Size Inequality Research Articles

General power-law temporal scaling for unequal-size microbubble coalescence.

We systematically study the effects of liquid viscosity, liquid density, and surface tension on global microbubble coalescence using lattice Boltzmann simulation. The liquid-gas system is characterized by Ohnesorge number Oh≡η_{h}/sqrt[ρ_{h}σr_{F}] with η_{h},ρ_{h},σ, and r_{F} being viscosity and density of liquid, surface tension, and the radius of the larger parent bubble, respectively. This study focuses on the microbubble coalescence without oscillation in an Oh range between 0.5 and 1.0. The global coalescence time is defined as the time period from initially two parent bubbles touching to finally one child bubble when its half-vertical axis reaches above 99% of the bubble radius. Comprehensive graphics processing unit parallelization, convergence check, and validation are carried out to ensure the physical accuracy and computational efficiency. From 138 simulations of 23 cases, we derive and validate a general power-law temporal scaling T^{*}=A_{0}γ^{-n}, that correlates the normalized global coalescence time (T^{*}) with size inequality (γ) of initial parent bubbles. We found that the prefactor A_{0} is linear to Oh in the full considered Oh range, whereas the power index n is linear to Oh when Oh<0.66 and remains constant when Oh>0.66. The physical insights of the coalescence behavior are explored. Such a general temporal scaling of global microbubble coalescence on size inequality may provide useful guidance for the design, development, and optimization of microfluidic systems for various applications.

Spatial size diversity in natural and planted forest ecosystems: Revisiting and extending the concept of spatial size inequality

Plant size diversity or plant size inequality is a much neglected aspect of plant diversity and biodiversity. And yet size diversity plays an important role in understanding the dynamics of plant diversity and natural mechanisms of maintaining plant diversity, which is of great significance in a time of ongoing global changes. In this study, we introduced and investigated a new measure of spatial size inequality, namely the size segregation function. The new characteristic depends on distance and turned out to be a meaningful and more general extension of the traditional size differentiation index, because it describes local size inequality more extensively. To test the size segregation function we analysed and modelled thirteen large, fully mapped plots from temperate and subtropical forest ecosystems in China. We tested and validated the new function through cluster analysis and a special variant of partial spatial reconstruction. Our results showed that the size segregation function discriminated well between different patterns of spatial size diversity in the complex, mostly natural forests of China. Two random-labelling tests used in the study also highlighted how closely linked spatial species and size diversity are in such species-rich forest ecosystems: Often each species represents a distinctive size range and then spatial size inequality can be interpreted as being a consequence of spatial species mingling. This close relationship between species and size should also be taken into account in analyses of species-rich plant populations. For practical conservation this implies that high size inequality can often be found where there is high species mingling and vice versa.

Mapping forest structural heterogeneity of tropical montane forest remnants from airborne laser scanning and Landsat time series

Abstract Tropical montane forests are important reservoirs of carbon and biodiversity and have a central role in the hydrological cycle. They are, however, very fragmented and degraded, leaving isolated remnants across the landscape. These montane forest remnants have considerable differences in forest structure, depending on factors such as tree species composition and degree of forest degradation. Our objectives were (1) to analyse the reliability of airborne laser scanning (ALS) in modelling forest structural heterogeneity, as described by the Gini coefficient (GC) of tree size inequality; (2) to determine whether models are improved by including tree species-sensitive spectral-temporal metrics from the Landsat time series (LTS); and (3) to evaluate differences between three forest remnants and different forest types using the resulting maps of predicted GC. The study area was situated in Taita Hills, Kenya, where indigenous montane forests have been partly replaced by single-species plantations. The data included field measurements from 85 sample plots and two ALS data sets with different pulse densities (9.6 and 3.1 pulses m−2). GC was modeled using beta regression. We found that GC was predicted more accurately by the ALS data set with a higher point density (a cross-validated relative root mean squared error (rRMSECV) 13.9%) compared to ALS data set with lower point density (rRMSECV 15.1%). Furthermore, important synergies exist between ALS and LTS metrics. When combining ALS and LTS metrics, rRMSECV was improved to 12.5% and 13.0%, respectively. Therefore, if the LTS metrics are included in models, ALS data with lower pulse density are sufficient to yield similar accuracy to more expensive, higher pulse density data acquired from the lower altitude. In Ngangao and Yale, forest canopy has multiple layers of variable tree sizes, whereas elfin forests in Vuria are of more equal tree size, and the GC value ranges of the indigenous forests are 0.42–0.71, 0.20–0.74, and 0.17–0.76, respectively. The single-species plantations of cypress and pine showed lower values of GC than indigenous forests located in the same remnants in Yale, whereas Eucalyptus plantations showed GC values more similar to the indigenous forests. These results show the usefulness of GC maps for identifying and separating forest types as well as for assessing their distinctive ecologies.

