Spatial and temperal patterns in bacterioplankton communities across a river-lake continuum

Bacterioplankton play critical roles in biogeochemical cycling. Although spatial and temporal variations in bacterioplankton community compositions (BCCs) within individual habitat have been reported, knowledge gaps remain for studies conducted within different habitats. In this work, we examined the seasonal and spatial variability of BCCs in Nanfei River and Lake Chaohu which had significant environmental heterogeneity using a high-throughput sequencing technique of 16S rRNA gene amplicons. The results showed that spatial variation has a more obvious impact on the BCCs than seasonal changes. The microbial diversity gradually decreased and BCCs changed obviously along water flow direction from Nanfei River to the western and estern parts of Lake Chaohu over all seasons. LEfSe analysis showed that Nanfei River had higer abundance of species belonging to the orders Rhodocyclales, Methylococcales, Campylobacterales and Flavobacteriales, samples from eastern part of Lake Chaohu were abundant in taxonomies including the order Rickettsiales, while the western part had high abundance of taxonomies belonging to the order Chroococcales. The redundancy analysis (RDA) indicated that BCCs in Nanfei River were associated with high nutrient (TP, PO₄-P, TN, NH₃-N, NO₂-N and NO₃-N) concentrations and electrical conductivity. Variance partitioning RDA analysis indicated that the combined effects of all variables may be most important affecting BCCs. This study may provide a framework for modeling the change in bacterioplankton communities through different habitats from a river to lake.     

Variation in the rate of land subsidence induced by groundwater extraction and its effect on the response pattern of soil microbial communities

Excessive extraction of groundwater leads to (irreversible) changes in the physical soil properties, causing land subsidence associated with soil compaction to occur. Using a combined image processing and field approach, we examined: (1) how variation in the land subsidence rate induces different soil compaction degrees; and (2) the response patterns of microbial communities to such variations. By using Sentinel Synthetic Aperture Radar image processing, we selected three locations that exhibited different land subsidence rates, including high (HSR), moderate (MSR), and low (LSR). Then, soil sampling was undertaken within these representative locations. Indicators of soil compaction, including total porosity, air-filled porosity, water-filled porosity, and bulk density, were measured. The soil microbial community was determined using qPCR and sequencing. The highest and lowest values for bulk density were observed in the HSR–MSR and LSR zones, respectively. The greatest values of total porosity and macropore volume were displayed in the LSR zone compared to other zones. Bacterial abundance in the LSR zone was significantly greater than that in the HSR and MSR zones. The relative abundances of bacterial taxa indirectly demonstrated that the anaerobic phyla were significantly increased (by 10–13%), and the aerobic phyla decreased (by 30–40%) in the HSR zone compared to the LSR zone. This result demonstrates that the aerobes declined as larger volumes of the soil became more anaerobic. Indeed, the increased abundance of anaerobes was not able to compensate for the larger decrease in the abundance of aerobes. Our work showed that at the increased rates of land subsidence, the abundance distribution of the microbial community critically declined. These findings highlight the critical impacts of increasing the land subsidence rate on the emergence of high soil compaction degrees, which can significantly affect the resilience thresholds of the microbial communities in dryland soils.     

Spatial and temporal changes in microbial diversity of the Marmara Sea sediments

Spatial (10 different locations) and temporal (2 years) changes in characteristics of the Marmara Sea Sediments were monitored to determine interactions between the chemical and microbial diversity. The sediments were rich in terms of hydrocarbon, nitrate, Ni and microbial cell content. Denitrifying, sulfate reducing, fermentative and methanogenic organisms were co-abundant in 15 cm below the sea floor. The local variations in the sediments’ characteristics were more distinctive than the temporal ones. The sulfate and nitrate contents were the main drivers of the changes in the microbial community compositions. N and P were limited for microbial growth in the sediments, and their levels determined the total cell abundance and activity. Seasonal shifts in temperatures of the shallow sediments were also reflected in the active cell abundances. It was concluded that the Marmara Sea is a promising ecosystem for the further investigation of the ecologically important microbial processes.     

