No abstract

Atmospheric water is one of the main water resources for plants in arid ecosystems. However, whether deep-rooted, tomentum-less desert trees can absorb atmospheric water via aerial organs and transport the water into their bodies remains poorly understood. In the present study, a woody, deep-rooted, tomentum-less plant, Haloxylon ammodendron (C.A. Mey.) Bunge, was selected as the experimental object to investigate the preconditions for and consequences of foliar water uptake. Plant water status, gas exchange, and 18 O isotopic signatures of the plant were investigated following a typical rainfall pulse and a high-humidity exposure experiment. The results showed that a high content of atmospheric water was the prerequisite for foliar water uptake by H. ammodendron in the arid desert region. After atmospheric water was absorbed via the assimilating branches, which perform the function of leaves due to leaf degeneration, the plant transported the water to the secondary branches and trunk stems, but not to the taproot xylem or the soil, based on the 18 O isotopic signatures of the specimen. Foliar water uptake altered the plant water status and gas exchange-related traits, i.e., water potential, stomatal conductance, transpiration rate, and instantaneous water use efficiency. Our results suggest that atmospheric water might be a subsidiary water resource for sustaining the survival and growth of deep-rooted plants in arid desert regions. These findings contribute to the knowledge of plant water physiology and restoration of desert plants in the arid regions of the planet.

In an arid region, water is the limiting factor for the performance of plants and, hence, the input of water significantly affects the ecological processes. Although the dew phenomenon often occurs in the desert, whether plants can absorb and utilise this water source is still unknown. In this study, we tested the effects of 3 amounts of dew, that is, total natural amount of dew, half amount of natural dew, and no amount of (zero) dew, in order to investigate variations in functional traits and demographic traits in relation to the life history of an ephemeral plant Lappula semiglabra. Results showed that variations in functional traits including plant height, crown area, leaf area, leaf thickness, leaf relative water content, chlorophyll content, and net photosynthetic rate were significantly increased with increasing dew amount. Leaf water potential was significantly decreased, whereas root length and root diameter showed no significant differences among 3 amounts of dew. Demographic traits including survival rate, survival, total age, and mean life expectancy increased with increasing dew amount, whereas the vanish rate percentage, mortality rate, mortality, and fatal number decreased. In combination, our results showed that leaf and stem traits L. semiglabra related to dew absorption increased with increasing of dew amount, and hence, obtained more water, whereas root traits related to uptake of soil water remain unchanged. We conclude that leaves and stem of L. semiglabra can absorb and efficiently utilise dew as a water resource for better suitability in the arid desert region.

Patterns of species diversity are determined by both species interactions and environmental adaptations. The species composition and environmental factors of the Tugai forest on the north shore of the Aqikesu River was investigated to determine species diversity and the ecological niche of dominant species in the Ebinur basin. Using a multivariate regression tree based on the content of soil water and salinity, our results showed that the plant communities were divided into three associations. The three associations are the Ass. Populus euphratica-Apocynum venetum-Phragmites australis (type I), the Ass. Populus euphratica-Reaumuria songonica (type II), and the Ass. Kalidium foliatum ǁ Populus euphratica-Apocynum venetum + Alhagi sparsifolia (type III). Association I had a weak ability to tolerate extreme environments, including 5 •研究报告• 第 1 期 龚雪伟和吕光辉: 艾比湖流域杜加依林荒漠植物群落多样性及优势种生态位 35 quadrats, while Association II could tolerate mild salt and drought stress, including 3 quadrats, and Association III had a certain degree of adaptability to salty and dry habitats, including 22 quadrats. With succession of typical associations from type I to III, psammophytes and halophytes gradually occupied the habitats and become the dominant species. The Shannon-Wiener biodiversity index and Margalef richness index initially decreased and then increased along with environmental degradation, while the Simpson dominance index and Pielou evenness index showed the opposite trend. The variation of associations and species diversity along the environmental gradient reflects the succession of plant communities. The Bray-Curtis similarity analysis of niche breadth clustered 13 dominant species into two groups, with an average similarity of 96.89% and 97.66%, respectively, reflecting that the niche breadth of species has a high similarity. The pressure coefficient of non-metric multidimensional scaling (NMDS) ordination was 0.04 and except for Halimodendron halodendron and Glycyrrhiza uralensis, and species distribution also had a high similarity. In summary, soil water and salt contents are the main environmental factors that are responsible for plant structure and diversity, and determine the direction of succession. The niche and distribution of dominant species show high similarity, indicating obvious competitive relationship between them.