Biomass Allocation Research Articles

Root-shoot ratio and its relationships with physiological characteristics, growth and biomass yield of Gynura procumbens under different shade levels and plant density

Gynura procumbens is one of the most common medicinal plants in the Asteraceae family, with extensive pharmacological properties. The experiment was conducted to evaluate the effects of different shade levels (0 and 30% shade) and plant density (9, 15, and 25 plants m-2) on root-shoot ratio and it is a relationship with physiology, growth, and biomass yield using split-plot design with three replications. Increasing shade level to 30% shade significantly decreased root-shoot ratio (RSR) by22.54%, while total leaf dry weight per plant (TLDW) and total leaf dry weight per square meter (TLDW m-2) increased by 35.64, 11.58, and 32.18%, respectively due to negative correlation with RSR. Increasing plant density from 9 to 25 plants m-2 significantly increased RSR and TLDW m-2 by 67.71 and 18.54%, respectively, while TLDW decreased by 57.31%. There was a negative correlation between RSR and biomass yield per plant. Under stressed conditions (full sunlight and high plant density), G. procumbent plants appeared to change strategy to absorb limited resources, allocate more biomass to the root system, and reduce aboveground parts' size to survive, resulting in high RSR. Keywords: Gynura procumbens, shade, plant density, root-shoot ratio, physiology, growth, biomass

Steps toward developing legume cover crop varieties: Study of biomass and nitrogen partitioning and within‐plant δ115N variation of faba bean at different growth stages

AbstractModern legumes are engineered to enhance nutrient allocation to grains and maximize harvest index (HI) and yield. Breeding legumes for cover crop requires optimizing source‐sink relationship to prolong nutrient allocation to vegetative organs, support post‐flowering nodule activity, and extend biological nitrogen fixation (BNF). We studied the variation of faba bean (Vicia faba) germplasm for biomass (DM) and nitrogen (N) allocation to plant organs at the lower and upper parts of the canopy. Three genotypes were established during the 2019 and 2020 growing seasons, and DM, N, and δ15N of upper and lower leaves, stems, pods, seeds, and pod shells were quantified at vegetative, first‐pod, and full‐pod stages. Of the three genotypes, PI 678631 displayed early vigor, allocated more DM and N in vegetative organs, and accumulated more total DM and N than Windsor and PI 655333 by first‐pod stage. The advantage of PI 678631 over the other two genotypes seemed to be associated with smaller allocation of DM and N in pods at early reproductive phase. These findings support existing variations within faba bean germplasm that can be used to improve its ecosystem service as cover crop. Within‐plant variation of δ15N was minimal, suggesting that under favorable soil N and moisture where N remobilization is low, vegetative organs can serve as proxies to estimate the entire plant %Ndfa (proportion of plant N derived from the atmosphere) prior to plant maturity. The δ15N of plant organs at vegetative and early‐pod stages were similar and consistent with the only whole plant δ15N measurement in 2020.

Elucidating the genomic regions through genome-wide association study (GWAS) for root traits in cowpea (Vigna unguiculata (L) Walp) mini-core collection

