不同退耕年限下菜子湖湿地土壤磷素组分特征变化

选取菜子湖区不同退耕年限(2、5、8、10a和20a)湿地为研究对象,以仍耕作油菜地和原始湿地为参照,分析了土壤全磷(TP)、有效磷(AP)、有机磷(OP)和无机磷(IP)各形态含量,探讨退耕还湖后湿地土壤磷素组分特征变化规律。结果表明:研究区土壤无机磷各形态含量大小顺序为:铁磷(Fe-P:73.55—391.76 mg/kg)钙磷(Ca-P:21.64—108.04 mg/kg)闭蓄态磷(O-P:17.15—29.57 mg/kg)铝磷(Al-P:5.84—25.97 mg/kg),其中Fe-P占了土壤无机磷总量的54.20%—74.13%;退耕还湖2—8a期间,湿地土壤Al-P、Fe-P和O-P含量有逐渐降低趋势,而退耕8—20a后逐渐上升,以Fe-P为主的这3形态磷左右着退耕后土壤无机磷的变化;Ca-P随退耕年限增加整体呈上升趋势,对土壤无机磷的贡献逐渐增加;无机磷占土壤全磷的比例为35.90%—67.27%,主导着退耕后湿地土壤全磷变化;有机磷占土壤全磷的17.82%—50.51%,在退耕2a后下降,随后开始逐渐上升,对退耕后湿地土壤磷库恢复的贡献逐渐增加;其中Fe-P、O-P和Al-P控制着退耕后土壤磷素有效性变化。退耕后水文条件、植被生长和土壤黏粒含量变化不仅影响退耕后湿地土壤磷素组分特征,也影响着退耕后湿地土壤磷素有效性。     

哈尼梯田湿地土壤不同形态磷的时空分布特征

磷是湿地和农业生态系统中的重要元素之一,其中土壤磷形态的迁移转化广受关注。以哈尼梯田湿地为例,分别在哈尼梯田湿地的水稻生长期、收获期和休闲期,采集湿地不同海拔（梯田区上部、中部和下部）和不同深度的土壤（0-20 cm,20-40 cm,40-60 cm,60-80 cm）进行磷形态分析,研究了哈尼梯田湿地土壤中不同形态磷的时空分布规律和影响因素。结果表明：（1）哈尼梯田湿地土壤中总磷（TP）含量均值为318.74 mg/kg,在水稻收获期含量最高,无机磷（IP）含量均值在水稻休闲期最高（85.95 mg/kg）,湿地土壤磷总体呈缺乏状态。（2）受外源磷输入影响,铁铝结合态磷（NaOH-P）占无机磷比重最大,且季节差异性显著（P<0.05）;而钙结合态磷（HCl-P）在各季节无显著差异（P>0.05）,这与湿地生态环境和地质背景有关。（3）哈尼梯田湿地对磷的迁移有截留作用,表现为各形态磷含量总体呈现在上部梯田湿地较高,并随海拔的降低而降低;不同形态磷含量在20-40 cm土层富集。（4）除HCl-P外,其余形态磷与土壤粒径在不同土层表现为负相关;不同土层TP和有机磷（OP）与pH值呈正相关;土壤总有机碳（TOC）与不同形态磷在收获期呈显著负相关（P<0.05）。研究表明了哈尼梯田湿地立体空间结构和人为活动能影响湿地生态系统中磷的分布与迁移循环,该结论可为梯田湿地的可持续发展提供参考。     

农田杂草还田对土壤磷素形态的影响

提高农田土壤磷素的可利用性,减少磷肥施用,对促进农业的可持续发展及缓解全球磷素危机具有重要意义。通过盆栽试验模拟夏季田间植物还田,比较红薯(Ipomoea batatas)、绿豆(Vigna radiata)以及杂草(千金子(Leptochloa chinensis)+水苋菜(Ammannia baccifera)混合) 3种夏季经营模式在还田期间土壤磷形态的变化,探索农田杂草还田提高土壤磷素可利用性的潜力。结果表明:绿豆还田主要通过增加碱性磷酸酶和土壤微生物活性促进有机磷矿化;红薯还田在腐解前期增加土壤速效磷,而后期磷素易流失或被固定成有效性较低的磷形态;杂草还田可以显著提升土壤速效磷,使有效性较低的闭蓄态磷(OP)、磷灰石(Ca₁₀-P)及磷酸铁盐(Fe-P)持续性地向有效性较高的磷酸二钙(Ca₂-P)、磷酸八钙(Ca₈-P)及磷酸铝盐(Al-P)转化,并整体保持在有效性较高的水平。杂草还田使以Ca₈-P形式保留在土壤中的磷素显著增加,提升土壤磷素可利用性的同时减小磷素流失的风险;杂草还田也显著...     

