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Abstract The Himalayas are experiencing dramatic warming and drought events, which occur at a faster rate than the global average. How will the high-elevation ecosystems cope with such changing conditions? This study aims to combine cambial phenology with quantitative wood anatomy to understand how the growth dynamics affect the trade-off between safety and efficiency of water transport in the Himalayan forests. We investigated the timing of xylogenesis and its relationship with hydraulic wood anatomical traits in Himalayan birch (Betula utilis D. Don) at two altitudes in the central Himalayas. Xylogenesis was monitored weekly from April to September 2014 by collecting microcores. We measured vessel area on histological sections, calculated the hydraulic diameter, and assessed the effects of climate on xylem production rate. Xylogenesis occurred from June to September in both study sites. Moisture availability influenced positively xylem growth besides thermal conditions. The onset and duration of vessel enlargement were correlated with the hydraulic diameter. Trees with earlier onsets and longer durations of vessel enlargement exhibited larger hydraulic diameters. The close relationship between cambial phenology and hydraulic diameter suggests that earlier growth resumption induced by climate changes may result in larger vessels, which are more efficient in water transport, but vulnerable to drought-induced cavitation. The ongoing warming and drying climate conditions may menace the survival of birch forest in the central Himalayas.

Abstract Monitoring paddy rice cultivation is essential for ensuring food security and for land resource management in agrarian countries of South Asia. In this study, we investigated the spatial and temporal variation of rice cultivated area and phenological metrics in Nepal between 2003 and 2018 using the time series MODIS data and PhenoRice algorithm. Comparisons of PhenoRice outputs with ancillary data show that implementation of PhenoRice with the MODIS data can be used for long-term change analysis of rice cultivation. Results on spatial distribution illustrate: rice cultivation is concentrated in the low elevation belt in the south; the cultivation begins earlier in the western region compared to the eastern region and begins earlier in the hilly region compared to the plains. The inter-annual trend analysis found a statistically significant decrease of rice cultivated area at the rate of 19.13 thousand hectares per year during the recent decade; the loss of rice fields was more prominent in the eastern plains while rice farming expanded in the mid-hills in the western region. Our study provides insights regarding timely and cost-efficient monitoring of rice farming at a large scale in the mountainous region.