Robust leaf trait relationships across species under global environmental changes

Recent studies show coordinated relationships between plant leaf traits and their capacity to predict ecosystem functions. However, how leaf traits will change within species and whether interspecific trait relationships will shift under future environmental changes both remain unclear. Here, we examine the bivariate correlations between leaf economic traits of 515 species in 210 experiments which mimic climate warming, drought, elevated CO2, and nitrogen deposition. We find divergent directions of changes in trait-pairs between species, and the directions mostly do not follow the interspecific trait relationships. However, the slopes in the logarithmic transformed interspecific trait relationships hold stable under environmental changes, while only their elevations vary. The elevation changes of trait relationship are mainly driven by asymmetrically interspecific responses contrary to the direction of the leaf economic spectrum. These findings suggest robust interspecific trait relationships under global changes, and call for linking within-species responses to interspecific coordination of plant traits

Benefit versus cost trade-offs of masting across seed-to-seedling transition for a dominant subtropical forest species

Masting is a common reproductive strategy regulating seedling regeneration in many perennial plant species. The evolutionary origins and functional benefits of masting have been explained by well-supported hypotheses relating to economies of scale of seed production. Nevertheless, our understanding of the potential costs of masting for the plant seed-to-seedling transitions remains limited. We tracked the seed fate and documented changes in the seed spatial distribution patterns during the seed-to-seedling transition process of Castanopsis fargesii, a dominant species of subtropical evergreen broad-leaved forests in China under natural conditions for more than 6 years. Masting resulted in a high proportion of seeds escaping predation by vertebrates and rodents, supporting the predator satiation hypothesis. However, it increased the pre-dispersal seed predation by insects, and decreased the seed germination rate due to a negative effect on seed mass. This resulted in seed-to-seedling transition rates during mast years to be roughly half as much as during non-mast years. In addition, masting negatively affected the spatial rearrangement of seeds, resulting in a spatial aggregative distribution pattern of newly germinated seedlings. The combined negative effects of smaller seeds and spatially aggregated seedlings reduced the survival rate of newly germinated seedlings at seedling establishment stage. Synthesis. Considering the whole seed-to-established seedling transition process, the benefits of masting on seedling recruitment due to the effective seed predator situation by vertebrates and rodents were decreased by the additional costs on seed mass, seed germination, seed spatial arrangement and seedling establishment. Our results highlight the importance of considering both the positive and negative effects of masting at each stage of the seed-to-seedling transition. Inferences based on seed predation and recruitment of newly germinated seedlings alone would lead to an overly optimistic conclusion about the benefits of masting. © 2021 British Ecological Societ

Data-JEcol-2018-0401

Data from: Tree species diversity promotes litterfall productivity through crown complementarity in subtropical forests. Lists the variables used in structural equation models

Bifurcations and chaos of a vibration isolation system with magneto-rheological damper

Magneto-rheological (MR) damper possesses inherent hysteretic characteristics. We investigate the resulting nonlinear behaviors of a two degree-of-freedom (2-DoF) MR vibration isolation system under harmonic external excitation. A MR damper is identified by employing the modified Bouc-wen hysteresis model. By numerical simulation, we characterize the nonlinear dynamic evolution of period-doubling, saddle node bifurcating and inverse period-doubling using bifurcation diagrams of variations in frequency with a fixed amplitude of the harmonic excitation. The strength of chaos is determined by the Lyapunov exponent (LE) spectrum. Semi-physical experiment on the 2-DoF MR vibration isolation system is proposed. We trace the time history and phase trajectory under certain values of frequency of the harmonic excitation to verify the nonlinear dynamical evolution of period-doubling bifurcations to chaos. The largest LEs computed with the experimental data are also presented, confirming the chaotic motion in the experiment. We validate the chaotic motion caused by the hysteresis of the MR damper, and show the transitions between distinct regimes of stable motion and chaotic motion of the 2-DoF MR vibration isolation system for variations in frequency of external excitation

Real-time diagnosis of high-speed rail traction transformer in different topologies

High-speed railway (HSR) traction transformer, as a connection between traction power supply system and the power grid, is critical in electrified railway design, which requires a drastic change of traction load and frequent external short circuits. In the actual operation process, the traction transformer can produce minor faults that are difficult to detect such as the deformation of the winding, which may result in a serious problem. This study analyses the topology structures and winding fault characteristics of six HSR traction transformers consisting of single phase, Vv, YNd11, Scott, YNvd and impedance matching wiring. Both circuit models of normal operation and fault operation of HSR traction transformer are established. Results show that real-time diagnosis of HSR traction transformer can be accomplished through measuring the voltage signal of the input and output points during operation and establishing real-time monitoring statistics of small faults standardisation（I^2 and squared prediction error）based on fast independent component analysis algorithm, as well as the signal statistics distribution, thereby improving the safety and reliability of HSR operation

