Characteristic of Stomatal Conductance and Optimal Stomatal Behaviour in an Arid Oasis of Northwestern China

Stomatal conductance (gs), the process that governs plant carbon uptake and water loss, is fundamental to most Land Surface Models (LSMs). With global change accelerating, more attention should be paid to investigating stomatal behavior, especially in extremely arid areas. In this study, gas exchange measurements and environmental/biological variables observations during growing seasons in 2016 and 2017 were combined to investigate diurnal and seasonal characteristics of gs and the applicability of the optimal stomatal conductance model in a desert oasis vineyard. The results showed that the responses of gs to environmental factors (photosynthesis active radiation, PAR; vapor pressure deficit, VPD; and temperature, T) formed hysteresis loops in the daytime. The stomatal conductance slope, g1, a parameter in the unified stomatal optimal model, varied in different growing seasons and correlated with the soil-to-leaf hydraulic conductance (KL). These results indicated the potential bias when using a constant g1 value to simulate gs and highlighted that the water-use strategy of oasis plants might not be consistent throughout the entire growing season. Our findings further help to achieve a better understanding of stomata behavior in responding to climate change and encourage future efforts toward a more accurate parameterization of gs to improve the modeling of LSMs.

New radiocarbon dating and archaeological evidence reveal the westward migration of prehistoric humans in the drylands of the Asian interior

The vast drylands of the Asian interior were an integral part of a transcontinental network connecting east to west, that acted periodically as corridors and routeways for human migration. However, our understanding of the prehistoric human occupation of and interaction with this inhospitable environment has been hindered by a lack of direct evidence from settlements. Here we present the results of the first systematic study of archaeological material and radiocarbon dates from newly-discovered Bronze Age settlements in the hyper-arid Lop Nur region, in the eastern Tarim Basin. The studied settlement (the North Loulan Settlement, NLS), apparently associated with the prehistoric Xiaohe Culture, which is known from the Xiaohe and Gumugou cemeteries, is especially significant for the study of the prehistoric desert-oasis civilization in the drylands of the Asian interior, because it is quite different from any of the contemporary cultures in the surrounding regions. Based on a synthesis of Bayesian-modeled radiocarbon dates, the age of the NLS falls within the range of ca. 2051–1774 BC. Our field investigations indicate that the inhabitants of the site occupied semi-subterranean/semi-cave dwellings on the upper part of high yardangs, suggesting that they were able to utilize island-like yardangs in order to adapt to lake or wetland terrains. The new chronological framework for the Xiaohe cultural sites indicates that the NLS was the first Xiaohe settlement in the Tarim Basin. The earliest settlers, who were influenced by oriental culture, may have migrated to the NLS along the eastern or northeastern corridors. Later, there was the migration of populations westward along rivers.