Properties and distribution of sediment in the Salton Sea,California: an assessment of predictive models

The Salton Sea is the largest lake, on a surface area basis, in California (939 km²). Although saline (>44 g/l) and shallow (mean depth approximately 9.7 m), it provides valuable habitat for a number of endangered species. The distribution of sediments and their properties within the Salton Sea are thought to have significant influence on benthic ecology and water quality. Sediment properties and their distribution were quantified and compared with predicted distributions using several sediment distribution models. Sediment samples (n = 90) were collected using a regular staggered-start sampling grid and analyzed for water content, organic carbon (C), calcium carbonate, total nitrogen (N), total phosphorus (P), organic phosphorus, and other properties. Water content, total N, and total and organic P concentrations were all highly correlated with organic C content. The organic C concentration showed a non-linear increase with depth, with low organic C contents (typically 1–2%) present in sediments found in depths up to 9 m, followed by a strong increase in organic C at greater depths (to about 12% at 15 m depth). The models of Hakanson, Rowan et al., Blais and Kalff, and Carper and Bachmann yielded very different predicted critical depths for accumulation (10.5–22.8 m) and areas of accumulation (0–49.5%). Hakanson’s dynamic ratio model more reasonably reproduced the observed zone of elevated organic C concentrations in the Salton Sea than either exposure- or slope-based equations. Wave theory calculations suggest that strong winds occurring less than 1% of the time are sufficient to minimize accumulation of organic matter in sediments that lie at depths less than 9 m in this system. Guest editor: S. H. Hurlbert The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife and People, 1905–2005, held in San Diego, California, USA, March 2005     

The Ratios of Carbon,Nitrogen, and Phosphorus in a Wetland Coastal Ecosystem of Southern India

The fertility of the coastal and estuarine waters is of great concern because of its influence on the productivity of these waters. Seasonal variations in the distribution of organic carbon, total nitrogen and total phosphorus in the sediments of Kuttanad Waters, a part of the tropical Cochin Estuary on the south west coast of India, are examined to identify the contribution of sediments to the fertility of the aquatic systems. The adjoining region has considerable agricultural activity. The fresh water zones had higher quantities of silt and clay whereas the estuarine zone was more sandy. Organic carbon, total phosphorus and total nitrogen were higher in the fresh water zones and lower in the estuarine zones. Total phosphorus and organic carbon showed the lowest values during monsoon periods. No significant trends were observed in the seasonal distributions of total nitrogen. Ratios of C/N, C/P and N/P, and the phosphorus and nitrogen content indicate significant modification in the character of the organic matter. Substantial amounts of the organic matter can contribute to reducing conditions and modify diagenetic processes.     

不同林窗马尾松凋落叶与土壤养分变化研究

以现有42年生的马尾松（Pinus massoniana）人工纯林,经过采伐形成4种不同大小有效面积的林窗（100、400、900和1 600 m²）为研究对象,以未经采伐的42年生马尾松人工纯林为对照样地,采用凋落叶分解袋法,研究不同大小有效面积林窗对马尾松凋落叶、土壤C、N、P及化学计量比和养分损失率的影响。研究结果表明：（1）不同大小有效面积林窗下的马尾松凋落叶、土壤C、N、P含量及养分损失率除土壤P含量和马尾松凋落叶P养分损失率外,均存在显著差异。随着林窗有效面积G1~G4的增大,马尾松凋落叶C、N、P含量均呈降低趋势,三者均在G3林窗体现出较小值。马尾松凋落叶C、N、P养分损失率、土壤C、N、P养分含量多呈抛物线趋势,且均在G2或G3林窗体现出最大值。（2）不同大小有效面积林窗下的马尾松凋落叶、土壤C/N/P均存在显著差异。随着林窗有效面积G1~G4的增大,马尾松人工林土壤C/N/P基本呈抛物线变化趋势,土壤C/N在G3林窗出现最大值,土壤C/P、N/P均在G2林窗体现出最大值;土壤C/N、C/P、N/P变异系数分别为13.31%、16.51%、17.21%。马尾松凋落叶C/N、C/P均在G3体现出最小值。（3）马尾松凋落叶C、N含量与土壤C、C/N/P及环境因子的相关性较强,P含量与它们的相关性较弱;C/N与土壤P、C/N/P及环境因子的相关性较强,C/P、N/P与土壤C/P及环境因子的相关性较强;C、N养分损失率与土壤C、C/N、C/P及环境因子的相关性较强,P养分损失率与土壤C、N、P含量及其化学计量比和环境因子的相关性较弱。土壤C、N、P含量及其化学计量比与环境因子的相关性较强。     

