The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Michael G Ryan - One of the best experts on this subject based on the ideXlab platform.
-
wood co2 Efflux in a primary tropical rain forest
Global Change Biology, 2006Co-Authors: Molly A Cavaleri, Steven F Oberbauer, Michael G RyanAbstract:The balance between photosynthesis and plant respiration in tropical forests may substantially affect the global carbon cycle. Woody tissue CO2 Efflux is a major component of total plant respiration, but estimates of ecosystem-scale rates are uncertain because of poor sampling in the upper canopy and across landscapes. To overcome these problems, we used a portable scaffolding tower to measure woody tissue CO2 Efflux from ground level to the canopy top across a range of sites of varying slope and soil phosphorus content in a primary tropical rain forest in Costa Rica. The objectives of this study were to: (1) determine whether to use surface area, volume, or biomass for modeling and extrapolating wood CO2 Efflux, (2) determine if wood CO2 Efflux varied seasonally, (3) identify if wood CO2 Efflux varied by functional group, height in canopy, soil fertility, or slope, and (4) extrapolate wood CO2 Efflux to the forest. CO2 Efflux from small diameter woody tissue (o10cm) was related to surface area, while CO2 Efflux from stems 410cm was related to both surface area and volume. Wood CO2 Efflux showed no evidence of seasonality over 2 years. CO2 Efflux per unit wood surface area at 251 (FA) was highest for the N-fixing dominant tree species Pentaclethra macroloba, followed by other tree species, lianas, then palms. Small diameter FA increased steeply with increasing height, and large diameter FA increased with diameter. Soil phosphorus and slope had slight, but complex effects on FA. Wood CO2 Efflux per unit ground area was 1.34 � 0.36lmolm � 2 s � 1 , or 508 � 135gCm � 2 yr � 1 . Small diameter wood, only 15% of total woody biomass, accounted for 70% of total woody tissue CO2 Efflux from the forest; while lianas, only 3% of total woody biomass, contributed one-fourth of the total wood CO2 Efflux.
Ayumi Katayama - One of the best experts on this subject based on the ideXlab platform.
-
vertical variations in wood co2 Efflux for live emergent trees in a bornean tropical rainforest
Tree Physiology, 2014Co-Authors: Ayumi Katayama, Tomonori Kume, Hikaru Komatsu, Mizue Ohashi, Kazuho Matsumoto, Ryuji Ichihashi, Tomoomi Kumagai, Kyoichi OtsukiAbstract:Difficult access to 40-m-tall emergent trees in tropical rainforests has resulted in a lack of data related to vertical variations in wood CO2 Efflux, even though significant variations in wood CO 2 Efflux are an important source of errors when estimating whole-tree total wood CO2 Efflux. This study aimed to clarify vertical variations in wood CO 2 Efflux for emergent trees and to document the impact of the variations on the whole-tree estimates of stem and branch CO2 Efflux. First, we measured wood CO2 Efflux and factors related to tree morphology and environment for seven live emergent trees of two dipterocarp species at four to seven heights of up to ~40 m for each tree using ladders and a crane. No systematic tendencies in vertical variations were observed for all the trees. Wood CO2 Efflux was not affected by stem and air temperature, stem diameter, stem height or stem growth. The ratios of wood CO2 Efflux at the treetop to that at breast height were larger in emergent trees with relatively smaller diameters at breast height. Second, we compared whole-tree stem CO2 Efflux estimates using vertical measurements with those based on solely breast height measurements. We found similar whole-tree stem CO2 Efflux estimates regardless of the patterns of vertical variations in CO2 Efflux because the surface area in the canopy, where wood CO 2 Efflux often differed from that at breast height, was very small compared with that at low stem heights, resulting in li ttle effect of the vertical variations on the estimate. Additionally, whole-tree branch CO2 Efflux estimates using measured wood CO 2 Efflux in the canopy were considerably different from those measured using only breast height measurements. Uncertainties in wood CO2 Efflux in the canopy did not cause any bias in stem CO2 Efflux scaling, but affected branch CO 2 Efflux.
Xuhui Zhou - One of the best experts on this subject based on the ideXlab platform.
-
source components and interannual variability of soil co2 Efflux under experimental warming and clipping in a grassland ecosystem
Global Change Biology, 2007Co-Authors: Xuhui ZhouAbstract:Partitioning soil CO2 Efflux into autotrophic (RA) and heterotrophic (RH) components is crucial for understanding their differential responses to climate change. We conducted a long-term experiment (2000‐2005) to investigate effects of warming 21C and yearly clipping on soil CO2 Efflux and its components (i.e. RA and RH) in a tallgrass prairie ecosystem. Interannual variability of these fluxes was also examined. Deep collars (70cm) were inserted into soil to measure RH. RA was quantified as the difference between soil CO2 Efflux and RH. Warming treatment significantly stimulated soil CO2 Efflux and its components (i.e. RA and RH) in most years. In contrast, yearly clipping significantly reduced soil CO2 Efflux only in the last 2 years, although it decreased RH in every year of the study. Temperature sensitivity (i.e. apparent Q10 values) of soil CO2 Efflux was slightly lower under warming (P40.05) and reduced considerably by clipping (Po0.05) compared with that in the control. On average over the 4 years, RH accounted for approximately 65% of soil CO2 Efflux with a range from 58% to 73% in the four treatments. Over seasons, the contribution of RH to soil CO2 Efflux reached a maximum in winter ( � 90%) and a minimum in summer ( � 35%). Annual soil CO2 Efflux did not vary substantially among years as precipitation did. The interannual variability of soil CO2 Efflux may be mainly caused by precipitation distribution and summer severe drought. Our results suggest that the effects of warming and yearly clipping on soil CO2 Efflux and its components did not result in significant changes in RH or RA contribution, and rainfall timing may be more important in determining interannual variability of soil CO2 Efflux than the amount of annual precipitation.
