Sand Dune Height Increases Water Use Efficiency at the Expense of Growth and Leaf Area in Mongolian Pine Growing in Hulunbeier Steppe, Inner Mongolia, China

Abstract

The Mongolian pine (Pinus sylvestris var. mongolica) is one of the most common tree species in semiarid and arid areas of China, especially in the sand dunes of the Hulunbeier steppe. This study addresses the morphological and physiological characteristics of the Mongolian pine according to sand dune height. Five sites were chosen with various sand dune heights (P1–P5). Nine years after planting, tree growth, leaf area, leaf mass per leaf unit area (LMA), diameter at breast height (DBH), tree height, diameter at root collar (DRC), longest shoot length, carbon isotope composition, and intrinsic water use efficiency (iWUE) were measured to explore the responses of Mongolian pine trees to drought. DBH, tree height, DRC, leaf area, leaf length, and longest shoot length significantly decreased with greater sand dune height (p < 0.05). However, the carbon isotope actually increased with dune height (p < 0.05). Conversely, the iWUE of current-year pine needles was significantly higher at measurement points P3 (132.29 μmol CO2 mol −1 H2O), P4 (132.96 μmol CO2 mol −1 H2O), and P5 (125.34 μmol CO2 mol −1 H2O) than at the lower points P1 (95.18 ± 9.87 μmol CO2 mol −1 H2O) and P2 (103.10 ± 11.12 μmol CO2 mol −1 H2O). Greater sand dune height increases the distance to groundwater, which in this study led to an increase in iWUE in the Mongolian pines, thus these trees appear to adapt to increased sand dune height by increasing their iWUE and decreasing their leaf area. However, prolonged periods characterized by such adaptations can lead to tree death. We expect these findings to be useful when selecting plantation sites for Mongolian pines in semiarid and arid climates.

Genetic Diversity and Association Analysis among Germplasms of Diospyros kaki in Zhejiang Province Based on SSR Markers

“…In this study, mean temperature of the quarter showed little significance in morphological traits, perhaps due to all sampling sites belonging to the subtropical monsoon climate and no strict temperature limit for persimmon survival. Consistent with previous studies of many fruit trees, which revealed that light [59][60][61] and water supply [62][63][64][65][66] played an important cue in both leaf and fruit development, and precipitation and solar radiation were the main climate factors affecting the morphological traits of persimmon in Zhejiang Province. There were also longitudinal differences in morphological trait diversity.…”

Tree-Ring Analysis Reveals Density-Dependent Vulnerability to Drought in Planted Mongolian Pines

“…A survey of Liaoning Province revealed that 62.75% of the trees in the Mongolian pine forests (in total 38,300 ha, of which the majority were high-density stands) declined in condition [25]. Previous studies on this species focused on the relationship between growth and climatic variables [26], intrinsic water use efficiency [27], sap flow and canopy water use [28], hydraulic limits underlying the low growth rate [21], and stand decline resulting from land use [29]. However, few studies investigated the response and adaptation of Mongolian pine in stands of different densities to drought, especially severe drought events.…”