鄱阳湖湿地景观恢复的物种选择及其对环境因子的响应

湿地是重要的生态系统,对人类和野生生物都具有极其重要的价值。由于自然因素的变化和人类活动的干扰,湿地退化严重。近年来,湿地恢复已成为世界环境问题改善的重要工具之一。选择适用的湿地植物是退化湿地恢复的关键途径。本文以鄱阳湖湿地为研究对象,通过专家赋值、野外调查、定位观测等方法,筛选了苦草、野菱、芦苇、苔草等25种鄱阳湖常见植物作为湿地景观恢复的优先物种。对苦草、黑藻、菹草、菖蒲、芦苇等5种植物对环境因子的响应进行观测。结果表明,苦草在清水环境130-140cm处的生长最好;黑藻在清水环境中100-110cm处的生长最好;菹草在不同水深(50-160cm)下都能够生长,菹草高度随水深增加而增加;菖蒲具有一定的耐淹能力(< 80cm),但完全淹水(水深100-120cm)明显影响到菖蒲根状茎萌发、幼苗生长和生物量的积累;芦苇根状茎萌发对水深要求严格,土壤要湿润且透气性良好才是芦苇萌发的最好条件,芦苇根状茎萌发前淹水超过20 cm其萌发将会受到明显抑制,淹水超过30 cm则无法萌发。通过对沉水植物的透明度研究表明,植物对水质的透明度都有一定的要求,透明度较好更利于湿地植物的生长发育。

Species selection for landscape rehabilitation and their response to environmental factors in Poyang Lake wetlands

Wetlands are not only an important habitat for many plants and wildlife but also a buffer zone between land and aquatic ecosystems. Wetland degradation has been found more prominent than any other natural ecosystems on Earth. Global wetland area has decreased over 50% during the past century. To effectively restore wetland ecosystems, the selection of optimum plant species is one of the most important steps. Poyang Lake wetlands, the largest freshwater lake in China, are experiencing severe degradation because of climate change and anthropogenic interventions. To find out the optimum plant species for restoring Poyang Lake wetlands, this study first identified 25 plant species from 4 plant groups based on previous field investigation data. These plant groups are: hygrophyte, emerged plants, floating-leaved plants, and submerged plants. The hygrophyte includes Arundo donax, Carex sp.(Carex cinerascens), Artemisia selengensis, Triarrhena lutarioriparia, Vetiveria zizanioides, the emerged plants include Phragmites australis, Acorus calamus, Zizania latifolia, Sagittaria trifolia, Oenanthe javanica, Heleocharis dulcis, Nelumbo nucifera, Typha orientalis, the floating-leaved plants include Trapa incisa, Euryale ferox, Ipomoea aquatica, Nymphaea tetragona, and the submerged plants include Vallisneria spirolis, Hydrilla verticillata, Potamogeton crispus, Ceratophyllum demersum, Potamogeton malaianus, Potamogeton pectinatu, Myriophyllum spicatum. These species are resistant to contamination, with good purification effect and high economic benefits. These plant species have adapted to the hydrological regimes of Poyang Lake, therefore they are likely to be used as the optimum wetland restoration species. As the first stage of the Poyang Lake wetland restoration project, in this study, we only select 5 species out of the 25 plant species to test the responses of these species to changes in environmental factors based on in-situ observations. The results indicate that the optimum water depths for Vallisneria spirolis, Hydrilla verticillata, and Potamogeton crispus are 130-140 cm, 100-110 cm, 50-160 cm, respectively. Potamogeton crispus adapted to a large range of water depth and plant height increased with depth. Acorus calamus is tolerant to shallow water depth (< 80 cm) and the rhizomes germination, seedling growth, as well as biomass accumulation are inhibited obviously in deep water (e.g., 100-120cm). Phragmites australis is very sensitive to water depth, the moist and permeability soil is beneficial for its rhizomes germination. Rhizomes germination is inhibited when the water depth is above 20 cm; while it completely stopped when the water depth is above 30 cm. We also examine the responses of submerged macrophytes to water transparency. The result shows that these wetland plant species require suitable water transparency. Better transparency is more beneficial to their growth and development. However, it is multiple system projects to mitigate and construct wetlands; especially some degraded wetlands were transferred to natural level of wetlands. People perhaps need pay a long time to observe and test to accomplish ideal result. It is the key that Plants fit in the environment of wetlands; we have to observe and test to study plants how to fit in the environment of wetlands in a long period. Consequently, it is very important to study the relation between the plants and the environment of wetlands; This study only observed the short-term responses of these plant species to environmental factors. A longer time period is needed to confirm these plant responses and behaviors in the near future.