[Seasonal dynamics in photosynthetic characteristics and growth of Cunninghamia lanceolata saplings and their response to soil warming]. / æ‰æœ¨å¹¼æ ‘å ‰åˆç‰¹æ€§ä¸Žç”Ÿé•¿çš„å­£èŠ‚å˜åŒ–åŠå ¶å¯¹åœŸå£¤å¢žæ¸©çš„å“åº”.

In order to understand the response and adaptation mechanisms of photosynthetic characteristics and growth for Cunninghamia lanceolata saplings in the subtropical region to global warming, we conducted the root-box warming experiment (ambient, ambient+4 ℃) at the Sanming Forest Ecosystem National Observation and Research Station in Fujian Province to investigate the effects of soil warming on the photosynthetic characteristics and growth of C. lanceolata saplings in different seasons. The results showed that the net photosynthetic rate (Pn) and stomatal conductance (gs) of C. lanceolata significantly decreased in summer compared with in spring and autumn. Soil warming had no effect on the Pn and gs of C. lanceolata. However, the interaction between warming and season significantly impacted the leaf water use efficiency (WUE). The tree height and ground diameter growth of C. lanceolata significantly increased in spring compared with in summer and autumn. Warming significantly reduced ground diameter growth, and it diminished the net diameter growth by 48.1% in autumn. However, warming had no impact on the tree height growth of C. lanceolata in each season. The specific leaf area, soluble sugar, and non-structural carbohydrates contents of C. lanceolata significantly improved in summer and autumn compared with in spring. Warming had rarely influence on leaf functional traits in each season. In conclusion, the response of photosynthesis for C. lanceolata to soil warming was insignificant. The photosynthesis of C. lanceolata exhibited significant seasonal dynamics, primarily controlled by gs. C. lanceolata adapted to soil warming by adjusting WUE, and it adjusted to high temperatures and drought stress in summer by increasing soluble sugar content and specific leaf area. The effect of warming on ground diameter growth of C. lanceolata was primarily driven by soil moisture. The seasonal difference in the growth of C. lanceolata was influenced by the photosynthesis of C. lanceolata and the trade-off between the utilization and storage of photosynthetic products.

[Effect of environmental factors on mineral soil respiration: A review]. / çŽ¯å¢ƒå› å­å¯¹çŸ¿è´¨åœŸå£¤å‘¼å¸å½±å“çš„ç ”ç©¶è¿›å±•.

Mineral soil respiration, a major component of CO2 emissions from soil to atmosphere, plays a critical role in driving terrestrial ecosystem carbon cycling and is highly sensitive to environmental changes, including soil temperature, soil moisture, and substrate availability. The changes of environmental factors can affect mineral soil respiration and its temperature sensitivity thereby alters global carbon balance. We reviewed studies on the effects of environmental factors on mineral soil respiration and its temperature sensitivity. The effect of environmental factors on mineral soil respiration and its temperature sensitivity significantly differed among ecosystems. Environmental factors directly and indirectly affect mineral soil respiration and its temperature sensitivity by altering soil microbial biomass and community structure, extracellular enzyme activity, and soil porosity. Based on the results of this review, we suggested: 1) combining multiple observation techniques and methods to study the effects of environmental factors on mineral soil respiration; 2) exploring the interactive effects of multiple environmental factors on mineral soil respiration; 3) carrying out experiments on mineral soil respiration at different temporal and spatial scales; 4) improving the prediction model of mineral soil respiration and its temperature sensitivity; 5) streng-thening the role of substrate supply of recent photosynthates in the regulation of mineral soil respiration and its temperature sensitivity.

Effects of warming on fine root lifespan of forests: A review.

As an important parameter of forests growth, fine root lifespan plays an important role in plant water and nutrient absorption, and affects underground distribution of photosynthetic products and forest ecosystem carbon cycling. The impact of climate warming on fine root lifespan has become a hot issue under the context of global change. The responses of fine root lifespan to global warming will affect ecosystem carbon balance. We reviewed the research progress of the response characteristics and mechanism of fine root lifespan of trees to warming. Most stu-dies proposed that warming would affect fine root lifespan by changing rhizosphere soil environment, fine root morphology, and tree phenology. However, the growth and death of fine roots were affected by lots of factors, leading to differences in the research results on fine root lifespan due to natural environment of the study area, the way of warming, and the research objects. Therefore, it is of importance to comprehensively analyze the responses of fine root lifespan in forests under the background of climate warming to study the underground ecological process. In the future, the following research should be strengthened: 1) Combining multiple methods to warming underground and aboveground simutaneously, and explore more accurate and effective non-destructive observation methods. 2) Combining multiple observations to study the effects of warming on fine root lifespan. 3) Carrying out research on the effect of warming on fine root lifespan of different tree species, and deeply understand the response mechanism of fine root lifespan of different trees to warming. 4) A comprehensive analysis of the effects of warming on fine root lifespan from various perspectives, and an investigation into the mechanism of the combined effects of various factors on fine root lifespan. 5) The interaction between warming and other environmental factors fine root lifespan. 6) The effect of root architecture on the fine root lifespan after warming. 7) The effects of rhizosphere microorganisms (bacteria and fungi) on fine root lifespan after warming.