土壤中铁锰的形态分布及其有效性研究

以乌鲁木齐雅马里克山的土壤为研究对象,采用Tessier连续提取法对土壤铁、锰各种化学形态进行浸提.研究了土壤中有效铁、锰和土壤的理化性质与土壤铁、锰形态之间的关系,及对铁、锰在土壤中存在形态的影响;并通过盆栽试验对铁、锰的植物有效性进行了分析.结果表明,土壤铁主要以残渣态为主,占全铁的92.3%,其它形态含量均小于全量的8%.土壤锰主要是以铁锰氧化态和残渣态为主,分别占全锰的49%和41.6%,其它形态含量均小于全量的10%.用二级出水灌溉处理可增加铁、锰的有效性,原污水灌溉不利于铁、锰的供应,土壤缺铁、锰的现象可通过施加一定量的铁盐和锰盐而得以改善.相关分析还表明,土壤的理化性质与铁锰形态之间有一定的相关性.供试土壤的pH值、CaCO3含量、有机质及阳离子交换态等对土壤铁、锰的有效性影响较大.逐步回归分析表明,铁的氧化物结合态对植物最为有效,锰的有机结合态对植物有效性贡献最大.     

鹭鸟栖息对杭州湾湿地土壤磷累积及形态分布的影响

土壤中磷含量对维持生态系统平衡起着重要作用。为研究杭州湾湿地迁徙候鸟栖息以及鸟粪的输入对栖息地土壤生态环境的影响,开展了鹭鸟筑巢树林下（影响区）和无鹭鸟筑巢树林下（对照区）土壤磷累积、土壤及鸟粪磷形态分布研究。结果表明：鹭鸟影响区土壤有机碳（Soil Organic Carbon,SOC）、全氮（Total Nitrogen,TN）、全磷（Total Phosphorus,TP）、有效磷（Available Phosphorus,AP）含量显著高于对照区（P<0.05）;对照区土壤TP含量为718.33 mg/kg,影响区土壤TP平均含量最高可达2040 mg/kg,其中钙结合态磷（Ca-bound P,Ca-P）含量最高,约占55.22%-62.96%,其次是残渣态磷（Residual Phosphorus,RP）、有机磷（Organic Phosphorus,OP）、铁铝结合态磷（Fe/Al-bound P,（Al+Fe）-P））、交换态磷（Exchangeable P,Exch-P）。鸟粪中有机碳（Organic Carbon,OC）、TN、TP含量分别是表层土壤的11.18-40.90倍,94.22-148.11倍,15.41-43.22倍,差异极显著（P<0.01）。TP含量与Exch-P、（Fe+Al）-P、Ca-P、AP极显著正相关,与RP显著正相关,与pH显著负相关。结果表明鸟粪输入使杭州湾湿地土壤TP含量显著提高,Exch-P、（Fe+Al）-P、Ca-P、AP含量均有提高,且占TP百分比增大,鸟粪输入造成了该地土壤磷素累积的同时增加了土壤磷素的流失风险。     

农田土壤中磷素有效性及影响因素

土壤中磷的有效性直接决定着农田生产力. 基于分布于我国不同气候区长期定位施肥试验,总结了不同农田土壤的磷素含量、有效性及转化的影响因素.结果表明： 目前我国不同类型的土壤中全磷含量在0.31～1.72 g·kg^-1,速效磷含量在0.1～228.8 mg·kg^-1.土壤母质、理化性质和施肥方式是影响农田土壤磷素有效性的主要因素,未来应注重有机肥和化肥的混合施用以提高农田土壤磷素有效性,并关注可能导致的环境影响.     

