辽东山区次生林生态系统主要林型土壤磷素特征

磷是植物生长发育所必需的营养元素之一，由于磷在土壤中的难溶性和难移动性，使得磷在陆地生态系统的循环越来越受到重视，尤其是在明确土壤磷素存在形态和分布特征的基础上，探讨土壤磷素与土地利用方式以及植被生长发育状况之间的关系，对于指导土地利用和恢复植被建设具有重要意义。本研究以辽东山区天然次生林主要林型胡桃楸林、杂木林（由蒙古栎、花曲柳和山杨等树种组成）和蒙古栎林为主要研究对象，系统研究了辽东山区天然次生林土壤磷素的分布特征，并比较研究了落叶松人工林取代天然次生林后土壤磷素的变化特征。主要结论如下： 1. 辽东山区天然次生林土壤磷素特征：（1）次生林0-30 cm土壤全磷含量的变化范围为326.5 mg kg-1-984.9 mg kg-1，土壤总有机磷含量、总无机磷含量、Olsen-P含量和土壤微生物量磷含量占全磷含量的比例变化范围分别为47%-76%、24%-53%、1.23%-1.40%和2.67%-3.45%，土壤全磷与土壤有机碳、全氮之间呈显著正相关，说明次生林土壤有机质含量是影响土壤磷素含量的主要因素之一；土壤Olsen-P和微生物量磷季节变化明显，均表现为夏季最高，且土壤Olsen-P和微生物量磷的季节变化规律不受植被类型的影响；另外，土壤Olsen-P、土壤微生物量磷的季节变化均与土壤含水量相关。（2）三个林型土壤酸性磷酸酶与土壤有机碳、全氮、全磷、Olsen-P和微生物量磷之间存在密切的相关性，酸性磷酸酶可以作为评价次生林土壤磷素状况的一个指标。（3）不同林型土壤各形态无机磷分布不同，胡桃楸林以Fe-P（铁结合的磷酸盐）和Ca-P（钙结合的磷酸盐）为主，杂木林和蒙古栎林以O-P（闭蓄态磷）为主；不同林型土壤各形态无机磷随季节的变化规律不同，与Olsen-P的关系也不同，胡桃楸林土壤Olsen-P与Al-P（铝结合的磷酸盐）之间具有显著的相关性，杂木林土壤Olsen-P与Fe-P和Ca-P之间相关性显著，蒙古栎林土壤Olsen-P与Ca-P之间显著相关，说明辽东山区不同林型土壤磷素的有效来源不同。（4）辽东山区有机磷各形态的分布特征为：中等活性有机磷 > 中等稳定性有机磷 > 高稳定性有机磷 > 活性有机磷；土壤活性有机磷的季节变化与Olsen-P变化一致，中等活性有机磷、中等稳定性有机磷和高等稳定性有机磷的含量随季节变化无此规律；胡桃楸林、蒙古栎林土壤Olsen-P与活性有机磷、中等稳定性有机磷和高等稳定性有机磷之间显著相关，杂木林土壤Olsen-P与活性有机磷、中等活性有机磷、中等稳定性有机磷和高等稳定性有机磷之间相关性显著，说明在本研究区土壤有机磷对磷素有效性的贡献较大。（5）三个林型内主要树种叶片磷含量均较高，且叶片N/P < 10，土壤磷素不是辽东山区次生林植被生长的限制性养分因子。 2. 落叶松人工林取代天然次生林后土壤磷素特征的变化：（1）和天然次生林相比，落叶松人工林土壤全磷、总有机磷、Olsen-P、土壤微生物量磷和磷酸酶活性均显著降低（P<0.05），土壤总无机磷含量无明显变化，这说明次生林转变为落叶松人工林后土壤磷素状况下降。（2）随着次生林转变为落叶松人工林和落叶松人工林连栽后，土壤无机磷各形态含量变化显著，土壤Fe-P和Ca-P含量逐渐降低，O-P含量升高，土壤Olsen-P与无机磷形态中的Fe-P和Ca-P之间显著正相关，表明了Fe-P和Ca-P是Olsen-P的主要无机磷来源。（3）落叶松人工林取代次生林后，土壤活性有机磷、中等活性有机磷、中等稳定性有机磷和高等稳定性有机磷含量均降低，土壤Olsen-P与活性有机磷显著正相关，活性有机磷是补充Olsen-P的直接有机磷源；土壤微生物量磷与各有机磷组分及 Olsen-P含量之间均呈显著正相关，这说明微生物量磷在有机磷转化中起着重要作用。

