Ingrowth Core Method Research Articles

Fine-root production in boreal peatland forests: Effects of stand and environmental factors

Fine roots are an important component of ecosystem carbon (C) cycling in boreal forests and peatlands. We aimed to estimate fine-root production (FRP) for a range of peatland forests, examine the patterns in, and develop models for estimating, the relationships between FRP and tree stand characteristics as well as environmental conditions.Fine-root production of 28 drained boreal peatland forest sites in Finland, representing different site types and soil water-table conditions, was measured using the ingrowth-core method. Total FRP and FRP of conifers decreased from south to north but long-term mean annual temperature sum and precipitation alone did not significantly explain this trend. Tree stand basal area predicted FRP better than any other stand variable alone, explaining 16 % of the variation in stand-level total FRP. Basal areas of pine and spruce correlated positively with the FRP of conifers. Total FRP varied considerably among the site types and, with the exception of the most fertile site type, decreased with decreasing fertility. A model that included stand basal area and site type accounted for 47% of the variation in stand-level total FRP. Total FRP was generally higher with a deeper water-table level (WT). Together, WT and basal area explained 25 % of the variation in stand-level total FRP. Most FRP occurred in the top 20-cm layer comprising 76–95% of total FRP. The most fertile site type showed lower FRP in deeper layers than the other site types. These results can be used for estimation of FRP with forest inventory data.

Fine Root Production and Its Benefaction to carbon storage of the Sundarbans Mangrove Forest

The quantification of fine root production (FRP) and biomass (FRB) is of utmost importance in gaining insights into ecosystem dynamics. However, these aspects have received limited attention in mangrove forests, primarily due to the considerable time and labor required for accurate assessment. Therefore, our study aims to estimate FRP and FRB stocks in the Sundarbans mangrove forest in Bangladesh, specifically focusing on two distinct saline zones: oligohaline and mesohaline. To accomplish our objectives, we employed soil coring and long-term ingrowth core methods to collect soil samples from 20 study plots, each covering an area of 200 square meters. Additionally, we assessed the forest structure by measuring the tree height and diameter at breast height. Our findings revealed that the mean FRB and FRP across the study area were 12.65±1.12 Mgha-1 and 2.25±0.13 Mgha-1 y-1, respectively. Notably, the oligohaline zone, characterized by lower salinity levels, exhibited higher FRB stocks and FRP compared to the mesohaline zone. Furthermore, our analysis showed that FRP in the diameter class of 1-2 mm surpassed that of the 0.5-1 mm and ≤0.5 mm classes. In terms of biomass, the mean above-ground, below-ground, and total biomass carbon were determined to be 87.18 ± 18.3, 48.38 ± 8.0, and 135.57 ± 26.3 Mgha-1, respectively. Through species importance value (Iv) analysis, we identified Excoecaria agallocha as the dominant species in the oligohaline zone, while Sonneratia apetala exhibited the highest Iv value in the mesohaline area. Heritiera fomes emerged as the primary contributor to total biomass carbon, particularly in the oligohaline zone, whereas S. apetala contributed the most biomass carbon in the mesohaline zone. These findings emphasize the importance of protecting and conserving mangrove ecosystems as valuable contributors to global carbon dynamics due to its higher fine root production and its contribution to carbon stocks.

Fine root dynamics of Kandelia obovata, Rhizophora stylosa and Bruguiera gymnorrhiza in a mangrove environment in Okinawa, Japan

