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1.
Wetlands in the United States are protected by law and are identified by their hydric soils, wetland hydrology, and vegetation. Hydric soils are easily identified by color characteristics termed hydric soil field indicators, that form under saturated and anaerobic conditions, but wetland hydrology is difficult to assess. This study determines how often seven hydric soil field indicators met wetland hydrology requirements which require a water table be within 30 cm of the surface for 14 days or more during the growing season in over half the years. Studies were conducted at five sites in North Carolina in both wetland and upland plots. Soils ranged from Aquic Paleudults to Typic Haplosaprists across all sites. The water-table simulation model DRAINMOD was calibrated to soil conditions in individual plots. Long-term rainfall data were used with the calibrated models to compute 40 years of daily water table data to represent both wet and dry years. It was found that the hydric soils with field indicators composed of organic materials in layers over 20 cm thick (Histosol and Histic epipedon field indicators) met wetland hydrology requirements each year, and in addition were ponded with water for periods between 67 to 139 days on average each year during the growing season. Plots in mineral soils having the Dark Surface (S7) indicator as well as the Sandy Mucky Mineral (S1) indicator also met the saturation requirements for wetland hydrology every year, and were ponded for only 3 days per year on average. Other mineral soils with an Umbric Surface (F13) or a Depleted Matrix (F3) field indicator met wetland hydrology requirements in approximately 95% of the years, and had water tables within 30 cm of the surface for 40 days per year on average. The Redox Depressions (F8) field indicator occurred in a small depression that was saturated for 87% of the year for periods averaging approximately 30 days. These results showed that hydric soil field indicators can be calibrated to long-term water table data that will allow precise assessments of wetland hydrology on-site. 相似文献
2.
《CATENA》2004,58(2):183-213
Standard field indicators, currently used for hydric soil delineations [USDA-NRCS, 1998. Field indicators of hydric soils in the United States, Version 4.0. In: G.W. Hurt et al. (Ed.), United States Department of Agriculture-NRCS, Fort Worth, TX], are useful, but in some cases, they can be subjective, difficult to recognize, or time consuming to assess. Magnetic susceptibility (MS) measurements, acquired rapidly in the field with a portable meter, have great potential to help soil scientists delineate and map areas of hydric soils more precisely and objectively. At five sites in Illinois (from 5 to 15 ha in area) with contrasting soil types and glacial histories, the MS values of surface soils were measured along transects, and afterwards mapped and contoured. The MS values were found to be consistently higher in well-drained soils and lower in hydric soils, reflecting anaerobic deterioration of both detrital magnetite and soil-formed ferrimagnetics. At each site, volumetric MS values were statistically compared to field indicators to determine a critical MS value for hydric soil delineation. Such critical values range between 22×10−5 and 33×10−5 SI in silty loessal or alluvial soils in Illinois, but are as high as 61×10−5 SI at a site with fine sandy soil. A higher magnetite content and slower dissolution rate in sandy soils may explain the difference. Among sites with silty parent material, the lowest critical value (22×10−5 SI) occurs in soil with low pH (4.5–5.5) since acidic conditions are less favorable to ferrimagnetic mineral neoformation and enhance magnetite dissolution. Because of their sensitivity to parent material properties and soil pH, critical MS values must be determined on a site specific basis.The MS of studied soil samples (0–5 cm depth) is mainly controlled by neoformed ultrafine ferrimagnetics and detrital magnetite concentrations, with a minor contribution from anthropogenic fly ash. Neoformed ferrimagnetics are present in all samples but, based on high χFD% (∼5% to 10%), are most prevalent in high pH Mollisols of northeastern Illinois. Scanning electron microscope images display significantly more detrital magnetite alteration in hydric soils, substantiating that reductive dissolution of magnetite (aided by microorganisms) is a primary cause for lower MS. Fly ash comprises 8–50% of the >5 μm strongly magnetic particles and typically accounts for 5–15% of the total MS signal. The proportion of fly ash in >5 μm strongly magnetic fractions is greater in hydric soils because of lower natural magnetite contents, possibly combined with historical topsoil accumulation in lower landscapes. Magnetic fly ash particles are also more altered in low MS soils, implying that significant magnetite dissolution can occur in less than 150 years. 相似文献
3.
