Search

Arbuscular mycorrhizal fungi (AMF) form beneficial partnerships with most plant species, helping to improve crop resilience in tough environmental conditions. This paper analyzed how different genotypes responded to AMF inoculation, focusing on root colonization percentage (RCP) and the impact of AMF on above-ground agronomic traits. However, RCP alone may not fully explain genotype variation, and AMF effects cannot be judged solely on above-ground traits. This research aims to explore the variation in ninety tef genotypes under AMF conditions and assess how AMF and genotypes affect root and shoot morphology traits. Genotypes were sorted into six cluster groups, showing varied responsiveness to AMF, with RCP ranging from 25.03 to 72.29%. Despite similar RCP, variations in morphological traits were observed, and groups with lower RCP exhibited important traits not found in those with higher RCP, indicating RCP alone cannot indicate genotype variability. Wider Mahalanobis distance (D2) between clusters IV and VI, I and VI, and V and VI were crucial for developing different varieties and advancing root traits through hybridization. Among the tested genotypes, Wehni and Tsaeda zezew, followed by Gureaza, exhibited higher scores for plant height (PH), panicle length (PL), shoot biomass yield (SBY), root length (RL), and specific root length (SRL) compared to Simada. However, Wehni, Tsaeda zezew, and Gureaza showed similar results for days to maturity (DM), grain yield (GY), harvest index (HI), root dry weight (RDW), and root depth distribution (RDD) but differed from Simada genotype. Moreover, the inoculated Wehni genotype increased in days to panicle emergence (DPE) by 72%, DM by 84.11%, PH by 73.93%, PL by 73.68%, SBY by 144.17%, GY by 254.58%, HI by 133.33%, RL by 74.16%, RDW by 216.92%, SRL by 220%, and RDD by 93.28% as compared to the non-inoculated Simada. Improved performance of inoculated genotypes despite genotype variability could be because AMF enhances nutrient and water uptake by increasing root and shoot growth and the inherent growth strategy of the genotypes. Small-seeded crops planted shallowly benefit from AMF, which promotes deeper root growth for better nutrient and water uptake. [ABSTRACT FROM AUTHOR]

Global interest and investment in nature‐based solutions (NbS) are rapidly increasing because of the potential of this approach to concurrently counter biodiversity loss, provide cost‐effective measures for climate change adaptations, and maintain natural processes that underpin human health and wellbeing.Recognition is growing that grasslands in many regions will protect carbon stores more effectively than forests in the warmer, drier, more fire‐prone conditions of the future while also serving as hotspots for biodiversity. Yet grasslands have received less attention for their NbS potential. Despite the wide‐ranging goals of this approach, many investments in nature‐based solutions also have focused narrowly on using plants to meet climate pledges, often without considering plant interactions with herbivores and the abiotic environment that jointly control ecosystem functioning and underpin the success of nature‐based solutions.Here, we review the roles that large and small vertebrate and invertebrate herbivores play in the ability of the world's grasslands to provide nature‐based solutions, with a focus on wild herbivore impacts on biodiversity and carbon storage.Synthesis. Planning for nature‐based solutions with a holistic, ecologically informed view that includes the role of herbivores and their interaction with plants and the environment will allow NbS investments to more likely achieve successful, sustainable outcomes. [ABSTRACT FROM AUTHOR]

Abstract Arbuscular mycorrhizal fungi (AMF) form beneficial partnerships with most plant species, helping to improve crop resilience in tough environmental conditions. This paper analyzed how different genotypes responded to AMF inoculation, focusing on root colonization percentage (RCP) and the impact of AMF on above-ground agronomic traits. However, RCP alone may not fully explain genotype variation, and AMF effects cannot be judged solely on above-ground traits. This research aims to explore the variation in ninety tef genotypes under AMF conditions and assess how AMF and genotypes affect root and shoot morphology traits. Genotypes were sorted into six cluster groups, showing varied responsiveness to AMF, with RCP ranging from 25.03 to 72.29%. Despite similar RCP, variations in morphological traits were observed, and groups with lower RCP exhibited important traits not found in those with higher RCP, indicating RCP alone cannot indicate genotype variability. Wider Mahalanobis distance (D2) between clusters IV and VI, I and VI, and V and VI were crucial for developing different varieties and advancing root traits through hybridization. Among the tested genotypes, Wehni and Tsaeda zezew, followed by Gureaza, exhibited higher scores for plant height (PH), panicle length (PL), shoot biomass yield (SBY), root length (RL), and specific root length (SRL) compared to Simada. However, Wehni, Tsaeda zezew, and Gureaza showed similar results for days to maturity (DM), grain yield (GY), harvest index (HI), root dry weight (RDW), and root depth distribution (RDD) but differed from Simada genotype. Moreover, the inoculated Wehni genotype increased in days to panicle emergence (DPE) by 72%, DM by 84.11%, PH by 73.93%, PL by 73.68%, SBY by 144.17%, GY by 254.58%, HI by 133.33%, RL by 74.16%, RDW by 216.92%, SRL by 220%, and RDD by 93.28% as compared to the non-inoculated Simada. Improved performance of inoculated genotypes despite genotype variability could be because AMF enhances nutrient and water uptake by increasing root and shoot growth and the inherent growth strategy of the genotypes. Small-seeded crops planted shallowly benefit from AMF, which promotes deeper root growth for better nutrient and water uptake.

Many plants rely on soil seedbanks to persist in fire‐prone ecosystems. However, knowledge of plant responses to fire is largely based on above‐ground dynamics. Quantifying how fire influences the seedbank of a diverse range of species will improve fire management.Here, we aim to understand how the timing of fires influences species occurrence in the soil seedbank, and how this relates to species traits, in a Mediterranean‐type ecosystem. We sampled the soil seedbank across 57 sites that represent a range of fire frequencies (1–9 fires in 81 years) and time since fire (1–81 years). Through a 15‐month germination experiment, we identified 39,701 germinates from 245 plant species. Using nonlinear models, we quantified the responses of 75 species' soil seedbanks to fire history and compared these to above‐ground responses.Fire influenced species' soil seedbanks according to seed longevity and species' life‐history traits. We observed a response of 15 species' seedbanks to time since fire: All were species with long‐lived seed, including eight annuals, five resprouters and an obligate seeder. Similarly, we observed a response of 17 species' seedbanks to fire frequency, 16 of which had long‐lived seed. Extensive periods without fire (>40 years) increase seedbank availability for annuals that form a long‐lived seedbank, and frequent fire (every ≤15 years) depletes it. We did not detect a consistent influence of fire on species from several other functional types. Many (53%) species found in the soil seedbank were not found in the above‐ground vegetation, and seven of the 22 modelled displayed an above‐ground influence of fire.Synthesis and applications: Fire frequency influences the probability of species occurrence in the soil seedbank. Frequent fire depletes seed availability of species that depend on long‐lived soil seedbanks for persistence. Yet, other species, including perennials with short‐lived seed storage, appear to be resilient to the frequency of fires experienced to date. We suggest fire management should aim to generate variation in fire frequencies within the landscape, including areas of low fire frequency, tailored to maintain rich plant diversity within the soil seedbank. [ABSTRACT FROM AUTHOR]

