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1.
The Dinghushan flux observation site, as one of the four forest sites of ChinaFLUX, aims to acquire long-term measurements of CO 2 flux over a typical southern subtropical evergreen coniferous and broad-leaved mixed forest ecosystem using the open path eddy covariance method. Based on two years of data from 2003 to 2004, the characteristics of temporal variation in CO 2 flux and its response to environmental factors in the forest ecosystem are analyzed. Provided two-dimensional coordinate rotation, WPL correction and quality control, poor energy-balance and underestimation of ecosystem respiration during nighttime implied that there could be a CO 2 leak during the nighttime at the site. Using daytime ( PAR > 1.0 μmol ?1·m ?2·s ?1) flux data during windy conditions ( u* > 0.2 m·s ?1), monthly ecosystem respiration ( Reco) was derived through the Michaelis-Menten equation modeling the relationship between net ecosystem C0 2 exchange ( NEE) and photosynthetically active radiation ( PAR). Exponential function was employed to describe the relationship between Reco and soil temperature at 5 cm depth ( Ts05), then Reco of both daytime and nighttime was calculated respectively by the function. The major results are: (i) Derived from the Michaelis-Menten equation, the apparent quantum yield ( α) was 0.0027±0.0011 mgCO 2·μmol ?1 photons, and the maximum photosynthetic assimilation rate ( Amax) was 1.102±0.288 mgCO 2·m ?2·s ?1. Indistinctive seasonal variation of α or Amax was consistent with weak seasonal dynamics of leaf area index ( LAf) in such a lower subtropical evergreen mixed forest, (ii) Monthly accumulated Reco was estimated as 95.3±21.1 gC·m ?2mon ?1, accounting for about 68% of the gross primary product ( GPP). Monthly accumulated WEE was estimated as ?43.2±29.6 gC·m ?2·mon ?1. The forest ecosystem acted as carbon sink all year round without any seasonal carbon efflux period. Annual NEE of 2003 and 2004 was estimated as ?563.0 and ?441.2 gC·m ?2·a ?1 respectively, accounting for about 32% of GPP. 相似文献
2.
As one component of ChinaFLUX, the measurement of CO 2 flux using eddy covariance over subtropical planted coniferous ecosystem in Qianyanzhou was conducted for a long term. This paper discusses the seasonal dynamics of net ecosystem exchange (NEE), ecosystem respiration (RE) and gross ecosystem exchange (GEE) between the coniferous ecosystem and atmosphere along 2003 and 2004. The variations of NEE, RE and GEE show obvious seasonal variabilities and correlate to each other, i.e. lower in winter and drought season, but higher in summer; light, temperature and soil water content are the main factors determining NEE; air temperature and water vapor pressure deficit (VPD) influence NEE with stronger influence from VPD. Under the proper light condition, drought stress could decrease the temperature range for carbon capture in planted coniferous, air temperature and precipitation controlled RE; The NEE, RE, and GEE for planted coniferous in Qianyanzhou are ?387.2 g C·m ?2 a ?1, 1223.3 g C·m ?2 a ?1, ?1610.4 g C·m ?2 a ?1 in 2003 and ?423.8 g C·m ?2 a ?1, 1442.0 g C·m ?2 a ?1, ?1865.8 g C·m ?2 a ?1 in 2004, respectively, which suggest the intensive ability of plantation coniferous forest on carbon absorbing in Qianyanzhou. 相似文献
3.
