Fine Root Production Research Articles

Seasonal and interspecific variations in the water uptake depth of trees in a moist cool-temperate mixed forest in Japan

ABSTRACT The water uptake depth of trees affects their overall water use and the water cycle of forest ecosystems. However, empirical data on the depth from which water is drawn are lacking for many moist forests. In this study, we estimated the water uptake depths of 24 coexisting tree species in a moist cool-temperate mixed forest in Japan using stable oxygen isotopes. Our goal was to clarify the factors influencing water uptake depth including season, species, slope position, and tree height under moist conditions. Water uptake depth was determined during three periods in which temperatures differed but soil moisture levels remained similar. Season was shown as one of the factors affecting water uptake depth, which was shallowest in August, when temperatures reached maximum values, and deepest during May, when temperatures were lowest. This seasonal variation is likely to be related to physiological processes such as increasing transpiration which leads to water uptake shifting to the water-rich shallow soil layer and/or activation of fine root production at the soil surface, where temperatures are high. Water uptake depth also varied with tree species, suggesting the occurrence of belowground resource segregation among moist forest tree species. Slope position and tree height did not affect water uptake depth. This study highlights the importance of considering temperature-driven physiological processes when examining water uptake depth in moist forests, which could have implications for predicting the responses of these ecosystems to climate change.

Fine Roots in Hemiboreal Forest Stands and Clearcut Areas with Nutrient-Rich Organic Soils in Latvia: Morphological Traits, Production and Carbon Input

Within this study, we evaluated the fine root (trees and understory vegetation combined) morphological traits, fine root production (FRP), and carbon (C) input with fine root litter in forest stands (dominated by either coniferous or deciduous trees) and clearcut areas (previously dominated by coniferous trees) with nutrient-rich organic soils. The study was conducted in 26 sites in hemiboreal forest land in Latvia and summarizes the results obtained in a two-year study (2020–2022) using the root ingrowth method. Traits and production of fine roots varied significantly depending on forest development stage (stand or clearcut area), dominant tree species type (coniferous or deciduous), and soil drainage status (drained or naturally wet). According to the results of the second study year, mean FRP among groups of study sites varied from 0.58 ± 0.13 to 1.38 ± 0.28 t ha−1 yr−1, while C input with fine root litter ranged from 0.28 ± 0.06 to 0.68 ± 0.14 t C ha−1 yr−1. More than half (59 ± 4%) of the total FRP occurred in the upper 0–20 cm soil layer. FRP tended to correlate positively with soil C/N ratio and negatively with soil pH and soil nutrient concentration. Incubating ingrowth cores for at least two years is strongly recommended to accurately estimate annual FRP and C input. This helps to avoid potential underestimation that may occur when using results of only one incubation year (12 months after ingrowth core installation). This study provided new insights into the dynamics and traits of fine roots and will help to improve the accuracy of C flow estimation in hemiboreal forests with nutrient-rich organic soils in Latvia.

Fine root production and turnover rate responses to long-term warming and nitrogen addition in a semi-arid grassland

Soil carbon pool is closely linked to fine root production and turnover rate. Lack of knowledge about the effects of nitrogen addition and warming on fine root production and turnover rate limits our ability to accurately predict soil carbon stocks. We studied the responses of fine root production and turnover rate with an 8-year soil warming (ambient +1 °C) and nitrogen addition (ambient + 4.42 g N m−2 yr−1) experiment in a semi-arid grassland on the Loess Plateau of China. Warming significantly decreased fine root production but increased fine root turnover rate due to warming-induced reduction in soil water content. Conversely, nitrogen addition significantly increased fine root production due to decreased soil phosphorus availability. Combined warming and nitrogen addition had no significant effect on fine root production, but decreased fine root turnover rate due to low phosphorus availability caused by nitrogen addition and low soil moisture induced by warming. Our findings have important implications for more accurately predicting the belowground responses of dryland to global changes.

