Grazing by ungulate herbivores can greatly alter nitrogen (N) and phosphorus (P) concentrations in plants and soils. It is not clear, however, how grazing might affect N:P co‐limitation in grasslands ...depending on soil N and P availability.
Here we selected 173 peer‐reviewed studies, which measured 12 key variables associated with changes in N, P and N:P ratios (i.e. N:P stoichiometry) in soils and plants in the presence or absence of herbivore grazing. Subsequently, we addressed the magnitude and direction of grazing effects on these variables using a meta‐analysis approach.
Grazing increased leaf N and P but decreased total and available soil N and P. Grazing also increased leaf N:P ratios while decreasing root and total soil N:P ratios.
The response ratio (RR) of leaf N:P was negatively correlated with RR of plant‐available soil P and positively correlated with RR of available soil N:P ratio (rather than with RR of total soil N:P).
Intensive grazing (e.g. heavy grazing or long‐term grazing) had in general more positive effects on plant N:P stoichiometry and negative effects on soil N:P stoichiometry than light grazing. Responses of plant‐soil N:P stoichiometry to grazing greatly varied depending on plant functional group identity, plant organizational level (i.e. species and community) and grassland type.
Synthesis and applications. Our study suggests that understanding changes in available soil N:P stoichiometry (rather than total soil N:P) in response to grazing is crucial to predict nutrient co‐limitation in grassland biomes. Our findings show that P is more important for plant growth than generally thought due to greater reduction of plant‐available soil P under grazing. A better mechanistic understanding of the relationships between plant and available soil N:P stoichiometry under grazing will greatly help improve the sustainability of natural and semi‐natural grassland ecosystems.
摘要
放牧会显著改变植物和土壤的氮 (N) 磷 (P) 养分浓度, 但是尚不清楚不同放牧方式如何影响植物和土壤N:P化学计量特征 (包括氮浓度、磷浓度及N:P) , 特别是还不清楚放牧条件下植物N:P化学计量特征与土壤养分有效性的关系。
本文通过整合分析的方法定量了与植物和土壤N:P化学计量特征变化相关的12个关键响应变量对放牧的响应。
放牧显著提高叶片和根系氮磷浓度, 降低了土壤氮磷浓度。同时放牧提高了叶片N:P, 但降低了根系和土壤全量N:P。
放牧条件下, 叶片N:P的提高与土壤有效磷的降低和有效N:P (有效氮: 有效磷) 的提高显著相关, 而与土壤全量氮磷浓度的变化不相关, 表明土壤有效磷的变化对植物磷吸收和叶片氮磷平衡更重要。
植物和土壤的N:P化学计量特征受放牧强度、放牧周期、放牧动物类型和草原类型等因素的调控。与短期轻度放牧相比, 长期重度放牧会加剧植物‐土壤系统的氮磷失衡。
将来的研究应更多关注放牧对土壤有效养分及N:P的影响及其与植物养分限制因子转变的关系。理解植物和土壤有效N:P在放牧利用下的变化能够对不同草原生态系统放牧管理措施的制定提供理论依据。
Our study suggests that understanding changes in available soil N:P stoichiometry (rather than total soil N:P) in response to grazing is crucial to predict nutrient co‐limitation in grassland biomes. Our findings show that P is more important for plant growth than generally thought due to greater reduction of plant‐available soil P under grazing. A better mechanistic understanding of the relationships between plant and available soil N:P stoichiometry under grazing will greatly help improve the sustainability of natural and semi‐natural grassland ecosystems.
Identifying the epidemic risk for infectious disease is crucial in order to effectively perform control measures. In a series of our work, from an analytical aspect we study the effects of epidemic ...risk and population movement on the spatiotemporal transmission of infectious disease via an SIS epidemic reaction–diffusion model proposed by Allen et al. (2008) in 36. In Allen et al. (2008) 36, Peng (2009) 37, it was assumed that the habitat of the populations consists of only the low and high risk areas. The present paper concerns a more complicated heterogeneous environment where the moderate risk area occurs, and deals with two cases: (i) only the moderate and high risk areas exist; (ii) the low, moderate and high risk areas coexist. In each case, we rigorously determine the asymptotic profile of the positive steady state (i.e., the endemic equilibrium) as the migration rate of either the susceptible or infected population tends to zero. Our results show how epidemic risk and population movement affect the spatial distribution of infectious disease and thereby suggest important implications for predicting the patterns of disease occurrence and designing optimal control strategies. Numerical simulations are carried out to support the theoretical results.
