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1.
The glycerol contents in diapause larvae of the orange wheat blossom midge, Sitodiplosis mosellana (Gehin), collected from various seasons, were measured. The results showed that there was less glycerol content in larvae during living on the wheat head. Content of glycerol began to increase significantly when the larvae left the wheat head and entered the soil. A change trend of upper- lower- upper- lower in larvae glycerol contents during diapause in soil was observed from June to April of next year. More glycerol could be examined in larvae collected in summer and winter than in spring and autumn. There was not more glycerol in cocooned larvae than that in non-cocooned larvae during various seasons from the point of statistics. Comparing the glycerol content of larvae being diapause in the first year with that of larvae in the second year, there was yet no obvious difference when larvae were collected in the same season belonged to different years. Therefore, it is shown that the content of glycerol in larvae of the wheat midge in diapause is affected mainly by the seasons or diapause intensity.  相似文献   

2.
Aims: It is important to study the effects of land use change and reduced precipitation on greenhouse gas fluxes (CO2, CH4 and N2O) of forest soils. Methods: The fluxes of CO2, CH4 and N2O and their responses to environmental factors of primary forest soil, secondary forest soil and artificial forest soil under a reduced precipitation regime were explored using the static chamber and gas chromatography methods during the period from January to December in 2014. Important findings: Results indicate that CH4 uptake of primary forest soil ((-44.43 ± 8.73) μg C·m-2·h-1) was significantly higher than that of the secondary forest soil ((-21.64 ± 4.86) μg C·m-2·h-1) and the artificial forest soil ((-10.52 ± 2.11) μg C·m-2·h-1). CH4 uptake of the secondary forest soil ((-21.64 ± 4.86) μg C·m-2·h-1) was significantly higher than that of the artificial forest ((-10.52 ± 2.11) μg C·m-2·h-1). CO2 emissions of the artificial forest soil ((106.53 ± 19.33) μg C·m-2·h-1) were significantly higher than that of the primary forest soil ((49.50 ± 8.16) μg C·m-2·h-1) and the secondary forest soil ((63.50 ± 5.35) μg C·m-2·h-1) (p < 0.01). N2O emissions of the secondary forest soil ((1.91 ± 1.22) ug N·m-2·h-1) were higher than that of the primary forest soil ((1.40 ± 0.28) μg N·m-2·h-1) and the artificial forest soil ((1.01 ± 0.86) μg N·m-2·h-1). Reduced precipitation (-50%) had a significant inhibitory effect on CH4 uptake of the artificial forest soil, while it enhanced CO2 emissions of the primary forest soil and the secondary forest soil. Reduced precipitation had a significant inhibitory effect on CO2 emissions of the artificial forest soil and N2O emissions of the secondary forest (p < 0.01). Reduced precipitation promotes N2O emissions of the primary forest soil and the artificial forest soil. CH4 uptake of the primary forest and the secondary forest soil increased significantly with the increase of soil temperature under natural and reduced precipitation. CO2 and N2O emission fluxes of the primary forest soil, secondary forest soil and artificial forest soil were positively correlated with soil temperature (p < 0.05). Soil moisture inhibited CH4 uptake of the secondary forest soil and the artificial forest soil (p < 0.05). CO2 emissions of the primary forest soil were significantly positively correlated with soil moisture (p < 0.05). N2O emissions of primary forest soil and secondary forest soil were significantly correlated with the nitrate nitrogen content (p < 0.05). It was implied that reduced precipitation and land use change would have significant effects on greenhouse gas emissions of subtropical forest soils.  相似文献   

