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The Qilian Mountains, a national key ecological function zone in Western China, play a pivotal role in ecosystem services. However, the distribution of its dominant tree species, Picea crassifolia (Qinghai spruce), has decreased dramatically in the past decades due to climate change and human activity, which may have influenced its ecological functions. To restore its ecological functions, reasonable reforestation is the key measure. Many previous efforts have predicted the potential distribution of Picea crassifolia, which provides guidance on regional reforestation policy. However, all of them were performed at low spatial resolution, thus ignoring the natural characteristics of the patchy distribution of Picea crassifolia. Here, we modeled the distribution of Picea crassifolia with species distribution models at high spatial resolutions. For many models, the area under the receiver operating characteristic curve (AUC) is larger than 0.9, suggesting their excellent precision. The AUC of models at 30 m is higher than that of models at 90 m, and the current potential distribution of Picea crassifolia is more closely aligned with its actual distribution at 30 m, demonstrating that finer data resolution improves model performance. Besides, for models at 90 m resolution, annual precipitation (Bio12) played the paramount influence on the distribution of Picea crassifolia, while the aspect became the most important one at 30 m, indicating the crucial role of finer topographic data in modeling species with patchy distribution. The current distribution of Picea crassifolia was concentrated in the northern and central parts of the study area, and this pattern will be maintained under future scenarios, although some habitat loss in the central parts and gain in the eastern regions is expected owing to increasing temperatures and precipitation. Our findings can guide protective and restoration strategies for the Qilian Mountains, which would benefit regional ecological balance. [ABSTRACT FROM AUTHOR]

This study examines the relationship between needle age and rust resistance in Picea crassifolia, focusing on the needle morphology, including size, shape, and physiological traits. One-year-old spruce needles are more susceptible to rust, while two-year-old needles show effective resistance. Using RNA-seq on the Illumina HiSeq500 platform, we analyzed both healthy and diseased one-year-old needles (N and B), as well as healthy one-year-old and two-year-old needles (N and L). We applied a fold change (FC) threshold of ≥2 and a false discovery rate (FDR) of <0.01, alongside GO annotation and KEGG pathway enrichment, to identify differentially expressed genes (DEGs). In N vs. B, DEGs were significantly enriched in processes such as metabolism, cellular function, catalysis, binding, ribosomal function, plant-pathogen interactions, endoplasmic reticulum protein processing, and signal transduction, revealing a polygenic network regulating the rust response. Similarly, in N vs. L, electron microscopy highlighted morphological differences in the wax layers of needles, with subsequent transcriptome sequencing uncovering genes involved in the development of one-year-old and two-year-old needles. DEGs were primarily found in pathways related to cutin, suberin, wax biosynthesis, fatty acid metabolism, photosynthesis, and phenylalanine synthesis. Two-year-old needles displayed reduced stomatal density, higher lignin content, and a thicker wax layer compared to one-year-old needles. Validation of the RNA-seq data through RT-qPCR on 10 DEGs confirmed the consistency of gene expression trends, enhancing our understanding of Picea crassifolia's genetic response to rust and supporting future research into its disease resistance. [ABSTRACT FROM AUTHOR]

Qinghai spruce (Picea crassifolia Kom.) is an ecologically important species in the forest ecosystem of the Qilian Mountains region in China. Natural regeneration of this species is critical to maintaining forest ecosystem function. Here, we analyzed several biological indicators among naturally regenerating Qinghai spruce across several elevations in the Pailugou watershed. Specifically, seedling density, basal diameter (BD), and plant height were measured, as were soil physicochemical parameters, at 2700 m, 3000 m, and 3300 m above sea level. Differences in the regeneration indicators and correlations between the indicators and soil parameters were then assessed across elevations. The results showed that soil stoichiometry was more sensitive to changes in elevation than seedling indicators were. Furthermore, seedling density was positively correlated with soil pH, whereas BD was positively correlated with the carbon-to-nitrogen ratio (C/N), the carbon-to-phosphorus ratio (C/P), and soil organic carbon (SOC) contents. None of the analyzed soil stoichiometry parameters had a significant impact on elevation-specific differences in seedling density. However, soil pH, SOC, and C/N significantly affected variations in seedling basal diameter at different elevations. Finally, soil pH, SOC, C/N, and the carbon-to-phosphorus ratio significantly affected variations in seedlings' heights at different elevations. This study provides a strong theoretical basis for further understanding of the mechanisms associated with Qinghai spruce regeneration, ultimately contributing to rational protection and management strategies for this important natural resource. [ABSTRACT FROM AUTHOR]

