Growth Ring Measurements of Shorea robusta Reveal Responses to Climatic Variation

Many tropical species are not yet explored by dendrochronologists. Sal (Shorea robusta Gaertn.) is an ecologically important and economically valuable tree species which grows in the southern plains and mid-hills of Nepalese Central Himalayas. Detailed knowledge of growth response of this species provides key information for the forest management. This paper aims to assess the dendroclimatic potential of Shorea robusta and to understand climatic effects on its growth. A growth analysis was done by taking 60 stem disc samples that were cut 0.3 m above ground and represented different diameter classes (>10 cm to 50 cm). Samples were collected and analysed following standard dendrochronological procedures. The detailed wood anatomical analysis showed that the wood was diffuse-porous, with the distribution of vessels in the entire ring and growth rings mostly marked with gradual structural changes. The basal area increment (BAI) chronology suggested that the species shows a long-term positive growth trend, possibly favoured by the increasing temperature in the region. The growth-climate relationship indicated that a moist year, with high precipitation in spring (March–May, MAM) and summer (June–September, JJAS), as well as high temperature during winter (November–February) was beneficial for the growth of the species, especially in a young stand. A significant positive relationship was observed between the radial trees increment and the total rainfall in April and the average total rainfall from March to September. Similarly, a significant positive relationship between radial growth and an average temperature in winter (November–January) was noted

Estimating Fuelwood Demand and Supply for Forest User Groups from Community Forests

Main objectives of this study were to estimate annual fuelwood demand in Community Forest Users Group (CFUG), and annual sustainable supply of the same from Community Forest (CF). Study was done each one community fores

Spatio-temporal dynamics of two alpine treeline ecotones and ecological characteristics of their dominate species at the eastern margin of Qinghai-Xizang Plateau

热量匮乏是高山树线的主要成因,在全球变暖趋势下对高山树线及其建群种的生态学过程及特征的研究具有重要意义。该文以青藏高原东缘的折多山和剪子弯山两处高山树线(海拔分别为4 265 m和4 425 m)作为研究对象,通过设置垂直样带,同时结合区域温度、降水的长时间序列分析,探究两处树线的时空动态过程,并明确了建群种冷杉(Abies spp.)的生态学特征。结果表明: 1)折多山和剪子弯山区域的气温在过去58年均存在显著的上升趋势(分别上升了0.72和0.91 ℃),而折多山和剪子弯山区域降水均存在微弱的降低趋势。2)折多山的峨眉冷杉(A. fabri)龄级结构呈反J形,剪子弯山的鳞皮冷杉(A. squamata)龄级结构呈双峰形,二者种群结构均相对稳定。3)在小尺度上,种子扩散限制使得两处树线的冷杉聚集分布。在大尺度上,折多山峨眉冷杉亦呈聚集分布,而剪子弯山鳞皮冷杉受生长环境以及种内或种间关系的影响呈随机分布。4)两处样地建群树种的树高和基径均随海拔升高而降低,位于树线交错带上部的冷杉均呈现树高生长大于径向生长的异速生长关系,而位于样地中、下部位的冷杉大部分呈等速生长关系。5)相比10年前,折多山和剪子弯山的树线及树种线位置均无明显变化,剪子弯山鳞皮冷杉种群的树木密度亦无明显变化,而折多山的树木个体数提高了约25%;相比20年前,折多山和剪子弯山的树种线分别上移了50和30 m,树线位置分别升高了75和40 m,树木个体数亦明显增加,分别提高了约220%和100%。树线及其建群种在较大时空尺度上主要受热量的控制,而在较小时空尺度上受温度及生长环境共同作用的影响

Moisture, Not Temperature, in the Pre-Monsoon Influences Pinus wallichiana Growth along the Altitudinal and Aspect Gradients in the Lower Himalayas of Central Nepal

