Predicting the Growth Interactions between Plants in Mixed Species Stands using a Simple Mechanistic Model

The Conductance model is a simple mechanistic model used topredict the growth of species in monoculture or mixtures fromparameter values derived from plants grown in isolation. Incontrast to many mechanistic models that require extensive parameterization,the Conductance model is able to capture the growth of a broadrange of species using a few simplified assumptions regardingplant growth and easily derived species-specific parameter values.We examine the assumptions within the Conductance model thattotal leaf area per plant is proportional to total plant weight,and that an isolated plant has a projected crown zone area thatis proportional to the 2/3 power of its weight. Power ratherthan linear relations were found between weight and leaf areafor Brassica oleracea, Daucus carota, Matricaria inodora, Solanumnigrum,Stellaria media , Trifolium repens and Veronica persica.For all seven species, the value of the power was less thanunity. All species also exhibited a power relation between crownzone area and weight, with the slope of this relation beingless than 2/3 for B. oleracea, D. carota and S. media. Althoughmorphology type accounted for some of the variation in the parametervalues relating to light interception, there were considerabledifferences between species within upright or prostrate foliagespecies groups. The Conductance model was used to predict yieldsof B. oleracea, S. nigrum and V. persica grown in both monocultureand binary weed-crop mixtures over a range of temporal and spatialscales. After calibrating the model to non-competing plants,the model was used to predict growth of the weed and crop speciesin contrasting densities and stand types. In some crop-weedcombinations, predicted crop and weed weights were within 17%of observed values, with no systematic deviations. In others,systematic and large deviations occurred.Copyright 2001 Annalsof Botany Company Brassica oleracea L., Daucus carota L., Matricaria inodora L., Solanum nigrum L.,Stellaria media L., Trifolium repens L., Veronica persica L., competition, growth, leaf area, crown zone area, light, shoot morphology, canopy architecture     

Root Growth and Recovery in Temperate Broad-Leaved Forest Stands Differing in Tree Species Diversity

In contrast to studies on aboveground processes, the effect of species diversity on belowground productivity and fine-root regrowth after disturbance is still poorly studied in forests. In 12 old-growth broad-leaved forest stands, we tested the hypotheses that (i) the productivity and recovery rate (regrowth per standing biomass) of the fine-root system (root diameter < 2 mm) increase with increasing tree species diversity, and that (ii) the seasonality of fine-root biomass and necromass is more pronounced in pure than in tree species-rich stands as a consequence of non-synchronous root biomass peaks of the different species. We investigated stands with 1, 3, and 5 dominant tree species growing under similar soil and climate conditions for changes in fine-root biomass and necromass during a 12-month period and estimated fine-root productivity with two independent approaches (ingrowth cores, sequential coring). According to the analysis of 360 ingrowth cores, fine-root growth into the root-free soil increased with tree species diversity from 72 g m⁻² y⁻¹ in the monospecific plots to 166 g m⁻² y⁻¹ in the 5-species plots, indicating an enhanced recovery rate of the root system after soil disturbance with increasing species diversity (0.26, 0.34, and 0.51 y⁻¹ in 1-, 3-, and 5-species plots, respectively). Fine-root productivity as approximated by the sequential coring data also indicated a roughly threefold increase from the monospecific to the 5-species stand. We found no indication of a more pronounced seasonality of fine-root mass in species-poor as compared to species-rich stands. We conclude that species identification on the fine root level, as conducted here, may open new perspectives on tree species effects on root system dynamics. Our study produced first evidence in support of the hypothesis that the fine-root systems of more diverse forest stands are more productive and recover more rapidly after soil disturbance than that of species-poor forests.     

