Banj Oak Research Articles

Evaluation of anti-hypertensive activity of Quercus leucotrichophora A. camus methanolic extract on DOCA-salt induced hypertensive rats

Quercus leucotrichophora A. camus, commonly known as Banj oak or Ban tree, belongs to the Fagaceae family and is abundantly found in the regions of Shimla, Kullu-Manali, and upper Mandi in Himachal Pradesh. This study explores the medicinal properties of plant seeds, known for their antioxidant and diuretic activity, traditionally utilized in the treatment of hypertension and hypolipidemic, hepatoprotective conditions. PurposeTo investigate the antihypertensive effect of methanolic extract of Quercus leucotrichophora A. camus seeds in DOCA sat induced rats. Material and methodsGround seeds of Quercus leucotrichophora A. camus were stored in an airtight container. A total of 100 gs of dried seed powder were subjected to extraction using 250 ml of methanol and a Soxhlet extractor maintained at 60–65 °C for five hours. The resulting dried extract (5 gs) was stored in an airtight container in a refrigerator at low temperature and administered by rats to test its antihypertensive impact. The assessment of obtained extract impact on hypertension induced by DOCA-salt was conducted through blood pressure measurement and biochemical analysis. ResultsOur study revealed that the methanolic extract of Quercus leucotrichophora A. camus seeds exerted blood pressure-lowering effects, associated with an increase in serum Nitric Oxide (NO) levels. The attenuation of hypertension by extract was further linked to the normalization of serum Na+ and K+concentrations, indicating an improvement in electrolyte imbalance. Additionally, the antioxidant properties of Quercus leucotrichophora A. camus were evident through increased activities of Glutathione (GSH), Glutathione Peroxidase (GHPx), Superoxide Dismutase (SOD), and decrease activity of Thiobarbituric acid reactive substances (TBARS). ConclusionThe findings of our investigation suggest that the antihypertensive action of Quercus leucotrichophora A. camus is correlated with enhanced endothelial nitric oxide synthase (eNOS) activation and an augmented antioxidant defense system. This sheds light on the potential therapeutic benefits of plant under investigation in managing hypertension, emphasizing its role in promoting cardiovascular health. Further research is warranted to elucidate the underlying mechanisms and to explore the full pharmacological potential of Quercus leucotrichophora A. camus in the field of cardiovascular medicine.

Underlying plant trait strategies for understanding the carbon sequestration in Banj oak Forest of Himalaya

Plant functional attributes are subjected to environmental adjustments, which lead to modulations in forest processes under environmental changes. However, a comprehensive assessment of the relationships between plant traits and carbon stock remains subtle. The present study attempted to accomplish the gap of knowledge by examining the linkages between forest carbon with plant traits within the Banj Oak forest in the Garhwal Himalaya. Twelve individuals from three major species in the Banj Oak forest were randomly selected for trait measurements, and soil samples were collected randomly across the area for evaluation of soil nutrients and carbon. Forest biomass and soil carbon were estimated following standard protocols. A Structural Equation Model (SEM) was applied to establish the relationship between above ground carbon (AGC) and soil organic carbon (SOC) with leaf and stem traits, and soil nutrients. Stem traits were tree height and tree diameter; whereas leaf morphological traits were leaf area, specific leaf area, leaf dry matter content; leaf physiological traits were photosynthesis rate, stomatal conductance, and transpiration rate; and leaf biochemical traits were leaf carbon concentration, leaf nitrogen concentration, and leaf phosphorus concentration. Soil nutrients were available nitrogen, available phosphorus, and exchangeable potassium. Based on SEM results, AGC of the forest was positively correlated with stem traits and leaf physiological traits, while negatively correlated with leaf morphological traits. SOC was positively correlated with soil nutrients and leaf biochemical traits, whereas negatively correlated with stem traits. These findings may support for precise quantification of forest carbon and modeling of forest carbon stocks besides providing inputs to forest managers for devising effective forest management strategies.

People's Perception and Awareness towards Plant Invasion, Its Impacts on Forest Ecosystem Services and Livelihood: A Tale of Central Himalayas.

