Soil microbial biomass C and N along a climatic transect in the Mongolian steppe

The relationships of soil microbial biomass C (C_mic) or N (N_mic) with mean annual precipitation and temperature were studied along a climatic transect in the Mongolian steppe. Soil organic C (C_org) and total N (N_t), respiration rate, C_mic and N_mic at depths of 0–5 and 5–10 cm decreased with increasing aridity. The contents of C_org and N_t in the 0- to 5-cm soil layers decreased linearly with precipitation reduction along the transect. C_mic and N_mic changes with precipitation were not linear, with higher changes between 330 and 128 mm mean annual precipitation. C_mic/C_org and N_mic/N_t increased with increasing aridity. The metabolic quotient qCO₂ of 0- to 5-cm soil layers was low between 330 and 273 mm precipitation. The relationship between the qCO₂ of the 0- to 5-cm soil layers and the mean annual precipitation was well fitted with a quadratic function y =0.0006x² –0.40x +86.0, where y is the qCO₂ (µmol CO₂-C mmol^–1 C_mic) and x is the mean annual precipitation (mm). C_org, N_t, C_mic, N_mic and respiration rate decreased exponentially with increasing mean annual temperature in both the 0- to 5- and 5- to 10-cm soil layers, and change rate was lower when the mean annual temperature was higher than 2.6°C. The close relationships of the mean annual precipitation or temperature with soil C_org, N_t, C_mic, N_mic, C_mic/C_org and qCO₂ indicate that each parameter can be calculated by determining the other parameters in this specific climatic range.     

热带地区不同香蕉长期轮作体系对土壤微生物和生物化学性质的影响

Soil microbiological and biochemical properties under various field crop rotations such as grains, pastures and vegetables have been studied intensively under short-term period. However, there is limited information about the influence of banana-based rotations on soil organic C, total N(TN), microbial biomasses and enzyme activities under long-term crop rotations. A field experiment arranged in a randomized complete block design with three replicates was carried out at the Wanzhong Farm in Ledong(18?37′–18?38′N, 108?46′–108?48′E), Hainan Province, China, to compare the responses of these soil parameters to long-term(10-year) banana(Musa paradisiaca)-pineapple(Ananas) rotation(AB), banana-papaya(Carica) rotation(BB) and banana monoculture(CK) in a conventional tillage system in the Hainan Island. Soil p H, total organic C(TOC), dissolved organic C(DOC), TN, total P(TP) and available P(AP) were found to be significantly higher(P 0.01) in AB and BB than CK at 0–30 cm soil depth. Microbial biomass C(MBC) and N(MBN) were observed 18.0%–35.2% higher in AB and 8.6%–40.5% higher in BB than CK at 0–30 cm. The activities of urease(UA), invertase(IA), dehydrogenase(DA) and acid phosphatase(APA) showed a mean of 21.5%–59.6% increase in AB and 26.7%–66.1% increase in BB compared with CK at 0–30 cm. Higher p H, TOC and DOC at 0–10 and 10–20 cm than at 20–30 cm were obtained despite of the rotations. Soil MBC and MBN and activities of UA, IA and DA decreased markedly(P 0.01) with increasing soil depth in the different rotation soils as well as the monoculture soil. In general, soil microbial biomass and enzymatic activities were more sensitive to changes in banana-based rotations than soil chemical properties, and consequently they were well-established as early indicators of changes due to crop rotations in the tropics.     

Microbial and enzyme properties of apple orchard soil as affected by long-term application of copper fungicide