3.
Seasonal changes of thermogenic capacity in Melano-bellied oriental voles (Eothenomysmelanogaster) were studied by measurements of body mass, basal metabolic rate (BMR), non-shivering thermogenesis (NST), thermogenic properties of brown adipose tissue (BAT), relative weight of liver mass, mitochondrial protein (MP) content, and activities of mitochondrial cytochrome C oxidase (COX) in autumn (October), winter (December), spring (April) and summer (July), respectively.
Results showed that: (1) Body mass of E.melanogaster was the highest in autumn, and the lowest in summer. The seasonal change in body mass was subject not only by environment temperature but also to other factors such as reproduction, feeding habit and climate in the habitat. Reproductive periods of E.melanogaster were in early spring (February–March) and late autumn (September–October), and therefore, the body mass was higher in spring and autumn. In addition, E.melanogaster feeds on leaves and stems of plants in spring and summer, whereas mainly on fruits in autumn and winter as they contain more energy. The difference in the feeding habit could result in higher body mass in the late half of the year, but lower body mass in winter. The lower body mass in winter provides E.melanogaster with an advantage in motility. (2) The BMR and NST of E.melanogaster was higher in winter than in other seasons, which suggests that the regulating thermogenic capacity is an important adaptive strategy for E.melanogaster. However, there was no difference in relative oxygen consumption (NST–BMR/BMR), suggesting that the regulative capacity of BMR is approximately equal to NST in E.melanogaster. This is different from some small mammal species in north China, which have higher regulative capacity in NST than E.melanogaster. Melano-bellied oriental voles live in mountainous area with subtropical zone monsoon climate and abundant food resource, and therefore have lower regulative capacity in NST, which can reduce an absolute request for energy. The low regulative capacity in NST can also help E.melanogaster to maintain energy balance and stable body temperature. (3) The relative mass of BAT in winter was significantly higher than that in summer. Different seasons significantly affected the MP content of BAT. The MP content of BAT was in the following order: winter > fall > spring > summer. The trend as following was observed for the mitochondrial COX activity of BAT: winter > spring > fall > summer. In experimental conditions, the thermogenic rate of many small mammal species increased under cold acclimation. Short photoperiod alone could also induce E.melanogaster to increase NST and mitochondrial COX activity of BAT. Therefore, ambient temperature and photoperiod are important environmental cues to induce seasonal changes in thermogenic capacity in E.melanogaster. (4) The relative mass of liver in summer was higher than that in other seasons, but no seasonal changes were found among other seasons. The MP contents of liver showed highest level in winter and lowest in spring and summer. Significant seasonal changes were also observed in the mitochondrial COX activity of liver. It increased significantly in winter, but not in other seasons. This indicates that liver participate in adjustment of thermogenesis. These data indicate that both increasing whole-animal thermogenesis rate and thermogenic capacity at the cells of BAT and liver play an important role in the adaption of E.melanogaster to seasonal changes, and they are also closely correlated with the habitat condition and their life habit.  相似文献   

4.
Seasonal changes of thermogenic capacity in Melano-bellied oriental voles (Eothenomysmelanogaster) were studied by measurements of body mass, basal metabolic rate (BMR), non-shivering thermogenesis (NST), thermogenic properties of brown adipose tissue (BAT), relative weight of liver mass, mitochondrial protein (MP) content, and activities of mitochondrial cytochrome C oxidase (COX) in autumn (October), winter (December), spring (April) and summer (July), respectively.
Results showed that: (1) Body mass of E.melanogaster was the highest in autumn, and the lowest in summer. The seasonal change in body mass was subject not only by environment temperature but also to other factors such as reproduction, feeding habit and climate in the habitat. Reproductive periods of E.melanogaster were in early spring (February–March) and late autumn (September–October), and therefore, the body mass was higher in spring and autumn. In addition, E.melanogaster feeds on leaves and stems of plants in spring and summer, whereas mainly on fruits in autumn and winter as they contain more energy. The difference in the feeding habit could result in higher body mass in the late half of the year, but lower body mass in winter. The lower body mass in winter provides E.melanogaster with an advantage in motility. (2) The BMR and NST of E.melanogaster was higher in winter than in other seasons, which suggests that the regulating thermogenic capacity is an important adaptive strategy for E.melanogaster. However, there was no difference in relative oxygen consumption (NST–BMR/BMR), suggesting that the regulative capacity of BMR is approximately equal to NST in E.melanogaster. This is different from some small mammal species in north China, which have higher regulative capacity in NST than E.melanogaster. Melano-bellied oriental voles live in mountainous area with subtropical zone monsoon climate and abundant food resource, and therefore have lower regulative capacity in NST, which can reduce an absolute request for energy. The low regulative capacity in NST can also help E.melanogaster to maintain energy balance and stable body temperature. (3) The relative mass of BAT in winter was significantly higher than that in summer. Different seasons significantly affected the MP content of BAT. The MP content of BAT was in the following order: winter > fall > spring > summer. The trend as following was observed for the mitochondrial COX activity of BAT: winter > spring > fall > summer. In experimental conditions, the thermogenic rate of many small mammal species increased under cold acclimation. Short photoperiod alone could also induce E.melanogaster to increase NST and mitochondrial COX activity of BAT. Therefore, ambient temperature and photoperiod are important environmental cues to induce seasonal changes in thermogenic capacity in E.melanogaster. (4) The relative mass of liver in summer was higher than that in other seasons, but no seasonal changes were found among other seasons. The MP contents of liver showed highest level in winter and lowest in spring and summer. Significant seasonal changes were also observed in the mitochondrial COX activity of liver. It increased significantly in winter, but not in other seasons. This indicates that liver participate in adjustment of thermogenesis. These data indicate that both increasing whole-animal thermogenesis rate and thermogenic capacity at the cells of BAT and liver play an important role in the adaption of E.melanogaster to seasonal changes, and they are also closely correlated with the habitat condition and their life habit.  相似文献   

