祁连山青海云杉(Picea crassifolia)林土壤有机碳与化学性质的相互关系

通过对祁连山大野口流域的青海云杉林大样地进行土壤剖面取样, 分析了样地土壤有机碳与pH值、养分和阳离子交换量等基本化学性质的变化规律及其相互关系. 结果表明: 随土层深度不断增加, 土壤有机碳含量逐渐减小, 在20～30 cm以下趋于稳定(P > 0.05); 土壤pH值不断增大, 仅在0～10 cm与10～20 cm差异显著(P<0.05); 土壤全氮、速效氮、全磷和阳离子交换量不断减小, 全氮含量在30～40 cm以下趋于稳定(P > 0.05), 速效氮含量变化剧烈(P<0.05), 全磷含量差异性不显著(P > 0.05), 阳离子交换量与有机碳含量变化规律相同; 土壤速效磷、全钾和速效钾含量没有明显的变化规律, 速效磷和全钾含量差异性不显著(P > 0.05), 速效钾含量仅在0～10 cm与10～20 cm差异显著(P<0.05). 土壤有机碳与全氮、速效氮、全磷、速效磷、速效钾和阳离子交换量之间呈极显著和显著正相关, 与土壤pH值和全钾含量之间呈极显著和显著负相关. 土壤有机碳与其他基本化学性质的回归方程具有较高精度(R²=0.793), 影响土壤有机碳含量的主要化学因子依次为土壤阳离子交换量、速效钾和全磷含量.     

我国不同区域农田养分平衡对土壤肥力时空演变的影响

区域农田养分盈亏是驱动农田土壤肥力时空变化的主要因素。对我国6个农业生态试验站（海伦、沈阳、 栾城、长武、常熟、鹰潭）站区农田土壤肥力在近年来时空演变的研究表明,除了海伦站黑土和常熟站水稻土的有机质和全氮平均含量下降外,其他站区均呈现增加趋势,主要原因是黑土和乌栅土有机质和全氮含量较高,目前农田有机C和N投入水平无法维持其平衡;6个站区土壤速效磷有增有减,而土壤速效钾除了栾城和鹰潭站区域外均呈降低趋势。从站区农田养分的年平衡与土壤养分的年变化量关系看,农田氮、磷、钾的盈亏量决定了土壤养分的变化方向。土壤有机碳和全氮的初始含量过高（分别超过15.1 g/kg和1.60 g/kg）时,也会导致其年际间的变化方向从增加变为降低。农田氮素盈亏量与土壤全氮变化量之间相关不显著,主要是由于化肥投入和作物籽粒输出的农田氮平衡不能完全代表土壤氮素的真实盈亏情况;而农田磷素和钾素的盈亏量与土壤速效磷和速效钾的年变化量的显著相关。     

Variations in soil characteristics among urban green spaces in Kumasi,Ghana

Urban soils, although crucial to defining urban vegetation types and strengthening the resilience of urban ecosystems, can be severely modified by human activities. Yet understanding of these modifications and their implications for soil properties is limited. This study examined the vertical and spatial variability of selected soil physicochemical properties (pH, SOM, OC, TN, and bulk density) in Kumasi, Ghana, using a stratified random sampling technique. Soil samples were collected at three depths (0–15, 15–30, and 30–60 cm) from 161 plots in eight green space types within two urban zones. Mean topsoil pH ranged between 5.0 in the natural forest and 6.5 in home gardens. Mean bulk density, nitrogen, and carbon concentrations differed among green space types and depths (p?<?0.0001). Soil nitrogen and carbon concentrations in the 0–15 cm depth were two times greater than those of the 30–60 cm depth. Soil pH and organic matter concentrations were higher in the core urban soils than in the peri-urban while the reverse was true for total soil N and bulk density. Canonical discriminant analysis showed considerable separation of green space types based on the soil physicochemical properties. Higher total nitrogen and C:N ratios separated natural forest and cemetery from the other UGS types, whereas higher pH and bulk densities separated plantations and home gardens from the rest of the UGS types. Furthermore, the subsoil layers were laden with undecomposed cloths, plastics, concrete, and metal parts which can obstruct root growth and water movement. Results generally demonstrate considerable variability in soil properties among urban green spaces and highlight the need for a better understanding of these patterns to ensure continued support for plant growth, green space sustenance and maintenance, and the ecosystem services derived from them.     