Nitrogen and potassium limit fine root growth in a humid Afrotropical forest

Nutrient limitations play a key regulatory role in plant growth, thereby affecting ecosystem productivity and carbon uptake. Experimental observations identifying the most limiting nutrients are lacking, particularly in Afrotropical forests. We conducted an ecosystem-scale, full factorial nitrogen (N)-phosphorus (P)-potassium (K) addition experiment consisting 32 40 × 40 m plots (eight treatments × four replicates) in Uganda to investigate which (if any) nutrient limits fine root growth. After two years of observations, added N rapidly decreased fine root biomass by up to 36% in the first and second years of the experiment. Added K decreased fine root biomass by 27% and fine root production by 30% in the second year. These rapid reductions in fine root growth highlight a scaled-back carbon investment in the costly maintenance of large fine root network as N and K limitations become alleviated. No fine root growth response to P addition was observed. Fine root turnover rate was not significantly affected by nutrient additions but tended to be higher in N added than non-N added treatments. These results suggest that N and K availability may restrict the ecosystem’s capacity for CO2 assimilation, with implications for ecosystem productivity and resilience to climate change.

Above- and belowground phenology responses of subtropical Chinese fir (Cunninghamia lanceolata) to soil warming, precipitation exclusion and their interaction

Plant phenology plays an important role in nutrient cycling and carbon balance in forest ecosystems, but its response to the interaction of global warming and precipitation reduction remains unclear. In this study, an experiment with factorial soil warming (ambient, ambient +5 °C) and precipitation exclusion (ambient, ambient −50 %) was conducted in a subtropical Chinese fir (Cunninghamia lanceolata) plantation. We investigated the effects of soil warming, precipitation exclusion, and their interactions on Chinese fir phenology involving tree height and fine root growth. In the meantime, the impact of tree height growth and related climatic factors on fine root production was also assessed. The results showed that: (1) more variable phenology responses were observed in fine root growth than in tree height growth to the climatic treatments; the duration of fine root growth and tree height growth was significantly reduced by the precipitation exclusion and warming treatment, respectively; phenology differences of fine root and tree height growth caused by the solo warming and precipitation exclusion treatment were further enhanced by the combined treatment; and despite the greater inter-annual phenology stability of tree height growth than that of fine root growth, both of them showed insignificant response to all the climate treatments; (2) asynchrony of phenology between tree height and fine root growth was significantly enlarged by solo warming and precipitation exclusion treatments, and further enlarged by the combined treatment; (3) fine root production was significantly and positively correlated with air, and soil temperature, and tree height growth as well, which was altered by warming and precipitation exclusion treatments. Our results demonstrated that climatic changes significantly and differently alter phenology of, and extend the phenology asynchrony between, above and below ground plant components, and also highlight the climate-sensitive and variable nature of root phenology. Overall, these phenology responses to climatic change may weaken the close link between fine root production and tree height growth, which may result in temporal mismatch between nutrient demand and supply in Chinese fir plantation.

The effect of drainage on fine‐root biomass, production, and turnover in hemiboreal old‐growth forests on organic soils

