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1.
《Applied Geochemistry》2001,16(1):123-136
Concentrations of several elements extractable with BaCl2 and acid ammonium acetate (pH 4.65) were measured in the organic and 4 mineral soil layers on the national forest inventory plots of the Finnish Forest Research Institute. The soil data also includes total concentrations of elements in the organic layer and site and soil physical characteristics. Data were compared with the aqua regia extractable element concentrations measured in the nationwide regional till geochemical mapping carried out by the Geological Survey of Finland.Correlations between concentrations in surface soil and underlying basal till were generally highest for K, Mg, Mn, P and Zn; in the organic layer and till they were highest for Cr and Cu. The strength of these correlations did not increase regularly from surface to deeper soil layers. All soil base cations with the exception of Ca, which is of relatively low solubility, were well correlated. The elements Zn, K, P, Al and Mn in till were the most reliable indicators of surface soil chemistry.Fuzzy clustering showed that the correlation between element concentrations in basal till and the two uppermost layers of mineral soil was better within areas of distinct till geochemistry, such as the schist belts in southwestern Finland, the Lake Ladoga–Bothnian Bay zone and the Kuusamo schist belt.Surface soil chemical variables were clearly better in discriminating fertility classes of forest sites than were element concentrations in basal till. The independent ability of till geochemistry to distinguish these productivity classes and to explain surface soil fertility was nevertheless demonstrated.  相似文献   

2.
The aim of this article is to analyse the influence of commodified cotton production on soil fertility in southern Mali. From the late 1950s and until recently, production of both cash-crop cotton and food crops have increased rapidly in this region, giving it a reputation of being an African ‘success story’. The flip side of this economic success is, however, said to be environmental degradation especially in terms of loss of soil fertility. We collected 273 soil samples in 19 villages located in various zones of land use intensity. In each village, the samples were collected on up to six different land use types varying with intensification. The analysis of the soil samples showed that soil fertility was highest in the sacred groves that have been protected and never cultivated. However, comparing soils under continuous cultivation and soils under fallow no clear trends in soil fertility were found. Cotton yields have declined since the early 1990s, while the total use of fertilisers has increased. This is often interpreted as proof of soil exhaustion, but there is no clear indication in this study that cotton-cereal rotation as practiced by smallholders in southern Mali reduces soil fertility. We argue that the decline in yields has been caused by an extensification process. Cotton fields expanded rapidly, due to attractive cotton prices in the 1990s, leading to falling investments per ha and cultivation of more marginal lands. These findings also have implications for a political ecology of commodity production and lead us to argue for an open-ended and empirically based ‘critical political ecology’.  相似文献   

3.
The relationships between phytoplankton productivity, nutrient distributions, and freshwater flow were examined in a seasonal study conducted in Escambia Bay, Florida, USA, located in the northeastern Gulf of Mexico. Five sites oriented along the salinity gradient were sampled 24 times over the 28-mo period from 1999 to 2001. Water column profiles of temperature and salinity were measured along with surface chlorophyll and surface inorganic nutrient concentrations. Primary productivity was measured at 2 sites on 11 dates, and estimated for the remaining dates and sites using an empirical regression model relating phytoplankton net production to the product of chlorophyll, euphotic zone depth, and daily solar insolation. Freshwater flow into the system varied markedly over the study period with record low flow during 2000, a flood event in March 2001, and subsequent resumption of normal flow. Flushing times ranged from 1 d during the flood to 20 d during the drought. Freshwater input strongly affected surface salinity distributions, nutrient flux, chlorophyll, and primary productivity. The flood caused high turbidity and rapid flushing, severely reducing phytoplankton production and biomass accumulation. Following the flood, phytoplankton biomass and productivity sharply increased. Analysis of nutrient distributions suggested Escambia Bay phytoplankton alternated between phosphorus limitation during normal flow and nitrogen limitation during low flow periods. This study found that Escambia Bay is a moderately productive estuary, with an average annual integrated phytoplankton production rate of 290 g C m−2 yr−1.  相似文献   