To explore the interaction between the fine roots of Picea crassifolia and soil microorganisms in the Qinghai cold region and clarify the contribution of microorganisms in the fine root development process, P. crassifolia forests were selected, incorporating varying degrees of mingling (0, 0.2, 0.4 and 0.6) as the focal points of this research. The study aimed to explore the impact of mingling on parameters such as fine root biomass density, root length density, root surface area density, specific root surface area, and specific root length. Additionally, an investigation was conducted on the soil bacterial and fungal communities within the 0-20 cm and 20-40 cm soil layers. The study also sought to establish connections between fine root morphological indices and soil microorganisms. The results showed that the fine root biomass density, root length density, root surface area density, specific root surface area, and specific root length in the 0-20 cm soil layer of P. crassifolia forest with mingling 0.4 reached the maximum. At the phylum level, Proteobacteria, Acidobacteria, and Basidiomycota are the dominant microorganisms in the soil, whereas at the genus level, Gp4, Gemmatimonas, Sebacina, and Inocybe are the dominant microorganisms in the soil. The correlation between fine root morphology and microbial community showed that specific root surface area and specific root length were negatively correlated with bacterial ACE, Chao1, and Shannon indexes. Sphingomonas and Sebacina are the key factors affecting biomass density, while Gaiella and Membranomyces are the key factors affecting root length density, root surface area density, specific root surface area, and specific root length. P. crassifolia forest with a mingling of 0.4 can promote the growth of fine roots within the constructive species community and improve the stability of the soil microbial community. In the future, the management of this natural forest area should thoroughly account for the impact of mingling on community stability while also preventing external activities from disrupting the growth of topsoil and fine roots. [ABSTRACT FROM AUTHOR]

The connections between the primary and secondary growth of trees allows better understanding of the dynamics of carbon sequestration in forest ecosystems. The relationship between primary and secondary growth of trees could change due to the diverging responses of meristems to climate warming. In this study, the bud phenology and radial growth dynamics of Qinghai spruce (Picea crassifolia) in arid and semi-arid areas of China in 2019 and 2020 were weekly monitored to analyze their response to different weather conditions and their links with carbon sink. Xylem anatomical traits (i.e. lumen radial diameter and cell wall thickness) were quantified along cell radial files after the end of xylem lignification to calculate the early-to-latewood transition date. Winter and early spring (January–March) were warmer in 2020 with a colder April compared with 2019. Precipitation in April–June was lower in 2020 than in 2019. In 2019, bud phenology occurred earlier, while the onset of xylem formation and the early-to-latewood transition date were delayed. The duration from the beginning of split bud and exposed shoot to the early-to-latewood transition date was positively correlated with the radial width of earlywood (accounting for ~80% of xylem width) and total xylem width. The longer duration of xylem cell division did not increase xylem cell production and radial width. Moreover, the duration from bud burst to the early-to-latewood transition date in 2020 was negatively linked with early phloem cell production as compared with 2019. Our findings suggest that warm conditions in winter and early spring promote the xylogenesis of Qinghai spruce, but might delay bud burst. However, the xylem width increments largely depend on the duration from bud burst to the start of latewood cell division rather than on the earlier xylogenesis and longer duration of xylem cell differentiation induced by warm conditions. [ABSTRACT FROM AUTHOR]