•Study an SIS model in a more complicated heterogeneous environment.•Apply PDE theory to conduct rigorous mathematical analysis.•Show how epidemic risk and population movement affect disease transmission.•Suggest important implications for optimal disease control strategies.•Perform numerical simulations to support theoretical results.
Rapid progress in the power conversion efficiency (PCE) of polymer solar cells (PSEs) is beneficial from the factors that match the irradiated solar spectrum, maximize incident light absorption, and ...reduce photogenerated charge recombination. To optimize the device efficiency, a nanopatterned ZnO:Al2O3 composite film is presented as an efficient light‐ and charge‐manipulation layer (LCML). The Al2O3 shells on the ZnO nanoparticles offer the passivation effect that allows optimal electron collection by suppressing charge‐recombination loss. Both the increased refractive index and the patterned deterministic aperiodic nanostructure in the ZnO:Al2O3 LCML cause broadband light harvesting. Highly efficient single‐junction PSCs for different binary blends are obtained with a peak external quantum efficiency of up to 90%, showing certified PCEs of 9.69% and 13.03% for a fullerene blend of PTB7:PC71BM and a nonfullerene blend, FTAZ:IDIC, respectively. Because of the substantial increase in efficiency, this method unlocks the full potential of the ZnO:Al2O3 LCML toward future photovoltaic applications.
Highly efficient polymer solar cells based on nanopatterned ZnO:Al2O3 composite film achieve a peak external quantum efficiency up to 90% and a certified power conversion efficiency of 13.03%. Optical and electrical studies demonstrate enhanced light harvesting due to passivation‐ and dipole‐induced suppression of charge recombination loss and broadband absorption enhancement.
A Rh(III)‐catalyzed ortho C−H functionalization of N‐nitrosoanilines with α‐sulfonylcarbenes had been developed. The reaction was carried out under mild conditions and the products were obtained with ...good to excellent yields. The diverse transformations of the products to ortho‐functionalized anilines and nitrogen heterocycles were achieved. Furthermore, a cascade reaction of N‐nitrosoanilines and α‐sulfonyl‐α‐diazo‐ketones provided 3‐sulfonyl‐indoles efficiently.
Abstract
How serpentinites in the forearc mantle and subducted lithosphere become involved in enriching the subarc mantle source of arc magmas is controversial. Here we report molybdenum isotopes for ...primitive submarine lavas and serpentinites from active volcanoes and serpentinite mud volcanoes in the Mariana arc. These data, in combination with radiogenic isotopes and elemental ratios, allow development of a model whereby shallow, partially serpentinized and subducted forearc mantle transfers fluid and melt from the subducted slab into the subarc mantle. These entrained forearc mantle fragments are further metasomatized by slab fluids/melts derived from the dehydration of serpentinites in the subducted lithospheric slab. Multistage breakdown of serpentinites in the subduction channel ultimately releases fluids/melts that trigger Mariana volcanic front volcanism. Serpentinites dragged down from the forearc mantle are likely exhausted at >200 km depth, after which slab-derived serpentinites are responsible for generating slab melts.
Abstract
Herein, an intelligent biodegradable hollow manganese dioxide (H-MnO
2
) nano-platform is developed for not only tumor microenvironment (TME)-specific imaging and on-demand drug release, but ...also modulation of hypoxic TME to enhance cancer therapy, resulting in comprehensive effects favoring anti-tumor immune responses. With hollow structures, H-MnO
2
nanoshells post modification with polyethylene glycol (PEG) could be co-loaded with a photodynamic agent chlorine e6 (Ce6), and a chemotherapy drug doxorubicin (DOX). The obtained H-MnO
2
-PEG/C&D would be dissociated under reduced pH within TME to release loaded therapeutic molecules, and in the meantime induce decomposition of tumor endogenous H
2
O
2
to relieve tumor hypoxia. As a result, a remarkable in vivo synergistic therapeutic effect is achieved through the combined chemo-photodynamic therapy, which simultaneously triggers a series of anti-tumor immune responses. Its further combination with checkpoint-blockade therapy would lead to inhibition of tumors at distant sites, promising for tumor metastasis treatment.
