外源低分子量有机酸对碳酸钙预处理的酸性土壤中活性铝钙镁影响的研究

通过在所研究的第四纪红黏土发育的红壤中混入CaCO3,研究在pH缓冲体系中外加低分子量有机酸对土壤中Al、Ca和Mg的影响。结果表明:无论加CaCO3与否,在pH 4.5的条件下外源草酸、柠檬酸、苹果酸的加入均使土壤可溶性Al显著提高,交换性Al显著下降和交换性Ca显著升高;加入CaCO3的情况下,3种有机酸处理的交换性Mg均显著提高。3种有机酸促进Al溶解能力的大小顺序为:柠檬酸>草酸>苹果酸,这一结果与有机酸和Al形成络合物的稳定常数大小一致。另一方面,3种有机酸处理下,CaCO3预处理均引起可溶性Al的显著升高和交换性Al的下降。双因素方差分析表明,有机酸通过络合作用或沉淀作用对可溶性和交换性Al、Ca和Mg均具有绝对的影响优势,CaCO3仅对可溶性和交换性Al、交换性Ca有显著影响,由于实验中pH缓冲体系的控制,这种影响主要通过Al与Ca、Mg的竞争交换作用实现。总体来说,外源低分子量有机酸的加入使土壤活性Al显著升高,活性Ca、Mg略有升高,有机酸在酸性土壤中的作用需从有机酸溶解阳离子的角度进一步评价。     

Changes in aluminum pools of andisols due to soil acidification

Abstract

Aluminum concentrations in soil solutions are not only controlled by inorganic clay minerals but also by organically bound aluminum. The objective of this study was to determine which pools contribute to Al dissolution. Soil samples were taken at various distances from tree trunks and at various depths at the Rolling Land Laboratory (RLL), Hachioji, Tokyo. Selective dissolution techniques were used to analyze the changes in pools of solid-phase aluminum. Soil pH values around Hinoki cypresses were in the aluminum buffer range. Exchangeable aluminum contents in soils under Hinoki cypresses were 104 mmol_c kg-^?1 on the average. This value was similar to that of the cation exchange capacity (CEC) of Andisols at RLL at a soil pH of 4. The relationship between the soil pH and exchangeable, organically bound, and amorphous aluminum pools showed that dissolved aluminum ions in the soil solution were primarily derived from the amorphous Al pool. Dissolved aluminum ions were substituted with base cations of soils, resulting in the increase of the content of exchangeable Al and/or the formation of complexes with organic matter which increased the proportion of organically bound Al pools. Increase in the proportion of organically bound Al pools indicated the importance of complexation with soil organic matter for controlling the aluminum concentration in the soil solution.     

The influence of acid soil factors on the growth of snapbeans in major appalachian soils

Abstract

Acid soil limitations to plant growth were assessed In 55 horizons of 14 major Appalachian hill land soils. Aluminum sensitive “Romano” and Al‐tolerant “Dade” snapbeans (Phaseolus vulgaris L.) were grown for 5 weeks in limed and unlimed treatments of the 55 horizons. Shoot and root growth was depressed >20% in unlimed relative to limed treatments in approximately 2/3 of the horizons. Dade snapbeans were generally more tolerant of the acid soil conditions and had higher Ca concentrations in the shoots than Romano snapbeans. However, the sensitive‐tolerant snapbean pair could not consistently be used to identify horizons with soil Al problems. Growth of both snapbeans was generally best in A horizons and worst in E horizons. The E horizons in this study were characterized by low Ca saturation (exchangeable Ca x 100/cation exchange capacity) and high Al saturation (exchangeable Al x 100/cation exchange capacity). Exchangeable Ca, soil Ca saturation and total soil solution Ca were positively correlated (p<0.01) with snapbean root and shoot growth. Soil Al saturation, total soil solution Al and soil solution Al reacting in 15 seconds with 8‐hydroxyquinoline were negatively correlated (p<0.01) with growth. The ratio of Ca/Al in soil solution was more closely related to snapbean growth than the soil solution concentration of any individual element. Soil and soil solution Mn were, in general, not significantly correlated with snapbean growth. Many of the horizons in this study had both Al toxicity and Ca deficiency problems and interaction between Ca and Al affected both snapbean growth and Ca uptake. These findings confirm the importance of considering Ca as well as Al when investigating Al phytotoxicity.     