河套平原盐渍化地区非饱和带氮的分布特征及影响因素

土壤氮在植物生长、土壤理化性质和微生物活动中扮演着重要的角色.为了识别盐渍化地区非饱和带氮的迁移过程,以河套灌区典型盐渍化耕地为例,通过非饱和带监测和水化学统计分析,探究了土壤剖面中氮素分布的差异性及主要影响因素.结果表明,研究区0～100 cm土层深度土壤氮含量处于较低水平,NO3-N、NH4-N和NO2-N含量平均...     

黑龙江海伦地区垦殖前后典型黑土剖面主要养分元素垂直分布特征

垦殖前后典型黑土主要养分元素特征研究对东北黑土资源的可持续利用和保护东北大粮仓具有重要作用.在松嫩平原东部海伦地区对比研究了典型黑土区40年间土地利用未发生改变的地区（本次对比研究林地和耕地）,布设了4条典型黑土剖面,对垦殖前后典型黑土剖面中土壤肥力的主要指标元素（有机质、全氮、全磷、C：N及pH值）分别对比分析.结果表明：有机质、全氮、全磷含量表现为随土壤深度急剧下降—缓慢下降—基本稳定的变化趋势;垦殖虽然改变了各土层土壤中养分元素的含量,但是并未改变其随土壤深度的变化规律;垦殖在一定程度上影响了表层黑土土壤的pH值,导致耕地表层黑土土壤慢慢酸化.研究结果可为黑土资源的可持续利用、保护及修复提供科学依据.     

Soil organic carbon fractions and microbial community and functions under changes in vegetation: a case of vegetation succession in karst forest

The vegetation community succession influences soil nutrient cycling, and this process is mediated by soil microorganisms in the forest ecosystem. A degraded succession series of karst forests were chosen in which vegetation community changed from deciduous broadleaved trees (FO) toward shrubs (SH), and shrubs–grasses (SHG) in the southwest China. Soil organic carbon (SOC), total nitrogen (TN), labile organic carbon (LOC), water extractable organic matter (WEOM), microbial biomass carbon and nitrogen (MBC and MBN), bacterial and fungal diversity, as well as soil enzyme activities were tested. The results showed that SOC, LOC, MBC, MBN, and enzyme activities declined with vegetation succession, with the relatively stronger decrease of microbial biomass and functions, whereas WEOM was higher in SHG than in other systems. In addition, soil bacterial and fungal composition in FO was different from both SH and SHG. Despite positive relationship with SOC, LOC, and TN (p < 0.01), MBC, MBN appeared to be more significantly correlated to LOC than to SOC. It suggested that vegetation conversion resulted in significant changes in carbon fractions and bioavailability, furthermore, caused the change in soil microbial community and function in the forest ecosystem.     

Spatial variability of soil nutrients in disturbed riverine mangrove forests at different stages of regeneration in the San Juan River estuary,Venezuela

Geostatistical analysis of selected soil properties were performed in two mangrove sites (B7 and B9) dominated by the mangrove speciesRhizophora mangle along the San Juan River, Venezuela, to evaluate the effect of forest disturbance on nutrient spatial distributions. Plots within area B7 were clear-cut in 1972–1973 and in area B9 in 1982–1983. Four plots within each area were systematically selected and represented natural (2) and regenerated (2) forests. Individual plots were 1.5 ha in B7 and 1.25 ha in B9 and sampled at a resolution of 25 m. Soil samples were obtained at the intersection of an aligned grid with 90 points in B7 and 78 points in B9. Measured soil properties included salinity, total nitrogen, total carbon, total phosphorus, osmolality, and pore water cation concentrations (potassium, calcium, magnesium, and sodium). Sites were sampled in May 1996 and 1997, although spatial analysis was performed only for the data obtained in May 1997. Geostatistical analysis showed that most of the variables tested were spatially auto-correlated within each area and that there were no differences between regenerated and natural plots. Structural variance as a proportion of sample variance ranged from 55–99% for most of the properties. The significant spatial dependence observed for most of the variables in natural and regenerated plots, despite management schedules, indicates that clear-cutting did not have an effect on modifying the distribution of nutrient concentrations. These results suggest that after 15 and 25 yr following forest disturbance nutrient distributions were reestablished either there was not a net effect on patterns of element loss or tidal input was stronger than plant modifications of soils.     