坡向对毛竹林土壤养分及其生态化学计量特征的影响

采集浙江省龙游县境内毛竹林地不同坡向(阴坡和阳坡)的土壤样品进行对比分析,研究坡向对毛竹林地土壤养分及其生态化学计量特征的影响.结果表明: 土壤养分受坡向和土层深度的影响,采样区内土壤的养分水平呈阴坡＞阳坡、表层土壤＞底层土壤的变化趋势.阴坡土壤的阳离子交换量、总有机碳、全氮、碱解氮、速效磷、全钾和速效钾含量显著高于阳坡,分别高43.7%、103.8%、92.0%、75.5%、22.4%、89.4%和240.7%,而阴坡和阳坡土壤的全磷含量并无显著性差异.0～20 cm、20～40 cm和40～60 cm 3个土层中,无论是阴坡还是阳坡,其土壤C/N差异均不显著,而阴坡土壤C/P显著高于阳坡,分别高180.8%、42.0%和54.3%;各土层中,阴坡和阳坡土壤的C/K和N/K之间的差异不显著,而阴坡和阳坡土壤的C/K和N/K在3个土层间存在极显著性差异.采样区域内阴坡土壤有机碳与全氮、全磷和全钾之间呈极显著的正相关关系,并且与各速效养分间也均呈极显著的正相关关系.总体而言,毛竹林阴坡的土壤养分及其生态化学计量特征优于阳坡.     

海河流域水体沉积物碳、氮、磷分布与污染评价

从全流域尺度上研究海河流域水体沉积物碳、氮、磷元素含量与分布特征,对研究海河流域水环境污染现状具有重要意义.本研究采集海河流域河流与水库163个表层沉积物(0～10 cm)样品,测定沉积物有机碳(TOC)、总氮(TN)、总磷(TP)的含量,运用有机指数与有机氮方法评价沉积物污染状况.结果表明: 海河流域沉积物TOC、TN、TP含量具有较大的空间异质性,下游平原区明显高于山区,北四河下游平原、黑龙港及运东平原含量较高,永定河山区、北三河山区、滦河流域含量相对较低,河流沉积物TOC含量显著高于水库沉积物,而TN、TP含量与水库沉积物没有显著差异.TN与TOC、TP含量呈显著正相关(r=0.704,P<0.01;r=0.250,P<0.01).全流域有机指数总体属于“较清洁”水平,北四河下游平原总体已接近有机污染水平.全流域有机氮总体处在“尚清洁”水平,北四河下游平原、黑龙港及运东平原流域存在有机氮污染.海河流域河流、水库沉积物具有相似的污染强度.沉积物C/N平均值为12.71,表明TOC多来源于藻类等浮游动植物,其次是高等植物,水库C/N值比河流高,陆源物质输入对水库沉积物TOC的贡献比对河流大.     

广西猫儿山不同海拔土壤碳氮磷生态化学计量特征

为探究我国华南地区山地土壤有机碳(C)、氮(N)、磷(P)含量垂直分布特征,阐明土壤C、N、P生态化学计量特征对海拔和土层深度的响应,以广西猫儿山为研究对象,选取不同海拔的10个地点,采集了不同发生层的土壤,测定有机C、N、P、pH、容重和机械组成等土壤性质,探讨了不同海拔及深度土壤C、N、P生态化学计量特征及其影响因素.结果表明: 随着海拔升高,土壤C、N、C/P、N/P均呈增加趋势,土壤P呈先增后降趋势,C/N则呈先增后保持平稳趋势;随着土壤深度增加,土壤C、N、P、C/P、N/P均呈显著降低趋势,C/N无显著变化,C、N在不同发生层土壤间具有较高的耦合性(C/N变异系数为4.0%);土壤P在空间上的变异较小(不同海拔、发生层间变异系数分别为31.0%和22.0%).冗余分析结果显示,前2个排序轴反映了土壤C、N、P化学计量特征变异信息量的74.8%,土壤pH、容重和海拔对土壤C、N、P化学计量特征有显著影响,而黏粒、粉粒和砂粒影响效果不显著.     

