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Dendrochronological analysis of Pinus merkusii (Merkus pine) collected from Mishmi Hills, Arunachal Pradesh, North–east India shows its potential to provide continuous and long–term information about changes in river flow of Lohit River Basin (LRB). A 170 years (1830–1999 C.E.) long regional tree-ring width chronology of Merkus pine was prepared using 80 tree cores. Based on the correlation analysis between tree-ring chronology and river discharge data, the river flow was reconstructed for the month of May from 1846 to 1999 C.E. The reconstruction showed long term low and high flow periods along with extreme drought and pluvial years. Past river flow reconstruction for hydro–climatic variability in this southwest monsoon-dominated region of North–east India requires further notice. Longer tree–ring records along with wider spatio-temporal network of discharge data from Arunachal Pradesh will help to develop better records of river flow reconstructions of the region.

A regional, 175 year long, tree-ring width chronology (spanning 1840–2014 C.E.) was developed for Pinus wallichiana A. B. Jacks. (Himalayan Blue pine) from the Lidder Valley, Kashmir, Northwest Himalaya. Simple and seasonal correlation analysis (SEASCORR) with monthly climate records demonstrates a significant direct positive relationship of tree growth with winter temperature. A linear regression model explains 64% of the total variance of the winter temperature and is used to reconstruct December–March temperatures back to 1855 C.E. The most noticeable feature of the reconstruction is a marked warming trend beginning in the late twentieth century and persisting through the present. This reconstruction was compared with instrumental records and other proxy based local and regional temperature reconstructions and generally agrees with the tree-ring records and is consistent with the marked loss of glacial ice over the last few decades. Spectral analysis reveals a periodicity likely associated with the Atlantic Multidecadal Oscillation and El Nino–Southern Oscillation. Spatial correlation patterns of sea surface temperatures with the observed and reconstructed winter temperatures are consistent with larger scale warming in the region.

Climate driven changes have impacted various civilizations and have major influence on human population globally. Remote regions such as the Himalaya also archived these climatic events in various proxies. The Eastern Himalaya region has recorded the Holocene climate change events in numerous proxy records. A multi–proxy record of the early to late–mid Holocene climate change from the catchment of PankangTeng Tso (PT Tso) Lake at an altitude of 3935 m asl in the Tawang district of Arunachal Pradesh was studied. A 90 cm sediment profile showed a synchronous pattern of Holocene climate changes in the palynological, environmental magnetic and carbon isotope data recorded. Dominant cold-humid conditions at 4625 cal yr BP followed by a cold-dry period was documented in the proxy data. The vegetation vis–a–vis climate varied throughout the Holocene and cold–dry conditions along with sub-alpine vegetation prevailed in the region around the “4.2ka event”. Human activities and environmental changes in the Tawang district during the Holocene probably impacted the vegetation during this significant period of the development and demise of major global civilizations.

Improvement of dendrochronological crops yield reconstruction by separate application of earlywood and latewood width chronologies succeeded in rain-fed semiarid region. (1) Background: Tree-ring width chronologies have been successfully applied for crops yield reconstruction models. We propose application of separated earlywood and latewood width chronologies as possible predictors improving the fitness of reconstruction models. (2) Methods: The generalized yield series of main crops (spring wheat, spring barley, oats) were investigated in rain-fed and irrigated areas in semiarid steppes of South Siberia. Chronologies of earlywood, latewood, and total ring width of Siberian larch (Larix sibirica Ledeb.) growing in forest-steppe in the middle of the study area were tested as predictors of yield reconstruction models. (3) Results: In the rain-fed territory, separation of earlywood and latewood allowed increasing variation of yield explained by reconstruction model from 17.4 to 20.5%, whereas total climatic-driven component of variation was 41.5%. However, both tree-ring based models explained only 7.7% of yield variation in the irrigated territory (climate inclusion increased it to 34.8%). Low temperature sensitivity of larch growth was the main limitation of the model. A 240-year (1780–2019) history of crop failures and yield variation dynamics were estimated from the actual data and the best reconstruction model. (4) Conclusions: Presently in the study region, breeding of the environment-resistant crops varieties compensates the increase of temperature in the yield dynamics, preventing severe harvest losses. Tree-ring based reconstructions may help to understand and forecast response of the crops to the climatic variability, and also the probability of crop failures, particularly in the rain-fed territories.

Tree-rings of Pinus kesiya from southern region of Manipur, Northeast India were used to develop chronologies of multiple tree-ring parameters that are: total-ring width (TRW), earlywood width (EW), latewood width (LW) and adjusted latewood (LWadj). The time span of these chronologies is 39 years (1980–2018 C.E.) and we compared their growth responses with monthly and daily climatic records. The comparison revealed a broadly consistent pattern of climate sensitivity with daily climate exhibiting higher correlation. The climate signals during pre-monsoon (March–May) were recorded in TRW and EW, whereas late-monsoon to post-monsoon climate signals were recorded in LW and LWadj. The spatial correlation analysis of tree-ring parameters and global sea surface temperature (SST) showed a positive relationship between tree growth with tropical Pacific Ocean and Indian Ocean during winter (December–February) and pre-monsoon (March–May) seasons. The LW and LWadj were also correlated with peak summer monsoon (July–August) SST over the tropical Pacific Ocean. IADFs observed in EW (E-IADF) were caused by dry and warm conditions during March–April. IADFs in LW ( L -IADF) occurred due to a combination of enhanced rainfall and temperature during post-monsoon (October–November) season. Evidence of stand-specific micro-climatic conditions in the formation IADFs in this species was also found. This study showed that multiple parameters of P. kesiya provides a lucid understanding of climate response on its growth and can be considered as a proxy for studying sub-seasonal changes in past environmental conditions in longer records.

