Fine Root Biomass Research Articles

Fine root biomass and its contribution to the mangrove communities in three saline zones of Sundarbans, Bangladesh

Globally, sea levels are rising due to climate change which would influence the salinity levels in mangroves. In the framework of this study, we focused on the influence of salinity and differences of forest structure on the fine root biomass (FRB) and carbon stocks in the Sundarbans mangrove forest, Bangladesh. Also, the relationships FRB to different stand structural parameters were investigated using the data obtained from 50 sample plots (100 sq. m each) in different salinity zones in Sundarbans. Four random soil samples (30 cm in length) were taken within study plots, which were further divided into 10 cm, 20 cm, and 30 cm to identify the most active soil layer for FRB stocks. Results suggest differences in forest structural parameters and diversity indices with salinity changes in different saline zones. The low and medium saline zone is dominated by Heriteira fomes, while Excoecaria agallocha dominates the high saline zone. The carbon stocks (Mg C ha−1) in Sundarbans show a significant decrease with increasing salinity in different saline zones, e.g. oligohaline (252 ± 60.2), mesohaline (199 ± 37.7), and polyhaline (171 ± 20.0) zone. FRB carbon (Mg C ha−1) allocation in different saline zones also followed a decreasing order, such as oligohaline (12.8), mesohaline (7.9), and polyhaline (7.3). Fine root biomass showed a decreasing trend with increasing soil depth, where the differences, however, were not significant (p > 0.05) among the soil layers. Our results provide evidence on FRB variations in Sundarbans, which has implications on the mangrove species conservation and management. The mature stands at different saline zones of Sundarbans mangrove forest, Bangladesh has a high fine root biomass, which is valuable for mangrove restoration and the studied species plantation in the shore line or coastal area which can help to decrease the erosion effects of tidal inundation.

Soil Bacterial and Archaeal Communities and Their Potential to Perform N-Cycling Processes in Soils of Boreal Forests Growing on Well-Drained Peat.

Peatlands are unique wetland ecosystems that cover approximately 3% of the world’s land area and are mostly located in boreal and temperate regions. Around 15 Mha of these peatlands have been drained for forestry during the last century. This study investigated soil archaeal and bacterial community structure and abundance, as well as the abundance of marker genes of nitrogen transformation processes (nitrogen fixation, nitrification, denitrification, and dissimilatory nitrate reduction to ammonia) across distance gradients from drainage ditches in nine full-drained, middle-aged peatland forests dominated by Scots pine, Norway spruce, or Downy birch. The dominating tree species had a strong effect on the chemical properties (pH, N and C/N status) of initially similar Histosols and affected the bacterial and archaeal community structure and abundance of microbial groups involved in the soil nitrogen cycle. The pine forests were distinguished by having the lowest fine root biomass of trees, pH, and N content and the highest potential for N fixation. The distance from drainage ditches affected the spatial distribution of bacterial and archaeal communities (especially N-fixers, nitrifiers, and denitrifiers possessing nosZ clade II), but this effect was often dependent on the conditions created by the dominance of certain tree species. The composition of the nitrifying microbial community was dependent on the soil pH, and comammox bacteria contributed significantly to nitrate formation in the birch and spruce soils where the pH was higher than 4.6. The highest N2O emission was recorded from soils with higher bacterial and archaeal phylogenetic diversity such as birch forest soils. This study demonstrates that the long-term growth of forests dominated by birch, pine, and spruce on initially similar organic soil has resulted in tree-species-specific changes in the soil properties and the development of forest-type-specific soil prokaryotic communities with characteristic functional properties and relationships within microbial communities.