The Dinghushan flux observation site, as one of the four forest sites of ChinaFLUX, aims to acquire long-term measurements of CO2 flux over a typical southern subtropical evergreen coniferous and broad-leaved mixed forest ecosystem using the open path eddy covariance method. Based on two years of data from 2003 to 2004, the characteristics of temporal variation in CO2 flux and its response to environmental factors in the forest ecosystem are analyzed. Provided two-dimensional coordinate rotation, WPL correction and quality control, poor energy-balance and underestimation of ecosystem respiration during nighttime implied that there could be a CO2 leak during the nighttime at the site. Using daytime (PAR > 1.0 μmol−1·m−2·s−1) flux data during windy conditions (u* > 0.2 m·s−1), monthly ecosystem respiration (Reco) was derived through the Michaelis-Menten equation modeling the relationship between net ecosystem C02 exchange (NEE) and photosynthetically active radiation (PAR). Exponential function was employed to describe the relationship between Reco and soil temperature at 5 cm depth (Ts05), then Reco of both daytime and nighttime was calculated respectively by the function. The major results are: (i) Derived from the Michaelis-Menten equation, the apparent quantum yield (α) was 0.0027±0.0011 mgCO2·μmol−1 photons, and the maximum photosynthetic assimilation rate (Amax) was 1.102±0.288 mgCO2·m−2·s−1. Indistinctive seasonal variation of α or Amax was consistent with weak seasonal dynamics of leaf area index (LAf) in such a lower subtropical evergreen mixed forest, (ii) Monthly accumulated Reco was estimated as 95.3±21.1 gC·m−2mon−1, accounting for about 68% of the gross primary product (GPP). Monthly accumulated WEE was estimated as −43.2±29.6 gC·m−2·mon−1. The forest ecosystem acted as carbon sink all year round without any seasonal carbon efflux period. Annual NEE of 2003 and 2004 was estimated as −563.0 and −441.2 gC·m−2·a−1 respectively, accounting for about 32% of GPP. 相似文献
4.
Long-term measurement of carbon metabolism of old-growth forests is critical to predict their behaviors and to reduce the uncertainties of carbon accounting under changing climate. Eddy covariance technology was applied to investigate the long-term carbon exchange over a 200 year-old Chinese broad-leaved Korean pine mixed forest in the Changbai Mountains (128°28′E and 42°24′N, Jilin Province, P. R. China) since August 2002. On the data obtained with open-path eddy covariance system and CO 2 profile measurement system from Jan. 2003 to Dec. 2004, this paper reports (i) annual and seasonal variation of F NEE, F GPP and R E; (ii) regulation of environmental factors on phase and amplitude of ecosystem CO 2 uptake and release Corrections due to storage and friction velocity were applied to the eddy carbon flux. LAI and soil temperature determined the seasonal and annual dynamics of FGPP and RE separately. VPD and air temperature regulated ecosystem photosynthesis at finer scales in growing seasons. Water condition at the root zone exerted a significant influence on ecosystem maintenance carbon metabolism of this forest in winter.The forest was a net sink of atmospheric CO 2 and sequestered ?449 g C·m ?2 during the study period; ?278 and ?171 gC·m ?2 for 2003 and 2004 respectively. F GPP and F RE over 2003 and 2004 were ?1332, ?1294 g C·m ?2. and 1054, 1124 g C·m ?2 respectively. This study shows that old-growth forest can be a strong net carbon sink of atmospheric CO 2.There was significant seasonal and annual variation in carbon metabolism. In winter, there was weak photosynthesis while the ecosystem emitted CO 2. Carbon exchanges were active in spring and fall but contributed little to carbon sequestration on an annual scale. The summer is the most significant season as far as ecosystem carbon balance is concerned. The 90 days of summer contributed 66.9, 68.9% of F GPP, and 60.4, 62.1% of R E of the entire year. 相似文献
5.
Based on the light-photosynthesis response measurement at leaf level, combined with over-and under-canopy eddy covariance measurements, research on photosynthetic characteristics of single trees and forest canopy was conducted. The relationship between light intensity and photosynthetic rates for leaves and canopy can be well fitted by a non-rectangular hyperbola model. Mongolian oak presented a high light compensation point, L cp (28 μmol·m ?2·s ?1), a light saturation point L sp (>1800 μmol·m ?2·s ?1), and a maximal net photosynthetic rate P max (9.96 μmol·m ?2·s ?1), which suggest that it is a typical heliophilous plant. Mono maple presented the highest apparent quantum efficiency α (0.066) but the lowest, L cp (16 μmol·m ?2·s ?1), L sp (≈800 μmol·m ?2·s ?1), and P max (4.51 μmol·m ?2·s ?1), which suggest that it is heliophilous plant. Korean pine showed the lowest α value but a higher P max, which suggest that it is a semi-heliophilous plant. At the canopy level, the values of both α and P max approached the upper limit of reported values in temperate forests, while L cp was within the lower limit. Canopy photosynthetic characteristics were well consistent with those of leaves. Both showed a high ability to photosynthesize. However, environmental stresses, especially high vapor pressure deficits, could significantly reduce the photosynthetic ability of leaves and canopy. 相似文献
6.
