Root tips are the main components of absorptive fine roots,but their seasonal dynamics and relationship to environmental factors remain unclear due to the difficulties in methodology.In this study,we explored the temp...Root tips are the main components of absorptive fine roots,but their seasonal dynamics and relationship to environmental factors remain unclear due to the difficulties in methodology.In this study,we explored the temporal patterns of root-tip production and mortality in monoculture plantations of five temperate tree species at a common site in northeastern China,and identified the general environmental controls on such processes.We made monthly in-situ assessments of root tip length(RTL)production and mortality in two hardwood and three coniferous species with a minirhizotron(MR)method during the growing seasons of 2008 and 2009.Air temperature,rainfall,soil temperature and water content at 10 cm depth were determined concurrently.RTL production in all species exhibited consistent peaks in summer(June–August)in two growing seasons.RTL mortality showed substantial interannual and interspecific variability,with peaks in autumn and winter in 2008,but various patterns in 2009.RTL production positively correlated with monthly soil and air temperature across all species,and with monthly rainfall in three coniferous species.However,there was no significant correlation between RTL production and soil water content.By contrast,RTL mortality was weakly related to environmental factors,showing positive correlations with soil temperature in Korean spruce,and with rainfall in Korean pine and Korean spruce.Our findings suggest that the seasonal patterns of RTL production are convergent across the five temperate tree species due to the overlapped distribution of heat and rainfall,which can conduce roots to maximizing the acquisition of nutrient resources in the soil.展开更多
Climate change is a pressing global environmental issue^([1]).The gradual rise in global surface temperature is the most immediate and direct among its public health impacts.Influenza,the leading cause of human respir...Climate change is a pressing global environmental issue^([1]).The gradual rise in global surface temperature is the most immediate and direct among its public health impacts.Influenza,the leading cause of human respiratory viral infections,remains a substantial public health concern owing to its considerable disease burden,particularly in highrisk groups.Mounting epidemiological evidence has linked influenza to extreme heat and cold weather^([2–4]).展开更多
Temperate forests exert significant biogeophysical influences on local and regional climates through modulating the energy and moisture exchanges between the land surface and the atmosphere,thereby serving as crucial ...Temperate forests exert significant biogeophysical influences on local and regional climates through modulating the energy and moisture exchanges between the land surface and the atmosphere,thereby serving as crucial barriers with significant buffering impacts on the productivity of adjacent agricultural ecosystems.However,the extent and underlying mechanisms of these biogeophysical and buffering effects of temperate forest barriers remains insufficiently understood.In this study,we integrated the dynamic crop model Noah-MP-Crop with the Weather Research and Forecasting(WRF)model to investigate the biogeophysical climate regulation of temperate forests and its buffering effects on crop yields in adjacent agricultural lands across Northeast China.Our findings revealed that temperate forest barriers induced significant local climate effects by cooling air and surface temperatures and reducing wind speeds within forested areas during the growing season,while also regulating non-local climate,particularly by altering regional precipitation patterns,2 m water vapor mixing ratio(Q2),and soil moisture,predominantly in adjacent cropland areas.Furthermore,these forest barriers were found to modulate climate extremes,through affecting maximum temperature and wind speed on a local scale,as well as both maximum and minimum Q2 in non-local croplands.Our study also observed that temperate forest barriers,through biogeophysical climate regulation,enhanced GPP,NPP,and grain yields across most cropland areas.This productivity boost was especially pronounced,with yield increases up to 20%in certain regions during the extreme drought conditions of 2017,underscoring the critical role of temperate forest barriers in sustaining and enhancing crop yields under severe climatic stress.Our findings underscore the significant buffering effects of temperate forest barriers on regional agricultural production,having important implications for climate adaptation strategies aimed at bolstering agricultural resilience in the face of increasing climate variability and extremes.展开更多
Prescribed burning is commonly used to maintain forest ecosystem functions and reduce the risk of future wildfires.Although many studies have investigated the response of microbial community to wildfires in forest eco...Prescribed burning is commonly used to maintain forest ecosystem functions and reduce the risk of future wildfires.Although many studies have investigated the response of microbial community to wildfires in forest ecosystems,the effects of prescribed burnings on soil microbial community structure are less studied.It is also unclear that how post-fire soil physiochemical properties changes affected soil microbial communities.Here,we studied the impacts of prescribed burning on soil microbiome in three typical temperate forests of northern China by collecting soil physicochemical and high-throughput sequencing for 16S rRNA and 18S rRNA was applied to analyze the diversity and community composition of soil microbes(bacteria and fungi).Compared with pre-fire condition,prescribed burning significantly decreased Chaol index and altered soil bacterial communities(P<0.05),whereas it had no significant effect on fungal diversity and community structure of the(P>0.05).Planctomycetes and Actinobacteria made the greatest contributions to the bacterial community dissimilarity between the pre-fire and post-fire conditions.The main variables influencing the post-fire soil microbial community structure are soil pH,available phosphorus,total nitrogen,and the ratio of soil total carbon to soil total nitrogen,which could account for 73.5% of the variation in the microbial community structure in these stands.Our findings demonstrated a great discrepancy in the responses of bacteria and fungi to prescribed burning.Prescribed burning altered the soil microbial structure by modifying the physicochemical properties.Our results pointed that it is essential to evaluate the impact of prescribed burnings on forest ecosystem functions.These findings provide an important baseline for assessing post-fire microbial recovery in the region and offer critical guidance for restoration efforts.展开更多
Tree growth synchrony serves as a valuable ecological indicator of forest resilience to climate stress and disturbances.However,our understanding of how increasing temperature affects tree growth synchrony during rapi...Tree growth synchrony serves as a valuable ecological indicator of forest resilience to climate stress and disturbances.However,our understanding of how increasing temperature affects tree growth synchrony during rapidly and slowly warming periods in ecosystems with varying climatic conditions remains limited.By using tree-ring data from temperate broadleaf(Fraxinus mandshurica,Phellodendron amurense,Quercus mongolica,and Juglans mandshurica)and Korean pine(Pinus koraiensis)mixed forests in northeast China,we investigated the effects of climate change,particularly warming,on the growth synchrony of five dominant temperate tree species across contrasting warm-dry and cool-wet climate conditions.Results show that temperature over water availability was the primary factor driving the growth and growth synchrony of the five species.Growth synchrony was significantly higher in warm-dry than in cool-wet areas,primarily due to more uniform climate conditions and higher climate sensitivity in the former.Rapid warming from the 1960s to the 1990s significantly enhanced tree growth synchrony in both areas,followed by a marked reversal as temperatures exceeded a certain threshold or warming slowed down,particularly in the warm-dry area.The growth synchrony variation patterns of the five species were highly consistent over time,although broadleaves exhibited higher synchrony than conifers,suggesting potential risks to forest resilience and stability under future climate change scenarios.Growing season temperatures and non-growing season temperatures and precipitation had a stronger positive effect on tree growth in the cool-wet area compared to the warm-dry area.High relative humidity hindered growth in the cool-wet area but enhanced it in the warm-dry area.Overall,our study highlights that the diversity and sensitivity of climate-growth relationships directly determine spatiotemporal growth synchrony.Temperature,along with water availability,shape long-term forest dynamics by affecting tree growth and synchrony.These results provide crucial insights for forest management practice to enhance structural diversity and resilience capacity against climate changeinduced synchrony shifts.展开更多
