Biomass Allocation Patterns Research Articles

Correlation of Leaf and Root Traits of Two Angiosperm Tree Species in Northeast China under Contrasting Light and Nitrogen Availabilities

Light and nitrogen availability are among the most important environmental factors influencing leaf and root morphological traits and forest ecosystems. Understanding the variation in leaf and root traits is pivotal to the adaptive plasticity and leaf-root-specific traits in response to low light and N availability. The effects of light and N availability on leaf and root traits and their interrelations are still not clear. We aimed to measure the response of leaf and root traits and their interrelations to light and N availability in a temperate region. Thus, a factorial experiment was conducted with two angiosperm tree species under two light (L+, L−) and two nitrogen (N−, N+) levels. Results showed that the leaf density (LD) and leaf mass per area (LMA) increased, while leaf thickness (LT) decreased under low light availability. Under N availability, the LD and LMA decreased, while LT increased in sun-exposed plots and remained stable under low light availability across two species. The root diameter, root length, specific root length (SRL), and specific root area (SRA) decreased, while the root tissue density (TD) increased under low light availability. Root diameter, root length, SRA, and SRL increased, while the TD decreased under N+ in L+ plots and remained stable under L− plots. LMA and LT were significantly positively correlated to root length and SRL while significantly negatively correlated to TD. However, LD was significantly positively correlated to TD. We observed that low light availability has significantly decreased the plant biomass and root mass fraction (RMF) and increased the leaf mass fraction (LMF), while the stem mass fraction (SMF) remained stable―indicating the shade in-tolerances in both species. Correlation analyses revealed that LMF is generally, and particularly under L− conditions, less related to leaf and root morphological traits, while RMF was frequently positively correlated to both leave and root traits under all environmental conditions. This illustrates a divergent regulation of morphological traits above and below ground under varying biomass allocation patterns.

Growth and biomass allocation dynamics of Artemisia ordosica in sand-fixing vegetation of the Tengger Desert of China.

Aims Resource allocation pattern is an important trait of plant ecological adaptive strategy. The composite sub-shrub Artemisia ordosica is widely distributed in the sandy land of northern China and is an important sand-stabilizing plant. However,its growth dynamics and resource allocation pat-terns are poorly known. Our objectives were to determine:1) the growth dynamics of vegetative and re-productive organs and the biomass allocation pattern in different growth periods; 2) the relationship between reproductive and vegetative growth and 3) variations of biomass allocation pattern with age of sand-fixing vegetation. Methods A field experiment was conducted on revegetated areas in Shapotou,located at southeastern fringe of Tengger Desert,from April to November 2007. Twenty-five A. ordosica were sampled monthly in sand-fixing vegetation planted in 1956,1964,1981,1987 and 1991 to measure the number,size and biomass of vegetative organs and reproductive organs such as leaves,vegetative shoots,flow-ering shoots,capitula and seeds. Important findings In different growth periods,there were different growth rates and proportion of photosynthate allocation to organs. So the energy accumulation center and growth center vary with growth period. The vegetative growth,reproductive output and size of panicle in 2007 were significantly greater than those in the year when precipitation was less than half that in 2007,while no significant differences were found in reproductive allocation and size of capitula between these years. The individuals with greater vegetative biomass were also characterized by higher reproductive output,but the vegetative and reproductive growth were unsynchronized with different increment speed,which indicated that there was a trade-off between reproduction and vegetative growth. Annual biomass,reproductive output and reproductive allocation showed a trend of decrease with time extension of the sand-fixing project,but no statistically significant differences of the three indices were found among these five vegetation areas with different ages.

