A Comparative Study of Element Cycling in the Soil-Plant System: A Case Study of Shaly and Calcareous Soils, Southern Benue Trough, Nigeria

This study focused on the cycling of major and trace elements in the soil-plant system in parts of Southern Benue Trough, Nigeria. Surface soil samples and cassava crop samples were collected from cultivated farmlands underlined by shaly and calcareous soils and were analysed using standard techniques. The results show that shaly soils are relatively acidic (pH, 4.8 - 6.6) with high level of organic matter content (OM, 3.2% - 8.7%) compared to calcareous soils (pH, 5.6 - 7.2;OM 1.6% - 7.0%). The soils are enriched in elemental composition relative to the world average abundances in soil. The maximum levels of K, Al, and Zn were obtained from shaly soils. The computed accumulation factors are generally <1. Elemental levels decreased in the plant parts in the order tuber > leaf > stem. Significant correlation was obtained between elemental associations of calcareous surface soils compared to that of shaly soils. R-mode factor analysis revealed the controls of soil geochemistry to include lithology, anthropogenic and environmental factors. A stepwise linear regression analysis identified soil elemental component, pH and organic matter as some of the factors influencing soil-plant metal uptake.

Temporal variation of soil carbon stock and its controlling factors over the last two decades on the southern Song-nen Plain,Heilongjiang Province

Against the current background of global climate change, the study of variations in the soil carbon pool and its controlling factors may aid in the evaluation of soil＇s role in the mitigation or enhancement of greenhouse gas. This paper studies spatial and temporal variation in the soil carbon pool and their controlling factors in the southern Song-nen Plain in Heilongjiang Province, using soil data collected over two distinct periods by the Multi-purpose Regional Geochemical Survey in 2005-2007, and another soil survey conducted in 1982-1990. The study area is a carbon source of 1479 t/km2 and in the past 20 years, from the 1980s until 2005, the practical carbon emission from the soil was 0.12 Gt. Temperature, which has been found to be linearly correlated to soil organic carbon, is the domi- nant climatologic factor controlling soil organic carbon contents. Our study shows that in the relevant area and time period the potential loss of soil organic carbon caused by rising temperatures was 0.10 Gt, the potential soil carbon emission resulting from land-use change was 0.09 Gt, and the combined potential loss of soil carbon （0.19 Gt） caused by warming and land-use change is comparable to that of fossil fuel combustion （0.21 Gt）. Due to the time delay in soil carbon pool variation, there is still 0.07 Gt in the potential emission caused by warming and land-use change that will be gradually released in the future.

Evolution and significance of soil magnetism of basalt-derived chronosequence soils in tropical southern China

Soil samples were collected from eight basalt- derived chronosequence soils with the ages of 0.01, 0.58, 0.92, 1.33, 2.04, 3.04, 3.76 and 6.12 Ma respectively from Leizhou Peninsula and northern Hainan Island of tropical southern China. Magnetic parameters of magnetic susceptibility (MS), percentage of frequency-dependent magnetic susceptibility (FDS%), anhysteretic remanent magnetization (ARM), saturation isothermal remanent magnetization (SIRM), soft and hard isothermal remanent magnetization (IRMs and IRMh) of the collected samples were measured to study the evolution and the significance of the magnetism with soil age. The results show that the magnetic parameters changed fast from Primosols to Ferrosols (0.01 ~ 0.92 Ma) but slowly at Ferralosols stage (1.33 Ma~), it suggests a stable phase occurred for soil magnetism at Ferralosols, the existence of this phase could be supported by the little changes in the contents of clay, Fet and Fed. Obvious differences existed in the values of magnetic parameters between Ferralosols and other soil types (Primosols and Ferrosols), FDS%: Ferralosols > 10%, Primosols and Ferrosols –8· SIm3·kg–1, Primosols and Ferrosols > 8000 × 10–8 SIm3·kg–1, thus, it is possible to differentiate Ferralosols from other soil types in tropical region by using magnetic indices.