Stephanie A. Schmidt 《Communications in Soil Science and Plant Analysis》2019,50(11):1293-1309
Soil color patterns are essential to understand hydrologic regime and biogeochemical processes in wetland ecosystems. Munsell Soil Color Chart (MSCC) has been traditionally and predominantly used to identify and quantify hydric soil field indicators, but several simple, low-cost alternatives have become recently available to compare their efficacy in complementing the MSCC in soil color assessment. We conducted an intensive literature review on studies utilizing different methods to identify and quantify hydric soil colors and associated patterns; these include 1) the MSCC, 2) the Nix Color Sensor, 3) mobile phone camera (MPC) and medium-end digital camera photography, and 4) colorimetry and spectrometry. A review of these methods elucidates their respective strengths and weaknesses and highlights the importance of considering study-specific attributes in determining which method to choose for field studies of hydric soil colors. Redoximorphic features (RMFs) require methods capable of capturing small and heterogeneous soil surfaces and features such that the MSCC and digital photography are the most appropriate methods; on the other hand, the Nix Color Sensor provides rapid assessment of soil color that does not necessitate rigorous training to overcome biases that might come about in more subjective methods such as the MSCC. Overall, all alternative methods reviewed have their own merits and capacity to complement measurements made by the MSCC. 相似文献
4.
三江平原退化湿地土壤物理特征变化分析 总被引：9，自引：2，他引：9
针对不同退化程度的湿地土壤物理特征的变化进行了分析。首先对退化湿地土壤剖面特征进行了阐述,然后分析了退化湿地土壤的温度特征变化、电导率状况变化、土壤的水分特征变化和土壤容重变化。研究表明,不同退化程度的湿地土壤具有不同的土壤物理性质,在未退化湿地→轻度退化湿地→中度退化湿地→重度退化湿地→已垦湿地(农田)的湿地退化研究样带上,湿地土壤温度呈现逐渐升高的变化趋势、土壤电导率呈降低变化、土壤水分呈降低趋势、土壤容重则呈现升高的变化规律。土壤表层与下层相比较,土壤表层温度、含水量与容重均高于土壤下层;在电导率的变化中,除了未退化湿地土壤的下层高于表层以外,其它退化状态的湿地土壤均为表层高于下层。另外,对退化湿地土壤的各物理特征在空间距离上的退化过程进行模型模拟,发现指数增加(或分解)模型能够较好地模拟出湿地土壤物理特征的空间退化过程。本研究将有助于理解退化湿地土壤物理特征的变化规律和查明湿地的退化机理,为退化湿地的恢复与重建研究奠定科学基础。 相似文献
5.
《Geoderma》2005,124(1-2):181-192
Contents of soil organic matter (SOM) and total nitrogen (TN) in the surface soils and subsurface soils were measured in five types of floodplains classified with different flood frequencies in river marginal wetlands of Erbaifangzi, China, in 1999. Contour maps and profile maps were constructed to describe the spatial distribution of SOM and TN in order to identify the influences of flood frequency on them. Results showed that spatial distributions of both SOM and TN were very similar in soil profiles (0–120 cm) of the five areas, decreasing gradually with depth except an accumulation peak in the flooded floodplain (B area). Also, the accumulation peak in the soil profile of B area was relevant to water table, nitrogen leaching, denitrification and mineralization. However, their horizontal distributions in surface soils (0–10 cm) were different in the five areas. Although the flood could bring the deposit of nutrients and sands, the highest content of SOM or TN did not appear in B area but in the floodplain with certain flood frequency. For example, SOM content (6.76%) in 5-year floodplain wetland was highest, and the highest content of TN (3666.4 mg/kg) appeared in 1-year floodplain wetland. However, SOM and TN contents in soils of B area were 4.08% and 2605.4 mg/kg, respectively. Soil clay content, wetland plant (Phragmites australis) litter inputs, soil moisture and water table greatly affected the spatial distribution of SOM and TN in floodplain wetlands. The ratios of carbon to nitrogen of wetland soils in this region were relatively lower than those in paddy soils. SOM and TN contents were significantly correlated with total phosphorus (TP) contents in floodplain wetlands except the 100-year floodplain wetland, but they were significantly influenced by soil pH values only in B area. Denitrification and ammonia volatilization were the main mechanisms resulting in nitrogen loss of surface soils in B area. Flood frequency significantly influenced the ecological functions such as nutrient retention and water quality maintenance of floodplains. 相似文献
6.
