Effects of chlorophyll fluorescence on environment and gross primary productivity of moso bamboo during the leaf-expansion stage.

Chlorophyll fluorescence is the long-wave light released by the residual energy absorbed by vegetation after photosynthesis and dissipation, which can directly and non-destructively reflect the photosynthetic state of plants from the perspective of the mechanism of photosynthetic process. Moso bamboo has a substantial carbon sequestration ability, and leaf-expansion stage is an important phenological period for carbon sequestration. Gross primary production (GPP) is a key parameter reflecting vegetation carbon sequestration process. However, the ability of chlorophyll fluorescence in moso bamboo to explain GPP changes is unclear. The research area of this study is located in the bamboo forest near the flux station of Anji County, Zhejiang Province, where an observation tower is built to monitor the carbon flux and meteorological change of bamboo forest. The chlorophyll fluorescence physiological parameters (Fp) and fluorescence yield (Fy) indices were measured and calculated for the leaves of newborn moso bamboo (I Du bamboo) and the old leaves of 4- to 5-year-old moso bamboo (Ⅲ Du bamboo) during the leaf-expansion stage. The chlorophyll fluorescence in response to the environment and its effect on carbon flux were analyzed. The results showed that: Fv/Fm, Y(II) and α of Ⅰ Du bamboo gradually increased, while Ⅲ Du bamboo gradually decreased, and FYint and FY687/FY738 of Ⅰ Du bamboo were higher than those of Ⅲ Du bamboo; moso bamboo was sensitive to changes in air temperature(Ta), relative humidity(RH), water vapor pressure(E), soil temperature(ST) and soil water content (SWC), the Fy indices of the upper, middle and lower layers were significantly correlated with Ta, E and ST; single or multiple vegetation indices were able to estimate the fluorescence yield indices well (all with R2 greater than 0.77); chlorophyll fluorescence (Fp and Fy indices) of Ⅰ Du bamboo and Ⅲ Du bamboo could explain 74.4% and 72.7% of the GPP variation, respectively; chlorophyll fluorescence and normalized differential vegetation index of the canopy (NDVIc) could estimate GPP well using random forest (Ⅰ Du bamboo: r = 0.929, RMSE = 0.069 g C·m-2; Ⅲ Du bamboo: r = 0.899, RMSE = 0.134 g C·m-2). The results of this study show that chlorophyll fluorescence can provide a basis for judging the response of moso bamboo to environmental changes and can well explain GPP. This study has important scientific significance for evaluating the potential mechanisms of growth, stress feedback and photosynthetic carbon sequestration of bamboo.

Spatiotemporal evolution and impacts of climate change on bamboo distribution in China.

Understanding the impact and restriction of climate change on potential distribution of bamboo forest is crucial for sustainable management of bamboo forest and bamboo-based economic development. In this study, climatic variables and maximum entropy model were used to simulate the potential distribution of bamboo forest in China under the future climate scenarios. Seven climatic variables, such as Spring precipitation, Summer precipitation, Autumn precipitation, average annual relative humidity, Autumn average temperature, average annual temperature range and annual total radiation, were selected as input variables of maximum entropy model based on the relative importance of those climate variables for predicting bamboo forest presence. The suitable ranges of the seven climatic variables for potential distribution of bamboo forest were 337-794 mm, 496-705 mm, 213-929 mm, 74.3%-83.4%, 16.6-23.8 °C, 2.3-10.1 °C and 3.2 × 104-4.3 × 104 W m-2, respectively. Under RCP4.5 and RCP8.5 climate scenarios, the suitable area of bamboo forest growth first increased and then decreased, and showed range contractions towards the interior and expansions towards southwest in China. The results of the present study can serve as a useful reference to dynamic monitoring of the spatial distribution and sustainable utilization of bamboo forest in the future under climate change.

Response of carbon uptake to abiotic and biotic drivers in an intensively managed Lei bamboo forest.