Meta-analysis reveals that vertebrates enhance plant litter decomposition at the global scale

The dataset consists of comprehensive information on litter mass loss, elemental recycling (specifically nitrogen and phosphorus release rates), and associated environmental factors. The data was collected using standardized methods and includes details such as study location coordinates, climatic conditions (temperature and precipitation), ecosystem types (terrestrial and aquatic), study subjects (species identity), litterbag specifics (exclusion method and mesh size), and litter tissue types (woody and non-woody). Missing climatic data were obtained from the WorldClim database. The dataset comprises 1568 sets of pairwise comparisons, with 1060 for plant decomposition, 360 for nitrogen release, and 148 for phosphorus release. This comprehensive dataset serves as a valuable resource for studying litter decomposition, nutrient cycling, and the interplay between environmental factors and decomposition processes

Differential magnitude of rhizosphere effects on soil aggregation at three stages of subtropical secondary forest successions

Hosseini Bai, S ORCiD: 0000-0001-8646-6423Background and aims: Roots and their rhizosphere considerably influence soil structure by regulating soil aggregate formation and stabilization. This study aimed to examine the rhizosphere effects on soil aggregation and explore potential mechanisms along secondary forest successions. Methods: Effects of roots and their rhizosphere on soil aggregation in two subtropical secondary forest successions were examined by separating soils into rhizosphere and bulk soils. Soil aggregate mean weight diameter (MWD), soil organic carbon (SOC), soil nutrients, and fine-root traits were simultaneously measured. Results: Soil aggregate MWD increased significantly in the bulk soils along secondary forest successions, but did not differ in the rhizosphere soils. Rhizosphere effects on soil aggregate MWD (i.e., root-induced differences between the rhizosphere and bulk soils) were thus significantly higher at the early-successional stage of subtropical forest with low soil fertility than those at the late stages with high fertility. Rhizosphere significantly increased SOC and soil total nitrogen (TN) throughout the entire secondary forest successions, which was nonlinearly correlated with soil aggregate MWD. Principal components regression analysis showed that SOC was the primary abiotic factor and positively correlated with soil aggregate MWD. As for biotic factors, fine-root length density and N concentration were two important root traits having significant effects on soil aggregate stability. An improved conceptual framework was developed to advance our understanding of soil aggregation and rhizosphere effects, highlighting the roles of soil fertility (i.e., SOC and available nutrients), root traits, and forest age in driving soil aggregation. Conclusions: Impacts of root-derived organic compounds inputs to rhizosphere on soil aggregation were stronger at the early-successional stage of subtropical forest than those at the late stages. This succession-specific pattern in rhizosphere effects largely resulted from the nonlinear relationships between soil aggregate MWD and SOC concentration with a plateau at high SOC. Incorporating the SOC-dependent rhizosphere effects on biogeochemical cycle into Earth system models might improve the prediction of forest soil C dynamics. © 2019, Springer Nature Switzerland AG

Root Production and Microbe-Derived Carbon Inputs Jointly Drive Rapid Soil Carbon Accumulation at the Early Stages of Forest Succession

Plants and microbes are the primary drivers in affecting the formation and accrual of soil organic carbon (SOC) for natural ecosystems. However, experimental evidence elucidating their underlying mechanisms for SOC accumulation remains elusive. Here, we quantified plant and microbial contributions to SOC accrual in successional subtropical forests by measuring leaf-, root-, and microbial biomarkers, root and leaf litter inputs, and microbial C decomposition. The long-term monitoring results showed that SOC accumulated rapidly at the early-successional stage, but changed little at the mid- and late-successional stages. SOC accrual rate was positively correlated with fine-root production and microbial C turnover, but negatively with annual litterfall. Biomarker data exhibited that the rapid SOC accumulation was jointly driven by root- and microbe-derived C inputs from the early- to mid-successional stages. In contrast, aboveground litterfall considerably contributed to soil C accrual from the mid- to late-successional stages compared to belowground processes, although SOC accumulation is low. Our study revealed the importance of root production and microbial anabolism in SOC accrual at the early stages of forest succession. Incorporating these effects of belowground C inputs on SOC formation and accumulation into earth system models might improve model performance and projection of long-term soil C dynamics