有机肥替代化学氮肥提升红壤抗酸化能力

  【目的】  长期过量施用化学氮肥加剧了红壤区农田土壤酸化,严重制约着该区域农业的可持续发展。施用石灰和有机肥是防治红壤酸化的主要措施,我们研究了有机无机肥配合提高红壤抗酸化能力的作用与机理。  【方法】  本研究基于2009年在湖南祁阳中国农业科学院红壤站开展的有机肥替代化学氮肥长期定位试验,其中4个处理分别为单施化肥(由于酸化严重,于2018年底添加石灰改良)、有机肥替代化肥氮20%、40%和60%,供试有机肥为猪粪。采集2018和2020年的土壤样品,分析各施肥处理红壤pH、交换性酸铝、阳离子交换量、有机质、酸缓冲能力等指标的变化及相互关系。  【结果】  至2018年,单施化肥处理较试验之初土壤pH降低了0.48个单位,交换性酸、铝分别增加了2.74和1.06 cmol/kg;添加石灰改良后,土壤pH升高了0.58个单位,交换性酸、铝分别降低了2.62和1.45 cmol/kg。有机肥替代化肥氮40%和60%处理均可有效防治红壤酸化,其中以替代60%处理效果最佳;至2020年60%有机替代处理土壤pH较初始值提高了0.78个单位,交换性酸和交换性铝分别降低了1.10和1.25 cmol/kg。有机肥替代化肥氮40%和60%处理较单施化肥处理显著提高了土壤阳离子交换量,而石灰改良前后土壤阳离子交换量无显著变化。土壤酸缓冲曲线表明,土壤交换性铝含量随着pH的降低而显著升高,单施化肥、有机肥替代化肥氮20%、40%和60%处理的斜率分别为2.71、2.42、1.93和0.16;土壤交换性铝对pH响应斜率与土壤pH、交换性镁、阳离子交换量、交换性钾、有机质含量呈极显著或显著负相关关系。  【结论】  有机肥替代40%以上化学氮肥既能防治红壤酸化,又能提升红壤抗酸化能力。土壤阳离子交换量和有机质可能是导致土壤交换性铝对pH响应差异的主要因素,即阳离子交换量和有机质含量高的土壤pH降低1个单位时,交换性铝增幅较小,但其作用机理还有待进一步研究。     

Effect of wood ash on soil chemistry of a pine stand in Northern Germany

Addition of wood ash to acid soils will affect the soil chemistry of forests in a number of ways which were assessed for a pine stand in northern Germany. A field experiment was carried out in a fifty‐year old pine stand on a sandy Podzol at Fuhrberg (Lüneburger Heide, Lower Saxony/Germany) which involved depositing wood ash (2.4 t ha^—1) on the surface. Soil solution chemistry was investigated monthly at different depths for 24 months. Prior to and 19 months after the ash addition, exchangeable cations and amounts of heavy metals were determined at different depths. Two to four months after addition of wood ash, maximum mean concentrations in the soil solution of Ca were 240 μmol l^—1 at 0 cm (surface of mineral soil) and 100 μmol l^—1 at 100 cm and of K 980 μmol l^—1 and 140 μmol l^—1, respectively. The pH values in soil solutions dropped temporarily by 0.3 units at 0 and 10 cm depth. Nitrate concentrations increased at all depths and maximum mean concentration was 230 μmol l^—1 at 100 cm. Concentrations of Pb and Cr in soil solution did not change significantly (p < 0.05) after ash addition. Concentrations of Cd and Zn increased significantly at some depths but stayed well below the legal limit for drinking water and below the limits given by the German recommendation for soil conservation. Nineteen months after ash addition, the cation exchange capacity (corrected for the release of cations from the ash) of the upper 6 cm of the organic layer was almost doubled and amounts of exchangeable Ca and Mg increased significantly in the upper 8 cm of the organic layer. Amounts of Zn were increased in the entire organic layer, but changes were significant only in the upper 4 cm. The results of this study suggest that ash from untreated wood (using modest additions) may be recommended for amelioration of forest soils.     