Intense decalcification of fine‐grained organic‐rich soils subject to periodic oxidation and reduction takes place in the Biesbosch, a freshwater, tidally influenced wetland area in the Rhine–Meuse delta in The Netherlands. Soil chemical (sulphide concentration and pore‐water characteristics) and hydrological variables (drainage) were measured in three representative Fluvisols differing in hydrology to identify processes inducing calcium carbonate dissolution. Both oxidation of previously formed iron sulphides during periods of low ground water and infrequent inundation, and increased carbon dioxide pressure in the soil during periods of waterlogging combined with drainage of pore‐water solutes, contribute significantly to decalcification of the hydric soils. The effects of these individual processes on decalcification are in the same order of magnitude in the studied soils. Depending on site‐specific hydrological conditions, approximately 0.1–0.3% calcium carbonate may be dissolved per year by a combination of these two processes, which is comparable to actual decalcification rates at these sites. Estimates of long‐term decalcification rates, based on knowledge of the hydrogeochemistry, may be used to assess the risks accompanying the conversion of agricultural soils into wetlands. 相似文献
7.
Shen Yu 《Soil biology & biochemistry》2009,41(12):2394-2405
Wetlands are subject to changes in soil moisture as a result of both short-term seasonal climate variations and long-term changes in regional water resource management, both of which can modify the dynamics of ground and surface water inputs. In the New Jersey Pinelands, forested wetlands that differ in both plant communities and soil structure occur along a topographic and hydrological gradient associated with an unconfined aquifer. Proposed groundwater withdrawals may affect water content of soils along this gradient. We hypothesized that prolonged changes in soil moisture would alter net nitrogen mineralization and nitrification rates in proportion to the amount of moisture change, and that these changes would be similar for the different soils along the drainage catena. Soils from two catenary sequences of wetlands, including pine-dominated (driest landscape position), hardwood-dominated, and Atlantic white-cedar-dominated (wettest landscape position) communities were used in long-term laboratory incubations (36 weeks). Production of NH4+-N, NO3−-N, and dissolved organic N were measured under two sets of conditions: constant moisture levels of 100%, 60% and 30% water-holding capacity (WHC), and fluctuating moisture levels (alternating 2 week periods at 100% and 30% WHC). In soils from most of the wetlands, we observed increases in net mineralization and nitrification when constant low-moisture conditions were established, but not under fluctuating conditions. Contrary to expectations, responses to the drying treatments varied between wetland types and between replicate wetlands of each type. Under constant-moisture conditions, nitrification increased more in cedar swamps than in either type of pine wetland. Under all conditions, soils from all the wetlands within one of the catenas produced more inorganic and organic soluble N than did the wetlands from the other catena, suggesting that area-wide effects are as important as wetland type in regulating production of soluble N. Within both catenas, pine-hardwood wetlands generated more soluble N under all moisture conditions than did either pine-dominated or cedar wetlands. Our results suggest that changes in soil moisture due to management of water resources will affect N cycling in wetland soils, but that the magnitude of the effects, and the potential for large releases of nitrate, will depend on the specific soil properties of affected wetlands. 相似文献
8.
