Effects ofAgeratina adenophoraInvasion on the Understory Community and Soil Phosphorus Characteristics of Different Forest Types in Southwest China

Understanding the influence of invasive species on community composition and ecosystem properties is necessary to maintain ecosystem functions. However, little is known about how understory plant communities and soil nutrients respond to invasion under different land cover types. Here, we investigated the effects of the invasive species Ageratina adenophora on the species and functional diversity of understory communities and on soil phosphorus (P) status in three forest types: CF, coniferous forest; MF, coniferous and broadleaf mixed forest; and EBF, evergreen broadleaf forest. We found that the species and functional diversity indices of the understory community significantly varied by forest type. Among the invaded plots, the greatest decrease in functional diversity (functional richness, functional divergence, and functional dispersion) and biotic homogenization were found in the CF rather than the MF or EBF. In addition, the invasion by A. adenophora significantly increased the soil NaHCO3-extractable inorganic P and organic P in the MF and EBF, respectively, while obviously decreasing the soil maximum P sorption capacity and maximum buffering capacity in the CF. However, the changes in the species and functional attributes of the understory communities were weakly associated with changes in the soil P status, probably because of the different response times to invasion in different forest types. The implication of these changes for ecosystem structure and function must be separately considered when predicting and managing invasion at a landscape scale

Eucalyptus Trees - Ageratina adenophora Complex System: A New Eco-environmental Protection Model

Eucalyptus trees and Ageratina adenophora complex system, a new ecological phenomenon that is worthy of attention, was proposed firstly in this paper, and some scientific problems were summarized from the new phenomenon. Causes of the new phenomenon were analyzed tentatively from the perspective of ecology. It was pointed out that ecological degradation of Eucalyptus plantation and strong invasiveness of A. adenophora are two apparent reasons for formation of Eucalyptus trees and A. adenophora complex system. Basic view of the authors on causes of the new phenomenon was put forward that resistance unbalance between chemical defensive potential of Eucalyptus trees and chemical invasive potential of A. adenophora might be the fundamental reason for formation of Eucalyptus trees and A. adenophora complex system, based on the two apparent reasons respectively connected with allelopathic effects of Eucalyptus trees and A. adenophora as dominant species of the complex system. Some proofs from studies on chemical components and biological activities of Eucalyptus species and A. adenophora have proved the basic view of the authors. It was discussed that formation of the complex system would influence some environmental elements such as soil environment, hydrology environment, and biology environment. It was proposed that three key scientific issues, namely chemical mechanism of formation of the complex system, ecological effects of formation of the complex system, and succession trends and impact factors of the complex system should be mainly studied as special researches to probe ecological relationship of exotic species because of absence study on the complex system and objective requirements of production practice in future. It was emphasized that the proposed researches might be of guidance significance to scientific management and sustainable operation of Eucalyptus plantation under the condition of biological invasion.Eucalyptus trees and Ageratina adenophora complex system, a new ecological phenomenon that is worthy of attention, was proposed firstly in this paper, and some scientific problems were summarized from the new phenomenon. Causes of the new phenomenon were analyzed tentatively from the perspective of ecology. It was pointed out that ecological degradation of Eucalyptus plantation and strong invasiveness of A. adenophora are two apparent reasons for formation of Eucalyptus trees and A. adenophora complex system. Basic view of the authors on causes of the new phenomenon was put forward that resistance unbalance between chemical defensive potential of Eucalyptus trees and chemical invasive potential of A. adenophora might be the fundamental reason for formation of Eucalyptus trees and A. adenophora complex system, based on the two apparent reasons respectively connected with allelopathic effects of Eucalyptus trees and A. adenophora as dominant species of the complex system. Some proofs from studies on chemical components and biological activities of Eucalyptus species and A. adenophora have proved the basic view of the authors. It was discussed that formation of the complex system would influence some environmental elements such as soil environment, hydrology environment, and biology environment. It was proposed that three key scientific issues, namely chemical mechanism of formation of the complex system, ecological effects of formation of the complex system, and succession trends and impact factors of the complex system should be mainly studied as special researches to probe ecological relationship of exotic species because of absence study on the complex system and objective requirements of production practice in future. It was emphasized that the proposed researches might be of guidance significance to scientific management and sustainable operation of Eucalyptus plantation under the condition of biological invasion

Patterns and relationships of plant traits, community structural attributes, and eco-hydrological functions during a subtropical secondary succession in central Yunnan, Southwest China