Changing climate can strongly affect tree growth and forest productivity. The dendrochronological approach to assessing the impact of climate change on tree growth is possible through climate–growth correlation analysis. This study uses an individual tree-based approach to model Pinus wallichiana (P. wallichiana) radial growth response to climate across the physiographic gradients in the lower distributional range of Nepal. This study sampled six sites across the Makwanpur district of central Nepal that varied in elevation and aspect, obtaining 180 tree-ring series. Climate data series were obtained from Climate Research Unit (CRU 4.0). The pair correlation approach was used to assess P. wallichiana growth response to climate and site-level physiographic variables such as site-level environmental stress. The study also determined long-term growth trends across the elevation and aspect gradients. Trees at sites with higher elevation and northeast aspect (NEA) were more responsive to winter and spring precipitation, whereas trees with lower elevation and northwest aspect (NWA) were more responsive to winter and spring precipitation. Basal area increment (BAI) analysis showed the variation of growth at site-level environmental stress, suggesting that the sensitivity of forest ecosystems to changing climate will vary across the lower growth limit of P. wallichiana due to differences in local physiographic conditions

Growth dynamics of Shorea robusta Gaertn in relation to climate change: a case study from tropical region of Nepal

Key message: The growth of Shorea robusta is positively correlated with temperature, whereas the relation to moisture is weak. Abstract: Tree-ring analyses provide a rich archive of information on environmental attributes affecting tree growth. Tree-ring studies conducted so far have mostly focused on temperate species, and research on tropical trees is limited. This study aims to develop a tree-ring chronology of Shorea robusta and understand the climatic sensitivity of its growth in the tropical region of Nepal. Tree-ring samples of S. robusta were analysed following the standard dendrochronological sample analysis procedure. A 134-year-long ring-width chronology of S. robusta was developed, extending from 1851 to 2018, which is the longest chronology reported for this species. The chronology statistics revealed its high dendroclimatic potential with moderate R-bar, high expressed population signal, and low autocorrelation. The mean annual radial growth was 2.87 mm per year, while the mean basal area increment (BAI) was 9.245 cm2 per year. The ring width, BAI chronology and size-based growth analysis revealed an increasing growth trend of the species, which is likely favoured by the ongoing climate change. The tree growth of the species was positively correlated to temperature throughout the year; however, the relation to moisture parameters was weak. The temperature sensitivity of the species is stable over time, though a slight temporal difference exists in the strength of association

Spring Season in Western Nepal Himalaya is not yet Warming: A 400-Year Temperature Reconstruction Based on Tree-Ring Widths of Himalayan Hemlock (Tsuga dumosa)

The Himalayan region has already witnessed profound climate changes detectable in the cryosphere and the hydrological cycle, already resulting in drastic socio-economic impacts. We developed a 619-yea-long tree-ring-width chronology from the central Nepal Himalaya, spanning the period 1399–2017 CE. However, due to low replication of the early part of the chronology, only the section after 1600 CE was used for climate reconstruction. Proxy climate relationships indicate that temperature conditions during spring (March–May) are the main forcing factor for tree growth of Tsuga dumosa at the study site. We developed a robust climate reconstruction model and reconstructed spring temperatures for the period 1600–2017 CE. Our reconstruction showed cooler conditions during 1658–1681 CE, 1705–1722 CE, 1753–1773 CE, 1796–1874 CE, 1900–1936 CE, and 1973 CE. Periods with comparably warmer conditions occurred in 1600–1625 CE, 1633–1657 CE, 1682–1704 CE, 1740–1752 CE, 1779–1795 CE, 1936–1945 CE, 1956–1972 CE, and at the beginning of the 21st century. Tropical volcanic eruptions showed only a sporadic impact on the reconstructed temperature. Also, no consistent temperature trend was evident since 1600 CE. Our temperature reconstruction showed positive teleconnections with March–May averaged gridded temperature data for far west Nepal and adjacent areas in Northwest India and on the Southwest Tibetan plateau. We found spectral periodicities of 2.75–4 and 40–65 years frequencies in our temperature reconstruction, indicating that past climate variability in central Nepal might have been influenced by large-scale climate modes, like the Atlantic Multi-decadal Oscillation, the North Atlantic Oscillation, and the El Niño-Southern Oscillation