Growth of a Mixed Species Lactic Starter in a Continuous "pH-Stat" Fermentor

Optimum growth conditions for mixed species starter FDs 0172 in skim milk, whey medium, and tryptone medium at 25 C in a “pH-stat” continuous fermentor were investigated. Specific growth rate and productivity were found to be influenced both by the medium and the pH value. Highest productivity was found in skim milk medium between pH 5.5 and 5.9. Lactic acid-producing activity of harvested cells decreased by continuous cultivation at pH values lower than 5.9 to 6.1, especially in tryptone and whey medium. Bacterial balance, CO₂ production, and aroma formation were comparable to the control in skim milk and whey medium at any pH, but differed significantly for cells grown in tryptone medium.     

Predicting the Effects of Atmospheric Nitrogen Deposition in Conifer Stands: Evidence from the NITREX Ecosystem-Scale Experiments

The NITREX project, which encompasses seven ecosystem-scale experiments in coniferous forests at the plot or catchment level in northwestern Europe, investigates the effect of atmospheric nitrogen (N) deposition in coniferous forests. The common factor in all of the experiments is the experimentally controlled change in N input over a period of 4–5 years. Results indicate that the status and dynamics of the forest floor are key components in determining the response of forests to altered N inputs. An empirical relationship between the carbon–nitrogen (C/N) ratio of the forest floor and retention of incoming N provides a simply measured tool through which the likely timing and consequences of changes in atmospheric N deposition for fresh waters may be predicted. In the terrestrial ecosystem, a 50% increase in tree growth is observed following the experimental reduction of N and sulfur inputs in a highly N-saturated site, illustrating the damaging effects of acidifying pollutants to tree health in some locations. Few biotic responses to the experimental treatments were observed in other NITREX sites, but the rapid response of water quality to changes in N deposition, and the link to acidification in sensitive areas, highlight the need for N-emission controls, irrespective of the long-term effects on tree health. The observed changes in ecosystem function in response to the experimental treatments have been considered within the framework of the current critical-load approach and thus contribute to the formulation of environmental policy.     

Predicting Gene Function from Uncontrolled Expression Variation among Individual Wild-Type Arabidopsis Plants

Gene expression profiling studies are usually performed on pooled samples grown under tightly controlled experimental conditions to suppress variability among individuals and increase experimental reproducibility. In addition, to mask unwanted residual effects, the samples are often subjected to relatively harsh treatments that are unrealistic in a natural context. Here, we show that expression variations among individual wild-type Arabidopsis thaliana plants grown under the same macroscopic growth conditions contain as much information on the underlying gene network structure as expression profiles of pooled plant samples under controlled experimental perturbations. We advocate the use of subtle uncontrolled variations in gene expression between individuals to uncover functional links between genes and unravel regulatory influences. As a case study, we use this approach to identify ILL6 as a new regulatory component of the jasmonate response pathway.     

Individual Growth and Foraging Responses of age-0 Largemouth Bass to Mixed Prey Assemblages during Winter

We conducted an outdoor pool experiment at a mid-temperate latitude (Ohio, 40°N) to determine how commonly occurring prey assemblages affect individual foraging and growth of individually marked, age-0 largemouth bass during winter. The treatments were low prey, bluegill prey only, macroinvertebrates only, and bluegill plus macroinvertebrates. Across all treatments, growth in mass (g) was unrelated to body size. Conversely, small individuals lost more energy (kJ) than large counterparts in all but the macroinvertebrate-only treatment. With low prey, overall growth of largemouth bass was negative, with losses varying among individuals by 30% and 60% for mass and energy content, respectively. Counterparts in bluegill-only pools also consistently lost mass and energy, with less variability (15% mass; 30% energy). In the macroinvertebrate-only treatment, 31% of individuals gained mass, reflecting the greatest range in mass (100%) and energy (60%) change. With macroinvertebrates plus bluegill, overall growth was generally negative, with intermediate variance among individuals. Variation in growth among individuals typically increased with the frequency that prey occurred in diets during sampling. Apparently, some individuals were inactive, foraged infrequently, and consistently lost intermediate quantities of mass and energy. Others were active and foraged with variable success. Because activity and growth vary among individuals as a function of prey composition during winter, prey assemblages during this season will affect patterns of first-year survival and cohort strength.     