Loblolly pine outperforms slash pine in the southeastern United States – A long-term experimental comparison study

Loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) are the two most important commercial timber species in the southeastern U.S. A long-term experimental comparison study, in which loblolly and slash pine plots were paired for combinations of planting density (741, 2224, 3706 trees ha−1) and cultural intensity (operational versus intensive), was established in the lower Coastal Plain to investigate species differences in growth dynamics. Using age 2–21-year inventory plot data and destructive biomass/nutrient sampling data, species comparisons were conducted comprehensively, and the reasons of the species differences and management implications were discussed. When compared to slash pine, loblolly pine had higher stand basal area carrying capacity and maximum stand density index, lower fusiform rust infection rate and less wind damage, leading to its lower mortality. With no species difference in average DBH, loblolly pine consistently had greater average height and live crown length and higher level of tree size inequality. Loblolly pine had lower foliar biomass and lower foliar density, and higher crown length/width ratios due primarily to its longer crowns, suggesting perhaps a slightly greater shade tolerance or less dense canopy. As a result, loblolly pine outperformed slash pine in terms of stand basal area, total volume, aboveground biomass and carbon accumulation. Loblolly pine consistently accumulated more potassium, and this species difference increased with increasing stand age; while slash pine had slightly higher nitrogen and phosphorus contents before age 12. Species differences in mortality patterns and in nutrient accumulations in aboveground biomass emphasized the need to develop species-specific management strategies including different thinning and fertilization regimes.

Asymmetric competition, ontogenetic growth and size inequality drive the difference in productivity between two-strata and one-stratum forest stands

Size inequality has been considered a key feature of plant population structure with impacts on ecosystem functions. In forest ecosystems, studies examining the relationship between tree size inequality and stand productivity have produced mixed outcomes. These studies found positive, neutral or negative relationships and discussed how this could be influenced by competition for light between trees (e.g. light interception efficiency), but far less attention has been paid to the role played by tree ontogenetic growth. In this article, we present a simple mathematical model that predicts the basal area growth of a two-strata stand as a function of tree basal areas and asymmetric competition. Comparing the growth of this stand to the growth of a spatially homogeneous one-stratum stand and a spatially heterogeneous one-stratum stand, we show that higher growth of the two-strata stand is achieved for concave shape, increasing functions of ontogenetic growth and for low intensities of absolute size-asymmetric competition. We also demonstrate that the difference in growth between the two-strata stand and the one-stratum stands depends on tree size inequality, mean tree basal area and total basal area in the two-strata stand. We finally found that the relationships between tree size inequality and productivity can vary from positive to negative and even non-monotonous. However, we highlight that negative relationships may be more frequent. As a conclusion, our results indicate that ontogenetic growth can have a major impact on the form and the magnitude of the size inequality–productivity relationship.