Study on soil erosion dynamics in typical regionof southern China based on remote sensing, GISand gray forecast model

This paper StUdies soil erosion dynamics in the typical region of southem China based onremote sensing, GIS tecndques and gray forecast model. The resultS of survey on Xingguo countyshown the soil eroded area and annual soil erosion amount decreased by 19.09% and 43.05%reSPectively from 1958 to 1988. The results of gray forecast model presented that soil eroded areaincreased from 818.04 km2 in 1988 to 1276.69 km2 in 1995. in the meanthne the total soil erosiollamount decreased from 607.21×104 ba in 1988 to 472. 12 ×104 t/a in 1995. By comparing differentlanduse types, the soil loss modulus of the forest was the lowest with 177. 16~187.75t/km2. a, on thecontraly the bare land was the highest with 10626.76~11265.48 t/km2. a. so the high vegetationcoverage can decrease soil and water loss effectively.

Soil carbon storage and stratification under different tillage/residue-management practices in double rice cropping system

The importance of soil organic carbon（SOC） sequestration in agricultural soils as climate-change-mitigating strategy has become an area of focus by the scientific community in relation to soil management.This study was conducted to determine the temporal effect of different tillage systems and residue management on distribution, storage and stratification of SOC, and the yield of rice under double rice（Oryza sativa L.） cropping system in the southern China.A tillage experiment was conducted in the southern China during 2005–2011, including plow tillage with residue removed（PT0）, plow tillage with residue retention（PT）, rotary tillage with residue retention（RT）, and no-till with residue retention on the surface（NT）.The soil samples were obtained at the harvesting of late rice in October of 2005, 2007 and 2011.Multiple-year residue return application significantly increased rice yields for the two rice-cropping systems; yields of early and late rice were higher under RT than those under other tillage systems in both years in 2011.Compared with PT0, SOC stocks were increased in soil under NT at 0–5, 5–10, 10–20, and 20–30 cm depths by 33.8, 4.1, 6.6, and 53.3%, respectively, in 2011.SOC stocks under RT were higher than these under other tillage treatments at 0–30 cm depth.SOC stocks in soil under PT were higher than those under PT0 in the 0–5 and 20–30 cm soil layers.Therefore, crop residues played an important role in SOC management, and improvement of soil quality.In the 0–20 cm layer, the stratification ratio（SR） of SOC followed the order NT〉RT〉PT〉PT0; when the 0–30 cm layer was considered, NT also had the highest SR of SOC, but the SR of SOC under PT was higher than that under RT with a multiple-year tillage practice.Therefore, the notion that conservation tillage lead to higher SOC stocks and soil quality than plowed systems requires cautious scrutiny.Nevertheless, some benefits associated with RT system present a greater potential for its adoption in view of the multiple-year environmental sustainability under double rice cropping system in the southern China.

SENSITIVITY OF MESOSCALE CONVECTIVE SYSTEMS AND ASSOCIATED HEAVY RAINFALL TO SOIL MOISTURE OVER SOUTH CHINA

The impacts of soil moisture(SM) on heavy rainfall and the development of Mesoscale Convection Systems(MCSs) are investigated through 24-h numerical simulations of two heavy rainfall events that occurred respectively on28 March 2009(Case 1) and 6 May 2010(Case 2) over southern China. The numerical simulations were carried out with WRF and its coupled Noah LSM(Land Surface Model). First, comparative experiments were driven by two different SM data sources from NCEP-FNL and NASA-GLDAS. Secondary, with the run driven by NASA-GLDAS data as a control one, a series of sensitivity tests with different degree of(20%, 60%) increase or decrease in the initial SM were performed to examine the impact of SM on the simulations. Comparative experiment results show that the 24-h simulated cumulative rainfall distributions are not substantially affected by the application of the two different SM data,while the precipitation intensity is changed to some extent. Forecast skill scores show that simulation with NASA-GLDAS SM data can lead to some improvement, especially in the heavy rain(芏50 mm) forecast, where there is up to 5% increase in the TS score. Sensitivity test analysis found that a predominantly positive feedback of SM on precipitation existed in these two heavy rain events but not with completely the same features. Organization of the heavy rainfall-producing MCS seems to have an impact on the feedback process between SM and precipitation. For Case 1, the MCS was poorly organized and occurred locally in late afternoon, and the increase of SM only caused a slight enhancement of precipitation. Drier soil was found to result in an apparent decrease of rainfall intensity,indicating that precipitation is more sensitive to SM reduction. For Case 2, as the heavy rain was caused by a well-organized MCS with sustained precipitation, the rainfall is more sensitive to SM increase, which brings more rainfall. Additionally, distinctive feedback effects were identified from different stages and different organization of MCS, with strong feedback between SM and precipitation mainly appearing in the early stages of the poorly organized MCS and during the late period of the well-organized MCS.

