Effect of NaCl-Induced Salinity and Human Urine Fertilization on Substrate Chemical Properties

We evaluated the effect of NaCl-induced salinity and successive urine fertilization on changes in cultivation substrate chemical properties in a greenhouse study. The substrate was composed of an equal volume ratio mixture of bio-waste compost, quartz sand and silty loam soil. Salinity was imitated by adding NaCl solutions to a known substrate weight achieving three target salinity treatments of ECe 1.3 (S0—no NaCl), 4.6 (S1) and 7.6 (S2) dS·m-1. Cultivation substrate had been cropped with two cycles of maize (Zea mays L.) (crop cycles I and II) and fertilized with human urine at N amounts of 0 (U0—no urine), 180 (U1) and 360 (U2) mg·kg-1 substrate in the first cycle and half of the urine-N dosages in cycle II. Substrate samples collected at the end of each cycle were analyzed for pHKCl, ECe, exchangeable and water extractable cations (Na+, K+, Ca2+, Mg2+), cation exchange capacity, water extractable anions (Cl-, , , ) and exchangeable sodium percentage (ESP). Exchangeable Na+, K+ and Ca2+ were significantly (p < 0.05) affected by salinity x urine interaction. ECe significantly increased by 7.3, 5.3 and 7.6 dS·m-1 in the S0, S1 and S2 treatments following an increase in urine from U0 to U2. In the S0 treatment, ESP increased in the order U0 and Cl- were significantly affected by crop cycle, salinity and urine interactions (p < 0.05) whereas the effect of urine fertilizer on extractable and depended on crop cycle alone. There was a tendency towards increasing soil sodicity with mounting urine fertilization. The level of NaCl salinity and the amount of urine applied are important determinants of substrate chemical properties. Adoption of appropriate management techniques to avoid salinity/sodicity build up should be included in urine fertilization planning.

Calibration of CO₂Trapping in Alkaline Solutions during Soil Incubation at Varying Temperatures Using a Respicond VI

Measurements of carbon dioxide (CO2)-evolution from soils are important in evaluating biomass and activity of soil microorganisms, as well as decomposition of soil organic matter. The Respicond VI is a fully computerized system allowing continuous measurement of CO2 evolution in short- and long-term soil incubation experiments in up to 96 incubation vessels. The measurement of CO2 evolution is based on the absorption of CO2 by an electrolyte (KOH solution) producing a change in the cell conductance measured using two electrodes. In this study, the Respicond VI was recalibrated yielding 174.5 mg CO2 as constant A expressing the theoretical maximum amount of CO2 absorbed in 10 ml 0.5 M KOH. This value of A corresponds to 34.9 mg CO2 ml-1 1 M KOH. The constant A does neither depend on the investigated incubation temperatures (5°C - 25°C) nor on the concentrations of the KOH solutions (0.5, 0.1, 0.05 M KOH). To eliminate any influence of changing incubation temperatures, either induced by uncertainties in temperature control or as a part of the experimental setup, on the conductance of KOH solution, a correction procedure was developed using a factor calculated from changing conductance of KOH solutions in incubation vessels without soil.

Contrasting responseS of hoverflies and wild bees to habitat structure and land use change in a tropical landscape （southern Yunnan, SW China）

The response of insects to monoculture plantations has mainly proceeded at the expense of natural forest areas, and is an outstanding and important issue in ecology and conservation biology, with pollination services declined around the world. In this study, species richness and distribution of hoverfly and wild bee communities were investigated in a changing tropical landscape in southern Yunnan, south-west China by Malaise traps periodically from 2008 to 2009. Species were recorded from the traditional land use types （natural forest, grassland, shrubland and rice field fallows）, and from recently established rubber plantations of different ages. Hoverflies （total 53 species） were most common in young successional stages of vegetation, including rice field fallow and shrubland. Species richness was highest in rice field fallows and lowest in forests and showed a highly significant relationship with the number of forb species and ground vegetation cover. In contrast, the highest richness of wild bees （total 44 species） was recorded from the natural forest sites, which showed a discrete bee community composition compared to the remaining habitat types. There was no significant relationship between the bee species richness and the environmental variables, including the numbers of different plant life forms, coverage of canopy and ground vegetation, successional age of vegetation and land use type. At the landscape scale, open land use systems, including young rubber plantations, are assumed to increase the species richness of hoverflies; however, this might decrease wild bee diversity. The present land use change by rubber cultivation can be expected to have negative impacts on the native wild bee communities.