2012年夏季三江平原湿地抚远地区浮游植物群落结构及多样性

2012年6月(夏季)对三江平原湿地抚远地区水域的浮游植物进行调查,设置了10个采样点,经鉴定共有浮游植物262个分类单元,包括239种19变种4变型,隶属于7门9纲22目32科73属.通过对浮游植物群落结构的初步分析,得出三江平原湿地抚远地区水域浮游植物群落结构组成以绿藻门、硅藻门、裸藻门为主,种类数为绿藻门(42.6％)＞硅藻门(22.8％)＞裸藻门(20.9％),细胞密度在3.88×104～278.07×104cells/L之间.聚类分析结果显示,可以将10个采样点分为两组,即农场区5个样点为一组,非农场区5个样点为另一组,两大区域的浮游植物群落结构差异明显,水体类型及生态环境的不同是其存在差异的主要原因.浮游植物多样性指数相对较为一致,Shannon-Wiener多样性指数均在2左右,Margalef丰富度指数均大于3,Pielou均匀度指数在0.3 ～0.5之间.综合群落结构以及多样性分析表明,三江平原湿地抚远地区水域浮游植物物种丰富度较高,多样性良好.     

生境过滤作用对长江下游菜子湖鱼类物种和功能组成的影响

于2018年6-8月在长江下游菜子湖流域沿岸带、敞水区、湖口和河道4种典型微生境分别设置样点进行鱼类调查,探讨生境过滤对鱼类物种和功能组成的影响.共采集鱼类5目31属43种,其中沿岸带湖泊定居性、山溪河流性及江湖洄游性鱼类物种数均较低,河道山溪河流性鱼类物种数较高.通过对各微生境间物种组成的差异分析,显示出4种微生境条件下的鱼类群落均有显著差异,且沿岸带、敞水区和河道的代表种分别为■、鳙、草鱼、鲢,华鳈、光唇蛇鮈、蛇鮈.通过单因素多元方差分析解析不同生境过滤条件下鱼类物种和功能多样性的差异,发现在物种多样性层面,沿岸带的Richness指数和Shannon-Wiener指数显著低于其他微生境;在功能多样性层面,不仅发现沿岸带显著较低的RaoQ指数,同时发现河道的FDiv指数显著高于其他微生境类型.     

Fast responses of microbial plankton communities associated to regime shifts in vegetated wetlands (free-floating plants vs phytoplankton-dominance): An experimental cross-transplant approach

Vegetated wetlands are naturally subjected to changes in their water-level and macrophyte coverage leading to high habitat heterogeneity. The opportunistic ecological strategy of many planktic algae and bacteria makes them suitable for studying adaptive mechanisms to environmental change in wetlands at different temporal and spatial scales. In this study, we assessed the response of microbial aquatic organisms to sudden changes in habitat conditions, resulting from regime shifts involving the presence/absence of a dense floating-macrophyte cover, by means of a 72 h cross-transplant experiment using dialysis bags. Contrasting conditions imposed by the existing regime, such as light availability and dissolved oxygen concentration, accounted for the differences in phytoplankton and picoplankton compositions. Communities newly exposed to improved light and oxygen conditions exhibited a short-term (hours) response of C-strategists algae, such as small flagellated chrysophyceans. The onset of oxygen depletion and light impoverishment favoured the development of anaerobic anoxygenic photosynthetic bacteria (AnAnPB) and low-light adapted S-strategists (thin filamentous oscillatoriales) algae in few days. These results provide in-field evidence that phytoplankton and picoplankton assemblages are highly sensitive to environmental changes in a brief time scale, less than 72 h. Thus, these microbial organisms can act as sentinels to fluctuations in vegetated wetlands, also giving a quick response to sudden changes deriving from anthropogenic practices that impact on wetlands water-level and provoke fluctuations in their floating vegetation cover.     

Experimental study of the zooplankton impact on the trophic structure of phytoplankton and the microbial assemblages in a temperate wetland (Argentina)