Enhancing the root traits through selection and breeding efforts can significantly improve the acquisition of soil resources, consequently boosting crop production in marginal environments. Cowpea is one of the important legume crops in arid and semi-arid regions, grown mostly in marginal environments under drought conditions. The roots play a crucial role in plant's ability to survive and adapt under such water stressed conditions. The understanding of cowpea genetic architecture related to root system architecture (RSA) remains limited due to difficulties in accurately measuring root traits. In the present study, a set 110 diverse mini-core collection of cowpea from IITA, Nigeria was evaluated for thirteen (13) different root-shoot traits under controlled conditions in the green house. Significant variation was recorded for all the root traits in the mini-core set. Most promising genotype for most of the root traits, viz., root volume, dry root weight, root biomass density and tap root diameter were identified. The correlation analysis revealed significant positive association (p < 0.001) of root weight with shoot weight (0.85), root volume (r = 0.61), and tap root diameter (0.56). In the principal component analysis (PCA), first three principal components explained the variance of 64.31%, with PC1 contributing 44.43%, PC2 10% and PC3 9.88%. All the root-shoot traits contribute positive variation to PC1especially dry root weight and dry shoot weight that had high component loading and in PC2 root shoot ratio had high loading. The root-shoot trait data was used with 6,574 good quality SNP data for discovery of genes/QTLs/marker-trait associations for root traits. The analysis of results of genome wide association study (GWAS) led to the identification of 52 unique SNPs associated significantly (p < 10−4) with thirteen root-shoot traits. Highest number of SNPs was found associated with root weight and chromosome 5 was identified as SNP hotspot for harboring majority of significant SNPs. We further delve candidate genes within 50 kb around the identified SNP that led to the identification of several important candidate genes underlying genomic regions responsible for root-shoot traits in cowpea. The promising cowpea genotypes for root traits and promising MTAs/candidate genes will prove useful in cowpea improvement programs including improvement of drought tolerance in cowpea.

Rhizome fragment weight and density of competing shoots determine belowground regrowth of Elymus repens

AbstractManagement of perennial weeds has become increasingly complex with the reduction of herbicide use and tillage. Their capacity to store nutrients into vegetative organs and to regenerate to establish new individuals makes them very persistent and hard to control. A key aspect for managing perennial weeds is to minimise storage reserves to reduce vegetative regeneration. For that prospect, better knowledge of the regrowth capacities from storage organs is needed. Our work focused on the mechanistic understanding of belowground regrowth dynamics from fragments of Elymus repens rhizomes by analysing the effect of source and sink factors. The effect of rhizome fragment weight (i.e., source) and the number of regrowing buds and belowground shoots (i.e., sinks) was assessed for four mechanisms: sprouting, belowground shoot elongation, belowground shoot biomass to length conversion and biomass allocation to belowground shoots versus roots. Heavier fragments contributed to faster sprouting, faster belowground shoot elongation and increased the proportion of remobilised biomass allocated to belowground shoots. Higher belowground shoot density increased the proportion of remobilised biomass allocated to belowground shoots but decreased individual elongation rate. In other words, larger reserves resulted in a better regeneration capacity and a higher number of growing belowground shoots increased the competition for reserves among them. The belowground shoot that sprouted first on a fragment grew faster and dominated the other shoots on the same fragment. Dominant belowground shoots were located toward the apical end of the fragment. These findings support the fact that tillage should aim at cutting storage organs into the smallest fragments possible to reduce regeneration capacity. This study also emphasised that belowground regrowth mechanisms are complex, and further studies should investigate other species with different types of storage organs.

Root Architectural Adaptations to Phosphorus Deficiency: Unraveling Genotypic Variability in Wheat Seedlings

Understanding the changes in the root system architecture of bread wheat under phosphorus (P)-limited conditions is critical for identifying specific traits contributing to improved P uptake. Phenotypic variability in root, biomass, and P index-related traits among 204 diverse wheat genotypes at the seedling stage was examined under low and optimum P treatments. Strong genotypic and phenotypic associations between P utilization efficiency (PUtE) and total root volume, dry weight of root and shoot, total P uptake, and total plant biomass were observed under optimum P. Under low P, strong positive correlations between PUtE and total root length, total root volume, total surface area, and total biomass were observed, while it was negatively correlated with average diameter. These traits exhibited medium to high heritability. Under low P, average root diameter, primary root length, root mass ratio, total root tips, and surface area showed high Shannon–Weaver diversity index (H’) values (&gt;0.79). The agglomerative hierarchical clustering analysis grouped the genotypes into four distinct clusters. The best performing genotypes in Clusters I and II indicated their strong relationship with P use efficiency due to higher percent increases in total root length, total surface area, total root volume, total root tips, total biomass, P efficiency ratio, specific root length, and PUtE under low P as compared to optimum P conditions. The present study identified specific root system architectural traits and P use-efficient genotypes (SHANGHAI, Pavon F76, BWL 5233, SONALIKA, KHARCHIA LOCAL, WH 102, BWL 4425, HD 2888.2, CBW 12, MN75136/PGO, KRL 19, and WH 1022) associated with efficient P uptake and utilization. These identified genotypes and traits may be useful in wheat breeding programs to develop P-efficient varieties with better adaptations for sustainable agriculture.

