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As Central Asia is a region with wide spread water scarcity as a result of excessive irrigation of agriculture, land use changes deserve research about potential impacts on the already strained water resources. Poplars have a long tradition as agroforestry tree across Central Asia, while paulownia is new to the region, but has been gaining extreme attention as a potential plantation and/or agroforestry tree. Therefore, the water productivity of those two tree species is investigated here on 3-year-old trees, in order to provide insights in how far the newly introduced Paulownia could put additional strain on water resources compared to paulownia. Poplar (P. deltoides × nigra) increased the stem biomass by 5.4 kg at an average water consumption of 4.18 l/d (water productivity 6.79 g/l). Paulownia’s (Paulownia tomentosa × fortunei) stem biomass grew by 4.81 kg at 2.36 l/d in average (water productivity 11.9 g/l). Expanding paulownia would not exert more pressure on Central Asia’s water resources than an expansion of poplar.

Central Asia is largely dominated by drylands; so agriculture depends on irrigation in most parts of the region, which results in large scale water withdrawal, mainly from rivers, and, consequently, water scarcity. Climate change is expected to aggravate such water shortages as river flows are predicted to be substantially reduced during the second half of this century, which will put additional strain on irrigated agriculture. Tree wind breaks are one option to reduce water consumption in irrigated agriculture, add to farm income, and are therefore prioritized by government policies. Still, many farmers fear that tree wind breaks may compromise crop yields and income. Therefore, based on preceding studies this paper investigates the water productivity – net present value by unit of water consumed – of tree wind break systems of single row tree rows combined with cotton (Gossypium hirsutum L.), corn (Zea mays L.), and rice (Oryza sativa L.) compared with those crops under open field conditions. The tree wind break systems attained higher water productivities across all crops, different discount rates, tree ages of tree wind breaks, and varying crop yields. Tree wind break systems at 200 m spacing attained higher water productivities than those at 1000 m spacing. In conclusion, tree wind breaks can be inserted into the irrigated agriculture as an additional source of farm income, source for wood resources, and help reducing overall water consumption in irrigated agriculture. Simple tree lines are put forward, as multiple tree rows have been shown not to attain financial gains and save less water than the single tree lines.

Agriculture in Central Asia largely relies on irrigation. The water is withdrawn from the rivers of the region, which predominantly originate from snowfields and glaciers. Due to global warming, these water resources are expected to decline substantially, resulting in an aggravation of already existing water scarcity. Tree shelterbelt systems, as the most prominent practice of agroforestry in Central Asia, are reported to help to reduce water consumption in irrigated agriculture. Populus. alba is one of the most important shelterbelt trees in Central Asia. Though, studies about water consumption of shelterbelts are lacking. Therefore, the objectives of this study are to (1) investigate water consumption of Populus alba trees in a shelterbelt system in Central Asia and (2) analyze the influence of local climatic conditions on the sap flow of such a shelterbelt. Tree water consumption was assessed through sap flow measurements on three trees in a crop shelterbelt system in the Chui Valley in South Eastern Kazakhstan during June and July 2016. The average daily water consumption was 187.6 l/d, 44.8 l/d, and 160 l/d for the trees, respectively. These results were extrapolated for a representative shelterbelt section. Water consumption of that section was 7.8 mm/d, while average ETo was 5.3 mm/d. Considerable influences of water vapor saturation deficit, air temperature and relative humidity on the sap flow could be observed. Solar radiation played a role, too, whereas little or no influence of wind speed on tree water consumption was found.

