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Despite the sensitivity to climate change in the alpine-gorge region on the eastern Qinghai-Tibetan Plateau, comprehensive information on the elevational variation patterns of plant intrinsic water use efficiency (iWUE) and plant nitrogen (N) availability in this region is still lacking. To explore the elevational patterns and their drivers of plant iWUE (calculated from leaf δ13C) and plant N availability (assessed by leaf δ15N) of different plant growth forms, plant iWUE and leaf δ15N of 654 observed samples of 158 species from seven typical vegetation types distributed along the elevation were investigated, and the effects of taxonomic identity, leaf functional traits, soil and climatic factors on them were explored by linear mixed-effects model. It was found that both plant iWUE and leaf δ15N differed significantly among different plant growth forms, with plant iWUE showed shrubs > herbs > trees and leaf δ15N showed herbs > shrubs > trees. The plant iWUE and leaf δ15N showed a U-shaped pattern along elevation, and the elevation patterns of different plant growth forms were consistent. The plant iWUE of different growth forms first decreased and then increased with increasing humidity index, and the humidity index breakpoints of different plant growth forms were different. The leaf δ15N of herbs and shrubs showed a significantly positive correlation with humidity index, whereas the leaf δ15N of trees had an insignificant correlation with humidity index. The elevation variations of plant iWUE and leaf δ15N of different plant growth forms were jointly influenced by biotic (i.e., plant taxonomy and leaf functional traits) and abiotic (i.e., soil and climate) factors, but were mainly determined by biotic factors. Our results showed that the significant coupling between plant iWUE and leaf δ15N did not vary by plant growth forms, thereby suggesting a close link between carbon and N cycles. This study deepens our knowledge regarding elevation variations and their drivers of plant iWUE and leaf δ15N, and confirms the importance of biotic factors on plant iWUE and leaf δ15N variations along elevation gradients in the alpine-gorge region. [ABSTRACT FROM AUTHOR]

Water use efficiency (WUE) is a key physiological trait in studying plant carbon and water relations. However, the determinants of WUE across a large geographical scale are not always clear, limiting our capacity to predict WUE in response to future global climate change. We propose that tree WUE is influenced by calcium (Ca) availability and precipitation. In addition, although it is well-known that transpiration is the major driving force for passive nutrient uptake, the linkage between these two processes has not been well-established. Because Ca uptake is an apoplastic and passive process that purely relies on transpiration, and there is no translocation once assimilated, we further developed a theoretical model to quantify the relationship between tree Ca accumulation and WUE using soil-to-plant calcium ratio (S Ca/ B Ca) and tree WUE derived from δ13C. We tested our theoretical model and predicted relationships using three common tree species across their native habitats in Northern China, spanning 2300 km and a controlled greenhouse experiment with soil Ca concentrations manipulated. We found that tree WUE was negatively related to precipitation of the growing season (GSP) and positively with soil Ca. A multiple regression model and a path analysis suggested a higher contribution of soil Ca to WUE than GSP. As predicted by our theoretical model, we found a positive relationship between WUE and S Ca/ B Ca across their distribution ranges in all three tree species and in the controlled experiment for one selected species. This relationship suggests a tight coupling between water and Ca uptake and the potential use of S Ca/ B Ca to indicate WUE. A negative relationship between S Ca/ B Ca and GSP also suggests a possible decrease in tree Ca accumulation efficiency in a drier future in Northern China. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhiza (AM) and ectomycorrhiza (ECM) are the two most common mycorrhizal types and are paid the most attention to, playing a vital common but differentiated function in terrestrial ecosystems. The leaf carbon isotope ratio (δ13C) is an important factor in understanding the relationship between plants and the environment. In this study, a new database was established on leaf δ13C between AM and ECM plants based on the published data set of leaf δ13C in China's C3 terrestrial plants, which involved 1163 observations. The results showed that the differences in leaf δ13C between AM and ECM plants related closely to life forms. Leaf δ13C of ECM plants was higher than that of AM plants in trees, which was mainly led by the group of evergreen trees. The responses of leaf δ13C to environmental changes were varied between AM and ECM plants. Among the four life forms, leaf δ13C of ECM plants decreased more rapidly than that of AM plants, with an increase of longitude, except for deciduous trees. In terms of the sensitivity of leaf δ13C to temperature changes, AM plants were higher than ECM plants in the other three life forms, although there was no significant difference in evergreen trees. For the response to water conditions, the leaf δ13C of ECM plants was more sensitive than that of AM plants in all life forms, except evergreen and deciduous trees. This study laid a foundation for further understanding the role of mycorrhiza in the relationship between plants and the environment. [ABSTRACT FROM AUTHOR]