Lei bamboo (Phyllostachys praecox) is widely distributed in southeastern China. We used eddy covariance to analyze carbon sequestration capacity of a Lei bamboo forest (2011-2013) and to identify the seasonal biotic and abiotic determinants of carbon fluxes. A machine learning algorithm called random forest (RF) was used to identify factors that affected carbon fluxes. The RF model predicted well the gross ecosystem productivity (GEP), ecosystem respiration (RE) and net ecosystem exchange (NEE), and displayed variations in the drivers between different seasons. Mean annual NEE, RE, and GEP were -105.2 ±â€¯23.1, 1264.5 ±â€¯45.2, and 1369.6 ±â€¯52.5 g C m-2, respectively. Climate warming increased RE more than GEP when water inputs were not limiting. Summer drought played little role in suppressing GEP, but low soil moisture contents suppressed RE and increased the carbon sink during drought in the summer. The most important drivers of NEE were soil temperature in spring, summer, and winter, and photosynthetically active radiation in autumn. Air and soil temperature were important drivers of GEP in all seasons.

Optimizing selective cutting strategies for maximum carbon stocks and yield of Moso bamboo forest using BIOME-BGC model.

The selective cutting method currently used in Moso bamboo forests has resulted in a reduction of stand productivity and carbon sequestration capacity. Given the time and labor expense involved in addressing this problem manually, simulation using an ecosystem model is the most suitable approach. The BIOME-BGC model was improved to suit managed Moso bamboo forests, which was adapted to include age structure, specific ecological processes and management measures of Moso bamboo forest. A field selective cutting experiment was done in nine plots with three cutting intensities (high-intensity, moderate-intensity and low-intensity) during 2010-2013, and biomass of these plots was measured for model validation. Then four selective cutting scenarios were simulated by the improved BIOME-BGC model to optimize the selective cutting timings, intervals, retained ages and intensities. The improved model matched the observed aboveground carbon density and yield of different plots, with a range of relative error from 9.83% to 15.74%. The results of different selective cutting scenarios suggested that the optimal selective cutting measure should be cutting 30% culms of age 6, 80% culms of age 7, and all culms thereafter (above age 8) in winter every other year. The vegetation carbon density and harvested carbon density of this selective cutting method can increase by 74.63% and 21.5%, respectively, compared with the current selective cutting measure. The optimized selective cutting measure developed in this study can significantly promote carbon density, yield, and carbon sink capacity in Moso bamboo forests.

Development of the BIOME-BGC model for the simulation of managed Moso bamboo forest ecosystems.

Numerical models are the most appropriate instrument for the analysis of the carbon balance of terrestrial ecosystems and their interactions with changing environmental conditions. The process-based model BIOME-BGC is widely used in simulation of carbon balance within vegetation, litter and soil of unmanaged ecosystems. For Moso bamboo forests, however, simulations with BIOME-BGC are inaccurate in terms of the growing season and the carbon allocation, due to the oversimplified representation of phenology. Our aim was to improve the applicability of BIOME-BGC for managed Moso bamboo forest ecosystem by implementing several new modules, including phenology, carbon allocation, and management. Instead of the simple phenology and carbon allocation representations in the original version, a periodic Moso bamboo phenology and carbon allocation module was implemented, which can handle the processes of Moso bamboo shooting and high growth during "on-year" and "off-year". Four management modules (digging bamboo shoots, selective cutting, obtruncation, fertilization) were integrated in order to quantify the functioning of managed ecosystems. The improved model was calibrated and validated using eddy covariance measurement data collected at a managed Moso bamboo forest site (Anji) during 2011-2013 years. As a result of these developments and calibrations, the performance of the model was substantially improved. Regarding the measured and modeled fluxes (gross primary production, total ecosystem respiration, net ecosystem exchange), relative errors were decreased by 42.23%, 103.02% and 18.67%, respectively.

Current and potential carbon stocks in Moso bamboo forests in China.

