Productivity of autotetraploids and frequency of aneuploidy in reproduction in Haplopappus gracilis L.]

Comparative studies of productivity of autotetraploid plants H. gracilis L. after selection for high productivity, without selection for high productivity and aneuploidity, and after selection for low productivity have been done. The results show considerable effectiveness of selection for productivity. Presence of hyperaneuploid forms in the population is a major cause of the decreasing of autotetraploid productivity.     

The surface ocean productivity response of deeper water benthic foraminifera in the Atlantic Ocean

We test the relationship of deep sea benthic foraminiferal assemblage composition to the surface ocean productivity gradient in the low latitude Atlantic Ocean using 81 surface sediment samples from a water depth range between 2800 and 3500 m. The samples are selected so that the surface ocean productivity gradient, controlling the flux of organic carbon to the seabed, will be the most important environmental variable. The first two principal components of the assemblage data account for 73% of data variance and are clearly linked to the productivity gradient across the Atlantic. These components show that under higher productivity the assemblages contain a higher abundance of Uvigerina peregrina, Melonis barleeanum, Globobulimina spp. and other taxa with probable infaunal microhabitats. Alabaminella weddellensis, a species linked to episodic phytoplankton debris falls, is also important in these assemblages. As productivity decreases there is a regular shift in assemblage composition so that low productivity assemblages are dominated by Globocassidulina subglobosa and several Cassidulina species along with Epistominella exigua. We hypothesize that these taxa are epifaunal to very shallow infaunal since nearly all organic carbon oxidation occurs near the sediment-water interface in low productivity settings. Discriminant function analysis of the foraminiferal assemblages, with groups selected on the basis of surface ocean productivity, shows clear separation among five productivity levels we used. This analysis demonstrates that productivity variations have a strong influence on assemblage composition. Finally, we used two groups of samples from the Rio-Grande Rise representing water depths from 2007 to 2340 m and 2739 to 3454 m to test for effects produced by changing water depth. All these samples are from a low productivity region and represent nearly identical environmental conditions. Although the low productivity nature of all the Rio-Grande Rise samples is obvious, there are assemblage differences between our depth groups. We cannot account for the assemblage differences with changes in organic carbon flux, dissolution effects or other physical/chemical properties of the ocean. Thus there are as yet unidentified factors related to water depth which cause some assemblage variation in the low productivity setting we investigated.     

Penicillium chrysogenum mycelial productivity in the 1st phase of penicillin biosynthesis]

The course of the mycelium low productivity during the first phase of the usual two-stage process of penicillin biosynthesis was studied. It was found that the low productivity of the mycelium at the beginning of the fermentation process was probably associated with catabolic regression of the penicillin-producing system. The high specific growth rate registered in the experiments (0.06-0.08 hours-1) had no negative effect on the mycelium productivity. It was not possible to connect the productivity level with the mycelium age, because young and mature mycelium had the same producitivity levels at any developmental stage under the same conditions.     

黄土半干旱区刺槐和侧柏林地土壤水分有效性及生产力分级研究

采用LI-6200型植物光合测定系统和LI-1600型稳态气孔计,对黄土半干旱区刺槐、侧柏的净光合速率、羧化效率、蒸腾速率、水分利用效率、气孔导度、气孔阻力、胞间CO2浓度和气孔限制值与土壤含水量的关系进行研究;并对林地土壤水分有效性及生产力进行分级与评价．结果表明,刺槐与侧柏林地土壤含水量分别在4．5％和4．0％以下为“无效水”;土壤含水量在4．5％～10．0％和4．0％～8．5％阈值内属于“低产低效水”;在10．0％～13．5％和85％～11．0％阈值内为“中产高效水”;在13．5％～17．0％和11．0％～16．0％阈值内属于“高产中效水”;在17．0％～19．0％和16．0％～19．0％阈值内为“中产低效水”;土壤含水量在19．0％以上也属于“低产低效水”。     

Patterns of exclusion in an intraguild predator-prey system depend on initial conditions

1. When intraguild (IG)-prey are superior to IG-predators in competing for a shared resource, theory predicts coexistence of the IG-prey or the IG-predator with the resource depending on the productivity level: (a) resource and IG prey coexist when productivity is low; (b) IG-predator and resource coexist at high productivity; (c) if IG-prey and IG-predators can coexist, it is only at intermediate productivity levels. 2. We tested the existence of productivity-dependent regions of coexistence using an experimental system of two predatory mites and a shared food source (pollen). 3. At high levels of pollen supply (i.e. high productivity), the IG-predator excluded the IG-prey in most, but not all, cases. The same pattern of exclusion was observed at low productivity, at which the IG-prey was expected to exclude the IG-predator. Therefore, species composition could not be predicted by productivity levels. Instead, our results show that initial conditions affected strongly the outcome of the interaction. 4. We emphasize the need for theory on IG-predation that takes the effects of stage structure, initial conditions and transient dynamics into account.     