D. D. Hook W. H. McKee Jr. T. M. Williams S. Jones D. Van Blaricom J. Parsons 《Water, air, and soil pollution》1994,77(3-4):293-320
A four hectare mixed bottomland hardwood site on Ninety Six Creek in the Piedmont of South Carolina near Ninety Six, SC was studied for two years to characterize wetland traits. The soils were thermic Fluventic or Fluvaquentic Dystrochrepts predominantly Shellbluff series and well drained. Overbank flooding occurred on the average of 4 times per year and 1.5 times during the growing season for a 13 year period. High water table levels during the early growing season were related to rainfall events. A hydrologic model (WATRCOM-2D), soils, water table levels, and GIS techniques were used to estimate the portion of the bottom that met wetland criteria similar to those defined in the 1987 and 1989 federal wetland delineation manuals. Less than one hectare met these criteria. The wetland “status” of the vegetation within the bottom and adjacent slope was not correlated with water table levels, predicted wetland areas, or landforms. Wetland traits of the site were closely related to hydric soil traits within the upper 25 cm of the Chewacla and Chenneby soils and landform characteristics. Wetlands in this bottom were primarily driven by local precipitation and not by overbank flooding as originally suspected. Songbirds and small mammals were relatively abundant in the small bottom during the spring and summer of 1992. Protection of only the jurisdictional wetlands in this bottom would not be adequate to sustain riverine functions (conveyor) and to provide wildlife travel corridors between adjacent forested areas. 相似文献
9.
Multistate assessment of wetland restoration on CO2 and N2O emissions and soil bacterial communities
Over the last 200 years, wetlands have been converted to other land uses leading to the loss of approximately 53% of wetlands in the continental United States. In the late 1980's, policies were instated to mitigate further wetland loss through wetland creation and restoration. Restored wetlands provide important ecosystem services, such as filtration of nutrients and wildlife habitat. However, these benefits could be offset by increased greenhouse gas production. We assessed the impact of wetland conversion to agriculture and restoration on CO2 and N2O emissions and microbial communities in three land use types: wetlands with native vegetation (natural); wetlands converted to agricultural management (converted); and restored wetlands (restored). Soil properties varied among land use types. Most notably, soils from restored and converted sites had the lowest C and N, and higher pH. Multivariate analysis of soil properties showed the pocosin wetlands in North Carolina separating from all other locations, regardless of land use. Soil bacterial communities showed a similar trend with communities from North Carolina soils separating from the others with no significant effect of land use or season. Furthermore, land use did not have a significant effect on CO2 or N2O emissions, although there was significant temporal variation in CO2 emissions. These findings indicate that while wetland conversion and restoration may alter some soil properties, these alterations do not appear to be great enough to override the underlying geographic and edaphic influences on soil bacterial communities. Furthermore, wetland restoration did not lead to increased N2O emission at the dates sampled. 相似文献
10.
Land usage is a strong determinant of soil microbial community composition and activity, which in turn determine organic matter decomposition rates and decomposition products in soils. Microbial communities in permanently flooded wetlands, such as those created by wetland restoration on Sacramento-San Joaquin Delta islands in California, function under restricted aeration conditions that result in increasing anaerobiosis with depth. It was hypothesized that the change from agricultural management to permanently flooded wetland would alter microbial community composition, increase the amount and reactivity of dissolved organic carbon (DOC) compounds in Delta waters; and have a predominant impact on microbial communities as compared with the effects of other environmental factors including soil type and agricultural management. Based on phospholipid fatty acid (PLFA) analysis, active microbial communities of the restored wetlands were changed significantly from those of the agricultural fields, and wetland microbial communities varied widely with soil depth. The relative abundance of monounsaturated fatty acids decreased with increasing soil depth in both wetland and agricultural profiles, whereas branched fatty acids were relatively more abundant at all soil depths in wetlands as compared to agricultural fields. Decomposition conditions were linked to DOC quantity and quality using fatty acid functional groups to conclude that restricted aeration conditions found in the wetlands were strongly related to production of reactive carbon compounds. But current vegetation may have had an equally important role in determining DOC quality in restored wetlands. In a larger scale analysis, that included data from wetland and agricultural sites on Delta islands and data from two previous studies from the Sacramento Valley, an aeration gradient was defined as the predominant determinant of active microbial communities across soil types and land usage. 相似文献
11.