林下养鸡年限对杨树人工林土壤磷素形态和生物有效性的影响

林下养殖是一种经济有效的林地空间利用方式,但长期高负载的林下养殖对林地土壤性状究竟产生何种影响,目前尚无定论.以不同林下养鸡年限(0年、1年、3年和5年)的美洲黑杨(Populus deltoides)人工林为对象,采用Hedley磷素分级法,分析其林地土壤的磷素组成和形态变化,探讨林下养鸡年限对土壤磷库特征及其生物有...     

农田开垦对三江平原湿地土壤种子库影响及湿地恢复潜力

种子库是湿地植被恢复的重要途径之一,不同时期的耕作土壤中残留的种子对开垦湿地恢复具有重要的作用.本文采用温室萌发法在两种水分条件下对三江平原天然湿地、不同开垦年限湿地种子库结构和规模进行了研究,以了解不同开垦年限湿地种子库特征及其在湿地植被恢复中的潜力.本次实验共萌发物种50种,随着开垦年限增加,萌发物种逐渐减少,天然湿地、开垦1年、3年、10年、20年的湿地分别为34种、31种、21种、21种和8种,萌发物种数与种子库规模均表现出极显著差异(F1=8.32,F2=5.946,P＜0.001).种子库密度以天然湿地和开垦1年湿地最大,分别为7624粒/m2,9836粒/m2.随着开垦年限增加,种子库规模逐渐减小,开垦3年、10年种子库密度为4336粒/m2,4872粒/m2.开垦20 a后,显著减少为432粒/m2.湿润条件下萌发物种数及种子密度显著高于淹水处理,种子库具有明显的分层现象,0-5 cm土层种子库规模显著高于5-10 cm.小叶章(Calamagrostis angustifolia)作为该地区优势物种,由最初的1192粒/m2,经过20 a开垦后在种子库中消失.研究表明,在一定的开垦年限范围内,开垦湿地土壤中仍然保留大量的湿地物种种子,在湿地恢复中具有重要的作用.     

丘岗稻田地下水位动态及对土壤氮磷有效性的影响

对红壤丘岗区渍潜田地下水位动态变化规律及对土壤氮磷有效性的影响进行了研究。结果表明,渍潜田地下水位的月变化具有十分明显的规律性,一般以秋冬季节（1－3月份和9－12月份）地下水位最低,而以春夏季节（4－8月份）地下水位最高,故以早稻受渍害最为严重,其原因主要是受降雨和灌溉的共同影响。根据渍潜田地下水位的变化特点不同,可将其分为地下水位和相对稳定型和非稳定型两种类型,并提出了相应的水分管理模式,地下水位的变化能明显影响土壤养分的有效性,随着地下水位的升高,土壤有效氮和磷含量下降。渍潜田土Fe-P和O－P含量也有随地下水位的升高而呈下降的趋势,其含量亦显著低于非渍潜田土壤,因而导致了土壤磷素有效性的下降。     

Improving fertiliser efficiency on calcareous and alkaline soils with fluid sources of P,N and Zn

Alkaline calcareous or sodic soils represent an important proportion of the world's arable soils and are important for cereal production. For calcareous soils in general, despite high applications of P fertiliser for many years, P deficiency in cereals is common. Field experiments were conducted to test the relative ability of granular (e.g. DAP, MAP and TSP) and fluid fertilisers to supply P to wheat on grey calcareous and red brown calcareous sandy loam soils (Calcixerollic xerochrepts). A pot experiment was also conducted with these soils and with two non-calcareous alkaline soils to investigate the effects of placement on the efficiency of fertiliser performance. In 1998, fluid and granular sources of P, N and Zn were compared in the field by banding below the seed at sowing. In 1999, MAP applied as granular, and technical grade MAP applied as fluid, were compared as sources of P in rate response experiments. First year results showed that fluid sources of P, N and Zn produced significantly more grain than the granular product. In the following year, fluid fertilisers were found to produce significantly higher response curves for shoot dry weight, grain yield and P uptake in grain. At a commercial rate of 8 kg P ha^–1, fluid fertiliser produced between 22% and 27% more grain than the granular product. Soil moisture and fertiliser placement effects are implicated in the higher efficiency of fluid fertilisers.     