Summary
Increasing demand of electricity and severer concerns to environment call for green energy sources as well as efficient energy conversion systems. SCO2 power cycles integrated with ...concentrating solar power (CSP) are capable of enhancing the competitiveness of thermal solar electricity. This article makes a comprehensive review of supercritical CO2 power cycles integrated with CSP. A detailed comparison of four typical CSP technologies is conducted, and the cost challenge of currently CSP technologies is pointed out. The thermophysical properties of sCO2 and the corresponding two real gas effects are analyzed elaborately to express the features of sCO2 power cycles. An extensive review of sCO2 layouts relevant for CSP including 12 single layouts and 1 combined layout is implemented logically. Strengths and weaknesses of sCO2 power cycles over traditional steam‐Rankine cycle generally adopted in current CSP plants are concluded, followed by metal material degration summary in CSP relevant temperature sCO2 environment, which shows that the nickel‐based alloy is a proper structural material candidate for sCO2‐CSP integration. Thermodynamic analyses of sCO2 power cycles when integrated with CSP are divided into three level of which design‐point analysis and off‐design modeling are conducted and compared, more researches into the off‐design point analysis, dynamic modeling, especially the transient behavior are suggested. Economic analysis of the integrated system is concluded and presents a considerable levelized cost of electricity reduction of 15.6% to 67.7% compared to that of state of art CSP. Taking the thermodynamic and economic analysis into consideration, target designs of sCO2 power cycles for CSP are summarized in three aspects. Finally, current theoretical and experimental researches of sCO2 power cycles integrated with CSP for market penetration are introduced. The strengths, weaknesses, and potential solutions to the gaps of three potential pathways (molten salt pathway, particle pathway, and gas phase pathway) to realize the integration of sCO2 power cycles in the next CSP generation plants up to 700°C are reviewed. In general, the integration of sCO2 power cycles with CSP technologies exhibits promising expectations for facilitating the competitiveness of thermal solar electricity.
Summary
Resource complementarity can contribute to enhanced ecosystem functioning in diverse plant communities, but the role of facilitation in the enhanced complementarity is poorly understood.
...Here, we use leaf manganese concentration (Mn) as a proxy for rhizosheath carboxylate concentration to explore novel mechanisms of complementarity mediated by phosphorus (P) facilitation.
In pot experiments, we showed that mixtures involving Carex korshinskyi, an efficient P‐mobilizing species, exhibited greater biomass and relative complementarity effect than combinations without C. korshinskyi on P‐deficient soils. Compared with monocultures, leaf Mn and P of species that are inefficient at P mobilization increased by 27% and 21% when grown with C. korshinskyi (i.e. interspecific P facilitation via carboxylates) rather than next to another inefficient P‐mobilizing species. This experimental result was supported by a meta‐analysis including a range of efficient P‐mobilizing species. Phosphorus facilitation enhanced the relative complementarity effect in low‐P environments, related to a greater change in several facilitated species of their root morphological traits relative to those in monoculture.
Using leaf Mn as a proxy, we highlight a vital mechanism of interspecific P facilitation via belowground processes and provide evidence for the pivotal role of P facilitation mediated by the plasticity of root traits in biodiversity research.
This paper performs qualitative analysis on an SIS epidemic reaction–diffusion system with a linear source in spatially heterogeneous environment. The main feature of our model lies in that its total ...population number varies, compared to its counterpart proposed by Allen et al. 2. The uniform bounds of solutions are derived, based on which, the threshold dynamics in terms of the basic reproduction number is established and the global stability of the unique endemic equilibrium is discussed when spatial environment is homogeneous. In particular, the asymptotic profile of endemic equilibria is determined if the diffusion rate of the susceptible or infected population is small or large. The theoretical results show that a varying total population can enhance persistence of infectious disease, and therefore the disease becomes more threatening and harder to control.
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