不同土壤磷流失过程模拟研究

本研究通过室内培养、淋溶模拟和径流模拟试验，分别对酸性土壤（红壤）和不同质地碱性土壤（潮褐土和黑钙土）磷流失过程进行模拟研究。结果表明，不同土壤相同水分条件下，土壤磷流失潜能不同：潮褐土磷流失潜能最强，黑钙土次之，红壤最低。不同水分条件下，相同土壤磷流失潜能也不同：淹水条件土壤磷流失潜能最高，其次为先干后湿条件和先湿后干条件，好气条件和淋溶最低。各种条件下土壤磷流失潜能均随施磷量的增加而增大。施肥初期或土壤环境变化初期，土壤磷通过地表径流和优先流流失的风险较高；通过基质流流失的磷在土壤中逐渐向下迁移，故磷流失风险发生在施肥后期。 分段模型（Split Line）方法适合于预测土壤磷通过径流向地表水或通过优先流向地下水体的流失，但不适合预测土壤磷通过基质流的流失。应针对土壤不同水分条件分别使用分段模型方法。若不考虑土壤不同水分条件，则用淹水条件下的临界值较为安全。在预测通过基质流淋失的磷时，使用深层土壤CaCl2-P磷含量较使用表层土壤磷含量更为合理。对于红壤，由于在各种培养条件下土壤Bray-P的变化趋势与CaCl2-P较为一致，且土壤Bray-P的分辨度较高，用土壤Bray-P表征磷流失潜能优于Olsen-P。 综合各种水分条件，红壤土壤磷流失安全值为Bray-P含量低于130 mg kg-1，黑钙土为Olsen-P含量低于138.2mg kg-1，潮褐土为Olsen-P含量低于88.9mg kg-1。

潮棕壤不同利用方式下植物线虫垂直分布研究(英文)

2003 年11 月,在中国科学院沈阳生态实验站潮棕壤经过不同利用方式后对水稻田、玉米地、撂荒地和林地开展了植物线虫垂直分布(0–15 cm 各土层)特征研究。研究结果表明:不同土地利用方式下的某些优势属线虫随着土壤深度增加而呈下降趋势。螺旋属(Helicotylenchus)线虫是4 种土地利用方式中最优势的属。水田丝尾属(Filenchus)、平滑属(Psilenchus)和垫刃属(Tylenchus)线虫主要分布在上层(0–20 cm),而撂荒地、林地中的针属(Paratylenchus)线虫及玉米地中的短体属(Pratylenchus)线虫能够分布在更深的土层(0–80 cm)。本研究揭示,植物线虫优势属数量与土壤化学特性指标存在显著相关关系。不同利用方式螺旋属线虫数量与土壤C/N 比、全碳、全氮、全磷、碱解氮及Olsen-P含量呈显著正相关;水田丝尾属和平滑属线虫、玉米地短体属线虫、撂荒地针属线虫与土壤pH 程显著负相关,与土壤全碳、全氮及碱解氮呈显著正相关。为了更正确地评价植物线虫种群数量,有必要根据植物线虫优势属的垂直分布特征来确定取样深度。图1 表1 参21。

