of Botany,Chinese Academy Of Sciences
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Effects of multi-resource addition on grassland plant productivity and biodiversity along a resource gradient
No full textThe change of plant biodiversity caused by resource-enhancing global changes has greatly affected grassland produc-tivity. However, it remains unclear how multi-resource enrichment induces the effects of multifaceted biodiversity on grassland productivity under different site resource constraints. We conducted a multiple resource addition (MRA) ex-periment of water and nutrients at three sites located along a resource gradient in northern China. This allowed us to assess the response of aboveground net primary productivity (ANPP), species (species richness and plant density), functional (functional richness and community-weighted mean of traits) and phylogenetic (phylogenetic richness) diversity to increasing number of MRA. We used structural equation model (SEM) to examine the direct and indirect effects of MRA and multifaceted biodiversity on ANPP. The combined addition of the four resources increased ANPP at all three sites. But with increasing number of MRA, biodiversity varied at the three sites. At the high resource constraint site, species richness, plant density and leaf nitrogen concentration (LNC) increased. At the medium resource con-straint site, plant height and LNC increased, leaf dry matter content (LDMC) decreased. At the low resource constraint site, species, functional and phylogenetic richness decreased, and height increased. The SEM showed that MRA in-creased ANPP directly at all three sites, and indirectly by increasing plant density at the high constraint site and height at the medium constraint site. Independent of MRA, ANPP was affected by height at the high resource constraint site and LNC at the low resource constraint site. Our results illustrate that multi-resource addition positively affects produc-tivity, while affects biodiversity depending on site resource constraint. The study highlights that site resource con-straint conditions need to be taken into consideration to better predict grassland structure and function, particularly under the future multifaceted global change scenarios
Mapping Chinese annual gross primary productivity with eddy covariance measurements and machine learning
No full textAnnual gross primary productivity (AGPP) is the basis for grain production and terrestrial carbon sequestration. Map-ping regional AGPP from site measurements provides methodological support for analysing AGPP spatiotemporal var-iations thereby ensures regional food security and mitigates climate change. Based on 641 site-year eddy covariance measuring AGPP from China, we built an AGPP mapping scheme based on its formation and selected the optimal map-ping way, which was conducted through analysing the predicting performances of divergent mapping tools, variable combinations, and mapping approaches in predicting observed AGPP variations. The reasonability of the selected op-timal scheme was confirmed by assessing the consistency between its generating AGPP and previous products in spa-tiotemporal variations and total amount. Random forest regression tree explained 85 % of observed AGPP variations, outperforming other machine learning algorithms and classical statistical methods. Variable combinations containing climate, soil, and biological factors showed superior performance to other variable combinations. Mapping AGPP through predicting AGPP per leaf area (PAGPP) explained 86 % of AGPP variations, which was superior to other ap-proaches. The optimal scheme was thus using a random forest regression tree, combining climate, soil, and biological variables, and predicting PAGPP. The optimal scheme generating AGPP of Chinese terrestrial ecosystems decreased from southeast to northwest, which was highly consistent with previous products. The interannual trend and interan-nual variation of our generating AGPP showed a decreasing trend from east to west and from southeast to northwest, respectively, which was consistent with data-oriented products. The mean total amount of generated AGPP was 7.03 +/- 0.45 PgC yr-1 falling into the range of previous works. Considering the consistency between the generated AGPP and previous products, our optimal mapping way was suitable for mapping AGPP from site measurements. Our results provided a methodological support for mapping regional AGPP and other fluxes
Natural lupeol level variation among castor accessions and the upregulation of lupeol synthesis in response to light
