Soil fungal community has higher network stability than bacterial community in response to warming and nitrogen addition in a subtropical primary forest.

Global change factors are known to strongly affect soil microbial community function and composition. However, as of yet, the effects of warming and increased anthropogenic nitrogen deposition on soil microbial network complexity and stability are still unclear. Here, we examined the effects of experimental warming (3°C above ambient soil temperature) and nitrogen addition (5 g N m-2 year-1) on the complexity and stability of the soil microbial network in a subtropical primary forest. Compared to the control, warming increased |negative cohesion|:positive cohesion by 7% and decreased network vulnerability by 5%; nitrogen addition decreased |negative cohesion|:positive cohesion by 10% and increased network vulnerability by 11%. Warming and decreased soil moisture acted as strong filtering factors that led to higher bacterial network stability. Nitrogen addition reduced bacterial network stability by inhibiting soil respiration and increasing resource availability. Neither warming nor nitrogen addition changed fungal network complexity and stability. These findings suggest that the fungal community is more tolerant than the bacterial community to climate warming and nitrogen addition. The link between bacterial network stability and microbial community functional potential was significantly impacted by nitrogen addition and warming, while the response of soil microbial network stability to climate warming and nitrogen deposition may be independent of its complexity. Our findings demonstrate that changes in microbial network structure are crucial to ecosystem management and to predict the ecological consequences of global change in the future. IMPORTANCE: Soil microbes play a very important role in maintaining the function and health of forest ecosystems. Unfortunately, global change factors are profoundly affecting soil microbial structure and function. In this study, we found that climate warming promoted bacterial network stability and nitrogen deposition decreased bacterial network stability. Changes in bacterial network stability had strong effects on bacterial community functional potentials linked to metabolism, nitrogen cycling, and carbon cycling, which would change the biogeochemical cycle in primary forests.

Assessing the Impact of Green Transformation on Ecological Well-Being Performance: A Case Study of 78 Cities in Western China.

The contradiction between the endless pursuit of material possessions and finite natural resources hampers ecological well-being performance (EWP) improvement. Green transformation, recognized as an emerging strategy in sustainable development, can help to coordinate ecological, social, and economic growth by optimizing resource usage, with the ultimate objective of enhancing EWP. This research quantifies how green transformation influences EWP by using panel data from 78 prefecture-level cities in western China from 2012 to 2019. Using the super-SBM and entropy weight models, we assess the EWP and green transformation index (GTI) of 78 prefecture-level cities in western China. On this basis, we quantify the spatial characteristics of EWP by an analysis of the Theil index and spatial autocorrelation. Finally, we examine how GTI affects EWP using the Spatial Durbin model. The results demonstrate that the GTI can raise the EWP of local and nearby cities in western China. According to a GTI analysis of internal indicators, the industrial solid waste usage, harm-less treatment rate of domestic waste, savings level, and R&D expenditure significantly affect EWP. In contrast, the soot emission and consumption levels impede EWP advancement. The analysis of effect decomposition indicates that the sewage treatment rate, expenditure on science and technology, and green patents have a significant spatial spillover effect on the improvement of EWP.

Contamination and source-specific risk analysis of soil heavy metals in a typical coal industrial city, central China.

Source-specific risk apportionment for soil heavy metals (HMs) is crucial for pollution mitigation and risk control in coal-mining areas. The ecological and human health risks resulting from different sources were evaluated through an integrated method that combines risk assessments with positive matrix factorization (PMF) model. Thirty soil samples were collected from a typical coal-mining city in central China and analyzed for six HMs (Cu, Ni, Pb, Cd, As, and Hg). The results indicate that surface soil in the study area suffered from moderate HMs pollution, especially pollution by Cd and Hg. Four potential sources of soil HMs were identified and quantified in the study area, including natural source (27.7%), traffic emissions (33.4%), agricultural practices (16.2%), and industrial activities (22.7%). The ecological risk of the study area was at moderate level, and the leading contributions in urban and suburban areas were from industrial activities and agricultural practices, respectively. The non-carcinogenic risks for adults and children were lower than the risk threshold, while the carcinogenic risks ranged between 1E-06 and 1E-04, suggesting that carcinogenic risks and hazards to human health should not be neglected. Traffic emissions and natural sources mainly contributed to the non-carcinogenic and carcinogenic risks, due to the strong non-carcinogenicity and carcinogenicity of As and Ni. These findings highlight the ecological and health risks linked to potential sources of soil HMs contamination and provide valuable information on the reduction of corresponding risks for local environmental managers.