Tree rings from forest-steppes of temperate continental Asia are useful proxies for the moisture regime reconstructions, encompassing environmental variations such as warming climate, changing frequency and intensity of droughts. Heterogeneity of precipitation leaves open the question of the probability of spatially large-scale droughts in this macro-region. Theoretically, such events could be driven by global tele-connections and/or common astronomic cycles. We have attempted the precipitation reconstructions of two distant (~1000 km) intermountain valleys in South Siberia, based on the tree ring width of Pinus sylvestris L. To enhance the quality of the precipitation reconstruction models, networks of existing tree-ring data were expanded and daily precision of instrumental precipitation series was implemented for calibration. Within-region (150-200 km) common signal between local chronologies r=0.37-0.90 (p Data Availability Statement Temperature and precipitation series of climatic stations were obtained from the website of All-Russia Research Institute of Hydrometeorological Information, World Data Centre (RIHMI-WDC, http://meteo.ru/data ). Other climatic time series and solar activity series were obtained from the website of The Royal Netherlands Meteorological Institute (KNMI) Climate Explorer ( https://climexp.knmi.nl ). Used in the study tree-ring width measurements will be submitted to the International Tree-Ring Data Bank (ITRDB; https://www.ncei.noaa.gov/products/paleoclimatology/tree-ring ) upon publication of the manuscript and with reference to it.

The vegetation distribution in Tripura, Northeast India was studied from the modern pollen assemblages at various sites in the region. Sediment samples and moss cushions were collected along transects from North to South Tripura to assess the modern pollen taxa dominant in the region. A number of taxa showing a modern day distribution of moist deciduous mixed vegetation dominant in Tripura were observed in the modern pollen data. Statistical significance of the modern–pollen data was verified using one–way ANOVA technique. Despite the limited pollen taxa recorded in the surface samples the analysis proved the potential of the pollen data and scope for future palynological studies. The impact of anthropogenic activity is clearly visible through the low sample yield and presence of taxa such as Poaceae, Amaranthaceae, Solanaceae, etc. Other factors such as entomophilous tendency and/or low yield of pollen in tropical plants, excessive rainfall, sediment distribution and jhum cultivation could contribute to the lack of pollen preservation in the region.

We present a 180-years long (1824–2003C.E.) tree–ring width chronology of the fast growing broadleaf tree Toon (Toona ciliata Roem.) from the subtropical wet hill forests of Kalimpong, in the eastern Himalaya of India. The majority of tree ring studies conducted in the Himalaya have been based on conifers. Our analyses demonstrate that winter temperature prior to the season of growth, current year April precipitation and April–May drought (scPDSI) exhibit direct relationship with the ring–width chronology when correlated with monthly or seasonal climate data. The observation of the tree–growth and climate relationship showed that optimum temperature, precipitation and soil moisture together serve to modulate the radial growth of Toon in the region, however the mean minimum temperature of winter season (October–February) is the most significant climatic factor. Based on the expressed population signal (EPS) statistic, our record is reliable only back to 1945C.E., however this study clearly establishes the dendroclimatic potential of this tropical broadleaf species to carry out future tree–ring based long–term climate reconstruction in the sub-tropical Himalaya.

Vegetation and climate during later part of Late Pleistocene have been reconstructed from Ziro valley, Arunachal Pradesh, Eastern Himalaya based on pollen data along with carbon isotope and magnetic susceptibility data The study reveals that the area and the vicinity is occupied by mixed broad leaved – conifer forest and pine grass savanah at variable densities at least since 66,000yr BP. The phases of expansions and declines of Oaks with decline and increase of Pines and grasses probably occurred under increase (warm–moist) and decrease (cool–dry) of S.W. monsoon precipitation respectively. The increasing trend of S.W. monsoon and temperature is recorded during ∼44,000 to 34,000 cal yr BP synchronizing with the peat development, and which peaked at around 35,000 cal yr BP. This may link to the interstadial phase during the last major glacial cycle in the Himalayan region. It is also reflected in the decline of δ13C value indicating dominance of C-3 type of vegetation. The increased values of χFD%, and lower values χLF magnetic susceptibility, recorded during the phase of the peat deposit, further advocate's higher monsoon intensity. Impact of expansion of glacier felt with peak (LGM) around 20,000 cal yr BP is perceived. Tree line had moved to lower altitudes due to increased aridity and low temperature. During this time existence of savannah type of vegetation is also evident by the increase of C4 taxa. Decreased FD% and increased χLF susceptibility also indicate reduced S.W. monsoon intensity.

This paper deals with the review of pollen based palaeoclimatic records available from the South-west monsoon dominated northeast part of India. Here, a complete overview of available Late Pleistocene–Holocene records of the past vegetation vis-a-vis climate is structured based on a latitudinal subdivision of the region. The broad spectrum of the past climate in terms of humid/dry, warm/cold inferred by variations of some key pollen or group of pollen taxa is depicted diagrammatically, thereby providing a glimpse of spatio-temporal vegetation vis-a-vis climatic changes. Here, we attempt to create a standard diagrammatic scale with more reliability than using relative terminology to infer past climate records, based on pollen data from sub-surface sediments.

Palynological analysis of sub surface samples at 1.20 m deep sediment profile from Srinagar, southwest Tripura, provides information on vegetation and climate during 7000–3000 years B.P. During this time span, the area is occupied by moist deciduous forest under warm humid climate with intermittent changes in precipitation regime i.e., comparatively less humid around 6.8 Kyr B.P. and 3.7–3.8 Kyr B.P.