The present study investigates the fine root dynamics including comparison of fine root production, mortality and decomposition of Kandelia obovata (S., L.) Yong, Rhizophora stylosa Griff. and Bruguiera gymnorrhiza (L.) Lamk. in the Manko Wetland of Okinawa, Japan considering the importance of fine root to the ecosystem carbon dynamics. Our objective was to investigate seasonal dynamics of fine root of the three species and explore whether there is variation among species using sequential core and ingrowth core methods. The root systems were separated into living and dead mass fractions and these were subsequently separated as very fine roots (<0.5 mm) and fine roots (0.5—2 mm). Total fine root production of K. obovata, R. stylosa and B. gymnorrhiza ranged from 4.7 to 7.1 Mg ha −1 y−1, 1.7 to 3.6 Mg ha −1 y−1 and 2.9 to 4.9 Mg ha −1 y−1, respectively whereas mortality ranged 2.9 to 5.9 Mg ha −1 y−1, 0.6 to 2.3 Mg ha −1 y−1 and 0.8 to 3 Mg ha −1 y−1. The mean fine root turnover of K. obovata, R. stylosa and B. gymnorrhiza were estimated as 3.42, 2.78 and 3.37 y−1 having a longevity of 3.46, 4.32 and 3.56 months, respectively. The amount of decomposition through sequential core and ingrowth core methods for K. obovata, was estimated at 47 and 28 g m−2y−1, respectively, whereas for R. stylosa and B. gymnorrhiza these were 6 and 11 g m−2y−1, and 15 and 19 g m−2y−1, respectively. Significant variation of soil salinity, soil N, soil pH among three species plots was observed although the result was insignificant in different seasons. Using ingrowth core method, we observed significant correlations of fine root production with soil salinity and soil pH, but the results were insignificant with sequential core data. Finally, the significant effect of soil pH was found in the regression model as the predictor of fine root production. Although the seasonal pattern was absent in fine root production, the seasonal change in the biomass and necromass was obvious. The high amount of fine root necromass available can be a great source of organic matter in the forest for carbon and nutrient cycling.

Grazing exclusion reduces below‐ground biomass of temperate subhumid grasslands of South America: A meta‐analysis and a database

AbstractThere are several plant below‐ground biomass databases for grasslands, but the contribution from the southern hemisphere is minimal. Particularly, no study has compiled the published values of plant below‐ground biomass for the temperate subhumid grasslands of South America. In these grasslands, called Río de la Plata grasslands, grazing is the most frequent disturbance. We set two objectives: (1) to compile and synthesize data of four variables: below‐ground biomass, fraction of total biomass allocated below‐ground, below‐ground net primary productivity and below‐ground biomass turnover rate; (2) to estimate the effect of grazing exclusion on below‐ground biomass by means of a meta‐analysis. There are 15 studies published on six out of eight regional sub‐divisions of the Río de la Plata grasslands. The most evaluated variable was below‐ground biomass, followed by below‐ground net primary productivity, while the other two variables were scarcely registered. Below‐ground biomass in the shallow portion of the soil (0–10 cm) was on average 877 g m−2. Below‐ground net primary productivity resulted in an average of 245 g m−2 year−1 (estimated using the ingrowth core method) or 560 g m−2 year−1 (core method). The fraction of total biomass allocated below‐ground was on average 0.75. Below‐ground biomass turnover rate presented an average of 2.5 years. On average, the effect of grazing exclusion on below‐ground biomass depended on exclusion time. When exclusion time was shorter than or equal to 3 years, grazing exclusion did not affect below‐ground biomass. In contrast, when exclusion time was longer than 3 years, grazing exclusion reduced below‐ground biomass by 62% (0–10 cm depth) and by 40% (total depth). Excluding South American grasslands from the global databases may introduce some biases in the observed patterns.

Fine root dynamics and its contribution to soil organic carbon stocks with Caragana intermedia plantation development in alpine sandy land.

Shrubs are the main species in desert ecosystems. Better understanding shrubs fine root dynamics and its contribution to soil organic carbon (SOC) stocks can improve the accuracy of carbon sequestration estimation and provide basic data for the calculation of carbon sequestration potential. The ingrowth core method was used to investigate the fine root (< 1mm in diameter) dynamics of Caragana intermedia Kuang et H. C. Fu plantation with different age (4-, 6-, 11-, 17-, and 31-year-old) in Gonghe Basin of the Tibetan Plateau, and the annual fine root mortality was used for calculation the annual carbon input to SOC pool. The results showed that fine root biomass, production, and mortality first increased and then decreased as the plantation age increased. Fine root biomass peaked in 17-year-old plantation, production and mortality peaked in 6-year-old plantation, and turnover rate of 4- and 6-year-old plantations were significantly higher than other plantations. Fine root production and mortality were negative correlated with soil nutrients at depth of 0-20 and 20-40 cm. The variation range of carbon input by fine root mortality across different plantation age at 0-60 cm soil depth was 0.54-0.85 Mg ha-1 year-1, accounting for 2.40-7.54% of the SOC stocks. C. intermedia plantation has a strong carbon sequestration potential from long time scale. Fine roots regenerate faster in young stands and lower soil nutrients environment. Our results suggest that the influences of plantation age and soil depth should be taken into account when calculating the contribution of fine root to SOC stocks in desert ecosystems.