Planktonic phosphorus pool sizes and cycling efficiency in coastal and interior British Columbia lakes

1. Limnologists have long acknowledged the importance of phosphorus (P) in determining the organism biomass and productivity of lake ecosystems. Despite a relatively large number of studies that have examined P cycling in lake ecosystems, there remain several substantial methodological issues that have impeded our understanding of P cycling in limnetic plankton communities. Two critical issues confronting ecologists are (1) a lack of precise measurements of the dissolved inorganic phosphorus (PO) and (2) accurate or complete measurements of dissolved P regeneration rates by plankton communities. 2. Here, we examine patterns of epilimnetic planktonic P pool sizes and turnover rates in eight lakes in British Columbia, Canada over a 2‐year period. We determine the concentrations and turnover times of P in various planktonic compartments (dissolved and various planktonic size fractions), using recently developed methods for estimating phosphate concentration and planktonic regeneration rates. 3. The pico‐ and nanoplankton size fraction (0.2–20 μm) played a central role in planktonic P cycling in lakes examined by this study. On average across lakes, pico‐ and nanoplankton contained >60% of the planktonic P, accounted for >90% PO uptake, and contributed 50% of the plankton community dissolved P regeneration rate. 4. PO concentrations determined by steady state bioassays (ssPO) were extremely low (87–611 pmol L⁻¹) and were 2–3 orders of magnitude less than simultaneously measured colorimetric soluble reactive phosphorus estimates. Lake ssPO concentrations increased linearly with total phosphorus (TP), and the slope of this relationship was approximately 1, indicating that PO remained a consistent proportion of the TP pool across a range of TP concentrations. 5. Turnover rates of the total planktonic P pool and the <20 μm pool became more rapid with increasing lake TP, indicating that, according to this metric, planktonic P cycling efficiency increased with TP concentrations. We also detected a significant relationship between particulate phosphorus (PP) <20 μm turnover time and seston N : P ratios, with PP <20 μm turnover times becoming slower with increasing seston N : P. These findings suggest that long‐standing conceptual models of nutrient cycling that predict slower cycling rates and decreasing cycling efficiency with increasing TP concentrations require further empirical examination. We postulate that patterns in lake P turnover and cycling efficiency are a result of complex interactions between plankton biomass and composition, and the ratios of multiple nutrients (C, N, P), rather than solely a function of the TP pool.     

湿地农田生态系统的特点及其调节

所谓湿地,系一个笼统的名称,直到目前并没有确切的定义。通常认为凡受地下水与地表水影响的土地均可称为湿地。它又可区分为两大类,即自然湿地与人工湿地,区别在于受不受人为活动干扰及其干扰程度。湿地包括沼泽型土壤、草甸型土壤与稻田土壤,稻田土壤在我国早期的土壤分类系统中也归为湿地族。近年来,国外对湿地研究十分活跃,从已有文献看其概念也欠确切,且因目的不同而有一定出入。例如在W.Z.Mitsh所著《湿地》一书中就引用了如下几种概念: 1.湿地系为浅水或间歇浅水层所淹没的低地,包括有植被着生的浅水湖区。2.水位接近或高于地表的土地,或者由于长期水分饱和形成的湿地,或者是具有水成土过程的土地,包括水成土以及适于水生植物     

Dynamics of nitrogen and phosphorus retention during wetland ecosystem succession