Research on the spatial patterns of tree populations is critical for understanding the structure and dynamic processes of forests. However, little is known about how the underlying drivers shape these patterns and species interactions in forest systems. In this study, spatial point pattern analysis investigated the combined effects of intraspecific interactions and environmental heterogeneity on the spatial structure and internal maintenance mechanisms of Picea crassifolia in the Qilian Mountain National Nature Reserve, China. Data were obtained from a 10.2-ha dynamic monitoring plot (DMP) and sixteen 0.04-ha elevation gradient plots (EGPs). Under complete spatial randomness, both mature trees and saplings in the DMP demonstrated large-scale aggregation with negative correlations. In EGPs, saplings were clustered in small mesoscales, mature trees were randomly distributed, and the interactions of saplings-trees at all elevations were not correlated. By eliminating the interference of environmental heterogeneity through the inhomogeneous Poisson process, saplings in the DMP and EGPs were clustered in small scales and trees randomly distributed. Intraspecific associations were negatively correlated, in the DMP and at low elevations, and no correlations in high elevations of EGPs. In the vertical scale, saplings showed a small-scale aggregation pattern with increase in elevation, and the aggregation degree first decreased and then increased. The interactions of saplings-trees and saplings–saplings showed inhibitions at small scales, with the degree of inhibition gradually decreasing. Spatial patterns and associations of adults–adults did not change significantly. The results revealed that intraspecific interactions and environmental heterogeneity regulated the spatial patterns of P. crassifolia at small and large scales, respectively. Environmental heterogeneity might be the most decisive factor affecting the spatial patterns of saplings, while trees were more affected by intraspecific interactions. Moreover, competition between trees in this area could be more common than facilitation for the growth and development of individuals. [ABSTRACT FROM AUTHOR]

Key message: The decline in Qinghai spruce forests was not aggravated by increasing temperatures; rather, excess cloud cover was the main trigger of forest decline. Forest declines accompanied by global warming have been increasingly reported worldwide. However, such declines are less frequently observed on the Tibetan Plateau. To assess the decline risk in Tibetan Plateau forests, we studied tree rings from two spruce (Picea crassifolia) forests in the Qilian Mountains of the northeastern Tibetan Plateau. We collected increment cores from 35 spruce trees at each sampling site in Qilian and Menyuan counties. Tree-ring widths were measured, crossdated and detrended. Growth decline in trees was identified based on low tree-ring index values lasting at least eight years. The percentage of the number of declining trees in all the samples was used to evaluate the occurrence and degree of forest decline events. The results showed that forest declines occurred at a low level during 1915–1933 and 1994–2005 in Qilian County and during 1996–2003 in Menyuan County. The radial growth of spruce had a significant negative correlation with the amount of cloud cover in the growing season. The results suggest that the growth declines of the spruce forests were not directly induced by the recent climate warming but were more likely related to stress conditions under increased cloud cover. Our findings provide insights into the assessment of forest decline risks and planning of forest protection. [ABSTRACT FROM AUTHOR]

This study examines the relationship between needle age and rust resistance in Picea crassifolia, focusing on the needle morphology, including size, shape, and physiological traits. One-year-old spruce needles are more susceptible to rust, while two-year-old needles show effective resistance. Using RNA-seq on the Illumina HiSeq500 platform, we analyzed both healthy and diseased one-year-old needles (N and B), as well as healthy one-year-old and two-year-old needles (N and L). We applied a fold change (FC) threshold of ≥2 and a false discovery rate (FDR) of Picea crassifolia’s genetic response to rust and supporting future research into its disease resistance.