Plant functional traits along an old-field succession in the high tropical andes

The páramo, a high tropical Andean ecosystem, presents very distinct climatic, floristic and ecological features. Paramo plants have adapted to pronounced daily temperature fluctuations, freezing temperatures any night of the year, high incoming radiation and seasonal unfavorable water availability conditions. Long fallow agricultural systems are common in the páramo, permitting partial recuperation of the vegetation through a secondary succession. Different hypothesis related to plant traits (water relations and gas exchange characteristics or biomass allocation patterns) during succession have been proposed. Particular traits have been associated to the stages along successional gradients from early species (traits related to high resource acquisition abilities) to late species (traits linked to internal conservation of resources). Our purpose was to study plant functional responses of different herbaceous species in an old-field succession in the high tropical Andes. Plant traits (specific leaf area (SLA), maximum CO2 assimilation rates (Amax), leaf nitrogen content (Nleaf), leaf water relations and biomass allocation) were studied in grasses and forbs along different successional stages. Clear trends in SLA, Amax on a mass basis, Nleaf and aboveground/belowground biomass allocation were found along the successional gradient for grasses, while patterns were not as well-defined for forbs in the latter two traits. No patterns in leaf water relations characteristics were observed for either plant-growth forms. Strategies associated to plant traits significantly influence plant species dominance and community assembly during secondary succession in tropical alpine open environments like the páramos. Plant traits linked to rapid growth (SLA, Amax and Nleaf) dominate during early succession. In contrast to previous studies, drought resistance traits were not found to dominate in late succession stages for either grasses or forbs.

Changes of Aboveground and Belowground Biomass Allocation in Four Dominant Grassland Species Across a Precipitation Gradient.

Climate change is predicted to affect plant growth, but also the allocation of biomass to aboveground and belowground plant parts. To date, studies have mostly focused on aboveground biomass, while belowground biomass and allocation patterns have received less attention. We investigated changes in biomass allocation along a controlled gradient of precipitation in an experiment with four plant species (Leymus chinensis, Stipa grandis, Artemisia frigida, and Potentilla acaulis) dominant in Inner Mongolia steppe. Results showed that aboveground biomass, belowground biomass and total biomass all increased with increasing growing season precipitation, as expected in this water-limited ecosystem. Biomass allocation patterns also changed along the precipitation gradient, but significant variation between species was apparent. Specifically, the belowground biomass: aboveground biomass ratio (i.e., B:A ratio) of S. grandis was not impacted by precipitation amount, while B:A ratios of the other three species changed in different ways along the gradient. Some of these differences in allocation strategies may be related to morphological differences, specifically, the presence of rhizomes or stolons, though no consistent patterns emerged. Isometric partitioning, i.e., constant allocation of biomass aboveground and belowground, seemed to occur for one species (S. grandis), but not for the three rhizome or stolon-forming ones. Indeed, for these species, the slope of the allometric regression between log-transformed belowground biomass and log-transformed aboveground biomass significantly differed from 1.0 and B:A ratios changed along the precipitation gradient. As changes in biomass allocation can affect ecosystem functioning and services, our results can be used as a basis for further studies into allocation patterns, especially in a context of environmental change.

Effects of biotic and abiotic factors on forest biomass fractions.

The extent to which key factors at the global scale influence plant biomass allocation patterns remains unclear. Here, we provide a theory about how biotic and abiotic factors influence plant biomass allocation and evaluate its predictions using a large global database for forested communities. Our analyses confirm theoretical predictions that temperature, precipitation, and plant height and density jointly regulate the quotient of leaf biomass and total biomass, and that they have a much weaker effect on shoot (leaf plus stem) biomass fractions at a global scale. Moreover, biotic factors have larger effects than abiotic factors. Climatic variables act equally on shoot and root growth, and differences in plant body size and age, as well as community species composition, which vary with climate in ways that drown out the variations in biomass fractions. The theory and data presented here provide mechanistic explanations of why climate has little effect on biomass fractions.