Philip Grime's fourth corner: are there plant species adapted to high disturbance and low productivity?

Grime's CSR species life‐strategy theory (competition–stress–ruderality) provides a conceptual framework to classify species into competitive (growing under high productivity, low disturbance), stress‐tolerant (low productivity, low disturbance) and ruderal (high productivity, high disturbance). Importantly, this classification is based on the assumption that the niche space of disturbance and productivity is filled unevenly: while in productive habitats species can adapt to different disturbance regimes, species of low‐productivity and disturbed habitats do not exist, resulting in a triangular distribution of species optima along axes of disturbance and productivity. This assumption has often been criticised, but it has not yet been put under a rigorous test. Here we use existing data on niche positions of central European plant species to test this hypothesis, namely its prediction that species adapted to jointly stressed (low‐productive) and disturbed habitats do not exist. We use Ellenberg indicator values and newly developed indicator values for disturbance as proxies of species positions in the space of productivity and disturbance. We found that positions of species optima along the gradients of productivity and disturbance severity are not independent of each other, with very few species adapted to low‐productive and severely disturbed habitats. In contrast, there is no relationship between productivity and disturbance frequency; a number of species occur in low‐productive and frequently disturbed habitats. The relationship between productivity and disturbance severity can be either due to tradeoffs between life history traits responsible for response to disturbance and productivity (as originally assumed by Grime) or due to historical rarity of severely disturbed habitats in unproductive conditions and consequent absence of evolution of species adapted to them. Our data are based on one specific flora, shaped by glaciations and early introduction of agriculture, but the question of what causes this pattern can be resolved by future analyses of floras with different evolutionary and ecological histories.     

Co-limitation of plant primary productivity by nitrogen and phosphorus in a species-rich wooded meadow on calcareous soils

High small-scale species richness of calcareous grasslands is generally thought to result from evening of species competitive potentials by limited N availability, because of relatively low herb N/P ratios in these communities. However, P mobility is low in alkaline soils as well. We studied soil chemistry and productivity of herb and moss layers in a very diverse calcareous meadow (up to 76 vascular plant species per m²) to test the hypotheses of a co-limitation of herb productivity by both soil N and P availabilities and moss productivity primarily by P availability. The effect of nutrient supply on productivity was investigated using both a natural productivity gradient as well as fertilization experiments. We observed strong positive correlations of soil P availability and total soil N with the above-ground productivity of herb layer. A long-term fertilization experiment demonstrated that P alone and N and P together increased productivity of vascular species, and that the productivity continuously declined after cessation of fertilization with the effect of previous fertilization occasionally visible even 14 years after treatment termination. A short-term fertilization experiment further demonstrated that N and P when supplied alone increase productivity of vascular plants, suggesting that both elements were limiting. Furthermore, there was a significant interaction between N and P on productivity, indicating that simultaneous N and P supply increased productivity more than separate nutrient additions. Moss productivity was negatively associated with vascular plant productivity. In particular, N addition decreased moss productivity, but moss productivity did not decline in P addition treatments. P requirements of mosses were larger than those of vascular plants. Our data indicate co-limitation of herb productivity by both soil N and P in this highly diverse grassland, while limitation of moss productivity mainly by P. We suggest that N and P co-limitations are common in calcareous diverse grasslands, and may partly explain the extreme small-scale species diversity in these communities.     

