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Chen W.,Beijing Forestry University | Jia X.,Beijing Forestry University | Zha T.,Beijing Forestry University | Zha T.,Chinese Institute of Green Carbon | And 8 more authors.
European Journal of Soil Biology | Year: 2013

We investigated how soil temperature (Ts) and water content (VWC) affect soil respiration (Rs) in a mixed urban forest. Continuous half-hourly measurements of soil surface efflux were made during the period March-December 2011 in a mixed forest in Beijing Olympic Forest Park, China. Daily mean Rs varied from 0.28 to 3.62 μmol CO2 m-2 s-1. Over this period of record, Rs increased exponentially with rising temperature; a Q10 model with 5-cm soil temperature as the independent variable explained 76% of the variation in half-hourly Rs. The temperature sensitivity of respiration (Q10) varied seasonally, being greater in fall than in spring, suggesting seasonal hysteresis in the Rs-Ts relationship. During the summer months (June-August 2011), when Ts was high and had relatively little day-to-day variation, Rs was hyperbolically related to VWC, increasing with increasing VWC up to a VWC threshold of 0.17 m3 m-3, but decreasing with increasing VWC above the threshold. A bivariate Q10-hyperbolical model, which incorporated both Ts and VWC effects, improved the performance of Rs simulation in summer, but not annually. These results indicated that Rs was dominantly controlled by soil temperature over the annual cycle. However, VWC served as the dominant control in summer. The annual total of Rs estimated from the Q10 model was 475 g C m-2. We recommend the use of the Q10 model for predicting annual soil respiration due to its good performance and physiological basis. © 2012 Elsevier Masson SAS.


Cao J.,Beijing Forestry University | Cao J.,Chinese Academy of Forestry | Wang X.,Beijing Forestry Carbon Administration | Wang X.,Chinese Institute of Green Carbon | And 4 more authors.
Ecological Research | Year: 2012

The pattern of carbon (C) allocation across different stages of stand development of Chinese pine (Pinus tabulaeformis) forests is poorly documented. In order to understand the effects of stand age on the C pool of the Chinese pine forest ecosystem, we have examined the above- and belowground C pools in three differently aged stands of Chinese pine in the northern mountains of Beijing, China, by plot-level inventories and destructive sampling. Our results suggest that tree branch and foliage biomass should be estimated by age-specific equations. Reasonably accurate estimates of tree stem, tree root, aboveground, and total tree biomass in a Chinese pine forest at different development stages were obtained using age-independent allometric equations from tree diameter only. The ratio of belowground to aboveground tree biomass was relatively constant with stand aging, remaining around 21 %. The contribution of aboveground tree biomass C increased from 21 % of the total ecosystem C in a 25-year-old stand to 44 % in a 65-year-old stand, subsequently falling to 41 % in a 105-year-old stand, while the contribution of mineral soil C decreased from 64 % of the total ecosystem C in 25-year-old stand to 38 % in a 65-year-old stand, subsequently increasing to 41 % in a 105-year-old stand. The C stock of the total ecosystem and its aboveground tree, tree root, forest floor, and mineral soil components continuously increased with stand ageing, whereas the C stock of the understory showed a declining trend and contributed little to the total site C pool. © 2012 The Ecological Society of Japan.


Jia X.,Beijing Forestry University | Zha T.,Beijing Forestry University | Wu B.,Beijing Forestry University | Zhang Y.,Beijing Forestry University | And 4 more authors.
PLoS ONE | Year: 2013

Although the temperature response of soil respiration (Rs) has been studied extensively, several issues remain unresolved, including hysteresis in the Rs-temperature relationship and differences in the long- vs. short-term Rs sensitivity to temperature. Progress on these issues will contribute to reduced uncertainties in carbon cycle modeling. We monitored soil CO2 efflux with an automated chamber system in a Pinus tabulaeformis plantation near Beijing throughout 2011. Soil temperature at 10-cm depth (Ts) exerted a strong control over Rs, with the annual temperature sensitivity (Q10) and basal rate at 10°C (Rs10) being 2.76 and 1.40 μmol m-2 s-1, respectively. Both Rs and short-term (i.e., daily) estimates of Rs10 showed pronounced seasonal hysteresis with respect to Ts, with the efflux in the second half of the year being larger than that early in the season for a given temperature. The hysteresis may be associated with the confounding effects of microbial population dynamics and/or litter input. As a result, all of the applied regression models failed to yield unbiased estimates of Rs over the entire annual cycle. Lags between Rs and Ts were observed at the diel scale in the early and late growing season, but not in summer. The seasonality in these lags may be due to the use of a single Ts measurement depth, which failed to represent seasonal changes in the depth of CO2 production. Daily estimates of Q10 averaged 2.04, smaller than the value obtained from the seasonal relationship. In addition, daily Q10 decreased with increasing Ts, which may contribute feedback to the climate system under global warming scenarios. The use of a fixed, universal Q10 is considered adequate when modeling annual carbon budgets across large spatial extents. In contrast, a seasonally-varying, environmentally-controlled Q10 should be used when short-term accuracy is required. © 2013 Jia et al.