The olfactory system of above‐ground insects is among the best described perceptual architectures. However, remarkably little is known about how below‐ground insects navigate in the dark for foraging. Here, we investigated host plant preferences, olfactory sensilla and characterise olfactory proteins in below‐ground larvae of the striped flea beetle (SFB) Phyllotreta striolata Fabricius (Coleoptera: Chrysomelidae). Both the adults and larvae of this coleopteran pest cause serious damage to Brassicaceous crops above and below ground, respectively. To elucidate the role of olfactory system in host location of below‐ground larvae, we initially demonstrated that SFB larvae distinctly favoured Brassicaceae over other plant families by two‐choice behavioural bioassay. Subsequently, scanning electron microscopy of sensilla in SFB larval head showed a significant reduction in the number of olfactory sensilla in larvae compared with adults. However, essential olfactory sensilla such as sensilla basiconica are underscoring the indispensability of the larval olfactory system. We selected four larval‐specific odorant binding proteins for functional validation from our previous transcriptome data. Functional studies revealed that PstrOBP23 exhibits robust binding affinity to 24 volatiles of Brassicaceae plants, including seven isothiocyanate compounds. This suggests a pivotal role of PstrOBP23 in the foraging behaviour of the larvae below the ground. Moreover, two ligands displaying strong binding capacity exhibit apparent attractive or repellent activity towards SFB larvae. Our findings provide a crucial insight into the olfactory system of below‐ground larvae in SFB, highlighting the highly selective tuning of larvae specific OBP to host plant volatiles. These results offer potential avenues for developing effective pest control strategies against SFB. [ABSTRACT FROM AUTHOR]

Rhizosphere microbial community assembly results from microbe‐microbe‐plant interactions mediated by small molecules of plant and microbial origin. Studies with Arabidopsis thaliana have indicated a critical role of glucosinolates in shaping the root and/or rhizosphere microbial community, likely through breakdown products produced by plant or microbial myrosinases inside or outside of the root. Plant nitrile‐specifier proteins (NSPs) promote the formation of nitriles at the expense of isothiocyanates upon glucosinolate hydrolysis with unknown consequences for microbial colonisation of roots and rhizosphere. Here, we generated the A. thaliana triple mutant nsp134 devoid of nitrile formation in root homogenates. Using this line and mutants lacking aliphatic or indole glucosinolate biosynthesis pathways or both, we found bacterial/archaeal alpha‐diversity of the rhizosphere to be affected only by the ability to produce aliphatic glucosinolates. In contrast, bacterial/archaeal community composition depended on functional root NSPs as well as on pathways of aliphatic and indole glucosinolate biosynthesis. Effects of NSP deficiency were strikingly distinct from those of impaired glucosinolate biosynthesis. Our results demonstrate that rhizosphere microbial community assembly depends on functional pathways of both glucosinolate biosynthesis and breakdown in support of the hypothesis that glucosinolate hydrolysis by myrosinases and NSPs happens before secretion of products to the rhizosphere. Summary statement: This research demonstrates differential effects of lacking root nitrile‐specifier proteins and glucosinolate biosynthesis pathways on Arabidopsis rhizosphere microbiota. The results strengthen the hypothesis that glucosinolate hydrolysis in planta precedes secretion of products to the rhizosphere. [ABSTRACT FROM AUTHOR]

Sustainable agroecosystems with systematic crop rotation and crop diversity can promote the maintenance of soil fertility and sustainable carbon cycling including CO2 sequestration from the atmosphere and formation of organic matter. To contribute to the implementation of the goals of the European Green Deal course, it is necessary to assess CO2 uptake capacity for the widest possible range of agricultural crops grown in a certain region. This study determined the amount of above-ground (ResidAG) and below-ground (ResidBG) residues of plants and the content of C and N fixed in them looking for relationships with the yield for six alternative crops for cereals grown in Latvia: winter rape (WRa), buckwheat (BW), peas (P), potatoes (PO), maize (M), and green fallow (GF) compared to cereals in two different regions of Latvia over a three-year period. Significant differences were found between alternative species in the amount of total (AG + BG) plant residues (g m-2 DM) left in the field: 1840 ± 67.8 for winter rape, 740 ± 30.7 for buckwheat, 767 ± 54.7 for peas, 323 ± 11.2 for potatoes, 172 ± 5.2 for maize, and 470.2 ± 30.9 for green fallow. The results showed that the winter crops - rape, triticale (WT), and rye (WR) - left the most total plant residues in the field with the most C content exceeding 80 g m-2 C in ResidBG and 600 g m-2 C in ResidAG. A significant variation in the amount of plant residues within the species depending on the year, cultivar, fertilisation, and soil properties was found, so for more accurate calculation of C and N inputs, the data set should be enlarged, or average statistical data be used. [ABSTRACT FROM AUTHOR]

Background and Aims Arbuscular mycorrhizal (AM) fungi enhance the uptake of water and minerals by the plant hosts, alleviating plant stress. Therefore, AM fungal–plant interactions are particularly important in drylands and other stressful ecosystems. We aimed to determine the combined and independent effects of above- and below-ground plant community attributes (i.e. diversity and composition), soil heterogeneity and spatial covariates on the spatial structure of the AM fungal communities in a semiarid Mediterranean scrubland. Furthermore, we evaluated how the phylogenetic relatedness of both plants and AM fungi shapes these symbiotic relationships. Methods We characterized the composition and diversity of AM fungal and plant communities in a dry Mediterranean scrubland taxonomically and phylogenetically, using DNA metabarcoding and a spatially explicit sampling design at the plant neighbourhood scale. Key Results The above- and below-ground plant community attributes, soil physicochemical properties and spatial variables explained unique fractions of AM fungal diversity and composition. Mainly, variations in plant composition affected the AM fungal composition and diversity. Our results also showed that particular AM fungal taxa tended to be associated with closely related plant species, suggesting the existence of a phylogenetic signal. Although soil texture, fertility and pH affected AM fungal community assembly, spatial factors had a greater influence on AM fungal community composition and diversity than soil physicochemical properties. Conclusions Our results highlight that the more easily accessible above-ground vegetation is a reliable indicator of the linkages between plant roots and AM fungi. We also emphasize the importance of soil physicochemical properties in addition to below-ground plant information, while accounting for the phylogenetic relationships of both plants and fungi, because these factors improve our ability to predict the relationships between AM fungal and plant communities. [ABSTRACT FROM AUTHOR]

