Litter and forest-floor dynamics in aPinus resinosa plantation in Wisconsin

Summary Breakdown of dry matter and release of nutrients from decomposing leaf litter and forest-floor material were measured in a 34-year-old red pine (Pinus resinosa Ait.) plantation in central Wisconsin using (1) leaf-litter bags (2) litterfall and forest-floor nutrient data and an exponential decay function, and (3) nutrient flux data and a mass balance equation. After one year of decomposition, 77% of the original dry matter in leaf-litter bags remained. The release of macronutrients in decomposing leaf litter was K>Mg>P, S>N>Ca, and the release of micronutrients and aluminum was Mn, B>Al>Cu>Zn. Nitrogen in decomposing leaf litter showed the leaching, accumulation, and final release phases delineated by Berg and Staff⁴. Half-lives of dry matter and nutrients in the forest floor ranged from 0.5 (K) to 39 (Al) yr. Forest-floor turnover rates of the various elements followed the same trends as in leaf-litter bags except that Ca turned over more readily than P, S, and N and Zn turned over more readily than the other micronutrients. A forest-floor nutrient balance sheet confirmed that the macronutrients N and Ca are accumulating most readily in the forest floor. The overall implications of these trends for tree nutrition are discussed.     

羊草草原植物-土壤之间主要营养元素动态的研究

羊草草原土壤中N、P、K含量的季节变化规律是生长季初期较高,6—8月生长旺季较低,生长季末再度升高。营养元素在植物体内的分配是地下部分大于地上部分。地下部分N的贮量为地上部分的3.6倍,K为2.9倍,P为2.8倍。地上部分3种元素含量的季节变化曲线呈单峰型,从生长初期开始上升,最大值出现在8月,生长末期逐渐下降。地下部分的季节变化规律,大体上在整个生长季内呈上升趋势,随着根系的生长,营养元素的积累量不断增加。对植物—土壤之间营养元素动态分析结果表明,随着时间的推移,N、P、K在各状态中的比例趋于恒定。在稳定状态下,3种元素在土壤中的比例逐渐减少,与初始量相比N、P、K的含量分别减少21.23%、5.14%和2.99%。在其它状态中,3种元素的含量均有提高,特别在枯枝落叶和死根中增加的幅度较大。     

Effects of phosphorus supply on growth and nitrogen fractions in xylem sap and foliage of Eucalyptus regnans (F.Muell.), E. nitens (Maiden) and E. globulus (Labill.) seedlings: implications for herbivory

Rates of growth of seedlings of E. globulus, E. regnans and E. nitens were related to phosphorus supply in two soils but concentrations of total nitrogen and total phosphorus in most plant tissues did not vary significantly among soil or phosphorus treatments. Differences in concentrations of nitrogen and phosphorus and in the composition of the pool of free amino-acids among leaves at different stages of development were far greater than differences between treatments. The most significant of these differences were several-fold greater concentrations of arginine in the oldest leaves and these are most likely due to protein degradation and/or in situ synthesis since arginine is not generally phloem mobile. The concentration of reduced nitrogen in xylem sap was inversely related to growth and glutamine was by far the dominant nitrogenous solute. We suggest that specific nitrogenous solutes may be useful indices of the nitrogen status of eucalypt tissues for insect herbivores.     

Seasonal and spatial patterns of foliar nutrients in cork oak (Quercus suber L.) growing on siliceous soils in Provence (France)

Cork oak forests in Mediterranean, southeastern France represent animportant ecosystem in terms of both ecological and economical values, but aredeclining due to conservation problems. While management protocols are now inplace for the long-term conservation of this ecotype, we require a betterunderstanding of cork oak nutrition to assist with management. Here we usefoliar nutrient analyses for two objectives: firstly, to assess to what extentvariations in nutrient content are explained by seasonal and spatialvariability, and second, to document the nutrient dynamics of cork oak trees innatural conditions during one biological cycle (16 months) in the Maures massif(western part of the siliceous Provence). Main results showed that time was theprimary factor influencing cork oak nutrition and was mainly expressed by leafageing process. Spatial variability was a 'secondary determinant' of nutrient variations, but was more important at the very early stages of leafgrowth according to leafing and nutrient flushing, and reduced with leaf age.Nutritional responses of cork oak trees fitted general trends observed in theliterature, with some regional differences. The properties of siliceous soilalso influenced the uptake of some nutrients.     

