Quantification of organic carbon and primary nutrients in litter and soil in a foothill forest plantation of eastern Himalaya

The present study was an effort to understand the amount of litter fall and its subsequent decomposition and quantify the release of available nutrients and soil physicochemical characteristics in plantations of four forest tree species(Lagerstroemia parviflora, Tectona grandis, Shorea robusta and Michelia champaca) in the Chilapatta Reserve Forest of the Cooch Behar Wildlife Division in the Terai zone of West Bengal, India. The most litter(5.61 Mg ha~(-1))was produced by T. grandis plantation and the least(4.72 Mg ha~(-1)) by L. parviflora. The material turnover rate to the soil through decomposition from total litter was fastest during the first quarter of the year and subsequently decreased during the next two quarters. The material turnover rate was only 1 year, which indicates that more than90% of the total litter produced decomposed within a year.The available primary nutrient content in litter varied across the four plantations over the year. The plantations generally did not significantly influence the soil physical characteristics but did significantly influence the availability of primary nutrients and organic carbon at two depths(1–15 and16–30 cm) over the year. The availability of soil primary nutrients in the four plantations also increased gradually from the first quarter of the year to the third quarter and then decreased during the last quarter to the same level as in the first quarter of the year at both depths. The availability for soil organic carbon in the plantations followed a similar trend. The amount of litter produced and the material turnover in the soil in the different plantations differed, influencing the nutrient availability and organic carbon at the plantations. The amount of soil organic carbon was highest for T. grandis(2.52 Mg ha~(-1)) and lowest for L. parviflora(2.12 Mg ha~(-1)). Litter is the source of soil organic matter,and more the litter that is produced by the plantations, the higher will be the content and amount of soil organic carbon in the plantation.     

Field test of new poplar clone in Shangdong Province

Poplar is one of the dominant tree species for the establishment of fast growing plantations in Shandong Province.Eighteen poplar clones belonging to Populus aigeiros section were introduced from Italy, Turkey and domestic regions. Populus deltoides cv. ‘Lux‘ 1-69/55 (1-69), which was widely used in Shandong Province, China, was taken as control clone (1-69).Following a randomized complete block design, seedling test and controlled afforestation trials were carried out at Juxian County,Caoxian County and Laiyang City. The results showed that the poplar clone (Populus x euramericana cv. ‘102/74‘), namely 102/74, performed well both in terms of adaptability and growth rate. The mean height of 13.9 m (H), diameter at breast height of 18.0 cm (DBH) and volume growth of 0.1445 m3 (V) were 2.2 %, 21.6% and 52.9% higher than those of 1-69 (CK), respectively,at the age of 5 years at three experimental sites. Moreover, the clone can be propagated easily and showed high resistance to poplar disease, pest as well as salinity and had longer growing period. Furthermore, wood basic density and fiber length of new poplar clone (102/74) were as same as 1-69 (CK). It was concluded that the selected clone (102/74) was ideal for the estab-lishment of fast-growing poplar plantations, especially for the pulpwood plantations in Shandong Province.     

Positive nitrogen balance of <Emphasis Type="Italic">Acacia mangium</Emphasis> woodlots as fallows in the Philippines based on <Superscript>15</Superscript>N natural abundance data of N<Subscript>2</Subscript> fixation

Nitrogen inputs from biological nitrogen fixation contribute to productivity and sustainability of agroforestry systems but they need to be able to offset export of N when trees are harvested. This study assessed magnitudes of biological nitrogen fixation (natural ¹⁵N abundance) and N balance of Acacia mangium woodlots grown in farmer’s fields, and determined if N₂ fixation capacity was affected by tree age. Tree biomass, standing litter, understory vegetation and soil samplings were conducted in 15 farmer’s fields growing A. mangium as a form of sequential agroforestry in Claveria, Misamis Oriental, Philippines. The trees corresponded to ages of 4, 6, 8, 10 and 12 years, and were replicated three times. Samples from different plant parts and soils (0–100 cm) were collected and analyzed for δ¹⁵N and nutrients. The B-value, needed as a reference of isotopic discrimination when fully reliant on atmospheric N, was generated by growing A. mangium in an N₂-free sand culture in the glasshouse. Isotopic discrimination occurring during N₂ fixation and metabolic processes indicated variation of δ¹⁵N values in the order of nodules > old leaves > young leaves > stems > litterfall and roots of the trees grown in the field, with values ranging from −0.8 to 3.5‰ except nodules which were enriched and significantly different from other plant parts (P < 0.0001). Isotopic discrimination was not affected by tree age (P > 0.05). Plants grown in N free sand culture exhibited the same pattern of isotopic discrimination as plants grown in the field. The estimated B-value for the whole plant of A. mangium was −0.86‰. Mature tree stands of 12 years accumulated up to 1994 kg N ha⁻¹ in aboveground biomass. Average proportion of N derived from N₂ fixation of A. mangium was 54% (±22) and was not affected by age (P > 0.05). Average yearly quantities of N₂ fixed were 128 kg N ha⁻¹ in above-ground biomass amounting to 1208 kg N fixed ha⁻¹ over 12 years. Harvest of 12-year old trees removed approximately 91% of standing aboveground biomass from the site as timber and fuel wood. The resulting net N balance was +151 kg N ha⁻¹ derived from remaining leaves, twigs, standing litter, and +562 kg N ha⁻¹ when tree roots were included in the calculation. The fast growing A. mangium appears to be a viable fallow option for managing N in these systems. However, other nutrients have to be replaced by using part of the timber and fuel wood sales to compensate for large amounts of nutrient removed in order for the system to be sustainable.     

