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Hu Z.,Chinese Academy of Forestry | Hu Z.,Key Laboratory of Forest Ecology and Environment | Hu Z.,Sichuan Agricultural University | Liu S.,Chinese Academy of Forestry | And 4 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica

Both soil temperature and soil water condition are important factors that influencing soil respiration at different temporal scales. There is still intra and inter-seasonal variations in soil temperature and soil water content although they are seasonally correlated. In this study, a field experiment was carried out to explore effects of diurnal variations in soil temperature and soil water on soil respirations (Rs) in the alpine meadows in Balang Mountain in West Sichuan of China. The objectives of our study are to: 1) understand the seasonal pattern of day- and night-time Rs, in particular, nocturnal variations of Rs, 2) elucidate the partitioning pattern of day- and night-time Rs, and 3) compare Q10 values of day- and night-time Rs. We examined both day- and night-time Rs by using LI-8100 Automated Soil CO2 Flux System on monthly basis from April to November, 2011. The effects of soil temperature and soil water on Rs of alpine meadow were analyzed based on field measurements of diurnal soil respiration. The results indicated that Rs showed large seasonal variations in day- and night-time during the measurements period, with a two-peak curve in the day-time and parabola curve at the night-time. During the measurements period (April to November), the means of Rs in the day- and night-time are 1. 83 μmol·m-2· s-1 and 1. 61μmol· m-2· s-1, respectively. The means of daytime and nighttime Rs were significantly higher in growing seasons (Jun to September) than that in green up period (April to May) and withering period (October to November) which accounted largest contribution to annual soil respiration. The nocturnal soil respiration appeared to have similar tendency of variations among measurements, and it was relatively low at night-time, with the lowest between 06:30 and 07: 00am. During the measurement period, Van't Hoff equation and Lloyd & Taylor function were the same to be used for describing the relationships between soil respiration and soil temperature. The two-factor equations (soil temperature and moisture content) were much better to describe responses of nocturnal soil respiration compared to the single-factor equations. Soil respiration rates in the day-time and night-time exhibited a significantly exponential correlation with soil temperature during green up period, growing season and weathering periods, while the linear positive relationships between soil respiration and soil water content were found for nocturnal respiration in green up period and for both day-time and nocturnal respirations in weathering period. Q10 values were estimated to be 3. 90 and 3. 74 for the day-time and night-time respirations respectively, during the whole measurement period. Soil Q10 values varied with season, but daytime soil respiration during the green up period was most sensitive to temperature, and the nocturnal soil respiration during the peak months of growing seasons was least sensitive to temperature. Our results demonstrated that soil temperature, soil water, and their interactive effects had distinct effects on soil respiration of either the day-time or night-time during the measurements period in the subalpine meadow. Therefore, more measurements of the soil nocturnal CO2 efflux are essential to accurately estimate the seasonal and annual carbon fluxes based on instantaneous measurements of soil respiration. At the same time, soil temperature, soil water and other biotic factors affecting soil respiration should be taken into account. Source

Luan J.,Key Laboratory of Forest Ecology and Environment | Luan J.,Chinese Academy of Forestry | Liu S.,Key Laboratory of Forest Ecology and Environment | Liu S.,Chinese Academy of Forestry | And 4 more authors.
Soil Biology and Biochemistry

Plot trenching and root decomposition experiments were conducted in a warm-temperate oak chronosequence (40-year-old, 48-year-old, 80-year-old, and 143-year-old) in China. We partitioned total soil surface CO2 efflux (RS) into heterotrophic (RH) and rhizospheric (RR) components across the growing season of 2009. We found that the temporal variation of RR and RH can be well explained by soil temperature (T5) at 5 cm depth using exponential equations for all forests. However, RR of 40-year-old and 48-year-old forests peaked in September, while their T5 peaks occurred in August. RR of 80-year-old and 143-year-old forests showed a similar pattern to T5. The contribution of RR to RS (RC) of 40-year-old and 48-year-old forests presented a second peak in September. Seasonal variation of RR may be accounted for by the different successional stages. Cumulative RH and RR during the growing season varied with forest age. The estimated RH values for 40-year-old, 48-year-old, 80-year-old and 143-year-old forests averaged 431.72, 452.02, 484.62 and 678.93 g C m-2, respectively, while the corresponding values of RR averaged 191.94, 206.51, 321.13 and 153.03 g C m-2. The estimated RC increased from 30.78% in the 40-year-old forest to 39.85% in the 80-year-old forest and then declined to 18.39% in the 143-year-old forest. We found soil organic carbon (SOC), especially the light fraction organic carbon (LFOC), stock at 0-10 cm soil depth correlated well with RH. There was no significant relationship between RR and fine root biomass regardless of stand age. Measured apparent temperature sensitivity (Q10) of RH (3.93 ± 0.27) was significantly higher than that of RR (2.78 ± 0.73). Capillary porosity decreased as stand age increased and it was negatively correlated to cumulative RS. Our results emphasize the importance of partitioning soil respiration in evaluating the stand age effect on soil respiration and its significance to future model construction. © 2010 Elsevier Ltd. Source

Lu R.C.,Chinese Academy of Forestry | Lu R.C.,Key Laboratory of Forest Ecology and Environment | Lu R.C.,University of Shanghai for Science and Technology | Wang H.B.,Chinese Academy of Forestry | And 7 more authors.

