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

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

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

Growth Rates of Poplar Cultivars across Central Asia

Research Highlights: Despite a long tradition of using poplars as wood source across Central Asia, recent international breeding developments have not penetrated that region yet. This study therefore explored growth performance of 30 local and international poplar cultivars. Background and Objectives: The Central Asian countries are forest poor countries, which need to cover the domestic wood demand through costly imports. Therefore, fast growing trees, such as poplars, are gaining increasing attention as option to grow wood domestically. The most common cultivars date back to Soviet Union times. As recent breeding developments have not reached the region, this study aims at investigate the growth performance of a number of newly developed poplar cultivars. Materials and Methods: The investigated cultivars were planted as cuttings across nine sites in Kyrgyzstan, Kazakhstan, and Tajikistan between 2018 and 2020. Results: Under warm climate conditions, i.e., low elevations, P. deltoides x nigra hybrids attained highest stem volumes and biomass yields, up to 16.9 t/ha*a after two years, followed by P. nigra xmaximoviczii hybrids. One of the P. deltoides xnigra hybrids reached a tree height of 10.5 m after three years. On higher elevations, e.g., in the Pamirs and in Naryn, P. maximoviczi x trichocarpa hybrids and P. trichocarpa cultivars grew faster than the former hybrids. Conclusions: The cultivars explored in this study should be included into plantations or agroforestry systems that are being established, provided that land users are able to thoroughly control weeds and ensure nutrient and water supply. If sufficient weed control, nutrient supply, or water supply cannot be ensured, then land users should opt for local cultivars (e.g., Mirza Terek) or the P. nigra xmaximoviczii hybrids or P. trichocarpa, in order to avoid failure