Shaanxi Sheng cheng tu /

Scale ca. 1:15,000.Wood block print.Includes text

Why does oriental arborvitae grow better when mixed with black locust: Insight on nutrient cycling?

To identify why tree growth differs by afforestation type is a matter of prime concern in forestry. A study was conducted to determine why oriental arborvitae (Platycladus orientalis) grows better in the presence of black locust (Robinia pseudoacacia) than in monoculture. Different types of stands (i.e., monocultures and mixture of black locust and oriental arborvitae, and native grassland as a control) were selected in the Loess Plateau, China. The height and diameter at breast height of each tree species were measured, and soil, shoot, and root samples were sampled. The arbuscular mycorrhizal (AM) attributes, shoot and root nutrient status, height and diameter of black locust were not influenced by the presence of oriental arborvitae. For oriental arborvitae, however, growing in mixture increased height and diameter and reduced shoot Mn, Ca, and Mg contents, AM fungal spore density, and colonization rate. Major changes in soil properties also occurred, primarily in soil water, NO3-N, and available K levels and in soil enzyme activity. The increase in soil water, N, and K availability in the presence of black locust stimulated oriental arborvitae growth, and black locust in the mixed stand seems to suppress the development of AM symbiosis in oriental arborvitae roots, especially the production of AM fungal spores and vesicles, through improving soil water and N levels, thus freeing up carbon to fuel plant growth. Overall, the presence of black locust favored oriental arborvitae growth directly by improving soil water and fertility and indirectly by repressing AM symbiosis in oriental arborvitae roots

New design of external heat-ratio method for measuring low and reverse rates of sap flow in thin stems

Sap-flow techniques had limited application to thin-stemmed woody and herbaceous species and to diverse functional plant organs until the recent development of the external heat-ratio (EHR) method. Existing EHR techniques using miniature gauge configurations, however, are limited to thin stems with diameters of 2-5 mm. This study introduces a new design of an EHR gauge adapted to thin stems with diameters up to 15 mm and sapflux densities < 50 cm h(-1). The gauge was calibrated on cut stems of the shrubs Caragana korshinskii and Salix psammophila, with the measured heat-pulse velocity (V-h) compared to gravimetric measurements of sap-flux density (V-s) under controlled conditions. A validation test was also carried out by comparing MR method with the stem heat-balance (SHB) method through in situ and long-term monitoring of V-s on standing stems of C. korshinskii. Vh in the tested cut stems of both species was linearly correlated with V, up to approximately 50 cm h(-1) (R-2 up to 0.96, P < 0.001) in a range of stem diameters of 4.1-15.6 mm. An empirical multiplier for converting the measured V-h to V-s, however, varied between the two species, 2.02 and 1.15 for C. korshinskii and S. pscunmophila, respectively. The EHR technique sensitively captured the diurnal dynamics of V-s in field tests, within a range from zero to nearly 30 cm h(-1) on C. korshinskii stems, and hourly V-s was linearly correlated with the reference evapotranspiration (R-2 = 0.70, P < 0.001) over 26 successive days without drought stress. The tested SHB method, however, poorly detected the sap-flux density, especially at low densities. The gauges for the EHR method were easy to build and capable of accurate estimating bidirectional sap flow, especially at low densities. This technique, with variable EHR gauge configurations, has broader applications than SHB methods for understanding plant-water relations in understories, shrubs and ecosystems dominated by herbage

Spectral Characteristics of Biological Soil Crusts under the Different Types in the Water-Wind Erosion Crisscross Region on the Loess Plateau

The study on spectral characteristics of biological soil crust in the water-wind erosion crisscross region in the Loess Plateau has important scientific value for the identification of biological soil crust based on remote sensing technology at regional scale, also provides important technical support for estimating the effect of biological soil crust on regional soil erosion control. The spectra of higher vegetation as well as the biological soil crust of algae with different coverage and different types of mosses were measured and quantified by Surface Species Spectrometry. The results are as follows, the algal bio-soil crust has similar spectral characteristics with soil in the water-wind erosion crisscross region in the Loess Plateau, and there is no obvious "peak valley" characteristic in the spectral curve. The reflectivity was reduced by the increasing coverage of the biological soil crust. Compared with the bare area, the spectral reflectance normalized mean of algae biological soil crust deceased 8. 64%, 15. 80% and 23. 09% respectively in the coverage of 10% to 20%, 30% to 40% and 50% to 60% in the visible area. The absorption characteristic at 680 nm (Chlorophyll) became increasingly obvious and the absorption valley at 2 200 nm (secondary mineral) became smaller as the coverage of algae biological soil crust increased. The spectral curve of moss biological soil crust showed the reflection peak of the green band, the absorption valley of the red light band and the high reflection of the near infrared band, which is similar with the vegetation. In the range of 760 similar to 930 nm, the slope of moss biological soil crust was 2. 5 to 4. 5 timed higher than that of vegetation. The study can provide some theoretical basis and technical support for the identification of biological soil crust

Immobilization of lead by application of zeolite: Leaching column and rhizobox incubation studies

Application of zeolite can reduce lead (Pb) mobility in soil. Leaching columns and rhizobox incubation experiments were carried out to investigate the leaching processes and rhizosphere behavior of Pb in a Pb-contaminated soil amended with zeolite. Zeolite addition reduced Pb release from the contaminated soil as well as increasing leachate pH and decreasing the bioavailable Pb concentration. Leachate pH was not significantly different among different zeolite dose treatments at the same measurement time. Leaching of Pb from the treated soil was lower than that from the untreated soil for the first nine weeks but the trend was reversed for the final weeks of the study. The Pb concentration in the leachate did not appear to be sensitive to changes in pH. It was concluded that when a relatively low amount of zeolite was added (<20 mg kg(-1)), the cation exchange capacity was the dominant factor for regulating Pb leaching behavior. The DTPA extractable Pb in the rhizosphere was similar to 15% higher than that in the close-root and bulk soil. In addition, the amounts of DTPA extractable Pb in the rhizosphere soil not treated with zeolite were 10% and 16% higher than in the rhizosphere soil with 10 and 20 g kg-1 zeolite addition, respectively. It could be concluded that zeolite addition inhibits uptake of Pb by affecting rhizospheric behavior. (C) 2013 Elsevier B.V. All rights reserved.Application of zeolite can reduce lead (Pb) mobility in soil. Leaching columns and rhizobox incubation experiments were carried out to investigate the leaching processes and rhizosphere behavior of Pb in a Pb-contaminated soil amended with zeolite. Zeolite addition reduced Pb release from the contaminated soil as well as increasing leachate pH and decreasing the bioavailable Pb concentration. Leachate pH was not significantly different among different zeolite dose treatments at the same measurement time. Leaching of Pb from the treated soil was lower than that from the untreated soil for the first nine weeks but the trend was reversed for the final weeks of the study. The Pb concentration in the leachate did not appear to be sensitive to changes in pH. It was concluded that when a relatively low amount of zeolite was added (<20 mg kg(-1)), the cation exchange capacity was the dominant factor for regulating Pb leaching behavior. The DTPA extractable Pb in the rhizosphere was similar to 15% higher than that in the close-root and bulk soil. In addition, the amounts of DTPA extractable Pb in the rhizosphere soil not treated with zeolite were 10% and 16% higher than in the rhizosphere soil with 10 and 20 g kg-1 zeolite addition, respectively. It could be concluded that zeolite addition inhibits uptake of Pb by affecting rhizospheric behavior. (C) 2013 Elsevier B.V. All rights reserved