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Plants respond to resource stress by changing multiple aspects of their biomass allocation, morphology, physiology and architecture. To date, we lack an integrated view of the relative importance of these plastic responses in alleviating resource stress and of the consistency/variability of these responses among species. We subjected nine species (legumes, forbs and graminoids) to nitrogen and/or light shortages and measured 11 above-ground and below-ground trait adjustments critical in the alleviation of these stresses (plus several underlying traits). Nine traits out of 11 showed adjustments that improved plants’ potential capacity to acquire the limiting resource at a given time. Above ground, aspects of plasticity in allocation, morphology, physiology and architecture all appeared important in improving light capture, whereas below ground, plasticity in allocation and physiology were most critical to improving nitrogen acquisition. Six traits out of 11 showed substantial heterogeneity in species plasticity, with little structuration of these differences within trait covariation syndromes. Such comprehensive assessment of the complex nature of phenotypic responses of plants to multiple stress factors, and the comparison of plant responses across multiple species, makes a clear case for the high (but largely overlooked) diversity of potential plastic responses of plants, and for the need to explore the potential rules structuring them.

Aboveground biomass (AGB) and belowground biomass (BGB) allocation and productivity–richness relationship are controversial. Here, we assessed AGB and BGB allocation and the productivity–richness relationship at community level across four grassland types based on the biomass data collected from 80 sites across the Qinghai Plateau during 2011–2012. The reduced major axis regression and general linear models were used and showed that (a) the median values of AGB were significantly higher in alpine meadow than in other three grassland types; the ratio of root to shoot (R/S) was significantly higher in desert grassland (36.06) than intemperate grassland (16.60), alpine meadow (13.35), and meadow steppe (19.46). The temperate grassland had deeper root distribution than the other three grasslands, with about 91.45% roots distributed in the top 30 cm soil layer. (b) The slopes between log AGB and log BGB in the temperate grassland and meadow steppe were 1.09 and 1, respectively, whereas that in the desert grassland was 1.12, which was significantly different from the isometric allocation relationship. A competitive relationship between AGB and BGB was observed in the alpine meadow with a slope of −1.83, indicating a trade‐off between AGB and BGB in the alpine meadow. (c) A positive productivity–richness relationship existed across the four grassland types, suggesting that the positive productivity–richness relationship might not be affected by the environmental factors at the plant location. Our results provide a new insight for biomass allocation and biodiversity–ecosystem functioning research. The median values of aboveground biomass (AGB) were significantly higher in alpine meadow than in other three grassland types. The temperate grassland had deeper root distribution than the other three grasslands, with about 91.45% roots distributed in the top 30 cm soil layer. A positive productivity–richness relationship existed across the four grassland types.

A rapidly growing population demands greater access to food, feed, and shelter, thereby increasing the strain on natural resources. Human activities, such as converting forests into arable land and increasing CO2 emissions, intensify atmospheric CO2 concentrations. Following a significant increase in atmospheric carbon levels, global temperatures have surged, resulting in frequent droughts worldwide. Drought, a protracted episode of unusually low rainfall, has detrimental effects on ecosystems in dry zones. Reduced growth, altered phenology, and higher tree mortality are the results of physiological and ecological changes. This review focuses on shifts in biomass allocation between aboveground (leaves and stems) and belowground (roots) components. It assesses how these drought-induced changes affect overall tree growth, carbon storage capacity, and long-term resilience. This review aims to identify patterns and knowledge gaps to understand how arid zone forests respond to and influence the global carbon cycle under increasing drought conditions in the future.

• Decades of atmospheric nitrogen (N) deposition in the northeastern USA have enhanced this globally important forest carbon (C) sink by relieving N limitation. While many N fertilization experiments found increased forest C storage, the mechanisms driving this response at the ecosystem scale remain uncertain. • Following the optimal allocation theory, augmented N availability may reduce belowground C investment by trees to roots and soil symbionts. To test this prediction and its implications on soil biogeochemistry, we constructed C and N budgets for a long-term, whole-watershed N fertilization study at the Fernow Experimental Forest, WV, USA. • Nitrogen fertilization increased C storage by shifting C partitioning away from belowground components and towards aboveground woody biomass production. Fertilization also reduced the C cost of N acquisition, allowing for greater C sequestration in vegetation. Despite equal fine litter inputs, the C and N stocks and C : N ratio of the upper mineral soil were greater in the fertilized watershed, likely due to reduced decomposition of plant litter. • By combining aboveground and belowground data at the watershed scale, this study demonstrates how plant C allocation responses to N additions may result in greater C storage in both vegetation and soil.