An experimental study using mesocosms was conducted in the main shallow lake of a temperate wetland (Otamendi Natural Reserve, Argentina) to analyse the impact of zooplankton on phytoplankton and the microbial assemblages. The lake is characterised by the presence of a fluctuating cover of floating macrophytes, whose shading effects shape the phytoplakton community and the ecosystem functioning, which was absent during the study period. The experiment was run in situ using polyethylene bags, comparing treatments with and without zooplankton. The cascade effect of zooplankton on phytoplankton and the lower levels of the microbial food web (ciliates, heterotrophic nanoflagellates (HNF) and picoplankton) were analysed.A significant zooplankton grazing on the nano-phytoplankton fraction (3–30 μm) was observed. Conversely, large algae (filamentous cyanobacteria, colonial chlorophytes and large diatoms) increased in all mesocosms until day 10, suggesting that they were not actively grazed by zooplankton during this period. However, from day 10 until day 17 this fraction decreased in the enclosures with mesozooplankton, probably due to an increase in the abundance of large herbivores.The results of the experiment would also indicate a trophic cascade effect on the lower levels of the microbial community. In the treatment where zooplankton was removed, the abundance of ciliates followed the same increasing pattern as the abundance of HNF, but with a time lag in its response. In the enclosures without zooplankton, HNF remained relatively constant throughout the experiment, whereas ciliates strongly decrease during the last week. Total picoplankton abundance increased in the enclosures with mesozooplankton, thus supporting the existence of a four-link trophic cascade (copepods–microzooplankton–HNF–picoplankton). Zooplankton composition changed significantly from the beginning until the end of the experiment; cyclopoid nauplii and rotifers were notoriously dominant at t₀, whereas 10 days later the community showed a more equitable proportion of cyclopoids, calanoids, nauplii, cladocerans and rotifers.     

Sustainable impact of mussel farming in the Adriatic Sea (Mediterranean Sea): evidence from biochemical, microbial and meiofaunal indicators

We have investigated the impact of a large mussel farm on the benthic environment using a battery of benthic indicators of environmental quality (including biochemical, microbial and meiofaunal parameters). These were analysed through a multi-control sampling strategy over one year. The differences across the seasons are typically higher than those between the impacted and the control stations. No effects are seen in terms of the sediment oxygen penetration and the downward fluxes (as the total mass, organic and phytopigment fluxes). The indicators based on the biochemical compositions of the sediment organic matter and the microbial parameters also show no evidence of the eutrophication process, except as a slight increase in the bacterial density in the sediments beneath the long-lines of the farm during the period of highest mussel stocks. Finally, no effects are observed in terms of the benthic faunal indicators, as the meiofaunal abundance, the community structure and the taxa richness are all indistinguishable between the farm sediments and the controls. These results show that mussel farming in the investigated system is eco-sustainable and does not significantly alter the coastal marine ecosystem, both in terms of the functioning and the trophic state. The battery of indicators selected in this study represents a useful tool for the monitoring of the potential ecological impact of mussel farms, towards guaranteeing the sustainable development of aquacultures in shallow coastal environments.     

Fish communities and migrations in the vicinity of fishways in a regulated river (Enz, Baden-Württemberg, Germany)

We evaluated the effects of fishway design and stream habitat on fish distribution and migrations within a 50 km section of the Enz River (108 km long, 16.7 m³ · s⁻¹ mean annual discharge), a second order tributary of the Rhine River. On 12 different occasions between August 1994 and September 1995, we collected fish electrically upstream, downstream, and inside three different types of fish-passes: a concrete channel (site I), an artificial stream (site II), and a step and pool fishway (site III). During electrofishing, species identity and fish lengths were recorded separately for specific habitats or sections within the fishways, and traps were installed for 3–5 week long periods at the upstream outlets of the fishways. More than 3550 fish >5 cm and approximately 5800 young-of-year individuals of 28 species were captured. 772 fish marked by subcutaneous injection of alcian blue dye were released downstream of two fishways. Almost 1150 fish, including 5 marked individuals, were captured in the traps, providing direct evidence for migration through the fishway. The total number of species recorded decreased downstream from 21 at site I to 18 at site II, and 17 at site III. This shift in numbers and also in species composition between sites could be partially related to differences in the available habitat. There were pronounced changes in the abundance of most of the dominant species downstream and upstream of the fishway at site III, and, to a lesser degree at sites I and II, indicating species (and size) specific differences in the effectiveness of the three designs for fish passage. Furthermore, marked differences in relative fish abundance between downstream locations and inside the fishway itself, and in the relative numerical composition of the trap catch at sites I and II, clearly demonstrate that some species (Cottus gobio, Barbatula barbatula, Salmo trutta, Leuciscus cephalus) use these fishways as a habitat, whereas others (Phoxinus phoxinus, Gobio gobio) simply migrate through. Only inside the artificial stream did we find early life stages of seven species, suggesting that passage of the other fishways is restricted to older fish. Our results demonstrate that fishway design is crucial in providing continuous fish passage for all species and life-stages, and that a nature-like fishway is the most functional solution.     

