Punching Shear Retrofit Method Using Shear Bolts for Reinforced Concrete Slabs under Seismic Loading

Reinforced concrete slab-column structures are widely used because of their practicality. However, this type of structures can be subject to punching-shear failure in the slab-column connections. Without shear reinforcement, the slab-column connection can undergo brittle punching failure, especially when the structure is subject to lateral loading in seismic zones. The shear bolts are a new type of transverse reinforcement developed for retrofit of existing structures against punching. This research focuses on how the shear bolts can improve the punching-shear capacity and ductility of the existing slab-column connections under vertical service and lateral seismic loads. A set of nine full-scale reinforced concrete slab-column connection specimens were tested under vertical service and cyclic loads. The vertical (gravity) load for each specimen was kept at a constant value throughout the testing. The cyclic lateral drift with increasing intensity was applied to the columns. The specimens were different in number of bolts, concrete strength, number of openings, and level of gravity punching load. Strains in flexural rebars in the slabs, crack widths, lateral loads, and displacements were obtained. The peak lateral load (moment) and its corresponding drift ratio, connection stiffness, crack width, and ductility were compared among different specimens. The testing results show that shear bolts can increase lateral peak load resisting capacity, lateral drift capacity at peak load, and ductility of the slab-column connections. Shear bolts also change the failure mode of the slab-column connections and increase the energy dissipation capacity. The thesis includes also research on the development of guidelines for shear bolt design for concrete slab retrofitting, including the punching shear design method of concrete slab (with shear bolts), dimensions of bolts, spacing, and influence of bolt layout patterns. Suggestions are given for construction of retrofitting method using shear bolts. Recommendations are also presented for future research

Plant Functional Traits Are the Mediators in Regulating Effects of Abiotic Site Conditions on Aboveground Carbon Stock-Evidence From a 30 ha Tropical Forest Plot

Understanding the relative contribution of abiotic and biotic factors to the formation of ecosystem functioning across scales is vital to evaluate ecosystem services. Here, we elucidate the effects of abiotic site conditions (i.e., soil and topographic properties) and plant functional traits on variations of stand aboveground carbon (AGC) stock in an old-growth tropical montane rain forest. The response-effect framework in functional ecology is adopted in examining how plant functional traits respond to environmental changes and affect ecosystem functioning. We measured specific leaf area and wood density of 270 woody plant species and estimated stand AGC stocks in a 30-ha forest plot. The relationships among environmental factors (ENVIRONMENT), community-weighted means of functional traits (TRAITS) and stand AGC stocks across nested spatial scales were disentangled by structural equation modeling. The results showed that the stands composed of ‘acquisitive’ species (high specific leaf area and low wood density) had low AGC, whereas stands composed of ‘conservative’ species (low specific leaf area and high wood density) had high AGC. TRAITS responded to ENVIRONMENT and affected AGC directly. ENVIRONMENT had an indirect effect on AGC through its direct effect on TRAITS. TRAITS were more important than ENVIRONMENT in driving variations of AGC. The effects of TRAITS on AGC increased, while the effects of ENVIRONMENT on AGC decreased with the increase of spatial scales in the tropical montane rain forest. Our study suggests that plant functional traits are the mediators in regulating effects of abiotic site conditions on ecosystem functions

Effect of functional training on physical fitness among athletes: a systematic review

There is evidence that functional training is beneficial for the overall physical fitness of athletes. However, there is a lack of a systematic review focused on the effects of functional training on athletes’ physical fitness. Thus, the aimed of the present review is to clarify the effects of functional training on physical fitness among athletes. In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA) Statement guidelines, the systematic search of PubMed, SCOPUS, EBSCOhost (SPORTDiscus), and CINAHL Plus databases was undertaken on the 2nd November 2020 to identify the reported studies, using a combination of keywords related to functional training, physical fitness, and athletes. From the 145 studies, only nine articles met all eligibility criteria and were included in the systematic review. The assessment was performed on the Pedro scale, and the quality of the study included in the nine studies was fair (ranging from 3 to 4). The results showed that speed (n = 6) was the aspect of physical fitness studied in functional training interventions, followed by muscular strength (n = 5), power (n = 4), balance (n = 3), body composition (n = 3), agility (n = 3), flexibility (n= 1) and muscular endurance (n = 1). Existing evidence concludes that functional training significantly impacts speed, muscular strength, power, balance, and agility. Furthermore, there are still limit numbers of evidence showing effect of functional training on flexibility and muscular endurance. In contrast, no significant improvement was found in body composition where functional training was conducted

Field observed relationships between biodiversity and ecosystem functioning during secondary succession in a tropical lowland rainforest