Copper-based fungicides have been applied in apple orchards for a long time, which has resulted in increasing soil Cu concentration. However, the microbial and enzyme properties of the orchard soils remain poorly understood. This study aimed to evaluate the effect of long-term application of Cu-based fungicides on soil microbial (microbial biomass carbon (C_mic), C mineralization, and specific respiration rate) and enzyme (urease, acid phosphatase, and invertase activities) properties in apple orchards. Soil samples studied were collected from apple orchards 5, 15, 20, 30, and 45 years old, and one adjacent forest soil as for reference. The mean Cu concentrations of orchard soils significantly increased with increasing orchard ages ranging from 21.8 to 141 mg kg⁻¹, and the CaCl₂-extractable soil Cu concentrations varied from 0.00 to 4.26 mg kg⁻¹. The soil mean C_mic values varied from 43.6 to 116 mg kg⁻¹ in the orchard soils, and were lower than the value of the reference soil (144 mg kg⁻¹). The ratio of soil C_mic to total organic C (C_org) increased from 8.10 to 18.3 mg C_mic g⁻¹ C_org with decreasing orchard ages, and was 26.1 mg C_mic g⁻¹ C_org for the reference soil. A significant correlation was observed between total- or CaCl₂-extractable soil Cu and soil C_mic or C_mic/C_org, suggesting that the soil Cu was responsible for the significant reductions in C_mic and C_mic/C_org. The three enzyme activity assays also showed the similar phenomena, and declined with the increasing orchard ages. The mean soil C mineralization rates were elevated from 110 to 150 mg CO₂-C kg⁻¹ soil d⁻¹ compared with the reference soil (80 mg CO₂-C kg⁻¹ soil d⁻¹), and the mean specific respiration rate of the reference soil (0.63 mg CO₂-C mg⁻¹ biomass C d⁻¹) was significantly smaller than the orchard soils from 1.19 to 3.55 mg CO₂-C mg⁻¹ biomass C d⁻¹. The soil C mineralization rate and the specific respiration rate can be well explained by the CaCl₂-extractable soil Cu. Thus, the long-term application of copper-based fungicides has shown adverse effects on soil microbial and enzyme properties.     

Substrate inputs and pH as factors controlling microbial biomass, activity and community structure in an arable soil

Our aim was to determine whether the smaller biomasses generally found in low pH compared to high pH arable soils under similar management are due principally to the decreased inputs of substrate or whether some factor(s) associated with pH are also important. This was tested in a soil incubation experiment using wheat straw as substrate and soils of different pHs (8.09, 6.61, 4.65 and 4.17). Microbial biomass ninhydrin-N, and microbial community structure evaluated by phospholipid fatty acids (PLFAs), were measured at 0 (control soil only), 5, 25 and 50 days and CO₂ evolution up to 100 days. Straw addition increased biomass ninhydrin-N, CO₂ evolution and total PLFA concentrations at all soil pH values. The positive effect of straw addition on biomass ninhydrin-N was less in soils of pH 4.17 and 4.65. Similarly total PLFA concentrations were smallest at the lowest pH. This indicated that there is a direct pH effect as well as effects related to different substrate availabilities on microbial biomass and community structure. In the control soils, the fatty acids 16:1ω5, 16:1ω7c, 18:1ω7c&9t and i17:0 had significant and positive linear relationships with soil pH. In contrast, the fatty acids i15:0, a15:0, i16:0 and br17:0, 16:02OH, 18:2ω6,9, 17:0, 19:0, 17:0c9,10 and 19:0c9,10 were greatest in control soils at the lowest pHs. In soils given straw, the fatty acids 16:1ω5, 16:1ω7c, 15:0 and 18:0 had significant and positive linear relationships with pH, but the concentration of the monounsaturated 18:1ω9 PLFA decreased at the highest pHs. The PLFA profiles indicative of Gram-positive bacteria were more abundant than Gram-negative ones at the lowest pH in control soils, but in soils given straw these trends were reversed. In contrast, straw addition changed the microbial community structures least at pH 6.61. The ratio: [fungal PLFA 18:2w6,9]/[total PLFAs indicative of bacteria] indicated that fungal PLFAs were more dominant in the microbial communities of the lowest pH soil. In summary, this work shows that soil pH has marked effects on microbial biomass, community structure, and response to substrate addition.     

