Xiaoyong Chen
Governors State University, Biology, Faculty Member
Thinning is a common silviculture technology in forestry, but there is considerable uncertainty about the changes of soil nutrients due to thinning practice in different aged forests. The influence of light thinning (reduction of 20% of... more
Thinning is a common silviculture technology in forestry, but there is considerable uncertainty about the changes of soil nutrients due to thinning practice in different aged forests. The influence of light thinning (reduction of 20% of stand density) on soil organic carbon (SOC) and other mineral elements (N, P, K, Cu, Fe, Zn, Mn and S), as well as soil pH and soil bulk density were investigated in 6-, 13-, and 23-year-old growth stands of Chinese fir forests in subtropical China. Six 10m ×10m plots (three thinning and three non-thinning plots) were set up in each aged forests. Soil samples were taken from different soil layers from these plots for nutrient analysis. Results showed that SOC increased 59.4, 48.9, and 62.0% in topsoil layer (0-30 cm) in 6, 13, and 23 year-old growth stands, respectively when compared to the control, and the content of N increased by 20.5, 44.6, and 54.1% corresponding after two year post-thinning. In the thinned forests, soil P slightly increased at ...
Research Interests:
Tropical savannas cover a quarter of the Australian landmass and the biome represents a significant potential carbon sink. However, these savannas are subject to frequent and extensive fire. Fire regimes are likely to affect the... more
Tropical savannas cover a quarter of the Australian landmass and the biome represents a significant potential carbon sink. However, these savannas are subject to frequent and extensive fire. Fire regimes are likely to affect the productivity and carbon sequestration potential of savannas, through effects on both biomass and carbon emissions. The carbon sequestration potential has been estimated for some savanna sites by quantifying carbon storage in biomass and soil pools, and the fluxes to these pools. Using different techniques, previous work in these savannas has indicated that net ecosystem productivity [NEP, net primary productivity (NPP) less heterotrophic respiration] was about –3 t C ha–1 y–1 (i.e. a carbon sink). However, the impacts of fire were not accounted for in these calculations. Estimates of NEP have been combined with remotely-sensed estimates of area burnt and associated emissions for an extensive area of mesic savanna in Arnhem Land, NT, Australia. Combining NEP ...
Research Interests:
A series of posters representing updated data and information about climate change science are displayed along the walkway on the first floor in Building F. These posters are collected, summarized and synthesized from peer-reviewed... more
A series of posters representing updated data and information about climate change science are displayed along the walkway on the first floor in Building F. These posters are collected, summarized and synthesized from peer-reviewed publications from the UN Intergovernmental Panel on Climate Change; UN Food and Agriculture Organization; U.S. Environmental Agency; U.S. Climate Change Science Program and U.S. National Research Council. The overall objective of the project is to increase the Governors State University community\u27s awareness of the climate change issue and enhance the intellectual pursuits for better understanding of interaction between human activities and the environments
Large woody debris (LWD) is an important component in the biogeochemistry cycle of carbon and nutrients in forested stream ecosystems. In-stream LWD volume, biomass and carbon pool were investigated in 19 forested streams in the south... more
Large woody debris (LWD) is an important component in the biogeochemistry cycle of carbon and nutrients in forested stream ecosystems. In-stream LWD volume, biomass and carbon pool were investigated in 19 forested streams in the south central interior of British Columbia. The stream channels were classified into four disturbance categories based upon condition of the adjacent riparian forest. The categories are: (1) riparian forest harvested approximately10 years ago (HT10), (2) riparian forest harvested approximately 30 years ago (HT30), (3) riparian forest burned by a wildfire approximately 40 years ago (WF), and (4) undisturbed old-growth riparian forest (OF). Streams with riparian forests that were affected by wildfire or were recently harvested were observed to have significantly higher LWD volumes, biomass, and carbon pool as compared to streams flowing through old-growth riparian forests. LWD stocks averaged 376 m À3 ha À1 (volume), 112 Mg ha À1 (biomass), 52 Mg C ha À1 (carbon) in WF, 258 m À3 ha À1 , 78 Mg ha À1 and 36 Mg C ha À1 in HT10, 180 m À3 ha À1 , 52 Mg ha À1 and 23 Mg C ha À1 in HT30, and 114 m À3 ha À1 , 37 Mg ha À1 and 17 Mg C ha À1 in OF. Volume, biomass, and carbon stock were 2.3, 2.0, 2.1, and 1.3, 1.1 and 1.1 times higher in WF and HT10 than in OF, respectively, but LWD loading did not differ significantly between HT30 and OF. Major differences were also observed in the state of decay of LWD between the four disturbance categories based upon three decomposition classes. Our study supports the conclusion that harvesting creates a short-term increase in LWD stocks. However, harvesting may greatly reduce LWD loadings over the long-term due to relatively rapid decomposition of LWD due to increased rate of decay, transport, and reduced recruitment from the adjacent riparian forest. In the study streams, the wood density of LWD ranged from 0.273 to 0.427 g cm À3 depending upon the species and decomposition level. An average decay rate constant of 0.0095 year À1 was calculated for the LWD based upon wood density. Based upon this decay rate, the time required to loss 50% (t 0.5) and 95% (t 0.95) of wood is 74 and 316 years, respectively.
