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.     

Possible role of disturbance in shaping the northern distribution of Pinus resinosa

Abstract. The objective of this study is to determine the factors responsible for the distribution of Pinus resinosa (red pine) at its northern limit in northwestern Québec. Pinus resinosa is found only on islands and protected lake shores at its northern distribution boundary. The influence of climate on the germination of P. resinosa seed and on the phenology of P. resinosa was investigated in the Lake Duparquet region of northwestern Québec. The results indicate that P. resinosa seed readily germinates at island- and inland sites, which indicates that germination is not responsible for the distribution of P. resinosa in the Lake Duparquet region. Also, cones and seeds developed normally at island sites and an inland plantation, which suggests that seed production is not hindering the expansion of P. resinosa. These results, together with other studies in the literature, suggest that no climatic factor could explain the present distribution of P. resinosa nor its northern limit. The fire regime appears to be responsible for the restriction of P. resinosa to lake environments and hinders the northward expansion of P. resinosa. The typical crown fire regime of the boreal forest is not conducive for P. resinosa regeneration and restricts the species to fire-sheltered locations such as islands and protected lake shores.     

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     

Efficiency of nitrogen,phosphorus, and potassium use by corn,sunflower, and sugarbeet for the synthesis of organic matter

Summary A three-year experiment was conducted in natural conditions on chernozem soil to examine the efficiency of nitrogen, phosphorus, and potassium use by corn (C₄ type), sunflower and sugarbeet (C₃ type) grown in optimum conditions of mineral nutrition (N₁₀₀P₁₀₀K₁₀₀ kg/ha). Plant materials were analysed for the concentration of nitrogen, phosphorus, and potassium and dry matter mass per individual plant parts and the whole plant.Leaves of different age, of all three plant species, were analysed to find eventual differences in the efficiency of use of nitrogen, phosphorus, and potassium in the synthesis of organic matter depending on leaf age.It was found that corn had the lowest concentration of the elements studied but the highest dry matter mass. In other words, corn was more efficient than sunflower or sugarbeet in the use of these elements for the synthesis of an organic matter unit. Such results were arrived at in both sets of analyses, i.e., the analyses of leaves performed in the course of ontogenetic plant development as well as the analyses of leaves of different age.     

羊草草地枯枝落叶中N、P、K变化动态

On Aneurolepidium chinease grassland, the amounts of N, P and Ktransferred from deadplants into the litters are respectively 0.7227, 0.1137 and 0.4974g·m^-2·yr^-1.After oneyear, the loss rates of them are respectively 59.71, 73.21 and 83.26%.Under imbalancestate, the input of these three elements is larger than their output, being at accumulationstage, while under stable state, their contents in litters are respectively 1.1859, 0.1565 and 0.5963g·m^-2.     

黄淮海平原农林生态系统N、P、K营养元素循环——以泡桐-小麦、玉米间作系统为例

农林生态系统泡桐-小麦、玉米间作类型N、P、K营养元素循环研究表明,在整个群落中,P发生亏损,N和K基本平衡;在植物组分库和枯落物库中,N、P、K均发生累积;在土壤库中,N、P、K均发生亏损。土壤表层(0—20cm)中N和P的含量是限制农作物生长的主要因子。20—80cm土层中P的含量是限制泡桐生长的主要因子。群落内N、P、K的吸收系数分别为0.078、0.014、0.052,利用系数分别为0.95、0.90、0.94,循环系数分别为0.042、0.05、0.063.     

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.     

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.     

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...     

N、P营养盐对塔玛亚历山大藻(Alexandrium tamarense)生长的影响

模拟自然海水营养盐浓度状况,在N、P浓度分别为10-500μg L-1 N和0.74-74μg L-1 P时,研究N、P双因子限制(N、P浓度同时降低,N:P固定为15:1)及单因子限制(保持N或P为最高浓度,只降低一种营养盐浓度)对有毒赤潮藻塔玛亚历山大藻(Alexandrium tamarense)生长的影响。结果表明,塔玛亚历山大藻细胞能较快进入对数生长期,但N、P双因子限制能明显影响其生长,在N、P浓度分别低于100μg L-1 N和15μg L-1 P时,细胞密度无明显增长;而N或P分别受限时,生长态势明显优于N、P同时受到限制的试验组,而且N、P单因子中度限制对生长影响较小。结果说明塔玛亚历山大藻对单因子营养元素限制较强的适应能力,可使其在常常出现单营养因子限制的自然水体中维持一定生长速率和细胞密度,并有助于滤食该藻的贝类体内麻痹性贝类毒素的积累。     

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.     

Nutrient concentrations in tidal creeks as indicators of the water quality role of mangrove wetlands in Southwest Florida

Coastal mangroves have the potential to improve the water quality of urban and rural runoff before it is discharged into adjacent coastal bays and oceans; but they also can be impaired by excessive pollutants from upstream. Nutrients (phosphorus and nitrogen), salinity, and other water quality parameters were measured in five mangrove tidal creeks in different hydrogeomorphic and urbanization settings during high and low tides over a calendar year of wet (June and August 2015) and dry (February and April 2016) seasons in the Greater Naples Bay area in Southwest Florida, USA. Nutrient concentrations (ave. ± std error) in the tidal creeks were 0.055 ± 0.008 mg-P/L for total phosphorus (TP) and 0.610 ± 0.020 mg-N/L for total nitrogen (TN), with an average N:P ratio of 11.4:1. Average wet season TP (0.075 ± 0.010 mg-P/L) was significantly higher than the dry season TP (0.033 ± 0.003 mg-P/L; p < 0.01, f = 15.17, f_crit = 3.89) and the average wet season TN (0.75 ± 0.03 mg-N/L) was significantly higher than dry season TN (0.52 ± 0.02 mg/L; p < 0.01, f = 64.14, f_crit = 3.89), suggesting that urban stormwater runoff is directly or indirectly affecting the nutrient conditions in these mangroves. Significant differences in nutrient concentrations between low tide and high tide were not found for either TP (p = 0.43, f = .63, f_crit = 3.88) or TN (p = 0.20, f = 1.66, f_crit = 3.89). These differences were confirmed by a PCA and cluster analyses, which found differences to be seasonal. We could not conclude from these results whether these five mangrove wetlands were sources nor sinks of nutrients based simply on the measurement of nutrient concentrations. But we illustrated that nutrient concentrations were indicators of the mangroves’ hydrogeomorphic settings, their tidal fluxes from Naples Bay, and the Bay's upstream watersheds, and less by direct urban runoff.     

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.