德国东部扬尘沉积山坡上松林中土壤的性质

Physical, chemical, and microbial properties of forest soils subjected to long-term fly ash depositions were analyzed in spruce （Picea abies （L.） Karst.） stands of eastern Germany on three forest sites along an emission gradient of 3 （high input）, 6, and 15 km （low input） downwind of a coal-fired power plant. Past emissions resulted in an atypical high mass of mineral fly ash constituents in the organic horizons at the high input site of 128 t ha^-1 compared to 58 t ha^-1 at the low input site. Magnetic susceptibility measurements proved that the high mineral content of the forest floor was a result of fly ash accumulation in these forest stands. Fly ash deposition in the organic horizons at Site I versus III significantly increased the pH values, effective cation exchange capacity, base saturation and, with exception of the L horizon, concentrations of mobile heavy metals Cd, Cr, and Ni, while stocks of organic C generally decreased. A principal component analysis showed that organic C content and base status mainly controlled soil microbial biomass and microbial respiration rates at these sites, while pH and mobile fractions of Cd, Cr, and Ni governed enzyme activities. Additionally, it was hypothesized that long-term fly ash emissions would eventually destabilize forest ecosystems. Therefore, the results of this study could become a useful tool for risk assessment in forest ecosystems that were subjected to past emissions from coal-fired power plants.     

辽宁省不同土地利用对土壤微生物量碳氮的影响

通过野外调查采样和室内氯仿熏蒸提取法分析,研究了辽宁省旱地、稻田、湿地、草地、森林、果园6种不同土地利用方式共计35个样地表层土壤（0～10 cm、10～20 cm、20～30 cm）对土壤微生物量碳（SMBC）和土壤微生物量氮（SMBN）的影响。结果表明,土地利用方式对土壤微生物量有显著影响,其中土壤微生物量碳依次为森林〉湿地〉稻田〉旱地〉果园〉草地;土壤微生物量氮则为森林〉旱地〉稻田〉果园〉湿地〉草地。土壤微生物量碳氮均表现为森林显著高于其他土地利用方式,湿地、稻田、旱地、果园高于草地。除旱地和稻田,土壤微生物量碳随土层加深含量递减;而土壤微生物量氮在6种土地利用类型中,均表现为随土层加深含量递减。相关分析表明,土壤微生物量碳、氮之间显著相关,土壤微生物量碳、氮是可以表征土壤肥力的敏感因子。     

果草套种对南方丘陵山地表层土壤微生物量碳氮及酶活性的影响

[目的]探究不同果草套种模式下0—10cm土层土壤微生物量碳、氮及酶活性的差异,为改善土壤肥力条件、促进桂林旅游城市生态循环农业经济的发展提供理论依据。[方法]在桂林潮田河流域大山口农业综合示范区内设置样地,采集表层(0—10cm)土壤样品,测定与分析不同果草套种模式下表层土壤微生物量碳、氮及酶活性的差异。[结果]0—10cm土层土壤氮磷钾、土壤微生物量碳氮和土壤酶活性大小基本表现为:阳朔金桔+牧草桂橙1号+牧草翠冠梨+牧草对照样地。其中,阳朔金桔+牧草模式对0—10cm土层土壤微生物量碳、氮含量和土壤酶活性的影响最为明显(p0.05)。相关性分析表明,土壤微生物量碳氮和3种土壤酶活性存在极显著正相关关系。[结论]果草套种模式特别是阳朔金桔+牧草模式对南方丘陵山地表层土壤肥力条件的改善作用较为明显。     

Soil moisture variability along transects over a well-developed gully in the Loess Plateau,China

Knowledge of soil moisture distributions in gullies, which are highly variable spatially and temporally, is important for both restoring vegetation and controlling erosion in them, but little attention has been paid to this spatio-temporal variability to date. Therefore, we examined soil moisture profiles and their variability along three transects traversing sidewalls of a well-developed gully with steep slopes in a hilly area of the Chinese Loess Plateau. We took intensive measurements at 20-cm intervals from 0 to 160 cm depth, using a portable time domain reflectometer, from September 3 to October 20 2009 and from April 5 to July 20 2010. The results indicate that the mean, standard deviation and coefficient of variation of moisture content vary with time, their responses to precipitation vary at different depths, and moisture content is most variable when mean values are moderate (15–20%). Revised fitting functions developed and introduced by Famiglietti et al. (2008) captured with confidence the relationship between spatial variability (SD and CV) and spatial mean of moisture content (RMSE ranging from 0.0015 to 0.0293). Soil moisture clearly varied along the transects, the vertical distribution of soil moisture differed in different seasons, and correlation analysis showed that soil texture influenced the variability of surface soil moisture more strongly than terrain attributes (except during distinct rainfall events, when this pattern reversed). The results presented here should improve understanding of spatio-temporal variations in soil moisture profiles in well-developed gullies in the Loess Plateau, and potentially elsewhere.     

