Elevational plant species richness patterns and their drivers across non-endemics,endemics and growth forms in the Eastern Himalaya

Despite decades of research, ecologists continue to debate how spatial patterns of species richness arise across elevational gradients on the Earth. The equivocal results of these studies could emanate from variations in study design, sampling effort and data analysis. In this study, we demonstrate that the richness patterns of 2,781 (2,197 non-endemic and 584 endemic) angiosperm species along an elevational gradient of 300–5,300 m in the Eastern Himalaya are hump-shaped, spatial scale of extent (the proportion of elevational gradient studied) dependent and growth form specific. Endemics peaked at higher elevations than non-endemics across all growth forms (trees, shrubs, climbers, and herbs). Richness patterns were influenced by the proportional representation of the largest physiognomic group (herbs). We show that with increasing spatial scale of extent, the richness patterns change from a monotonic to a hump-shaped pattern and richness maxima shift toward higher elevations across all growth forms. Our investigations revealed that the combination of ambient energy (air temperature, solar radiation, and potential evapo-transpiration) and water availability (soil water content and precipitation) were the main drivers of elevational plant species richness patterns in the Himalaya. This study highlights the importance of factoring in endemism, growth forms, and spatial scale when investigating elevational gradients of plant species distributions and advances our understanding of how macroecological patterns arise.     

Growth phenological variations in the narrow-leaved ash (Fraxinus angustifolia) over the Mediterranean region: A simulation study

Tree species inhabiting riparian forests under Mediterranean climate have evolved to face summer water shortage but may fail to cope with future increases in drought severity. Thus, understanding tree growth phenological variations in response to environmental conditions is necessary to assess the impact of seasonal drought in riparian forests. In this study, we investigated the response of stem radial growth to climate in the narrow-leaved ash (Fraxinus angustifolia) over its distribution in southern Europe. We simulated intra- and inter-annual growth patterns using the Vaganov-Shashkin (VS) model considering five sites subjected to summer drought but showing different climate conditions. The growth pattern in this species varied from unimodal in cool-wet sites to facultative bimodal in warm-dry sites. Bimodal patterns were characterized by two growth peaks coinciding with favorable climate conditions in spring and autumn. The spring growth peak occurs earlier (May) in warm-dry sites than in wet-cool sites (June–July). The variation in the season growth length and growth timing suggests different strategies adopted by this species to cope with summer drought. The VS model revealed different growth patterns across which would be relevant in predicting the response of this and other riparian tree species to climate warming and aridification. Differences in the length of the growing season, timings of growth peaks and the shift from unimodal to bimodal growth patterns should be considered when assessing growth adjustments to future climate scenarios.     

In vitro growth of bacteria in hemolymph of Galleria mellonella

The in vitro growth patterns of three nonpathogenic species of bacteria in the hemolymph of Galleria mellonella were determined. Similarly, the growth patterns of three pathogenic bacterial species in the hemolymph of normal larvae were compared to patterns in hemolymph from immunized insects. Over the 12-hr observation period, the nonpathogenic species never attained growth in hemolymph that was comparable to that in broth controls. The pathogens in normal hemolymph grew very similarly to controls, whereas, in immune hemolymph the growth of pathogens was greatly inhibited. The growth patterns of both pathogenic and nonpathogenic species of bacteria in normal hemolymph were similar to the in vitro growth patterns previously obtained in whole insect tissue. The possible role of hemolymph in inhibition of growth of bacteria is discussed.     

Patterns of plant species richness in relation to different environments: An appraisal

Abstract. We review patterns of plant species richness with respect to variables related to resource availability and variables that have direct physiological impact on plant growth or resource availability. This review suggests that there are a variety of patterns of species richness along environmental gradients reported in the literature. However, part of this diversity may be explained by the different types and lengths of gradients studied, and by the limited analysis applied to the data. To advance in understanding species richness patterns along environmental gradients, we emphasise the importance of: (1) using variables that are related to the growth of plants (latitudinal and altitudinal gradients have no direct process impact on plant growth); (2) using multivariate gradients, not single variables; (3) comparing patterns for different life forms; and (4) testing for different shapes in the species richness response (not only linear) and for interaction between variables.     