Elevation gradients provide natural laboratories for investigating tropical tree ecophysiology in the context of climate warming. Previously observed trends with increasing elevation include decreasing stem diameter growth rates (GR), increasing leaf mass per area (LMA), higher root-to-shoot ratios (R:S), increasing leaf δ13C, and decreasing leaf δ15N. These patterns could be driven by decreases in temperature, lower soil nutrient availability, changes in species composition, or a combination thereof. We investigated whether these patterns hold within the genus Flindersia (Rutaceae) along an elevation gradient (0–1,600 m) in the Australian Wet Tropics. Flindersia species are relatively abundant and are important contributors to biomass in these forests. Next, we conducted a glasshouse experiment to better understand the effects of temperature, soil nutrient availability, and species on growth, biomass allocation, and leaf isotopic composition. In the field, GR and δ15N decreased, whereas LMA and δ13C increased with elevation, consistent with observations on other continents. Soil C:N ratio also increased and soil δ15N decreased with increasing elevation, consistent with decreasing nutrient availability. In the glasshouse, relative growth rates (RGR) of the two lowland Flindersia species responded more strongly to temperature than did those of the two upland species. Interestingly, leaf δ13C displayed an opposite relationship with temperature in the glasshouse compared with that observed in the field, indicating the importance of covarying drivers in the field. Leaf δ15N increased in nutrient-rich compared to nutrient-poor soil in the glasshouse, like the trend in the field. There was a significant interaction for δ15N between temperature and species; upland species showed a steeper increase in leaf δ15N with temperature than lowland species. This could indicate more flexibility in nitrogen acquisition in lowland compared to upland species with warming. The distinguishing feature of a mountaintop restricted Flindersia species in the glasshouse was a very high R:S ratio in nutrient-poor soil at low temperatures, conditions approximating the mountaintop environment. Our results suggest that species traits interact with temperature and nutrient availability to drive observed elevation patterns. Capturing this complexity in models will be challenging but is important for making realistic predictions of tropical tree responses to global warming.

Summary: The least‐cost economic theory of photosynthesis shows that water and nitrogen are mutually substitutable resources to achieve a given carbon gain. However, vegetation in the Sahel has to cope with the dual challenge imposed by drought and nutrient‐poor soils.We addressed how variation in leaf nitrogen per area (Narea) modulates leaf oxygen and carbon isotopic composition (δ18O, δ13C), as proxies of stomatal conductance and water‐use efficiency, across 34 Sahelian woody species.Dryland species exhibited diverging leaf δ18O and δ13C values, indicating large interspecific variation in time‐integrated stomatal conductance and water‐use efficiency. Structural equation modeling revealed that leaf Narea is a pivotal trait linked to multiple water‐use traits. Leaf Narea was positively linked to both δ18O and δ13C, suggesting higher carboxylation capacity and tighter stomatal regulation of transpiration in N‐rich species, which allows them to achieve higher water‐use efficiency and more conservative water use.These adaptations represent a key physiological advantage of N‐rich species, such as legumes, that could contribute to their dominance across many dryland regions. This is the first report of a robust mechanistic link between leaf Narea and δ18O in dryland vegetation that is consistent with core principles of plant physiology. [ABSTRACT FROM AUTHOR]