Soil chemical properties and microbial biomass after 16 years of no-tillage farming on the Loess Plateau, China

Data from a 16-year field experiment conducted in Shanxi, on the Chinese Loess Plateau, were used to compare the long-term effects of no-tillage with straw cover (NTSC) and traditional tillage with straw removal (TTSR) in a winter wheat (Triticum aestivum L.) monoculture. Long-term no-tillage with straw cover increased SOM by 21.7% and TN by 51.0% at 0–10 cm depth and available P by 97.3% at 0–5 cm depth compared to traditional tillage. Soil microbial biomass C and N increased by 135.3% and 104.4% with NTSC compared to TTSR for 0–10 cm depth, respectively. Under NTSC, the metabolic quotient (CO₂ evolved per unit of MBC) decreased by 45.1% on average in the top 10 cm soil layer, which suggests that TTSR produced a microbial pool that was more metabolically active than under NTSC. Consequently, winter wheat yield was about 15.5% higher under NTSC than under TTSR. The data collected from our 16-year experiment show that NTSC is a more sustainable farming system which can improve soil chemical properties, microbial biomass and activity, and thus increase crop yield in the rainfed dryland farming areas of northern China. The soil processes responsible for the improved yields and soil quality, in particular soil organic matter, require further research.     

环境因子对山西太岳山土壤微生物量的影响

本文以山西太岳山两个林型(华北落叶松人工林、灌木林)下阴坡和阳坡的土壤样品为研究对象,研究了不同坡向下土壤微生物量碳、氮、土壤理化性质、土壤微生物碳氮比值的变化特征。研究结果表明:土壤有机碳、全氮、微生物量碳、氮含量在0~10 cm土层均显著高于10~20 cm土层。在华北落叶松人工林和灌木林下,土壤微生物量碳、可溶性有机碳及两者之和在阳坡均显著高于阴坡;土壤微生物量碳占两者之和的比例约为81%~87%,在不同坡向下没有显著性差异。土壤微生物量碳氮比在灌木林阳坡下为6.5~7.2,阴坡为7.3~9.9;在华北落叶松人工林阳坡下为7.3~8.6,阴坡为8.2~8.6。两种林型下土壤微生物熵在阳坡均高于阴坡。相关性分析结果表明,土壤微生物量碳、氮与土壤pH值、可溶性有机碳呈显著正相关,土壤有机碳与土壤全氮、微生物量碳、pH值和含水率均有显著正相关性。总的来说,不同坡向对土壤微生物量产生重要影响,进而使土壤微生物熵不同,阴坡土壤有机碳活性较小,碳库的稳定性较好。本文从土壤微生物量及其与环境因子相互关系的角度探讨了土壤环境对土壤微生物的影响,以期为更好的理解该地区土壤碳周转和植被恢复生态效应提供参考。     

宁夏贺兰山东麓酿酒葡萄基地土壤酶活性

调查了宁夏御马酿酒葡萄基地不同栽培年限下土壤的蔗糖酶、磷酸酶、脲酶、过氧化氢酶的活性,并与土壤的基本理化性质进行了回归分析。结果表明,供试土壤为强碱性反应,耕作施肥对土壤pH和全盐含量影响不显著;土壤有机质、全氮、铵态氮、速效磷、阳离子代换量大都处于最低的六级水平,但肥力随耕种年限的延长显著增加;随栽培年限的延长,表层土壤磷酸酶活性、蔗糖酶和脲酶活性显著增加;蔗糖酶、脲酶活性随剖面深度的加深而显著减小;表土过氧化氢酶活性随栽培年限的延长而显著下降,但不同土地利用下表层以下各层次土壤过氧化氢酶活性总体上高于表层,且差异显著。磷酸酶活性与土壤有机质、全氮、全磷、速效磷、缓效钾、速效钾之间存在着极显著相关关系;磷酸酶活性、蔗糖酶和脲酶活性与土壤有机质、全氮、全磷、速效磷、缓效钾、速效钾之间存在着极显著相关关系;四种酶之间,磷酸酶与脲酶之间存在极显著相关关系,脲酶与蔗糖酶之间存在极显著相关关系。由此表明,磷酸酶、脲酶、蔗糖酶活性的大小可以代表宁夏贺兰山东麓酿酒葡萄栽培区土壤肥力的高低。     