5.
The extent and biomass of the Gracilaria beds in the Lüderitz Bay area, Namibia were surveyed in winter and summer. The beds covered most of the suitable sediments available (grain size 106–212 μm) and did not occur in water shallower than 1 m or deeper than 11 m. Total surface area, most of which occurred in the Bay system, changed very little from winter to summer but biomass increased by 3.5 fold. In winter, total Gracilaria biomass was 200 t and 650 t and in summer, 150 t and 2850 t respectively in the Lagoon and Bay. Maximum biomass occurred at 3–4 m in the Lagoon and 5–6 m in the Bay in both winter and summer. Gracilaria beach cast data from 1987 to 1991 for the area were analysed for seasonality and, depending on the specific site, correlated with swell, southerly wind velocity and sea temperature. Beach cast in the Lagoon system is a more continuous process than in the Bay, where beach casts at most sites follow an annual pattern. Wind driven currents and chop were the most important causative parameters of beach cast in the Lagoon whereas the depth at which the plants were growing and swell were more important in the Bay system. The two systems viz. Lagoon and Bay are independent of one another with very little or no exchange of Gracilaria between them. This was evidenced by the similar percentage each contributes to the total beach cast and the similar pattern of beach cast from year to year. The decrease in total beach cast from 1989 to the end of the study period was attributed to a trend towards increasing swell height and low sea temperatures in 1991.  相似文献   

6.
Teleconnection between the early immigration of brown planthopper (BPH) and El Nino/Southern Oscillation (ENSO) indices from January of two years previously to the current June was investigated to make long-term forecast. The teleconnection results were as follows: ENSO indices which were significantly correlated with the early immigration of BPH were primarily sea surface temperature anomalies (SSTA) in N3, N4 and N3.4 regions, accounting for 71.8% of the total. Significant ENSO indices from two years and one year before the immigration events had a proportion of about 84%, while those in the current year only accounted for 16.7%. There was significantly negative correlation between the early immigration of BPH and SSTA in each Nino region from two years before to the previous spring, whereas there was significantly positive correlation between these two factors during the period from the previous winter to the current spring. The significant correlation between the early immigration of BPH and SSTA in each Nino region in the last summer and autumn did not show any obvious tendencies. The relationship between the southern oscillation index (SOI) and the early immigration of BPH was opposite to that between the immigration and SSTA in each Nino region. The above mentioned significant ENSO indices were used as key factors to build forecasting models for the early immigration of BPH by step-wise multiple linear regression analysis. Finally, 12 integrated forecasting models were obtained, which could make predictions 3–27 months ahead and had a predictive accuracy of 88.9%.  相似文献   