Effects of buckwheat growth on variation of aluminum and major metals in root‐zone soil solutions

The variation in and relationships between aluminum and other major metals including Ca, Mg, Mn, and K in root‐zone soil solutions were studied by growing buckwheat (Fagopyrum esculentum Moench. cv. Jiangxi), an Al accumulator, in pots filled with an acid soil amended with CaCO₃ and unamended controls with a preinstalled nondestructive soil‐solution sampler. Soil solutions were collected every 7 d with a syringe connected to the sampler. The results showed that pH of the soil solution was not the only factor controlling the concentration of Al. Significant positive linear correlations were found between Al and Ca as well as between Al and Mg in soil solutions from the controls. The ratio of base cations (BC, Ca+Mg) to Al might partly explain the high Al resistance of buckwheat. Oxalate secretion from roots significantly activated Al in acid soils, which may be important for changes of Al in soil solutions, but it also caused decreased concentrations of Ca, Mg, and Mn. It is concluded that the variation of metal concentrations including Al, Ca, Mg, and Mn is a holistic effect involving competition for exchange sites among Ca, Mg, H, and Al, the chelation by oxalate secreted from roots, and metal uptake by buckwheat.     

Nutrient concentrations and acidity in ferralitic soil under perennial cropping, fallow and primary forest in central Amazonia

The long‐term productivity on the acidic, nutrient‐poor upland soils of central Amazonia depends to a large extent on the chemical soil fertility as influenced by vegetation type and management. We compared soil and soil solution data from permanent cropping, fallow and primary forest on a Xanthic Ferralsol in central Amazonia to evaluate changes of soil fertility following forest conversion, agricultural use at different intensities and setting aside agricultural land. The agricultural systems included a perennial polyculture at two fertilizer inputs and a monoculture plantation. Soil and soil solution were collected to 2 m depth, and the soil solution was monitored over 2 years. Both soil and soil solution data showed decreasing soil fertility in the sequence: monoculture and polyculture at large input, polyculture at small input, forest and fallow. The soil solution data were more sensitive to effects of systems and fertilizer inputs on subsoil fertility. Fractionation of the N in the soil solution showed a larger proportion of dissolved organic N in the N‐poor fallow soil than in the soil under forest and agriculture. The soil under fallow, forest and low‐input agriculture had larger exchangeable acidity than that under high‐input agriculture, but the Al concentrations in the soil solution were very small because there were few cations with which to exchange and less nitrification. In high‐input agriculture, pronounced acidification peaks in the topsoil solution followed fertilization. The comparison of soil and soil solution data explained why the spontaneous vegetation thrives at very large exchangeable acidity in these soils, whereas agricultural systems often depend on liming to reduce the concentration of toxic Al in the soil.     

Dynamics of Microbial Community in Japanese Andisol of Apple Orchard Production Systems

Abstract

In this study, two fields of temperate Andisols from high‐input and low‐input (zero‐input) management practices of an apple orchard were selected to assess microbial community dynamics based on environmental variables. Soils from an Ap horizon were sampled in five consecutive months from May to September and assessed for phospholipid fatty acids as a biomarker of soil microbial community, soil hardness, bulk density, porosity, pH, electrical conductivity (EC), organic carbon (C), available nitrogen (N) and phosphorus (P), and exchangeable cations as soil environmental variables. For all sample dates, total phospholipid fatty acids (PLFAs), total bacterial PLFAs, fungal PLFA, mycorrhizal PLFA, PLFA for actinomycetes, and earthworm were higher in low‐input management than high‐input management. Total PLFAs showed a high degree of seasonality, having August maxima and May minima. Significant effect on the relationships among soil environmental variables and microbiological attributes were observed. Soil management practices also showed a remarkable effect on the relationships among microbiological traits, indicating that some mechanism regulated soil microbial dynamics under two soil management practices. Comparatively higher correlations among the microbiological attributes were observed in low‐input management than high‐input management. Irrespective of soil management practices, bacterial and fungal lipid biomarkers were negatively correlated, suggesting that these subsets of fatty acids are contrasting components of the microbial biomass. Bulk density has negative influence on all soil microbial communities except fungi. On the other hand, linoleic acid and organic C were positively correlated, referring to the distribution of soil organic C implying an upper layer of soils. Microbial community composition and structure were greatly affected by sampling date and to a lesser extent by long‐term management practice. In this study, both ecosystems were characterized by a very diverse microbial community.     