Soil nitrogen transformations varied with plant community under Nanchang urban forests in mid-subtropical zone of China

Soil N transformations using the polyvinyl chloride （PVC） closed-top tube in situ incubation method were studied in Nanchang urban forests of the mid-subtropical region of China in different months of 2007. Four plots of 20 m × 20 m were established in four different plant communities that represented typical successional stages of forest development including shrubs, coniferous forest, mixed forest and broad- leaved forest. Average concentrations of soil NH4^＋-N from January to December were not different among the four plant communities. The concentrations of soil NO3^--N and mineral N, and the annual rotes of ammonification, nitrification and net N-mineralization under the early successional shrub community and coniferous forest were generally lower than that of the late successional mixed and broad-leaved forests （p〈0.05）. Similar differences among the plant communities were also shown in the relative nitrification index （NH4^＋-N/NO3^--N） and relative nitrification intensity （nitrification rate/net N-mineralization rate）. The annual net N-mineralization rate was increased from younger to older plant communities, from 15.1 and 41.4 kg.ha^-1.a^-1 under the shrubs and coniferous forest communities to 98.0 and 112.9 kg.ha^-1.a^-1 under the mixed and broad-leaved forests, respectively. Moreover, the high annual nitrification rates （50-70 kg.ha^-1.a^-1） and its end product, NO3-N （2.4-3.8 mg·kg^-1）, under older plant communities could increase the potential risk of N loss. Additionally, the temporal patterns of the different soil N variables mentioned above varied with different plant community due to the combined affects of natural biological processes associated with forest maturation and urbanization. Our results indicated that urban forests are moving towards a state of＂N saturation＂ （extremely niUification rate and NO3^--N content） as they mature.

宁南山区不同植被类型土壤水分变化特征

以宁夏南部山区山杏林、沙棘林、山杏×沙棘混交林3种典型植被为试材,采用野外定位监测法,对3种植被0~100 cm不同深度土壤水分进行连续1年定位观测,研究了不同植被类型土壤水分时间变化和垂直变化规律,以期了解宁南山区主要植被类型的土壤水分状况及耗水特性。结果表明:不同植被类型土壤储水量在年内变化趋势整体呈“M”型,土壤储水量按照从大到小的排序为山杏林(158.35 mm)>山杏×沙棘混交林(139.72 mm)>沙棘林(123.24 mm)。不同植被类型日平均土壤含水量的变化动态相似,其变化趋势与降雨量密切相关,9月山杏林、沙棘林、山杏×沙棘混交林地的土壤含水量分别是8月的1.56、1.41、1.49倍;3种植被类型平均土壤含水量最大值均在10月,最小值均在8月。在垂直方向上,3种植被土壤水分的变化有一定的差异性,随着土层深度的增加,沙棘林土壤含水量呈先增加后降低的趋势,山杏林、山杏×沙棘混交林土壤含水量呈波形变化趋势;3种植被类型土壤水分的变异系数总体呈下降趋势,沙棘林各土层变异系数的均值最大,为39.36%。综上,山杏林土壤水分状况最好,其次是山杏×沙棘林,为该区域植被恢复与可持续管理提供重要参考依据。

