[Effects of experimental warming on soil nitrogen transformation in alpine scrubland of eastern Qinghai-Tibet Plateau, China]. / 模拟增温对青藏高原东部高寒灌丛土壤氮转化的影响.

We investigated the effects of warming on soil nitrogen cycling process in alpine scrub ecosystem, with an in-situ simulated warming experiment at Sibiraea angustata alpine scrubland on the eastern Qinghai-Tibet Plateau, China. We examined the responses of soil nitrogen transformation rate to warming in three critical periods (the early, late, and non-growing seasons). The results showed that warming increased soil temperature by 1.2 ℃, but decreased soil moisture by 2.5%. The soil net nitrogen mineralization rates (i.e., ammonification and nitrification) in the growing season were significantly higher than those in the non-growing season. The rates of soil net nitrogen fixation in the non-growing season were significantly higher than that in the growing season. Soil nitrification was the major process of soil nitrogen transformation in the early growing season, while soil ammonification was the major one in the late growing season and non-growing season. The effects of experimental warming on soil nitrogen transformation differed among those three periods. Experimental warming significantly increased soil net ammonification, nitrification, nitrogen mine-ralization and fixation in the early growing season, and enhanced soil net nitrification and nitrogen mineralization in the non-growing season. However, warming significantly decreased soil net nitrification, nitrogen mineralization and fixation in the late growing season and soil net ammonification in the non-growing season. Moreover, warming did not affect soil net nitrogen fixation rates in the non-growing season and soil net nitrification rates in the late growing season. Future climate warming would significantly change soil nitrogen transformation by accelerating soil nitrogen cycling in the alpine scrub ecosystem on the eastern Qinghai-Tibet Plateau.

[Responses of polyphenoloxidase and catalase activities of rhizosphere and bulk soils to warming during the growing season in an alpine scrub ecosystem.] / é«˜å¯’çŒä¸›ç”Ÿé•¿å­£æ ¹é™ å’Œéžæ ¹é™ åœŸå£¤å¤šé šæ°§åŒ–é ¶å’Œè¿‡æ°§åŒ–æ°¢é ¶æ´»æ€§å¯¹å¢žæ¸©çš„å“åº”.

To understand the effects of climate warming on rhizosphere ecological processes in the alpine scrub ecosystem, the responses of polyphenoloxidase and catalase activities in the rhizosphere and bulk soils to experimental warming (1.3 ℃) were examined during the growing season in a Sibiraea angustata scrub ecosystem on the eastern Qinghai-Tibetan Plateau, China. The results showed that the activities of polyphenoloxidase in rhizosphere and bulk soils in the middle growing season were significantly higher than those in the early or late growing season. The activities of catalase in the bulk soil increased gradually during the growing season, while they showed no seasonal changes in the rhizosphere soil. In the bulk soil, warming significantly increased the activity of polyphenoloxidase by 17.5% in the late growing season and increased that of catalase by 2.2% in the middle growing season, whereas it did not affect soil enzyme activities in early or late growing seasons. In the rhizosphere soil, warming only significantly increased the activities of polyphenoloxidase and catalase by 6.5% and 1.3% in the early growing season. The rhizosphere effect of soil polyphenoloxidase activity was positive throughout the growing season, while there was no obvious rhizosphere effect for soil catalase activity. Furthermore, warming significantly decreased the rhizosphere effect of soil polyphenoloxidase activity by 15.2% during the late growing season. These results indicated that the activities of polyphenoloxidase and catalase activities differed between rhizosphere and bulk soils, with consequences on the rhizosphere soil ecological processes under climate warming in the alpine scrub ecosystem on the eastern Qinghai-Tibetan Plateau.

[Effects of warming on microbial biomass carbon and nitrogen in the rhizosphere and bulk soil in an alpine scrub ecosystem]. / å¢žæ¸©å¯¹é«˜å¯’çŒä¸›æ ¹é™ å’Œéžæ ¹é™ åœŸå£¤å¾®ç”Ÿç‰©ç”Ÿç‰©é‡ç¢³æ°®çš„å½±å“.