AbstractInformation on the capacity of organic soils to capture and store carbon in old‐growth forests in the hemiboreal forest zone is scarce and fragmented. However, fine‐root data can provide valuable insights into soil carbon fluxes. Thus, the aim of the current study was to provide estimates of the fine‐root biomass (FRB), fine‐root production (FRP), and fine‐root turnover (FRT) rate by tree species and other functional groups in old‐growth (stand age 131–179 years) forests on mesotrophic organic soils dominated by Scots pine (Pinus sylvestris L.), with and without the effects of forest drainage. The sequential soil coring method was used to estimate the FRB and FRP. The total FRB was significantly higher in the undrained sites (6.8 ± 0.3 t ha−1) than in the drained sites (3.97 ± 0.1 t ha−1). The FRB of Scots pine in the undrained forest was significantly higher (1.7 ± 0.1 t ha−1) than in the drained forest (0.5 ± 0.1 t ha−1), supporting an extensive foraging strategy. The significantly higher mean FRB of Norway spruce (Picea abies [L.] Karst.) (1.4 ± 0.1 t ha−1) in the drained sites than the undrained sites (0.7 ± 0.2 t ha−1) can be explained by there being a higher proportion of spruce in the stand compositions, thus a higher standing volume of this species and an increased FRB. The FRB of dwarf shrubs (2.43 ± 0.2 t ha−1) formed the largest part of the total FRB in the undrained sites and the second largest (1.16 ± 0.1 t ha−1), following Norway spruce, in the drained sites. The total FRP was similar between the undrained (2.05 ± 0.31 t ha−1 year−1) and drained (1.82 ± 0.26 t ha−1 year−1) stands. However, considerable variability in the FRP was observed between different sites of the same forest site type. The FRT rate of Scots pine was twice as high in the drained sites than the undrained sites, suggesting faster nutrient and carbon input into the drained soil compared with the undrained soil. Estimates of FRB, FRP, and FRT rates for different functional groups can be used in carbon‐cycle modeling and in further calculations to estimate the carbon budget (balance) in forests on organic soils.

Fine root production, mortality, and turnover in response to simulated nitrogen deposition in the subtropical Abies georgei (Orr) forest

Increased nitrogen deposition has important effects on below-ground ecological processes. Fine roots are the most active part of the root system in terms of physiological activity and the main organs for nutrient and water uptake by plants. However, there is still a limited understanding of how nitrogen deposition affects the fine root dynamics in subtropical Abies georgei (Orr) forests. Consequently, a three-year field experiment was conducted to quantify the effects of three forms of nitrogen sources ((NH4)2SO4, NaNO3, and NH4NO3) at four levels (0, 5, 15, and 30 kg N·ha−1·yr−1) on the fine root dynamics in Abies georgei forests using a randomized block-group experimental design and minirhizotron technique. The first year of nitrogen addition did not affect the first-class fine roots (FR1, 0 < diameter < 0.5 mm) and second-class fine roots (FR2, 0.5 < diameter < 1.0 mm). The next two years of nitrogen addition significantly increased the production, mortality, and turnover of FR1 and FR2; the three year of nitrogen addition did not affect the dynamics of the third- class fine roots (FR3, 1.0 < diameter < 1.5 mm) and fourth- class fine roots (FR4,1.5 < diameter < 2.0 mm). Nitrogen addition positively affected the dynamics of FR1, FR2, FR3 and FR4 by positively affecting the carbon, nitrogen, and phosphorus contents of fine roots and indirectly affecting the soil pH. Increased carbon allocation to FR1 and FR2 may represent a phosphorus acquisition strategy when nitrogen is not the limiting factor. The nitrogen addition forms and levels affected the fine root dynamics in the following orde: NH4NO3 > (NH4)2SO4 > NaNO3 and high nitrogen > medium nitrogen > low nitrogen. The results suggest that the different-diameter fine root dynamics respond differently to different nitrogen addition forms and levels, and linking the different-diameter fine roots to nitrogen deposition is crucial.

Long-term nitrogen addition modifies fine root growth and vertical distribution by affecting soil nutrient availability in a Mongolian pine plantation

