Responses of Leaf Hydraulic Traits of Schoenoplectus Tabernaemontani To Increasing Temperature and CO2 Concentrations

Background Against the background of a changing climate, the responses of functional traits of plateau wetland plants to increasing temperatures and CO2 concentrations need to be understood. Hydraulic traits are the key for plants to maintain their ecological functions and affect their growth and survival. However, few studies have comprehensively considered the response strategies of wetland plants' hydraulic traits to environmental changes in the context of water and matter transport, loss, and retention. According to the latest IPCC prediction results, we performed experiments under increased temperature (2℃) and CO2 levels (850 µmol/mol) in an artificial Sealed-top Chamber (STC) to investigate the responses of the hydraulic characteristics of Schoenoplectus tabernaemontani, the dominant species in plateau wetlands in China. Results Compared with the CK group, net photosynthetic rate, transpiration rate, stomatal length, cuticle thickness, vascular bundle length, vascular bundle width, and vascular bundle area of S. tabernaemontani in the ET group were significantly reduced, whereas stomatal density and vein density increased significantly. Compared with the CK group, the hydraulic traits of S. tabernaemontani in the EC group were reduced considerably in stomatal length and cuticle thickness but increased dramatically in stomatal density, and there were no significant differences between other parameter values and the control group. Net photosynthetic rate was significantly positively correlated with stomatal length, cuticle thickness, and vascular bundle length, and stomatal conductance was significantly positively correlated with cuticle thickness. The transpiration rate was significantly positively correlated with cuticle thickness, epidermal cell area, vascular bundle length, vascular bundle width, and vascular bundle area. Regarding the hydraulic traits, there was a significant negative correlation between stomatal density and stomatal length, or cuticle thickness, and a significant positive correlation between the latter two. The epidermal cell area was significantly positively correlated with epidermal thickness, vascular bundle length, vascular bundle width, and vascular bundle area Conclusions Increased temperature and CO2 levels are not conducive to the photosynthetic activity of S. tabernaemontani. Photosynthetic rate, stomatal density and size, vein density, epidermal structure size, and vascular bundle size play an essential role in the adaptation of this species to changes in temperature and CO2 concentration. In the process of adaptation, hydraulic traits are not isolated from each other, and there is a functional association among traits. This study provide a scientific basis for the management and protection of plateau wetlands.

Distribution and Ecology of a New Species of Water-lily, Nymphaea loriana (Nymphaeaceae), in Western Canada

Nymphaea loriana Wiersema, Hellq. & Borsch (Lori’s Water-lily) is a newly described, Canadian endemic species that has been found in central Manitoba and east-central Saskatchewan. To assess the status of a species, data regarding its distribution, population size, habitat, and search effort are needed. The purpose of this paper is to document these factors for this species. The extent of occurrence of N. loriana is approximately 15 100 km2 but the known area of occupancy is a mere 20 km2. The estimated population size of N. loriana is about 750 individual plants, although more may exist on poorly explored rivers and lakes within the extent of occurrence and possibly in northeastern Ontario. Nymphaea loriana occurs in fresh, stagnant, or slowly moving water in boreal lakes and rivers and is typically associated with N. leibergii (Dwarf Water-lily), Schoenoplectus tabernaemontani (Soft-stemmed Bulrush), Potamogeton natans (Floating-leaved Pondweed) and Nuphar variegata (Variegated Pondlily). Potential threats to the persistence of this species include low water quality resulting from mining, forestry, and agriculture, and changes to water flow because of dam construction and climate change. Monitoring known populations and searching for additional ones may be needed to assess the status of this species.

