Coarse Root Biomass Research Articles

Increased leaf area index and efficiency drive enhanced production under elevated atmospheric [CO2 ] in a pine-dominated stand showing no progressive nitrogen limitation.

Enhancement of net primary production (NPP) in forests as atmospheric [CO2 ] increases is likely limited by the availability of other growth resources. The Duke Free Air CO2 Enrichment (FACE) experiment was located on a moderate-fertility site in the southeastern US, in a loblolly pine (Pinus taeda L.) plantation with broadleaved species growing mostly in mid-canopy and understory. Duke FACE ran from 1994 to 2010 and combined elevated [CO2 ] (eCO2 ) with nitrogen (N) additions. We assessed the spatial and temporal variation of NPP response using a dataset that includes previously unpublished data from 6 years of the replicated CO2 × N experiment and extends to 2 years beyond the termination of enrichment. Averaged over time (1997-2010), NPP of pine and broadleaved species were 38% and 52% higher under eCO2 compared to ambient conditions. Furthermore, there was no evidence of a decline in enhancement over time in any plot regardless of its native site quality. The relation between spatial variation in the response and native site quality was suggested but inconclusive. Nitrogen amendments under eCO2 , in turn, resulted in an additional 11% increase in pine NPP. For pine, the eCO2 -induced increase in NPP was similar above- and belowground and was driven by both increased leaf area index (L) and production efficiency (PE = NPP/L). For broadleaved species, coarse-root biomass production was more than200% higher under eCO2 and accounted for the entire production response, driven by increased PE. Notably, the fraction of annual NPP retained in total living biomass was higher under eCO2 , reflecting a slight shift in allocation fraction to woody mass and a lower mortality rate. Our findings also imply that tree growth may not have been only N-limited, but perhaps constrained by the availability of other nutrients. The observed sustained NPP enhancement, even without N-additions, demonstrates no progressive N limitation.

Carrying capacity for tree biomass of a subtropical mangrove along a river in Japan inferred from forest structural features

AbstractA subtropical mangrove along the Miyara River in Ishigaki Island, Japan was studied for evaluating the carrying capacity for biomass of the mangrove stands. The stem diameters D, tree height H, and fine roots mass were measured, while aboveground biomass (AGB) and belowground coarse root biomass (BGBcoarse) were estimated. The AGB, BGBcoarse, and fine root mass were estimated as 130, 31, and 13 Mg ha−1 in the Rhizophora stylosa; 271, 94, and 11 Mg ha−1 in the downstream Bruguiera gymnorrhiza; and, 228, 81, and 6.4 Mg ha−1 in the upstream B. gymnorrhiza stand, respectively. The AGB and BGBcoarse in the R. stylosa stand were significantly lower than B. gymnorrhiza stands, and fine root mass was significantly higher than upstream B. gymnorrhiza stand. Significantly lower mean individual phytomass wt specific to tree density ρ of R. stylosa stand than B. gymnorrhiza stand in the ρ − wt relationship denoted the lower carrying capacity for AGB of R. stylosa than that of B. gymnorrhiza. The results showed that high soil pore water salinity and low pH at the downstream did not limit biomass and potential canopy height Hmax of mangrove along a river gradient but AGB and BGBcoarse differed between different species at the same edaphic environment. Analysis of aboveground and belowground biomass variations between stands of two mangrove species along environmental gradients from upstream to downstream could be useful in assessing the consequences of sea level rise in relation to climate change on the evolution of blue carbon dynamics.