7.
The influence of climate change on the terrestrial vegetation health (condition) is one of themost significant problems of global change study. The vegetation activity plays a key role in the globalcarbon cycle. The authors investigated the relationship of the advanced very high resolution radiometer-normalized difference vegetation index (AVHRR-NDVI) with the large-scale climate variations on the inter-annual time scale during the period 1982-2000 for the growing seasons (April to October). A singular valuedecomposition analysis was applied to the NDV! and surface air temperature data in the time-domain todetect the most predominant modes coupling them. The first paired-modes explain 60.9%, 39.5% and 24.6%of the squared covariance between NDV! and temperature in spring (April and May), summer (June andAugust), and autumn (September to October), respectively, which implies that there is the highest NDVIsensitivity to temperature in spring and the lowest in autumn. The spatial centers, as revealed by themaximum or minimum vector values corresponding to the leading singular values, indicate the highsensitive regions. Only considering the mode 1, the sensitive center for spring is located in westernSiberia and the neighbor eastern Europe with a sensitivity of about 0.308 0 NDVI/℃. For summer, thereare no predominantly sensitive centers, and on average for the relatively high center over 100^o-120^o E by 45^o-60^o N, the (110^o-140^o E,55^o-65^oN)sitivity is 0.248 0 NDVI/℃. For autumn, the center is located over the high latitudes ofeastern Asia (110^o-140^o E, 55^o-65^o N), and the sensitivity is 0.087 5 NDVI/℃. The coherent patters asrevealed by the singular decomposition analysis remain the same when coarser resolution NDVI data wereused, suggesting a robust and stable climate/vegetation relationship.  相似文献   

8.
A developing trophic mismatch between the peak of energy demands by reproducing animals and the peak of forage availability has caused many species'reproductive success to decrease.The match-mismatch hypothesis(MMH)is an appealing concept that can be used to assess such fitness consequences.However,concerns have been raised on applying the MMH on capital breeders such as reindeer because the reliance on maternal capita rather than dietary income may mitigate negative effects of changing phenologies.Using a long-term dataset of reindeer calving dates recorded since 1970 in a semidomesticated reindeer population in Finnish Lapland and proxies of plant phenology;we tested the main hypothesis that the time lag between calving date and the plant phenology in autumn when females store nutrient reserves to finance reproduction would lead to consequences on reproductive success,as the time lag with spring conditions would.As predicted,the reproductive success of females of the Kutuharju reindeer population was affected by both the onset of spring green-up and vegetative senescence in autumn as calves were born heavier and with a higher first-summer survival when the onset of the vegetation growth was earlier and the end of the thermal growing season the previous year was earlier as well.Our results demonstrated that longer plant growing seasons might be detrimental to reindeer's reproductive success if a later end is accompanied by a reduced abundance of mushrooms.  相似文献   

9.
Aims Nitrous oxide (N2O) is one of the most important greenhouse gases, which contributes a lot to global warming. However, considerable variations are observed in the responses of soil N2O emissions to experimental warming, and the underlying microbial processes remain unknown. Methods A warming experiment based on open-Top chambers (OTCs) was set up in a typical alpine steppe on the Qinghai-Xizang Plateau. The static chamber combined gas chromatography method was applied to investigate soil N2O flux under control and warming treatments during the growing seasons in 2014 and 2015. Gene abundances of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) were quantified using quantitative real-Time PCR. Important findings Our results showed that the warming treatments increased soil temperature by 1.7 and 1.6 °C and decreased volumetric water content by 2.5% and 3.3% respectively during the growing season (May to October) in 2014 and 2015. However, there were no significant differences in other soil properties. Our results also revealed that, the magnitude of soil N2O emissions exhibited substantial variations between the two experi mental years, which were 3.23 and 1.47 μg·m-2·h-1 in 2014 and 2015, respectively, but no significant difference in N2O fluxes was observed between control and warming treatments. AOA and AOB abundances are 15.2 × 107 and 10.0 × 105 copies·g-1 in 2014, and 5.0 × 107 and 4.7 × 105 copies·g-1 in 2015, with no significant differences between control and warming treatments during the experimental period. Furthermore, warming-induced changes in N2O emissions had no significant relationship with the changes in soil temperature, but showed a significant positive correlation with the changes in soil moisture at seasonal scale. Overall, these results demonstrate that soil moisture regulates the responses of N2O emissions to experimental warming, highlighting the necessity to consider the warming-induced drying effect when estimating the magnitude of N2O emissions under future climate warming. © 2018 Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.  相似文献   