From 2006 to 2010, low water levels resulted in the drying of previously submerged inland acid sulphate soils (IASS) in wetlands of the Murray–Darling Basin (MDB). The potential for widespread severe acidification resulting from the oxidation of pyrite in these wetland soils triggered a basin‐wide study to assess the occurrence and risks posed by IASS material in the floodplain wetlands of the MDB. The results of pH measurements before and following soil incubation from more than 7200 samples (representing ca. 2500 profiles from 1055 georeferenced wetlands) were used to assess the potential occurrence of sulphuric and sulphidic material in IASS across the MDB. Their occurrence was investigated on a regional basis by dividing the MDB into 13 geographical regions whose boundaries roughly follow hydrological catchment boundaries. A total of 238 floodplain wetlands, representing 23% of the total wetlands assessed, were found to contain soils that became ultra‐acidic (pH < 4) when oxidized and therefore present a severe acidification hazard. These soils, the majority of which are likely to be IASS materials, were found in 11 of the 13 geographical regions. Among the 11 geographical regions likely containing IASS materials, the proportion of wetlands that presented an acidification hazard varied between 2 and 52% of those assessed. The geographical regions found to present the greatest acidification hazard were in the southern MDB, downstream of the Murray–Darling confluence, and in catchments on the southern side of the Murray River channel in Victoria. This study provided policy makers with a valuable screening tool, which helped them to identify priority wetlands and regions that required more detailed IASS investigations. 相似文献
12.
Junu Shrestha Jean Christophe Clément Joan G. Ehrenfeld Peter R. Jaffe 《Water, air, and soil pollution》2011,220(1-4):213-223
Riparian wetlands are subject to nitrogen enrichment from upgradient agricultural and urban land uses and also from flooding by nitrogen-enriched surface waters. The effects of this N enrichment on wetland soil biogeochemistry may be mediated by both the presence of plants and the presence of redox-active compounds, specifically iron oxides in the soil. Despite the extensive research on wetland N cycling, the relative importance of these two factors on nitrogen is poorly known, especially for forested wetlands. This study evaluates the responses of the N and the Fe cycles to N enrichment in a riparian forested wetland, contrasting vegetated field plots with plots where the vegetation was removed to test the role of plants. Furthermore, in vitro anaerobic incubations of the experimental soils were performed to track Fe chemical changes over time under anoxic or flooded conditions. Wetland soils treated with N in form of urea, as expected, had significantly higher amounts inorganic nitrogen. In the soils where vegetation was also removed, in addition to inorganic nitrogen pool, increase in organic nitrogen pool was also observed. The results demonstrate the role of vegetation in limiting the effects excess urea has on different soil nitrogen pools. Results from anaerobic incubation of the experimental soils demonstrated the effects of N enrichment on the wetland Fe cycle. The effects of excess nitrogen and the role of vegetation on the Fe cycle in riparian wetland soil became more evident during anaerobic incubation experiments. At the end of the field experiment, Fe concentrations in the soils under the treatments were not significantly different from the control soils at the 5% confidence level. However, during the anaerobic incubation experiment of soils collected at the end of the experiment from these plots, the N-enriched soils and the unvegetated soils maintained significantly elevated concentrations of reducible Fe(III) for the initial 2-week period of incubation, and the soils collected from the plots with both the treatments had the highest Fe(III) concentrations. After 20 days of incubation, however, the Fe(III) concentrations decreased to the similar concentrations in all the incubated soils. The study clarifies the roles vegetation play in mediating the effects of N enrichment and also demonstrates that N enrichment does affect wetland redox cycle, which has strong implications on ecosystem services such as water quality improvement. 相似文献
13.
