Over half of threatened species require targeted recovery actions to avert human-induced extinction

Averting human-induced extinctions will require strong policy commitments that comprehensively address threats to species. A new Global Biodiversity Framework is currently being negotiated by the world's governments through the Convention on Biological Diversity. Here we explored how the suggested targets in this framework could contribute to reducing threats to threatened vertebrates, invertebrates, and plants, and assessed the importance of a proposed target to implement recovery actions for threatened species. Although many of the targets benefit species, we found that extinction risk for over half (57%) of threatened species would not be reduced sufficiently without a target promoting recovery actions, including ex situ conservation, reintroductions, and other species-specific interventions. A median of 54 threatened species per country require such actions, and most countries of the world hold such species. Preventing future human-induced extinctions requires policy commitments to implement targeted recovery actions for threatened species in addition to broader efforts to mitigate threats, underpinned by transformative change

Hydrodynamic and geochemical controls on soil carbon mineralization upon entry into aquatic systems

Erosion is the most widespread form of soil degradation and an important pathway of carbon transfer from land into aquatic systems, with significant impact on water quality and carbon cycle. However, it remains debatable whether erosion induces a carbon source or sink, and the fate of eroded soil carbon in aquatic systems remains poorly constrained. Here, we collect 41 representative soils from seven erosion-influenced basins and conduct microcosm simulation experiments to examine the fate of soil carbon under three different scenarios. We showed that soil carbon mineralization was generally promoted (by up to 10 times) in water under turbulence relative to in soils, but suppressed under static conditions upon entering into aquatic systems. Moreover, the enhancement of mineralization in turbulent systems is primarily related to soil aggregate content, while suppression in static systems positively relates to macromolecule abundance, indicating that soil geochemistry affects the magnitude of hydrodynamic effects on carbon mineralization. Random forest model further predicts that erosion may induce significant carbon sources in basins dominated by turbulent waters and aggregate-rich soils. Our findings demonstrate hydrodynamic and geochemical controls on soil carbon mineralization upon delivery into aquatic systems, which is a non-negligible part of the boundless carbon cycle and must be considered when making region-specific conservation strategies to reduce CO2 emissions from inland waters

The response of two nutrient acquisition strategies: root traits and leaf nutrient resorption and their relationships to long-term mowing in a temperate steppe

Purpose Mowing may exert profound influences on nutrient acquisition strategies of herbaceous species due to the nutrient removal along with the mown plants. Nutrient uptake by roots and nutrient resorption from senescent leaves, are two main nutrient acquisition strategies of perennial herbaceous species. However, few studies have considered both nutrient acquisition strategies in exploring the effects of long-term mowing on the nutrient acquisition of perennial herbs. Methods We measured root traits of absorptive roots and leaf nitrogen resorption efficiency (NRE) of seven herbaceous species with different plant height on a long-term mowing experimental platform (2003-2020) in a temperate steppe. Results We found that root traits of tall and short species had little response to long-term mowing. While, mowing exerted opposite effects on leaf NRE of the two plant groups, i.e., mowing significantly decreased the NRE of tall species, but increased that of short species (except for Potentilla acaulis). Furthermore, root absorption capacity (indicated by root traits) was positively correlated with leaf NRE for tall species in control plots, but mowing eliminated this relationship. In contrast, for short species, root traits and leaf NRE had no correlation in control plots, while, mowing led to synergic relationship between root absorption capacity and leaf resorption rates. Conclusions Our results suggested that perennial herbs changed the relationships between alternative resource acquisition strategies in response to long-term mowing in temperate steppe. These findings provide new perspectives for understanding the adaptation of herbaceous species to mowing in the temperate steppe

Mutational meltdown or controlled chain reaction: The dynamics of rapid plastome evolution in the hyperdiversity of Poaceae

The 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

Multidimensional stoichiometric mismatch explains differences in detritivore biomass across three forest types