Introduction: Understanding the underlying mechanisms of microbial community assembly is a fundamental topic in microbial ecology. As an integral part of soil organisms, ectomycorrhizal (EM) fungi play vital roles in ecosystems. Picea crassifolia is an important pine species in the Helan Mountains in Inner Mongolia, China, with high ecological and economic values. However, studies of EM fungal diversity and mechanisms underlying community assembly on this pine species are limited. Methods: In this study, we investigated EM fungal communities associated with P. crassifolia from 45 root samples across three sites in the Helan Mountains using Illumina Miseq sequencing of the fungal rDNA ITS2 region. Results: A total of 166 EM fungal OTUs belonging to 24 lineages were identified, of which Sebacina and Tomentella-Thelephora were the most dominant lineages. Ordination analysis revealed that EM fungal communities were significantly different among the three sites. Site/fungus preference analysis showed that some abundant EM fungal OTUs preferred specific sites. Ecological process analysis implied that dispersal limitation and ecological drift in stochastic processes dominantly determined the community assembly of EM fungi. Discussion: Our study indicates that P. crassifolia harbors a high EM fungal diversity and highlights the important role of the stochastic process in driving community assembly of mutualistic fungi associated with a single plant species in a semi-arid forest in northwest China. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Botanical Research is the property of Bulletin of Botanical Research Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As an important part of ecological hydrology, transpiration is the basis for analyzing forest water cycle and healthy growth, and important for forest protection and scientific management. We used thermal diffusion probes (TDP) to continuously monitor sap flow of Picea crassifolia in the Qilian Mountains from 2017 to 2018 to explore water consumption of P. crassifolia, and analyze the main controlling factors for the growth and transpiration of spruce. The results showed that the instantaneous change of P. crassifolia sap flow showed a single-peak curve in sunny days, a multi-peak or double-peak curve in cloudy days, and basically no obvious regularity in rainy days. The sap flow density of Qinghai spruce was consistent with the dynamics of solar radiation. The sap flow started earlier and ended later on sunny days, and lasted for 12 to 14 hours. Due to the high altitude (2700 m), low air temperature, and low vapor pressure difference (VPD) in this area, the overall sap flow density was low, with an average of (0.86±0.49) kg · d-1. On the hourly scale, the instantaneous rate of sap flow was significantly affected by solar radiation and VPD. On the daily scale, soil temperature and soil moisture content of the 0-40 cm layer were significantly related to sap flow density. The spruce sap flow density decreased with the decreases of solar radi-ation, air temperature, and VPD. In the high-altitude forest area of Qilian Mountains, lower soil and air temperature as well as lower VPD and solar radiation were the causes of low sap flow in Picea crassifolia in this area. [ABSTRACT FROM AUTHOR]

Spruce dwarf mistletoe (Arceuthobium sichuanense) is an important vascular parasite of spruce. In this study of the virome of A. sichuanense parasitizing Picea crassifolia using public domain RNA-seq datasets, potential coding-complete genomes or segments of seven putative novel RNA viruses (Arceuthobium sichuanense-associated virus 1–7: ASaV1–7) were identified. ASaV1, a putative emaravirus, contained five genomic segments with one open reading frame (ORF) in each, while ASaV2, a putative varicosavirus, had two segments. ASaV3 genome resembled that of an unusual plant virus- Dactylorhiza hatagirea beny-like virus. ASaV4, a putative amalgavirus contained two ORFs, while ASaV5–7 are putative deltapartitiviruses with one ORF per segment. [ABSTRACT FROM AUTHOR]

Environmental variances in temperature, moisture, and soil fertility caused by elevation gradients affect tree growth. However, the variability in regional climate and differences in tree physiology give rise to much uncertainty regarding the effects of elevation on tree growth patterns and resource allocation. In order to clarify the growth-limiting factors and physiological mechanisms of trees at different elevations, we selected Picea crassifolia (Qinghai spruce) at high (3300 m), middle (2850 m) and low (2585 m) elevations to analyze the interannual trends of tree radial growth and the resource allocation trade-offs involving nonstructural carbohydrates (NSC). The results were as follows: 1) the limiting factor for the growth of Qinghai spruce changed from growth limitation to carbon limitation with an increase in elevation; this was supported by the higher concentrations of NSC and its components in the whole plant and all tissues at middle and low elevations compared to high elevation, while the basal area increment (BAI) showed a decreasing trend at middle and low elevations and an increasing trend at high elevation. 2) The greatest concentrations of NSC were found in the leaves and thick roots at all three elevations, but soluble sugar (SS) and starch (ST) mainly accumulated in overground tissues (leaves and trunks) and underground tissues (fine and thick roots), respectively. 3) The ratios of soluble sugar to starch (SS/ST) at high elevations were significantly greater than those at middle and low elevations, indicating that more carbon was used for growth at high elevations, while more carbon was used for long-term energy storage at middle and low elevations. The results elucidate the growth constraints of Qinghai spruce at different elevations and the resource allocation trade-off mechanism, and offer reference points for ecological adaptation theory and conservation measures for trees at different elevations. [ABSTRACT FROM AUTHOR]