Bamboo forests provide important ecosystem services and play an important role in terrestrial carbon cycling. Of the approximately 500 bamboo species in China, Moso bamboo (Phyllostachys pubescens) is the most important one in terms of distribution, timber value, and other economic values. In this study, we estimated current and potential carbon stocks in China's Moso bamboo forests and in their products. The results showed that Moso bamboo forests in China stored about 611.15 ± 142.31 Tg C, 75% of which was in the top 60 cm soil, 22% in the biomass of Moso bamboos, and 3% in the ground layer (i.e., bamboo litter, shrub, and herb layers). Moso bamboo products store 10.19 ± 2.54 Tg C per year. The potential carbon stocks reach 1331.4 ± 325.1 Tg C, while the potential C stored in products is 29.22 ± 7.31 Tg C a(-1). Our results indicate that Moso bamboo forests and products play a critical role in C sequestration. The information gained in this study will facilitate policy decisions concerning carbon sequestration and management of Moso bamboo forests in China.

Responses of Soil Carbon and Microbial Residues to Degradation in Moso Bamboo Forest.

Moso bamboo (Phyllostachys heterocycla cv. Pubescens) is known for its high capacity to sequester atmospheric carbon (C), which has a unique role to play in the fight against global warming. However, due to rising labor costs and falling bamboo prices, many Moso bamboo forests are shifting to an extensive management model without fertilization, resulting in gradual degradation of Moso bamboo forests. However, many Moso bamboo forests are being degraded due to rising labor costs and declining bamboo timber prices. To delineate the effect of degradation on soil microbial carbon sequestration, we instituted a rigorous analysis of Moso bamboo forests subjected to different degradation durations, namely: continuous management (CK), 5 years of degradation (D-5), and 10 years of degradation (D-10). Our inquiry encompassed soil strata at 0-20 cm and 20-40 cm, scrutinizing alterations in soil organic carbon(SOC), water-soluble carbon(WSOC), microbial carbon(MBC)and microbial residues. We discerned a positive correlation between degradation and augmented levels of SOC, WSOC, and MBC across both strata. Furthermore, degradation escalated concentrations of specific soil amino sugars and microbial residues. Intriguingly, extended degradation diminished the proportional contribution of microbial residuals to SOC, implying a possible decline in microbial activity longitudinally. These findings offer a detailed insight into microbial C processes within degraded bamboo ecosystems.

Spatiotemporal patterns of net primary productivity of subtropical forests in China and its response to drought.

Net primary productivity (NPP) is an important indicator used to evaluate the carbon sequestration capacity of forest ecosystems. Subtropical forest ecosystems play an indispensable role in maintaining the global carbon balance, while frequently occurring drought events in recent years have seriously damaged their productivity. However, the spatiotemporal patterns of NPP, as well as its response to drought, remain uncertain. In this study, the multiscale drought characteristics in subtropical China during 1981-2015 were analyzed based on the standardized precipitation evapotranspiration index. Then, simulated and analyzed the spatiotemporal NPP of subtropical forests by the boreal ecosystem productivity simulator model. Finally, the response of NPP to drought was analyzed based on multiple statistical indices. The results show that most regions in subtropical China experienced mild and moderate drought during 1981-2015. In particular, the extent of drought severity has shown a noticeable increasing trend after 2000. The forest NPP ranged from 622.64 to 1323.82 gC·m-2·a-1, with an overall increase rate of 16.15 gC·m-2·a-1; in particular, the contribution of the western forest NPP became increasingly important. Drought stress has limited the growth of subtropical forest NPP in China, with summer and wet season time scales of drought having the greatest impact on forest NPP anomalies, followed by autumn time scales. The limitation is mostly because the drought duration continually increased, leading to differences in the impact of drought on forest NPP before and after 2000, with declines of 59.55 % and 82.45 %, respectively, mainly concentrated in southwestern regions, such as Yunnan, Guangxi, and Sichuan provinces. This study quantitatively analyzed the impact of drought on subtropical forest NPP, and provides scientific basis for subtropical forest response and adaptation to climate change.

Personal Microenvironment Management by Smart Textiles with Negative Oxygen Ions Releasing and Radiative Cooling Performance.

