[Litter storage and water-holding capacity of typical forests in mountainous area of Southwest China]. / è¥¿å—å±±åŒºå ¸åž‹æ£®æž—æž¯è½ç‰©å‚¨é‡åŠæŒæ°´èƒ½åŠ›.

Current studies on water conservation capacity of litter in the mountainous area of Southwest China (MASC) mainly focus on local scale. Such results are difficult to evaluate the storage and water-holding capacity of litter in the whole MASC. In this study, the results of site-scale research in the MASC from 2004 to 2021 were collated (a total of 16 research sites and 70 data), as well as the storage and water-holding characteristics of litters of three typical forests in the MASC were compared and analyzed. The results showed that the water-holding processes of litter in coniferous forest, broadleaved forest and mixed forest were similar, which could be divided into three stages: rapid water absorption, gradual slowing, and stable. The absorption rate and duration of different forests were different in each stage. The broadleaved forest had the fastest water absorption rate, while coniferous forest had the slowest with the longest duration to reach stability. There was no significant difference in litter storage among diffe-rent forest types. The total litter storage of coniferous forest, broadleaved forest and mixed forest ranged from 8.26 to 8.82 t·hm-2. The significant spatial variations of litter storage in semi-decomposed layer resulted in that of total litter storage. The total maximum water-holding capacity of litters of the three forests ranged from 17.85 t·hm-2 to 19.87 t·hm-2, and the maximum water-holding rate of litter ranged from 200.6% to 228.0%. There was a positive correlation between the maximum water-holding capacity and litter storage in different forests. The total effective retention capacity of three forest litters ranged from 11.66 to 12.29 t·hm-2, while the total effective retention rate of three forests ranged from 128.1% to 145.2%. There were no significant differences in litter storage and water holding capacity among three forest types with two decomposition degrees in MASC.

Dynamics and sources of colloids in shallow groundwater in lowland wells and fracture flow in sloping farmland.

Field-scale studies of natural colloid mobilization and transport in finely fractured aquifer as well as the source identification of groundwater colloids are of great importance to the safety of shallow groundwater. In this study, the daily monitoring of fracture flow from a sloping farmland plot and the biweekly monitoring of three lowland shallow wells within the same catchment were carried out simultaneously in 2013. The effects of physicochemical perturbations on groundwater colloid dynamics were explored in detail using partial redundancy analysis, structural equation modeling, Pearson correlation and multi-linear regression analyses. The characterization and source identification of groundwater colloids were addressed via multiple parameters. The daily colloid concentration in the fracture flow varied between 0.54 and 31.90 mg/L (1.64 mg/L on average). Unique periods of high colloid concentration (5.59 mg/L on average) occurred during the initially generated flow following the dry season. In comparison, a narrower colloid concentration range of 0.24-11.66 mg/L was observed in the lowland shallow wells, with a smaller temporal variation than that of the fracture flow. A low percentage (2.4-7.0%) of colloids and a high percentage (47.7-92.0%) of coarse particles (2-10 µm) were present in the lowland well water. Hydraulic perturbation by rainwater infiltration in the sloping farmland was the dominant mechanism for colloid mobilization in general; this effect retreated to secondary importance behind chemical perturbations (pH, Mg2+ and DOC) at low flow discharges (<1.3 L/min). In contrast, water chemistry (e.g., EC, cations and DOC concentrations) exhibited a major effect on colloid dynamics in the water of the lowland wells, except for the extremely high-salinity water of one well, in which water temperature showed a negative dominant influence on colloid stability. The combined use of multiple parameters (e.g., mineral composition and organic matter, calcium carbonate and δ13C contents) traced groundwater colloids to the shallow soil in the upper farmlands. It is strongly advised that in finely fractured aquifers within agricultural catchments, not only the small colloids but also the coarse particles in the size range of 2-10 µm should be monitored in case of colloid-associated contamination from agricultural wastes e.g., N, P, pesticides and/or heavy metals, especially at the early stages of the rainy seasons.