We compared the mechanisms of nitrogen (N) and phosphorus (P) removal in four young (<15 years old) constructed estuarine marshes with paired mature natural marshes to determine how nutrient retention changes during wetland ecosystem succession. In constructed wetlands, N retention begins as soon as emergent vegetation becomes established and soil organic matter starts to accumulate, which is usually within the first 1–3 years. Accumulation of organic carbon in the soil sets the stage for denitrification which, after 5–10 years, removes approximately the same amount of N as accumulating organic matter, 5–10 g/m²/yr each, under conditions of low N loadings. Under high N loadings, the amount of N stored in accumulating organic matter doubles while N removal from denitrification may increase by an order of magnitude or more. Both organic N accumulation and denitrification provide for long-term reliable N removal regardless of N loading rates. Phosphorus removal, on the other hand, is greatest during the first 1–3 years of succession when sediment deposition and sorption/precipitation of P are greatest. During this time, constructed marshes may retain from 3 g P/m²/yr under low P loadings to as much as 30 g P/m²/yr under high loadings. However, as sedimentation decreases and sorption sites become saturated, P retention decreases to levels supported by organic P accumulation (1–2 g P/m²/yr) and sorption/precipitation with incoming aqueous and particulate Fe, Al and Ca. Phosphorus cycling in wetlands differs from forest and other terrestrial ecosystems in that conservation of P is greatest during the early years of succession, not during the middle or late stages. Conservation of P by wetlands is largely regulated by geochemical processes (sorption, precipitation) which operate independently of succession. In contrast, the conservation of N is controlled by biological processes (organic matter accumulation, denitrification) that change as succession proceeds.     

Mobility, solubility and lability of fluid and granular forms of P fertiliser in calcareous and non-calcareous soils under laboratory conditions

Despite a long history of application of phosphorus fertilisers, P deficiency is still a major limitation to crop production on calcareous soils. Recent field research conducted in highly calcareous soils in southern Australia has demonstrated that both grain yield and P uptake of wheat (Triticum aestivum L.) is greater when fluid forms of P are used compared to granular forms. To improve our understanding of the mechanisms underlying this response to P in the field, we compared the lability, solubility and mobility of P applied as either a fluid (3 products) or granular (3 products) form to two calcareous and one alkaline non-calcareous soils in the laboratory. Over a five-week period, between 9.5 and 18 % of the P initially present in the fertiliser granules did not diffuse into the surrounding soil. The degree of granule dissolution was independent of the soil type. In contrast, P solubility, lability and diffusion were significantly greater when fluid products were applied to the calcareous soils, but not to the alkaline non-calcareous soil. These findings are discussed in relation to field trials results where fluid products outperformed granular fertilisers.     

Phosphorus cycling and partitioning in an oligotrophic Everglades wetland ecosystem: a radioisotope tracing study

1. Our goal was to quantify short‐term phosphorus (P) partitioning and identify the ecosystem components important to P cycling in wetland ecosystems. To do this, we added P radiotracer to oligotrophic, P‐limited Everglades marshes. ³²PO₄ was added to the water column in six 1‐m² enclosed mesocosms located in long‐hydroperiod marshes of Shark River Slough, Everglades National Park. Ecosystem components were then repeatedly sampled over 18 days. 2. Water column particulates (>0.45 μm) incorporated radiotracer within the first minute after dosing and stored 95–99% of total water column ³²P activity throughout the study. Soluble (<0.45 μm) ³²P in the water column, in contrast, was always <5% of the ³²P in surface water. Periphyton, both floating and attached to emergent macrophytes, had the highest specific activity of ³²P (Bq g^?131P) among the different ecosystem components. Fish and aquatic macroinvertebrates also had high affinity for P, whereas emergent macrophytes, soil and flocculent detrital organic matter (floc) had the lowest specific activities of radiotracer. 3. Within the calcareous, floating periphyton mats, 81% of the initial ³²P uptake was associated with Ca, but most of this ³²P entered and remained within the organic pool (Ca‐associated = 14% of total) after 1 day. In the floc layer, ³²P rapidly entered the microbial pool and the labile fraction was negligible for most of the study. 4. Budgeting of the radiotracer indicated that ³²P moved from particulates in the water column to periphyton and floc and then to the floc and soil over the course of the 18 day incubations. Floc (35% of total) and soil (27%) dominated ³²P storage after 18 days, with floating periphyton (12%) and surface water (10%) holding smaller proportions of total ecosystem ³²P. 5. To summarise, oligotrophic Everglades marshes exhibited rapid uptake and retention of labile ³²P. Components dominated by microbes appear to control short‐term P cycling in this oligotrophic ecosystem.     