Introduction: Under current global warming, the relationship between season changes of plants and environmental factors is focused on high-elevation and latitude regions. Due to the desynchronized growth of above- and below-ground and the buffering of soil, the driving factors in leaf and root show seasonal dynamics. Methods: We measured above- and below-ground intensity in the alpine steppe over the non-growing season (October-April) and growing season (May-September). Air temperature, precipitation, soil moisture, and soil temperature were used to analyze the correlation based on the growth rhythm. Results: Results showed that an earlier growth in spring and a delayed dormancy in autumn of root than leaf was observed. Our results strongly suggest that soil moisture plays a more important role in leaf unfolding while temperature is consistent with the withering of the shoots. Soil moisture comes from soil melt driving the spring phenology of roots, which derived from the storage of the subsoil layer in the last autumn. Discussion: Climate change will affect the strong seasonal patterns that characterized these precipitation-limited systems, especially in the spring and fall shoulder seasons. As seasonality changes in the alpine steppe, divergent responses of leaf and fine root would be explored. [ABSTRACT FROM AUTHOR]

The recent invention of hybrid breeding technology for potato has led to an increased interest in hybrid potato R&D. Hybrid true potato seeds (TPS) are used to produce planting materials such as transplants and seedling tubers, but can also be used for direct seeding of seed or ware crops. Transplants and seedling tubers can be used to produce seed tubers or ware tubers. The rise in R&D in hybrid breeding creates the need for phenological scales of growth and development of plants produced by the various planting material types of hybrid‐TPS. The BBCH (Biologische Bundesanstalt, Bundessortenamt and CHemical Industry) scale is one of the phenological scales developed for the description of the growth and development stages of plants. In 1993, a BBCH scale with descriptions for potato plants was released. The original BBCH scale gave standardised descriptions for TPS‐ and tuber‐grown plants. Differences in the morphology of plants originating from the different planting materials in terms of types of branches and differences in below‐ground growth and development were not included. Moreover, for reproductive growth stages, crucial for hybrid breeding, the original scale is incomplete as it does not carefully take the complex sympodial branching into account. Methods of describing growth of tubers and berries are complex and impossible to use when final tuber mass or berry size is unknown. The current paper augments the original BBCH scale, while retaining its structure and logic. It provides alternative and comprehensive descriptions of growth stages suitable for potato plants grown from different types of planting materials, and for all end uses of these plants. The proposed scale is detailed enough for research and breeding but still general enough for agricultural use. [ABSTRACT FROM AUTHOR]

Background and Aims Lessons from above-ground trait ecology and resource economics theory may not be directly translatable to below-ground traits due to differences in function, trade-offs and environmental constraints. Here we examine root functional traits within and across species along a fine-scale hydrological gradient. We ask two related questions: (1) What is the relative magnitude of trait variation across the gradient for within- versus among-species variation? (2) Do correlations among below-ground plant traits conform with predictions from resource-economic spectrum theory? Methods We sampled four below-ground fine-root traits (specific root length, branching intensity, root tissue density and root dry matter content) and four above-ground traits (specific leaf area, leaf size, plant height and leaf dry matter content) in vascular plants along a fine-scale hydrological gradient within a wet heathland community in south-eastern Australia. Below-ground and above-ground traits were sampled both within and among species. Key Results Root traits shifted both within and among species across the hydrological gradient. Within- and among-species patterns for root tissue density showed similar declines towards the wetter end of the gradient. Other root traits showed a variety of patterns with respect to within- and among-species variation. Filtering of species has a stronger effect compared with the average within-species shift: the slopes of the relationships between soil moisture and traits were steeper across species than slopes of within species. Between species, below-ground traits were only weakly linked to each other and to above-ground traits, but these weak links did in some cases correspond with predictions from economic theory. Conclusions One of the challenges of research on root traits has been considerable intraspecific variation. Here we show that part of intraspecific root trait variation is structured by a fine-scale hydrological gradient, and that the variation aligns with among-species trends in some cases. Patterns in root tissue density are especially intriguing and may play an important role in species and individual response to moisture conditions. Given the importance of roots in the uptake of resources, and in carbon and nutrient turnover, it is vital that we establish patterns of root trait variation across environmental gradients. [ABSTRACT FROM AUTHOR]

Background and Aims Herbaceous plants can survive periods of prolonged freezing as below-ground structures or seed, which can be insulated from cold air by soil, litter or snow. Below-ground perennial structures vary in both form and their exposure to soil frost, and this structural variation thus may be important in determining the responses of plant communities to frost stress. Methods We conducted a suite of snow removal experiments in a northern temperate old field over 3 years to examine the relative freezing responses of different plant functional groups based on below-ground perennation traits. A litter removal treatment was added in the third year. Species-level percentage cover data were recorded in May, June and September then pooled by functional group. Key Results Snow removal decreased total plant cover, and this response was particularly strong and consistent among years for tap-rooted and rhizomatous species. The snow removal responses of cover for plants with root buds and new recruits from seed varied from positive to negative among years. The cover of rootstock plants consistently increased in response to snow removal. Rhizomatous species were generally the most vulnerable to litter removal. Conclusions This study is the first to explore the effects of variation in frost severity on the responses of different plant perennation trait functional groups. The responses of herbaceous species to frost may become increasingly important in northern temperate regions in the coming decades as a result of declining snow cover and increasing temperature variability. Our results reveal substantial variation in responses among perennation trait functional groups, which could drive changes in species abundance in response to variation in soil frost. [ABSTRACT FROM AUTHOR]