Demographic history,range size and habitat preferences of the groundwater amphipod Niphargus puteanus (C.L. Koch in Panzer, 1836)

Niphargus puteanus is the oldest described species of its genus and, in the past, was used as a taxonomic annotation for any subterranean amphipod record. For that reason, no clear knowledge exists about its actual range size and habitat preferences. We here applied a molecular taxonomic and phylogeographical approach based on mitochondrial and nuclear DNA to shed light on its distribution and to infer its demographic history. Furthermore, we analysed aquifer types and water flow regimes to provide a clearer picture of the species’ ecological requirements.Our results indicate that N. puteanus is widely distributed north of the Alps, having its core range in the geomorphological natural region of the ‘South German Scarplands’ (SGS). Additionally, isolated satellite populations exist in the Taunus and the Sauerland, and two single individuals were collected in Luxembourg and in Austria, respectively. The species’ maximal distribution range reaches 756 km between the two single-specimen records and 371 km within the SGS. A very high haplotype diversity was observed, revealing the presence of seven haplotype groups. All the haplogroups were present in the SGS and exhibited distinct spatial-genetic patterns. We thus inferred a high degree of population isolation, with the SGS being a potential long-term refugium for N. puteanus. Historical drift of specimens along major riverine networks (Rhine, Danube) may provide an evolutionary dispersal mechanism explaining the formation of satellite populations.From an ecological perspective, populations of N. puteanus were found to be closely associated with fast-flowing spring environments within fissured aquifers. This species should therefore be classified as both crenophile and stygophile, effectively exploiting resources of surface as well as subsurface spring waters.     

Application of biomarkers for assessing the biological impact of dredged materials in the Mediterranean: the relationship between antioxidant responses and susceptibility to oxidative stress in the red mullet (Mullus barbatus)

In the period 1997-2000, approximately 1,800,000 m3 of material dredged from the Port of Leghorn was discharged into a sea dumping site located 14 miles from the coast. The red mullet (Mullus barbatus) was used as a bioindicator species for monitoring the biological impact of these discharges on a geographical and temporal scale. Organisms were sampled over three years (1998-2000) at different stations and several biomarkers, both of exposure and effect, were analyzed. Bioavailability of specific classes of pollutants was evaluated by analyzing levels of metallothioneins, the activity of cytochrome P450 1A (CYPIA) and of glutathione S-transferases. Among biomarkers of effect, special attention was paid to the balance between prooxidant challenge and antioxidant defenses, and to the appearance of damage caused by oxidative stress. The analyses of the main components of the antioxidant system included superoxide dismutase, catalase, glutathione peroxidases, glutathione reductase, glyoxalase I and II, and total glutathione. These data were integrated with the measurement of total oxyradical scavenging capacity (TOSC) as an indication of the overall biological resistance to toxicity of different forms of oxyradicals (peroxyl radicals, hydroxyl radicals and peroxynitrite). Results indicated a biological impact in organisms sampled near the disposal site; the impact was particularly evident during 1999 and mainly related to organic chemicals such as PAH. Exposure to these pollutants also caused variations in the levels and activity of several antioxidants. The analysis of TOSC, however, revealed that the overall capacity of specific tissues of organisms to absorb various oxidants was not seriously compromised when challenged with increased prooxidant pressures. Variations of single antioxidants were useful in revealing early warning "biological responses", while integration with TOSC analyses indicated if such changes also reflect a more integrated and functional "biological effect" with possible consequences at the organisms level. The red mullet appears to be a useful sentinel species for a biomarker approach to monitoring impact caused by dredged materials.     

Assessment of the ecological status of transitional waters in Sicily (Italy): First characterisation and classification according to a multiparametric approach

A 1-year cycle of observations was performed in four Sicilian transitional water systems (Oliveri-Tindari, Cape Peloro, Vendicari and Marsala) to characterise their ecological status. A panel of variables among which trophic and microbial (enzyme activities, abundance of hetetrophic bacteria and of bacterial pollution indicators) parameters, were selected. Particulate organic carbon (POC) and nitrogen (PON) and chlorophyll-a (Chl-a) contents defined the trophic state, while microbial hydrolysis rates and abundance gave insights on microbial community efficiency in organic matter transformation and on allochthonous inputs. To classify the trophic state of examined waters, the synthetic trophic state index (TRIX) was calculated.Microbial hydrolysis rates correlated positively with POC and Chl-a, which increased along the eutrophication gradient. The significant relationships among TRIX, trophic and microbial parameters suggested the use of leucine aminopeptidase, alkaline phosphatase and POC as suitable parameters to implement the Water Framework Directive when assessing the ecological status of transitional water systems.     