Conspecific plant-soil feedbacks of temperate tree species in the southern Appalachians, USA

Many tree species have seedling recruitment patterns suggesting that they are affected by non-competitive distance-dependent sources of mortality. We conducted an experiment, with landscape-level replication, to identify cases of negative distance-dependent effects and whether variation in these effects corresponded with tree recruitment patterns in the southern Appalachian Mountains region. Specifically, soil was collected from 14 sites and used as inocula in a 62 day growth chamber experiment determining whether tree seedling growth was less when interacting with soil from conspecific (like) than heterospecific (other) tree species. Tests were performed on six tree species. Three of the tree species had been previously described as having greater recruitment around conspecifics (i.e. facilitator species group) compared to the other half (i.e. inhibitor species group). We were then able to determine whether variation in negative distance-dependent effects corresponded with recruitment patterns in the field. Across the six species, none were negatively affected by soil inocula from conspecific relative to heterospecific sources. Most species (four of six) were unaffected by soil source. Two species (Prunus serotina and Tsuga canadensis) had enhanced growth in pots inoculated with soil from conspecific trees vs. heterospecifics. Species varied in their susceptibility to soil pathogens, but trends across all species revealed that species classified as inhibitors were not more negatively affected by conspecific than heterospecific soil inocula or more susceptible to pathogenic effects than facilitators. Although plant-soil biota interactions may be important for individual species and sites, it may be difficult to scale these interactions over space or levels of ecological organization. Generalizing the importance of plant-soil feedbacks or other factors across regional scales may be especially problematic for hyperdiverse temperate forests where interactions may be spatially variable.     

A meta-analysis of the relation between mating system,growth form and genotypic diversity in clonal plant species

Next to its well-described ecological advantages, clonal growth in plants may incur fitness costs, which are associated with the effects of typically large clonal individuals on the patterns of pollen dispersal. These fitness costs include increased selfing and inbreeding depression in self-compatible species, and reduced mate availability in self-incompatible species. Although fitness costs may affect mating system evolution, there is currently no strong evidence available that either self-compatibility or self-incompatibility is associated with clonality. One reason for this may be the variety in growth forms (from guerrilla to phalanx habits) within clonal species, and the fact that growth form may strongly affect mating patterns. We present the results of a formal meta-analysis of 72 published studies, aiming at reporting genotypic diversities across studies and at relating mating system with clonal growth form and genotypic diversity. We found lower genotypic diversities in clonal self-incompatible species compared to self-compatible species, suggesting that mate availability may indeed be reduced in clonal self- incompatible species. We also cannot confirm that mating system is associated with clonal growth form.     

Effects of contemporary environment and Quaternary climate change on drylands plant diversity differ between growth forms

Previous studies on large‐scale patterns in plant richness and underlying mechanisms have mostly focused on forests and mountains, while drylands covering most of the world's grasslands and deserts are more poorly investigated for lack of data. Here, we aim to 1) evaluate the plant richness patterns in Inner Asian drylands; 2) compare the relative importance of contemporary environment, historical climate, vegetation changes, and mid‐domain effect (MDE); and 3) explore whether the dominant drivers of species richness differ across growth forms (woody vs herbaceous) and range sizes (common vs rare). Distribution data and growth forms of 13 248 seed plants were compiled from literature and species range sizes were estimated. Generalized linear models and hierarchical partitioning were used to evaluate the relative contribution of different factors. We found that habitat heterogeneity strongly affected both woody and herbaceous species. Precipitation, climate change since the mid‐Holocene and climate seasonality dominated herbaceous richness patterns, while climate change since the Last Glacial Maximum dominated woody richness patterns. Rare species richness was strongly correlated with precipitation, habitat heterogeneity and historical climatic changes, while common species richness was strongly correlated with MDE (woody) or climate seasonality (herbaceous). Temperature had little effects on the species richness patterns of all groups. This study represents the first evaluation of the large‐scale patterns of plant species richness in the Inner Asian drylands. Our results suggest that increasing water deficit due to anthropogenic activities combined with future global warming may increase the extinction risk of many grassland species. Rare species (both herbaceous and woody) may face severe challenges in the future due to increased habitat destruction caused by urbanization and resource exploitation. Overall, our findings indicate that the hypotheses on species richness patterns based on woody plants alone can be insufficient to explain the richness patterns of herbaceous species.     

