Asia Khamzina

SMALL-SCALE FARMERS' PERCEPTIONS AND KNOWLEDGE OF TREE INTERCROPPING SYSTEMS IN THE KHOREZM REGION OF UZBEKISTAN

ABSTRACT Despite compelling evidence supporting the contribution of Tree Intercropping Systems (TIS) to farmers livelihoods, little research has addressed farmers knowledge of TIS in the ecologically deteriorated zones of Uzbekistan, Central Asia. Similarly, farmers understanding of the motivation for practicing TIS is poorly known. A survey conducted with 133 households during 2003–2005 showed that the surveyed farmers managed 17 different tree-crop simultaneous systems with 97% of all sites including fruit species. The annual components were commercially the more important and were given the highest priority—with cereals (47%), vegetables (27%), fodder (19%) and cash crops (7%). Irrespective of tree species and plantation age, the most frequently observed tree density was 200–500 trees ha−1, although subject to large variations. The dominance of younger trees <10 years (41%) was evidence of the recent interest in TIS and was obviously linked to recent land reforms and change in land ownership. The knowledge of TIS management among those surveyed was rather superficial. Training and educating of farmers and gardeners would help to achieve the potential benefits of TIS. The interaction between agroforestry, environmental research and farmers practices must be improved given the growing interest and significance of TIS for the rural population, and the government must increase private landowners participation in farm management and decision-making.

Forest cover mapping in post-Soviet Central Asia using multi-resolution remote sensing imagery

Despite rapid advances and large-scale initiatives in forest mapping, reliable cross-border information about the status of forest resources in Central Asian countries is lacking. We produced consistent Central Asia forest cover (CAFC) maps based on a cost-efficient approach using multi-resolution satellite imagery from Landsat and MODIS during 2009–2011. The spectral-temporal metrics derived from 2009–2011 Landsat imagery (overall accuracy of 0.83) was used to predict sub-pixel forest cover on the MODIS scale for 2010. Accuracy assessment confirmed the validity of MODIS-based forest cover map with a normalized root-mean-square error of 0.63. A general paucity of forest resources in post-Soviet Central Asia was indicated, with 1.24% of the region covered by forest. In comparison to the CAFC map, a regional map derived from MODIS Vegetation Continuous Fields tended to underestimate forest cover, while the Global Forest Change product matched well. The Global Forest Resources Assessments, based on individual country reports, overestimated forest cover by 1.5 to 147 times, particularly in the more arid countries of Turkmenistan and Uzbekistan. Multi-resolution imagery contributes to regionalized assessment of forest cover in the world’s drylands while developed CAFC maps (available at https://data.zef.de/) aim to facilitate decisions on biodiversity conservation and reforestation programs in Central Asia.

Quantification of symbiotic nitrogen fixation by Elaeagnus angustifolia L. on salt-affected irrigated croplands using two 15N isotopic methods

Afforestation with fast growing N-fixing trees is an option for ecological restoration of highly-salinized irrigated croplands, but information about the N-fixing capability of trees on saline soils is sparse. The 15N-enrichment technique (15NET) and the A value (AV) method were used to quantify in lysimeters the proportion of atmospheric N2 (%Ndfa) fixed by Elaeagnus angustifolia L., with a reference to non-N-fixing Gleditsia triacanthos L. and Ulmus pumila L. Twenty kgxa0Nxa0ha−1 of 5 atom %15N excess ammonium nitrate (35% N) was applied to 1-year-old trees in 2007 and 2-year-olds in 2008. Since this rate was insufficient for the older reference trees, 60xa0kgxa0Nxa0ha−1 was applied in 2008. With 15NET, the %Ndfa of E. angustifolia in 2007 was 79% when referenced against U. pumila and 68% against G. triacanthos. With the AV method, the %Ndfa of 2-year-old E. angustifolia was 80 and 68% when referenced against U. pumila and G. triacanthos, respectively. Over 2xa0years, E. angustifolia fixed 17xa0kgxa0Nxa0ha−1 when related to U. pumila and 14xa0kgxa0Nxa0ha−1 with G. triacanthos (assumed density: 5,000 treesxa0ha−1). N-fixing E. angustifolia has the potential to be self-sufficient in N when planted in the strongly saline soils.

