm) were determined in the main types of alluvial soils (mucky gley, desertified soddy calcareous, hydrometamorphic dark-humus soils) in the Volga River delta. Fungal mycelium and alga cells predominate in the biomass of the microorganisms (35–50% and 30–47%, respectively). The proportion of prokaryotes in the microbial biomass of the alluvial soils amounts to 2–6%. No significant seasonal dynamics in the number and biomass of microorganisms were revealed in the alluvial soils. The share of carbon of the microbial biomass in the total carbon content of the soil organic matter is 1.4–2.3% in the spring. High coefficients of microbial mineralization and oligotrophy characterize the processes of organic matter decomposition in the alluvial soils of the mucky gley, desertified soddy calcareous, and hydrometamorphic dark humus soil types.  相似文献   

13.
Summary We investigated the effects of pitch pine seedling roots on extractable N, microbial growth rate, biomass C and N, and nematodes and microarthropods in microcosms with either organic (41% C, 1.14% N) or mineral (0.05% C, 0.01% N) horizon soils of a spondosol. Root quantity was manipulated by varying plant density (0, 1, 2, or 4 seedlings) and rhizosphere soil was separated from non-rhizosphere soil by a 1.2 m mesh fabric. In the rhizosphere of organic soil horizons, moisture, microbial growth rate, biomass C and N, and extractable N declined as root density was increased, but there was little effect on nematodes or microarthropods. High levels of extractable N remained after 5 months, suggesting that N mineralization was stimulated during the incubation. In the rhizosphere of mineral soil horizons, microbial growth rate, and nematode and microarthropod abundances increased at higher root density, and in the absence of roots faunal abundance approached zero. Faunal activity was concentrated in the rhizosphere compared to non-rhizosphere soil. In organic soil horizons, roots may limit microbial activity by reducing soil moisture and/or N availability. However, in mineral soil horizons, where nutrient levels are very low, root inputs can stimulate microbial growth and faunal abundance by providing important substrates for microbial growth. Our results demonstrate a rhizosphere effect for soil fauna in the mineral soil, and thus extends the rhizosphere concept to components of the soil community other than microbes for forest ecosystems. Although our results need to be verified by field manipulations, we suggest that the effects of pine roots on nutrient cycling processes in coniferous forests can vary with soil nutrient content and, therefore, position in the soil profile.  相似文献   

14.
A three-year field trial on an upland loessial soil (Belmont silt loam) in New Zealand investigated the effects of ripping, application of fertilizer N and grazing management on the recovery of some physical, chemical and biochemical properties of soil and pasture productivity following removal (mining) of topsoil. Removing the top 31 cm of soil by mining (all of the A horizon and part of the AB horizon) also removed most of the soil's labile organic matter fractions, and to a lesser extent its total organic matter. After three years, the microbial C and mineralizable N in the 0–10 cm depth of mined soil had reached 65 and 62 per cent of the corresponding levels in unmined soil. Ripping to a depth of 30 cm, application of fertilizer N and lenient grazing of the pasture failed to enhance the recovery of soil fertility. A soil sampling depth of 20 cm provided a reasonable basis to assess the microbial biomass and potential fertility. Pasture productivity was, on average, 30 per cent lower on mined land than on unmined land over the first three years after mining. Application of N proved uneconomic in terms of farm production, although a good pasture response to N fertilizer was obtained. The results from this and related trials are summarized as a series of recommendations for the monitoring and regulation of topsoil mining. An incentive regime is also recommended to encourage land owners and/or topsoil miners to use successful restoration techniques on topsoil-mined land. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

