International Journal of Environment

Response of Phenological Events of Aesculus indica Colebr. to Climate Change Along an Altitudinal Gradient in Kumaun Himalaya, Uttarakhand

2019-06-17T17:33:41+00:00

The present study investigated the timing and duration of phenological events of A. indica in different elevational range Kumaun Himalayan forest. A total of four sites at elevation ranging between 1,900m and 2,200m were selected and at each site 10 s were marked for observations. The phenological events, i.e. leaf bud formation, leaf bud busting, leafing, flowering bud formation, flowering bud busting, flowering, fruit/seed formation, seed fall and leaf fall were monitored. Phenological duration and asynchrony of these phenophases were determined at 10 day intervals and every 2-3 day intervals during the period of peak activities. The minimum length displayed leaf bud formation (44 days) and maximum by leaf fall (86 days) across the elevation. The environmental conditions, particularly temperature, affected the phenological patterns of A. indica. The leaf bud busting activity of A. indica was 51 days. Flowering activity started on May 1^st and was extended over 76 days until July 15^th. Seed fall activity was extended over 66 day across elevations. ANOVA showed the longevity of phenophases were varied significantly respective to elevations (p<0.05). Our observation showed that all the phenological events of A. indica appear early at lower (1900 m) and are delayed with increasing elevation. All corresponding phenological events were earlier at lower elevations because the optimum (9.0 to 19.5°C) is met earlier in these conditions.

Urban Heat Island in Kathmandu, Nepal: Evaluating Relationship between NDVI and LST from 2000 to 2018

2019-06-17T17:33:40+00:00

The term “urban heat island” (UHI) describes increased surface and atmospheric temperatures in an urban core relative to surrounding non-urbanized areas. Although the phenomenon has been studied to a great extent throughout the world, it is less understood for Kathmandu, Nepal. This study used the Moderate Resolution Imaging Spectro-radiometer (MODIS) 8-day product (MOD11A2) to evaluate land surface temperatures (LSTs), the MODIS-derived Normalized Difference Vegetation Index (NDVI) 16-day product (MOD13Q1) to quantify land surface characteristics, and the MODIS annual land cover classification product (MCD12Q1) to identify major land cover classes. We evaluated the spatial correlation between significant changes in LSTs and NDVI between 2000–2018. Overall, urban (permanently developed areas) LSTs were consistently greater than non-urban (forests and dynamic agriculture lands) LSTs; however, the rate of increase in temperature was higher outside the central Kathmandu developed urban area. Furthermore, significant changes in NDVI values over time were more widespread and not always spatially coincident with significant changes in LST values, particularly for forested land areas. These results provide insight into systematic planning of open and green areas, construction of new infrastructure in peripheral areas, and highlight the challenges in applying traditional UHI conceptual models to rapidly developing urban areas such as Kathmandu, Nepal.

Phytoremediation of Heavy Metals by Water Hyacinth in Sewage Wastewater Stabilization Ponds Under Humid Lowland Tropical Climatic Conditions

2019-06-17T17:33:40+00:00

Plant macrophytes in wastewater treatment systems are important for providing various ecological and environmental benefits, e.g. detoxification and removal of toxic heavy metals. In this study, phytoremediation of four heavy metals (Cd, Cu, Pb and Zn) by water hyacinth (E. crassipes) in sewage wastewater stabilization ponds under humid lowland tropical climatic conditions in Papua New Guinea was studied using a purposive design and grab sampling technique. The wastewater and plant samples collected were analysed for the heavy metals. In almost all cases, an increasing concentration of heavy metals exceeding the standard (FAO and WHO) minimum permissible levels was measured in both the wastewater and the leaves. The general trend in concentration of the effluent pond was such that Pb>Zn>Cu>Cd in the wastewater and Zn>Cu>Pb>Cd in the leaves, respectively. The high variability in heavy metal concentration ranged from between 57-99% in the wastewaters and 61-63% in the leaves, respectively. The availability in the effluent wastewater probably results from decomposition of plant matters and release of the heavy metals bioaccumulated back into the wastewater. A management option to address high availability and mobility in the wastewater is to remove the plant macrophytes well before senescence and turnover of plant matters.

Impact of Texture on Sesquioxide Distribution in Southeastern Nigerian Soils

2019-06-17T17:33:39+00:00

Sesquioxides which play significant roles in soil classification and dominant soil properties vary in soils with particle size fractions. Using randomized complete block design, this study was conducted in the month of June 2018 to evaluate the impact of texture on sesquioxide distribution in humid rainforest soils of Southeastern Nigeria. Four mini-pedons were dug at four landscape positions (upslope, midslope, downslope and flat surface) and triplicate soil samples taken from 0-20, 20-40 and 40-60 cm depths, summing to total of 36 samples. Crystalline and amorphous Al, Fe, Mn and Si oxides were then determined at a depth of 0-20 cm using Dithionate Citrate Bicarbonate (DCB) and ammonium oxalate reagents. Dithionate and oxalate fractions in bulk soil ranged between 9300-11,400 (Fe_d), 390-1580 (Fe_ox), 4600-6700 (Al_d), 660-890 (Al_ox), 3300-5600 (Mn_d), 350-580 (Mn_ox) and 9600-13,500 (Si_d) and 1690-1790 mg kg^-1 (Si_ox), with dithionate superior indicating high crystallinity and low mobility of the sesquioxides. Ratios of bulk soil oxalate/dithionate fractions were low and ranged between 0.04-0.17 (Fe_ox/Fe_d), 0.11-0.15 (Al_ox/Al_d), 0.10-0.16(Mn_ox/Mn_d) and 0.13-0.18 (Si_ox/Si_d) and confirming their crystallinity. Low Fe_ox/Fe_d ratios signified that soils were well drained (< 0.35), old (< 0.65) and highly weathered (< 0.50) with the order being a decreasing sequence of upslope > flat surface > down slope > midslope. Sesquioxide contents and reactivity in soil particle size fractions (sand, silt and clay) varied with landscapes. Regression models indicated that particle size fractions accounted for 50% of 2/3^rd of the bulk soil sesquioxide concentrations and that averaged over landscapes, sand fraction was more enriched with various sesquioxides than the other soil particle size fractions. Correlations between most bulk soil sesquioxide fractions and sesquioxide fractions with selected soil properties (sand, silt, clay, moisture content, total porosity, organic matter, pH, Ca and ECEC) were significant (P < 0.05).