Recovery of the topological charge of a vortex beam propagated through a scattering layer.

Coherent vortex beams have shown great potential in many applications including information transmission under non-ideal conditions, as information can be encoded in the orbital angular momentum. However, inhomogeneity of atmosphere tends to scramble the vortex structure and give rise to speckle. It is therefore of great interest to reconstruct the topological charge of a vortex beam after it propagates through a scattering medium. Here, we propose a feasible solution for this. The proposed method measures holographically the scattered field and reconstructs the spiral phase from it by taking advantage of both the deterministic nature and the ergodicity of the scattering process. Our preliminary experiments show promising results and suggest that the proposed method can have great potential in information transmission under non-ideal conditions.

Influence of multiple global change drivers on terrestrial carbon storage: additive effects are common.

The interactive effects of multiple global change drivers on terrestrial carbon (C) storage remain poorly understood. Here, we synthesise data from 633 published studies to show how the interactive effects of multiple drivers are generally additive (i.e. not differing from the sum of their individual effects) rather than synergistic or antagonistic. We further show that (1) elevated CO2 , warming, N addition, P addition and increased rainfall, all exerted positive individual effects on plant C pools at both single-plant and plant-community levels; (2) plant C pool responses to individual or combined effects of multiple drivers are seldom scale-dependent (i.e. not differing from single-plant to plant-community levels) and (3) soil and microbial biomass C pools are significantly less sensitive than plant C pools to individual or combined effects. We provide a quantitative basis for integrating additive effects of multiple global change drivers into future assessments of the C storage ability of terrestrial ecosystems.

Cyphertext-only attack on the double random-phase encryption: Experimental demonstration.

We demonstrate experimentally that the traditional double random phase encoding (DPRE) technique is vulnerable to the cyphertext-only attack (COA). With the statistical ergodic property of the speckle, we show that the plaintext image can be recovered from the cyphertext alone owing to the fact that their energy spectral density functions are identical. Our result reveals the most serious security issue with the DRPE as it suggests that even the one-time-pad does not guarantee its security. This will open up new inside understanding of current optical security techniques.

Effects of three global change drivers on terrestrial C:N:P stoichiometry: a global synthesis.

Over the last few decades, there has been an increasing number of controlled-manipulative experiments to investigate how plants and soils might respond to global change. These experiments typically examined the effects of each of three global change drivers [i.e., nitrogen (N) deposition, warming, and elevated CO2 ] on primary productivity and on the biogeochemistry of carbon (C), N, and phosphorus (P) across different terrestrial ecosystems. Here, we capitalize on this large amount of information by performing a comprehensive meta-analysis (>2000 case studies worldwide) to address how C:N:P stoichiometry of plants, soils, and soil microbial biomass might respond to individual vs. combined effects of the three global change drivers. Our results show that (i) individual effects of N addition and elevated CO2 on C:N:P stoichiometry are stronger than warming, (ii) combined effects of pairs of global change drivers (e.g., N addition + elevated CO2 , warming + elevated CO2 ) on C:N:P stoichiometry were generally weaker than the individual effects of each of these drivers, (iii) additive interactions (i.e., when combined effects are equal to or not significantly different from the sum of individual effects) were more common than synergistic or antagonistic interactions, (iv) C:N:P stoichiometry of soil and soil microbial biomass shows high homeostasis under global change manipulations, and (v) C:N:P responses to global change are strongly affected by ecosystem type, local climate, and experimental conditions. Our study is one of the first to compare individual vs. combined effects of the three global change drivers on terrestrial C:N:P ratios using a large set of data. To further improve our understanding of how ecosystems might respond to future global change, long-term ecosystem-scale studies testing multifactor effects on plants and soils are urgently required across different world regions.

Simple additive simulation overestimates real influence: altered nitrogen and rainfall modulate the effect of warming on soil carbon fluxes.