Presence of understory dwarf bamboo determines ecosystem fine root production in a cool-temperate forest in northern Japan

ABSTRACT Fine root biomass (FRB) and production (FRP) are crucial in forest carbon and nutrient cycling, but the factors controlling FRB and FRP are not well understood. Here, we examined FRB, FRP, aboveground environmental and stand factors, and soil environmental factors in four stands in a forest covered with dense understory vegetation of dwarf bamboo, Sasa senanensis (hereafter, Sasa). The four stands had different tree species composition and included a primary forest (PF), secondary forest (SF), conifer plantation (CP), and Sasa area (SA). We quantified the FRB and FRP of trees and Sasa separately using the ingrowth core method. Total FRP was higher in stands with substantial presence of Sasa (99–130 g m−2 yr−1) than in CP with scarce Sasa (69 g m−2 yr−1). Despite being occupied by Sasa alone, SA had high FRP, suggesting that the presence of Sasa regardless of trees is a key determinant of ecosystem FRP. Tree FRB increased with increasing tree aboveground biomass, tree density, or basal area at breast height, but Sasa FRB and total FRB decreased. Total FRP was also lower at higher values of these aboveground stand factors. In Sasa, specific root length was significantly higher, and root tissue density was significantly lower, than in trees, indicating the capacity of Sasa for explosive growth. Positive correlations between Sasa FRB or FRP and soil inorganic N or ammonium contents (i.e. N availability) were detected. We conclude that Sasa is important in determining FRB and FRP in this northern forest with understory vegetation.

Fine root dynamics and associated nutrient flux in Sal dominated forest ecosystems of Central Himalaya, India

The belowground systems of trees have a major role in forest functioning through absorption of water and nutrient cycling. This study deals with the fine root dynamics including fine root biomass, necromass, production, turnover, and nutrient return in transitional Sal (Shorea robusta Gaertn. f.) dominated sub-tropical forest ecosystems of Central Himalaya, India. Four sites namely, Site-1 (Kaladhungi), Site-2 (Fatehpur), Site-3 (Ranibagh), Site-4 (Amritpur) were selected in Sal forest within an elevational range between 405 and 580 m above sea level. The dominant and associated co-dominant species were selected from each site for the estimation of fine root dynamics by using sequential core and ingrowth core methods. The results revealed that the fine root biomass, necromass, and production were significantly (p &amp;lt; 0.05) affected by location, seasons, and soil properties. The fine root biomass and production decreased with increasing soil depth and also influenced by stand characteristics including tree density and basal area. The rainy season was most productive with maximum fine root biomass (507.37 kg ha–1) as well as fine root production (600.26 kg ha–1 season–1) in the dominant tree species S. robusta. Among the associated co-dominant tree species highest fine root biomass (330.48 kg ha–1) and fine root production (410.04 kg ha–1 season–1) was reported for Tectona grandis L. during the rainy season, while lowest fine root biomass (126.72 kg ha–1) and fine root production (195.59 kg ha–1 season–1) in the Glochidion velutinum Wight tree species during the winter season. Annual fine root production ranged from 460.26 to 1583.55 kg ha–1 yr –1, while turnover rate varied from 1.37 to 4.45 yr–1 across all the studied sites. The fine roots added carbon input of 154.38 to 564.20 kg ha–1 yr–1 and nitrogen input of 6.58 to 24.34 kg ha–1 yr–1 to the soil through annual flux. The study improves our understanding on fine root parameters under the influence of sites, soils and seasonal and spatial variation. The return of nutrients to the soil through fluxes from the roots illustrates the role of fine roots in carbon and nitrogen cycling of the forests and this potential can be harnessed to assess the long-term carbon and nitrogen pool estimations in forests and to plan and manage the forest ecosystems.