Comparison of the acid-base responses to CO2 and acidification in Japanese flounder (Paralichthys olivaceus)

To investigate whether the biological toxicity of aquatic hypercapnia is due to the direct effects of CO2 or to the effects of acidification of seawater by CO2, the Japanese flounder (Paralichthys olivaceus) was subjected to seawater equilibrated with a gas mixture of air containing 5% CO2 (pH 6.18) or seawater acidified to the same pH with 1 N H2SO4. All the fish died within 72 h in the CO2 exposure group, whereas no mortality occurred in the acid group. Acid-base parameters as well as plasma ion concentrations were severely perturbed in the CO2 exposure group, whereas they were minimally affected in the acid group. These results clearly demonstrate that the mortality in the CO2 group is a direct result of the elevated levels of dissolved CO2 and not to the effects of the reduced water pH.     

Comparison of benthic foraminiferal and macrofaunal responses to organic pollution in the Firth of Clyde (Scotland)

By comparing benthic foraminiferal and macrofaunal responses to sewage sludge disposal in the Firth of Clyde (Scotland), we wanted to investigate the possibility of using foraminifera as bio-indicators of marine environmental degradation. Both groups present a similar distributional pattern, with poor faunas composed of species tolerant to strong oxygen depletion near to the disposal site, surrounded by high density of opportunistic species. Farther away, faunal density decreases and equilibrium taxa gradually replace opportunistic species. No more environmental impact is perceptible beyond 3 km. Nevertheless, some differences exist: foraminifera appear to be more impacted at the disposal site, probably as a consequence of the low pH, a supplementary stress factor for organisms provided with a calcareous test. At 3 km west of the disposal site, macrofauna is comparable to the reference station, whereas foraminifera still indicate environmental degradation, suggesting their higher sensitivity to this type of pollution. It appears that benthic foraminifera may add valuable information to open marine environmental monitoring.     

Using chlorofluorocarbons (CFCs) and tritium to improve conceptual model of groundwater flow in the South Coast Aquifers of Laizhou Bay,China

The southern coastal plain of Laizhou Bay, which is the area most seriously affected by salt water intrusion in north China, is a large alluvial depression, which represents one of the most important hydrogeological units in the coastal region of northern China. Chlorofluorocarbons (CFCs, including CFC‐11, CFC‐12 and CFC‐113) and tritium were used together for dating groundwater up to 50 years old in the study area. There are two cones of depression, caused by intensive over‐exploitation of fresh groundwater in the south and brine water in the north. The assigned CFC apparent ages for shallow groundwater range from 8 a to >50 a. A binary mixing model based on CFC‐113 and CFC‐12 concentrations in groundwater was used to estimate fractions of young and pre‐modern water in shallow aquifers and to identify groundwater mixing processes during saltwater intrusion. Discordance between concentrations of different CFC compounds indicate that shallow groundwater around the Changyi cone of depression is vulnerable to contamination. Pumping activities, CFC contamination, mixing and/or a large unsaturated zone thickness (e.g. >20 m) may be reasons for some groundwater containing CFCs without tritium. Saline intrusion mainly occurs because of large head gradients between fresh groundwater in the south and saline water bodies in the north, forming a wedge of saline water below/within fresh aquifer layers. Both CFC and tritium dates indicate that the majority of the saline water is from >50 a, with little or no modern seawater component. Based on the distribution of CFC apparent ages, tritium contents plus chemical and physical data, a conceptual model of groundwater flow along the investigated Changyi‐Xiaying transect has been developed to describe the hydrogeological processes. Three regimes are identified from south to north: (i) fresh groundwater zone, with a mixing fraction of 0.80–0.65 ‘young’ water calculated with the CFC binary mixing model (groundwater ages <34 a) and 1.9–7.8TU of tritium; (ii) mixing zone characterized by a mixing fraction of 0.05–0.65 young groundwater (ages of 23–44 a), accompanied by local vertical recharge and upward leakage of older groundwater; and (iii) salt water zone, mostly comprising waters with ages beyond the dating range of both CFCs and tritium. Some shallow groundwater in the north of the Changyi groundwater depression belongs to the >50a water group (iii), indicating slow velocity of groundwater circulation and possible drawing in of saline or deep groundwater that is tracer‐free. Copyright © 2012 John Wiley & Sons, Ltd.     

