The functional division of arbuscular mycorrhizal fungi and earthworm to efficient cooperation on phytoremediation in molybdenum (Mo) contaminated soils.

Single phytoremediation has limited capacity to restore soil contaminated with extreme Mo due to its low metal accumulation. Soil organisms can help compensate for this deficiency in Mo-contaminated soils. However, there is limited information available on the integrated roles of different types of soil organisms, particularly the collaboration between soil microorganisms and soil animals, in phytoremediation. The objective of this study is to investigate the effects of a combination of arbuscular mycorrhizal fungi (AMF) and earthworms on the remediation of Mo-contaminated soils by alfalfa (Medicago sativa L.). The results indicated that in the soil-alfalfa system, earthworms effectively drive soil Mo activation, while AMF significantly improve the contribution of the translocation factor to total Mo removal (TMR) in alfalfas (p < 0.05). Meanwhile, compared to individual treatments, the combination of AMF and earthworm enhanced the expression of alfalfa root specific Mo transporter - MOT1 family genes to increase alfalfa uptake Mo (p < 0.05). This alleviated the competition between P/S nutrients and Mo on non-specific Mo transporters-P/S transporters (p < 0.05). Additionally, the proportion of organelle-bound Mo in the root was reduced to decrease Mo toxicity, while the cell wall-bound Mo proportion in the shoot was increased to securely accumulate Mo. The contributions of inoculants to alfalfa TMR followed the order (maximum increases): AMF + E combination (274.68 %) > alone treatments (130 %). Overall, the "functional division and cooperation" between earthworm and AMF are of great importance to the creation of efficient multi-biological systems in phytoremediation.

Evaluation of SMOS, SMAP, AMSR2 and FY-3C soil moisture products over China.

Microwave remote sensing can provide long-term near-surface soil moisture data on regional and global scales. Conducting standardized authenticity tests is critical to the effective use of observed data products in models, data assimilation, and various terminal scenarios. Global Land Data Assimilation System (GLDAS) soil moisture data were used as a reference for comparative analysis, and triple collocation analysis was used to validate data from four mainstream passive microwave remote sensing soil moisture products: Soil Moisture and Ocean Salinity (SMOS), Soil Moisture Active and Passive (SMAP), Global Change Observation Mission-Water using the Advanced Microwave Scanning Radiometer 2 (AMSR2) instrument, and Fengyun-3C (FY-3C). The effects of topography, land cover, and meteorological factors on the accuracy of soil moisture observation data were determined. The results show that SMAP had the best overall performance and AMSR2 the worst. Passive microwave detection technology can accurately capture soil moisture data in areas at high altitude with uniform terrain, particularly if the underlying surface is soil, and in areas with low average temperatures and little precipitation, such as the Qinghai-Tibet Plateau. FY-3C performed in the middle of the group and was relatively optimal in northeast China but showed poor data integrity. Variation in accuracy between products, together with other factors identified in the study, provides a baseline reference for the improvement of the retrieval algorithm, and the research results provide a quantitative basis for developing better use of passive microwave soil moisture products.

Asymmetric interaction and concurrent remediation of copper and atrazine by Acorus tatarinowii in an aquatic system.

To clarify the influence of organic pesticides on phytoremediation of potentially toxic metal elements, hydroponically-grown Acorus tatarinowii was used to repair copper pollution at six concentration levels with and without atrazine. Removal outcomes and processes exhibited asymmetry in an aquatic system. In plants, the addition of atrazine brought as much as 20.5% copper than control. Total amounts, percentage of protein or pectin combined copper and leaf: root ratio of copper were enhanced correspondingly. In solutions, cupric ions (Cu2+) were eliminated as much as 95.6% in plant remediation system. Though atrazine resulted in a quarter more absorption equilibrium concentration, the absorption reaction rate half declined. Copper removal in the system was contributed by both bound copper in solution and plant accumulation, and atrazine magnified contribution weight of the later one. Concurrent copper decreased absolute and relative amounts of atrazine in A. tatarinowii, indicating the influence of copper was mainly to reduce atrazine uptake by A. tatarinowii rather than to change the transformation of atrazine in plants. Copper exhibited antagonistic effects with atrazine in term of plant biomass, photosynthesis and oxidative-related responses (malondialdehyde, Ca, Fe and Mn), which might give support to asymmetry interaction between copper and atrazine accumulation in A. tatarinowii.

Effects of 8-Year Nitrogen and Phosphorus Treatments on the Ecophysiological Traits of Two Key Species on Tibetan Plateau.