The McMansion Effect: Top Size Inequality, House Satisfaction and Home Improvement in U.S. Suburbs

This paper provides direct field-level evidence of positional externalities in the size of neighboring houses. Combining data from the American Housing Survey with a geolocalized data set of three million suburban houses, I find that new constructions at the top of the house size distribution lower the satisfaction that neighbors derive from their own house size. Positional externalities are stronger among people living in larger houses and decrease with the distance from so-called McMansions. I provide further evidence that homeowners exposed to the construction of large houses in their suburb put a lower price on their home, are more likely to upscale to a larger house, and take up more debt.

Cover crop effects on horseweed (Erigeron canadensis) density and size inequality at the time of herbicide exposure

AbstractProactive integrated weed management (IWM) is critically needed in no-till production to reduce the intensity of selection pressure for herbicide-resistant weeds. Reducing the density of emerged weed populations and the number of larger individuals within the population at the time of herbicide application are two practical management objectives when integrating cover crops as a complementary tactic in herbicide-based production systems. We examined the following demographic questions related to the effects of alternative cover-cropping tactics following small grain harvest on preplant, burndown management of horseweed (Erigeron canadensis L.) in no-till commodity-grain production: (1) Do cover crops differentially affect E. canadensis density and size inequality at the time of herbicide exposure? (2) Which cover crop response traits are drivers of E. canadensis suppression at time of herbicide exposure? Interannual variation in growing conditions (study year) and intra-annual variation in soil fertility (low vs. high nitrogen) were the primary drivers of cover crop response traits and significantly affected E. canadensis density at the time of herbicide exposure. In comparison to the fallow control, cover crop treatments reduced E. canadensis density 52% to 86% at the time of a preplant, burndown application. Cereal rye (Secale cereale L.) alone or in combination with forage radish (Raphanus sativus L.) provided the most consistent E. canadensis suppression. Fall and spring cover crop biomass production was negatively correlated with E. canadensis density at the preplant burndown application timing. Our results also show that winter-hardy cover crops reduce the size inequality of E. canadensis populations at the time of herbicide exposure by reducing the number of large individuals within the population. Finally, we advocate for advancement in our understanding of complementarity between cover crop– and herbicide-based management tactics in no-till systems to facilitate development of proactive, herbicide-resistant management strategies.

Firm Size and Concentration Inequality: A Flexible Extension of Gibrat’s Law

Firm Size and Concentration Inequality: A Flexible Extension of Gibrat’s Law

Elucidating space, climate, edaphic, and biodiversity effects on aboveground biomass in tropical forests

AbstractAim and hypothesisThis study aims to disentangle the direct and indirect roles of space, climate, edaphic, and biodiversity effects on aboveground biomass in natural tropical forests, thereby evaluating the relative effects and contribution of abiotic and biotic factors on aboveground biomass. We hypothesized that the space effect drives the longitudinal, latitudinal, and elevational patterns in climatic and edaphic factors, thereby directly and indirectly determining the relationships between biodiversity and aboveground biomass in natural tropical forests.MethodsWe used structural equation modelling for linking spatial, climatic, edaphic, and biotic factors of aboveground biomass, using data from 247,691 trees across 907 tropical forest plots (total sampling area of 145.23 ha) of Hainan Island in Southern China.ResultsAboveground biomass increased directly with functional dominance, individual tree size inequality, and climatic water availability but decreased directly with space and edaphic effects. However, space effect increased aboveground biomass indirectly via simultaneously differential direct changes (positive, negative, and non‐significant) in climatic, edaphic, and biotic factors. As such, indirect effects of mean annual temperature and climatic water availability decreased aboveground biomass through differential direct changes in biotic factors, but opposite was true for soil fertility.ConclusionsWe argue that, despite the high relative contribution of biodiversity to aboveground biomass, the direct and indirect roles of space, climatic, and edaphic effects are also important for explaining biotic factors and aboveground biomass under the predictions of several abiotic‐based hypotheses. Hence, conserving biodiversity across space is important for forest management and land development under climate change.