Natural regeneration of Pinus resinosa on burned and unburned sites in Newfoundland

Abstract. Natural regeneration of Pinus resinosa (red pine) seedlings around mature trees was studied in burned and unburned stands. Growth inhibitory effects of the forest organic matter on red pine seedlings was tested by a stair-step experiment using leachate of forest soil monoliths and also by a seed germination bio-assay using forest floor substrates. To test if higher burning temperatures can remove the allelopathic effects of red pine-Kalmia organic matter, a laboratory bio-assay was conducted by germinating red pine seeds on the organic matter burned at 200, 400, 600 and 800°C. Deposition of dry needles and a thick duff layer under red pine stands affected seedling establishment. Red pine seedling establishment increased with the decreasing thickness of duff layer away from the stump of the seed-bearing trees. Wildfire helped in removing the duff layer and increased seedling establishment. A high fuel load within a 0 - 1 m radius around the tree stump caused a deep burn of the organic matter including part of the soil seed reserve. On a burned-over surface, more seedlings established in a band between 1 and 2 m around the stump than inside and outside the band. Primary root growth of red pine was severely inhibited when the seedlings were grown in unburned forest floor organic matter where Kalmia was the principal understory species. Water leachate of a Pinus resinosa-Kalmia soil monolith was inhibitory to red pine seedling growth. In greenhouse conditions, the seedlings grew well in burned-over soil from a Pinus resinosa stand. Burned organic matter from a red pine forest showed an increase in pH with a burning temperature of 600°C. Primary root growth of red pine seedlings was similarly increased with increasing temperature up to 600°C; at higher temperatures the root length of seedlings did not increase any further.     

Floristic gradients of herbaceous vegetation and P/N ratio in soil in a Mediterranean area

A broad range of herbaceous plant comunities in a Mediterranean Landscape in central Italy, running from heavily urbanized areas to semi-natural pastures, has been studied. These communities can be easily arranged along a gradient of ruderality. We inspected which of a series of soil parameters could better explain this gradient (pH, CaCO₃, granulometry, N, P, C/N, P/N). We show that (1) the single most important explanatory variable is P/N ratio of soil; (2) nitrogen and carbon pools in soil are related, in the set of communities studied, with another gradient of decreasingly frequent, predictable, moderate disturbance such as trampling. We discuss the meaning of these results. Nomenclature: Anzalone (1994, 1996).     

Comparative studies of ectomycorrhiza formation in Alnus glutinosa and Pinus resinosa with Paxillus involutus

 Mycorrhiza ontogeny and details of Hartig net and mantle structure were compared in ectomycorrhizas synthesized in growth pouches between the broad host range fungus Paxillus involutus and the tree species European black alder (Alnus glutinosa) and red pine (Pinus resinosa). In Alnus glutinosa, a paraepidermal Hartig net was restricted to the proximal (basal) portion of first-order laterals; the hypodermal layer appeared to be a barrier to fungal penetration. Phi-thickenings were present in some cortical cells but these were not related to lack of fungal ingress into the cortex. The mantle was often present close to the root apex but in many roots it was loosely organized and patchy. In several instances, the mantle formed around the root apex was only temporary; renewed root growth occurred without the formation of a mantle. In Pinus resinosa, the Hartig net developed between cortical cell layers of monopodial and dichotomously branched first–order laterals. Fungal hyphae in the Hartig net exhibited a complex labyrinthine mode of growth. The mantle had a pseudoparenchymatous structure and covered the root, including apices of dichotomously branched roots. The Paxillus–Pinus resinosa interaction had all the characteristics of a compatible ectomycorrhizal association. The Paxillus–Alnus glutinosa interaction, however, showed only aspects of superficial ectomycorrhizas, including the presence of a minimal (sometimes absent) and mostly proximal Hartig net and variable mantle development. Sclerotia were produced in the extraradical mycelium of Paxillus involutus when associated with either Alnus glutinosa or Pinus resinosa. Accepted: 22 October 1998     

