土壤的石灰反应强度估测CaCO_3含量和pH研究——以山西省黄土性母质土壤为例

pH和CaCO_3含量是土壤常规分析的两个测定指标,但其室内测定均需借助相应的仪器设备完成,耗时费力。以山西省土系调查采集的110个典型土壤剖面的426个发生层土样的野外测定的石灰反应强度和实验室测定的土壤pH、CaCO_3含量、交换性钠饱和度(Exchangeable Sodium Percentage,ESP)数据为基础,尝试建立石灰反应强度与pH、CaCO_3含量之间的定量关系模型。结果表明:北方黄土性母质土壤,当pH9.0时,CaCO_3含量是影响土壤pH的重要因素,二者的回归拟合最优关系符合幂函数曲线;当pH9.0时,CaCO_3与pH之间无明显关系。石灰反应强度在一定程度上可以半定量地反映pH或CaCO_3含量,但其确定的pH或CaCO_3含量尚是一个范围,并非精确值。同时,从发生学意义角度,土壤中CaCO_3含量高低对形态学研究具有重要意义,在这种情况下,如果需要用pH或CaCO_3含量来确定准确的土壤系统分类类型(如确定土体是否为酸性、具有钙积层/钙积现象等),为慎重起见建议还是以实验室的准确测定数据为准;对于非碱化(pH9.0)、野外有泡沫反应的北方黄土性母质土壤,无论泡沫反应强弱和CaCO_3含量高低,土壤pH基本稳定在8.51±0.49,这一pH范围对作物生长基本没有制约,如果仅从pH或CaCO_3含量是否影响作物生长角度考虑,无需实验室测定pH或CaCO_3含量。     

种植苹果树对渭北果园土壤胶结物质分布的影响

本研究通过系统研究种植果树对土壤胶结性物质的演化规律及其与土壤团聚体稳定性之间关系的影响,探索影响果园土壤团聚体状态的因素,以期为果园科学管理提供理论依据。在渭北旱塬苹果主产区分别选取10 a、20 a的苹果园和农田(冬小麦-夏玉米轮作,对照)各4个,在果树冠层投影范围内距树干2/3处逐层采集0~100 cm土层土壤样品和0~50 cm土层原状土壤样品,研究不同植果年限果园及农田土壤剖面黏粒、有机质、CaCO_3等团聚体胶结物质的分布及其与团聚体稳定性之间的关系。结果发现:在0~100 cm土层范围内,各果园土壤黏粒含量基本随土层深度的增加而递增,且在0~40 cm土层表现为农田10 a果园20 a果园,40 cm以下土层则呈现相反的态势;种植果树相比农田可显著增加0~100 cm土层土壤有机质总储量,但随着种植果树年限的增加,土壤有机质总储量呈递减趋势;在0~100 cm土层土壤CaCO_3总储量表现为10 a果园农田20a果园,但在0~40 cm土层CaCO_3含量及储量表现为10 a果园农田20 a果园,而40~100 cm土层则为20 a果园10 a农田。皮尔森相关分析发现(29)0.25 mm土壤团聚体的数量和平均重量直径(MWD)与土壤黏粒、有机质和CaCO_3含量密切相关,其中机械稳定性团聚体的数量和稳定性主要受土壤中CaCO_3、有机质含量的影响,水稳性团聚体的数量和稳定性主要受土壤中黏粒和CaCO_3的影响。总之,植果显著改变了土壤中黏粒、有机质、CaCO_3的演化过程和趋势,随植果年限增加,果园土壤黏粒和CaCO_3在土壤较深土层淋溶淀积明显;各果园土壤有机质总储量虽然高于农田,但随植果年限增加,有逐渐减少的趋势。可见植果明显加速了渭北黄土塬地土壤的残积黏化和钙化过程,影响着表层土壤团聚作用和底层土壤的紧实化和坚硬化程度。     