No full textLupeol, a plant-derived lupane-type pentacyclic triterpenoid, has many pharmacological activities. Although lupeol is found widely in many fruits, vegetables, and medicinal plants, its low content and difficult extraction limit its current applications. The castor plant (Ricinus communis L.) is a potential candidate plant for producing lupeol because it accumulates at high levels as a dominant wax component in the epidermal surface. The lupeol content varies significantly among castor individuals/cultivars. To identify castor lines for further breeding and uncover the molecular mechanism of lupeol biosynthesis and regulation, several castor varieties with various lupeol levels were identified, including 26 lines with higher lupeol contents and 12 glossy lines with very low lupeol contents. A deletion of the coding sequence of castor lupeol synthase RcLUS-1 was identified in glossy1, which possibly affects the binding ability of the substrate. The role of RcLUS-1 in lupeol production was determined using a virus-induced gene silencing (VIGS) assay. The promoter region of RcLUS-1 was analyzed further to uncover the factors affecting lupeol synthesis. Several potential cis-acting elements responding to light present were enriched in this region. Further study showed that light intensity affects RcLUS-1 expression and lupeol production. Overall, this study evaluated several potential castor resources for future breeding and expanded the knowledge of the lupeol regulation mechanism
Soil nitrate mediates the responses of plant community production to the frequency of N addition in a temperate grassland: a decadal field experiment
No full textPurpose Nitrogen (N) enrichment through either artificial N application or atmospheric N deposition often increases ecosystem aboveground net primary productivity (ANPP). Therefore, results from N addition experiments have been used to assess the effects of atmospheric N deposition on ecosystems. However, the frequency of atmospheric N deposition is higher than that of artificial N addition. Whether the frequency of N addition alters the long-term response of ecosystem ANPP remains unclear. Methods We conducted a N addition frequency experiment from 2010 in a temperate grassland, northern China. Plant community ANPP was collected in 2019 and 2020, and soil physicochemical properties were measured in 2020. Results Plant community ANPP was significantly enhanced by N addition, whereas these increments declined with the frequency of N addition. The responses of the grasses ANPP were similar to those of the plant community ANPP. Forbs ANPP was not significantly altered. Meanwhile, soil ammonium and nitrate (NO3--N) concentrations decreased with increasing N addition frequency, while the soil water content (SWC) and pH were similar among the frequencies of N addition. Regardless of the frequency of N addition, SWC and soil NO3--N jointly promoted grasses ANPP, ultimately increasing the plant community ANPP. Conclusion Our findings demonstrate that the frequency of N addition affects plant community biomass production through altering soil nitrate concentration in the semi-arid grassland. Therefore, this study illustrates that a higher frequency of N addition is more suitable for assessing the long-term impacts of atmospheric N deposition on ecosystems
Mutational meltdown or controlled chain reaction: The dynamics of rapid plastome evolution in the hyperdiversity of Poaceae
No full textThe study of genomic structural evolution associated with accelerated evolutionary rates that result in avoidance of meltdown and increase biodiversity is becoming ever more possible as the number of available plastomes increases. To more comprehensively analyze rate heterogeneity among monocots and within Poaceae, we sequenced plastomes from four Poaceae species, combined them with publicly available data from similar to 200 plastomes, and conducted comparative analyses to quantify the pattern of rate heterogeneity between different lineages, functional groups, and periods of evolutionary time. We compared structural differences across the Poaceae to quantify how changes in plastome size correspond to different genomic subunits and the evolution of IR-SC junction boundaries. The substitution rates among ancestral Poaceae were inferred to be exceptionally rapid compared to other monocots but slowed after divergence into extant lineages, which could not be sufficiently explained by positive selection. As such, rapid rates in the ancestral lineage leading to Poaceae might be more closely linked to large-scale structural changes like the loss of ycf1 and ycf2. The total increase in plastome size across Poaceae was positively correlated with the total length of intergenic spacers, tandem repeats, and dispersed repeats as well as large single copy, and inverted repeats (IRs). The continuous evolution of IR-SC junction boundaries was asynchronous with sizes of total genome and subunits across Poaceae. Future work is needed to better understand what factors in ancestral Poaceae evolved to harness such rapid rates of plastome evolution, avoid a mutational meltdown, and escape the stagnation of strong purifying selection as well as if these factors could be utilized to synthetically control rates