Carbon storage in old hedgerows: The importance of below‐ground biomass

AbstractAmbitious climate change mitigation goals require novel carbon (C) sinks in agricultural systems. Thus, the establishment of new hedgerows is increasingly attracting attention as a C sequestration measure. Despite hedgerows being a traditional agroforestry system, few studies have been conducted on hedgerow C stocks. Data on below‐ground biomass (BGB) in particular are limited. The aim of this study was therefore to quantify both above‐ground biomass (AGB) and BGB C stocks, as well as litter and soil organic C stocks, of established hedgerow systems by destructive sampling at three sites in northern Germany. The total biomass C (TBC) stock of the sampled hedgerows was 105 ± 11 Mg ha−1 on average. An additional 11 ± 2 Mg ha−1 were found in hedgerow litter and dead roots. Coarse roots (34% of TBC), stumps (22%) and harvestable biomass (20%) were the largest biomass C pools of the hedgerows. The BGB:AGB ratio was 0.7 ± 0.1, showing the importance of BGB in old hedgerow systems. Compared with other woody systems, these old hedgerows seem to have a different biomass distribution, with more biomass allocated below‐ground. About 15% of BGB C stock was stored in fine roots, whereas 85% was stored in coarse roots. The topsoil (0–30 cm) contained 85% of coarse root biomass C and 51% of fine root biomass C. Hedgerow C stock exceeded that of average German forests, and thus demonstrated their large potential for C sequestration when newly planted. This study provides detailed empirical data on C stocks in old hedgerow systems, and thus can be used to take hedgerow C sinks into account in C farming frameworks.

Uptake and distribution of the inorganic components NH4+ and NO3− in PM2.5 by two Chinese conifers

Plants can effectively purify PM2.5 in the air, thereby improving air quality. Understanding the mechanisms of the uptake and distribution of PM2.5 in plants is crucial for enhancing their ecological benefits. In this study, the uptake and distribution of the water-soluble inorganic compounds ammonium (NH4+) and nitrate (NO3−) ions in PM2.5 by the two native Chinese conifers Manchurian red pine (Pinus tabuliformis) and Bunge's pine (P. bungeana) were investigated using a one-time aerosol treatment method combined with 15N tracing. The results showed the following: (1) Plants can efficiently uptake NH4+ (0.08–0.21 μg/g) and NO3− (0.03–0.68 μg/g) from PM2.5. Manchurian red pine uptakes these compounds more effectively with increases of 2.01-fold for NH4+ and 1.02-fold for NO3− compared with Bunge's pine. (2) The aboveground organs of the plants uptake and distribute more 15N than the belowground organs. The branches had the highest unit mass uptake (0.08–1.60 μg/g) and rate of distribution (16.91–53.60 %) for NH4+, while the leaves had the highest unit mass uptake (0.15–1.18 μg/g) and rate of distribution (50.78–84.88 %) for NO3−. (3) The ability of the aboveground organs to uptake 15N is influenced by the concentration of PM2.5, which showed an overall increase with increasing concentrations with some fluctuations in specific organs. However, the belowground organs were not affected by the concentration of PM2.5. (4) A larger specific leaf area, root-shoot ratio, branch biomass ratio, coarse root biomass ratio, and lower trunk biomass ratio favors the uptake of NH4+ from PM2.5, whereas these traits had a minimal influence on the uptake of NO3−. Manchurian red pine uptaked significantly more NH4+ compared with Bunge's pine, which benefited from the traits described above. These findings further revealed the mechanism of PM2.5 uptake by plants and its relationship with PM2.5 concentration and plant traits, and provided a scientific basis for how to effectively utilize plants to reduce PM2.5 pollution and purify the environment in areas with different pollution concentrations.

Decomposition and nutrient dynamics of stumps and coarse roots of Eucalyptus plantations in southern China