10.
Li H Q  Lian Z M  Chen C G  Wu S B 《农业工程》2009,29(5):302-306
A study on the seasonal changes in the ranging area of Brown-eared pheasant and its affecting factors was conducted in the Huanglongshan Nature Reserve, Huanglong County, Shaanxi Province, China, from March 2006 to January 2007. Forty used sites and forty random plots were selected along 8–9 transects crossing the study area. Fifteen factors related to the changes of altitude were measured in each site. The results showed that the altitude of home range of Brown-eared pheasant varied with seasons: the highest home range was found in summer, and the lowest one was found in winter, while the home range in autumn was higher than that in spring. According to the frequency of occurrences of Brown-eared pheasant in different seasons, we found that its home range occurred mainly at an altitude below 1400 m in spring, above 1500 m in summer, between 1200 m and 1500 m in autumn and below 1300 m in winter. The possible reason that Brown-eared pheasants preferred to live at lower altitude in spring was to have access to water sources and the abundance of food, correlated to the slope locations, number of trees and number of shrubs; in summer, they tended to appear at highest altitude, and the average height of shrubs, average height of grasses, sheltering class and distance to edge of woods, and human disturbance were affecting factors; in autumn, they appeared at higher altitude which was correlated with the covers of trees, shrubs and grasses, and ultimately related to the abundance of food; in winter, they lived at lowest altitude, which was correlated to the distance from the edge of woods, cover of trees and sheltering class, and ultimately related to the abundance of food and shelter.  相似文献   

11.
A study on the seasonal changes in the ranging area of Brown-eared pheasant and its affecting factors was conducted in the Huanglongshan Nature Reserve, Huanglong County, Shaanxi Province, China, from March 2006 to January 2007. Forty used sites and forty random plots were selected along 8–9 transects crossing the study area. Fifteen factors related to the changes of altitude were measured in each site. The results showed that the altitude of home range of Brown-eared pheasant varied with seasons: the highest home range was found in summer, and the lowest one was found in winter, while the home range in autumn was higher than that in spring. According to the frequency of occurrences of Brown-eared pheasant in different seasons, we found that its home range occurred mainly at an altitude below 1400 m in spring, above 1500 m in summer, between 1200 m and 1500 m in autumn and below 1300 m in winter. The possible reason that Brown-eared pheasants preferred to live at lower altitude in spring was to have access to water sources and the abundance of food, correlated to the slope locations, number of trees and number of shrubs; in summer, they tended to appear at highest altitude, and the average height of shrubs, average height of grasses, sheltering class and distance to edge of woods, and human disturbance were affecting factors; in autumn, they appeared at higher altitude which was correlated with the covers of trees, shrubs and grasses, and ultimately related to the abundance of food; in winter, they lived at lowest altitude, which was correlated to the distance from the edge of woods, cover of trees and sheltering class, and ultimately related to the abundance of food and shelter.  相似文献   