Most of Rwanda's wetlands are being reclaimed under government schemes with the aim of growing rice as the main crop. In the present study, information on farmers' knowledge and perceptions of agricultural wetland management was collected in Cyabayaga and Rugeramigozi wetlands. The two wetlands were selected as representatives for typical reclaimed wetland agriculture in Rwanda. They provide contrasts in both environmental and social terms. Three tools were used to investigate farmers' knowledge and perception of agricultural wetland management: (i) household survey; (ii) focus group discussions; and (iii) transect walk. The major constraints identified by farmers in the two wetlands were water shortage and lack of availability of improved seeds and high prices of fertilisers. The primary benefits from wetlands for farmers are income generation in Cyabayaga and food security in Rugeramigozi. The most commonly reported concern about the wetlands in the Cyabayaga and Rugerameragozi was that they are a source of malaria. Rice is an important crop in both wetlands, whereas farmers in Cyabahaga wish to continue cultivating rice, Rugeramigozi farmers prefer to grow rice only after it has been tested for its adaptability. Farmers have sufficient knowledge on the causes and the potential solutions to overcome most constraints. They know that soil suitability is closely related to relief. They classify soils by a number of criteria and choose crops accordingly. Any programme designed to address wetland management in the region will have to take account of farmers' knowledge and adopt a holistic view of wetland management. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
14.
Xiaofei Yu 《Soil biology & biochemistry》2011,43(6):1308-1320
Soil freeze-thaw cycles in the winter-cold zone can substantially affect soil carbon, nitrogen and phosphorus cycling, and deserve special consideration in wetlands of cold climates. Semi-disturbed soil columns from three natural wetlands (Carex marsh, Carex marshy meadow and Calamagrostis wet grassland) and a soybean field that has been reclaimed from a wetland were exposed to seven freeze-thaw cycles. The freeze-thaw treatments were performed by incubating the soil columns at −10 °C for 1 d and at 5 °C for 7 d. The control columns were incubated at 5 °C for 8 d. After each freeze-thaw cycle, the soil solution was extracted by a solution extractor installed in each soil layer of the soil column, and was analyzed for dissolved organic carbon (DOC), NH4+-N, NO3−-N and total dissolved phosphorus (TDP). The results showed that freeze-thaw cycles could increase DOC, NH4+-N and NO3−-N concentrations in soil solutions, and decrease TDP concentrations. Moreover, the changes of DOC, NH4+-N, NO3−-N and TDP concentrations in soil solutions caused by freeze-thaw cycles were different in various sampling sites and soil layers. The increments of DOC concentrations caused by freeze-thaw cycles were greater in the wetland soil columns than in the soybean field soil columns. The increments of NH4+-N concentrations caused by freeze-thaw cycles decreased with the increase of soil depth. The depth variation in the increments of NO3−-N concentrations caused by freeze-thaw cycles in the wetland soil columns was different from that in the soybean field soil columns. The decrements of TDP concentrations caused by freeze-thaw cycles were greater in columns of Carex marsh and Carex marshy meadow than in columns of Calamagrostis wet grassland and the soybean field. The study results provide information on the timing of nutrient release related to freezing and thawing in natural versus agronomic soils, and have implications for the timing of nutrient application in farm fields in relation to water quality protection. 相似文献
15.