4.
Primary productivity of three size classes of phytoplankton (<5 μm, 5–22 μm, >22 μm) was measured monthly at six sites within San Francisco Bay throughout 1980. These sites in the three principal embayments were chosen to represent a range of environments, phytoplankton communities, and seasonal cycles in the estuary. Temporal variations in productivity for each size class generaly followed the seasonality of the corresponding fraction of phytoplankton biomass. The 5–22 μm size class accounted for 40 to 50% of the annual production in each embayment, but production by phytoplankton >22 μm ranged from 26% in the southern reach to 54% of total phytoplankton production in the landward embayment of the northern reach. A productivity index is derived that predicts daily productivity for each size class as a function of ambient irradiance and integrated chlorophylla in the photic zone. For the whole phytoplankton community and for each size class, this index was constant and estimated as ?0.76 g C m?2 (g chlorophylla Einstein)?1. The annual means of maximum carbon assimilation numbers were usually similar for the three size classes. Spatial and temporal variations in size-fractionated productivity are shown to be primarily due to differences in biomass rather than size-dependent carbon assimilation rates. *** DIRECT SUPPORT *** A01BY034 00005  相似文献   

5.
祁乐  高明  杨来淑  王丹  邓炜 《中国岩溶》2015,34(1):86-94
文章以重庆市丰都县三坝乡土地整理项目为例,分别对土地整理前（2012年12月）52个采集点和土地整理后（2013年3月）28个采集点,采用野外采样和室内分析相结合的方法,研究了土地整理对岩溶区土壤微生物群落结构、土壤微生物生物量碳(SMBC)、氮(SMBN)及酶活性(过氧化氢酶、脲酶、蔗糖酶)的影响,结果表明:（1）土地整理对土壤微生物影响显著,土地整理后比整理前土壤中的放线菌数量降低,真菌数量增加。（2）在0～20 cm土层,整理前后SMBC和SMBN含量变化显著,SMBC含量整理后比整理前降低了20.33%,SMBN含量整理后比整理前减少了47.84%;土地整理改变了整理前SMBC、SMBN含量随土层深度变化递减的规律,使SMBC、SMBN含量分别在亚表层（20～40 cm）出现最小值68.34 mg/kg和最大值33.58 mg/kg。（3）整理前后土壤脲酶和过氧化氢酶均在0～20 cm和20～40 cm同一土层差异显著,蔗糖酶活性在各土层差异均显著。土地整理使土壤脲酶和过氧化氢酶活性降低,蔗糖酶活性提高。（4）有机质对表层SMBC、SMBN含量和脲酶活性呈显著正相关,pH值与土壤酶活性呈显著正相关。   相似文献   

6.
Qatar economy has been growing rapidly during the last two decades during which waste generation and greenhouse gas emissions increased exponentially making them among the main environmental challenges facing the country. Production of biochar from municipal solid organic wastes (SOWs) for soil application may offer a sustainable waste management strategy while improving crop productivity and sequestering carbon. This study was conducted to (1) investigate the physicochemical parameters of biochars for SOW, (2) select the best-performing biochars for soil fertility, and (3) evaluate the potential benefits of these biochars in lowering greenhouse gases (GHGs) during soil incubation. Biochars were produced from SOW at pyrolysis temperatures of 300–750 °C and residence times of 2–6 h. Biochars were characterized before use in soil incubation to select the best-performing treatment and evaluation of potential GHG-lowering effect using CO2 emission as proxy. Here, soil–biochar mixtures (0–2%w/w) were incubated in greenhouse settings for 120 days at 10% soil moisture. Soil properties, such as pH, EC, TC, and WHC, were significantly improved after soil amendment with biochar. Two biochars produced from mixed materials at 300–500 °C for 2 h and used at 0.5–1% application rate performed the best in enhancing soil fertility parameters. A significant decrease in CO2 emission was observed in vials with soil–biochar mixtures, especially for biochars produced at 500 °C compared the corresponding raw materials which exhibited an exponential increase in the CO2 emission. Hence, application of biochar to agricultural soils could be beneficial for simultaneously improving soil fertility/crop productivity while sequestering carbon, thereby reducing anthropogenic emissions of GHGs.  相似文献   