Functional fungal communities dominate wood decomposition and are modified by wood traits in a subtropical forest.

Wood decomposition is a fundamental process of the carbon cycle in forest ecosystems and differs under varying environmental conditions. However, it remains unclear whether exposure situation and litter removal affect wood decomposition, especially in subtropical forests. Therefore, we chose wood from four dominant species and carried out an experiment with treatments consisting of placing wood in ground contact with and without litter input and above ground exposure. The experiment was performed for 2.5 consecutive years in the subtropical forest of Southwest China to reveal the potential effects of microenvironmental changes due to above ground exposure and nutrient input changes due to litter removal. In this study, neither above ground exposure nor litter removal significantly changed the fungal communities, microbial respiration rates or decomposition rates of the wood, but significant differences among tree species were observed. The abundance of Ascomycota (70.2%) was higher than that of Basidiomycota (24.3%), and there was a significant negative relationship between their abundances, suggesting competition. Moreover, negative (Ascomycota) and positive (Basidiomycota) relationships with microbial respiration and explained 21.5 and 25.5% of the variation in microbial respiration, respectively. The wood density was directly controlled by the sugar, cellulose, and lignin contents and influenced the water content in the wood. The abundances of saprotrophic and pathotrophic fungi were significantly and directly regulated by the water content of the wood. The abundance of pathotrophic fungi was unaffected by wood traits, but these fungi may limit saprotrophic fungal colonization, thereby affecting microbial respiration and decomposition processes. We confirmed that the saprotrophic fungal abundance, rather than fungal diversity, determined wood microbial respiration. These results are of great significance for the comprehensive assessment of wood decomposition and the carbon cycle in subtropical forests, although long-term fungal community dynamics and decomposition rates under different conditions require further study.

Effects of short-term grazing prohibition on soil physical and chemical properties of meadows in Southwest China.

BACKGROUND: Grassland plays an important role in the ecosystem, but overgrazing harms the grassland system in many places. Grazing prohibition is an effective method to restore grassland ecosystems, and it plays a great role in realizing the sustainable development of grassland systems. Therefore, it is necessary to carry out research on the influence of regional grazing prohibition on the physical and chemical properties of different grassland systems. METHODS: In Potatso National Park, Southwest China, we selected experimental plots in the artificial grazing meadow area to study the effects of grazing prohibition on plant and soil indexes in subalpine meadows and swamp meadows. We investigated the biomass and species diversity of grazing prohibition treatment and grazing treatment plots and sampled and tested the soil index. The variation percentage was used to remove the original heterogeneity and yearly variation, allowing us to compare differences in plant index and soil index values between grazing prohibition and grazing treatments. RESULTS: Grazing prohibition increased the aboveground biomass, total biomass, total meadow coverage, average height, richness index, Shannon diversity index and evenness index and reduced the belowground biomass and root/shoot ratio in the subalpine meadow and swamp meadow. Additionally, grazing prohibition reduced the pH and soil bulk density and increased the soil total carbon, soil organic carbon, soil total nitrogen, soil hydrolyzable nitrogen, soil total phosphorus and soil available phosphorus in the subalpine meadow and swamp meadow. Nonmetric multidimensional scaling (NMDS) analysis showed that both plant indexes and soil indexes were significantly different between grazing and grazing prohibition treatments and between meadow types. Short-term grazing prohibition had a great impact on improving the fertility of meadow soil in the study area. We suggest that long-term and extensive research should be carried out to promote the restoration and sustainable development of regional grassland systems.

Stable Mercury Isotope Transition during Postdepositional Decomposition of Biomass in a Forest Ecosystem over Five Centuries.