Key messagePrimary remains of Eucalyptus (E. urophylla × E. grandis) plantations following clear-cutting are the stumps and coarse roots. A chrono-sequence approach revealed that the biomass of coarse roots is higher than that of stumps, while they have a smaller rate of biomass loss than stumps. This implies that coarse roots serve as long-term stock for nutrients (carbon, nitrogen, and phosphorus).ContextA significant quantity of stumps and coarse roots persist in the forest floor following the clear-cutting of Eucalyptus plantations in China. The decomposition of these stumps and coarse roots is a crucial aspect of the nutrient stocks in plantation ecosystems.AimsWe described the stock and decomposition dynamics of stumps and coarse roots on Eucalyptus plantations, as well as the nutrient loss rate associated with them.MethodsWe used a chrono-sequence of 0–6-year-old clear-cutting stands of Eucalyptus plantations in southern China. The biomass and nutrient stocks of these samples were assessed at different times of decomposition.ResultsThe highest biomass of stump-root system was 33.8 Mg·ha−1, with nutrient stocks were 16.3 Mg·ha−1, and 63.0 kg·ha−1, and 6710.9 g·ha−1, for C, N, and P. The coarse roots accounted for 81–96% of the biomass of the stump-root system. The loss rate of biomass and nutrients from stumps was higher than that of coarse roots. This suggests that the decomposition of coarse roots could serve as a long-term source of nutrients, thereby improving the nutrient status of the plantations.ConclusionStumps and coarse roots serve as significant nutrient stocks that decay at varying rates. The loss of nutrients must be considered while analyzing the decomposition dynamics following clear-cutting in Eucalyptus plantations.

Effects of Tree Competition on Biomass Allocation of Stump and Coarse Roots of Larix olgensis of Different Site Classes

Site class is a quantitative indicator used to evaluate site quality. It reflects site conditions, mainly climate, the suitability of soil for tree species and soil fertility. Despite the economic and ecological importance of tree competition and site class in sustainable forest management, there has been little research on its impact on the stump and coarse root biomass allocation within plantations. The stump and coarse roots were divided into five components ((stump disc (SD), stump knot (SK), coarse roots (>10 cm in diameter) (CR1), medium coarse roots (5–10 cm) (CR2) and fine coarse roots (2–5 cm) (CR3)), and the biomass of each component was obtained via the weighing method. It was found that the biomass of SD, CR1, CR2 and CR3 was mainly affected by competition (p ≤ 0.01). In the three site classes, the biomass of CR3 increased significantly with the increase in the competition index (CI) (p < 0.01); the biomass of CR1 decreased gradually. In site V, the biomass of SK, sapwood and heartwood increased significantly with the increase in CI. The results show that competition affects the allocation of stump and coarse root biomass mainly by changing the coarse root biomass. The development of stump knots is greatly influenced by site class. This study provides a reference for solving the competition mechanism underlying larch wood forest development, which will in turn promote more effective utilization of larch wood forests. This study also provides a scientific basis for accurately estimating the belowground biomass and carbon storage of artificial plantation forests.

Effect of planting density on root biomass and distribution, and soil organic carbon stock of Acacia decurrens stands in Northwestern Ethiopia

Background:The expandingAcacia decurrenswoodlots in Northwestern Ethiopia is recognized for carbon storageviaroot biomass and soil organic carbon (SOC) enhancement but its planting densities have varied considerably. This study evaluated the effect of planting density on the root biomass, SOC stock, and vertical distributions in the stands.Methods:Five planting densities (0.5 m x 0.5 m, 0.75 m x 0.75 m, 1 m x 1 m, 1.25 m x 1.25 m, and 1.5 m x 1.5 m) were replicated four times with randomized complete block design. Soil core (6.67 cm diameter) and pit (900 cm2area) methods were used to collect fine and coarse root samples within 0–50 cm soil depth (having five soil layers in 10 cm intervals), respectively. Fine root biomass samples were classified as live and dead (necromass) and further as tree and herbaceous root. All root biomass samples were washed, oven-dried, weighed, and standardized into gram per meter square (g m-2) for root biomass comparisons for each planting density and soil depth, then summed up for 0–50 cm depth as a total root biomass. The vertical distributions of fine and coarse root biomass at each depth were expressed as a percentage (in decimal) of the total root biomass (0–50 cm).Conclusions:Planting density had significant effects on root biomass, SOC stock, and root distributions (P < 0.05) but inconsistent for the percentage of SOC stock at all soil layers except at 40-50 cm. PlantingA. decurrenswith high density is recommended to increase root biomass, SOC, and percentage of roots in deep soil layers. Further study is suggested for the effects of stand age on root biomass dynamics and SOC stock with large scale.