In recent years, significant strides have been made in the development of smart clothing, which combines traditional apparel with advanced technology. As our climate and environment undergo continuous changes, it has become critically important to invent and refine sophisticated textiles that enhance thermal comfort and human health. In this study, we present a "wearable forest-like textile". This textile is based on helical lignocellulose-tourmaline composite fibers, boasting mechanical strength that outperforms that of cellulose-based and natural macrofibers. This wearable microenvironment does more than generate approximately 18625 ions/cm3 of negative oxygen ions; it also effectively purifies particulate matter. Furthermore, our experiments demonstrate that the negative oxygen ion environment can slow fruit decay by neutralizing free radicals, suggesting promising implications for aging retardation. In addition, this wearable microenvironment reflects solar irradiation and selectively transmits human body thermal radiation, enabling effective radiative cooling of approximately 8.2 °C compared with conventional textiles. This sustainable and efficient wearable microenvironment provides a compelling textile choice that can enhance personal heat management and human health.

Partitioning of respired CO2 in newly sprouted Moso bamboo culms.

Stem respiration (R s) plays a vital role in ecosystem carbon cycling. However, the measured efflux on the stem surface (E s) is not always in situ R s but only part of it. A previously proposed mass balance framework (MBF) attempted to explore the multiple partitioning pathways of R s, including sap-flow-transported and internal storage of R s, in addition to E s. This study proposed stem photosynthesis as an additional partitioning pathway to the MBF. Correspondingly, a double-chamber apparatus was designed and applied on newly sprouted Moso bamboo (Phyllostachys edulis) in leafless and leaved stages. R s of newly sprouted bamboo were twice as high in the leafless stage (7.41 ± 2.66 µmol m-2 s-1) than in the leaved stage (3.47 ± 2.43 µmol m-2 s-1). E s accounted for ~80% of R s, while sap flow may take away ~2% of R s in both leafless and leaved stages. Culm photosynthesis accounted for ~9% and 13% of R s, respectively. Carbon sequestration from culm photosynthesis accounted for approximately 2% of the aboveground bamboo biomass in the leafless stage. High culm photosynthesis but low sap flow during the leafless stage and vice versa during the leaved stage make bamboo an outstanding choice for exploring the MBF.

Age effects of Moso bamboo on leaf isoprene emission characteristics.

Isoprene is a highly reactive volatile organic compound that significantly affects atmospheric oxidant capacity, regional air quality, and climate change. Moso bamboo (Phyllostachys edulis), a species widely distributed in tropical and subtropical regions, particularly in China, is a strong isoprene emitter with great potential for carbon sequestration. Carbon sequestration is negatively correlated with culm age; however, the effect of this correlation on isoprene emissions remains unknown. In this study, we investigated the photosynthetic and isoprene emission characteristics of Moso bamboo at different culm ages. The results showed that the age effect on isoprene emission was different from that on photosynthesis; the net photosynthesis rate (Pn) was the highest in young, followed by mature, and then old bamboo, whereas the isoprene emission rate (Iso) was the highest in young, followed by old, and then mature bamboo. Moreover, the percentage of carbon loss as isoprene emission (C-loss) during photosynthesis of old bamboo was 35% higher than that of mature bamboo under standard conditions (leaf temperature: 30°C; light intensity: 1000 µmol m-2 s-1). Therefore, we strongly recommend considering the culm age when establishing an isoprene emission model of Moso bamboo. Additionally, because the Iso and C-loss of old bamboo were higher than those of mature bamboo, we suggest that attention should be paid to the management of bamboo age structure and timely felling of aged bamboo to reduce environmental risk.

Degradation reduces greenhouse gas emissions while weakening ecosystem carbon sequestration of Moso bamboo forests.