Wang J.,Beijing Forestry University | Yu H.,Beijing Forestry Carbon Administration | Li G.,Beijing Forestry University | Zhang F.,Beijing Forestry Carbon Administration
Silva Fennica | Year: 2016

Stored nutrient reserves are closely correlated with survival and growth of transplanted seedlings. Previous studies have proven that combining pre-hardening fertilization (PF) with fall fertilization (FF) built seedling nutrient reserves more effectively; however, their effect on transplanting performance is poorly documented. We investigated the independent and interacting effects of 2 levels of PF and 4 levels of FF on seedling growth, nutrient acquisition and accumulation during different growth phases 1 year after transplanting of Quercus variabilis Blume in a nursery. High PF benefited nutrient reserves and subsequent transplanted seedling growth and tissue nutrient storage at the end of the rapid growth and hardening phases. Fall fertilization with 36 mg N increased stem dry mass and tissue nutrient content at the end of the hardening phase. At the conclusion of establishment, PF and FF showed a significant interaction for N and K uptake from soil. At the end of the rapid growth and hardening phases, high PF consistently increased nutrient uptake. Enhanced N and K uptake occurred following application of 36 mg N of FF at the end of the hardening phase. Distinct roles for PF and FF on 3 phases of transplanted seedlings demonstrated the necessity to evaluate fertilization in terms of nutrient reserves and subsequent transplanting performance in consecutive phases. Combining 100 mg N seedling–1 during pre-hardening with 36 mg N seedling–1 during fall yielded ideal transplanting performance for Quercus variabilis seedlings. © 2016, Finnish Society of Forest Science. All right reserved.


Jin Y.,Beijing Forestry University | Zhang Z.,Beijing Forestry University | Fang X.,Beijing Forestry University | Kang M.,Beijing Forestry University | And 3 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2012

Footprint source area analysis is an important approach to study qualitatively and quantitatively the relationship between the flux information and the surface condition. Fluxes measured with eddy covariance system over a heterogeneous surface are usually of uncertainty, hard to control and difficult to interpret. As a result, the credibility of energy and mass exchanges between the atmosphere and the land surface could be questionable. Therefore, it is critically important to identify the fluxes measurement by improved understanding the footprint source area. We calculated the footprint source area from continuous flux measurement by an eddy covariance system from Jan 1, 2009 to Dec 31, 2009 using FSAM (Footprint Source Area Model) model over a poplar plantation in the southern part of Beijing (DanXing; 39°31'50"N,116°15'07E"). Our objectives are to analyze the spatiotemporal distribution of footprint source area and to interpret the representativeness of the flux measurement data. Changing with the seasons, the prevailing wind directions were 146. 25°-213. 7°and 326-25°-33. 75°and non-prevailing wind directions remained 33. 75°-146. 25°and 213. 75°-326. 25°, respectively. On the spatial variation, stable stratification inhibits turbulence diffusion and contributes to the downwind flux information. Our results indicated that the more stable the atmosphere stability conditions were, the larger the source areas were. During the study period, the source areas in the dormant season were larger than those in the growing season, except for the wind direction between 326. 25°to 33. 75°. According to our result, the source area became smaller while the wind frequents and strength became higher. Based on computing the one year measurement data, the upwind ranges were about 50-400 m mainly characterized with unstable stratification around the measurement site. Moreover, our results indicated that 69. 3% of the flux information came from northwest and southwest, and approximately, 42. 56% of which came from the southwest. According to the combined action of atmosphere conditions and wind directions, the footprint that measured in the growing season was from the southern part of the tower. In addition, with the stronger of the atmosphere conditions, the smallest region of source area changed from west to east. On the time scale, unstable stratification dominated the measurement site during almost all wind directions, only when the winds blew from the east did it switch to stable stratification. In particular, during the growing season when the winds came from the north, the source regions were mostly affected by atmospheric conditions. Generally speaking, the source area is related to the measurement height, canopy height, roughness length, wind direction and atmospheric conditions and the source areas enlarge with the stability of atmospheric stratification.