Drought is one of the abiotic stresses controlling plant function and ecological stability. In the context of climate change, drought is predicted to occur more frequently in the future. Despite numerous attempts to clarify the overall effects of drought stress on the growth and physiological processes of plants, a comprehensive evaluation on the impacts of drought stress on biomass allocation, especially on reproductive tissues, remains elusive. We conducted a meta‐analysis by synthesizing 164 published studies to elucidate patterns of plant biomass allocation in relation to drought stress. Results showed that drought significantly increased the fraction of root mass but decreased that of stem, leaf, and reproductive mass. Roots of herbaceous plants were more sensitive to drought than woody plants that reduced reproductive allocation more sharply than the former. Relative to herbaceous plants, drought had a more negative impact on leaf mass fraction of woody plants. Among the herbaceous plants, roots of annuals responded to drought stress more strongly than perennial herbs, but their reproductive allocation was less sensitive to drought than the perennial herbs. In addition, cultivated and wild plants seemed to respond to drought stress in a similar way. Drought stress did not change the scaling exponents of the allometric relationship between different plant tissues. These findings suggest that the allometric partitioning theory, rather than the optimal partitioning theory, better explains the drought‐induced changes in biomass allocation strategies. Drought significantly increased the fraction of root mass but decreased the mass fractions of stem, leaf, and reproductive parts. Roots of herbaceous plants are more sensitive to drought than woody plants that reduced reproductive allocation more sharply than the former. Drought stress did not alter the scaling exponents of the allometric relationship between different plant tissues.

We compiled a global database for leaf, stem and root biomass representing c. 11 000 records for c. 1200 herbaceous and woody species grown under either controlled or field conditions. We used this data set to analyse allometric relationships and fractional biomass distribution to leaves, stems and roots. We tested whether allometric scaling exponents are generally constant across plant sizes as predicted by metabolic scaling theory, or whether instead they change dynamically with plant size. We also quantified interspecific variation in biomass distribution among plant families and functional groups. Across all species combined, leaf vs stem and leaf vs root scaling exponents decreased from c. 1.00 for small plants to c. 0.60 for the largest trees considered. Evergreens had substantially higher leaf mass fractions (LMFs) than deciduous species, whereas graminoids maintained higher root mass fractions (RMFs) than eudicotyledonous herbs. These patterns do not support the hypothesis of fixed allometric exponents. Rather, continuous shifts in allometric exponents with plant size during ontogeny and evolution are the norm. Across seed plants, variation in biomass distribution among species is related more to function than phylogeny. We propose that the higher LMF of evergreens at least partly compensates for their relatively low leaf area: leaf mass ratio.

• The optimal partitioning theory predicts that plants of a given species acclimate to different environments by allocating a larger proportion of biomass to the organs acquiring the most limiting resource. Are similar patterns found across species adapted to environments with contrasting levels of abiotic stress? • We tested the optimal partitioning theory by analysing how fractional biomass allocation to leaves, stems and roots differed between woody species with different tolerances of shade and drought in plants of different age and size (seedlings to mature trees) using a global dataset including 604 species. • No overarching biomass allocation patterns at different tolerance values across species were found. Biomass allocation varied among functional types as a result of phenological (deciduous vs evergreen broad-leaved species) and broad phylogenetical (angiosperms vs gymnosperms) differences. Furthermore, the direction of biomass allocation responses between tolerant and intolerant species was often opposite to that predicted by the optimal partitioning theory. • We conclude that plant functional type is the major determinant of biomass allocation in woody species. We propose that interactions between plant functional type, ontogeny and species-specific stress tolerance adaptations allow woody species with different shade and drought tolerances to display multiple biomass partitioning strategies.

Plants adapt phenotypically to different conditions of light and nutrient supply, supposedly in order to achieve colimitation of these resources. Their key variable of adjustment is the ratio of leaf area to root length, which relies on plant biomass allocation and organ morphology. We recorded phenotypic differences in leaf and root mass fractions (LMF, RMF), specific leaf area (SLA) and specific root length (SRL) of 12 herbaceous species grown in factorial combinations of high/low irradiance and fertilization treatments. Leaf area and root length ratios, and their components, were influenced by nonadditive effects between light and nutrient supply, and differences in the strength of plant responses were partly explained by Ellenberg's species values representing ecological optima. Changes in allocation were critical in plant responses to nutrient availability, as the RMF contribution to changes in root length was 2.5× that of the SRL. Contrastingly, morphological adjustments (SLA rather than LMF) made up the bulk of plant response to light availability. Our results suggest largely predictable differences in responses of species and groups of species to environmental change. Nevertheless, they stress the critical need to account for adjustments in below‐ground mass allocation to understand the assembly and responses of communities in changing environments.