Moso bamboo (Phyllostachys heterocycla cv. Pubescens) is well known for its high capacity to sequester atmospheric carbon, which has a unique role to play in combating global warming. Many Moso bamboo forests are gradually degrading due to rising labor costs and falling prices for bamboo timber. However, the mechanisms of carbon sequestration of Moso bamboo forest ecosystems in response to degradation are unclear. In this study, a space-for-time substitution approach was used to select Moso bamboo forest plots with the same origin and similar stand types, but different years of degradation, and four degradation sequences, continuous management (CK), 2 years of degradation (D-I), 6 years of degradation (D-II) and 10 years of degradation (D-III). A total of 16 survey sample plots were established based on the local management history files. After a 12-month monitoring, the response characteristics of soil greenhouse gases (GHG) emissions, vegetation, and soil organic carbon sequestration in different degradation sequences were evaluated to reveal the differences in the ecosystem carbon sequestration. The results indicated that under D-I, D-II, and D-III, the global warming potential (GWP) of soil GHG emissions decreased by 10.84 %, 17.75 %, and 31.02 %, while soil organic carbon (SOC) sequestration increased by 2.82 %, 18.11 %, and 4.68 %, and vegetation carbon sequestration decreased by 17.30 %, 33.49 %, and 44.76 %, respectively. In conclusion, compared to CK, the ecosystem carbon sequestration was reduced by 13.79 %, 22.42 %, and 30.31 %, respectively. This suggests that degradation reduces soil GHG emissions but weakens the ecosystem carbon sequestration capability. Therefore, in the background of global warming and the strategic goal of carbon neutrality, restorative management of degraded Moso bamboo forests is critically needed to improve the carbon sequestration potential of the ecosystem.

[Spectral reflectance response of plant leaf to simulated UVB stress].

In the present study, we evaluate the relative content of chlorophyll and spectral reflectance variations in the visible light under different intensity of UVB (L-UVB, CK and UVB) of three typical evergreen broadleaf plants in China subtropical area. In different simulated UVB condition, the experiment shows that different tree species have different UVB sensitivity, and chlorophyll content varies greatly with species, and the chlorophyll relative content with the filter UVB w as significantly higher than with enhanced UVB. In the spectral reflectance of the visible part, it is generally higher with enhanced UVB's treatment than with L-UVB treatment; and any treatments present adaptation, species under different stress. After roles of the different UVB intensity, for each tree species the visible part of the spectral reflectance shows difference between green and red mainly. The study results show that the subtropical evergreen broad-leaved species has a strong sensitivity to the UVB, and UVB response of different tree species varies greatly.

Simulated net ecosystem productivity of subtropical forests and its response to climate change in Zhejiang Province, China.

Net ecosystem productivity (NEP) is an important index that indicates the carbon sequestration capacity of forest ecosystems. However, the effect of climate change on the spatiotemporal variability in NEP is still unclear. Using the Integrated Terrestrial Ecosystem Carbon-budget (InTEC) model, this study takes the typical subtropical forests in the Zhejiang Province, China as an example, simulated the spatiotemporal patterns of forest NEP from 1979 to 2079 based on historically observed climate data (1979-2015) and data from three representative concentration pathway (RCP) scenarios (RCP2.6, RCP4.5, and RCP8.5) provided by the Coupled Model Intercomparison Project 5 (CMIP5). We analyzed the responses of NEP at different forest age classes to the variation in meteorological factors. The NEP of Zhejiang's forests decreased from 1979 to 1985 and then increased from 1985 to 2015, with an annual increase rate of 9.66 g C·m-2·yr-1 and a cumulative NEP of 364.99 Tg·C. Forest NEP decreased from 2016 to 2079; however, the cumulative NEP continued to increase. The simulated cumulative NEP under the RCP2.6, RCP4.5, and RCP8.5 scenarios was 750 Tg·C, 866 Tg·C, and 958 Tg·C, respectively, at the end of 2079. Partial correlation analysis between forest NEP at different age stages and meteorological factors showed that temperature is the key climatic factor that affects the carbon sequestration capacity of juvenile forests (1979-1999), while precipitation is the key climatic factor that affects middle-aged forests (2000-2015) and mature forests (2016-2079). Adopting appropriate management strategies for forests, such as selective cutting of different ages, is critical for the subtropical forests to adapt to climate change and maintain their high carbon sink capacity.