Robinia pseudoacacia decline and fine root dynamics in a plantation chronosequence in the Yellow River Delta, China

Abstract Fine roots (&amp;lt;2 mm in diameter) play a significant role in tree growth and stand productivity. However, knowledge of fine root dynamics in saline alkali soil remains limited. Using sequential soil core and ingrowth core methods, we assessed the dynamics of aboveground biomass (AGB) and production (AGP), fine root biomass (FRB), production (FRP) and turnover (FRT), and soil properties (water content [SWC], salt content [SSC], pH and nutrients) in 2-, 18-, 32- and 42-year-old black locust (Robinia pseudoacacia L.) stands in the Yellow River Delta, China. Corresponding to the unimodal growth pattern in AGP, the AGB of black locust rapidly increased until age 32 and then slowed down. In contrast, across all depths, FRB and FRP took a unimodal pattern with a decrease in growth around age 32, and FRT continually decreased with stand age. SWC and soil nutrients increased with stand age, whereas SSC and pH decreased with stand age until age 32 and then increased. Based on the correlation analysis, we may presume that in addition to the age effect, the decline of black locust in AGP is most likely caused by SWC, SSC, and pH stresses through the dysfunction in nutrient absorption by fine roots.

Estimation of fine root production, mortality, and decomposition by using two core methods and litterbag experiments in a mangrove forest

AbstractMangrove forests are characterized by high rates of carbon sequestration, with much of this carbon being derived from fine roots. In this study, we sought to estimate the dynamics of the fine (&lt;2 mm) and small (≥2 mm) roots of Kandelia obovata, one of the mangrove forest species found on Okinawa Island, southern Japan, and to evaluate annual root production considering root decomposition estimated using root litterbags. To estimate root production and mortality, we applied two approaches, sequential soil core sampling and ingrowth core methods. We found that annual root production determined by sequential soil core sampling was 3.2 times higher than that estimated by ingrowth core methods. The annual production of fine roots (545 and 294 g m−2 year−1 for sequential soil core sampling and ingrowth core methods, respectively) was higher than that of small roots (536 and 44 g m−2 year−1 for sequential soil core sampling and ingrowth core methods, respectively). The results obtained using sequential soil core sampling indicated a high proportion of fine root necromass to total fine root mass (81%), most of which comprised very fine roots (&lt;0.5 mm). We also established that the decomposition ratio of fine roots was lower than that of small roots. Collectively, our observations indicate that the slow rate of decomposition and high rate of production of fine roots contribute significantly to the accumulation of fine root necromass, particularly that of very fine roots, in the mangrove forest.

Monoculture or Mixed Culture? Relevance of Fine Root Dynamics to Carbon Sequestration Oriented Mangrove Afforestation and Restoration

Fine root dynamics have the potential to contribute to ecosystem biogeochemical cycling, especially for carbon. This is particularly true in mangroves which are the most productive and carbon-rich ecosystems of the world. However, few studies comprehensively evaluated the contribution of mangrove fine root dynamics to soil organic carbon accumulation. In southern China, while the introduced fast-growing Sonneratia apetala and native shrubby Kandelia obovata have been widely used in mangrove reforestation/afforestation programs since the mid-1980s, their implications and ecosystem services are still unclear. Here we show distinct differences in fine root dynamic among 12-year-old S. apetala, K. obovata monocultures, and their mixed stand using root coring, ingrowth core, and intact-core methods. Soil organic carbon storage was examined by soil coring method. One-year observation showed significant differences among the three mangrove plantations in fine root biomass, necromass, turnover rate, and decomposition decay rate constant. Soil organic carbon stock was 15.8 ± 0.8, 7.8 ± 0.5, and 11.9 ± 1.6 Mg C ha–1 for K. obovata, S. apetala monocultures and their mixed stand, respectively. Live fine root biomass, fine root necromass, annual fine root production and fine root mass decay rate constant are significantly correlated to soil organic carbon content across plantations. We suggest that mangrove fine root dynamics were mainly affected by soil nutrient conditions and species composition. Mixed stands may not have higher soil organic carbon storage than monocultures. The functional trait of different mangrove species is responsible to determine the carbon storage function of mixed stands. Fine roots play an important role in carbon storage, and fine root dynamics have a significant effect on carbon sequestration in mangrove ecosystems. The shrubby native K. obovata had a higher potential for belowground carbon sequestration and storage than the tall introduced S. apetala.