Research Interests:
Research Interests:
Fine roots and their turnover represent a dynamic aspect of below-ground biomass (BGB) and nutrient capital in forest ecosystems, and account for a significant fraction of net primary productivity (NPP) (Cuevas 1995, Vogt et al. 1990). On... more
Fine roots and their turnover represent a dynamic aspect of below-ground biomass (BGB) and nutrient capital in forest ecosystems, and account for a significant fraction of net primary productivity (NPP) (Cuevas 1995, Vogt et al. 1990). On a weight basis, coarse roots contribute more to total ecosystem biomass than fine roots, but they account for only a small portion of annual root production (Eamus et al. 2002). Despite the fact that fine roots may compose less than 2% of total ecosystem biomass, they may contribute up to 40% of total ecosystem production (Vogt et al. 1990). Therefore, estimates of root production, like estimates of root biomass, should differentiate between coarse- and fine-root production.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
In-stream large woody debris (LWD), defined as dead wood ≥ 10 cm in diameter and ≥ 1 m in length, has played multiple structural and functional roles in aquatic ecosystems. Despite the importance of LWD to fluvial ecosystems, few studies... more
In-stream large woody debris (LWD), defined as dead wood ≥ 10 cm in diameter and ≥ 1 m in length, has played multiple structural and functional roles in aquatic ecosystems. Despite the importance of LWD to fluvial ecosystems, few studies have been conducted in low-gradient Midwestern rivers and streams. In this study, the quantity and characteristics of LWD were investigated in the upper-, middleand down-stream sections along Thorn Creek located in Northeastern Illinois. The results showed that LWD abundance ranged from 18 to 58 pieces . 100 m-1, LWD volume ranged from 1.87 to 5.37 m3 . 100 m-2, and total LWD length ranged from 44.2 to 170.0 m per 100 m of stream length in the study sites. The quantity of woody pieces per 100 m of stream length was significantly higher in the downstream section than in both upperand middle-stream sections. Over 80% of LWD pieces were ≤ 20 cm in diameter and ≤ 4 m in length. Approximately 90% of wood pieces were in the medium and latter decomposition...
Intercropping is one of the most widely used agroforestry techniques, reducing the harmful impacts of external inputs such as fertilizers. It also controls soil erosion, increases soil nutrients availability, and reduces weed growth. In... more
Intercropping is one of the most widely used agroforestry techniques, reducing the harmful impacts of external inputs such as fertilizers. It also controls soil erosion, increases soil nutrients availability, and reduces weed growth. In this study, the intercropping of peanut (Arachishypogaea L.) was done with tea plants (Camellia oleifera), and it was compared with the mono-cropping of tea and peanut. Soil health and fertility were examined by analyzing the variability in soil enzymatic activity and soil nutrients availability at different soil depths (0–10 cm, 10–20 cm, 20–30 cm, and 30–40 cm). Results showed that the peanut–tea intercropping considerably impacted the soil organic carbon (SOC), soil nutrient availability, and soil enzymatic responses at different soil depths. The activity of protease, sucrase, and acid phosphatase was higher in intercropping, while the activity of urease and catalase was higher in peanut monoculture. In intercropping, total phosphorus (TP) was 14....