Relationship between shoot and root of woody species of phenological functional groups of dry forest

Water availability in arid and semi-arid environments is the most limiting environmental factor for the development of plants, which use different mechanisms to capture the water from the soil. The objective of this work was to evaluate if there is differential allocation of resources between root and shoot of woody species of Brazilian dry forest and its relationship with the phenological functional groups of known adult woody: evergreen (EG), deciduous high density woody species (DHDW) and deciduous low density woody species (DLDW). The experiment was carried out in a greenhouse with a duration of six months, with plans submitted to two treatments: controlled irrigation (CI) and abundant irrigation (AI). Results showed that there was no interaction between phenological groups and applied treatments. However, the treatment with AI presented values of total biomass higher than those presented by CI. Fine root biomass was the only variable that did not differ between abundant irrigation and controlled irrigation. DLDW plants had higher root: shoot ratio compared to DHDW and EG. DLDW presented a differentiated strategy, being an indicative factor of these groups high thick root biomass, followed by low fine root biomass, with lower proportion of leaf biomass, and higher total biomass. These results show that CI reduces the development of seedlings in the groups and hence they invest in fine-root biomass. DLDW species presented higher investment in root biomass than in shoot, in addition to higher values of total biomass and specific leaf area.

Fine Roots Dynamics and Biomass of Phyllanthus Emblica-Based Agroforestry System in Bundelkhand Region of Central India

Fine Roots Dynamics and Biomass of Phyllanthus Emblica-Based Agroforestry System in Bundelkhand Region of Central India

Fine Root and Soil Nitrogen Dynamics during Stand Development Following Shifting Agriculture in Northeast India

Nitrogen (N) dynamics during changes in land use patterns in tropical forests may profoundly affect fine root dynamics and nutrient cycling processes. Variations in fine root biomass and soil N dynamics were assessed in developing stands of increasing ages following shifting agriculture in Mizoram, Northeast India, and comparisons were made with a natural forest stand. Concentrations of soil available N (NH4-N and NO3-N) and the proportion of NH4-N in total available N increased with stand age. The N-mineralization rate also increased with stand age whilst the proportion of nitrification relative to ammonification declined during succession. Fine root biomass and N-mineralization increased, and available N decreased during the monsoon season while this pattern was reversed during the winter season. A greater proportion of fine roots were <0.5 mm diameter in the younger sites, and turnover of fine roots was more rapid in the developing stands compared to the natural forest. Fine root biomass was correlated positively with N-mineralization rate and soil water content. Thus, it can be concluded that the fine root growth was aided by rapid N-mineralization, and both fine root growth and N-mineralization increase as stands redevelop following shifting cultivation disturbance.

Variation in Fine Root Characteristics and Nutrient Dynamics Across Alaskan Ecosystems

Carbon cycle perturbations in high-latitude ecosystems associated with rapid warming can have implications for the global climate. Belowground biomass is an important component of the carbon cycle in these ecosystems, with, on average, significantly more vegetation biomass belowground than aboveground. Large quantities of dead root biomass are also in these ecosystems owing to slow decomposition rates. Current understanding of how live and dead root biomass carbon pools vary across high-latitude ecosystems and the environmental conditions associated with this variation is limited due to the labor- and time-intensive nature of data collection. To that end, we examined patterns and factors (abiotic and biotic) associated with the variation in live and dead fine root biomass (FRB) and FRB carbon (C), nitrogen (N) and phosphorus concentrations for 23 sites across a latitudinal gradient in Alaska, spanning both boreal forest and tundra biomes. We found no difference in the live or dead FRB variables between these biomes, despite large differences in predominant vegetation types, except for significantly higher live FRB C:N ratios in boreal sites. Soil C:N ratio, moisture, and temperature, along with moss cover, explained a substantial portion of the dead:live FRB ratio variability across sites. We find all these factors have negative relationships with dead FRB, while having positive or no relationship with live FRB. This work demonstrates that FRB does not necessarily correlate with aboveground vegetation characteristics, and it highlights the need for finer-scale measurements of abiotic and biotic factors to understand FRB landscape variability now and into the future.