Biological invasion hotspots: a trait‐based perspective reveals new sub‐continental patterns

Invader traits (including plant growth form) may play an important, and perhaps overlooked, role in determining macroscale patterns of biological invasions and therefore warrant greater consideration in future investigations aimed at understanding these patterns. To assess this need, we used empirical data from a national‐level survey of forest in the contiguous 48 states of the USA to identify geographic hotspots of forest plant invasion for three distinct invasion characteristics: invasive species richness, trait richness (defined as the number of the five following plant growth forms represented by the invasive plants present at a given location: forbs, grasses, shrubs, trees, and vines), and species richness within each growth form. Three key findings emerged. 1) The hotspots identified encompassed from 9 to 23% of the total area of our study region, thereby revealing many forests to be not only invaded, but highly invaded. 2) Substantial spatial disagreement among hotspots of invasive species richness, invasive trait richness, and species richness of invasive plants within each growth form revealed many locations to be hotspots for invader traits, or for particular growth forms of invasive plants, rather than for invasive plants in general. 3) Despite eastern forests exhibiting higher levels of plant invasion than western forests, species richness for invasive forbs and grasses in the west were respectively greater than and equivalent to levels found in the east. Contrasting patterns between eastern and western forests in the number of invasive species detected for each growth form combined with the spatial disagreement found among hotspot types suggests trait‐based variability in invasion drivers. Our findings reveal invader traits to be an important contributor to macroscale invasion patterns.     

Invasibility of neutral communities

Comparative data in invasion ecology show that (i) disturbance enhances community invasibility, (ii) there is a positive relationship between residence time of an invader and its success, (iii) there are broadly constant proportions of newly arrived species to those that become established and dominant (“tens rule”), and (iv) invasive species have higher growth rates in comparison with non-invasive species. I use a simple neutral model to test whether these patterns occur in communities with all species identical and no species-specific interactions. In the model, local communities are grouped into continents with immigration rates smaller between than within the continents. Species coming from the other continent are considered to be alien and their fates are recorded. In the model, disturbance predictably increases species numbers and numbers of individuals of aliens. However, the model makes different predictions on effects of disturbance on three processes involved in alien species spreading: establishment (positive effect of disturbance), naturalization (negative effect) and dominance (positive effect). The predictions do not change if variation of growth rates is incorporated into the model. The model also predicts positive relationship between residence time and abundance. Total community size had little effect on success of alien species. The broad agreement of the predictions of the neutral model with the patterns from the field suggests that some of these general patterns of community invasibility are to some degree fully independent of any specific biological assumptions and by themselves may not provide many insights on underlying biological processes. Aggregate data should therefore be used with great caution and statistical patterns must be removed by means of generating null model predictions.     

Variation in tropical forest growth rates: combined effects of functional group composition and resource availability

Rates of tree growth in tropical forests reflect variation in life history strategies, contribute to the determination of species' distributional limits, set limits to timber harvesting and control the carbon balance of the stands. Here, we review the resources that limit tree growth at different temporal and spatial scales, and the different growth rates and responses of functional groups defined on the basis of regeneration strategy, maximum size, and species' associations with particular edaphic and climatic conditions.Variation in soil water availability determines intra- and inter-annual patterns of growth within seasonal forests, whereas irradiance may have a more important role in aseasonal forests. Nutrient supply limits growth rates in montane forests and may determine spatial variation in growth of individual species in lowland forests. However, its role in determining spatial variation in stand-level growth rates is unclear. In terms of growth rate, we propose a functional classification of tropical tree species which contrasts inherently fast-growing, responsive species (pioneer, large-statured species), from slow-growing species that are less responsive to increasing resource availability (shade-bearers, small-statured species). In a semi-deciduous forest in Ghana, pioneers associated with high-rainfall forests with less fertile soils, had significantly lower growth rates than pioneers that are more abundant in low-rainfall forests with more fertile soils. These results match patterns found in seedling trials and suggest for pioneers that species' associations with particular environmental conditions are useful indicators of maximum growth rate.The effects of variation in resource availability and of inherent differences between species on stand-level patterns of growth will not be independent if the functional group composition of tropical forests varies along resource gradients. We find that there is increasing evidence of such spatial shifts at both small and large scales in tropical forests. Quantifying these gradients is important for understanding spatial patterns in forest growth rates.     