Potential nitrogen fixation changes under different land uses as influenced by seasons and biochar amendments

Soil nutrient dynamics, potential biological nitrogen fixation (BNF) changes, and their relations were studied using four land use types. Further, we investigated BNF changes in the presence of biochar in soils. Soil samples were collected from arable, vineyard, grassland, and forest soils during four seasons, and analyzed for abiotic contents of total nitrogen, NH₄⁺-N, NO₃^?-N, ammonium lactate (AL)-soluble K₂O, P₂O₅, and soil organic carbon (SOC) concentrations. Potential N₂ fixation was measured as ethylene (C₂H₄) production from acetylene (C₂H₂) reduction (ARA). The study focused on the changes in ARA when different types of biochars (T600, T650, and T700) were applied to soil samples in different amounts (0, 0.5, 2.5, and 5.0% wt wt^?1) under laboratory conditions. We found strong correlations between soil chemical parameters and ARA values, especially in the case of soil pH, total N, SOC, and P₂O₅ contents. In the case of arable soil, the ARA measurements were up to 227 times higher compared to grassland and forest samples. Biochar application affected N₂-fixing microbial responses among land use types, most notably decreases in arable lands and forest soils. We found that a high amount of biochar added to the soils can greatly suppress N₂-fixing activities. Our results highlight the strong relationship between soil nutrient changes and the intensity of anthropogenic influence.     

半干旱岩溶区土壤次生碳酸盐比例及对岩溶碳汇计算的影响

定量评价半干旱岩溶区土壤次生碳酸盐比例和来源有助于认识土壤系统影响岩溶作用的机理。选取山西晋中盆地西南,吕梁山东侧的半干旱岩溶区马跑神泉小流域为研究对象,通过对林地、退耕地、灌丛地土壤剖面进行分层取样并测定碳酸盐含量及其δ13C、CO2浓度及其δ13C值,分析其随深度的变化规律和控制因素;并结合研究区碳酸盐岩的δ13C值计算3个剖面各层土壤次生碳酸盐所占比例。研究结果表明:3个土壤剖面的碳酸盐含量、CO2浓度在0~50 cm土层随深度增加而增加,在50~70 cm土层随深度增加而减少;土壤碳酸盐δ13C值、δ13CCO2值在0~50 cm土层随深度增加而偏负,在50~70 cm土层随深度增加而偏重;土壤碳酸盐含量及其δ13C值主要受次生碳酸盐比例控制,而土壤CO2及其δ13CCO2值在上层主要受大气CO2和土壤有机质分解生成的CO2共同影响,下层还受土-岩界面岩溶作用过程制约;退耕地、林地、灌丛剖面次生碳酸盐所占比例的均值分别为52%、42%和32%,证实北方半干旱岩溶区土壤中存在原生碳酸盐向次生碳酸盐转化过程。      

Soil characteristics and nutrient status in a Northern Australian mangrove forest

The results of a study of soil factors in relation to plant growth for a tropical mangrove forest in northern Australia are presented and discussed. Basic soil properties are described briefly in terms of particle size distribution, bulk density and total carbon, nitrogen and phosphorus. Soil redox potential, pH, salinity and extractable nitrogen and phosphorus were monitored monthly over a 14 month period commencing April 1979. Sampling was carried out at 9 sites along a 370 m transect which exhibits strong gradients in topography, above ground biomass, canopy height and species distribution. Statistical analysis of the data shows that above ground biomass correlates significantly with the following soil factors, averaged over depth within the rooting zone and over time: Extractable P (r=0.85, p<0.01), redox potential (r=0.89, p<0.01) and salinity (r=?0.79, p<0.05). The strong biomass-E_H correlation may be partly due to oxygen translocation by the plants to the root zone. Soil ammonium levels were within the range of 1–14 μg N per g (dry wt) and, unlike the above parameters, showed only minor variation with position along the transect. Variation of ammonium levels with time was apparent, but no significant correlation with rate of new shoot growth could be demonstrated, although depth profiles indicated depletion of ammonium by plant uptake during rapid growth periods. In addition neither soil ammonium, extractable phosphorus nor rate of plant growth showed any definite seasonal periodicity in this tropical system.     