南方土壤中导致大豆皱叶的因子分析

为找出南方大豆皱叶症发生的诱因,本研究从南方土壤中非生物因素和生物因素两个角度进行探索研究。利用混池法和ICP-OES技术研究正常叶混池和皱叶混池的差异元素,利用构建的皱叶残留异质系中皱叶家系材料GY_C和正常叶家系材料GY_N,采用单因素随机区组试验设计,研究皱叶土壤的不同土层、营养液、灰烬、叶浆,进行土壤浸泡液、土壤消毒、氮肥等处理后大豆皱叶材料皱叶症的变化。结果表明:皱叶环境土壤的表层、中层和底层土均可导致GY_C叶片皱缩,中层土中的GY_C叶片皱缩程度略高于表层和底层土。氮磷钾配比失衡的营养液处理GY_C叶片未发生皱缩。ICP-OES分析皱叶混池E 1和正常叶混池E 0的31种元素后,未发现E 1/E 0比值为1.7倍以上的元素,且E 1中锰元素含量低于E 0。皱叶灰烬及土壤浸泡液处理基质后GY_C叶片未发生皱缩。移栽试验表明,南方土壤和基质比例超过3∶1时GY_C长出的新叶依然皱缩,而复种的盆栽中南方土壤和基质比例低于1∶8时GY_C叶片也会发生皱缩,且随着复种次数增加,皱叶程度有所增加。解剖观察皱叶材料的根、茎、叶柄未发现明显的虫害痕迹。-80,60,80,100和120℃处理的南方土壤中GY_C叶片不发生皱缩。综上所述,南方土壤中的微生物因素可能是导致大豆皱叶的关键因子。

南方崩岗调查内容与方法探讨

崩岗是我国南方水土流失的一种特殊类型,广泛分布于南方红壤区,是该区域严重的生态问题之一。第一次崩岗调查距今已近20年,相关情况已发生巨大变化。崩岗现状不清直接影响了行政管理部门对崩岗防治相关工作的规划和决策,因此急需开展新一轮崩岗调查。新时代水土保持高质量发展为崩岗调查提供了机遇,差别化分类防治和分步实施对崩岗调查提出了更高要求,现代信息技术为崩岗调查提供了新方法,以服务崩岗风险评估和防治规划为导向,在充分利用第一次崩岗调查成果基础上,补充崩岗发育的小山体调查,将典型调查改为全面普查,系统探讨崩岗调查对象与范围、调查内容、调查程序与方法,以期为行政管理部门和技术单位启动新一轮崩岗调查工作提供参考。

2010–2020年塔里木盆地南部荒漠草地凋落物回收量月动态数据集

中国科学院新疆策勒荒漠草地生态系统国家野外科学观测研究站(以下简称“策勒站”)地处塔里木盆地南缘,南依昆仑山,北临我国最大的塔克拉玛干沙漠。具有植被群落简单,土壤有机质积累缓慢等特点。凋落物是该区域重要的养分来源。基于对策勒站荒漠植物群落的长期定位观测,通过对不同植物凋落物器官(枝、叶、果)分组,本文整理统计得到2010–2020年塔里木盆地南部荒漠草地凋落物的回收量月动态数据,同时记载了观测场群落以及土壤养分的年度变化情况。数据的产生严格遵照CERN生物观测规范执行,数据的审核及质量控制由台站与分中心质控人员共同完成。本数据集以期为深入研究塔里木盆地南部荒漠草地凋落物动态变化提供基础数据,为了解和评估极端干旱荒漠生态系统养分循环过程提供理论支撑。

南方红壤区典型母质发育土壤硒素特征及影响因素

为探究南方红壤区不同母质土壤硒素特征及理化性质对硒有效性的影响,以广西典型红壤区不同母质土壤为研究对象,通过测定硒形态特征及理化性质,并利用AMOS路径分析模型及土壤培养试验,量化了不同因子对不同母质土壤有效硒的影响。结果表明:南方红壤区不同母质土壤总硒含量均高于0.4 mg/kg,其中以花岗岩母质土壤总硒含量最高,以砂页岩母质土壤有效硒含量最高,且变幅最大。土壤硒形态主要以残渣态和有机结合态为主,不同形态硒含量由高到低均表现为:残渣态硒>有机结合态硒>铁锰氧化物结合态硒>交换态硒>可溶态硒。AMOS路径分析模型结果表明,影响不同母质土壤硒形态分配贡献的主要因素是全磷、有机质和pH,第四纪红色黏土母质土壤中的全氮及砂页岩母质土壤中的速效氮的影响也值得关注。利用贡献较大的理化因子开展土壤培养试验,外源理化因子添加后均在一定的时间及剂量条件下出现土壤有效硒含量最大值,且不同母质土壤获得的最佳因子条件不同。因此,不同土壤母质因土壤理化性质的不同,其硒形态特征存在较大差异,不同理化因子作用于土壤后,土壤硒会因土壤环境的变化而重新分配。