Fine roots are the primary organ of tree species in water and nutrient acquisition, and are the major contributor of forest soil organic carbon (C). However, it remains largely unknown how fine root growth dynamics and vertical distribution respond to long-term nitrogen (N) enrichment, which prevents us from accurately evaluating forest C sequestration potential under N deposition. Here, we investigated the effects of nine-year N addition (0 and 10 g N m−2 year−1) on fine root nutrients, biomass, production, turnover rate and vertical distribution in three soil layers (0–10, 10–20 and 20–40 cm) of a Mongolian pine (Pinus sylvestris var. mongolica) plantation in the Keerqin Sandy Lands, Northeast China. We found that soil inorganic N was increased and Olsen-P was decreased by N addition. N addition increased fine root N, C:P and N:P ratios, but reduced fine root P and C:N ratio across all soil layers. N addition reduced fine root biomass in 0–10 cm soil layer but increased it in 20–40 cm soil layer. N addition accelerated fine root turnover rate in 0–10 cm soil layer, and increased fine root necromass across all soil layers. Moreover, N addition significantly enhanced biomass of ectomycorrhizal extraradical hyphae in the 0–10 cm soil layer. Redundancy analysis showed that variations of fine root traits were well explained by soil NO3−-N in 0–10 and 10–20 cm soil layers, and by soil NH4+-N and Olsen-P in 20–40 cm soil layer. Collectively, our results highlight the shift from N limitation to P limitation of Mongolian pine plantations under long-term N addition, and suggest that changes in fine root growth and vertical distribution induced by N addition could accelerate belowground C allocation in Mongolian pine plantations.

Functional organic matter components in mangrove soils revealed by density fractionation

ABSTRACT The mechanisms underlying stabilization of soil organic matter (SOM) in vegetated coastal ecosystems, including mangrove forests, are poorly understood, limiting our ability to predict the consequences of disturbances. Here, we introduce density fractionation to mangrove soils to identify the distribution and properties of the functional components of SOM regarding degradation state, stability, and origin, namely, the free low-density fraction (f-LF), mineral-associated LF (m-LF), and high-density fraction (HF). Three soil cores (1 m) were collected in a mangrove forest on Ishigaki Island, Japan, and cut into 10 cm intervals and analyzed. Although HF was the most abundant, the massive production of mangrove fine roots resulted in a high abundance of LFs throughout the cores, which markedly differed from terrestrial soils. Relative abundance of LFs together accounted for 38–66% of total soil C. The m-LF was as abundant as f-LF and 1.6 times higher in relative abundance than the global average of terrestrial soils. The C/N ratios and δ13C values clearly increased with depth in all fractions, which was attributed to the increased contribution from roots. We found a consistent pattern in Δ14C values of density fractions. HF was the oldest with Δ14C between −149‰ and −97‰ followed by m-LF (between −130‰ and −87‰) and then f-LF (between −89‰ and 78‰), suggesting that mineral association may be pivotal in long-term carbon storage in the mangrove mineral soil. Our analysis successfully identified meaningful functional components of mangrove SOM, yet several questions remained unanswered, including a large variability in Δ14C in different cores. Future studies would benefit from a coupled analysis of the quantity and quality of density fractions and geochemical factors in mangrove soils.

Can models adequately reflect how long-term nitrogen enrichment alters the forest soil carbon cycle?

Abstract. Changes in the nitrogen (N) status of forest ecosystems can directly and indirectly influence their carbon (C) sequestration potential by altering soil organic matter (SOM) decomposition, soil enzyme activity, and plant–soil interactions. However, model representations of linked C–N cycles and SOM decay are not well validated against experimental data. Here, we use extensive data from the Fernow Experimental Forest long-term whole-watershed N fertilization study to compare the response to N perturbations of two soil models that represent decomposition dynamics differently (first-order decay versus microbially explicit reverse Michaelis–Menten kinetics). These two soil models were coupled to a common vegetation model which provided identical input data. Key responses to N additions measured at the study site included a shift in plant allocation to favor woody biomass over belowground carbon inputs, reductions in soil respiration, accumulation of particulate organic matter (POM), and an increase in soil C:N ratios. The vegetation model did not capture the often-observed shift in plant C allocation with N additions, which resulted in poor predictions of the soil responses. We modified the parameterization of the plant C allocation scheme to favor wood production over fine-root production with N additions, which significantly improved the vegetation and soil respiration responses. Additionally, to elicit an increase in the soil C stocks and C:N ratios with N additions, as observed, we modified the decay rates of the POM in the soil models. With these modifications, both models captured negative soil respiration and positive soil C stock responses in line with observations, but only the microbially explicit model captured an increase in soil C:N. Our results highlight the need for further model development to accurately represent plant–soil interactions, such as rhizosphere priming, and their responses to environmental change.

