Long-term effect of chemical fertilizer,straw, and manure on labile organic matter fractions in a paddy soil

To assess the effect of long-term fertilization on labile organic matter fractions, we analyzed the C and N mineralization and C and N content in soil, particulate organic matter (POM), light fraction organic matter (LFOM), and microbial biomass. Results showed that fertilizer N decreased or did not affect the C and N amounts in soil fractions, except N mineralization and soil total N. The C and N amounts in soil and its fractions increased with the application of fertilizer PK and rice straw. Generally, there was no significant difference between fertilizer PK and rice straw. Furthermore, application of manure was most effective in maintaining soil organic matter and labile organic matter fractions. Soils treated with manure alone had the highest microbial biomass C and C and N mineralization. A significant correlation was observed between the C content and N content in soil, POM, LFOM, microbial biomass, or the readily mineralized organic matter. The amounts of POM–N, LFOM–N, POM–C, and LFOM–C closely correlated with soil organic C or total N content. Microbial biomass N was closely related to the amounts of POM–N, LFOM–N, POM–C, and LFOM–C, while microbial biomass C was closely related to the amounts of POM–N, POM–C, and soil total N. These results suggested that microbial biomass C and N closely correlated with POM rather than SOM. Carbon mineralization was closely related to the amounts of POM–N, POM–C, microbial biomass C, and soil organic C, but no significant correlation was detected between N mineralization with C or N amounts in soil and its fractions.     

First record of <Emphasis Type="Italic">Grewia tenax</Emphasis> (Forssk.) Fiori in northern Oman,a valuable fruit producing shrub

Grewia tenax (Forssk.) Fiori is a wild fruit species with multiple uses in different parts of the Tropics and Subtropics. It is common on the Arabian Peninsula and has also been recorded in southern Oman. To date, no record of the species exists for the northern part of this country. To close this distributional gap, three sites in the al-Hajar mountains of northern Oman were surveyed in summer 2005 and spring 2006. During the botanical fieldwork, several flowering and fruiting plants were found in Wadi Bani Awf and Wadi Muaydin. In the latter area G. tenax fruits are eaten by local people. In addition to G. tenax, nine woody perennials with edible fruit were recorded. In northern Oman, fruits of Sideroxylon mascatense (A. DC.) Penn. and Ziziphus spina-christi (L.) Desf. are widely collected and sold on local markets. G. tenax shrubs were found to be heavily grazed indicating its high palatability to goats and sheep. The occurrence of G. tenax in the al-Hajar mountains is a new record to the flora of northern Oman and calls for further investigation of botanists and germplasm collectors.     

Diversity in White Lupin (<Emphasis Type="Italic">Lupinus albus</Emphasis> L.) Landraces from Northwest Iberianplateau

All the accessions (35) of white lupin (Lupinus albus L.) landraces collected from northwest Iberian plateau and maintained at the Spanish germplasm collection (CRF of INIA), were studied with the general objective of assessing the biodiversity of these landraces and to ascertain their value as genetic resources for the development of germplasm adapted to the areas where they were collected with long and chilly winters. The characterization study comprised 51 qualitative and 50 quantitative characters. Quantitative parameters were analyzed by Principal Components Analysis (PCA). The 2-dimensional plot (49.3% of cumulative variability) formed a main group of accessions and 4 outliers (#1, #9, #27 and #28) separated in the first PC. The characters with a higher contribution to the first PC were inflorescence length, leaf petiole length and leaf central foliole area. The presence of alkaloids, the percentage of plants killed by soil borne fungal diseases, the phenology, the yield per plant and yield components were also assessed. Twenty six accessions (the main group in the PCA plot) showed high homogeneity, with the following highlights: bitterness, indeterminate growth habit, early ripeness and spring sowing with the exception of #18, in which seeding date is unknown and it had a later phenology. By contrast accessions #9 and #27 were bitter of autumn sowing with determinate growing habit and they had the longest values of primary inflorescence length and a later phenology when they were sown in spring. Average values for yield and yield components showed a broad range of variation between accessions. The main yield component was the number of pods per plant. Accession #22 had the highest mean seed mass, although this had not significant influence in yield. Accession #17 showed the highest yield and #1 the lowest. This last also had the lowest values of inflorescence length, leaf petiole length and leaf central foliole area. No significant differences of resistance to soil-borne fungi were found between accessions. The year had a significant effect in the phenology, yield and yield components except for number of seeds per pod. The studied material might be of interest for the development of spring sowing germplasm adapted to north Iberian peninsula.     