Across Central Asia, agriculture largely depends on irrigation due to arid and semi-arid climatic conditions. Water is abstracted from rivers, which are largely fed by glacier melt. In the course of climate change, glaciers melt down so that a reduced glacier volume and reduced water runoffs are expected being available for irrigation. Tree wind breaks are one option to reduce water consumption in irrigated agriculture and build resilience against climate change. This paper therefore assessed water consumption of major crops (cotton, wheat, corn, rice, potato, and barley) in Kyrgyzstan and adjacent areas in combination with tree wind breaks. Crop water consumption was assessed through the Penman Monteith approach. Tree wind break types investigated were single rows from poplars and multiple rows with undergrowth by elm and poplar, respectively. Tree water consumption was determined through sapflow measurements. Seasonal ETo for field crops was 876 mm to 995 mm without wind breaks and dropped to less than half through multiple row wind breaks with undergrowth (50 m spacing). Tree water consumption was 1125 mm to 1558 mm for poplar and 435 mm for elm. Among the wind break crop systems, elm wind breaks resulted in highest reductions of water consumption, followed by single row poplars, at spacing of 50 m and 100 m, respectively. Yet, elm grows much slower than poplar so that poplars might be more attractive for farmers. Furthermore, single row wind breaks might by much easier to be integrated into the agrarian landscape, as they consume less space.

In Central Asia, agriculture, notably irrigated agriculture, is the largest water consumer. Currently, flood and furrow irrigation are the dominant irrigation methods in Central Asia, in particular in the post-Soviet countries. Against the background of current and increasing competition for water—e.g., through reduced river runoffs in the course of climate change—water consumption of agriculture needs to be reduced. On the field plot level, improved irrigation technologies, like drip irrigation or plastic mulch, can reduce water consumption substantially. Alternatively, tree lines as wind breaks (shelterbelts) also can reduce crop water consumption, as shown by research from many drylands around the world. As previous research has concentrated on crop water consumption and not on tree water consumption, this paper brings the two together, in order to approach a more holistic picture, in how far shelterbelt systems, including the trees, may have the potential to save water or not. Crop water consumption was assessed through the Penman–Monteith approach for corn, wheat, potato, barley, and pear under open field conditions and under an assumed influence of a tree shelterbelt. Tree water consumption was investigated through sap flow measurements. Crop water consumption was reduced by 10–12% under influence of a shelterbelt compared to open field conditions. When water consumption of shelterbelts was added, a slight reduction of water consumption of the whole crop-shelterbelt system was found for corn, potato, and pear under the assumption 25 ha (500 × 500 m) field sizes. Under an assumption of 4 ha (200 × 200 m) field size, water consumption of the whole crop-shelterbelt system was higher for all crops investigated except for pear. The results suggest that shelterbelts may play a role in improving water resource management in Central Asia in the context of water demanding crops, like corn or cotton. In further research, other effects of shelterbelts, like increased crop yields and additional income from trees, need to be investigated.

Across Central Asia, agriculture largely depends on irrigation due to arid and semi-arid climatic conditions. Water is abstracted from rivers, which are largely fed by glacier melt. In the course of climate change, glaciers melt down so that a reduced glacier volume and reduced water runoffs are expected to be available for irrigation. Tree wind breaks are one option to reduce water consumption in irrigated agriculture and build resilience against climate change. This paper therefore assesses the water consumption of major crops in Kyrgyzstan and adjacent areas, i.e., cotton (Gossypium hirsutum L.), wheat (Triticum aestivum L.), corn (Zea mays L.), rice (Oryza sativa L.), potato (Solanum tuberosum L.), and barley (Hordeum vulgare L.) in combination with tree wind breaks. Crop water consumption was assessed through the Penman Monteith approach. Tree wind break types investigated were single rows from poplars (Populus spec.) and multiple rows with understory vegetation by elm (Ulmus minor L.) and poplar, respectively. Tree water consumption was determined through sapflow measurements. The seasonal reference evapotranspiration (ETo) for field crops was 876&ndash, 995 mm without wind breaks and dropped to less than half through multiple row wind breaks with understory vegetation (50 m spacing). Tree water consumption was 1125&ndash, 1558 mm for poplar and 435 mm for elm. Among the wind break crop systems, elm wind breaks resulted in the highest reductions of water consumption, followed by single row poplars, at spacing of 50 and 100 m, respectively. However, elm grows much slower than poplar, so poplars might be more attractive for farmers. Furthermore, single row wind breaks might by much easier to be integrated into the agrarian landscape as they consume less space.