Effects of Mepiquat Chloride on Physiology of Soybean under Drought Stress

Background: Drought is an important factor restricting the development of agriculture. In recent years, plant growth regulators have achieved more results in improving crop stress resistance. The physiological mechanism of exogenous application of mepiquat chloride on soybean seedlings has undergone significant changes under drought stress. Methods: In order to study the effect of exogenous chlorine on the physiology of soybean under drought stress., ‘Heinong 65’ was used as the experimental material, 15% PEG-6000 was used to simulate drought stress and different concentrations of mepiquat chloride solution (100, 300, 500, 700 mg/L) were sprayed at the three-leaf stage of soybean growth by pot method. The dry matter accumulation, auxin (IAA), zeatin (ZA), gibberellin (GA3), abscisic acid (ABA) content and superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) activity of soybean were determined. Result: The results showed that the activities of antioxidant enzymes SOD, POD, CAT and APX in soybean leaves under drought stress were significantly increased by the treatment of appropriate concentration of mepiquat chloride solution. IAA, GA3 and ZA endogenous hormone levels increased, dry matter accumulation increased, root-shoot ratio and ABA endogenous hormone levels decreased significantly. It can be seen that mepiquat chloride treatment can improve the antioxidant capacity, promote the growth of soybean seedlings under drought stress and effectively alleviate the inhibition of drought stress on soybean growth and development.

Nitrogen and phosphorus availability alters tree‐grass competition intensity in savannas

Abstract Plant essential macronutrients like nitrogen (N) and phosphorus (P) can limit savanna tree growth and are important determinants of savanna vegetation dynamics, along with rainfall, fire and herbivory. How nitrogen and phosphorus shape tree‐grass competition and their coexistence remain unclear, hindering our ability to predict how savannas may respond to altered nutrient cycling. Here, we evaluate (1) if trees and grasses respond differently to N versus P availability, or (2) if grasses are more competitive in low nutrient environments while trees are more competitive in high nutrient environments. To do this, we grew saplings of 6 tree and 1 grass species from the Kruger National Park, South Africa, for 16 weeks under fully factorial nutrient and competition treatments (with/without competitors, low/high rate of N supply and low/high rate of P supply) under a watering regime designed to mimic wet season rainfall in a mesic savanna. Trees and grasses foraged most aggressively for nitrogen and allocated biomass differently depending on nitrogen availability. Overall, tree growth decreased in competition with grass, even in high nutrient environments where they grew faster. Grasses were always better below‐ground competitors, utilising aggressive nutrient foraging strategies, including high root phosphatase activity in response to nitrogen and large root biomass allocation. Synthesis. In low nutrient environments (e.g. on nutrient‐poor sandy soils), nutrients may limit tree growth. Nutrient rich environments enable tree growth, but grasses continue to compete effectively with trees. Understanding what this means for ecosystem responses to nutrient availability is not trivial, especially in the context of fire and herbivory. However, it is clear that soil nutrients likely affect tree and grass growth and competition in savannas, which suggests that future changes in nutrient cycling, such as N deposition, may have important effects on savanna vegetation.