[Effect of simulative warming on growth and antioxidative characteristics of Kobresia pygmaea and K. tibetica in the permafrost region of Qinghai-Tibetan Plateau, China]. / 模拟增温对青藏高原多年冻土区小嵩草和藏嵩草生长与抗氧化特征的影响.

In the present study, open top chambers (OTCs) were employed to simulate temperature increase at Fenghuoshan site, located on the hinterland of Qinghai-Tibetan Plateau. To explore the potential response mechanism of alpine plants under warmer temperature, the leaf morphological and antioxidative characteristics of two dominant species of alpine meadow (Kobresia pygmaea) and alpine swamp meadow (K. tibetica) were analyzed. The results showed that length and numbers of leaves in K. pygmaea increased by 40.0% and 72.7% by warming, respectively. Plant height and leaf length in K. tibetica increased by 11.9% and 19.3% by warming, respectively. Warming improved plant growth and aboveground biomass accumulation in both species. However, warming did not affect leaf membrane permeability (electrolyte leakage), active oxygen species (hydrogen peroxide and superoxide anion), activities of superoxide dismutase, peroxidase, ascorbate peroxidase and catalase, and malondialdehyde content in both species. Ascorbic acid and free proline contents in K. tibetica increased by 29.8% and 53.8%, respectively, but no change was found in K. pygmaea. In conclusion, K. pygmaea and K. tibetica could adapt under warmer temperature through keeping a steady antioxidative status.

[A review on carbon and water interactions of forest ecosystem and its impact factors].

Interaction between carbon and water in forest ecosystem is a coupling process in terrestrial ecosystem, which is an indispensable aspect for the study of forest carbon pool, ecohydrological processes and the responses to global change. In the context of global change, the interaction and coupling of carbon and water in forest ecosystem has attracted much attention among scientists. In this paper, we reviewed the process mechanism of forest carbon and water relationships based on previous studies, which consisted of advance in forest water use efficiency, carbon and water interactions at different scales, scaling, and model simulation. We summed up the factors affecting for- est water and carbon interaction, including water condition, carbon dioxide enrichment, warming, nitrogen deposition, ozone concentration variation, solar radiation, and altitudinal gradients. Finally, we discussed the problems in the previous studies, and prospected the possible future research fields, among which we thought the inherent dynamics mechanism and scaling of forest carbon and water interactions should be enhanced.

Bryophyte species richness and composition along an altitudinal gradient in Gongga Mountain, China.

An investigation of terrestrial bryophyte species diversity and community structure along an altitudinal gradient from 2,001 to 4,221 m a.s.l. in Gongga Mountain in Sichuan, China was carried out in June 2010. Factors which might affect bryophyte species composition and diversity, including climate, elevation, slope, depth of litter, vegetation type, soil pH and soil Eh, were examined to understand the altitudinal feature of bryophyte distribution. A total of 14 representative elevations were chosen along an altitudinal gradient, with study sites at each elevation chosen according to habitat type (forests, grasslands) and accessibility. At each elevation, three 100 m × 2 m transects that are 50 m apart were set along the contour line, and three 50 cm × 50 cm quadrats were set along each transect at an interval of 30 m. Species diversity, cover, biomass, and thickness of terrestrial bryophytes were examined. A total of 165 species, including 42 liverworts and 123 mosses, are recorded in Gongga mountain. Ground bryophyte species richness does not show any clear elevation trend. The terrestrial bryophyte cover increases with elevation. The terrestrial bryophyte biomass and thickness display a clear humped relationship with the elevation, with the maximum around 3,758 m. At this altitude, biomass is 700.3 g m(-2) and the maximum thickness is 8 cm. Bryophyte distribution is primarily associated with the depth of litter, the air temperature and the precipitation. Further studies are necessary to include other epiphytes types and vascular vegetation in a larger altitudinal range.