Plant invasion is a leading threat to biodiversity, ecosystem services and human wellbeing worldwide. In the central Himalayas intentionally or accidentally introduced invasive alien plant species (IAPS) facilitate their own establishment and spread, which is altering forest structure, vegetation composition, species diversity and livelihood. To understand the perception and awareness amongst local communities about invasive alien and native plants and its effect on local livelihood, a questionnaire-based study was conducted in 10 villages of Nainital district, Uttarakhand, India. Household data of 179 respondents were triangulated with key informants such as community leaders, teachers and older people. A majority of the respondents were found to be more familiar with the native species (Berberis asiatica, Pyracantha crenulata and Rubus ellipticus) than IAPS (Ageratina adenophora and Lantana camara). Both the IAPS negative impacts on native biodiversity, ecosystem services and livelihood. During the last two decades IAPS have encroached on various forests and caused a decrease in native species in the study area. According to the local perception, deforestation, forest fire, climate change, increased transport, light weight seed, no use and grazing etc. have been the main factors behind the spread of IAPS. A. adenophora invaded both chir pine (Pinus roxburghii) and banj oak (Quercus leucotrichophora) forests while L. camara remained more prominent in low elevation open canopy chir pine forest. Uprooting is the primary method used to control IAPS in crop fields and forests. The studied villages have not reported awareness and education programs about the IAPS. Our study demonstrates the wide range of perspectives on the threat posed by IAPS to forest ecosystems and natural resources. Education could help to raise awareness about the issue and could be beneficial in managing and controlling invasion in the Himalayan region.

Ecological status and spatial extent of non-native shrubs Lantana camara L. and Ageratina adenophora Sprengel in the forest communities of western Himalaya

This research elucidates the ecological status and spatial extent of two non-native invasive species, Lantana camara L. and Ageratina adenophorum Sprengel, within dominant forest communities across an altitude gradient in the western Himalayan region. The study, conducted from 2017 to 2019 in the Nainital district of Kumaun Himalaya, focused on four forest communities; Sal, Chir-pine, Banj-oak, and Mixed-oak, spanning an altitudinal range from 300 to 2250 meters. Environmental predictors encompassing topographic, physiographic, and climatic factors, along with species occurrence records, were employed to determine spatial extent. The MaxEnt statistical model, a machine learning algorithm, facilitated the assessment of the spatial distribution of invasives. Results indicate that L. camara has invaded Sal, Chir-pine, and Banj oak forests but has not established in high-elevation mixed-oak stands. Conversely, A. adenophora has invaded Chir-pine, Banj-oak, and Mixed-oak stands but has not been observed in low-altitude Sal forests. No significant variation in species number, diversity, or distribution pattern along the elevation gradient was observed for either species. Spatial assessment using MaxEnt revealed an estimated area of 380 km² for A. adenophora and 285 km² for L. camara. The study highlights the mid-altitude zone as the most vulnerable to species invasion. This scientific inquiry contributes valuable insights for the conservation of non-native shrubs, offering guidance for effective, species-specific conservation and management strategies in the Himalayan region.

Population Structure and Regeneration Dynamics of Tree Species in Banj Oak Forests of Tehri Garhwal, Western Himalaya

Forest regeneration is a natural process of forest resource reclamation through production of young ones (saplings and seedlings). Tree species show variable regeneration potential in different associations and response to natural and man-made factors. Banj oak (Quercus leucotrichophora A. Camus), one of the important forest forming tree species in western montane Himalaya, is facing regeneration failure in different locations. The present study attempted to assess the population structure and regeneration of Q. leucotrichophora and associated tree species in five different stands (sites) of a less explored region (Tehri Garhwal, Uttarakhand, Western Himalaya). To investigate the phytosociological attributes, ten sampling quadrats (400 m2) were laid in random sampling manner in each forest stand for surveying tree layer, 2 sub-quadrats (25 m2) for saplings, and 5 sub-quadrats (1 m2) for seedlings in each sampling quadrat. Among the studied forest stands, tree species richness ranged 8 to 11 (8.8±1.3), total stem density (ind/ha) 750 to 950 (846±85.6), and total basal area (m2/ha) 18.68 to 29.18 (24.1±3.9). Based on abundance data the banj oak showed ‘good’ regeneration statuses (density of seedling > saplings > adult trees) in all forests. The distribution of adult tree individuals into different size classes (DBH classes) also indicate ‘good’ regeneration pattern (higher density in lower size classes and gradual decrease in density towards higher classes or forming a reverse J-shaped pattern). However, majority of the banj oak associated species (e.g. Prunus cerasoides, Pyrus pashia, Rhododendron arboreum, etc.) represented ‘fair’ regeneration statuses (seedlings > or ≤ saplings ≤ adult trees). Overall, the results of this study shed light on the positive prospects for Q. leucotrichophora regeneration and the importance of sustainable coexistence between human communities and these vital forest ecosystems.