Human-induced changes in land use lead to major changes in plant community composition and structure which have strong effects on eco-hydrological processes and functions. We here tested the hypothesis that changes in traits of living plants have resulted in changes in structural attributes of the community that influenced eco-hydrological functions by altering eco-hydrological processes. This was done in the context of a subtropical secondary forest suc­cession following land abandonment in Central Yunnan (Southwest China). During the succession, species with high specific leaf area (SLA), high leaf nitrogen concentration (LNC), high specific root length (SRL), and low leaf dry matter content (LDMC) were progressively replaced by species with the opposite characteristics. The obtained results of correlation analyses were as follows: (1) Correlations were significant between community-aggregated SLA, LNC, and the leaf area index (LAI). Significant correlations were detected between LAI, canopy interception and stemflow, and surface runoff and soil erosion. (2) Significant correlations were also found between community-aggregated SLA, LNC, LDMC, and accumulated litter biomass. High accumulated litter biomass strongly increases the maximum water-retaining capac­ity of litter. However, significant correlations were not found between the maximum water-retaining capacity of litter and surface runoff and soil erosion. (3) Correlations were significant between community-aggregated SLA, LNC, and fine root biomass. Fine root biomass was not significantly related to the maximum water-retaining capacity of the soil, but was significantly related to surface runoff and soil erosion. These results suggest that canopy characteristics play a more important role in control of runoff and soil erosion at the studied site. It follows that plant functional traits are closely linked with canopy characteristics, which should be used as a standard for selecting species in restoration and revegetation for water and soil conservation

PATTERNS AND RELATIONSHIPS OF PLANT TRAITS, COMMUNITY STRUCTURAL ATTRIBUTES, AND ECO-HYDROLOGICAL FUNCTIONS DURING A SUBTROPICAL SECONDARY SUCCESSION IN CENTRAL YUNNAN (SOUTHWEST CHINA)

Abstract —Human-induced changes in land use lead to major changes in plant community composition and structure which have strong effects on eco-hydrological processes and functions. We here tested the hypothesis that changes in traits of living plants have resulted in changes in structural attributes of the community that influenced eco-hydrological functions by altering eco-hydrological processes. This was done in the context of a subtropical secondary forest succession following land abandonment in Central Yunnan (Southwest China). During the succession, species with hig

Genome-Wide Analysis of the ATP-Binding Cassette (ABC) Transporter Family in <i>Zea mays</i> L. and Its Response to Heavy Metal Stresses

The ATP-binding cassette (ABC) transporter family is one of the largest eukaryotic protein families. Its members play roles in numerous metabolic processes in plants by releasing energy for substrate transport across membranes through hydrolysis of ATP. Maize belongs to the monocotyledonous plant family, Gramineae, and is one of the most important food crops in the world. We constructed a phylogenetic tree with individual ABC genes from maize, rice, sorghum, Arabidopsis, and poplar. This revealed eight families, each containing ABC genes from both monocotyledonous and dicotyledonous plants, indicating that the amplification events of ABC gene families predate the divergence of plant monocotyledons. To further understand the functions of ABC genes in maize growth and development, we analyzed the expression patterns of maize ABC family genes in eight tissues and organs based on the transcriptome database on the Genevestigator website. We identified 133 ABC genes expressed in most of the eight tissues and organs examined, especially during root and leaf development. Furthermore, transcriptome analysis of ZmABC genes showed that exposure to metallic lead induced differential expression of many maize ABC genes, mainly including ZmABC 012, 013, 015, 031, 040, 043, 065, 078, 080, 085, 088, 102, 107, 111, 130 and 131 genes, etc. These results indicated that ZmABC genes play an important role in the response to heavy metal stress. The comprehensive analysis of this study provides a foundation for further studies into the roles of ABC genes in maize

Resistance mechanisms and remediation potential of hexavalent chromium in Pseudomonas sp. strain AN-B15

The understanding of bacterial resistance to hexavalent chromium [Cr(VI)] are crucial for the enhancement of Cr(VI)-polluted soil bioremediation. However, the mechanisms related to plant-associated bacteria remain largely unclear. In this study, we investigate the resistance mechanisms and remediation potential of Cr(VI) in a plant-associated strain, AN-B15. The results manifested that AN-B15 efficiently reduced Cr(VI) to soluble organo-Cr(III). Specifically, 84.3 % and 56.5 % of Cr(VI) was removed after 48 h in strain-inoculated solutions supplemented with 10 and 20 mg/L Cr(VI) concentrations, respectively. Transcriptome analyses revealed that multiple metabolic systems are responsible for Cr(VI) resistance at the transcriptional level. In response to Cr(VI) exposure, strain AN-B15 up-regulated the genes involved in central metabolism, providing the reducing power by which enzymes (ChrR and azoR) transformed Cr(VI) to Cr(III) in the cytoplasm. Genes involved in the alleviation of oxidative stress and DNA repair were significantly up-regulated to neutralize Cr(VI)-induced toxicity. Additionally, genes involved in organosulfur metabolism and certain ion transporters were up-regulated to counteract the starvation of sulfur, molybdate, iron, and manganese induced by Cr(VI) stress. Furthermore, a hydroponic culture experiment showed that toxicity and uptake of Cr(VI) by plants under Cr(VI) stress were reduced by strain AN-B15. Specifically, strain AN-B15 inoculation increased the fresh weights of the wheat root and shoot by 55.5 % and 18.8 %, respectively, under Cr(VI) stress (5 mg/L). The elucidation of bacterial resistance to Cr(VI) has an important implication for exploiting microorganism for the effective remediation of Cr(VI)-polluted soils

