Organizers: Cindy Prescott (University of British Columbia, Canada), Douglas Godbold (University of Natural Resources and Life Sciences, Austria), Heljä-Sisko Helmisaari (University of Helsinki) &
Shalom Daniel Addo-Danso (Forestry Research Institute of Ghana & University of British Columbia, Canada)
The relationship between fi ne root and litterfall dynamics across various types of temperate deciduous and coniferous forests. An, J. (Kyoto University, Japan; jiyoung.an.63c@st.kyoto-u.ac.jp), Park, B. (Chungnam National University, Republic of Korea; bbpark@cnu.ac.kr), Osawa, A. (Kyoto University, Japan; aosawa@kais.kyoto-u.ac.jp), Park, G. (Korea Forest Research Institute, Republic of Korea; graceh03@snu.ac.kr).
We have little understanding of the relationship between litterfall and fi ne root dynamics in temperate forest ecosystems, even though these are major components in carbon and nutrient cycling. We studied litterfall, fi ne root biomass, and production in fi ve deciduous and four coniferous forests at the Gwangneung Long Term Ecological Research Site in Korea. We used ingrowth cores to measure fi ne root turnover for 2 years. Collected roots were divided into living and dead roots of <0.5, 0.5–1, 1–2, and 2–5 mm in diameter. Litterfall was separated into leaves, twig, bark, seed, and others and all leaves were further separated by species. Our preliminary results show that fi ne root turnover rate was 1.68/year for deciduous forests and 2.07/year for coniferous forests. Annual fi ne root (<2 mm) production ranged from 47 to 335 g/m2 in the fi rst year and from 138 to 490 g/m2 in the second year. The annual litterfall production ranged from 340 to 597 g/m2. For further research, we will test the relationships between the fi ne root production, litterfall production, and environmental variables and the contribution of fi ne root and litterfall to nutrient dynamics by forest types.
Tree root systems and nutrient mobilization: mineral weathering by rhizospheres and deep roots. Boyle, J. (Oregon State University, USA; forsol40@comcast.net), Harrison, R. (University of Washington, USA; robh@uw.edu), Raulund-Rasmussen, K.
(University of Copenhagen, Denmark; krr@life.ku.dk), Zabowski, D. (University of Washington, USA; zabow@u.washington.edu), Stupak, I., Callesen, I. (University of Copenhagen, Denmark; ism@ign.ku.dk; ica@ign.ku.dk), Hatten, J. (Oregon State University, USA; Jeff.Hatten@oregonstate.edu).
Roots mobilize nutrients via deep penetration and rhizosphere processes inducing weathering of primary minerals. These contribute to C transfer to soils and to tree nutrition. Assessments of these characteristics and processes of root systems are important for understanding long-term supplies of nutrient elements essential for forest growth and resilience. Research and techniques have signifi cantly advanced since Olof Tamm’s 1934 base mineral index for Swedish forest soils, and basic nutrient budget estimates for whole-tree harvesting systems of the 1970s. Recent research in areas that include some of the world’s most productive intensively managed forests, including Brazil and the Southeast and Pacifi c Northwest regions of the United States, have shown that root systems are often several meters in depth, and often extend deeper than soil is sampled. Large amounts of carbon are also sometimes stored at depth. Other recent studies on potential release of nutrients due to chemical weathering indicate the importance of root access to deep soil layers. Release profi les clearly indicate depletion in the top layers and a much higher potential in B and C horizons. Review of evaluations of potential sustainability of nutrient supplies for biomass harvesting and other intensive forest management systems will advance understanding of these important ecosystem properties, processes, and services.
Tree species identity infl uences the accumulation of recalcitrant deep soil carbon. Godbold, D., Ahmed, I. (University of Natural Resources and Life Sciences, Austria; douglas.godbold@boku.ac.at; iua@dhaka.net), Smith, A. (Bangor University, UK;
a.r.smith@bangor.ac.uk).