Dryland montane forests are important agents for soil and water resource conservation. The growth of these forests under climate warming is strongly affected by local environmental factors. However, how environmental factors impact intra-annual stem growth dynamics across environmental gradients in these regions remains unclear. This work focused on assessing seasonal patterns of stem growth across different elevations and how environmental factors impact stem growth in the Qilian Mountains, northwestern China. The stem growth of 50 Qinghai spruce trees was monitored for two years across an elevation gradient from 2500 m to 3300 m above sea level (a.s.l.). We found that growth initiation occurred later as the elevation increased, and growth commenced when elevation-specific temperature thresholds were reached. However, growth cessation presented large elevational differences: cessation occurred much earlier at low elevations (2500 m and 2700 m a.s.l.). Exceptionally early growth cessation occurred predominantly at 2700 m a.s.l., which was correlated with seasonal drought/insufficient rainfall and low soil moisture occurring since mid-July 2015. Temperature and soil moisture were the key factors governing the daily rate of stem growth in the beginning, rapid growth, and end stages. Overall, due to effects of seasonal drought and low temperature on growth cessation and growth rate, the annual growth of Qinghai spruce was rather low at both low (2500–2700 m a.s.l.) and high (3100–3300 m a.s.l.) elevations; middle elevations (approximately 2900 m a.s.l.) might be the most favorable Qinghai spruce growth. Our results implied that tree growth will likely decline at low elevations and that the optimal elevation for Qinghai spruce growth in northwestern China is expected to shift upward under future climate warming. [ABSTRACT FROM AUTHOR]

A long-standing hypothesis in biogeography predicts that a species' abundance is highest at the center of its geographical range and decreases toward its edges. In this study, we test the abundant-center hypothesis of ectomycorrhizal (ECM) fungal communities associated with Picea crassifolia , an endemic species widely distributed in northwest China. We analyzed the taxonomic richness and the relative abundance of ECM fungi in four main distribution areas, from center to edges. In total, 234 species of ECM fungi were detected, and of these, 137 species were shared among all four sites. Inocybe , Sebacina , Tomentella , and Cortinarius were the dominant genera. ECM fungal richness and biodiversity were highest at the central and lower at peripheral sites. Our results indicated that ECM fungal species richness was consistent with the abundant-center hypothesis , while the relative abundances of individual fungal genera shifted inconsistently across the plant's range. [ABSTRACT FROM AUTHOR]

A long-standing hypothesis in biogeography predicts that a species’ abundance is highest at the center of its geographical range and decreases toward its edges. In this study, we test the abundant-center hypothesis of ectomycorrhizal (ECM) fungal communities associated with Picea crassifolia, an endemic species widely distributed in northwest China. We analyzed the taxonomic richness and the relative abundance of ECM fungi in four main distribution areas, from center to edges. In total, 234 species of ECM fungi were detected, and of these, 137 species were shared among all four sites. Inocybe, Sebacina, Tomentella, and Cortinarius were the dominant genera. ECM fungal richness and biodiversity were highest at the central and lower at peripheral sites. Our results indicated that ECM fungal species richness was consistent with the abundant-center hypothesis, while the relative abundances of individual fungal genera shifted inconsistently across the plant’s range.

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The impact of drought on terrestrial ecosystems is increasing, and the spatiotemporal heterogeneity of drought changes exacerbates the difficulty of determining ecosystem responses, especially in arid regions far from oceans. Tree rings have been widely used to understand how forest ecosystems respond to drought. However, the link between local hydroclimate variations related to tree rings and large-scale climate changes is not clear in the Qilian Mountains. Here, we used the tree ring width index to analyze the trend of Picea crassifolia growth and its relationship with climate in the middle Qilian Mountains. The results showed that the radial growth trend of Picea crassifolia is synchronized in the middle Qilian Mountains by calculating the Gleichläufigkeit index (GLK). Our analyses indicated that tree radial growth is positively correlated with drought during the growing season. Tree growth responds stably to drought (scPDSI and SPEI) and precipitation but unstably to temperature during 1950-2019. We further traced the meteorological factors that cause regional drought changes associated with radial growth. An increased total precipitation and decreased evaporation contribute to drought alleviation, favoring an increased tree radial growth. The increased total precipitation is mainly due to increased large-scale precipitation, which is related to water vapor transport changes. This study attempts to explore the influence of large-scale meteorology on regional drought change and its related tree radial growth response, which helps us to better understand the changes in forest ecosystems under climate change. • Tree radial growth responds stably to drought but not to temperature. • Large-scale precipitation contributes to drought alleviation in northwest China. • This study established a linkage between tree ring width and large-scale signals. [ABSTRACT FROM AUTHOR]