宁南黄土区不同人工植被类型深层土壤水分亏缺评价

【目的】开展评估不同人工植被类型深层土壤水分亏缺程度,能为区域科学合理实施植被恢复策略提供理论依据。【方法】以宁夏彭阳中庄小流域5种不同植被类型(山桃林、沙棘林、柠条林、苜蓿地,农田为对照)为研究对象,采用土壤水分相对亏缺指数(CSWDI)和干燥化指数(SDI)定量评价模型,对不同植被类型下0~1 000 cm土壤水分亏缺及干燥化程度进行定量化分析与评价。【结果】不同植被类型深层土壤水分变化特征差异明显,0~1 000 cm平均土壤水分含量呈现出农地(16.29%)>山桃林(13.06%)>沙棘林(12.22%)>柠条林(9.12%)>苜蓿地(8.08%)。在垂直剖面上,土壤水分随土层深度增加总体呈现先减小后增加再逐渐稳定的趋势。在0~1 000 cm农地基本没有水分亏缺和干层发生,山桃林、柠条林、沙棘林和苜蓿地均呈现不同程度的土壤水分亏缺现象,平均土壤水分相对亏缺指数分别为0、0.22、0.62、0.35、0.79,平均土壤干燥化指数分别为185.5%、67.45%、51.55%、87.35%、36.10%,5种植被类型中苜蓿地土壤水分亏缺最严重,其次为柠条林、沙棘林、山桃林、农地。山桃林、柠条林、沙棘林、苜蓿地均有不同程度的干层分布,分别呈现中度、轻度和严重干燥化,干层厚度(DSLT)分别为890、860、800、920 cm,DSL-SWC分别为12.42%、8.14%、11.56%、7.76%。【结论】宁南黄土区不同人工植被类型对深层土壤水分亏缺具有明显影响,导致不同程度土壤干层发生,其中苜蓿地土壤水分亏缺最严重,应采取相应措施恢复土壤水分,促进区域水土资源可持续利用和生态健康发展。

长期施肥模式对陕南核桃园土壤水分动态的影响

为了探究不同施肥模式下不同土层水分动态的差异,共设置3种不同施肥模式:不施肥(CK)、单施化肥(T1)及化肥配施有机肥和生物有机肥(T2),对陕南山阳县长期定位施肥的核桃林地不同土层(0~20,20~40,40~60,60~80 cm)进行为期1 a的动态监测。结果表明,研究区0~80 cm各土层含水量随着降雨量的季节性变化呈现出明显的波动,化肥配施有机肥和生物有机肥对降雨的响应度最高;核桃树生长关键期20~60 cm土层土壤含水量T2>CK>T1,说明化肥配施有机肥和生物有机肥可缓解生育期内水分供需矛盾;不同施肥处理下核桃园均存在季节性水分亏缺状况,表现为较一致的季节性,化肥配施有机肥和生物有机肥处理下0~80 cm土层土壤储水量最高,有效缓解土壤的水分亏缺状况。3种不同施肥模式中,化肥配施有机肥和生物有机肥能提高土壤对雨水的保蓄和利用能力,对土壤水分条件改善效果最好,建议在核桃水分管理中推广应用。

