Impact of sheep grazing on nutrient budgets of dry heathlands

Questions: What effect does sheep grazing have on the nutrient budgets of heathlands? Can grazing compensate for atmospheric nutrient loads in heathland ecosystems? What are the conclusions for heathland management? Location: Lüneburg Heath, NW Germany. Methods: During a one-year grazing experiment (stocking rate 1.1 sheep/ha) nutrient balances for N, Ca, K, Mg and P were calculated by quantifying input rates (atmospheric deposition, sheep excrement) and output rates (biomass removal, leaching). Results: Atmospheric nutrient deposition amounted to 22.8 kg.ha⁻¹.a⁻¹ for N and < 0.2 kg.ha⁻¹.a⁻¹ for P. Sheep excrement increased the inputs for N and P by ca. 3.5 and 0.2 kg.ha⁻¹.a⁻¹, respectively. Grazing reduced N- and P-stores in the above-ground biomass by 25.6 and 1.9 kg.ha⁻¹.a⁻¹, respectively. N-and P-losses via leaching amounted to 2.2 and < 0.2 kg.ha⁻¹.a⁻¹. Output:input ratios for P were high, indicating that grazing severely affected P-budgets of heaths. Conclusions: Our results suggest that sheep grazing has the potential to compensate for atmospheric nutrient loads (particularly for current N deposition rates). However, in the long term the combination of elevated N-deposition and P-loss due to grazing may cause a shift from N-(co-) limited to more P-(co-) limited plant growth. To counteract an aggravation of P-deficiency in the long term, grazing may be combined with management measures that affect P-budgets to a lesser extent (e.g. prescribed burning).     

细叶百合的生物量和营养分配

 以栽培的2年生细叶百合（Lilium pumilum）为材料,于2000年的生长季从蕾期至种子成熟期进行6次取样,对其各器官生物量和氮、磷元素的配置进行了动态研究。结果表明,细叶百合虽然以种子繁殖为主,但在整个生长季用于生殖器官的生物量投资的比例并不很大,大量干物质分配到地下器官鳞茎中（平均为60.17%）;茎、叶的生物量分配比例仅次于鳞茎;雄蕊生物量分配比例明显高于雌蕊。在叶萌动及展叶初期植株全氮百分含量最高;从春季萌动至秋季果实成熟,叶中的氮呈逐渐递减的趋势;茎和生殖器官的全氮含量在蕾期最大;生殖器官与叶、鳞茎的全氮含量相关显著。磷在生殖器官的含量较高,这与磷在植物有性生殖过程中的重要作用相一致;生殖器官与茎的全磷含量相关显著。地下器官全氮、全磷随季节变化有增多的趋势;地上各器官全氮、全磷相关显著,随季节变化有明显减少的趋势。     

Effect of typhoon disturbance on fine litterfall and related nutrient input in a subtropical forest on Okinawa Island, Japan

Typhoons are frequent on Okinawa Island, southwestern Japan. The effects of typhoon disturbance on the patterns of fine litterfall and related nutrient inputs in a subtropical evergreen broad-leaved forest were studied over 5 years from May 1996 to April 2001. Annual fine litterfall averaged 7558 kg ha⁻¹ (range from 6188 to 9439 kg ha⁻¹) for six sampling plots over 5 years, which differed significantly among years (p<0.001) but not among plots (p=0.122). A seasonal maximum was most evident for leaf litter component. Woody litter fell more irregularly through the year, and peak fall varied with typhoon and windstorm. The mean ratio of annual litterfall mass of sexual organs to leaves was 0.06, much lower than that in other tropical and subtropical rain forests. Nutrient concentrations varied in litterfall components, but were not significantly different among plots. The lowest concentrations of N and P in leaf litter were observed in March, which is also the month with the greatest leaf fall. However, the highest concentrations were recorded in typhoon season. Nitrogen and P concentrations were 34% and 106% greater in the green leaves that fell during typhoons than in senescent leaves. Mean nutrient inputs by litterfall were: N 83, P 3.2, K 25, Ca 71, Mg 19, Al 12, Na 10, Fe 0.86 and Mn 3.9 kg ha⁻¹ yr⁻¹, and differed significantly among years for all elements (p<0.0005) and among plots only for K (p<0.05) and Mn (p<0.0001). Typhoon disturbance strongly affected annual fine litterfall and related nutrient inputs, which contributed an average of 30% of the annual litterfall mass, and from 30% to 39% (for different nutrient elements) of annual total nutrient inputs. The results from this study suggest that typhoon-driven maintenance of rapid cycling of P and N and their high availability in soil appears to be an important mechanism to maintain productivity in the subtropical forest on Okinawa Island.     

