Intra-Annual Xylem Growth of Larix principis-rupprechtii at Its Upper and Lower Distribution Limits on the  Luyashan Mountain in North-Central China

Knowledge of intra-annual stem growth dynamics across environmental gradients is important for advancing our ability to understand the adaptability and vulnerability of subtropical tree species to future climate change. To assess the effects of seasonal drought on intra-annual stem growth, stem radial variation of Taiwan pine (Pinus taiwanensis Hayata) was monitored with band dendrometers for two years along an elevation transect from 921 to 1402 m in the Lushan Mountains, a transect that covers the contrasting climatic growing conditions for Taiwan pine in southeastern China. We found that the onset of stem growth was nearly synchronous across the transect, in early April 2017 and in late March 2018, whereas large elevational differences were observed for the end of the growing season, which was much earlier at lower elevations. Tree stems frequently rehydrated during the dry growing seasons at the two higher elevations, suggesting that seasonal drought had minor influence on the offset of high-elevation stem growth. A substantial and continuous tree water deficit of low-elevation Taiwan pine was detected during dry seasons, leading to an early growth cessation in late July in both years. Tree water status (reflected by tree water deficit) revealed a higher sensitivity to precipitation and soil water content across wet- and dry-seasons at the lowest elevation than at high elevations, indicating that low-elevation stem radial growth was highly dependent on moisture variables over the whole growing season. Due to the influences of seasonal drought on growth cessation and rates, Taiwan pine produced a rather narrow annual growth at the lowest site, whereas high-elevation Taiwan pine could benefit from the optimal wet-season environmental conditions and the reactivation of cambial activity during dry seasons. Our findings suggest that the more frequent and intensive drought episodes in the future will reduce tree growth of Taiwan pine at the dry edge, probably resulting in upward shifting of the optimal elevation for Taiwan pine in subtropical China.

Section: Seasonal Drought Effects On Stem Radial Growthsupporting

confidence: 69%

Section: Intra-annual Stem Growth Dynamics Along the Elevation Transectsupporting

confidence: 63%

Seasonal Drought Effects on Intra-Annual Stem Growth of Taiwan Pine along an Elevational Gradient in Subtropical China

Liu

Wang

Zhao

2019

“…The rapid stem radius growth in this study was observed in the time from May to July (stage 1), coincident with the most rapid division rate of cambial cells [37]. The rapid growth stage is considered as a critical stage for the formation of early wood cell and stem radius growth.…”

Section: Intra-annual Variations Of Stem Radiusmentioning

confidence: 58%

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

Liu

Wang

Tian

et al. 2017

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.

“…In our study, soil temperature was important for both primary growth and secondary growth (Table 4). Previous research in this study area has shown that soil temperature played a key role for the initiation of radial growth for both larch and spruce [8,44]. The threshold value of soil temperature for larch xylogenesis was above 0 • C as frozen soil will inhibit water uptake and activity in root systems [45].…”

Section: Environmental Effect On Growthmentioning

confidence: 88%

“…Studies on secondary growth have revealed an early onset of cambium activity, as well as a longer duration of xylem formation, and this has often been related to the influences of ongoing climate change [5,6]. Therefore, investigations on primary and secondary growth help to assess the physiological adaptation of species to the local environment [7] and predict changes in the growing season under current global warming [8].…”

Section: Introductionmentioning

confidence: 99%

Comparing Primary and Secondary Growth of Co-Occurring Deciduous and Evergreen Conifers in an Alpine Habitat

Zhang

Jiang

Yan

et al. 2019

Self Cite

Investigations on primary and secondary growth in co-occurring species will aid in assessment of the physiological adaptation of species and the prediction of forest stand structure dynamics. To explore the correlation and coordination between primary and secondary growth, we monitored the leaf phenology, shoot elongation, and stem growth of co-occurring Larix principis-rupprechtii Mayr. and Picea meyeri Rehd. et Wils. in an alpine habitat, Luya Mountain (North-Central China), during the growing season of 2014. We measured bud development on terminal branches three days per week by direct observations and intra-annual stem xylem formation at weekly intervals by the microcores method. The onset sequence of three organs was the needle, shoot, and stem, without species-specific differences. Needles appeared one month earlier than stem growth in larch, while it was only one week earlier in spruce. The duration of needle growth was the shortest, followed by the shoot and stem. The timing of primary growth (i.e., onset, end, and maximum growth rate) between the two species was asynchronous, but secondary growth was synchronic with the same date of the maximum growth rate occurrence, potentially indicating species competition for resources. Unlike larch, spruce staggered growth peaks among different organs, which may effectively mitigate trees’ internal competition for resources. Soil temperature was positively correlated with both shoot and stem growth in the two species, whereas air temperature and soil water content were positively correlated with needle growth only in larch. Therefore, it can be inferred that the spruce will probably outcompete the larch at cold alpine treeline sites due to its high adaptability to acquiring and allocating resources. These results provide insight into the potential physiological correlation between primary and secondary growth and allow better prediction of future climate change effects on forest ecosystem productivity.