Clonal integration reduced sexual reproduction of Leymus chinensis clones in heterogeneous environments regardless of stress/disturbance intensities

Clonal integration can benefit the performance and fitness of clonal plants in heterogeneous environments. Although trade-offs of sexual and asexual reproduction are key life-history strategies to assess the plant fitness and adaptive abilities, the effects of clonal integration on these is less studied. In this study, a pot experiment was conducted to test how reproductive strategies were affected by clonal integration of clonal plant species Leymus chinensis growing in heterogeneous saline-alkali soils. The results showed that clonal integration had no significant effect on total biomass of whole clone of L. chinensis. The total biomass of younger ramets was higher (+32.8%, P < 0.001) under integration condition, while at the cost of the older ramets (-21.7%, P < 0.001). Moreover, the ratio of ear biomass to clonal growth organs (CGO) biomass was slightly reduced by 31.7% (P = 0.09). For younger ramets, clonal integration enhances biomass allocation towards CGO, while reducing allocation towards ear growth, and the ratio of ear/CGO biomass was significantly reduced by 39.1% (P < 0.01). Results indicated that clonal integration reduced the ratio of ear to clonal growth organ biomass of whole clone, and more biomass was allocated to younger ramets for spatial expansion. Clonal integration influenced reproductive strategies of L. chinensis, while its impact is not depended on nutrient levels or defoliation interference. The study emphasized the significance of clonal integration in promoting the growth of offspring ramets and, consequently, enhancing their abilities to expand rapidly. It could enhance the spatial expansion of L. chinensis on a site scale and provide high potential for restoration of patchy degraded grassland where it is dominant.

Disentangling the effect of growth from development in size-related trait scaling relationships.

In plant ecology, the terms growth and development are often used interchangeably. Yet these constitute two distinct processes. Plant architectural traits (e.g. number of successive forks) can estimate development stages. Here, we show the importance of including the effect of development stages to better understand size-related trait scaling relationships (i.e. between height and stem diameter). We focused on one common savanna woody species (Senegalia nigrescens) from the Greater Kruger Area, South Africa. We sampled 406 individuals that experience different exposure to herbivory, from which we collected four traits: plant height, basal stem diameter, number of successive forks (proxy for development stage), and resprouting. We analysed trait relationships (using standardized major axis regression) between height and stem diameter, accounting for the effect of ontogeny, exposure to herbivory, and resprouting. The number of successive forks affects the scaling relationship between height and stem diameter, with the slope and strength of the relationship declining in more developed individuals. Herbivory exposure and resprouting do not affect the overall height-diameter relationship. However, when height and stem diameter were regressed separately against number of successive forks, herbivory exposure and resprouting had an effect. For example, resprouting individuals allocate more biomass to both primary and secondary growth than non-resprouting plants in more disturbed conditions. We stress the need to include traits related to ontogeny so as to disentangle the effect of biomass allocation to primary and secondary growth from that of development in plant functional relationships.

Climate Factors Influence Above- and Belowground Biomass Allocations in Alpine Meadows and Desert Steppes through Alterations in Soil Nutrient Availability.

Biomass is a direct reflection of community productivity, and the allocation of aboveground and belowground biomass is a survival strategy formed by the long-term adaptation of plants to environmental changes. However, under global changes, the patterns of aboveground-belowground biomass allocations and their controlling factors in different types of grasslands are still unclear. Based on the biomass data of 182 grasslands, including 17 alpine meadows (AMs) and 21 desert steppes (DSs), this study investigates the spatial distribution of the belowground biomass allocation proportion (BGBP) in different types of grasslands and their main controlling factors. The research results show that the BGBP of AMs is significantly higher than that of DSs (p < 0.05). The BGBP of AMs significantly decreases with increasing mean annual temperature (MAT) and mean annual precipitation (MAP) (p < 0.05), while it significantly increases with increasing soil nitrogen content (N), soil phosphorus content (P), and soil pH (p < 0.05). The BGBP of DSs significantly decreases with increasing MAP (p < 0.05), while it significantly increases with increasing soil phosphorus content (P) and soil pH (p < 0.05). The random forest model indicates that soil pH is the most important factor affecting the BGBP of both AMs and DSs. Climate-related factors were identified as key drivers shaping the spatial distribution patterns of BGBP by exerting an influence on soil nutrient availability. Climate and soil factors exert influences not only on grassland biomass allocation directly, but also indirectly by impacting the availability of soil nutrients.