黄芩干物质累积和氮磷钾吸收、分配规律研究

为了探讨黄芩干物质累积和氮、磷、钾吸收与分配的特点及两者间的相互关系,通过田间试验和采样分析,研究了黄芩不同生育期植株的干物质和氮、磷、钾累积量.结果表明,黄芩干物质的累积量随生育进程不断地增加,出苗后52～85 d干物质累积量占总累积量的61.62％.在整个生育期,黄芩对K2O的吸收累积量最大,N次之,P2O5最小,N、P2O5、K2O吸收比例约为2.8∶1.0∶2.9,并且黄芩地上部氮磷钾的累积量大于根部,不同生育期,根部N、P2O5、K2O的累积比例呈现增加—降低—增加的趋势.黄芩对氮磷钾的积累量与干物质积累量呈极显著正相关关系.在供试的土壤和施肥条件下,每生产100 kg的黄芩根需要从土壤和肥料中吸收6.34 kg的N,2.60 kg的P2O5,7.02 kg的K2O.     

Long-term changes in nutrient concentrations of the Changjiang River and principal tributaries

We present long-term nutrient data on the Changjiang River (Yangtze River) at six hydrological stations and eight principal tributaries during the period 1958–1985. Three patterns of temporal changes were observed in nitrate and nitrite : minimal variations in the upper catchment area, rapid increases in the middle watershed towards the end of the 1970s, and a gradual increase in the lower drainage basin. Prior to the 1970s, the level of throughout the Changjiang River system remained fairly constant. In the 1980s, however, this changed, with the lowest values in the upper Changjiang changing rapidly to the highest in the middle reaches and then declining slowly but steadily in the lower courses. Compared to and ammonium and soluble reactive phosphorus (SRP) showed smaller increases or no long-term variations, while dissolved silica (DSi) concentration generally decreased at most stations. These three patterns of and changes in the Changjiang River system were reflective of the difference in chemical fertilizer use and landscape features (e.g., slope, soil type and water body area) of the drainage basins of the primary tributaries. The decreases in DSi were most likely attributed to a reduction in suspended sediment loading due to dam constructions and increasing diatom consumption. The increase in and with a reduction in DSi concentrations in the Changjiang River could have significant effects on the stoichiometric balance of nutrients delivered to the East China Sea and the ecosystem in this dynamic region.     

羊草草地枯枝落叶中N,P,K变化动态

羊草草地枯枝落叶中Ｎ、Ｐ、Ｋ变化动态郭继勋,祝廷成（东北师范大学国家草地生态工程实验室,长春１３００２４）ＤｙｎａｍｉｃｓｏｆＮ,ＰａｎｄＫｉｎｌｉｔｔｅｒｓｏｎＡｎｅｕｒｏｌｏｐｉｄｉｕｍｃｈｉｎｅｎｓｅｇｒａｓｓｌａｎｄ．￥ＧｕｏＪｉｘｕｎａｎｄ...     

Effects of fertilization on the nutrient distribution of aboveground components ofAbies balsamea (L.) Mill

Summary The following fertilizer treatments were applied to a 20-year-old aspen-birch-sprucefir stand in southeastern Maine: N at 448 kg/ha, P at 112 kg/ha, N and P applied as above in addition to 1751 kg/ha Ca and 27 kg/ha Mg. Five years after treatment, foliar concentrations of N, P and Ca for understory blasam fir exhibited significant increases in response to fertilization with those nutrients. Mean five-year height growth, adjusted for pretreatment differences, increased 36 percent in response to fertilization with N alone and in combination with P and lime.     

In vitro induction of genetic variability in cotton (Gossypium spp.)

Summary Through the in vitro culture of excised embryos and ovules, interspecific hybrids have been obtained from cultivated and wild species of Gossypium. The hybrids matured upon transfer to the field. The anthers, ovules and embryos from both the diploid (2n=26) and tetraploid (2n=52) species underwent proliferation, and this response was genotypic. The diploid species invariably showed profuse callusing in comparison with the tetraploid. The callus showed various chromosome numbers, ranging from haploids to hexaploids, and from high polyploidy to aneuploidy. Hybrid callus culture may augment the genetic variability by providing a means for obtaining genetic exchange in interspecific hybrids. The implications of the in vitro induction of genetic variability for cotton improvement are discussed.     

