Relating Water Use to Tree Vitality of Populus euphratica Oliv. in the Lower Tarim River, NW China

Abstract

Abstract:This study aimed to compare the hydraulic characteristics of different vitalities of Populus euphratica to reveal the differences in their water use strategies and water consumption to provide useful data to scale water use of riparian poplar forests in the lower reaches of the Tarim River, Northwestern China. Our results showed that the sapwood area of P. euphratica could be estimated based on its correlation with tree biometric parameters. The sapwood area of vital poplars tended to be larger than the senesced poplar despite both having the same diameter at breast height. This indicates that poplar vitality should be taken into account when estimating its sapwood area. Therefore, we established two different sapwood area estimation models for vital and senesced poplar (sapwood area = 1.452 × DBH 1.553 , R 2 = 0.891; sapwood area = 0.915 × DBH 1.618 , R 2 = 0.718; DBH: diameter at breast height). The sap flow process of vital and senesced poplar had certain differences and similarities; the average diurnal sap flow velocity and water consumption of vital poplar were 15.85 cm/h and 45.95 L, respectively; for the senesced poplar, it was 9.64 cm/h and 18.17 L, respectively, which were smaller than that of vital poplars. The influence of environmental factors on the sap flow velocity of two different P. euphratica was similar; the sap flow of both vital and senesced poplar had positive correlation with air temperature (R 2 = 0.800 and 0.851), solar radiation (R 2 = 0.732 and 0.778), vapor pressure deficit (R 2 = 0.508 and 0.643) and groundwater depth (R 2 = 0.301 and 0.171), while negative correlation with air humidity (R 2 = −0.313 and −0.478).

Tree Water Dynamics in a Semi-Arid, Pinus brutia Forest

“…Observations showed very little difference in the depth of the sapwood cores taken from the four azimuthal directions of the trunk (Supplementary Material, Table S1). A similar power relation between sapwood area and DBH (Ax = 1.452 * DBH 1.553 ) was found by Keyimu et al [34], for Populus euphratica trees in an arid climate, at the lower reaches of the Tarim River in China. Our results show a larger increase in sapwood area with increasing DBH for P. brutia compared to the relations for Populus euphratica.…”

“…We applied indicator dye (methyl orange and methyl blue) to the augured cores and determined the sapwood depth by the difference in colour between the sapwood and heartwood area on both sites, which is a method similar to previous studies [4,8,[48][49][50]. Like Keyimu et al [34], we developed a power relation between the DBH and the sapwood area of the P. brutia trees. We used a log transform of the variables to test the statistical significance of a non-zero slope of the linear regression equation with a t-test.…”

Biomass Carbon Sequestration Potential by Riparian Forest in the Tarim River Watershed, Northwest China: Implication for the Mitigation of Climate Change Impact

“…At present, water diversion practices are the main environmental driver for eco-hydrological processes of the riparian ecosystem in the region. Seventeen water diversions in the lower reaches of the Tarim River have played a significant role in raising groundwater tables near to the main river course and in recovering floodplain forests to a certain degree [30,47,48]. On the other hand, these practices might be a major contributor for producing a higher biomass by means of improving water availability and leading to the sequestration of carbon.…”

Trading Natural Riparian Forests for Urban Shelterbelt Plantations—A Sustainability Assessment of the Kökyar Protection Forest in NW China

“…Since the natural vegetation is better adapted to the local hyper-arid conditions, the Tugai forests have far lower water consumption rates [56] than the artificial plantations at Kökyar. Evapotranspiration calculations reveal an annual water consumption of only 480 mm for Euphrates poplar (Populus euphratica).…”

“…The Tarim Basin represents one of the last refuge areas of Euphrates poplar forests, one of the world's rare biospheres [17,27]. Most animal species in the Tarim Basin, of which many are classified as endangered, rely on them and on the Tugai vegetation in general as a habitat [17,28,56].…”