The net primary productivity(NPP)of forest ecosystems plays a crucial role in regulating the terrestrial carbon cycle under global climate change.While the temporal effect driven by ecosystem processes on NPP variatio...The net primary productivity(NPP)of forest ecosystems plays a crucial role in regulating the terrestrial carbon cycle under global climate change.While the temporal effect driven by ecosystem processes on NPP variations is well-documented,spatial variations(from local to regional scales)remain inadequately understood.To evaluate the scale-dependent effects of productivity,predictions from the Biome-BGC model were compared with moderate-resolution imaging spectroradiometer(MODIS)and biometric NPP data in a large temperate forest region at both local and regional levels.Linear mixed-effect models and variance partitioning analysis were used to quantify the effects of environmental heterogeneity and trait variation on simulated NPP at varying spatial scales.Results show that NPP had considerable predictability at the local scale,with a coefficient of determination(R^(2))of 0.37,but this predictability declined significantly to 0.02 at the regional scale.Environmental heterogeneity and photosynthetic traits collectively explained 94.8%of the local variation in NPP,which decreased to 86.7%regionally due to the reduced common effects among these variables.Locally,the leaf area index(LAI)predominated(34.6%),while at regional scales,the stomatal conductance and maximum carboxylation rate were more influential(41.1%).Our study suggests that environmental heterogeneity drives the photosynthetic processes that mediate NPP variations across spatial scales.Incorporating heterogeneous local conditions and trait variations into analyses could enhance future research on the relationship between climate and carbon cycles at larger scales.展开更多
Investigating the spatial distribution of vegetation in monsoonal-climate-dominated high mountain area and detecting its changes that occurred in paraglacial areas is crucial for understanding the cascading environmen...Investigating the spatial distribution of vegetation in monsoonal-climate-dominated high mountain area and detecting its changes that occurred in paraglacial areas is crucial for understanding the cascading environmental effects of shrinking glaciers.We used Landsat images from 1994 to 2022,obtained landscape distribution patterns of glaciers and vegetation in Mt.Gongga,and detected paraglacial vegetation changes under deglaciating environments.We observed there is a pronounced difference in glacier and vegetation coverage between the eastern and western slopes in Mt.Gongga,the eastern slope occupies 78.68% of vegetation area and 61.02% of glacier area,whilst the western slope occupies lower area.Exaggerate warming accelerated glacier retreat,and proglacial areas are generally characterized by very fast primary succession,resulting in an increase of 0.32 km^(2)in vegetation area within two typical glacier forefields on the eastern slope.The phenomenon of paraglacial slope failure following glacier thinning is widespread in Mt.Gongga,resulting in vegetation area decreased by 0.34 km^(2).Concurrently,the fast retreat of glaciers and changes in ice surface geomorphology have caused rapid dynamics in supraglacial vegetation developed on its lower debris-covered sections.We suggested that rapid changes of temperate glaciers can significantly influence paraglacial landform,leading to rapid dynamic changes of vegetation in a balance between colonization and destruction.展开更多
Middle-sized chambers (40cmx40cmx20 cm) and an infrared gas analyzer (IRGA) were used for the measurement of net photosynthesis of the grass layer and soil CO2 evolution, in Quercus liaotungensis Koidz. forest, which ...Middle-sized chambers (40cmx40cmx20 cm) and an infrared gas analyzer (IRGA) were used for the measurement of net photosynthesis of the grass layer and soil CO2 evolution, in Quercus liaotungensis Koidz. forest, which is a typical temperate forest ecosystem in the mountainous areas of Beijing. Changes of CO2 concentrations in both the atmosphere (2m above canopy) and the forest canopy (2m below the top of the canopy) together with those of net photosynthesis and soil CO2 evolution were also examined, in order to find the characteristics of CO2 exchange between the different components of the temperate forest ecosystem and the atmosphere. Atmospheric CO2 averaged (323+10) and (330+1) mol mol-1 respectively in summer and autumn. During the 24-hour measurements, large differences as much as -46 and -61 mol mol-1 respectively in the atmosphere and forest were found. Net photosynthesis of the grass layer in summer was (2. 59 9+ 1.05) mol CO2 m-2 S-1, two times of that in autumn, (1.31+0.39) mol CO2 s-1 In summer, there was much more CO2 evolved from soil than in autumn, averaging (5.18+0.75) mol CO2 m-2 s-1 and (1.96 + 0.57) (mol CO2 m-2 s-1, respectively. A significant correlation was found between soil CO2 evolution and ground temperature, with F =-0.864 2+0.310 1X,r=0.7164, P<0.001 (n=117). Both the minimal atmospheric CO2 level and the maximum net photosynthesis occurred around 14:00; and an increase in atmospheric CO2 and of soil CO2 evolution during night times were also found to be remarkable.展开更多
Within a forested watershed at the Uryu Experimental Forest of Hokkaido University in northern Hokkaido, overstory litterfall and related nutrient fluxes were measured at different landscape zones over two years. The ...Within a forested watershed at the Uryu Experimental Forest of Hokkaido University in northern Hokkaido, overstory litterfall and related nutrient fluxes were measured at different landscape zones over two years. The wetland zone covered with Picea glehnii pure stand. The riparian zone was deciduous broad-leaved stand dominated by Alnus hirsuta and Salix spp., while the mixture of deciduous broadleaf and evergreen conifer dominated by Betula platyphylla, Quercus crispula and Abies sachalinensis distributed on the upland zone. Annual litterfall averaged 1444, 5122, and 4123 kg.hm^-2·a^-1 in the wetland, riparian and upland zones, respectively. Litterfall production peaked in September-October, and foliage litter contributed the greatest amount （73.4%-87.6 %） of the annual total litterfall. Concentrations of nutrients analyzed in foliage litter of the dominant species showed a similar seasonal variation over the year except for N in P glehnii and A. hirsuta. The nutrient fluxes for all elements analyzed were greatest on riparian zone and lowest in wetland zone. Nutrient fluxes via litterfall followed the decreasing sequence： N （11-129 kg.hm-2.aq） 〉 Ca （9-69） 〉 K （5-20） 〉 Mg （3-15） 〉 P （0.4-4.7） for all stands. Significant differences were found in litterfall production and nutrient fluxes among the different landscape components. There existed significant differences in soil chemistry between the different landscape zones. The consistently low soil C：N ratios at the riparian zone might be due to the higher-quality litter inputs （largely N-fixing alder）.展开更多
Understory plants are important components of forest ecosystems and play a crucial role in regulating community structures,function realization,and community succession.However,little is known about how abiotic and bi...Understory plants are important components of forest ecosystems and play a crucial role in regulating community structures,function realization,and community succession.However,little is known about how abiotic and biotic drivers affect the diversity of understory species in cold temperate coniferous forests in the semiarid climate region of North China.We hypothesized that(1)topographic factors are important environmental factors affecting the distribution and variation of understory strata,and(2)different understory strata respond differently to environmental factors;shrubs may be significantly affected by the overstory stratum,and herbs may be more affected by surface soil conditions.To test these hypotheses,we used the boosted regression tree method to analyze abiotic and biotic environmental factors that influence understory species diversity,using data from 280 subplots across 56 sites in cold temperate coniferous forests of North China.Elevation and slope aspect were the dominant and indirect abiotic drivers affecting understory species diversity,and individual tree size inequality(DBH variation)was the dominant biotic driver of understory species diversity;soil water content was the main edaphic factors affecting herb layers.Elevation,slope aspect,and DBH variation accounted for 36.4,14.5,and 12.1%,respectively,of shrub stratum diversity.Shrub diversity decreased with elevation within the range of altitude of this study,but increased with DBH variation;shrub diversity was highest on north-oriented slopes.The strongest factor affecting herb stratum species diversity was slope aspect,accounting for 25.9%of the diversity,followed by elevation(15.7%),slope(12.2%),and soil water content(10.3%).The highest herb diversity was found on southeast-oriented slopes and the lowest on northeast-oriented slopes;herb diversity decreased with elevation and soil water content,but increased with slope.The results of the study provide a reference for scientific management and biodiversity protection in cold temperate coniferous forests of North China.展开更多