典型菜地土壤剖面N2O、CH4与CO2分布特征研究

为探究菜地土壤剖面N2O、CH4与CO2时空分布特征,利用地下气体原位采集系统与气相色谱法,周年动态监测3种典型菜地,即休闲裸地、轮作地Ⅰ(芹菜?空心菜?小白菜?苋菜)以及轮作地Ⅱ(菜心?芹菜?空心菜?大青菜)7 cm、15 cm、30 cm与50 cm土层N2O、CH4与CO2浓度变化。结果表明,0~50 cm土层范围内,N2O、CH4与CO2 3种气体浓度周年变异性较大,变幅分别为0.63~1 657.0μL(N2O)?L?1、0.8~72.5μL(CH4)?L?1和0.41~36.6 m L(CO2)?L?1。轮作地Ⅰ与轮作地Ⅱ的N2O平均浓度随土壤深度增加而增加,休闲裸地则呈现先增加(0~30 cm)后降低(30~50 cm)的变化趋势。两种轮作菜地4个土层N2O平均浓度均显著高于休闲裸地,二者氮肥施用量不同并未造成相同土层间N2O平均浓度的显著差异。3种菜地CH4与CO2平均浓度均呈现50 cm30 cm15 cm7 cm的梯度特征。轮作地Ⅰ与轮作地Ⅱ0~15 cm土层CH4平均浓度均大于休闲裸地,而在15~50 cm土层则分别大于和小于休闲裸地。CO2浓度呈现明显的季节性变化,除轮作地Ⅰ50 cm土层外,两种轮作菜地其他土层CO2平均浓度均小于休闲裸地对应土层。可见,蔬菜地高氮肥施用、多频次耕作等复杂管理使得N2O、CH4与CO2表现出较大的时空变异特征,其中氮肥施用对N2O的影响大于CH4与CO2,CH4受施肥与耕作的影响均较小,CO2显著受土壤温度与耕作措施的影响,在此基础上需进一步探究N2O、CH4与CO2的其他影响因素。     

土地利用方式对黄土丘陵土壤CaCO_3含量及分布的影响

本文以具有典型黄土丘陵特征的砖窑沟流域为例,对该流域梁峁地主要土壤类型上不同土地利用方式下0～200cm层土壤剖面CaCO3含量进行了分析。结果表明:土壤CaCO3含量耕地>林地>荒草地;耕地土壤CaCO3有明显的累积层,累积深度约在20～100cm之间;林地累积层深度约在20～60cm之间;而荒草地无明显累积层。这种现象与一般干旱半干旱地区不同。     

黄土台塬不同土地利用方式土壤CH4通量特征及主控因子分析

土地利用转变会导致土壤微环境及生理生化过程发生改变,继而影响土壤温室气体的产生和排放。目前关于土地利用转变对温室气体通量的研究主要集中于CO_2,而对CH_4研究甚少。本文以黄土台塬为研究区,重点分析不同土地利用方式的土壤CH_4通量特征与其影响因素的关系,并明确其关键影响因子,为预测整个黄土台塬土地利用方式转变对温室效应的贡献提供基础数据。以陕西省永寿县马莲滩林场为研究对象,于2015年4月—2016年3月,采用静态箱-气相色谱法,对耕地、天然草地、灌木林地、乔灌混交林地、乔木林地和果园的CH_4通量特征进行研究,并分析土壤CH_4通量与土壤温度、地表温度、含水量及全氮的关系。不同土地利用方式土壤CH_4平均通量差异显著(P0.05),但表现相似的季节变化,呈现夏秋季高于冬春季特征。林地、园地、耕地土壤均为CH_4吸收汇,其吸收能力(平均值)为乔灌混交林(51.24μg·m~(-2)·h~(-1))乔木林(44.80μg·m~(-2)·h~(-1))灌木林(31.52μg·m~(-2)·h~(-1))草地(25.89μg·m~(-2)·h~(-1))果园(18.97μg·m~(-2)·h~(-1))耕地(14.89μg·m~(-2)·h~(-1))。不同土地利用方式土壤CH_4吸收与土壤温度、全氮和地表大气温度均呈正相关;与土壤含水量呈负相关。其土壤表层(0~20 cm)温度是6种土地利用方式土壤CH_4吸收的主要影响因素。总之,自然条件下的土壤CH_4吸收率明显高于农业土壤CH_4吸收率,耕地转变为林地后土壤的CH_4吸收能力增强,土壤对减缓温室效应的贡献增大。     