Co-limitation of plant primary productivity by nitrogen and phosphorus in a species-rich wooded meadow on calcareous soils

High small-scale species richness of calcareous grasslands is generally thought to result from evening of species competitive potentials by limited N availability, because of relatively low herb N/P ratios in these communities. However, P mobility is low in alkaline soils as well. We studied soil chemistry and productivity of herb and moss layers in a very diverse calcareous meadow (up to 76 vascular plant species per m²) to test the hypotheses of a co-limitation of herb productivity by both soil N and P availabilities and moss productivity primarily by P availability. The effect of nutrient supply on productivity was investigated using both a natural productivity gradient as well as fertilization experiments. We observed strong positive correlations of soil P availability and total soil N with the above-ground productivity of herb layer. A long-term fertilization experiment demonstrated that P alone and N and P together increased productivity of vascular species, and that the productivity continuously declined after cessation of fertilization with the effect of previous fertilization occasionally visible even 14 years after treatment termination. A short-term fertilization experiment further demonstrated that N and P when supplied alone increase productivity of vascular plants, suggesting that both elements were limiting. Furthermore, there was a significant interaction between N and P on productivity, indicating that simultaneous N and P supply increased productivity more than separate nutrient additions. Moss productivity was negatively associated with vascular plant productivity. In particular, N addition decreased moss productivity, but moss productivity did not decline in P addition treatments. P requirements of mosses were larger than those of vascular plants. Our data indicate co-limitation of herb productivity by both soil N and P in this highly diverse grassland, while limitation of moss productivity mainly by P. We suggest that N and P co-limitations are common in calcareous diverse grasslands, and may partly explain the extreme small-scale species diversity in these communities.     

Small-Scale Spatial Variation in Population Dynamics and Fishermen Response in a Coastal Marine Fishery

A major challenge for small-scale fisheries management is high spatial variability in the demography and life history characteristics of target species. Implementation of local management actions that can reduce overfishing and maximize yields requires quantifying ecological heterogeneity at small spatial scales and is therefore limited by available resources and data. Collaborative fisheries research (CFR) is an effective means to collect essential fishery information at local scales, and to develop the social, technical, and logistical framework for fisheries management innovation. We used a CFR approach with fishing partners to collect and analyze geographically precise demographic information for grass rockfish (Sebastes rastrelliger), a sedentary, nearshore species harvested in the live fish fishery on the West Coast of the USA. Data were used to estimate geographically distinct growth rates, ages, mortality, and length frequency distributions in two environmental subregions of the Santa Barbara Channel, CA, USA. Results indicated the existence of two subpopulations; one located in the relatively cold, high productivity western Channel, and another in the relatively warm, low productivity eastern Channel. We parameterized yield per recruit models, the results of which suggested nearly twice as much yield per recruit in the high productivity subregion relative to the low productivity subregion. The spatial distribution of fishing in the two environmental subregions demonstrated a similar pattern to the yield per recruit outputs with greater landings, effort, and catch per unit effort in the high productivity subregion relative to the low productivity subregion. Understanding how spatial variability in stock dynamics translates to variability in fishery yield and distribution of effort is important to developing management plans that maximize fishing opportunities and conservation benefits at local scales.     

Immobilization can improve the stability of hybridoma antibody productivity in serum-free media

Hybridoma cells (S3H5/gamma2bA2) were cultivated in spinner flasks with 1% serum media and serum-free media. Monoclonal antibody productivity was maintained in 1% serum media. However, cells in serum-free media showed a decrease in antibody productivity, and it completely disappeared in IMDM-based low protein medium. This loss of antibody productivity was not observed when the cells were immobilized in alginate beads. In fact, immobilization enhanced the specific MAb productivity.     

Antagonistic coevolution across productivity gradients: an experimental test of the effects of dispersal

Coevolution commonly occurs in spatially heterogeneous environments, resulting in variable selection pressures acting on coevolving species. Dispersal across such environments is predicted to have a major impact on local coevolutionary dynamics. Here, we address how co‐dispersal of coevolving populations of host and parasite across an environmental productivity gradient affected coevolution in experimental populations of bacteria and their parasitic viruses (phages). The rate of coevolution between bacteria and phages was greater in high‐productivity environments. High‐productivity immigrants (～2% of the recipient population) caused coevolutionary dynamics (rates of coevolution and degree of generalist evolution) in low‐productivity environments to be largely indistinguishable from high‐productivity environments, whereas immigration from low‐productivity environments (～0.5% of the population) had no discernable impact. These results could not be explained by demography alone, but rather high‐productivity immigrants had a selective advantage in low‐productivity environments, but not vice versa. Coevolutionary interactions in high‐productivity environments are therefore likely to have a disproportionate impact on coevolution across the landscape as a whole.     