Soil variability through spatial scales in a permanently disturbed natural spruce-fir-beech forest

Soil variability was assessed in a 74.2-ha area within the Žofínsky prales natural forest. Parameters evaluated for 1765 soil profiles inside 353 graticule plots were as follows: (1) thickness of organic horizons, (2) thickness and form of mineral horizons, (3) humus form (HF), (4) soil taxonomic unit (STU) and (5) anomalies. In addition, soil reaction (pH_KCl) and oxidizable carbon content (C_ox) were measured in the laboratory for 734 samples from the upper mineral (A) and lower mineral (B) horizons. The most frequently occurring humus form was mor followed by moder, hydromor and peaty T-horizon. Entic Podzols, Dystric Cambisols, Haplic Cambisols, Albic Podzols, Histic (or Haplic) Gleysols, Endogleyic Stagnosols, Fibric or Hemic or Sapric Histosols and Stagnic Gleysols were all present at the site despite its homogeneous geological bedrock. Overall coefficient of variance (CV) was lower in terrestrial soils compared with (semi-)hydromorphic soils. Overall variance decreased in both soil groups with increasing depth, as did CV differences between the fine (up to 10 m) and the locality scales. The lowest CV values occurred for C_ox and pH_KCl. The CV values differed between STUs as well. Compared to lower horizons, variograms of upper horizons showed greater autocorrelation at the intermediate spatial scale (10–320 m)—ranging from 50 to 150 m. Semivariance values, however, reached 70–80% of sill already at a distance of 10 m. The most significant factor of variability at all studied spatial scales is presumably the soil disturbance regime, followed by terrain micro-topography and the effect of tree species.     

Intra-varietal genetic diversity of the grapevine (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L.) cultivar ‘Nero d’Avola’ as revealed by microsatellite markers

The Sicilian grape cultivar ‘Nero d’Avola’ is among the oldest and most cultivated in the island, taking part in the production of several red wines exported worldwide, including DOC wines (Etna Rosso and Cerasuolo di Vittoria). Due to the ancient origin and repeated clonally propagation of the cultivar, phenotypic variability has been observed. Clone identification in this important cultivar has so far relied on phenotypic and chemical traits analyses, often affected by environmental conditions. Genetic markers, such as microsatellites, are particularly useful for cultivar identification, parentage testing, pedigree reconstruction and population structure studies. In the present paper, microsatellites were used to analyze the intra-varietal genetic diversity among 118 plants of ‘Nero d’Avola’, collected in 30 vineyards displaced in different areas of Sicily. Out of 22 microsatellites, 11 showed polymorphism among samples and 15 different phylogenetic groups were identified. Results show that ‘Nero d’Avola’ actually comprises different genetic profiles, although most of clones share a common origin.     

Estimating Distance Sampling Detection Functions When Distances Are Measured With Errors

Distance sampling methods assume that distances are known but in practice there are often errors in measuring them. These can have substantial impact on the bias and precision of distance sampling estimators. In this paper we develop methods that accommodate both systematic and stochastic measurement errors. We use the methods to estimate detection probability in two surveys with substantial measurement error. The first is a shipboard line transect survey in the North Sea in which information on measurement error comes from photographically measured distances to a subset of detections. The second is an aerial cue-counting survey off Iceland in which information on measurement error comes from pairs of independently estimated distances to a subset of detections. Different methods are required for measurement error estimation in the two cases. We investigate by simulation the properties of the new estimators and compare them to conventional estimators. They are found to perform better than conventional estimators in the presence of measurement error, more so in the case of cue-counting and point transect estimators than line transect estimators. An appendix on the asymptotic distributions of conditional and full likelihood estimators is available online.     

