Root Mortality Research Articles

Feedbacks Regulating the Salinization of Coastal Landscapes.

The impact of saltwater intrusion on coastal forests and farmland is typically understood as sea-level-driven inundation of a static terrestrial landscape, where ecosystems neither adapt to nor influence saltwater intrusion. Yet recent observations of tree mortality and reduced crop yields have inspired new process-based research into the hydrologic, geomorphic, biotic, and anthropogenic mechanisms involved. We review several negative feedbacks that help stabilize ecosystems in the early stages of salinity stress (e.g., reduced water use and resource competition in surviving trees, soil accretion, and farmland management). However, processes that reduce salinity are often accompanied by increases in hypoxia and other changes that may amplify saltwater intrusion and vegetation shifts after a threshold is exceeded (e.g., subsidence following tree root mortality). This conceptual framework helps explain observed rates of vegetation change that are less than predicted for a static landscape while recognizing the inevitability of large-scale change.

Response on root regrowth potential to soil moisture in Sedum species during winter in Særheim, Norway

PurposeThe impact of winter moisture on root metabolism and root integrity has potential consequences for the geographical distribution of drought-adapted succulent species and for their long-term performance on green roofs. The interacting effects of soil characteristics and precipitation frequency on root mortality under winter conditions and the potential to grow new roots in spring were evaluated for six Sedum species under controlled conditions. MethodsTo test for the impact of soil moisture during winter on root regrowth potential in six Sedum species, we used a combination of two substrates with differing water-holding capacity and four contrasting watering regimes. Specially, for the fine and coarse substrates, total pore volume was 42 and 46 %, respectively, and maximum water-holding capacity (i.e. field capacity) was 0.50 and 0.33 kg water per L, respectively. The four watering treatments involved overhead watering to runoff (approx. 10 mm): once every second week, once a week, three times per week and three times per week with 1 cm standing water in trays from January to March 2019. ResultsIt was found that winter soil moisture had no major impact on root mortality or root regrowth potential in spring. Root mortality was not affected by watering frequency and regrowth potential showed no directional response to increased watering frequency, although species-specific responses were involved. Root diameter did not differ between the substrates, but there were some differences between the species. Sedum rupestre had on average the thickest roots (0.17 mm), followed by S. acre, S. anglicum and S. sexangulare (0.15–0.16 mm), while S. album and S. hispanicum had the thinnest roots (0.12–0.13 mm). Moreover, effects of watering frequency on root mortality and regrowth potential were not influenced by soil water-holding capacity across species. We concluded that winter soil moisture had no negative effects on root performance within the range of treatments tested here. ConclusionsRoot response to transient waterlogging or moist but unsaturated soil may not be an important mechanism for determining the survival and distribution of temperate Sedum species during winter.

Effects of reduced snowpack due to climate warming on abiotic and biotic soil properties in alpine and boreal forest systems

Reduction in snow cover, depth, onset, and duration of seasonal snow in mid-latitude regions due to climate warming has multiple global and local scale ecosystem impacts. These effects include modulations of the hydrological cycles and increases in land surface solar radiation absorption due to decreased albedo. Changes in snow cover characteristics also affect underlying soils. Snow has an insulating effect on soils by decoupling air and soil temperatures, thus seasonal snow cover reduction leads to overall lower soil temperatures and an increase in freeze-thaw cycles. This is especially prominent during the fall and spring thaw seasons when the snow cover is not as extensive. This in turn has downstream impacts on soil physical, chemical, and biological properties. Among these impacts are soil moisture reduction, temperature, frost regimes, soil pH shifts, and alteration in nutrient flux dynamics during winter, snowmelt period and the following summer growing season. These changes in soil physicochemical properties due to snowpack reduction can then impact the biological soil properties via increased plant root mortality, reduced abundance and diversity of soil arthropods, and shifts in composition, abundance and activity of soil microbial communities. All these soil biotic factors can in turn alter the dynamics of soil nutrient fluxes and future greenhouse gas emissions. Here, we integrate data on the effects of snow cover reduction on abiotic and biotic soil properties, with focus on temperate alpine and forest ecosystems and with an outlook on future impacts.

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.