Experiments and models have led to a consensus that there is positive feedback between carbon (C) fluxes and climate warming. However, the effect of warming may be altered by regional and global changes in nitrogen (N) and rainfall levels, but the current understanding is limited. Through synthesizing global data on soil C pool, input and loss from experiments simulating N deposition, drought and increased precipitation, we quantified the responses of soil C fluxes and equilibrium to the three single factors and their interactions with warming. We found that warming slightly increased the soil C input and loss by 5% and 9%, respectively, but had no significant effect on the soil C pool. Nitrogen deposition alone increased the soil C input (+20%), but the interaction of warming and N deposition greatly increased the soil C input by 49%. Drought alone decreased the soil C input by 17%, while the interaction of warming and drought decreased the soil C input to a greater extent (-22%). Increased precipitation stimulated the soil C input by 15%, but the interaction of warming and increased precipitation had no significant effect on the soil C input. However, the soil C loss was not significantly affected by any of the interactions, although it was constrained by drought (-18%). These results implied that the positive C fluxes-climate warming feedback was modulated by the changing N and rainfall regimes. Further, we found that the additive effects of [warming × N deposition] and [warming × drought] on the soil C input and of [warming × increased precipitation] on the soil C loss were greater than their interactions, suggesting that simple additive simulation using single-factor manipulations may overestimate the effects on soil C fluxes in the real world. Therefore, we propose that more multifactorial experiments should be considered in studying Earth systems.

Variations in bacterial communities during foliar litter decomposition in the winter and growing seasons in an alpine forest of the eastern Tibetan Plateau.

Bacterial communities are the primary engineers during litter decomposition and related material cycling, and they can be strongly controlled by seasonal changes in temperature and other environmental factors. However, limited information is available on changes in the bacterial community from winter to the growing season as litter decomposition proceeds in cold climates. Here, we investigated the abundance and structure of bacterial communities using real-time quantitative PCR and denaturing gradient gel electrophoresis (DGGE) during a 2-year field study of the decomposition of litter of 4 species in the winter and growing seasons of an alpine forest of the eastern Tibetan Plateau. The abundance of the bacterial 16S rRNA gene was relatively high during decomposition of cypress and birch litter in the first winter, but for the other litters 16S rRNA abundance during both winters was significantly lower than during the following growing season. A large number of bands were observed on the DGGE gels, and their intensities and number from the winter samples were lower than those from the growing season during the 2-year decomposition experiment. Eighty-nine sequences from the bands of bacteria that had been cut from the DGGE gels were affiliated with 10 distinct classes of bacteria and an unknown group. A redundancy analysis indicated that the moisture, mass loss, and elemental content (e.g., C, N, and P) of the litter significantly affected the bacterial communities. Collectively, the results suggest that uneven seasonal changes in climate regulate bacterial communities and other decomposers, thus affecting their contribution to litter decomposition processes in the alpine forest.

Cadmium contamination of soil and crops is affected by intercropping and rotation systems in the lower reaches of the Minjiang River in south-western China.

Cadmium (Cd) accumulation and pollution in arable soils are particularly serious in the lower reaches of the Minjiang River in southwest of China. In this study, the remediation efficiency of Cd contamination in arable soils, the distribution pattern of Cd concentration in crops, and the food safety to humans of three typical cropping systems (S1: maize + sweet potato-Chinese cabbage, S2: maize + ginger-stem mustard, and S3: rice) were investigated and evaluated. After 1-year rotation, the percentage of Cd extracted by crops from the plough soil layer was observed in three system fields with the trend of S1 (2.30 %) > S2 (1.16 %) > S3 (0.21 %) and Cd extraction amount in crops was maximum in sweet potato, then in maize. The same kind of crop had the same pattern of Cd distribution in organs, and the edible parts generally accumulated less Cd amount than the inedible parts. Further, the grain crops were found to possibly be suitable one for using as phytoaccumulators of Cd contamination for farmlands. Direct consumption of these crops from the three systems would pose a high health risk to local inhabitants since it would result in the monthly intake of Cd (247 µg kg(-1) body weight) being nearly 10 times higher than the recommended tolerable monthly intake (RTMI) (25 µg kg(-1) body weight), resulting mainly from the consumption of vegetables rather than the grains, which would be potentially reduced by these foods being consumed by livestock firstly.

The effects of arbuscular mycorrhizal fungi on sex-specific responses to Pb pollution in Populus cathayana.