Substrate and adenylate limit subtropical tree fine-root respiration under soil warming.

How root respiration acclimates to global warming remains unclear, especially in subtropical forests that play a key role in the global carbon budget. In a large-scale in situ soil warming experiment, the occurrence of, and mechanisms controlling over, the acclimation of fine-root respiration of Cunninghamia lanceolata during the fourth year of warming were investigated. Specific respiration rates (at reference temperature of 20°C; SRR20 ) were measured with exogenous glucose addition, uncoupler addition, or no addition, and root morphological and chemical traits were also measured. Warming decreased SRR20 by 18.4% only during summer, indicating partial thermal acclimation of fine-root respiration under warming. Warming did not change fine-root N concentration, showing no possible enzyme limitation on respiration. Warming decreased root soluble sugar/starch ratio in summer, and glucose addition increased respiration only under warming, indicating a warming-induced substrate limitation on respiration. Uncoupler addition also stimulated respiration only under warming, showing a warming-induced adenylate limitation on respiration. These findings suggest that thermal acclimation of root respiration in subtropical forests, which is at least partially constrained by substrate and adenylate use, is conducive to reducing ecosystem carbon emissions and mitigating the positive feedback between atmospheric CO2 and climate warming.

Soil warming decreased dissolved organic carbon quantity and quality in subtropical forests.

Soil dissolved organic carbon (DOC) is the most active part in forest soil carbon pool, the responses of which to climate warming has profound effects on forest carbon cycling. Based on a manipulative soil warming experiment in subtropical evergreen broad-leaved forests, we collected soil solutions in situ and used ultraviolet-visible, infrared and three-dimensional fluorescence spectroscopy analyses to explore the effects of soil warming (+4 ℃, 1 year) on soil DOC quantity and quality along the soil profile. The results showed that soil DOC flux remained constant along the soil profile. Soil DOC mainly included two humic-like fractions and one microbial metabolite. Warming significantly decreased soil DOC flux and the abundance of aromatic and hydrophobic components, and increased the amount of low molecular weight carbohydrates. Furthermore, soil warming increased the relative proportion of humic-like fractions in the surface soil layer (0-10 cm) and microbial metabolite in the deep soil layer (30-40 cm), indicating that warming might accelerate microbial turnover in the deep layer. Overall, soil warming not only decreased soil DOC content, but also simplified the composition of soil DOC in subtropical evergreen broad-leaved forests.

Effects of warming on quantity and structure of litter-derived dissolved organic matter in subtropical natural Castanopsis kawakamii forests.

Litter-derived dissolved organic matter (DOM) is an important source of soil DOM, and the response of which to climate warming may change forest soil carbon and nitrogen dynamics, such as soil carbon and nitrogen mineralization. In this study, we conducted a field manipulative warming experiment in natural Castanopsis kawakamii forests. Combined with litter leaching solution collected in the field and ultraviolet-visible and three-dimensional fluorescence spectroscopy analyses, we explored the effects of warming on the content and structure of litter-derived DOM in subtropical evergreen broad-leaved forests. The results showed that litter-derived dissolved organic carbon and nitrogen content exhibited monthly dynamics, with the peak (in April) and the mean monthly content being 1.02 and 0.15 g·m-2, respectively. Litter-derived DOM had higher fluorescence index and lower biological index, indicating the microbial-origin of DOM from litter. The litter DOM mainly included humic-like fractions and tryptophan-like substances. Warming did not affect the content, aromaticity, hydrophobicity, molecular weight, fluorescence index, biological index and humification index of DOM, suggesting neutral effect of warming on the quantity and structure of litter DOM. Warming also did not affect the relative contribution of main components in DOM, indicating that the temperature variation exerted no effects on microbial degradation. In summary, warming did not change the quantity and quality of litter-derived DOM in subtropical evergreen broadleaved forests, indicating warming had little effect on litter-derived DOM input to soil.

