Nitrogen and phosphorus addition exerted different influences on litter and soil carbon release in a tropical forest.

Terrestrial soils release large amount of carbon dioxide (CO2) each year, which are mainly derived from litter and soil carbon (C) decomposition. Nutrient availability, especially nitrogen (N) and phosphorus (P), plays an important role in both litter and soil C decomposition. Therefore, understanding the underlying mechanism is crucial for mitigating CO2 emission and climate changes. Here, we assessed patterns of litter and soil C decomposition after 11 yrs. in-situ N and P addition in a tropical forest where corn leaves or corn roots were added as litter C. The total CO2 efflux was quantified and partitioned using 13C isotope signatures to determine the sources (litter or soil C) every three months. In addition, Changes in C-degrading enzyme activities: ß-1,4-glucosidase (BG), phenol oxidase (PHO) and peroxidase (PER), and microbial biomarkers were assessed to interpret the underlying mechanism. Total C-release was enhanced up to17% by the long-term N addition but inhibited up to 15% by P addition. Precisely, N addition only accelerated the litter decomposition and increased about 42% and 6% of the litter C release at 0-5 cm and 5-10 cm soil depths, respectively; while P addition only impeded the soil C decomposition and decreased about 9% and 11% of the soil C release at 0-5 cm and 5-10 cm, respectively. The enhanced C release under N addition might be attributed to the enhanced microbial biomass, the ratio of fungi to bacteria and C-degrading enzyme activities. However, P addition resulted in the reverse result in microbial properties and C-degrading enzyme activities, associated with a decreased C release. Our study suggests that the long-term N and P addition selectively affected the litter and soil C decomposition because of their different physiochemical properties and this tendency might be more pronounced in tropical forests exposed to increasing atmospheric N deposition in the future. The study indicates that the different patterns of litter and soil C decomposition under climate change should be taken account in the future C management strategies.

Removal of Total Nitrogen and Phosphorus Using Single or Combinations of Aquatic Plants.

Phytoremediation is a potentially suitable technology for taking up large amounts of N and P during plant growth and the removal of plant material, thereby avoiding eutrophication. We compared the capacity of nine different aquatic plant species for removing total P (TP), total N (TN), and NH4+-N from raw domestic sewage wastewater collected from a living area located in Guangzhou city, China, and different concentrations of artificial wastewater. The experiments were performed in two stages, namely screening and modification. In the screening stage, four plant species were identified from the nine grown in raw domestic sewage water for 36 days. In the modification stage, the TN and TP removal ability of different plant combinations were determined in artificial wastewater at different N/P concentrations. After having been grown in monocultures for 46 days, Ipomoea aquatica (90.6% and 8.8%) and Salvinia natans (67.3% and 14.2%) obtained the highest TP removal efficiency in lightly and highly polluted wastewater, respectively. The combination of S.natans and Eleocharis plantagineiformis effectively removed TP and TN from lightly polluted water, suggesting that this combination is suitable for phytoremediation of eutrophic wastewater.

Heavy metal availability, bioaccessibility, and leachability in contaminated soil: effects of pig manure and earthworms.

A pot experiment and a leaching experiment were conducted to investigate the effects of earthworms and pig manure on heavy metals (Cd, Pb, and Zn) immobility, in vitro bioaccessibility and leachability under simulated acid rain (SAR). Results showed manure significantly increased soil organic carbon (SOC), dissolved organic carbon (DOC), available phosphorus (AP), total N, total P and pH, and decreased CaCl2-extractable metals and total heavy metals in water and SAR leachate. The addition of earthworms significantly increased AP (from 0.38 to 1.7 mg kg-1), and a downward trend in CaCl2-extractable and total leaching loss of heavy metals were observed. The combined earthworm and manure treatment decreased CaCl2-extractable Zn, Cd, and Pb. For Na4P2O7-extractable metals, Cd and Pb were decreased with increasing manure application rate. Application of earthworm alone did not contribute to the remediation of heavy metal polluted soils. Considering the effects on heavy metal immobilization and cost, the application of 6% manure was an alternative approach for treating contaminated soils. These findings provide valuable information for risk management during immobilization of heavy metals in contaminated soils.