Root overlap and allocation of above- and belowground growth of European beech in pure and mixed stands of Douglas fir and Norway spruce

Site conditions and species identity have a combined effect on fine root growth of trees in pure and mixed stands. However, mechanisms that may contribute to this effect are rarely studied, even though they are essential to assess the potential of species to cope with climate change. This study examined fine root overlap and the linkage between fine root and stem growth of European beech (Fagus sylvatica) growing in pure and mixed stands with Douglas fir (Pseudotsuga menziesii) or Norway spruce (Picea abies) at two different study sites in northwestern Germany.The study sites represented substantially different soil and climate conditions. At each site, three stands, and at each stand, three pairs of trees were studied. In the pure beech stand, the pairs consisted of two beech trees, while in the mixed stands each pair was composed of a beech tree and a conifer. Between each pair, three evenly spaced soil cores were taken monthly throughout the growing season. In the pure beech stands, microsatellite markers were used to assign the fine roots to individual trees. Changes in stem diameter of beech were quantified and then upscaled to aboveground wood productivity with automatic high-resolution circumference dendrometers.We found that fine root overlap between neighboring trees varied independently of the distance between the paired trees or the stand types (pure versus mixed stands), indicating that there was no territorial competition. Aboveground wood productivity (wood NPP) and fine root productivity (root NPP) showed similar unimodal seasonal patterns, peaking in June. However, this pattern was more distinct for root NPP, and root NPP started earlier and lasted longer than wood NPP. The influence of site conditions on the variation in wood and root NPP of beech was stronger than that of stand type. Wood NPP was, as expected, higher at the richer site than at the poorer site. In contrast, root NPP was higher at the poorer than at the richer site.We concluded that beech can respond to limited resources not only above- but also belowground and that the negative relationship between above- and belowground growth across the study sites suggests an ‘optimal partitioning’ of growth under stress.

Impact of progressive and retrogressive land use changes on ecosystem multifunctionality: Implications for land restoration in the Indian Eastern Himalayan region

Land use change, anthropogenic exploitation and climate change have impacted the flow of services in the Himalayan region. The dominant land uses in the region including natural forest, degraded forest, rubber (Hevea brasiliensis) plantations, Areca catechu plantations, Areca agroforestry and Piper agroforestry were considered for the study. A progressive shift in land use was defined as the conversion and restoration of a less productive system like degraded land to plantations or agroforestry systems. A land use shift was considered retrogressive when it entails the establishment of plantations after clearing natural forests or anthropogenic disturbance of natural forests resulting in forest degradation. The objectives of the current study were to estimate changes in soil properties, stand structure, tree biomass, fine root production and carbon storage following a progressive and retrogressive shift in land usage. The aboveground biomass (105.9 Mg ha−1) was highest in the natural forest, followed by Areca agroforestry (100.2 Mg ha−1) and least in the degraded forest (55.3 Mg ha−1). The aboveground biomass carbon (47.1 Mg ha−1) of Areca agroforestry was comparable with that of natural forest (51.3 Mg ha−1). The highest proportion of passive carbon concentrations was observed under Areca agroforestry, whereas the lowest (4.13 g kg−1) was found under Areca plantations in the 0–25 cm soil depth. With the progressive shift in land use from degraded forest to agroforestry, SOC stocks increased by 27.6 % and 3 % under Piper and Areca agroforests, respectively. SOC stocks decreased by 8.5 % with a shift in land use from natural forests to Areca plantations. The production of fine roots was maximum in the Areca agroforest (13.2 Mg ha−1) and lowest under rubber plantations (4.2 Mg ha−1). The results show that progressive shifts from degraded forest to agroforestry can considerably increase carbon stocks, plant species diversity and multifunctionality than shifts to monoculture plantations thereby supporting improved biodiversity and mitigation of climate change.