7.
近年来农用地土壤质量受重金属污染影响进而导致农产品受到威胁的问题愈发严重,然而关于土壤质量评价的研究很少考虑土壤污染状况,忽略了土壤污染风险对土壤质量的影响。本文以某典型制造业县级市为例,在以土壤理化性质为主要指标的土壤肥力状况评价基础上,对研究区土壤重金属进行污染风险管控类型划分。通过建立分段函数将土壤污染风险管控类型划分结果引入土壤质量评价体系,对农用地土壤质量进行评价。结果表明：研究区土壤理化指标的变异系数从大到小为速效磷(AP)含量>土壤电导率(SEC)>全磷(TP)含量>土壤有机碳(SOC)含量>阳离子交换量(CEC)>全氮(TN)含量>pH。土壤肥力状况随地势降低和河流增加呈现升高的趋势,高肥力区主要分布在平原区西北部和平原区东北部,低肥力区主要分布在东南部丘陵山区和西部低洼区,肥力过渡区环绕低肥力区分布。农用地土壤污染风险管控类型的划分结果表明,Cd、Hg、As、Pb、Cr、Ni、Cu和Zn 8种重金属中至少有88.89%的Cd样点和98.61%的Cr样点属于优先保护类,11.11%的Cd样点、1.39%的Cr样点属于安全利用类,该区重金属污染以Cd为主。土壤质量评价结果表明,土壤质量总体分布与土壤肥力状况分布规律类似,但由于受土壤污染风险的影响,研究区西南部低质量土壤范围向东扩张,东南部低质量土壤分布范围更小,更密集化。上述研究结果说明,引入土壤污染风险管控类型划分结果一般会对土壤肥力状况作减幅修正,并在一定程度上改变原土壤肥力状况的空间分布格局。  相似文献   

8.
The basal area and productivity of managrove wetlands are described in relation to selected soil properties to understand the general pattern of optimum forest stature at the mouth of estuaries in the Everglades, such as the Shark River Slough, Florida (U.S.). The basal area of mangroves decreases from 40.4 m2 ha−1 and 39.7 m2 ha−1 at two stations 1.8 km and 4.1 km from the estuary mouth to 20.7 m2 ha−1 and 19.6 m2 ha−1 at two sites 9.9 km and 18.2 km from the mouth, respectively. The gradient in basal area at these four sites is mostly the result of approximately 34 yr of growth since Hurricane Donna. Wood productivity is higher in the lower estuary (10.7 Mg ha−1 yr−1 and 12.0 Mg ha−1 yr−1) than in the upper estuary (3.2 Mg ha−1 yr−1 and 4.2 Mg ha−1 yr−1). Porewater salinity among these four mangrove sites during seasonal sampling in 1994 and 1995 ranged from 1.6 g kg−1 to 33.5 g kg−1, while sulfide was generally<0.15 mM at all sites. These soil values indicate that abiotic stress cannot explain the decrease in forest structure along this estuarine gradient. Concentrations of nitrogen (N) and phosphorus (P) are more closely related to patterns of forest development, with higher soil fertility at the mouth of the estuary as indicated by higher concentrations of extractable ammonium, total soil P, and available P, along with higher ammonium production rates. The more fertile sites of the lower estuary are dominated by Laguncularia racemosa, whereas the less fertile sites in the intermediate and upper estuary are dominated by Rhizophora mangle. Relative N mineralization per unit of total N is higher in the lower estuary and is related positively to concentrations of available P, indicating the importance of turnover rates and nutrient interactions to soil fertility. Concentrations of Ca-bound P per volume soil in the lower estuary is 40-fold higher than in the upper estuary, and along with an increase in residual P in the upper estuary, indicate a shift from mineral to organic P along the estuarine gradient. Mineral inputs to the mouth of Shark River estuary from the Gulf of Mexico (rather than upland inputs) apparently control the patterns of mangrove structure and productivity.  相似文献   