The relationship between biodiversity and ecosystem functioning (BEF) is one of the most concerned topics in ecology. However, most of the studies have been conducted in controlled experiments in grasslands, few observational, field studies have been carried out in forests. In this paper, we report variations of species diversity, functional diversity and aboveground biomass (AGB) for woody plants (trees and shrubs) along a chronosequence of four successional stages (18-year-old fallow, 30-year-old fallow, 60-year-old fallow, and old-growth forest) in a tropical lowland rainforest recovered after shifting cultivation on Hainan Island, China. Fifty randomly selected sample plots of 20 m x 20 m were investigated in each of the four successional stages. Four functional traits (specific leaf area, wood density, maximum species height and leaf dry matter content) were measured for each woody plants species and the relationships between species/functional diversity and AGB during secondary succession were explored. The results showed that both plant diversity and AGB recovered gradually with the secondary succession. AGB was positively correlated with both species and functional diversity in each stage of succession. Consistent with many controlled experimental results in grasslands, our observational field study confirms that ecosystem functioning is closely related to biodiversity during secondary succession in species rich tropical forests. (C) 2013 Elsevier Masson SAS. All rights reserved

Improved allometric models to estimate the aboveground biomass of younger secondary tropical forests

Frequent human activities have resulted in a large number of tropical old-growth forests being replaced by secondary forests at different succession stages. The secondary forests have great potential for carbon accumulation, especially the younger secondary forests (≤ 20 years). Accurately quantifying the biomass of younger secondary forests could help in the implementation of global warming mitigation projects. Biomass estimation of species in different successional stages (i.e., specific functional groups) is helpful to understand the recovery process of younger secondary forests. However, there are few local biomass models developed for younger secondary tropical forests (YSTF), so it is necessary to verify the applicability of biomass models outside the region. In this study, we destructively sampled trees to generate biomass models of mixed species and specific functional groups in YSTF in Hainan Island, China. Improved allometric equations with DBH, tree height and wood density were more accurate in estimating biomass of YSTF (adjusted R2 ≥ 0.960). Models that included branch wood density had the same ability to estimate aboveground biomass as those that included stem wood density (P = 0.885). The existing allometric equations of mature forest or secondary forest have large deviations in estimating the aboveground biomass of YSTF in Hainan Island. Optimal biomass models for specific functional groups include different predictors. We propose that branch wood density can be used as an important predictor for estimating biomass in YSTF, thus reducing the time to disruptive sampling and tree damage in the field. In addition, different predictors play an important role in estimating biomass of functional groups, and hierarchical modeling based on functional groups can improve the accuracy of estimating biomass of younger secondary forests

Positive effects of tree species richness on fine-root production in a subtropical forest in SE-China

Aims: Fine roots play an important role in the biogeochemical cycles of terrestrial ecosystems and are vital for understanding forest ecosystem functioning and services. Higher plant species diversity has been largely reported to increase aboveground community biomass, but how biodiversity affects fine-root production and the related mechanisms in forests remain unclear. In this study, we aim to answer two questions: (i) does fine-root production increase with tree species richness? (ii) Can this effect be explained by niche complementarity among species? Methods: We analyzed data from a large forest biodiversity experiment (BEF-China) with 5-year-old trees. Fine-root growth was measured as standing biomass and annual fine-root regrowth was estimated using ingrowth cores. Moreover, relative yield was calculated to test whether over- or under-yielding occurred when mixtures were compared with the average monoculture of the species included in the mixtures. We calculated functional diversity for fine-root (≤2mm in diameter) traits by Rao’s quadratic entropy index for each species mixture. The effects of manipulated tree species richness and identity on fine-root traits were analyzed with linear mixed-effects models. Mixed models were also used to test the relationships between tree species richness and fine-root standing biomass, annual regrowth and vertical heterogeneity. Important Findings: Fine roots of more than one species were found in half of the soil cores in mixtures indicating that belowground interactions in these young forest stands occurred much earlier than canopy closure. We found significant differences among species in fine-root traits such as diameter and specific root length (SRL), which suggested different resource-use strategies and niche partitioning among species. Mean fine-root diameter of species ranged from 0.31 to 0.74mm, mean SRL ranged from 12.43 m·g−1 to 70.22 m·g−1 and mean vertical distribution index β ranged from 0.68 to 0.93. There was a significant positive relationship between species richness and the evenness of the vertical distribution of fine-root standing biomass. Moreover, marginally significant positive relationships existed between species richness and standing biomass as well as annual regrowth of fine roots. Relative yields and Rao’s quadratic entropy index were both not significantly affected by species richness. However, the relative yield of fine-root standing biomass was marginally correlated with Rao’s quadratic entropy index, implying that belowground niche complementarity between species does contribute to diversity effects. In conclusion, our study showed positive effects of species richness on the filling of soil volume by fine roots in the studied experimental forest communities. This has positive effects on fine-root standing biomass and may also lead to increased aboveground biomass