Litter decomposition is the fundamental process in nutrient cycling and soil carbon（C） sequestration in terrestrial ecosystems. The global-wide increase in nitrogen（N） inputs is expected to alter litter decomposit...Litter decomposition is the fundamental process in nutrient cycling and soil carbon（C） sequestration in terrestrial ecosystems. The global-wide increase in nitrogen（N） inputs is expected to alter litter decomposition and,ultimately, affect ecosystem C storage and nutrient status. Temperate grassland ecosystems in China are usually N-deficient and particularly sensitive to the changes in exogenous N additions. In this paper, we conducted a 1,200-day in situ experiment in a typical semi-arid temperate steppe in Inner Mongolia to investigate the litter decomposition as well as the dynamics of litter C and N concentrations under three N addition levels（low N with 50 kg N/（hm2？a）（LN）, medium N with 100 kg N/（hm2？a）（MN）, and high N with 200 kg N/（hm2？a）（HN）） and three N addition forms（ammonium-N-based with 100 kg N/（hm2？a） as ammonium sulfate（AS）, nitrate-N-based with 100 kg N/（hm2？a） as sodium nitrate（SN）, and mixed-N-based with 100 kg N/（hm2？a） as calcium ammonium nitrate（CAN）） compared to control with no N addition（CK）. The results indicated that the litter mass remaining in all N treatments exhibited a similar decomposition pattern： fast decomposition within the initial 120 days, followed by a relatively slow decomposition in the remaining observation period（120–1,200 days）. The decomposition pattern in each treatment was fitted well in two split-phase models, namely, a single exponential decay model in phase I（〈398 days） and a linear decay function in phase II（≥398 days）. The three N addition levels exerted insignificant effects on litter decomposition in the early stages（〈398 days, phase I; P〉0.05）. However, MN and HN treatments inhibited litter mass loss after 398 and 746 days, respectively（P〈0.05）. AS and SN treatments exerted similar effects on litter mass remaining during the entire decomposition period（P〉0.05）. The effects of these two N addition forms differed greatly from those of CAN after 746 and 1,053 days, respectively（P〈0.05）. During the decomposition period, N concentrations in the decomposing litter increased whereas C concentrations decreased, which also led to an exponential decrease in litter C：N ratios in all treatments. No significant effects were induced by N addition levels and forms on litter C and N concentrations（P〉0.05）. Our results indicated that exogenous N additions could exhibit neutral or inhibitory effects on litter decomposition, and the inhibitory effects of N additions on litter decomposition in the final decay stages are not caused by the changes in the chemical qualities of the litter, such as endogenous N and C concentrations. These results will provide an important data basis for the simulation and prediction of C cycle processes in future N-deposition scenarios.展开更多
Increased nitrogen （N） deposition will often lead to a decline in species richness in grassland ecosystems but the shifts in functional groups and plant traits are still poorly understood in China. A field experimen...Increased nitrogen （N） deposition will often lead to a decline in species richness in grassland ecosystems but the shifts in functional groups and plant traits are still poorly understood in China. A field experiment was conducted at Duolun, Inner Mongolia, China, to investigate the effects of N addition on a temperate steppe ecosystem. Six N levels （0, 3, 6, 12, 24, and 48 g N/（m2-a）） were added as three applications per year from 2005 to 2010. Enhanced N deposition, even as little as 3 g N/（m2.a） above ambient N deposition （1.2 g N/（m2.a））, led to a decline in species richness of the whole community. Increasing N addition can significantly stimulate aboveground biomass of perennial bunchgrasses （PB） but decrease perennial forbs （PF）, and induce a slight change in the biomass of shrubs and semi-shrubs （SS）. The biomass of annuals （AS） and perennial rhizome grasses （PR） accounts for only a small part of the total biomass. Species richness of PF decreased significantly with increasing N addition rate but there was a little change in the other functional groups. PB, as the dominant functional group, has a relatively higher height than others. Differences in the response of each functional group to N addition have site-specific and species-specific characteristics. We initially infer that N enrichment stimulated the growth of PB, which further suppressed the growth of other functional groups.展开更多
Climate warming and nitrogen （N） deposition change ecosystem processes, structure, and functioning whereas the phosphorus （P） composition and availability directly influence the ecosystem structure under condi- ti...Climate warming and nitrogen （N） deposition change ecosystem processes, structure, and functioning whereas the phosphorus （P） composition and availability directly influence the ecosystem structure under condi- tions of N deposition. In our study, four treatments were designed, including a control, diurnal warming （DW）, N deposition （ND）, and combined warming and N deposition （WN）. The effects of DW, ND, and WN on P composition were studied by 3~p nuclear magnetic resonance （3~p NMR） spectroscopy in a temperate grassland region of China. The results showed that the N deposition decreased the soil pH and total N （TN） concentration but increased the soil OIsen-P concentration. The solution-state 31p NMR analysis showed that the DW, ND and WN treatments slightly decreased the proportion of orthophosphate and increased that of the monoesters. An absence of myo-inositol phosphate in the DW, ND and WN treatments was observed compared with the control. Furthermore, the DW, ND and WN treatments significantly decreased the recovery of soil P in the NaOH-EDTA solution by 17%-20%. The principal component analysis found that the soil pH was positively correlated with the P recovery in the NaOH-EDTA solution. Therefore, the decreased soil P recovery in the DW and ND treatments might be caused by an indirect influence on the soil pH. Additionally, the soil moisture content was the key factor limiting the available P. The positive correlation of total carbon （TC） and TN with the soil P composition indicated the influence of climate warming and N deposition on the biological processes in the soil P cycling.展开更多
Although carbon(C), nitrogen(N), and phosphorous(P) stoichiometric ratios are considered good indicators of nutrient excess/limitation and thus of ecosystem health, few reports have discussed the trends and the recipr...Although carbon(C), nitrogen(N), and phosphorous(P) stoichiometric ratios are considered good indicators of nutrient excess/limitation and thus of ecosystem health, few reports have discussed the trends and the reciprocal effects of C:N:P stoichiometry in plant–litter–soil systems. The present study analyzed C:N:P ratios in four age groups of Chinese pine, Pinus tabulaeformis Carr., forests in Shanxi Province, China: plantation young forests(AY,<20 year-old); plantation middle-aged forests(AM, 21–30 year-old); natural young forests(NY,<30 year-old); and natural middle-aged forests(NM,31–50 year-old). The average C:N:P ratios calculated for tree, shrub, and herbaceous leaves, litter, and soil(0–100 cm) were generally higher in NY followed by NM,AM, and AY. C:N and C:P ratios were higher in litter than in leaves and soils, and reached higher values in the litter and leaves of young forests than in middle-aged forests;however, C:N and C:P ratios were higher in soils of middle-aged forests than in young forests. N:P ratios were higher in leaves than in litter and soils regardless of stand age; the consistent N:P<14 values found in all forests indicated N limitations. With plant leaves, C:P ratios were highest in trees, followed by herbs and shrubs, indicating a higher efficiency in tree leaf formation. C:N ratios decreased with increasing soil depth, whereas there was no trend for C:P and N:P ratios. C:N:P stoichiometry of forest foliage did not exhibit a consistent variation according to stand age. Research on the relationships between N:P, and P, N nutrient limits and the characteristics of vegetation nutrient adaptation need to be continued.展开更多