Using an acid hydrolysis approach, easily degradable labile and recalcitrant C pools in soils from single and mixed tree stands of Betula pendula, Alnus glutinosa, and Fagus sylvatica and adjacent grassland were determined, in relation to leaf litter inputs and fi ne root distribution and turnover. The vertical distribution and turnover of fi ne roots did not differ between species planted in monoculture or polyculture. In the upper layers, no signifi cant differences in C storage or fractionation pools were found between the treatments; however, in the deeper soil layers, the greatest storage of recalcitrant C was found in the polyculture. The C storage in the polyculture soil at depth was signifi cantly greater compared to the B. pendula, A. glutinosa, and grassland soil, but not statistically different compared to F. sylvatica. In the lower soil profi le, both F. sylvatica and the polyculture had a statistically higher C storage in the recalcitrant pool compared to under grass. In the grassland soil, only 17% of the total recalcitrant C pool was accumulated within the 40- to100-cm layer, whereas in F. sylvatica and the polyculture soils, 53% of the total recalcitrant C pool was determined.
Revaluating the role of roots and mycorrhizal hyphae in belowground carbon and nutrient cycling in forests. Guo, D.
(Chinese Academy of Sciences, China; guodl@igsnrr.ac.cn).
Fine roots of trees are complex branching structures composed of multiple branch orders. The two to three fi nest branch orders confi ned to primary development are truly absorptive roots that turn over quickly. These absorptive roots have much less biomass that that of the entire fi ne root pool, thus previous estimates of fi ne root mortality and turnover treating all fi ne roots as one dynamic unit may have substantially overestimated total absorptive root turnover. Moreover, these absorptive roots contain high concentrations of C and N, contributing to their slow decomposition. The absorptive roots of many tree species also bear abundant root hairs and/or mycorrhizal hyphae, which turn over more rapidly than absorptive roots. These microscopic structures also infl uence total C and nutrient input into the soil and subsequent soil C sequestration. Reevaluating turnover for absorptive roots and including mycorrhizal and root hair turnover would signifi cantly improve the accuracy of total belowground C and nutrient turnover and subsequent C storage in the soil.
Carbon input into forest soil from below- and aboveground litter in climatically contrasting Norway spruce forests.
Helmisaari, H., Leppälammi-Kujansuu, J. (University of Helsinki, Finland; helja-sisko.helmisaari@helsinki.fi ; jaana.leppalammi-kujansuu@helsinki.fi ), Hansson, K. (Swedish University of Agricultural Sciences, Sweden; karna.hansson@slu.se), Salemaa, M., Aro, L. (Finnish Forest Research Institute, Finland; maija.salemaa@metla.fi ; lasse.aro@metla.fi ).
Boreal forests are known to store a great amount of global C both in vegetation and in soils, but the contribution of different sources to soil C is poorly known. We determined fi ne-root and aboveground litter C fl ux of Norway spruce stands located in a climate gradient from southern Sweden to northern Finland, and related it to climate as well as stand and site characteristics. Tree and understory fi ne root litter was estimated using soil coring for biomass and minirhizotrons for longevity. Aboveground litterfall was estimated from litter traps and understory litter production from the annual biomass production. Spruce and understory fi ne root (<1 mm in diameter) litter C inputs were high in the northern sites. The contribution of understory vegetation litter, both below- and aboveground, to the C input into the forest soil was also substantial in the northern sites. Ignoring these C fl uxes in ecosystem studies or models leads to serious underestimations of soil C inputs.
The quantity and storage mechanisms of carbon in deep soil horizons of the Pacifi c Northwest. James, J., Harrison, R.
(University of Washington, USA; jajames@uw.edu; robh@uw.edu), Devine, W. (Joint Base Lewis-McChord, USA;
wdevine27@yahoo.com).
Carbon storage has become a major objective in forest management, and soil is the largest sink for C in forest ecosystems.
Nonetheless, soil C is overlooked in ecosystem C budgets and underreported in the literature. This has led to a lack of under-standing about mechanisms for soil C storage, particularly in subsurface horizons. This paper examines the quantity of soil C to 2.5 m depth in the Pacifi c Northwest Douglas-fi r zone, and investigates mineral-surface adsorption, occlusion in aggregates, and inherent chemical recalcitrance as mechanisms for soil C storage. We demonstrate that 1) on average, 66% of soil C can be found below 0.2 m and >20% below 1.0 m in these soils; 2) mathematical models can help us estimate soil C in deep layers given sampling depths of 1.0 m; and 3) adsorption reactions are the major mechanism for stabilizing soil C in deep layers, especially in soils dominated by noncrystalline minerals such as allophane, imogolite, and ferrihydrite. Whether C enters the soil system via decomposition of forest litter or through root exudates and turnover, a thorough mechanistic understanding of soil C storage is necessary to understand belowground C dynamics and potential for C sequestration.