Management strategies alter competitive interactions and structural properties of Norway spruce in mixed stands of Bialowieża Forest, Poland

A deep understanding of vertical and horizontal structure of old-growth Norway spruce mixed forests is critical for anticipating management outcomes and developing appropriate strategies for sustaining these complex forests. In most cases, the forest structure is assessed at stand level; however, the outcomes and impacts of natural disturbances (e.g., competition-induced mortality) and human interventions on development of spruce mixed forests occur across a landscape. We compared spatial interactions and size inequality on 148 plots randomly distributed across spruce-dominated stands in the national park (NP), protected stands (PS), and managed stands (MS) of the Bialowieża Forest (BF) in north-eastern Poland. Spatial pattern analyses and Gini coefficient (GC) were used to describe the conditions of spruce mixed stands with different management strategies. Scale-dependent density of conspecifics and heterospecifics around spruce individuals, inhibition between the dbh of spruce and neighbouring trees, negative correlation between neighbourhood density and spruce dbh, and size inequality of spruce were the structural properties negatively influenced by human activities in spruce mixed stands and highlight the lasting effect of management on these structural conditions. In contrast, there was no evidence of significant difference between some structural properties, including spruce mean dbh and mean GC values of NP, PS, and MS. The vertical and horizontal structure observed across three parts of the BF reveal the importance of having variation in spatial distribution and size irregularity across PS and MS to approximate these attributes in NP. In addition, the lower dbh of spruce individuals having a conspecific neighbour compared to nearby heterospecifics due to intense intraspecific competition documented in this and other comparisons between pure and mixed spruce forests argues for an increased emphasis on mixture of spruce and other species if the sustainability of spruce is considered as a management objective.

Damage Diversity as a Metric of Structural Complexity after Forest Wind Disturbance

This study presents a new metric for quantifying structural complexity using the diversity of tree damage types in forests that have experienced wind disturbance. Structural complexity studies of forests have to date not incorporated any protocol to address the variety of structural damage types experienced by trees in wind disturbances. This study describes and demonstrates such a protocol. Damage diversity, defined as the richness and evenness of types of tree damage, is calculated analogously to species diversity using two common indices, and termed a ‘Shannon Damage Heterogeneity Index’ (Sh-DHI) and an inverse Simpson Damage Heterogeneity Index (iSi-DHI). The two versions of the DHI are presented for &gt;400 plots across 18 distinct wind disturbed forests of eastern North America. Relationships between DHI and pre-disturbance forest species diversity and size variability, as well as wind disturbance severity, calculated as the fraction of basal area downed in a wind disturbance event, are examined. DHIs are only weakly related to pre-disturbance tree species diversity, but are significantly positively related to pre-disturbance tree size inequality (size diversity). Damage diversity exhibits a robust curvilinear relationship to severity; both versions of the DHI show peaks at intermediate levels of wind disturbance severity, suggesting that in turn structural complexity may also peak at intermediate levels of severity.

Effects of different disturbance patterns on stand structure of infected pure Pinus massoniana plantation