Effect of Root and Mycelia on Fine Root Decomposition and Release of Carbon and Nitrogen Under Artemisia halodendron in a Semi-arid Sandy Grassland in China.

Plant fine root turnover is a continuous process both spatially and temporally, and fine root decomposition is affected by many biotic and abiotic factors. However, the effect of the living roots and the associated mycorrhizal fungal mycelia on fine root decomposition remains unclear. The objective of this study is to explore the influence of these biotic factors on fine root decomposition in a semi-arid ecosystem. In this study, we investigated the effect of fine roots and mycelia on fine root decomposition of a pioneer shrub (Artemisia halodendron) in Horqin sandy land, northeast China, by the ingrowth core method combined with the litterbag method. Litterbags were installed in cores. Results showed that core a allowed the growth of both fine roots and mycelia (treatment R + M), core b only allowed the growth of mycelia (treatment M), and in core c the fine root and mycelia growth were restricted and only bulk soil was present (treatment S). These findings suggest that the process of root decomposition was significantly affected by the living roots and mycelia, and carbon (C) and nitrogen (N) concentration dynamics during root decomposition differed among treatments. Mycelia significantly stimulated the mass loss and C and N release during root decomposition. Treatment R + M significantly stimulated the accumulation of soil total C, total N, and organic N under litterbags. The mycelia significantly stimulated the accumulation of the inorganic N (ammonium-N and nitrate-N) but the presence of fine roots weakened nitrate-N accumulation. The presence of living roots and associated mycelia strongly affected the process of root decomposition and matter release in the litter-soil system. The results of this study should strengthen the understanding of root-soil interactions.

Long-term variability of root production in bioenergy crops from ingrowth core measurements

Abstract Aims Long-term determination of root biomass production upon land-use conversion to biofuel crops is rare. To assess land-use legacy influences on belowground biomass accumulation, we converted 22-year-old Conservation Reserve Program (CRP) grasslands and 50+-year-old agricultural (AGR) lands to corn (C), switchgrass (Sw) and restored prairie (Pr) biofuel crops. We maintained one CRP grassland as a reference (Ref). We hypothesized that land-use history and crop type have significant effects on root density, with perennial crops on CRP grasslands having a higher root biomass productivity, while corn grown on former agricultural lands produce the lowest root biomass. Methods The ingrowth core method was used to determine in situ ingrowth root biomass, alongside measurements of aboveground net primary productivity (ANPP). Ancillary measurements, including air temperature, growing season length and precipitation were used to examine their influences on root biomass production. Important Findings Root biomass productivity was the highest in unconverted CRP grassland (1716 g m−2 yr−1) and lowest in corn fields (526 g m−2 yr−1). All perennial sites converted from CRP and AGR lands had lower root biomass and ANPP in the first year of planting but peaked in 2011 for switchgrass and a year later for restored prairies. Ecosystem stability was higher in restored prairies (AGR-Pr: 4.3 ± 0.11; CRP-Pr: 4.1 ± 0.10), with all monocultures exhibiting a lower stability. Root biomass production was positively related to ANPP (R2 = 0.40). Overall, attention should be given to root biomass accumulation in large-scale biofuel production as it is a major source of carbon sequestration.