贵阳市花溪区耕地土壤养分状况与评价

辐射诱变育种经过几十年的研究,在方法技术、诱变手段、突变体筛选等方面取得较大进步,已成为种质资源创新、挖掘新基因和培育新品种的一个重要途径。本文简要介绍了植物辐射诱变育种技术的发展情况,总结了辐射诱变育种中诱变剂量、突变体类型及主要的突变体选择方法,并对比了各种突变体选择方法的优缺点,以期为提高植物诱变育种的效率提供参考。     

桂林典型岩溶区和非岩溶区土壤剖面钙镁形态迁移对比

文章以桂林典型岩溶区和非岩溶区土壤剖面为研究对象,采用改进的Tessier元素形态连续提取法,测定岩溶区和非岩溶区土壤钙（Ca）和镁（Mg）元素离子交换态（包括水溶态）、碳酸盐结合态、腐殖酸结合态、铁锰氧化物结合态、强有机质结合态（包括部分硫化物）和残渣态等形态,探讨岩溶区和非岩溶区土壤Ca、Mg形态在土壤剖面中的迁移变化特征。结果表明:（1）岩溶区石灰土剖面中,随剖面深度加深,pH值增大,而土壤有机质、全氮（N）、全磷（P）含量减少,Ca元素主要以交换态存在且在各土壤剖面中含量相近,Mg元素主要是以残渣态赋存在土壤剖面中,随着土壤剖面深度腐殖酸结合态百分比减少,存在累积现象;（2）在非岩溶地区酸性土壤中,土壤总钙较低。在土壤剖面0~60 cm以强有机结合态为主,深层剖面（大于60 cm）以残渣态为主;Mg元素有效态含量较低,非岩溶区土壤Mg元素以腐殖酸结合态和残渣态为主,与岩溶区土壤类似,非岩溶区Mg元素在土壤中也存在一定累积。      

青藏高原多年冻土区两种高寒草地生态系统土壤氮季节变化及其与环境因子的关系

在气候变化背景下,青藏高原多年冻土区生态环境发生着一系列变化并进一步影响土壤氮循环过程,但目前冻融循环及植被生长周期中土壤氮的动态变化还不清楚。以青藏高原腹地的风火山和特大桥地区的两种典型草地生态系统为研究对象,分析了土壤可利用氮（NH₄⁺-N、NO₃^--N、DON）及微生物量氮（MBN）的季节变化。结果表明：土壤铵态氮（NH₄⁺-N）及可溶性有机氮（DON）含量在非生长季高于生长季,土壤硝态氮（NO₃^--N）在生长季高于非生长季;风火山地区高寒草甸生态系统中土壤NH₄⁺-N在融化期含量较高;土壤MBN在植被生长旺盛期降低,在植被生长后期升高;风火山地区高寒草甸生态系统中土壤MBN含量、特大桥地区高寒草原生态系统中土壤可利用氮总量与土壤全氮（TN）含量显著正相关。这表明,土壤全氮含量、植被吸收以及冻融作用均可引起土壤可利用氮及MBN的季节变化。     

基于高光谱的土壤养分含量反演模型研究

为实现土壤养分（有机质SOM、全氮TN、全磷TP、全硫TS）含量的快速测定,以建三江创业农场为例,对土壤原始反射率进行了一阶微分（FD）、倒数对数（RL）、倒数一阶微分（FDR）、多元散射校正（MSC）和连续统去除（CR）变换,分析6种光谱变量与土壤养分的相关性,将在α=0.01水平上显著相关的波段作为特征波段,运用多元逐步回归（SMLR）、偏最小二乘回归（PLSR）和BP神经网络（BPNN）三种分析方法分别建立有机质、全氮、全磷和全硫的高光谱预测模型,并利用决定系数（R²）、均方根误差（RMSE）和相对分析误差（RPD）对预测模型进行评价.结果显示,PLSR和BPNN建立的土壤养分含量预测模型均优于SMLR,能极好地预测有机质和全氮含量,同时具有粗略估算全硫含量的能力.三种方法中仅有CR-BPNN能对全磷含量进行粗略估算.对有机质、全氮、全磷和全硫预测效果最佳的模型及其验证集决定系数分别为：MSC-PLSR （0.86）、MSC-PLSR （0.75）、CR-BPNN （0.56）、FDR-BPNN （0.67）.     

