The establishment of woody fallow systems is an option for the improvement of degraded agricultural landscape within the ecologically deteriorated Aral Sea area in northwest Uzbekistan. Growth and development of ten tree species, differing in tolerance to drought and salinity, were studied over 24 months. To determine species suitability for afforestation, conventional diameter and height measurements were compared to Relative Growth Rate (RGR) and its underlying components, Net Assimilation Rate (NAR), Specific Leaf Area (SLA) and Leaf Weight Ratio (LWR), as well as the Crop Growth Rate (CGR) as a function of NAR and Leaf Area Index (LAI). RGRs varied between 0.46 and 2.16 mg g -1 day-1 and showed highly significant differences among species, but also between years, which reduces the parameter's suitability for species selection. The same is true for NAR and SLA. CGR values ranged from 0.01 to 0.71 g m-2 day-1, increased with age of the trees, and showed significant species differences. CGR correlated better with NAR (r = 0.89) and SLA (r = 0.86) than RGR. Overall CGR correlated highly with the RGRs in height and diameter (in 80% and 71% of all cases, respectively). Thus, CGR appears to be a suitable indicator complementing RGR, NAR and SLA estimates to decide on species suitability for afforestation. The intensive measurements for RGR should be done later, rather than earlier in the tree life cycle. At an early age, CGR and diameter measurements are more meaningful. A combination of estimates, not a single factor, best assesses the long-term sustainable growth under natural conditions and allows early selection of species suitable for afforestation of degraded patches in the agricultural landscape. Ranking of all parameters concurrently showed the high potential of Elaeagnus angustifolia and Populus euphratica, which matched previous rankings based on total biomass production and financial added value.
Bibliographical noteFunding Information:
The German Ministry for Education and Research (BMBF; project number 0339970A) and the Ministry for Schools, Science and Research of the State of Northrhine-Westfalia funded this study. Additional funds from DAAD (German Academic Exchange Service) are gratefully acknowledged. The study was conducted at the forest research station of the Uzbek Forestry Research Institute in Khorezm, and within the framework of the ZEF/UNESCO landscape restructuring project. The authors thank the editor and two anonymous referees whose comments greatly improved the manuscript.
- Aral Sea Basin
- Crop growth rate
- Net assimilation rate
- Relative growth rate
- Specific leaf area
- Tree species
ASJC Scopus subject areas
- Nature and Landscape Conservation
- Management, Monitoring, Policy and Law