Eddy covariance technique was used to measure carbon flux during two growing seasons in 2003 and 2004 over typical steppe in the Inner Mongolia Plateau, China. The results showed that there were two different CO 2 flux diurnal patterns at the grassland ecosystem. One had a dual peak in diurnal course of CO 2 fluxes with a depression of CO 2 flux after noon, and the other had a single peak. In 2003, the maximum diurnal uptake and emitting value of CO 2 were ?7.4 and 5.4 g·m ?2·d ?1 respectively and both occurred in July. While in 2004, the maximum diurnal uptake and release of CO 2 were ?12.8 and 5.8 g·m ?2·d ?1 and occurred both in August. The grassland fixed 294.66 and 467.46 g CO 2·m ?2 in 2003 and 2004, and released 333.14 and 437.17 g CO 2·m ?2 in 2003 and 2004, respectively from May to September. Water availability and photosynthetic active radiation ( PAR) are two important factors of controlling CO 2 flux. Consecutive precipitation can cause reduction in the ability of ecosystem carbon exchange. Under favorable soil water conditions, daytime CO 2 flux is dependent on PAR. CO 2 flux, under soil water stress conditions, is obviously less than those under favorable soil water conditions, and there is a light saturation phenomena at PAR=1200 μmol·m ?2·s ?1. Soil respiration was temperature dependent when there was no soil water stress; otherwise, this response became accumulatively decoupled from soil temperature. 相似文献
7.
Long-term measurement of carbon metabolism of old-growth forests is critical to predict their behaviors and to reduce the uncertainties of carbon accounting under changing climate. Eddy covariance technology was applied to investigate the long-term carbon exchange over a 200 year-old Chinese broad-leaved Korean pine mixed forest in the Changbai Mountains (128°28′E and 42°24′N, Jilin Province, P. R. China) since August 2002. On the data obtained with open-path eddy covariance system and CO2 profile measurement system from Jan. 2003 to Dec. 2004, this paper reports (i) annual and seasonal variation of F
NEE, F
GPP and R
E; (ii) regulation of environmental factors on phase and amplitude of ecosystem CO2 uptake and release Corrections due to storage and friction velocity were applied to the eddy carbon flux. LAI and soil temperature determined the seasonal and annual dynamics of FGPP and RE separately. VPD and air temperature regulated ecosystem photosynthesis at finer scales in growing seasons. Water condition at the root zone exerted a significant influence on ecosystem maintenance carbon metabolism of this forest in winter. The forest was a net sink of atmospheric CO2 and sequestered −449 g C·m−2 during the study period; −278 and −171 gC·m−2 for 2003 and 2004 respectively. F
GPP and F
RE over 2003 and 2004 were −1332, −1294 g C·m−2. and 1054, 1124 g C·m−2 respectively. This study shows that old-growth forest can be a strong net carbon sink of atmospheric CO2. There was significant seasonal and annual variation in carbon metabolism. In winter, there was weak photosynthesis while the ecosystem emitted CO2. Carbon exchanges were active in spring and fall but contributed little to carbon sequestration on an annual scale. The summer is the most significant season as far as ecosystem carbon balance is concerned. The 90 days of summer contributed 66.9, 68.9% of F
GPP, and 60.4, 62.1% of R
E of the entire year. 相似文献
8.
