of Botany,Chinese Academy Of Sciences
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Distribution of biomass dynamics in relation to tree size in forests across the world
No full textTree size shapes forest carbon dynamics and determines how trees interact with their environment, including a changing climate. Here, we conduct the first global analysis of among-site differences in how aboveground biomass stocks and fluxes are distributed with tree size. We analyzed repeat tree censuses from 25 large-scale (4-52 ha) forest plots spanning a broad climatic range over five continents to characterize how aboveground biomass, woody productivity, and woody mortality vary with tree diameter. We examined how the median, dispersion, and skewness of these size-related distributions vary with mean annual temperature and precipitation. In warmer forests, aboveground biomass, woody productivity, and woody mortality were more broadly distributed with respect to tree size. In warmer and wetter forests, aboveground biomass and woody productivity were more right skewed, with a long tail towards large trees. Small trees (1-10 cm diameter) contributed more to productivity and mortality than to biomass, highlighting the importance of including these trees in analyses of forest dynamics. Our findings provide an improved characterization of climate-driven forest differences in the size structure of aboveground biomass and dynamics of that biomass, as well as refined benchmarks for capturing climate influences in vegetation demographic models
Even short-term revegetation complicates soil food webs and strengths their links with ecosystem functions
No full textDegradation of dryland ecosystems is a worldwide problem caused by climate change and human activities. To restore these degraded ecosystems, governments have implemented projects that often include revegetation, but we still lack an understanding of how soil food webs and ecosystem functions are affected by revegetation. By conducting a large-scale revegetation experiment under two degradation intensities (low and high) on the Inner Mongolian degraded grassland, we tested the effects of revegetation on primary producers (plants), key components of soil food webs (bacteria, fungi and nematodes) and ecosystem functions (soil C and N mineralization). After 4 years, revegetation greatly increased the biomass of plants and soil bacteria and fungi but had less effects on soil nematode functional groups. Revegetation increased vegetation and bacterial diversity and soil C and N mineralization rates, altered the structures of vegetation and soil microbial communities, but did not affect soil fungal or nematode diversity. The stronger effects of revegetation on plants, soil bacteria, soil fungi and soil nematodes in plots with low degradation intensity than in plots with high degradation intensity indicated that future revegetation efforts should consider the degree of degradation. Revegetation also increased the interactions among plants, soil food webs and ecosystem functions, indicating that the revegetation-induced changes in soil food webs could facilitate the recovery of soil nutrients and vegetation productivity in degraded grasslands. Synthesis and applications. The effects of revegetation were stronger on plants (primary producers) and soil micro-organisms (intermediate trophic levels) than on soil nematodes (higher trophic levels), and even short-term revegetation increased the complexity of soil food webs and strengthened their relationships with soil functions in degraded grasslands. These results highlight the effects of restoration on multiple trophic levels in degraded drylands, and suggest that some aspects of plant-soil interactions in global drylands could be rapidly improved by appropriate restoration
Re-evaluation of the identities of Glossadelphus borneensis and its associated synonyms, G. attenuatus and G. nitidus
No full textAn investigation of the type specimen of Glossadelphus borneensis (and its basionym Ectropothecium borneense) and those of its purported synonyms, G. attenuatus and G. nitidus, revealed that these names apply to three distinct taxa belonging to two different genera. The following changes are proposed: Vesicularia borneensis is reinstated for G. borneensis, G. attenuatus is synonymized to Ectropothecium cyperoides and G. nitidus (lectotypified herein) is synonymized to E. obtusulum
Assembly dynamics of East Asian subtropical evergreen broadleaved forests: New insights from the dominant Fagaceae trees
No full textThe dominant species of a biome can be regarded as its genuine indicator. Evergreen broadleaved forests (EBLFs) in subtropical East Asia harbor high levels of species biodiversity and endemism and are vital to regional carbon storage and cycling. However, the historical assembly of this unique biome is still controversial. Fagaceae is the most essential family in East Asian subtropical EBLFs and its dominant species are vital for the existence of this biome. Here, we used the dominant Fagaceae species to shed light on the dynamic process of East Asian subtropical EBLFs over time. Our results indicate high precipitation in summer and low temperature in winter are the most influential climatic factors for the distribution of East Asian subtropical EBLFs. Modern East Asian subtropical EBLFs did not begin to appear until 23 Ma, subsequently experienced a long-lasting development in the Miocene and markedly deteriorated at about 4 Ma, driven jointly by orogenesis and paleoclimate. We also document that there is a lag time between when one clade invaded the region and when its members become dominant species within the region. This study may improve our ability to predict and mitigate the threats to biodiversity of East Asian subtropical EBLFs and points to a new path for future studies involving multidisciplinary methods to explore the assembly of regional biomes