磷素活化剂对黑土磷形态及有效性影响的研究

试验研究了不同温度下活化剂对黑土各形态磷的影响,阐述了活化剂对Olsen-P影响的机制。结果显示,活化剂具有很好的增加土壤中有效磷的能力,在不同的温度条件下作用效果不同,施肥条件下,高温加速磷的固定。10℃时,3种活化剂活化能力为柠檬酸铵>腐植酸>活化剂H2,分别提高土壤Olsen-P的含量达40.93%、33.06%、23.20%;20℃时,活化能力为腐植酸>柠檬酸铵>活化剂H2,分别提高土壤Olsen-P含量达32.35%、24.89%、16.72%;30℃时,与CK相比Olsen-P含量没有明显增加。活化剂能促进各形态无机磷之间的转化,活化能力随温度升高而逐渐降低。SPSS分析结果证实,Al-P和Ca2-P是黑土有效磷的主要组分,与Olsen-P极相关;Ca8-P起负作用,而Fe-P作用效果不显著,但它们仍能通过影响Al-P和Ca2-P来间接影响Olsen-P。

长期定位施肥对黑垆土剖面养分分布特征的影响

对黄土高原旱地 1 5年连续施肥后土壤剖面养分分布的研究发现 ,施化肥对土壤剖面有机质、全N、全P含量的影响深达 1 0 0cm以下 ,所有施肥处理有机质、全N、全P、NO3- N、有效P含量在耕层 (0～ 2 0cm)都有不同程度增加 ;40～ 60、60～ 80cm土层有机质、全N、全P都低于长年不施肥处理 ,造成土壤下层养分的亏缺。长期大量施用氮肥造成N素养分下淋累积 ;长期大量施用磷肥土壤耕层有效P显著提高 ,而 2 0cm以下土层变化不大。

田块尺度下土壤磷素的空间变异性

采用经典统计学与地统计学相结合的方法,对中国科学院沈阳生态实验站30 m×42 m样地进行网格法分层(0~10和10~20 cm)取样,研究了田块尺度下土壤全P和Olsen-P的空间变异特征.结果表明,49对样本土壤Olsen-P的变异系数(46.56%~56.42%)远高于全P(11.68%~13.33%);全P和Olsen-P具有较好的空间结构且具有较相近的空间相关距离.最佳理论模型的参数显示各变量空间变异主要受结构性因素的影响,各变量半方差变异函数的C/(C0+C)均高于66%.全P和Olsen-P之间及在2个土层之间均具有较相似的空间分布格局.变异系数结合空间格局分析可以大大降低试验取样的数量.

温度对黑土磷形态及有效性影响

试验研究了不同温度对黑土磷形态及有效性的影响,结果显示:不施磷和施磷情况下,Ca2-P、Ca8-P、Fe-P含量均随温度的升高而增加;Al-P含量则随温度升高而减少;Olsen-P的含量,在不施磷时随温度升高而增加,且30℃时效果要明显好于10℃和20℃,施磷时,则随温度升高而减少。不施磷情况下,有效磷和各形态的无机磷含量均随培养时间的延长而增加;施磷时,除Ca8-P含量增加外,其它各形态磷均随培养时间延长而减少。通过相关分析和回归分析得出,黑土中磷的主要组分是Al-P和Ca2-P,并得出了它们与Olsen-P的回归方程:Y=-0.958+0.675X(1 Ca2-P)+0.286X(3 Al-P)。

Controls on the contemporary distribution of lake thecamoebians (testate amoebae) in the Greater Toronto Area and their potential as water quality indicators.