Major carbon losses from degradation of Mauritia flexuosa peat swamp forests in western Amazonia

AbstractTropical peat swamp forests are major global carbon (C) stores highly vulnerable to human intervention. In Peruvian Amazonia, palm swamps, the prevalent peat ecosystem, have been severely degraded through recurrent cutting of Mauritia flexuosa palms for fruit harvesting. While this can transform these C sinks into significant sources, the magnitude of C fluxes in natural and disturbed conditions remains unknown. Here, we estimated emissions from degradation along a gradient comprising undegraded (Intact), moderately degraded (mDeg) and heavily degraded (hDeg) palm swamps. C stock changes above- and below-ground were calculated from biomass inventories and peat C budgets resulting from the balance of C outputs (heterotrophic soil respiration (Rh), dissolved C exports), C inputs (litterfall, root mortality) and soil CH4 emissions. Fluxes spatiotemporal dynamics were monitored (bi)monthly over 1–3 years. The peat budgets (Mg C ha−1 year−1) revealed that medium degradation reduced by 88% the soil sink capacity (from − 1.6 ± 1.3 to − 0.2 ± 0.8 at the Intact and mDeg sites) while high degradation turned the soil into a high source (6.2 ± 0.7 at the hDeg site). Differences stemmed from degradation-induced increased Rh (5.9 ± 0.3, 6.2 ± 0.3, and 9.0 ± 0.3 Mg C ha−1 year−1 at the Intact, mDeg, and hDeg sites) and decreased C inputs (8.3 ± 1.3, 7.1 ± 0.8, and 3.6 ± 0.7 Mg C ha−1 year−1 at the same sites). The large total loss rates (6.4 ± 3.8, 15.7 ± 3.8 Mg C ha−1 year−1 under medium and high degradation), originating predominantly from biomass changes call for sustainable management of these peatlands.

The effect of experimental warming on fine root functional traits of woody plants: Data synthesis

Fine root traits are critical to plant nutrition and water uptake, and soil nutrient cycling. The impacts of climate warming on woody plants are predicted to be severe, but the effects on the fine root traits of woody plants remain unclear. To evaluate the effects of warming on fine-root traits of woody plants, we synthesized 431 paired observations of 13 traits from 78 studies. The result showed that warming increased the fine root nitrogen (N) concentration, root mortality, and root respiration, but decreased fine root phosphorus (P) concentration, root C:N and root nonstructural carbohydrates (NSC) concentration. However, warming had no significant effect on fine root biomass, root production and morphological traits. Warming effects on fine root biomass and root diameter decreased with warming magnitude, while root P concentration increased. Moreover, with increasing warming duration, the effect size of specific root length (SRL), root length, root C:N and root NSC increased. The effects size of root biomass, root diameter, root length and root C:N decreased with mean annual temperature (MAT) and mean annual precipitation (MAP) increase. However, the effect size of root N concentration increased with higher MAT and MAP. Furthermore, warming increased the fine root biomass of ectomycorrhiza (ECM) plants, but decreased that of plants associated with arbuscular mycorrhizal (AM) fungi. These results indicate that the effect of warming on fine root traits of woody plants was not only modulated by warming duration and magnitude, but also MAT and MAP. Our findings highlight the differential warming responses to fine root traits of woody plants, which have strong implications for shrubs and tree-dominated ecosystems soil nutrients cycling and carbon stocks.

Taxonomical, functional, and cytopathological characterization of Bacillus spp. from Lake Magadi, Kenya, against Rhizoctonia solani Kühn in Phaseolus vulgaris L.

A decline in common bean production and the ineffectiveness of synthetic chemical products in managing plant pathogens has led to exploiting Kenyan soda lakes as an alternative search for biocontrol agents. This study aimed to identify phylogenetically Bacillus spp. from Lake Magadi and their antagonistic activity against Rhizoctonia solani under in vitro and in vivo conditions. The 16 S ribosomal RNA (rRNA) subunit sequences of six bacterial strains isolated from Lake Magadi showed diversity similar to the Bacillus genus; Bacillus velezensis, Bacillus subtilis, and Bacillus pumilus. In vitro, antagonism showed varied mycelium inhibition rates of fungi in the coculture method. Enzymatic assays showed the varied ability of isolates to produce phosphatase, pectinase, chitinase, protease, indole-3-acetic acid (IAA), and hydrogen cyanide (HCD). The in vivo assay showed M09 (B. velezensis) with the lowest root mortality and incidence of postemergence wilt. Pre-emergence wilt incidence was recorded as lowest in M10 (B. subtilis). Isolate M10 had the highest phenylalanine ammonia-lyase (PAL) for defense enzymes, while polyphenol oxidase (PPO) and peroxidase were recorded as highest in M09. For the phenolic content, M10 recorded the highest phenolic content. In conclusion, Lake Magadi harbors Bacillus spp, which can be used as a potential biocontrol of R. solani.