Root nitrogen uptake capacity of Chinese fir enhanced by warming and nitrogen addition.

There is a knowledge gap in the effects of climate warming and nitrogen (N) deposition on root N absorption capacity, which limits our ability to predict how climate change alters the N cycling and its consequences for forest productivity especially in subtropical areas where soil N availability is already high. In order to explore the effects and mechanism of warming and the N deposition on root N absorption capacity of Chinese fir (Cunninghamia lanceolata), a subtropical arbuscular mycorrhizal conifer, the fine root 15NH4+ and 15NO3- uptake kinetics at a reference temperature of 20 °C were measured across different seasons in a factorial soil warming (ambient, +5 °C) × N addition (ambient, +40 kg N ha-1 yr-1) experiment. The results showed that (i) compared with the control, warming increased the maximal uptake rate of NH4+ (Vmax,20 °C-NH4+) in summer, while N addition enhanced it in spring and summer; compared with non-warming treatments, warming treatments increased the uptake rate of NO3- at a reference concentration of 100 µmol (V100,20 °C-NO3-) in spring. (ii) The analysis of covariance showed that Vmax,20 °C-NH4+ was positively correlated with root mycorrhizal colonization rate (MCR) and V100,20 °C-NO3- was positively correlated with specific root respiration rate (SRR), whereas no N uptake kinetic parameter was correlated with specific root length, root N and non-structural carbon concentrations. Thus, our results demonstrate that warming-increased root NH4+ uptake might be related to warming-increased MCR, whereas warming-increased root NO3- uptake might be related to warming-increased SRR. We conclude that root NH4+ and NO3- uptake capacity of subtropical Chinese fir can be elevated under warming and N deposition, which could improve plantation productivity and mitigate N leaching loss and soil acidification.

Analysis and Prediction of Influence Factors of Green Computing on Carbon Cycle Process in Smart City.

Global warming has become the focus of attention of the international community, and the control of carbon dioxide emissions has become one of the necessary choices for the development strategies of countries around the world. Cities are places where carbon dioxide emissions are concentrated. The key to controlling carbon emissions is to control the carbon emissions of cities. My country is currently in the process of rapid urbanization. Quantitative studies of the carbon cycle at the city level will help to take stock of carbon dioxide emissions in cities. On the other hand, it is helpful to understand the status and role of the urban carbon cycle in the process of the regional carbon cycle. Through the analysis and prediction of the elements influencing the carbon cycle of smart cities, this paper first determines the factors affecting smart cities in the carbon cycle process as industrial carbon emission strength factors, industrial structure effects, economic development factors, and population elements. It is found that the major positive factors affecting the significant add of CO2 emissions in smart cities from 2010 to 2019 are economic development factors and demographic factors, including economic development factors GDP/per capita GDP. The per capita contribution to CO2 emissions is higher than the model established by adjusting the affecting elements of overall CO2 emissions, except that the proportion of economic development factors in total CO2 emissions from 2013 to 2015 was lower than the increase in total CO2 emissions. The comparison can better reflect the relation between CO2 emissions and influencing elements. The main determinants affecting CO2 emissions are the expansion of the financial condition, the increase in the average daily population, and the increase in construction work. The adaptation index is judged to be consistent, indicating that the model adjustment effect is good; finally, the green computing in the smart city predicts the carbon cycle process, and the actual value trend line and the predicted value trend line are not much different from the practical value, the forecast error is small, and the prediction results are credible. Global warming has become the focus of attention of the international community, and carbon emission control has become one of the necessary options in the development strategies of countries around the world. Cities are the places where carbon emissions are concentrated. The key to controlling carbon emissions is to control urban carbon emissions. At present, my country is in the process of rapid urbanization. Quantitative research on the carbon cycle at the city level will help to establish an inventory accounting of urban carbon emissions. On the other hand, it is convenient to deeply understand the status and role of the urban carbon cycle in the process of the regional carbon cycle.

[Effects of management on the content and spectral characteristics of soil dissolved organic carbon in a subtropical forest]. / ç»è¥æ–¹å¼å¯¹äºšçƒ­å¸¦æ£®æž—åœŸå£¤å¯æº¶æ€§æœ‰æœºç¢³å«é‡å’Œå ‰è°±å­¦ç‰¹å¾çš„å½±å“.