Carbon cycle feedbacks from permafrost ecosystems are expected to accelerate global climate change. Shifts in vegetation productivity and composition in permafrost regions could influence soil organic carbon (SOC) turnover rates via rhizosphere (root zone) priming effects (RPEs), but these processes are not currently accounted for in model predictions. We use a radiocarbon (bomb‐14C) approach to test for RPEs in two Arctic tall shrubs, alder (Alnus viridis (Chaix) DC.) and birch (Betula glandulosa Michx.), and in ericaceous heath tundra vegetation. We compare surface CO2 efflux rates and 14C content between intact vegetation and plots in which below‐ground allocation of recent photosynthate was prevented by trenching and removal of above‐ground biomass. We show, for the first time, that recent photosynthate drives mineralization of older (>50 years old) SOC under birch shrubs and ericaceous heath tundra. By contrast, we find no evidence of RPEs in soils under alder. This is the first direct evidence from permafrost systems that vegetation influences SOC turnover through below‐ground C allocation. The vulnerability of SOC to decomposition in permafrost systems may therefore be directly linked to vegetation change, such that expansion of birch shrubs across the Arctic could increase decomposition of older SOC. Our results suggest that carbon cycle models that do not include RPEs risk underestimating the carbon cycle feedbacks associated with changing conditions in tundra regions. [ABSTRACT FROM AUTHOR]

Fine roots and above‐ground litterfall play a pivotal role in carbon dynamics in forests. Nonetheless, direct estimation of stocks of fine roots remains methodologically challenging. Models are thus widely used to estimate these stocks and help elucidate drivers of fine root growth and turnover, at a range of scales.We updated a database of fine root biomass, necromass and production derived from 454 plots across European forests. We then compared fine root biomass and production to estimates obtained from 19 different models. Typical input variables used for the models included climate, net primary production, foliage and above‐ground biomass, leaf area index (LAI), latitude and/or land cover type. We tested whether performance could be improved by fitting new multiple regression models, and explored effects of species composition and sampling method on estimated fine root biomass.Average fine root biomass was 332 g/m2, and necromass 379 g/m2, for European forests where the average fine root production was 250 g m−2 year−1. Carbon fraction in fine roots averaged 48.4%, and was 1.5% greater in broadleaved species than conifers.Available models were poor predictors of fine root biomass and production. The best performing models assumed proportionality between above‐ and below‐ground compartments, and used remotely sensed LAI or foliage biomass as key inputs. Model performance was improved by use of multiple regressions, which revealed consistently greater biomass and production in stands dominated by broadleaved species as well as in mixed stands even after accounting for climatic differences.Synthesis. We assessed the potential of existing models to estimate fine root biomass and production in European forests. We show that recalibration reduces by about 40% errors in estimates currently produced by the best available models, and increases three‐fold explained variation. Our results underline the quantitative significance of fine roots (live and dead) to the global carbon cycle. [ABSTRACT FROM AUTHOR]

In this study, we explore how a hurricane disturbance influenced carbon allocation for the production of new fine roots. Before and after a hurricane, we measured the age of carbon (time since fixation from the atmosphere) in fine root structural tissues using natural abundance radiocarbon (14C) measured by accelerator mass spectrometry. Roots were sampled from five seasonally dry tropical forests ranging in age from 6 yr to a mature forest. Structural carbon in combined live + dead roots picked from soil cores sampled 1 month before the hurricane had mean ages ranging from 4 to 11 yr, whereas live roots alone had ages of 1-2 yr. Structural carbon in new live fine roots produced over a period lasting from 3 wk before the hurricane to 2 months after the event had mean ages of between 2 and 10 yr. Contrary to expectations, our results showed that plants allocate long-lived storage carbon pools to the production of new fine roots after canopy defoliation and root mortality. The age of the carbon allocated for new roots increased with forest age and forest above-ground biomass, suggesting an adaptation of plants to survive and recover from severe disturbances.

Many benefits of cover crops such as prevention of nitrate leaching, erosion reduction, soil organic carbon enhancement and improvement of soil structure are associated with roots. However, including root characteristics as a criterion for cover crop selection requires more knowledge on their root growth dynamics. Seven cover crop species (crimson clover, winter rye, bristle oats, blue lupin, oil radish, winter turnip rape and phacelia) were grown in a two-year organically managed field experiment in Germany to screen them for root intensity and vertical root distribution. Root length density (RLD) and proportion of root length in large-sized biopores were determined before and after winter with the profile wall method. RLD and cumulative root length were analysed using a three-parameter logistic function, and a logistic dose-response function, respectively. Fibrous rooted winter rye and crimson clover showed high RLD in topsoil and had a shallow cumulative root distribution. Their RLD increased further during winter in topsoil and subsoil. The crops with the highest RLD in the subsoil were taprooted oil radish, winter turnip rape and phacelia. Bristle oat had intermediate features. Blue lupin had low RLD in topsoil and subsoil. Phacelia, oil radish, winter turnip rape and bristle oat showed the highest share of root length in biopores. These complementary root characteristics suggest that combining cover crops of different root types in intercropping may be used to enhance overall RLD for maximizing cover crop benefits.

Question Below-ground processes are key determinants of above-ground plant population and community dynamics. Still, our understanding of how environmental drivers shape plant communities is mostly based on above-ground diversity patterns, bypassing below-ground plant diversity stored in seed banks. As seed banks may shape above-ground plant communities, we question whether concurrently analysing the above- and below-ground species assemblages may potentially enhance our understanding of community responses to environmental variation. Location Temperate deciduous forests along a 2000 km latitudinal gradient in NW Europe. Methods Herb layer, seed bank and local environmental data including soil pH, canopy cover, forest cover continuity and time since last canopy disturbance were collected in 129 temperate deciduous forest plots. We quantified herb layer and seed bank diversity per plot and evaluated how environmental variation structured community diversity in the herb layer, seed bank and the combined herb layer-seed bank community. Results Seed banks consistently held more plant species than the herb layer. How local plot diversity was partitioned across the herb layer and seed bank was mediated by environmental variation in drivers serving as proxies of light availability. The herb layer and seed bank contained an ever smaller and ever larger share of local diversity, respectively, as both canopy cover and time since last canopy disturbance decreased. Species richness and β-diversity of the combined herb layer-seed bank community responded distinctly differently compared to the separate assemblages in response to environmental variation in, e.g. forest cover continuity and canopy cover. Conclusions The seed bank is a below-ground diversity reservoir of the herbaceous forest community, which interacts with the herb layer, although constrained by environmental variation in e.g. light availability. The herb layer and seed bank co-exist as a single community by means of the so-called storage effect, resulting in distinct responses to environmental variation not necessarily recorded in the individual herb layer or seed bank assemblages. Thus, concurrently analysing above- and below-ground diversity will improve our ecological understanding of how understorey plant communities respond to environmental variation. [ABSTRACT FROM AUTHOR]