Relation of fi ne root vertical distribution to soil carbon in Cunninghamia lanceolata forest in subtropical China. Liao, Y., Wang, H. (Chinese Academy of Sciences, China; liaoyingc@163.com; wanghm@igsnrr.ac.cn).
The objective of the study was to assess the root mass density (RMD) and root carbon density (RCD), and the relation of their distribution to soil C, in Cunninghamia lanceolata forest in subtropical region of China. The vertical root distribution and soil bulk in the 0- to 40-cm soil profi le were investigated by a soil excavating method. The roots were classifi ed into non-woody short-lived roots, woody long-lived roots, dead roots, live herb roots, and gross roots. The results showed that soil C content, RMD, and RCD of short-lived roots, dead roots, and herb roots peaked in the 0- to 10-cm soil layer and decreased with soil depth, while RMD and RCD of long-lived roots peaked in the 10- to 20-cm soil layer. Soil C and soil N had strong correlation with each other (P < 0.01) in the three soil layers. RMD and RCD of herb roots and dead roots were positively correlated with soil C in the 0- to 10- and 10- to 20-cm soil layers (P < 0.1), while RMD and RCD of short-lived roots and long-lived roots had strong correlations to soil C in the 10- to 20-cm soil layer. However, the distribution of RMD and RCD of gross roots had a strong correlation with soil C in each soil layer.
Estimates of forest fi ne root productivity based on functional classifi cation of fi ne roots and root traits. McCormack, M., Guo, D., Tian, J., Jingyuan, W. (Chinese Academy of Sciences, China; mltmcc@gmail.com; guodl@igsnrr.ac.cn; tianj@igsnrr.
ac.cn; wangj@igsnrr.ac.cn).
Carbon fl ow into soil through the turnover of fi ne root biomass in most forest ecosystems is thought to range from 10 to 60%, with 33% serving as a de facto best guess in many cases. Most previous estimates have been based on the assumption that fi ne roots consist of a single class of roots with relatively fast turnover times of a few months to a few years. However, recent studies have highlighted a clear functional divide within traditionally defi ned fi ne roots with the most distal roots being active in resource acquisition and having fast turnover times and more proximal fi ne roots functioning more as storage and transport structures with slower turnover times. We conducted a rigorous characterization of ephemeral and persistent fi ne root biomass and estimated the total fl ow of carbon through fi ne root turnover on a species-specifi c basis in a diverse, northern temperate forest in northeastern China. Our results generally indicate lower estimates of annual carbon loss through fi ne root turnover than previously expected.
We discuss these fi ndings and their implications for leftover carbon and carbon allocation to root exudation and mycorrhizal fungi.
Applicability of mesh methods to the estimates of fi ne root production in forest ecosystems. Ohashi, M. (University of Hyogo, Japan; ohashi@shse.u-hyogo.ac.jp), Hirano, Y. (Nagoya University, Japan; yhirano@nagoya-u.jp), Noguchi, K. (Forestry and Forest Products Research Institute, Japan; kyotaro@affrc.go.jp), Ikeno, H. (University of Hyogo, Japan; ikeno@shse.u-hyogo.
ac.jp), Finér, L. (Finnish Forest Research Institute, Finland; leena.fi ner@metla.fi ), Nakano, A. (University of Hyogo, Japan;
aiko.na0518@gmail.com).
Determination of fi ne root production is important for estimation of carbon storage and understanding the mechanisms of carbon cycling in forest ecosystems. The mesh sheet method is one of the most recent techniques for measuring fi ne root production.
However, the methodological protocol is still uncertain; for example, no study examined the effects of mesh materials and physical properties on the results. In this study, therefore, we aimed to compare fi ne root production estimated by mesh methods using different mesh materials with different mesh sizes and hardness in forest ecosystems. We prepared four different mesh materials (stainless, polyamide, polyethylene, polyester) whose hardness was separated into two classes (soft, hard). Two different sizes (2 and 4 mm) were used for the mesh sheet made by polyester. The estimated value of fi ne root production was 7 ± 7 g/m2/year in a Japanese cedar forest in Japan and 71 ± 65 g/m2/year in a tropical rainforest in Malaysia. We could not fi nd
any clear impact of mesh material, size, and hardness on the estimates. This suggests that mesh sheet method is widely applicable, which would make the comparison of fi ne root production estimated by this method comparable among different forest ecosystems in future.