Shrubland biomass and root-shoot allocation along a climate gradient in China

Background – Shrublands are receiving increasing attention because of climate change. However, knowledge about biomass allocation of shrublands at the community level and how this is regulated by climate is of limited availability but critical for accurately estimating carbon stocks and predicting global carbon cycles. Methods – We sampled 50 typical shrublands along a climate gradient in China and investigated the biomass allocation of shrubland at the community level and the effect of climate on biomass allocation. Shrub biomass was estimated using species-specific allometric relationships and the biomass of understory herbs was collected by excavating the whole plant. Regression analysis was used to examine the relationships between the biomass and the climate factors. RMA were conducted to establish the allometric relationships between the root and the shoot biomass at the community level.Key results – Shoot, root, and total biomass of shrub communities across different sites were estimated with median values of 206.5, 145.8, and 344.5 g/m2, respectively. Shoot, root, and total biomass of herb communities were estimated at 68.2, 58.9, and 117.2 g/m2, respectively. The median value of the R/S ratio of shrub communities was 0.58 and that of herb communities was 0.84. The R/S ratio of the shrub community showed a negative relationship with mean annual temperature and mean annual precipitation and a positive relationship with total annual sunshine and the aridity index. The R/S ratio of the herb community however showed a weak relationship with climate factors. Shoot biomass of the shrub community was nearly proportional to root biomass with a scaling exponent of 1.17, whereas shoot biomass of the herb community was disproportional to root biomass with a scaling exponent of 2.1.Conclusions – In shrublands, root biomass was more affected than shoot biomass by climate factors and this is related to water availability as a result of biomass allocation change of the shrub community. The understory herb community was less affected by climate due to the modification of the overstory–understory interaction to the climate-induced biomass allocation pattern. Shoot biomass of shrubs scales isometrically with root biomass at the community level, which supports the isometric theory of above-ground and below-ground biomass partitioning.

Biomass partitioning in response to intraspecific competition depends on nutrients and species characteristics: A study of 43 plant species

Abstract Competition simultaneously limits the availability of above‐ and below‐ground resources for plants. How plants respond to density with changes in patterns of biomass allocation is poorly understood. Previous studies had inconsistent results, but emphasised increased biomass allocation to stems in response to density. However, the response of plants to density may depend on environmental conditions and on characteristics of the species. We grew 43 herbaceous plant species at three densities (1, 8 and 64 individuals per pot) and two nutrient levels in a common garden and measured biomass allocation to roots (RMF), leaves (LMF) and stems (SMF), and specific root (SRL) and stem length (SSL). The species differed in functional group (grasses, forbs and legumes), life span and realised niche with respect to nutrients (Ellenberg's nutrient indicator value). Intraspecific competition and self‐thinning increased with nutrient supply. Overall, plants increased their RMF with density independent of nutrient level, indicating that competition was mainly for below‐ground resources. However, characteristics of the species influenced their responses to density and nutrients in terms of biomass allocation, SRL and SSL. At high densities, legumes were more productive than the other functional groups and hardly changed their allocation patterns, suggesting that they were less nutrient limited due to their mutualism with nitrogen‐fixing rhizobia. The SRL of perennials was lower, and their RMF was higher and increased more strongly in response to density than that of annuals, which could be interpreted as mechanisms to increase survival. The realised niche of species with respect to nutrients influenced the response to density and nutrients in terms of SMF, LMF, SRL and SSL in line with adaptations to both nutrient availability and competition for light in the typical habitats. Synthesis. We found that intraspecific competition was mainly for below‐ground resources, which may be typical for many species growing in moderately nutrient‐rich but high‐light habitats. Our results show that growth conditions, species characteristics and their interactions influence patterns of biomass allocation and plant morphology.

Aboveground biomass allocation patterns and model construction of Bambusa rigida

Aboveground biomass allocation patterns and model construction of Bambusa rigida

Developmental plasticity of Brachypodium distachyon in response to P deficiency: Modulation by inoculation with phosphate-solubilizing bacteria.