The differences of artificial measures, such as logging residue management, between assisted natural regeneration and afforestation may change the content and structure of soil dissolved organic carbon (DOC) and affect forest carbon cycle. In this study, we investigated the effects of managements on the content and spectral characteristics of DOC in a subtropical forest, which contained the forest of assisted natural regeneration (Ⅱ), and the plantation (Ⅲ), both were converted from mature secondary forests (Ⅰ). Results showed that DOC content in the 0-10 cm soil layer was significantly decreased by 21% and 50% in Ⅱ and Ⅲ, respectively, compared with that in Ⅰ. The DOC/SOC (soil organic carbon) ratios of 0-10 cm and 10-20 cm soil layers were significantly decreased by 27% and 43% after the conversion, respectively. In the 0-10 cm soil layer, the aromatic index and humification index of DOC in Ⅱ were significantly higher than that in Ⅲ. The infrared absorption ratio of soil DOC in the range of 3700-3000 cm-1, 1650-1620 cm-1, 1160-1000 cm-1, and 690-530 cm-1 in Ⅱ was higher than that in Ⅲ, indicating that the DOC in Ⅱ had higher carboxylic acids and aromatic substances than Ⅲ. The fluorescence index of DOC in Ⅱ and Ⅲ ranged from 1.4 to 1.9, and the biological index of Ⅱ was significantly higher than that of Ⅲ, indicating that Ⅲ had higher protein components in DOC and being more bioavailable. Thus, the differences of the content and structure of DOC between Ⅱ and Ⅲ might cause higher soil carbon pool of Ⅱ than that of Ⅲ.

[Effects of forest conversion on litterfall nutrient return and nutrient use efficiency in Mid-subtropical China.] / ä¸­äºšçƒ­å¸¦æ£®æž—è½¬æ¢å¯¹å‡‹è½ç‰©å »åˆ†å½’è¿˜åŠå »åˆ†åˆ©ç”¨æ•ˆçŽ‡çš„å½±å“.

To understand the impacts of mid-subtropical forest conversion on carbon and nutrient cycling, we conducted a 4-year investigation to examine litterfall, nutrient return and nutrient use efficiency of Castanopsis carlesii natural forest, C. carlesii secondary forest and Cunninghamia lanceolata plantation which were transformed from C. carlesii natural forest. The results showed that after C. carlesii natural forest was transformed into C. carlesii secon-dary forest and C. lanceolata plantation, the annual litter production decreased by 29.0% and 45.7%, nitrogen return of litter decreased by 34.0% and 72.7%, and phosphorus return decreased by 38.1% and 56.4%, respectively. The amount of carbon returned from litterfall in C. carlesii natural forest was 25.6% and 44.3% higher than that in C. carlesii secondary forest and C. lanceolata plantation, respectively. For C. lanceolata plantation, C. carlesii secondary forest and C. carlesii natural forest, nitrogen use efficiency of litterfall was 175.4, 94.8 and 92.0 kg·kg-1, respectively, and phosphorus use efficiency of litterfall was 3031.0, 2791.6 and 2537.2 kg·kg-1, respectively. It was concluded that C. lanceolata plantation was more limited by nitrogen compared with C. carlesii natural forest and secondary forest, and the effects of phosphorus limitation had similar effects on the three forests.

Root age-related response of fine root respiration of Chinese fir seedlings to soil warming.

The variation in fine root respiration with root age provides insight into root adaptation to climate warming, but the mechanism is poorly understood. In this study, we investigated the respiratory response of fine roots (<1 mm and 1-2 mm) of different ages (2-, 4- and 6-month old) of Chinese fir (Cunninghamia lanceolata (Lamb.)) seedlings to soil warming (4 °C above the control using cable heating). Fine roots were excised to measure the specific respiration rate at a reference temperature of 20 °C (SRR20), and root morphological and chemical traits were measured. Soil warming significantly increased SRR20 by 40% compared with the control, potentially indicating limited acclimation on a short time scale (6 months). However, soil warming increased SRR20 significantly in 2-month-old roots (by 72%) compared with 4- and 6-month-old roots, leading to a steeper decline in SRR20 with root age. This result suggests possible increased nutrient uptake efficiency in young fine roots under warmer temperatures. Soil warming significantly increased specific root length (SRL) but not root tissue nitrogen concentration (RTN). The variation in SRR20 between warming treatments, but not across root ages, was predicted by SRL and RTN individually or together. Our findings conclusively indicate that soil warming increased the respiration cost of young fine roots, which was predicted by adjusting for SRL and RTN, indicating that Chinese fir may adopt a faster fine root turnover strategy to enhance nutrient uptake and soil exploitation under warmer temperatures. Future studies should simultaneously investigate age-related root respiration and nutrient uptake in warming experiments to better understand the effects of warming on root metabolic activity.