Biomass allocation in five semi-arid afforestation species is driven mainly by ontogeny rather than resource availability

Key messageThe changes in the relative biomass allocation to roots in juvenile stands of fast-growing (Leucaena leucocephalaLam.,Moringa oleiferaLam., andJatropha curcasL.) and slow-growing (Anacardium occidentaleL. andParkia biglobosaJacq.) afforestation species are driven mainly by ontogeny rather than resource availability. However, silvicultural management aiming at increasing availability of water and particularly nutrients enhances biomass production in all species.ContextUnderstanding the patterns of biomass allocation among tree species in response to ontogeny and to variation in resource availability is key to the successful restoration of degraded land using forest plantations.AimsThis study assessed the effects of resource availability and ontogeny on biomass accumulation and partitioning in five semi-arid afforestation species.MethodsThe aboveground and belowground biomass production of fast-growing Leucaena leucocephala Lam., Moringa oleifera Lam., and Jatropha curcas L. and slow-growing Anacardium occidentale L. and Parkia biglobosa Jacq. was monitored following the application of manure (1xa0kg plant−1) and/or supplemental irrigation (0.5xa0L per sapling daily) during the first two rainy seasons and the intervening dry season on degraded cropland in Northern Benin.ResultsBiomass accumulation in the fast-growing species was positively impacted by fertilization and irrigation during both rainy seasons. The slow-growing species responded positively to the silvicultural treatments during the dry and second rainy season. The application of fertilizer alone increased the biomass of P. biglobosa by up to 335% during the dry season. Fifteen months after planting, manure-treated L. leucocephala accumulated the most biomass (2.9xa0kg tree−1). The root fraction decreased with increasing tree size in all species. The comparison of root versus shoot allocation in trees of equal size indicated that the treatment-induced shifts in biomass partitioning were controlled by ontogeny, which explained 86–95% of the variation in root-shoot biomass relationships.ConclusionWhile ontogeny was the main driver of biomass partitioning, increased resource availability induced a larger production of biomass, overall leading to greater aboveground production in all species.

Sapling biomass allometry and carbon content in five afforestation species on marginal farmland in semi-arid Benin

Allometric equations are routinely used in the estimation of biomass stocks for carbon accounting within forest ecosystems. However, generic equations may not reflect the growth trajectories of afforestation species that are introduced to degraded farmland characterized by water and nutrient limitations. Using sequential measurements of the height, basal diameter, and above- and belowground biomass of juvenile trees, we developed allometric equations for five woody species (Moringa oleifera Lam., Leucaena leucocephala Lam., Jatropha curcas L., Anacardium occidentale L. and Parkia biglobosa Jacq.) subjected to a gradient of water and nutrient availability in an afforestation trial on degraded cropland in the semi-arid zone of Benin, West Africa. For three of the species studied, the allometric relationships between basal diameter and biomass components (i.e. leaves, stems and roots) were described best by a simple power-law model (R2xa0>xa00.93). The incorporation of species-specific height–diameter relationships and total height as additional predictors in the power-law function also produced reasonable estimates of biomass. Fifteen months after planting, roots accounted for 10–58% of the total biomass while the root-to-shoot ratio ranged between 0.16 and 0.73. The total biomass of the saplings ranged between 1.4 and 10.3xa0Mgxa0ha−1, yielding 0.6–4.3xa0Mgxa0Cxa0ha−1, far exceeding the biomass in the traditional fallow system. The rate of stem carbon sequestration measured ca. 0.62xa0Mgxa0Cxa0ha−1xa0year−1. Overall, the allometric equations developed in this study are generally useful for assessing the standing shoot and root biomass of the five afforestation species during the juvenile growth stage and can help in reporting and verifying carbon stocks in young forests.

Above- and belowground litter stocks and decay at a multi-species afforestation site on arid, saline soil

We evaluated the annual stocks and decay rates of leaf litter, green foliage, and fine roots at a multiple-species afforestation site using the litterbag technique over 3xa0years. During the course of each year the decomposition of all residue types exhibited a pattern of initially rapid loss of mass over winter followed by decomposition rates that were effectively zero for the rest of the year. Depending on the year of measurement and tree species, decay constants defined by the asymptotic function (ka) for foliar materials ranged between 3 and 16xa0year−1, with 55–74xa0% of the initial mass remaining after 1xa0year of field exposure. The greatest amount of mass remaining was observed in the third year when topsoil salinity increased to a point (11–18xa0dSxa0m−1) that it inhibited decomposition, superseding the influences of species characteristics and soil moisture. For foliar materials, the remaining stable fraction was smaller in Elaeagnus angustifolia that also showed a slower decay rate than other species. Fine roots (at a depth of 30xa0cm) degraded faster in all species, with 33–38xa0% of the initial mass remaining. The decay rates were lowest for Ulmus pumila roots, which were characterized by relatively dense tissue. The greater production and decomposition of nitrogen-rich residue might explain the superior performance of E. angustifolia in improving saline soil productivity. Irrespective of species, the carbon returns through the relatively fast decomposition of fine roots benefit soil fertility, whereas large inputs of slowly decomposing foliar residues represent carbon sequestration in the aboveground litter pool.