Understanding the variations in plant traits across elevations may provide valuable insights into the species structure and function of forests and their responses to climate change. To explore the patterns of trait variation across elevations, we analysed 14 leaf and stem traits associated with resource acquisition and stress tolerance in Schima superba Gardner & Champion, Castanopsis chinensis (Sprengel) Hance, and Pinus massoniana Lambert trees at two elevations in a subtropical forest in southern China. Wood density increased, whereas crown width, leaf water potential at 0700 hours (ΨL-0700), and leaf δ18O decreased in high-elevation plants. Vessel diameter, daily maximum sap flux density, leaf δ13C, and leaf C and N concentrations per unit mass were comparable across elevations. We found species-specific variations in specific leaf area, midday leaf water potential, and leaf P concentration across elevations. Decreasing crown width with increasing elevation was associated with decreasing leaf δ18O and ΨL-0700, suggesting that higher stomatal conductance may moderate the loss of carbon assimilation. We elucidated the adaptive strategies of plants in response to environmental change, and showed that physiological traits varied in coordination with structural traits. Future studies incorporating multi-dimensional trait analyses can improve our understanding of the responses of forest ecosystems to climate change and global warming. [ABSTRACT FROM AUTHOR]

Parasitic plants are known for their high transpiration rates and low water use efficiency (WUE), which the N-parasitism hypothesis posits is driven by N limitation. Thus, availability of N-fixing hosts may affect parasite's WUE and in turn impact the surrounding plant community. Here, I investigate how the availability of an N-fixing host affects the root hemiparasite, Castilleja applegatei, and examines host-mediated effects on community structure and soil moisture. I surveyed plant diversity and percent cover and measured soil moisture in 120 1 × 1 m plots within Sagehen Experimental Forest, CA. Fifty percent of the plots included C. applegatei. In a subset of plots, I measured leaf N, C/N, δ13C, and δ15N in C. applegatei and in one N-fixer (Ceanothus prostratus) and two non-N-fixing plants (Artemisia tridentata and Wyethia mollis). In C. applegatei availability of N-fixing hosts corresponded to a significant increase in leaf %N, a distinct δ15N signature, and an increase in δ13C (which typically signifies an increased WUE). The presence of parasites was associated with a marginally significant decrease in WUE in N-fixing neighbors, but had no effect on the two non-N-fixing species. The presence of parasites did not impact diversity, percent cover, or soil moisture. These results broadly support the N-parasitism hypothesis and indicate that host type can affect parasite's physiology and therefore have the potential to mediate parasite's effects in the community; however, community-level impacts were not found here. [ABSTRACT FROM AUTHOR]

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Arbuscular mycorrhiza (AM) and ectomycorrhiza (ECM) are the two most common mycorrhizal types and are paid the most attention to, playing a vital common but differentiated function in terrestrial ecosystems. The leaf carbon isotope ratio (δ13C) is an important factor in understanding the relationship between plants and the environment. In this study, a new database was established on leaf δ13C between AM and ECM plants based on the published data set of leaf δ13C in China’s C3 terrestrial plants, which involved 1163 observations. The results showed that the differences in leaf δ13C between AM and ECM plants related closely to life forms. Leaf δ13C of ECM plants was higher than that of AM plants in trees, which was mainly led by the group of evergreen trees. The responses of leaf δ13C to environmental changes were varied between AM and ECM plants. Among the four life forms, leaf δ13C of ECM plants decreased more rapidly than that of AM plants, with an increase of longitude, except for deciduous trees. In terms of the sensitivity of leaf δ13C to temperature changes, AM plants were higher than ECM plants in the other three life forms, although there was no significant difference in evergreen trees. For the response to water conditions, the leaf δ13C of ECM plants was more sensitive than that of AM plants in all life forms, except evergreen and deciduous trees. This study laid a foundation for further understanding the role of mycorrhiza in the relationship between plants and the environment.