Changes in soil chemistry associated with the establishment of forest gardens on eroded,acidified grassland soils in Sri Lanka

Topsoil properties were determined in forest gardens established about 20 years ago on eroded grassland soils (abandoned tea lands) in the wet zone of the Sri Lankan highlands. They were compared with adjacent, eroded grasslands (abandoned tea lands) on strongly weathered soils vs soils at earlier stages of pedogenic development in a two-way analysis of variance. Soil pH in forest gardens was, on average, 6.1, nearly one unit higher than in the adjacent grasslands. In the garden soils, the cation exchange capacity (CEC measured at pH 4.8) was nearly double, exchangeable calcium concentrations five times and exchangeable magnesium three times as high as in the grasslands soils. Total soil N content was found to be nearly 40% higher in the gardens. Topsoil gravel contents in the gardens were less than half as high as in the grasslands. The increases in exchangeable bases and N in gardens, relative to grasslands, were attributed to increased nutrient retention and acquisition. Higher retention was partly due to the higher CEC_pH4.8, and probably to reduced erosion and increased, continuous fine root density in the garden topsoils. Higher field CEC in gardens was likely to result from generally higher C contents and from the reversal of acidification, presumably caused by base accumulation and decomposition processes. Our results suggest that forest garden establishment on degraded grasslands can lead to accumulation of mobile nutrients in the topsoil, probably due to increased nutrient retention, subsoil uptake and litter input exceeding nutrient uptake by the standing biomass.     

The effect of moisture on nitrous oxide emissions from soil and the N<Subscript>2</Subscript>O/(N<Subscript>2</Subscript>O+N<Subscript>2</Subscript>) ratio under laboratory conditions

Nitrous oxide (N₂O) contributes to greenhouse effect; however, little information on the consequences of different moisture levels on N₂O/(N₂O+N₂) ratio is available. The aim of this work was to analyze the influence of different soil moisture values and thus of redox conditions on absolute and relative emissions of N₂O and N₂ at intact soil cores from a Vertic Argiudoll. For this reason, the effect of water-filled porosity space (WFPS) values of soil cores of 40, 80,100, and 120% (the last one with a 2-cm surface water layer) was investigated. The greatest N₂O emission occurred at 80% WFPS treatment where conditions were not reductive enough to allow the complete reduction to N₂. The N₂O/(N₂O+N₂) ratio was lowest (0–0.051) under 120% WFPS and increased with decreasing soil moisture content. N₂O/(N₂O+N₂) ratio values significantly correlated with soil Eh; redox conditions seemed to control the proportion of N gases emitted as N₂O. N₂O emissions did not correlate satisfactorily with N₂O/(N₂O+N₂) ratio values, whereas they were significantly explained by the amount of total N₂O+N₂ emissions.     

Evaluating estimators of the numbers of females with cubs-of-the-year in the yellowstone grizzly bear population

Current management of the grizzly bear (Ursus arctos) population in Yellowstone National Park and surrounding areas requires annual estimation of the number of adult female bears with cubs-of-the-year. We examined the performance of nine estimators of population size via simulation. Data were simulated using two methods for different combinations of population size, sample size, and coefficient of variation of individual sighting probabilities. We show that the coefficient of variation does not, by itself, adequately describe the effects of capture heterogeneity, because two different distributions of capture probabilities can have the same coefficient of variation. All estimators produced biased estimates of population size with bias decreasing as effort in creased. Based on the simulation results we recommend the Chao estimator for model M _h be used to estimate the number of the female bears with cubs of the year; however, the estimator of Chao and Shen may also be useful depending on the goals of the research.     