Effects of acid deposition on acidity and exchangeable cations in podzols of the Kola Peninsula

Response of soil and soil water of podzols in the Kola Peninsula to acid deposition was estimated under both field and laboratory conditions. A significant increasing trend of exchangeable acidity in organic (O) horizons and exchangeable Al in podzolic (E) horizons of podzols with distance from the nickel smelter was observed. The simulated rain at pH 4.5 did not alter chemical properties of soils and soil solutions. As much as 95–99% of the applied H⁺ ions were retained by soils and appeared in the percolates after a treatment period that depended on acid load and soil thickness. Ca and Mg in soil solutions were highly sensitive to acid loading. Simulated acid rain enhanced the leaching of exchangeable base cations out of root zone. Acid inputs resulted in decreased pH, amount of exchangeable base cations and base saturation, in elevated exchangeable acidity and it's Al fraction in soil solid phase. The most significant changes occurred in O and E horizons. Substantial amounts of both Ca and Mg can be lost from the root zone of podzols in the north-western Kola, subjected to acid deposition, thus leading to forest productivity damage.     

长期定位施肥对亚热带丘陵地区红壤旱地质量的影响Ⅰ.酸度

研究了中国科学院红壤生态实验站长期定位施肥试验5种不同施肥处理对土壤pH、土壤交换性氢、铝的影响,及其与土壤有机质之间的相关性。结果表明,长期不同施肥处理均提高了土壤pH,降低了土壤交换性氢和交换性铝含量,改良了红壤的酸性。施用有机肥(M)、有机肥+菌剂(BM)、有机肥+菌剂+微量元素(BMT)显著优于施用化肥(F)和化肥+微量元素(TF)的处理。添加微量元素和有效菌剂后土壤交换性氢、铝含量略有提高。土壤有机质与土壤pH呈显著正相关,与土壤交换性氢含量的相关性不显著,而与土壤交换性铝含量呈显著负相关。随着土壤有机质含量的增加,土壤交换性氢占土壤交换性酸度比例越大。长期施用有机肥、提高土壤有机质含量是改良红壤酸度和减轻铝毒较好的农艺措施。     

Effect of additions of brown coal and peat on soil solution composition and root growth in acid soil from wheatbelt of western Australia

Abstract

Additions of several categories of organic materials including fresh plant materials, compost, manure, coal derived products, and peat have been shown to ameliorate soil acidity. The main effect is increased soil pH and the corresponding decrease in soil solution and exchangeable aluminum (Al). The organic matter addition is expected to decrease the solubility of soil aluminum so that lower activities are maintained at a given pH value, but this effect has not been tested. Aluminum solubility was investigated after addition of brown coal and peat to an acid soil. Root length was used as a bioassay for the acid ameliorating properties of the organic materials. Addition to soil of brown coal and peat resulted in changes in Al activity in the soil solution. The negative log of Al activity (pAl) was directly proportional to the soil solution pH. A single pAl‐pH line could describe the control, calcium chloride and organically treated soil samples. This line was parallel to that of gibbsite. The intercept was greater suggesting undersaturation with respect to that mineral. The coal and peat applied at the rate of 1 and 2% had little effect on the solubility of soil Al. Any decrease in Al activity was solely dependent on increased soil pH. Relative root length was inversely related to Al activity. This relationship was improved by including base cations in the index of Al phytotoxicity. This index could provide the basis for evaluating the value of brown coal and peat in ameliorating soil acidity.     