15.
基于室内模拟培养试验,研究改良剂(生物质炭、过氧化钙)对旱地红壤微生物量碳、氮及可溶性有机碳、氮的影响。试验设置4个处理,即CK、Ca(过氧化钙,1.72g/kg)、C(生物质炭,21.46g/kg)、C+Ca。结果表明:各处理土壤微生物量碳、氮以及可溶性有机碳具有相同的变化趋势,即前期(3d内)都增加较快,在第3天达到最大值,随试验进行有所下降,配施效果优于单施。各处理可溶性有机氮在21d内缓慢增加;第21天时,C+Ca、Ca、C相比CK分别显著增加了62.1%,55.5%,40.9%;35d以后,配施(C+Ca)与单施过氧化钙(Ca)的效果显著优于单施生物质炭(C)和对照(CK)。120d培养期内,配施(C+Ca)处理能够明显提高微生物量碳、氮以及可溶性有机碳、氮的平均含量;微生物量碳的平均含量大小顺序为C+CaCCKCa,微生物量氮的平均含量C+Ca处理显著高于其他处理;可溶性有机碳的平均含量大小顺序为C+CaCaCCK,可溶性有机氮的平均含量C+Ca、Ca处理显著高于CK、C处理。微生物量碳、氮以及可溶性有机碳之间互为极显著正相关(P0.01),而微生物量碳与可溶性有机氮之间呈极显著负相关。因此,生物质炭和过氧化钙能有效提高旱地红壤微生物量碳、氮及可溶性有机碳、氮,且生物质炭与过氧化钙配合施用更有助于土壤改良。  相似文献   

16.
在黑龙江东部的张广才岭选择典型次生杂木林进行不同采伐处理,一个生长季后测定了土壤潜在碳矿化速率和活性有机碳含量.结果表明:在28℃条件下经过90d的培养,土壤潜在碳矿化速率和碳矿化总量在所测定的土层中(0-10 cm,10-20 cm,20-30 cm)均表现为:50%强度采伐>皆伐后农作>25%强度采伐≌对照>皆伐后造林的变化趋势,但各处理间差异不显著.土壤易氧化碳含量在3个土层50%强度采伐均显著高于对照.土壤微生物碳含量在0-10 cm和10-20 cm土层,50%强度采伐显著高于对照.在0-10 cm土层,皆伐后造林显著低于对照.水溶性有机碳含量在0-10 cm和10-20 cm土层,50%强度采伐显著高于对照,在20-30cm土层,皆伐后造林显著低于对照,这说明在东北温带次生林中,较大强度的择伐短期内可增加土壤活性有机碳含量.而皆伐后造林可导致土壤活性有机碳出现下降趋势.  相似文献   

17.
《Soil biology & biochemistry》2001,33(7-8):1113-1121
In this study, the influence of temperature and vegetation cover on soluble inorganic and organic nitrogen in a spodosol from north east Scotland was investigated. Firstly, soil cores were incubated at 5, 10 and 15°C for up to 8 weeks. Net mineralisation was observed at all temperatures with larger rates observed at higher temperatures. In contrast, water extractable dissolved organic nitrogen (DON) displayed no clear trend with time and showed little response to temperature. Secondly, intact cores of the same soil, with and without vegetation, were leached with artificial rain for 6 weeks at 6.5 and 15°C. Temperature and the presence of vegetation interacted to have a significant (P<0.01) effect on the concentration of NO3− in leachates; highest concentrations were observed in leachates from cores without vegetation at 15°C, whereas lowest concentrations were observed in leachates from cores with vegetation at 6.5°C. In contrast, concentrations of DON and dissolved organic carbon (DOC) were significantly (P<0.001) higher in leachates from cores with vegetation than without vegetation and were not affected by temperature. The cumulative amounts of DON and DOC leached from the cores with vegetation were 4 and 2.5 times greater, respectively, than those leached from the cores without vegetation. Comparison of soil solution (extracted by centrifugation at 0–5 and 5–10 cm depth) after leaching for 6 weeks, showed that the upper layer contained more than twice the amount of DON than the 5–10 cm layer and that the difference in concentration between the two depths was enhanced in the presence of vegetation. The results indicate that vegetation is an important source of DON and DOC. However, the removal of vegetation did not lead to an increase in the quantity of total dissolved nitrogen (TDN) in soil water, but resulted in a change in the dominant N fraction from DON to NO3−. In addition, the results show that DON, in both the incubated and leached cores, did not change as inorganic N was mineralised. This suggests that if water extractable DON was acting as a source of NH4+ or NO3−, then it was being replenished by, and in equilibrium with, a large reserve of organic N. Evidence of such a pool was indirect in the form of additional DON (equivalent to 2 g N m−2) being extracted by 0.5 M K2SO4.  相似文献   