Wetlands play an important role in the global carbon cycle, but there are still considerable uncertainties in the estimation of wetland carbon storage and a dispute on whether wetlands are carbon sources or carbon sin...Wetlands play an important role in the global carbon cycle, but there are still considerable uncertainties in the estimation of wetland carbon storage and a dispute on whether wetlands are carbon sources or carbon sinks. Xiaoxing’anling are one of several concentrated distribution areas of forested wetland in China, but the carbon storage and carbon sink/source of forested wetlands in this area is unclear. We measured the ecosystem carbon storage (vegetation and soil), annual net carbon sequestration of vegetation and annual carbon emissions of soil heterotrophic respiration of five typical forested wetland types (alder swamp, white birch swamp, larch swamp, larch fen, and larch bog) distributed along a moisture gradient in this area in order to reveal the spatial variations of their carbon storage and quantitatively evaluate their position as carbon sink or source according to the net carbon balance of the ecosystems. The results show that the larch fen had high carbon storage (448.8 t ha^(−1)) (6.8% higher than the larch bog and 10.5–30.1% significantly higher than other three wetlands (P < 0.05), the white birch swamp and larch bog were medium carbon storage ecosystems (406.3 and 420.1 t ha^(−1)) (12.4–21.8% significantly higher than the other two types (P < 0.0 5), while the alder swamp and larch swamp were low in carbon storage (345.0 and 361.5 t ha^(−1), respectively). The carbon pools of the five wetlands were dominated by their soil carbon pools (88.5–94.5%), and the vegetation carbon pool was secondary (5.5–11.5%). At the same time, their ecosystem net carbon balances were positive (0.1–0.6 t ha^(−1) a^(−1)) because the annual net carbon sequestration of vegetation (4.0–4.5 t ha^(−1) a^(−1)) were higher than the annual carbon emissions of soil heterotrophic respiration (CO_(2) and CH_(4)) (3.8–4.4 t ha^(−1) a^(−1)) in four wetlands, (the alder swamp being the exception), so all four were carbon sinks while only the alder swamp was a source of carbon emissions (− 2.1 t ha^(−1) a^(−1)) due to a degraded tree layer. Our results demonstrate that these forested wetlands were generally carbon sinks in the Xiaoxing’anling, and there was obvious spatial variation in carbon storage of ecosystems along the moisture gradient.展开更多
Freshwater reservoirs are regarded as an important anthropogenic source of methane(CH_(4))emissions. The temporal and spatial variability of CH_(4) emissions from different reservoirs results in uncertainty in the est...Freshwater reservoirs are regarded as an important anthropogenic source of methane(CH_(4))emissions. The temporal and spatial variability of CH_(4) emissions from different reservoirs results in uncertainty in the estimation of the global CH_(4) budget. In this study, surface water CH_(4) concentrations were measured and diffusive CH_(4) fluxes were estimated via a thin boundary layer model in a temperate river–reservoir system in North China, using spatial(33 sites) and temporal(four seasons) monitoring;the system has experienced intensive aquaculture disturbance. Our results indicated that the dissolved CH_(4) concentration in the reservoir ranged from 0.07 to 0.58 μmol/L, with an annual average of 0.13 ± 0.10 μmol/L, and the diffusive CH_(4) flux across the water–air interface ranged from 0.66 to 3.61 μmol/(m^(2)·hr),with an annual average of 1.67 ± 0.75 μmol/(m^(2)·hr). During the study period, the dissolved CH_(4) concentration was supersaturated and was a net source of atmospheric CH_(4) . Notably,CH_(4) concentration and diffusive flux portrayed large temporal and spatial heterogeneity.The river inflow zone was determined to be a hotspot for CH_(4) emissions, and its flux was significantly higher than that of the tributary and main basin;the CH_(4) flux in autumn was greater than that in other seasons. We also deduced that the CH_(4) concentration/diffusive flux was co-regulated mainly by water temperature, water depth, and water productivity(Chla, trophic status). Our results highlight the importance of considering the spatiotemporal variability of diffusive CH_(4) flux from temperate reservoirs to estimate the CH_(4) budget at regional and global scales.展开更多
Litter and root activities may alter the temperature sensitivity(Q_(10))of soil respiration.However,existing studies have not provided a comprehensive understanding of the effects of litter and root carbon inputs on t...Litter and root activities may alter the temperature sensitivity(Q_(10))of soil respiration.However,existing studies have not provided a comprehensive understanding of the effects of litter and root carbon inputs on the Q_(10)of soil respiration in different seasons.In this study,we used the trench method under in situ conditions to measure the total soil respiration(R_(total)),litter-removed soil respiration(R_(no-litter)),root-removed soil respiration(R_(no-root)),and the decomposition of soil organic matter(i.e.,both litter and root removal;R_(SOM))in different seasons of pioneer(Populus davidiana Dode)and climax(Quercus liaotungensis Mary)forests on the Loess Plateau,China.Soil temperature,soil moisture,litter biomass,fine root biomass,litter carbon,and root carbon were analyzed to obtain the drive mechanism of the Q_(10)of soil respiration in the two forests.The results showed that the Q_(10)of soil respiration exhibited seasonality,and the Q_(10)of soil respiration was higher in summer.The litter enhanced the Q_(10)of soil respiration considerably more than the root did.Soil temperature,soil moisture,fine root biomass,and litter carbon were the main factors used to predict the Q_(10)of different soil respiration components.These findings indicated that factors affecting the Q_(10)of soil respiration highly depended on soil temperature and soil moisture as well as related litter and root traits in the two forests,which can improve our understanding of soil carbon–climate feedback in global warming.The results of this study can provide reference for exploring soil respiration under temperate forest restoration.展开更多
Spatial models are effective in obtaining local details on grassland biomass,and their accuracy has important practical significance for the stable management of grasses and livestock.To this end,the present study uti...Spatial models are effective in obtaining local details on grassland biomass,and their accuracy has important practical significance for the stable management of grasses and livestock.To this end,the present study utilized measured quadrat data of grass yield across different regions in the main growing season of temperate grasslands in Ningxia of China(August 2020),combined with hydrometeorology,elevation,net primary productivity(NPP),and other auxiliary data over the same period.Accordingly,non-stationary characteristics of the spatial scale,and the effects of influencing factors on grass yield were analyzed using a mixed geographically weighted regression(MGWR)model.The results showed that the model was suitable for correlation analysis.The spatial scale of ratio resident-area index(PRI)was the largest,followed by the digital elevation model,NPP,distance from gully,distance from river,average July rainfall,and daily temperature range;whereas the spatial scales of night light,distance from roads,and relative humidity(RH)were the most limited.All influencing factors maintained positive and negative effects on grass yield,save for the strictly negative effect of RH.The regression results revealed a multiscale differential spatial response regularity of different influencing factors on grass yield.Regression parameters revealed that the results of Ordinary least squares(OLS)(Adjusted R^(2)=0.642)and geographically weighted regression(GWR)(Adjusted R^(2)=0.797)models were worse than those of MGWR(Adjusted R^(2)=0.889)models.Based on the results of the RMSE and radius index,the simulation effect also was MGWR>GWR>OLS models.Ultimately,the MGWR model held the strongest prediction performance(R^(2)=0.8306).Spatially,the grass yield was high in the south and west,and low in the north and east of the study area.The results of this study provide a new technical support for rapid and accurate estimation of grassland yield to dynamically adjust grazing decision in the semi-arid loess hilly region.展开更多
基金supported by the National Natural Science Foundation of China(32071749)。
文摘Root tips are the main components of absorptive fine roots,but their seasonal dynamics and relationship to environmental factors remain unclear due to the difficulties in methodology.In this study,we explored the temporal patterns of root-tip production and mortality in monoculture plantations of five temperate tree species at a common site in northeastern China,and identified the general environmental controls on such processes.We made monthly in-situ assessments of root tip length(RTL)production and mortality in two hardwood and three coniferous species with a minirhizotron(MR)method during the growing seasons of 2008 and 2009.Air temperature,rainfall,soil temperature and water content at 10 cm depth were determined concurrently.RTL production in all species exhibited consistent peaks in summer(June–August)in two growing seasons.RTL mortality showed substantial interannual and interspecific variability,with peaks in autumn and winter in 2008,but various patterns in 2009.RTL production positively correlated with monthly soil and air temperature across all species,and with monthly rainfall in three coniferous species.However,there was no significant correlation between RTL production and soil water content.By contrast,RTL mortality was weakly related to environmental factors,showing positive correlations with soil temperature in Korean spruce,and with rainfall in Korean pine and Korean spruce.Our findings suggest that the seasonal patterns of RTL production are convergent across the five temperate tree species due to the overlapped distribution of heat and rainfall,which can conduce roots to maximizing the acquisition of nutrient resources in the soil.