Kyoichi Otsuki - One of the best experts on this subject based on the ideXlab platform.
-
vertical variations in wood co2 Efflux for live emergent trees in a bornean tropical rainforest
Tree Physiology, 2014Co-Authors: Ayumi Katayama, Tomonori Kume, Hikaru Komatsu, Mizue Ohashi, Kazuho Matsumoto, Ryuji Ichihashi, Tomoomi Kumagai, Kyoichi OtsukiAbstract:Difficult access to 40-m-tall emergent trees in tropical rainforests has resulted in a lack of data related to vertical variations in wood CO2 Efflux, even though significant variations in wood CO 2 Efflux are an important source of errors when estimating whole-tree total wood CO2 Efflux. This study aimed to clarify vertical variations in wood CO 2 Efflux for emergent trees and to document the impact of the variations on the whole-tree estimates of stem and branch CO2 Efflux. First, we measured wood CO2 Efflux and factors related to tree morphology and environment for seven live emergent trees of two dipterocarp species at four to seven heights of up to ~40 m for each tree using ladders and a crane. No systematic tendencies in vertical variations were observed for all the trees. Wood CO2 Efflux was not affected by stem and air temperature, stem diameter, stem height or stem growth. The ratios of wood CO2 Efflux at the treetop to that at breast height were larger in emergent trees with relatively smaller diameters at breast height. Second, we compared whole-tree stem CO2 Efflux estimates using vertical measurements with those based on solely breast height measurements. We found similar whole-tree stem CO2 Efflux estimates regardless of the patterns of vertical variations in CO2 Efflux because the surface area in the canopy, where wood CO 2 Efflux often differed from that at breast height, was very small compared with that at low stem heights, resulting in li ttle effect of the vertical variations on the estimate. Additionally, whole-tree branch CO2 Efflux estimates using measured wood CO 2 Efflux in the canopy were considerably different from those measured using only breast height measurements. Uncertainties in wood CO2 Efflux in the canopy did not cause any bias in stem CO2 Efflux scaling, but affected branch CO 2 Efflux.
Shouguo Mu - One of the best experts on this subject based on the ideXlab platform.
-
factors controlling soil co2 Effluxes and the effects of rewetting on Effluxes in adjacent deciduous coniferous and mixed forests in korea
Soil Biology & Biochemistry, 2010Co-Authors: Shouguo Mu, Sinkyu KangAbstract:Abstract To better understand the factors that control forest soil CO 2 Efflux and the effects of rewetting on Efflux, we measured soil CO 2 Efflux in adjacent deciduous, coniferous, and mixed forests in the central part of the Korean Peninsula over the course of one year. We also conducted laboratory rewetting experiments with soil collected from the three sites using three different incubation temperatures (4 °C, 10 °C, and 20 °C). Soil moisture (SM), soil organic matter (SOM), and total root mass values of the three sites were significantly different from one another; however, soil temperature (ST), observed soil CO 2 Efflux and sensitivity of soil CO 2 Efflux to ST (i.e., Q 10 = 3.7 ± 0.1) were not significantly different among the three sites. Soil temperature was a dominant control factor regulating soil CO 2 Efflux during most of the year. We infer that soil CO 2 Efflux was not significantly different among the sites due to similar ST and Q 10 . Though a significant increase in soil CO 2 Efflux following rewetting of dry soil was observed both in the field observations (60–170%) and laboratory incubation experiments (100–1000%), both the increased rates of soil CO 2 Efflux and the magnitude of change in SM were not significantly different among the sites. The increased rates of soil CO 2 Efflux following rewetting depended on the initial SM before rewetting. During drying phase after rewetting, a significant correlation between SM and soil CO 2 Efflux was found, but the effect of ST on increased soil CO 2 Efflux was not clear. Cumulative peak soil CO 2 Efflux (11.3 ± 0.7 g CO 2 m −2 ) following rewetting in the field was not significantly different among the sites. Those evidences indicate that the observed similar rewetting effects on soil CO 2 Efflux can be explained by the similar magnitude of change in SM after rewetting at the sites. We conclude that regardless of vegetation type, soil CO 2 Efflux and the effect of rewetting on soil CO 2 Efflux do not differ among the sites, and ST is a primary control factor for soil CO 2 Efflux while SM modulates the effect of rewetting on soil CO 2 Efflux. Further studies are needed to quantify and incorporate relationship of initial dryness of the soil and the frequency of the dry–wet cycle on soil CO 2 Efflux into models describing carbon (C) processes in forested ecosystems.