Driving mechanisms of community biomass allocation along environmental gradients in different grasslands in China

A variable future climate would lead to changes in the biomass allocation pattern of plant communities, but its divergent changes under different environments have not been clearly explored, greatly limiting a better understanding of the responsess of grassland ecosystems to environmental changes. Herein, we conducted field samplings at 215 grassland sites in the Qinghai-Tibetan and Inner Mongolian Plateaus to analyze community biomass allocation patterns (specifically, the ratio of root to shoot, R/S) in various grasslands along environmental gradients. We found a gradual increase in R/S from humid to semi-arid and arid environments across both plateaus. In humid environment, soil factor had a significant effect on the R/S of alpine humid grassland, while climate factor had a significant effect on the R/S of humid grassland. In semi-arid environment, both climate and plant factors had significant effects on R/S in semi-arid grassland. In arid environments, climate and plant factors had significant effects on R/S in arid grassland. These findings emphasize the multifaceted role of environmental factors in shaping biomass allocations across diverse ecosystems, enriching our understanding of ecological dynamics. The current results are timely in advancing the fundamental understanding of the mechanisms of biomass allocation in grasslands and are useful for global research on grasslands in different environments.

Unveiling the mechanism of source-sink rebalancing in cucumber-pumpkin heterografts: the buffering roles of rootstock cotyledon.

Grafting onto pumpkin rootstock is widely applied in cucumber production to improve growth and yield, as well as to overcome soil-borne diseases and enhance resistance to abiotic stresses. In this study, we constructed the cucumber-pumpkin heterografts with the one-cotyledon grafting method, and examined the effects of heterografting on biomass allocation and sugar partitioning, with cucumber and pumpkin self-grafts used as control. Compared with cucumber self-grafts, heterografting onto pumpkin rootstock promoted photosynthesis in cucumber scion, and led to higher sucrose contents in the 1st true leaf (source) and newly emerged leaf (sink). Thereby, the scion part of heterografts accumulated more biomass than cucumber self-grafts. In contrast, when compared to pumpkin self-grafts, grafting with cucumber scion reduced root vigor and biomass but promoted cotyledon growth in pumpkin rootstock. The roots (sink) of heterografts contained less sucrose and hexoses, and showed reduced sucrose synthase (SuSy) and hexokinase (HXK) activities. However, the rootstock cotyledon (source) contained more sucrose and starch, and showed higher activities of HXK, cell-wall invertase (CWIN), and enzymes for starch synthesis and degradation. Furthermore, removal or shade of rootstock cotyledon led to reduced growth of root and scion. Silencing of CmoMEX1a gene in rootstock cotyledon inhibited maltose export and reduced root growth of heterografts. These results indicated that rootstock cotyledon, especially its starch content, played a buffering role in the growth regulation of cucumber-pumpkin heterografts. Taken together, our results provided a major contribution to our understanding of source-sink sugar partitioning and scion-rootstock growth balancing in cucumber-pumpkin heterografts.

Nitrogen addition affected the root competition in Cunninghamia lanceolata-Phoebe chekiangensis mixed plantation.

Little is known about below-ground competition in mixed-species plantations under increasing nitrogen (N) deposition. This study aims to determine the effects of N addition on root competition in coniferous and broad-leaved species mixed plantations. A pot experiment was conducted using the coniferous species Cunninghamia lanceolata and the broad-leaved species Phoebe chekiangensis planted in mixed plantations with different competition intensities under N addition (0 or 45 kg N ha-1 yr-1). Biomass allocation, root morphology, root growth level, and competitive ability were determined after five months of treatment. Our findings indicated that root interactions in mixed plantations did not influence biomass allocation in either C. lanceolata or P. chekiangensis but promoted growth in C. lanceolata when no N was added. However, N addition decreased biomass accumulation in both species in the mixed plantation and had a negative effect on the root growth of C. lanceolata due to intensified competition. Addition of N increased the relative importance of root predatory competition in P. chekiangensis, and increased the allelopathic competitive advantage in C. lanceolata. This suggests that N addition causes a shift in the root competitive strategy from tolerance to competition. Overall, these findings highlight the significant impact that the addition of N can have on plant interactions in mixed plantations. Our results provide implications for the mechanisms of root competition in response to increasing atmospheric N deposition in mixed plantations.