Effects of warming and fertilization interacting with intraspecific competition on fine root traits of Picea asperata

Abstract Aims Competition, temperature and nutrient are the most important determinants of tree growth in the cold climate on the eastern Tibetan Plateau. Although many studies have reported their individual effects on tree growth, little is known about how the interactions of competition with fertilization and temperature affect root growth. We aim to test whether climate warming and fertilization promote competition and to explore the functional strategies of Picea asperata in response to the interactions of these factors. Methods We conducted a paired experiment including competition and non-competition treatments under elevated temperature (ET) and fertilization. We measured root traits, including the root tip number over the root surface (RTRS), the root branching events over the root surface (RBRS), the specific root length (SRL), the specific root area (SRA), the total fine root length and area (RL and RA), the root tips (RTs) and root branching (RB) events. These root traits are considered to be indicators of plant resource uptake capacity and root growth. The root biomass and the nutrient concentrations in the roots were also determined. Important Findings The results indicated that ET, fertilization and competition individually enhanced the nitrogen (N) and potassium (K) concentrations in fine roots, but they did not affect fine root biomass or root traits, including RL, RT, RA and RB. However, both temperature and fertilization, as well as their interaction, interacting with competition increased RL, RA, RT, RB and nutrient uptake. In addition, the SRL, SRA, RTRS and RBRS decreased under fertilization, the interaction between temperature and competition decreased SRL and SRA, while the other parameters were not affected by temperature or competition. These results indicate that P. asperata maintains a conservative nutrient strategy in response to competition, climate warming, fertilization and their interactions. Our results improve our understanding of the physiological and ecological adaptability of trees to global change.

Variations in humus and fine root properties related to development stages in a temperate natural Beech forest

Understanding variations in soil humus and fine root properties in Oriental beech (Fagus orientalis L.) stand in response to development stages in temperate Hyrcanian forests is essential for sustainable forest management. The development stages of beech stand (initial, optimal and decay) were determined, and three plots of 100 × 100 m (1 ha) were chosen at each development stage. Five subplots in size 20 × 20 m were randomly selected at plots of 1 ha. The concentrations of humus elements (C, P, K, Mg, Fe and Zn) differed significantly among the development stages in spring and autumn seasons within Beech forest. The comparison of mean chemical compounds of humus layer in spring and autumn seasons using t test showed significant difference for each the development stage. Differences in C, N and P concentrations and also C/N and N/P ratios in fine roots of beech trees were significant among development stages, while C/P ratio was insignificant. The mean values of N and P for initial stage were higher, but C and N/P ratio were higher for optimal stage. The highest C/N value was observed in decay stage. There were statistically significant effects of development stages on fine root biomass and morphology traits at different diameter classes in beech trees. No statistically significant impacts of development stages were observed on fine root morphology of beech trees, except for fine root density. Our results reveal the important role that different development stages may play in Beech forest regarding variations in chemical properties of fine roots and soil humus.

Effect of tree mixtures and water availability on belowground complementarity of fine roots of birch and pine planted on sandy podzol

We investigated whether tree species growing in mixtures and under different water supply would segregate their fine roots vertically, produce more fine roots overall, or only in specific soil layers. We examined the biomass, morphology, and distribution of fine roots down to 90 cm (forest floor, 0–5, 5–15, 15–30, 30–60, 60–90 cm) in pure and mixed stands of 10-year-old birch and pine trees, planted on a sandy podzol with discontinuous hardpan and seasonal high water table, following a randomized block design with four blocks receiving irrigation and four blocks left unirrigated during summer. Our results did not show any vertical root segregation between birch and pine in mixed plots. None of the species overyielded belowground throughout, but pine developed more roots in the top soil layer under irrigation. Both species had shallower fine root distributions in wet conditions, especially birch that was more plastic than pine in response to irrigation. Both species followed similar ecological strategies, occupying and competing for the same layers of the soil profile, under both control and irrigated conditions. However, the greater allocation of pine roots at the top soil horizons under irrigated conditions suggests locally favourable niches can lead to depth-specific asymmetric competition. This sheds new light on vertical niche partitioning of young tree mixtures under varying environmental conditions.