长期不同施肥模式对日光温室土壤硝态氮时空分布及累积的影响

通过连续7 年的定位试验, 研究了日光温室生产中不同施肥模式(常规模式、无公害模式和有机模式)对土壤NO₃^--N 时空分布及累积的影响。结果表明, 随着种植年限的增加, 3 种施肥模式土壤剖面各层次NO₃^--N含量均呈上升趋势, 年增加量顺序为常规施肥模式＞无公害施肥模式＞有机施肥模式。受氮素输入量(施肥)的影响, NO₃^--N 主要分布在0~40 cm 土层, 0~60 cm 土层NO₃^--N 含量总体呈作物生长前期低、中期高、后期低的趋势; 与上层土壤相比, 100 cm 以下土层NO₃^--N 含量有不同程度的增加。0～200 cm 土体NO₃^--N 平均累积量有机施肥模式比无公害施肥模式低33.8%, 比常规施肥模式低45.9%; 无公害施肥模式比常规施肥模式低18.3%。3 种施肥模式下, NO₃^--N 都有向2 m 以下土体淋洗的趋势。与施用化学肥料相比, 施用有机肥能明显降低土壤剖面NO₃^--N 含量, 控制其累积峰的下移, 但不合理施用有机肥也会产生NO₃^--N 淋洗而污染环境。     

干旱地区土壤碳酸钙淀积过程模拟

根据化学热力学过程吧及土壤剖面碳酸钙淀积过程的机理,借鉴前人的建模经验,构建了干旱地区土壤碳酸钙淋溶淀积过程模型ＣＡＥＤＰ,并以晋西北黄土丘陵土壤为例进行了验证。     

苏北滨海土壤碳酸钙含量反射光谱估算研究

土壤属性的快速、精确测定是实现现代精细农业的基础。本研究分析了江苏省北部滨海土壤的属性特征以及碳酸钙的可见-近红外反射光谱特征,探讨利用可见-近红外光谱估算滨海土壤碳酸钙含量的可行性,比较不同光谱反射率数据集、不同预处理方法以及不同建模方法定量反演的优劣。结果表明:(1)苏北滨海土壤有机质含量较低、碳酸钙含量较高,其光谱曲线在2 340 nm处有较明显的碳酸钙吸收特征;(2)滨海土壤碳酸钙含量与土壤的可见-近红外波段反射率呈正相关,且碳酸钙含量高低对于土壤的近红外波段反射率的影响高于可见光波段;(3)可见-近红外反射光谱可用于估算滨海土壤碳酸钙含量。就建模结果而言,381~2 459 nm波段反射光谱数据集、log(1/R)预处理、偏最小二乘回归三者结合的效果比较理想。     

西北黑河流域土壤pH与CaCO_3相当物含量关系研究

干旱-半干旱地区的石灰性土壤中pH与CaCO_3相当物含量之间有一定关系,但目前黑河流域土壤中pH与CaCO_3相当物含量之间的关系及其影响因素尚不明确。从区域、海拔、土壤母质、土壤类型、土地利用方式五个方面分析了我国西北黑河流域土壤中pH与CaCO_3相当物含量之间的关系。结果表明,黑河流域土壤pH与CaCO_3相当物含量之间存在显著的非线性相关,pH随着CaCO_3相当物含量的增加而逐渐升高,当CaCO_3相当物含量升高到某一阈值后,pH增幅迅速降低,最终趋于稳定;不同区域、海拔、土纲、成土母质和土地利用方式下,pH与CaCO_3相当物含量之间的相关程度不同,表现为上游土壤pH与CaCO_3含量呈显著正相关,不同的海拔高度区间pH与CaCO_3含量之间具显著正相关,人为土、盐成土、均腐土、雏形土的pH与CaCO_3含量显著正相关,冰碛物、残积-坡积物、湖积物发育的土壤pH与CaCO_3含量具有极显著正相关,土地利用方式对pH与CaCO_3含量的关系影响较小;不同区域、海拔、土纲、成土母质和土地利用方式下,pH与CaCO_3相当物含量的最佳回归模型不同,有幂函数模型、一元二次模型、一元三次模型和线性模型。     

Soil CO2 flux in six monospecific forest plantations in Southern Rwanda

Forest soils contain the largest carbon stock of all terrestrial biomes and are probably the most important source of carbon dioxide (CO₂) to atmosphere. Soil CO₂ fluxes from 54 to 72-year-old monospecific stands in Rwanda were quantified from March 2006 to December 2007. The influences of soil temperature, soil water content, soil carbon (C) and nitrogen (N) stocks, soil pH, and stand characteristics on soil CO₂ flux were investigated. The mean annual soil CO₂ flux was highest under Eucalyptus saligna (3.92 μmol m⁻² s⁻¹) and lowest under Entandrophragma excelsum (3.13 μmol m⁻² s⁻¹). The seasonal variation in soil CO₂ flux from all stands followed the same trend and was highest in rainy seasons and lowest in dry seasons. Soil CO₂ flux was mainly correlated to soil water content (R² = 0.36-0.77), stand age (R² = 0.45), soil C stock (R² = 0.33), basal area (R² = 0.21), and soil temperature (R² = 0.06-0.17). The results contribute to the understanding of factors that influence soil CO₂ flux in monocultural plantations grown under the same microclimatic and soil conditions. The results can be used to construct models that predict soil CO₂ emissions in the tropics.     