Biogeochemical changes in the sediments of Lake Cantara South,a saline lake in South Australia

Biogeochemical studies were undertaken of a 65-cm long sediment core from Lake Cantara South, South Australia. ¹⁴C determinations indicated that the sediments had been deposited over 2000 years. Changes with sediment depth in the concentration or ratio of the following were determined: (i) total organic carbon, total carbonate (inorganic) carbon, total sulfur, total carbon, total inorganic and organic sulfur, atomic C/N, and sulfate/chloride; (ii) n-alkanes; (iii) a highly branched isoprenoid alkane, and (iv) steroids. Interpretation of the changes with sediment depth indicated the nature of changes that took place when the system changed from a protected marine lagoon to an isolated (athalassic) saline lake. This change took place about 1000 years ago.     

长期施肥下农田土壤-有机质-微生物的碳氮磷化学计量学特征

探讨外源养分的输入对土壤系统内碳、氮、磷化学计量特征的影响,对于深刻认识农田土壤有机碳(C)和养分循环及其相互作用过程具有重要意义。以26年的农田长期定位施肥试验为平台,分析长期不同施肥条件下土壤、有机态及微生物生物量碳、氮、磷含量及其化学计量学特征,并根据内稳性模型y=c x~(1/H)计算其化学计量内稳性指数H。结果表明:与长期撂荒处理(CK_0)相比,种植作物条件下26年化肥配施有机肥处理(MNPK和1.5MNPK)显著降低微生物生物量氮含量,但显著提高了微生物生物量磷的含量。相对于撂荒处理,即使长期配施化肥磷处理(NP、PK、NPK),其土壤有机磷降低显著。对于C∶N比而言,化肥配施有机物料处理(秸秆或有机肥)的土壤C∶N比、有机质C∶N及微生物生物量C∶N比均显著低于化肥处理(N、NP、PK和NPK)。对于C∶P比而言,相对于撂荒处理,26年施用磷肥(化肥磷或有机磷)显著降低了土壤C∶P比和微生物生物量C∶P比,而CK和偏施化肥处理(N、NP和PK)显著降低了土壤有机质C∶P比。对于土壤N∶P比而言,撂荒处理土壤N∶P比显著高于其他处理,而撂荒处理土壤有机质N∶P比显著高于CK和化肥处理,表明不施肥或化肥条件下作物种植加剧了土壤有机质中氮素的消耗。微生物生物量C∶N、C∶P、N∶P比的内稳性指数H分别为0.24、0.75、0.64,不具有内稳性特征。微生物生物量C∶N、C∶P、N∶P比分别与土壤C∶N、C∶P、N∶P比呈显著正相关关系,但与土壤有机质碳氮磷化学计量比之间无显著相关性。表明土壤碳、氮、磷元素的改变会直接导致微生物生物量碳、氮、磷化学计量比的改变,但微生物生物量碳氮磷化学计量比对土壤有机质碳氮磷化学计量比无显著影响,土壤有机质的碳氮磷计量比可能更多是受到作物和施肥等养分管理措施的影响。     

Macronutrients along the sediment profile in a subtropical monsoonal wetland in India