To explore the effects of different disturbance patterns on restoring the health of an infected stand, concentrated disturbance of not cutting trees before 10 years after infection, mode-rate disturbance of cutting infected pine trees, and strong distrubance of cutting infected pine trees, the neighboring trees and poorly growing pine trees were compared in a pure Pinus massomiana plantation infected by Bursaphelenchus xylophlius in Anji, Zhejiang, China. After 16 years, the importance values of P. massoniana in the three treatments were: concentrated disturbance &gt; mode-rate disturbance &gt; strong disturbance. However, the importance values of broad-leaved trees showed the opposite trend. Compared with the concentrated disturbance, the average DBH of P. massoniana in the moderate and strong disturbance treatments were 1.2 and 1.7 times higher, respectively, and those of broad-leaved species were 1.3 and 1.9 times higher, respectively. The average height of pine trees in the moderate and strong disturbance treatments increased 1.5 and 2.0 times, respectively, and those of broad-leaved species 1.2 and 1.8 times, respectively. The tree volume per hectare in moderate and strong disturbance treatments were 5.2 and 3.8 times that of concentrated disturbance treatment, respectively. In the moderate and strong disturbance treatments, the number of trees in each diameter class was greater than in the concentrated disturbance treatment. The stand diameter distribution in the multi-storied moderate and strong disturbance treatments followed an inverse J-shaped curve. The species richness and biodiversity were significantly higher in the mode-rate and strong disturbance treatments than in the concentrated disturbance treatment. The individual size inequality and structural complexity indices followed the order of moderate disturbance &gt; strong disturbance &gt; concentrated disturbance. Under moderate and strong disturbance treatments, the single-storied and evenly aged pure P. massoniana plantation became multi-storied and unevenly aged mixed stands. All the three disturbance patterns promoted the succession of broad-leaved trees, with the pace of succession in the order of strong disturbance &gt; moderate disturbance &gt; concentrated disturbance. In conclusion, moderate disturbance achieved better restoration. Thinning pure P. massoniana plantation could accelerate the succession of a mixed stand to enhance resistance against Bursaphelenchus xylophlius invasion.

Covariation between tree size and shade tolerance modulates mixed-forest productivity

In tree communities, tree size inequality reduces productivity and interacts with tree shade tolerance to modulate stand productivity, with a higher productivity in stands where shade-intolerant species dominate shade-tolerant species in size. Positive diversity–productivity relationships have been reported in different plant communities, including tree communities. These effects may be strongly related to both structural diversity and functional diversity, but also to their interactions if there is a non-random distribution of species functional characteristics among canopy layers. We explore the relative effects on forest productivity of tree species diversity, tree size inequality, and species shade tolerance diversity, as well as the effect of the distribution of tree shade tolerance in the canopy. We used 11,054 mixed-species forest plots from the French Forest Inventory (IGN) distributed throughout France (2006–2011). We analyzed the effects of species richness, shade tolerance diversity, and height inequality on forest plot productivity, represented by basal area annual increment over a period of 5 years, while controlling for first-order structure characteristics (basal area and quadratic mean diameter) and environmental factors (soil water budget and sum of growing degree days). Using the covariance between tree height and shade tolerance in mixed species canopies, we also explored the effect of the distribution of species’ shade tolerance among canopy layers. The results showed a positive effect of species richness (effect size, 0.02) and a negative effect of height inequality (− 0.05) on mixed-forest productivity. We also showed that a negative covariance between shade tolerance and height (e.g., higher proportion of shade-tolerant species in lower height classes) increased productivity (0.01). Shade tolerance diversity did not affect productivity. In tree communities, as shown previously in monospecific forest stands, tree size inequality reduces productivity. This effect is modulated by the distribution of shade tolerance among canopy layers. Previous studies on species diversity effect have generally overlooked the importance of the size structure and the size hierarchy of functional characteristics. These effects are, however, crucial and deserve to be explored in greater detail.

Effects of endogenous and exogenous processes on aboveground biomass stocks and dynamics in Andean forests