黄淮海平原集约化种植条件下的土壤剖面硝态氮变化

通过田间试验研究玉米-冬小麦轮作系统下,两种不同水平的N肥施用量对NO3--N在黄淮海平原土壤剖面的分布及其动态变化规律的影响,并评估其对环境的潜在污染能力.土壤NO3--N监测为每间隔20 cm至剖面深180 cm.结果表示:作物收获后土壤剖面0～180 cm的残留NO3--N含量为107～443 kg/hm2,年际间和不同作物间的变异性较大.土壤剖面NO3--N含量随着施肥量的增加有增加的趋势,但差异不显著.当前当地农民常规施肥量处理和为常规施肥量2倍处理在试验期间出现的土壤剖面NO3--N含量峰值均在2003年的玉米生长季节,分别为688 kg/hm2和881 kg/hm2,但该玉米生长季节出现的大雨导致占0～180 cm土层50%左右的NO3--N积累在100～180 cm土层深处,该深度的NO3--N比较容易通过淋洗迁移出作物-土壤系统,也有可能是潜在的作物N素来源.由于类似大雨在当地出现的频率比较高,因此,即使在当前当地农民的传统耕作管理措施下,土壤NO3--N可能存在对环境的污染威胁,但程度如何,尚需进一步研究.     

Changes in forest soil organic matter pools after a decade of elevated CO2 and O3

The impact of rising atmospheric carbon dioxide (CO₂) may be mitigated, in part, by enhanced rates of net primary production and greater C storage in plant biomass and soil organic matter (SOM). However, C sequestration in forest soils may be offset by other environmental changes such as increasing tropospheric ozone (O₃) or vary based on species-specific growth responses to elevated CO₂. To understand how projected increases in atmospheric CO₂ and O₃ alter SOM formation, we used physical fractionation to characterize soil C and N at the Rhinelander Free Air CO₂-O₃ Enrichment (FACE) experiment. Tracer amounts of ¹⁵NH₄⁺ were applied to the forest floor of Populus tremuloides, P. tremuloides-Betula papyrifera and P. tremuloides-Acer saccharum communities exposed to factorial CO₂ and O₃ treatments. The ¹⁵N tracer and strongly depleted ¹³C-CO₂ were traced into SOM fractions over four years. Over time, C and N increased in coarse particulate organic matter (cPOM) and decreased in mineral-associated organic matter (MAOM) under elevated CO₂ relative to ambient CO₂. As main effects, neither CO₂ nor O₃ significantly altered ¹⁵N recovery in SOM. Elevated CO₂ significantly increased new C in all SOM fractions, and significantly decreased old C in fine POM (fPOM) and MAOM over the duration of our study. Overall, our observations indicate that elevated CO₂ has altered SOM cycling at this site to favor C and N accumulation in less stable pools, with more rapid turnover. Elevated O₃ had the opposite effect, significantly reducing cPOM N by 15% and significantly increasing the C:N ratio by 7%. Our results demonstrate that CO₂ can enhance SOM turnover, potentially limiting long-term C sequestration in terrestrial ecosystems; plant community composition is an important determinant of the magnitude of this response.     

