Rajesh Malla

Soil organic carbon (SOC) is the major constituent of the soil organic matter. SOC stocks are determined by several factors such as altitude, slope, aspect, canopy cover, and vegetation type. Using the Third National Forest Inventory (2010–2014) data of Nepal, we assessed SOC status in forests at a national scale for the better understanding of the SOC distribution within Nepal. In this study, we estimated SOC against different factors and tested the spatial distribution of SOC using analysis of variance (ANOVA). The results showed that the forests located at a higher altitude have higher SOC accumulation. In particular, broadleaved forests exhibit a higher amount of carbon stock compared to other forest types. Moreover, forests with a larger canopy cover, located on a higher slope, and with a cooler aspect are associated with a higher accumulation of SOC. The SOC stock in the forest varies according to altitude, slope, aspect, canopy cover, and forest type, which might be attributed to the change in the microclimate of the area. The significant increase in SOC amount with the increase in slope, altitude, and crown cover helps to understand the extent of SOC distribution in forests. Broadleaved forests with a larger canopy cover in the higher altitude region have a higher SOC retention potential, which is likely to contribute to mitigating the impacts of climate change by sinking more carbon into the soil.

The relationship of forest diversity and aboveground carbon has been poorly explored in tropical forests under different management regimes. An assessment of the linkage between forest diversity and carbon has become important, particularly to devise effective approaches to forest management and policy formulation. To assess the relation between forest diversity and carbon stock, we correlated the structural attributes (i.e., DBH, height, wood density, and stem density), diversity attributes (i.e., species richness, Shannon Weiner index and Shannon equitability index) and aboveground carbon of tree species ≥ 5cm in DBH from Bardia National Park and adjoining Buffer zone Community Forest. Our results showed that most structural attributes are correlated to aboveground carbon in both forest types. While the diversity attributes (i.e., species richness and Shannon index) and stem density had no relation with aboveground carbon in both forests. Similarly, species evenness had a significant inverse relation with aboveground carbon in both forests. The correlation of DBH and height was stronger with aboveground carbon in community managed forest while the same was moderate in national park. In addition, the carbon stock was found slightly higher in the community managed forest than in national park. This indicates that forest structural diversity enhances the aboveground carbon in tropical forests, and community managed forest promotes the better growth of vegetation. These results provide a better insight into forest management and its effects on forest diversity and aboveground carbon.

Introduction: Many factors, such as climate, topography, forest management, or tree/forest attributes, influence soil organic carbon (SOC) and above-ground tree biomass (AGTB). This study focuses on assessing relationship between various predictor variables and response variables (SOC and AGTB) in the perspective of climate change scenario. The study was conducted throughout in Nepal using forest resource assessment data (2010–2014).Methods: Our study applied a random forest model to assess the status of SOC and AGTB under future climate change scenarios using 19 bioclimatic variables accompanied by other variables such as altitude, aspect, basal area, crown cover development status, distance to settlement forest types, number of trees, macro-topography, management regime, physiographic zones, slope, and soil depth. The study used 737 (70%) samples as a training data for model development while 312 (30%) samples as a testing data for model validation.Results and discussion: The respective RMSE, RMSE% and adjusted R² of the Random Forest Model for SOC estimation were found to be 9.53 ton/ha, 15% and 0.746 while same for the AGTB were 37.55 ton/ha, 21.74% and 0.743. Particularly, changes in temperature and precipitation showed an effect on the amount of SOC and AGTB in the projected scenario i.e., CMIP6, SSP2 4.5 for 2040–2060. The study found the amount of SOC decreased by 3.85%, while AGTB increased by 2.96% in the projected scenario. The proposed approach which incorporates the effect of bioclimatic variables can be a better option for understanding the dynamics of SOC and AGTB in the future using climatic variables.