The burial of aboveground woody debris: an important source of soil carbon. Stokland, J. (Norwegian Forest and Landscape Institute, Norway; jogeir.stokland@skogoglandskap.no), Moroni, M. (Forestry Tasmania, Australia; Martin.Moroni@forestrytas.
com.au), Okabe, K. (Forestry and Forest Products Research Institute, Japan; kimikook@ffpri.affrc.go.jp), Hagemann, U. (Leibniz Centre for Agricultural Landscape Research, Germany; Ulrike.Hagemann@zalf.de), Morris, D. (Ministry of Natural Resources, Canada; Dave.M.Morris@ontario.ca), Shaw, C. (Canadian Forest Service, Canada; Cindy.Shaw@NRCan-RNCan.gc.ca), Harmon, M. (Oregon State University, USA; mark.harmon@oregonstate.edu), Merganic, J., Merganicova, K. (Technical University Zvolen, Slovakia; j.merganic@forim.sk; merganicova@tuzvo.sk), Fenton, N. (Université du Québec en Abitibi-Témiscamingue, Canada;
nicole.fenton@uqat.ca).
Buried wood from aboveground parts of trees is a common, yet poorly studied source of soil carbon. Downed trunks are frequently overgrown by ground vegetation before complete decomposition and they become incorporated into forest soils. This study gives an overview of published and unpublished buried wood studies from 11 countries across North America, Europe, Asia, and Australia. Buried wood is particularly common in boreal coniferous forests. The probability of wood burial is affected by wood dimension, decay stage, rot type, ground vegetation, and soil type. Coniferous forests with a dominant and active bryophyte layer represent conditions where large amounts of buried wood have been recorded (20–935 m3/ha). The bryophyte layer and bryophyte-derived organic soils lower soil temperature and enhance soil moisture to the extent that below-ground wood decay rates are signifi cantly reduced as compared with aboveground decay rates. Wood decomposition is further slowed down by paludifi ed (poorly drained) soil. The long-term preservation can accumulate subterranean dead wood amounts that greatly exceed those above ground. The widespread occurrence of bryophyte-dominated as well as paludifi ed forests, especially in the boreal zone, suggests that carbon dynamics of dead wood should be revised and updated to include below-ground decomposition rates.
Posters
Methods for quantifying root dynamics for forest carbon studies: a review. Addo-Danso, S. (Forestry Research Institute of Ghana and University of British Columbia, Canada; shalomdanso@hotmail.com), Prescott, C. (University of British Columbia, Canada; cindy.prescott@ubc.ca).
Belowground components including coarse (>2 mm) and fi ne (≤2 mm) roots are key components of forest biomass and productiv-ity, as well as the biogeochemical cycle. Despite the critical roles they play, roots and other belowground components have been understudied compared to the aboveground components due mainly to technical diffi culties and methodological challenges. There is no consensus regarding fi ne roots about how root dynamics (biomass, production, turnover, and mortality) can be estimated, and which method is the most suitable. Critical evaluations of the assumptions, strengths, and inherent limitations associated with the various methods are required to inform investigators about the conditions for which a particular method should be preferred.
From literature the use of indirect methods such as allometric equations are widely accepted as a cost-effective and reliable means to estimate coarse root biomass and production, although most are not validated. The use of the ground-penetrating radar (GPR) to quantify root biomass looks very promising for future carbon studies. The sequential coring and ingrowth methods still remain the preferred choices for estimating fi ne root biomass, production, and turnover. Indirect methods like the stable or isotopic radiocarbon are becoming very important due to their increased use in global carbon models.
Response of autotrophic and heterotrophic soil respiration to long-term management in tree-based and treeless grassland ecosystems. Adewopo, J. (University of Florida, USA; adewopo@ufl .edu).