Research Interests:
Grazing affects nutrient cycling processes in grasslands, but little is known by researchers about effects on the nutrient stoichiometry of plant–soil–microbe systems. In this study, the influence of grazing intensity (0, 0.23, 0.34,... more
Grazing affects nutrient cycling processes in grasslands, but little is known by researchers about effects on the nutrient stoichiometry of plant–soil–microbe systems. In this study, the influence of grazing intensity (0, 0.23, 0.34, 0.46, 0.69, and 0.92 AU ha−1) on carbon (C), nitrogen (N) and phosphorus (P) and their stoichiometric ratios in plants, soil, and microbes was investigated in a Hulunber meadow steppe, Northeastern China. The C:N and C:P ratios of shoots decreased with grazing increased. Leaf N:P ratios <10 suggested that the plant communities under grazing were N-limited. Heavy grazing intensities increased the C:N and C:P ratios of microbial biomass, but grazing intensity had no significant effects on the stoichiometry of soil nutrients. The coupling relationship of C:N ratio in plant–soil–microbial systems was tightly significant compared to C:P ratio and N:P ratio according to the correlation results. The finding suggested grazing exacerbated the competition betw...
Research Interests:
Little information is available on horizontal precipitation in forest land in semi-humid climate regions. In this study, the quantity and duration of horizontal precipitation were investigated using the high precision weighing lysimeter... more
Little information is available on horizontal precipitation in forest land in semi-humid climate regions. In this study, the quantity and duration of horizontal precipitation were investigated using the high precision weighing lysimeter system in the mountainous areas of northern China during the experiment year 2011 and 2012. The purpose of this study was to better understand the formation mechanisms of horizontal precipitation in the semi-humid climate region. The results showed that hourly values of horizontal precipitation distributed between 0 and 0.1 mm, and that the one-night values distributed between 0.2 and 0.4 mm. The number of days with horizontal precipitation accounted for about 45% of the whole year. The average monthly amount of horizontal precipitation was 4.5 mm in the non-growing season, while it was a mere 1.6 mm in the growing season. The total amount of horizontal precipitation in the year was about 33 mm. Horizontal precipitation represented about 4.61% and 4....
Research Interests:
Antibiotic residues in the aquatic environment have become a global problem posing a serious threat to the environment and an inherent health risk to human beings. In this study, experiments were carried to investigate the use of carbon... more
Antibiotic residues in the aquatic environment have become a global problem posing a serious threat to the environment and an inherent health risk to human beings. In this study, experiments were carried to investigate the use of carbon material modified by liquid nitrogen treatment (CM1) and carbon material unmodified by liquid nitrogen treatment (CM2) as adsorbents for the removal of the antibiotic ampicillin from aqueous solutions. The properties of the CMs (CM1 and CM2) and the effects of variations of the key operating parameters on the removal process were examined, and kinetic, isothermal and thermodynamic experimental data were studied. The results showed that CM1 had larger specific surface area and pore size than CM2. The ampicillin adsorption was more effective on CM1 than that on CM2, and the maximum adsorption capacity of ampicillin onto CM1 and CM2 was 206.002 and 178.423 mg/g, respectively. The kinetic data revealed that the pesudo-second order model was more suitable...
Research Interests:
Contamination by heavy metals has become a serious environmental pollution issue today due to its potential threat to plant, wildlife, and human health. Photosynthesis, a process in which light energy is used to produce sugar and other... more
Contamination by heavy metals has become a serious environmental pollution issue today due to its potential threat to plant, wildlife, and human health. Photosynthesis, a process in which light energy is used to produce sugar and other organic compounds, is sensitive to heavy metals. In the present study, the response of photosynthetic process and carbon assimilation of Schima superba was investigated under cadmium (Cd) stress. Three Cd concentrations (0, 300, and 600 mg kg) were used designated as control (CK), low Cd (L), and high Cd treatment (L) of plants. Results showed that photosystem II (PSII) acceptor and donor side electron transport were more easily blocked in treatment compared to control, and L have more significant changes than L. A substantial decrease of 820 nm reflection curve absorption was observed both in L and L treatments. Special energy fluxes showed significant difference between the control group and the treated group, which indicated that low concentration ...
