Effect of complete and skeleton photoperiods in baya weaver, Ploceus philippinus

A study was performed to investigate the effects of complete and skeleton photoperiods on gonadal stimulation in baya weaver, Ploceus philippinus. In August 2003, five groups of acclimatized birds (n = 7 each) were exposed to 6L: 13D: 1L: 4D, 6L: 6D: 1L: 11D, 11L: 13D and 13L: 11D. Birds were refractory and their exposure to 6L:13D:1L:4D, 6L:6D:1L:11D, 11L:13D and 13L:11D did not evoke any response. This clearly indicates that the birds were insensitive to the stimulatory effects of these photoperiods and perceived them as short days. An attempt was made to test the responsivity by subjecting all these groups to long day exposure after 16 weeks of experiment. Under 16L: 8D, birds did not show a response during the first 4 weeks of exposure (week 16 to week 20), but thereafter there was a significant photoinduction except 11L:13D (week 24), but the rate and magnitude was different. Until the end of the experiment (32 weeks), all groups of birds had maximum testicular volume except 11L:13D. Birds pre-exposed to 6L:13D:1L:4D, 6L:6D:1L:11D, 11L:13D and 13L:11D responded to 16L:8D, which suggests that these photoperiods helped the birds in recovering their photosensitivity. The results from this experiment indicate that baya weaver interprets a light period depending when the light falls relative to its endogenous circadian system.     

Cool temperature performance of a wheat straw biofilter for treating dairy wastewater

A wheat straw biofilter was evaluated for attenuating pollutants in dairy (milkhouse and milking parlor) wastewater. During the 14-day study, the biofilter was operated in a sequential aerobic-anaerobic mode in a temperature range of 8-14 degrees C. While the biofilter was very effective (89% removal) in attenuating total suspended solids and moderately effective (76% removal) in attenuating oil and grease, its effectiveness in attenuating chemical oxygen demand was low (37% removal). The biofilter was ineffective in attenuating nitrate, while its effectiveness in attenuating ammonium (20% removal) and total Kjeldahl nitrogen (15% removal) was low. The biofilter was not effective in attenuating ortho-phosphate, total phosphorus, and fecal coliform. Though microbial degradation accounted for some pollutant removal, filtration seemed to be the primary mechanism. Lower temperature of operation and high oil and grease concentration (that reduced nutrient transfer to the biofilm) decreased microbial activity, reducing pollutant attenuation. Biofilter performance could be enhanced by using residual heat in the wastewater to raise the operating temperature of the biofilter and by removing oil and grease prior to applying the wastewater to the biofilter.     

深化改革努力开发环境监测站的科技优势和经济优势

深化改革努力开发环境监测站的科技优势和经济优势林仁伦，曹继英（四川省南充市环境监测站６３７０００）我国的环境监测站目前正面临种种危机，严竣的事实告诉我们，不改革就没有出路，就难以生存。如何改？必须从监测站的实际出发，不能凭空想象。笔者认为，监测站最重...     

Fungicidal elements accumulated in Cryptothecia punctulata (Ascomycetes lichen) of an arecanut orchard in South India

Different nutrient elements were analyzed in the lichen Cryptothecia punctulata collected from the arecanut trees which were exposed to several sprays of a fungicide Bordeaux mixture. The study revealed the accumulation of fungicidal elements such as Cu, Ca and S in higher concentration of 575.4, 10,000 and 21,000 microg g(-1), respectively.     

Growth and cadmium uptake in barley under cadmium stress

Effect of various additions of cadmium (5 to 3125 microg g(-1) air dried soil) was studied on growth and Cd uptake in barley grown in pots containing two soil types- a loamy sand and a sandy loam, during different stages of growth. While lower doses (5 to 25 microg g(-1)) led to an increase, the higher doses resulted in a substantial decrease in barley growth. The plant Cd content increased with an increase in soil applied Cd. A decrease in translocation ratio prevailed at higher soil applied Cd, indicating the existence of an exclusion mechanism.     

Performance of seed germination and growth of Vicia faba L. in fly ash amended soil

The performance of Vicia faba L. in soil amended by different concentrations of fly ash has been studied. The parameters considered are seed germination, growth behaviour and nodulation frequency of the plant. Results revealed that while fly-ash amendment to the soil improved the growth performance at initial stages with application of lower concentrations, it was inhibitory at higher exposure concentrations. Although there was no difference in survival rates, but the seedling growth was reduced in comparison to control plants. Fly ash delayed the nodulation as lesser number of nodules was recorded at higher amendments. Results suggested feasibility of growing V. faba in fly ash contaminated area.     

Bioleaching of cadmium and nickel from synthetic sediments by Acidithiobacillus ferrooxidans

The microbial leaching process was evaluated for the treatment of synthetic sediments contaminated with cadmium and nickel sulfides. A series of batch leaching experiments was conducted to compare metal solubilization in sediment inoculated with Acidithiobacillus ferrooxidans -inoculated sediments to that in sterile control sediment. The rate and extent of metal solubilization were significantly higher in A. ferrooxidans -inoculated reactors than in acidified sterile reactors. The efficiency of cadmium (Cd) solubilization (80) in the bioleaching process was higher than that of nickel (Ni) solubilization (60). The performance of leaching reactors containing only culture supernatants was comparable to that of A. ferrooxidans -inoculated reactors, indicating that indirect non-contact leaching by the products of microbial metabolism is the predominant mechanism for metal solubilization rather than direct microbial sulfide oxidation. Moreover, the similar (60–75%) extents of Cd²⁺ leaching with A. ferrooxidans , cell-free filtrate, and Fe³⁺ suggest that abiotic oxidation of CdS by Fe³⁺ controls the overall leaching rate, and the role of A.␣ferrooxidans is most likely not to oxidize CdS mineral directly but to regenerate Fe³⁺ as an oxidant.     