Copyright of Mountain Research (10082786) is the property of Mountain Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Key message: Canopy and stem phenology of Qinghai spruce, central Qilian Mountains, respond to different environmental factors depending on season and elevation. To understand vegetation species response to climate change, much research has been devoted to changes in forest phenology. Results of such studies are not only of scientific interest; they are potentially of great use in forest management. This study focuses on variations in canopy and stem phenology as affected by climate and elevation. We collected data on canopy phenology (as recorded in the Normalized Differential Vegetation Index) and stem phenology [using the Vaganov–Shashkin (V–S) model] in Qinghai spruce (Picea crassifolia) growing at two sites in the central Qilian Mountains, Northeast Tibetan Plateau. One site was at a higher elevation, near the local alpine tree-line, and the other was near the local lower tree-line. At both sites, a significant correlation was found between canopy and stem spring phenology. This would seem to be mainly due to spring temperatures. No such correlation was found between canopy and stem autumn phenology. The study suggests that the main factors affecting stem growth after the beginning of growing season would be temperature and soil moisture, and that these have different effects depending on elevation. At the lower elevation, soil moisture seems to be the main factor limiting growth. At the higher elevation, temperature was the determining factor. Climate change will have different effects depending on elevation. [ABSTRACT FROM AUTHOR]

Highlights • Temporal stability of soil water storage (SWS) in high-elevation forests are analyzed. • Temporal changes and spatial variation of SWS decreased with increasing soil depth. • One time-stable location (TSL) can be representative of the mean SWS. • These TSLs be with average LAI or relatively low canopy interception loss locations. • Temporal stability of SWS was mainly affected by soil and vegetation properties. Abstract Understanding soil water storage (SWS) dynamics in soil profiles is important for hydrological modeling and restoration of vegetation in semi-arid areas. Using the temporal stability method, we aimed to investigate the temporal stability of SWS at 0–40, 40–80, and 80–120 cm depth, and to identify representative sites for reliable estimates of the mean SWS in the permanent forest plot in the Qilian Mountains of China. Further, we wanted to identify correlations between temporal stability of SWS and soil, topography, and properties of the vegetation. Soil water content at soil depths 0–120 (for locations 1–40) and 0–70 cm (for locations 41–60) were measured using time-domain reflectometry (TDR) on 52 dates from 2016 to 2017. Results revealed that time-averaged mean SWS for the three layers differed significantly (P < 0.05), and the temporal changes and spatial variations of the mean SWS all decreased with increasing soil depth. Based on either the Spearman correlation coefficient or the standard deviation of relative difference (SDRD) index, the temporal stability of SWSs within the soil profiles under different soil layers were strong, and the number of time-stable locations increased with increasing soil depth, indicating that the SWS intended to be more temporally stable in deeper soil. One time-stable site can be representative of the mean SWS for multiple soil layers for the whole plot, and can accurately estimate the mean SWS for the three soil layers (R2 > 0.86, P < 0.001). Moreover, these time-stable locations should be those having average LAI, SBD or relatively low canopy interception loss compared to the corresponding field means. Soil bulk density, canopy interception rate, and aboveground biomass of mosses can significantly (P < 0.05) affect the stability of SWSs in this high-elevation forests. Such effects, however, differed among the different soil layers due to different conditions of soil characteristics, distribution of root biomass, and freeze–thawing processes. These results suggest that the influence of vegetation properties of the temporal stability of SWS should attract more attention and that both the relative importance of and interactions among different determining factors is helpful for better understanding the mechanistic determinants of SWS temporal stability in these areas. [ABSTRACT FROM AUTHOR]