Research Interests:
With the increasing trend of converting monocultures into mixed forests, more and more studies have been carried out to investigate the admixing effects on tree growth and aboveground carbon storage. However, few studies have considered... more
With the increasing trend of converting monocultures into mixed forests, more and more studies have been carried out to investigate the admixing effects on tree growth and aboveground carbon storage. However, few studies have considered the impact of mixed forests on belowground carbon sequestration, particularly changes in soil carbon and nitrogen stocks as a forest grows. In this study, paired pure <i>Pinus massoniana</i> plantations, <i>Cinnamomum camphora</i> plantations and mixed <i>Pinus massoniana</i>–<i>Cinnamomum camphora</i> plantations at ages of 10, 24 and 45 years were selected to test whether the mixed plantations sequestrate more organic carbon (OC) and nitrogen (N) in soils and whether this admixing effect becomes more pronounced with stand ages. The results showed that tree species identification, composition and stand age significantly affected soil OC and N stocks. The soil OC and N stocks were the highest in mixed &...
Research Interests:
Research Interests:
ABSTRACT
ABSTRACT
ABSTRACT
Research Interests:
Research Interests:
The stock, rates of sequestration and allocation of carbon were estimated for trees in 14 0.1-ha plots at Kapalga in Kakadu National Park, Northern Territory, using new allometric relationships of carbon stock to stem cross-sectional area... more
The stock, rates of sequestration and allocation of carbon were estimated for trees in 14 0.1-ha plots at Kapalga in Kakadu National Park, Northern Territory, using new allometric relationships of carbon stock to stem cross-sectional area and measured growth rates of trees. Carbon stocks of trees ranged from 12 to 58 t ha–1, with sequestration representing ~9% of the total stocks. More than half of the sequestered carbon is allocated to leaves and twigs and ~20% to wood. Only ~25% is retained in the live trees with leaf and twig fall accounting for 80%–84% of the total transfers to the environment. An alternative method of calculating sequestration rates from consideration of water use and carbon-isotope discrimination data had a close to 1 : 1 match with estimates from allometric relationships. We developed and applied algorithms to predict the impacts of fire on carbon stocks of live trees. This showed that the reduction in live carbon stocks caused by single fires increased with ...
Research Interests:
Savanna communities dominate the wet–dry tropical regions of the world and are an important community type in monsoonal northern Australia. As such they have a significant impact on the water and carbon balance of this region. Above the... more
Savanna communities dominate the wet–dry tropical regions of the world and are an important community type in monsoonal northern Australia. As such they have a significant impact on the water and carbon balance of this region. Above the 1200-mm isohyet, savanna’s are dominated by Eucalyptus miniata–E. tetrodonta open forests. We have described in detail the composition and structure as well as seasonal patterns of leaf area index and above-ground biomass in the E. miniata–E. tetrodonta open forests of the Gunn Point region near Darwin in the Northern Territory of Australia. In all, 29 tree species from four phenological guilds were recorded in these forests. Stand structure suggests that the forests were still recovering from the impacts of cyclone Tracy and subsequent frequent fires. Eucalyptus miniata and E. tetrodonta were significant contributors to overstorey leaf area index and standing biomass (>70%), and both leaf area index and biomass were strongly correlated to basal a...
Research Interests:
Research Interests:
Research Interests:
Below-ground biomass of a Eucalyptus savanna forest was estimated following trenching to depths of 2 m around 16 mature trees in a tropical savanna of north Australia. Correlations among below-ground and various components of above-ground... more
Below-ground biomass of a Eucalyptus savanna forest was estimated following trenching to depths of 2 m around 16 mature trees in a tropical savanna of north Australia. Correlations among below-ground and various components of above-ground biomass were also investigated. In addition, root morphology was investigated by fractal analyses and a determination of an index of shallow-rootedness was undertaken. Total root biomass was 38.4 t ha–1, including 1 t ha–1 of fine roots. About 77–90% of total root biomass was found in the upper 0.5 m of soil. While fine-root biomass density was approximately constant (0.1 kg m–3) in the top soil, irrespective of distance from a tree stem, coarse-root biomass showed large variation with distance from the tree stem. Significant positive correlations among total root biomass, total above-ground biomass, diameter at breast height, leaf biomass and leaf area were obtained. It is likely that total root biomass can be reasonably accurately estimate...
