Effect of Nutrient Addition on the Productivity and Species Richness of Grassland Along With an Elevational Gradient in Tajikistan.

Grasslands provide key resource for the millions of people who are dependent on livestock in Tajikistan. Productivity and species richness (SR) are important characteristics of grassland ecosystems and are greatly affected by nutrient inputs. The effect that climate change might have on these characteristics remains unclear. Here, an in situ nitrogen (N) and phosphorus (P) fertilization experiment was conducted at four sites along with an elevational gradient (650, 1,100, 1,250, and 2,000 m) in western Tajikistan over 2 years (2018 and 2019) to examine the influences of nutrient availability and climate change on aboveground biomass (AGB) and SR; precipitation and temperature were also considered to analyze the responses. It demonstrated that enrichment with N, P, and their combinations significantly increased AGB along with an elevational gradient (p < 0.05). AGB increased as the concentrations of nutrients added increased. The maximum AGB, which was 2-fold higher compared with control, was observed when 90 kg N ha-1year-1 and 30 kg P ha-1year-1 were added. In addition, nitrogen addition alone stimulated greater AGB than P addition, although no significant difference was observed between these two treatments. Enrichment with N, P, and their combination had no significant effect on SR; however, SR significantly changed at different elevation. Elevation had direct effect on precipitation and temperature, which, in turn, resulted in variation in AGB and SR. Moreover, both nutrient and elevation had significant effect on AGB and SR, but there was no interaction effect of them. AGB and SR interacted with significant negative correlation. In the high-elevation area, plants grew better in the warmer year (2018); this indicates that grasslands in high mountain areas in Tajikistan might have higher productivity as the climate warms, which will positively affect the economic development of the country.

[Nitrogen and phosphorus stoichiometry of aquatic macrophytes in Kaidu River of Xinjiang and the potential influencing factors].

Nitrogen (N) and phosphorus (P) are two common mineral elements constraining plant growth. Nutrients in aquatic macrophytes are mainly absorbed from water and sediments, and thus elemental composition in plant tissues can reflect the nutritional status in freshwater ecosystems. Kaidu River is an important river flowing through the alpine meadows, deserts, and desert oases in Xinjiang. Herein, samples of aquatic macrophytes, water, and sediments across the Kaidu River were collected. Foliar stoichiometric characteristics of N and P in plants were examined among life forms and phylogeny. The differences and correlations among the stoichiometric characteristics of plants, water bodies, and sediments in the upstream and downstream and across different land use types were elaborated. Results showed that the means of leaf N and P concentrations and N/P mass ratio were 24.9 mg·g-1, 2.49 mg·g-1, and 12.6, respectively. There were significant differences in the leaf N and P stoichiometry among various life forms. Specifically, leaf N and P concentrations in submerged species were significantly higher than that in floating-leaved species and emergent species. The N/P of floating-leaved species was 19.2 and significantly higher than that in other two life-forms, indicating that their growth might be limited by P. Leaf N and P concentrations were higher in the upstream than in the downstream. Nitrogen contents in water and sediment were the higher in the upstream of the river. Compared with the river reaches in farming areas, the higher N and P concentrations of aquatic macrophytes in the grassland regions might be related to the higher contents of organic matter in grassland soils and of animal slurries from flocks and herds, suggesting that grazing exerted larger impact on the stoichiometric characteristics of the Kaidu River ecosystem. Our findings highlighted that overgrazing might accelerate the deterioration of water quality in the upstream of the Kaidu River, disturb the balance of N and P in the aquatic ecosystem, and potentially influence the biogeochemical cycling.

[Leaf C:N:P stoichiometry of 67 plant species and its relations with climate factors across the deserts in Xinjiang, China.] / 新疆67ç§è’æ¼ æ¤ç‰©å¶ç¢³æ°®ç£·è®¡é‡ç‰¹å¾åŠå ¶ä¸Žæ°”å€™çš„å ³ç³».

