Tree rings: A key ecological indicator for reconstruction of groundwater depth in the lower Tarim River, Northwest China

Abstract

Groundwater is becoming increasingly important in extremely arid areas due to climate change and human activities. Little is known, however, regarding the longterm dynamics of groundwater due to the lack of long-term historical records of groundwater depth data. In this study, we investigated the relationship between hydrometeorology and tree rings of Populus euphratica (P. euphratica) and the feasibility of reconstructing historical groundwater depths from these tree rings in the lower reaches of the Tarim River, an extremely arid area in China. Tree-ring growth of P. euphratica mainly reflected historical changes in regional water environments (including runoff and shallow groundwater), rather than climatic variables (including temperature, precipitation, relative humidity, and sunshine hours). Groundwater depth constituted the key environmental factor for directly controlling P. euphratica growth.Linear regression models using tree rings were developed to reconstruct historical changes of groundwater depths in the calendar year (January-December) and the growing season (April-August) from 1950 to 2015. Results tracked well with the main hydrological events in the study area. Our findings demonstrate that tree rings of P. euphratica are a key and effective ecological indicator for quantitatively reconstructing and elucidating historical changes of groundwater depth in the lower reaches of the Tarim River. Additionally, the suitable sampling range for establishing tree-ring chronologies of P. euphratica and reconstructing groundwater depth is 0-300 m from the river channel in the lower Tarim River. Taking into consideration the lagged effect between runoff of the Ecological Water Conveyance Project (EWCP), decrease in groundwater and tree growth, we recommend that the optimal implementation time of ecological water conveyance is between the previous September and November in the lower Tarim River. This application will effectively improve the groundwater environment in the current year and ensure the growth of riparian trees.

What we talk about when we talk about seasonality – A transdisciplinary review

“…Depending on their eco-hydrological setting, tree-ring records have been used to reconstruct time series of seasonal 1904 streamflow (e.g. [103]), and fluctuations of the water table [633].…”

Warming Increases the Carbon Sequestration Capacity of Picea schrenkiana in the Tianshan Mountains, China

“…Cores were brought back to the laboratory, air-dried, fixed, and polished with successively finer grades of sandpaper until annual rings could be distinguished easily [37]. Tree-ring widths were then measured with a precision of 0.001 mm by using a LINTAB system.…”

“…Tree-ring widths were then measured with a precision of 0.001 mm by using a LINTAB system. The quality and accuracy of cross-dated tree-ring series were assessed using COFECHA software [37]. In order to accurately determine the growth characteristics of each age group of trees, standardization techniques were avoided, such as detrending, which removed age-related or non-climatic trends from tree-ring data that were commonly used for climate reconstructions [1].…”

Reconstructing groundwater and lake level histories in Northern Wisconsin: isolation of groundwater’s influence on tree rings from climatic and environmental drivers

“…One specific knowledge gap is how historic groundwater levels influence tree growth and how this interaction could be isolated from climate in tree ring signals. In arid environments, changing groundwater levels strongly influence tree growth (Zhou et al 2019), and recent research has highlighted depth to groundwater (DTG) as an underappreciated driver of tree growth in humid regions (Ciruzzi and Loheide 2021). However, groundwater level histories rarely span more than a few decades in most parts of the world and are notoriously challenging to reconstruct (Jackson et al 2016).…”