Phenocam observed flowering anomaly of Rhododendron arboreum Sm. in Himalaya: a climate change impact perspective

Contradistinctive floral attributes, pollination guilds and their consequence on the outcrossing rate in two elevational morphs of Rhododendron arboreum Sm

Infraspecific floral trait variations may appear in response to elevational differences in alpine plant species. There is enormous information on the selection of such morphs mediated by biotic and/or abiotic variables. Whether such differences contribute to differences in reproductive strategy and mating outcomes is rarely investigated. We investigated these aspects in two distinct elevational floral morphs (Red and Pink) of Rhododendron arboreum Sm. in Western Himalaya. The red morphs occupy the lower elevations while pink morphs the higher elevations. The two morphs differ in floral traits like phenology, dimension, display, quality of floral rewards, and pollinators that happen to influence interaction with available pollinator pool at each elevation. The pink morph exhibits entomophily, while the red ones show ornithophily. Although experimental pollinations established that both the morphs are self-compatible, selfing results in significantly lower fruit-set than either cross- or open-pollinations. The outcrossing rate in the red morph, as determined by using simple sequence repeat (SSR) markers, was higher (tm=0.82) than that in the pink morph (tm=0.76), with a tendency of the latter to be shifting towards mixed-mating strategy. However, the extent of biparental inbreeding was comparable among the two morphs. It is inferred that the differences in the mating outcomes among the morphs in the tree species are linked to those emerging from floral traits and the pollination by different functional groups of floral visitors.

Spatial characterization of forest ecosystem services and human-induced complexities in Himalayan biodiversity hotspot area

The forest ecosystem of Indian Himalayan Region offers various ecosystem services (ESs) that are crucial for the sustenance of human beings. However, the rapid expansion of human activities (HA) poses a significant threat to the provision of the forest ecosystem services (FES). For simple and definitive assessments of FES and HA, the use of indicators has become an indispensable approach. In the present study, we performed: (i) indicator-based mapping of FES and HA, and (ii) evaluated the impact of HA on FES with the aid of geospatial techniques. Village-level analysis was conducted for FES and HA in the Aglar watershed of Uttarakhand, India for 2015. Four dominant forest types in the watershed-Quercus mixed, Pinus roxburghii, Cedrus deodara, and mixed forest were considered. For spatial characterization of FES, indicators such as forest carbon stock, net primary productivity, total water retention, and sediment yield were assessed, whereas human activity index (HAI) was evaluated using indicators of HAs, namely population density, road density, farmland, and habitation ratio. The integration of normalized values of FES indicators generated multiple ecosystem services indicator (MESI), and HAI was contructed using analytical hierarchical process based assignment of weights to HA indicators. Spatial analysis techniques such as ordinary least-square regression (OLS) and geographically weighted regression (GWR) models were used to derive the spatial relationship between them. The adjusted R2 and AIC were utilized to evaluate the effectiveness of the model. The GWR model had a better fit with an adjusted R2 of 0.68 and a lower AIC of 42.940, compared to the OLS model with an adjusted R2 of 0.21 and an AIC of 60.52. The statistics showed that GWR performed better than OLS and ably captured the heteroscedasticity of the phenomena. An inverse relation was observed between MESI and HAI. The findings of the study highlight the close link between the supply of FES and the impact of human-induced disturbances over the provision of FES, which has the potential to increase over time. The study provides a scientific basis for structuring policy dialogues to coordinate the long-term regional sustainability of FES provisioned from the Himalayan regions.

Phenological variations in relation to climatic variables of moist temperate forest tree species of western Himalaya, India

Phenology, an important ecological attribute, deals with the development of vegetative and reproductive parts of trees called "phenophases", which are important determinants of primary productivity and sensitive to climate change. The present study recorded various phenophases of major tree species (i.e., Quercus leucotrichophora, Rhododendron arboreum, and Myrica esculenta) as per the two-digit numerical system of Biologische Bundesanstalt, Bundessortenamt, Chemische Industrie (BBCH) scale. A total of 72 individual trees, twenty-four from each species, distributed between 1400 and 1980 m. a.s.l elevations were tagged and measured fortnightly for two consecutive years (2019-2021) in the moist temperate forest of Western Himalaya and compared with earlier existing records. Various phenophases were correlated with climatic factors along with duration and thermal time for each phenological growth stage. We found 24 growth stages for Q. leucotrichophora and M. esculenta and 28 for R. arboreum distributed across seven principal growth stages (e.g. bud development, 0; leaf development, 1; shoot development, 3; inflorescence development, 5; flower development, 6; fruit development, 7; and fruit maturation, 8) of trees as per BBCH scale. Maximum growing degree was 748.87 and 627.95 days recorded for R. arboreum and M. esculenta during leaf development, and 796.17 days for Q. leucotrichophora during fruit development. Flower emergence was observed pre, during, and post-emergence of new leaves for R. arboreum, M. esculenta, and Q. leucotrichophora, respectively, which varied at spatial scale with previous findings. Longevity of fruit development to ripening took 17, 4, and 2 months, respectively in Q. leucotrichophora, R. arboreum and M. esculenta. Duration of leaf initiation and flowering was positively correlated with climatic variables, whereas, the reverse was observed for fruiting in the studied tree species. The study concludes that the variations in phenophases of the three species were strongly influenced by climatic variations, especially minimum temperature. The result of the present study would be important in enabling us to formulate efficient forest management strategies by understanding the short-term adaptation of the climate-sensitive important tree species in the western Himalaya.