Climate change will increase uncertainty in restoration outcomes due to greater water stress and other abiotic filters that limit plant survival. Drought‐related plant functional traits can help species withstand filters in a semi‐arid environment. Our objective was to provide guidance for selecting species to improve restoration success in a changing climate.We planted 12 native species in ambient rainfall and under 60% rain‐out shelters in an invaded coastal grassland in central California. We measured survival and size annually for 4 years and quantified plant community and trait composition in the third and fourth years. We measured growth rate, specific leaf area (SLA), leaf C:N, leaf lobedness and leaf δ13C of all planted species and dominant extant species, and evaluated the effect of treatments, traits and phylogenetics on mortality risk using Cox proportional hazards.Native perennial species cover was greater, whereas thatch depth and per cent cover of shrubs and non‐native annual grasses were lower, on drought plots. Drought plots had lower community‐weighted leaf C:N and higher leaf lobedness.Planted species with resource conservative traits, such as higher leaf lobedness and lower growth rate, had lower mortality risk. Increased plasticity of morphological traits (SLA and lobedness) was associated with decreased mortality risk, whereas increased plasticity of physiological traits (leaf C:N and δ13C) and risk was positively correlated. Trait plasticity explained a greater degree of plant mortality risk compared to absolute trait values.Plants that were more phylogenetically related to the surrounding plant community had lower mortality risk. Traits of planted species that were important for determining plant mortality in this coastal grassland may be conserved, which was supported by a phylogenetic signal (Blomberg's K = 0.380, Pagel's λ = 0.830) in leaf C:N.Synthesis and applications. Our results suggest that leaf traits and phylogenetics could serve as plant selection criteria for reducing plant mortality risk during drought, thereby improving restoration outcomes. Because some traits have a phylogenetic signal that explains drought survival, restoration practitioners could expand the use of trait‐based selection for closely related species when restoring other arid‐ and semi‐arid ecosystems. ​ [ABSTRACT FROM AUTHOR]

Aims Both dominance distribution of species and the composition of the dominant species determine the distribution of traits within community. Leaf carbon (C) and nitrogen (N) isotopic composition are important leaf traits, and such traits of dominant species are associated with ecosystem C, water and N cycling. Very little is known how dominant species with distinct traits (e.g. N-fixing leguminous and non-leguminous trees) mediate resource utilization of the ecosystems in stressful environment. Methods Leaves of 81 dominant leguminous and non-leguminous trees were collected in forest (moist semi-deciduous and dry semi-deciduous ecosystems) and savanna (costal savanna, Guinean savanna and west Sudanian savanna ecosystems) areas and the transitional zone (between the forest and the savanna) along the transect from the south to the north of Ghana. We measured leaf traits, i.e. leaf δ13C, leaf δ15N, leaf water content, leaf mass per area (LMA) and C and N concentration. Correlation analyses were used to examine trait- trait relationships, and relationships of leaf traits with temperature and precipitation. We used analysis of covariance to test the differences in slopes of the linear regressions between legumes and non-legumes. Important Findings Leaf δ13C, δ15N, leaf water content and LMA did not differ between leguminous and non-leguminous trees. Leaf N concentration and C:N ratio differed between the two groups. Moreover, leaf traits varied significantly among the six ecosystems. δ13C values were negatively correlated with annual precipitation and positively correlated with mean annual temperature. In contrast, leaf δ15N of non-leguminous trees were positively correlated with annual precipitation and negatively correlated with mean annual temperature. For leguminous trees, such correlations were not significant. We also found significant coordination between leaf traits. However, the slopes of the linear relationships were significantly different between leguminous and non-leguminous trees. Our results indicate that shifts in dominant trees with distinct water-use efficiency were corresponded to the rainfall gradient. Moreover, leguminous trees, those characterized with relative high water-use efficiency in the low rainfall ecosystems, were also corresponded to the relative high N use efficiency. The high proportion of leguminous trees in the savannas is crucial to mitigate nutrient stress. [ABSTRACT FROM AUTHOR]

