Niels Thevs

Restoring Central Asian Floodplain Ecosystems as Natural Capital and Cultural Heritage in a Continental Desert Environment

In recent decades, the restoration of degraded and damaged ecosystems has become a challenge for landscape management, nature conservation, and sustainable land-use development throughout the world. As rivers and their floodplains provide many ecosystem services, e.g. the purification of water, combating desertification, the accumulation of carbon, and providing habitats for plants and animals, a particular focus is on their restoration. As a case study, we focus on the Tarim River and its floodplain in continental-arid Southern Xinjiang, NW China, and aim at an interdisciplinary approach to the landscape, taking ecological as well as socio-economic aspects and cultural history into account. Therefore, we describe the natural environment, as well as outline the historical development and the cultural and economic background. Key species of the floodplain ecosystem, such as Populus euphratica, Phragmites australis, Tamarix sp. and Apocynum venetum are particularly taken into account as part of the natural environment, as well as being important species providing ecosystem services and sustainable land-use perspectives. On the basis of our own investigations, we develop a future strategy for the sustainable development of the Tarim river floodplain.

A comparison of the functional traits of common reed (Phragmites australis) in northern China: aquatic vs. terrestrial ecotypes.

Common reed (Phragmites australis (Cav.) Trin. ex Steud.) is distributed widely throughout the world with various ecotypes. This research compares the functional traits and biomass allocation patterns of two contrasting reed ecotypes. Twelve pairs of aquatic and terrestrial reed samples were collected in northern China. Significant differences in functional traits between the two reed ecotypes were observed, while biomass allocation patterns of reed organs did not differ significantly except for at the root. The dry matter content (DMC) in the whole of the reed plant, leaf, root, and rhizome was higher; while the specific leaf area (SLA) and specific root length (SRL) were lower in terrestrial versus aquatic reed. The biomass allocation in organs of the two forms of reed was isometric, only root in the terrestrial habitat increased faster with an increase in the whole plant biomass. It can be affirmed that aquatic and terrestrial reed that adapt to different environments generally has distinct leaf and root functional traits but isometric biomass allocation patterns. This suggests different resource acquisition strategies: (1) aquatic reed grows faster with high SLA and SRL and is more responsive to the environment, while (2) terrestrial reed with high DMC grows slower and is less responsive to the adverse environment (e.g. dry soil conditions).

Development scenarios on Hetao irrigation area (China): a qualitative analysis from social, economic and ecological perspectives

Lakes are threatened ecosystems in drylands of Central Asia. The Wuliangsuhai Lake (“W-Lake”) is a case in point. Located in the Hetao Irrigation Area (“HIA”), W-Lake is a rare multifunctional inland lake in arid North China. It provides a wide range of ecosystem services, including provision of products, regulation of water and climate, water purification, biodiversity conservation and cultural services. The lake’s major water input is the drainage water from HIA’s farmlands. Those farmlands divert water directly from the Yellow River for irrigation. Unsustainable agricultural practice in HIA has gravely impacted on W-Lake in terms of reduced water quantity and degraded water quality. However, the linkage between agricultural practice in HIA and the environmental changes of W-Lake has been rarely investigated. Existing data focus mainly either on W-Lake or on HIA’s farmlands with overwhelmingly technical and end-of-the-pipe solutions. In view of the above, this paper develops four qualitative scenarios on HIA from social, economic and ecological perspectives. The four scenarios are: (a) green growth; (b) strong sustainability; (c) shift to swamp; and (d) worst case. The main aims of this paper are (1) to assist local decision makers of HIA in policy-making and (2) to develop concepts and strategies within the larger framework of integrated water management that shall inspire conservation efforts in other Central Asian regions.

Cutting of Phragmites australis as a lake restoration technique: Productivity calculation and nutrient removal in Wuliangsuhai Lake, northern China

Reed is one of the most frequent and dominant species in wetlands all over the world, with common reed ( Phragmites australis (Cav.) Trin. ex Steud.) as the most widely distributed species. In many wetlands, P. australis plays a highly ambivalent role. On the one hand, in many wetlands it purifies wastewater, provides habitat for numerous species, and is a potentially valuable raw material, while on the other hand it is an invasive species which expands aggressively, prevents fishing, blocks ditches and waterways, and builds monospecies stands. This paper uses the eutrophic reed-swamp of Wuliangsuhai Lake in Inner Mongolia, northern China, as a case to present the multiple benefits of regular reed cutting. The reed area and aboveground biomass production are calculated based on field data. Combined with data about water and reed nutrient content, the impact of reed cutting on the lake nutrient budget (N and P) is investigated. Currently, at this lake around 100, 000 tons of reed are harvested in winter annually, removing 16% and 8% of the total nitrogen and phosphorus influx, respectively. Harvesting all available winter reed could increase the nutrient removal rates to 48% and 24%, respectively. We also consider the effects of summer harvesting, in which reed biomass removal could overcompensate for the nutrient influx but could potentially reduce reed regrowth.