Copyright of Forest Research is the property of Forest Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Close-to-nature forest management has been proposed as an effective method for improving the quality of plantation forests. Knowledge of spatial distribution patterns, structure, and succession trajectories in natural forests can provide guidelines for the establishment of close-to-nature forest plantations. Such knowledge is lacking in natural spruce (Picea crassifolia) forests in the Qilian Mountains of China, impeding the establishment of production forests. We conducted a case study in the Qilian Mountains to analyze the relationships between the naturally-formed forest patches and terrain factors, spatial heterogeneity of stand characteristics, and stand structure following harvesting disturbance. Our results suggested that spruce plantations will be effective on the N, NE, and NW slopes, at elevations between 2700 and 3300 m, and on slopes ranging from 15° to 45°. Further, planted forest patches should occupy 64% of the slope area on semi-shady slopes (NE, NW). Spatial patterns in the studied forest exhibited a strong scale-effect, and an area of 0.25 ha could be used as the most efficient plot scale for the management of spruce plantations. Partial logging is an effective method for the conversion of spruce planted forests into nearnatural forests, and the intensity of partial logging can be determined from the negative exponential function relationship between stand density and DBH. Our results provided critical information for the development of spruce plantations and conversion of existing plantations. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Botanical Research is the property of Bulletin of Botanical Research Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The response of radial growth to climate and the climate sensitivity of tree growth at different ages in different drought conditions are essential for predicting forest dynamics and making correct forest management policies. In this study, we analyzed the growth responsiveness of Picea crassifolia Kom. to climate and explored the relationship between age and climate sensitivity of radial growth at the individual tree scale in the wetter eastern area and drier western area of the Qilian Mountains. Pearson correlation coefficients were calculated between the chronology of each tree and climatic factors to examine the climate-growth relationships. Linear fitting, quadratic polynomial fitting and exponential fitting were used to test the relationships between age and mean sensitivity, standard deviation and radial growth's response to climate. Trees in the wetter eastern area showed a weaker response to climate than those in the drier western area and were significantly correlated with precipitation and mean temperature in the previous and current mid-late summer. Trees in the drier western area were mainly limited by precipitation of the previous August, the current May and June, as well as limited by temperature in the previous and current early-middle summer. In the wetter area, the younger trees were more sensitive to both precipitation and temperature than the older trees. In the drier area, younger/older trees showed a stronger sensitivity to precipitation in the current August and September/May, whereas trees 120-140 years old showed a stronger correlation with temperature factors in the summer. It was determined that mature trees in the drier area were more strongly influenced by the climate, especially in the context of increasing temperature. These trees should be paid special attention in forest management. [ABSTRACT FROM AUTHOR]

Carbon storage of mountain forests is vulnerable to climate change but the changes in carbon flux through time are poorly understood. Moreover, the relative contributions to carbon flux of drivers such as climate and atmospheric CO2 still have significant uncertainties. We used the dynamic model LPJ-GUESS with climate data from twelve meteorological stations in the Qilian Mountains, China to simulate changes in carbon mass of a montane boreal forest, and the influence of temperature, precipitation, and CO2 concentration from 1964 to 2013 on carbon flux. The results showed that the carbon mass has increased 1.202 kg/m2 from 1964 to 2013, and net primary productivity (NPP) ranged from 0.997 to 1.122 kg/m2/year. We concluded that the highest carbon mass proportion for this montane boreal forest was at altitudes 2700-3100 m (proportion of ecosystem carbon was between 93-97%), with maximum carbon density observed at 2700-2900 m. In the last 50 years, the increase in precipitation and in CO2 concentration is expected to increase carbon mass and NPP of Picea crassifolia Kom. (Pinaceae) (Qinghai spruce). The effect of temperature on NPP was positive but that on carbon mass was not clear. The increase in CO2 concentration over the past 50 years was a major contributor to the increase in carbon storage, and drought was the foremost limiting factor in carbon storage capacity of this montane boreal forest. Picea crassifolia forest was vulnerable to climate change. Further studies need to focus on the impact of extreme weather, especially drought, on carbon storage in Picea crassifolia forests. [ABSTRACT FROM AUTHOR]