Using fast-growing trees to remediate soils polluted by heavy metals (HMs) has received increasingly more attention, especially for recalcitrant Pb, as one of the most seriously toxic HMs. However, little is known about the responses of plants to a diffused level of Pb pollution, and a more combined phytoremediation technique is needed to explore. In this study, an arbuscular mycorrhizal fungus (AMF), i.e., Funneliformis mosseae, isolated from Populus euphratica distributed in a tailing of Pb/Zn ore, was introduced to investigate its effects on sex-specific responses of P. cathayana in morphology, physiology, and Pb phytoremediation capacity, when exposed to a diffused level of Pb pollution (100mg Pb(2+) kg(-1) dry soil). Symbiosis with exotic AMF did not significantly affect growth of both sexes and biomass allocation. However, when inoculated with AMF, both sexes absorbed more P, but not N in the roots, especially when exposed to the exogenous addition of Pb. The improvement of nutrient status under such conditions might be associated with a further increase in activity of antioxidant enzymes (particularly for superoxide dismutase (SOD) and catalase (CAT)), and the mitigation of oxidation stress induced by excessive reactive oxygen species (ROS). We also observed that exotic AMF could promote the uptake and accumulation of Pb in roots of females, but not in that of males. Therefore, under this diffused pollution level, the infected females might be more suitable for remediation of this metal than infected males, due to the higher capacity of HM accumulation without obvious negative effects on growth and physiological traits. Moreover, field surveys are needed to testify our experimental results, due to diversity of soil microbial community and complexities of their interaction.

Abundance and composition dynamics of soil ammonia-oxidizing archaea in an alpine fir forest on the eastern Tibetan Plateau of China.

Real-time qPCR and clone library sequencing targeting amoA genes were used to investigate the seasonal dynamics of an ammonia-oxidizing archaea (AOA) community in an alpine fir forest in western China. AOA were detected at all sampling dates, and there were significant variations in archaeal amoA gene copy numbers (7.63 × 10(5) to 8.35 × 10(8) per gram of dry soil) throughout the nongrowing season. Compared with ammonia-oxidizing bacteria (AOB), the AOA displayed a higher abundance on the majority of sampling dates during the freeze-thaw period. All of the AOA sequences fell within soil and sediment lineages and were affiliated with 7 clusters. Compared with the other clusters, cluster 1 was more sensitive to low temperature and was the dominant group in August. In contrast, cluster 3 dominated the AOA community in winter and probably represents a group of cold-adapted archaea. Redundancy analysis (RDA) revealed that the seasonality of the AOA community was mainly attributed to changes in soil temperature and nutrient availability (e.g., dissolved organic nitrogen and carbon). Our results indicate that AOA exist in frozen soils in the alpine coniferous forest ecosystem of the eastern Tibetan Plateau. Moreover, soil temperature may directly and (or) indirectly affect AOA abundance and composition and may further influence the soil N cycle during the winter.

Phylogeny of Libellulidae (Odonata: Anisoptera): comparison of molecular and morphology-based phylogenies based on wing morphology and migration.

BACKGROUND: Establishing the species limits and resolving phylogenetic relationships are primary goals of taxonomists and evolutionary biologists. At present, a controversial question is about interspecific phylogenetic information in morphological features. Are the interspecific relationships established based on genetic information consistent with the traditional classification system? To address these problems, this study analyzed the wing shape structure of 10 species of Libellulidae, explored the relationship between wing shape and dragonfly behavior and living habits, and established an interspecific morphological relationship tree based on wing shape data. By analyzing the sequences of mitochondrial COI gene and the nuclear genes 18S, 28S rRNA and ITS in 10 species of dragonflies, the interspecific relationship was established. METHOD: The wing shape information of the male forewings and hindwings was obtained by the geometric morphometrics method. The inter-species wing shape relationship was obtained by principal component analysis (PCA) in MorphoJ1.06 software. The inter-species wing shape relationship tree was obtained by cluster analysis (UPGMA) using Mesquite 3.2 software. The COI, 18S, ITS and 28S genes of 10 species dragonfly were blasted and processed by BioEdit v6 software. The Maximum Likelihood(ML) tree was established by raxmlGUI1.5b2 software. The Bayes inference (BI) tree was established by MrBayes 3.2.6 in Geneious software. RESULTS: The main difference in forewings among the 10 species of dragonfly was the apical, radial and discoidal regions dominated by the wing nodus. In contrast, the main difference among the hindwings was the apical and anal regions dominated by the wing nodus. The change in wing shape was closely related to the ability of dragonfly to migrate. The interspecific relationship based on molecular data showed that the species of Orthetrum genus branched independently of the other species. Compared to the molecular tree of 10 species, the wing shape clustering showed some phylogenetic information on the forewing shape (with large differences on the forewing shape tree vs. molecular tree), and there was no interspecific phylogenetic information of the hindwing shape tree vs. molecular tree. CONCLUSION: The dragonfly wing shape characteristics are closely related to its migration ability. Species with strong ability to migrate have the forewing shape that is longer and narrower, and have larger anal region, whereas the species that prefer short-distance hovering or standing still for a long time have forewing that are wider and shorter, and the anal region is smaller. Integrating morphological and molecular data to evaluate the relationship among dragonfly species shows there is some interspecific phylogenetic information in the forewing shape and none in the hindwing shape. The forewing and hindwing of dragonflies exhibit an inconsistent pattern of morphological changes in different species.

