Biotic and Abiotic Contribution to Diurnal Soil CO2 Fluxes from Saline/Alkaline Soils.

As the second largest carbon flux in terrestrial ecosystems, the soil CO2 flux is closely related to the atmospheric CO2 concentration. The soil CO2 flux is the sum of biotic respiration and abiotic geochemical CO2 exchange; however, little is known about abiotic CO2 fluxes in arid areas. To investigate the relative contribution of abiotic and biotic soil CO2 fluxes over a diurnal course, the abiotic CO2 flux was distinguished by autoclaving sterilization in both saline and alkaline soils at an arid site in northwestern China. The results demonstrated that: (1) Over the diurnal course, the abiotic CO2 was a significant component of the soil CO2 flux in both saline and alkaline soil, which accounted for more than 56% of the diurnal soil CO2 flux. (2) There was a dramatic difference in the temperature response between biotic and abiotic CO2 fluxes: the response curves of biotic respiration were exponential in the saline soil and quadratic in the alkaline soil, while the abiotic CO2 flux was linearly correlated with soil temperature. They were of similar magnitude but with opposite signs: resulting in almost neutral carbon emissions on daily average. (3) Due to this covering up effect of the abiotic CO2 flux, biotic respiration was severely underestimated (directly measured soil CO2 flux was only one-seventh of the biotic CO2 flux in saline soil, and even an order of magnitude lower in alkaline soil). In addition, the soil CO2 flux masked the temperature-inhibition of biotic respiration in the alkaline soil, and veiled the differences in soil biological respiration between the saline and alkaline soils. Hence, the soil CO2 flux may not be an ideal representative of soil respiration in arid soil. Our study calls for a reappraisal of the definition of the soil CO2 flux and its temperature dependence in arid or saline/alkaline land. Further investigations of abiotic CO2 fluxes are needed to improve our understanding of arid land responses to global warming and to assist in identifying the underlying abiotic mechanisms.

Fixed allocation patterns, rather than plasticity, benefit recruitment and recovery from drought in seedlings of a desert shrub.

The response of plants to drought is controlled by the interaction between physiological regulation and morphological adjustment. Although recent studies have highlighted the long-term morphological acclimatization of plants to drought, there is still debate on how plant biomass allocation patterns respond to drought. In this study, we performed a greenhouse experiment with first-year seedlings of a desert shrub in control, drought and re-water treatments, to examine their physiological and morphological traits during drought and subsequent recovery. We found that (i) biomass was preferentially allocated to roots along a fixed allometric trajectory throughout the first year of development, irrespective of the variation in water availability; and (ii) this fixed biomass allocation pattern benefited the post-drought recovery. These results suggest that, in a stressful environment, natural selection has favoured a fixed biomass allocation pattern rather than plastic responses to environmental variation. The fixed 'preferential allocation to root' biomass suggests that roots may play a critical role in determining the fate of this desert shrub during prolonged drought. As the major organ for resource acquisition and storage, how the root system functions during drought requires further investigation.

Apparent plasticity in functional traits determining competitive ability and spatial distribution: a case from desert.

Species competitive abilities and their distributions are closely related to functional traits such as biomass allocation patterns. When we consider how nutrient supply affects competitive abilities, quantifying the apparent and true plasticity in functional traits is important because the allometric relationships among traits are universal in plants. We propose to integrate the notion of allometry and the classical reaction norm into a composite theoretical framework that quantifies the apparent and true plasticity. Combining the framework with a meta-analysis, a series of field surveys and a competition experiment, we aimed to determine the causes of the dune/interdune distribution patterns of two Haloxylon species in the Gurbantonggut Desert. We found that (1) the biomass allocation patterns of both Haloxylon species in responses to environmental conditions were apparent rather than true plasticity and (2) the allometric allocation patterns affected the plants' competition for soil nutrient supply. A key implication of our results is that the apparent plasticity in functional traits of plants determines their response to environmental change. Without identifying the apparent and true plasticity, we would substantially overestimate the magnitude, duration and even the direction of plant responses in functional traits to climate change.

Poly[(dimethyl-formamide)(µ(4)-2,2'-sulfanediyldibenzoato)nickel(II)].

The title centrosymmetric dinuclear Ni(II) complex, [Ni(C(14)H(8)O(4)S)(C(3)H(7)NO)](n), was prepared via reaction of Ni(NO(3))(2)·6H(2)O and thio-salicylic acid, with H(2)O and dimethyl-formamide (DMF) as the mixed solvent. The central Ni(II) ion is five-coordinated by five O atoms from DMF and from the carboxyl-ate groups of the organic ligand. The symmetry-related coordination polyhedra inter-link into centrosymmetric dimeric units and these, in turn, are linked into infinite chains propagating parallel to [100].

[Spectral analysis and photoluminescence properties of Eu-Tb codoped polymer].

In the present paper, Eu0.5 Tb0.5 (TTA)3 Phen was synthesized and Eu0.5 Tb0.5 (TTA)3 Phen/PMMA was prepared by in-situ polymerization. The structure of Eu0.5 Tb0.5 (TTA)3 Phen/PMMA was characterized by FTIR spectra. Microscopic morphology and photoluminescence properties were investigated by SEM photographs and fluorescence spectra. The results indicated that polymer parts were attached with the rare-earth molecular parts in the composite luminescent materials. And Eu0.5 Tb0.5 (TTA)3 Phen/PMMA could emit mostly characteristic fluorescence of europium ion and intense red fluorescence with a peak wavelength at 611.8 nm and a bandwidth of 10.4 nm (Purity: 0.9905) under UV excitation at 365 nm. Its fluorescence intensity was found to be influenced with the content of MMA. It w as demonstrated that Eu0.5 Tb0.5 (TTA)3 Phen/PMMA was an excellent red photoluminescent rare-earth polymer material.