Arceuthobium sichuanense is an aerial parasitic plant (dwarf mistletoe) which causes severe damage to spruce forests on the Qinghai-Tibet Plateau. Picea crassifolia and Picea purpurea, two main host species of A. sichuanense, have different growth characteristics and elevational distributions. The effects of A. sichuanense infection on P. crassifolia and P. purpurea trees were evaluated by examining needle and current-year shoot morphology, needle water use efficiency and needle nitrogen concentration, with 30 needle samples, 30 current-year shoot samples and 10 A. sichuanense aerial shoot samples for each host species. The most apparent effects were significant reductions in both needle size and current-year shoot length. The high degree of correlation in foliar δ N values between the dwarf mistletoe and its host trees indicated that nitrogen in the dwarf mistletoe was derived entirely from its host. Percent reductions in needle and current-year shoot length were smaller for P. purpurea than for P. crassifolia, possibly suggesting that P. purpurea exhibits a lesser capacity to accommodate the parasitic effects of mistletoe infection by adjusting the growth of needles and current-year shoots. The reductions in needle nitrogen concentration and δ C values were lower in P. purpurea than in P. crassifolia, indicating that P. purpurea suffered more nitrogen and water stresses and exhibited lower vigor compared to P. crassifolia. Our results demonstrated that P. purpurea may suffer more negative effects induced by dwarf mistletoe infections at needle and branch levels than P. crassifolia. [ABSTRACT FROM AUTHOR]

Key message: The influence of climate in the previous year on radial growth was stronger than that in the current year and climatic influence became weaker as the altitude increased. Abstract: The climate conditions during the previous year often influence the radial growth of trees in the current year, which is known as the lingering effect of climate. To explore this lingering effect in depth, we compare the influence of climate in the previous and current year on radial growth and find variations in climatic effects on growth along the altitudinal gradient. We also relate radial growth of Picea crassifolia to climate variables from 24 different timescales (from 1 month to the previous 24 months) at different altitudes in the middle of the Qilian Mountains. In the study area, accumulated monthly precipitation before November in the previous year benefited radial growth in the current year at all altitudes. At lower altitudes, July could be seen as a demarcation point that precipitation from the current May-July significantly affected radial growth in the current year, but precipitation from the current July-October significantly affected radial growth in next year. At the same time, radial growth there responded stronger to precipitation from the previous July-October than that from the current May-July. Radial growth at higher altitudes responded weaker to climatic factors than that at lower altitudes and rarely correlated with precipitation from the current year. [ABSTRACT FROM AUTHOR]

Understanding the effects of environmental variables on seedling-sapling distributions can help gain insight into changes in population recruitment in the context of global warming. Six transects were used to survey the distribution of seedling-saplings and the variability in environmental variables along altitudinal gradients. In addition, laboratory experiments measuring the effects of moss on Picea crassifolia seedling emergence were conducted to identify seedling development characteristics of Picea crassifolia . The results show that the seedling-sapling distribution of Picea crassifolia is determined by altitudinal gradients over the large scale and is influenced by moss at the small scale. We found the largest number of seedling-saplings occurring at middle altitudes (3050–3250 m a.s.l.). The crucial abiotic factors in the seedling-sapling distribution for this species are precipitation at lower altitudes and temperature at higher altitudes. Moss mats can promote the recruitment of Picea crassifolia when the moss depth is less than 5 cm and moss cover is less than 50%. Conversely, with increasing moss depth and cover, the effects are shifted towards a negative relationship. Moss can promote moist conditions, implying that recruitment may be facilitated by moss in lower altitude areas where drought stress may occur. However, both air temperature in moss layers and soil temperature below moss are reduced, suggesting that the presence of moss may result in a shortened growing season for Picea crassifolia . More research into the seedling-sapling distribution of Picea crassifolia at both the large and small scales is necessary for artificial forestation and forest management, especially for those alpine plant species that are sensitive to climate change. [ABSTRACT FROM AUTHOR]