Climate and soil factors co-derive the functional traits variations in naturalized downy thorn apple (Datura innoxia Mill.) along the altitudinal gradient in the semi-arid environment

Plant functional traits are consistently linked with certain ecological factors (i.e., abiotic and biotic), determining which components of a plant species pool are assembled into local communities. In this sense, non-native naturalized plants show more plasticity of morphological traits by adopting new habitat (an ecological niche) of the invaded habitats. This study focuses on the biomass allocation pattern and consistent traits-environment linkages of a naturalized Datura innoxia plant population along the elevation gradient in NW, Pakistan. We sampled 120 plots of the downy thorn apple distributed in 12 vegetation stands with 18 morphological and functional biomass traits during the flowering season and were analyzed along the three elevation zones having altitude ranges from 634.85 m to 1405.3 m from sear level designated as Group I to III identified by Ward's agglomerative clustering strategy (WACS). Our results show that many morphological traits and biomass allocation in different parts varied significantly (p < 0.05) in the pair-wise comparisons along the elevation. Likewise, all plant traits decreased from lower (drought stress) to high elevation zones (moist zones), suggesting progressive adaptation of Datura innoxia with the natural vegetation in NW Pakistan. Similarly, the soil variable also corresponds with the trait's variation e.g., significant variations (P < 0.05) of soil organic matter, organic carbon, Nitrogen and Phosphorus was recorded. The trait-environment linkages were exposed by redundancy analysis (RDA) that was co-drive by topographic (elevation, r = −0.4897), edaphic (sand, r = -0.4565 and silt, r = 0.5855) and climatic factors. Nevertheless, the influences of climatic factors were stronger than soil variables that were strongly linked with elevation gradient. The study concludes that D. innoxia has adopted the prevailing environmental and climatic conditions, and further investigation is required to evaluate the effects of these factors on their phytochemical and medicinal value.

Bornean tropical forests recovering from logging at risk of regeneration failure.

Active restoration through silvicultural treatments (enrichment planting, cutting climbers and liberation thinning) is considered an important intervention in logged forests. However, its ability to enhance regeneration is key for long-term recovery of logged forests, which remains poorly understood, particularly for the production and survival of seedlings in subsequent generations. To understand the long-term impacts of logging and restoration we tracked the diversity, survival and traits of seedlings that germinated immediately after a mast fruiting in North Borneo in unlogged and logged forests 30-35 years after logging. We monitored 5119 seedlings from germination for ~1.5 years across a mixed landscape of unlogged forests (ULs), naturally regenerating logged forests (NR) and actively restored logged forests via rehabilitative silvicultural treatments (AR), 15-27 years after restoration. We measured 14 leaf, root and biomass allocation traits on 399 seedlings from 15 species. Soon after fruiting, UL and AR forests had higher seedling densities than NR forest, but survival was the lowest in AR forests in the first 6 months. Community composition differed among forest types; AR and NR forests had lower species richness and lower evenness than UL forests by 5-6 months post-mast but did not differ between them. Differences in community composition altered community-weighted mean trait values across forest types, with higher root biomass allocation in NR relative to UL forest. Traits influenced mortality ~3 months post-mast, with more acquisitive traits and relative aboveground investment favoured in AR forests relative to UL forests. Our findings of reduced seedling survival and diversity suggest long time lags in post-logging recruitment, particularly for some taxa. Active restoration of logged forests recovers initial seedling production, but elevated mortality in AR forests lowers the efficacy of active restoration to enhance recruitment or diversity of seedling communities. This suggests current active restoration practices may fail to overcome barriers to regeneration in logged forests, which may drive long-term changes in future forest plant communities.