滨海湿地不同密度柽柳林土壤调蓄水功能

为探求黄河三角洲湿地土壤调蓄水功能的合理柽柳林密度,采用测量土壤入渗过程和水分物理参数相结合的方法,对不同密度柽柳林的土壤蓄水功能和水分调节能力进行研究。结果表明:①柽柳林随密度的增大具有显著提高细砂粒和降低粉黏粒含量的作用;中密度林分降盐抑碱效应明显,各密度林分表层盐碱含量低于20~40 cm土层;②土壤容重随林分密度增大表现为先减小后增大,孔隙度状况则与之相反,中密度、高密度、草地总孔隙度均值分别比低密度林分高12.9%、6.2%、4.4%;对表层的改良效果好于20~40 cm土层;③Horton模型可较好地模拟柽柳林的土壤入渗过程,中密度林分渗透性能最好,高密度次之,低密度最差;④饱和蓄水量、吸持蓄水量、滞留蓄水量及涵蓄降水量均表现为中密度>高密度>草地>低密度,表土层的水分调蓄功能好于下层;中密度、高密度、草地涵蓄降水量分别比低密度林分高28.4%、23.8%、14.1%。中密度柽柳林具有巨大的水分调蓄空间,其次为高密度,而低密度林分较差。     

Spatial variability of reconstructed soil properties and the optimization of sampling number for reclaimed land monitoring in an opencast coal mine

Drastically disturbed soils caused by opencast mining can result in the severe loss of soil structure and increase in soil compactness. To assess the effects of mining activities on reconstructed soils and to track the changes in reclaimed soil properties, the variability of soil properties (soil particle distribution, penetration resistance (PR), pH, and total dissolved salt (TDS)) in the Shanxi Pingshuo Antaibao opencast coal-mine inner dump after dumping and before reclamation was analyzed using a geostatistics method, and the number of soil monitoring points after mined land reclamation was determined. Soil samples were equally collected at 78 sampling sites in the study area with an area of 0.44 km². Soil particle distribution had moderate variability, except for silt content at the depth of 0–20 cm with a low variability and sand content at the depth of 20–40 cm with a high variability. The pH showed a low variability, and TDS had moderate variability at all depths. The variability of PR was high at the depth of 0–20 cm and moderate at the depth of 20–40 cm. There was no clear trend in the variance with increasing depth for the soil properties. Interpolation using kriging displayed a high heterogeneity of the reconstructed soil properties, and the spatial structure of the original landform was partially or completely destroyed. The root-mean-square error (RMSE) can be used to determine the number of sampling points for soil properties, and 40 is the ideal sampling number for the study site based on cross-validation.     

岩溶区农业种植对土壤有机氮矿化的影响

土壤有机氮矿化是供应无机氮的主导过程，研究其变化对于认识土壤氮素有效性和指导氮肥施用具有重要意义。本研究分别在云南建水、蒙自和勐腊岩溶区选取脐橙地、玉米地和橡胶地作为研究对象，并以临近未受人为扰动的草地或原始林地作为对照，采用15N同位素标记方法，研究了岩溶区草地或原始林地开垦种植农作物后石灰土有机氮矿化(MNorg)速率变化，并区分了易分解有机氮矿化(MNlab)和难分解有机氮矿化(MNrec)对MNorg的贡献。结果表明，原始林地土壤MNorg (8.94 mg N?kg-1 d-1)显著高于草地(1.41~2.46 mg N?kg-1 d-1)，且均以MNlab为主。其中，草地MNlab对MNorg贡献率可达80.6%~93.1%，而在原始林地中该贡献率达到62.2%。岩溶区草地或林地开垦种植经济作物显著降低MNorg速率，其MNorg速率为0.53~0.89 mg N?kg-1 d-1，下降比例达62.5%~90.1%。这种差异主要受MNlab和MNrec影响，由草地开垦种植脐橙和玉米后土壤MNorg下降主要归于MNlab速率下降，而MNrec并未发生显著变化；原始林地开垦种植橡胶后土壤MNorg下降主要归于MNlab和MNrec速率的共同下降。岩溶区草地或原始林地开垦种植农作物后土壤有机碳、全氮、全磷、全钙和全镁含量及土壤田间持水量、pH、阳离子交换量均显著降低，且与土壤MNorg和MNlab呈显著正相关，表明农业种植对土壤理化性质的改变是影响矿化速率的重要因素。      