There is compelling evidence from experiments and observations that climate warming prolongs the growing season in arctic regions. Until now, the start, peak, and end of the growing season, which are used to model influences of vegetation on biogeochemical cycles, were commonly quantified using above-ground phenological data. Yet, over 80% of the plant biomass in arctic regions can be below ground, and the timing of root growth affects biogeochemical processes by influencing plant water and nutrient uptake, soil carbon input and microbial activity., We measured timing of above- and below-ground production in three plant communities along an arctic elevation gradient over two growing seasons., Below-ground production peaked later in the season and was more temporally uniform than above-ground production. Most importantly, the growing season continued c. 50% longer below than above ground., Our results strongly suggest that traditional above-ground estimates of phenology in arctic regions, including remotely sensed information, are not as complete a representation of whole-plant production intensity or duration, as studies that include root phenology. We therefore argue for explicit consideration of root phenology in studies of carbon and nutrient cycling, in terrestrial biosphere models, and scenarios of how arctic ecosystems will respond to climate warming. [ABSTRACT FROM AUTHOR]

Introduction: Under current global warming, the relationship between season changes of plants and environmental factors is focused on high-elevation and latitude regions. Due to the desynchronized growth of above- and below-ground and the buffering of soil, the driving factors in leaf and root show seasonal dynamics., Methods: We measured above- and below-ground intensity in the alpine steppe over the non-growing season (October-April) and growing season (May-September). Air temperature, precipitation, soil moisture, and soil temperature were used to analyze the correlation based on the growth rhythm., Results: Results showed that an earlier growth in spring and a delayed dormancy in autumn of root than leaf was observed. Our results strongly suggest that soil moisture plays a more important role in leaf unfolding while temperature is consistent with the withering of the shoots. Soil moisture comes from soil melt driving the spring phenology of roots, which derived from the storage of the subsoil layer in the last autumn., Discussion: Climate change will affect the strong seasonal patterns that characterized these precipitation-limited systems, especially in the spring and fall shoulder seasons. As seasonality changes in the alpine steppe, divergent responses of leaf and fine root would be explored., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Qin, Nie, Wang, Hong and Yan.)

Aim Climate change, especially the wider occurrence of extreme events, is likely to increase the intensity and frequency of insect/pathogen outbreaks (referred to as biotic disturbance), which may considerably affect plant ecophysiological traits and thus the ecosystem carbon ( C) cycle. Little is known, however, about the ways in which biotic disturbance quantitatively affects ecosystem C processes, especially those that occur below ground. We reveal the general patterns of below-ground C responses to biotic disturbance from field manipulative experiments and opportunistic events. Location Global. Method We carried out a meta-analysis examining the effects of biotic disturbance on 16 variables associated with below-ground C processes, based on 64 experimental studies. Results Biotic disturbance significantly decreased below-ground C pools with relatively long residence times (e.g. root biomass and soil organic carbon, SOC), but increased labile C pools (e.g. microbial biomass carbon, MBC; dissolved organic carbon, DOC), soil respiration ( Rs) and its components, and microbial population sizes. Compared with the neutral or positive effects of other environmental changes on below-ground C pools and fluxes, biotic disturbance had a negative effect on plant biomass and SOC but a larger positive effect on MBC, DOC and Rs. Main conclusions Biotic disturbance can have stronger impacts on below-ground C processes than other environmental changes, and the sensitive responses of soil labile C pools and C fluxes to biotic disturbance decrease long-term below-ground C sequestration. More research efforts are, however, needed to reduce the uncertainties in quantifying the effects of biotic disturbance and to improve forecasting of the feedback between the carbon cycle and climate. [ABSTRACT FROM AUTHOR]

Ectomycorrhizal symbiosis is omnipresent in boreal forests, where it is assumed to benefit plant growth. However, experiments show inconsistent benefits for plants and volatility of individual partnerships, which calls for a re-evaluation of the presumed role of this symbiosis., We reconcile these inconsistencies by developing a model that demonstrates how mycorrhizal networking and market mechanisms shape the strategies of individual plants and fungi to promote symbiotic stability at the ecosystem level., The model predicts that plants switch abruptly from a mixed strategy with both mycorrhizal and nonmycorrhizal roots to a purely mycorrhizal strategy as soil nitrogen availability declines, in agreement with the frequency distribution of ectomycorrhizal colonization intensity across a wide-ranging data set. In line with observations in field-scale isotope labeling experiments, the model explains why ectomycorrhizal symbiosis does not alleviate plant nitrogen limitation. Instead, market mechanisms may generate self-stabilization of the mycorrhizal strategy via nitrogen depletion feedback, even if plant growth is ultimately reduced., We suggest that this feedback mechanism maintains the strong nitrogen limitation ubiquitous in boreal forests. The mechanism may also have the capacity to eliminate or even reverse the expected positive effect of rising CO2 on tree growth in strongly nitrogen-limited boreal forests. [ABSTRACT FROM AUTHOR]

We review the effects of root and shoot competition on plant biomass by meta-analysis of 38 published studies, each reporting on the factorial effects of root-competition and shoot-competition on herbaceous plants., There were significant differences in the overall effects of root, shoot and full competition. Root competition generally resulted in larger biomass reduction than shoot competition, particularly among the smaller of the two competitors. An interaction between root and shoot competition was observed in some experiments but was generally not significant., While root competition was generally stronger than shoot competition at lower nutrient levels, there was no overall difference at higher nutrient levels due to much lower levels of root competition. In contrast, the overall effect of full competition increased considerably with nutrient level., Root competition was generally more important when the neighbour was a grass as compared with a herb or a legume, and when domesticated plants competed with wild neighbours, suggesting that wild genotypes are stronger competitors for below-ground resources than are crop plants., Effects of competition were generally stronger in experiments with additive designs than in those with substitutive designs. Also, experiments using single target individuals showed stronger effects of competition, root competition in particular, than did experiments using groups targets., Synthesis. Despite large variation among experiments, some general patterns were supported: effects of root competition are generally stronger than shoot competition, particularly (i) for smaller competitors, (ii) at low fertility levels, (iii) when the competitor is a grass rather than an herb, (iv) when the competitor is a wild rather than a domesticated species, and (v) in additive design experiments. The effects of root and shoot competition appear to be additive under many conditions. Whereas root competition may often be the primary limitation on mean plant performance, shoot competition will influence the variation around this mean and may determine which individuals or species dominate. [ABSTRACT FROM AUTHOR]