Variation in Phenology of Banj Oak (Quercus Leucotrichophora) Tree Across Different Elevations in the Kumaun Himalayas, India.

Changes in phenological events have been caused by the present phenomenon of climate change. The elevation is another important factor which leads to the variations in phenological events. The Banj Oak plays holds a vital position as a keystone species in the moist temperate forests of the Central Himalayas, and contribute to human well-being by providing essential benefits such as biodiversity conservation, maintenance of soil organic matter, and the ability to retain water. Thus, this study aims to evaluate the various phenological events of Q. leucotrichophora tree species along the elevation gradients. The elevation gradients are low (1400-1600 m), mid (1700-1900 m) and high (2000-2200 m). At each elevation, three sites were selected for the detailed phenological study. The observations were made from bud initiation to seed fall. In general, leaf bud break and leaf fall were initiated earlier in low-elevation species. In comparison with the middle and high elevation, at low elevation the growth initiation occurred in February and March when the temperature had begun. Comparisons with previous studies have shown that some phenological events began to occur early. The study clearly indicates that climatic irregularities have influenced or altered the phenological events of species. It can be said that the phenological events changes with climatic factors, which are responsible for earlier or delayed phenophases. Understanding phenology and its variations can offer significant data. Consequently, this knowledge can be highly valuable for agricultural practices, which necessitate advanced information on particular stages of tree growth.

Rhizosphere soil properties and microbial biomass changes with the chronosequence of stand age of broadleaf banj oak and coniferous deodar forests in the central Himalaya, India

This research investigates the changes in rhizosphere soil (RS) properties in a chronosequence of the stand age of banj oak (Quercus leucotrichophora A. Campus) and deodar (Cedrus deodara D. Don) forests in the Kumaon Himalaya, India. Tree individuals of different girth classes (young, mature and old) were cored for tree age estimation using increment borer at breast height (1.37 m). Soil samples were collected in triplicate using a cubical section (15 × 15 × 15 cm) underneath the soil surface. Soil tightly adhered to the roots was brushed off on a paper bag and considered RS. Soil moisture content, pH, soil organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (MBC) and nitrogen (MBN) were analyzed. Two-way ANOVA followed by Tukey's post-hoc was used to test the significant difference among the stand age and between species. SOC and MBC increased significantly (p < 0.05) from juvenile to mature and declined in old age, while TN and MBN decreased from juvenile to old age. SOC/TN ratios increased from juvenile to mature stand age, suggesting that plants require more nitrogen for canopy growth in mature stand age. PCA results reflected a strong coupling between juvenile age and MBN/TN ratio, confirming the higher accumulation of nitrogen in the living biomass of microbes. However, MBC/SOC and MBN/TN decreased with the stand age, reflecting that during the initial phase of growth, the microbial community requires more C and N for ecosystem functioning and development. MBC/MBN ratio increased from juvenile to mature stand age, indicating the nitrogen-poor litter quality in mature and old stand age. Overall, forest stand ages can significantly impact RS properties and microbial biomass. These changes can have important implications for ecosystem function and services such as nutrient cycling, water regulation, and carbon sequestration.

Chir pine and banj oak responses to pre-monsoon drought across slope aspects and positions in Central Himalaya

The difference in maintaining a safety margin with regard to hydraulic conductance between pine and oak species influences their distribution in a region. Chir pine (Pinus roxburghii) and banj oak (Quercus leucotrichophora) are the principal species of Central Himalayan forests between 1000 and 2000m elevations. Nearly 80% of annual precipitation of ~ 1400mm in the region occurs during monsoon, from mid-June to September, whereafter droughts of varying length and intensity are common. The main objective of the study is to find out the responses of these two evergreen tree species to pre-monsoon (March to mid-June) water stress and topographical heterogeneity that occur in Central Himalaya. We measured soil and tree water potential and osmotic adjustment across five seasons on three slope positions, namely, hill base, mid-slope, and hill top, on north and south slope aspects. Chir pine showed an early response to pre-monsoon drought by restraining daily change in Ψ to 0.89MPa, while predawn Ψ (ΨPD) was still moderate (isohydric tendency). In contrast, the daily reduction in Ψ of banj oak kept on increasing up to 1.49MPa, despite severely low ΨPD (anisohydric tendency). In both tree species, Ψ was invariably lower on south aspect than north aspect and declined from hill base to hill top. Such responses to slope aspect and position, however, were relatively less apparent in chir pine, which tended to maintain a wide safety margin when under stress. As for soil Ψ, banj oak site retained monsoon rainwater more effectively than chir pine.