A simple rapid method for the measurement of exchangeable cations and effective cation exchange capacity

Abstract

A simple single‐extraction procedure for measuring exchangeable cations and effective CEC (ECEC, the CEC at natural pH and ionic strength) has been developed for routine advisory soil analysis. The method is based on the use of Sr (1.26M SrCl₂) to displace exchangeable cations and effective CEC is taken as the sum of the exchangeable cations. A ten minute shaking time at 5 g:80 ml, soil solution ratio, was found to be optimum. Good agreement was found between the proposed method and the standard neutral IN ammonium acetate leaching procedure with correlation coefficients (r) for the individual cations Mg, Ca, Na and K of 0.99***, 0.99***, 0.83*** and 0.96*** respectively. Strontium chloride extracted more Al but less Mn (P<0.01) than IN KC1, but because of the low levels of these cations in relation to the total cations present, there was still a good relationship (r= 0.99) between ECEC determined by 1.26M SrCl₂ and that determined as the sum of ammonium acetate extractable Mg, Ca, Na and K plus IN KCl‐extracted Al and Mn.     

The influence of soil properties on the structure of bacterial and fungal communities across land-use types

Land-use change can have significant impacts on soil conditions and microbial communities are likely to respond to these changes. However, such responses are poorly characterized as few studies have examined how specific changes in edaphic characteristics do, or do not, influence the composition of soil bacterial and fungal communities across land-use types. Soil samples were collected from four replicated (n = 3) land-use types (hardwood and pine forests, cultivated and livestock pasture lands) in the southeastern US to assess the effects of land-use change on microbial community structure and distribution. We used quantitative PCR to estimate bacterial–fungal ratios and clone libraries targeting small-subunit rRNA genes to independently characterize the bacterial and fungal communities. Although some soil properties (soil texture and nutrient status) did significantly differ across land-use types, other edaphic factors (e.g., pH) did not vary consistently with land-use. Bacterial–fungal ratios were not significantly different across the land-uses and distinct land-use types did not necessarily harbor distinct soil fungal or bacterial communities. Rather, the composition of bacterial and fungal communities was most strongly correlated with specific soil properties. Soil pH was the best predictor of bacterial community composition across this landscape while fungal community composition was most closely associated with changes in soil nutrient status. Together these results suggest that specific changes in edaphic properties, not necessarily land-use type itself, may best predict shifts in microbial community composition across a given landscape. In addition, our results demonstrate the utility of using sequence-based approaches to concurrently analyze bacterial and fungal communities as such analyses provide detailed phylogenetic information on individual communities and permit the robust assessment of the biogeographical patterns exhibited by soil microbial communities.     

Soil morphology,depth and grapevine root frequency influence microbial communities in a Pinot noir vineyard

The composition of microbial communities responds to soil resource availability, and has been shown to vary with increasing depth in the soil profile. Soil microorganisms partly rely on root-derived carbon (C) for growth and activity. Roots in woody perennial systems like vineyards have a deeper vertical distribution than grasslands and annual agriculture. Thus, we hypothesized that vineyard soil microbial communities along a vertical soil profile would differ from those observed in grassland and annual agricultural systems. In a Pinot noir vineyard, soil pits were excavated to ca. 1.6–2.5 m, and microbial community composition in ‘bulk’ (i.e., no roots) and ‘root’ (i.e., roots present) soil was described by phospholipid ester-linked fatty acids (PLFA). Utilization of soil taxonomy aided in understanding relationships between soil microbial communities, soil resources and other physical and chemical characteristics. Soil microbial communities in the Ap horizon were similar to each other, but greater variation in microbial communities was observed among the lower horizons. Soil resources (i.e., total PLFA, or labile C, soil C and nitrogen, and exchangeable potassium) were enriched in the surface horizons and significantly explained the distribution of soil microbial communities with depth. Soil chemical properties represented the secondary gradient explaining the differentiation between microbial communities in the B-horizons from the C-horizons. Relative abundance of Gram-positive bacteria and actinomycetes did not vary with depth, but were enriched in ‘root’ vs. ‘bulk’ soils. Fungal biomarkers increased with increasing depth in ‘root’ soils, differing from previous studies in grasslands and annual agricultural systems. This was dependent on the deep distribution of roots in the vineyard soil profile, suggesting that the distinct pattern in PLFA biomarkers may have been strongly affected by C derived from the grapevine roots. Gram-negative bacteria did not increase in concert with fungal abundance, suggesting that acidic pHs in lower soil horizons may have discouraged their growth. These results emphasize the importance of considering soil morphology and associated soil characteristics when investigating effects of depth and roots on soil microorganisms, and suggest that vineyard management practices and deep grapevine root distribution combine to cultivate a unique microbial community in these soil profiles.     