Modelling the temperature dependent growth rates of planktic foraminifera

The temperature influence on foraminifera growth rate was analysed using a mechanistic formulation that take into account enzyme inactivation at extreme temperatures. Growth rates are calculated using available published and unpublished laboratory culture experiments for eight species, including Neogloboquadrina pachyderma (sinistral and dextral forms), Neogloboquadrina dutertrei, Globigerina bulloides, Globigerinoides ruber, Globigerinoides sacculifer, Globigerinella siphonifera and Orbulina universa. Modeled growth formulas readily reproduce the observed growth patterns for all species. Similar growth patterns are observed for the species that have the same symbiotic algae G. ruber, G. sacculifer, and O. universa. However, different growth patterns are observed for herbivorous species (Neogloboquadrina genus) compared to carnivorous species with or without symbionts. Our growth estimates correspond well to in situ observations from both plankton tows and sediment traps. These estimates will help to improve the quantification of the effects of environmental parameters on foraminifera species distribution and abundance.     

Demographic controls of aboveground forest biomass across North America

Ecologists have limited understanding of how geographic variation in forest biomass arises from differences in growth and mortality at continental to global scales. Using forest inventories from across North America, we partitioned continental‐scale variation in biomass growth and mortality rates of 49 tree species groups into (1) species‐independent spatial effects and (2) inherent differences in demographic performance among species. Spatial factors that were separable from species composition explained 83% and 51% of the respective variation in growth and mortality. Moderate additional variation in mortality (26%) was attributable to differences in species composition. Age‐dependent biomass models showed that variation in forest biomass can be explained primarily by spatial gradients in growth that were unrelated to species composition. Species‐dependent patterns of mortality explained additional variation in biomass, with forests supporting less biomass when dominated by species that are highly susceptible to competition (e.g. Populus spp.) or to biotic disturbances (e.g. Abies balsamea).     

Comparative examination of soluble red muscle proteins of fifteen Sparidae species

Soluble red muscle proteins from the lateral line of 15 Sparidae species were analysed by isoelectric focusing. Species-specific patterns were found. The species-specific protein fractions could be correlated with different metabolic activities and with different growth indexes. More protein fractions were identified for Pagellus acarne (Risso) and Diplodus annularis (L.) than for the other 13 species. This would appear to be related to growth index. The existence of red muscle with a greater number of protein bands than white muscle was confirmed in almost all species. The similarity coefficients have shown that closely related species have similar patterns and, thus, higher similarity coefficients. The derived dendrogram agrees with previous classifications based on morphological information.     

Comparative demography of an epiphytic lichen: support for general life history patterns and solutions to common problems in demographic parameter estimation

Lichens are major components in many terrestrial ecosystems, yet their population ecology is at best only poorly understood. Few studies have fully quantified the life history or demographic patterns of any lichen, with particularly little attention to epiphytic species. We conducted a 6-year demographic study of Vulpicida pinastri, an epiphytic foliose lichen, in south-central Alaska. After testing multiple size-structured functions to describe patterns in each V. pinastri demographic rate, we used the resulting estimates to construct a stochastic demographic model for the species. This model development led us to propose solutions to two general problems in construction of demographic models for many taxa: how to simply but accurately characterize highly skewed growth rates, and how to estimate recruitment rates that are exceptionally difficult to directly observe. Our results show that V. pinastri has rapid and variable growth and, for small individuals, low and variable survival, but that these traits are coupled with considerable longevity (e.g., >50?years mean future life span for a 4-cm(2) thallus) and little deviation of the stochastic population growth rate from the deterministic expectation. Comparisons of the demographic patterns we found with those of other lichen studies suggest that their relatively simple architecture may allow clearer generalities about growth patterns for lichens than for other taxa, and that the expected pattern of faster growth rates for epiphytic species is substantiated.     

