Vegetation, Ökosystemdynamik und Renaturierung von zentralasiatischen Flussauen am Beispiel des Tarim in Xinjiang, NW-China

Naturally, the floodplains of Central Asian rivers harbour riparian, so-called ‘Tugai’ forests, reeds with Phragmites australis, and shrub communities which form a mosaic depending on the variety of available ground water. In recent decades, these natural ecosystems have been strongly altered anthropogenically or even completely destroyed. In order to restore those ecosystems, knowledge on vegetation, ecosystem dynamics, and natural regeneration processes is essential. In our study, we present results of ecological investigations at the Tarim River. We gathered comprehensive data on soil, vegetation, forest stand age, tree vitality, river course dynamics, and land use and brought it to the landscape level. Thus, recommendations are derived for the maintenance of these floodplain ecosystems, in particular with regard to their biological diversity.Entlang der Flussauen Zentralasiens findet sich natürlicherweise ein Mosaik aus Auenwäldern (‚Tugai-Wäldern‘), Schilfröhrichten mit Phragmites australis und Sträuchern, welches von der Verfügbarkeit des Grundwassers abhängt. In den vergangenen Jahrzehnten wurden diese natürlichen Ökosysteme durch den Menschen stark beeinträchtigt bis hin zu völlig zerstört. Um diese Ökosysteme wiederherzustellen, sind genaue Kenntnisse über die Vegetation, die Ökosystemdynamik und natürliche Regenerationsprozesse unabdingbar. In der vorliegenden Studie berichten wir über Ergebnisse unserer langjährigen ökologischen Untersuchungen am Tarim-Fluss. Diese umfassen Untersuchungen des Bodens, der Vegetation, der Altersstruktur und Vitalität der Tugai-Wälder, der Flusslaufdynamik und der Landnutzung, welche auf Landschaftsebene ausgewertet wurden. Auf dieser Grundlage leiten wir Empfehlungen zum dauerhaften Erhalt dieser Flussauenökosystem ab unter besonderer Berücksichtigung der biologischen Vielfalt

Water consumption of industrial hemp (Cannabis sativa L.) during dry growing seasons (2018–2022) in NE Germany

In den Jahren 2018, 2019 und 2020 war Europa von einer ex­tremen Dürre betroffen. Im Zuge des Klimawandels wird davon ausgegangen, dass Dürren häufiger auftreten und extremer ausfallen, so dass die Landwirtschaft sich an Trockenperioden anpassen muss. Der Anbau von Hanf (Cannabis sativa L.) wird als eine Möglichkeit der Anpassung an Trockenperioden angesehen. Hanf liefert Biomasse als Rohstoff für eine Reihe von Wertschöpfungsketten, z. B. für Fasern und Textilien, als Baumaterial, Chemikalien oder als Nahrungsmittel.Hanf bildet ein tiefgehendes Wurzelsystem, durch das die Hanfpflanze ihren Wasserbedarf auch während längerer Trockenphasen aus tieferen Bodenschichten decken kann, was zu einem Entzug der Bodenfeuchte aus dem Unterboden führen kann. Vor diesem Hintergrund wurde in dieser Studie der Wasserverbrauch von Hanf auf Standorten in Nordostdeutschland (Uckermark) in den Jahren 2018–2022 ermittelt. Dafür wurde der Penman-Monteith Ansatz verwendet, wobei die fernerkundungsbasierte Methode S-SEBI, mit Landsat Satellitenbildern als Datengrundlage, eingesetzt wurde, um Crop-Koeffizienten in diese Penman Monteith Berechnungen einzuspeisen.Der Wasserverbrauch von Hanf lag zwischen 310 mm und 407 mm, jeweils für die Vegetations­perioden 2018–2022 bei Stängelerträgen von 9 t ha-1 (außer 2018 mit 7,8 t ha-1). Diese Wasser­verbräuche überstiegen die Niederschläge während der jeweiligen Vegetationsperioden, sie über­stiegen jedoch nicht die Jahresniederschläge der jeweiligen hydrologischen Jahre. Daher übernutzt Hanf nicht die Bodenfeuchte, sondern Hanf nutzt die Bodenfeuchte, die im Herbst und Winter in den Boden infiltriert war, so dass Hanf dadurch gut an ein trockeneres, wärmeres und variableres Klima angepasst ist.Europe experienced unprecedented droughts during the years 2018, 2019, and 2020. In the course of climate change, it is expected that such drought events will occur more frequently so that agriculture needs to adapt to droughts. Hemp (Cannabis sativa L.) has been promoted as an adaptation to water limited conditions. Hemp delivers biomass as a raw material to a variety of different value chains, such as fibers and textiles, house construction, chemicals, or food applications.Hemp develops a deep root system, which enables it to cover its water demand even during longer dry periods. This may lead to an over exploitation of soil moisture of deeper soil layers or of the groundwater in the long-term. Against this background, this study assessed the water consumption of hemp in Northeastern Germany (region Uckermark) during the growing seasons 2018–2022. The Penman Monteith approach was used to calculate the water consumption, whereby the remote sensing based S-SEBI approach was employed, with Landsat satellite images as input data, to feed crop coefficients into those calculations.The water consumption of hemp ranged from 310 to 407 mm over the growing seasons 2018–2022, while stem yields were 9 t ha-1 (except 2018 with 7.8 t ha-1). This water consumption did exceed the precipitation during the growing seasons, but did not exceed the total precipitation of the given hydrological years so that growing hemp does not constitute an over-exploitation of water. Instead, hemp taps the soil moisture that has infiltrated into the soil during autumn and winter. This makes hemp a crop well suited for an adaptation to a drier, hotter, and more variable climate