Natural controls and human impacts on stream nutrient concentrations in a deforested region of the Brazilian Amazon basin

This study documents regional patterns in stream nitrogen and phosphorus concentrations in the Brazilian state of Rondônia in the southwestern Amazon basin, and interprets the patterns as functions of watershed soil properties, deforestation extent, and urban population density. The survey includes 77 different locations sampled in the dry and wet seasons, with a watershed size range from 1.8 to 33,000km² over a total area of approximately 140,000km². A sequential regression technique is used to separate the effects of natural watersheds properties and anthropogenic disturbance on nutrients and chloride. Natural variation in soil texture explains most of the variance in stream nitrate concentrations, while deforestation extent and urban population density explain most of the variance in stream chloride (Cl) and total dissolved nitrogen (TDN) concentrations. Stream TDN, total dissolved phosphorus (TDP), particulate phosphorus (PP) and Cl concentrations all increase non-linearly with deforestation extent in the dry season after controlling for natural variability due to soil type. Stream nutrient and Cl disturbances are observed only in watersheds more than 66–75% deforested (watershed area range 2–300km²), suggesting stream nutrient concentrations are resistant to perturbation from vegetation conversion below a 66–75% threshold. In heavily deforested watersheds, stream Cl shows the largest changes in concentration (12±6 times forested background), followed by TDP (2.3±1.5), PP (1.9±0.8) and TDN (1.7±0.5). Wet season signals in Cl and TDP are diluted relative to the dry season, and no land use signal is observed in wet season TDN, PN, or PP. Stream TDN and TDP concentrations in non-urban watersheds both correlate with stream Cl, suggesting that sources other than vegetation and soil organic matter contribute to enhanced nutrient concentrations. Small, urbanized watersheds (5–20km²) have up to 40 times the chloride and 10 times the TDN concentrations of forested catchments in the dry season. Several large watersheds (1000–3000km²) with urban populations show higher Cl, TDN and TDP levels than any small pasture watershed, suggesting that human impacts on nutrient concentrations in large river systems may be dominated by urban areas. Anthropogenic disturbance of dry-season stream Cl and TDN is detectable in large streams draining deforested and urbanized watersheds up to 33,000km². We conclude that regional deforestation and urbanization result in changes in stream Cl, N and P concentrations at wide range of scales, from small pasture streams to large river systems.     

Effect of phosphorus and potassium deficiency on keto acid and amino acid content of peanut (Arachis hypogaea L.) leaves

Summary Lack of both phosphorus and potassuium results in accumulation of all the keto acids and amino acids in 30 days and 20 days old peanut leaves respectively. This is due to te sluggish metabolism of the tissue under P and K deficienty. Decrease of all the keto acids in 20 days old plants suggests that their synthesis might be affecte under P and K deficiency.     

Genetic variability in callus formation and regeneration of garlic (Allium sativum L.)

Twenty garlic Allium sativum (L.) genotypes were analysed for genetic variation in their ability to form callus (in one medium) and regenerate shoots (in four different media). Genotypes showed significant differences in the analysis of variance of all the traits tested. The accession Printanor showed the best general behaviour, with 83% callus-producing explants, 44.7% organogenic explants, and 15.35 shoots/g of callus. The best regeneration medium was MBO, without growth regulators. Shoot production capacity was examined with the additive main effects and multiplicative interaction model that proved to be a powerful tool for analysis and easy comprehension of the strong genotype×medium interactions frequently observed in in vitro culture systems. Received: 5 February 1998 / Revision received: 11 May 1998 / Accepted: 1 June 1998     

Association mapping of loci linked to copper,phosphorus, and potassium concentrations in the seeds of C. arietinum and C. reticulatum