Soil organic carbon (SOC) plays a crucial role in global carbon cycling. The amount of SOC is influenced by many factors (climate, topography, forest type, forest disturbance, etc.). To investigate this potential effect, we performed a multiple regression model using six different predictor variables in the third national-level forest resource assessment data of Nepal. We found a significant correlation between the SOC and altitude (r = 0.76) followed by crown cover and slope. The altitude alone explains r² = 58 percent of the variability of the SOC and shows an increasing rate of change of SOC with the increase of altitude. Altitude was identified as a suitable predictor of SOC for large areas with high altitudinal variation followed by crown cover and slope. Increasing amounts of SOC with increasing altitude shows the significance of high-altitude forests in the perspective of climate change mitigation. Altitude, a proxy of temperature, provides insights into the influence of changing temperature patterns on SOC due to future climate change. Further study on forest types and SOC along the altitudinal gradient in Nepal is recommended to deal with the climate change problem in the future.

Large-scale plantations of pine species were done in the bare hills of the Middle Mountain region of Nepal during the early 1980s. There is a growing concern on the sustainability of the planted pine forests in the country due to the presence of invasive alien plant species (IAPS). Invasive alien plant species are considered as one of the drivers of forest degradation and deforestation. Ageratina adenophora is one of the problematic IAPS found in the planted pine forests throughout the country. In this study, we employed different treatments to control the invasion of A. adenophora in the planted pine (Pinus patula) forest. The research design included four different treatments, viz., (i) control, (ii) stem felling, (iii) floor clearance, and (iv) stem felling cum floor clearance in one block (Block I), which was replicated in another block (Block II). The data were collected using circular sample plots with 2m radius. The ANOVA and TukeyHSD Tests were applied during the analysis process so as to determine the effects of treatments on invasion of A. adenophora. The "floor clearance treatment" was found to be significantly effective to reduce the presence of A. adenophora in the planted pine forest. On the contrary, the "opening of forest cover treatment" was found to be conducive to this invasive species to invade the area. The "stem felling cum floor clearance treatment" could be an effective strategy to control invasion of A. adenophora in planted forest, but as it demands a high cost, it is likely to be appropriate for small forest areas where promotion of regeneration is of high priority.

BackgroundThe soil organic carbon (SOC), an important carbon pool among the five forest carbon pools, plays a crucial role in global carbon cycling. However, it is affected by various factors like topography and climate. Some studies conducted for smaller areas have shown a dependence of the SOC on altitude, but do not allow a general statement for larger regions. Nepal, which has the world's most dynamic terrain elevation, is ideally suited for studying the dependence of the SOC on altitude. ResultsWe found a significant correlation between SOC and altitude (r=0.81). In our study, altitude alone can explain about 66 percent of the variability of the SOC. On the basis of our data, we developed a model which, with altitude as the only independent variable, can predict around 61 percent of the SOC. ConclusionsOnly altitude has been found to be a sound predictor of SOC at the national level. Other factors with potential impacts on SOC predictors such as crown cover, slope or basal area have only a minor contribution to the improvement of prediction accuracy of the model.

Sal (Shorea robusta ) has ecological, economical and socio-cultural importance. It is a dominant species in the Terai and Chure region of Nepal. Natural regeneration is the only relevant regeneration method for Sal in Nepal. This study intended to assess natural regeneration potential of Sal in ploughed and unploughed (control) sites. The study was carried out in Chetaradei of Kapilvastu district in an area of 4.79 ha. Two treatments (control and ground work i.e. ploughed) were applied to assess regeneration potential of Sal. The radius of the sample plots was 2 m, which were laid out systematically and the data were recorded from these plots in three consecutive years. Regeneration density was found higher in control site than ploughed site. T-test for regeneration density in three consecutive measurements showed that there was no significant difference between ploughed and unploughed conditions. The species composition was dominated by Sal in both ploughed and unploughed sites. Species diversity (Shannon Weiner) index was found higher in ploughed site than unploughed site in three consecutive measurements. Moreover, T-test showed that mean height of Sal was not significant in both ploughed and unploughed sites except in the first measurement. This study shows that protection from grazing and fire is essential for natural regeneration of Sal. However, ground work helps to increase tree species diversity but it is not necessary in degraded Sal forest.Banko JanakariA Journal of Forestry Information for NepalVol. 28, No. 1, 2018, page: 3-10