Desert ecosystem has unique drought-enduring plants and stoichiometric characteristics. We collected leaf samples of 67 plant species from 63 desert sites in Xinjiang, and explored foliar carbon (C), nitrogen (N) and phosphorus (P) stoichiometry and the relationship between leaf nutrient stoichiometry and climatic factors. The results showed that the average content of leaf C, N and P in these plants were 394, 18.4 and 1.14 mg·g-1, respectively. The mean values of C:N, C:P and N:P were 28, 419 and 18, respectively. In general, shrubs had higher leaf N content than trees and herbs, while leaf P content was lower (higher) in shrubs than in herbaceous plants (trees). Plants with C3 photosynthesis pathway had higher leaf C, N, C:P and N:P than those with C4 pathway. With increasing mean annual precipitation, leaf C first decreased and then increased, while both leaf N and P showed the opposite trend. Leaf C:N and C:P first decreased and then increased, while leaf N:P changed insignificantly. With increasing mean annual temperature, leaf C first decreased and then increased, and leaf N and P decreased, while leaf C:P and N:P increased. Leaf C:N did not change significantly with mean annual temperature. Mean annual precipitation generally showed stronger control on the variation of leaf nutrient stoichiometry than MAT and plant functional types. These results could help predict responses of the biogeochemical cycling of C, N and P to the global climate changes and provide reference and basic data for biogeochemical modeling in the arid regions.

Environmental and spatial variables determine the taxonomic but not functional structure patterns of microbial communities in alpine grasslands.

There is considerable debate regarding how the taxonomic diversity of microbial communities relates to the functional diversity across space while similar questions have been explored in macro-organism communities. Here, we investigated the taxonomic and functional diversity patterns of soil microbial communities by coupling the data obtained from marker genes sequencing and functional gene surveys. Meanwhile, we evaluated the relative effects of environment and geographic distance on shaping these patterns in alpine grasslands of northern China. Although the taxonomic diversity and composition of microbial communities varied across sites, we found no consistent changes in the functional structure. Both the environmental factors and geographic distance concurrently affected the taxonomic diversity patterns but they had no effects on the spatial variations in functional genes. The functional alpha diversity was weakly correlated to the taxonomic alpha diversity across sites. Moreover, we found no significant relationship between the taxonomic and functional composition similarity among microbial communities. Together, our results provide evidence that spatial variation in microbial functions could be independent of their variations in taxonomic diversity. Even the drivers of spatial variations in the functional structure could be totally different from those of taxonomic variations such as environmental differences and dispersal limitation. Our findings suggest that spatial variations of microbial function structure within a community would not follow the variations of taxonomic structures due to different drivers between both of them over space.

Novel Xanthomonas campestris Long-Chain-Specific 3-Oxoacyl-Acyl Carrier Protein Reductase Involved in Diffusible Signal Factor Synthesis.

The precursors of the diffusible signal factor (DSF) family signals of Xanthomonas campestris pv. campestris are 3-hydroxyacyl-acyl carrier protein (3-hydroxyacyl-ACP) thioesters having acyl chains of 12 to 13 carbon atoms produced by the fatty acid biosynthetic pathway. We report a novel 3-oxoacyl-ACP reductase encoded by the X. campestris pv. campestris XCC0416 gene (fabG2), which is unable to participate in the initial steps of fatty acyl synthesis. This was shown by the failure of FabG2 expression to allow growth at the nonpermissive temperature of an Escherichia colifabG temperature-sensitive strain. However, when transformed into the E. coli strain together with a plasmid bearing the Vibrio harveyi acyl-ACP synthetase gene (aasS), growth proceeded, but only when the medium contained octanoic acid. In vitro assays showed that FabG2 catalyzes the reduction of long-chain (≥C8) 3-oxoacyl-ACPs to 3-hydroxyacyl-ACPs but is only weakly active with shorter-chain (C4, C6) substrates. FabG1, the housekeeping 3-oxoacyl-ACP reductase encoded within the fatty acid synthesis gene cluster, could be deleted in a strain that overexpressed fabG2 but only in octanoic acid-supplemented media. Growth of the X. campestris pv. campestris ΔfabG1 strain overexpressing fabG2 required fabH for growth with octanoic acid, indicating that octanoyl coenzyme A is elongated by X. campestris pv. campestrisfabH Deletion of fabG2 reduced DSF family signal production, whereas overproduction of either FabG1 or FabG2 in the ΔfabG2 strain restored DSF family signal levels.IMPORTANCE Quorum sensing mediated by DSF signaling molecules regulates pathogenesis in several different phytopathogenic bacteria, including Xanthomonas campestris pv. campestris DSF signaling also plays a key role in infection by the human pathogen Burkholderia cepacia The acyl chains of the DSF molecules are diverted and remodeled from a key intermediate of the fatty acid synthesis pathway. We report a Xanthomonas campestris pv. campestris fatty acid synthesis enzyme, FabG2, of novel specificity that seems tailored to provide DSF signaling molecule precursors.