Efficiency of leaf litter mulch in the restoration of soil physiochemical properties and enzyme activities in temporary skid roads in mixed high forests

Various engineering measures, such as mulching, have been applied on decommissioned skid trails to suppress the adverse effects of overland flow and flood hazards. However, very little research has been done on the effects of such treatments on soil recovery. The aim of this study is to determine the effectiveness of different leaf litter levels on the restoration of soil properties and enzyme activity, when spread on decommissioned skid trails over a four-year period after soil compaction. In total, 90 soil samples in 18 runoff plots were measured under six treatments, including undisturbed (control) treatment, UND; untreated skid trail, U; and four levels of leaf litter, LML1, LML2, LML3, and LML4, with levels of 0.42, 0.81, 1.31, and 1.69 kg m−2, respectively. Soil bulk density and penetration resistance under the litter mulch treatments were lower than that under the U treatment, and at the lowest in the UND treatment. The total porosity, macroporosity, and aggregate stability were at the highest level in UND, followed by LML4 ≈ LML3 > LML2 ≈ LML1. Soil organic C, total N, C/N ratio, C and N sequestration, available nutrients (i.e., P, K, Ca, and Mg), and fulvic and humic acids were at the highest level in UND followed by LML4, and at the lowest level in U followed by LML1 ≈ LML2. The highest earthworm density and dry mass, fine root biomass, soil microbial respiration, microbial biomass carbon, NH4+, NO3−, nitrogen mineralization, and microbial biomass nitrogen were measured in UND, followed by LML4. Compared with U, all litter mulch treatments enhanced enzyme activity. Four years after mulch application, the values of soil biological and microbial properties and enzyme activity were significantly higher in LML4 ≈ LML3 followed by LML2 ≈ LML1, compared to U, but were still lower than the values of the UND treatment. We can conclude that the increased levels of leaf litter mulch moderately improved soil physio-chemical, biological, and microbial properties, as well as enzyme activity, after mechanized operations over a four year period, compared to the U treatment. However, the values of soil properties and enzyme activity were still lower than those in the UND treatment, indicating that four years is not long enough to restore the soil properties to pre-harvest levels in the study area. In conclusion, leaf litter level of LML3 with 1.31 kg m−2 can be applied as an optimal level for spreading leaf litter on skid trails to modify and enhance soil quality.

Global responses of fine root biomass and traits to plant species mixtures in terrestrial ecosystems

AbstractAimFine root traits underpin terrestrial ecosystem functioning. Despite ongoing plant diversity loss due to anthropogenic activities, our understanding of the effects of plant diversity on fine root traits remains elusive. We addressed: (a) Do fine roots modify their traits in response to species mixtures? (b) Do these responses change with the species richness in mixtures, stand age, and soil depth? (c) Do plant‐mixture induced responses of root traits differ across terrestrial ecosystems?LocationGlobal.Time periodPublication years: 1985–2019.Major taxa studiedPlants.MethodsWe conducted a global meta‐analysis of 852 paired observations from 103 published studies to assess the effects of species mixtures on fine root biomass and traits (including root/shoot ratio, community‐weighted mean rooting depth, root length density, specific root length, mean root diameter and root nitrogen content).ResultsWe found that the effects of species mixtures were highly dependent on species richness in mixtures, stand age, and soil depth. The positive effects of species mixtures on root biomass increased with species richness, soil depth, and mean annual temperature. Species mixture effects on root length density shifted from negative to positive with increasing stand age and soil depth and with decreased temperatures. The effects of species mixtures on specific root length shifted from positive to negative with increasing species richness and soil depth, and from negative to positive with increasing stand age.Main conclusionsOur meta‐analysis highlights that the community‐level consequences of changes in plant diversity on fine root traits are not consistent, and that predicting these consequences requires taking into account the extent of changes in plant species richness, stand age, soil depth investigated, background climates, and importantly, particular fine root traits.