Temporal and Spatial Dynamics of Carbon Fixation by Moso Bamboo (Phyllostachys pubescens) in Subtropical China.

To study the temporal and spatial dynamics of carbon fixation by Moso bamboo (Phyllostachys pubescens) in subtropical China, carbon fixation of leaves within the canopy of P. pubescens was measured with a LI-6400 portable photosynthesis system. The results showed that the capability of carbon fixation of P. pubescens leaves had obvious temporal and spatial dynamic variations. It was revealed that there were two peak periods and two low periods in the season variation of carbon fixation capability. Data also revealed that the capability of carbon fixation by five-year-old P. pubescens was more than that of one-year-old and three-year-old. Daily and seasonal carbon fixation showed a negative correlation with the CO(2) concentration. The temporal and spatial dynamics of carbon fixation by P. pubescens described above provided a scientific basis for development of technologies in bamboo timber production.

Understanding farmers' commitments to carbon projects.

This study focuses on identifying the factors that influence farmers' commitment to carbon projects. Based on studying the components of organizational commitment, project commitment and environmental commitment, we developed a regression model that consists of five independent variables, i.e., project-related incomes, persistence in the project, perception of government support, perception of the project and knowledge about carbon sequestration. The model was tested using survey data from 127 smallholder farmers taking part in a carbon project in Suichang, China. The results indicate that farmers' commitment to carbon projects depends on project-related incomes, persistence in the project, and perception of the project. Governmental support and environmental belief do not necessarily affect farmers' commitment.

Growing in Mixed Stands Increased Leaf Photosynthesis and Physiological Stress Resistance in Moso Bamboo and Mature Chinese Fir Plantations.

Mixed-stand plantations are not always as beneficial for timber production and carbon sequestration as monoculture plantations. Systematic analyses of mixed-stand forests as potential ideal plantations must consider the physiological-ecological performance of these plantations. This study aimed to determine whether mixed moso bamboo (Phyllostachys pubescens (Pradelle) Mazel ex J. Houz.) and Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) stands exhibited better physiological-ecological performance than monoculture plantations of these species. We analyzed leaf photosynthesis, chlorophyll fluorescence, antioxidant enzyme activities, chlorophyll content and leaf chemistry in a moso bamboo stand, a Chinese fir stand and a mixed stand with both species. The results showed that both species in the mixed stand exhibited significantly higher leaf net photosynthesis rate (Amax), instantaneous carboxylation efficiency (CUE), chlorophyll content, maximum quantum yield of photosynthesis (Fv/Fm), photochemical quenching coefficient (qP), PSII quantum yield [Y(II)], leaf nitrogen content, and antioxidant enzyme activities than those in the monoculture plantations. However, the non-photochemical quenching (NPQ) in Chinese fir and 2-year-old moso bamboo was significantly lower in the mixed stand than in the monocultures. In addition, the water use efficiency (WUE) of Chinese fir was significantly higher in the mixed stand. The results suggest that the increase in leaf net photosynthetic capacity and the improved growth in the mixed stand could be attributed primarily to the (i) more competitive strategies for soil water use, (ii) stronger antioxidant systems, and (iii) higher leaf total nitrogen and chlorophyll contents in the plants. These findings suggest that mixed growth has beneficial effects on the leaf photosynthesis capacity and physiological resistance of moso bamboo and Chinese fir.

Interactions between soil properties and the rhizome-root distribution in a 12-year Moso bamboo reforested region: Combining ground-penetrating radar and soil coring in the field.