基金supported by a Grant-inAid for Scientific Research(KAKENHI)from the Japan Society for the Promotion of Science(grant no.22J23183)。
文摘Climate change is a pressing global environmental issue^([1]).The gradual rise in global surface temperature is the most immediate and direct among its public health impacts.Influenza,the leading cause of human respiratory viral infections,remains a substantial public health concern owing to its considerable disease burden,particularly in highrisk groups.Mounting epidemiological evidence has linked influenza to extreme heat and cold weather^([2–4]).
基金supported by National Key R&D Program of China(Grant No.2024YFD1501600)the National Natural Science Foundation of China(Grants No.42071025,42371075)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2023240).
文摘Temperate forests exert significant biogeophysical influences on local and regional climates through modulating the energy and moisture exchanges between the land surface and the atmosphere,thereby serving as crucial barriers with significant buffering impacts on the productivity of adjacent agricultural ecosystems.However,the extent and underlying mechanisms of these biogeophysical and buffering effects of temperate forest barriers remains insufficiently understood.In this study,we integrated the dynamic crop model Noah-MP-Crop with the Weather Research and Forecasting(WRF)model to investigate the biogeophysical climate regulation of temperate forests and its buffering effects on crop yields in adjacent agricultural lands across Northeast China.Our findings revealed that temperate forest barriers induced significant local climate effects by cooling air and surface temperatures and reducing wind speeds within forested areas during the growing season,while also regulating non-local climate,particularly by altering regional precipitation patterns,2 m water vapor mixing ratio(Q2),and soil moisture,predominantly in adjacent cropland areas.Furthermore,these forest barriers were found to modulate climate extremes,through affecting maximum temperature and wind speed on a local scale,as well as both maximum and minimum Q2 in non-local croplands.Our study also observed that temperate forest barriers,through biogeophysical climate regulation,enhanced GPP,NPP,and grain yields across most cropland areas.This productivity boost was especially pronounced,with yield increases up to 20%in certain regions during the extreme drought conditions of 2017,underscoring the critical role of temperate forest barriers in sustaining and enhancing crop yields under severe climatic stress.Our findings underscore the significant buffering effects of temperate forest barriers on regional agricultural production,having important implications for climate adaptation strategies aimed at bolstering agricultural resilience in the face of increasing climate variability and extremes.
基金financially supported by the National Natural Science Foundation(No.32471868,No.32001324)Youth Lift Project of China Association for Science and Technology(No.YESS20210370)+1 种基金Fundamental Research Funds for the Central Universities(2572023CT01)We thank the Grassland Bureau and the National Innovation Alliance of Wildland Fire Prevention and Control Technology of China for supporting this research.
文摘Prescribed burning is commonly used to maintain forest ecosystem functions and reduce the risk of future wildfires.Although many studies have investigated the response of microbial community to wildfires in forest ecosystems,the effects of prescribed burnings on soil microbial community structure are less studied.It is also unclear that how post-fire soil physiochemical properties changes affected soil microbial communities.Here,we studied the impacts of prescribed burning on soil microbiome in three typical temperate forests of northern China by collecting soil physicochemical and high-throughput sequencing for 16S rRNA and 18S rRNA was applied to analyze the diversity and community composition of soil microbes(bacteria and fungi).Compared with pre-fire condition,prescribed burning significantly decreased Chaol index and altered soil bacterial communities(P<0.05),whereas it had no significant effect on fungal diversity and community structure of the(P>0.05).Planctomycetes and Actinobacteria made the greatest contributions to the bacterial community dissimilarity between the pre-fire and post-fire conditions.The main variables influencing the post-fire soil microbial community structure are soil pH,available phosphorus,total nitrogen,and the ratio of soil total carbon to soil total nitrogen,which could account for 73.5% of the variation in the microbial community structure in these stands.Our findings demonstrated a great discrepancy in the responses of bacteria and fungi to prescribed burning.Prescribed burning altered the soil microbial structure by modifying the physicochemical properties.Our results pointed that it is essential to evaluate the impact of prescribed burnings on forest ecosystem functions.These findings provide an important baseline for assessing post-fire microbial recovery in the region and offer critical guidance for restoration efforts.
基金supported by the National Natural Science Foundation of China(Nos.42107476 and 42177421)the China Postdoctoral International Exchange Fellowship Program(No.PC2021099)+1 种基金the Science and Technology Innovation Program of Hunan Province(No.2020RC2058)the China Scholarship Council(CSC,No.202206600004,to D.Yuan).
文摘Tree growth synchrony serves as a valuable ecological indicator of forest resilience to climate stress and disturbances.However,our understanding of how increasing temperature affects tree growth synchrony during rapidly and slowly warming periods in ecosystems with varying climatic conditions remains limited.By using tree-ring data from temperate broadleaf(Fraxinus mandshurica,Phellodendron amurense,Quercus mongolica,and Juglans mandshurica)and Korean pine(Pinus koraiensis)mixed forests in northeast China,we investigated the effects of climate change,particularly warming,on the growth synchrony of five dominant temperate tree species across contrasting warm-dry and cool-wet climate conditions.Results show that temperature over water availability was the primary factor driving the growth and growth synchrony of the five species.Growth synchrony was significantly higher in warm-dry than in cool-wet areas,primarily due to more uniform climate conditions and higher climate sensitivity in the former.Rapid warming from the 1960s to the 1990s significantly enhanced tree growth synchrony in both areas,followed by a marked reversal as temperatures exceeded a certain threshold or warming slowed down,particularly in the warm-dry area.The growth synchrony variation patterns of the five species were highly consistent over time,although broadleaves exhibited higher synchrony than conifers,suggesting potential risks to forest resilience and stability under future climate change scenarios.Growing season temperatures and non-growing season temperatures and precipitation had a stronger positive effect on tree growth in the cool-wet area compared to the warm-dry area.High relative humidity hindered growth in the cool-wet area but enhanced it in the warm-dry area.Overall,our study highlights that the diversity and sensitivity of climate-growth relationships directly determine spatiotemporal growth synchrony.Temperature,along with water availability,shape long-term forest dynamics by affecting tree growth and synchrony.These results provide crucial insights for forest management practice to enhance structural diversity and resilience capacity against climate changeinduced synchrony shifts.