Site Class Effects on Stump and Coarse Root Biomass Models of Larix olgensis in Northeastern China

The stump and coarse root biomass remaining after tree harvesting are often overlooked by researchers, which may lead to underestimation of their role in carbon cycling, so we constructed two sets of additive models for larch (Larix olgensis Henry) plantations in Northeast China. Due to the absence of tree diameter at breast height data after harvesting, only the sole predictor variable stump disc diameter could be used to predict stump and coarse root biomass, and the results showed that stump disc diameter predicted stump biomass with higher accuracy than coarse root biomass predictions. In addition, to investigate the effect of the site class of complex stands on the predictive capability of the model, the generic model in this study was employed with all site class data and a specific model was developed and employed with all the site class data. We found that the generic model had different degrees of error compared to the predicted results for each site class, overestimating the total biomass by 15% and underestimating it by 10%, especially for site class IV. In conclusion, to obtain a biomass prediction model with reliable results, the impact of more complex site class effects should be considered.

The Unique Ability of Fine Roots to Reduce Vegetated Coastal Dune Erosion During Wave Collision

Vegetated coastal sand dunes can be vital components of flood risk reduction schemes due to their ability to act as an erosive buffer during storm surge and wave attack. However, the effects of plant morphotypes on the wave-induced erosion process are hard to quantify, in part due to the complexity of the coupled hydrodynamic, morphodynamic, and biological processes involved. In this study the effects of four vegetation types on the dune erosion process under wave action was investigated in a wave flume experiment. Sand dune profiles containing real plant arrangements at different growth stages were exposed to irregular waves at water levels producing a collision regime to simulate storm impact. Stepwise multivariate statistical analysis was carried out to determine the relationship of above- and below-ground plant variables to the physical response. Plant variables included, among others, fine root biomass, coarse root biomass, above-ground surface area, stem rotational stiffness, and mycorrhizal colonization. Morphologic variables, among others, included eroded sediment volume, cross-shore area centroid shift, and scarp retreat rate. Results showed that vegetation was able to reduce erosion during a collision regime by up to 37%. Although this reduction was found to be related to both above- and belowground plant structures and their effect on hydrodynamic processes, it was primarily accounted for by the presence of fine root biomass. Fine roots increased the shear strength of the sediment and thus lowered erosional volumes and scarp retreat rates. For each additional 100 mg/L of fine roots (dry) added to the sediment, the erosional volume was reduced by 6.6% and the scarp retreat rate was slowed by 4.6%. Coarse roots and plant-mediated mycorrhizal colonization did not significantly alter these outcomes, nor did the apparent enhancement of wave reflection caused by the fine roots. In summary, fine roots provided a unique ability to bind sediment leading to reduced dune erosion.

Root biomass under different soil uses and native Cerrado in Tocantins, Brazil

Studies on the importance of root biomass and the effects that changes in vegetation coverage cause on carbon amount and stock are scarce, especially in the cerrado biome. Taking into account the scarcity of information about root biomass estimates, this work aimed to quantify root biomass under different land uses and native cerrado in Tocantins, Brazil. The research was conducted in different land uses: agriculture, pasture, eucalyptus and control with native cerrado forest. Six trenches with dimensions of 70 x 70 cm were opened and root biomass was collected at depths of 0-10, 10-20, 20-30, 30-40 and 40-50 cm. With the aid of a sieve, root biomass was collected and separated into fine and coarse roots. The amounts of fine and coarse root biomass showed the highest mean values of 7.7 and 12.9 g, respectively, in the eucalyptus area. Root biomass stocks were higher in the eucalyptus area, with maximum values above 3.68 Mg ha-1. Root biomass amounts and stocks were greater in eucalyptus areas, since forest areas, whether planted or native, manage to keep the environment in balance due to their long-term cycles, greater stability and low degree of disturbance.