BackgroundMineral phosphorus (P) fertilizers must be used wisely in order to preserve rock phosphate, a limited and non‐renewable resource. The use of bio‐inoculants to improve soil nutrient availability and trigger an efficient plant response to nutrient deficiency is one potential strategy in the attempt to decrease P inputs in agriculture.MethodAn in vitro co‐cultivation system was used to study the response of Brachypodium distachyon to contrasted P supplies (soluble and poorly soluble forms of P) and inoculation with P solubilizing bacteria. Brachypodium's responses to P conditions and inoculation with bacteria were studied in terms of developmental plasticity and P use efficiency.Results Brachypodium showed plasticity in its biomass allocation pattern in response to variable P conditions, specifically by prioritizing root development over shoot productivity under poorly soluble P conditions. Despite the ability of the bacteria to solubilize P, shoot productivity was depressed in plants inoculated with bacteria, although the root system development was maintained. The negative impact of bacteria on biomass production in Brachypodium might be attributed to inadequate C supply to bacteria, an increased competition for P between both organisms under P‐limiting conditions, or an accumulation of toxic bacterial metabolites in our cultivation system. Both P and inoculation treatments impacted root system morphology. The modulation of Brachypodium's developmental response to P supplies by P solubilizing bacteria did not lead to improved P use efficiency.ConclusionOur results support the hypothesis that plastic responses of Brachypodium cultivated under P‐limited conditions are modulated by P solubilizing bacteria. The considered experimental context impacts plant–bacteria interactions. Choosing experimental conditions as close as possible to real ones is important in the selection of P solubilizing bacteria. Both persistent homology and allometric analyses proved to be useful tools that should be considered when studying the impact of bio‐inoculants on plant development in response to varying nutritional context.

Responses of biomass allocation patterns to nitrogen addition of <i>Cunninghamia lanceolata</i> seedlings

Responses of biomass allocation patterns to nitrogen addition of <i>Cunninghamia lanceolata</i> seedlings

Genotype-dependent architectural and physiological responses regulate the strategies of two oregano cultivars to water excess and deficiency regimes

Plants can exhibit alternative strategies to cope with water stress regimes by reconfiguring different morphophysiological processes. Nonetheless, the physiological bases that define the response of oregano genotypes to water stress are still poorly understood. A pot experiment in a greenhouse was conducted to evaluate the changes in the configuration of plant architecture and physiological traits and the strategies displayed by two novel oregano cultivars (Origanum vulgare ssp. hirtum ‘Alpa Sumaj FCA-INTA’ and Origanum x majoricum Cambess. ‘Aguanda FCA-INTA’) in response to two water stress regimes (water excess and deficit) in vegetative phenological stages. To do this, water relations and morphological, developmental, and physiological traits were measured. The architectural and physiological responses were dependent upon stressful water regimes and oregano cultivars. Two strategies were found to face water excess regime: Alpa Sumaj remained quiescent whereas Aguanda followed an escape strategy. Biomass production of Alpa Sumaj was halved since physiological and architectural traits were mostly reduced, especially the leaf area. In contrast, Aguanda was more tolerant because of its altered biomass allocation pattern, leading to taller plants with mild reductions of the leaf area and transpiration rate. Therefore, relative water content and biomass yield were preserved. Contrastingly, the strategy to face water deficit regime in both cultivars was dehydration avoidance. All traits were reduced in a similar way, but interesting genotypic differences in water relation traits were observed. Thereby, leaf water potential decrease was highlighted in Alpa Sumaj cultivar, whereas the lessening in transpiration rate as the leaf area is reduced represented the outstanding physiological trait of Aguanda.

Nitrogen addition affects plant biomass allocation but not allometric relationships among different organs across the globe

Abstract Aims Biomass allocation to different organs is a fundamental plant ecophysiological process to better respond to changing environments; yet, it remains poorly understood how patterns of biomass allocation respond to nitrogen (N) additions across terrestrial ecosystems worldwide. Methods We conducted a meta-analysis using 5474 pairwise observations from 333 articles to assess how N addition affected plant biomass and biomass allocation among different organs. We also tested the ‘ratio-based optimal partitioning’ vs. the ‘isometric allocation’ hypotheses to explain potential N addition effects on biomass allocation. Important Findings We found that (i) N addition significantly increased whole plant biomass and the biomass of different organs, but decreased root:shoot ratio (RS) and root mass fraction (RMF) while no effects of N addition on leaf mass fraction and stem mass fraction at the global scale; (ii) the effects of N addition on ratio-based biomass allocation were mediated by individual or interactive effects of moderator variables such as experimental conditions, plant functional types, latitudes and rates of N addition and (iii) N addition did not affect allometric relationships among different organs, suggesting that decreases in RS and RMF may result from isometric allocation patterns following increases in whole plant biomass. Despite alteration of ratio-based biomass allocation between root and shoot by N addition, the unaffected allometric scaling relationships among different organs (including root vs. shoot) suggest that plant biomass allocation patterns are more appropriately explained by the isometric allocation hypothesis rather than the optimal partitioning hypothesis. Our findings contribute to better understand N-induced effects on allometric relationships of terrestrial plants, and suggest that these ecophysiological responses should be incorporated into models that aim to predict how terrestrial ecosystems may respond to enhanced N deposition under future global change scenarios.