Terrestrial food webs are woven from complex interactions, often underpinned by plant-mediated interactions between herbivores and higher trophic groups. Below- and above-ground herbivores can influence one another via induced changes to a shared host plant, potentially shaping the wider community. However, empirical evidence linking laboratory observations to natural field populations has so far been elusive., This study investigated how root-feeding weevils ( Otiorhynchus sulcatus) influence different feeding guilds of herbivore (phloem-feeding aphids, Cryptomyzus galeopsidis, and leaf-chewing sawflies, Nematus olfaciens) in both controlled and field conditions., We hypothesized that root herbivore-induced changes in plant nutrients (C, N, P and amino acids) and defensive compounds (phenolics) would underpin the interactions between root and foliar herbivores, and ultimately populations of natural enemies of the foliar herbivores in the field., Weevils increased field populations of aphids by ca. 700%, which was followed by an increase in the abundance of aphid natural enemies. Weevils increased the proportion of foliar essential amino acids, and this change was positively correlated with aphid abundance, which increased by 90% on plants with weevils in controlled experiments., In contrast, sawfly populations were 77% smaller during mid-June and adult emergence delayed by >14 days on plants with weevils. In controlled experiments, weevils impaired sawfly growth by 18%, which correlated with 35% reductions in leaf phosphorus caused by root herbivory, a previously unreported mechanism for above-ground-below-ground herbivore interactions., This represents a clear demonstration of root herbivores affecting foliar herbivore community composition and natural enemy abundance in the field via two distinct plant-mediated nutritional mechanisms. Aphid populations, in particular, were initially driven by bottom-up effects (i.e. plant-mediated effects of root herbivory), but consequent increases in natural enemies triggered top-down regulation. [ABSTRACT FROM AUTHOR]

1. Primary production and decomposition, two fundamental processes determining the functioning of ecosystems, may be sensitive to changes in biodiversity and food web interactions. 2. The impacts of food web interactions on ecosystem functioning are generally quantified by experimentally decoupling these linked processes and examining either primary production-based (green) or decomposition-based (brown) food webs in isolation. This decoupling may strongly limit our ability to assess the importance of food web interactions on ecosystem processes. 3. To evaluate how consumer trophic diversity mediates predator effects on ecosystem functioning, we conducted a mesocosm experiment and a field study using an assemblage of invertebrates that naturally co-occur on North Atlantic coastal saltmarshes. We measured the indirect impact of predation on primary production and leaf decomposition as a result of prey communities composed of herbivores alone, detritivores alone or both prey in combination. 4. We find that primary consumers can influence ecosystem process rates not only within, but also across green and brown sub-webs. Moreover, by feeding on a functionally diverse consumer assemblage comprised of both herbivores and detritivores, generalist predators can diffuse consumer effects on decomposition, primary production and feedbacks between the two processes. 5. These results indicate that maintaining functional diversity among primary consumers can alter the consequences of traditional trophic cascades, and they emphasize the role of the detritus-based sub-web when seeking key biotic drivers of plant production. Clearly, traditional compartmentalization of empirical food webs can limit our ability to predict the influence of food web interactions on ecosystem functioning. [ABSTRACT FROM AUTHOR]

Question Does the below-ground bud bank mediate response to drought in restored grasslands? Location Platte River Valley region of south-central Nebraska, USA. Methods We imposed severe drought for one growing season using rainfall manipulation structures and measured the response of above- and below-ground plant communities (ramet and below-ground bud densities) with respect to non-drought controls during the drought year and a recovery year. Results Drought reduced below-ground bud bank density and above-ground stem density. However, bud bank density recovered, and bud production was higher on previously droughted subplots relative to controls in the year following drought. The response of below-ground bud and above-ground stem density to drought differed according to functional identity ( C3 grass, C4 grass, and forb), with forbs least resistant to, but having the greatest recovery from, drought. Conclusions While overall density in restored grasslands was resilient, drought effects on below-ground bud banks may have longer-term impacts on plant community structure. Reduced density above- or below-ground during the growing season following drought may allow for the persistence of species relatively more reliant on recruitment from seed banks in favourable micro-sites. [ABSTRACT FROM AUTHOR]

Studying the effects of climate or weather extremes such as drought and heat waves on biodiversity and ecosystem functions is one of the most important facets of climate change research. In particular, primary production is amounting to the common currency in field experiments world-wide. Rarely, however, are multiple ecosystem functions measured in a single study in order to address general patterns across different categories of responses and to analyse effects of climate extremes on various ecosystem functions. We set up a long-term field experiment, where we applied recurrent severe drought events annually for five consecutive years to constructed grassland communities in central Europe. The 32 response parameters studied were closely related to ecosystem functions such as primary production, nutrient cycling, carbon fixation, water regulation and community stability. Surprisingly, in the face of severe drought, above- and below-ground primary production of plants remained stable across all years of the drought manipulation. Yet, severe drought significantly reduced below-ground performance of microbes in soil indicated by reduced soil respiration, microbial biomass and cellulose decomposition rates as well as mycorrhization rates. Furthermore, drought reduced leaf water potential, leaf gas exchange and leaf protein content, while increasing maximum uptake capacity, leaf carbon isotope signature and leaf carbohydrate content. With regard to community stability, drought induced complementary plant-plant interactions and shifts in flower phenology, and decreased invasibility of plant communities and primary consumer abundance. Synthesis. Our results provide the first field-based experimental evidence that climate extremes initiate plant physiological processes, which may serve to regulate ecosystem productivity. A potential reason for different dynamics in various ecosystem services facing extreme climatic events may lie in the temporal hierarchy of patterns of fast versus slow response. Such data on multiple response parameters within climate change experiments foster the understanding of mechanisms of resilience, of synergisms or decoupling of biogeochemical processes, and of fundamental response dynamics to drought at the ecosystem level including potential tipping points and thresholds of regime shift. Future work is needed to elucidate the role of biodiversity and of biotic interactions in modulating ecosystem response to climate extremes. [ABSTRACT FROM AUTHOR]