Effects of Pb and Ni stress on oxidative stress parameters in three moss species.

Antioxidative responses of the mosses Hypnum plumaeforme, Thuidium cymbifolium, and Brachythecium piligerum to short-term Pb and Ni stress were investigated. Both Pb and Ni treatment increased the formation of reactive oxygen species and lipid peroxidation, decreased superoxide dismutase (SOD), and catalase (CAT) activities in H. plumaeforme and T. cymbifolium. However, SOD activity in B. piligerum was increased under 10mM Pb stress and Ni increased CAT activity in B. piligerum under 1mM Ni stress. Peroxidase (POX) activity in the three mosses was increased by Pb and Ni exposure, indicating that POX plays an important role in preventing heavy metal-induced oxidative stress. The accumulation of O(2)(-) and H(2)O(2) in mosses is related to the decline in SOD and CAT activities. B. piligerum is the most sensitive and T. cymbifolium is the most tolerant species to Pb and Ni stress among the three bryophytes.

Heavy metal-induced physiological alterations and oxidative stress in the moss Brachythecium piligerum chad.

Antioxidative enzymes (superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX)), as well as lipid peroxidation and proline were studied in moss Brachythecium piligerum Card. collected from different sites in Shanghai, China, to validate the physiological parameters as biomarkers of atmospheric heavy metal pollution. Results demonstrated that the responses of POD and CAT activities, as well as MDA and proline contents were in accordance with the heavy metal contents in mosses. That is, POD activity, MDA, and proline content were activated and CAT activity was inhibited in heavier polluted sites, indicating that POD and CAT activities, and MDA and proline contents could be used as biomarkers for biomonitoring atmospheric heavy metal pollution.

[Spatial variability characteristics of soil organic carbon and nitrogen reveal typical alpine meadow degradation on Qinghai-Tibetan Plateau].

The principle of geo-statistics method was used to analyse the spatial heterogeneity of soil organic carbon and total nitrogen (0-10 cm) of alpine meadow of the Qinghai-Tibetan Plateau. The results show that the mean contents of soil organic carbon and total nitrogen at depth 0-10 cm are 11.45 g x kg(-1) and 1.02 g x kg(-1), 0.23 and 0.21 of co-variation coefficient, respectively. As mentioned above all factors reflect oligotrophic condition of soil fertility at this habitat. Organic carbon and entire nitrogen of soil random factor dissociation take up mutant proportion of general space heterogeneity being 44.7% and 49.9% respectively. Mutant dimension is 210.9 m and 200.1 m respectively. The soil organic carbon and the entire nitrogen show on the research territory vacates to oneself the factor to be bigger than machine the factor the different pattern. On space structure dissociation, from inherent attribute of soil, if space such as soil mineral substance, land form is certainly relevance, the factor and the artificial factor play role if the random factors that be trampled on to soil super crust arouses such as grazing and engineering construction is common, Medium memorial level affecting degree.

Treated wastewater irrigation effect on soil, crop and environment: wastewater recycling in the loess area of China.

A study was carried out at the Loess Plateau in Dongzhi, China, to test the feasibility of using secondary treatment sewage effluent and to determine whether the water quality would then meet the recommended irrigation norm. Seven crops, including celery, wheat, maize, millet, apples, rapeseed and yellow beans, were tested in the study. Physical and chemical properties of the soil, crop yield and quality and leachate at different soil depths were measured. In most cases, the quality of the crops that made use of treated sewage was not distinctively different from those that did not use treated sewage. However, yields for the former were much higher than they were for the latter. Leachates at different soil depths were analyzed and the results did not show alarming levels of constituents. For a period of approximately 14 months, the treated sewage irrigation had no significant effect on the loess soil and no cases of illness resulting from contact with the treated sewage were reported. With treated sewage irrigation, a slight increase in the organic content of the soil was observed.