Interactive effects of ozone and climate on tree growth and water use in a southern Appalachian forest in the USA

* A lack of data on responses of mature tree growth and water use to ambient ozone (O(3)) concentrations has been a major limitation in efforts to understand and model responses of forests to current and future changes in climate. * Here, hourly to seasonal patterns of stem growth and sap flow velocity were examined in mature trees from a mixed deciduous forest in eastern Tennessee (USA) to evaluate the effects of variations in ambient O(3) exposure and climate on patterns of stem growth and water use. * Ambient O(3) caused a periodic slowdown in seasonal growth patterns that was attributable in part to amplification of diurnal patterns of water loss in tree stems. This response was mediated by statistically significant increases in O(3)-induced daily sap flow and led to seasonal losses in stem growth of 30-50% for most species in a high-O(3) year. * Decreased growth and increased water use of mature forest trees under episodically high ambient O(3) concentrations suggest that O(3) will amplify the adverse effects of increasing temperatures on forest growth and forest hydrology.     

A boundary current drives synchronous growth of marine fishes across tropical and temperate latitudes

Entrainment of growth patterns of multiple species to single climatic drivers can lower ecosystem resilience and increase the risk of species extinction during stressful climatic events. However, predictions of the effects of climate change on the productivity and dynamics of marine fishes are hampered by a lack of historical data on growth patterns. We use otolith biochronologies to show that the strength of a boundary current, modulated by the El Niño‐Southern Oscillation, accounted for almost half of the shared variance in annual growth patterns of five of six species of tropical and temperate marine fishes across 23° of latitude (3000 km) in Western Australia. Stronger flow during La Niña years drove increased growth of five species, whereas weaker flow during El Niño years reduced growth. Our work is the first to link the growth patterns of multiple fishes with a single oceanographic/climate phenomenon at large spatial scales and across multiple climate zones, habitat types, trophic levels and depth ranges. Extreme La Niña and El Niño events are predicted to occur more frequently in the future and these are likely to have implications for these vulnerable ecosystems, such as a limited capacity of the marine taxa to recover from stressful climatic events.     

Annual growth rings, rainfall-dependent growth and long-term growth patterns of tropical trees from the Caparo Forest Reserve in Venezuela

1 Tree-ring analyses and dendrometer measurements were carried out on 37 tree species in a semi-deciduous forest of the Reserva Forestal de Caparo, Venezuela, where the mean annual rainfall is about 1700 mm and there is a dry season from December to March. The main purposes of the investigation were to show the seasonality of cambial growth, and the connection between precipitation patterns and tree-ring curves. Long-term rates of wood increment were also estimated.
2 Cambial markings in consecutive years showed that annual rings were formed by many species.
3 The distinctiveness of growth zones was usually greater in deciduous species than in evergreen species, although not all deciduous species had distinct rings.
4 Dendrometer measurements showed that the annual growth rhythm was related to precipitation patterns. Evergreen species tended to show only a short interruption of wood growth (during the later part of the dry season), whereas deciduous species stopped growth completely at the end of the rainy season.
5 For deciduous species, regression analyses showed close relations between tree-ring width and the sum of precipitation outside the rainy seasons (i.e. November to April). Evergreen species reacted to the total annual amount of precipitation.
6 Variation in longest available ring chronology (for Terminalia guianensis ) showed little correlation with the El Niño–Southern Oscillation effect.
7 On average trees from natural forests showed relatively constant growth over the entire life span. Plantation trees grew fast up to an age of 15–20 years, but annual increments then decreased to values seen in natural forest trees.     

