Forest canopy resists plant invasions: a case study of Chromolaena odorata in Sal (Shorea robusta) forests of Nepal

Invasive alien species are a major threat to global biodiversity due to the tremendous ecological and economic damage they cause in forestry, agriculture, wetlands, and pastoral resources. Understanding the spatial pattern of invasive alien species and disentangling the biophysical drivers of invasion at the forest stand level is essential for managing forest ecosystems and the wider landscape. However, forest-level and species-specific information on Invasive Alien Plant Species (IAPS) abundance and their spatial extent are largely lacking. In this context, we analysed the cover of one of the world’s worst invasive plants, Chromolaena odorata, in Sal (Shorea robusta) forest in central Nepal. Vegetation was sampled in four community forests using 0.01 ha square quadrats, covering the forest edge to the interior. C. odorata cover, floral richness, tree density, forest canopy cover, shrub cover, tree basal area, and disturbances were measured in each plot. We also explored forest and IAPS management practices in community forests. C. odorata cover was negatively correlated with forest canopy cover, distance to the road, angle of slope, and shrub cover. Tree canopy cover had the largest effect on C. odorata cover. No pattern of C. odorata cover was seen along native species richness gradients. In conclusion, forest canopy cover is the overriding biotic covariate suppressing C. odorata cover in Sal forests.

Timber Losses during Harvesting in Managed Shorea robusta Forests of Nepal

Logging and sawing of timber using conventional tools by unskilled workers causes enormous damage to the valuable timber, residual stand, regeneration, and forest soil in Nepal. The purpose of this study was to find out the volume reduction factor and identify major strategies to reduce timber losses in the tree harvesting process in the Terai Shorea robusta forest of Nepal. Field measurements and product flow analysis of 51 felled trees from felling coupes and randomly selected 167 sawed logs were examined to study harvesting losses. Responses from 116 forest experts were analyzed to explore strategies for reducing harvesting and processing losses. The results showed that timber losses in the felling and bucking stage with and without stem rot were 23% and 22%, respectively. Similarly, timber losses in the sawing stage with and without stem rot were 31% and 30%, respectively. Paired t-test at 5% level of significance revealed that there was significant loss in both tree felling and log sawing stages with present harvesting practice. The most leading factor contributing to timber loss in all of the three stages was the use of inappropriate equipment during tree harvesting. Use of synthetic ropes for directional felling and skidding as well as flexible and portable sawing machine with size adjustment options during sawing were mainly recommended as strategies to reduce timber losses. This study serves as a baseline study to identify and quantify timber losses in different stages of tree conversion and also formulate their reduction strategies in Nepal.

Regeneration Status of Sal (Shorea robusta Gaertn.) in Community Managed Forests, Tanahun District, Nepal

The present research aims to know the regeneration status of community managed Shorea robusta (Sal) forests; managed for 6-21 years in Tanahun district, a part of Gandaki Province, Nepal. These forests were categorized into two groups according to management duration (more than 10 years and equal or less than 10 yrs). The regeneration status of the forest was estimated by calculating the density of each species in each developmental phase (seedling, sapling and tree). The total tree density of community forest managed for more than 10 years (MCF forest; 1230 plants/ha) was less than the community forest managed for equal or less than 10 years (LCF forest; 1314 plants/ha). The results suggest that the size class distribution of the trees resembling inverse-J shaped indicates the good regenerating capability of both forests. After the handover of forests to the community, Sal density had increased rapidly in both the forests. Community management had a significant positive impact on the regeneration of the forest, and thus, the productivity of the forest. Thus, the study of regeneration of forest trees has important implications for the conservation and management of natural forests.

Biomass and Carbon Stock in the Sal (Shorea robusta) Forest of Dang District Nepal

The study was conducted to find the net carbon stock in the Sal (Shorea robusta) forest in Bagdaila Chisapani community forest of Dang district, Nepal. The inventory was done by a stratified sampling technique with 0.5% sampling intensity taking into account the woody plants with ≥ 5cm DBH. A total of 49 sample plots of radius 8.94m and 5.64 were established to measure tree biomass and sapling biomass respectively in the forest. The mean above-ground carbon (AGC) was 160.4 t ha-1 and the mean below-ground carbon (BGC) was 24.1t ha-1. The mean total carbon stock in the study area was estimated to be 99.02 t ha-1; of which maximum carbon stock of 143.51 t ha-1 was found in block number 5. Sal was the major tree species in the CF. The biomass and carbon content in this forest is found quite low as compared to other studies in the Sal forest and other tropical forests which were due to the presence of tree stands of less diameter and height. This study would be helpful in the long-term management of forests, planning, and research purposes. The data from this study could also be taken as a reference document for the participation of community forests in carbon accounting under the REDD+ scheme in Nepal.