Influence of Anthropogenic Activities on Forest Carbon Stocks—A Case Study from Gori Valley, Western Himalaya

Carbon stock assessment in various ecosystems is vital for monitoring the health of these ecosystems and national accounting for the United Nations convention on climate change. The influence of various anthropogenic drivers on carbon stock in different ecosystems has not been examined comprehensively. This study aims to determine the impact of anthropogenic pressures (lopping, cutting, grazing) on soil physico-chemical properties and carbon stock in four temperate broadleaf forests dominated by different species of oak, viz., Banj oak (Quercus leucotrichophora), Rianj oak (Quercus lanuginosa), Moru oak (Quercus floribunda) and Kharsu oak (Quercus semecarpifolia) along an elevation gradient from 1700–3000 m asl in Gori valley, western Himalaya. Biomass data were collected from 120 quadrats of 10 × 10 m size at three distinct altitudes (4 forest sites × 3 altitudes × 10 quadrats) and analysed for carbon stock, whereas soil samples were randomly collected in triplicate from three depths of each altitude of the forest site and further analysed for their physico-chemical properties. A total of 767 individual trees with a diameter of ≥31 cm were measured at twelve sites and standing biomass was estimated following the growing stock volume equations. Mean carbon stock was highest in Moru oak (396.6 ± 29.5 Mg C ha−1) and lowest in Banj oak forest (189.3 ± 48.6 Mg C ha−1). We also found soil to be the largest pool of forest carbon (43.0–59.7%) followed by aboveground biomass (31.5–45.0%), belowground biomass (8.4–11.7%) and litter (0.4–0.5%). The basal area showed significant effect on altitude and carbon stock, whereas disturbance showed significant (p &lt; 0.05) negative correlation with the total carbon stock. Soil nitrogen exhibited a significant positive correlation (R2 = 0.60) with the basal area, indicating that nitrogen enhances tree growth and forest carbon stock. However, anthropogenic disturbance showed a significant negative impact on the basal area, soil nutrients and carbon stock of oak forests. This concludes that forest structure, anthropogenic pressure and soil parameters contribute to the carbon stock of the area. Considering the significance of these overexploited oak forests, it is recommended to conserve the old-growth forest species in the study area, since they have the highest carbon accumulation potential.

Seasonal dynamics of soil and microbial respiration in the banj oak and chir pine forest of the central Himalaya, India

This research investigates seasonal changes of root respiration (Rroot), total soil respiration (Rtotal) and microbial respiration (Rmicrobial) in three central Himalayan forest types: banj oak (BO), chir pine (CP) and banj oak regenerated (BOR). The trenching method is used to separate Rroot from Rtotal. Soil physicochemical and biological properties were compared among the forest type and seasons using one-way ANOVA. Results indicated the significant (p < 0.05) influence of forest type and season on Rtotal, Rroot and Rmicrobial. BO forest had significantly (p < 0.05) higher Rtotal than the CP forest. This was attributed to lower bulk density (BD), pH and high soil moisture, soil organic carbon (SOC), total nitrogen (TN) and microbial biomass carbon (MBC) in the BO forest. Higher soil moisture, SOC, TN and MBC in BO reflects higher microbial metabolic activity than the CP, with low soil moisture and nutrient content. The Rroot/Rtotal ratio ranged from 35 to 62 % for BO, 12 to 58 % for CP and 14 to 45 % for BOR, indicating that Rroot was an important contributor to Rtotal. The contribution of Rroot was at a maximum in the rainy season (53 %) and a minimum in the winter season (11 %), indicating the synergistic effect of optimum soil micro-climatic conditions and soil nutrient content to Rroot. In an exponential regression analysis, soil temperature better explained Rtotal (r2 = 0.81–0.82, p < 0.001). In comparison to Rmicrobial (r2 = 0.58–0.85, p < 0.001), Rroot is better explained by soil moisture (r2 = 0.59–0.88, p < 0.001) in a linear regression model. Present findings suggest that the positive effect of temperature, moisture and litter nitrogen on Rtotal are majorly regulated by forest types, which potentially increases the understanding of climate change and nutrient dynamic processes on a global scale.