Competition and cooperation between bark beetles, Tomicus yunnanensis Kirkendall and Faccoli and Tomicus minor (Hartig) (Coleoptera: Scolytinae) were examined when they coexisted together in living Yunnan pine trees (Pinus yunnanensis Franchet) in Yunnan province in Southwest China. T. yunnanensis bark beetles were observed to initiate dispersal from pine shoots to trunks in November, while the majority of T. minor begins to transfer in December. T. yunnanensis mainly attacks the top and middle parts of the trunk, whereas T. minor mainly resides in the lower and middle parts of the trunk. The patterns of attack densities of these two species were similar, but with T. yunnanensis colonizing the upper section of the trunk and T. minor the lower trunk. The highest attack density of T. Yunnanensis was 297 egg galleries/m 2, and the highest attack density of T. minor was 305 egg galleries/m 2. Although there was significant overlap for the same bark areas, the two species generally colonize different areas of the tree, which reduces the intensity of competition for the relatively thin layer of phloem-cambium tissues where the beetles feed and reside. Copyright © 2012 Rong Chun Lu et al. Source

Slik J.W.F.,CAS Xishuangbanna Tropical Botanical Garden | Paoli G.,Daemeter Consulting | Mcguire K.,Barnard College | Amaral I.,A+ Network | And 63 more authors.
Global Ecology and Biogeography

Aim: Large trees (d.b.h.≥70cm) store large amounts of biomass. Several studies suggest that large trees may be vulnerable to changing climate, potentially leading to declining forest biomass storage. Here we determine the importance of large trees for tropical forest biomass storage and explore which intrinsic (species trait) and extrinsic (environment) variables are associated with the density of large trees and forest biomass at continental and pan-tropical scales. Location: Pan-tropical. Methods: Aboveground biomass (AGB) was calculated for 120 intact lowland moist forest locations. Linear regression was used to calculate variation in AGB explained by the density of large trees. Akaike information criterion weights (AICc-wi) were used to calculate averaged correlation coefficients for all possible multiple regression models between AGB/density of large trees and environmental and species trait variables correcting for spatial autocorrelation. Results: Density of large trees explained c. 70% of the variation in pan-tropical AGB and was also responsible for significantly lower AGB in Neotropical [287.8 (mean)±105.0 (SD) Mg ha-1] versus Palaeotropical forests (Africa 418.3±91.8 Mg ha-1; Asia 393.3±109.3 Mg ha-1). Pan-tropical variation in density of large trees and AGB was associated with soil coarseness (negative), soil fertility (positive), community wood density (positive) and dominance of wind dispersed species (positive), temperature in the coldest month (negative), temperature in the warmest month (negative) and rainfall in the wettest month (positive), but results were not always consistent among continents. Main conclusions: Density of large trees and AGB were significantly associated with climatic variables, indicating that climate change will affect tropical forest biomass storage. Species trait composition will interact with these future biomass changes as they are also affected by a warmer climate. Given the importance of large trees for variation in AGB across the tropics, and their sensitivity to climate change, we emphasize the need for in-depth analyses of the community dynamics of large trees. © 2013 John Wiley & Sons Ltd. Source

Zhang C.L.,Guangxi University | Yao B.,Key Laboratory of Forest Ecology and Environment | Zhang P.,Guangxi University | Wang T.T.,Guangxi University
Journal of Residuals Science and Technology

Investigation involved soil microbial biomass carbon contents (SMBC) and dissipation of metsulfuron-methyl (MSM) in paddy soils. Results suggested organic amendments enhanced SMBC and MSM dissipation. The largest increment of SMBC was observed in treatments of decomposed pig manure (DM), followed by addition of Chinese Clover (CC) and then rice straw (RS). The shortest dissipation half-life of MSM resulted from a paddy field quaternary red clay (PRC), followed by a blue clay paddy soil (BCP) and a desalting muddy polder soil (PMP). This indicates organic materials not only effect microbial activity but also they effect fractions of extractable MSM all having an impact on MSM dissipation. © 2011 DEStech Publications, Inc. Source

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