A technique for studying rhizosphere processes in tree crops: soil phosphorus depletion around camellia (Camellia japonica L.) roots

Rhizosphere studies on tree crops have been hampered by the lack of a satisfactory method of sampling soils at various distances in the rhizosphere. A modified root study container (RSC) technique developed for annual crops, grasses and legumes was used to study the mechanisms by which camellia plants (Camellia japonica L.) utilise soil P in the glasshouse and field. Plants belonging to the Camellia family (e.g. tea) have the ability to utilise P from relatively unavailable native P sources and for this reason camellia plants were selected for this study.In the glasshouse trial, the RSCs were filled with a Recent soil, treated with P fertilisers; North Carolina phosphate rock (NCPR), diammonium phosphate (DAP), mono calcium phosphate (MCP) and single superphosphate (SSP) at 200 g P g^-1 soil. A planar mat of roots was physically separated by a 24 m polyester mesh and the soil on the other side of this mesh was cut into thin slices parallel to the rhizoplane and analysed for pH, and different forms of P (organic, P_o and inorganic, P_i) to understand P depletion at different distances from camellia roots. In the field trial this technique was modified and used to study the rhizosphere processes in mature camellia trees fertilised with only SSP and NCPR.In both field and glasshouse trials, all P fertilisers increased all the bulk soil P fractions except NaOH-P_o over unfertilised soil with the greatest increases being in the H₂SO₄-P_i fraction in the NCPR treatment and NaOH-P_i in the SSP treatment. Resin-P, NaOH-P_i and H₂SO₄-P_i were significantly lower in the rhizosphere soil compared to the bulk soil whereas NaOH-P_o was higher in the rhizosphere soil than in the bulk soil. Plant and microbial P uptake were thought to be the major causes for the low resin-P rather than P fixation by Fe and Al because the NaOH-P_i fraction which is a measure of Fe-P and Al-P, also decreased in the rhizosphere soil. The rhizo-deposition of NaOH-P_o suggests that labile inorganic P was immobilized by rhizosphere microbes which were believed to have multiplied as a result of carbon exudates from the roots. A marked reduction in pH (about 0.2–0.4 in the glasshouse and 0.2 in the field trial) was observed near the rhizoplane compared to that in the bulk soil in all treatments. The pH near the rhizoplane as well as in the bulk soil was highest for NCPR treated soil. The increase in pH in the NCPR treatment over the control was consistent with the number of protons consumed during the dissolution of NCPR. In both trials, the dissolution of NCPR in the rhizosphere was higher than in the bulk soil due to lower pH and plant uptake of solution P in the rhizosphere. The RSC technique proved to be a viable aid to study the rhizosphere processes in tree crops.     

白骨壤模拟湿地系统中磷的分配循环及其净化效应

在温室中建立红树林植物白骨壤模拟湿地系统 ,分别用正常、5倍和 10倍 3种不同浓度的人工配置的污水每周定时定量对模拟系统进行污灌 1a。研究营养污染物 P在系统中的分配、循环及其被净化的效果。结果表明 :随污水处理浓度的升高 ,被更换的潮汐水中的含 P量和土壤含 P量都有明显提高 ;植物体各部分含 P量的高低顺序排列为 :叶 >茎 >根 ;在植物 -土壤系统中4个组分 CA0 、CA1 、CA5和 CA1 0 植物中 P元素的周转期依次为 4 .70 a、4 .6 1a、3.80 a和 5 .4 4 a;模拟植物 -土壤系统对污水中 P的净化效果显著 ,CA1 、CA5和 CA1 0 组的净化率分别为 81.2 3%、94 .4 0 %和 95 .6 3%。     

水溶性有机物对水田土壤中水溶性氮磷含量及其利用率的影响

采用田间微区试验,研究了施用有机物料对土壤氮磷的变化动态及活性的影响.结果表明,水稻生长过程中土壤溶液中水溶性氮（铵态氮、硝态氮）及磷的含量都随着时间的延长而下降,且氮、磷含量的变化与施入的化学肥料量以及溶液中DOC含量有关;有机物料施用增加了水稻的生物量和对氮、磷的吸收利用;15N示踪显示,与对照的化肥处理相比,施用有机物料处理的微区氮肥利用率及土壤残留率明显增加,同时减少了土壤氮磷的损失.