The ecological stoichiometry theory provides a framework to understand organism fitness and population dynamics based on stoichiometric mismatch between organisms and their resources. Recent studies have revealed that different soil animals occupy distinct multidimensional stoichiometric niches (MSNs), which likely determine their specific stoichiometric mismatches and population responses facing resource changes. The goals of the present study are to examine how long-term forest plantations affect multidimensional elemental contents of litter and detritivores and the population size of detritivores that occupy distinct MSNs. We evaluated the contents of 10 elements of two detritivore taxa (lumbricid earthworms and julid millipedes) and their litter resources, quantified their MSNs and the multidimensional stoichiometric mismatches, and examined how such mismatch patterns influence the density and total biomass of detritivores across three forest types spanning from natural forests (oak forest) to plantations (pine and larch forests). Sixty-year pine plantations changed the multidimensional elemental contents of litter, but did not influence the elemental contents of the two detritivore taxa. Earthworms and millipedes exhibited distinct patterns of MSNs and stoichiometric mismatches, but they both experienced severer stoichiometric mismatches in pine plantations than in oak forests and larch plantations. Such stoichiometric mismatches led to lower density and biomass of both earthworms and millipedes in pine plantations. In other words, under conditions of low litter quality and severe stoichiometric mismatches in pine plantations, detritivores maintained their body elemental contents but decreased their population biomass. Our study illustrates the success in using the multidimensional stoichiometric framework to understand the impact of forest plantations on animal population dynamics, which may serve as a useful tool in addressing ecosystem responses to global environmental changes

Effects of Moderate Water Deficit on the Accumulation and Translocation of Stem Non-Structural Carbohydrates, Yield and Yield Components in a Sink-Limited Rice Variety Under Elevated CO2 Concentration

To investigate the effects of moderate water deficit (MD) on ? non-structural carbohydrates (NSC), ? yield and yield components in a sink-limited rice variety under elevated CO2 concentration ([CO2]), a japonica rice (Oryza sativa L.) cultivar Nangeng 9108 was planted at ambient [CO2] (a[CO2]) and elevated [CO2] (e[CO2], a[CO2] + 200 ppm) in open-top chambers with MD treatment set during grain filling stage. The content, accumulation, and translocation of NSC as well as yield components were determined, and the relationships among them were analyzed. Compared to e[CO2] + CK, e[CO2] + MD treatment decreased the content (by 42%) and accumulation (by 57%) of NSC in stems, and greatly promoted NSC translocation (by 325%). At MD treatment, e[CO2] stimulated ATM(NSC) and AC(NSC), and the re-accumulation of stem NSC at maturity was limited under both CO2 treatment. With higher NSC translocation, the 1000-grain weight was lowered, but seed setting rate and harvest index were improved. Grain yield of Nangeng 9108 was not changed by MD treatment, which implied that the sink-limited rice varieties may be more adaptable to balance the survival (root growth to obtain more water) and reproduction with potential drought stress at future CO2-enriched environment

Elevated ozone decreases the multifunctionality of belowground ecosystems

Elevated tropospheric ozone (O-3) affects the allocation of biomass aboveground and belowground and influences terrestrial ecosystem functions. However, how belowground functions respond to elevated O-3 concentrations ([O-3]) remains unclear at the global scale. Here, we conducted a detailed synthesis of belowground functioning responses to elevated [O-3] by performing a meta-analysis of 2395 paired observations from 222 publications. We found that elevated [O-3] significantly reduced the primary productivity of roots by 19.8%, 16.3%, and 26.9% for crops, trees and grasses, respectively. Elevated [O-3] strongly decreased the root/shoot ratio by 11.3% for crops and by 4.9% for trees, which indicated that roots were highly sensitive to O-3. Elevated [O-3] impacted carbon and nitrogen cycling in croplands, as evidenced by decreased dissolved organic carbon, microbial biomass carbon, total soil nitrogen, ammonium nitrogen, microbial biomass nitrogen, and nitrification rates in association with increased nitrate nitrogen and denitrification rates. Elevated [O-3] significantly decreased fungal phospholipid fatty acids in croplands, which suggested that O-3 altered the microbial community and composition. The responses of belowground functions to elevated [O-3] were modified by experimental methods, root environments, and additional global change factors. Therefore, these factors should be considered to avoid the underestimation or overestimation of the impacts of elevated [O-3] on belowground functioning. The significant negative relationships between O-3-treated intensity and the multifunctionality index for croplands, forests, and grasslands implied that elevated [O-3] decreases belowground ecosystem multifunctionality

Climate and forest attributes influence above-ground biomass of deciduous broadleaf forests in China

Forests 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

Effects of multi-resource addition on grassland plant productivity and biodiversity along a resource gradient

The 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

Annual 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