Thecamoebians were examined from 71 surface sediment samples collected from 21 lakes and ponds in the Greater Toronto Area to (1) elucidate the controls on faunal distribution in modern lake environments; and (2) to consider the utility of thecamoebians in quantitative studies of water quality change. This area was chosen because it includes a high density of kettle and other lakes which are threatened by urban development and where water quality has deteriorated locally as a result of contaminant inputs, particularly nutrients. Fifty-eight samples yielded statistically significant thecamoebian populations. The most diverse faunas (highest Shannon Diversity Index values) were recorded in lakes beyond the limits of urban development, although the faunas of all lakes showed signs of sub-optimal conditions. The assemblages were divided into five clusters using Q-mode cluster analysis, supported by Detrended Correspondence Analysis. Canonical Correspondence Analysis (CCA) was used to examine species-environment relationships and to explain the observed clusterings. Twenty-four measured environmental variables were considered, including water property attributes (e.g., pH, conductivity, dissolved oxygen), substrate characteristics, sediment-based phosphorus (Olsen P) and 11 environmentally available metals. The thecamoebian assemblages showed a strong association with phosphorus, reflecting the eutrophic status of many of the lakes, and locally to elevated conductivity measurements, which appear to reflect road salt inputs associated with winter de-icing operations. Substrate characteristics, total organic carbon and metal contaminants (particularly Cu and Mg) also influenced the faunas of some samples. A series of partial CCAs show that of the measured variables, sedimentary phosphorus has the largest influence on assemblage distribution, explaining 6.98% (P < 0.002) of the total variance. A transfer function was developed for sedimentary phosphorus (Olsen P) using 58 samples from 15 of the studied lakes. The best performing model was based on weighted averaging with inverse deshrinking (WA Inv, r jack 2= 0.33, RMSEP = 102.65 ppm). This model was applied to a small modern thecamoebian dataset from a eutrophic lake in northern Ontario to predict phosphorus and performed satisfactorily. This preliminary study confirms that thecamoebians have considerable potential as quantitative water quality indicators in urbanising regions, particularly in areas influenced by nutrient inputs and road salts.

Development of an Arcellacean (testate lobose amoebae) based transfer function for sedimentary phosphorous in lakes.

Arcellacea (testate lobose amoebae) communities were assessed from 73 sediment-water interface samples collected from 33 lakes in urban and rural settings within the Greater Toronto Area (GTA), Ontario, Canada, as well as from forested control areas in the Lake Simcoe area, Algonquin Park and eastern Ontario. The results were used to: (1) develop a statistically rigorous arcellacean-based training set for sedimentary phosphorus (Olsen P (OP)) loading; and (2) derive a transfer function to reconstruct OP levels during the post-European settlement era (AD1870s onward) using a chronologically well-constrained core from Haynes Lake on the environmentally sensitive Oak Ridges Moraine, within the GTA. Ordination analysis indicated that OP most influenced arcellacean assemblages, explaining 6.5% (p < 0.005) of total variance. An improved training set where the influence of other important environmental variables (e.g. total organic carbon, total nitrogen, Mg) was reduced, comprised 40 samples from 31 lakes, and was used to construct a transfer function for lacustrine arcellaceans for sedimentary phosphorus (Olsen P) using tolerance downweighted weighted averaging (WA-Tol) with inverse deshrinking (RMSEPjack-77pp; r2jack = 0.68). The inferred reconstruction indicates that OP levels remained near pre-settlement background levels from settlement in the late AD 1970s through to the early AD 1970s. Since OP runoff from both forests and pasture is minimal, early agricultural land use within the lake catchment was as most likely pasture and/or was used to grow perennial crops such as Timothy-grass for hay. A significant increase in inferred OP concentration beginning ~ AD 1972 may have been related to a change in crops (e.g. corn production) in the catchment resulting in more runoff, and the introduction of chemical fertilizers. A dramatic decline in OP after ~ AD 1985 probably corresponds to a reduction in chemical fertilizer use related to advances in agronomy, which permitted a more precise control over required fertilizer application. Another significant increase in OP levels after ~ AD 1995 may have been related to the construction of a large golf course upslope and immediately to the north of Haynes Lake in AD 1993, where significant fertilizer use is required to maintain the fairways. These results demonstrate that arcellaceans have great potential for reconstructing lake water geochemistry and will complement other proxies (e.g. diatoms) in paleolimnological research.