To understand the effects of climate warming on the rhizosphere ecological process in the alpine scrub ecosystem, the responses of microbial biomass carbon and nitrogen in the rhizosphere and bulk soil to experimental warming were examined in a Sibiraea angustata scrubland on the eas-tern Qinghai-Tibetan Plateau, China. The results showed that the concentrations of microbial biomass carbon and nitrogen in the rhizosphere and bulk soil in the early growing season were significantly higher than those in the middle and late growing seasons. Experimental warming did not significantly affect the concentrations of microbial biomass carbon and nitrogen of the rhizosphere soil in the most growing seasons. In the bulk soil, however, the effects of experimental warming on the microbial biomass carbon and nitrogen differed among the growing season. Experimental warming significantly decreased microbial biomass carbon but increased microbial biomass nitrogen in the early growing season. In the middle growing season, warming significantly increased both microbial biomass carbon and nitrogen. In the late growing season, there was no significant effect. The rhizosphere effects of soil microbial biomass carbon and nitrogen also differed with the growing season. The rhizosphere effects of microbial biomass carbon and nitrogen were negative in the early growing season but positive in the middle growing season. In the late growing season, there were negative rhizosphere effects of soil microbial biomass carbon and positive rhizosphere effects of soil microbial biomass nitrogen. Furthermore, experimental warming significantly increased the rhizosphere effects of soil microbial biomass carbon and nitrogen in the early growing season, but decreased those in the middle and late growing seasons. These results uncovered the changing mechanism of the biologi-cal process in the rhizosphere and bulk soil in the alpine scrub ecosystems under the background of climate warming.

Research progress on the responses of soil respiration components to climatic warming.

Global carbon cycle is being profoundly altered by climate change. As an important component of the global carbon cycle, soil respiration is tightly linked to the carbon transfer among plants-soil-microbes. Soil respiration can be divided into the heterotrophic respiration and root-derived respiration (i.e., actual root respiration and rhizomicrobial respiration). Responses of soil respiration to climate warming may be different, since its components differ in occurrence sites and sources of soil organic carbon. However, the current literatures can not fully clarify the precise partition and quantification of soil respiration components. The influences of climate warming on soil respiration and related mechanisms are still unclear, which greatly limits our understanding of the accurate assessments of soil carbon cycle as well as the changes in the carbon balance of terrestrial ecosystems under climate change. We systematically summarized the progress of partitioning techniques of soil respiration components, and compared the results of partitioning of soil respiration components using different techniques. We further discussed the progress on the responses of soil respiration components to climate warming. To exactly distinguish and quantify soil respiration components, we proposed that the present techniques should be modified. Furthermore, future studies should focus on how to accurately partitioning root-derived respiration in the field for comprehensively understand soil carbon cycle and the changes of carbon budget in terrestrial ecosystems under global change. Moreover, more attention should be paid on the responses of soil respiration components to various environmental factors.

[Responses of soil invertase and urease activities to warming and plant removal during the growing season in an alpine scrub ecosystem.] / é«˜å¯’çŒä¸›ç”Ÿé•¿å­£åœŸå£¤è½¬åŒ–é ¶ä¸Žè„²é ¶æ´»æ€§å¯¹å¢žæ¸©å’Œæ¤ç‰©åŽ»é™¤çš„å“åº”.

To understand the effects of climate warming and vegetation disturbance on soil ecological process during different stages of growing season in the alpine scrub ecosystem, the responses of soil invertase and urease activities to warming (0.6-1.3 ℃) and plant removal were investigated in a Sibiraea angustata scrubland on the eastern Qinghai-Tibetan Plateau, China. The results showed that experimental warming significantly increased soil invertase activity by 3.7%-13.3% in the removal- and unremoval-plant plots throughout the entire growing season. Warming significantly increased soil urease activity by 10.8%-56.3% in the removal- and unremoval-plant plots, except the late growing stage, during which warming had no significant effect on soil urease activity in the unremoval-plant plots. The effects of plant removal treatments on soil invertase and urease activities varied with warming and growing stages. Plant removal significantly decreased soil invertase activity of the warmed plots during the entire growing season and the unwarmed plots during the early and late growing stages, but did not affect soil invertase activity in the unwarmed plots during the mid-growing stage. Plant removal only significantly decreased soil urease activity by 10.5% in the unwarmed plots during the late growing stage. However, in the warmed plots, plant removal significantly decreased soil urease activity by 16.0%-18.7% during the early and mid growing stages. The results would increase our understanding of soil carbon and nitrogen cycling process in the alpine scrub ecosystems.

Possible Association of IFN-γ Gene -316A/G SNP with Humoral Immune Response to Killed H5N1 HPAI Vaccine in a Red Junglefowl Population.

To understand the role of interferon (IFN)-γ gene (IFNG) single-nucleotide polymorphisms (SNPs) in the resistance to H5N1 highly pathogenic avian influenza (HPAI), we determined the SNPs, the log2-transformed specific antibody titers, and ex vivo recall antigen-specific IFN-γ production by peripheral blood mononuclear cells (PBMCs) in 62 red junglefowls (Gallus gallus) immunized twice with inactivated H5N1 HPAI vaccine. Consequently, 52 SNPs were detected in the amplified 1137-bp length covering the promoter region and all exons, with +2133A/T SNP in the coding DNA sequence that caused a missense mutation and was identified in G. gallus for the first time. For -316A/G SNP genotypes, the chi-squared test showed that the bird sample was in the Hardy-Weinberg equilibrium (P=0.369>0.05), and the least squares analysis revealed an increasing tendency in the antibody titers with G to A substitution so that a significant difference occurred between the AA genotype (8.031±0.247) and the GG genotype (6.571±0.528) (P=0.015<0.05, 95% confidence interval [CI]: 0.0004-0.0866), as basically consistent with the antigen-induced IFN-γ protein expression, which indicated possible association of the -316A/G SNP with a secondary humoral immune response to the HPAI vaccine in the bird population. These findings may help to improve genetic resistance using cross-breeding and enhance HPAI vaccine-induced immunity in chicken production.