Understanding how nitrogen (N) and/or phosphorus (P) addition affects plants carbon- and water- related ecophysiological characteristics is essential for predicting the global change impact on the alpine meadow ecosystem structure and function in carbon and water cycling. The Qinghai-Tibetan Plateau (QTP) with the largest alpine meadow in the world is regarded as the third pole in the earth and has been experiencing increased atmospheric N deposition. In this project, we focused on two key species (Elymus dahuricus and Gentiana straminea) of the alpine meadow on the Tibetan Plateau and investigated the variability of photosynthetic and stomatal responses to 8-year N and/or P treatments through field measurements and modeling. We measured photosynthesis- and gs-response curves to generate parameter estimates from individual leaves with two widely used stomatal models (the BWB model and MED model) for validation of growth and ecosystem models and to elucidate the physiological basis for observed differences in productivity and WUE. We assessed WUE by means of gas exchange measurements (WUEi) and stable carbon isotope composition (Δ13C) to get the intrinsic and integrated estimates of WUE of the two species. P and N+P treatments, but not N, improved the photosynthetic capacity (Anet and Vcmax) for both species. Stomatal functions including instaneous measurements of stomatal conductance, intrinsic water-use efficiency and stomatal slope parameters of the two widely used stomatal models were altered by the addition of P or N+P treatment, but the impact varied across years and species. The inconsistent responses across species suggest that an understanding of photosynthetic, stomatal functions and water-use should be evaluated on species separately. WUE estimated by Δ13C values had a positive relationship with Anet and gs and a negative relationship with WUEi. Our findings should be useful for understanding the underlying mechanisms of the response of alpine plants growth and alpine meadow ecosystem to global change.

Analyzing the impact of climate and management factors on the productivity and soil carbon sequestration of poplar plantations.

It is crucial to investigate how climate and management factors impact poplar plantation production and soil carbon sequestration interactively. We extracted above-ground net primary production (ANPP), climate and management factors from peer-reviewed journal articles and analyzed impact of management factor and climate on the mean annual increment (MAI) of poplar ANPP statistically. Previously validated mechanistic model (ED) is used to perform case simulations for managed poplar plantations under different harvesting rotations. The meta-analysis indicate that the dry matter MAI was 6.3 Mg ha(-1) yr(-1) (n=641, sd=4.9) globally, and 5.1 (n=292, sd=4.0), 8.1 (n=224, sd=4.7) and 4.4 Mg ha(-1) yr(-1) (n=125, sd=3.2) in Europe, the US and China, respectively. Poplar MAI showed a significant response to GDD, precipitation and planting density and formed a quadratic relationship with stand age. The low annual production for poplar globally was probably caused by suboptimal water availability, rotation length and planting density. SEM attributes the variance of poplar growth rate more to climate than to management effects. Case simulations indicated that longer rotation cycle significantly increased soil carbon storage. Findings of this work suggests that management factor of rotation cycle alone could have dramatic impact on the above ground growth, as well as on the soil carbon sequestration of poplar plantations and will be helpful to quantify the long-term carbon sequestration through short rotation plantation. The findings of this study are useful in guiding further research, policy and management decisions towards sustainable poplar plantations.

Acclimation of photosynthetic tolerance to acute heat stress at elevated CO2 and N.

Determining interactive effects of pre-heat-stress, CO2 and N on photosynthetic thermotolerance is necessary for predicting plant responses to global change. We grew Hordeum vulgare (barley, C3) and Zea mays (corn, C4) at current or elevated CO2 (370 and 700 ppm) and limiting or optimal soil N (0.5 and 7.5mM). We assessed basal and inducible thermotolerance of net photosynthesis (Pn), photosystem II efficiency [Formula: see text] , photochemical quenching (qp), carboxylation efficiency (CE), and rubisco activase content. Inducible thermotolerance was measured on plants which were pre-heat-stressed (PHS) for 4h before heat stress. We also assayed content of several major heat-shock proteins (HSPs), as HSPs are primary adaptations to heat stress and affected by N. Acclimation of photosynthetic thermotolerance was dependent on species, CO2 and N treatment and the component in the photosynthetic processes. PHS had a positive effect on the production of HSP60 and sHSP in low-N barley and corn. These results indicate that stimulatory effects of elevated CO2 at normal temperatures on photosynthesis may be partly changed by the different interactive effects of CO2, heat stress and N for species with different photosynthetic pathways. Thus, PHS, CO2 and N effects on photosynthetic thermotolerance may contribute to changes in plant productivity, distribution, and diversity.