NADP+ supply adjusts the synthesis of photosystem I in Arabidopsis chloroplasts
No full textIn oxygenic photosynthesis, NADP(+) acts as the final acceptor of the photosynthetic electron transport chain and receives electrons via the thylakoid membrane complex photosystem I (PSI) to synthesize NAPDH by the enzyme ferredoxin:NADP(+) oxidoreductase. The NADP(+)/NADPH redox couple is essential for cellular metabolism and redox homeostasis. However, how the homeostasis of these two dinucleotides is integrated into chloroplast biogenesis remains largely unknown. Here, we demonstrate the important role of NADP(+) supply for the biogenesis of PSI by examining the nad kinase 2 (nadk2) mutant in Arabidopsis (Arabidopsis thaliana), which demonstrates disrupted synthesis of NADP(+) from NAD(+) in chloroplasts. Although the nadk2 mutant is highly sensitive to light, the reaction center of photosystem II (PSII) is only mildly and likely only secondarily affected compared to the wild-type. Our studies revealed that the primary limitation of photosynthetic electron transport, even at low light intensities, occurs at PSI rather than at PSII in the nadk2 mutant. Remarkably, this primarily impairs the de novo synthesis of the two PSI core subunits PsaA and PsaB, leading to the deficiency of the PSI complex in the nadk2 mutant. This study reveals an unexpected molecular link between NADK activity and mRNA translation of psaA/B in chloroplasts that may mediate a feedback mechanism to adjust de novo biosynthesis of the PSI complex in response to a variable NADPH demand. This adjustment may be important to protect PSI from photoinhibition under conditions that favor acceptor side limitation. Mutation of NAD KINASE2 leads to NADP+ deficiency and impairs the synthesis of photosystem I in chloroplasts of Arabidopsis
Transcriptomic analysis reveals the role of FOUR LIPS in response to salt stress in rice
No full textKey message An R2R3-MYB transcription factor FOUR LIPS associated with B-type Cyclin-Dependent Kinase 1;1 confers salt tolerance in rice. The Arabidopsis FOUR LIPS (AtFLP), an R2R3 MYB transcription factor, acts as an important stomatal development regulator. Only one orthologue protein of AtFLP, Oryza sativa FLP (OsFLP), was identified in rice. However, the function of OsFLP is largely unknown. In this study, we conducted RNA-seq and ChIP-seq to investigate the potential role of OsFLP in rice. Our results reveal that OsFLP is probably a multiple functional regulator involved in many biological processes in growth development and stress responses in rice. However, we mainly focus on the role of OsFLP in salt stress response. Consistently, phenotypic analysis under salt stress conditions showed that osflp exhibited significant sensitivity to salt stress, while OsFLP over-expression lines displayed obvious salt tolerance. Additionally, Yeast one-hybrid assay and electrophoretic mobility shift assay (EMSA) showed that OsFLP directly bound to the promoter region of Oryza sativa B-type Cyclin-Dependent Kinase 1;1 (OsCDKB1;1), and the expression of OsCDKB1;1 was repressed in osflp. Disturbing the expression of OsCDKB1;1 remarkably enhanced the tolerance to salt stress. Taken together, our findings reveal a crucial function of OsFLP regulating OsCDKB1;1 in salt tolerance and largely extend the knowledge about the role of OsFLP in rice
Artemisia pollen dataset for exploring the potential ecological indicators in deep time
No full textArtemisia, along with Chenopodiaceae, is the dominant component growing in the desert and dry grassland of the Northern Hemisphere. Artemisia pollen with its high productivity, wide distribution, and easy identification is usually regarded as an eco-indicator for assessing aridity and distinguishing grassland from desert vegetation in terms of the pollen relative abundance ratio of Chenopodiaceae/Artemisia (C/A). Nevertheless, divergent opinions on the degree of aridity evaluated by Artemisia pollen have been circulating in the palynological community for a long time. To solve the confusion, we first selected 36 species from nine clades and three outgroups of Artemisia based on the phylogenetic framework, which attempts to cover the maximum range of pollen morphological variation. Then, sampling, experiments, photography, and measurements were taken using standard methods. Here, we present pollen datasets containing 4018 original pollen photographs, 9360 pollen morphological trait measurements, information on 30 858 source plant occurrences, and corresponding environmental factors. Hierarchical cluster analysis on pollen morphological traits was carried out to subdivide Artemisia pollen into three types. When plotting the three pollen types of Artemisia onto the global terrestrial biomes, different pollen types of Artemisia were found to have different habitat ranges. These findings change the traditional concept of Artemisia being restricted to arid and semi-arid environments. The data framework that we designed is open and expandable for new pollen data of Artemisia worldwide. In the future, linking pollen morphology with habitat via these pollen datasets will create additional knowledge that will increase the resolution of the ecological environment in the geological past. The Artemisia pollen datasets are freely available at Zenodo (https://doi.org/10.5281/zenodo.6900308; Lu et al., 2022)
Low carbon availability in paleosols nonlinearly attenuates temperature sensitivity of soil organic matter decomposition