Influence of Plant Residues after Steam-Treatment with High Temperature and Pressure on Soil Microbial Biomass C and N, Water-Soluble C and N, and pH

Steam-treated grass trimmings (GrT), and wooden chips of pine (PnT) and walnut branches (WnT) or non-treated grass trimmings (GrNoT) and wooden chips of pine (PnNoT) and walnut branches (WnNoT) were mixed with soil (S) and then incubated for 10 weeks to measure microbial biomass C (MBC) and N (MBN), water-soluble C (WSC) and N (WSN), and soil pH. The results showed that there were a larger amount of MBC and WSC in steam-treated samples, principally in early period. It was probably due to the steam-treatment facilitating solubilization of organic C that served with substrate for microbial biomass. In grass trimming, the MBN and WSN had differences between treated and non-treated. No such differences in wooden chips was probably because the low total N content in these plants. The higher value of WSN showed in S+GnNoT showed more potential of nitrate pollution. The steam-treatment did not influence on soil pH after 1 week of incubation.     

Soil microbiological properties and its stratification ratios for soil quality assessment under different cover crop management systems in a semiarid vineyard

In vineyards in Spain, tillage and semiarid Mediterranean climatic conditions accelerate organic matter loss from the soil. Cover crops are a conservation management practice that can provoke changes in soil quality which requires evaluation. Stratification ratios of soil properties such as soil organic C and labile C fractions have been proposed for the assessment of soil quality under different soil management systems. Our objective was to study the effect of different cover crop management on various soil parameters and their stratification ratios. We evaluated three different soil managements in a Typic Haploxerept from NE Spain: conventional tillage (CT); 5‐y continuous cover crop of resident vegetation (RV); and 4‐y continuous cover crop of Festuca longifolia Thuill., followed by 1‐y Bromus catharticus L. after resowing (BV). We monitored soil organic C, particulate organic C, water soluble C, potentially mineralizable N, microbial biomass C, β‐glucosidase and urease enzymatic activities, and water stable aggregates at 0–2.5, 2.5–5, 5–15, 15–25, and 25–45 cm soil depths. We calculated soil depth stratification ratios of those soil properties. Resident cover crop increased microbiological properties, labile C fractions, and aggregation with respect to conventional tillage at 0–2.5 and 2.5–5 cm soil depths. However, for Bromus cover crop the same soil properties were lower than for the resident cover crop at 0–2.5 cm depth. Stratification ratios of β‐glucosidase and urease enzymatic activities, and particulate organic C showed a higher sensitivity than other soil properties; therefore, they would be the best indicators for soil quality assessment in semiarid Mediterranean vineyards.     

盐渍化土壤肥力演变规律研究

本文是在曲周试验区的长期定位试验和大田调查的基础上　，研究了盐渍化土壤在改良、利用及培肥过程中，构成土壤肥力的主要因素的演变规律．研　究结果表明：土壤有机质含量从治理初期的小于５ｇ／ｋｇ提高到１５　ｇ／ｋｇ左右；土壤碱解氮从开　始的富氮假象，逐步出现土壤碱解氮含量迅速下降的现象，再缓慢上升到７０～８０ｍｇ／ｋｇ，有　的甚至超过了１３０　ｍｇ／ｋｇ；土壤有效磷含量从２～３　ｍｇ／ｋｇ或者只有０．５～１　ｍｇ／ｋｇ左右，有的　地块近于零提高到１５～２０　ｍｇ／ｋｇ，有的已接近６０　ｍｇ／ｋｇ；土壤速效钾含量则由治理初期的２０　０　ｍｇ／ｋｇ，下降到３０　ｍｇ／ｋｇ左右；土壤微生物量明显增加，理化性状不断改善，熟化程度逐　步提高；土壤肥力的变化表现出了阶段性特征．提出了盐渍化土壤的合理施肥技术．     