[Inorganic N deposition in the Bayinbuluk alpine grassland of the central Tianshan mountains].

N deposition has increased significantly with economic development and intensive human activities in China and has affected natural ecosystems in remote areas. To evaluate the atmospheric N deposition of the Bayinbuluk alpine grassland of the central Tianshan Mountains, the dry and wet N depositions were monitored from May 2010 to December 2011. Fluxes of HNO3, NH3, NO2, particulate ammonium and nitrate (pNH4+ and pNO3-) averaged at 1.47, 0.68, 0.13, 0.23 and 0.25 kg N x hm(-2) x a(-1), respectively. Wet depositions of NH(4+)-N and NO(3-)-N were 2.47 and 1.59 kg N x hm(-2) x a(-1), respectively. Total atmospheric inorganic N deposition fluxes averaged at 6.82 kg N x hm(-2) x a(-1), and the wet and dry depositions were 4.06 and 2.76 kg N x hm(-2) x a(-1), respectively. Nitrogen deposition fluxes showed a significant seasonal change, with 72.1% of dry N deposition occurring in spring and summer, and 78.3% of wet N deposition concentrating in summer and autumn.

Poly[aqua-[µ-1,2-bis-(pyridin-4-yl)ethene-κ(2)N:N'][µ-5-(diphenyl-phosphino-yl)iso-phthalato-κ(3)O(1),O(1'):O(3)]nickel(II)].

In the title compound, [Ni(C(20)H(13)O(5)P)(C(12)H(10)N(2))(H(2)O)](n), the Ni(II) cation is coordinated by three O atoms from two 5-(diphenyl-phosphino-yl)isophthalate anions, two N atoms from two 1,2-bis-(pyridin-4-yl)ethene ligands and one water mol-ecule in a distorted octa-hedral geometry. Both 1,2-bis-(pyridin-4-yl)ethene and 5-(diphenyl-phosphino-yl)iso-phthal-ate bridge the Ni(II) cations to form polymeric layers parallel to (001). In the crystal, O-H⋯O hydrogen bonding links layers into a three-dimensional supra-molecular structure.

Poly[bis-[µ-1,4-bis-(imidazol-1-ylmeth-yl)benzene]-dichloridomanganese(II)].

In the crystal structure of the title compound, [MnCl(2)(C(14)H(14)N(4))(2)](n), the Mn(II) atom, lying on an inversion center, is coordinated by four N atoms from four 1,4-bis-(imidazol-1-ylmeth-yl)benzene (bimb) ligands and two Cl(-) anions in a distorted octa-hedral geometry. The bimb ligands bridge the Mn(II) atoms, forming a two-dimensional polymeric complex, which is composed of a 52-membered [Mn(4)(bimb)(4)] ring with distances of 7.7812 (2) and 27.4731 (9) Šbetween opposite metal atoms. Weak C-H⋯π inter-actions are present in the crystal structure.

Diaqua-(5-carb-oxy-benzene-1,3-di-carboxyl-ato-κO)(4,4'-dimethyl-2,2'-bipyridine-κN,N')zinc.

In the title compound, [Zn(C(9)H(4)O(6))(C(12)H(12)N(2))(H(2)O)(2)], the Zn(II) atom is five-coordinated by two N atoms from a 4,4'-dimethyl-2,2'-bipyridine ligand, one O atom from a 5-carb-oxy-benzene-1,3-dicarboxyl-ate ligand and two water mol-ecules in a distorted trigonal-bipyramidal geometry. The complex mol-ecules are linked by inter-molecular O-H⋯O hydrogen bonds and partly overlapping π-π inter-actions [centroid-centroid distance = 4.017 (2) Å] into a three-dimensional supra-molecular network.

4-Cyano-1-(4-nitro-benz-yl)pyridinium bis-(2-thioxo-1,3-dithiole-4,5-dithiol-ato-κS,S)nickelate(III).