Perinatal ontogeny of brain growth in the domestic pig

The perinatal development of the brain is highlighted by a growth spurt whose timing varies among species. The growth of the porcine cerebrum was investigated from the third trimester of gestation (70 days postconception) through the first 3.5 weeks of postnatal life (140 days postconception). The shape of the growth curves for cerebrum weight, total protein mass, total cell number (estimated by DNA content), and myelination (estimated by cholesterol accretion) were described. The growth velocity of cerebrum weight had two peaks, one at 90 days and the other at 130 days postconception, whereas that of total protein was greatest from 90 to 130 days postconception, and that of total DNA was greatest between 90 and 110 days and again at 130 days postconception. The growth velocity for total cholesterol continued to increase during the entire period, suggesting that myelination continued after the growth spurts for cells (protein and DNA). The growth velocity patterns observed in these contemporary pigs suggest that this species may be an appropriate model for human brain development, not only in the perinatal pattern of increase in mass of the cerebrum, as established previously, but also with regard to the patterns of cellular development and myelination.     

Seasonal development of annual shoots in some terrestrial orchids from Russia and Japan

Annual shoots of 46 terrestrial orchid species commonly found in wide ranges of temperate climates in Russia and Japan change their patterns of growth recurrence from the dormancy state, through formation and growth, to the next dormancy state during the course of yearly response to seasonal cycles of environmental conditions. Each of the species has its own strategy in seasonal development of aerial shoots, rhizomes, tubers and roots, and shows seasonal differentiation of shoot morphogenesis at the early stage of new shoot apex formation in accordance with its growth habit, habitat and range size of geographical distribution. Perennial orchids with sympodial growth patterns and primitive life forms are characterized by long duration of shoot and inflorescence development inside the bud. Among the species studied, the orchids that have annually regenerating root-stem tubers have the shortest duration of root and shoot morphogenesis. The species that have predominant patterns of monopodial growth show variability in duration of lateral shoot growth due to the energy budget of the mother plant. The species which have latitudinally long ranges of distribution from northern colder regions to southern warmer regions tend to take longer for shoot development inside the bud, and aerial shoots have a shorter life-span in the northern regions than those in the south.     

Effects of climate on the growth of exotic and indigenous trees in central Zambia

Aim Climate change has far‐reaching effects on species and ecosystems. The aims of this study were to determine how climate factors affect the growth pattern of indigenous and exotic trees in Zambia and to predict tree growth responses to a warmer climate with the use of mathematical models. Location Two savanna sites in central Zambia. Methods Diameter at breast height (1.3 m above ground, d.b.h.) of 91 permanently marked trees belonging to three indigenous and four exotic species was measured fortnightly for periods of 1–2 years from 1998 to 2003. Correlation and regression analysis was used to determine the effect of climate factors (minimum, maximum and average temperature and rainfall) on monthly daily d.b.h. increment of each species. Regression models were used to predict the growth behaviour of trees under a 0.5 °C warmer climate. Results Interactions between temperature and rainfall explained 60–98% of the variation in d.b.h. increment in all the tree species, except the exotic Eucalyptus grandis. For deciduous species, stem expansion was delayed by 2–12 weeks following leaf‐flush and d.b.h. increment peaked during the rainy season. Evergreen and deciduous species could not be separated on the basis of annual d.b.h. increment because the higher growth rates of deciduous species compensated for the shorter growing period. Mathematical models predicted slight changes in d.b.h. growth pattern under a 0.5 °C warmer climate in five of the seven species. Significant changes in d.b.h. growth patterns were predicted in the indigenous Bridelia micrantha and exotic Gmelina arborea under a warmer climate. However, models failed to adequately represent potential soil water stress that might result from changes in tree growth patterns and a warmer climate. Main conclusions Climate factors explained a large proportion of the variation in diameter growth of both indigenous and exotic trees, rendering it possible to model tree growth patterns from climate data. Tree growth models suggest that a rise in temperature of 0.5 °C is unlikely to induce significant changes in the growth behaviour of the majority of the studied species. However, because the growth behaviour of some species may be substantially affected by climate change, it is recommended that strategies for the future production of such climate‐sensitive trees should incorporate aspects of climate change.