Influence of shade intensity on growth, biomass allocation, yield and quality of pineapple in mango-based intercropping system

Fruit tree-based intercropping system is commonly practiced in India; however, optimization of light environment for intercrops is essentially required to enhance their productivity. Influence of three shade intensities were examined on growth, biomass allocation pattern, leaf chlorophyll content, nutrient uptake, fruit yield and quality of pineapple in mango-based intercropping system. Compared to the monoculture pineapple system (LE0), the mean shade intensity under LE1, LE2 and LE3 were 23.8 %, 48.6 % and 73.3 %, respectively, whereas the mean PAR availability was 76.2 %, 51.4 % and 26.7 %, respectively. Significantly higher absolute growth rate (AGR), crop growth rate (CGR) and relative growth rate (RGR) was recorded under medium shade intensity (LE2). Dry matter accumulation was significantly high under LE2 followed by LE3. The biomass accumulation was significantly high in leaf followed by fruit and stem, whereas root system exhibited minimum biomass accumulation. Biomass of leaf and crown decreased with the plant biomass, whereas the biomass of fruit, stem and sucker increased. Contents of Chl a, Chl b and Chl a + b increased with the shade intensity and were found maximum under LE3. A gradual increase in N and P contents were observed in the leaves of pineapple with the reduction in PAR transmittance. However, the K content was relatively high under LE2. Increased fruit yield, fruit weight and fruit/crown ratio were recorded under moderate shade intensity (LE2). Total soluble solids and sugar content marginally decreased with the reduction in light intensity, whereas titratable acidity increased. Sunburn intensity significantly reduced under LE2 and LE3. Path analysis studies indicated that plant biomass was that most important predictor for fruit yield in pineapple. Our findings demonstrate that in eastern tropical region of India pineapple may be cultivated as an intercrop with ∼50 % shade intensity since the performance of crop is significantly affected under monoculture system.

Trade‐offs in above‐ and below‐ground biomass allocation influencing seedling growth in a tropical forest

Abstract Plants allocate biomass to different organs in response to resource variation for maximizing performance, yet we lack a framework that adequately integrates plant responses to the simultaneous variation in above‐ and below‐ground resources. Although traditionally, the optimal partition theory (OPT) has explained patterns of biomass allocation in response to a single limiting resource, it is well‐known that in natural communities multiple resources limit growth. We study trade‐offs involved in plant biomass allocation patterns and their effects on plant growth under variable below‐ and above‐ground resources—light, soil N and P—for seedling communities. We collected information on leaf, stem and root mass fractions for more than 1,900 seedlings of 97 species paired with growth data and local‐scale variation in abiotic resources from a tropical forest in China. We identified two trade‐off axes that define the mass allocation strategies for seedlings—allocation to photosynthetic versus non‐photosynthetic tissues and allocation to roots over stems—that responded to the variation in soil P and N and light. Yet, the allocation patterns did not always follow predictions of OPT in which plants should allocate biomass to the organ that acquires the most limiting resource. Limited soil N resulted in high allocation to leaves at the expense of non‐photosynthetic tissues, while the opposite trend was found in response to limited soil P. Also, co‐limitation in above‐ and below‐ground resources (light and soil P) led to mass allocation to stems at the expense of roots. Finally, we found that growth increased under high‐light availability and soil P for seedlings that invested more in photosynthetic over non‐photosynthetic tissues or/and that allocated mass to roots at the expense of stem. Synthesis. Biomass allocation patterns to above‐ and below‐ground tissues are described by two independent trade‐offs that allow plants to have divergent allocation strategies (e.g. high root allocation at the expense of stem or high leaf allocation at the expense of allocation to non‐photosynthetic tissues) and enhance growth under different limiting resources. Identifying the trade‐offs driving biomass allocation is important to disentangle plant responses to the simultaneous variation in resources in diverse forest communities.