Linking green bond yields to the species composition of forests for improving forest quality and sustainability

Forests in India's Himalayan region are undergoing rapid degradation owing to various climatic and man-made stressors, such as invasive species spread and excessive lopping and harvesting of trees. Invasive plants, such as L. camara, pose significant threats to the rich biodiversity of the region due to their ability to replace native vegetation and spread rapidly under a warming climate. Additionally, chir pines (P. roxburghii) are replacing banj oak (Q. leucotrichophora) forests. Oak forests support rich biodiversity and are also preferred by the local communities for meeting their livelihood requirements. In this study, we ask whether green bonds could be utilized for financing the restoration of desirable forest species and enhancing their resilience to natural hazards such as fires. In particular, we explore the possibility of linking green bond yields to the species composition of forests for incentivizing the protection of oak forests. We develop an optimization model of community led restoration of oak and pine forests that are infested with L. camara. Restoring oak forests mitigates the risk of forest fires, improves forest water supply, and controls the spread of the invasive lantana. Findings indicate that such species composition based green bonds, when coupled with payments for ecosystem services programs, can indeed incentivize higher restoration efforts, resulting in an improvement in the biodiversity richness of the region.

Seed germination behaviour of Quercus leucotrichophora (Banj oak) in Western Himalaya

Quercus leucotrichophora A.Camus (Banj oak) is one of the keystone species in the mid-elevation forests across western and central Himalaya. Its regeneration in many parts is reported to be poor due to low germination and seedling emergence. Present study aims to investigate the germination behaviour of Quercus leucotrichophora. Seeds were collected from 5 different sites and sown in polybags under open, poly-house and shade-net-house conditions. Seed germination started in 20 days and was completed in 92 days. Higher seed germination was observed in poly-house conditions (76.66%-82.66%) followed by shade-net-house conditions (68.23-76.66%), while, minimum germination was observed in seeds placed under open conditions (61.66%-74.33%). Mean Germination Time was found rapid in poly-house conditions (8.4-10.13) followed by shade-net house conditions (8.79-12.71) and open conditions (20.39-24.66). Among all the sites, higher germination was recorded for the seeds collected from the mid altitude regions (1300-1400 m asl). A significant positive correlation (P&lt;0.05) between seed size class with cumulative germination percentage was also noticed. The findings of the present study indicated that, site of seed collection can play a crucial role in seed germination. Thus, for raising quality planting material of Q. leucotrichophora, seed collection should be done from specific habitats that ultimately help in restoring the declining population.

A REVIEW ON THE CURRENT STATUS OF FOREST FIRE IN UTTARAKHAND STATE OF INDIA

Forest fires have caused a huge loss to the Himalayan biodiversity, which has adversely affected the productive capacity and natural regeneration of forests species. The Uttarakhand state of India is severely affected by forest fire every year, which is one of the main reasons for loss of biodiversity and ecosystem services of the precious forest resources. As per as record, approximate 700 species of bird and animals are at the high risk of extinction as a consequence of adverse effects of forest fire. In the Uttarakhand state, majority of fire occurs in Chir Pine forests, which later on extends to the associated species, such as, Banj Oak. Worldwide, forest fire has been viewed as a serious issue responsible for the climate change. Subjecting forest areas to regular controlled burning can reduce the incidence of forest fire to the great extent. Further, imparting education, training and awareness on forest fire to the local people and state govt. official can considerably control fire incidence as well as fuel load in the forests.

Predicting the effects of climate change on prospective Banj oak (Quercus leucotrichophora) dispersal in Kumaun region of Uttarakhand using machine learning algorithms

Predicting the effects of climate change on prospective Banj oak (Quercus leucotrichophora) dispersal in Kumaun region of Uttarakhand using machine learning algorithms

Analysis of Vegetation Structure in Moist Temperate Forest of &lt;i&gt;Quercus leucotrichophora&lt;/i&gt; A. Camus in Garhwal Himalaya