基金supported by the National Key R&D Program of China(No.2023YFF1304001-01)the Science and Technology Project of the Department of Transportation of Heilongjiang Province(No.HJK2023B024-3)the Program of National Natural Science Foundation of China(No.32371870).
文摘The net primary productivity(NPP)of forest ecosystems plays a crucial role in regulating the terrestrial carbon cycle under global climate change.While the temporal effect driven by ecosystem processes on NPP variations is well-documented,spatial variations(from local to regional scales)remain inadequately understood.To evaluate the scale-dependent effects of productivity,predictions from the Biome-BGC model were compared with moderate-resolution imaging spectroradiometer(MODIS)and biometric NPP data in a large temperate forest region at both local and regional levels.Linear mixed-effect models and variance partitioning analysis were used to quantify the effects of environmental heterogeneity and trait variation on simulated NPP at varying spatial scales.Results show that NPP had considerable predictability at the local scale,with a coefficient of determination(R^(2))of 0.37,but this predictability declined significantly to 0.02 at the regional scale.Environmental heterogeneity and photosynthetic traits collectively explained 94.8%of the local variation in NPP,which decreased to 86.7%regionally due to the reduced common effects among these variables.Locally,the leaf area index(LAI)predominated(34.6%),while at regional scales,the stomatal conductance and maximum carboxylation rate were more influential(41.1%).Our study suggests that environmental heterogeneity drives the photosynthetic processes that mediate NPP variations across spatial scales.Incorporating heterogeneous local conditions and trait variations into analyses could enhance future research on the relationship between climate and carbon cycles at larger scales.
基金Science and Technology Research Program of Institute of Mountain Hazards and Environment,Chinese Academy of Sciences,No.IMHE-CXTD-02,No.IMHE-ZDRW-06。
文摘Investigating the spatial distribution of vegetation in monsoonal-climate-dominated high mountain area and detecting its changes that occurred in paraglacial areas is crucial for understanding the cascading environmental effects of shrinking glaciers.We used Landsat images from 1994 to 2022,obtained landscape distribution patterns of glaciers and vegetation in Mt.Gongga,and detected paraglacial vegetation changes under deglaciating environments.We observed there is a pronounced difference in glacier and vegetation coverage between the eastern and western slopes in Mt.Gongga,the eastern slope occupies 78.68% of vegetation area and 61.02% of glacier area,whilst the western slope occupies lower area.Exaggerate warming accelerated glacier retreat,and proglacial areas are generally characterized by very fast primary succession,resulting in an increase of 0.32 km^(2)in vegetation area within two typical glacier forefields on the eastern slope.The phenomenon of paraglacial slope failure following glacier thinning is widespread in Mt.Gongga,resulting in vegetation area decreased by 0.34 km^(2).Concurrently,the fast retreat of glaciers and changes in ice surface geomorphology have caused rapid dynamics in supraglacial vegetation developed on its lower debris-covered sections.We suggested that rapid changes of temperate glaciers can significantly influence paraglacial landform,leading to rapid dynamic changes of vegetation in a balance between colonization and destruction.
基金This is a key project of National Natural Science Foundation of China.
文摘Middle-sized chambers (40cmx40cmx20 cm) and an infrared gas analyzer (IRGA) were used for the measurement of net photosynthesis of the grass layer and soil CO2 evolution, in Quercus liaotungensis Koidz. forest, which is a typical temperate forest ecosystem in the mountainous areas of Beijing. Changes of CO2 concentrations in both the atmosphere (2m above canopy) and the forest canopy (2m below the top of the canopy) together with those of net photosynthesis and soil CO2 evolution were also examined, in order to find the characteristics of CO2 exchange between the different components of the temperate forest ecosystem and the atmosphere. Atmospheric CO2 averaged (323+10) and (330+1) mol mol-1 respectively in summer and autumn. During the 24-hour measurements, large differences as much as -46 and -61 mol mol-1 respectively in the atmosphere and forest were found. Net photosynthesis of the grass layer in summer was (2. 59 9+ 1.05) mol CO2 m-2 S-1, two times of that in autumn, (1.31+0.39) mol CO2 s-1 In summer, there was much more CO2 evolved from soil than in autumn, averaging (5.18+0.75) mol CO2 m-2 s-1 and (1.96 + 0.57) (mol CO2 m-2 s-1, respectively. A significant correlation was found between soil CO2 evolution and ground temperature, with F =-0.864 2+0.310 1X,r=0.7164, P<0.001 (n=117). Both the minimal atmospheric CO2 level and the maximum net photosynthesis occurred around 14:00; and an increase in atmospheric CO2 and of soil CO2 evolution during night times were also found to be remarkable.
基金The project was supported by Japanese Society for Promotion of Sciences (15P03118).
文摘Within a forested watershed at the Uryu Experimental Forest of Hokkaido University in northern Hokkaido, overstory litterfall and related nutrient fluxes were measured at different landscape zones over two years. The wetland zone covered with Picea glehnii pure stand. The riparian zone was deciduous broad-leaved stand dominated by Alnus hirsuta and Salix spp., while the mixture of deciduous broadleaf and evergreen conifer dominated by Betula platyphylla, Quercus crispula and Abies sachalinensis distributed on the upland zone. Annual litterfall averaged 1444, 5122, and 4123 kg.hm^-2·a^-1 in the wetland, riparian and upland zones, respectively. Litterfall production peaked in September-October, and foliage litter contributed the greatest amount （73.4%-87.6 %） of the annual total litterfall. Concentrations of nutrients analyzed in foliage litter of the dominant species showed a similar seasonal variation over the year except for N in P glehnii and A. hirsuta. The nutrient fluxes for all elements analyzed were greatest on riparian zone and lowest in wetland zone. Nutrient fluxes via litterfall followed the decreasing sequence： N （11-129 kg.hm-2.aq） 〉 Ca （9-69） 〉 K （5-20） 〉 Mg （3-15） 〉 P （0.4-4.7） for all stands. Significant differences were found in litterfall production and nutrient fluxes among the different landscape components. There existed significant differences in soil chemistry between the different landscape zones. The consistently low soil C：N ratios at the riparian zone might be due to the higher-quality litter inputs （largely N-fixing alder）.
基金supported by the National Natural Science Foundation of China(Grant No.31470630)Shanxi Forestry Science and Technology Innovation Project
文摘Understory plants are important components of forest ecosystems and play a crucial role in regulating community structures,function realization,and community succession.However,little is known about how abiotic and biotic drivers affect the diversity of understory species in cold temperate coniferous forests in the semiarid climate region of North China.We hypothesized that(1)topographic factors are important environmental factors affecting the distribution and variation of understory strata,and(2)different understory strata respond differently to environmental factors;shrubs may be significantly affected by the overstory stratum,and herbs may be more affected by surface soil conditions.To test these hypotheses,we used the boosted regression tree method to analyze abiotic and biotic environmental factors that influence understory species diversity,using data from 280 subplots across 56 sites in cold temperate coniferous forests of North China.Elevation and slope aspect were the dominant and indirect abiotic drivers affecting understory species diversity,and individual tree size inequality(DBH variation)was the dominant biotic driver of understory species diversity;soil water content was the main edaphic factors affecting herb layers.Elevation,slope aspect,and DBH variation accounted for 36.4,14.5,and 12.1%,respectively,of shrub stratum diversity.Shrub diversity decreased with elevation within the range of altitude of this study,but increased with DBH variation;shrub diversity was highest on north-oriented slopes.The strongest factor affecting herb stratum species diversity was slope aspect,accounting for 25.9%of the diversity,followed by elevation(15.7%),slope(12.2%),and soil water content(10.3%).The highest herb diversity was found on southeast-oriented slopes and the lowest on northeast-oriented slopes;herb diversity decreased with elevation and soil water content,but increased with slope.The results of the study provide a reference for scientific management and biodiversity protection in cold temperate coniferous forests of North China.