12.
Aims Alpine shrub-meadows and steppe-meadows are the two dominant vegetation types on the Qinghai-Xizang Plateau, and plays an important role in regional carbon cycling. However, little is known about the temporal- spatial patterns and drivers of CO2 fluxes in these two ecosystem types. Methods Based on five years of consecutive eddy covariance measurements (2004-2008) in an eastern alpine shrub-meadow at Haibei and a hinterland alpine steppe-meadow at Damxung, we investigated the seasonal and annual variation of net ecosystem productivity (NEP) and its components, i.e. gross primary productivity (GPP) and ecosystem respiration (Re). Important findings The CO2 fluxes (NEP, GPP and Re) were larger in the shrub-meadow than in the steppe-meadow during the study period. The shrub-meadow functioned as a carbon sink through the five years, with the mean annual NEP of 70 g C·m-2·a-1. However, the steppe-meadow acted as a carbon neutral, with mean annual NEP of -5 g C·m-2·a-1. The CO2 fluxes of steppe-meadow exhibited large variability due to the inter-Annual and seasonal variations in precipitation, ranging from a carbon sink (54 g C·m-2·a-1) in 2008 to a carbon source (-88 g C·m-2·a-1) in 2006. The differences in carbon budget between the two alpine ecosystems were firstly attributed to the discrepancy of normalized difference vegetation index (NDVI) because NDVI was the direct factor regulating the seasonal and inter-Annual NEP. Secondly, the shrub-meadow had higher carbon use efficiency (CUE), which was substantially determined by annual precipitation (PPT) and NDVI. Our results also indicated that the environmental drivers of CO2 fluxes were also different between these two alpine ecosystems. The structure equation model analyses showed that air temperature (Ta) determined the seasonal variations of CO2 fluxes in the shrub-meadow, with NEP and GPP being positively correlated with Ta. By contrast, the seasonal CO22 fluxes in the steppe-meadow were primarily co-regulated by soil water content (SWC) and Ta, and increased with the increase of SWC and Ta. In addition, the changes of Re during the growing season in two ecosystems were directly affected by GPP and soil temperature at 5 cm depth (Ts), while Re during non-growing season were determined by Ts. These results demonstrate that the synergy of soil water and temperature played crucial roles in determining NEP and GPP of the two alpine meadows on the Qinghai-Xizang Plateau. © 2018 Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.  相似文献   

13.
Contents of rutin and catechin in leaves and under-ground part of Potentilla fragarioides L.in spring and autumn were determined by HPLC technology.The results show that in spring,rutin content in leaves and under-ground part of P.fragarioides is 1.670 3 and 0.054 4 mg·g-1,and catechin content is 0.263 5 and 0.723 5 mg·g-1,respectively.In autumn,rutin content is 0.586 9 and 0.010 7 mg·g-1,and catechin content is 0.784 3 and 0.366 4 mg·g-1,respectively.The rutin content in leaves is the highest in spring,and catechin content in leaves is the highest in autumn.Therefore,collecting leaves in spring is suitable for taking rutin as a purpose,while collecting leaves in autumn is suitable for taking catechin as a purpose.  相似文献   

14.
Teleconnection between the early immigration of brown planthopper (BPH) and El Nino/Southern Oscillation (ENSO) indices from January of two years previously to the current June was investigated to make long-term forecast. The teleconnection results were as follows: ENSO indices which were significantly correlated with the early immigration of BPH were primarily sea surface temperature anomalies (SSTA) in N3, N4 and N3.4 regions, accounting for 71.8% of the total. Significant ENSO indices from two years and one year before the immigration events had a proportion of about 84%, while those in the current year only accounted for 16.7%. There was significantly negative correlation between the early immigration of BPH and SSTA in each Nino region from two years before to the previous spring, whereas there was significantly positive correlation between these two factors during the period from the previous winter to the current spring. The significant correlation between the early immigration of BPH and SSTA in each Nino region in the last summer and autumn did not show any obvious tendencies. The relationship between the southern oscillation index (SOI) and the early immigration of BPH was opposite to that between the immigration and SSTA in each Nino region. The above mentioned significant ENSO indices were used as key factors to build forecasting models for the early immigration of BPH by step-wise multiple linear regression analysis. Finally, 12 integrated forecasting models were obtained, which could make predictions 3–27 months ahead and had a predictive accuracy of 88.9%.  相似文献   