中国湿地土壤碳氮磷生态化学计量学特征研究 总被引：27，自引：0，他引：27
明确区域及全球湿地土壤中是否存在类似“Redfield比值(Redfield ratio)”的碳氮磷(C∶N∶P)比例,是认识湿地生态系统中元素循环,构建湿地物质循环模型的基础。本文基于《中国沼泽志》中有详细土壤理化性质记录的119块沼泽湿地数据,利用数理统计方法,分析了区域尺度上湿地土壤中碳C∶N∶P生态化学计量学特征及分布格局,并探讨了其可能的影响因素。结果表明,中国湿地土壤中C∶N、C∶P和N∶P(摩尔比)平均为18.22、245.22和13.60,高于中国及世界土壤中C∶N、C∶P和N∶P的平均值,C∶N∶P比例平均值为245∶13.6∶1。碳、氮、磷三者之间并不具备显著的两两相关性,说明中国湿地土壤中不存在类似于“Redfield比值”的C∶N∶P比例。相比于N元素,湿地生态系统更多受到P供应的限制。不同湿地类型或不同盐度情况下湿地土壤中C∶N、C∶P和N∶P存在显著性差异,而植被类型对土壤中C∶N、C∶P和N∶P影响不大。相关性分析表明,海拔高度、温度(年平均气温、1月平均气温、7月平均气温、活动积温)及p H是决定湿地土壤中C∶N、C∶P和N∶P的主要因素。考虑到海拔与C∶P及N∶P之间极显著的相关关系,海拔这一非地带性因子是决定湿地土壤C∶N∶P计量学特征的主要因素。 相似文献
16.
黄河口滨岸潮滩不同类型湿地土壤氮素分布特征 总被引：9，自引：0，他引：9
对黄河口滨岸潮滩不同类型湿地土壤氮分布特征进行了对比研究。结果表明,湿地土壤氮以有机氮为主,无机氮所占比例较低且以铵态氮为主。土壤氮水平分布特征明显,TN、NH4+-N和NO3--N含量较高的分别是芦苇湿地、碱蓬-柽柳湿地(过渡带)湿地和芦苇湿地;土壤氮垂直分布特征亦明显,表现为表层土壤氮含量大于下层,其中,TN、NH4+-N和NO3--N含量垂直变化最明显的分别是三棱蔗草-朝天委陵菜湿地、碱蓬湿地和芦苇湿地。影响土壤氮分布的主要因素有水分条件、植被类型及微生物活动等。相关分析表明TN与有机氮、有机质呈极显著正相关(P<0.01),NH4+-N与TP呈显著负相关(P<0.05)。研究发现,植被对调整湿地氮的空间分布有一定作用,从而为湿地生态修复提供了理论依据。 相似文献
17.
鄱阳湖典型洲滩湿地土壤环境因子对植被分布影响研究 总被引：4，自引：0，他引：4
湿地植被生长的影响因素包括非生物因素和生物因素两部分。其中,非生物因素中对湿地植被格局影响较大的主要是水文和土壤环境因子,也是当今湿地生态水文过程研究的热点和重点。通过研究鄱阳湖典型洲滩湿地4种植物群落带下各土壤环境因子的含量变化特征,结合研究区20个植被样方的典范对应分析(Canonical Correspondence Analysis,CCA)排序,分析了鄱阳湖典型洲滩湿地主要土壤环境因子及其对植被分布的影响。结果表明:不同植被群落下的全氮含量有明显差异,依次为苔草带藜蒿-狗牙根带芦苇-苔草带苔草-虉草带;总有机碳与全氮含量大小在不同植被群落带的分异趋势相同,二者存在极显著相关关系;土壤全磷含量随植被群落不同的变化规律不明显;随植被群落带离湖泊水体距离逐渐减小,土壤中速效钾含量有增大的趋势,但程度较小。鄱阳湖典型洲滩湿地土壤有机碳与全氮、有效磷呈极显著相关关系,土壤含水量与土壤有效磷呈显著负相关关系,有效磷与全氮呈极显著相关关系。土壤含水量是影响鄱阳湖湿地研究区植被分布的最主要因素,土壤pH、全钾含量也是影响湿地植被分布的重要土壤环境因子。 相似文献
18.
