The relationship between water quality and black fly (Diptera: Simuliidae) abundance in Tambunan District, Sabah

Black flies (Diptera : Simuliidae) have been extensively studied almost worldwide (Hamada & Grillet, 2001). This is because blackflies are among the best-known aquatic insects and globally distributed (Adler et al., 2004). Black flies in Malaysia are less known and research about this aquatic insect is still scarce especially in Borneo region. Most of the earlier studies on black flies in Sabah were related to taxonomy (Takaoka, 2001). However, studies on ecology and the role of black flies as bio-indicator has so far not been well reported yet. The aim of this study is to determine the relationship of water quality against the abundance of black flies pupa (Simuliidae). Regression test shows that relationship between dissolve oxygen (r2=0.57, p=0.02), total dissolve substance (TDS) (r2=0.18,p=0.04) and conductivity (r2=0.14, p=0.04) appeared significant to the abundance of black flies pupae. All the study sites (6 rivers) were classified into Class 1 based on Water Quality Index Classification (DOE, 2006)

Climate classification of Asian university forests under current and future climate

Species diversity and the distribution of forests are closely related to climate, and climate classifications have been used to characterize vegetation distribution for over a century at the global scale. In contrast, climate type and dominant forest species may not be accurately classified at the forestry stand scale due to limited observational data and the influence of terrain. The collaboration of Asian university forests traverses 37.4° of latitude, from Hokkaido in Japan to Sabah in Malaysia. This study used both long-term observations and Worldclim 1-km resolution gridded datasets to classify well-managed Asian university forests according to the Trewartha climate classification method. Outputs from circulation models of the Coupled Model Inter-comparison Project Phase 5 (CMIP5) were then used to assess projected changes in future climate. Results showed that the current climate subtypes of the Asian university forests were consistent between the observations and Worldclim database. Ensemble projections of future climate suggested two likely drastic forest changes under a moderate emissions scenario during 2041–2060; parts of the Seoul National University Forests are likely to shift from a temperate to a subtropical climate, while sections of forests in Thailand are likely to shift from a subtropical to a tropical climate

The effects of water stress on leaf water relations, transpiration and photosynthesis of kapur paji (dryobalanops lanceolata burck) wildings in Kawang Forest Reserve, Sabah.

The occurrence of drought due to the changing global environment has led to water stress in tropical forest. The effects of water stress on Kapur Paji (Dryobalanops lanceolata Burck) species has been carried out to study the changes in its water relation, the rate of transpiration and photosynthesis. Two blocks of study areas, each with 2 subplots of 5 m x 10 m were established in Kawang Forest Reserve, Papar, Sabah. Each block had 1 subplot acting as a treatment plot and the other as a control plot. A total of 240 wildings with a mean height of 64.5 cm and 5.6 cm diamater were sampled throughout 3 months of the study period. The water stress was induced by a ground covering method using a high quality transparent plastic sheet adapted from the rainfall reduction technique. The results showed that the water potentials become more negative over time, with some fluctuation during the second week after experimental begun. The water potentials ranged between -0.28±0.08 MPa to -0.64±0.20 MPa. The relative content showed a fluctuating trend throughout the data collection period with mean ranged between 94.3±4.00% to 97.8±1.31%. The mean transpiration and photosynthesis were between 1.20±0.20 to 1.83±0.70 mol m-2 S-1 and 3.30±1.90 to 17.31±6.77 µ mol m-2 S-1 respectively. The ANOVA revealed that there was a significant difference in the interaction of time and treatment in producing water stress effect for water potentials, relative water content and on the rate of photosynthesis of Dryobalanops lanceolate. The predawn water potential was significant at p<0.001, while the midday water potential had the reading of p=0.0005. Relative water content also produced a significant interaction where p=0.0005. The rate of photosynthesis also proved to have a significant interaction of time and treatment in producing water stress with the value of p<0.001

Relationship between water quality & black flies (Diptera: simuliidae) abundance in Tambunan district, Sabah

A study to investigate the relationship between black flies (Simuliidae) pupa abundance and physio-chemical parameters such as velocity, water temperature, pH, dissolved oxygen, conductivity and total dissolved solid was conducted at Tambunan district, Sabah. A total of six rivers were selected as sampling stations. Five sampling points located at a distance of 5-10 meters were established in each sampling station. Sampling was conducted every fortnight for a duration of six months from October 2015 until March 2017. Samples of black flies’ larvae and pupae were manually collected from substrates consisting of grasses, plant roots and plastics which were found stuck in between the rocks with running water area. Water quality parameters that were measured during every sampling, include water temperature, velocity, pH, dissolved oxygen, conductivity and total dissolve solids (TDS). Results from this study showed that The Principal Component Analysis (PCA) revealed two PC’s which had eigenvalues >1.0 and together accounted for 78% total variability of the physio-chemical parameters. PC-1 which accounted 56% of variability defined a normal temperature (23-250C), high water velocity, high dissolved oxygen, low conductivity and low total dissolved solid. While PC-2 explained 22% of the variability was related to water pH. Pearson’s correlation result shows that only velocity had a significant relationship with the abundance of black flies (r=0.512, p<0.01), while other parameters did not show any significant relationship with its abundance. In conclusion, results from this study revealed that only water velocity had a significant relationship with the abundance of black flies