Plant Species for the Removal of Na+ and Cl– from Greenhouse Nutrient Solution

Certain ions such as Na+ and Cl– can accumulate in recirculating greenhouse nutrient solutions and can reach levels that are damaging to crops. An option for the treatment of this problem is phytodesalinization with Na+ and Cl– hyperaccumulating plants that could be added to existing water treatment technologies such as constructed wetlands (CWs). Two microcosm experiments were conducted to evaluate eight plant species including Atriplex prostrata L. (triangle orache), Distichlis spicata (L.) Greene (salt grass), Juncus torreyi Coville. (Torrey’s rush), Phragmites australis (Cav.) Trin. ex Steud. (common reed), Spartina alterniflora Loisel. (smooth cordgrass), Schoenoplectus tabernaemontani (C.C. Gmel.) Palla (softstem bulrush), Typha angustifolia L. (narrow leaf cattail), and Typha latifolia L. (broad leaf cattail) for their Na+ and Cl– accumulation potential. An initial (indoor) experiment determined that J. torreyi, S. tabernaemontani, T. angustifolia, and T. latifolia were the best candidates for phytodesalinization because they had the highest Na+ and Cl– tissue contents after exposure to Na+ and Cl–-rich nutrient solutions. A second (outdoor) experiment quantified the Na+ and Cl– ion uptake (grams of each ion accumulated per m2 of microcosm). J. torreyi, S. tabernaemontani, T. angustifolia, and T. latifolia accumulated 5.8, 3.9, 8.3, and 9.2 g·m−2 of Na+ and 25.7, 18.2, 31.6, and 27.2 g·m−2 of Cl–, respectively. Of the eight species, T. latifolia and S. tabernaemontani showed the greatest potential to accumulate Na+ and Cl– in a CW environment, whereas S. alterniflora, D. spicata, and P. australis showed the least potential.

Optimization of low-cost phosphorus removal from wastewater using co-treatments with constructed wetlands

Eighteen wastewater treatment systems were operated for one year to investigate phosphorus (P) removal. Systems paired co-treatment reactors containing iron or calcium drinking water treatment residuals with vertical-flow constructed wetland mesocosms planted with Schoenoplectus tabernaemontani (K.C. Gmel.) Palla. For secondary municipal wastewater, soluble reactive P (SRP) concentrations were reduced from 0.70 to 0.03 mg L−1 (95%) or 0.01 mg L−1 (98%) by systems with the calcium or iron co-treatments, respectively (compared to 0.09 mg L−1 or 87% by controls). Total P (TP) concentrations were reduced from 1.00 to 0.07 mg L−1 (93%) and 0.05 mg L−1 (95%) by the same treatments (compared to 0.16 mg L−1 or 84% by controls). For anaerobically digested dairy wastewater, SRP was reduced from 7.68 to 6.43 mg L−1 (16%) or 5.95 mg L−1 (22%) by the systems with calcium or iron, respectively (compared to 7.37 mg L−1 or 4% by controls). For this wastewater, the TP was reduced from 48.5 to 22.5 mg L−1 (53%) and 22.7 mg L−1 (53%) by the same treatments (compared to 24.1 mg L−1 or 50% by controls) but performance improved substantially with a design modification tested.

Accumulation of organic matter fractions in a gravel-bed constructed wetland

The function of a gravel-bed wetland in treating wastewaters is dependent on the turn-over rate of organic matter (OM) fractions in accumulated solids. Organic deposits from a gravel-bed planted (Schoenoplectus tabernaemontani) wetland, which had experienced pore clogging after 5 years of receiving farm dairy wastewater were therefore collected and determined for labile (water-soluble) and stable (humic acid, fulvic acid and humin) OM fractions, total carbon (C), microbial biomass and microbial respiration rate. Over 90% of the accumulated organic solids was present as stable fractions, with humic compounds at least 2-fold higher in surface deposits and the top 100mm of the gravel bed than the lower gravel substratum. Clogging of the gravel pore spaces over a 5-year wetland operation was probably due to the accumulation of refractory (stable) organic solids, particularly in the top 100 mm of the gravel bed. Microbial respiration rate and microbial biomass were significantly correlated with stable OM fractions, suggesting that these microbial parameters may be used to predict the nature of accumulated OM fractions. Further research is required to evaluate the use of these parameters as indicators of labile and stable fractions in wetlands with a range of OM loadings and accumulation.