南疆铁门关土壤白云石与氟元素的耦合关系

南疆环塔里木盆地的绿洲土壤发育了大量的碳酸盐矿物,同时该地区土壤和地下水的氟(F)元素含量较高,存在较大的F污染风险。探讨两者的耦合关系,对开展干旱区土壤无机碳汇的综合利用、提高区域F污染的防治水平有重要意义。文章选择新疆铁门关市15个典型表层土壤,通过XRD、扫描电镜等分析手段对土壤样品进行测试,同时分析常量、微量元素和碳酸盐Sr同位素组成,并结合室内选择性溶解实验方法,对该地区土壤矿物学与地球化学特征进行了系统研究,获得了F与碳酸盐矿物耦合变化机制的地质证据。研究发现,铁门关地区土壤中矿物组成较为复杂,其主要元素含量接近于上部大陆地壳,化学风化指数CIA值在50~60之间,风化程度较弱。土壤中含较高的方解石和白云石等碳酸盐矿物(平均含量为20.1%),碳酸盐平均Sr,Mn含量分别为1434×10^(-6)和1736×10^(-6),^(87)Sr/^(86)Sr比值为0.710左右。土壤中F与碳酸盐矿物有关的元素高度正相关,并且与白云石呈现很好的耦合变化。推测土壤中的F异常主要来自源区的氟镁石,在地质、气候等综合因素下共同迁移变化。

间伐对秦岭松栎混交林土壤异养呼吸的影响

【目的】研究间伐对秦岭松栎混交林土壤异养呼吸的影响,可深入了解该地区间伐对森林土壤异养呼吸造成的碳损失情况,为研究区森林经营碳汇提供科学依据。【方法】以秦岭松栎混交林为研究对象,对未间伐样地(ck)、间伐4 a、间伐12 a的样地采用静态箱-气相色谱法监测生长季土壤异养呼吸速率的月变化,并计算各处理异养呼吸的温度敏感性(Q_(10))。【结果】①相比ck,间伐4 a、间伐12 a的样地土壤微生物生物量碳均显著下降(P<0.05),土壤pH均显著上升(P<0.05),土壤总有机碳质量分数在间伐4 a的样地中显著下降(P<0.05)。间伐12 a样地的理化指标相比间伐4 a的样地更接近ck。②生长季土壤异养呼吸呈现“双峰型”变化规律,峰值分别出现在6和10月。异养呼吸累计通量在间伐后略有上升但不显著,不同样地从大到小依次为间伐12 a、间伐4 a、ck。③土壤温度与异养呼吸呈极显著指数正相关(P<0.001);间伐后Q_(10)降低,不同样地Q_(10)从大到小依次为ck、间伐12 a、间伐4 a。【结论】土壤温度是影响松栎混交林异养呼吸的关键因素。间伐没有导致秦岭松栎混交林异养呼吸通量显著增大。

南疆沙区不同林龄四翅滨藜人工林植物多样性与土壤理化性质

为明确南疆沙区四翅滨藜人工林植物多样性与土壤理化性质的关系,为该区植被建设与恢复提供科学依据。以南疆沙区沙漠前沿种植的四翅滨藜为对象,研究不同林龄(1、2、4龄)四翅滨藜灌木林的植物多样性、土壤理化性质变化,分析各多样性指数与土壤理化性质的相关关系,并采用主成分分析方法对林分状况进行评价。结果表明,1)四翅滨藜人工林共出现植物6科13种,且各林龄的Margalef指数、Simpson指数、Shannon-Wiener指数和Pielou指数表现为2年生地>4年生地>1年生地>裸地。2)种植四翅滨藜能够提高土壤SMC、TN、TP、AN和AP含量,降低土壤Sa、pH、TK及AK含量。并且随林龄的增加,土壤SMC、TP和AP含量“先升后降”;TK含量“先降后升”;SOM、TN、AN和AK含量“逐渐上升”;土壤Sa含量、pH“逐渐下降”。3)土壤SMC、TP、TN含量与群落Shannon-Wiener指数、Simpson指数和Margalef指数呈显著或极显著正相关,但与pielou指数无显著性相关关系。灌木层与草本层中,多样性指数主要受土壤TP、TK含量影响。4)主成分分析表明多样性指数、SMC、TP、TK和SOM对林分贡献率较大,各林龄综合得分依次为4年生>2年生>1年生>裸地。种植四翅滨藜能够提高植物多样性指数,改善土壤理化性质。