Sustainable biomass sourcing through agroforestry systems based on poplar and eucalyptus as fast-growing trees

Global biomass demand is expected to increase during the next decades, which bears risks of accelerating food insecurity and biodiversity loss. Therefore, guidelines and standards have been developed to ensure sustainable biomass sourcing as feedstock for material or energetic purposes. This review addresses the question of how fast-growing trees in agroforestry systems increase biomass production and serve as sustainably sourced biomass feedstock. The Land Equivalency Ratio (LER), a measure of productivity gains by agroforestry, was positively correlated with the number of trees per hectare (R = 0.561) and with the spacing between tree rows (R = 0.26). The former corresponds to a high wood yield of the given agroforestry systems, while the latter corresponds to high crop yields within the agroforestry systems. The LER of tree windbreak systems (spacing between tree rows >100 m) was 1.1-2.1. Tree windbreak systems adhered to principles of sustainable biomass sourcing, while other agroforestry systems often provided lower food crop yields compared to the corresponding crop monoculture. Still, such agroforestry systems help to diversify incomes, have the potential to protect croplands against erosion, and improve the microclimate. Depending on local conditions, biomass from those agroforestry systems can be considered sustainable, too

Productivity and carbon sequestration of Populus euphratica at the Amu River, Turkmenistan

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Economic Performance of Cotton and Fruit Plantations in arid Regions: Observation from the Tarim River Basin, NW China

Arid lands cover 17% of the world’s land. There, crop production largely depends on irrigation and frequently faces water shortages. Cotton is grown in arid lands, e.g. Central Asia and Northwest China. Today, the Tarim Basin, Xinjiang, China has turned into the world’s most important cotton production region with an annual cotton lint production of 2.1 million t (8.85% of the world production). Against the background of water shortages, cotton farmers in parts of the Tarim Basin have shifted to more highly valuable fruit production, especially Zyzyphus jujube (Chinese Date) and the so-called Korla Fragrant Pear (Pyrus bretschneideri Rdhd.). This paper thus aims at assessing the costs, revenues, and profits as well as the return to land and the return to family labor obtained by farmers from those three crops in the Tarim Basin. Data were gathered through farm interviews. Seed cotton yield was 4482 kg/ha in average, with 6155 kg/ha attained by farms under the Xinjiang Production and Construction Corps (XPCC). XPCC, family farms, and commercial farms attained profits of 16846 CNY/ha, 1480 CNY/ha, and 3165 CNY/ha, respectively. Profits from Chinese Date were 53255 CNY/ha and 64279 CNY/ha for family farms and commercial farms, respectively. Among the cotton farm types, the XPCC have the highest profits and return to land. This largely can be explained by the high seed cotton yields of the XPCC farms. Though the XPCC farms are operated by single families, they belong to a strict organization, the XPCC, which urges the families to plant cotton, but provides extension services, too. Chinese Date has become an attractive alternative for small family farms. The value of this study lies in the primary data, household interviews, used. This especially applies for commercial farms which are located outside villages and their statistics

Ecology and utilization of salt-tolerant plants in the river basins of Central Asia

In Central Asia soil salinization is a wide-spread concern. Biomass harvested from the moderate salt-tolerant species Haloxylon aphyllum and Apocynum pictum can be used as fodder as well as for textile fibers and medicinal purposes, respectively. These plants offer opportunities to generate income from saline soils

Productivity of reed (Phragmites australis Trin. ex Steud.) in continental-arid NW China in relation to soil, groundwater, and land-use