Evaluation of spatial and temporal variation in fine root dynamics in a temperate mixed forest using a scanner method

ABSTRACT Understanding fine root phenology at the stand scale is crucial for elucidating how carbon and nutrient cycling in forest systems respond to climate change. This study aimed to reveal the spatio-temporal variations in the fine root phenology in a mixed temperate forest in Japan using scanner method. The spatio-temporal variation in the fine root areas was evaluated using two scales: among four plots in the stand and among four partitioned areas in the scanner image. Here, we hypothesized that root phenology would vary on both scales due to the mixture of species-specific phenologies, which means endogenous factors to have a larger impact than exogenous factors such as temperature and precipitation. The timing of the production peak varied among years, though it concentrated within a specific period of the year in all plots. In all plots, active root mortality dynamics were observed in the summer. These results suggested exogenous factors as stronger regulators of fine root production and mortality than endogenous factors. Root phenology within the scanner images is highly heterogeneous, suggesting the significance of broad observation surfaces, such as those acquired using the scanner method, in comprehending the representative phenology of root dynamics at a stand scale. This study revealed that fine root phenology had a synchronized pattern on the stand scale, even though high spatial variation existed in the scale size of the scanner. Differences in root phenology that were influenced by internal factors of the species were masked on the stand scale.

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

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

Dynamics of spatial and temporal growth of the root system of grapevine (Vitis vinifera L.) under nitrogen levels in sandy soil in subtropical climate

• N addition promotes the increase in the surface area of live fine roots. • Fine root production is higher in grapevine flowering stage. • N concentration in leaves is promoted by the increase in the fine roots. • Total number of dead and mortality of fine roots is increased by the addition of N. Nitrogen (N) supply to the soil via fertilization can influence important processes of the root system growth, which can increase N uptake and, consequently, the shoot growth. In this context, the study aimed to evaluate how the application of N levels can affect the dynamics of spatial and temporal growth of the root system of grapevines ( Vitis vinifera L.) in sandy soil and subtropical climate. ‘Alicante Bouschet’ grapevines, grafted on ‘Paulsen 1103’ rootstock, implanted in 2011. The N addition were: Low N: control (without the N addition; 0 kg N ha −1 year −1 ); Medium N (40 kg N ha −1 year −1 ); and High N (100 kg N ha −1 year −1 ). The study was carried out during 2016/17 and 2017/18 crop seasons. N concentration in the leaves and morphological parameters of fine roots were evaluated using the minirhizotron technique. The addition of Medium N and High N significantly increased the values ​​of the total surface area of ​​live fine roots and the total number of live and dead fine roots, at 0-20, 20-40 and 40-60 cm soil depth, in both crop seasons evaluated. The addition of Medium N and High N also directly influenced the production rates of live fine roots, with patterns of seasonal changes, especially increased in the flowering stage of the grapevines. This occurs due to the increase in the physiological demand of growing plant tissues, such as new roots, leaves and fruits.

Separating the effects of air and soil temperature on silver birch. Part I. Does soil temperature or resource competition determine the timing of root growth?

The aboveground parts of boreal forest trees mostly grow earlier, and the roots later, in the growing season. We aimed to experimentally test whether the extrinsic driver of soil temperature or the intrinsic driver (resource competition between plant parts) is a more important control for the root and shoot growth of silver birch (Betula pendula Roth) seedlings. Sixteen two-year-old seedlings were grown in controlled environment rooms for two simulated growing seasons (GS1, GS2). In GS1, all the seedlings were acclimatized under the same conditions, but in GS2, the soil temperature treatments were: (i) constant 10°C (Cool); (ii) constant 18°C (Warm); (iii) early growing season at 10°C, switched to 18°C later (Early Cool Late Warm, ECLW) and (iv) early growing season 18°C, switched to 10°C later (Early Warm Late Cool, EWLC). The treatments did not affect growth allocation between shoots and roots. Warm soil benefitted shoot elongation as it slowed down in EWLC and accelerated in ECLW after the soil temperature switch. However, whole-tree biomasses were similar to Cool and the seedlings grew largest in Warm. Phenology was not strongly affected by soil temperature, and root and shoot growth did not usually peak simultaneously. Short root mortality increased strongly in ECLW and decreased in EWLC after the soil temperature switch. Long root longevity was not significantly affected but long root growth ceased earliest in ECLW. Soil warming increased foliar nutrient contents. Growth dynamics were not solely driven by soil temperature, but resource competition also played a significant role. The study showed the importance of soil temperature for fine root dynamics not only through root growth but also via root mortality, as soil warming increased mortality even more than growth. Soil temperature has complex effects on tree and soil functioning, which further affects carbon dynamics in forest ecosystems that have a climate feedback.