Above and belowground carbon stock of acacia mangium stand in Sabah, Malaysia

This study aimed to estimate above and belowground carbon stock in Acacia mangium stands of different silvicultural systems (planted and regeneration) at the Bengkoka Forest Plantation, Pitas, Sabah, Malaysia. Aboveground biomass (AGB) and belowground biomass (BGB), and soil organic carbon content (SOC) at depth of 30 cm were quantified. A comparison was done between the two different silvicultural systems of Acacia mangium. A random systematic sampling method was used for conducting the forest inventory. Three circular plots of 0.25 ha were established in each of the Acacia mangium systems. Diameter at breast high (DBH) of every tree was measured using a diameter tape. Shrub layer and organic layer were measured at five randomly selected positions in each plot. Five litter fall traps (1m x 1m) were set up in the same position as the shrub and organic layer. Three holes (25 cm x 25 cm x 30 cm) were dug to get the roots for quantifying the roots biomass and soil for carbon content. The soil bulk density was determined by using undisturbed soil samples collected by using 51 mm diameter ring (100 cc.). The results showed that the total amount of carbon stock was 73.56 t ha-1 and 82.40 t ha-1 for planted and regeneration stands, respectively. The study revealed that the major contributor to total carbon stock for both planted and regeneration Acacia mangium stands was the aboveground biomass with mean values of 46.99 t ha-1 and 53.83 t ha-1 followed by belowground biomass with mean values of 26.57 t ha-1 and 28.57 t ha-1 , respectively

Canopy precipitation interception in a lowland tropical forest in relation to stand structure

It is generally accepted that vegetation provides important ecosystem services especially in term of rainfall partitioning. This study aims to evaluate the influence of canopy structure namely crown area (CA), diameter at breast height (DBH), tree height (TH) and crown spread (CS) and stand density on the partitioning of rainfall. Twelve throughfall plots of 20 x 20 m with 64 gauges randomly placed within each plot were established. For stemflow measurements, all trees within a 100 m2 plot within the study area were collared. Interception loss was computed as the difference between precipitation and throughfall plus stemflow. Throughfall ranged from 73.47 - 82.32 % of the gross rainfall. Stemflow was found to be roughly around 2.01% of the gross rainfall. Highest interception was 24.52 % attributed to the plot having the highest above ground biomass (AGB) density. The relation between canopy interception and forest structure were analyzed by regression method. Multiple regression analysis on the potential influence of stand structure to the throughfall percentage shows that all the forest structures variables measured in this study are negatively correlated to the amount of throughfall generated. This study suggests that forests with higher value of DBH, CA, CS and TH had higher interception rate

Mapping pre and post earthquake land cover change in Melangkap, Kota Belud Sabah using multi-temporal satellite Landsat 8/OLI and Sentinel 2 Imagery

It is generally accepted that vegetation provides important ecosystem services especially in term of rainfall partitioning. This study aims to evaluate the influence of canopy structure namely crown area (CA), diameter at breast height (DBH), tree height (TH) and crown spread (CS) and stand density on the partitioning of rainfall. Twelve throughfall plots of 20 x 20 m with 64 gauges randomly placed within each plot were established. For stemflow measurements, all trees within a 100 m2 plot within the study area were collared. Interception loss was computed as the difference between precipitation and throughfall plus stemflow. Throughfall ranged from 73.47 – 82.32 % of the gross rainfall. Stemflow was found to be roughly around 2.01% of the gross rainfall. Highest interception was 24.52 % attributed to the plot having the highest above ground biomass (AGB) density. The relation between canopy interception and forest structure were analyzed by regression method. Multiple regression analysis on the potential influence of stand structure to the throughfall percentage shows that all the forest structures variables measured in this study are negatively correlated to the amount of throughfall generated. This study suggests that forests with higher value of DBH, CA, CS and TH had higher interception rate

Effect of soil physical properties on soil infiltration rates

The physical properties of the soil are studied to understand the influence of soil properties on infiltration rate. The results of simple regression analyses showed that there was little association of the physical properties of the soil and the infiltration rate. This study suggests that high variation of infiltration rate in this study site is attributed to the high spatial variability of soil properties