Reed (Phragmites australis Trin. ex Steud.) is a cosmopolitan plant species which can build up large stands in wetlands, floodplains, and on sites where groundwater is available. Phragmites australis provides many ecosystem services, such as the production of raw material (e.g. house construction or organic fuel). In the desert regions of Central Asia, reed occurs along river, e.g. the Tarim, Syr Darya, Amu Darya, and serves as fodder plant and raw material for construction and paper production. In those arid regions, reed occurs on submerged sites as well as non-flooded sites in a wide variety of phenotypes, ranging from so-called „giant reed“ (2-4 m high) to dwarf-like thorny reed not exceeding 40 cm stem length. We investigated the net primary production of the different phenotypes and their distribution with regard to soil and groundwater salt content and regarding grazing. The phenotypes were characterized through stem length, stem diameter, number of leaves per stem length, leaf weight ratio, leaf length, and leaf width. The net primary production reached 6,004 kg/ha·a on a non-grazed site, which is submerged for one month in late summer. The depth of the closed capillary fringe before onset of the flood was 2.2 m. The electric conductivity at the closed capillary fringe (determined from a water saturated soil extract) was 2 mS/cm. Stem length and stem diameter did not decrease with increasing soil and groundwater salt content, as expected. Conversely, stem length and stem diameter decreased and leaf weight ratio increased with increasing grazing intensity. Thus, grazing turned reed into dwarf-like thorny phenotypes. Non-grazed reed stands are the most productive ecosystems of the riparian vegetation at the Tarim and have a high potential to be used as raw material plant. We conclude that biomass harvesting could be an alternative to grazing with regard to sustainable land use

Evapotranspiration of Cotton, Apocynum pictum, and Zyzyphus juju-ba in the Tarim Basin

Abstract Evapotranspiration is a crucial component of the water balance of ecosystems and landscapes, especially under arid climates. In the Tarim Basin, China, there is an increasing competition for water between irrigated agriculture, mainly cotton, and natural ecosystems, which results in periods of water shortage. Such water shortages also impact on cotton. Therefore, alternative crops have been searched for, which eventually withstand such periodical water shortages better than irrigated cotton, notably Zyzyphus jujuba and Apocynum pictum. The fruit tree Z. jujuba has been promoted from the previous decade onward in parts of the Tarim Basin. A. pictum is used as medicinal plant and in a small scale as fiber crop. A. pictum is a perennial herb, which is part of the natural riparian vegetation along the rivers of the Tarim Basin and which grows without irrigation. Therefore, the objective of this paper is to investigate the crop evapotranspiration (ETc) of those three plant species over the growing season. In this paper, the Penman-Monteith approach was employed. Daily means of stomatal resistance in June was 118 s/m, 222 s/m, and 927 s/m for cotton, A. pictum leafs, and Z. jujuba, respectively. In October, those daily mean stomatal resistance climbed to 885 s/m and 742 s/m for cotton and A. pictum leafs, respectively. ETc over the growing season was 514.7 mm for cotton, 217.2 mm for A. pictum, and 339 mm for Z. jujuba. The Kc value of Z. jujuba was in the range of other fruit trees. In this study cotton attained high yields compared to world average yields at a low ETc. This high water use efficiency was achieved through a shift from flood to drip irrigation, the utilization of plastic mulch, and breeding of cotton varieties

Biomass Resources of Phragmites australis in Kazakhstan: Historical Developments, Utilization, and Prospects

Common reed (Phragmites australis (Cav.) Trin. Ex Steud.) is a highly productive wetland plant and a potentially valuable source of renewable biomass worldwide. There is more than 10 million ha of reed area globally, distributed mainly across Eurasia followed by America and Africa. The literature analysis in this paper revealed that Kazakhstan alone harbored ca. 1,600,000–3,000,000 ha of reed area, mostly distributed in the deltas and along the rivers of the country. Herein, we explored the total reed biomass stock of 17 million t year−1 which is potentially available for harvesting in the context of wise use of wetlands. The aim of this paper is to reveal the distribution of reed resource potential in wetland areas of 13 provinces of Kazakhstan and the prospects for its sustainable utilization. Reed can be used as feedstock as an energy source for the production of pellets and biofuels, as lignocellulosic biomass for the production of high strength fibers for novel construction and packaging materials, and innovative polymers for lightweight engineering plastics and adhesive coatings. Thereby, it is unlikely that reed competes for land that otherwise is used for food production

Apocynum venetum L. and Apocynum pictum Schrenk (Apocynaceae) as multi-functional and multi-service plant species in Central Asia: a review on biology, ecology, and utilization

During the second half of the 20th century cotton was strongly promoted along the rivers of Central Asia. The irrigation agriculture resulted in wide spread soil salinization and severe water shortages within the river systems. Most prominent example is the desiccation of the Aral Sea. The natural vegetation along the rivers of Central Asia is adapted to periods of water shortage, is very productive, and contains plant species with valuable utilization opportunities. We reviewed the literature about Apocynum venetumL. and A. pictum Schrenk, two plant species of those riparian ecosystems, which are used as fibre and medicinal plants. A. venetum and A. pictum yield fibres, which can be used as textiles, though the fibres best are blended with cotton and/or chemical fibres. Though, the fibre extraction process needs more research attention. Furthermore, the literature shows that Apocynum leafs are used to produce antihypertonic tea and medicine. Both species grow under the arid climate of Central Asia without irrigation, because they exploit groundwater. Furthermore, both species can withstand higher soil salinization levels than cotton. Both species can be used and provide an income to local people under conditions, which are unfavourable to grow crops under irrigation. Such conditions are unreliable water supply for irrigation systems and/or saline soils