Density manipulation and pruning on fine root production and decomposition dynamics in a mature Acacia mangium Willd. stand in Kerala, India

Fine roots play a major role in water and mineral uptake and nutrient cycling in woody perennial-based ecosystems. Just as other biomass components, stand density manipulation and tree pruning may influence fine root production (FRP) and its decomposition dynamics. However, quantitative information on FRP and its turnover under different density and pruning regimes are meagre for most tropical trees. A field study was conducted to characterize FRP and associated nutrient release under varying stand density and pruning regimes in a 12-year-old Acacia mangium stand in Kerala, India. Soil ingrowth core method was employed for quantifying FRP and sequential core method for estimating standing fine root biomass. Annual FRP estimates were 5.78, 5.39, 3.74, and 3.38 Mg ha–1 for the 5000, 2500, 1250 and 625 trees ha−1 treatments, respectively. Allometric models based on tree diameter and basal area gave a good fit for annual FRP. Fine root turnover rates ranged from 2.81 to 3.16 yr−1, which however, was not influenced by stand density. Carbon stocks ranged from 1.36 to 2.39 Mg ha−1 with highest FRP during rainy season and lowest during the dry period. The litterbag study using nylon mesh bags indicated that annual fine root mass loss ranged from 76.2 (5000 trees ha−1) to 96.8% (625 trees ha−1). Tree pruning had only modest effects on tree growth, FRP, and carbon and nutrient release patterns. The study highlights the importance of stand density manipulation in altering A. mangium FRP, soil carbon and mineral nutrient dynamics.

Drip fertigation promotes water and nitrogen use efficiency and yield stability through improved root growth for tomatoes in plastic greenhouse production

Drip fertigation increases water and nitrogen use efficiency, and reduces nitrogen leaching in comparison to conventional flood irrigation and over fertilization in plastic greenhouse vegetable production. However, it is unknown whether this also improves yield stability, possibly through improved root growth. A two-factor field trial was conducted in a randomized block experimental design with drip vs. flood fertigation and with vs. without straw application over eleven growing seasons for six years with following treatments: (i) flood irrigation with over fertilization (conventional practice, hereafter CIF); (ii) CIF + Straw; (iii) drip fertigation with reduced irrigation and fertilization (hereafter DIF); (iv) DIF + Straw. The CIF treatments had application rates of 600 mm + 900 kg N ha−1 season−1 and DIF had 300 mm + 200 kg N ha−1 season−1. The ingrowth core method was used to measure root-growth characteristics, including root dry weight, root length density and specific root length. The water and nitrogen use efficiency and the inter-annual variation coefficient of tomato yield were also measured and calculated. There was no significant effect of straw on any of the variables measured, but there were significant differences related to CIF and DIF treatments. DIF had 101 % higher water use efficiency (p < 0.05; 25 kg m−3) and 296 % higher partial nitrogen fertilizer productivity (p < 0.05; 423 kg kg-1 N) in comparison to CIF. Furthermore, the inter-annual coefficient of variation in tomato yield was less in the DIF treatment by 18 %. Root dry weight (+31 %) and root length density (+34 %) for the DIF treatment were significantly higher for the 0−30 cm depth as compared to the CIF treatment, but lower at 30−50 cm depth (7 % and 11 %, respectively). Compared with autumn-winter growing season, winter-spring season significantly increased root dry weight and tomato yield and reduced inter-annual variation coefficient of yield (p < 0.05), and meanwhile the treatments did not significantly affect these seasonal differences. Our results highlight that drip fertigation improves the resource use efficiency and production stability due to the promotion of better root growth in plastic shed vegetable production regardless of growing season, and is therefore a more sustainable and effective technology of saving water and reducing risk of environment pollution.

Spatial and Seasonal Pattern of Fine Root Biomass and Turnover Rate in Different Land Use Systems in Central Himalaya, India

Variation in fine root biomass (FRB) and turnover rate (TOR) were examined in four land use systems at two altitudes by using ingrowth core method. The aim of the study was to analyse the effect of altitude, depth and distance from tree stem on FRB and TOR. Significant variations (p < 0.05) were observed among land use systems, over seasons, depth and distances from the tree stem. The FRB varied between 47.09 and 528.59 kg ha–1. It was maximum in agri-horticulture (AH) system in bhabhar region and in homegarden (HG) system in hill region. In each land use system at both the altitudes FRB was maximum at uppermost layer (0‒20 cm) during rainy season at 50 cm distance from tree stem while, TOR did not showed any particular trend with soil depth and distance from the tree bole. FRB and turnover rate showed significance correlation with distance from tree bole at both the altitudes i.e. (r2 = 0.898 for low and r2 = 0.899 for high altitude).