有机物料对酸性红壤铝毒的缓解效应

利用盆栽试验研究了施用不等量稻草对酸性红壤旱耕地铝毒的缓解效应。结果表明,添加不等量的秸秆碳(C)后,土壤pH值显著提高,土壤交换性铝和吸附态羟基铝的含量则明显降低,土壤有机络合态铝的含量也呈增加趋势。添加铝盐并不影响秸秆碳对降低土壤交换性铝和吸附态羟基铝含量的作用。在本研究中,土壤pH值与土壤交换性铝和土壤吸附态羟基铝均呈显著负相关,方程分别为y=-2193.9x+11545,R2=0.9798**,y=-655.34x+9748,R2=0.7837**。土壤交换性铝和吸附态羟基铝与玉米主根长,地上部磷、钾含量均呈显著负相关,是抑制玉米吸收养分的主要限制因素,土壤吸附态羟基铝是次于交换性铝的又一活性较大的铝化合物。     

Soil disturbance and elemental dynamics in a Northern Hardwood forest soil,USA

Loss of soil nutrients due to disturbance may serve as an index of the homeostasis of biogeochemical cycling and ecosystem stability. Soil and the surrounding root system were disturbed during the installation of Soil Containment Systems (SCSs) in the hill slope at the Bear Brook Watershed in Maine (BBWM). The SCSs were constructed from high density PVC pipe (24 cm i.d. and 30 cm height) implanted at field. Leachate cations and anions, soil organic matter and exchangeable cations were analyzed. Leachate NO₃ ^? was higher by an order of magnitude compared to undisturbed soils from the same research site and other hardwood forest soils in the northeast U.S. The concentrations of cations in the leachate from SCSs were also higher and loss of NO₃ ^? was positively correlated with the loss of most cations. Calcium was the dominant cation representing 55% of the base cation composition of soil leachate. Monthly losses of Ca²⁺, Mg²⁺ and K⁺ were 1.8, 1.6 and 1.2% of total exchangeable pools, respectively. Disturbance of the BBWM soil ecosystem caused high rates of NO₃ ^? leaching which markedly changed the soil biogeochemistry. These results and other supporting data from watershed mass balances and experimental chemical additions suggest that BBWM may be N saturated.     

Forms of Al in soil and soil solution in a long‐term fertilizer application experiment

Under the conditions of a long‐term fertilizer experiment, this study aimed to determine the contents of total and exchangeable aluminium in soil as well as the Al concentration in the soil solution. Additionally, Al speciation was evaluated with the use of the MINTEQA2 software. The results obtained indicated that under the conditions of long‐term application of different mineral fertilizers or farmyard manure, the soil reaction changed to a great extent (pH 3.58–6.78). At the same time, the content of total Al in soil fluctuated from 18.85 to 22.13 g/kg and that of exchangeable Al ranged from 1.42 to 102.66 mg/kg. The concentration of Al in the soil solution was highly differentiated (5.19–124.07 μmol/L) as well as that of free aluminium ions (Al³⁺) (0–16.9 μmol/L). In acidic soils, aluminium complexes with organic matter are the predominant forms of Al in the soil solution. In soils with neutral soil reaction, there were no free aluminium ions. Soil liming and addition of organic amendment were the treatments that restricted the presence of toxic aluminium forms in soil.     