Research Interests:
Research Interests:
To determine the influence of forest structures on runoff characteristics, the hydrological effects of Chinese fir plantations were studied by analysing runoff patterns at different growth and development stages (stand age classes I to V)... more
To determine the influence of forest structures on runoff characteristics, the hydrological effects of Chinese fir plantations were studied by analysing runoff patterns at different growth and development stages (stand age classes I to V) from 1984 to 2004 at the Huitong Ecosystem Research Station, Central South University of Forestry and Technology, Hunan Province, Central South China. Results for two small experimental Chinese fir watersheds showed different peak values for surface runoff amount and coefficients at different ages, with lowest values in age classes I and V and highest values in age classes II and III. However, both underground and total runoff coefficients decreased with increasing age class. Total runoff coefficient was about twice as high in age class I (30·8%) as that in age class V (15·8%). Higher underground and total runoff coefficients were found in young forests. This was mainly attributed to soil disturbance due to human management practices such as site ploughing. Results indicate that Chinese fir plantations play a significant role in regulating water distribution in the watershed. Useful information is provided on the effects of forest management practices on hydrological processes in forest plantations. Copyright © 2008 John Wiley & Sons, Ltd.
Research Interests:
It is well known that large woody debris (LWD) plays an important functional role in aquatic organisms' life. However, the influence of LWD on channel morphology and aquatic environments at watershed levels is still unclear. The... more
It is well known that large woody debris (LWD) plays an important functional role in aquatic organisms' life. However, the influence of LWD on channel morphology and aquatic environments at watershed levels is still unclear. The relationships between wood and surface structure and aquatic habitat in 35 first through fifth order streams of southern interior British Columbia were investigated. Study streams in the channel networks of the study watersheds were classified into four size categories based on stream order and bankfull width: Stream size I: bankfull width was less than 3 m, Stream size II: 3–5 m, Stream size III: 5–7 m, Stream size IV: larger than 7 m. We found the number of functional pieces increased with stream size and wood surface area in stream sizes I, II and III (24, 28 and 25 m2/100 m2, respectively) was significantly higher than that in stream size IV (12 m2/100 m2). The contribution of wood pieces to pool formation was 75% and 85% in stream sizes II and III, respectively, which was significantly higher than those in stream size I (50%) and size IV (25%). Between 21% and 25% of wood pieces were associated with storing sediment, and between 20% and 29% of pieces were involved in channel bank stability in all study streams. Due to long-term interactions, LWD in the intermediate sized streams (Size II and III) exhibited much effect on channel surface structure and aquatic habitats in the studied watersheds. Copyright © 2008 John Wiley & Sons, Ltd.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
In-stream large woody debris (LWD) is a structurally and functionally important component of forested stream ecosystems. To assess the role played by LWD in sustaining aquatic ecosystems at the watershed scale, the amount, distribution,... more
In-stream large woody debris (LWD) is a structurally and functionally important component of forested stream ecosystems. To assess the role played by LWD in sustaining aquatic ecosystems at the watershed scale, the amount, distribution, dynamics and function of LWD within channel networks have to be determined. We surveyed 35 sites in first- through fifth-order streams within forested watersheds in the southern interior of British Columbia, and the spatial variation and distribution of LWD characteristics (frequency, density, volume, biomass, orientation, submersion, and decay state) were quantified based on four stream size categories. We found that the average diameter, length, volume and biomass of individual LWD pieces increased as a function of increasing bankfull width. However, LWD density (piece per 100 m2 of the stream area) decreased with an increase in bankfull width. LWD volume ranged from 0.78 to 1.58 m3/100 m2 of stream area, with intermediate sized streams (sizes II and III) having the largest value and large sized streams (size IV) having the lowest values. Results showed that LWD biomass averaged 383 kg/100 m2 (range 265–651 kg/100 m2) in stream size I, increased to 491 kg/100 m2 (range 81–1254 kg/100 m2) in stream size II, and slightly decreased to 465 kg/100 m2 (range 247–938 kg/100 m2) in stream size III and further decreased to 250 kg/100 m2 (range 88–533 kg/100 m2) in stream size IV. The large majority of LWD pieces in the smallest sized streams was orientated perpendicular to streamflow and was located in spanning the channel. Conversely, most LWD pieces in intermediate sized streams were orientated parallel to the direction of flow and were situated below the bankfull height of the channel. With a difference in the orientation and position, LWD pieces within different sized streams are expected to have varying potentials to affect streamflow and channel habitats. These results highlight the need to recognize spatial variation of in-stream LWD loading and function through channel networks when maintaining suitable LWD pieces and making riparian management decisions at watershed scales.