The influence of the frequency of periodic disturbances on the maintenance of phytoplankton diversity

The influence of periodic disturbances of various frequency on the maintenance of the phytoplankton diversity was studied by semicontinuous competition experiments. Disturbances consisted of dilution events, which meant both addition of fresh nutrients and elimination of organisms. The intervals between dilution events varied from 1 to 14 days. Diversity was found to increase with increasing intervals between disturbances. coexisting species belonged to different strategy types: (a) species with rapid growth under enriched conditions, (b) species with good competitive abilities under impoverished conditions, (c) species with the ability to build up storage pools of the limiting nutrient. An increase of the number of coexisting species over the number that would have coexisted in steady state was only found when the interval exceeded one generation time.     

Water column oxygen demand and sediment oxygen flux: patterns of oxygen depletion in tidal creeks

Low dissolved oxygen (DO) levels often occur during summer in tidal creeks along the southeastern coast of the USA. We analyzed rates of oxygen loss as water-column biochemical oxygen demand (BOD₅) and sediment oxygen flux (SOF) at selected tidal creek sites monthly over a 1-year period. Ancillary physical, chemical and biological data were collected to identify factors related to oxygen loss. BOD₅ rates ranged from 0.0 mg l^?1 to 7.6 mg l^?1 and were correlated positively with organic suspended solids, total suspended solids, chlorophyll a concentrations, temperature, and dissolved oxygen, and negatively with pH and nitrate + nitrite. SOF rates ranged from 0.0 to 9.3 g O₂ m^?2 d^?1, and were positively correlated with temperature, chlorophyll a, and total suspended solids, but negatively with dissolved oxygen. Both forms of oxygen uptake were seasonally dependent, with BOD₅ elevated in spring and summer and SOF elevated in summer and fall. Average oxygen loss to sediments was greater and more variable than oxygen loss in the water column. Oxygen deficits at three of five locations were significantly related to BOD₅ and SOF, but not at two sites where ground water discharges were observed. Correlation and principal component analyses suggested that BOD₅ and SOF responded to somewhat different suites of environmental variables. BOD₅ was driven by a set of parameters linked to warm season storm water inputs that stimulated organic seston loads, especially chlorophyll a, while SOF behaved less strongly so. Runoff processes that increase loads of organic material and nutrients and ground water discharges low in dissolved oxygen contribute to occurrences of low dissolved oxygen in tidal creeks.     

Ki-67 as a prognostic marker in mantle cell lymphoma��consensus guidelines of the pathology panel of the European MCL Network

Mantle cell lymphoma (MCL) has a heterogeneous clinical course and is mainly an aggressive B cell non-Hodgkin lymphoma; however, there are some indolent cases The Ki-67 index, defined by the percentage of Ki-67-positive lymphoma cells on histopathological slides, has been shown to be a very powerful prognostic biomarker. The pathology panel of the European MCL Network evaluated methods to assess the Ki-67 index including stringent counting, digital image analysis, and estimation by eyeballing. Counting of 2 × 500 lymphoma cells is the gold standard to assess the Ki-67 index since this value has been shown to predict survival in prospective randomized trials of the European MCL Network. Estimation by eyeballing and digital image analysis showed a poor concordance with the gold standard (concordance correlation coefficients [CCC] between 0.29 and 0.61 for eyeballing and CCC of 0.24 and 0.37 for two methods of digital image analysis, respectively). Counting a reduced number of lymphoma cells (2 × 100 cells) showed high interobserver agreement (CCC = 0.74). Pitfalls of the Ki-67 index are discussed and guidelines and recommendations for assessing the Ki-67 index in MCL are given.     

Process for the integrated extraction, identification and quantification of metabolites, proteins and RNA to reveal their co-regulation in biochemical networks

A novel extraction protocol is described with which metabolites, proteins and RNA are sequentially extracted from the same sample, thereby providing a convenient procedure for the analysis of replicates as well as exploiting the inherent biological variation of independent samples for multivariate data analysis. A detection of 652 metabolites, 297 proteins and clear RNA bands in a single Arabidopsis thaliana leaf sample was validated by analysis with gas chromatography coupled to a time of flight mass spectrometer for metabolites, two-dimensional liquid chromatography coupled to mass spectrometry for proteins, and Northern blot analysis for RNA. A subset of the most abundant proteins and metabolites from replicate analysis of different Arabidopsis accessions was merged to form an integrative dataset allowing both classification of different genotypes and the unbiased analysis of the hierarchical organization of proteins and metabolites within a real biochemical network.     