Multistate modeling of habitat dynamics: factors affecting Florida scrub transition probabilities

Many ecosystems are influenced by disturbances that create specific successional states and habitat structures that species need to persist. Estimating transition probabilities between habitat states and modeling the factors that influence such transitions have many applications for investigating and managing disturbance-prone ecosystems. We identify the correspondence between multistate capture-recapture models and Markov models of habitat dynamics. We exploit this correspondence by fitting and comparing competing models of different ecological covariates affecting habitat transition probabilities in Florida scrub and flatwoods, a habitat important to many unique plants and animals. We subdivided a large scrub and flatwoods ecosystem along central Florida's Atlantic coast into 10-ha grid cells, which approximated average territory size of the threatened Florida Scrub-Jay (Aphelocoma coerulescens), a management indicator species. We used 1.0-m resolution aerial imagery for 1994, 1999, and 2004 to classify grid cells into four habitat quality states that were directly related to Florida Scrub-Jay source-sink dynamics and management decision making. Results showed that static site features related to fire propagation (vegetation type, edges) and temporally varying disturbances (fires, mechanical cutting) best explained transition probabilities. Results indicated that much of the scrub and flatwoods ecosystem was resistant to moving from a degraded state to a desired state without mechanical cutting, an expensive restoration tool. We used habitat models parameterized with the estimated transition probabilities to investigate the consequences of alternative management scenarios on future habitat dynamics. We recommend this multistate modeling approach as being broadly applicable for studying ecosystem, land cover, or habitat dynamics. The approach provides maximum-likelihood estimates of transition parameters, including precision measures, and can be used to assess evidence among competing ecological models that describe system dynamics.     

Herbivores on a dominant understory shrub increase local plant diversity in rain forest communities

Indirect effects of trophic interactions on biodiversity can be large and common, even in complex communities. Previous experiments with dominant understory Piper shrubs in a Costa Rican rain forest revealed that increases in herbivore densities on these shrubs caused widespread seedling mortality as a result of herbivores moving from Piper to seedlings of many different plant genera. We tested components of the Janzen-Connell hypothesis by conducting focused studies on the effects of specialist and generalist Piper herbivores on local seedling diversity. Whereas specialist herbivores are predicted to increase mortality to neighboring seedlings that are closely related to the source plant, true generalists moving from source plants may cause density-dependent mortality of many species, and possibly increase richness if new species replace abundant species that have been thinned by herbivores. Therefore, we hypothesized that seedling richness would be greater in understory control plots created in patches of Piper that had normal densities of generalist herbivores compared to plots from which we removed generalist herbivores manually from all Piper shrubs. After 15 months, generalist-herbivore-removal plots had > 40% fewer seedlings, > 40% fewer species, and 40% greater seedling evenness, on average, than control plots with generalist herbivores intact. Using a complementary approach in unmanipulated plots in four forests, we used path analysis to test for a positive association between seedling diversity and herbivore damage on Piper species. In unmanipulated plots, for both generalist and specialist herbivores, our data were significant fits to the causal model that Piper herbivores decrease evenness and increase plant species richness, corroborating the experimental results. Because herbivores changed how individuals were apportioned among the species and families present (lower evenness), one interpretation of these associations between herbivores on Piper shrubs and local seedling richness is that high seedling mortality in dominant families allowed the colonization or survival of less common species. If interspecific or apparent competition allowed for a relative increase in species richness, then the Janzen-Connell hypothesis may extend its predictions to generalist seedling predators. We speculate that apparent competition may explain some of the deviations from neutral model predictions, especially at small scales.     

Effect of organic materials and rice cultivars on methane emission from rice field

A field experiment was conducted for two years on a sandy loam (Typic Ustochrept) soil of Punjab to study the effect of organic materials and rice cultivars on methane emission from rice fields. The methane flux varied between 0.04 and 0.93 mg m(-2) hr(-1) in bare soil and transplanting of rice crop doubled the methane flux (0.07 to 2.06 mg m(-2) hr(-1)). Among rice cultivars, significantly (p < 0.05) higher amount of methane was emitted from Pusa 44 compared to PR 118 and PR 111. Application of organic materials enhanced methane emission from rice fields and resulted in increased soil organic carbon content. The greatest seasonal methane flux was observed in wheat straw amended plots (229.6 kg ha(-1)) followed by farmyard manure (111.6 kg ha(-1)), green manure (85.4 kg ha(-1)) and the least from rice straw compost amended plots (36.9 kg ha(-1)) as compared to control (21.5 kg ha(-1)). The differential effect of organic materials in enhancing methane flux was related to total carbon or C:N ratio of the material. The results showed that incorporation of humified organic matter such as rice straw compost could minimize methane emission from rice fields with co-benefits of increased soil fertility and crop productivity.