Research Interests:
Large woody debris (LWD) is an important component in the biogeochemistry cycle of carbon and nutrients in forested stream ecosystems. In-stream LWD volume, biomass and carbon pool were investigated in 19 forested streams in the south... more
Large woody debris (LWD) is an important component in the biogeochemistry cycle of carbon and nutrients in forested stream ecosystems. In-stream LWD volume, biomass and carbon pool were investigated in 19 forested streams in the south central interior of British Columbia. The stream channels were classified into four disturbance categories based upon condition of the adjacent riparian forest. The categories are: (1) riparian forest harvested approximately10 years ago (HT10), (2) riparian forest harvested approximately 30 years ago (HT30), (3) riparian forest burned by a wildfire approximately 40 years ago (WF), and (4) undisturbed old-growth riparian forest (OF).Streams with riparian forests that were affected by wildfire or were recently harvested were observed to have significantly higher LWD volumes, biomass, and carbon pool as compared to streams flowing through old-growth riparian forests. LWD stocks averaged 376 m−3 ha−1 (volume), 112 Mg ha−1 (biomass), 52 Mg C ha−1 (carbon) in WF, 258 m−3 ha−1, 78 Mg ha−1 and 36 Mg C ha−1 in HT10, 180 m−3 ha−1, 52 Mg ha−1 and 23 Mg C ha−1 in HT30, and 114 m−3 ha−1, 37 Mg ha−1 and 17 Mg C ha−1 in OF. Volume, biomass, and carbon stock were 2.3, 2.0, 2.1, and 1.3, 1.1 and 1.1 times higher in WF and HT10 than in OF, respectively, but LWD loading did not differ significantly between HT30 and OF. Major differences were also observed in the state of decay of LWD between the four disturbance categories based upon three decomposition classes. Our study supports the conclusion that harvesting creates a short-term increase in LWD stocks. However, harvesting may greatly reduce LWD loadings over the long-term due to relatively rapid decomposition of LWD due to increased rate of decay, transport, and reduced recruitment from the adjacent riparian forest. In the study streams, the wood density of LWD ranged from 0.273 to 0.427 g cm−3 depending upon the species and decomposition level. An average decay rate constant of 0.0095 year−1 was calculated for the LWD based upon wood density. Based upon this decay rate, the time required to loss 50% (t0.5) and 95% (t0.95) of wood is 74 and 316 years, respectively.
Research Interests:
To determine the influence of forest structures on runoff characteristics, the hydrological effects of Chinese fir plantations were studied by analysing runoff patterns at different growth and development stages (stand age classes I to V)... more
To determine the influence of forest structures on runoff characteristics, the hydrological effects of Chinese fir plantations were studied by analysing runoff patterns at different growth and development stages (stand age classes I to V) from 1984 to 2004 at the Huitong Ecosystem Research Station, Central South University of Forestry and Technology, Hunan Province, Central South China. Results for two small experimental Chinese fir watersheds showed different peak values for surface runoff amount and coefficients at different ages, with lowest values in age classes I and V and highest values in age classes II and III. However, both underground and total runoff coefficients decreased with increasing age class. Total runoff coefficient was about twice as high in age class I (30·8%) as that in age class V (15·8%). Higher underground and total runoff coefficients were found in young forests. This was mainly attributed to soil disturbance due to human management practices such as site ploughing. Results indicate that Chinese fir plantations play a significant role in regulating water distribution in the watershed. Useful information is provided on the effects of forest management practices on hydrological processes in forest plantations. Copyright © 2008 John Wiley & Sons, Ltd.