Biology and control of the fruit borer, Conopomorpha sinensis Bradley on litchi （Litchi chinensis Sonn.） in northern Thailand

Fruit and leaf shoot of litchi （Litchi chinensis） infestation by naturally occurring populations of the fruit bprer, Conopomorpha sinensis larvae and C. sinensis parasitization rates were determined in litchi orchards in northern Thailand at high （ca. 1 400 m ASL） and low （ca. 800 m ASL） elevations with different, non-overlapping fruiting seasons. In addition, spray applications of Bacillus thuringiensis var. aizawai, the natural compound spinosad and the chemical pesticide imidacloprid were conducted in the field to test the effects of these agents on C. sinensis fruit infestation rate. Fruit infestation rate and fruit growth, studied in a low elevation orchard, were sigmoidal and showed a highly significant positive correlation （P ≤ 0.01）. Leaf shoot infestation rate in the low elevation orchard decreased in the course of the fruiting season （March until May）, but increased in the high elevation orchard, where no fruits were present within the same period of time. Together, these results indicate that females of C. sinensis clearly prefer fruits over shoots for oviposition. If no fruits are available, which was the case in the high elevation orchard during that time, they are constrained to lay their eggs on shoots. The parasitization rate of C. sinensis larvae in untreated fruits was 54.3%. The parasitoid species were Chelonus chailini （90.8%） and Phanerotoma sp. （9.2%）. In the leaf shoots, C. sinensis was found to be parasitized by Phanerotoma sp. and Apanteles briareus. The applications of the different active agents had no significant effect on C. sinensis fruit infestation compared to the untreated control. Besides the cryptic life of the larvae, this is most probably explained by the fact that C. sinensis has several generations during the fruiting season. Because of the high parasitization rates recorded, an alternative and more effective control measure than the application of pesticides might be the augmentative release of parasitoids.

Spatial and temporal effects on seed dispersal and seed predation of Musa acuminata in southern Yunnan, China

Wild bananas are abundant in tropical areas and many ecologists have observed that the succession process is quicker following increased disturbance.This study was conducted to analyze animal–seed interactions and their effects on the seed fate of a wild banana species(Musa acuminata)in tropical southern Yunnan(China)through experiments considering spatial(site and habitat)and temporal(seasons)variation.The largest proportion of fruits(81%)was removed by frugivorous seed dispersers,especially by bats at nighttime.Only 13%of the fruits were removed by climbing seed predators(different species of rats).In the exclosure treatment,rodents accounted for a significantly higher total artificially exposed seed removal number than ants,but with spatial and temporal differences.The highest seed predation rate by rodents(70%)was found in forest with wild banana stands,corresponding with the highest rodent diversity(species numbers and abundance)among the habitat types.In contrast,the seed removal number by ants(57%)was highest in the open land habitats,but there was no close correlation with ant diversity.Seed removal numbers by ants were significantly higher in the dry compared to the rainy season,but rodent activity showed no differences between seasons.The overall results suggest that the largest proportion of seeds produced by wild banana are primarily dispersed by bats.Primary seed dispersal by bats at nighttime is essential for wild banana seeds to escape seed predation.

CO_2 mitigation potential in farmland of China by altering current organic matter amendment pattern

The estimation of the global warming mitigation potential in terrestrial ecosystems is of great importance for decision makers to adopt measures to increase soil organic carbon (SOC) as well as to reduce greenhouse gas (GHGs) emissions. In this paper, we compiled data published in peer-reviewed journals, and conducted a holistic analysis of the effects of organic matter amendment on soil organic carbon sequestration, methane (CH4) and nitrous oxide (N2O) emissions in paddy and upland systems. Results showed that organic matter amendment increased soil organic carbon content, and apparent conversion rate of organic matter carbon to soil organic carbon in paddies was constant, while that in uplands decreased along with amendment years at 25 years time scale. Organic matter amendment during the rice season led to large CH4-C emissions, e.g on average 99.5 g CH4-C per kg organic carbon input under intermittent flood conditions, and 191.7 g CH4-C per kg organic carbon input under continuous flood conditions, respectively. By alteration of organic matter amendment from rice season to off-rice upland crop season, estimated CH4-C emissions in China could be cut by 3.5 Tg yr-1, accounting for 63% of current CH4-C emissions (5.5 Tg). If organic matter amendment percentage was increased from current 30% to future 50% of organic matter production and by alteration of organic matter amendment from rice season to off-rice upland crop season, the equivalent CO2-C mitigation potential in farmland of China would be 49.2 Tg yr-1 at the 10th year organic matter amendment and 36.0 Tg yr-1 at the 30th year amendment. These findings are important not only for China but also for the other rice production countries to increase farmland global warming mitigation.