Evaluating the Efficacy of Point-of-Use Water Treatment Systems Using the Water Quality Index in Rural Southwest China

Rural China faces a shortage of safe drinking water. There are significant challenges associated with small centralized water supply systems and decentralized water supply systems. Many rural residents use point-of-use water treatment systems to ensure the safety of their drinking water. The actual water purification effect and applicability of these water treatment systems in small centralized and decentralized water supply systems need to be determined urgently. In this study, the water quality index (WQI) method was applied for the first time in rural areas to evaluate the effectiveness of point-of-use water treatment systems. A total of 67 reverse osmosis water treatment systems were tested. The rate of compliance with drinking water standards of the decentralized water supply was low (37%). Compared with untreated water, the use of a reverse osmosis water treatment system improved the rate of compliance with drinking water standards, but this effect was not satisfactory (8%). Among the factors potentially affecting the purified water quality of point-of-use water treatment systems (e.g., service time of the water treatment system, service time of the filter element, and type of water source), the service time of the filter element had the most significant influence on the water quality. If the filter element had not been replaced for a long period, the removal effect of the water treatment system on the total hardness, sulfide, copper, and ammonia nitrogen was significantly affected, reducing the quality of the purified water. To ensure the safety of drinking water, it is recommended to replace the filter element of a reverse osmosis water treatment system at least once a year

Plant Traits Guide Species Selection in Vegetation Restoration for Soil and Water Conservation

Great efforts have been made to improve the soil and water conservation capacity by restoring plant communities in different climatic and land-use types. However, how to select suitable species from local species pools that not only adapt to different site environments, but also achieve certain soil and water conservation capacities is a great challenge in vegetation restoration for practitioners and scientists. So far, little attention has been paid to plant functional response and effect traits related to environment resource and ecosystem functions. In this study, together with soil properties and ecohydrological functions, we measured the seven plant functional traits for the most common species in different restoration communities in a subtropical mountain ecosystem. Multivariate optimization analyses were performed to identify the functional effect types and functional response types based on specific plant traits. We found that the community-weighted means of traits differed significantly among the four community types, and the plant functional traits were strongly linked with soil physicochemical properties and ecohydrological functions. Based on three optimal effect traits (specific leaf area, leaf size, and specific root length) and two response traits (specific leaf area and leaf nitrogen concentration), seven functional effect types in relation to the soil and water conservation capacity (interception of canopy and stemflow, maximum water-holding capacity of litter, maximum water-holding capacity of soil, soil surface runoff, and soil erosion) and two plant functional response types to soil physicochemical properties were identified. The redundancy analysis showed that the sum of all canonical eigenvalues only accounted for 21.6% of the variation in functional response types, which suggests that community effects on soil and water conservation cannot explain the overall structure of community responses related to soil resources. The eight overlapping species between the plant functional response types and functional effect types were ultimately selected as the key species for vegetation restoration. Based on the above results, we offer an ecological basis for choosing the appropriate species based on functional traits, which may be very helpful for practitioners involved in ecological restoration and management

Structure of Bacterial Communities in Phosphorus-Enriched Rhizosphere Soils

Although phytoremediation is the main method for P-removal and maintaining ecosystem balance in geological phosphorus-enriched soils (PES), little is known about the structure and function of microbial communities in PES. Interactions between plants and soil microorganisms mainly occur in the rhizosphere. The aim of this work was to investigate the composition and diversity of bacterial communities found in rhizosphere soils associated with the following three dominant plant species: Erianthus rufipilus, Coriaria nepalensis, and Pinus yunnanensis. In addition, we compared these rhizosphere bacterial communities with those derived from bulk soils and grassland plots in PES from the Dianchi Lake basin of southwestern China. The Illumina MiSeq platform for high-throughput sequencing of 16S rRNA was used for the taxonomy and the analysis of soil bacterial communities. The results showed higher bacterial diversity and nutrient content in rhizosphere soils as compared with bulk soils. Rhizosphere bacteria were predominantly comprised of Proteobacteria (24.43%) and Acidobacteria (21.09%), followed by Verrucomicrobia (19.48%) and Planctomycetes (9.20%). A comparison of rhizosphere soils of the selected plant species in our study and the grassland plots showed that Acidobacteria were the most abundant in the rhizosphere soil of E. rufipilus; Bradyrhizobiaceae and Rhizobiaceae in the order Rhizobiales from C. nepalensis were found to have the greatest abundance; and Verrucomicrobia and Planctomycetes were in higher abundance in P. yunnanensis rhizosphere soils and in grassland plots. A redundancy analysis revealed that bacterial abundance and diversity were mainly influenced by soil water content, soil organic matter, and total nitrogen