18.
为了解东北黑土旱田改种稻田后土壤团聚体中微生物群落功能多样性的变化,将东北黑土旱田(种植玉米为主)改种为稻田(简称“旱改稻”),采用Biolog-Eco微平板技术,研究了“旱改稻”后不同粒径土壤团聚体微生物的多样性指数以及其对碳源利用能力的变化。结果表明,“旱改稻”显著增加了黑土土壤水稳性微团聚体数量,增加了不同粒径土壤团聚体内有机碳(SOC)的含量。旱田和稻田不同粒径土壤团聚体内的土壤微生物群落平均颜色变化率(AWCD)表现为旱田淤泥+粘土>旱田大团聚体>旱田微团聚体>稻田大团聚体>稻田淤泥+粘土>稻田微团聚体。“旱改稻”明显降低了各粒径土壤团聚体微生物的多样性指数以及碳源利用能力,尤其对氨基酸与碳水化合物最为明显。主成分分析结果表明,旱田和稻田不同粒径土壤团聚体微生物群落功能多样性差异显著。综上,“旱改稻”明显改变了黑土土壤团聚体微生物群落功能多样性,降低了以碳源为底物的土壤微生物代谢活性。本研究结果为东北黑土区土壤可持续利用提供了理论参考。  相似文献   

19.
Summary Oniscus asellus produced changes in the nutrients leached from Oie and Oa horizons of a hardwood forest soil. Soil with isopods lost more K+ (54%) from the Oie horizon and more Ca2+ (25%), Mg2+ (40%), and water-extractable S (23%) from the Oa horizon than soil without isopods. In contrast, soils with isopods lost less Ca2+ (39076) from the Oie horizon and less dissolved C-bonded S (33%) from the Oa horizon than soil without isopods. In addition, the Oia and Oa horizons exhibited different nutrient dynamics. When isopods were present, the Oa horizon leachates accumulated more Na+ K+, Ca2+, Mg2+, NO3 – , water-soluble SO4 2–, and dissolved C-bonded S, and the Oie horizon retained more of these nutrients. The type of leaching solution also had a major effect on nutrients. Leaching with a simulated soil solution resulted in smaller nutrient losses for K+ and Mg2+ in both horizons and for Na+, Ca2+, and NO3 – in the Oa horizon than leaching with distilled water.  相似文献   

20.
毛竹林土壤有机碳及微生物量碳特征研究   总被引：7，自引：0，他引：7  
通过对湖南会同林区集约经营毛竹林地土壤有机碳和微生物量碳进行测定,结果表明,毛竹林地土壤(0-60 cm)有机碳和微生物量碳含量平均值分别为1.727%和551.84 mg/kg,不同土壤层次有机碳和微生物量碳含量差异极显著,其中,0-20 cm土层有机碳含量平均值为2.607%,分别是20-40 cm和40-60 cm土层有机碳含量的1.67倍和2.57倍;0-20 cm土层的微生物量碳占土壤总微生物量碳的58.9%,分别是20-40 cm和40-60 cm土层的2.69倍和3.08倍。不同季节间土壤微生物量碳有明显变化规律,即土壤微生物量碳含量1-7月份呈上升的趋势,7月达到最大值,8-12月份呈逐渐下降趋势;不同季节间有机碳含量差异不显著。毛竹林地土壤表层土壤微生物量熵为1.118 6%,与40-60 cm土壤层相当,略高于20-40 cm土壤层,说明毛竹林不同土壤层次有机碳积累强度相当。  相似文献   

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