No full textTemperature sensitivity (Q(10)) of soil organic matter (SOM) decomposition is an important parameter in models of the global carbon (C) cycle. Previous studies have suggested that substrate quality controls the intrinsic Q(10), whereas environmental factors can impose large constraints. For example, physical protection of SOM and its association with minerals attenuate the apparent Q(10) through reducing substrate availability and accessibility ([S]). The magnitude of this dampening effect, however, has never been quantified. We simulated theoretical Q(10) changes across a wide range of [S] and found that the relationship between Q(10) and the log(10)-transformed [S] followed a logistic rather than a linear function. Based on the unique Holocene paleosol chronosequence (7 soils from ca. 500 to 6900 years old), we demonstrated that the Q(10) decreased nonlinearly with soil age up to 1150 years, beyond which Q(10) remained stable. Hierarchical partitioning analysis indicated that an integrated C availability index, derived from principal component analysis of DOC content and parameters reflecting physical protection and mineral association, was the main explanatory variable for the nonlinear decrease of Q(10) with soil age. Microbial inoculation and C-13-labelled glucose addition showed that low C availability induced by physical protection and minerals association attenuated Q(10) along the chronosequence. A separate soil incubation experiment indicated that Q(10) increased exponentially with activation energy (E-a) in the modern soil, suggesting that SOM chemical complexity regulates Q(10) only when C availability is high. In conclusion, organic matter availability strongly decreased with soil age, whereas Michelis-Menten kinetics defines the Q(10) response depending on C availability, but Arrhenius equation describes the effects of increasing substrate complexity
The biogeography of relative abundance of soil fungi versus bacteria in surface topsoil
No full textFungi and bacteria are the two dominant groups of soil microbial communities worldwide. By controlling the turnover of soil organic matter, these organisms directly regulate the cycling of carbon between the soil and the atmosphere. Fundamental differences in the physiology and life history of bacteria and fungi suggest that variation in the biogeography of relative abundance of soil fungi versus bacteria could drive striking differences in carbon decomposition and soil organic matter formation between different biomes. However, a lack of global and predictive information on the distribution of these organisms in terrestrial ecosystems has prevented the inclusion of relative abundance of soil fungi versus bacteria and the associated processes in global biogeochemical models. Here, we used a global-scale dataset of > 3000 distinct observations of abundance of soil fungi versus bacteria in the surface topsoil (up to 15 cm) to generate the first quantitative and high-spatialresolution (1 km(2)) explicit map of soil fungal proportion, defined as fungi/fungi + bacteria, across terrestrial ecosystems. We reveal striking latitudinal trends where fungal dominance increases in cold and high-latitude environments with large soil carbon stocks. There was a strong nonlinear response of fungal dominance to the environmental gradient, i.e., mean annual temperature (MAT) and net primary productivity (NPP). Fungi dominated in regions with low MAT and NPP and bacteria dominated in regions with high MAT and NPP, thus representing slow vs. fast soil energy channels, respectively, a concept with a long history in soil ecology. These high-resolution models provide the first steps towards representing the major soil microbial groups and their functional differences in global biogeochemical models to improve predictions of soil organic matter turnover under current and future climate scenarios. Raw datasets and global maps generated in this study are available at https://doi.org/10.6084/m9.figshare.19556419 (Yu, 2022)
Effects of warming on starch structure, rice flour pasting property, and cooked rice texture in a double rice cropping system
No full textBackground and objectives Climate warming has significant effects on rice quality. However, the effects of warming on starch structure, rice flour pasting properties, and cooked rice texture are unclear in double rice cropping systems. Therefore, a free-air temperature increase experiment was conducted with two indica rice cultivars. The objectives of this study were to explore the changes in rice flour pasting properties and cooked rice texture under warming conditions and their relationships with starch structures. Findings Under warming conditions, rice starch had a lower amylose content (Peak 3) and proportion of long amylopectin branch chains (B3 chains) but a higher proportion of short amylopectin branch chains (A chains and B1 chains), amylopectin branching degree, relative crystallinity, ratio of 1045/1022 cm(-1), and swelling power. Compared to the control treatment, warming significantly increased the peak viscosity, breakdown, and pasting temperature but decreased the setback of rice flour. Moreover, the hardness of cooked rice was significantly decreased, while its stickiness was significantly increased under warming conditions. Conclusions The changes in starch molecular structures resulted in lower hardness and setback but a higher stickiness, peak viscosity, breakdown, and pasting temperature of cooked rice or rice flour, which means better eating quality and worse cooking quality of double-cropped indica rice under climate warming conditions. Significance and novelty These findings are expected to provide important information for improving rice cooking and eating quality and developing the rice industry under future climate warming conditions