Organic soil is an important transient reservoir of mercury (Hg) in terrestrial ecosystems, but the fate of deposited Hg in organic forest soil is poorly understood. To understand the dynamic changes of deposited Hg on forest floor, the composition of stable Hg and carbon (C) isotopes in decomposing litters and organic soil layer was measured to construct the 500 year history of postdepositional Hg transformation in a subtropical evergreen broad-leaf forest in Southwest China. Using the observational data and a multiprocess isotope model, the contributions of microbial reduction, photoreduction, and dark reduction mediated by organic matter to the isotopic transition were estimated. Microbial reduction and photoreduction play a dominant role in the initial litter decomposition during first 2 years. Dark redox reactions mediated by organic matter become the predominant process in the subsequent 420 years. After that, the values of Hg mass dependent fractionation (MDF), mass independent fractionation (MIF), and Δ199Hg/Δ201Hg ratio do not change significantly, indicating sequestration and immobilization of Hg in soil. The linear correlations between the isotopic signatures of Hg and C suggest that postdepositional transformation of Hg is closely linked to the fate of natural organic matter (NOM). Our findings are consistent with the abiotic dark reduction driven by nuclear volume effect reported in boreal and tropical forests. We recommend that the dark reduction process be incorporated in future model assessment of the global Hg biogeochemical cycle.

Soil warming increases soil temperature sensitivity in subtropical Forests of SW China.

BACKGROUND: Soil respiration (R S ) plays an important role in the concentration of atmospheric CO2 and thus in global climate patterns. Due to the feedback between R S and climate, it is important to investigate R S responses to climate warming. METHODS: A soil warming experiment was conducted to explore R S responses and temperature sensitivity (Q 10) to climate warming in subtropical forests in Southwestern China, and infrared radiators were used to simulate climate warming. RESULTS: Warming treatment increased the soil temperature and R S value by 1.4 °C and 7.3%, respectively, and decreased the soil water level by 4.2% (%/%). Both one- and two-factor regressions showed that warming increased the Q 10 values by 89.1% and 67.4%, respectively. The effects of water on Q 10show a parabolic relationship to the soil water sensitivity coefficient. Both R S and Q 10 show no acclimation to climate warming, suggesting that global warming will accelerate soil carbon release.

Comparison of two noninvasive methods for measuring the pigment content in foliose macrolichens.

Chlorophyll content in lichens is routinely used as an accurate indicator of lichen vigor, interspecific differences, and the effect of site-related environmental parameters. Traditional methods of chlorophyll extraction are destructive, time-consuming, expensive, and inoperable, especially when measuring large quantities of chlorophyll. However, non-destructive methods of measurement using portable chlorophyll meters are rarely used for lichens. Considering the characteristics of lichens such as rough blade surface and absence of chlorophyll b in cyanolichens, we compared the non-destructive methods with traditional methods and evaluated their applicability in studying lichen pigment content. Two instruments, SPAD-502 and CCM-300, were used to measure the pigment content of seven foliose lichen species. These pigment readings were compared with those determined using the dimethyl sulphoxide (DMSO) extraction method. Significant correlations were observed between SPAD/CCM values and pigments (chlorophyll and total carotenoids) extracted from chlorolichens, especially species with a smooth surface. The CCM-300 was more accurate in detecting the pigment content of foliose chlorolichens. However, both instruments showed certain limitations in the determination of pigment content in cyanolichens, especially gelatinous species. For example, CCM-300 often failed to give specific values for some cyanolichen samples, and both instruments showed low measurement accuracy for cyanolichens. Based on the high correlation observed between chlorophyll meter readings and pigments extracted from chlorolichens, equations obtained in this study enabled accurate prediction of pigment content in these lichens.

Stable Isotope Evidence Shows Re-emission of Elemental Mercury Vapor Occurring after Reductive Loss from Foliage.