Testate amoebae (thecamoebians) as water quality indicators in lakes: development of a modern distributional dataset from the Greater Toronto Area

Thecamoebians were examined from 123 surface sediment samples collected from 45 lakes in the Greater Toronto Area (GTA) and the surrounding region to i) elucidate the controls on faunal distribution in modern lake environments; and ii) to consider the utility of thecamoebians in quantitative studies of water quality change. This area was chosen because it includes a high density of lakes that are threatened by urban development and where water quality has deteriorated locally as a result of contaminant inputs, particularly nutrients. Canonical Correspondence analysis (CCA) and a series of partial CCAs were used to examine species-environment relationships. Twenty-four environmental variables were considered, including water properties (e.g. pH, DO, conductivity), substrate characteristics, nutrient loading, and environmentally available metals. The thecamoebian assemblages showed a strong association with Olsen's Phosphorus, reflecting the eutrophic status of many of the lakes, and locally to elevated conductivity measurements, which appear to reflect road salt inputs associated with winter de-icing operations. A transfer function was developed for Olsen P using this training set based on weighted averaging with inverse deshrinking (WA Inv). The model was applied to infer past changes in Phosphorus enrichment in core samples from several lakes, including eutrophic Haynes Lake within the GTA. Thecamoebian-inferred changes in sedimentary Phosphorus from a 210Pb dated core from Haynes Lake are related to i) widespread introduction of chemical fertilizers to agricultural land in the post WWII era; ii) a steep decline in Phosphorous with a change in agricultural practices in the late 1970s; and iii) the construction of a golf course in close proximity to the lake in the early 1990s. This preliminary study confirms that thecamoebians have considerable potential as indicators of eutrophication in lakes and can provide an estimate of baseline conditions.

Response of organically managed grassland to available phosphorus and potassium in the soil and supplementary fertilization: field trials using grass-clover leys cut for silage

Effective use and recycling of manures together with occasional and judicious use of supplementary fertilizing materials forms the basis for management of phosphorus (P) and potassium (K) within organic farming systems. Replicated field trials were established at three sites across the UK to compare the supply of P and K to grass-clover swards cut for silage from a range of fertilizing materials, and to assess the usefulness of routine soil tests for P and K in organic farming systems. None of the fertilizing materials (farmyard manure, rock phosphate, Kali vinasse, volcanic tuff) significantly increased silage yields, nor was P offtake increased. However, farmyard manure and Kali vinasse proved effective sources of K to grass and clover in the short to medium term. Available P (measured as Olsen-P) showed no clear relationship with crop P offtake in these trials. In contrast, available K (measured by ammonium nitrate extraction) proved a useful measurement to predict K availability to crops and support K management decisions.

Effects of manure and fertilizer on grain yield, soil carbon and phosphorus in a 13-year field trial in semi-arid Kenya

Long-term indicators of soil fertility were assessed by measuring grain yield, soil organic carbon (SOC) and soil Olsen phosphorous for a P-deficient soil. In one set of treatments, goat manure was applied annually for 13 years at 0, 5 and 10 t ha(-1), and intercrops of sorghum/cowpea, millet/green gram and maize/pigeonpea were grown. Yield depended on rainfall and trends with time were not identifiable. Manure caused an upward trend in SOC, but 10 t ha(-1) manure did not give significantly more SOC than 5 t ha(-1). Only 10 t ha(-1) manure increased Olsen P. Measurements of both SOC and Olsen P are recommended. In another set of treatments, manure was applied for four years; the residual effect lasted another seven to eight years when assessed by yield, SOC and Olsen P Treatment with mineral fertilizers provided the same rates of N and P as 5 t hat manure and yields from manure and fertilizer were similar. Fertilizer increased Olsen P but not SOC. Management systems with occasional manure application and intermediate fertilizer applications should be assessed. Inputs and offtakes of C, N and P were measured for three years. Approximately 16, 25 and 11% of C, N and P respectively were stabilized into soil organic matter from 5 t ha(-1) a(-1) manure. The majority of organic P was fixed as soil inorganic P.

