Green foliage decomposition in tree plantations on degraded, irrigated croplands in Uzbekistan, Central Asia
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Afforestation is a prospective strategy to improve soil fertility of salt-affected, irrigated croplands in Central Asia. The effect of macro- and mesofauna and microflora on the decomposition of tree leaves, collected ca. 2 weeks before natural fall, was monitored during 367 days. The three-year-old tree plantations consisted of Elaeagnus angustifolia L., Ulmus pumila L., and Populus euphratica Oliv. The leaf decay rate was determined in 25 × 25 cm sized polyester litterbags with mesh sizes of 10,000 μm (coarse), 250 μm (medium), and 20 μm (fine). Decomposition in the coarse litterbags, allowing access by the entire decomposer community, was highest in P. euphratica at 61% weight loss after 367 days. In the same period, the weight loss in E. angustifolia was 51% and in U. pumila 52%. Combined correlation and multiple regression analyses revealed that decomposability was determined by mesh size, initial C/N ratio, crude fiber-to-N (CF/N) ratio, leaf area, and specific leaf area. A high correlation existed between traits impacting decomposition by the entire decomposer population and the digestibility of leaves by animals as measured in the laboratory (the in vitro digestibility). Initial leaf N (34 g N kg−1 DM) content was highest in E. angustifolia, followed by 23 g N kg−1 DM in U. pumila and 22 g N kg−1 DM in P. euphratica. The C/N ratio followed the order of P. euphratica (21.8) > U. pumila (19.4) > E. angustifolia (13.1). The CF/N ratio followed the order P. euphratica (5.2) > E. angustifolia (3.9) > U. pumila (2.9). Despite a lower decay rate and a higher N content remaining in leaves after 367 days in comparison to both other species, E. angustifolia had the highest potential for soil bio-amelioration. This was due to its foliage production (6 t ha−1 on average), which was about 2.5 times higher than that of the other species, giving a total leaf N loss of about 97 kg N ha−1 in coarse mesh bags. The N loss from U. pumila and P. euphratica leaves amounted to 33 and 23 kg N ha−1, respectively. The potential of leaf decomposition for supplementing soil N in the region depends on the decay rate, the initial leaf N content, the annual leaf biomass production, and differences between N contents over the course of the decomposition period. These can be additional criteria for selecting tree species suitable for afforestation of the degraded, irrigated croplands in Central Asia.
KeywordsDecomposition rate Digestibility Leaf nitrogen content Litterbag technique Multipurpose trees Specific leaf area Tree foliage
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. The research was carried out within the framework of the ZEF/UNESCO landscape restructuring project (www.uni-bonn.de/khorezm). The authors thank Ms. Margaret Shanafield for the English corrections and two anonymous reviewers for their helpful comments on an earlier version of this manuscript.
- Fielding JL, Gilbert GN (2000) Understanding social statistics. Sage Publications, London, p 329Google Scholar
- Kumar BM (2008) Litter dynamics of plantation and agroforestry systems of the tropics—a review of observations and methods, pp 187–216. In: Batish DR, Kohli RK, Jose S, Singh HP (eds) Ecological basis of agroforestry. CRC press, Taylor & Francis, London, 382 ppGoogle Scholar
- Lal R (2007) Soil and environment degradation in Central Asia. In: Lal R (ed) Climate change and terrestrial carbon sequestration in Central Asia. Taylor & Francis, London, pp 127–137Google Scholar
- Lavelle P, Spain AV (2001) Soil ecology. Kluwer, Dordrecht, 654 ppGoogle Scholar
- Massucati LFP (2006) Monitoring of soil macrofauna and soil moisture in a cotton field: an assessment of the ecological potential in irrigated agriculture in Central Asia (Khorezm province, Uzbekistan). Faculty of Agriculture, University of Bonn. http://www.zef.de/fileadmin/webfiles/downloads/projects/khorezm/downloads/Publications/Master_Theses/Massucati-MSc.pdf
- Menke KH, Steingass H (1987) Schätzung des energetischen Futterwerts aus der in vitro mit Pansensaft bestimmten Gasbildung und der chemischen Analyse. II. Regressionsgleichungen. Übersicht Tierernährung 15:59–93Google Scholar
- Naumann K, Bassler R, Seibold R, Barth K (1983) Methodenbuch Band III. Die chemische Untersuchung von Futtermitteln. Naumann, Neudamm, GermanyGoogle Scholar
- Protasov PV (1977) Methods of agro-chemical analyses of soils and plants. All-Union Research Institute of Cotton Science, TashkentGoogle Scholar
- UNESCO-WWAP (2006) Water a shared responsibility. The United Nations world water development report 2. http://unesdoc.unesco.org/images/0014/001454/145405E.pdf. 584 pp