Moso bamboo (Phyllostachys pubescens) plays an important role in mitigating climate change and ameliorating soil degradation because of its high carbon sequestration capacity and erosion resistance. Its strong underground rhizome-root systems form the basic framework of the aboveground system of Moso bamboo forest and define the basic ecological characteristics. However, studies on the relationship between the spatial distribution of roots and soil resources have often been neglected due to methodological limitations. The objective of this study was to test the detectability of rhizomes in the field by ground-penetrating radar (GPR) and to understand the interactions between rhizome-root systems and soil characteristics. The rhizome-root system distribution was investigated using GPR; and the soil texture, soil organic carbon and soil nutrients were investigated using a soil coring method to prepare 50-cm soil profiles. A few key findings were emphasized. First, the rhizome-root system was mainly distributed over a soil depth of 0-30 cm; and the rhizomes were larger in diameter (often greater than 1.0 cm). Therefore, GPR can accurately detect rhizomes in the field, making the non-invasive and long-term estimation of rhizome biomass and monitoring of changes in rhizome dynamics possible under field conditions. Second, the spatial heterogeneity of the soil moisture content, alkaline hydrolysed nitrogen and available phosphorus had a greater effect on the rhizomes spatial distribution than did the spatial heterogeneity of other soil characteristics. The rhizomes clonal growth led to increases in soil organic carbon, which promoted the amelioration of degraded soil. Third, the results provide insights for bamboo forest management, such as the application of GPR to prevent bamboo invasion and to determine the appropriate fertilizer level for a rhizome system. More field tests are needed to validate the application of GPR to rhizome systems and enhance the detection and quantification of rhizome systems in bamboo forest ecosystems.

[Relationship between simulated acid rain stress and leaf reflectance].

Acid rain is a worldwide environmental problem. Serious acid rain pollution in subtropical China has constituted a potential threat to the health of the local forest. In the present paper, the changing properties of the chlorophyll concentration and spectral reflectance at the visible wavelengths for the six subtropical broad-leaved tree species leaves under simulated acid rain (SAR) treatment with different pH levels were studied. With the increasing strength of the SAR, the chlorophyll concentrations of the experimental species under pH 2.5 and pH 4.0 treatment were higher than that under pH 5.6; the spectral reflectance at the visible wavelengths for pH 2.5 and pH 4.0 were lower than that for pH 5.6 in general; while there weren't significant differences between pH 2.5 and pH 4.0. After the treatment with different levels of SAR, the differences in spectral reflectance at the visible wavelengths mainly focused around the green peak and red edge on the reflectance curve. The subtropical broad-leaved tree species studied were relatively not sensitive to acid rain stresses; some stronger acid rain may accelerate the growth of the tree species used here to some extent.

Silicate fertilizer application reduces soil greenhouse gas emissions in a Moso bamboo forest.

Silicate fertilizer application in croplands is effective in mitigating soil methane (CH4) emissions and increasing rice yield. However, the effects of silicate fertilizer on soil greenhouse gas (GHG) emissions in Moso bamboo forests, and the underlying mechanisms are poorly understood. In the present study, a two-year field experiment was conducted to investigate the effect of silicate fertilizer rates (0 (CK), 0.225 and 1.125 Mg ha-1) on soil GHG emissions in a Moso bamboo forest. The results showed that silicate fertilizer application significantly reduced soil CO2 and N2O emissions, and increased soil CH4 uptakes. Compared to the CK treatments, the cumulative soil CO2 emission fluxes decreased by 29.6% and 32.5%, and the cumulative soil N2O emission fluxes decrease by 41.9% and 48.3%, the CH4 uptake fluxes increased by 13.5% and 32.4% in the 0.225 and 1.125 Mg ha-1 treatments, respectively. The soil GHG emissions were significantly positively related to soil temperature (P < 0.05), but negatively related to soil moisture; however, this relationship was not observed between CH4 uptake fluxes and moisture in CK treatment. Soil CO2 emission and CH4 uptake were significantly positively related with water-soluble organic C (WSOC) and microbial biomass C (MBC) concentrations in all treatments (P < 0.05). Soil N2O emissions were significantly positively related to MBC, NH4+-N, NO3--N, and microbial biomass N (MBN) concentrations in all treatments (P < 0.05), but not with WSOC concentration. Structural equation modeling showed that application of silicate fertilizer directly reduced soil GHG emission by decreasing the labile C and N pools, and indirectly by influencing the soil physicochemical properties. Our findings suggest that silicate fertilizer can be an effective tool in combatting climate change by reducing soil GHG emissions in Moso bamboo forests.