Nitrogen and phosphorus distribution and utilization bySpartina alterniflora in a Louisiana gulf coast marsh

Nitrogen and phosphorus content ofSpartina alterniflora Loisel and soil nitrogen were measured along a transect perpendicular to a stream in a Louisiana salt marsh in order to provide information on differences between the so-called streamside and inland regions. Total plant nitrogen and phosphorus levels in June and September tended to be greater at streamside than inland sites. Total soil nitrogen on a dry soil weight basis increased with distance inland from a natural stream toward an interdistributary basin in the marsh. Soil extractable ammonium-nitrogen levels measured in June were very low in vegetated streamside and inland areas, but they were much higher in inland areas devoid of plants. Nitrogen and phosphorus utilization byS. alterniflora was also investigated at an inland location in the salt marsh. Labelled ammonium-nitrogen and phosphate-phosphorus were added in May at a rate of 200 kg/ha to the soil of replicated plots. Added nitrogen significantly increased total above-ground plant biomass and plant height by 28 and 25%, respectively, 4 months after application. The ratio of belowground macro-organic matter to total aboveground biomass was decreased from 5.7 to 4.7 by the additional nitrogen. Added phosphorus did not significantly affect plant height and biomass. The use of¹⁵N-depleted nitrogen tracers showed that about half of the nitrogen in the aboveground portion ofS. alterniflora from 1 to 4 months after the nitrogen addition was derived from the added ammonium-nitrogen. After 4 months, 28 and 29% of the added labelled nitrogen was recovered in the aboverground and belowground biomass ofS. alterniflora, respectively. Recovery of added nitrogen was overestimated with a non-tracer method based on the difference in total nitrogen uptake between nitrogen-amended plots and untreated plots. Soil organic nitrogen comprised the majority of the nitrogen in the salt marsh. Nitrogen in the standing crop biomass ofS. alterniflora represented only about 2% of the total nitrogen in the plantsoil system of an inland marsh to a 20 cm soil depth.     

Organic matter and nutrient contents of soils under four types of bush fallow vegetation in SW Nigeria

The organic matter and nutrient contents of soils under four types of bush fallow in a part of the forest zone of SW Nigeria were analysed. The soils were formed from the same parent material of sandstone. The fallows studied were: 1) grass, 2) forb, 3) forb/woody and 4) woody fallows. The total nitrogen and organic matter contents and the cation exchange capacity values of soils under the forb/woody and woody fallow on the one hand were higher than those of the grass and forb fallow on the other. This is due to the greater age, biomass and greater capacity of the forb/woody and woody fallows to generate litter and to protect the soil against organic matter diminution through erosion and thermal decomposition. Of the four fallow types, the woody had the highest organic matter and nitrogen contents and cation exchange capacity. The fallows exert differential effects on soil mineral-nutrients. Compared to the woody fallow, there was a build-up of exchageable calcium in the topsoils of the grass and forb fallow. In contrast, there was a marked accumulation of exchageable sodium and potassium in the topsoils of the forb/woody and woody fallows. The woody and the grass or forb fallows appear to complement one another in restoring soil organic matter and nutrient content after cropping. It is suggested that the woody fallow should be alternated with grass or forb fallow in order to maintain the balance of soil nutrients over time.     

富硒区土壤养分质量评价:以陕西省紫阳县闹热村为例

为在典型富硒土壤分布地区科学种植和大力发展绿色富硒农产品,选取陕西省紫阳县闹热村为研究区,进行土壤养分质量评价.共采集138件表层土壤样品,测试分析了氮、磷、钾等植物营养元素以及土壤有机质、pH等16项指标.结果表明:(1)研究区硒资源丰富,表层土壤硒元素含量范围在0.50～25.30 mg/kg之间,平均含量为3.8...