The mechanism of elemental mercury (Hg0) re-emission from vegetation to the atmosphere is currently poorly understood. In this study, we investigated branch-level Hg0 atmosphere-foliage exchange in a pristine evergreen forest by systematically combining Hg isotopic composition, air concentration and flux measurements to unravel process information. It is found that the foliage represents a diurnally changing sink for atmospheric Hg0 and its Hg content increases with leaf age and mass. Atmospheric Hg0 is the dominant source of foliar Hg and the involvement of HgII is not supported by isotopic evidence. Upon Hg0 uptake, maturing foliage becomes progressively enriched in lighter Hg isotopes and depleted in odd mass isotopes. The measured isotopic composition of foliage Hg and isotopic shift caused by Hg0 evasion from foliage supports that Hg0 emitted from foliage is derived from Hg previously metabolized and bound in the leaf interior then subsequently recycled after reduction, and not merely a retroflux of recently deposited Hg0 on foliar surface. An isotopic differential mass balance model indicates that the proportion of foliar Hg0 efflux to uptake gradually increase from emergence to senescence with an average flux ratio of 30%.

Dry-hot stress significantly reduced the nitrogenase activity of epiphytic cyanolichen.

Nitrogen (N) fixed by epiphytic cyanolichens (i.e. lichens that contain cyanobacterial symbionts) is thought to be the most important resource of this nutrient in some natural forest ecosystems. Although a great deal of work has been carried out to evaluate the biomass of this group as well as its contribution to ecosystem N budgets, empirical studies are needed to confirm the N input responses by cyanolichens under climate change conditions (dry-hot stress) as well as to determine the factors that control this process. We simulated climate change conditions by transplanting Lobaria retigera, a common cyanolichen in the area, to lower elevations, and measured nitrogenase activity in response to warmer and drier conditions. In addition, we conducted a series of laboratory and greenhouse experiments to determine the dominant factors influencing nitrogenase activity in this species. The results of this study show that mean annual nitrogenase activity at the higher site was 1.5 and 2.4 times that at the simulated warmer and drier (middle and lower) sites, respectively. Combining laboratory experimental conclusions, we show that thallus water content is a key factor determining the nitrogenase activity of L. retigera in early transplantation while insufficient carbon storage resulting from a combination of warming and desiccation was likely responsible for reducing nitrogenase activity in later months of the transplant experiment. The results of this study imply that the negative impact of climate change (dry-hot stress) on ecosystems not only impacts the distribution and growth of species, but also nutrient circles and budgets.

Carbon exchanges and their responses to temperature and precipitation in forest ecosystems in Yunnan, Southwest China.

Forest ecosystems play an increasingly important role in the global carbon cycle. However, knowledge on carbon exchanges, their spatio-temporal patterns, and the extent of the key controls that affect carbon fluxes is lacking. In this study, we employed 29-site-years of eddy covariance data to observe the state, spatio-temporal variations and climate sensitivity of carbon fluxes (gross primary productivity (GPP), ecosystem respiration (Reco), and net ecosystem carbon exchange (NEE)) in four representative forest ecosystems in Yunnan. We found that 1) all four forest ecosystems were carbon sinks (the average NEE was -3.40tCha-1yr-1); 2) contrasting seasonality of the NEE among the ecosystems with a carbon sink mainly during the wet season in the Yuanjiang savanna ecosystem (YJ) but during the dry season in the Xishuangbanna tropical rainforest ecosystem (XSBN), besides an equivalent NEE uptake was observed during the wet/dry season in the Ailaoshan subtropical evergreen broad-leaved forest ecosystem (ALS) and Lijiang subalpine coniferous forest ecosystem (LJ); 3) as the GPP increased, the net ecosystem production (NEP) first increased and then decreased when the GPP>17.5tCha-1yr-1; 4) the precipitation determines the carbon sinks in the savanna ecosystem (e.g., YJ), while temperature did so in the tropical forest ecosystem (e.g., XSBN); 5) overall, under the circumstances of warming and decreased precipitation, the carbon sink might decrease in the YJ but maybe increase in the ALS and LJ, while future strength of the sink in the XSBN is somewhat uncertain. However, based on the redundancy analysis, the temperature and precipitation combined together explained 39.7%, 32.2%, 25.3%, and 29.6% of the variations in the NEE in the YJ, XSBN, ALS and LJ, respectively, which indicates that considerable changes in the NEE could not be explained by variations in the temperature and precipitation. Therefore, the effects of other factors (e.g., CO2 concentration, N/P deposition, aerosol and other variables) on the NEE still require extensive research and need to be considered seriously in carbon-cycle-models.