Forest Management and Plant Species Diversity in Chestnut Stands of Three Mediterranean Areas

Over many centuries, chestnut fruits had an important role as food, while chestnut wood was used for local purposes. Today sweet chestnut stands are very common around the western Mediterranean Basin, and it is necessary to analyze the dynamic of plant species diversity in different chestnut stand types (groves and coppices) to guide management strategies that will allow the conservation of biodiversity. Our objective was to analyze consequences on plant species diversity of various management strategies in chestnut stands of three Mediterranean areas, Salamanca (Spain), the Cévennes (France), and Etna volcano (Italy). We found that plant species diversity is different according to management types; it is higher in groves than in coppice stands. We also demonstrated that Castanea sativa cultivated groves were characterized by small heliophillous therophytes. C. sativa abandoned groves, mixed C. sativa–Quercus pyrenaica coppice stands, Q. pyrenaica coppice stands, and young C. sativa coppice stands were characterized by hemicryptophytes with anemochorous dispersal mode and chamaephytes. Medium and old C. sativa coppice stands (that differ by the shoot age) were characterized by phanerophytes with zoochorous dispersal mode. Human perturbations maintain a quite high level of species diversity. In contrast, the abandonment of chestnut stands leads to homogeneous vegetation with decreasing diversity. One solution could be to maintain a landscape mosaic constituted of diverse chestnut stands modified by human activities (groves, cultivated or abandoned, and coppice stands). This could enhance regional plant diversity.     

Modelling Tree Roots in Mixed Forest Stands by Inhomogeneous Marked Gibbs Point Processes

The aim of the paper is to apply point processes to root data modelling. We propose a new approach to parametric inference when the data are inhomogeneous replicated marked point patterns. We generalize Geyer's saturation point process to a model, which combines inhomogeneity, marks and interaction between the marked points. Furthermore, the inhomogeneity influences the definition of the neighbourhood of points. Using the maximum pseudolikelihood method, this model is then fitted to root data from mixed stands of Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus sylvatica L.) to quantify the degree of root aggregation in such mixed stands. According to the analysis there is no evidence that the two root systems are not independent.     

Predicting Achievable Fundamental Frequency Ranges in Vocalization Across Species

Vocal folds are used as sound sources in various species, but it is unknown how vocal fold morphologies are optimized for different acoustic objectives. Here we identify two main variables affecting range of vocal fold vibration frequency, namely vocal fold elongation and tissue fiber stress. A simple vibrating string model is used to predict fundamental frequency ranges across species of different vocal fold sizes. While average fundamental frequency is predominantly determined by vocal fold length (larynx size), range of fundamental frequency is facilitated by (1) laryngeal muscles that control elongation and by (2) nonlinearity in tissue fiber tension. One adaptation that would increase fundamental frequency range is greater freedom in joint rotation or gliding of two cartilages (thyroid and cricoid), so that vocal fold length change is maximized. Alternatively, tissue layers can develop to bear a disproportionate fiber tension (i.e., a ligament with high density collagen fibers), increasing the fundamental frequency range and thereby vocal versatility. The range of fundamental frequency across species is thus not simply one-dimensional, but can be conceptualized as the dependent variable in a multi-dimensional morphospace. In humans, this could allow for variations that could be clinically important for voice therapy and vocal fold repair. Alternative solutions could also have importance in vocal training for singing and other highly-skilled vocalizations.     