Seasonal patterns of fine root dynamics and their contribution to net primary production in hinoki cypress (Chamaecyparis obtusa) and konara oak (Quercus serrata) forests

Key messageFine root and litterfall are major contributor of NPP and fine root production may reflect forest productivity in a warm-temperate forest in Japan.Forest ecosystems play an important role as the major carbon sink on land, with fine root dynamics and litterfall representing major carbon fluxes. The objectives of this research were to estimate NPP including annual fine root production values, to investigate fine root dynamics and the relationships between above– and belowground organs in konara oak (Quercus serrata) and hinoki cypress (Chamaecyparis obtusa) forests. Litterfall was collected seasonally for 1 year from June 2013. The ingrowth core method and the sequential soil core method were applied with a root litterbag experiment to estimate fine root (< 2 mm) production (FRP), mortality (FRM), and decomposition (FRD) for 1 year (from 2013 to 2014), using the continuous inflow estimate method and the simplified decision matrix. The total NPP ranged from 8.2 to 13.9 (t ha− 1 yr− 1), and the sum of aboveground litterfall and FRP accounted for 60% of the total NPP on average, confirming the significance of above- and belowground litter for the forest NPP as a source of detritus for the decomposer system. In hinoki cypress stand, fine root biomass peaked in the end of winter while fine root necromass showed the highest peak in late summer. In konara oak stand, only very fine root (< 0.05 mm) biomass and necromass demonstrated significant seasonal patterns. The seasonal patterns of fine root production did not differ between forest types and root diameter classes. We found a possible relationship between above- and belowground production and fine root production tended to be high in productive forests. This study improves our understanding of different patterns of carbon dynamics between temperate broadleaved and coniferous forest ecosystems.

Decoupling the Complementarity Effect and the Selection Effect on the Overyielding of Fine Root Production Along a Tree Species Richness Gradient in Subtropical Forests

The mechanism whereby tree species richness and identity affect the production of fine roots (≤ 2 mm) in forests remains controversial. Complementarity effects (via resource partitioning and facilitation, CEs) and selection effects (that is, dominant of species with particular traits, SEs) are the two hypotheses to explain biodiversity effects on ecosystem functions. This study aimed to (1) examine how tree species diversity affects fine root production and (2) disentangle the complementarity effect and the selection effect on the relationship between biodiversity and fine root production. A total of 60 tree clusters with 15 combinations of diversity gradients consisting of 1–4 tree species (Pinus massoniana, Choerospondias axillaris, Cyclobalanopsis glauca and Lithocarpus glaber) were established in subtropical forests. The sequential soil core and ingrowth core methods were used in each cluster to measure fine root biomass and productivity. Fine root production increased with increase in tree species richness. The biodiversity effects on fine root production mostly resulted from CEs. In the nongrowing season, in most cases, the CE on biomass was positive and became stronger as richness increased, but the opposite situation was observed in the growing season. The strong positive and negative effects of the proportions of C. glauca and L. glaber in the tree clusters on fine root biomass, CEs and SEs, suggest the coordinated action of species diversity and identity in modulating biodiversity effects on belowground processes.

Core-labelling technique (CLT): a novel combination of the ingrowth-core method and tracer technique for deep root study