Experimental comparison of competition and facilitation in alpine communities varying in productivity

Question. Competitive and facilitative interactions among plant species in different abiotic environments potentially link productivity, vegetation structure, species composition and functional diversity. We investigated these interactions among four alpine communities along an environmental productivity gradient in a generally harsh climate. We hypothesised that the importance of competition would be higher in more productive sites. Location. Mt. M. Khatipara (43°27′N, 41°41′E, altitude 2750 m), NW Caucasus, Russia. Communities ranged from low‐productivity alpine lichen heath (ALH) and snowbed communities (SBC), to intermediate productivity Festuca grassland (FVG), and high‐productivity Geranium‐Hedysarum meadow (GHM). Methods. We quantified the relative influence of competition and facilitation on community structure by expressing biomass of target species within each natural community proportionally to biomass of the species in a “null community” with experimental release from interspecific competition by removing all other species (for 6 years). An overall index of change in community composition due to interspecific interactions was calculated as the sum of absolute or proportional differences of the component species. Results. Species responses to neighbour removal ranged from positive to neutral. There was no evidence of facilitation among the selected dominant species. As expected, competition was generally most important in the most productive alpine community (GHM). The intermediate position for low‐productivity communities of stressful environments (ALH, SBC) and the last position of intermediately productive FVG were unexpected. Conclusions. Our results appear to support the Fretwell‐Oksanen hypothesis in that competition in communities of intermediate productivity was less intense than in low‐ or high‐productive communities. However, the zero net effect of competition and facilitation in FVG might be the result of abiotic stress due to strong sun exposure and high soil temperatures after neighbour removal. Thus, non‐linear relationships between soil fertility, productivity and different abiotic stresses may also determine the balance between competition and facilitation.     

Effects of light fluctuations on the growth and productivity of Antarctic diatoms in culture

Summary This work shows that the low division rates observed in diatoms in Antarctic waters seem to be due to conditions of irradiance rather than to the low temperature: low light intensity and light fluctuations are two factors which depress the division rate of diatoms. However, with regard to the productivity, Antarctic diatoms seem well-adapted to their turbulent environment. Cells grown in alternating periods of light and dark, notably a 2:2 regime which simulates conditions of vertical mixing, reach a higher rate of productivity than algae grown in continuous light. This difference may be due to the better use of light energy observed in the former group. In the Antarctic Ocean, which is characterized by frequent mixing of water masses, this increased efficiency of light utilization could be a way of adaptation, allowing the algae to overcome the restraints imposed by low light and low temperature, and to reach a higher productivity than expected. The low values of I_k and I_max as well as the absence of detectable photoinhibition indicate that Antarctic diatoms are capable to sustain their maximum primary production rate over a wide range or irradiance levels. On the other hand, the highest productivity in 2:2 regime shows that these species are more efficient when grown under fluctuating light. These results lead us to assume that the Antarctic species are well-adapted to live in the extreme conditions of light encountered in Antarctic Ocean: low irradiance and alternance of low and high light intensities.     

Primary productivity,phytoplankton and limiting nutrient factors in labrador lakes

The primary productivity of some lakes and reservoirs in western Labrador was measured by the ¹⁴C method in order to determine the range of productivities and the effects of impoundment. No primary productivity data previously existed for this part of Canada. Both the primary productivity and standing crops of phytoplankton were found to be low in a newly impounded lake but later rose to levels greater than in surrounding natural lakes. In nutrient enrichment experiments, carbon was never found to be limiting but phosphorus stimulated primary productivity when added alone or in combination with nitrogen.     

Productivity and photosynthetic efficiency ofSpirulina platensis as affected by light intensity,algal density and rate of mixing in a flat plate photobioreactor

The effect of the rate of mixing on productivity of algal mass in relation to photon flux density and algal concentration was quantitatively evaluated in cultures ofSpirulina platensis grown in a newly designed flat-plate photobioreactor. Special emphasis was placed on elucidating the principles underlying efficient utilization of high photon flux density for maximal productivity of algal-mass. Whereas the rate of mixing exerted little influence on productivity and photosynthetic efficiency in cultures of relatively low algal density, its effect became ever more significant as algal concentration was increased. Maximal mixing-enhanced cell concentrations and productivity of biomass were obtained at the highest light intensity used. At each level of incident light intensity, maximum productivity and photosynthetic efficiency could be achieved only when algal concentration and mixing rates were optimized. The higher the intensity of the light source, the higher became the optimal culture density, highest algal concentrations and productivity of biomass being obtained at the highest light intensity used. The rate of mixing required careful optimization: when too low, maximal productivity resulting from the most efficient utilization of light could not be obtained. Too high a rate of mixing resulted in cell damage and reduced output rate.Author for correspondence     