Drought-induced events of massive tree mortality appear to be increasing worldwide. Species-specific vulnerability to drought mortality may alter patterns of species diversity and affect future forest composition. We have explored the consequences of the extreme drought of 2005, which caused high sapling mortality (approx. 50 %) among 10-year-old saplings of two coexisting pine species in the Mediterranean mountains of Sierra Nevada (Spain): boreo-alpine Pinus sylvestris and Mediterranean P. nigra. Sapling height growth, leaf δ 13C and δ 18O, and foliar nitrogen concentration in the four most recent leaf cohorts were measured in dead and surviving saplings. The foliar isotopic composition of dead saplings (which reflects time-integrated leaf gas-exchange until mortality) displayed sharp increases in both δ 13C and δ 18O during the extreme drought of 2005, suggesting an important role of stomatal conductance (g s) reduction and diffusional limitations to photosynthesis in mortality. While P. nigra showed decreased growth in 2005 compared to the previous wetter year, P. sylvestris maintained similar growth levels in both years. Decreased growth, coupled with a sharper increase in foliar δ 18O during extreme drought in dead saplings, indicate a more conservative water use strategy for P. nigra. The different physiological behavior of the two pine species in response to drought (further supported by data from surviving saplings) may have influenced 2005 mortality rates, which contributed to 2.4-fold greater survival for P. nigra over the lifespan of the saplings. This species-specific vulnerability to extreme drought could lead to changes in dominance and distribution of pine species in Mediterranean mountain forests. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ground cover rice production system increase grain yield by 18% at regional scales. [•] Success of GCRPS is depending on suitable water management avoiding excess water. [•] GCRPS is an invaluable technique in regions where temperature and water limited. [ABSTRACT FROM AUTHOR]

Global change factors affect plant carbon uptake in concert. In order to investigate the response directions and potential interactive effects, and to understand the underlying mechanisms, multifactor experiments are needed. The focus of this study was on the photosynthetic response to elevated CO2 [CO2; free air CO2 enrichment (FACE)], drought (D; water-excluding curtains), and night-time warming (T; infrared-reflective curtains) in a temperate heath. A/Ci curves were measured, allowing analysis of light-saturated net photosynthesis (Pn), light- and CO2-saturated net photosynthesis (Pmax), stomatal conductance (gs), the maximal rate of Rubisco carboxylation (Vcmax), and the maximal rate of ribulose bisphosphate (RuBP) regeneration (Jmax) along with leaf δ13C, and carbon and nitrogen concentration on a monthly basis in the grass Deschampsia flexuosa. Seasonal drought reduced Pn via gs, but severe (experimental) drought decreased Pn via a reduction in photosynthetic capacity (Pmax, Jmax, and Vcmax). The effects were completely reversed by rewetting and stimulated Pn via photosynthetic capacity stimulation. Warming increased early and late season Pn via higher Pmax and Jmax. Elevated CO2 did not decrease gs, but stimulated Pn via increased Ci. The T×CO2 synergistically increased plant carbon uptake via photosynthetic capacity up-regulation in early season and by better access to water after rewetting. The effects of the combination of drought and elevated CO2 depended on soil water availability, with additive effects when the soil water content was low and D×CO2 synergistic stimulation of Pn after rewetting. The photosynthetic responses appeared to be highly influenced by growth pattern. The grass has opportunistic water consumption, and a biphasic growth pattern allowing for leaf dieback at low soil water availability followed by rapid re-growth of active leaves when rewetted and possibly a large resource allocation capability mediated by the rhizome. This growth characteristic allowed for the photosynthetic capacity up-regulations that mediated the T×CO2 and D×CO2 synergistic effects on photosynthesis. These are clearly advantageous characteristics when exposed to climate changes. In conclusion, after 1 year of experimentation, the limitations by low soil water availability and stimulation in early and late season by warming clearly structure and interact with the photosynthetic response to elevated CO2 in this grassland species. [ABSTRACT FROM PUBLISHER]