Epiphytic bryophytes as bio-indicators of atmospheric nitrogen deposition in a subtropical montane cloud forest: Response patterns, mechanism, and critical load.

Increasing trends of atmospheric nitrogen (N) deposition due to pollution and land-use changes are dramatically altering global biogeochemical cycles. Bryophytes, which are extremely vulnerable to N deposition, often play essential roles in these cycles by contributing to large nutrient pools in boreal and montane forest ecosystems. To interpret the sensitivity of epiphytic bryophytes for N deposition and to determine their critical load (CL) in a subtropical montane cloud forest, community-level, physiological and chemical responses of epiphytic bryophytes were tested in a 2-year field experiment of N additions. The results showed a significant decrease in the cover of the bryophyte communities at an N addition level of 7.4 kg ha-1 yr-1, which is consistent with declines in the biomass production, vitality, and net photosynthetic rate responses of two dominant bryophyte species. Given the background N deposition rate of 10.5 kg ha-1yr-1 for the study site, a CL of N deposition is therefore estimated as ca. 18 kg N ha-1 yr-1. A disordered cellular carbon (C) metabolism, including photosynthesis inhibition and ensuing chlorophyll degradation, due to the leakage of magnesium and potassium and corresponding downstream effects, along with direct toxic effects of excessive N additions is suggested as the main mechanism driving the decline of epiphytic bryophytes. Our results confirmed the process of C metabolism and the chemical stability of epiphytic bryophytes are strongly influenced by N addition levels; when coupled to the strong correlations found with the loss of bryophytes, this study provides important and timely evidence on the response mechanisms of bryophytes in an increasingly N-polluted world. In addition, this study underlines a general decline in community heterogeneity and biomass production of epiphytic bryophytes induced by increasing N deposition.

Water use efficiency in a primary subtropical evergreen forest in Southwest China.

We calculated water use efficiency (WUE) using measures of gross primary production (GPP) and evapotranspiration (ET) from five years of continuous eddy covariance measurements (2009-2013) obtained over a primary subtropical evergreen broadleaved forest in southwestern China. Annual mean WUE exhibited a decreasing trend from 2009 to 2013, varying from ~2.28 to 2.68 g C kg H2O-1. The multiyear average WUE was 2.48 ± 0.17 (mean ± standard deviation) g C kg H2O-1. WUE increased greatly in the driest year (2009), due to a larger decline in ET than in GPP. At the diurnal scale, WUE in the wet season reached 5.1 g C kg H2O-1 in the early morning and 4.6 g C kg H2O-1 in the evening. WUE in the dry season reached 3.1 g C kg H2O-1 in the early morning and 2.7 g C kg H2O-1 in the evening. During the leaf emergence stage, the variation of WUE could be suitably explained by water-related variables (relative humidity (RH), soil water content at 100 cm (SWC_100)), solar radiation and the green index (Sgreen). These results revealed large variation in WUE at different time scales, highlighting the importance of individual site characteristics.

Physiological Responses of Two Epiphytic Bryophytes to Nitrogen, Phosphorus and Sulfur Addition in a Subtropical Montane Cloud Forest.

Atmospheric depositions pose significant threats to biodiversity and ecosystem function. However, the underlying physiological mechanisms are not well understood, and few studies have considered the combined effects and interactions of multiple pollutants. This in situ study explored the physiological responses of two epiphytic bryophytes to combined addition of nitrogen, phosphorus and sulfur. We investigated the electrical conductivity (EC), total chlorophyll concentration (Chl), nutrient stoichiometry and chlorophyll fluorescence signals in a subtropical montane cloud forest in south-west China. The results showed that enhanced fertilizer additions imposed detrimental effects on bryophytes, and the combined enrichment of simulated fertilization exerted limited synergistic effects in their natural environments. On the whole, EC, Chl, the effective quantum yield of photosystem II (ΦPSII) and photochemical quenching (qP) were the more reliable indicators of increased artificial fertilization. However, conclusions on nutrient stoichiometry should be drawn cautiously concerning the saturation uptake and nutrient interactions in bryophytes. Finally, we discuss the limitations of prevailing fertilization experiments and emphasize the importance of long-term data available for future investigations.