油松侧柏混交林及其纯林枯枝落叶生态效益的研究

枯枝落叶作为森林生态系统中净第一性生产力的重要组成部分,是物质循环过程中的一个物质库,起着涵养水分,减少地表蒸发,改善土壤肥力,防止水土流失的重要作用。油松(Pinus tabulaeformis)和侧柏(Platicladus orientalis)是我国北方山区防护林的主要造林树种,目前多为人工纯林。这种针叶纯林一般生长缓慢,郁闭较迟,保持水土的能力也较差,并易受自然灾害的影响,从而不能有效地     

Biotic Interactions between Two Species of Microalgae in Mixed Culture

Biotic interactions in a mixed culture of two microalgae species—Scenedesmus quadricauda (Turp.) Breb. and Monoraphidium arcuatum (Korsch.) Hind.—used in bioassay in monocultures as test objects were studied. The toxic effect of cell-free filtrates from different “age” monoculture (2, 7, 10, 15, 21, and 28 days) of S. quadricauda on the growth of the “young” test culture of M. arcuatum and, conversely, the toxic effect of cell-free filtrates from the different “age” (2, 7, 10, 15, 21, and 28 days) monoculture of M. arcuatum on the growth of the “young” test culture of S. quadricauda was evaluated. Simultaneously, the toxicity of their own filtrates of different “ages” was monitored by a test culture of each species. The interactions of the species in the mixed culture can be regarded as negative, as an antagonistic one, when both populations inhibit the growth of each other through metabolites and food resource competition, while the effect of S. quadricauda on M. arcuatum is much stronger. The main factor constraining the growth of monoculture S. quadricauda is the rapid depletion of the food resource from the medium and not the inhibition of growth by its own metabolites. The depletion of the food resources from the medium in monoculture of M. arcuatum occurs much later than in monoculture of S. quadricauda. Metabolites of S. quadricauda cause a strong inhibitory effect on the growth of M. arcuatum, and the metabolites of M. arcuatum cause a weak inhibitory effect on the growth of S. quadricauda. The filtrates of the “old” culture of S. quadricauda (21–28 days) cause the greatest inhibitory effect on cell division of M. arcuatum. The filtrates of the “old” culture of S. quadricauda (21–28 days) cause the greatest inhibitory effect on cell division of M. arcuatum. Comparative analysis of the cell number dynamics of two species, S. quadricauda and M. arcuatum, in mono- and two-species algal cultures, as well as experiments with filtrates of these monocultures, showed that the interaction of species can be explained by the food resource competition and allelopathic interaction (exometabolite effect).     

Radioisotopic Method for Measuring Cell Division Rates of Individual Species of Diatoms from Natural Populations

Silicon is an essential element for diatom frustule synthesis and is usually taken up only by dividing cells. With ⁶⁸Ge, a radioactive analog of Si, the cell cycle marker event of frustule formation was identified for individual species of diatom. The frequency of cells within a population undergoing this division event was estimated, and the cell division rate was calculated. In laboratory cultures, these rates of cell division and those calculated from changes in cell numbers were similar. By dual labeling with ⁶⁸Ge(OH)₄ and NaH¹⁴CO₃, rates of cell division and photosynthesis were coincidently measured for diatoms both in laboratory cultures and when isolated from natural populations in estuarine, offshore, and polar environments. These techniques permit the coupling between photosynthesis and cell division to be examined in situ for individual species of diatom.     

Allometric Growth in Four Species of Digenetic Trematodes of Marine Fishes from Belize

Four species of digenetic trematodes of marine fishes from Belize are studied for allometric growth: Multitestis rotundus Sparks, 1954 (Lepocreadiidae), Stenopera equilata Manter, 1933 (Opecoelidae), Leurodera decora Linton, 1910 (Hemiuridae), Prosorhynchus pacificus Manter, 1940 (Bucephalidae). These are compared with six other species for which allometric growth is known. Positive growth is exhibited in all species only by the hindbody, whereas the forebody, suckers, and pharynx are negative in all. The body width, post-testicular body, and gonads are positive in some species and negative in others. At times the body proportion or organ is growing at about the same rate as the body length.     