A report of Siwalik forest around Letang Raja-Rani wetland, Morang, eastern Nepal

Species composition, phytosociological status and soil characteristics of Siwalik forest occurring around Raja-Rani wetland, Letang municipality, eastern Nepal was studied. A total of 47 tree species belonging to 40 genera and 26 families were reported. Dominant and co-dominant trees were Shorea robusta (IVI=133.4) and Schima wallichii (IVI=70.6), respectively. In the forest total tree density, basal cover area, seedling density, fallen dead density and dead standing density were 378.4 trees ha-1, 163.7 m2 ha-1, 105250 individual ha-1, 4 trees ha-1 and 1.6 trees ha-1, respectively. Irregular girth class distribution and high stump density (136.8 tree ha-1) denote disturbance. Soil physicochemical characteristics were: acidic soil (pH 4.8), moisture (12.5%), water holding capacity (50.05%), bulk density (1.17 g cm-3), porosity (0.55%), humus (8.6%), organic carbon (0.52%), nitrogen (0.1%), phosphorus (33 kg ha-1), and potassium (300 kg ha-1). Regulating human encroachment to ensure natural regeneration of species to maintain the viability of the Letang Raja-Rani wetland site and integrity of the local ecosystem is strongly recommended.

Vegetation Structure and Carbon Stock of Two Community Managed Shorea robusta Forests of Dhangadhi, Nepal

Community forests play a vital role in sustainable development and storing carbon stock to mitigate global warming. This study aimed to assess the plant diversity, carbon stock and regeneration status of two Shorea robusta forests managed by the community - Manehara Community Forest (MCF) and Siddhanath community forests (SCF) of Kailali district, Nepal. These two forests differ in the moisture regime- MCF is with ponds and streams and is mostly wet, but SCF is primarily dry with no ponds and streams. To examine vegetation status and carbon stock in these two forests, twenty circular plots of 20 m radius was laid in each forest using stratified random sampling. Within each main plot, two subplots of 5m radius and three subplots of 2m radius were laid to study shrub and herb characteristics, respectively. Soil sampling was also done to analyze the role of soil moisture in carbon stock and regeneration. For this, soil samples of each plot were collected up to 20cm depth. Altogether 100 plant species were recorded from the study forests. Tree and shrub diversity was higher in MCF than in SCF, but herb diversity and seedling numbers were higher in relatively dry SCF than in MCF. The carbon stock of MCF (92.99t/ha) was higher than in SCF (51.94 t/ha). In both forests, carbon stock increased with the increasing basal area (P = 0.0001). A significant strong positive relationship (P = 0.0001) between density and carbon stock was found in SCF, but this relation was weak (P = 0.018) in MCF. Both community forests were fairly regenerating with a good number of small aged individuals, SCF shows an inverted J shaped density diameter (d-d) curve, whereas MCF shows a bell-shaped d-d curve.

Impact of Disturbances on Species Diversity and Regeneration of Nepalese Sal (Shorea robusta) Forests Managed under Different Management Regimes

Sal (Shorea robusta) forests, a dominant forest type in Nepal, experience different disturbance intensities depending on management regimes. This study compares the impact of disturbance on Nepalese Sal forests, which are managed on three major management regimes: protected area, state-managed forest, and buffer zone community forest. Using a systematic sampling approach, we sampled 20 plots, each covering 500 square meters, and nested plots within each main plot to measure pole and regeneration for each management regime. We recorded forest characteristics including tree species, counts, diameter, height, crown cover, and disturbance indicators. We compared forest attributes such as diversity indices, species richness, and stand structure by management regime using analysis of variance and regression analysis. The forest management regimes were classified into three disturbance levels based on disturbance factor bundles, and the buffer zone community forest was found to have the highest disturbance while the protected forest had the lowest disturbance. Species richness, diversity, evenness, abundance, density and basal area were higher, but regeneration was lower in protected area and state-managed forest compared to the buffer zone community forests. This suggests positive impacts of moderate disturbance on regeneration. The management plan should prioritize the minimization of excessive disturbance to balance forest conservation and provide forest resources to local users.

Corticolous Lichen Species Diversity on Dominant Trees in Selected Sacred Groves of Paschim Medinipur District, West Bengal, India

Sacred groves are the fairly well-protected system of community-based conservation of tree patches on account of their association with village gods, and repository of many rare and threatened elements of biodiversity. There are, however, few publications on lichens of sacred groves. The lichens have long been regarded as sensitive indicators for monitoring environmental state. The present study reports one hundred and sixteen species of lichens from forty-four genera of nineteen families in four selected sacred groves of Paschim Medinipur district, West Bengal. These lichens represent two different growth forms, i.e. crustose (105 species) and foliose (11 species). Shorea robusta, a dominant tree species in two sacred groves bears the highest lichen diversity with seventy-four species. To better understand the related biodiversity and climate, this work is likely to promote further studies on lichen diversity in other regions of West Bengal.

Fuel Briquettes from Sal (Shorea robusta) Forest Litter as an Alternative Cooking Fuel

Sal (Shorea robusta) forest leaf litter strongly influences seed germination and seedling survivorship. Therefore, it is crucial to open up the litter layer in such a forest with abundant leaf litter. Briquetting of Sal forest leaf litter can be an option for its management and meet the increasing energy demand. This research work is performed to quantify the amount of Sal forest litter and study the briquette’s combustion properties. The study was carried out in the Namuna Community Forest of Jhapa district. The average weight of leaf litter in the field was observed to be 851 g/m2 . Five varieties of briquettes were produced using different briquetting technologies. Proximate analysis results, calorific value and water boiling tests show these briquettes have good fuel characteristics and can be used as alternative cooking fuel.