Isotopic Composition of Atmospheric Mercury in China: New Evidence for Sources and Transformation Processes in Air and in Vegetation.

The isotopic composition of atmospheric total gaseous mercury (TGM) and particle-bound mercury (PBM) and mercury (Hg) in litterfall samples have been determined at urban/industrialized and rural sites distributed over mainland China for identifying Hg sources and transformation processes. TGM and PBM near anthropogenic emission sources display negative δ(202)Hg and near-zero Δ(199)Hg in contrast to relatively positive δ(202)Hg and negative Δ(199)Hg observed in remote regions, suggesting that different sources and atmospheric processes force the mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) in the air samples. Both MDF and MIF occur during the uptake of atmospheric Hg by plants, resulting in negative δ(202)Hg and Δ(199)Hg observed in litter-bound Hg. The linear regression resulting from the scatter plot relating the δ(202)Hg to Δ(199)Hg data in the TGM samples indicates distinct anthropogenic or natural influences at the three study sites. A similar trend was also observed for Hg accumulated in broadleaved deciduous forest foliage grown in areas influenced by anthropogenic emissions. The relatively negative MIF in litter-bound Hg compared to TGM is likely a result of the photochemical reactions of Hg(2+) in foliage. This study demonstrates the diagnostic stable Hg isotopic composition characteristics for separating atmospheric Hg of different source origins in China and provides the isotopic fractionation clues for the study of Hg bioaccumulation.

Organic nitrogen uptake is a significant contributor to nitrogen economy of subtropical epiphytic bryophytes.

Without any root contact with the soil, epiphytic bryophytes must experience and explore poor, patchy, and heterogeneous habitats; while, the nitrogen (N) uptake and use strategies of these organisms remain uncharacterized, which obscures their roles in the N cycle. To investigate the N sources, N preferences, and responses to enhanced N deposition in epiphytic bryophytes, we carried out an in situ manipulation experiment via the (15)N labelling technique in an Asian cloud forest. Epiphytic bryophytes obtained more N from air deposition than from the bark, but the contribution of N from the bark was non-negligible. Glycine accounted for 28.4% to 44.5% of the total N in bryophyte tissue, which implies that organic N might serve as an important N source. Increased N deposition increased the total N uptake, but did not alter the N preference of the epiphytic bryophytes. This study provides sound evidence that epiphytic bryophytes could take up N from the bark and wet deposition in both organic and inorganic N forms. It is thus important to consider organic N and bark N sources, which were usually neglected, when estimating the role of epiphytic bryophytes in N cycling and the impacts of N deposition on epiphytic bryophytes in cloud forests.

Heterotrophic respiration does not acclimate to continuous warming in a subtropical forest.

As heterotrophic respiration (R(H)) has great potential to increase atmospheric CO2 concentrations, it is important to understand warming effects on R(H) for a better prediction of carbon-climate feedbacks. However, it remains unclear how R(H) responds to warming in subtropical forests. Here, we carried out trenching alone and trenching with warming treatments to test the climate warming effect on R(H) in a subtropical forest in southwestern China. During the measurement period, warming increased annual soil temperature by 2.1 °C, and increased annual mean R(H) by 22.9%. Warming effect on soil temperature (WE(T)) showed very similar pattern with warming effect on R(H) (WE(RH)), decreasing yearly. Regression analyses suggest that WE(RH) was controlled by WE(T) and also regulated by the soil water content. These results showed that the decrease of WE(RH) was not caused by acclimation to the warmer temperature, but was instead due to decrease of WE(T). We therefore suggest that global warming will accelerate soil carbon efflux to the atmosphere, regulated by the change in soil water content in subtropical forests.

