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Tree wind break systems are found in many parts of the world. In particular in windy and arid regions they help to increase crop yields and reduce crop water consumption. Due to these reasons, tree wind breaks have a long tradition in Central Asia and were strongly propagated there during Soviet Union times. After the Soviet Union had disintegrated and the countries in Central Asia had become independent, energy supplies from Russia ceased and fuel wood became the primary energy source for large parts of the population, in particular rural population. Consequently, most of those tree wind breaks were cut down for fuel wood during the 1990s. Now, governments wish to restore these systems, but many farmers are skeptical about the economic returns from investment in tree wind breaks. Against this background, this study calculated revenues, costs, and profits for tree wind break systems of poplars combined with wheat, barley, corn, alfalfa, cotton, and rice in Kyrgyzstan, based on interviews and field observations. Tree wind breaks with more than one row of trees (multiple row type) did not result in financial gains for most crop tree wind break systems compared to open field conditions, while single tree wind breaks were cost-neutral or resulted in small economic gains, also under different discount rates and revenues attained from crops and trees. Among the different grid sizes, the 200 m × 200 m grid attained the highest financial surplus compared with open field conditions and other grid sizes. Thereby, effectively it is recommended to establish tree wind breaks along existing field borders or irrigation ditches while keeping an average distance between tree lines of 200 m, in order not to impede farm operations.

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.

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.

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.

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.

Kyrgyzstan is home to one of the largest areas of natural walnut forest in the world. These forests support significant genetic diversity of many important ancestral strains of fruit and nut tree species. The walnuts from those forests are a major source of cash income for many households in that region. Most of the walnut forests are overgrazed, which effectively hinders natural rejuvenation. This has resulted in overaged and degraded forests. Currently, tree cutting for timber is forbidden under a moratorium. In some instances, walnut trees grow in agroforestry systems together with potato and corn as annual crops or apples and berries, alongside hay. Reforestation and afforestation in the walnut forest region is imperative to secure walnut harvests and associated incomes once the existing trees start bearing fewer nuts. The objective of this study was to analyze the economic performance of a range of representative combinations of annual crops, berries, and fast-bearing fruit trees in reforestation and afforestation plots. This included hypothetical timber utilization in order to be able to bridge the income gap until newly planted walnut trees bear nuts. Data were based on semistructured household and expert interviews. In all plots there was grassy vegetation, which was harvested for hay. In some of the plots, corn and potatoes were grown as annual crops. Additionally, in part of the plots apple and berries were grown next to walnuts. The net present value of the farming systems for a 20-year period was highest for the 2 systems that included hypothetical timber utilization. Walnut and haymaking performed worst, with a negative net present value. All non-timber systems yielded an income gap until around year 10, when walnut trees begin to fruit.