Variations in Rainfall Affect the Responses of Foliar Chemical Properties of Cunninghamia lanceolata Seedlings to Soil Warming.

Climate warming is becoming an increasingly serious threat. Understanding plant stoichiometry changes under climate warming is crucial for predicting the effects of future warming on terrestrial ecosystem productivity. Nevertheless, how plant stoichiometry responds to warming when interannual rainfall variation is considered, remains poorly understood. We performed a field soil warming experiment (+5°C) using buried heating cables in subtropical areas of China from 2015 to 2018. Stoichiometric patterns of foliar C:N:P:K:Ca:Mg, non-structural carbohydrate, and stable isotope of Cunninghamia lanceolata seedlings were studied. Our results showed that soil warming decreased foliar P and K concentrations, C:Ca, P:Ca, and P:Mg ratios. However, soil warming increased foliar Ca concentration, δ15N value, C:P and N:P ratios. The response ratios of foliar N, C:N, and δ15N to soil warming were correlated with rainfall. Our findings indicate that there was non-homeostasis of N and C:N under warming conditions. Three possible reasons for this result are considered and include interannual variations in rainfall, increased loss of N, and N limitation in leaves. Piecewise structural equation models showed that stoichiometric non-homeostasis indirectly affected the growth of C. lanceolata seedlings in response to soil warming. Consequently, the growth of C. lanceolata seedlings remained unchanged under the warming treatment. Taken together, our results advance the understanding of how altered foliar stoichiometry relates to changes in plant growth in response to climate warming. Our results emphasize the importance of rainfall variations for modulating the responses of plant chemical properties to warming. This study provides a useful method for predicting the effects of climate warming on economically important timber species.

[Fine root production in initial stage of Castanopsis carlesii under different regeneration modes in Sanming, Fujian Province, China].

Fine root biomass and production in initial stage of three different regeneration approaches, i.e., natural regeneration with anthropogenic promotion (AR) , the Castanopsis carlesii plantation ( CC) and the Cunninghamia lanceolata plantation ( CL) on the clear-cutting sites of the secondary forest of C. carlesii (CK), in Sanming, Fujian Province, were investigated by using both minrhizotrons and the soil coring methods. The results of a year observation showed that the average fine root biomass was 422.5, 253.1, 197.2 and 162.8 g · m(-2), and the fine root production was 284.0, 182.6, 136.7 and 15.4 g · m(-2) · a(-1) for AR, CC, CL and CK, respectively. The maximum value of production was found in spring for AR and CC, in autumn for CL, and in winter for CK. Fine root production of other plants was higher than that of target tree species in CC, and vice verse in CL. There was a significant positive correlation between monthly fine root production and monthly precipitation in AR and CC. Significant positive correlation was found between monthly fine root production of other plants and monthly temperature in CL. The fine root under annual production and annual average biomass of these three young forests mainly distributed in the soil layer of 20- 40 cm, and mainly in the diameter class of 0-1 mm. The study demonstrated that the biomass and production of fine root under anthropogenic promotion were greater than that of the plantation, and the method of anthropogenic promotion were more conducive to increase the returning of organic matter, improve soil fertility, and maintain a high productivity in initial stage of forest regeneration.

[Effects of tree species diversity on fine-root biomass and morphological characteristics in subtropical Castanopsis carlesii forests].

Fine roots in the Castanopsis carlesii plantation forest (MZ), the secondary forest of C. carlesii through natural regeneration with anthropogenic promotion (AR), and the secondary forest of C. carlesii through natural regeneration (NR) in Sanming City, Fujian Province, were estimated by soil core method to determine the influence of tree species diversity on biomass, vertical distribution and morphological characteristics of fine roots. The results showed that fine root biomass for the 0-80 cm soil layer in the MZ, AR and NR were (182.46 +/- 10.81), (242.73 +/- 17.85) and (353.11 +/- 16.46) g x m(-2), respectively, showing an increased tendency with increasing tree species diversity. In the three forests, fine root biomass was significantly influenced by soil depth, and fine roots at the 0-10 cm soil layer accounted for more than 35% of the total fine root biomass. However, the interaction of stand type and soil depth on fine-root distribution was not significant, indicating no influence of tree species diversity on spatial niche segregation in fine roots. Root surface area density and root length density were the highest in NR and lowest in the MZ. Specific root length was in the order of AR > MZ > NR, while specific root surface area was in the order of NR > MZ > AR. There was no significant interaction of stand type and soil depth on specific root length and specific root surface area. Fine root morphological plasticity at the stand level had no significant response to tree species diversity.