Tree dissimilarity determines multi-dimensional beta-diversity of herbivores and carnivores via bottom-up effects
No full text1. Global biodiversity decline and its cascading effects through trophic interactions pose a severe threat to human society. Establishing the impacts of biodiversity decline requires a more thorough understanding of multi-trophic interactions and, more specifically, the effects that loss of diversity in primary producers has on multi-trophic community assembly.2. Within a synthetic conceptual framework for multi-trophic beta-diversity, we tested a series of hypotheses on neutral and niche- based bottom- up processes in assembling herbivore and carnivore communities in a subtropical forest using linear models, hieratical variance partitioning based on linear mixed-effects models (LMMs) and simulation.3. We found that the observed taxonomic, phylogenetic and functional beta-diversity of both herbivorous caterpillars and carnivorous spiders were signifi-cantly and positively related to tree dissimilarity. Linear models and variance partitioning for LMMs jointly suggested that as a result of bottom- up effects, producer dissimilarities were predominant in structuring consumer dissimilarity, the strength of which highly depended on the trophic dependencies on produc-ers, the diversity facet examined, and data quality. Importantly, linear models for standardized beta-diversities against producer dissimilarities implied a transition between niche- based processes such as environmental filtering and competitive exclusion, which supports the role of bottom- up effect in determining consumer community assembly.4. These findings enrich our mechanistic understanding of the Diversity Begets Diversity' hypothesis and the complexity of highertrophic community assembly, which is fundamental for sustainable biodiversity conservation and ecosystem management
Climate and forest attributes influence above-ground biomass of deciduous broadleaf forests in China
No full textForests provide a huge carbon pool, a substantial portion of which is stored in above-ground biomass (AGB). Deciduous broadleaf forests in China are an essential component of global deciduous broadleaf forests, yet the impacts of climate and forest attributes on their AGB are not well understood. Using a comprehensive forest inventory database from 772 plots distributed across temperate and subtropical deciduous broadleaf forests in China (23.51 degrees-42.53 degrees N and 104.24 degrees-128.27 degrees E), we applied variance partitioning analysis, model selection analysis and structural equation models to explore how climate and forest attributes (species diversity, community-level functional traits and stand structures) affect AGB in different climatic forests (semi-arid forests, semi-humid forests and humid forests). Community-level functional traits and stand structures together explained a great portion of the variance in AGB. The effect of community-level functional traits was greater than that of stand structures in semi-arid forests and semi-humid forests, but smaller in humid forests. Further analyses showed that community-level maximum tree height, stem density and tree size inequality were important explanatory variables. Although climate and species diversity had minor effects, the direct positive effect of mean annual precipitation (MAP) was still important, especially in semi-arid forests. Synthesis. Community-level functional traits but not species diversity were key drivers of AGB, indicating that tree species diversity loss may not impair AGB substantially in deciduous broadleaf forests in China. Moreover, stand structures also had strong effects on AGB in both semi-arid forests and humid forests, highlighting the importance of structural complexity. In addition, MAP had a direct positive effect on AGB in semi-arid forests and semi-humid forests, and a future increase in drought might potentially reduce carbon storage in these forests
Arabidopsis EXECUTER1 interacts with WRKY transcription factors to mediate plastid-to-nucleus singlet oxygen signaling