We analyzed 144 composite sediment samples to appraise the seasonal variation in select major nutrients in the bed sediments of Keoladeo National Park (KNP), Bharatpur, a subtropical monsoonal wetland system in India, from September 2003 to July 2005. Total organic carbon (TOC, %) and total nitrogen (TN, %) in the sediments were in the range of 0.61–14.01 and 0.26–0.68, respectively. The total available phosphorus (TAP, %) and total available sulphur (TAS, %) ranged from 0.001 to 0.034 and from 0.001 to 0.012, respectively. While C:N ratio was within a narrow range (1.38–13.56), C:P ratios varied widely (18.81–5995.83). Similar wide variations were seen in C:S ratio (352.2–3929.5) as well as N:P ratio (9.34–56.6). All the parameters except TAS showed depth-wise declines along the sediment profile. In contrast, the pH gradually increased along the depth. Most of the parameters significantly varied across months and sediment layers. A positive correlation (Two-tailed, P < 0.05) existed between TOC and all the nutrients and their ratios except TAP and N:P. TAP was positively correlated with electrical conductivity (EC) and water soluble substances (WSS), suggesting the contribution of phosphate to the dissolved salts. During certain months elements such as P were comparatively low in concentration, in spite of input through agricultural runoff and large scale bird droppings, probably due to its higher uptake by macrophytes growing luxuriantly in the wetland. Organic materials appear to decay at a faster rate during the drier periods as indicated by the fall in TOC and the rise in TN. Principal Component Analysis (PCA) shows that three components contributed to 68.9% of the total variance. The first component that accounted for 26.4% of the total variance reflects the importance of total organic carbon in wetland sediments and the ratio of carbon to other nutrients. The second one accounting for 23.7% of the variance correlated with water soluble substances (EC, WSS and TAS). The third component accounting for 18.7% of the variance reflects the influence of two major nutrients, nitrogen and phosphorus, in sediments those affect the biogeochemical processes in wetlands. Thus, the three PCA components can be characterized as ‘sediment organic carbon and its ratios with other elements’, ‘WSS, TAS’ and ‘the limiting nutrients such as N and P’, respectively.     

Use of ATP and carbon: nitrogen ratio as indicators of food quality of stream detritus

SUMMARY. 1. Differences in food quality of suspended and benthic organic detritus, as measured by ATP content and C/N ratio, were assessed along three contrasting headwater streams in southern Ontario.
2. Large differences in ATP content of sediments between cooler upstream reaches and warmer downstream reaches were detected. Sediment ATP content was highly correlated with stream temperature, presumably as a result of faster microbial growth, and with stream gradient. C/N ratios of sediments showed much the same pattern of differences as ATP, but were less variable.
3. By contrast, the ATP content (or BIOC/POM ratio) and C/N ratios of suspended organic matter showed no systematic variation between upstream and downstream or between warmer open and cooler shaded areas, probably due to the very short residence time of suspended particles.     

黄壤稻田土壤微生物生物量碳磷对长期不同施肥的响应

本研究以进行了22年的黄壤稻田长期定位试验为依托,分析了不同施肥模式下土壤碳(C)、磷(P)与微生物生物量C(MBC)、P(MBP)的变化及其耦合特征,旨在探讨黄壤地区合理培肥模式以提高土壤磷素有效性.试验包括10个处理,分别为不施肥(CK)、单施氮肥(N)、磷钾配合(PK)、氮钾配合(NK)、氮磷配合(NP)、氮磷钾配合(NPK)、单施有机肥(M)、3种有机无机肥配施(1/4M+3/4NP、0.5MNP、MNPK).结果表明:与不施肥相比,N和NK处理土壤有机碳(TOC)、全磷(TP)、MBC、MBP均有不同程度的降低,施磷处理(PK、NP、NPK)则有不同程度的提升;与不施肥和施用无机肥相比,施用有机肥各处理TOC、MBC、MBP及MBP/TP均显著增加,其中M和MNPK处理增幅最大.MBC/MBP、TOC/MBP、MBC/TP以施用有机肥处理最低,N处理最高.土壤MBC、MBP及其耦合关系与土壤TOC和有效磷均呈极显著相关,TOC是影响MBC、MBP、MBP/TP的直接因素,而有效磷则是影响MBC/MBP、TOC/MBP、MBC/TP的直接因素.土壤MBP及碳、磷耦合关系各指标可以有效区分单施化肥和施用有机肥的不同施肥方式,可作为评价黄壤稻田磷素肥力的生物学指标.配施有机肥是增加黄壤稻田磷有效性、提高土壤供磷潜力和保持土壤生物健康的有效途径.     