A New Growth Effecting Peptide of Bacillus Species from Soybean Cake

A new peptide, which has a marked effect on the growth of Bacillus species, was purified from soybean cake by a procedure employing ammonium sulfate fractionation, and active charcoal-, DEAE-Sephadex A–25- and Sephadex gel-column chromatographies. The purified peptide gave a single band on paper electrophoresis. The peptide possessed the following properties: specific extinction (E at 280nm), 11.9; N-terminal amino acid, glutamate; molecular weight, 8058; total number of amino acid, 70; chemical composition (%), C, 49.12; H, 6.26; N, 16.44; and S, 2.34; isoelectric point, pH4.3. The hydrolyzed peptide had no stimulative effect on the growth of Bacillus species. Especially, those microorganisms belonging to the genera of Bacillus, Arthrobacter and Xanthomonas were remarkably sensitive to the peptide.     

生物量分配影响三种不同海拔起源的松树生长

松属的思茅松（Pinus kesiya var．1angbianensis）、云南松（P．yunnanensis）和高山松（P．densata）是组成中国西南不同海拔针叶森林的主要树种,然而这三个树种在发育速度尤其是高生长方面表现出明显的差异。为了弄清引起这些变异的生理和形态学原因．本文将三种松树种植于同一环境下,对其光合作用、生物量分配、生长速率和叶片性状进行了研究。研究发现,与来源于高海拔的树种相比,低海拔的树种有更高的株高、以及更大的干物质重量、相对生长速率、叶质比、茎质比和比叶面积,但叶片氮含量、碳含量和根质比较低。高海拔树种的光合速率并不明显低于低海拔树种。相对生长速率和树高均与叶质比呈显著正相关,与根质比负相关,但与最大光合速率没有显著关系。这些结果表明,生物量的分配式样和长期的形态特性能够更好地预测不同海拔松树的生长表现。     

Above- and Below-ground Growth of Forest Stands: a Carbon Budget Model

The utilization and allocation of carbon by a forest stand areexamined through a simple dynamic, mechanistic model which incorporatesradiation interception, photosynthesis, respiration, assimilatepartitioning, litterfall, root mortality and turnover. Qualitativemathematical analysis of the balance between carbon gains andlosses provides an intuitive insight into the determinants ofabove- and below-ground growth. The patterns of dry matter accumulationproduced by the model are compared with observed trends in standdevelopment. Reported differences between biomass distributionon sites of high and low productivity are reproduced by adjustingthe coefficients of assimilate partitioning. Forest stand growth, model forest growth, carbon budget, photosynthesis, assimilate partitioning     

Links between Belowground and Aboveground Resource-Related Traits Reveal Species Growth Strategies that Promote Invasive Advantages

Belowground processes are rarely considered in comparison studies of native verses invasive species. We examined relationships between belowground fine root production and lifespan, leaf phenology, and seasonal nitrogen dynamics of Lonicera japonica (non-native) versus L. sempervirens (native) and Frangula alnus (non-native) versus Rhamnus alnifolia (native), over time. First and second order fine roots were monitored from 2010 to 2012 using minirhizotron technology and rhizotron windows. ¹⁵N uptake of fine roots was measured across spring and fall seasons. Significant differences in fine root production across seasons were seen between Lonicera species, but not between Frangula and Rhamnus, with both groups having notable asynchrony in regards to the timing of leaf production. Root order and the number of root neighbors at the time of root death were the strongest predictors of root lifespan of both species pairs. Seasonal ¹⁵N uptake was higher in spring than in the fall, which did not support the need for higher root activity to correspond with extended leaf phenology. We found higher spring ¹⁵N uptake in non-native L. japonica compared to native L. sempervirens, although there was no difference in ¹⁵N uptake between Frangula and Rhamnus species. Our findings indicate the potential for fast-growing non-native Lonicera japonica and Frangula alnus to outcompete native counterparts through differences in biomass allocation, root turnover, and nitrogen uptake, however evidence that this is a general strategy of invader dominance is limited.