Arbuscular mycorrhiza increases the facilitation between adult plant and seedling but root‐knot nematode inhibits it

AbstractSoil biotic and abiotic factors can affect the interaction between invasive and native species. However, it is not yet clear how arbuscular mycorrhizal (AM) symbiosis affects the interaction between adult invasive plants and neighboring seedlings. We used an invasive weed (Bidens frondosa) to test the hypothesis that adult invasive plants facilitate the growth of neighboring seedlings through AM symbiosis, and this facilitation can be inhibited by the biological stress of root‐knot nematode infection. The results showed that the height and total biomass of seedlings near the adult plant increased, indicating that the belowground effects mediated by AM symbiosis played a facilitative role. The positive growth response to resource allocation between adult plant and neighboring seedlings through mycorrhizal connection was inhibited when adult plants were infected by root‐knot nematode. Only the total biomass and root–shoot ratio of adult plants were increased, while seedling growth performance did not change. Our results supported the hypothesis that adult invasive plants can facilitate their neighboring seedlings growth through AM symbiosis and the benefits vary with biotic stress on adult plant. These findings provided important evidence to explain the role of AM symbiosis in plant invasion.

Nutrient Dynamics in a Coupled Terrestrial Biosphere and Land Model (ELM‐FATES‐CNP)

AbstractWe present a representation of nitrogen and phosphorus cycling in the Functionally Assembled Terrestrial Ecosystem Simulator, a demographic vegetation model within the Energy Exascale Earth System land model. This representation is modular, and designed to allow testing of multiple hypothetical approaches for carbon‐nutrient coupling in plants. Novel model hypotheses introduced in this work include, (a) the controls on plant acquisition of aqueous mineralized nutrients in the soil and (b) fairly straight forward methods of allocating nutrients to specific plant organs and their losses through live plant turnover as well as litter fluxes generated through plant mortality. This combines the new with pre‐existing hypotheses (such as nitrogen fixation and soil decomposition) into a system that can accommodate plant‐soil dynamics for a large number of size‐ and functional‐type‐resolved plant cohorts within a time‐since‐disturbance‐resolved ecosystem. Root uptake of nutrients is governed by fine root biomass, and plants vary in their fine root biomass allocation in order to balance carbon and nutrient limitations to growth. We test the sensitivity of the model to a wide range of parameter variations and structural representations, and in the context of observations at Barro Colorado Island, Panama. A key model prediction is that plants in the high‐light‐availability canopy positions allocate more carbon to fine roots than plants in low‐light understory environments, given the widely different carbon versus nutrient constraints of these two niches within a given ecosystem. This model provides a basis for exploring carbon‐nutrient coupling with vegetation demography within Earth system models.

Genetic variation in growth and leaf traits associated with local adaptation to climate in yellow birch (Betula alleghaniensis Britton)

Understanding patterns of variation in functional traits of hardwood trees is crucial for conserving and managing North American temperate forests under climate change. This study examined provenance variation of yellow birch ( Betula alleghaniensis Britton) in growth, biomass allocation, leaf morphology, and stable carbon isotope composition. Trees were grown from 10 seed sources originating from across Canada and the northern USA. Height and diameter were not significantly related to climate at seed origin, suggesting that variation may be better explained by site factors, such as soil pH and soil moisture. In contrast, carbon isotope composition and leaf morphological traits were significantly correlated to climate variables including temperature, precipitation, and solar radiation. Provenances from warmer, drier localities tended to have higher stable carbon isotope ratio (δ13C), greater specific leaf area, and narrower leaf width than their counterparts from cooler, wetter climates. Thus, variation in leaf morphological traits appears to be involved in adaptation of yellow birch to variation in temperature and moisture availability across the species’ range. Our results suggest that there may exist potential for selection and breeding of drought-resistant yellow birch genotypes to aid in reforestation under climate change.