Effect of manure application on crop yield and soil chemical properties in a long-term field trial of semi-arid Kenya

The sustainability of cereal/legume intercropping was assessed by monitoring trends in grain yield, soil organic C (SOC) and soil extractable P (Olsen method) measured over 13 years at a long-term field trial on a P-deficient soil in semi-arid Kenya. Goat manure was applied annually for 13 years at 0, 5 and 10 t ha(-1) and trends in grain yield were not identifiable because of season-to-season variations. SOC and Olsen P increased for the first seven years of manure application and then remained constant. The residual effect of manure applied for four years only lasted another seven to eight years when assessed by yield, SOC and Olsen P. Mineral fertilizers provided the same annual rates of N and P as in 5 t ha(-1) manure and initially ,gave the same yield as manure, declining after nine years to about 80%. Therefore, manure applications could be made intermittently and nutrient requirements topped-up with fertilizers. Grain yields for sorghum with continuous manure were described well by correlations with rainfall and manure input only, if data were excluded for seasons with over 500 mm rainfall. A comprehensive simulation model should correctly describe crop losses caused by excess water.

Dissolution of phosphorus from animal bone char in 12 soils

Heat-treated animal bone char (ABC) has not previously been evaluated for its potential as a phosphorus (P) fertilizer. ABC, Gafsa phosphate rock (GPR) and triple superphosphate fertilizer (TSP) were incubated in 12 soils. Dissolved-P was assessed by extraction with NaOH and bioavailability with the Olsen extractant. The rate of P dissolution from ABC was described almost equally well by the Elovich and Power equations. After 145 days, the fraction of P dissolved ranged from 0 to 73% and to 56% for ABC and GPR, respectively. The most important soil properties determining P dissolution from ABC were pH and P sorption. P dissolution was not significant at soil pH > 6.1 (ABC) and > 5 (GPR) and the lower the pH, the greater the Dissolved-P. Dissolved-P also correlated positively and significantly with inorganic P sorption, measured by the Freundlich isotherm and the P sorption index of Bache and Williams (1971). Soil pH and P sorption index could be combined in multiple regression equations that use readily measured soil properties to predict the potential for ABC dissolution in a soil. Dissolution of P from GPR correlated with soil pH and exchangeable acidity. In comparison with GPR, ABC was a better source of available P, assessed by Olsen-P. In most soils, ABC increased Olsen-P immediately after application, including soils of relatively high pH in which GPR was ineffective. ABC is a P fertilizer of solubility intermediate between GPR and TSP.

The effect of soil phosphorus on particulate phosphorus in land runoff

Accumulation of surplus phosphorus (P) in the soil and the resulting increased transport of P in land runoff contribute to freshwater eutrophication. The effects of increasing soil P (19–194 mg Olsen-P (OP) kg−1) on the concentrations of particulate P (PP), and sorption properties (Qmax, k and EPCo) of suspended solids (SS) in overland flow from 15 unreplicated field plots established on a dispersive arable soil were measured over three monitoring periods under natural rainfall. Concentrations of PP in plot runoff increased linearly at a rate of 2.6 μg litre−1 per mg OP kg−1 of soil, but this rate was approximately 50% of the rate of increase in dissolved P (< 0.45 μm). Concentrations of SS in runoff were similar across all plots and contained a greater P sorption capacity (mean + 57%) than the soil because of enrichment with fine silt and clay (0.45–20 μm). As soil P increased, the P enrichment ratio of the SS declined exponentially, and the values of P saturation (Psat; 15–42%) and equilibrium P concentration (EPCo; 0.7–5.5 mg litre−1) in the SS fell within narrower ranges compared with the soils (6–74% and 0.1–10 mg litre−1, respectively). When OP was < 100 mg kg−1, Psat and EPCo values in the SS were smaller than those in the soil and vice-versa, suggesting that eroding particles from soils with both average and high P fertility would release P on entering the local (Rosemaund) stream. Increasing soil OP from average to high P fertility increased the P content of the SS by approximately 10%, but had no significant (P > 0.05) effect on the Psat, or EPCo, of the SS. Management options to reduce soil P status as a means of reducing P losses in land runoff and minimizing eutrophication risk may therefore have more limited effect than is currently assumed in catchment management.