Participatory plant breeding approach for host plant resistance to bean fly in common bean under semi-arid Kenya conditions

Common bean (Phaseolus vulgaris L.) is the most important legume crop in Kenya. It is cultivated across a wide range of agro-ecologies which include high potential and marginal areas. Eastern Kenya alone, largely semi-arid, accounts for 35% of the country’s total bean production. Bean farmers mainly small-scale have limited access to quality seed, chemical pesticides and fertilizer. Therefore, bean yield under on-farm conditions still remains below 500 kg ha⁻¹ while the potential is about 1,200 kg ha⁻¹ under semi-arid conditions. To asses the farmers’ views on bean varieties and a key insect pest and associated constraints contributing to yield loss, research was undertaken. The research included survey to quantify the yield loss and Participatory Rural Appraisal to determine the level of adoption and criteria for variety choice in semi-arid eastern Kenya (SAEK). The results show that farmers consider drought and insect pest problems as main causes for low yields. The adoption rate for improved varieties is high but self sufficiency in beans stands at 23% in the dry transitional (DT) agro-ecology and at 18% in the dry mid-altitude (DM) agro-ecology, respectively. This could be attributed to low adaptability since most of the improved varieties grown were selected for high potential areas but now found in marginal areas. Drought, earliness, yield stability, and insect pest resistance are the main reasons for choice of varieties by farmers. Bean fly (Ophiomyia sp.) was identified as one of the key crop pests of beans limiting yield. Besides, African bollworm (Helicoverpa armigera) and bean aphid (Aphis fabae) were ranked higher. Due to limitations of the conventional breeding approach, a participatory plant breeding approach is suggested so as to provide an opportunity to develop insect pest resistant varieties adapted to the SAEK region.     

Genetic analysis and genotype × environment (G × E) for grey leaf spot disease resistance in elite African maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) germplasm

Maize grey leaf spot (GLS) disease remains an important foliar disease in sub-Saharan Africa accounting for more than 25% yield losses in maize. Information on inheritance of GLS resistance of germplasm adapted to African environments is required in new sources being identified. Therefore, hybrids generated from a 10 × 10 half-diallel mating of tropical advanced maize inbred lines were evaluated in six environments to determine combining ability, genotype × environment interaction (G × E) and the impact of GLS disease on grain yield. General combining ability effects were highly significant and accounted for 72 and 68% of the variation for GLS resistance and grain yield, respectively. Significant specific combining ability effects associated with reduced disease levels were observed in some hybrids when one parent was resistant, and these may be exploited in developing single cross maize hybrids. Regression analysis showed a 260–320 kg ha^?1 decrease in maize grain yield per each increase in GLS disease severity score, and significant associations (r = ?0.31 to ?0.60) were observed between grain yield and GLS severity scores. This showed the potential of GLS disease to reduce yield in susceptible varieties grown under favourable disease conditions, without control measures. Genotype and genotype × environment biplots and correlation analysis indicated that the significant G × E observed was not due to changes in hybrid ranking, implying absence of a significant crossover interaction. Therefore, predominance of additive gene effects imply that breeding progress for GLS disease resistance would be made through selection and this could be achieved at a few hot-spot sites, such as Baynesfield and Cedara locations in South Africa, and still deploy the resistant germplasm to other environments in which they are adapted.     

Genetic analysis and associated SRAP markers for flowering traits of chrysanthemum (<Emphasis Type="Italic">Chrysanthemum morifolium</Emphasis>)

The inheritance of two flowering traits of chrysanthemum, initial blooming time and the duration of flowering, was investigated using segregation within an F ₁ population derived from a cross between the autumn-flowering ‘Yuhualuoying’ and the summer-flowering ‘Aoyunhanxiao’ cultivars. The analysis, based on a single segregating generation and the major gene plus polygene mixed inheritance model, showed that the inheritance of both traits was compatible with the presence of two pairs of major genes displaying additivity–dominance–epistasis, with additivity predominating. As the heritability of both pairs of major genes was high (initial blooming time ~65%, duration of flowering ~72%), it should be possible to select for both traits in early breeding generations. A marker-trait association analysis based on sequence-related amplified polymorphism (SRAP) genotyping uncovered 10 (initial blooming time) and 12 (duration of flowering) markers significantly associated with phenotype, cumulatively explaining, respectively, 46 and 54% of the variation. Some potentially useful markers were identified.