Reports of two peculiar pigmented new species of genus Homidia (Collembola: Entomobyridae) from Southern China, with description of subadults chaetotaxy.

Two new species with peculiar pigmentation of the genus Homidia from Guangdong Province, Southern China are described here, Homidia chroma sp. nov. and Homidia leniseta sp. nov. H. chroma is characterized by chrome pigmentation on lateral side of terga, two macrochaetae on medial abdominal segment (Abd.) III and six macrochaetae on postero-medial Abd. IV, up to 68 sensory chaetae present on Abd. IV, and five apical smooth chaetae on posterior face of ventral tube. H. leniseta is easily identified by unique colour pattern, smooth labial chaetae l2, G1-4 and H1-3, and short trichobothria on Abd. II-IV. Illustrations of adults of this two new species, chaetotaxy of the first instar larvae of H. chroma and subadults of H. leniseta are provided herein.

Litter removal reduced soil nitrogen mineralization in repeated freeze-thaw cycles.

Repeated freeze-thaw cycles (FTCs) can alter the relationships between plant litter and soil nitrogen (N) mineralization in subalpine ecosystems, but little information is available about the underlying mechanisms. Therefore, a controlled soil incubation experiment was carried out to study the effects of litter removal on soil N mineralization during FTCs, and the results indicated that FTCs promoted soil N mineralization more than the continuously frozen or nonfrozen condition did. Litter removal promoted soil ammonium N (NH4+-N) and dissolved organic N (DON) as well as the cumulative N mineralization (CNM) and ammonification, but it reduced the soil microbial biomass N (MBN) in the early stage of FTCs. With an increasing number of FTCs, litter removal significantly reduced the CNM but increased the soil MBN. The modified first-order kinetics model was verified under incubation conditions and predicted a lower soil N mineralization rate in FTCs with litter removal. In addition, the dominant factor impacting soil N mineralization was soil NO3--N, and soil MBN had a greater influence on soil N mineralization when litter remained than when it was removed. These results further clarify the mechanism driving the effect of plant residues on soil N cycling.

Effects of naphthalene on soil fauna abundance and enzyme activity in the subalpine forest of western Sichuan, China.

Naphthalene has been widely used to study the role of soil fauna, but its potential non-target effects on soil enzyme activity remain unknown in subalpine forests. We added naphthalene for two years and determined the effect of such additions on the abundance of soil fauna and soil enzyme activities (ß-glucosidase, cellobiohydrolase, invertase, peroxidase, polyphenol oxidase, N-acetyl-ß-D-glucosaminidase, leucine arylamidase, urease, nitrate reductase and nitrite reductase) in a subalpine forest. Naphthalene could efficiently suppress the individual density and population of soil fauna in situ. The individual density and number of groups were decreased by 72.6-84.8% and 15.0-28.0%, respectively. Naphthalene significantly affected the activities of ß-glucosidase, cellobiohydrolase, polyphenol oxidase, N-acetyl-ß-D-glucosaminidase, leucine arylamidase and nitrite reductase and the activity increased in the first litter peak of naphthalene addition, and decreased at the later. The activities of ß-glucosidase, cellobiohydrolase, polyphenol oxidase, peroxidase, N-acetyl-ß-D-glucosaminidase, leucine arylamidase and nitrite reductase showed a negative correlation with the soil microbial PLFAs. Conversely, the activities of invertase, urease and nitrate reductase were positively correlated with the soil microbial PLFAs. Our results suggest that naphthalene is an effective method to reduce soil fauna in subalpine forest. The enzyme activity was influenced by soil fauna and microbial PLFAs.

Immobilization of heavy metals during aquatic and terrestrial litter decomposition in an alpine forest.