以东北寒温带不同纬度典型湿地土壤碳氮分布关系为研究对象,遴选漠河湿地、洪河湿地及七星河湿地进行土壤样品的调查采集并进行土壤碳氮分布相关分析,通过构建不同纬度沼泽湿地土壤碳氮含量垂直分布结构,考察不同湿地不同植被类型土壤碳氮分布规律及土壤对植被生长状况的影响。结果表明:土壤氨氮及硝态氮在土壤垂直分布中有明显的表聚现象,含量随土壤深度的增加呈明显下降趋势;七星河湿地及洪河湿地土壤碳氮含量呈显著的线性相关关系,而漠河湿地土壤碳氮含量相关性不显著。本研究通过对东北寒温带不同纬度沼泽湿地土壤碳氮含量分布的研究,旨在对全球沼泽湿地氮循环的研究提供一定的参考作用。 相似文献
19.
Zhongsheng Zhang Xianguo Lu Xiaolin Song Yue Guo Zhenshan Xue 《Journal of Soils and Sediments》2012,12(9):1309-1315
Purpose
The theory of ecological stoichiometry has improved understanding of nutrient circulation processes in ecosystems. The purpose of this work was to study ecological stoichiometric characteristics of carbon, nitrogen and phosphorus in wetland soils of Sanjiang Plain, northeast China.Materials and methods
A Deyeuxia angustifolia wetland (swamp meadow) and a Carex lasiocarpa wetland (marsh) were chosen for collection of soil cores (0?C30?cm depth). Soil organic carbon, total nitrogen and phosphorus were analyzed to study patterns of C/N (R CN), C/P (R CP), N/P (R NP), and C/N/P (R CNP) in wetland soils.Results and discussion
Soil carbon, nitrogen and phosphorus stoichiometry differed between the two wetlands. Soil RCN (0?C30?cm depth) in the D. angustifolia wetland was close to that in C. lasiocarpa wetland (12.97 and 12.80, respectively), but R CP and R NP in C. lasiocarpa soils were significantly higher than those in D. angustifolia soils. R CN changed little within soil profile, without obvious trends in both wetlands. Both R CP and R NP decreased with depth from the surface, and both R CP and R NP were higher at every depth interval in C. lasiocarpa soils compared to D. angustifolia soils. R CN in surface soil (0?C10?cm, organic-rich ??Lo?? layer) was not significantly different from R CN in the entire profile (0?C30?cm, ??La layer??) of D. angustifolia wetland, while R CP and R NP were both significantly different between the Lo and La layers. In Carex lasiocarpa wetland, R CN, R CP and R NP in Lo layer were significant higher than those in La layer. R CNP in La layer of D. angustifolia and C. lasiocarpa wetlands were 65:5:1 and 163:13:1, respectively.Conclusions
Soil R CN was relatively consistent, while R CP and R NP reflected P limitation in wetlands of Sanjiang Plain. Further research is needed to determine whether these ratios hold among other wetland ecosystems. 相似文献20.
William B. Ainslie 《Water, air, and soil pollution》1994,77(3-4):433-444
Section 404 of the dean Water Act (CWA) regulates the discharge of dredged or fill material, which is defined as a pollutant, into waters of the United States by requiring potential dischargers to obtain a permit for such activities. The Section 404(b)(1) Guidelines provide the substantive environmental criteria by which all dredge and fill permit applications are reviewed. The Guidelines consist of 4 basic steps: 1) evaluation of practicable alternatives; 2) evaluation of relation of discharge to other environmental standards; 3) assessment of significant degradation to waters of the U.S.; and 4) assessment of appropriate steps to minimize impacts. Wetland functional assessment is important in steps 1, 3, and 4. The use of wetland functional assessment techniques has typically been hindered by lack of time and resources, among other technical concerns, by the resource agencies implementing the Section 404 program. Functional assessment is critical to the Section 404 program since most decisions revolve around an assessment of wetland functions. The Hydrogeomorphic Classification for Wetlands (Brinson, 1993) and the developing functional assessment procedure shows potential for being rapid and inexpensive, scientifically-based and replicable. It is based upon functional indicators which can be recognized in the field and can form the basis for functional indices. The utility of the HGM procedure is illustrated using an example from West Kentucky. 相似文献