9.
Heavy rainfall in 1978 and 1980 caused flooding of southern California salt marshes. Examination of three marshes demonstrated a broad range of freshwater effects which correlated with the degree of change in soil salinity. At Tijuana Estuary (1980), a short-term reduction in the salinity of normally hypersaline soils was followed by a 40% increase in the August biomass of Spartina foliosa. At Los Penasquitos Lagoon (1978), a longer period of brackish water influence was followed by a 160% increase in August biomass of Salicornia virginica. At the San Diego River (1980), flood flows were augmented by major reservoir discharge. Continuous freshwater flow leached most of the marsh soil salts and caused replacement of halophytes by freshwater marsh species. The first two cases probably fell within the normal range of flooding events, even though the hydrology of both watersheds has been modified. The vegetation response was functional; productivity increased but there was no major change in species composition. As expected, vegetation rapidly returned to preflood conditions. However, the long-term freshwater flow in the Dan Diego River was unnatural. Floral composition changed as soils were leached of salts. Recovery following the return of saline soils has been slow because many native halophytes are not good colonizers. The system's resilience is limited, and modification of natural stream discharge can cause permanent changes in coastal wetlands.  相似文献   

10.
The Pampa de Chaparrí (Pampa) in hyperarid northwest coastal Peru is an ideal area to study late prehispanic agricultural technology and production because irrigation canals and furrowed fields have been preserved since abandonment approximately 500 years ago. We collected 55 samples for soil characterization, fertility, and micromorphic analyses and compared these results to a noncultivated control soil previously sampled in an adjacent valley. Natural soil fertility levels for maize, cotton, and bean production were generally high during late prehispanic cultivation in the Pampa. Maintaining adequate nitrogren levels for production, however, would have required external inputs from livestock manure, guano, or leguminous plants. The management of low soil salinity levels was possible because of rapidly permeable soils and irrigation waters low in salt. Based on available water capacity and climate conditions, the Blaney‐Criddle Equation yields evapotranspiration rates indicating that irrigation frequency was necessary in a range of every 10–16 days during the growing season. © 2004 Wiley Periodicals, Inc.  相似文献   

11.
Estimation of spatial extent of soil erosion, one of the most serious forms of land degradation, is critical because soil erosion has serious implications on soil fertility, water ecosystem, crop productivity and landscape beauty. The primary objective of the current study was to assess and map the soil erosion intensity and sedimentation yield of Potohar region of Pakistan. Potohar is the rainfed region with truncated and complex topography lying at the top of the Indus Basin, the world’s largest irrigation networks of canals and barrages. Spatially explicit Revised Universal Soil Loss Equation (RUSLE) Model integrated with Remote Sensing-GIS techniques was used for detecting/mapping of erosion prone areas and quantification of soil losses. The results show that the Potohar region is highly susceptible to soil erosion with an average annual soil loss of 19 tons ha?1 year?1 of which the maximum erosion (70–208 tons ha?1 year?1) was near the river channels and hilly areas. The sediment yield due to the erosion is as high as 148 tons ha?1 year?1 with an average of 4.3 tons ha?1 year?1. It was found that 2.06% of the total area falls under severe soil erosion, 13.34% under high erosion, 15.35% under moderate soil erosion while 69.25% of the area lies in the low (tolerable) soil erosion. Chakwal and Jhelum districts of the region are seriously affected by erosion owing to their topography and soil properties. The information generated in this study is a step forward towards proper planning and implementation of strategies to control the erosion and for protection of natural resources. It is, hence, necessary that suitable water harvesting structures be made to control water to prevent soil erosion and provision of water in the lean season in this region. Tree plantation and other erosion control practices such as strip cropping can also minimize soil erosion in this region.  相似文献   

12.
潞安目标区煤层气赋存和生产的地质因素分析   总被引：2，自引：0，他引：2  
分析了影响潞安目标区煤层气赋存和生产的主要地质因素,提出了本区煤层气井产气量低、产水量高的原因。潞安目标区与晋城目标区相比较,张性断层发育,3号煤顶板砂岩条带发育。地下水从浅部接受大气降水补给,部分在文王山和二岗山断裂带排泄,煤层顶板砂岩含水层与煤层不仅构成了一个统一的地下水系统,又由于与断层的沟通作用形成了一个完整的地下水补径排系统,使得地层能量被释放,煤层气大量运移逸散,煤储层压力降低,煤层气井产能降低。   相似文献   