Effect of seed source, light, and nitrogen levels on biomass and nutrient allocation pattern in seedlings of Pongamia pinnata.

Nitrogen (N) and light are critical determinants of plant growth and productivity. The present study attempts to quantify the underlying mechanisms and effects of light, N levels, and seed source on growth, biomass, nutrient allocations, and nutrient use efficiencies (NUEs) in seedlings of Pongamia pinnata. The differential and fixed hypothesis and isometric and allometric relationships were also examined. Six morphologically superior seed sources of P. pinnata from three contrasting agro-climatic conditions of India were evaluated with application of two levels of both N (low dose @ 5g plant-1 and 15 g plant-1) and light regimes (full light-100% and low light-50%) in mother nursery. Among the seed sources, the native Raipur seed source was found outstanding in growth, biomass, and nutrient use efficiency. N was more critical than light in promoting growth in seedlings of P. pinnata. High N and high light regimes increased shoot/root ratios. The components showed allometric growth and followed a differential allocation pattern. The exploitation of suitable genetic resources combined with managerial interventions is necessary for development of quality planting stock of P. pinnata. Nutrient use efficiencies, biomass production, and their allocation were important indicators and criteria for selection. The study suggests that Raipur and Jabalpur seed sources having high NUE should be grown along with adequate N application (15 g plant-1) and light conditions.

Allometry rather than abiotic drivers explains biomass allocation among leaves, stems and roots of Artemisia across a large environmental gradient in China

Abstract Biomass allocation patterns reflect the adaptive strategies of plants growing in different environments, which is a central issue in comparative plant ecology and evolution. However, the factors underpinning specific allocation patterns across organs and the existence of general rules governing allocation remain contentious. Optimal partitioning theory (OPT) states that plants can respond to resource availability by allocating relatively more biomass to the organ that captures the most limiting resources to optimize growth. In contrast, allometric partitioning theory (APT) postulates that biomass allocation among organs is a power function of plant size independently of environmental variation. As phylogenetic and growth form constraints (e.g. formation of inert heartwood in tree clades) may also affect biomass allocation, comparison among and within closely related taxa of rather similar growth form may enable a more direct testing of which of these two theories prevails. To test whether OPT or APT was prevalent at wide geographical scale, we investigated biomass allocation patterns among leaves, stems and roots of 1,022 plants of 62 Artemisia species (Asteraceae) collected along broad climate (annual mean temperature range: −4.9 to 18.0°C, annual mean precipitation range: 193–1,668 mm) and soil gradients (soil carbon content range: 1.6–15.4 kg C m−2) in central and eastern China. There were strong allometric relationships among leaf mass (ML), stem mass (MS) and root mass (MR) at both interspecific and intraspecific levels. Moreover, the interspecific and intraspecific patterns were not different from general patterns for pooled plants, that is, ML/MR and ML/MS, but not MS/MR, generally decreased with plant size. However, the three organ mass ratios were not responsive to broad climatic or soil gradients after the effect of plant size was removed. Synthesis. Our results generally support APT instead of OPT, suggesting that Artemisia plants have evolved an allometric strategy rather than relying on adjustment of allocation among organs to adapt to the broadly varying environments at the regional scale. For follow‐up research, we hypothesize that the strong allometric constraints on biomass allocation should depend on strong physiological adaptive responses of the different organs of Artemisia to environmental gradients.