Upon facing biotic stresses, plants orchestrate defence mechanisms via internal and external mechanisms that are mediated by signalling molecules such as salicylic acid, jasmonic acid, ethylene and various other volatile compounds. Although pathogen- and chemical-induced plant resistance has been studied extensively within the same plant compartment, the effects of above-ground (AG) insect-elicited plant defence on the resistance expression in roots and the below-ground (BG) microbial community are not well understood. We assessed the effect of AG whitefly ( Bemisia tabaci) attack on the elicitation of induced resistance against a leaf pathogen, Xanthomonas axonopodis pv. vesicatoria, a soil-borne pathogen, Ralstonia solanacearum, and on BG modifications of the rhizosphere microflora in peppers ( Capsicum annuum). Symptom development caused by the two bacterial pathogens on leaves and roots was significantly reduced in whitefly-exposed plants as compared to controls. A combined treatment with benzothiadiazole (BTH) and whitefly caused an additive effect on induced resistance, indicating that whitefly-induced plant defence can utilize salicylic acid (SA)-dependent signalling. To obtain further genetic evidence of this phenomenon, we evaluated the gene expression of Capsicum annuum pathogenesis-related protein ( CaPR) 1, CaPR4, CaPR10 and Ca protease inhibitor II, and observed increased expression after BTH and/or whitefly treatment indicating that AG whitefly infestation elicited SA and jasmonic acid signalling in AG and BG. Since the expression pattern of PR genes in the roots differed, we assessed microbial diversity in plants treated with BTH and/or whitefly. In addition to eliciting BG defence responses, a whitefly infestation of the leaves augmented the population of root-associated Gram-positive bacteria and fungi, which may have positively affected plant growth and induced systemic resistance. Whitefly feeding reduced plant size, which usually occurs as a consequence of the high costs of direct resistance induction. Synthesis. Our results demonstrate that whitefly-induced resistance against bacterial pathogens can cross the AG-BG border and may cause further indirect benefits on future plant development, because it can positively affect the association or plant roots with putatively beneficial microorganisms. [ABSTRACT FROM AUTHOR]

Grazing can modify vegetation structure and species composition through selective consumption, modifying plant litter quality and hence decomposability. In most grasslands, moderate stocking rates maintain a mosaic of high-quality patches, preferentially used by herbivores ('grazing lawns'), and low-quality tall patches, which are avoided. In grazing lawns decomposition rates can be accelerated because of the higher litter quality of its component species and, besides, through the indirect effect of increased nutrient availability in soil. We aimed at testing this indirect effect using standard materials, comparing their decomposition in grazing lawns, open and closed tall tussock grasslands. We selected 10 patches of each type and sampled floristic composition, soil variables and cattle dung deposition. Standard materials were filter paper and Poa stuckertii litter. We prepared litterbags of 0.3 mm (thin mesh) and 1 mm mesh size (coarse mesh). Samples were incubated for 65 days in two ways: above-ground (thin and coarse mesh) and below-ground (only thin mesh), aiming at analysing the conditions for decomposition for surface litter and buried litter or dead roots, respectively. Physical and chemical soil variables did not differ among patch types, despite the differences in species composition. Closed tussock grasslands showed the lowest dung deposition, confirming the less intense use of these patches. Soil nitrogen availability (N-NO and N-NH) was not significantly different among patch types. Each standard material followed a different decomposition pattern across patch types. For above-ground incubated samples, Poa litter decomposed significantly faster in lawns, and slower in open tussock grasslands. Filter paper decomposed significantly faster in closed tussock grasslands than in the other two patch types. Decomposition of below-ground incubated samples did not significantly differ among patch types, in line with results for soil variables. Above-ground differences in decomposition may be associated with differences in microclimatic conditions resulting from differences in vegetation structure. [ABSTRACT FROM AUTHOR]

1. Plant facilitation has been studied mostly in the context of plant–plant interactions, whereas multitrophic interactions including those that occur below ground have not yet received much attention. Here, I will discuss how above-ground and below-ground natural enemies and their predators influence plant facilitation and its evolution. 2. Specific above-ground and below-ground plant enemies and their predators play a major role in structuring the composition and dynamics of plant communities. In successional sequences, above-ground and below-ground multitrophic level interactions may tip the balance from competitive to facilitative states and vice versa. 3. Little is known about how above-ground and below-ground multitrophic interactions develop along resource or stress gradients and how the outcomes of above-ground–below-ground interactions depend on variations in these environmental conditions. 4. Facilitated plants need to fit into the above-ground–below-ground multitrophic communities of their facilitators. 5. Little is known also about the evolution of plant facilitation. The observed distance in phylogeny between facilitators and facilitated plants suggests that host-specific enemies may very well co-determine which species become facilitated by which facilitators. 6. Further, very little attention has been given to how plant strategies (allelopathy, accumulation of enemies, monopolization of symbionts) may be the result of selection against being facilitative. 7. Synthesis. Plant facilitation cannot be understood without considering a plant’s natural enemies and also its enemies’ enemies. Plant enemies can turn competitive interactions into facilitative interactions, whereas the enemies’ enemies can turn facilitation back into competition. Below-ground interactions will have longer-lasting effects on facilitation than those above ground, because many organisms can persist in the soil, even when the host plants have disappeared. [ABSTRACT FROM AUTHOR]

Biodiversity effects on ecosystem functioning in forests have only recently attracted increasing attention. The vast majority of studies in forests have focused on above-ground responses to differences in tree species diversity, while systematic analyses of the effects of biodiversity on root systems are virtually non-existent. By investigating the fine root systems in 12 temperate deciduous forest stands in Central Europe, we tested the hypotheses that (1) stand fine root biomass increases with tree diversity, and (2) ‘below-ground overyielding’ of species-rich stands in terms of fine root biomass is the consequence of spatial niche segregation of the roots of different species. The selected stands represent a gradient in tree species diversity on similar bedrock from almost pure beech forests to medium-diverse forests built by beech, ash, and lime, and highly-diverse stands dominated by beech, ash, lime, maple, and hornbeam. We investigated fine root biomass and necromass at 24 profiles per stand and analyzed species differences in fine root morphology by microscopic analysis. Fine root biomass ranged from 440 to 480 g m−2 in the species-poor to species-rich stands, with 63–77% being concentrated in the upper 20 cm of the soil. In contradiction to our two hypotheses, the differences in tree species diversity affected neither stand fine root biomass nor vertical root distribution patterns. Fine root morphology showed marked distinctions between species, but these root morphological differences did not lead to significant differences in fine root surface area or root tip number on a stand area basis. Moreover, differences in species composition of the stands did not alter fine root morphology of the species. We conclude that ‘below-ground overyielding’ in terms of fine root biomass does not occur in the species-rich stands, which is most likely caused by the absence of significant spatial segregation of the root systems of these late-successional species. [ABSTRACT FROM AUTHOR]