镧的累积对红壤阳离子交换量及土壤溶液组成的影响

Pot and adsorption-exchange experiments were carried out by collecting the soil samples from the surface layer(0-15cm) of red soil at the Ecological Experiment Station of Red Soil,the Chinese Academy of Sciences,in Jiangxi Province of CHina.When concentration of the exogenous La^3 exceeded 400mg kg^-1,there was less non-exchangeable La^3 than exchangeable La^3 in the soil.Cation exchagne capacity of the soil changed slightly with increasing concentration of the exogenous La^3 in both experiments.However,in the adsorption-exchange experiment,when concentration of the exogenous La^3 was higher than 300mg kg^-1,exchangeable basic cations decreased significantly,while exchangeable hydrogen and exchangeable aluminum increased significantly compared with the control treatments.The amounts of base cations(Ca^2 ,Mg^2 ,k^ and Na^ )exchanged by La^3 in the supernatant solution increased with the concentration of the exogenous La^3 ,especially when concentration of the exogenous La^3 was higher than 50mg kg^-1.     

Organic Amendment Effects on the Transformation and Fractionation of Aluminum in Acidic Sandy Soil

Addition of organic amendments can alleviate the level of aluminum (Al) phytotoxicity in acid soils by affecting the nature and quantity of Al species. This study evaluated the transformation of Al in an acidic sandy Alaquod soil amended with composts (10 and 50 g kg^?1 soil of yard waste, yard + municipal waste, GreenEdge^®, and synthetic humic acid) based on soil Al fractionation by single and sequential extractions. Though the organic compost amendments increased total Al in soil, they alleviated Al potential toxicity in acidic soil by increasing soil pH and converting exchangeable Al to organically bound and other noncrystalline fractions, stressing the benefits of amending composts to improve acid soil fertility. The single‐extraction method appears to be more reliable for exchangeable Al than sequential extraction because of the use of nonbuffered pH extract solution.     

Application of leaf,soil, and tree ring chemistry to determine the nutritional status of sugar maple on sites of different levels of decline

Nutrient concentrations and D.R.I.S. indices of leaves, soil chemistry and dendrochronological changes of elemental concentrations in sugar maple (Acer saccharum Marsh.) were used to determine its nutritional status on three sites of contrasting levels of decline. We hypothesized that the ratio of Al to base cations in tree rings would increase more at the most severely declining site, and that the ratios of K⁺ to divalent cations (Ca²⁺ and Mg²⁺) would increase slower or decrease more rapidly over time than at the less severely declining sites. Forest health, based on percentage of foliage missing, and leaf K and Mg concentrations of the three sites were ranked as follows: Morgan Arboretum > Saint-Hippolyte > Entrelacs. Soil pH, Ca, Mg, E.C.E.C. and percentage of base saturation were highest at the Morgan Arboretum, and exchangeable Al in the organic horizon was highest at Entrelacs. Concentrations of K, Ca, Mg and Al, and ratios of these elements in wood were determined for each of the following periods: 1940–1956, 1957–1973 and 1974–1989. Variations in tree ring chemistry among sites were significant for K and Al and all elemental ratios except K:Mg. Al concentration and the ratios of Al to base cations in wood were all significantly higher at Entrelacs (7.0 vs 2.6 and 2.8 mg Al kg^?1 for the other two sites, respectively). Weak relationships were generally observed between leaf and soil elemental concentrations, and wood elemental concentrations. The D.R.I.S. K index and soil exchangeable K and Al showed good concordance with wood concentrations. With the exception of Mg, Al and Al:Mg, the effect of period was significant for all other elements and ratios of elements. The most severely declining stand (Entrelacs) differed from the healthiest stand by decreasing K:Ca and increasing A1:K from the 1940–1956 to the 1957–1973 period.