Organic Matter Content and Standard Material Decomposition Rate in Soils of the High Mountain Plant Communities of the Teberda National Park

Soils of the high mountain areas are very diverse by their organic matter content (SOM), by the factors underlying such diversity are still not fully known. In 16 subalpine, alpine and subnival plant communities of the Teberda national park (the north-western Caucasus) we studied physico-chemical and microbiological soil properties, and estimated parameters of standard material decomposition based on the Tea bag index (TBI): stabilization factor (STBI) and decomposition constant (kTBI). We tested the following hypitheses: (1) the SOM is one of predictors of STBI and kTBI in high mountain zone along with other physico-chemical soil properties; (2) the most of SOM content belongs to high STBI and low kTBI values; (3) the SOM content correlates with below-ground plant productivity. The main gradients of the studied soils are water content (automorphic vs. hydromorphic soils) and the concurrent SOM accumulation, as well as the altitudinal gradient with the decrease of soil basal respiration with elevation. The extent of nitrogen enrichment (e.g. SOM quality) of the labile fraction was the best predictor of the decomposition constant. STBI decreased with the increase of total carbon content and the losses on ignition, while the positive link between kTBI and SOM was observed only in automorphic soils. Thus, the soils rich in organic matter typically have low stabilization factor and relatively high decomposition constant. In the plant communities with herbaceous dominants, the SOM content was positively correlated with fine root production, this stresses the important role of productivity in the accumulation of organic matter.

Increased fine root production coupled with reduced aboveground production of plantations under a three-year experimental drought

Climate change has led to more frequent and intense droughts. A better understanding of forest production under drought stress is critical for assessing the resilience of forests and their capacity to deliver ecosystem services under climate change. However, the direction and magnitude of drought effects on aboveground and belowground forest ecosystem components remain poorly understood. Here, we conducted a drought experiment including 30 % and 50 % throughfall reduction in a poplar plantation in the eastern coast of China to test how different drought intensities affected aboveground and fine root production. We further investigated the responses of soil physicochemical properties (e.g., soil moisture, soil pH, soil carbon, and soil nitrogen), and microbial properties (e.g., total microbial biomass, fungi:bacteria ratios, and Gram+:Gram− bacteria ratios) to drought. We found that the aboveground production decreased by 12.2 % and 19.3 % following 30 % and 50 % drought intensities, respectively. However, fine root production increased by 21.6 % and 35.1 % under 30 % and 50 % drought intensities, respectively. Moreover, all above- and belowground components exhibited stronger responses to 50 % compared with 30 % drought intensity. Our results provide some of the first direct evidence for simultaneous responses of forest above- and belowground production to moderate and intense droughts, by demonstrating that fine root production is more sensitive than aboveground production to both levels of drought stress.

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 turnover and leaf litterfall of Salsola passerina facilitate soil restoration in Alxa steppe desert of northwest China

Nutrient cycling in desert ecosystems is heavily reliant on the fine root turnover and litter decomposition processes of dominant plant species. Based on field investigations and laboratory experiments, we explored fine root production (FRP) and turnover of Salsola passerina in Alxa steppe desert, and assessed fine root and leaf litter input and its correlation with soil C and N stocks, and then compared the variability of soil physicochemical properties at the site below and the interspace of S. passerina canopy. Results showed that fine root biomass dynamics of S. passerina were consistent with soil water content. Annual FRP of S. passerina was 243.3 g m−2 yr−1 and the turnover rate was 2.0 per year. S. passerina contributed 172.2 g C m−2 and 6.8 g N m−2 to soil from its fine root senescence and leaf litter input annually. Compared to the canopy interspace, the soil texture and fertility beneath the shrubs significantly improved, while the soil salinity decreased. The results indicated that the activities of desert shrub growth provided the degraded soil with abundant nutrients through fine root turnover and litter decomposition processes, which promoted soil texture and nutrition heterogeneity at the stand scale, and played an important role in degraded dryland restoration.