Effects of stand condition and root density on fine-root dynamics across root functional groups in a subtropical montane forest

Fine roots play key roles in belowground C cycling in terrestrial ecosystems. Based on their distinct functions, fine roots are either absorptive fine roots (AFRs) or transport fine roots (TFRs). However, the function-based fine root dynamics of trees and their responses to forest stand properties remain unclear. Here, we studied the dynamics of AFRs and TFRs and their responses to stand conditions and root density in a subtropical montane mixed forest based on a 2-a root window experiment. Mean (± SE) annual production, mortality, and turnover rate of AFRs were 7.87 ± 0.17 m m−2 a−1, 8.13 ± 0.20 m m−2 a−1and 2.96 ± 0.24 a−1, respectively, compared with 7.09 ± 0.17 m m−2 a−1, 4.59 ± 0.17 m m−2 a−1, and 2.01 ± 0.22 a−1, respectively, for TFRs. The production and mortality of fine roots were significantly higher in high root-density sites than in low-root density sites, whereas the turnover of fine roots was faster in the low root-density sites. Furthermore, root density had a larger positive effect than other environmental factors on TFR production but had no obvious impact on AFR production. Tree species diversity had an apparent positive effect on AFR production and was the crucial driver of AFR production, probably due to a complementary effect, but had no evident impact on TFR. Both tree density and tree species diversity were positively correlated with the mortality of AFRs and negatively related to the turnover of TFRs, suggesting that higher root density caused stronger competition for rooting space and that plants tend to reduce maintenance costs by decreasing TFR turnover. These findings illustrated the importance of root functional groups in understanding root dynamics and their responses to changes in environmental conditions.

How can process-based modeling improve peat CO2 and N2O emission factors for oil palm plantations?

Oil palm plantations on peat and associated drainage generate sizeable GHG emissions. Current IPCC default emission factors (EF) for oil palm on organic soil are based on a very limited number of observations from young plantations, thereby resulting in large uncertainties in emissions estimates. To explore the potential of process-based modeling to refine oil palm peat CO2 and N2O EFs, we simulated peat GHG emissions and biogeophysical variables over 30 years in plantations of Central Kalimantan, Indonesia. The DNDC model simulated well the magnitude of C inputs (litterfall and root mortality) and dynamics of annual heterotrophic respiration and peat decomposition N2O fluxes. The modeled peat onsite CO2-C EF was lower than the IPCC default (11 Mg C ha−1 yr−1) and decreased from 7.7 ± 0.4 Mg C ha−1 yr−1 in the first decade to 3.0 ± 0.2 and 1.8 ± 0.3 Mg C ha−1 yr−1 in the second and third decades of the rotation. The modeled N2O-N EF from peat decomposition was higher than the IPCC default (1.2 kg N ha−1 yr−1) and increased from 3.5 ± 0.3 kg N ha−1 yr−1 in the first decade to 4.7–4.6 ± 0.5 kg N ha−1 yr−1 in the following ones. Modeled fertilizer-induced N2O emissions were minimal and much less than 1.6% of N inputs recommended by the IPCC in wet climates regardless of soil type. Temporal variations in EFs were strongly linked to soil C:N ratio and soil mineral N content for CO2 and fertilizer-induced N2O emissions, and to precipitation, water table level and soil NH4+ content for peat decomposition N2O emissions. These results suggest that current IPCC EFs for oil palm on organic soil could over-estimate peat onsite CO2 emissions and underestimate peat decomposition N2O emissions and that temporal variation in emissions should be considered for further improvement of EFs.

