Intra-Annual Variation of Stem Radius of Larix principis-rupprechtii and Its Response to Environmental Factors in Liupan Mountains of Northwest China

Abstract

Abstract:Fine-resolution studies on the stem radius variation at short timescale can provide useful information about the tree growth process and the major environmental variables that trigger and drive stem radius variation. This study investigated the stem radius variation of Larix principis-rupprechtii Mayr growing in the semi-humid Liupan Mountains of Northwest China at daily and seasonal scales using high-resolution automatic band dendrometers from May to October in 2015. The results showed that the stem radius variation of Larix principis-rupprechtii has a clear diurnal pattern which can be divided into contraction, recovery, and increment phases; and also a seasonal pattern which can be divided into three stages: (1) the rapid growth stage in spring (stage 1) with the radius increment of 94.0% of the total in the entire growing period; (2) the persistent shrinkage stage in the dry summer (stage 2) with a negative diurnal radius increment for most days, and a significantly larger amplitude of stem contraction and recovery than other stages; (3) the minimal growth stage in autumn (stage 3), mainly caused by the lowering temperature and leaf area. The amplitude of stem contraction was significantly correlated with air temperature (both the mean and highest value) in all three stages: vapor pressure deficit (VPD) in stage 1; relative humidity (RH), VPD and soil moisture (M s ) in stage 2; and soil temperature (T s ) in stage 3. This indicates that the stem radius contraction was mainly controlled by the factors influencing tree transpiration rate in spring and autumn stages, but jointly controlled by the factors influencing both the tree transpiration rate and the soil moisture availability in the dry summer stage. The factors controlling the stem radius recovery was similar to the stem contraction. The amplitude of stem increment was significantly correlated with the rainfall amount and air temperature (both the mean and highest value) in stage 1 and 3, M s in stage 2, and the lowest air temperature and T s in stage 3. This indicates that temperature and precipitation were the key factors controlling the stem radius increment in the spring and autumn stages, and soil moisture was the main factor limiting the stem radius increment in the dry summer stage at the study site with semi-humid climate in Northwest China.

Environmental Controls of Diurnal and Seasonal Variations in the Stem Radius of Platycladus orientalis in Northern China

“…In addition, MDS was negatively correlated with SWC in this study. These results could be explained by the increase of water absorption by roots for plant transpiration under higher soil moisture conditions, thereby reducing the amount of stem tissue water required for transpiration and a concomitant reduction in MDS [5,42]. Garnier and Berger [43] observed similar results, wherein drought caused an increase in stem shrinkage.…”

“…However, these approaches do not allow one to study the effects of short-term environmental changes on tree growth at intra-annual scales. Thus, studies applying fine-resolution growth data complement longer-term, tree ring-based studies [4][5][6].…”

Stem Radius Variation in Response to Hydro-Thermal Factors in Larch

“…Changes in stem radius, TWD, and GRO are mainly concentrated in the moist season. Many previous studies [10][11][12][13] have proved that precipitation plays an important role in the increase of tree stem radius. The stem radius variation of the tree is positively correlated with precipitation.…”

Temporal stability analysis of soil moisture along a coniferous forest hillslope with subtropical monsoon climate in southwest China

“…Overall, whether representative locations are the same at different soil depths is not universal. The discrepancy may be ascribed to comprehensive factors including topography characteristics, hydrogeological setting, and soil properties, which virtually determine the temporal variability of soil moisture in a region (Liu et al 2017).…”