耕作与施肥对甘蔗地土壤微生物量碳、氮的影响

通过野外调查与室内分析,研究了云南蒲缥甘蔗地赤红壤不同耕作与施肥土壤剖面微生物量碳、氮特征。结果表明:不同耕作与施肥对土壤微生物量碳、氮均有一定影响,其中耕作对土壤微生物量碳、氮的影响较为一致,表现为免耕 > 翻耕。施肥对0—20 cm土层中微生物量碳的影响表现为翻耕施肥 > 翻耕,对20—40 cm,40—60 cm土层中微生物量碳的效应呈现为翻耕 > 翻耕施肥,而施肥对土壤微生物量氮影响则与其对微生物量碳的效应相反。耕作和施肥对各个土层土壤微生物商具有显著的影响（p<0.05）,表现为免耕 > 翻耕,翻耕施肥条件下0—20 cm土层的微生物商稍高于翻耕,而其他土层均为翻耕 > 翻耕施肥;土壤微生物量氮与全氮的比值与微生物量氮的变化趋势相近。在不同的耕作和施肥条件下,免耕有利于提高土壤微生物量,施肥在一定程度上也利于提高土壤微生物量。     

玉米地土壤微生物量碳、氮及微生物熵对不同物料还田的响应

在四川丘陵区紫色土上进行田间试验,以无物料还田为对照,对比分析了蚕豆秸秆、油菜秸秆、猪粪3种物料还田对夏玉米吐丝期和收获期0—20,20—40cm土层土壤有机碳、全氮、微生物量碳氮含量及微生物熵的影响,以期为农业废弃有机物料的综合利用及四川丘陵区土壤质量的提升提供理论参考。结果表明:(1)尽管有机物料还田于0—20cm土层中,0—20,20—40cm土层土壤有机碳(SOC)、全氮(TN)、微生物量碳(SMBC)、微生物量氮(SMBN)含量均受到有机物料的深刻影响。各处理0—20cm土层SOC、TN、SMBC、SMBN含量均显著高于20—40cm土层,且上下2层土壤SOC、TN、SMBC和SMBN含量在生育时期间均表现为吐丝期>收获期。(2)在2个生育时期,3种物料还田均能提高0—20,20—40cm土层SOC、TN、SMBC、SMBN含量。与对照相比,物料还田处理的SOC、TN、SMBC、SMBN含量分别提高2.6%~141.2%,1.9%~33.0%,5.1%~114.7%,41.5%~98.7%,其中收获期各处理0—20,20—40cm土层SOC、SMBC、SMBN均表现为油菜秸秆>蚕豆秸秆>猪粪>对照,TN表现为蚕豆秸秆>猪粪>油菜秸秆>对照。(3)各处理SMBC/SMBN、qMB、SMBN/TN分别为3.74~10.53,0.86%~2.19%,1.01%~3.41%,且物料还田降低SMBC/SMBN,提高土壤qMB和SMBN/TN值。相关分析表明,SMBC、SMBN与SOC、TN之间均存在极显著正相关关系。因此,农业生产中可通过物料还田提供给微生物足够的碳氮营养,提高土壤SMBC、SMBN、SOC、TN含量和qMB值,维持较高的农田生产力,提升土壤质量,但具体施用物料时还需寻求土壤肥力提升、玉米产量增加以及环境效益之间的平衡。     

Soil quality degradation processes along a deforestation chronosequence in the Ziwuling area, China

Accelerated erosion caused by deforestation and soil degradation has become the primary factor limiting sustainable utilization of soil resources on the Loess Plateau of Northwestern China. We studied the physical, chemical, and microbiological processes of soil degradation along a chronosequence of deforestation in the Ziwuling area of northwestern Shaanxi province. The results indicated that soil wet aggregate stability, mean aggregate diameter decreased with years following deforestation. Accelerated erosion resulted in soil nutrient loss, and a decrease in soil enzyme activities including notable losses of total soil N, organic C, alkaline phosphatase activity, and invertase activity. During the early time period, the rates of total soil N, organic C, alkaline phosphatase activity, and invertase activity decreasing were rapid and gradually decreased with deforestation years. Increased use of nitrogen fertilizers made determination of soil quality based on measured NO₃–N and NH₄–N inconclusive. The differences in measured parameters between the topsoil and subsoil horizons decreased with time since deforestation, and we concluded that soil erosion was the primary process responsible for the degradation of measured soil physical, chemical, and microbiological properties.     

