Aim: To study the impact of altitudinal variation on plant community composition, structure, dispersion and regeneration status of Quercus semecarpifolia forest in Kumaun Himalaya. Methodology: Along the altitudinal gradient, the forest stands between 2400 and 2610 m asl were selected at low, mid and high altitude. The phyto-sociological analysis was carried by laying ten quadrats of 10m × 10m at each site. Soil samples were collected with the help of soil corer from two depths. Various ecological indices and population structure were investigated for each forest stand and regeneration status of forest was predicted by the population size of seedlings, saplings and trees. Tree biomass was estimated using allomatric equations and carbon stock was determined by multiplying biomass of species to factor 0.475. Results: With increasing altitude the number of tree species decreased and the shrub species richness increased, while herb species showed a unimodel pattern. Q. semecarpifolia was the dominant tree species at all the three sites with the IVI values of 220.14, 255.22 and 286.23 at LA, MA and HA, respectively. A complete absence of Q. semecarpifolia seedlings indicated no regeneration in low and high altitude stands while low proportion of seedlings in mid altitude forest stand indicated poor regeneration. Soil was acidic (pH 5.66-5.86), with higher silt content and showed decreasing pattern in physico-chemical properties with increasing altitude. The biomass of tree layer ranged from 871.49 to 1050.17 t ha-1. The tree layer carbon stock was maximum in high altitude forest (498.84 t ha-1) which was largely contributed by bole, stump roots and branches. Interpretation: Variation in species richness, distribution pattern and regeneration potential is related to site characteristics governed by altitude and require various efforts to conserve and protect these forests to check ecosystem imbalance.

Ageratum conyzoides L. is an invasive weed that has severely infested cultivated lands and interferes with the growth of crops. In this study aqueous extracts of 50 and 100% concentration were prepared from fresh and air dried plant parts (Leaves and roots) of A. conyzoides and their allelopathic effect was observed on seed germination and seedling growth of two rice varieties namely Sava and Geru. In Sava variety, a significant reduction in seed germination, seedling length and dry weight was recorded under dry leaf extract while under fresh leaf extract seed germination and seedling length was increased at 50% concentration as compared to control. In Geru variety both fresh and dry leaf extracts resulted in decreased seed germination and seedling growth with increasing concentration. Similar patterns were recorded for fresh and dry root extracts. The inhibitory effect of leaf extracts was more pronounced than root extract and overall dry aqueous extracts of leaf and root were more inhibitory than fresh aqueous extracts. Among varieties, Sava was least affected as compared to the Geru. This study indicated that A. conyzoides exert allelopathic effect towards rice crop by releasing water soluble phytochemicals.

Coriaria nepalensis is one of the shrubs which have the ability to mitigate the frequency of perilous natural events or natural calamities. This paper elucidates the nutrient dynamics of C. nepalensis shrublands in degraded hills of Kumaun Himalaya. The average nutrient concentration (N, P, and K) in aboveground components of C. nepalensis was in the following order: Foliage > Twigs > Branches > Bole wood, whereas in belowground components the order was: Fine roots > Lateral roots > Stump root. The order of contribution to total nutrient storage in vegetation was: Tree > Herbs > Shrubs. The proportion of nutrients stored in the shrub layer was in the order: N > K > P. The soil stored a maximum proportion of nutrients at each site (79.48–87.54% N, 70.47–87.88% P, 74.33–88.27% K). Maximum nutrient storage in soil and vegetation was recorded for site 3 (Barapatthar) and minimum for site 1 (Pines). The uptake of N, P, and K by vegetation ranged from 428 to 1,353 kg ha–1 yr–1, 32–102 kg ha–1 yr–1, and 109–479 kg ha–1 yr–1, respectively. In the present study, the turnover time was 1.06–1.33 years for N, 1.03–1.15 years for P, and 1.02–1.13 years for K. Compartment models reflect the distribution of nutrients and net annual flux that will help to develop the management plan to maintain the fertility and productiveness of the degraded sites.

Coriaria nepalensis, a nitrogen-fixing actinorhizal shrub, is a prominent and successful colonizer of bare rocks and landslide affected degraded lands. Field experiments were conducted to determine the differences in biomass decomposition and nutrient release pattern of different plant parts of C. nepalensis using litter bag technique. Results showed that the leaves decomposed completely within 6 months while only 46.55% of the lateral roots were decomposed with slowest decomposition rate of 0.14% day–1. The decomposition rate was in the order: Leaves > Reproductive parts > Twigs (< 5 mm) > Twigs (> 5 mm) > Bark > Fine roots > Lateral roots. The decay rate coefficient was highest (0.003–0.014) for leaves and lowest (0.001–0.002) for lateral roots. During the decomposition cycle (364 days), overall increase was reported in nitrogen and phosphorus concentration, while potassium concentration decreased continuously in residual litters. The nutrient mobility was in the order: K > P > N. Climatic factors like temperature, relative humidity and rainfall significantly affected the decomposition process and among these factors, rainfall pattern emerged as a most effective environmental driver. Thus, taking into account initial nutrient content, nutrient release and decay rates, the leaves and reproductive parts of C. nepalensis proved to be more important as nutrient source than other components.

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