Effects of elevated CO2 and O3 on soil respiration under ponderosa pine

Soil respiration represents the integrated response of plant roots and soil organisms to environmental conditions and the availability of C in the soil. A multi-year study was conducted in outdoor sun-lit controlled-environment chambers containing a reconstructed ponderosa pine/soil-litter system. The study used a 2×2 factorial design with two levels of CO₂ and two levels of O₃ and three replicates of each treatment. The objectives of our study were to assess the effects of long-term exposure to elevated CO₂ and O₃, singly and in combination, on soil respiration, fine root growth and soil organisms. Fine root growth and soil organisms were included in the study as indicators of the autotrophic and heterotrophic components of soil respiration. The study evaluated three hypotheses: (1) elevated CO₂ will increase C assimilation and allocation belowground increasing soil respiration; (2) elevated O₃ will decrease C assimilation and allocation belowground decreasing soil respiration and (3) as elevated CO₂ and O₃ have opposing effects on C assimilation and allocation, elevated CO₂ will eliminate or reduce the negative effects of elevated O₃ on soil respiration. A mixed-model covariance analysis was used to remove the influences of soil temperature, soil moisture and days from planting when testing for the effects of CO₂ and O₃ on soil respiration. The covariance analysis showed that elevated CO₂ significantly reduced the soil respiration while elevated O₃ had no significant effect. Despite the lack of a direct CO₂ stimulation of soil respiration, there were significant interactions between CO₂ and soil temperature, soil moisture and days from planting indicating that elevated CO₂ altered soil respiration indirectly. In elevated CO₂, soil respiration was more sensitive to soil temperature changes and less sensitive to soil moisture changes than in ambient CO₂. Soil respiration increased more with days from planting in elevated than in ambient CO₂. Elevated CO₂ had no effect on fine root biomass but increased abundance of culturable bacteria and fungi suggesting that these increases were associated with increased C allocation belowground. Elevated CO₂ had no significant effect on microarthropod and nematode abundance. Elevated O₃ had no significant effects on any parameter except it reduced the sensitivity of soil respiration to changes in temperature.     

La(NO3)3 对盐胁迫下黑麦草幼苗生长及抗逆生理特性的影响

为探讨稀土元素镧(La)对牧草盐胁迫伤害的缓解作用, 采用水培法研究了叶面喷施20 mg·L^-1La(NO₃)₃ 对NaCl 胁迫下黑麦草幼苗生长及其抗逆生理特性的影响。结果表明: 盐胁迫显著抑制黑麦草幼苗的生长, 提高叶片电解质渗漏率及丙二醛(MDA)、O₂^- 和H₂O₂ 含量, 其作用随盐浓度的增大而增强。超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)活性和抗坏血酸(AsA)、谷胱甘肽(GSH)、可溶性蛋白质、脯氨酸含量随盐浓度增大呈先升后降趋势, 可溶性糖和Na⁺/K⁺比逐渐增大, 质膜H⁺-ATP 酶活性逐渐降低, 过氧化物酶(POD)活性及POD 同功酶数量表达增强。喷施La(NO₃)₃ 处理可降低盐胁迫下黑麦草幼苗叶片的O₂^- 和H₂O₂ 含量, 提高SOD、CAT、POD、APX 和质膜H⁺-ATP 酶的活性及POD 同功酶的表达, 使AsA、GSH、可溶性蛋白质、可溶性糖和游离脯氨酸含量及幼苗生物量增加, Na⁺/K⁺比降低。表明La(NO₃)₃ 可通过提高抗氧化系统的活性和积累渗透溶质减轻盐胁迫伤害, 从而提高黑麦草的耐盐性。     

Short-term effects of clearfelling on soil CO2, CH4, and N2O fluxes in a Sitka spruce plantation

We examined the effects of forest clearfelling on the fluxes of soil CO₂, CH₄, and N₂O in a Sitka spruce (Picea sitchensis (Bong.) Carr.) plantation on an organic-rich peaty gley soil, in Northern England. Soil CO₂, CH₄, N₂O as well as environmental factors such as soil temperature, soil water content, and depth to the water table were recorded in two mature stands for one growing season, at the end of which one of the two stands was felled and one was left as control. Monitoring of the same parameters continued thereafter for a second growing season. For the first 10 months after clearfelling, there was a significant decrease in soil CO₂ efflux, with an average efflux rate of 4.0 g m⁻² d⁻¹ in the mature stand (40-year) and 2.7 g m⁻² d⁻¹ in clearfelled site (CF). Clearfelling turned the soil from a sink (−0.37 mg m⁻² d⁻¹) for CH₄ to a net source (2.01 mg m⁻² d⁻¹). For the same period, soil N₂O fluxes averaged 0.57 mg m⁻² d⁻¹ in the CF and 0.23 mg m⁻² d⁻¹ in the 40-year stand. Clearfelling affected environmental factors and lead to higher daily soil temperatures during the summer period, while it caused an increase in the soil water content and a rise in the water table depth. Despite clearfelling, CO₂ remained the dominant greenhouse gas in terms of its greenhouse warming potential.