13.
通过野外采样和室内测定,以日照茶树种植区3个典型茶园为研究对象,每个茶园分别取鸠坑、黄山群体、福鼎大白各3个品种。最终取得9种茶样生长地的土样,研究分析土样的pH。有机质,全N,P,K,有效N,P,K等指标的土壤养分含量状况,并以此为评价指标,运用模糊综合评判法,对3个茶园的土壤肥力质量进行了综合评价。结果表明,茶园肥力综合水平为北垛春〉碧波山庄〉北叶青i茶园土壤总体上,pH值较适中,有机质含量很缺乏,全N含量偏低,全P含量中等,全K含量较高,有效N含量很缺乏,有效P含量非常丰富,有效K含量中等,并据此提出了关于该地区3个典型茶园今后合理施肥的一些建议。  相似文献   

14.
露天煤矿生态地质环境系统恢复过程中,排于地表的不同年代地质层组的岩土剥离物都有可能成为复垦土壤母质。为科学合理利用矿区岩土剥离物,重构高质量复垦土壤,并指导后期分类排放,以平朔露天矿区黄土母质作为对照,评价不同类型岩土理化性状差异,从复垦土壤母质来源进行造地的源头控制,为露天煤矿土地复垦与生态修复提供依据。结合单项养分含量及有益微量元素含量分析结果,借助修正的内梅罗综合指数法,评价各岩土层肥力质量;借助单因子质量指数法,评价各岩土层环境质量。结果表明:各岩土层综合肥力系数位于0.40～1.26范围内,属贫瘠或一般水平;安家岭矿中2个煤矸石层的有机质或全氮含量、上部页岩层的全钾含量,以及东露天矿中炭质泥岩层的全磷含量丰富,显著高于黄土母质层;东露天矿底部细砂岩层及安家岭矿中泥灰岩层硫含量过高;东露天矿镉元素环境质量指数为1.05,属轻微污染等级;安家岭矿底部细砂岩层pH值低至4.25,酸度过大。平朔露天矿大多岩土层环境质量较好,但综合肥力质量较差,其中单项养分含量丰富,环境质量安全且易于风化的岩土层,适宜作为重构复垦土壤的备选材料。  相似文献   

15.
土壤碳蓄积量变化的影响因素研究现状   总被引：37，自引：2，他引：37  
土壤碳库的动态平衡影响作物产量和土壤肥力的高低，是土壤肥力保持和提高的重要研究内容。简要评述了土壤理化特性、温度和降水变化、大气CO2浓度上升、人类的农业活动对土壤有机碳蓄积量的影响，介绍了当前对土壤碳蓄积量动态变化的研究进展，认为应加强气候变化和土地利用/土地覆被变化与土壤碳循环研究的结合，提高对陆地生态系统碳循环变化的认识，并需要从生态环境保护的利益和可持续发展的理论出发，进一步加强土地管理方式的改变，促进土壤有机质的积累，提高土壤对碳的固定。  相似文献   

16.
Prehistoric stone alignments and their associated terraces are common in upland ecozones of the American Southwest. These features are generally considered the archaeological consequences of “runoff agriculture” dedicated to domesticated‐plant production. Furthermore, researchers have theorized that such production decreased soil fertility and ultimately promoted abandonment of the alignments, terraces, and surrounding landscapes. Recent investigations show that cultivated Mollisols indeed have less organic matter and less available P, and elevated pH, as well as several textural changes. In contrast, cultivated Aridisols have elevated CaCO3, available Ca, and cation‐exchange capacity, as well as no textural changes. The developing picture, however, is that small‐scale runoff agriculture has had largely benign effects on soil fertility and that anthropogenic terraces likely were abandoned for reasons unrelated to their productivity. © 2000 John Wiley & Sons, Inc.  相似文献   

17.
苏南地区是我国重要的粮食产区之一,其耕地土壤的酸碱度特征直接影响着土地品质和粮食质量。本文通过调查 2010年以来苏南农耕土壤pH空间分布特征,发现苏南土壤pH呈现西酸东碱格局,这与自然条件和人为改造行为密切相 关。近30年来苏南土壤pH时空变化在2003年前后呈现两种模式：总体上,1980年至2003年期间,土壤发生酸化和碱化的 地区与1980年至2010年来的总变化特征基本一致,而2003年至2010年近10年来部分地区土壤酸碱变化趋势出现逆转,以 镇江句容地区的先碱化后酸化和苏州无锡地区的先酸化后碱化最为典型。本文分析认为,地区间土地利用格局和利用方式 的时空差异所导致的缓冲物质的增减更替,是造成苏南土壤pH时空变化区域差异的主要驱动力  相似文献   