CO 2 flux was measured continuously in a wheat and maize rotation system of North China Plain using the eddy covariance technique to study the characteristic of CO 2 exchange and its response to key environmental factors. The results show that nighttime net ecosystem exchange (NEE) varied exponentially with soil temperature. The temperature sensitivities of the ecosystem ( Q 10) were 2.94 and 2.49 in years 2002–2003 and 2003–2004, respectively. The response of gross primary productivity (GPP) to photosynthetically active radiation (PAR) in the crop field can be ex-pressed by a rectangular hyperbolic function. Average A max and α for maize were more than those for wheat. The values of α increased positively with leaf area index (LAI) of wheat. Diurnal variations of NEE were significant from March to May and from July to September, but not remarkable in other months. NEE, GPP and ecosystem respiration ( R ec) showed significantly seasonal variations in the crop field. The highest mean daily CO 2 uptake rate was ?10.20 and ?12.50 gC·m ?2?d ?1 in 2003 and 2004, for the maize field, respectively, and ?8.19 and ?9.50 gC?m ?2·d ?1 in 2003 and 2004 for the wheat field, respectively. The maximal CO 2 uptake appeared in April or May for wheat and mid-August for maize. During the main growing seasons of winter wheat and summer maize, NEE was controlled by GPP which was chiefly influenced by PAR and LAI. R ec reached its annual maximum in July when R ec and GPP contributed to NEE equally. NEE was dominated by R ec in other months and temperature became a key factor controlling NEE. Total NEE for the wheat field was ?77.6 and ?152.2 gC·m ?2·a ?1 in years 2002–2003 and 2003–2004, respectively, and ?120.1 and ?165.6 gC·m ?2·a ?1 in 2003 and 2004 for the maize field, respectively. The cropland of North China Plain was a carbon sink, with annual ?197.6 and ?317.9 gC·m ?2·a ?1 in years 2002–2003 and 2003–2004, respectively. After considering the carbon in grains, the cropland became a carbon source, which was 340.5 and 107.5 gC·m ?2·a ?1 in years 2002–2003 and 2003–2004, respectively. Affected by climate and filed managements, inter-annual carbon exchange varied largely in the wheat and maize rotation system of North China Plain. 相似文献
9.
The study by the eddy covariance technique in the alpine shrub meadow of the Qinghai-Tibet Plateau in 2003 and 2004 showed that the net ecosystem carbon dioxide exchange (NEE) exhibited noticeable diurnal and annual variations, with more distinct daily changes during the warmer seasons. The CO 2 emission of the shrub ecosystem culminated in April and September while the CO 2 absorption capacity reached a maximum in July and August. The absorbed carbon dioxide during the two consecutive years was 231.4 and 274.8 g CO 2·m ?2 respectively, yielding an average of 253.1 gCO 2·m ?2 per year: that accounts for a large proportion of absorbed CO 2 in the region. Obviously, the diurnal carbon flux was negatively related to temperature, radiation and other atmospheric factors. Still, minute discrepancies in kurtosis and duration of carbon emission/absorption were detected between 2003 and 2004. It was found that the CO 2 flux in the daytime was similarly affected by photosynthetic photon flux density in both years. Temperature appears to be the most important determinant of CO 2 flux: specifically, the high temperature during the plant growing season inhibits the carbon absorption capacity. One potential explanation is that soil respiration is enhanced under such condition. Analysis of biomass revealed that the annual net carbon fixed capacity of aboveground and belowground biomass was 544.0 in 2003 and 559.4 g C·m ?2 in 2004, which coincided with the NEE absorption capacity (63.1 g C·m ?2 in 2003 and 74.9 g C·m ?2 in 2004) in the corresponding plant growing season. 相似文献
10.
As one component of ChinaFLUX, the measurement of CO2 flux using eddy covariance over subtropical planted coniferous ecosystem in Qianyanzhou was conducted for a long term. This paper discusses the seasonal dynamics of net ecosystem exchange (NEE), ecosystem respiration (RE) and gross ecosystem exchange (GEE) between the coniferous ecosystem and atmosphere along 2003 and 2004. The variations of NEE, RE and GEE show obvious seasonal variabilities and correlate to each other, i.e. lower in winter and drought season, but higher in summer; light, temperature and soil water content are the main factors determining NEE; air temperature and water vapor pressure deficit (VPD) influence NEE with stronger influence from VPD. Under the proper light condition, drought stress could decrease the temperature range for carbon capture in planted coniferous, air temperature and precipitation controlled RE; The NEE, RE, and GEE for planted coniferous in Qianyanzhou are −387.2 g C·m−2 a−1, 1223.3 g C·m−2 a−1, −1610.4 g C·m−2 a−1 in 2003 and −423.8 g C·m−2 a−1, 1442.0 g C·m−2 a−1, −1865.8 g C·m−2 a−1 in 2004, respectively, which suggest the intensive ability of plantation coniferous forest on carbon absorbing in Qianyanzhou. 相似文献
11.