1 Light is thought to be the most limiting resource in tropical forests, and thus above-ground competition is commonly accepted as the mechanism that structures these communities. In many tropical forests, trees compete not only with other trees, but also with lianas, which compete aggressively for below-ground resources and thus may limit tree growth and regeneration. 2 Using a replicated experiment, we tested the relative strengths of above- and below-ground competition from lianas on tree saplings in a disturbed forest in Côte d’Ivoire with a heterogeneous canopy and relatively high light penetration. We planted seedlings of three tree species and subjected them to below-ground competition with lianas (BGC), above- and below-ground competition with lianas (ABGC), or a liana-free control treatment. After 2 years, we harvested the saplings and compared the amount of above-ground biomass and its relative allocation among the three experimental treatments and different tree species. 3 Lianas competed intensely with saplings in this tropical forest, substantially limiting sapling growth. Saplings grown in the ABGC and BGC treatments had only 18.5% and 16.8% of the above-ground dry biomass of those grown in the liana-free control treatment. 4 Sapling biomass did not differ significantly among the ABGC and BGC treatments, suggesting that below-ground competition was the driving force behind liana vs. tree competition in this forest. Above-ground competition with lianas, however, did affect the allocation of biomass in saplings, resulting in shorter, thicker stems and a poorly developed crown. 5 Collectively, our findings suggest that below-ground competition with lianas plays a substantial role in limiting the growth of saplings in disturbed and secondary tropical forests, and above-ground effects may be due to a combination of above-ground competition and mechanical stress. 6 Disentangling above- and below-ground competition between lianas and trees is critical for a comprehensive understanding of the dynamics of naturally regenerating tropical forests, as well as formulating successful management plans for sustainable timber harvest. [ABSTRACT FROM AUTHOR]

Question: Is it possible to determine the species composition of root samples containing multiple species. without first disentangling individual roots? Methods: The internal transcribed spacer (ITS) region of nuclear ribosomal DNA was amplified and sequenced from four California annual grassland species (two Poaceae and two Asteraceae). Restriction enzymes that cut the ITS region of each species into uniquely sized fragments were identified based on DNA sequence variation of the ITS regions. Mixed root samples were analysed to test the ability of the method to identify the presence or absence of each species in multi-species samples. Results: The technique successfully identified species present in multi-species samples. ITS regions were shorter in Poaceae than in Asteraceae. so size differences alone were sufficient to distinguish these taxonomic groups. At the species level. digestion of ITS regions with the appropriate restriction enzymes yielded at least one uniquely sized fragment for each species. Conclusions: This method is the first to identify the species composition of mixed root samples. It should he applicable to most plant species because the ITS region is flanked by universal primers and most species have unique ITS sequences. The ability to determine species-specific rooting distributions has broad applications in vegetation science. [ABSTRACT FROM AUTHOR]

We estimated the below-ground net plant productivity (BNPP) of different biomass components in an intensively and continuously 45-ha grazed site and in a neighbouring exclosure ungrazed for 16 years for a natural mountain grassland in central Argentina. We measured approximately twice as much dead below-ground biomass in the grazed site as in the ungrazed site, with a strong concentration of total below-ground biomass towards the upper 10 cm of the soil layer in both sites. The main contribution to total live biomass was accounted for by very fine (<0.5 mm) and fine roots (0.5–1.0 mm) both at the grazed (79%) and at the ungrazed (81%) sites. We measured more dead biomass for almost all root components, more live biomass of rhizomes, tap roots and bulbs, and less live biomass of thicker roots (>1 mm) in the grazed site. The seasonal variation of total live below-ground biomass mainly reflected climate, with the growing season being limited to the warmer and wetter portion of the year, but such variation was higher in the grazed site. Using different methods of estimation of BNPP, we estimated maximum values of 1241 and 723 g m−2 year−1 for the grazed and ungrazed sites, respectively. We estimated that very fine root productivity was almost twice as high at the grazed site as at the ungrazed one, despite the fact that both sites had similar total live biomass, and root turnover rate was twofold at the grazed site. [ABSTRACT FROM AUTHOR]

Fine roots and their turnover represent a dynamic aspect of below-ground biomass (BGB) and nutrient capital in forest ecosystems, and account for a significant fraction of net primary productivity (NPP) (Cuevas 1995, Vogt et al. 1990). On a weight basis, coarse roots contribute more to total ecosystem biomass than fine roots, but they account for only a small portion of annual root production (Eamus et al. 2002). Despite the fact that fine roots may compose less than 2% of total ecosystem biomass, they may contribute up to 40% of total ecosystem production (Vogt et al. 1990). Therefore, estimates of root production, like estimates of root biomass, should differentiate between coarse- and fine-root production. [ABSTRACT FROM PUBLISHER]

Twelve salt marshes in south Louisiana (USA) were classified as either ‘impaired’ or ‘healthy’ before a summer sample collection of above- and below-ground biomass and determination of sediment accretion rates. The above-ground biomass of plant tissues was the same at both impaired and healthy salt marshes and was not a good predictor of marsh health. However, below-ground root biomass in the upper 30 cm was much lower in the impaired marshes compared to the healthy marshes. Compromises to root production apparently occur before there is an obvious consequence to the above-ground biomass, which may quickly collapse before remedial action can be taken. The subsequent change in vertical position of the marsh surface may be equivalent to many years of accretion, and be irreversible within decades without considerable effort. These results are consistent with the hypothesis that it is the plant's below-ground accumulation of organic matter, not inorganic matter that governs the maintenance of salt marsh ecosystem in the vertical plane. Reversing the precursor conditions leading to marsh stress before the collapse of the above-ground biomass occurs is therefore a prudent management objective and could be easier than restoration. [ABSTRACT FROM AUTHOR]

Abstract Understanding how exogenous and endogenous factors control the distribution, production and mortality of fine roots is fundamental to assessing the implications of global change, yet our knowledge of control over fine root dynamics remains rudimentary. To improve understanding of these processes, the present study developed regression relationships between environmental variables and fine root dynamics within a northern hardwood forest in New Hampshire, USA, which was experimentally manipulated with a snow removal treatment. Fine roots (< 1 mm diameter) were observed using minirhizotrons for 2 years in sugar maple and yellow birch stands and analyzed in relation to temperature, water and nutrient availability. Fine root dynamics at this site fluctuated seasonally, with growth and mortality peaking during warmer months. Monthly fine root production was strongly associated with mean monthly air temperature and neither soil moisture nor nutrient availability added additional predictive power to this relationship. This relationship exhibited a seasonal temperature hysteresis, which was altered by snow removal treatment. These results suggest that both exogenous and endogenous cues may be important in controlling fine root growth in this system. Proportional fine root mortality was directly associated with mean monthly soil temperature, and proportional fine root mortality during the over-winter interval was strongly related to whether the soil froze. The strong relationship between fine root production and air temperature reported herein contrasts with findings from some hardwood forest sites and indicates that controls on fine root dynamics vary geographically. Future research must more clearly distinguish between endogenous and exogenous control over fine root dynamics in various ecosystems. [ABSTRACT FROM AUTHOR]