[Seasonal release characteristics of Ca, Mg and Mn of foliar litter of six tree species in subtropical evergreen broadleaved forest].

Seasonal release dynamics of Ca, Mg and Mn during decomposition of foliar litter of Pinus massoniana, Cryptomeria fortunei, Cunninghamia lanceolata, Cinnamomum camphora, Toona ciliate, and Quercus acutissima were investigated in subtropical evergreen broad-leaved forest employing the method of litterbag. After one-year decomposition, the release rates of Ca, Mg and Mn in foliar litter of the studied tree species ranged from -13.8% to 92.3%, from 4.0% to 64.8%, and from 41.6% to 81.1%, respectively. Ca dynamics in foliar litter of P. massoniana, C. camphora exhibited the pattern of accumulating early and releasing later, while that of the other four tree species showed direct release. Similarly, the dynamics of Mg released from foliar litter of C. camphora showed the pattern of accumulating early and then releasing, while that of the other five tree species exhibited continuous release. Meanwhile, the dynamics of Mn released from foliar litter of C. fortunei and T. ciliate exhibited early accumulation, and subsequent release, while that of the other four tree species showed continuous release. The releases of Ca, Mg and Mn in foliar litter were greatly influenced by seasonal rainfall, and varied with tree species. Furthermore, the rates and amounts of Ca, Mg and Mn released from foliar litter were higher in rainy season than in dry season. In conclusion, the initial nutrient concentrations and precipitation were two key factors influencing the release dynamics of Ca, Mg and Mn during decomposition of foliar litter in the subtropical evergreen broad-leaved forest.

[Effects of shading on the aboveground biomass and stiochiometry characteristics of Medicago sativa].

In order to provide scientific basis for inter-planting alfalfa in abandoned farmland, a shading experiment was conducted to simulate the effects of different light intensities on the aboveground biomass, the contents of carbon, nitrogen, phosphorus and potassium, and the stoichiometric characteristics of alfalfa under the plantation. The results showed that the aboveground biomass of alfalfa correlated significantly with the light intensity, and shading treatment reduced the aboveground biomass of alfalfa significantly. The aboveground alfalfa tissues under the 62% shading treatment had the highest contents of carbon, nitrogen and phosphorus, which was 373.73, 34.38 and 5.47 g · kg(-1), respectively, and significantly higher than those of the control. However, shading treatments had no significant effect on the potassium content of aboveground part. The C/N ratio in aboveground tissues under the 72% shading treatment was significantly higher than that of the control, but no significant differences among other treatments were found. The ratios of N/P and C/P in aboveground tissues showed a tendency that decreased firstly and then increased with the increase of light intensity.

[Seasonal dynamics of soil labile nitrogen pools and net nitrogen mineralization in subalpine forests along an elevational gradient in western Sichuan, China].

The seasonal dynamics of soil labile nitrogen pools and net nitrogen mineralization of three subalpine forests along an elevation gradient (3600, 3300 and 3000 m), western Sichuan, China were examined. Obvious seasonal dynamics were found in soil labile nitrogen pools (ammonium, nitrate, microbial biomass nitrogen and dissolved organic nitrogen) and net nitrogen mineralization rate, but the seasonality varied with the measured nitrogen pools. The concentrations of soil nitrate (8.38-89.60 mg x kg(-1)) were significantly higher than those of ammonium (0.44-8.43 mg x kg(-1)) in four sampling periods (non-growing season, early, middle and late growing season). Regardless of the elevation, the rate of soil net nitrogen mineralization was negative (-0.77 to -0.56 mg x kg(-1) x d(-1)) early in the growing season, but positive in the other three periods. Except for nitrate, the contents of ammonium, microbial biomass nitrogen and dissolved organic nitrogen varied significantly with elevation and the altitude effects on those pools were dependent on seasons. In summary, soil nitrification was the major process of net soil nitrogen mineralization and soil nitrogen mineralization was not affected by elevational gradient. Soil nitrogen mineralization (0.42-0.99 mg x kg(-1) x d(-1)) in winter was considerable in this area. Relatively high inorganic nitrogen in early spring might be favorable for vegetation growth, but might also be lost from soil ecosystem through leaching.