In the title salt, (C(13)H(10)N(3)O(2))[Ni(C(3)S(5))(2)], the Ni(III) cation is S,S'-chelated by two 2-thioxo-1,3-dithiole-4,5-dithiol-ate anions in a distorted square-planar geometry. The complex anion is approximately planar with a maximum deviation of 0.097 (1) Å. In the 1-(4-nitro-benz-yl)-4-cyano-pyridinium cation, the pyridine ring is twisted at a dihedral angle of 73.84 (16)° with respect to the benzene ring. π-π stacking is observed between nearly parallel [dihedral angle = 4.71 (7)°] dithiole and benzene rings, the centroid-centroid distance being 3.791 (2) Å.

[Effects of soil salt on the niche of main plant species in alpine meadow].

By using Levins niche breadth index and Cowell similarity index, the niche breadth and niche similarity of main plant species in Bayanbulak alpine meadow were calculated, based on 3 resources dimensions (soil moisture, organic matter, and available K) along four gradients of soil salt content. The results showed that with the increase of soil salt content, the average niche breadth of main constructive species Carex stenocarpa based on the 3 resources dimensions decreased from 0.4433 to 0.1740, while that of companion species Potentilla anserina increased from 0.1263 to 0.2215, indicating that the niche breadth of the species with low salt-endurance decreased gradually, while the species with relatively high salt-endurance had an increasing niche breadth, being able to be an important succession species. With the increase of soil salt content, the niche similarity between the species with low salt-endurance increased, while that between the species with high salt-endurance was in adverse. The niche similarity between C. stenocarpa and Kobresia capillifolia increased from 0.701 to 0.842, and that between P. anserina and Taraxacum pseudolpinum decreased from 1 to 0.708. The difference in biological characters among plant species should be the main reason for their different responses to soil salt content.

[Relationships between belowground biomass of alpine grassland and environmental factors along an altitude gradient].

Taking Bayanbulak alpine grassland on the southern slope of Tianshan Mountain, Xin-jiang as test object, the relationships between belowground biomass and environmental factors along an altitude gradient were analyzed. The results showed that with increasing altitude, the below-ground biomass of alpine steppe dominated by Stipa purpurea and Festuca ovina, alpine steppe meadow dominated by Kobresia capillifolia and S. purpurea, and alpine meadow dominated by Carex stenocarpa, Alchemilla tianschanica, and K. capillfolia all increased gradually. There was a significant positive correlation between altitude and belowground biomass (P<0.01). The belowground biomass decreased with soil deep and with a 'T' shape distribution. In alpine steppe, alpine steppe meadow, and alpine meadow, the belowground biomass in 0-10 cm soil layer occupied 68.1%, 84.1% and 86.7% of the total, respectively. The below-ground biomass of the alpine grassland was negatively correlated with air temperature and positively correlated with relative humidity and soil water content (P<0.01), but had no significant correlation with soil organic matter, available nitrogen, and pH value.

[Relationships between aboveground biomass and environmental factors along an altitude gradient of alpine grassland].

In order to analyze the relationships between aboveground biomass and environmental factors along an altitude gradient of Bayanbulak alpine grassland on the southern slope of Tianshan Mountain, nine plots were selected, with each at 100 m interval of altitude. The results showed that Stipa purpurea and Festuca ovina communities distributed at the altitude from 2460 to 2760 m, and the aboveground biomass were 52.2-75.9 g x m(-2). Kobresia capillifolia + S. purpurea communities distributed at altitude 2860 m, and the aboveground biomass was 53.2 g x m(-2). K. capillifolia, Aichemilla tianschanica and Carex stenocarpa distributed at the altitude from 2860 to 3260 m, and the aboveground biomass was 62.1-107.4 g x m(-2). The mean relative humidity in July and August had greater effects on the aboveground biomass. Altitude had a negative correlation with the aboveground biomass of gramineous functional group, but a positive correlation with that of sedge functional group. The mean air temperature in July and August was the key factor affecting the aboveground biomass of gramineous and sedge functional groups, and the stepwise regression equations were Y = 13.467X - 97.284 and Y = 171.699 - 15.331X, respectively (X represented mean air temperature, and Y represented aboveground biomass). Altitude was negatively correlated with mean air temperature and soil pH value (P < 0.01), and positively correlated with mean relative humidity (P < 0.01) and soil available nitrogen and water content (P < 0.05).