间作白三叶对苹果/白三叶复合系统土壤微生物量碳、氮及酶活性的影响

以渭北黄土高原苹果园土壤为研究对象,设置传统苹果（Malus domestica Borkh.）园清耕及间作白三叶（Trifolium repens L.）两个处理,测定和分析了不同土层（0—5 cm,5—10 cm,10—20 cm及20—40 cm）的土壤微生物量碳（SMBC）、氮（SMBN）、4种土壤酶活性、有机碳（SOC）和全氮（TN）等指标,从土壤微生物碳、氮及酶活性的角度探讨间作白三叶对苹果/白三叶复合系统土壤的影响。结果表明:间作白三叶能够显著提高土壤微生物量碳、氮的含量和土壤酶活性,提高土壤微生物对有机碳和全氮的利用效率,其作用随着土层深度的增加而降低,在表层土壤效果更为显著。土壤微生物量碳、氮及土壤酶活性与土壤有机碳、全氮呈极显著相关或显著性相关。苹果园土壤微生物量碳、氮及土壤酶活性能敏感响应生草间作,可以作为评价果园生草对果园土壤影响的良好指标。     

西藏色季拉山土壤微生物量碳和易氧化态碳沿海拔梯度的变化

为探讨不同海拔梯度对土壤活性有机碳库的影响,以西藏色季拉山(西坡)的高山灌丛(AS)、杜鹃林(RF)、急尖长苞冷杉林(AGSF1～6)和林芝云杉林(PLLF)为试验对象,研究林地土壤有机碳、微生物量碳和易氧化态碳的变化特征。结果表明:高海拔植被类型具有较高的土壤活性有机碳含量和分配比例。土壤有机碳含量与土壤pH值和容重呈显著负相关(p<0.05)。在土壤剖面垂直分布上,随着土壤深度增加,土壤总有机碳、微生物量碳和易氧化态碳含量均呈现随土层深度增加而逐渐减小的变化规律。土壤总有机碳、微生物量碳和易氧化态碳含量沿海拔梯度具有明显的变化规律,即随海拔的升高,土壤总有机碳、微生物量碳和易氧化态碳含量逐渐变大。土壤微生物量碳和总有机碳量有较好的正相关性,有机碳含量越高,土壤微生物量碳越大。     

氮素和水分对贝加尔针茅草原土壤酶活性和微生物量碳氮的影响

在内蒙古贝加尔针茅草原,分别设对照(N0)、1.5 g·m-2(N15)、3.0 g·m-2(N30)、5.0 g·m-2(N50)、10.0 g·m-2(N100)、15.0 g·m-2(N150)、20.0 g·m-2(N200)和30g·m-2(N300)(不包括大气沉降的氮量)8个氮素(NH4NO3)梯度和模拟夏季增加降水100 mm的水分添加交互试验,研究氮素和水分添加对草原土壤养分、酶活性及微生物量碳氮的影响。结果表明:氮素和水分添加对草原土壤理化性质和生物学特性有显著影响。随施氮量的增加土壤总有机碳、全氮、硝态氮、铵态氮含量呈增加的趋势,相反,土壤pH值呈降低的趋势。土壤脲酶和过氧化氢酶的活性随施氮量的增加而升高,多酚氧化酶则随施氮量的增加呈下降的趋势。氮素和水分添加对草原土壤微生物量碳氮含量有显著影响,高氮处理(N150、N200和N300)显著降低了微生物碳含量,微生物氮含量随施氮量的增加呈上升趋势。水分添加能够减缓氮素添加对微生物的抑制作用,提高微生物量碳、微生物量氮含量。草原土壤养分、土壤酶活性及土壤微生物量碳氮含量间关系密切,过氧化氢酶与全氮、总有机碳、硝态氮呈显著正相关,多酚氧化酶与铵态氮、硝态氮、全氮呈显著负相关。微生物量氮含量与土壤全氮、铵态氮、硝态氮含量以及过氧化氢酶和磷酸酶活性呈显著正相关,与多酚氧化酶呈负相关;微生物量碳与过氧化氢酶呈负相关,与多酚氧化酶活性呈正相关。