Pinus sylvestris L. and Fagus sylvatica L. effects on soil and root properties and their interactions in a mixed forest on the Southwestern Pyrenees

Tree species alter soil properties, potentially modifying forest nutrients cycling. In the current management context in which mixed species forests are favoured over monocultures due to their biodiversity and productivity-related advantages, the assessment of species effects on soils, as well as their interactions with other species, gains increasing relevance. In this study, the effects of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) on soil properties were evaluated. Fine roots were paid special attention, measuring their biomass, functional traits (specific root length, root tissue density) and vertical distribution in order to discern the direction of these species interaction, either complementary or competitive. The research was carried out in the Southwestern Pyrenees (northern Spain), in an originally Scots pine stand transformed nowadays into a mixed forest by European beech natural regeneration. Soil and root samples were taken close to pine trees surrounded by other pines in areas that remain similar to pine monospecific stands, and close to pine and beech trees surrounded by both species in mixed areas. A lower C/N ratio was found in the soil close to beech stems. This suggests better quality in mixed litter in comparison to pine litter, leading to higher decomposition rates. Higher fine root biomass was found in the mixed areas mainly due to beech fine roots great abundance, which correlated positively with microbial biomass. Fine roots functional traits such as specific root length and diameter did not vary depending on their proximity to different tree species, though Scots pine fine root biomass decreased sharply when close to beech trees. This reduction, together with the already more abundant fine root biomass of beech, with higher specific root length and root tissue density than pine, lead to a competitive interaction in which European beech tends to dominate the soil at all depths. In this case, no complementarity effect at belowground level, strong enough to allow Scots pines to cope with beech soil colonization, was found under natural conditions.

Effects of earthworms and warming on tree seedling growth: a small-scale microcosm experiment

Warming global temperatures are expected to strongly influence plant communities, yet there is limited knowledge of how these changes will interact with stressors such as the invasion of exotic earthworms. We conducted a small-scale microcosm experiment to assess the individual and interactive effects of warming and exotic anecic earthworms (Lumbricus terrestris L.) on the growth of sugar maple (Acer saccharum Marsh.) seedlings. After 50 days, the elevated-temperature chamber created warmer and drier soil conditions and increased several measures of plant growth, including stem width, ratio of stem width to stem height, stem biomass, and fine-root biomass. Earthworms did not have any clear impacts on plant growth on their own nor in interactions with the temperature chambers. However, earthworms both reduced surface leaf litter cover and exposed soils, which could exacerbate evaporative losses and moisture stress in field soils resulting from a warming climate under different growing conditions. Future studies should consider the long-term effects of earthworm–temperature interactions on sugar maple growth, as well as diurnal and seasonal changes in temperature.

Fine root distribution and morphological characteristics of switchgrass under different row spacings on semi-arid Loess Plateau, China

ABSTRACT To change row spacing is a common agricultural practice to adjust plant density to enhance plant growth and development. Here we examined the fine root (≤1.0 mm in diameter) distribution and morphological characteristics of switchgrass (Panicum virgatum L.) in the 7th growth year under three row spacing settings (20 cm, 40 cm and 60 cm) on a terrace field in the semi-arid Loess Plateau region. Roots from 0 to 150 cm soil layers were utilized to evaluate the root biomass, distribution and morphological traits in April and October 2016. Results showed that fine root biomass (FRB) mainly distributed in the 0–40 cm soil layer, and it was higher under the 20 cm and 40 cm than that under the 60 cm row spacing treatment. FRB in October was lower than in April under all three row spacings. Compared with 20 cm and 60 cm row spacing, root surface area, root length density and specific root length under 40 cm row spacing were higher, while root diameter was smaller. These conferred switchgrass with larger soil exploration and root-soil interface. It implied that switchgrass grown under 40 cm row spacing had stronger ability on exploiting soil resources in the semi-arid area.