Dry matter and nutrient inputs through litter fall in a dry tropical forest of India

The present paper elucidates the pattern of leaf and non-leaf fall and quantifies of the total annual input of litter in a dry tropical forest of India. In addition, concentration of selected nutrients in various litter species and their annual return to the forest floor are examined. Total annual input of litter measured in litter traps ranged between 488.0–671.0 g m^-2 of which 65–72% was leaf litter fall and 28–35% wood litter fall. 73–81% leaves fall during the winter season. Herbaceous litter fall ranged between 80.0–110.0 g m^-2 yr^-1. The annual nutrient return through litter fall amounted (kg ha^-1): 51.6–69.6 N, 3.1–4.3 P, 31.0–40.0 Ca, 14.0–19.0 K and 3.7–5.0 Na, of which 71–77% and 23–29% were contributed by leaf and wood litter fall, respectively for different nutrients. Input of nutrients through herbaceous litter was: 13.0–16.6 for N, 1.0–1.4 for P, 4.0–5.0 for Ca, 7.9–10.5 for K and 0.8–1.0 kg ha^-1 yr^-1 for Na.     

土壤类型对短葶飞蓬灯盏乙素和咖啡酸酯积累的影响

在相同栽培管理条件下,分别以黑色石灰土、红色石灰土、红壤、黄红壤、紫色土和腐殖土为生长介质对短葶飞蓬（Erigeron breviscapus）进行了人工栽培试验。结果显示,生长在不同土壤类型的短葶飞蓬植株体内总咖啡酸酯和灯盏乙素含量有显著的差异。红色石灰土、紫色土及黄红壤生长的植株总咖啡酸酯和灯盏乙素含量最高,黑色石灰土和腐殖土的最低。相同土类的不同亚类土壤生长植株间2种次生代谢产物含量的差异程度,会超过不同土类间的。植株总咖啡酸酯和灯盏乙素含量与土壤P和K含量没有显著相关关系,但与土壤速效N含量及植株含N量则都有极显著负相关关系。不同土壤生长植株叶片的最大光能转换效率（Fv／Fm）值与灯盏乙素和总咖啡酸酯含量都表现出极显著负相关关系。土壤类型对短葶飞蓬次生代谢影响规律与碳素／营养平衡假说（CNB）及资源获得假说（HA）的预测一致。     

Interaction between the macrophyte <Emphasis Type="Italic">Stratiotes aloides</Emphasis> and filamentous algae: does it indicate allelopathy?

The aquatic macrophyte Stratiotes aloides Linnaeus, which has recently received attention in studies on allelopathy, has been shown to suppress phytoplankton growth. In the Netherlands, S. aloides often co-occurs with floating filamentous algae. However, filamentous algae are generally absent in close proximity to S. aloides, resulting in gaps in filamentous algae mats. We analyzed whether those gaps may be caused by allelopathic substances excreted by S. aloides or by nutrient depletion. We studied in a field survey the colonization of natural S. aloides by filamentous algae and determined in situ nutrient concentrations in natural S. aloides stands. To analyze the relative importance of allelopathy and nutrient competition in the interaction between S. aloides and filamentous algae, we carried out field experiments. Introduction of artificial (non-allelopathic) plants in natural S. aloides stands enabled us to compare the colonization by filamentous algae of both Stratiotes sp. and artificial plants. The filamentous algae were absent in close vicinity to S. aloides. Significantly lower concentrations of ortho-phosphate and potassium were observed close to S. aloides as compared with the filamentous algae. In the field experiments the artificial plants were rapidly colonized by filamentous algae, mainly Cladophera Kützing and Spirogyra Link, while all natural plants remained free of such algae. Additionally, most nutrient concentrations did not significantly differ in the proximity of artificial or natural stands of S. aloides. The concentrations of the major growth-limiting nutrients, phosphate and nitrate, were significantly higher and nonlimiting in natural Stratiotes stands. Our main conclusion is that, although allelopathic interactions between S. aloides and filamentous algae do occur under natural conditions, nutrient competition between the two can also be an important factor.