Due to its high nutritional value, chickpea is one of the most important and cost-effective legumes for human diet. Nutrient elements, such as Cu, P, K have numerous essential functions for the human metabolism. In this study, association mapping of loci linked to the seed Cu, P and K concentrations were performed on a population consisting of 107 Cicer reticulatum and 73 Cicer arietinum individuals in four environments (two locations x two years). A total of 121,840 SNPs were genotyped across 180 individuals by GBS analysis. The association mapping between the SNP markers and the seed Cu, P, K concentrations were identified and eight SNPs were found to be significantly associated with variations in three nutrient elements in more than two environments This research suggests that association mapping is a useful methodology for the identification of loci controlling the Cu, P and K uptake in chickpea seeds for further association mapping, molecular breeding, and marker-assisted selection and plant breeding studies and provides a broader understanding of the relationship between the investigated Cicer species and the effects of environmental conditions.     

Organisation of the variability of abundant proteins in seven geographical origins of maritime pine (Pinus pinaster Ait.)

The comparison of 42 two-dimensional protein patterns from megagametophytes of maritime pine from seven geographical origins enabled the analysis of the genetic variability of abundant proteins. More than 84% of the polypeptides were variable. The intra- and inter-origin variability levels were of a similar magnitude. Correspondence analysis and a dendrogram computed using a dissimilarity index between individuals showed three main groups. The first group included the individuals from Landes (France), Portugal, eastern Spain, and Corsica, without individualising the provenances. The second group was composed of accessions from Italy and Sardinia, and the individuals of each location were separated. The third group included all of the individuals of Moroccan origin. This clustering was in agreement with the Atlantic, Mediterranean and North African structuration of maritime pine established from terpene data.     

菜地和一般农田土壤主要养分累积的差异

选取不同类型菜地和一般农田 ,测定了 0～ 2 0 0cm土壤剖面的有机质、全氮、硝态氮、铵态氮、速效磷、速效钾等主要养分含量及其分布 .结果表明 ,菜地土壤中养分大量累积 ,其中硝态氮和速效磷累积程度较高 .大棚和露天菜地 0～ 2 0 0cm土层的硝态氮累积总量分别为 15 2 0 .9kg·hm-2 和 135 8.8kg·hm-2 ,比农田高出 5 .2和 4.5倍 ;速效磷分别为 978.1kg·hm-2 和 5 0 3.3kg·hm-2 ,比农田高出 6 .2和 2 .7倍 .而其它养分增加相对较少 .有机质累积总量分别为 2 80 .5Mg·hm-2 和 2 6 9.3Mg·hm-2 ,比一般农田高出 12 .5 %和 8.0 % ;全氮分别为 37.5Mg·hm-2 和 32 .7Mg·hm-2 ,比农田高出 36 .2 %和 18.6 % ;铵态氮分别为 2 11.5kg·hm-2 和 197.8kg·hm-2 ,比农田高出 2 9.6 %和 2 1.2 % ;速效钾分别为 6 5 6 7.8kg·hm-2 和 5 5 2 3 .6kg·hm-2 ,比农田高出 30 .6 %和 9.8% .此外 ,菜地土壤中累积的养分不仅分布在表层 ,在深层土壤也大量存在 ,说明菜地存在严重的养分淋溶现象 .     

氮、磷、钾对豫麦50旗叶蔗糖和籽粒淀粉积累的影响

以豫麦50为对象,探讨了氮、磷、钾对小麦旗叶中蔗糖的积累及相关酶活性以及籽粒中淀粉含量和组分的影响.结果表明,施氮可以增加灌浆前期旗叶中的糖含量,施钾则提高了灌浆后期旗叶中的糖含量,而施磷则对旗叶中的糖含量影响不大.施氮、磷、钾均能增加蔗糖合成酶活性,但它们的作用时间不同：施氮活性增加在籽粒灌浆中期,施磷在灌浆前期,而施钾在灌浆前、中期.但氮亦可增加花后24 d的磷酸蔗糖合成酶活性,施磷增加了灌浆前、中期磷酸蔗糖合成酶活性,施钾则增加了灌浆后期旗叶磷酸蔗糖酶活性.施氮、磷、钾都提高了籽粒中总糖含量,增加籽粒中淀粉含量,其中施钾效果最为明显.施磷提高籽粒中直链淀粉的积累,而施钾则显著提高了籽粒中支链淀粉的含量.