Plant litter decomposition is an important pathway of heavy metal cycling in forested soil and watershed ecosystems globally, but is so far an overlooked aspects in the existing literature. To investigate the temporal dynamics of heavy metals in decomposing litter, we conducted a two-year field experiment using litterbag method across aquatic and terrestrial ecosystems in an alpine forest on the eastern Tibetan Plateau. Using multigroup comparisons of structural equation modeling with different litter mass-loss intervals, we assessed the direct and indirect effects of several biotic and abiotic factors on the release rates of lead (Pb), cadmium (Cd), and chromium (Cr). Results suggested that both the concentrations and amounts of Pb, Cd, and Cr increased during litter decomposition regardless of ecosystem type and litter species, showing an immobilization pattern. The release rates of Pb, Cd, or Cr shared a common hierarchy of drivers across aquatic and terrestrial ecosystems, with environmental factors and initial litter quality having both direct and indirect effects, and the effects of initial litter quality gained importance in the late decomposition stages. However, litter chemical dynamics and microbial diversity index have significant effects on release rates throughout the decomposition process. Our results are useful for better understanding heavy metal fluxes in aquatic and terrestrial ecosystems, and for predicting anthropogenic heavy metal pollution impacts on ecosystems. In addition, our results indicated that not only spatial but also temporal variability should be taken into consideration when addressing heavy metal dynamics accompanying litter decomposition process.

Non-target Effects of Naphthalene on the Soil Microbial Biomass and Bacterial Communities in the Subalpine Forests of Western China.

Naphthalene is a biocide of soil fauna, particularly of soil arthropods, that has been widely applied to test the functional roles of soil fauna in soil processes. However, whether the use of naphthalene to expel soil fauna has a non-target effect on soil bacteria in subalpine forests remains unclear. We conducted a naphthalene treatment experiment to explore the effects of naphthalene on the soil bacterial community in subalpine forest soil. The results suggested that naphthalene treatment (at 100 g.m-2 per month) significantly increased the abundances of total bacterial, gram-positive bacterial and gram-negative bacterial phospholipid fatty acids (PLFA) and did not change the microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) or MBC/MBN ratio. Moreover, a total of 1038 operational taxonomic units (OTUs) were detected by Illumina MiSeq sequencing analysis. Proteobacteria, Actinobacteria, and Acidobacteria Chloroflexi were the dominant phyla, and Bradyrhizobium was the most abundant genus. The naphthalene treatment did not affect soil bacterial diversity or community structure. Overall, these results demonstrated that the naphthalene treatment had non-target effects on the active bacterial community abundance but not the soil bacterial community structure. Thus, the non-target effects of naphthalene treatment should be considered before using it to expel soil fauna.

Imaging through scattering media with the auxiliary of a known reference object.

Imaging through scattering media has been one of the main challenges in optics, and are encountered in many different disciplines of sciences, ranging from biology, mesoscopic physics to astronomy. Recently, various methods have been proposed. In this manuscript, we propose a robust method for imaging through scattering media in a reflective geometry, a scenario widely encountered in non-invasive and marker-free biological imaging. The proposed method relies on the a priori information of a known reference object in the neighborhood of the target, and uses it as an auxiliary to reconstruct the target image. We show that the target image can be analytically reconstructed from the autocorrelation of the recorded speckle if the reference is point-like, otherwise, deconvolution with the reference speckle should be performed. We experimentally demonstrate the proposed method in a proof-of-concept system with an LED illumination through a thick ground glass.

Microclimate exerts greater control over litter decomposition and enzyme activity than litter quality in an alpine forest-tundra ecotone.

Plant litter decomposition is an important biogeochemical process in terrestrial ecosystems. Although climate and substrate quality controls over litter decomposition are reasonably well understood, their impacts on lignocellulose degradation and lignocellulolytic enzymes remain elusive. Here, the decomposition of three leaf litters derived from Salix paraplesia (SP), Deyeuxia scabrescens (DS), and Ajuga ovalifolia (AO), was studied across an alpine forest-tundra ecotone during one snow-covered season with the objective of distinguishing between the effects of microclimate and litter quality on litter decomposition rates and lignocellulolytic enzymes. The results showed that both microclimate and litter quality affected lignocellulose degradation rates and lignocellulolytic enzyme activities; however, microclimate factors had the greater effects. Interestingly, freeze-thaw cycles and moisture were the predominant factors explaining the variations in decomposition rate and enzyme activities. Higher cellulose degradation rates were associated with higher cellulose concentrations. Cellulolytic enzymes had a greater effect on litter decomposition than did ligninolytic enzymes at the early decomposition stage. Litter decomposition and enzyme activities should be given more attention under global climate change, as the direction and magnitude of changes in microclimate factors and litter quality could strongly influence the nutrient cycling and energy fluxes of alpine ecosystems.