基金funded by the National Natural Science Foundation of China (41073061, 41203054, 40730105, 40973057)the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-EW-302)
文摘Litter decomposition is the fundamental process in nutrient cycling and soil carbon（C） sequestration in terrestrial ecosystems. The global-wide increase in nitrogen（N） inputs is expected to alter litter decomposition and,ultimately, affect ecosystem C storage and nutrient status. Temperate grassland ecosystems in China are usually N-deficient and particularly sensitive to the changes in exogenous N additions. In this paper, we conducted a 1,200-day in situ experiment in a typical semi-arid temperate steppe in Inner Mongolia to investigate the litter decomposition as well as the dynamics of litter C and N concentrations under three N addition levels（low N with 50 kg N/（hm2？a）（LN）, medium N with 100 kg N/（hm2？a）（MN）, and high N with 200 kg N/（hm2？a）（HN）） and three N addition forms（ammonium-N-based with 100 kg N/（hm2？a） as ammonium sulfate（AS）, nitrate-N-based with 100 kg N/（hm2？a） as sodium nitrate（SN）, and mixed-N-based with 100 kg N/（hm2？a） as calcium ammonium nitrate（CAN）） compared to control with no N addition（CK）. The results indicated that the litter mass remaining in all N treatments exhibited a similar decomposition pattern： fast decomposition within the initial 120 days, followed by a relatively slow decomposition in the remaining observation period（120–1,200 days）. The decomposition pattern in each treatment was fitted well in two split-phase models, namely, a single exponential decay model in phase I（〈398 days） and a linear decay function in phase II（≥398 days）. The three N addition levels exerted insignificant effects on litter decomposition in the early stages（〈398 days, phase I; P〉0.05）. However, MN and HN treatments inhibited litter mass loss after 398 and 746 days, respectively（P〈0.05）. AS and SN treatments exerted similar effects on litter mass remaining during the entire decomposition period（P〉0.05）. The effects of these two N addition forms differed greatly from those of CAN after 746 and 1,053 days, respectively（P〈0.05）. During the decomposition period, N concentrations in the decomposing litter increased whereas C concentrations decreased, which also led to an exponential decrease in litter C：N ratios in all treatments. No significant effects were induced by N addition levels and forms on litter C and N concentrations（P〉0.05）. Our results indicated that exogenous N additions could exhibit neutral or inhibitory effects on litter decomposition, and the inhibitory effects of N additions on litter decomposition in the final decay stages are not caused by the changes in the chemical qualities of the litter, such as endogenous N and C concentrations. These results will provide an important data basis for the simulation and prediction of C cycle processes in future N-deposition scenarios.
基金supported by the One Hundred Person Project of Chinese Academy of Sciencesthe National Natural Science Foundation of China (40771188,41071151)+1 种基金the Innovative Group Grants from NSFC (30821003)the Sino-German project (DFG Research Training Group,GK1070)
文摘Increased nitrogen （N） deposition will often lead to a decline in species richness in grassland ecosystems but the shifts in functional groups and plant traits are still poorly understood in China. A field experiment was conducted at Duolun, Inner Mongolia, China, to investigate the effects of N addition on a temperate steppe ecosystem. Six N levels （0, 3, 6, 12, 24, and 48 g N/（m2-a）） were added as three applications per year from 2005 to 2010. Enhanced N deposition, even as little as 3 g N/（m2.a） above ambient N deposition （1.2 g N/（m2.a））, led to a decline in species richness of the whole community. Increasing N addition can significantly stimulate aboveground biomass of perennial bunchgrasses （PB） but decrease perennial forbs （PF）, and induce a slight change in the biomass of shrubs and semi-shrubs （SS）. The biomass of annuals （AS） and perennial rhizome grasses （PR） accounts for only a small part of the total biomass. Species richness of PF decreased significantly with increasing N addition rate but there was a little change in the other functional groups. PB, as the dominant functional group, has a relatively higher height than others. Differences in the response of each functional group to N addition have site-specific and species-specific characteristics. We initially infer that N enrichment stimulated the growth of PB, which further suppressed the growth of other functional groups.
基金National Natural Science Foundation of China(41171241)the National Basic Research Program of China(2011CB403204)
文摘Climate warming and nitrogen （N） deposition change ecosystem processes, structure, and functioning whereas the phosphorus （P） composition and availability directly influence the ecosystem structure under condi- tions of N deposition. In our study, four treatments were designed, including a control, diurnal warming （DW）, N deposition （ND）, and combined warming and N deposition （WN）. The effects of DW, ND, and WN on P composition were studied by 3~p nuclear magnetic resonance （3~p NMR） spectroscopy in a temperate grassland region of China. The results showed that the N deposition decreased the soil pH and total N （TN） concentration but increased the soil OIsen-P concentration. The solution-state 31p NMR analysis showed that the DW, ND and WN treatments slightly decreased the proportion of orthophosphate and increased that of the monoesters. An absence of myo-inositol phosphate in the DW, ND and WN treatments was observed compared with the control. Furthermore, the DW, ND and WN treatments significantly decreased the recovery of soil P in the NaOH-EDTA solution by 17%-20%. The principal component analysis found that the soil pH was positively correlated with the P recovery in the NaOH-EDTA solution. Therefore, the decreased soil P recovery in the DW and ND treatments might be caused by an indirect influence on the soil pH. Additionally, the soil moisture content was the key factor limiting the available P. The positive correlation of total carbon （TC） and TN with the soil P composition indicated the influence of climate warming and N deposition on the biological processes in the soil P cycling.
基金supported by the ‘‘Doctoral Scientific Research Foundation’’ of Heilongjiang Bayi Agricultural University,Grant No.XDB2015-02 and the ‘‘Strategic Priority Research Program’’ of the Chinese Academy of Sciences,Grant No.XDA05050203-04-01
文摘Although carbon(C), nitrogen(N), and phosphorous(P) stoichiometric ratios are considered good indicators of nutrient excess/limitation and thus of ecosystem health, few reports have discussed the trends and the reciprocal effects of C:N:P stoichiometry in plant–litter–soil systems. The present study analyzed C:N:P ratios in four age groups of Chinese pine, Pinus tabulaeformis Carr., forests in Shanxi Province, China: plantation young forests(AY,<20 year-old); plantation middle-aged forests(AM, 21–30 year-old); natural young forests(NY,<30 year-old); and natural middle-aged forests(NM,31–50 year-old). The average C:N:P ratios calculated for tree, shrub, and herbaceous leaves, litter, and soil(0–100 cm) were generally higher in NY followed by NM,AM, and AY. C:N and C:P ratios were higher in litter than in leaves and soils, and reached higher values in the litter and leaves of young forests than in middle-aged forests;however, C:N and C:P ratios were higher in soils of middle-aged forests than in young forests. N:P ratios were higher in leaves than in litter and soils regardless of stand age; the consistent N:P<14 values found in all forests indicated N limitations. With plant leaves, C:P ratios were highest in trees, followed by herbs and shrubs, indicating a higher efficiency in tree leaf formation. C:N ratios decreased with increasing soil depth, whereas there was no trend for C:P and N:P ratios. C:N:P stoichiometry of forest foliage did not exhibit a consistent variation according to stand age. Research on the relationships between N:P, and P, N nutrient limits and the characteristics of vegetation nutrient adaptation need to be continued.