BackgroundIngrowth-core method is a useful tool to determine fine root growth of standing crops by inserting root-free soil in mesh-bags for certain period of time. However, the root density observed by the method does not directly explain the nutrient uptake potential of crop plants as it varies over soil depth and incubation time. We have inserted an access-tube up to 4.2 m of soil depth with openings directly under crop plants, through which ingrowth-cores containing labelled soil with nutrient tracers were installed, called core-labelling technique (CLT). The main advantage of CLT would be its capacity to determine both root density and root activity from the same crop plants in deep soil layers. We tested the validity of the new method using a model crop species, alfalfa (Medicago sativa) against three depth-levels (1.0, 2.5 and 4.2 m), three sampling spots with varying distance (0–0.36, 0.36–0.72 and > 5 m from core-labelled spot), two sampling times (week 4 and 8), and two plant parts (young and old leaves) under two field experiments (spring and autumn).ResultsUsing CLT, we were able to observe both deep root growth and root activity up to 4.2 m of soil depth. Tracer concentrations revealed that there was no sign of tracer-leakage to adjacent areas which is considered to be advantageous over the generic tracer-injection. Root activity increased with longer incubation period and tracer concentrations were higher in younger leaves only for anionic tracers.ConclusionsOur results indicate that CLT can lead to a comprehensive deep root study aiming at measuring both deep root growth and root activity from the same plants. Once produced and installed, the access-tubes and ingrowth-cores can be used for a long-term period, which reduces the workload and cost for the research. Therefore, CLT has a wide range of potential applications to the research involving roots in deep soil layers, which requires further confirmation by future experiments.

Simulating warmer and drier climate increases root production but decreases root decomposition in an alpine grassland on the Tibetan plateau

Future ecosystem structure and function will largely depend on root responses to climate change. However, few studies have explored the responses of root production and decomposition to simultaneous warming and altered precipitation in high-latitude and high-altitude ecosystems. Using ingrowth core and root bag methods, we investigated root production and decomposition dynamics from 2013 to 2015 in a full-factorial warming (control, 1.5 ~ 1.8 °C warming) and precipitation (dry (−50% precipitation), ambient, and wet (+50% precipitation)) experiment established in 2011 in a Tibetan alpine grassland. Warming and precipitation effects on root production were independent. Dry plus warming treatments increased root production, while wet treatments did not significantly affect root production. In contrast, root decomposition accelerated along the increasing precipitation gradient. Warming tended to decrease root decomposition under dry treatments but did not affect root decomposition under wet treatments. The different responses of root production among the treatments were mainly driven by changes in soil moisture, whereas those of root decomposition were mainly due to the changes in the root carbon nitrogen ratio, soil microbial biomass and soil moisture. Given that altered precipitation had contrasting effects on root production and decomposition, our findings indicate that root-derived carbon may accumulate in soils on the Tibetan Plateau where precipitation decreases but not in the areas with projected increasing precipitation under future warming.

Root Responses of Five Japanese Afforestation Species to Waterlogging

The increase of waterlogged environments is of recent concern due to changes in precipitation regimes and the frequent occurrence of extreme rainfall events. Therefore, it is necessary to comprehend the effects and responses of waterlogging for a better understanding of forests and urban afforestation under changing environments. We investigated root responses of five Japanese afforestation species (Pinus thunbergii, Acer mono, Quercus serrata, Alnus hirsuta and Fraxinus mandshurica) to waterlogging. Potted seedlings grown under natural conditions were waterlogged at soil-surface level for 2.5 months during the growing season. The in-growth core method was used to distinctively measure root growth. As a result, fine root growth during the waterlogging period was significantly decreased for P. thunbergii, A. mono and Q. serrata. Furthermore, root tissue density (RTD) of pre-existing roots was decreased, which suggests root damage such as partial root death and root decay. On the other hand, for A. hirsuta and F. mandshurica, fine root growth was not decreased under waterlogging. For A. hirsuta, although fine root growth continued at the top half, it was decreased at the bottom half. Root damage such as a decrease in RTD was observed for pre-existing roots. For F. mandshurica, root growth continued at the top and bottom half, and root damage of pre-existing roots was not observed at either the top or the bottom. From our results, it was suggested that P. thunbergii was most sensitive, followed by A. mono and Q. serrata. A. hirsuta and F. mandshurica were relatively tolerant; however, the most tolerant was F. mandshurica, as pre-existing roots were not damaged by waterlogging. Overall, root responses could be grouped into three groups: (1) P. thunbergii, A. mono, Q. serrata; (2) A. hirsuta; (3) F. mandshurica. The observed responses may reflect the species’ natural distributions.