The present study aims to analyze the vegetation structure and species diversity in moist temperate banj oak ( Quercus leucotrichophora A. Camus ) forest of Anand chowk, Mussoorie forest division. The vegetation was analyzed via random sampling to obtain the most representative composition of the vegetation at 1400 amsl to 2000 amsl. Species compositions of surveyed forest area consist of 43 herbaceous species, 14 as a shrub and 4 as a tree species. In surveyed forest, Quercus leucotrichophora found as a dominant tree species whereas Rhododendron arboreum , Myrica esculenta and Lyonia ovalifolia as a codominant tree species in community. Shannon-Wiener Index ranges between 0.20 to 0.34 for trees and 0.05 to 0.31 for shrubs. Simpson's diversity index varies from 0.01 to 0.33 for tress. The present study is beneficial for forester, policy maker and stakeholder to understand altitude behavior on species composition. Thus, study suggests providing information on current status, conservation and management of forest.

Relationships between soil and microbial biomass properties and annual flux of nutrients in Central Himalaya forests, India

AbstractThe interrelationship among soil attributes and microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP) of Indian Central Himalaya forest soils were analyzed. The forest ecosystem studied composed of chir pine (CPF), banj oak (BOF), and mixed oak‐pine forest (MOPF). This study reported 429–739 mg kg−1 MBC, 67–121 mg kg−1 MBN, and 18–63 mg kg−1 MBP. The contribution of MBC, MBN, and MBP appears to be 1.47–4.11 (X = 2.66%), 2.65–11.17 (5.93%), and 5.61–19.0 (X = 10.47%) of the soil organic carbon, total nitrogen (N) and phosphorus (P), respectively. Significant variations were observed in terms of C:N, C:P, and N:P ratios among various sites which ranged between 5.95 and 8.08, 11.73 and 26.42, and 1.92 and 3.72, respectively. The linear association between MBP with MBC and MBN was observed. Further, a positive correlation was recorded between MBC, MBN, and MBP with various soil characteristics. The annual flux of N and P estimated by microbial biomass using the turnover rates of 0.67 was approximately 100–181 kg N and 27–94 kg P ha−1 yr−l, respectively, which was twice the level for mixed oak‐pine forest (MOPF) than CPF soils. Our study reports a significant decrease in soil microbial biomass C, N, and P with change in forest type from BOF to CPF. So, MOPF can be an alternative for sustainable management of degraded forest ecosystems in the Central Himalaya belt.

How resilient are the oak forests of Askot wildlife sanctuary, western Himalaya?

Monitoring resilience in Himalayan forest ecosystem requires an understanding of community structure, regeneration, and anthropogenic disturbances. Four classes of temperate broadleaf forest dominated by different species of oak viz., Banj oak (Quercus leucotrichophora), Rianj oak (Q. lanuginosa), Moru oak (Q. floribunda), and Kharsu oak (Q. semecarpifolia) were assessed between 1700-3000 m asl in Askot wildlife sanctuary, western Himalaya. A total of 300 quadrats of 10x10 m size were placed randomly in 30 forest sites at different altitudes using standard phytosociological methodologies. The tree density ranged from 503±33.8 to 694±75.9 indi. ha-1 with a basal area of 45.0±6.5 to 60.4±6.8 m2 ha-1. Across the forest communities, the sapling density was 590±54.9 to 755±63.4 indi. ha-1 and seedling density was 175±88.5 to 770±208.8 indi. ha-1. Principal component analysis was used to examine the impact of anthropogenic pressures on regeneration of different oak communities. The study reveals that despite the extractive pressures on oak forests in the study area, the regeneration of Q. leucotrichophora and Q. lanuginosa was fair. However, the regeneration of Q. semecarpifolia and Q. floribunda was poor which needs to be protected from livestock grazing. In addition to appropriate management inputs, sustainable forest harvesting practices must be implemented in the region.

Rhizosphere influence on soil microbial biomass and enzyme activity in banj oak, chir pine and banj oak regeneration forests in the central Himalaya