18.
In water repellent soil, Cr, Pb and Cu showed higher adsorption intensities than Zn, Cd and Ni did. Soil water repellency is much more widespread than formerly thought. In order to promote fertility and productivity, the irrigation of recycled water onto water repellent soil may be an applied technology to be used in some areas of Southern Australia. Therefore, heavy metals in recycled water potentially enter into the soil. The competitive sorption and retention capacity of heavy metals in soil are important to be determined, especially considering the special geochemical origin of water repellent soil that was caused by waxes on or between the soil particles. Batch equilibrium sorption experiments on Cd, Cr, Cu, Ni, Pb and Zn in their typical proportion in recycled water were conducted in water repellent soil. The sorption intensity, sorption isotherm in the experiments together showed that Cr, Pb and Cu have higher sorption intensity than those of Zn, Ni and Cd in the competitive system. The risk assessment for the application of recycled water onto water repellent soil is definitely necessary, especially for the metal cations with relatively weak sorption.  相似文献   

19.
桂东南荔枝生长营养元素农业地球化学研究   总被引：6，自引：0，他引：6  
叶荣  李蔚萍 《地学前缘》2006,13(1):119-127
桂东南是中国重要的荔枝产区,以梧州地区为例,重点对沙头和古凤两处荔枝种植园进行了生态地球化学调查,采集了荔枝园施肥圈内、外土壤,出露的代表性基岩,以及荔枝叶、青果和熟果样品,实测了大量和微量矿质元素、稀土元素,以及土壤营养元素有效态的含量。通过计算荔枝对土壤营养元素的吸收率及荔枝生长与结果期对营养元素的需求,查明本区荔枝生长的特征营养元素为Ca、K、Mg、Mn、P、Zn、Cu、B、Fe和REE。荔枝结果期的特需营养元素为P、Mg、Mo、Cu、Zn、Ko荔枝结果早和晚期特需元素分别为Ca、Si、B和Cu、Fe、K。在岩石-土壤-荔枝株生态循环系统中,本区营养元素在土壤中保持一定的积累,提供荔枝生长的需求,因此为荔枝宜种区;但全区土壤B缺乏,Zn、Mo局部不足。Ca、K、Zn在两区岩石土壤中分布不同,可能是造成沙头荔枝比古凤荔枝迟熟的主要农业地球化学因素。研究区有害元素Pb、Cd在土壤中积累是值得关注的土壤环境问题。  相似文献   

20.
Phytoplankton productivity and the factors that influence it were studied in the Logan River and southern Moreton Bay, a large embayment on the east coast of Australia. Phytoplankton productivity, dissolved and total nutrient concentrations, and turbidity were determined throughout high and low rainfall periods to characterize light and nutrient influences on productivity. Turbidity and nutrient concentrations were highest at upriver sites, but productivity was highest at the river mouth and within the river plume. Phytoplankton productivity peaked after rainfall events (>150 mg C m?3 h?1), commensurate with a decrease in dissolved nitrogen concentrations. Productivity responses to increased nutrient concentrations and light availability were determined in laboratory incubations. During summer, productivities at the bay sites were stimulated by nitrogen (N) enrichment, while productivities at upriver sites were stimulated by phosphorus (P) addition. Light stimulation of productivities was more pronounced at upriver sites than bay sites. The relative magnitude of nutrient and light stimulation of productivities indicate a predominance of light limitation upriver, significant N limitation within the Logan River plume, and little effect of light, N, or P at sites beyond the Logan River plume. Productivity decreased with seasonal decreases in temperature. Lower water temperatures in winter probably helped determine maximum rates of phytoplankton productivity. The combination of light and N limitation of productivity during summer, and temperature limitation during winter, account for low areal productivities (<0.6 g C m?2 d?1), compared with other rivers and estuaries worldwide.  相似文献   

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