Fine Root and Soil Organic Carbon Depth Distributions are Inversely Related Across Fertility and Rainfall Gradients in Lowland Tropical Forests

Humid tropical forests contain some of the largest soil organic carbon (SOC) stocks on Earth. Much of this SOC is in subsoil, yet variation in the distribution of SOC through the soil profile remains poorly characterized across tropical forests. We used a correlative approach to quantify relationships among depth distributions of SOC, fine root biomass, nutrients and texture to 1 m depths across 43 lowland tropical forests in Panama. The sites span rainfall and soil fertility gradients, and these are largely uncorrelated for these sites. We used fitted β parameters to characterize depth distributions, where β is a numerical index based on an asymptotic relationship, such that larger β values indicate greater concentrations of root biomass or SOC at depth in the profile. Root β values ranged from 0.82 to 0.95 and were best predicted by soil pH and extractable potassium (K) stocks. For example, the three most acidic (pH 6.0) and most K-rich (> 50 g K m−2) soils contained only 41 ± 9% of fine root biomass at this depth. Root β and SOC β values were inversely related, such that a large fine root biomass in surface soils corresponded to large SOC stocks in subsoils (50–100 cm). SOC β values were best predicted by soil pH and base cation stocks, with the three most base-poor soils containing 34 ± 8% of SOC from 50 to 100 cm depth, and the three most base-rich soils containing just 9 ± 2% of SOC at this depth. Nutrient depth distributions were not related to Root β or SOC β values. These data show that large surface root biomass stocks are associated with large subsoil C stocks in strongly weathered tropical soils. Further studies are required to evaluate why this occurs, and whether changes in surface root biomass, as may occur with global change, could in turn influence SOC storage in tropical forest subsoils.

Effect of acorn size on survival and growth of Quercus suber L. seedlings under water stress

While the effects of seed size on survival and early seedling growth have been demonstrated in Quercus spp., there is a knowledge gap regarding these effects under water limiting conditions. To address this need, we studied cork oak (Quercus suber L.) seedling development among treatments including three acorn classes (small: < 4 g, intermediate: 4–6 g), and large: ≥ 6 g) and two water regimes (well-watered versus water stressed). The following hypotheses were proposed: the reserve effect (larger seeds retain a larger proportion of reserves after germinating), the metabolic effect (seedlings from larger seeds have slower relative growth rates), the seedling-size effect (larger seeds produce larger seedlings), and that plant tolerance to water stress increases with increasing seed size. Acorn size had no effect on duration and rate of acorn germination nor on seedling survival, but it significantly affected almost all growth parameters, excepting the number of growth unit and leaves and leaf area. Seedlings coming from large acorns always showed the highest values for the affected growth parameters, followed by those coming from acorns of intermediate size; seedlings coming from small acorns always exhibited the lowest values. Water stress significantly affected survival rate (88.2% for well-watered seedlings versus 64.7% for water stressed seedlings) and biomass of fine roots and stems, but independently of acorn size. Our results are in line with both hypothesizes of the reserve effect and seedling-size effect, but not for the metabolic effect nor the plant tolerance to water stress increases with increasing seed size hypotheses. In general, our results show that large acorns had no advantage in survival or seedling growth under water stress comparatively to intermediate or small acorns, at least under the conditions of our experiment.

Benefit or Liability? The Ectomycorrhizal Association May Undermine Tree Adaptations to Fire After Long-term Fire Exclusion