Li H.,Beijing Forestry University | Li C.,Chinese Academy of Forestry | Zha T.,Beijing Forestry University | Liu J.,Beijing Forestry University | And 4 more authors.
Forestry Chronicle | Year: 2014

Tree biomass was investigated in an age-sequence of secondary lacebark pine (Pinus bungeana) forests to understand biomass partitioning patterns during stand development. Mean biomass of each tree component increased steadily as stands aged. Average growth rates and ratios of tree biomass to stand age increased with age. The ratio of below- to above-ground biomass remained relatively constant independent of stand age. Compared to DBH-H allometric equations, the DBH-only equations performed slightly better and are more efficient to apply. These new equations for lacebark pine are an important supplement to China's national tree biomass equations. These equations and the findings on biomass partitioning patterns during stand development are applicable for the accurate estimation of ecosystem carbon accounting and will contribute to the sustainable management of lacebark pine forests. © 2014 - Canadian Institute of Forestry.


Chen W.J.,Beijing Forestry University | Li C.Y.,Beijing Forestry University | He G.M.,Beijing Forestry Carbon Administration | He G.M.,Chinese Institute of Green Carbon | And 5 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2013

The area of urban forests and green-land is expanding dramatically across China in order to face rapid urbanization. Urban green-land ecosystems with plantations as their main vegetation type, have the great potential to sequestrate atmospheric carbon. Continuous measurements of CO2 flux were made using eddy covariance technique from December 2011 to November 2012 in a mixed forest in Beijing Olympic Forest Park to quantify the seasonal dynamics of net ecosystem CO2 exchange (NEE) and its responses to environmental factors. Gross ecosystem productivity (GEP), ecosystem respiration (Re), and net ecosystem productivity (NEP = -NEE) showed strong seasonal pattern, with CO2 uptake dominating during the growing season from April to November, and a respiratory release of CO2 dominating during the non-growing season. The carbon flux was influenced by photosynthetically active radiation (PAR), water vapor pressure deficit (VPD) and air temperature (Ta). In growing season, daytime net ecosystem carbon exchange (NEEday) increased with increasing PAR. The ecosystem quantum yield (α) and maximum photosynthesis (Amax) showed an apparent seasonal pattern, both peaking in July. VPD also affected NEE through its direct effect on photosynthesis. NEE increased with the increasing PAR up to a threshold of 1200 μmol·m-2·s-1, then decreased with increasing PAR above this threshold. GEP, Re and NEP were all influenced by Ta, but responded differently. Re increased exponentially with air temperature (Ta), with the temperature sensitivity (Q10) being 2.5. GEP also increased with Ta. This differential response of GEP and Re determined the relationship between NEP and Ta. NEP decreased with increasing Ta when Ta < 10.0 °C, but increased when Ta > 10.0 °C. NEEday increased with PAR. The ecosystem quantum yield (α) and maximum photosynthesis (Amax) showed an apparent seasonal pattern, both peaking in July with the value of 0.083 μmol CO2 /μmol PAR and 29.46 μmol·m-2·s-1, respectively, and reaching a minimum in November with the value of 0.017 μmol CO2/μmol PAR and 4.16 μmol·m-2·s-1. The predicted annual totals of GEP, Re and NEP were 1192, 1028 and 164 g C/m2, respectively. The present results could contribute to the carbon budget of urban ecosystems, and help make carbon-oriented management strategies for sustainable urban development under global climate change.


Chen B.,Beijing Forestry University | Wang X.,Beijing Forestry University | Chen J.,Beijing Forestry Carbon Administration | Zhu J.,Beijing Forestry Carbon Administration | Liu J.,Beijing Forestry University
Forestry Chronicle | Year: 2015

Tree planting has been proposed by Beijing's municipal government as a measure to alleviate airborne fine particulate matter (PM) in the city as trees have large surface areas to filter pollution out of the air. To maximize this eco-efficiency, a series of active measures have been taken by the city's forestry sector. These strategies are elaborated here to provide a valuable reference for other megacities facing similar challenges. © 2015 Published by NRC Research Press.

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