Research Interests:
It is well known that large woody debris (LWD) plays an important functional role in aquatic organisms' life. However, the influence of LWD on channel morphology and aquatic environments at watershed levels is still unclear. The... more
It is well known that large woody debris (LWD) plays an important functional role in aquatic organisms' life. However, the influence of LWD on channel morphology and aquatic environments at watershed levels is still unclear. The relationships between wood and surface structure and aquatic habitat in 35 first through fifth order streams of southern interior British Columbia were investigated. Study streams in the channel networks of the study watersheds were classified into four size categories based on stream order and bankfull width: Stream size I: bankfull width was less than 3 m, Stream size II: 3–5 m, Stream size III: 5–7 m, Stream size IV: larger than 7 m. We found the number of functional pieces increased with stream size and wood surface area in stream sizes I, II and III (24, 28 and 25 m2/100 m2, respectively) was significantly higher than that in stream size IV (12 m2/100 m2). The contribution of wood pieces to pool formation was 75% and 85% in stream sizes II and III, respectively, which was significantly higher than those in stream size I (50%) and size IV (25%). Between 21% and 25% of wood pieces were associated with storing sediment, and between 20% and 29% of pieces were involved in channel bank stability in all study streams. Due to long-term interactions, LWD in the intermediate sized streams (Size II and III) exhibited much effect on channel surface structure and aquatic habitats in the studied watersheds. Copyright © 2008 John Wiley & Sons, Ltd.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
In-stream large woody debris (LWD) is a structurally and functionally important component of forested stream ecosystems. To assess the role played by LWD in sustaining aquatic ecosystems at the watershed scale, the amount, distribution,... more
In-stream large woody debris (LWD) is a structurally and functionally important component of forested stream ecosystems. To assess the role played by LWD in sustaining aquatic ecosystems at the watershed scale, the amount, distribution, dynamics and function of LWD within channel networks have to be determined. We surveyed 35 sites in first- through fifth-order streams within forested watersheds in the southern interior of British Columbia, and the spatial variation and distribution of LWD characteristics (frequency, density, volume, biomass, orientation, submersion, and decay state) were quantified based on four stream size categories. We found that the average diameter, length, volume and biomass of individual LWD pieces increased as a function of increasing bankfull width. However, LWD density (piece per 100 m2 of the stream area) decreased with an increase in bankfull width. LWD volume ranged from 0.78 to 1.58 m3/100 m2 of stream area, with intermediate sized streams (sizes II and III) having the largest value and large sized streams (size IV) having the lowest values. Results showed that LWD biomass averaged 383 kg/100 m2 (range 265–651 kg/100 m2) in stream size I, increased to 491 kg/100 m2 (range 81–1254 kg/100 m2) in stream size II, and slightly decreased to 465 kg/100 m2 (range 247–938 kg/100 m2) in stream size III and further decreased to 250 kg/100 m2 (range 88–533 kg/100 m2) in stream size IV. The large majority of LWD pieces in the smallest sized streams was orientated perpendicular to streamflow and was located in spanning the channel. Conversely, most LWD pieces in intermediate sized streams were orientated parallel to the direction of flow and were situated below the bankfull height of the channel. With a difference in the orientation and position, LWD pieces within different sized streams are expected to have varying potentials to affect streamflow and channel habitats. These results highlight the need to recognize spatial variation of in-stream LWD loading and function through channel networks when maintaining suitable LWD pieces and making riparian management decisions at watershed scales.
Research Interests:
Large woody debris (LWD) is an important component in the biogeochemistry cycle of carbon and nutrients in forested stream ecosystems. In-stream LWD volume, biomass and carbon pool were investigated in 19 forested streams in the south... more
Large woody debris (LWD) is an important component in the biogeochemistry cycle of carbon and nutrients in forested stream ecosystems. In-stream LWD volume, biomass and carbon pool were investigated in 19 forested streams in the south central interior of British Columbia. The stream channels were classified into four disturbance categories based upon condition of the adjacent riparian forest. The categories are: (1) riparian forest harvested approximately10 years ago (HT10), (2) riparian forest harvested approximately 30 years ago (HT30), (3) riparian forest burned by a wildfire approximately 40 years ago (WF), and (4) undisturbed old-growth riparian forest (OF).Streams with riparian forests that were affected by wildfire or were recently harvested were observed to have significantly higher LWD volumes, biomass, and carbon pool as compared to streams flowing through old-growth riparian forests. LWD stocks averaged 376 m−3 ha−1 (volume), 112 Mg ha−1 (biomass), 52 Mg C ha−1 (carbon) in WF, 258 m−3 ha−1, 78 Mg ha−1 and 36 Mg C ha−1 in HT10, 180 m−3 ha−1, 52 Mg ha−1 and 23 Mg C ha−1 in HT30, and 114 m−3 ha−1, 37 Mg ha−1 and 17 Mg C ha−1 in OF. Volume, biomass, and carbon stock were 2.3, 2.0, 2.1, and 1.3, 1.1 and 1.1 times higher in WF and HT10 than in OF, respectively, but LWD loading did not differ significantly between HT30 and OF. Major differences were also observed in the state of decay of LWD between the four disturbance categories based upon three decomposition classes. Our study supports the conclusion that harvesting creates a short-term increase in LWD stocks. However, harvesting may greatly reduce LWD loadings over the long-term due to relatively rapid decomposition of LWD due to increased rate of decay, transport, and reduced recruitment from the adjacent riparian forest. In the study streams, the wood density of LWD ranged from 0.273 to 0.427 g cm−3 depending upon the species and decomposition level. An average decay rate constant of 0.0095 year−1 was calculated for the LWD based upon wood density. Based upon this decay rate, the time required to loss 50% (t0.5) and 95% (t0.95) of wood is 74 and 316 years, respectively.