Carbon Accumulation and Partitioning Above and Belowground under Coppiced and Replanted Eucalypt Plantations

Abstract The extent to which the C sink strength of eucalypt plantations can be affected by coppicing or replanting remains unclear. To address this issue, we evaluated variations in C stocks under coppiced or replanted eucalypt stands formed by clones or seedlings. For each field assessment (0 [T0], 2.5, 3.5, 4.5, 5.5 and 7.0 years [at harvest]), tree biomass, litterfall, and soil C stocks (0–120 cm depth) were determined. At harvest, debarked stemwood productivity was similar under coppice or replanting, about 50.0 Mg C ha–1. Generally, coppiced stands favored subsoil C storage (40–100 cm), whereas replanted stands favored soil C accrual in topsoil (0–20 cm), depending on the genetic material. Relative to T0, soil C increased about 2.14, 1.91, and 1.84 Mg C ha–1 yr–1 under coppice, replanting with seedlings and clones, respectively. Coarse root biomass under these stands were about 17.3, 13.4, and 9.5 Mg C ha–1, respectively, equivalent to 50% of total harvest residues. Hence, inputs from coarse roots could represent a large contribution to soil C over multiple rotations under coppiced or replanted stands. Otherwise, short-term C losses can be high where stumps and coarse roots are harvested, especially following successive coppice cycles. Study Implications: Our findings have important implications for forest managers growing eucalypt plantations aiming to maximize C accumulation. Both coppiced and replanted stands can fix up to 50 Mg C ha−1 only in debarked stemwood over 7 years, with a comparatively higher C storage in coarse roots under coppice. Despite the increasing demand for forest residues in bioenergy production, harvesting stumps and coarse roots should be avoided, especially upon replanting eucalypt stands after successive coppice cycles.

Root Biomass Distribution and Soil Physical Properties of Short-Rotation Coppice American Sycamore (Platanus occidentalis L.) Grown at Different Planting Densities

Short rotation woody crops (SRWCs) provide sustainable, renewable biomass energy and offer potential ecosystem services, including increased carbon storage, reduced greenhouse gas emissions, and improved soil health. Establishing SRWCs on degraded lands has potential to enhance soil properties through root and organic matter turnover. A better understanding of SRWC planting density and its associated root turnover impacts on soil–air–water relations can improve management. In this study, we investigate the effects of planting density for a low-input American sycamore SRWC (no fertilization/irrigation) on soil physical properties for a degraded agricultural site in the North Carolina piedmont. The objectives were (1) to estimate the distributions of coarse and fine root biomass in three planting densities (10,000, 5000, and 2500 trees per hectare (tph)) and (2) to assess the effects of planting density on soil hydraulic properties and pore size distribution. Our results show that planting at 10,000 tph produced significantly higher amounts of fine root biomass than at lower planting densities (p < 0.01). In the 25,000 tph plots, there was significantly higher amounts of coarse root biomass than for higher planting densities (p < 0.05). The 10,000 tph plots had lower plant available water capacity but larger drainable porosity and saturated hydraulic conductivity compared with lower planting densities (<0.05). The 10,000 tph plots total porosity was more dominated by larger pore size fractions compared with the 5000 and 2500 tph. Generally, our findings show similar patterns of soil hydraulic properties and pore size distributions for lower planting densities. The results from 10,000 tph indicate a higher air-filled pore space at field capacity and more rapid drainage compared with lower planting densities. Both characteristics observed in the 10,000 tph are favorable for aeration and oxygen uptake, which are especially important at wet sites. Overall, the results suggest that improved soil health can be achieved from the establishment of American sycamore SRCs on marginal lands, thereby providing a green pathway to achieving environmental sustainability with woody renewable energy.

Vegetation restoration and plant roots improve soil infiltration capacity after a severe forest fire in Daxing’anling, northeast China