Sediment geochemistry of phosphorus at two intertidal sites on the Great Ouse estuary,S.E. England

The Great Ouse estuary in southern England is a macrotidal estuary with rather coarse sediment. Two intertidal sites were sampled five times over the year at low tide. The sediments are suboxic, organic poor (approximately 1.5% organic carbon). They are composed mainly of detrital quartz and feldspar with some calcite. At both sites the total phosphorus in the sediments ranges from 0.03 – 0.12% dry weight and total iron from 0.42–1.22% dry weight. Of the total phosphorus 20% is organic and 80% is inorganic of which 10% is water extractable. Total iron and phosphorus correlate well and the ratio of iron:phosphorus is 8.4 which is similar to that found when phosphorus is adsorbed by iron oxyhydroxides, suggesting that iron oxyhydroxides are an important substrate for phosphorus sorption in these sediments. Fluxes of phosphorus from the sediment to the overlying water, measured in cores incubated in the laboratory, are low and show no seasonality. The sodium concentration in the porewaters at both sites is variable suggesting that there is movement of water through the sediment to depths of at least 20 cm. This is borne out by variable phosphorus, iron and phosphorus concentrations in the porewaters and ill defined redox zones in the sediments.     

呼伦贝尔草原辉河湿地不同淹水状态的土壤碳氮磷特征比较

碳(C)、氮(N)、磷(P)生态化学计量比是生态系统过程及其功能的重要特征。为了比较不同淹水状态下草原区河岸湿地土壤生态化学计量特征差异,探讨用土壤生态化学计量特征来表征草原河岸湿地的退化状态,以呼伦贝尔草原辉河河岸湿地为研究对象,分别选择完全退化和未退化河岸湿地,从中选取常年淹水区域(W)、年际干湿交替区域(WD)以及河岸带边缘多年未曾淹没的干燥区域(D)为观测样地,对比研究退化与未退化草原河岸湿地土壤C、N、P化学计量比在不同淹水状态下的表征。结果表明:(1)随着淹水状态的改变,不论是退化河岸湿地还是未退化河岸湿地,不同淹水状态下的土壤C/N、C/P、N/P均差异显著(P0.05);(2)退化河岸湿地的C/N、C/P和N/P的平均值分别为9.05、273.08和28.25,与未退化河岸湿地相比(7.85、95.48、11.41)值显著升高;(3)相关性分析结果显示,土壤总磷与有机碳、全氮显著正相关,与C/N、C/P、N/P负相关,这可能是限制退化河岸湿地土壤养分元素循环的主要因素。研究结果表明:呼伦贝尔草原辉河河岸湿地不同淹水状态的土壤碳、氮、磷特征差异明显(P0.05),尤其是土壤C/P和N/P。与未退化河岸湿地相比,退化河岸湿地的C/N、C/P、N/P均明显高于未退化河岸湿地(P0.05),因此可以将土壤碳、氮、磷化学计量比特征作为草原区河岸湿地退化的评价指标。     

黄河三角洲贝壳堤土壤微生物生物量对不同生境因子的响应

从土壤微生物生物量角度分析黄河三角洲贝壳堤不同生境的土壤肥力状况,基于黄河三角洲贝壳堤植被类型,以4种不同生境的土壤为研究对象,测定了微生物生物量碳、氮、磷和相关的土壤理化性质。结果表明,不同生境中土壤微生物生物量碳(MBC)、土壤微生物生物量(MBN)、土壤微生物生物量(MBP)均值均为滩脊背海侧高潮线向海侧,且表现出明显的垂直分布特征:0—5 cm5—10 cm10—20 cm20—40 cm40—60 cm。土壤MBC、MBN、MBP占土壤有机碳(SOC)、全氮(TN)、全磷(TP)百分比变化范围分别为1.09%—3.48%、2.62%—7.27%、0.78%—2.86%,滩脊、背海侧和高潮线处MBC/SOC无显著差异(P0.05),但显著高于向海侧MBC/SOC(P0.05)。土壤MBN/TN、MBP/TP的变化趋势为滩脊和背海侧向海侧和高潮线。滩脊和背海侧土壤微生物碳、氮、磷的非生物限制性因子为土壤含水量、p H值、含盐量;向海侧和高潮线区域土壤微生物碳、氮、磷的非生物限制性因子为含水量和pH值。滩脊、背海侧和高潮线土壤微生物生物量碳、氮、磷及土壤养分间的相关关系显著或极显著,且协同性和稳定性高,表明土壤微生物生物量碳、氮、磷可以作为判断黄河三角洲贝壳堤土壤肥力状况的生物学指标,这为黄河三角洲贝壳堤的土壤肥力管理和植被恢复提供一定的理论依据。     