Long-term fire exclusion may weaken ecosystem resistance to the return of fire. We investigated how a surface wildfire that occurred after several decades of fire exclusion affected a southern Appalachian forest transitioning from a fire-adapted to a fire-intolerant state. Tree traits associated with fire adaptation often co-occur with traits for nutrient conservation, including the ectomycorrhizal (ECM) association. In the absence of fire, the ECM association may facilitate the accumulation of organic matter, which becomes colonized by fine roots that then become vulnerable to consumption or damage by fire. Therefore, a deeper organic horizon might make stands of fire-adapted, ECM trees less resistant to a surface wildfire than stands of arbuscular mycorrhizal (AM), fire-intolerant trees. To test this hypothesis, we established plots in stands that fall along a gradient of mycorrhizal tree relative abundance both inside and outside the perimeter of the 2016 Rock Mountain wildfire. With increasing relative abundance of ECM trees, we found increasing organic horizon depth and mass and slower rates of decay, even for litter of ECM tree species. We calculated a major (73–83%) reduction in fine root biomass and length in the organic horizon following the wildfire. Over three years post-fire, we observed a higher probability of crown decline, basal sprouting and aboveground biomass mortality with increasing abundance of ECM trees. We propose that the biogeochemistry of mycorrhizal associations can help explain why fire exclusion makes stands of fire-adapted trees less resistant to a surface wildfire than those with fire-intolerant trees.

Effect of snow removal on the fine root biomass, dynamics, and carbon and nitrogen concentrations of oak and dwarf bamboo, Sasa in eastern Hokkaido, Japan

ABSTRACT Fine root is a significant component in carbon (C) and nitrogen (N) dynamics in temperate forests. Winter processes affect plant growth and nutrient concentration, however, the effect of reduced snowpack on fine root remains unclear. Here, we conducted snow removal manipulation and investigated the fine root biomass and necromass, dynamics (production, mortality and disappearance) and the C and N concentrations of Quercus crispula (oak) and Sasa nipponica (Sasa), in mineral topsoil (0–10 cm) throughout 1 year. The effect of snow removal on the fine root biomass and necromass was insignificant. The effect of snow removal on the production, mortality and disappearance of fine root, and on total C and N concentrations of fine root biomass and necromass were insignificant. The fine root biomass of oak was significantly greater than that of Sasa, although the fine root necromass of Sasa was significantly greater than that of oak. Fine root necromass showed clear seasonal change, although a seasonal change of fine root biomass was unclear. Total C concentration in the fine root biomass and necromass of oak was significantly higher than that of Sasa. Total N concentration in the fine root necromass in May 2015, when after the snow removal, of Sasa was significantly higher than that of oak, in both snow removal and control plots. Our results showed that the fine root necromass of Sasa supplies more N than that of oak in spring, regardless of snowpack depth.

Soil fungi and fine root biomass mediate drought‐induced reductions in soil respiration

Abstract Climate change has increased the frequency and intensity of droughts, with potential impacts on carbon (C) release from soil (i.e. soil respiration, Rs). Although numerous studies have investigated drought‐induced changes in Rs, how roots and the soil microbial community regulate responses of Rs to drought remains unclear. We conducted a 4‐year field experiment (2014–2017) with three treatments (i.e. 70% rainfall reduction, control and ambient) in a subtropical forest to examine effects of drought on Rs and its components [i.e. autotrophic (Ra) and heterotrophic respiration (Rh)] and explore the mechanisms underlying these effects. Drought significantly decreased Rs by 17% averaged over the 4 years, but it had no significant effect in the first experimental year. The decrease in Rs was mediated by soil fungi and fine root biomass. Fine root biomass was correlated negatively with Ra and Rs under drought, but positively in the control treatment. Furthermore, drought treatments increased physiological stress in the bacterial community. Structural equation model (SEM) analysis suggested that under drought conditions, microclimate affected Rs via its impact on fine root biomass and fungal biomass. Our results highlight the complex interactions between microclimate, roots and soil microbes in regulating Rs under drought in subtropical forest ecosystems. Incorporating these interactions into land surface models may improve predictions of climate change impacts on forest ecosystems. A free Plain Language Summary can be found within the Supporting Information of this article.

Biomass and Production Rates of Fine Roots in Two Mangrove Stands in Southern Thailand

Biomass and Production Rates of Fine Roots in Two Mangrove Stands in Southern Thailand