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Main Conclusion: The anatomical structures of Carex moorcroftii roots showing stronger plasticity during drought had a lower coefficient of variation in cell size in the same habitats, while those showing weaker plasticity had a higher coefficient of variation. The complementary relationship between these factors comprises the adaptation mechanism of the C. moorcroftii root to drought. To explore the effects of habitat drought on root anatomy of hygrophytic plants, this study focused on roots of C. moorcroftii. Five sample plots were set up along a soil moisture gradient in the Western Sichuan Plateau to collect experimental materials. Paraffin sectioning was used to obtain root anatomy, and one-way ANOVA, correlation analysis, linear regression analysis, and RDA ranking were applied to analyze the relationship between root anatomy and soil water content. The results showed that the root transverse section area, thickness of epidermal cells, exodermis and Casparian strips, and area of aerenchyma were significantly and positively correlated with soil moisture content (P < 0.01). The diameter of the vascular cylinder and the number and total area of vessels were significantly and negatively correlated with the soil moisture content (P < 0.01). The plasticity of the anatomical structures was strong for the diameter and area of the vascular cylinder and thickness of the Casparian strip and epidermis, while it was weak for vessel diameter and area. In addition, there was an asymmetrical relationship between the functional adaptation of root anatomical structure in different soil moisture and the variation degree of root anatomical structure in the same soil moisture. Therefore, the roots of C. moorcroftii can shorten the water transport distance from the epidermis to the vascular cylinder, increase the area of the vascular cylinder and the number of vessels, and establish a complementary relationship between the functional adaptation of root anatomical structure in different habitats and the variation degree of root anatomical structure in the same habitat to adapt to habitat drought. This study provides a scientific basis for understanding the response of plateau wetland plants to habitat changes and their ecological adaptation strategies. More scientific experimental methods should be adopted to further study the mutual coordination mechanisms of different anatomical structures during root adaptation to habitat drought for hygrophytic plants., (© 2024. The Author(s).)

The response of Carex lasiocarpa in riparian wetlands in Sanjiang Plain to the environmental gradient of water depth was analyzed by using the Gaussian Model based on the biomass and average height data, and the ecological water-depth amplitude of Carex lasiocarpa was derived. The results indicated that the optimum ecological water-depth amplitude of Carex lasiocarpa based on biomass was [13.45 cm, 29.78 cm], while the optimum ecological water-depth amplitude of Carex lasiocarpa based on average height was [2.31 cm, 40.11 cm]. The intersection of the ecological water-depth amplitudes based on biomass and height confirmed that the optimum ecological water-depth amplitude of Carex lasiocarpa was [13.45 cm, 29.78 cm] and the optimist growing water-depth of Carex lasiocarpa was 21.4 cm. The TWINSPAN, a polythetic and divisive classification tool, was used to classify the wetland ecological series into 6 associations. Result of TWINSPAN matrix classification reflected an obvious environmental gradient in these associations: water-depth gradient. The relation of biodiversity of Carex lasiocarpa community and water depth was determined by calculating the diversity index of each association.

Data from four components of the radiation balance were used to investigate the surface energy budgets for a Carex lasiocarpa mire in the Sanjiang Plain, Northeast China, and the controlling factors of the evapotranspiration (ET) were discussed in detail. During the growing season 2006, the shortwave radiation (SW↓) reaching the mire surface added up to 2,854.3 MJ m(-2) and the net radiation (Rn) was 1,637.4 MJ m(-2) in total, with an average of 9.86 MJ m(-2) day(-1). G was the smallest flux at the water-atmosphere interface, with an average of about 0.91 MJ m(-2) day(-1), but showed high relative variability, even changing its sign. The latent and sensible heat fluxes (LE and H) amounted to 787.48 and 476.26 MJ m(-2), respectively, and the total sum of LE and H accounted for 77.18% of Rn. By conversion from LE, the average value of ET from the mire was 1.84 mm day(-1), amounting to 298.8 mm. The total ET was almost 60% of the total rainfall in the same period, proving that ET is the primary water consumer in the mire. The growth of C. lasiocarpa was related closely with surface resistance (r (s)), and analysis of partial correlation indicated that r (s) correlated negatively with leaf area index (LAI) when the interference of the available energy, Rn-G, was removed. There was a strong linkage between r (s) and the evaporative fraction [LE/(LE + H)] as well as Bowen ratio (β). r (s) was the key factor in controlling the variation of ET and regulating energy partitioning between LE and H. During the whole growing season, r (s) and R (n)-G were the two main factors coupled in ET processes. In spring, r (s) dominated ET processes, and the increase in LAI led to a decrease in r (s), which in turn accelerated ET as vegetation developed until late August. After August, the available energy controlled the process of ET completely until ET reached an equilibrium in mid-October.