No full textChloroplasts produce singlet oxygen (O-1(2)), which causes changes in nuclear gene expression through plastid-to-nucleus retrograde signaling to increase plant fitness. However, the identity of this O-1(2)-triggered pathway remains unclear. Here, we identify mutations in GENOMES UNCOUPLED4 (GUN4) and GUN5 as suppressors of phytochrome-interacting factor1 (pif1) pif3 in regulating the photo-oxidative response in Arabidopsis thaliana. GUN4 and GUN5 specifically interact with EXECUTER1 (EX1) and EX2 in plastids, and this interaction is alleviated by treatment with Rose Bengal (RB) or white light. Impaired expression of GUN4, GUN5, EX1, or EX2 leads to insensitivity to excess light and overexpression of EX1 triggers photo-oxidative responses. Strikingly, upon light irradiation or RB treatment, EX1 transiently accumulates in the nucleus and the nuclear fraction of EX1 shows a similar molecular weight as the plastid-located protein. Point mutagenesis analysis indicated that nuclear localization of EX1 is required for its function. EX1 acts as a transcriptional co-activator and interacts with the transcription factors WRKY18 and WRKY40 to promote the expression of O-1(2)-responsive genes. This study suggests that EX1 may act in plastid-to-nucleus signaling and establishes a O-1(2)-triggered retrograde signaling pathway that allows plants adapt to changing light environments during chloroplast development. EX1 acts as a plastid-to-nucleus mobile protein that relays O-1(2) signals, thus bridging the communication gap between plastids and the nucleus
Controls on soil dissolved organic carbon along the 4000 km North-South forest transect in Eastern China
No full textDissolved organic carbon (DOC) is both a potential source and stability indicator of soil organic carbon (SOC), and plays a pivotal role in global C cycling and sequestration. However, at a large scale, still not enough in-formation is known about relations between DOC in soils and various controlling factors in natural forest eco-systems. We sampled 252 soil samples (6 replicates and 3 depths for each site) from four long-term forest ecosystem stations in Changbaishan, Beijng Donglingshan, Shennongjia and Dinghushan along a 4000 km North -South transect in Eastern China. We found that higher soil DOC concentrations were observed in subtropical forests over the North-South transect. The highest and lowest DOC concentrations in the upper 60 cm soil layer were found in monsoon evergreen broadleaved forest (DIII, 113.8 +/- 1.4 mg C/L) and Yue spruce-fir forest (CIII, 57.6 +/- 3.0 mg C/L), respectively. The Haplic ferralsol (DII-DIV, 89.7 mg C/L) and Haplic Andosol (CIII, 57.6 mg C/L) showed the highest and the lowest DOC concentrations in the upper 60 cm soil layer, respectively. The soil DOC concentrations generally decreased from surface soil to subsoil in the forests with mean annual precipitation (MAP) >= 1500 mm. The lower proportion of DOC accounting for SOC in the upper 20 cm soil layer in temperate forests, among which Yue spruce-fir forest (CIII, 3.2 %) presented the lowest ratio, indicated a larger long-term soil C sequestration potential. The DOC concentrations in the upper 60 cm soil layer significantly correlated with mean annual temperature (MAT) (R2 = 0.50) and MAP (R2 = 0.46). However, in the upper 20 cm soil layer, forest type (R2 = 0.48) was the most significant correlation factor to DOC concentration. We concluded that in the North-South transect of Eastern China, MAT, MAP and forest type are the most significant large-scale factors controlling soil DOC, with temperate forests (especially Yue spruce-fir forest) possessing the highest long-term soil C sequestration potential
Retention of deposited ammonium and nitrate and its impact on the global forest carbon sink
No full textThe impacts of enhanced nitrogen (N) deposition on the global forest carbon (C) sink and other ecosystem services may depend on whether N is deposited in reduced (mainly as ammonium) or oxidized forms (mainly as nitrate) and the subsequent fate of each. However, the fates of the two key reactive N forms and their contributions to forest C sinks are unclear. Here, we analyze results from 13 ecosystem-scale paired N-15-labelling experiments in temperate, subtropical, and tropical forests. Results show that total ecosystem N retention is similar for ammonium and nitrate, but plants take up more labelled nitrate (20(15)(25)%) (mean(minimum)(maximum)) than ammonium (12(8)(16)%) while soils retain more ammonium (57(49)(65)%) than nitrate (46(32)(59)%). We estimate that the N deposition-induced C sink in forests in the 2010s is 0.72(0.49)(0.96) Pg C yr(-1), higher than previous estimates because of a larger role for oxidized N and greater rates of global N deposition