Eddy covariance technique was used to measure carbon flux during two growing seasons in 2003 and 2004 over typical steppe in the Inner Mongolia Plateau, China. The results showed that there were two different CO2 flux diurnal patterns at the grassland ecosystem. One had a dual peak in diurnal course of CO2 fluxes with a depression of CO2 flux after noon, and the other had a single peak. In 2003, the maximum diurnal uptake and emitting value of CO2 were −7.4 and 5.4 g·m−2·d−1 respectively and both occurred in July. While in 2004, the maximum diurnal uptake and release of CO2 were −12.8 and 5.8 g·m−2·d−1 and occurred both in August. The grassland fixed 294.66 and 467.46 g CO2·m−2 in 2003 and 2004, and released 333.14 and 437.17 g CO2·m−2 in 2003 and 2004, respectively from May to September. Water availability and photosynthetic active radiation (PAR) are two important factors of controlling CO2 flux. Consecutive precipitation can cause reduction in the ability of ecosystem carbon exchange. Under favorable soil water conditions, daytime CO2 flux is dependent on PAR. CO2 flux, under soil water stress conditions, is obviously less than those under favorable soil water conditions, and there is a light saturation phenomena at PAR=1200 μmol·m−2·s−1. Soil respiration was temperature dependent when there was no soil water stress; otherwise, this response became accumulatively decoupled from soil temperature. 相似文献
12.
The study by the eddy covariance technique in the alpine shrub meadow of the Qinghai-Tibet Plateau in 2003 and 2004 showed that the net ecosystem carbon dioxide exchange (NEE) exhibited noticeable diurnal and annual variations, with more distinct daily changes during the warmer seasons. The CO2 emission of the shrub ecosystem culminated in April and September while the CO2 absorption capacity reached a maximum in July and August. The absorbed carbon dioxide during the two consecutive years was 231.4 and 274.8 g CO2·m−2 respectively, yielding an average of 253.1 gCO2·m−2 per year: that accounts for a large proportion of absorbed CO2 in the region. Obviously, the diurnal carbon flux was negatively related to temperature, radiation and other atmospheric factors. Still, minute discrepancies in kurtosis and duration of carbon emission/absorption were detected between 2003 and 2004. It was found that the CO2 flux in the daytime was similarly affected by photosynthetic photon flux density in both years. Temperature appears to be the most important determinant of CO2 flux: specifically, the high temperature during the plant growing season inhibits the carbon absorption capacity. One potential explanation is that soil respiration is enhanced under such condition. Analysis of biomass revealed that the annual net carbon fixed capacity of aboveground and belowground biomass was 544.0 in 2003 and 559.4 g C·m−2 in 2004, which coincided with the NEE absorption capacity (63.1 g C·m−2 in 2003 and 74.9 g C·m−2 in 2004) in the corresponding plant growing season. 相似文献
13.
Seasonal metrics and environmental responses to forestry soil surface CO 2 emission effluxes among three types of lower subtropical forests were consistently monitored over two years with static chamber-gas chromatograph techniques among three types of lower subtropical forests. Results showed that annual CO 2 effluxes (S+L) reached 3942.20, 3422.36 and 2163.02 CO 2 g·m ?2·a ?1, respectively in the monsoon evergreen broadleaf forest, mixed broadleaf-coniferous forest and coniferous forest. All the three types of forests revealed the same characteristics of seasonal changes with the CO 2 effluxes peaking throughout June to August. During this peaking period, the effluxes were 35.9%, 38.1% and 40.2% of the total annual effluxes, respectively. The CO 2 emission process responding to the environmental factors displayed significantly different patterns in forestry soils of the three types of forests. The coniferous forest (CF) was more sensitive to temperature than the other two types. The Q 10 values were higher, along with greater seasonal variations of the CO 2 efflux, indicating that the structurally unique forestry ecosystem has disadvantage against interferences. All the three types of forestry CO 2 effluxes showed significant correlation with the soil temperature ( T s), soil water content ( M s) and air pressure ( P a). However, stepwise regression analysis indicated no significant correlation between air pressure and the soil CO 2 efflux. With an empirical model to measure soil temperature and water content in 5 cm beneath the soil surface, the CO 2 effluxes accounting for 75.7%, 77.8% and 86.5% of the efflux variability respectively in soils of BF, MF and PF were calculated. This model can be better used to evaluate the CO 2 emission of soils under water stress and arid or semi-arid conditions. 相似文献
14.