Decadal soil warming decreased vascular plant above and belowground production in a subarctic grassland by inducing nitrogen limitation.

Below and aboveground vegetation dynamics are crucial in understanding how climate warming may affect terrestrial ecosystem carbon cycling. In contrast to aboveground biomass, the response of belowground biomass to long-term warming has been poorly studied. Here, we characterized the impacts of decadal geothermal warming at two levels (on average +3.3°C and +7.9°C) on below and aboveground plant biomass stocks and production in a subarctic grassland. Soil warming did not change standing root biomass and even decreased fine root production and reduced aboveground biomass and production. Decadal soil warming also did not significantly alter the root-shoot ratio. The linear stepwise regression model suggested that following 10 yr of soil warming, temperature was no longer the direct driver of these responses, but losses of soil N were. Soil N losses, due to warming-induced decreases in organic matter and water retention capacity, were identified as key driver of the decreased above and belowground production. The reduction in fine root production was accompanied by thinner roots with increased specific root area. These results indicate that after a decade of soil warming, plant productivity in the studied subarctic grassland was affected by soil warming mainly by the reduction in soil N.

First estimates of fine root production in tropical peat swamp and terra firme forests of the central Congo Basin

Tropical peatlands are carbon-dense ecosystems because they accumulate partially-decomposed plant material. A substantial fraction of this organic matter may derive from fine root production (FRP). However, few FRP estimates exist for tropical peatlands, with none from the world’s largest peatland complex in the central Congo Basin. Here we report on FRP using repeat photographs of roots from in situ transparent tubes (minirhizotrons), measured to 1 m depth over three one-month periods (spanning dry to wet seasons), in a palm-dominated peat swamp forest, a hardwood-dominated peat swamp forest, and a terra firme forest. We find FRP of 2.6 ± 0.3 Mg C ha−1 yr−1, 1.9 ± 0.5 Mg C ha−1 yr−1, and 1.7 ± 0.1 Mg C ha−1 yr−1 in the three ecosystem types respectively (mean ± standard error; no significant ecosystem type differences). These estimates fall within the published FRP range worldwide. Furthermore, our hardwood peat swamp estimate is similar to the only other FRP study in tropical peatlands, also hardwood-dominated, from Micronesia. We also found that FRP decreased with depth and was the highest during the dry season. Overall, we show that minirhizotrons can be used as a low-disturbance method to estimate FRP in tropical forests and peatlands.

Ridge tillage increased halophyte fine root production and turnover rates by altering soil properties in an abandoned farmland in northwest China

Ridge tillage is a common tillage practice used for farmlands and afforestation. However, the mechanisms by which ridges affect halophyte fine root dynamics in abandoned farmlands are still unknown. A field experiment was conducted to evaluate the effect of ridge tillage on root dynamics in an abandoned farmland over three consecutive years using a minirhizotron method. The rate of fine root production varied from 27 to 44 mm cm−2 each year, and the root turnover rate was between 7.46 and 16.99 times per year. Ridge tillage significantly decreased 0–1 mm diameter root production and root lifespan (28.98% and 19.77%, respectively) while increasing root mortality by 18.74%. Conversely, there was no significant effect of ridge tillage on roots within the 1–2 mm diameter range. Ridge tillage resulted in increased root production and root lifespan, which was mainly due to an increase in soil moisture. Clear seasonal patterns were observed for fine root production, root standing crop and root mortality due to increases in soil organic matter, soil water content and soil salt content in the abandoned farmland. Our results demonstrated that ridge tillage not only accelerated halophyte root production and lifetimes but also improved belowground productivity, providing a potential way to replant in the saline-alkaline soils of abandoned farmlands.