Research Interests:
A distributed hydrological model [Wigmosta, M.S., Vail, L.W., Lettenmaier, D.P., 1994. A distributed hydrology-vegetation model for complex terrain. Water Resource Research 30 (6), 1665–1679] is further developed to simulate the detailed... more
A distributed hydrological model [Wigmosta, M.S., Vail, L.W., Lettenmaier, D.P., 1994. A distributed hydrology-vegetation model for complex terrain. Water Resource Research 30 (6), 1665–1679] is further developed to simulate the detailed spatial and temporal variation patterns of evapotranspiration (ET) around a flux tower site. In addition to meteorological, topographical and soil data, the model utilizes optical remote sensing data (Landsat TM at 30 m resolution) to characterize the distributions of vegetation types and the leaf area index (LAI). The use of LAI allows process-based modeling of major hydrological processes including transpiration, precipitation interception, and evaporation from vegetation and soil. Water flows within and between five strata (overstore, understore, moss/litter, soil unsaturated zone, and soil saturated zone) are modeled on a daily basis. A moving window of nine pixels is used to consider the lateral subsurface flow. The model is applied to a small watershed of dimension of about 16 km×12 km in Saskatchewan, Canada. The temporal variations of simulated ET are compared with eddy-covariance ET measurements over a black spruce stand located within the watershed. The stand was the Old Black Spruce in the Southern Study Area during the Boreal Ecosystem-Atmosphere Study (BOREAS) in 1994. Although the black spruce site is located in a flat area with less than 1.5 m topographical variation within 150 m of the flux tower, there was about 10.5 mm water loss through saturated subsurface flow during the growing season of 1994, accounting for 5.7% of the rainfall in same period. Even though the watershed studied had gentle terrain variations, the topography had considerable influence not only on the water table but also on the soil moisture and saturated water redistribution. This suggests the importance of modeling hydrological processes as influenced by topography in mapping ET.
Research Interests: Remote Sensing, Hydrology, Multidisciplinary, Eddy Covariance, Evapotranspiration, and 15 moreWater Table, Landsat TM, Leaf Area Index, Water Loss, Complex terrain, Optical Remote Sensing, Water Resource, Indexation, Subsurface Flow, Black Spruce, Soil Water, Distributed Hydrological Model, Unsaturated Zone, Growing Season, and temporal variation
Through estimations of above- and below-ground standing biomass, annual biomass increment, fine root production and turnover, litterfall, canopy respiration and total soil CO2 efflux, a carbon balance on seasonal and yearly time-scales is... more
Through estimations of above- and below-ground standing biomass, annual biomass increment, fine root production and turnover, litterfall, canopy respiration and total soil CO2 efflux, a carbon balance on seasonal and yearly time-scales is developed for a Eucalypt open-forest savanna in northern Australia. This carbon balance is compared to estimates of carbon fluxes derived from eddy covariance measurements conducted at the same site. The total carbon (C) stock of the savanna was 204±53 ton C ha−1, with approximately 84% below-ground and 16% above-ground. Soil organic carbon content (0−1 m) was 151±33 ton C ha−1, accounting for about 74% of the total carbon content in the ecosystem. Vegetation biomass was 53±20 ton C ha−1, 39% of which was found in the root component and 61% in above-ground components (trees, shrubs, grasses). Annual gross primary production was 20.8 ton C ha−1, of which 27% occurred in above-ground components and 73% below-ground components. Net primary production was 11 ton C ha−1 year−1, of which 8.0 ton C ha−1 (73%) was contributed by below-ground net primary production and 3.0 ton C ha−1 (27%) by above-ground net primary production. Annual soil carbon efflux was 14.3 ton C ha−1 year−1. Approximately three-quarters of the carbon flux (above-ground, below-ground and total ecosystem) occur during the 5–6 months of the wet season. This savanna site is a carbon sink during the wet season, but becomes a weak source during the dry season. Annual net ecosystem production was 3.8 ton C ha−1 year−1.