Temporal dynamics of phosphorus during aquatic and terrestrial litter decomposition in an alpine forest.

Plant litter decomposition in forested soil and watershed is an important source of phosphorus (P) for plants in forest ecosystems. Understanding P dynamics during litter decomposition in forested aquatic and terrestrial ecosystems will be of great importance for better understanding nutrient cycling across forest landscape. However, despite massive studies addressing litter decomposition have been carried out, generalizations across aquatic and terrestrial ecosystems regarding the temporal dynamics of P loss during litter decomposition remain elusive. We conducted a two-year field experiment using litterbag method in both aquatic (streams and riparian zones) and terrestrial (forest floors) ecosystems in an alpine forest on the eastern Tibetan Plateau. By using multigroup comparisons of structural equation modeling (SEM) method with different litter mass-loss intervals, we explicitly assessed the direct and indirect effects of several biotic and abiotic drivers on P loss across different decomposition stages. The results suggested that (1) P concentration in decomposing litter showed similar patterns of early increase and later decrease across different species and ecosystems types; (2) P loss shared a common hierarchy of drivers across different ecosystems types, with litter chemical dynamics mainly having direct effects but environment and initial litter quality having both direct and indirect effects; (3) when assessing at the temporal scale, the effects of initial litter quality appeared to increase in late decomposition stages, while litter chemical dynamics showed consistent significant effects almost in all decomposition stages across aquatic and terrestrial ecosystems; (4) microbial diversity showed significant effects on P loss, but its effects were lower compared with other drivers. Our results highlight the importance of including spatiotemporal variations and indicate the possibility of integrating aquatic and terrestrial decomposition into a common framework for future construction of models that account for the temporal dynamics of P in decomposing litter.

Nutrient-limited conditions determine the responses of foliar nitrogen and phosphorus stoichiometry to nitrogen addition: A global meta-analysis.

To test the hypothesis that nutrient-limited conditions can determine the responses of nitrogen (N) and phosphorus (P) stoichiometry to N addition, a meta-analysis was conducted to identify the different responses of foliar N and P concentrations and N-to-P ratios to N addition under N limitation, N and P co-limitation and P limitation. N addition increased the foliar N-to-P ratios and N concentrations by 46.2% and 30.2%, respectively, under N limitation, by 18.7% and 19.7% under N and P co-limitation, and by 4.7% and 12.9% under P limitation. However, different responses of foliar P concentrations to N addition were observed under different nutrient limitations, and negative, positive, and neutral effects on P concentrations were observed under N limitation, P limitation and N and P co-limitation, respectively. Generally, the effects of N addition on N-to-P ratios and N concentrations in herbaceous plants were dramatically larger than those in woody plants (with the exception of the N-to-P ratio under N limitation), but the opposite situation was true for P concentrations. The changes in N-to-P ratios were closely correlated with the changes in N and P concentrations, indicating that the changes in both N and P concentrations due to N addition can drive N and P stoichiometry, but the relative sizes of the contributions of N and P varied greatly with different nutrient limitations. Specifically, the changes in N-to-P ratios may indicate a minimum threshold, which is consistent with the homeostatic mechanism. In brief, increasing N deposition may aggravate P limitation under N-limited conditions but improve P limitation under P-limited conditions. The findings highlight the importance of nutrient-limited conditions in the stoichiometric response to N addition, thereby advancing our ability to predict global plant growth with increasing N deposition in the future.

The effect of canopy exchange on input of base cations in a subalpine spruce plantation during the growth season.

Canopy exchange is one of the most important processes involved in the internal transfer of elements in forest ecosystems. However, little information is available on how canopy exchange influences the input of base cations in subalpine forests. Therefore, the concentrations and fluxes of base cations in throughfall and stemflow were investigated from August 2015 to July 2016 (except for the frozen season) in a representative subalpine spruce plantation in the eastern Tibet Plateau. Our results showed that the mean concentrations of K, Ca, Na and Mg were higher in the stemflow than in the throughfall and precipitation. The total input fluxes of K, Ca, Na and Mg in the internal forest were lower than those in the non-forest. Moreover, the results from the canopy budget model indicated that the canopy exchange fluxes of K, Ca and Mg were higher than the dry deposition fluxes, and Ca and Mg were uptaken, whereas K was leached when precipitation passed through the canopy. Therefore, the results suggested that the input of base cations is mainly controlled by canopy exchange during precipitation in subalpine forest ecosystems, and the canopy could alter the sinks and sources of base cations from precipitation.