Recent advances in optical designs and electronic circuits have allowed the transition from passive to active proximal sensors. Instead of relying on the reflectance of natural sunlight, the active sensors measure the reflectance of modulated light from the crop and so they can operate under all lighting conditions. This study compared the potential of active and passive canopy sensors for predicting biomass production in 25–32 randomly selected positions of a Merlot vineyard. Both sensors provided estimates of the normalized difference vegetation index (NDVI) from a nadir view of the canopy at veraison that were good predictors of pruning weight. Although the red NDVI of the passive sensors explained more of the variation in biomass ( R2 = 0.82), its relationship to pruning weight was nonlinear and was best described by a quadratic regression (NDVI = 0.55 + 0.50 wt−0.21 wt2). The theoretically greater linearity of the amber NDVI-biomass relationship could not be verified under conditions of high biomass. The linear correlation to stable isotope content in leaves (13C and 15N) provided evidence that canopy reflectance detected plant stresses as a result of water shortage and limited fertilizer N uptake. Thus, the canopy reflectance data provided by these mobile sensors can be used to improve site-specific management practices of vineyards. [ABSTRACT FROM AUTHOR]

The article presents a study which examined the ecophysiology of riparian cottonwood and willow in the southwestern U.S. forests within four growing seasons and two-year removal of soil water. The study showed the linkage between surface moisture and tree ecophysiology, and the impact of soil water deficits on riparian ecosystem. The study revealed the sensitivity of cottonwood to interannual water depletion as well as the sensitivity of willow to soil water reduction for a longer time.

• Water use strategies of three economic tree species were investigated. • Peach, walnut, and apple trees have different water use strategies. • Walnut trees have greater ecological plasticity by absorbing more deep soil water. • Peach and apple trees have higher water use efficiencies than walnut trees. Economic tree species growing in the semi-arid Loess Plateau of China are important for maintaining sound economic viability and protecting the fragile hydro-ecological environment. However, their water use strategies and ecological adaptation to dryland environments remain poorly understood. In this study, we measured variations in soil water content, root distribution, water isotopic signature for hydrogen (δ2H) and oxygen (δ18O) in xylem and soil water of peach (Prunus persica), walnut (Juglans regia L.), and apple (Malus pumila) trees, as well as carbon isotopic signature (δ13C) in their leaves during two consecutive growing seasons—2018 (normal year) and 2019 (wet year). The results showed all species consumed less deep soil water in 2019 than in 2018 due to the increased precipitation. Peach trees used more shallow soil water compared to walnut and apple trees that used more deep soil water during high water-demanding periods. Walnut trees depended more on deep soil water throughout the growing season, contributing 46.2% in 2018, compared to 26.0% for peach trees and 24.0% for apple trees. Moreover, walnut trees had lower deep soil water and leaf δ13C than peach and apple trees. The findings suggest differences in phenology periods of the three rainfed economic tree species to affect the water source used. The three tree species differed in their water use strategies: walnut trees had ecological plasticity for reducing water stress by absorbing deep soil water, and peach and apple trees had higher water use efficiencies. This study has significance for evaluating water use characteristics and drought stress responses of economic trees in water-limited environments. [ABSTRACT FROM AUTHOR]