Studying soil-ground thickness by means of new electroinvestigation technologies

A new approach to interpreting the data from vertical electrical probing (VEP) of soil-ground thickness has been approved for soil investigations. Formulas for the calculation of the electric resistance (ρ _i ) of layers of soil thickness were developed based on an electric current passing through heterogeneous earth and on an unconventional solution of the Laplace equation. The ρ _i of the layers was calculated and the capacity and the boundaries of separation where revised as well, using the intensities of the peculiarities, viz., lithology, natural composition, water content, salting, etc. The ρ _i values that were calculated according to the proposed formulas using the VEP data and also the laboratory measurements of this value ρ _i in soil-ground samples correlate very well. The proposed methodology is more informative in comparison with traditional ones, especially with the IPI2win program.     

Eco-geographical distribution of <Emphasis Type="Italic">Lactuca aculeata</Emphasis> natural populations in northeastern Israel

The wild lettuce, Lactuca aculeata Boiss. et Ky., is closely related and fully interfertile with cultivated lettuce, Lactuca sativa L. Altogether, 155 accessions of this wild species, which is rare conserved within the world’s germplasm collections, were collected from 12 localities throughout northeastern Israel. Ten of these localities represent different sites across the Golan Heights, while two, high-density populations were suprisingly found at the Hula Plain (first report of this species in this region). Lactuca aculeata was recorded at various elevations (222–968 m a.s.l.) and habitats. The taxonomic status of 30 L. aculeata accessions was morphologically validated during ex situ seed regeneration of 31 random accessions representing all 12 localities. Characterization of 12 traits showed that the Israeli populations of L. aculeata do not exhibit broad morphological variability, but more great levels of variation were obtained for developmental traits. Relatively little variability was observed in the morphology of cauline leaves or in the distribution of anthocyanin pigmentation in bracteae. In two cases, L. aculeata plants lacked trichomes in the inflorescence, a typical feature in the majority of plants. These unique collections of wild lettuce may carry novel sources of genetic variation for a wide range of traits and, thus, should be of interest for careful evaluation and exploitation in lettuce breeding.     

Investigation of recent population bottlenecks in Kenyan wild sorghum populations (<Emphasis Type="Italic">Sorghum bicolor</Emphasis> (L.) Moench ssp. <Emphasis Type="Italic">verticilliflorum</Emphasis> (Steud.) De Wet) based on microsatellite diversity and genetic disequilibria

Identifying populations that have recently suffered a severe reduction in size is particularly important for their conservation as they are likely to suffer an increased risk of genetic erosion. We investigated the presence of recent bottlenecks in two wild sorghum populations from different eco-geographical conditions in Kenya employing 18 microsatellite markers. Microsatellite analysis showed high allelic diversity in the two populations, with a mean of 4.11 and 6.94 alleles per locus in the North-West wild sorghum population (NWWSP) and the South-East wild sorghum population (SEWSP), respectively. The mean observed heterozygosity was 0.34 and 0.56 in NWWSP and SEWSP, respectively. A large long-term effective populations size for both populations was observed assuming either an infinite allele model or a stepwise mutation model. There was no apparent loss of genetic variability for either of the populations. Test of heterozygosity excess indicated that a recent bottleneck in the two populations is highly unlikely. Furthermore, analysis of the allele frequency distribution revealed an L-shaped distribution which would not have been observed in case a recent bottleneck had reduced genetic variability in the two populations. The fact that most loci displayed a significant heterozygosity deficiency could be explained by population subdivision and the mixed mating system exhibited by wild sorghum populations. Furthermore, the possibility of a historical expansion of wild sorghum populations and presence of null alleles could not be ruled out.