Tropical forests are paramount in regulating the global carbon cycle due to the storage of large amounts of carbon in their biomass. Using repeat censuses of permanent plots located at 15 sites in the Andes Mountains of northwest Colombia, we evaluate: (1) the relationship between aboveground biomass (AGB) stocks, AGB dynamics (mortality, productivity, and net change), and changes in temperature across a ca. 3000-m elevational gradient (≈ 16.1 °C); (2) how AGB mortality and AGB productivity interact to determine net AGB change; and (3) the extent to which either fine-grain (0.04-ha) or coarse-grain (1-ha) processes determine the AGB dynamics of these forests. We did not find a significant relationship between elevation/temperature and biomass stocks. The net AGB sequestered each year by these forests (2.21 ± 0.51 Mg ha−1 year−1), equivalent to approximately 1.09% of initial AGB, was primarily determined by tree growth. Both forest structural properties and global warming influenced AGB mortality and net change. AGB productivity increases with greater inequality of tree sizes, a pattern characteristic of forest patches recovering from disturbances. Overall, we find that global warming is triggering directional changes in species composition by thermophilization via increased tree mortality of species in the lower portions of their thermal ranges and that the inclusion of small-scale forest structural changes can effectively account for endogenous processes such as changes in forest structure. The inclusion of fine-grain processes in assessments of AGB dynamics could provide additional insights about the effects that ongoing climate change has on the functioning of tropical montane forests.

Factors influencing overyielding in young boreal mixedwood stands in western Canada

Mixtures of trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss) are a prominent component of the boreal forests of western Canada. Overyielding, indicating higher productivity in mixtures than in monocultures, has been observed in mature stands but has not been examined in young stands (<30 years old) in this region. We used data collected between 2006 and 2015 at 7 locations in Alberta and Saskatchewan for the Western Boreal Growth and Yield Association (WESBOGY) Long Term Study to examine whether overyielding occurs in young mixtures of these species and to identify factors (species composition, stand density, tree size, species proportion, site quality, and climate) that influence overyielding. Our results show that overyielding is occurring in these young boreal mixedwood stands in western Canada. Relative productivity total (RPT), indicating mixing effect (RPT > 1 indicates overyielding), varies from 0.921 to 1.537 among mixedwood treatments, and thinned aspen stands show higher production than unthinned aspen stands. Initial stand density (basal area) and initial aspen size (QMD at the start of the measurement interval) positively influence mixing effect while initial spruce size (QMD) negatively influences mixing effect. The magnitude of overyielding declines with increasing growing season length (DD5) and the relative productivity of aspen decreases with increasing site quality. Species mixtures support higher stocking than pure stands due to differences in growth rate and shade tolerance of the two species. Tree size is also important since productivity will decline when two species compete with each other for space and resources. Consequently, a mixed species stand that has space partitioning and size inequality between species, which reduces competition and favours expression of the functional traits (e.g., shade tolerance) of each species, tends to have better productivity.

Use of the Lorenz curve to measure size inequality and growth dominance in forest populations

ABSTRACTDevised in 1905, the Lorenz curve was used initially to study inequality in income distribution in human populations. Its principles have been adapted to provide measures of the size inequality between individuals in plant populations and to assess the degree to which plants of different sizes tend to dominate growth within the population. This work describes the principles on which these measures are based and the various mathematical methods available to determine their values. The potential for their use in forest populations is illustrated with an example describing their changes with age within a plantation forest stand and how these relate to inter-tree competitive processes within the stand. It is concluded that these measures have considerable value in studying the structure and growth behaviour of forest populations.

Plant growth-promoting rhizobacteria promote plant size inequality

The uniformity of crop yield is extremely important for consumers and of as much relevance to the grower as overall yield. However, size inequality within a plant population is rarely measured and has never before been considered in relation to the use of beneficial microbes for yield enhancement. For the first time, we show that addition of soil bacteria to calabrese plants significantly increased size inequality. These effects were usually more apparent in above-ground biomass. This was caused by some (but not all) plants growing very large when inoculated with bacteria, while control plants were mostly small. We suggest that the main reason is the incompatibility of the inoculated bacteria with those already present in the rhizosphere. In some cases the inoculum matched the indigenous community, providing a benefit to plant growth, while often it did not and plants remained relatively small. We conclude that analyses of size inequality should be an integral part of experiments using microbial soil amendments. These analyses can help to inform the production of more effective microbial products and to ensure that the integration of beneficial microbes into sustainable production systems does not impair uniformity in yield.