The present study aims to investigate the rhizosphere effect on soil organic carbon, nutrients and soil microbial biomass in three forests viz, banj oak (Quercus leucotrichophora), chir pine (Pinus roxburghii) and banj oak regeneration forest (banj oak regeneration in chir pine) in the central Himalaya. Soil samples were collected seasonally from three depths (0–10 cm, 10–20 cm, 20–30 cm) at two soil positions (i.e., rhizosphere and bulk soil). The soil physicochemical and biological properties were compared between rhizosphere soil (RS) and bulk soil (BS), among forest types using two-way ANOVA and comparison of means was assessed by Tukey’s HSD post-hoc test. Correlation analysis was performed to observe the association among physical, chemical and biological properties of the soil. Additionally, a Linear Mixed Effect Model (LMM) was applied to investigate the effect of forest types, soil positions, seasons, depths and their interactions on soil biological properties. In the rainy season, soil organic carbon (SOC) and total nitrogen (TN) in RS of banj oak were significantly higher (p < 0.05) than the BS in the upper soil layer (0–10 cm). However, the difference was less prominent in the middle (10–20 cm) and lower soil layer (20–30 cm). Soil microbial biomass (Cmic, Nimc and Pmic) in RS of banj oak and chir pine were significantly higher than the BS in upper and middle soil layers, while both RS and BS of banj oak regeneration did not vary significantly. Forests differed significantly in the rhizosphere effect. Banj oak showed a strong rhizosphere effect through the combined impact of favourable microclimatic conditions and high soil microbial biomass. Chir pine grows in nutrient-depleted soil, showed a low rhizosphere effect compared to the rhizosphere effect of banj oak. The SOC, Cmic and Pmic were generally higher in the RS of banj oak regeneration forest than the RS of chir pine, reflecting that oak regeneration enhances microbial diversity through an increased supply of root induced (root exudates) microbially mineralised nutrients. The rhizosphere effect changed significantly with soil depths and was found higher in the upper soil layer (due to high soil nutrients and microbial activity) and decreased with increasing soil depths. Across the forests, the rhizosphere effect was more prominent in the rainy season than the winter and summer seasons, mainly driven by high soil moisture content. Principal Component Analysis (PCA) was performed to obtain rhizosphere soil microbial index (RSMI). Our study suggests that Cmic, Cmic: SOC and Pmic: AP were the most important parameters to evaluate rhizosphere soil quality of this temperate forest of the central Himalaya.

Expansion of pine into mid-elevation Himalayan oak forests: Patterns and drivers in a multiple-use landscape

Oak species worldwide are experiencing declines, with negative consequences for hardwood forests and their associated biodiversity, but the causes of these declines vary across species and habitats. We examine changes in extent of banj oak-dominated (Quercus leucotrichophora) moist temperate hardwood forests in a Western Himalayan landscape between 1991 and 2017. Using classified satellite imagery from 1991, 2001 and 2017, we found that dense banj oak forests have undergone substantial degradation and loss of area, while chir pine (Pinus roxburghii) forests have expanded, largely by replacing degraded banj oak stands. This transition was most likely to occur at sites that had lower levels of winter precipitation and Topographic Wetness Index (TWI) values and more pine forest in the surrounding landscape. Our findings are consistent with known requirements of shade and moisture for the recruitment of banj oak. Loss of banj oak forests is likely to reduce biodiversity and a number of ecosystem services linked to the well-being of local communities.

Fine root production and nutrient dynamics in relation to stand characteristics of chir pine mixed banj oak forests in central Himalaya

Stand density and basal area are considered to be an important indicator of aboveground as well as belowground dynamics in forests. To understand the relationship between stand characteristics and fine root dynamics of chir pine (Pinus roxburghii) mixed banj oak (Quercus leucotrichophora) forests in central Himalaya we studied fine root mass, productivity, turnover rate and nutrient dynamics. Four sites were selected on the basis of increasing density and basal area of trees. From each site, ten random fine root samples were collected for one year by sequential coring method, using root corer of 8.0 cm diameter from three depths (0–10, 10–20 and 20–30 cm) on a monthly basis. Total mean fine root mass varied from 2.15 to 3.12 Mg ha−1, with biomass and necromass varying from 1.48 to 1.93 Mg ha−1 and 0.67 to 1.18 Mg ha−1, respectively. In terms of vertical distribution, values of both biomass and necromass decreased with increasing soil depth. Productivity was estimated between 1.24 and 1.51 Mg ha−1 y−1 while turnover rate varied from 0.78 to 0.84 y−1 throughout the sites. Concentration of nitrogen was found higher in live fine roots whereas, phosphorus, potassium and calcium did not show any significant variation between live and dead fine roots. In the present study, higher fine root mass upon increase in density and basal area of trees suggests that stand characteristics positively correlate with fine root mass while nutrient dynamics remain unaffected by stand characteristics as well as seasonal changes.