• Leaf δ15N was mainly affected by soil ectomycorrhizal fungi. • Biogeographic patterns for soil fungal guilds in forests of China. • Biogeographic patterns for leaf δ15N and δ13C in forests of China. • The linkage between leaf δ15N, δ13C and soil fungi of forests. Leaf δ15N and δ13C are important functional traits in biogeographic studies of forest ecosystems. However, little is known about their relationships with soil fungal biodiversity, ectomycorrhizal and plant pathogenic abundance at large scales. In this study, leaf and soil samples were collected from 33 forest reserves along a large range across China to explore the associations between leaf δ15N and δ13C and soil fungal biodiversity, ectomycorrhizal and plant pathogenic relative abundance, using molecular and stable isotope techniques. Leaf δ15N was significantly positively correlated with the soil fungal Shannon index, significantly negatively correlated with the relative abundance of plant pathogens, and significantly positively correlated with the relative abundance of ectomycorrhizas. Leaf δ13C was significantly positively correlated with the relative abundance of ectomycorrhizas and significantly inverted unimodal correlated with the relative abundance of plant pathogens. Soil–plant–microbial interactions may contribute to variations in leaf δ15N, δ13C, and soil fungal communities among different types of forest ecosystems. Temperature and precipitation were the main factors that affected large-scale latitudinal and longitudinal biogeographic patterns. Leaf δ15N was mainly affected by the relative abundance of ectomycorrhizal fungi and leaf δ13C was affected by the mean annual temperature and mean annual precipitation. Leaf δ15N and δ13C may be indicators that reflect soil fungal communities in forest ecosystems. [ABSTRACT FROM AUTHOR]

• Mountain ecosystems of Central Asia are a biodiversity hotspot under climatic risk. • Lagochilus species are key medicinal herbaceous plants native to Central Asia. • Lagochilus climate sensitivity was assessed by population structure and carbon 13. • Lagochilus populations regeneration and carbon 13 were highly sensitive to drought. • Conservation of Lagochilus should become a priority in drying Central Asia. The high-mountain ecosystems of Central Asia are a biodiversity hotspot with unique plant communities and many endemic species. Intense human pressure and global warming have caused habitat destruction in these areas and a parallel increase in the number of endangered species. Lagochilus species are key medicinal herbaceous plants native to Central Asia, many of which have been recently added to the endangered of species in Uzbekistan. To assess the climate sensitivity of Lagochilus species, we (1) located populations of six species in their native sites across Uzbekistan, and assessed their health by partitioning to ontogenetic stages along five consecutive years; (2) collected plant materials from these species, as well as from old herbarium samples (1918–1964); and (3) analyzed the carbon-13 composition in those samples, as an indicator for drouht stress. Over the course of five years (2014–2018) of continuous monitoring, fluctuations in annual precipitation in the region indicated a decrease by ∼20 %, and the fraction of young plants in each population decreased from 20–50% to 0–5 %, depending on the species. Comparing the carbon-13 composition in current and historical leaf samples showed an increase of 1.5–3.5‰ associated with a decrease in precipitation of 2–30 %, depending on the site and species. Our results show the high sensitivity of Lagochilus populations' regeneration to drying, among six species and in sites across Uzbekistan. On a multi-decadal temporal scale, the dramatic changes in carbon-13 indicate that the response to precipitation reduction is related with drought stress. Considering the expectation for drier and hotter climate in Uzbekistan in the coming decades, conservation of Lagochilus populations should become a priority in Central Asia. [ABSTRACT FROM AUTHOR]

Leaf stable isotope compositions (δ13C and δ15N) are influenced by various abiotic and biotic factors. Qinghai spruce (Picea crassifolia Kom.) as one of the dominant tree species in Qilian Mountains plays a key role in the ecological stability of arid region in the northwest of China. However, our knowledge of the relative importance of multiple factors on leaf δ13C and δ15N remains incomplete. In this work, we investigated the relationships of δ13C and δ15N to leaf age, tree age and leaf nutrients to examine the patterns and controls of leaf δ13C and δ15N variation of Picea crassifolia. Results showed that 13C and 15N of current-year leaves were more enriched than older ones at each tree age level. There was no significant difference in leaf δ13C values among trees of different ages, while juvenile trees (<50 years old) were 15N depleted compared to middle-aged trees (50–100 years old) at each leaf age level except for 1-year-old leaves. Meanwhile, relative importance analysis has demonstrated that leaf age was one of the most important indicators for leaf δ13C and δ15N. Moreover, leaf N concentrations played a dominant role in the variations of δ13C and δ15N. Above all, these results provide valuable information on the eco-physiological responses of P. crassifolia in arid and semi-arid regions. [ABSTRACT FROM AUTHOR]