高寒草甸植物群落物种多样性和生产力关系的光竞争研究

通过施肥形成的生产力由低到高的过程中,物种多样性往往降低。总体竞争假说认为对所有资源的竞争作用对多样性的影响随着生产力提高而加剧,导致物种多样性的下降;光竞争假说则认为随着生产力提高,种间竞争从低生产力时的地下竞争转向高生产力时的光竞争,是光竞争导致了物种多样性的下降。为了验证这两种假说,本文通过在甘南玛曲高寒草甸的均匀施肥实验,研究了光竞争对高寒草甸植物群落物种多样性和生产力关系的影响。结果表明：(1)随着施肥梯度的增加,大部分植物的生长速率加快,高度和叶面积增加;(2)随着施肥梯度的增加,植物群落地上总的生物量提高,叶面积指数增加,透光率降低,物种多样性减少;(3)个体大小不对称的光竞争导致了高寒草甸植物群落物种多样性随施肥梯度的增加而减少。     

Effect of Erosion on Productivity in Subtropical Red Soil Hilly Region: A Multi-Scale Spatio-Temporal Study by Simulated Rainfall

The effects of water erosion (including long-term historical erosion and single erosion event) on soil properties and productivity in different farming systems were investigated. A typical sloping cropland with homogeneous soil properties was designed in 2009 and then protected from other external disturbances except natural water erosion. In 2012, this cropland was divided in three equally sized blocks. Three treatments were performed on these blocks with different simulated rainfall intensities and farming methods: (1) high rainfall intensity (1.5 - 1.7 mm min⁻¹), no-tillage operation; (2) low rainfall intensity (0.5 - 0.7 mm min⁻¹), no-tillage operation; and (3) low rainfall intensity, tillage operation. All of the blocks were divided in five equally sized subplots along the slope to characterize the three-year effects of historical erosion quantitatively. Redundancy analysis showed that the effects of long-term historical erosion significantly caused most of the variations in soil productivity in no-tillage and low rainfall erosion intensity systems. The intensities of the simulated rainfall did not exhibit significant effects on soil productivity in no-tillage systems. By contrast, different farming operations induced a statistical difference in soil productivity at the same single erosion intensity. Soil organic carbon (SOC) was the major limiting variable that influenced soil productivity. Most explanations of long-term historical erosion for the variation in soil productivity arose from its sharing with SOC. SOC, total nitrogen, and total phosphorus were found as the regressors of soil productivity because of tillage operation. In general, this study provided strong evidence that single erosion event could also impose significant constraints on soil productivity by integrating with tillage operation, although single erosion is not the dominant effect relative to the long-term historical erosion. Our study demonstrated that an effective management of organic carbon pool should be the preferred option to maintain soil productivity in subtropical red soil hilly region.     

Pyrogeographic models,feedbacks and the future of global fire regimes

Conceptual and phenomenological macroecological models of current global fire activity have demonstrated the overwhelming control exerted by primary productivity. Fire activity is very high in savanna regions with intermediate primary productivity, and very low in both densely forested regions with high productivity and arid/cold regions with low productivity. However, predicting future global fire activity using such macroecological models of fire's global ‘niche’ may not be possible because of the feedbacks between fire, climate and vegetation that underpin the fire?productivity relationship. Improving forecasts of global fire activity demands the use of dynamic models to determine how climate, CO₂, vegetation (i.e. canopy closure and plant functional types) and primary productivity constrain fire and evaluation of the strength of feedbacks amongst these variables.     

The Diatoms,Productivity and Morphometry of 43 Lakes in New York State,U.S.A

Diatoms were examined in surface sediments collected from 43 lakes throughout New York State to determine the interrelationships among the abundances of various diatom taxa,' lake productivity and lake morphometry. Diatom ratios, including the A/C, C/P and five new quotients, were not well correlated with lake productivity, probably because of the diversity of the taxa which they employ. The abundance of individual genera or combinations of genera were better indicators of productivity. Cyclotella was the best single indicator of productivity being most abundant in low productivity lakes. Several fairly distinct diatom associations were identified by correlations between all possible pairs of diatom taxa. Finally, lake productivity was found to be significantly correlated with morphometry, being highest in small/shallow lakes.