南方典型红壤区不同枯死率芒萁的水土流失阻控效应

[目的]探究芒萁植丛不同枯死率(100%,50%和0%)下坡面的产流产沙规律,揭示不同生长状态下芒萁的水土流失阻控效果。[方法]采用人工模拟降雨试验,对不同芒萁枯死率下坡面产流产沙过程随雨强的变化特性进行了定量分析。[结果](1)不同降雨强度和芒萁枯死率下径流速率随降雨历时呈前期缓慢或快速增长,后期趋于稳定。较小雨强下,侵蚀速率除裸坡外随降雨历时呈前期缓慢增加、后期趋于稳定状态;较大雨强下,侵蚀速率随降雨历时变化呈前期快速增加,中后期逐渐下降趋于稳定。(2)除2 mm/min雨强下的累积产流量外,其余处理条件下累积产流产沙量差异明显,且产沙量随芒萁枯死率的增加而增加。(3)两种雨强不同处理下坡面累积产流量和累积产沙量关系符合幂函数模型(R2>0.99)。[结论]两种雨强芒萁植丛不同枯死率下径流速率和侵蚀速率随降雨历时变化前期迅速增加、后期逐渐波动稳定,各处理下累积径流量与累积产沙量的函数关系拟合回归效果良好,证实了枯死芒萁亦可在中国南方红壤侵蚀区起到良好的水土流失阻控效果。

南方主要河流水沙变化及人类活动的影响

为了解我国南方河流的水沙变化及主要成因,利用Mann-Kendall检验法和水文量累积曲线法,分析了南方主要河流代表站径流量和输沙量的变化特征,探讨了影响南方河流水沙变化的主要因素。结果表明,长江、珠江、钱塘江和闽江等南方河流代表站年径流量都没有显著的变化态势;除钱塘江代表站外年输沙量都有显著减少趋势;钱塘江2016—2020年为平水平沙期,2011—2020年为平水多沙期,其他河流2016—2020年和2011—2020年均为平水少沙期;影响南方河流水沙变化的人类活动包括水库拦沙、水土保持措施、河道采砂、流域过度建设等,其中水库拦沙是南方河流减沙的主要措施,水土保持措施在南方河流减沙过程中发挥了重要作用,河道采砂对河道减沙也发挥了一定的作用。

皖南山区不同类型森林土壤阳离子交换性能差异

为了解皖南山区不同类型森林土壤阳离子交换性能差异,为该区合理营林提供参考,选取皖南山区6种不同类型森林土壤(杉木林、马尾松林、栓皮栎林、外松林、天然阔叶林和杉木-栓皮栎混交林)为研究对象,比较森林土壤阳离子交换性能的差异。结果表明:(1)研究区土壤呈强酸性,土壤有机质含量为33.84~91.50 g·kg^(-1),总氮含量为0.94~3.37 g·kg^(-1),碱解氮含量为131.58~203.62 mg·kg^(-1),总磷含量为0.22~0.77 g·kg^(-1),有效磷含量为0.17~0.32 mg·kg^(-1);土壤主要缺乏速效磷养分。(2)阳离子交换量在8.09~12.57 cmol·kg^(-1)之间,排序为:天然阔叶林>外松林>马尾松林>混交林>杉木林>栓皮栎林,不同森林土壤间阳离子交换量的差异主要由其土壤有机质的差异引起。(3)交换性盐基总量在1.74~2.72 cmol·kg^(-1)g之间,排序为:马尾松林>外松林>杉木林>栓皮栎林>混交林>天然阔叶林,Ca^(2+)和Mg^(2+)是主要的盐基离子,是成土过程中Ca、Mg优先固持形成的。(4)盐基饱和度在13.97%~28.98%之间,排序为:马尾松林>杉木林>栓皮栎林>外松林>混交林>天然阔叶林,该差异是由淋溶作用和树木对盐基离子的吸收共同作用形成的差异。综上,研究区土壤保肥和缓冲性能较低且供肥能力较差,尤其是土壤速效磷供应能力差。其中松林的供肥保肥能力及缓冲性能明显优于其他树种森林,混交林的速效养分含量更高,故可通过营造松类混交林以及施肥来提高森林土壤供肥保肥能力和缓冲性能。