Environmentally relevant concentrations of mercury exposure alter thyroid hormone levels and gene expression in the hypothalamic-pituitary-thyroid axis of zebrafish larvae.

Mercury (Hg) is one of the most toxic heavy metals that can cause severe damage to fish. Studies have demonstrated that Hg has a specific affinity for the endocrine system, but little is known about the effects of Hg on thyroid endocrine system in fish. In this study, zebrafish embryos were exposed to environmentally relevant concentrations of 1, 4, and 16 µg/L Hg2+ (added as HgCl2) from 2 h post-fertilization (hpf) to 168 hpf. Thyroid hormone (TH) levels and mRNA expression levels of genes involved in the hypothalamus-pituitary-thyroid (HPT) axis were determined. The results showed that exposure to 16 µg/L Hg2+ increased the whole-body thyroxine (T4) and triiodothyronine (T3) levels. The transcription levels of corticotrophin releasing hormone (crh) and thyroid stimulating hormone (tshß) were up-regulated by Hg2+ exposure. Analysis of the mRNA levels of genes related to thyroid development (hhex, nkx2.1, and pax8) and THs synthesis (nis and tg) revealed that exposure to higher Hg2+ concentrations markedly up-regulated hhex, nkx2.1, nis, and tg expression, while had no significant effect on the transcripts of pax8. For the transcription of two types of deiodinases (deio1 and deio2), deio1 showed no significant changes in all the treatments, whereas deio2 was significantly up-regulated in the 16 µg/L Hg2+ group. In addition, Hg2+ exposure up-regulated thyroid hormone receptor ß (trß) mRNA level, while the transcription of trα was not changed. Overall, our study indicated that environmentally relevant concentrations of Hg2+ exposure could alter TH levels and the transcription of related HPT-axis genes, disturbing the normal processes of TH metabolism.

Synergistic improvement of crop physiological status by combination of cadmium immobilization and micronutrient fertilization.

Wollastonite application in cadmium-contaminated soils can reduce cadmium concentrations in plant, while the side effect is the synchronous immobilization of micronutrients, which reduces micronutrient uptake in plant, inducing micronutrient deficient symptoms. Accordingly, we investigated whether the supplement of Zn and Mn fertilizers after the wollastonite addition could promote the growth and photosynthesis in amaranth (Amaranthus tricolor L.). In this study, plants were cultivated in cadmium-contaminated soil under micronutrient fertilization alone, wollastonite addition, and combination of wollastonite and micronutrient fertilization treatments. Then, plant biomass; photosynthesis parameters; and total Cd, Zn, and Mn concentrations were investigated. Moreover, chemical extractions were performed on soil samples. The results show that application of wollastonite decreased Cd, Zn, and Mn concentrations in plant and availability in soil and it increased the gas exchange ability of plants. But, it reduced the chlorophyll content in leaves and had no positive influence on plant biomass. In comparison, Zn and Mn fertilization after wollastonite application greatly increased plant biomass and photosynthetic ability. It also reduced Cd phytoavailability more efficiently. Therefore, synergistic improvement of physiological status of farmland crop by sequential treatment with first wollastonite for cadmium immobilization, and then micronutrient fertilization to avoid micronutrient deficiency, was demonstrated.

Response of plant nutrient stoichiometry to fertilization varied with plant tissues in a tropical forest.