Soil CO 2 efflux in forest and grassland over 5 years from 2005 to 2009 in a semiarid mountain area of the Loess plateau, China, was measured. The aim was to compare the soil respiration and its annual and inter‐annual responses to the changes in soil temperature and soil water content between the two vegetation types for observing soil quality evolution. The differences among the five study years were the annual precipitation (320.1, 370.5, 508.8, 341.6, and 567.4 mm in 2005–2009, respectively) and annual distribution. The results showed that the seasonal change of soil respiration in both vegetation types was similar and controlled by soil temperature and soil water content. The mean soil respiration across 5 years in the forest (3.78 ± 2.68 µmol CO 2 m ?2 s ?1) was less than that in the grassland (4.04 ± 3.06 µmol CO 2 m ?2 s ?1), and the difference was significant. The drought soil in summer depressed soil respiration substantially. The Q10 value across 5‐year measurements was 2.89 and 2.94 for forest and grassland. When soil water content was between wilting point (WP) and field capacity (FC), the Q10 in both types increased with increasing soil water content, and when soil water content dropped to below WP, soil respiration and the Q10 decreased substantially. Although an exponential model was well fitted to predict the annual mean soil respiration for each single year data, it overestimated and underestimated soil respiration, respectively, in drought conditions and after rain for short periods of time during the year. The two‐variable models including temperature and water content variables could be well used to predict soil respiration for both types in all weather conditions. The models proposed are useful for understanding and predicting potential changes in the eastern part of Loess plateau in response to climate change. 相似文献
15.
The impacts of temperature, photosynthetic active radiation (PAR) and vapor pressure deficit (VPD) on CO2 flux above broad-leaved Korean pine mixed forest in the Changbai Mountains were studied based on eddy covariance and meteorological factors measurements.The results showed that, daytime CO2 flux was mainly controlled by PAR and they fit Michaelis-Menten equation. Meanwhile VPD also had an influence on the daytime flux. Drier air reduced the CO2 assimilation of the ecosystem, the drier the air, the more the reduction of the assimilation. And the forest was more sensitive to VPD in June than that in July and August. The respiration of the ecosystem was mainly controlled by soil temperature and they fit exponential equation. It was found that this relationship was also correlated with seasons; respiration from April to July was higher than that from August to November under the same temperature. Daily net carbon exchange of the ecosystem and the daily mean air temperature fit exponential equation. It was also found that seasonal trend of net carbon exchange was the result of comprehensive impacts of temperature and PAR and so on. These resulted in the biggest CO2 uptake in June and those in July and August were next. Annual carbon uptake of the forest ecosystem in 2003 was -184 gC. m-2. 相似文献
16.
The long-term and continuous carbon fluxes of Changbaishan temperate mixed forest (CBS), Qianyanzhou subtropical evergreen coniferous forest (QYZ), Dinghushan subtropical evergreen mixed forest (DHS) and Xishuangbana tropical rainforest (XSBN) have been measured with eddy covariance techniques. In 2003, different responses of carbon exchange to the environment appeared across the four ecosystems. At CBS, the carbon exchange was mainly determined by radiation and temperature. 0°C and 10°C were two important temperature thresholds; the former determined the length of the growing season and the latter affected the magnitude of carbon exchange. The maximum net ecosystem exchange ( N EE) of CBS occurred in early summer because maximum ecosystem photosynthesis ( G PP) occurred earlier than maximum ecosystem respiration ( R e). During summer, QYZ experienced severe drought and N EE decreased significantly mainly as a result of the depression of G PP. At DHS and XSBN, N EE was higher in the drought season than the wet season, especially the conversion between carbon sink and source occurring during the transition season at XSBN. During the wet season, increased fog and humid weather resulted from the plentiful rainfall, the ecosystem G PP was dispressed. The Q 10 and annual respiration of XSBN were the highest among the four ecosystems, while the average daily respiration of CBS during the growing season was the highest. Annual N EE of CBS, QYZ, DHS and XSBN were 181.5, 360.9, 536.2 and ?320.0 g·C·m ?2·a ?1, respectively. From CBS to DHS, the temperature and precipitation increased with the decrease in latitude. The ratio of N EE/ R e increased with latitude, while R e/ G PP, ecosystem light use efficiency ( L UE), precipitation use efficiency and average daily G PP decreased gradually. However, XSBN usually escaped such latitude trend probably because of the influence of the south-west monsoon climate which does not affect the other ecosystems. Long-term measurement and more research were necessary to understand the adaptation of forest ecosystems to climate change and to evaluate the ecosystem carbon balance due to the complexity of structure and function of forest ecosystems. 相似文献
17.