Soil infiltration plays an important role in the transformation of precipitation into surface water, soil water, and groundwater. Forest fires significantly alter soil quality and hydrological processes. Identifying a method to accelerate the restoration of soil infiltration capacity after forest fires is of major interest. Vegetation restoration may greatly influence soil infiltration capacity by altering soil and vegetation properties. However, little is known about the relationships among root biomass, soil properties, and infiltration capacity after severe forest fires. The objectives of this research were to assess soil infiltration capacity during vegetation restoration and to identify the strongest predictors of infiltration among various soil properties and the biomass of roots of different diameter classes. The influences of vegetation restoration approaches (planted regeneration and natural regeneration [NR]) on root biomass, soil properties, and infiltration rates in burnt areas were observed. Total root biomass increased each year following the burn (3.808 to 56.690 t hm^–2). The soil physical and chemical properties improved more after 24 years of restoration than after other restoration durations. The initial infiltration rate (IIR), steady infiltration rate (SIR), and average infiltration rate (AIR) of the soils increased as vegetation restoration progressed. The IIR, SIR, and AIR after 24 years of restoration were higher than those under NR. Correlation analysis showed that IIR, SIR, and AIR correlated significantly and positively with coarse root biomass (biomass of >2 cm diameter roots, RD_coarse), total root biomass (RD_total), and soil organic matter (SOM). The conceptual path model demonstrated that among the studied properties, RD_coarse and SOM most strongly affected soil infiltration, which increased as vegetation restoration progressed. Coarse roots (>2 cm diameter) played a more important role in improving soil infiltration than other root types. Planted regeneration is more conducive to accelerating the restoration of soil infiltration than NR in Daxing’anling, northeast China.

OsGF14b is involved in regulating coarse root and fine root biomass partitioning in response to elevated [CO2] in rice

Elevated [CO2] can increase rice biomass and yield, but the degree of this increase varies substantially among cultivars. Little is known about the gene loci involved in the acclimation and adaptation to elevated [CO2] in rice. Here, we report on a T-DNA insertion mutant in japonica rice exhibiting a significantly enhanced response to elevated [CO2] compared with the wild type (WT). The root biomass response of the mutant was higher than that of the WT, and this manifested in the number of adventitious roots, the average diameter of roots, and total root length. Furthermore, coarse roots (>0.6 mm) and thin lateral roots (<0.2 mm) were more responsive to elevated [CO2] in the mutant. When exposed to lower light intensity, however, the response of the mutant to elevated [CO2] was not superior to that of the WT, indicating that the high response of the mutant under elevated [CO2] was dependent on light intensity. The T-DNA insertion site was located in the promoter region of the OsGF14b gene, and insertion resulted in a significant decrease in OsGF14b expression. Our results indicate that knockout of OsGF14b may improve the response to elevated [CO2] in rice by enhancing carbon allocation to coarse roots and to fine lateral roots.

The response of coarse root biomass to long-term CO2 enrichment and nitrogen application in a maturing Pinus taeda stand with a large broadleaved component.

Elevated atmospheric CO2 (eCO2 ) typically increases aboveground growth in both growth chamber and free-air carbon enrichment (FACE) studies. Here we report on the impacts of eCO2 and nitrogen amendment on coarse root biomass and net primary productivity (NPP) at the Duke FACE study, where half of the eight plots in a 30-year-old loblolly pine (Pinus taeda, L.) plantation, including competing naturally regenerated broadleaved species, were subjected to eCO2 (ambient, aCO2 plus 200ppm) for 15-17years, combined with annual nitrogen amendments (11.2gNm-2 ) for 6years. Allometric equations were developed following harvest to estimate coarse root (>2mm diameter) biomass. Pine root biomass under eCO2 increased 32%, 1.80kgm-2 above the 5.66kgm-2 observed in aCO2 , largely accumulating in the top 30cm of soil. In contrast, eCO2 increased broadleaved root biomass more than twofold (aCO2 : 0.81, eCO2 : 2.07kgm-2 ), primarily accumulating in the 30-60cm soil depth. Combined, pine and broadleaved root biomass increased 3.08kgm-2 over aCO2 of 6.46kgm-2 , a 48% increase. Elevated CO2 did not increase pine root:shoot ratio (average 0.24) but increased the ratio from 0.57 to 1.12 in broadleaved species. Averaged over the study (1997-2010), eCO2 increased pine, broadleaved and total coarse root NPP by 49%, 373% and 86% respectively. Nitrogen amendment had smaller effects on any component, singly or interacting with eCO2 . A sustained increase in root NPP under eCO2 over the study period indicates that soil nutrients were sufficient to maintain root growth response to eCO2 . These responses must be considered in computing coarse root carbon sequestration of the extensive southern pine and similar forests, and in modelling the responses of coarse root biomass of pine-broadleaved forests to CO2 concentration over a range of soil N availability.