Plant N:P ratios are widely used as indices of nutrient limitation in terrestrial ecosystems, but the response of these metrics in different plant tissues to altered N and P availability and their interactions remains largely unclear. We evaluated changes in N and P concentrations, N:P ratios of new leaves (<1 yr), older leaves (>1 yr), stems and mixed fine roots of seven species after 3-years of an N and P addition experiment in a tropical forest. Nitrogen addition only increased fine root N concentrations. P addition increased P concentrations among all tissues. The N × P interaction reduced leaf and stem P concentrations, suggesting a negative effect of N addition on P concentrations under P addition. The reliability of using nutrient ratios as indices of soil nutrient availability varied with tissues: the stoichiometric metrics of stems and older leaves were more responsive indicators of changed soil nutrient availability than those of new leaves and fine roots. However, leaf N:P ratios can be a useful indicator of inter-specific variation in plant response to nutrients availability. This study suggests that older leaf is a better choice than other tissues in the assessment of soil nutrient status and predicting plant response to altered nutrients using nutrients ratios.

Depressive neurosis treated by acupuncture for regulating the liver--a report of 176 cases.

OBJECTIVE: To observe therapeutic effect of acupuncture for regulating the liver on depressive neurosis. METHODS: In a multi-center randomized controlled trial, 440 patients were divided into 3 groups: Acupuncture group for regulating the liver (Acup., 176 cases) was treated by acupuncture at Siguan Points, i.e., bilateral Hegu (LI 4) and Taichong (LR 3), Baihui (GV 20) and Yintang (EX-HN3) plus ear-acupuncture, Prozac group (P., 176 cases) by oral administration of Prozac, and Non-acupoint needling group (NAN, 88 cases) by acupuncture at non-acupoints as acupuncture placebo. Self-rating Depression Scale (SDS) was examined before treatment, and one month, two and three months after treatment respectively to evaluate therapeutic effect, and Rating Scale for Side Effects (SERS) was used to evaluate the safety. RESULTS: After one month of treatment, SDS scores in Acup. Group were significantly lower than that in P. Group (P < 0.05) and than that in NAN Group (P < 0.01), and SDS scores in P. Group were lower than that in NAN Group (P < 0.05), showing the SDS scores in Acup. Group < P. Group < NAN Group. After 2 months of treatment, SDS scores in Acup. Group were also significantly lower than that in P. Group (P < 0.01) and than that in NAN Group (P < 0.01), and SDS scores in P. Group were also lower than that in NAN Group (P < 0.05), showing the SDS scores in Acup. Group 0.05), showing the SERS scores in Acup. Group < NAN Group < P. Group. No side effect was found in Acup. and NAN groups. CONCLUSION: The therapeutic effect of acupuncture on depressive neurosis is better than or similar to that of Prozac but with less side effect.

[Acupuncture for treatment of depressive neurosis: a multi-center randomized controlled study].

OBJECTIVE: To observe the clinical therapeutic effect of acupuncture on depressive neurosis. METHODS: With a multi-center randomized controlled study, 440 cases were randomly divided into an acupuncture group, a prozac group, a non-acupoint needling group. In the acupuncture group, Hegu (LI 4) and Taichong (LR 3) were selected, and the Prozac group were treated with administration of 20 mg/d and the non-acupoint needling group were treated with needling the points deviating from the acupoints. The therapeutic effect was evaluated by HAMD score reduction rate, and Asberg's anti-depressant side-effect rating scale (SERS) and severe adverse reaction were used for safety evaluation, and the data were analyzed with ITT. RESULTS: The total effective rate was 86. 4% in the acupuncture group, which was better than 59.1% in the non-acupoint needling group and 72.7% in the prozac group; HAMD score in the acupuncture group was similar to that in the Prozac group, which was better than that in the non-acupoint needling group; the SERS scores in the acupuncture group and the non-acupoint needling group were significantly lower than that in the Prozac group, with no severe side-effects found for acupuncture. CONCLUSION: Acupuncture is an effective and safe therapy for depressive neurosis; therapeutic effect of acupuncture on depressive neurosis possibly is better than or similar to that of Prozac, but with less side-effects.