Fine root mortality under severe drought reflects different root distribution of Quercus robur and Ulmus laevis trees in hardwood floodplain forests

Key messageExtremely high fine root mortalities were observed under drought in 2018, increasing fine root mortality in young trees could be explained by differences in root distribution compared to old trees.Juvenile trees in floodplains are prone to high mortality leading to a low success in reforestation in these habitats. One of the reasons contributing to high mortality of juvenile trees could be limited water and nutrient uptake due to a high level of fine root mortality, especially during summer droughts on higher terraces of floodplains. Strategies of different tree species in hardwood floodplain forests (HFFs) on keeping fine roots alive are still poorly understood. During the record-breaking summer drought of 2018, we examined the relationship between tree age and fine root dynamics of Quercus robur and Ulmus laevis along the Elbe River in Germany. Root area index (RAI), live root density (LRD) and relative root mortality (RRM) of young and old Q. robur and U. laevis were analysed by taking soil cores three times during the progression of a summer drought. Old oaks had a lower RAI in the upper soil than young oaks, while RAI of elms did not differ between young and old trees. RRM was very high during summer reaching more than 100% on average. RRM of young trees of both species increased with increasing drought during summer, while RRM of old trees did not change. We argue that differences in the response of RAI between oaks and elms reflect the sink competition between growing deep roots and shallow roots, which is pronounced in oaks due to their characteristic tap root system. Differences in root distribution patterns and the ability to perform hydraulic redistribution may explain the differences in RRM between trees of different species and ages.

Praealpine Spruce (Picea Abies) Forest Dynamics During the Current Post-Little Ice Age Climate Era: A Case in the Swedish Scandes

This study focuses on structural change of a praealpine stand of Norway spruce (Picea abies), in a context of centennial climate warming, in the Swedish Scandes. Progressive stand building followed on the discontinuation of the Little Ice Age by the late 19th century. A distinct hiatus of this process occurred during the 1980s, as a consequence of exceptionally cold winters with a sparse snow cover, particularly 1886/87. Extensive defoliation, caused by frost desiccation and fine root mortality, followed and culminated 1994 and 1995. Subsequently, climate warming resumed and stand foliation increased steadily up to the present day, when the forest appears equally healthy as prior to the 1980s. Hereby, recent spruce stand evolution adds to current progressive climate-mediated restructuring of upper montane forests.

Estimation of total fine root production using continuous inflow methods in tropical mangrove forest on Pohnpei Island, Micronesia: Fine root necromass accumulation is a substantial contributor to blue carbon stocks

AbstractFine root decomposition, mortality, and production are fundamental components of belowground carbon dynamics in mangrove ecosystems. Mangroves are highly productive ecosystems with huge carbon stocks; however, information on the dynamics of submerged fine roots in mangrove soils is limited. To estimate fine root production in several sites of mangrove communities on Pohnpei Island, Micronesia, we estimated continuous inflows using a simple mass balance model to combine ingrowth core and litterbag experimental results. According to our findings, previously reported mangrove fine root production values were severely underestimated because the fine root decomposition process was disregarded during the experimental period. We estimated that annual fine root production up to 0.3 m in depth ranged from 13.8 (Bruguiera gymnorrhiza in a landward plot) to 56.3 Mg ha−1 year−1 (B. gymnorrhiza in a seaward plot). However, comparing the fine root production with respect to the unit of stem cross‐section area increase in the sample tree, the fine root production of Rhizophora spp. was greater than that of other species. The annual fine root mortality and decomposition to annual fine root production was 70%–105% and 11%–52% of annual production, respectively. The annual fine root production estimated here was much higher than that previously reported. These findings begin to quantify the contribution and importance of highly productive mangrove fine roots for carbon sequestration in blue carbon ecosystems. Moreover, this study provides new insights into the organic carbon dynamics in mangrove soils with mangrove vegetation succession.