Monsoon-phase regulates the decoupling of auto- and heterotrophic respiration by mediating soil nutrient availability and root biomass in tropical grassland

Soil respiration is considered as one of the most sensitive parameters regulated by the interplay of different soil biophysical parameters, ground cover and climatic conditions. As per the global predictions, monsoon variability in South Asian countries can affect various soil processes. However, studies exploring the interactive role of vegetation and precipitation conditions on soil respiration and its components (viz., auto- and heterotrophic) are lacking. A mini-trenching method was performed to explore the alterations in auto- and heterotrophic components of soil respiration as well as their regulatory variables in grassland vegetation under different summer monsoonal phases. Three vegetation densities (viz. low, medium and high) based on herbaceous cover, and three monsoon phases (viz. onset, active and end) of the tropical summer monsoon were considered. The findings revealed that heterotrophic respiration was the major contributor to the total soil respiration under medium- and high-density vegetation with percent contribution of 62–80% and 53–88% respectively. Contrastingly, autotrophic respiration was the major contributor (54–56%) to soil respiration in low-density vegetation during active- and monsoon-end phases. Amongst the three monsoon phases, variation in soil respiration components was most pronounced during the active-monsoon phase. Structural Equation Modelling results revealed microbial biomass and root biomass as key regulators of auto- and heterotrophic respiration. Remarkably, a partitioning of root biomass parallel to the soil respiration was observed during monsoon-end phase where coarse root biomass and fine root biomass emerged as regulators of auto- and heterotrophic respiration, respectively. Moreover, for monsoon-onset and -end phases, a completely different set of variables involved in regulation of soil respiration components were identified. Our results revealed that the monsoon-phase mediates the root and nutrient dynamics which led to the differential decoupling of the components of soil respiration. Thus, inclusion of (below)-ground cover and monsoon-phase wise variation in soil biophysical parameters in the global biogeochemical models would be more helpful for better prediction of carbon balance in different ecosystems.

Seasonal Differences in Water-Use Sources of Impatiens hainanensis (Balsaminaceae), a Limestone-Endemic Plant Based on “Fissure-Soil” Habitat Function

The southwestern mountains of Hainan Island are the southernmost region with tropical karst landform in China. The frequent alternation of dry and wet seasons leads to the loss of the mineral nutrients of limestone, creating karst fissure habitats. Plants living in karst fissure habitats for long periods of time have developed local adaptation mechanisms correspondingly. In the paper, hydrogen–oxygen stable isotope technology was applied to determine the water-use sources of Impatiens hainanensis in the dry and wet seasons, hoping to expound the adaptation mechanism of I. hainanensis in karst fissure habitats to the moisture dynamics in the wet and dry seasons. In the wet season (May to October, 2018), the air humidity is relatively high in the I. hainanensis habitat; in the dry season (November 2018 to April 2019), there is a degree of evaporation. In the wet season, fine-root biomass increases with soil depths, while coarse-root biomass decreases with soil depths; in the dry season, fine-root biomass is lower and coarse-root biomass is higher compared with the wet season. It was found that the average rainfall reached 1523 mm and the main water-use sources were shallow (0–5 cm) and middle (5–10 cm) soil water, epikarst water, and shallow karst fissure water during the wet season; the average rainfall reached 528 mm, and the deep (10–15 cm) soil water and shallow karst fissure water were the main water-use sources during the dry season. Fog water has a partial complementary effect in the dry season. The differences in the distribution of root biomass and each source of water in the wet and dry seasons of I. hainanensis also reflect the different water-use strategies of I. hainanensis in the wet and dry seasons. In both dry and wet seasons, I. hainanensis formed a water-use pattern dominated by soil water and shallow fissure water (0–15 cm) under the influence of the “fissure-soil-plant” system in the karst region.