1. Correlations among plant traits often reflect important trade-offs or allometric relationships in biological functions like carbon gain, support, water uptake, and reproduction that are associated with different plant organs. Whether trait correlations can be aggregated to \"spectra\" or \"leading dimensions,\" whether these dimensions are consistent across plant organs, spatial scale, and growth forms are still open questions. 2. To illustrate the current state of knowledge, we constructed a network of published trait correlations associated with the \"leaf economics spectrum,\" \"biomass allocation dimension,\" \"seed dimension,\" and carbon and nitrogen concentrations. This literature-based network was compared to a network based on a dataset of 23 traits from 2,530 individuals of 126 plant species from 381 plots in Northwest Europe. 3. The observed network comprised more significant correlations than the literature-based network. Network centrality measures showed that size traits such as the mass of leaf, stem, below-ground, and reproductive tissues and plant height were the most central traits in the network, confirming the importance of allometric relationships in herbaceous plants. Stem mass and stem-specific length were \"hub\" traits correlated with most traits. Environmental selection of hub traits may affect the whole phenotype. In contrast to the literature-based network, SLA and leaf N were of minor importance. Based on cluster analysis and subsequent PCAs of the resulting trait clusters, we found a \"size\" module, a \"seed\" module, two modules representing and N concentrations in plant organs, and a \"partitioning\" module representing organ mass fractions. A module representing the plant economics spectrum did not emerge. 4. Synthesis. Although we found support for several trait dimensions, the observed trait network deviated significantly from current knowledge, suggesting that previous studies have overlooked trait coordination at the whole-plant level. Furthermore, network analysis suggests that stem traits have a stronger regulatory role in herbaceous plants than leaf traits.

In recent years, belowground plant ecology has experienced a booming interest. This has resulted in major advances towards a greater understanding of belowground plant and ecosystem functioning focused on fine roots, mycorrhizal associations and nutrient acquisition. Despite this, other important functions (e.g., on‐spot persistence, space occupancy, resprouting after biomass removal) exerted by different belowground plant organs (e.g., roots, rhizomes, bulbs) remain largely unexplored. Here, we propose a framework providing a comprehensive perspective on the entire set of belowground plant organs and functions. We suggest a compartment‐based approach. We identify two major belowground compartments, that is, acquisitive and nonacquisitive, associated with biomass allocation into these functions. Also, we recommend the nonacquisitive compartment to be divided into structural (e.g., functional roles carried out by rhizomes, such as sharing of resources, space occupancy) and nonstructural (e.g., functional roles exerted by carbohydrates reserve affecting resprouting ability, protection against climate adversity) subcompartments. We discuss methodological challenges—and their possible solutions—posed by changes in biomass allocation across growth forms and ontogenetic stages, and in relation to biomass partitioning and turnover. We urge the implementation of methods and approaches considering all the belowground plant compartments. This way, we would make sure that key, yet less‐studied functions would be incorporated into the belowground plant ecology research agenda. The framework has potential to advance the understanding of belowground plant and ecosystem functioning by considering relations and trade‐offs between different plant functions and organs. At last, we identify four major areas where using the proposed compartment‐based approach would be particularly important, namely (a) biomass scaling, (b) clonality‐resource acquisition relations, (c) linkages between resprouting and changing environmental conditions and (d) carbon sequestration. A plain language summary is available for this article. Plain Language Summary Foreign Language Funkční ekologie podzemních částí rostlinSummary in Czech V posledních letech zažívá ekologie podzemních částí rostlin velký zájem výzkumníků po celém světě. Tento zájem přispěl k lepšímu porozumění funkce podzemních částí rostlin, zejména jemných kořenů a mykorhizy, které hrají významnou roli při získávání vody a živin. Jiné důležité funkce rostlin, jako je přežívání na daném místě, obsazování prostoru, nebo schopnost regenerace po poškození těla, zprostředkované například zásobními kořeny a oddenky, však zůstávají opomíjeny. S cílem napravit tuto situaci, navrhujeme integrovaný přístup, který umožní komplexnější pohled na celou řadu podzemních rostlinných orgánů a jejich funkcí. Na příkladech z literatury ukazujeme, jak zaměření pouze na jemné kořeny může omezit naši schopnost poznat ekologii rostlin. Navrhujeme přístup založený na rozlišení základních funkčních specializací podzemních orgánů. Identifikujeme dva hlavní funkční podzemní kompartmenty, za prvé akviziční, tj. podílející se na získávání vody a živin, a za druhé neakviziční, tj. podílející se na propojování různých částí rostliny, na klonálním růstu a na regeneraci po narušení. Diskutujeme metodologické problémy spojené s implementací tohoto přístupu a o jejich možných řešeních. Přestavujeme rozdíly v investicích do těchto podzemních kompartmentů u různých růstových forem a během života rostliny, stejně tak problémy související se stanovením biomasy a jejím obratem. Závěrem vyzýváme výzkumníky, aby při studium ekologie aplikovali metody a přístupy, které berou v úvahu všechny podzemní orgány rostlin. Pouze tímto způsobem zajistíme, aby méně studované, avšak zcela klíčové funkce podzemních orgánů rostlin, byly začleněny do výzkumného plánu funkčních ekologů. Příkladem může být jejich využití pro lepší odhad sekvestrace uhlíku v podzemních orgánech rostlin, což je důležité pro tvorbu celosvětových geochemických modelů.