基金This project was supported fi nancially by the National Key Research and Development Program of China(2016YFA0600803)the National Natural Science Foundation of China(31370461).
文摘Wetlands play an important role in the global carbon cycle, but there are still considerable uncertainties in the estimation of wetland carbon storage and a dispute on whether wetlands are carbon sources or carbon sinks. Xiaoxing’anling are one of several concentrated distribution areas of forested wetland in China, but the carbon storage and carbon sink/source of forested wetlands in this area is unclear. We measured the ecosystem carbon storage (vegetation and soil), annual net carbon sequestration of vegetation and annual carbon emissions of soil heterotrophic respiration of five typical forested wetland types (alder swamp, white birch swamp, larch swamp, larch fen, and larch bog) distributed along a moisture gradient in this area in order to reveal the spatial variations of their carbon storage and quantitatively evaluate their position as carbon sink or source according to the net carbon balance of the ecosystems. The results show that the larch fen had high carbon storage (448.8 t ha^(−1)) (6.8% higher than the larch bog and 10.5–30.1% significantly higher than other three wetlands (P < 0.05), the white birch swamp and larch bog were medium carbon storage ecosystems (406.3 and 420.1 t ha^(−1)) (12.4–21.8% significantly higher than the other two types (P < 0.0 5), while the alder swamp and larch swamp were low in carbon storage (345.0 and 361.5 t ha^(−1), respectively). The carbon pools of the five wetlands were dominated by their soil carbon pools (88.5–94.5%), and the vegetation carbon pool was secondary (5.5–11.5%). At the same time, their ecosystem net carbon balances were positive (0.1–0.6 t ha^(−1) a^(−1)) because the annual net carbon sequestration of vegetation (4.0–4.5 t ha^(−1) a^(−1)) were higher than the annual carbon emissions of soil heterotrophic respiration (CO_(2) and CH_(4)) (3.8–4.4 t ha^(−1) a^(−1)) in four wetlands, (the alder swamp being the exception), so all four were carbon sinks while only the alder swamp was a source of carbon emissions (− 2.1 t ha^(−1) a^(−1)) due to a degraded tree layer. Our results demonstrate that these forested wetlands were generally carbon sinks in the Xiaoxing’anling, and there was obvious spatial variation in carbon storage of ecosystems along the moisture gradient.
基金supported by the National Nature Science Foundation of China(Nos.41771516,41771122)the Bureau of Luanhe Diversion Project of the Haihe River Water Conservancy Commission,Ministry of Water Resources of China and Tianjin Water Affairs Bureau project(Nos.HYGP-2019-C-130,TJGC-2019-C-060)。
文摘Freshwater reservoirs are regarded as an important anthropogenic source of methane(CH_(4))emissions. The temporal and spatial variability of CH_(4) emissions from different reservoirs results in uncertainty in the estimation of the global CH_(4) budget. In this study, surface water CH_(4) concentrations were measured and diffusive CH_(4) fluxes were estimated via a thin boundary layer model in a temperate river–reservoir system in North China, using spatial(33 sites) and temporal(four seasons) monitoring;the system has experienced intensive aquaculture disturbance. Our results indicated that the dissolved CH_(4) concentration in the reservoir ranged from 0.07 to 0.58 μmol/L, with an annual average of 0.13 ± 0.10 μmol/L, and the diffusive CH_(4) flux across the water–air interface ranged from 0.66 to 3.61 μmol/(m^(2)·hr),with an annual average of 1.67 ± 0.75 μmol/(m^(2)·hr). During the study period, the dissolved CH_(4) concentration was supersaturated and was a net source of atmospheric CH_(4) . Notably,CH_(4) concentration and diffusive flux portrayed large temporal and spatial heterogeneity.The river inflow zone was determined to be a hotspot for CH_(4) emissions, and its flux was significantly higher than that of the tributary and main basin;the CH_(4) flux in autumn was greater than that in other seasons. We also deduced that the CH_(4) concentration/diffusive flux was co-regulated mainly by water temperature, water depth, and water productivity(Chla, trophic status). Our results highlight the importance of considering the spatiotemporal variability of diffusive CH_(4) flux from temperate reservoirs to estimate the CH_(4) budget at regional and global scales.
基金sponsored by the National Natural Science Foundation of China(41877538,41671511)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB40000000,XDA23070201)the Funding of Special Support Plan of Young Talents Project of China and National Forestry and Grassland Administration in China(20201326015)。
文摘Litter and root activities may alter the temperature sensitivity(Q_(10))of soil respiration.However,existing studies have not provided a comprehensive understanding of the effects of litter and root carbon inputs on the Q_(10)of soil respiration in different seasons.In this study,we used the trench method under in situ conditions to measure the total soil respiration(R_(total)),litter-removed soil respiration(R_(no-litter)),root-removed soil respiration(R_(no-root)),and the decomposition of soil organic matter(i.e.,both litter and root removal;R_(SOM))in different seasons of pioneer(Populus davidiana Dode)and climax(Quercus liaotungensis Mary)forests on the Loess Plateau,China.Soil temperature,soil moisture,litter biomass,fine root biomass,litter carbon,and root carbon were analyzed to obtain the drive mechanism of the Q_(10)of soil respiration in the two forests.The results showed that the Q_(10)of soil respiration exhibited seasonality,and the Q_(10)of soil respiration was higher in summer.The litter enhanced the Q_(10)of soil respiration considerably more than the root did.Soil temperature,soil moisture,fine root biomass,and litter carbon were the main factors used to predict the Q_(10)of different soil respiration components.These findings indicated that factors affecting the Q_(10)of soil respiration highly depended on soil temperature and soil moisture as well as related litter and root traits in the two forests,which can improve our understanding of soil carbon–climate feedback in global warming.The results of this study can provide reference for exploring soil respiration under temperate forest restoration.
文摘Spatial models are effective in obtaining local details on grassland biomass,and their accuracy has important practical significance for the stable management of grasses and livestock.To this end,the present study utilized measured quadrat data of grass yield across different regions in the main growing season of temperate grasslands in Ningxia of China(August 2020),combined with hydrometeorology,elevation,net primary productivity(NPP),and other auxiliary data over the same period.Accordingly,non-stationary characteristics of the spatial scale,and the effects of influencing factors on grass yield were analyzed using a mixed geographically weighted regression(MGWR)model.The results showed that the model was suitable for correlation analysis.The spatial scale of ratio resident-area index(PRI)was the largest,followed by the digital elevation model,NPP,distance from gully,distance from river,average July rainfall,and daily temperature range;whereas the spatial scales of night light,distance from roads,and relative humidity(RH)were the most limited.All influencing factors maintained positive and negative effects on grass yield,save for the strictly negative effect of RH.The regression results revealed a multiscale differential spatial response regularity of different influencing factors on grass yield.Regression parameters revealed that the results of Ordinary least squares(OLS)(Adjusted R^(2)=0.642)and geographically weighted regression(GWR)(Adjusted R^(2)=0.797)models were worse than those of MGWR(Adjusted R^(2)=0.889)models.Based on the results of the RMSE and radius index,the simulation effect also was MGWR>GWR>OLS models.Ultimately,the MGWR model held the strongest prediction performance(R^(2)=0.8306).Spatially,the grass yield was high in the south and west,and low in the north and east of the study area.The results of this study provide a new technical support for rapid and accurate estimation of grassland yield to dynamically adjust grazing decision in the semi-arid loess hilly region.