Higher clonal integration in the facultative epiphytic fern Selliguea griffithiana growing in the forest canopy compared with the forest understorey.

BACKGROUND AND AIMS: The advantage of clonal integration (resource sharing between connected ramets of clonal plants) varies and a higher degree of integration is expected in more stressful and/or more heterogeneous habitats. Clonal facultative epiphytes occur in both forest canopies (epiphytic habitats) and forest understories (terrestrial habitats). Because environmental conditions, especially water and nutrients, are more stressful and heterogeneous in the canopy than in the understorey, this study hypothesizes that clonal integration is more important for facultative epiphytes in epiphytic habitats than in terrestrial habitats. METHODS: In a field experiment, an examination was made of the effects of rhizome connection (connected vs. disconnected, i.e. with vs. without clonal integration) on survival and growth of single ramets, both young and old, of the facultative epiphytic rhizomatous fern Selliguea griffithiana (Polypodiaceae) in both epiphytic and terrestrial habitats. In another field experiment, the effects of rhizome connection on performance of ramets were tested in small (10 × 10 cm(2)) and large (20 × 20 cm(2)) plots in both epiphytic and terrestrial habitats. KEY RESULTS: Rhizome disconnection significantly decreased survival and growth of S. griffithiana in both experiments. The effects of rhizome disconnection on survival of single ramets and on ramet number and growth in plots were greater in epiphytic habitats than in terrestrial habitats. CONCLUSIONS: Clonal integration contributes greatly to performance of facultative epiphytic ferns, and the effects were more important in forest canopies than in forest understories. The results therefore support the hypothesis that natural selection favours genotypes with a higher degree of integration in more stressful and heterogeneous environments.

Water relations and gas exchange of fan bryophytes and their adaptations to microhabitats in an Asian subtropical montane cloud forest.

Fan life forms are bryophytes with shoots rising from vertical substratum that branch repeatedly in the horizontal plane to form flattened photosynthetic surfaces, which are well suited for intercepting water from moving air. However, detailed water relations, gas exchange characteristics of fan bryophytes and their adaptations to particular microhabitats remain poorly understood. In this study, we measured and analyzed microclimatic data, as well as water release curves, pressure-volume relationships and photosynthetic water and light response curves for three common fan bryophytes in an Asian subtropical montane cloud forest (SMCF). Results demonstrate high relative humidity but low light levels and temperatures in the understory, and a strong effect of fog on water availability for bryophytes in the SMCF. The facts that fan bryophytes in dry air lose most of their free water within 1 h, and a strong dependence of net photosynthesis rates on water content, imply that the transition from a hydrated, photosynthetically active state to a dry, inactive state is rapid. In addition, fan bryophytes developed relatively high cell wall elasticity and the osmoregulatory capacity to tolerate desiccation. These fan bryophytes had low light saturation and compensation point of photosynthesis, indicating shade tolerance. It is likely that fan bryophytes can flourish on tree trunks in the SMCF because of substantial annual precipitation, average relative humidity, and frequent and persistent fog, which can provide continual water sources for them to intercept. Nevertheless, the low water retention capacity and strong dependence of net photosynthesis on water content of fan bryophytes indicate a high risk of unbalanced carbon budget if the frequency and severity of drought increase in the future as predicted.

Hydrothermal Fabrication of WO3 Hierarchical Architectures: Structure, Growth and Response.

Recently hierarchical architectures, consisting of two-dimensional (2D) nanostructures, are of great interest for potential applications in energy and environmental. Here, novel rose-like WO3 hierarchical architectures were successfully synthesized via a facile hydrothermal method. The as-prepared WO3 hierarchical architectures were in fact assembled by numerous nanosheets with an average thickness of ~30 nm. We found that the oxalic acid played a significant role in governing morphologies of WO3 during hydrothermal process. Based on comparative studies, a possible formation mechanism was also proposed in detail. Furthermore, gas-sensing measurement showed that the well-defined 3D WO3 hierarchical architectures exhibited the excellent gas sensing properties towards CO.