A comparison of peak and plate electrodes in electrical resistivity tomography: application to the chalky groundwater of the Beauvais aquifer (northern part of the Paris basin,France)

Electrical resistivity tomography was used in order to explore an experimental site of the LaSalle Beauvais Polytechnic Institute (France). The test was conducted along a profile line of 315 m length, using 64 electrodes deployed at an inter‐electrode spacing of 5 m, and the data were recorded using gradient, Wenner and pole–dipole arrays. The performance of plate electrodes (non‐conventional flat‐based) is compared with the performance of peak electrodes (conventional spike). The hydrogeophysical investigation of the chalk aquifer system of Beauvais shows that the performance of plate electrodes is satisfactory, leading to inversions of small root‐mean‐square errors. Peak and the plate electrodes were tested before and after injection of a salt tracer in the piezometer of the experimental site. The study demonstrates the usefulness of plate electrodes (efficient, less time consuming) and the possibility of aquifer characterization by a salt tracer. Copyright © 2010 John Wiley & Sons, Ltd.     

Comparison of an Electrochemical and Luminescence‐Based Oxygen Measuring System for Use in the Biodegradability Testing According to Closed Bottle Test (OECD 301D)

The effects of persistent organic pollutants on the aquatic environment still can hardly be assessed. Therefore, ready biodegradability is a desired key characteristic of chemicals. Accordingly, biodegradation testing is of utmost importance and is a vital part within the risk assessment for organic chemicals. In the closed bottle test (CBT; OECD 301D) the degree of biological degradation of a chemical is assessed by monitoring the oxygen consumption so far with a Clark electrode as standard method. However, this method is time‐consuming, laborious and led to frequent fluctuations of the test results, which limited their validity. Due to these shortcomings, an optical system that enables contact‐free measuring of the oxygen concentration in a closed bottle, based on dynamic luminescence quenching, was examined. The test results were compared to those obtained with the “classical” electrochemical technique (Clark electrode). At first, a basic standard for the handling of the new instrument in the laboratory was developed. Then possible influencing factors, reliability, comparability, and reproducibility of the test results were investigated by running the CBTs in parallel with the electrode and optode method. The findings proved the new optode method to be unambiguously superior to the electrode technique. The frequency of fluctuations of the test results and time and effort necessary for the test run could considerably be reduced. The degradation kinetics of the test substances could be followed easily in the CBT by increasing the measuring points without much additional effort.     

Climatic significance of the stable carbon isotope composition of tree-ring cellulose: Comparison of Chinese hemlock (<Emphasis Type="Italic">Tsuga chinensis</Emphasis> Pritz) and alpine pine (<Emphasis Type="Italic">Pinus densata</Emphasis> Mast) in a temperate-moist region of China

In the reconstruction of past climate using stable carbon isotope composition (δ13C) in tree ring, the responses of the stable carbon composition (δ13C) of multiple tree species to environmental factors must be known detailedly. This study presented two δ13C series in annual tree rings for Chinese hemlock (Tsuga chinensis Pritz) and alpine pine (Pinus densata Mast), and investigated the relationships between climatic parameters and stable carbon discrimination (Δ13C) series, and evaluated the potential of climatic reconstruction using Δ13C in both species, in a temperate-moist region of Chuanxi Plateau, China. The raw δ13C series of the two species was inconsistent, which may be a result of different responses caused by tree's inherent physiological differences. After removing the low-frequency effects of CO2 concentration, the high-frequency (year-to-year) inter-series correlation of Δ13C was strong, indicating that Δ13C of the two tree species were controlled by common environmental conditions. The Δ13C series of the species were most significantly correlated with temperature and moisture stress, but in different periods and intensity between the species. During the physiological year, the impacts of temperature and moisture stress on Δ13C occur earlier for Chinese hemlock (previous December to February for moisture stress and February to April for temperature, respectively) than for alpine pine (March to May for moisture stress and April to July for temperature, respectively). In addition, in temperatemoist regions, the control on Δ13C of single climatic parameter was not strongly dominant and the optimal multiple regressions functions just explained the 38.5% variance of the total. Therefore, there is limited potential for using δ13C alone to identify clear, reliable climatic signals from two species.