根系分泌物C∶N对刺槐林地土壤理化特征和土壤呼吸的影响

为探究根系分泌物C∶N对土壤养分循环及微生物活性的影响,本研究以黄土高原人工刺槐林为对象,在生境条件基本一致的15、25、35、45 a刺槐林地取原位土壤,通过模拟不同C∶N的根系分泌物(只添加N、C∶N=10、C∶N=50、C∶N=100和只添加C)添加至土壤,以去离子水作为对照,分析根系分泌物C∶N对土壤碳、氮、磷、pH值等理化特征和土壤呼吸的影响。结果表明: 1)有机碳含量与根系分泌物C∶N呈正相关,根系分泌物C∶N=10时土壤有机碳(SOC)分解较快,高根系分泌物C∶N(C∶N=100)能延缓SOC分解,而只添加C处理对SOC无显著影响。2)不同C∶N根系分泌物处理对全氮的影响不明显,碳添加能促进微生物对铵态氮的吸收,氮添加能促进铵态氮的硝化,随着根系分泌物C∶N增加,土壤中铵态氮含量下降。3)氮添加会导致土壤pH值下降,增加土壤全磷含量。4)刺槐林地土壤呼吸值与根系分泌物C∶N呈正相关,随着C∶N增加,根系分泌物对25和35 a人工刺槐林土壤呼吸的促进作用更显著。综上,根系分泌物C∶N值越高,对人工刺槐林土壤呼吸的促进作用越显著。研究结果进一步加深了对森林根系-土壤-微生物互作过程的认识。     

不同立地铁杆蒿化学计量特征及其与土壤养分的关系

以陕西吴起杨青川流域铁杆蒿群落为研究对象,结合坡向、坡位及土壤养分变化探究不同立地铁杆蒿群落化学计量特征及其与土壤养分的关系.结果表明:从峁顶、阳坡、半阴坡到阴坡,铁杆蒿地上部分和根有机碳、全氮、全磷含量、碳氮比均逐渐增大;地上部分碳磷比和根氮磷比呈减小趋势;地上部分氮磷比、根碳磷比先减小后增大.从峁顶、上坡位、中坡位到下坡位,地上部分有机碳、全氮、全磷含量以及根有机碳含量先增加后减小;地上部分碳氮比、氮磷比先减小后增大.铁杆蒿群落植物化学计量特征一般与土壤化学计量特征呈正相关,但碳氮比、碳磷比、氮磷比及根全磷与土壤相应指标呈负相关,且植物地上部分与土壤的相关性大于根.综上,不同立地铁杆蒿群落植物在阴坡中坡位生长状态最佳,其化学计量特征与土壤养分状况具有明显的相关关系.坡向和坡位在铁杆蒿群落植物和土壤的化学计量特征中具有重要影响,适宜的铁杆蒿群落将有利于土壤养分的恢复.     

Palaeolimnology of Neusiedlersee,Austria

Eighteen sediment cores from the Neusiedlersee reed belt were analysed for organic and inorganic carbon, nitrogen, organic and inorganic phosphorus and trace metal content. The depth variation of the distribution patterns of C, P and N in the cores are influenced by: 1. temporal variability of organic matter deposition (e.g. burial of Phragmites litter) 2. the impact of a number of astatic phases in the history of the lake, and 3. early palaeo-ecological changes associated with the alteration of marine to lacustrine environment. At some sites, due to mineralisation, the organic phosphorus compartment in the Pannonian sediments is completely exhausted; accordingly there is a parallel decrease in carbon and nitrogen content in the profiles. These changes in the pattern of the distribution of the nutrients (especially organic phosphorus) can be used to differentiate between the recent and the upper boundary layer of the tertiary sediments. There is no clear trace metal distribution pattern observed in the cores but the Pannonian sediments recorded the lowest levels. In contrast, at some locations surface sediments register a two to three fold increase. The highest C, P, N, values and trace metal concentrations are recorded in the surface sediments deposited after the drying up of the lake a hundred and twenty-two years ago.     