Abiotic and biotic drivers of species diversity in understory layers of cold temperate coniferous forests in North China

Understory plants are important components of forest ecosystems and play a crucial role in regulating community structures, function realization, and community succession. However, little is known about how abiotic and biotic drivers affect the diversity of understory species in cold temperate coniferous forests in the semiarid climate region of North China. We hypothesized that (1) topographic factors are important environmental factors affecting the distribution and variation of understory strata, and (2) different understory strata respond differently to environmental factors; shrubs may be significantly affected by the overstory stratum, and herbs may be more affected by surface soil conditions. To test these hypotheses, we used the boosted regression tree method to analyze abiotic and biotic environmental factors that influence understory species diversity, using data from 280 subplots across 56 sites in cold temperate coniferous forests of North China. Elevation and slope aspect were the dominant and indirect abiotic drivers affecting understory species diversity, and individual tree size inequality (DBH variation) was the dominant biotic driver of understory species diversity; soil water content was the main edaphic factors affecting herb layers. Elevation, slope aspect, and DBH variation accounted for 36.4, 14.5, and 12.1%, respectively, of shrub stratum diversity. Shrub diversity decreased with elevation within the range of altitude of this study, but increased with DBH variation; shrub diversity was highest on north-oriented slopes. The strongest factor affecting herb stratum species diversity was slope aspect, accounting for 25.9% of the diversity, followed by elevation (15.7%), slope (12.2%), and soil water content (10.3%). The highest herb diversity was found on southeast-oriented slopes and the lowest on northeast-oriented slopes; herb diversity decreased with elevation and soil water content, but increased with slope. The results of the study provide a reference for scientific management and biodiversity protection in cold temperate coniferous forests of North China.

Aboveground carbon storage is driven by functional trait composition and stand structural attributes rather than biodiversity in temperate mixed forests recovering from disturbances

AbstractKey messageFunctional trait composition and stand structural complexity rather than biodiversity substantially enhance aboveground carbon storage in temperate mixed forests, while accounting for the effects of disturbance intensity. This study provides a strong support to the mass ratio effect in addition to the niche differentiation and facilitation effects.ContextThe underlying mechanisms for the relationships between biodiversity and ecosystem function remain hotly debated for the last four decades.AimsWe tested how do biodiversity, functional trait composition, stand structural attributes, and topographic variables explain aboveground C storage under different disturbance regimes.MethodsWe used linear mixed effects and structural equation models to simultaneously evaluate the effects of biodiversity, stand structure attributes, functional trait composition, and topographic variables on aboveground C storage while considering for the effects of disturbance intensity. We used biophysical data from 260 plots within 11 permanent temperate mixed forests in Northeastern China.ResultsAboveground C storage was driven by stand basal area, individual tree size inequality, community-weighted mean of maximum height and wood density, and diversity (functional evenness and mean nearest taxon distance). The structural equation model showed that aboveground C storage was positively affected by individual tree size inequality and trait composition (i.e., CWM of maximum height), after accounting for the strongest negative direct and indirect effects of disturbance intensity.ConclusionConserving functional identity of species and maintaining complex stand structure would be the alternative choices for higher aboveground C storage in temperate mixed forests.

Study on coalescence dynamics of unequal-sized microbubbles captive on solid substrate

The dynamics of bubble coalescence are of importance for a number of industrial processes, in which the size inequality of the parent bubbles plays a significant role in mass transport, topological change and overall motion. In this study, coalescence of unequal-sized microbubbles captive on a solid substrate was observed from cross-section view using synchrotron high-speed imaging technique and a microfluidic gas generation device. The bridging neck growth and surface wave propagation at the early stage of coalescence were investigated by experimental and numerical methods. The results show that theoretical half-power-law of neck growth rate is still valid when viscous effect is neglected. However, the inertial-capillary time scale is associated with the initial radius of the smaller parent microbubble. The surface wave propagation rate on the larger parent microbubble is proportional to the inertial-capillary time scale.