Differences in Allometric Relationship of Two Dominant Woody Species Among Various Terrains in a Desert Region of Central Asia

Combined effects of biochar and biodegradable mulch film on chromium bioavailability and the agronomic characteristics of tobacco

Biochar (BC) and biodegradable mulch film (BMF) are both commonly used means of production in agriculture. In recent years, most studies have focused on the effects of BC or BMF on soil heavy metal pollution, while they have neglected the combined effects. In this study, a pot experiment was conducted to examine the impacts of BMF, BC, and combined BMF and BC (CMB) on the mobility of chromium (Cr) and the agronomic characteristics of flue-cured tobacco. Compared with the control, BMF, BC, and CMB significantly reduced the concentrations of diethylenetriamine pentaacetic acid (DTPA) extractable Cr in soils by 29.07-29.75%, 45.35-48.54%, and 34.21-37.92%, respectively. In comparison to the application of BMF and BC alone, co-application reduced the availability of Cr in soil via increasing the adsorption of soil Cr and soil enzyme activity, which resulted in the decrease of Cr content and bioconcentration factor and in plants. Moreover, the combined application increased the plant height, stem diameter, leaf area, total root area, root tip number, and root activity of tobacco, which leaded to increase in leaf and root biomass by 11.40-67.01% and 23.91-50.74%, respectively. Therefore, the application of CMB can reduce the heavy metal residues in tobacco leaves and improve tobacco yield and quality.

Influence of surface water and groundwater on functional traits and trade-off strategies of oasis communities at the end of the Keriya River, China

Plant functional traits reflect the capacity of plants to adapt to their environment and the underlying optimization mechanisms. However, few studies have investigated trade-off strategies for functional traits in desert-wetland ecosystems, the mechanisms by which surface water disturbance and groundwater depth drive functional trait variation at the community scale, and the roles of intraspecific and interspecific variation. Therefore, this study analyzed specific differences in community-weighted mean traits among habitat types and obtained the relative contribution of intraspecific and interspecific variation by decomposing community-weighted mean traits, focusing on the Daliyabuyi Oasis in the hinterland of the Taklamakan Desert. We also explored the mechanisms by which surface water and groundwater influence different sources of variability specifically. The results showed that plant height, relative chlorophyll content, leaf thickness, leaf nitrogen content, and nitrogen-phosphorus ratio were the key traits reflecting habitat differences. As the groundwater depth becomes shallower and surface water disturbance intensifies, plant communities tend to have higher leaf nitrogen content, nitrogen-phosphorus ratio, and relative chlorophyll content and lower height. Surface water, groundwater, soil water content, and total soil nitrogen can influence interspecific and intraspecific variation in these traits through direct and indirect effects. As arid to wet habitats change, plant trade-off strategies for resources will shift from conservative to acquisitive. The study concluded that community functional traits are mainly contributed by interspecific variation, but consideration of intraspecific variation and the covariation effects that exist between it and interspecific variation can help to further enhance the understanding of the response of community traits in desert-wetland ecosystems to environmental change. Surface water disturbance has a non-negligible contribution to this adaptation process and plays a higher role than groundwater depth.

The spatial patterns and driving mechanisms of blue carbon 'loss' and 'gain' in a typical mangrove ecosystem: A case study of Beihai, Guangxi Province of China

The role of mangroves in carbon sequestration is critical in mitigating climate change. For better identifying the carbon conservation hotspots of mangroves influenced by environmental factors, the spatial distribution and driving mechanisms of mangrove vegetation and soil carbon sequestration, as well as the future carbon dynamics of mangroves, required clarification. Firstly, we assessed the spatial pattern of vegetation biomass and soil depth-varied soil total organic carbon (TOC) in Xiaoguansha, Guangxi Province of China, and its relationships with duration of inundation (DTI) were explored. Additionally, the carbon storage capacity of adjacent mangrove tidal flats as potential carbon reservoirs was quantified. Thirdly, freshwater, and nutrient inputs, biotic factors of mangrove, and soil composition were selected as impact factors, and their mechanisms in carbon sequestration were elucidated by using Partial least squares path modeling (PLS-PM). Finally, medium values of environmental factors on mangrove carbon sequestration were revealed, based on which future loss and gain patterns of carbon sequestration under the combined effects were fully discussed. The results showed that: (1) The Above-ground biomass (AGB) and TOC densities were 32.89 Mg C/ha and 185.10 Mg C/ha in the study area, and both were enriched in the Interior areas. The carbon sequestration in the tidal flats was equivalented to >1/5 of total carbon sequestration of mangroves. (2) DTI was the most critical factor affecting the carbon sequestration pattern and was found to be positive correlated with AGB and TOC via changing soil contents (SC), whereas it exhibits a negative correlation with AGB and TOC through influencing canopy density (CD). CD and TP were identified as significant predictors. (3) Median analysis indicated that future carbon 'gain' area will move nearshore, whereas the carbon-rich intertidal area may undergo carbon loss. This study provided new insights and scientific understanding for management of mangrove blue carbon function.

Differences and allometric relationships among assimilative branch traits of four shrubs in Central Asia

Shrubs play a major role in maintaining ecosystem stability in the arid deserts of Central Asia. During the long-term adaptation to extreme arid environments, shrubs have developed special assimilative branches that replace leaves for photosynthesis. In this study, four dominant shrubs with assimilative branches, namely Haloxylon ammodendron, Haloxylon persicum, Calligonum mongolicum, and Ephedra przewalskii, were selected as the research objects, and the dry mass, total length, node number, and basal diameter of their assimilative branches and the average length of the first three nodes were carefully measured, and the allometric relationships among five traits of four species were systematically compared. The results indicated that: (1) Four desert shrubs have different assimilative branches traits. Compared with H. persicum and H. ammodendron, C. mongolicum and E. przewalskii have longer internodes and fewer nodes. The dry mass of H. ammodendron and the basal diameter of H. persicum were the smallest; (2) Significant allometric scaling relationships were found between dry mass, total length, basal diameter, and each trait of assimilative branches, all of which were significantly less than 1; (3) The scaling exponents of the allometric relationship between four traits and the dry mass of assimilative branches of H. persicum were greater or significantly greater than those of H. ammodendron. The scaling exponents of the relationships between the basal diameter, dry mass, and total length of E. przewalskii were higher than those of the other three shrubs. Therefore, although different species have adapted to drought and high temperatures by convergence, there was great variability in morphological characteristics of assimilative branches, as well as in the scaling exponents of relationships among traits. The results of this study will provide valuable insights into the ecological functions of assimilative branches and survival strategies of these shrubs to cope with aridity and drought in desert environments.