15.
The structure and dynamics of periphytic algae in Jinyang Lake, the largest man-made lake in Taiyuan, Shanxi, have been studied by examining the periphytic algae samples collected from four sampling stations, during March 2006 to February 2007. In total, 227 species of periphytic algae (including varieties), belonging to three divisions, 27 families, 62 genera, have been identified. Diatoms were the dominant periphytic algae group. Taken the Shannon–Weaver, Margalef and Simpson diversity index together, it showed obvious temporal and spatial dynamics among different seasons and different sampling stations. The highest periphytic community structure evenness appeared at sampling station I in spring, summer and autumn, while at sampling station III in winter. The average biomass of periphytic algae varied from seasons. Our data showed that major factors affecting the periphytic algae in Jinyang Lake was water temperature, nutrient levels as well as human activities. In addition, the main effect caused by thermal power plant has been discussed.  相似文献   

16.
Feng J  Wang F  Xie S L 《农业工程》2011,31(6):310-316
The structure and dynamics of periphytic algae in Jinyang Lake, the largest man-made lake in Taiyuan, Shanxi, have been studied by examining the periphytic algae samples collected from four sampling stations, during March 2006 to February 2007. In total, 227 species of periphytic algae (including varieties), belonging to three divisions, 27 families, 62 genera, have been identified. Diatoms were the dominant periphytic algae group. Taken the Shannon–Weaver, Margalef and Simpson diversity index together, it showed obvious temporal and spatial dynamics among different seasons and different sampling stations. The highest periphytic community structure evenness appeared at sampling station I in spring, summer and autumn, while at sampling station III in winter. The average biomass of periphytic algae varied from seasons. Our data showed that major factors affecting the periphytic algae in Jinyang Lake was water temperature, nutrient levels as well as human activities. In addition, the main effect caused by thermal power plant has been discussed.  相似文献   

17.
Zhang W  Mo J M  Fang Y T  Lu X K  Wang H 《农业工程》2008,28(5):2309-2319
Nitrogen (N) deposition can alter the rates of microbial N- and C- turnover, and thus can affect the fluxes of greenhouse gases (GHG, e.g., CO2, CH4, and N2O) from forest soils. The effects of N deposition on the GHG fluxes from forest soils were reviewed in this paper. N deposition to forest soils have shown variable effects on the soil GHG fluxes from forest, including increases, decreases or unchanged rates depending on forest type, N status of the soil, and the rate and type of atmospheric N deposition. In forest ecosystems where biological processes are limited by N supply, N additions either stimulate soil respiration or have no significant effect, whereas in “N saturated” forest ecosystems, N additions decrease CO2 emission, reduce CH4 oxidation and elevate N2O flux from the soil. The mechanisms and research methods about the effects of N deposition on GHG fluxes from forest soils were also reviewed in this paper. Finally, the present and future research needs about the effects of N deposition on the GHG fluxes from forest soils were discussed.  相似文献   

18.
Global temperature has been Increased by 0.6 ℃ over the past century and is predicted to Increase by 1.4-5.8 ℃ by the end of this century. It is unclear what impacts global warming will have on tallgrass species. In the present study, we examined leaf net photosynthetic rate (P.) and leaf respiration rate in darkness (Rd) of Aster erlcoldes (L.) Nesom, Ambrosia psllostachya DC., Helianthus mollis Lam., and Sorghastrum nutans (L.) Nash In response to experimental warming in a tallgrass prairie ecosystem of the Great Plains, USA, in the autumn (fall) of 2000 and through 2001. Warming has been Implemented with infrared heaters since 21 November 1999. The P. increased significantly In spring, decreased in early fall, and did not change in summer and late fall in the four species under warming compared with control. The Rd of the four species increased significantly until mid-summer and then did not change under warming. Measured temperature-response curves of P. showed that warming Increased the optimum temperature of P. (Topt) by 2.32 and 4.59 ℃ for H. mollis and S. nutans, respectively, in August, whereas there were no changes in May and September, and A. ericoldes and A. psllostachya also showed no changes in any of the 3 months. However, P. at optimum temperature (Popt) showed downregulation in September and no regulation in May and August for all four species. The temperature-response curves of Rd Illustrate that the temperature sensitivity of Rd, Q10, was lower in the warmed plots compared with the control plots, except for A. ericoides in August, whereas there were no changes In May and September for all four species. The results of the present study indicate that photosynthetic and respiratory acclimation varies with species and among seasons, occurring In the mid-growing season and not in the early and late growing seasons.  相似文献   