Biotic and Abiotic Determinants of Soil Organic Matter Stock and Fine Root Biomass in Mountain Area Temperate Forests—Examples from Cambisols under European Beech, Norway Spruce, and Silver Fir (Carpathians, Central Europe)

Forest ecosystems significantly contribute to the global organic carbon (OC) pool, exhibiting high spatial heterogeneity in this respect. Some of the components of the OC pool in a forest (woody aboveground biomass (wAGB), coarse root biomass (CRB)) can be relatively easily estimated using readily available data from land observation and forest inventories, while some of the components of the OC pool are very difficult to determine (fine root biomass (FRB) and soil organic matter (SOM) stock). The main objectives of our study were to: (1) estimate the SOM stock; (2) estimate FRB; and (3) assess the relationship between both biotic (wAGB, forest age, foliage, stand density) and abiotic factors (climatic conditions, relief, soil properties) and SOM stocks and FRB in temperate forests in the Western Carpathians consisting of European beech, Norway spruce, and silver fir (32 forest inventory plots in total). We uncovered the highest wAGB in beech forests and highest SOM stocks under beech forest. FRB was the highest under fir forest. We noted a considerable impact of stand density on SOM stocks, particularly in beech and spruce forests. FRB content was mostly impacted by stand density only in beech forests without any discernible effects on other forest characteristics. We discovered significant impacts of relief-dependent factors and SOM stocks at all the studied sites. Our biomass and carbon models informed by more detailed environmental data led to reduce the uncertainty in over- and underestimation in Cambisols under beech, spruce, and fir forests for mountain temperate forest carbon pools.

Effects of wood ash, green residues and N-free fertiliser on naturally regenerated birch and field vegetation in a young Norway spruce stand in SW Sweden

ABSTRACT Treatments added to young conifer stands aiming to compensate for the loss of nutrients and alkalinity associated with whole-tree harvesting for bioenergy purposes have the potential to affect the growth of competitors to the conifers. Three different nutrient compensation treatments were applied to a young Picea abies (L.) Karst. stand in south-west Sweden, 2 or 3 years following final felling. The treatments were; fine fraction of harvest residues (15 Mg dw ha−1); granulated wood ash (4.1 Mg dw ha−1); nitrogen-free vitality fertiliser (twice 1.5 Mg ha−1); untreated control. Root biomass and total biomass of graminoids (mainly Deschampsia flexuosa (L.) Trin) were significantly greater in the wood ash and vitality fertiliser treatments than in the residues and control treatments. The aboveground and coarse root biomass of naturally regenerated birch (Betula spp.) and the aboveground biomass of dwarf shrubs (mainly Calluna vulgaris (L.) Hull.) and bottom layer were not affected by the treatments. Calcium and magnesium concentrations in the aboveground biomass of graminoids and phosphorus concentration in the biomass of bottom layer were significantly the highest in the vitality fertiliser treatment. Thus, nutrient compensation with vitality fertiliser or granulated wood ash may increase competition from graminoids in the establishment phase.

Relationships between mangrove root system and benthic macrofauna distribution

Despite the ability of mangrove trees to allocate a large proportion of the total biomass to the underground roots, little is known about the benthic macrofauna–root system relationships. We evaluated the above- and belowground structures of plants, soil properties, algal cover and their relationship with macrofauna as a function of soil strata (0–2.5, 2.5–5 and 5–10 cm) and distance (0–0.30 and 3–3.5 m) from trunks in three mangrove sites in southern Brazil. Coarse root biomass was higher near the trunks and in shallower layers, while fine root biomass predominated far from trunks and indifferent to the soil stratum. The macrofauna was more associated with changes in the root systems than with other soil properties. Most of the benthic taxa occurred in the upper layers of the soil (0–2.5 cm) and near trunks (< 0.30 m), where there was a lower proportion of fine roots. Fine root entanglement inhibited the presence of organisms with more complex body plans, which may hamper their locomotion and feeding activities. Therefore, the structure and function of macrofauna varied according to the depth stratum and distance from the trunks.