Elevation Influences Belowground Biomass Proportion in Forests by Affecting Climatic Factors, Soil Nutrients and Key Leaf Traits.

Forest biomass allocation is a direct manifestation of biological adaptation to environmental changes. Studying the distribution patterns of forest biomass along elevational gradients is ecologically significant for understanding the specific impacts of global change on plant resource allocation strategies. While aboveground biomass has been extensively studied, research on belowground biomass remains relatively limited. Furthermore, the patterns and driving factors of the belowground biomass proportion (BGBP) along elevational gradients are still unclear. In this study, we investigated the specific influences of climatic factors, soil nutrients, and key leaf traits on the elevational pattern of BGBP using data from 926 forests at 94 sites across China. In this study, BGBP data were calculated from the root biomass to the depth of 50 cm. Our findings indicate considerable variability in forest BGBP at a macro scale, showing a significant increasing trend along elevational gradients (p < 0.01). BGBP significantly decreases with increasing temperature and precipitation and increases with annual mean evapotranspiration (MAE) (p < 0.01). It decreases significantly with increasing soil phosphorus content and increases with soil pH (p < 0.01). Key leaf traits (leaf nitrogen (LN) and leaf phosphorus (LP)) are positively correlated with BGBP. Climatic factors (R2 = 0.46) have the strongest explanatory power for the variation in BGBP along elevations, while soil factors (R2 = 0.10) and key leaf traits (R2 = 0.08) also play significant roles. Elevation impacts BGBP directly and also indirectly through influencing such as climate conditions, soil nutrient availability, and key leaf traits, with direct effects being more pronounced than indirect effects. This study reveals the patterns and controlling factors of forests' BGBP along elevational gradients, providing vital ecological insights into the impact of global change on plant resource allocation strategies and offering scientific guidance for ecosystem management and conservation.

Contrasting biomass allocations explain adaptations to cold and drought in the world's highest-growing angiosperms.

Understanding biomass allocation among plant organs is crucial for comprehending plant growth optimization, survival and responses to the drivers of global change. Yet, the mechanisms governing mass allocation in vascular plants from extreme elevations exposed to cold and drought stresses remain poorly understood. We analysed organ mass weights and fractions in 258 Himalayan herbaceous species across diverse habitats (wetland, steppe, alpine), growth forms (annual, perennial taprooted, rhizomatous and cushiony) and climatic gradients (3500-6150 m elevation) to explore whether biomass distribution adhered to fixed allometric or optimal partitioning rules, and how variations in size, phylogeny and ecological preferences influence their strategies for resource allocation. Following optimal partitioning theory, Himalayan plants distribute more biomass to key organs vital for acquiring and preserving limited resources necessary for their growth and survival. Allocation strategies are mainly influenced by plant growth forms and habitat conditions, notably temperature, water availability and evaporative demands. Alpine plants invest primarily in below-ground stem bases for storage and regeneration, reducing above-ground stems while increasing leaf mass fraction to maximize carbon assimilation in their short growing season. Conversely, arid steppe plants prioritize deep roots over leaves to secure water and minimize transpiration. Wetland plants allocate resources to above-ground stems and below-ground rhizomes, enabling them to resist competition and grazing in fertile environments. Himalayan plants from extreme elevations optimize their allocation strategies to acquire scarce resources under specific conditions, efficiently investing carbon from supportive to acquisitive and protective functions with increasing cold and drought. Intraspecific variation and shared ancestry have not significantly altered biomass allocation strategies of Himalayan plants. Despite diverse evolutionary histories, plants from similar habitats have developed comparable phenotypic structures to adapt to their specific environments. This study offers new insights into plant adaptations in diverse Himalayan environments and underscores the importance of efficient resource allocation for survival and growth in challenging conditions.