19.
Aims Accurate estimation of variation tendency of photosynthetic electron flow response to CO 2 is of great significance to understand the photosynthetic processes. Methods A model of electron transport rate (J) response to CO 2 (model II) was developed based on a new model of photosynthesis response to CO 2 (model I). The data of maize (Zea mays) and grain amaranth (Amaranthus hypochondriacus) that were measured by LI-6400-40 portable photosynthetic apparatus were fitted by the two models, respectively. Important findings The results indicated that the model II could well characterize and fit the CO 2 -response curves of electron transport rate (J-C a curve) for maize and grain amaranth, and the maximum electron transport rates of maize and grain amaranth were 262.41 and 393.07 mol·m −2 ·s −1 , which were in very close agreement with the estimated values (p > 0.05), respectively. Based on these results, the allocation to other pathways of photosynthetic electronic flow were discussed. At 380 mol·mol −1 CO 2 , the photosynthetic electron flows for carbon assimilation of maize and grain amaranth carbon were 247.92 and 285.16 mol·m −2 ·s −1 , respectively, when the CO 2 for recovery of mitochondrial respiration was considered, and the photosynthetic electron flows for other pathways were 14.49 and 107.91 mol·m −2 ·s −1 , respectively. The photosynthetic electron flows for other pathways in grain amaranth were more six times than that in maize. The analysis shows that this difference is closely related to the types of catalytic decarboxylase and the locations of decarboxylation reactions. This finding provides a new perspective for investigating the differences between the two subtypes of nicotinamide adenine dinucleotide phosphate malic acid enzyme type and nicotinamide adenine dinucleotide malic acid enzyme type in C 4 species. In addition, the CO 2 -response model of electron transport rate offers us an alternative mathematical tool for investigating the photosynthetic electron flow of C4 crop. © 2018 Editorial Office of Chinese Journal of Plant Ecology. All Rights Reserved.  相似文献   

20.
Aims Our aim was to characterize the effects of nitrogen (N) addition on plant root standing crop, production, mortality and turnover in an alpine meadow on the Northwestern plateau of Sichuan Province, China. Methods A N addition experiment was conducted in an alpine meadow on the Northwestern plateau of Sichuan Province since 2012. Urea was applied at four levels: 0, 10, 20 and 30 g·m-2·a-1, referred to as CK, N10, N20 and N30. Root samples in surface (0-10 cm) and subsurface layers (10-20 cm) were observed using Minirhizotron from May 10th to Sept. 27th in 2015. The root standing crop, production, mortality and turnover rate were estimated using WinRHZIO Tron MF software. Repeated-measure ANOVA, one-way ANOVA and Pearson correlation were performed to analyze the effect of N addition on soil and root characteristics. Important findings N addition significantly increased soil available N content and decreased soil pH value, but did not alter soil total N and SOM contents under all treatments. N addition did not exhibit any significant effects on the mean root standing crop and cumulative root production in the 0-10 cm, but significantly reduced mean root standing crop and cumulative root production in 10-20 cm soil layer by 195.3 and 142.3 g·m-2 (N10), 235.8 and 212.1 g·m-2 (N20) and 198.0 and 204.4 g·m-2 (N30), respectively. The cumulative root mortality was significantly decreased by 206.1 g·m-2 in N10 treatment and root turnover rate was significantly increased with 17% for N30 treatment at the 0-10 cm soil depth, but the cumulative root mortality and root turnover rate was not significantly different at 10-20 cm soil depth. In addition, cumulative root production, mortality and turnover rate in 0-10 cm soil layer were significantly correlated with the soil available N content, whereas no significant associations were observed in 10-20 cm soil. Taken together, these results demonstrate that N addition alters the soil N availability and thus induces the root dynamics and changes in root distribution as well as C allocation in alpine meadow. © 2018 Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.  相似文献   

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