黄土丘陵区植被类型对土壤微生物量碳氮磷的影响

选择黄土丘陵区延河流域4种典型植被类型下的土壤为研究对象,测定了土壤微生物量碳、氮、磷和相关基本理化性质。结果表明,在此流域的典型天然草地、人工灌木林、人工乔木林和农地中土壤微生物量碳(MBC)的含量范围分别为315.15-400.89、246.56-321.25、267.76-347.05和118.96-245.14 mg/kg,土壤微生物量氮(MBN)的含量范围分别为35.87-47.63、27.63-42.89、24.66-36.20和15.64-22.56 mg/kg,土壤微生物量磷(MBP)的含量范围分别为14.14-22.96、12.89-19.75、11.54-14.40和7.23-11.59 mg/kg;土壤微生物量总体呈现出天然草地最高、人工乔、灌木林次之,且均显著高于农地的趋势,表明退耕还林还草对土壤微生物生物量有明显的促进作用。不同植被类型下,土壤微生物量碳氮比和碳磷比的变化范围分别为7.49-10.87和16.27-24.11,土壤微生物量碳、氮、磷占土壤有机碳(SOC)、全氮(TN)、全磷(TP)百分比的范围分别为2.70%-4.85%、2.56%-4.45%、2.08%-5.34%。其中天然草地、人工灌木林和农地土壤的微生物量碳氮比、碳磷比均显著小于人工乔木林(P < 0.05); MBC/SOC在不同植被类型下的差异不显著,MBN/TN和MBP/TP均呈现出天然草地>人工灌木林>人工乔木林和农地的趋势,且差异显著(P < 0.05)。微生物量碳、氮、磷与土壤有机碳、全氮和土壤含水率呈现极显著或显著相关性,与土壤pH值呈现出不同程度的负相关性,表明植被类型对这些与土壤微生物量紧密相关的理化性质也有显著影响。     

克氏针茅草原土壤生态化学计量特征对放牧强度的响应

生态化学计量学是研究生态系统中各元素间平衡的科学,对于探究土壤有机碳（C）、全氮（N）、全磷（P）元素循环以及土壤养分限制状况具有重要意义。为了解克氏针茅（Stipa kirschnii）草原土壤生态化学计量特征,以内蒙古克氏针茅草原区为研究对象,在不同放牧强度草场进行采样分析。结果表明：随着放牧强度的增加,C、P含量先降低后升高,N含量先升高后降低;土壤C/N先降低后升高、C/P逐渐升高、N/P先升高后降低。C/N随着放牧强度的增加与有机碳相关性逐渐增大、与全氮的相关性逐渐减小;轻牧区的C/P受有机碳作用有所增强;中牧区N/P受全氮作用增强。C/N主要限制因素是有机碳含量,C/P和N/P主要限制因素是全磷含量。不同放牧强度会影响土壤化学计量比与其他物质的关系,也会改变土壤化学计量比各制约因素的强度。     

喀斯特山地不同微地貌下土壤碳氮磷空间异质性及生态化学计量特征

喀斯特地区特殊地质背景造就复杂破碎的地形发育出多样的微地貌,这使得清晰地认识土壤碳氮磷的空间异质性及生态化学计量特征存在困难。基于实地调查、土壤采样、实验测试的结果数据,引入混合效应模型评估方法结合变异系数,分别从全量(土壤有机碳、全氮、全磷)及有效态(活性有机碳、碱解氮及速效磷)两方面,揭示不同微地貌类型下土壤碳氮磷空间异质性及其生态化学计量特征。结果显示：(1)不同微地貌类型下土壤有机碳、全氮、全磷对碳氮磷比值的耦合解释度为：土面(91.09%)>石沟(91.02%)>石坑(84.63%)>石洞(80.17%)>石缝(73.20%),土面的空间异质性最低而石缝最高。(2)有效态方面,活性有机碳、碱解氮和速效磷对碳氮磷比值的耦合解释度特征为：石缝(84%)>石洞(58.15%)>土面(47.80%)>石坑(44.06%)>石沟(32.18%),说明石缝微地貌的土壤活性有机碳、碱解氮及速效磷空间异质性最低。(3)不同微地貌类型下土壤全量碳氮磷生态化学计量的变异系数差异均在50%以上(C/N 80%、C/P 53.57%、N/P 69.33...