There is a general agreement that forest ecosystems in the Northern Hemisphere function as signifi-cant sinks for atmospheric CO2; however, their magnitude and distribution remain large uncertainties. In this paper, we report the carbon (C) stock and its change of vegetation, forest floor detritus, and mineral soil, annual net biomass increment and litterfall production, and respiration of vegetation and soils between 1992 to 1994, for three temperate forest ecosystems, birch (Betula platyphylla) forest, oak (Quercus liaotungensis) forest and pine (Pinus tabulaeformis) plantation in Mt. Dongling, Beijing, China. We then evaluate the C budgets of these forest ecosystems. Our results indicated that total C density (organic C per hectare) of these forests ranged from 250 to 300 t C ha-1, of which 35―54 t C ha-1 from vegetation biomass C and 209―244 t C ha-1 from soil organic C (1 m depth, including forest floor detritus). Biomass C of all three forests showed a net increase, with 1.33―3.55 t C ha-1 a-1 during the study period. Litterfall production, vegetation autotrophic respiration, and soil heterotrophic respira-tion were estimated at 1.63―2.34, 2.19―6.93, and 1.81―3.49 t C ha-1 a-1, respectively. Ecosystem gross primary production fluctuated between 5.39 and 12.82 t C ha-1 a-1, about half of which (46%―59%, 3.20―5.89 t C ha-1 a-1) was converted to net primary production. Our results suggested that pine forest fixed C of 4.08 t ha-1 a-1, whereas secondary forests (birch and oak forest) were nearly in balance in CO2 exchange between the atmosphere and ecosystems. 相似文献
18.
The belowground part of terrestrial ecosystem is a huge carbon pool. It is believed that of the total 2500Gt carbon stored in global terrestrial ecosystem, soil carbon storage within the 1 m surface layer ac- counts for 2000Gt, which is 4-fold of vegetation car- bon storage[1,2]. Compared with the carbon in the vegetation, carbon in the deep soil layers is much more stable, and it will stay in soil profile permanentlyunless geological vicissitude occurs. Essentially, forest restoration is the… 相似文献
19.
2010年4、5月份,用黑白瓶法对小江回水区春季浮游植物初级生产力进行了原位监测,并研究了初级生产力的分布特征及其与光强、叶绿素a浓度(Chl.a)、水温、二氧化碳分压(pCO2)等影响因素的相关关系.结果表明,4、5月份小江回水区的水柱总初级生产力(GPP)分别为1927.5、1325.0mg O2/( m2·d),... 相似文献
20.
A case study on a desert‐oasis wetland ecosystem in the arid region of Northwest China measured the seasonal and interannual variation in energy partitioning and evapotranspiration to analyse the response of water and energy exchange on soil moisture, groundwater, and environmental variables. Energy partitioning showed a clear seasonal and interannual variability, and the process of water and energy exchange differed significantly in the monthly and interannual scales. The net radiation was 7.31 MJ m ?2· day ?1, and sensible heat flux accounted for 50.42% of net radiation in energy fluxes, 40.56% for latent heat flux, and 9.02% for ground heat flux. The parameters in energy fluxes were best described by a unimodal curve, whereas sensible heat flux followed a bimodal curve. Variations in the daily evapotranspiration and crop evapotranspiration also exhibited a single peak curve with annual values of 569.84 and 644.47 mm, respectively. Canopy conductance averaged 20.77 ± 13.75 mm s ?1 and varied from 0.16 to 83.96 mm s ?1 during the two hydrological years. The variation in water and energy exchange reflected environmental conditions and depended primarily on vapour pressure deficit, net radiation, soil moisture, and water depth. Although the effects of precipitation on evapotranspiration showed that the response of this ecosystem to climate changes was not obvious, the variation of air temperatures had a strong influence on evapotranspiration, resulting in a significant increase in evapotranspiration ( R = 0.730; P < 0.01). Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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