Positive effects of tree species richness on fine-root production in a subtropical forest in SE-China

Aims Fine roots play an important role in the biogeochemical cycles of terrestrial ecosystems and are vital for understanding forest ecosystem functioning and services. Higher plant species diversity has been largely reported to increase aboveground community biomass, but how biodiversity affects fine-root production and the related mechanisms in forests remain unclear. In this study, we aim to answer two questions: (i) does fine-root production increase with tree species richness? (ii) Can this effect be explained by niche complementarity among species? Methods We analyzed data from a large forest biodiversity experiment (BEF-China) with 5-year-old trees. Fine-root growth was measured as standing biomass and annual fine-root regrowth was estimated using ingrowth cores. Moreover, relative yield was calculated to test whether over-or under-yielding occurred when mixtures were compared with the average monoculture of the species included in the mixtures. We calculated functional diversity for fine-root (<= 2 mm in diameter) traits by Rao's quadratic entropy index for each species mixture. The effects of manipulated tree species richness and identity on fine-root traits were analyzed with linear mixed-effects models. Mixed models were also used to test the relationships between tree species richness and fine-root standing biomass, annual regrowth and vertical heterogeneity. Important Findings Fine roots of more than one species were found in half of the soil cores in mixtures indicating that belowground interactions in these young forest stands occurred much earlier than canopy closure. We found significant differences among species in fine-root traits such as diameter and specific root length (SRL), which suggested different resource-use strategies and niche partitioning among species. Mean fine-root diameter of species ranged from 0.31 to 0.74 mm, mean SRL ranged from 12.43 m.g(-1) to 70.22 m.g(-1) and mean vertical distribution index beta ranged from 0.68 to 0.93. There was a significant positive relationship between species richness and the evenness of the vertical distribution of fine-root standing biomass. Moreover, marginally significant positive relationships existed between species richness and standing biomass as well as annual regrowth of fine roots. Relative yields and Rao's quadratic entropy index were both not significantly affected by species richness. However, the relative yield of fine-root standing biomass was marginally correlated with Rao's quadratic entropy index, implying that belowground niche complementarity between species does contribute to diversity effects. In conclusion, our study showed positive effects of species richness on the filling of soil volume by fine roots in the studied experimental forest communities. This has positive effects on fine-root standing biomass and may also lead to increased aboveground biomass

Correction: Wang, J.S., et al. Effects of Nitrogen Addition on Leaf Decomposition of Single-Species and Litter Mixture in Pinus tabulaeformis Forests. Forests, 2015, 6, 4462–4476

We discovered typographical errors in two sentences and, therefore, changes are needed to our published manuscript [1].[...

Interspecific and intraspecific variation in specific root length drives aboveground biodiversity effects in young experimental forest stands

Aims Although the net biodiversity effect (NE) can be statistically partitioned into complementarity and selection effects (CE and SE), there are different underlying mechanisms that can cause a certain partitioning. Our objective was to assess the role of resource partitioning and species interactions as two important mechanisms that can bring about CEs by interspecific and intraspecific trait variation. Methods We measured tree height of 2493 living individuals in 57 plots and specific root length (SRL) on first-order roots of 368 of these individuals across different species richness levels (1, 2, 4, 8 species) in a large-scale forest biodiversity and ecosystem functioning experiment in subtropical China (BEF-China) established in 2009. We describe the effects of resource partitioning between species by a fixed component of interspecific functional diversity (RaoQ) and further effects of species interactions by variable components of interspecific and intraspecific functional diversity (community weighted trait similarity and trait dissimilarity, CWS and CWD). Finally, we examined the relationships between biodiversity effects on stand-level tree height and functional diversity (RaoQ, CWS and CWD) in SRL using linear regression and assessed the relative importance of these three components of functional diversity in explaining the diversity effects. Important Findings Our results show that species richness significantly affected SRL in five and tree height in ten out of 16 species. A positive NE was generally brought about by a positive CE on stand-level tree height and related to high values of RaoQ and CWS in SRL. A positive CE was related to high values of all three components of root functional diversity (RaoQ, CWS and CWD). Our study suggests that both resource partitioning and species interactions are the underlying mechanisms of biodiversity effects on stand-level tree growth in subtropical forest