Different strategies in biomass allocation across elevation in two Gentiana plants on the Yunnan-Guizhou Plateau, China

Patterns of biomass allocation among organs in plants are important because they influence many growth processes. The Yunnan-Guizhou Plateau (YGP) is considered to be one of the most sensitive areas in China to climate changes, but we know little about how current climatic gradients on the plateau influence plant biomass allocation. Gentiana rigescens and G. rhodantha, on the YGP, are important species because they are used in traditional Chinese medicines. We therefore analyzed the biomass allocation patterns of the two species across an elevation gradient (1000–2810 m a.s.l.) on the YGP to understand and predict the impact of climate change on these plant species. We found that the total biomass, reproductive biomass, vegetative biomass, aboveground biomass, and belowground biomass in G. rigescens were all significantly larger than those in G. rhodantha (p<0.05). However, for both species the aboveground biomass was nearly isometrically related to belowground biomass, regardless of elevation, mean annual temperature (MAT) ranging from 8.4°C to 18.8°C, and mean annual precipitation (MAP) ranging from 681 to 1327 mm, while the reproductive biomass was allometrically related to vegetative biomass. Intriguingly, there was a significant positive relationship (p<0.05) between the slope of the allometric scaling of reproductive and vegetative biomass and elevation among G. rigescens populations, i.e. plants growing at high elevations allocate proportionately more biomass to reproduction at larger sizes and less at smaller sizes than plants growing at lower elevations. However, for G. rhodantha the reproductive allocation was negatively correlated with latitude. The results suggested different strategies in reproductive allocation in the two Gentiana plants on the YGP. Further studies are needed to investigate other environmental factors, such as nutrients and light, and genetic factors, in order to understand the trend of reproductive allometry along the environmental gradients. Our study has implications for the management and conservation practices of the two Gentiana species.

Altitudinal pattern of shrub biomass allocation in Southwest China.

Shrubs play an important role in the global carbon cycle and are particularly sensitive to climate change. However, the altitudinal pattern of biomass allocation in mountainous shrubs and its responses to climate change are still unclear. In this study, biomass accumulation and allocation of the shrub community and their relationships with climatic factors were investigated in 331 sampling sites along an extensive altitudinal gradient (311–4911 m) in Southwest China. The results showed that the above-ground biomass (AGB) and the total biomass (TB) of the shrub community decreased quadratically (R2 = 0.107) and linearly (R2 = 0.024) from 9.86 to 0.15 kg·m-2 and 15.61 to 0.26 kg·m-2 with increasing altitude, respectively. However, the below-ground biomass (BGB) and TB of the herb layer increased quadratically with increasing altitudes (R2 = 0.136 and 0.122, respectively. P<0.001). The root/shoot ratio (R/S) of the community and its component synusiae increased gradually with increasing altitudes (P<0.001). The standardized major axis (SMA) indicated an isometric relationship between AGB and BGB for the whole shrub community, but allometric relationships were found for the shrub and herb layer. Redundancy analysis and Pearson correlation analysis showed that the biomass and R/S were significantly correlated with mean annual temperature (MAT), mean annual precipitation (MAP) and reconnaissance drought index (RDI). These findings indicate that shrub biomass allocation is strongly affected by the altitude, MAT and MAP and support the isometric relationship of AGB and BGB partitioning at the community level on mountainous shrub biomes.

Global patterns of biomass allocation in woody species with different tolerances of shade and drought: evidence for multiple strategies.

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.

Aboveground and belowground biomass and its' allometry for Salsola passerina shrub in degraded steppe desert in Northwestern China

AbstractKnowledge of the biomass allometry and partitioning is essential for understanding shrub adaptive strategies to degraded habitats as well as for estimating organic carbon storage. We studied biomass accumulation, allocation patterns, and allometric models of Salsola passerina shrub in the Alxa Desert steppe, Northwestern China. We measured aboveground and belowground biomass accumulation across different ages (0–50 years) by destructive sampling. The biomass allocation patterns between aboveground biomass, leaves, branches, and roots were studied by fitting allometric functions for both pooled and age‐classed data. Allometric biomass models were developed by regressing on single‐input variable of basal diameter, crown area, height, and age alone or on the pairwise variables of above four parameters. Biomass accumulation increased with age, aboveground components represented 86–89% of the total biomass, root to shoot biomass ratios increased with shrub age. Allometry patterns of S. passerina were relatively constant, and the growth rate of root was faster than that of aboveground components. Allometric models with two‐input variables were obviously better than single variable models. Crown area and basal diameter were the best predictors for biomass of S. passerina shrub.