We assessed changes in total soil respiration (RS) and its components (autotrophic, RA and heterotrophic, RH), after >22 years of managing a gradient of pine-bahiagrass silvopasture, bahiagrass-pasture, and reference native-rangeland ecosystems. Using an EGM-2 soil respiration chamber, we measured in-situ RS, RA, RH, and critical control factors (soil temperature and moisture) for 12 weeks in winter (January to March) and summer (May to August). Relative to baseline native-rangeland, RS, RA, and RH did not change in silvopasture during the winter and summer (difference ~0.02–0.04 g CO2/m2/h; P > 0.05), but a signifi cant increase (up to 0.68 g CO2/m2/h in RS) was observed in bahiagrass-pasture during the summer. Similar to RS and RA,
temperature-sensitivity (Q10) of RH generally decreased from native-rangeland to bahiagrass-pasture (1.65 to 1.44) during winter, but increased in the same order during the summer (1.48 to 2.29). However, compared to reference native-rangeland, bahiagrass-pasture became less sensitive to the joint effects of temperature and moisture during winter (r2 = 0.71 and 0.95), while silvopasture became less sensitive in the summer (r2 = 0.23 and 0.51). Overall, our fi ndings suggest that tree-grass integrated silvopastures may reduce soil C loss through respiration during warmer period, but loss may be accelerated in bahiagrass-pastures.
Soil respiration across different scales and successional time scales in boreal mixedwood forests. Akande, O. (University of Alberta, Canada; oluwabun@ualberta.ca).
Carbon dioxide (CO2) is a major greenhouse gas that is rapidly increasing in the atmosphere, mostly as a result of anthropogenic emissions. The second largest store of carbon in the world is the soil, surpassed by that of the deep ocean. Boreal forests have the ability to capture and store large quantities of carbon dioxide. The fi rst objective of this research is to compare the spatial variability of large-scale soil respiration to that of fi ne-scale soil respiration. The second objective is to partition soil respiration in the fi eld into autotrophic and heterotrophic respiration, determining how scale affects the partitions individually. The third objective is to determine the relationship between biodiversity and soil respiration. The total soil respiration along with its heterotrophic and autotrophic partitions was measured during the growing seasons from 2012 to 2014. These results will be useful in climate change studies to understand how soils respire with various scales and timelines. We need to understand how CO2 is cycled through the ecosystem to create adaptation and mitigation plans by offsetting soil-CO2 effl ux through anthropogenic global warming.
Temporal and spatial variability of soil carbon fl ux in longleaf pine forests in the southeastern United States. ArchMiller, A., Samuelson, L. (Auburn University, USA; aaa0013@auburn.edu; samuelj@auburn.edu).
Longleaf pine (Pinus palustris Mill.) is being restored in the southeastern United States for many ecosystem services. Little is known about longleaf pine soil respiration (RS), the largest fl ux of carbon dioxide from forests. This research included three studies that together aimed to 1) quantify and predict soil carbon fl ux (RS) in longleaf pine forests; 2) determine factors control-ling temporal and spatial variability in RS, such as litter biomass, vegetative cover, forest structure, soil characteristics, and root biomass; and 3) partition RS into its heterotrophic component. Soil respiration ranged from 12.1 to 14.2 Mg C per hectare per year in longleaf pine forests ranging in age from 5 to 87 years old. Soil temperature accounted for 63 to 81% of the temporal variation in RS over an annual cycle but demonstrated little to no effect on RS spatial variation. More than 70% of the spatial variation in longleaf pine RS was accounted for by soil carbon and moisture, buried coarse woody debris, basal area, and litter biomass. The heterotrophic component of soil respiration was estimated to be 76–84% of RS. This presentation will also discuss
Longleaf pine (Pinus palustris Mill.) is being restored in the southeastern United States for many ecosystem services. Little is known about longleaf pine soil respiration (RS), the largest fl ux of carbon dioxide from forests. This research included three studies that together aimed to 1) quantify and predict soil carbon fl ux (RS) in longleaf pine forests; 2) determine factors control-ling temporal and spatial variability in RS, such as litter biomass, vegetative cover, forest structure, soil characteristics, and root biomass; and 3) partition RS into its heterotrophic component. Soil respiration ranged from 12.1 to 14.2 Mg C per hectare per year in longleaf pine forests ranging in age from 5 to 87 years old. Soil temperature accounted for 63 to 81% of the temporal variation in RS over an annual cycle but demonstrated little to no effect on RS spatial variation. More than 70% of the spatial variation in longleaf pine RS was accounted for by soil carbon and moisture, buried coarse woody debris, basal area, and litter biomass. The heterotrophic component of soil respiration was estimated to be 76–84% of RS. This presentation will also discuss