Degradation-driven changes in fine root carbon stocks, productivity, mortality, and decomposition rates in a palm swamp peat forest of the Peruvian Amazon

BackgroundAmazon palm swamp peatlands are major carbon (C) sinks and reservoirs. In Peru, this ecosystem is widely threatened owing to the recurrent practice of cutting Mauritia flexuosa palms for fruit harvesting. Such degradation could significantly damage peat deposits by altering C fluxes through fine root productivity, mortality, and decomposition rates which contribute to and regulate peat accumulation. Along a same peat formation, we studied an undegraded site (Intact), a moderately degraded site (mDeg) and a heavily degraded site (hDeg) over 11 months. Fine root C stocks and fluxes were monthly sampled by sequential coring. Concomitantly, fine root decomposition was investigated using litter bags. In the experimental design, fine root stocks and dynamics were assessed separately according to vegetation type (M. flexuosa palm and other tree species) and M. flexuosa age class. Furthermore, results obtained from individual palms and trees were site-scaled by using forest composition and structure.ResultsAt the scale of individuals, fine root C biomass in M. flexuosa adults was higher at the mDeg site than at the Intact and hDeg sites, while in trees it was lowest at the hDeg site. Site-scale fine root biomass (Mg C ha−1) was higher at the mDeg site (0.58 ± 0.05) than at the Intact (0.48 ± 0.05) and hDeg sites (0.32 ± 0.03). Site-scale annual fine root mortality rate was not significantly different between sites (3.4 ± 1.3, 2.0 ± 0.8, 1.5 ± 0.7 Mg C ha−1 yr−1 at the Intact, mDeg, and hDeg sites) while productivity (same unit) was lower at the hDeg site (1.5 ± 0.8) than at the Intact site (3.7 ± 1.2), the mDeg site being intermediate (2.3 ± 0.9). Decomposition was slow with 63.5−74.4% of mass remaining after 300 days and it was similar among sites and vegetation types.ConclusionsThe significant lower fine root C stock and annual productivity rate at the hDeg site than at the Intact site suggests a potential for strong degradation to disrupt peat accretion. These results stress the need for a sustainable management of these forests to maintain their C sink function.

Getting to the root of the problem: improving measurements of mangrove belowground production and carbon sequestration.

This article is a Commentary on Arnaud et al. (2021), 232: 1591–1602.

Root dynamics along a restoration chronosequence of revegetated grasslands in degraded alpine meadows of the Qinghai‐Tibetan Plateau, China

AbstractRevegetation using perennial grass, such as Elymus nutans is an effective approach in abating grassland degradation on the Qinghai‐Tibetan Plateau. However, knowledge of root dynamics along restoration chronosequences of revegetated grasslands are limited. To gain better insight into root dynamics, we used minirhizotrons to examine changes in root traits, including root standing crop, production, mortality, and turnover along a restoration chronosequence of three revegetated grasslands (cultivated in 2002, 2006, and 2010 corresponding to late, middle, and early recovery stage) in four consecutive growing seasons (2014, 2015, 2016, and 2017). We found that the aboveground plant biomass was higher in the middle recovery stage than that in the early and late recovery stages, while plant species richness showed an increasing trend from the early to late recovery stage. Similar with the plant biomass response, the belowground root standing crop and production were significantly higher in the middle recovery stage than in the early and late recovery stages. Root mortality was decreased and root turnover tend to be stable from the early to late recovery stage. Root turnover was positively correlated with soil NO3−‐N content and negatively correlated with aboveground plant biomass. Moreover, root standing crop and mortality increased from May to September across all growing seasons; however, root production decreased within this period. Our study highlighted significant links between aboveground and belowground plant parts that may help effectively manage revegetated grassland on the Qinghai‐Tibetan Plateau.

Estimation of Net Primary Productivity and Net Annual Assimilation in the Forests of Kumaun Himalaya

Estimation of carbon uptake by the forests is required to measure the carbon flux of a region. In present study, net primary productivity (NPP) and net annual assimilation (NAA) of carbon was estimated in forests of Kumaun Himalaya by integration of field based measurements and information generated using satellite data. Aboveground NPP was estimated by quantification of aboveground biomass increment, root mortality and litterfall. Root mortality value was added to the biomass accumulation of root component to compute the total belowground productivity. Net Annual Assimilation (NAA) was computed as a difference between carbon uptake in NPP and litterfall plus root mortality. NPP values ranged from 5.20 t/ha/yr (degraded sal forest) to 21.38 t/ha/yr (temperate conifer forest). Total estimated values of net annual uptake of carbon and net annual assimilation of carbon in the study area were 748.93 × 10 4 t/yr and 457.27 × 10 4 t/yr, respectively. Estimation of NPP and NAA are useful for further computation of carbon flux to know the status of forest as sink or source of carbon to the atmosphere.