Root Total Nonstructural Carbohydrate Research Articles

马尾松幼苗根系和光合碳供应对土壤性质变化和温室气体排放的驱动作用

PDF HTML阅读 XML下载 导出引用 引用提醒 马尾松幼苗根系和光合碳供应对土壤性质变化和温室气体排放的驱动作用 DOI: 10.5846/stxb202008012004 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划(2017YFC0505503)；国家自然科学基金面上项目(31370627) Root input and photosynthetic carbon supply effect on soil properties and greenhouse gases release of Pinus massoniana seedling Author: Affiliation: Fund Project: The National Key Technologies R&D Program of China 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:森林植被受全球气候变化、森林经营活动及病虫害等多种干扰,导致林地光合碳供应水平及根系输入量发生变化。在此背景下,土壤性质及土壤温室气体排放的响应及其机理是预测森林碳汇功能变化及森林可持续经营的重要依据。以2年生马尾松盆栽苗为对象,通过单株/盆和3株/盆栽植密度控制根系输入量、通过环割和截干控制光合碳向地下的供应能力,模拟森林植被干扰导致的根系输入量及光合碳供应变化对土壤理化性质、微生物群落结构及温室气体排放的影响。结果表明,苗木根系非结构性碳水化合物(TNC)含量和氮含量比单株/盆低;3株/盆的土壤速效氮含量比单株/盆低,土壤革兰氏阳性菌、厌氧菌、放线菌及丛枝菌根真菌丰富度均比单株/盆显著增加,3株/盆的土壤二氧化碳(CO2)排放速率较高,但土壤氧化亚氮(N2O)排放速率差异不显著。无论是单株/盆还是3株/盆,环割和截干处理后,根系生物量、根系长度及表面积均比对照显著下降;根系TNC含量显著下降。土壤和根系氮含量都有增加趋势;土壤微生物生物量碳(SMBC)含量降低,而土壤微生物生物量氮(SMBN)则提高。环割和截干后,土壤中各种微生物组成丰富度均有下降趋势,土壤CO2排放速率显著下降,土壤N2O排放速率则显著提高。根系输入量及光合碳供应对土壤细菌和真菌含量均有显著影响,土壤细菌含量与根系生物量、SMBC和SMBN显著正相关;土壤真菌含量与土壤温度显著负相关,与根系生物量、SMBC和SMBN显著正相关。相关分析表明,土壤CO2排放通量与土壤温度、土壤湿度及根系生物量显著正相关,与土壤硝态氮显著负相关;土壤N2O排放通量与土壤温度和土壤湿度显著正相关。以上研究表明,根系输入量与地上光合碳供应共同作用,改变土壤理化性质及微生物环境,进而影响土壤温室气体排放。 Abstract:Forest vegetation is affected by climate change, forest management activities, and diseases and pests, which can lead to changes in photosynthetic carbon supply, root input of forest land, composition of soil microbial community, and soil greenhouse gases emission. These changes and their underlying mechanisms are the basis for modelling change of forest ecological functions and for managing forest scientifically. Here, we studied level of root input of 2-year-old potted seedlings of Pinus massoniana under two densities, single-plant/pot and 3-plants/pot, and under two disturbance treatments, ring-barking and stem-severing to stop carbon transport to the root system. We aimed to simulate the effects of changes in root input and photosynthetic carbon supply on soil physical and chemical properties, microbial community structure and greenhouse gas emission under various conditions. Our results showed that the total nonstructural carbohydrate (TNC) and nitrogen in seedling roots were lower in 3-plants/pot treatment than in single-plant/pot treatment. The content of soil available nitrogen in 3-plants/basins was lower than that in single-plant/pot. In contrast, richness of soil Gram-positive bacteria, anaerobic bacteria, actinomycetes and arbuscular mycorrhizal fungi were higher in 3-plants/pot treatment than in single-plant/pot treatment. Further, the emission rate of soil carbon dioxide (CO2) was higher in 3-plants/pot treatment than in single-plant/pot treatment. Planting density had no significant effects on emission rate of soil nitrous oxide (N2O). Both the ring-barking and stem-severing treatments decreased the root biomass, root length, root surface and root TNC content in both single-plant/pot and 3-plants/pot treatments. Both the ring-barking and stem-severing treatments increased the content of nitrogen in soil and roots, the content of soil microbial biomass nitrogen (SMBN), and emission rate of soil N2O, but decreased the content of soil microbial biomass carbon (SMBC), the richness of soil microbial and the emission rate of soil CO2. Root biomass input and photosynthetic carbon supply have significant effect on soil bacterial and fungal contents. Soil bacterial contents were positively correlated with root biomass, SMBC and SMBN. Soil fungal content was negatively correlated with soil temperature, positively correlated with root biomass, SMBC and SMBN. Correlation analysis showed that soil CO2 emission flux was positively correlated with soil temperature, soil humidity and root biomass, while negatively correlated with soil nitrate nitrogen; soil N2O emission flux was positively correlated with soil temperature and soil humidity. The results suggest that root input and photosynthetic carbon supply work together to change soil physical and chemical properties and microbial environment, thus contribute to changes in the emissions rate of soil greenhouse gases. 参考文献 相似文献 引证文献

Root trait variation in African savannas

While patterns of variation in woody plant aboveground traits related to disturbance and resource availability in savanna ecosystems are fairly well understood, dimensions of variation in belowground traits remain poorly understood. We investigate how sapling coarse root (>2 mm diameter) traits and belowground storage organs vary with respect to differing disturbance regimes (i.e. fire or herbivore dominated) and soil fertility in Southern African savannas. We examined how sapling rooting strategies (type of rooting system, storage organs, root allocation) as well as root total non-structural carbohydrate concentrations [TNC], root N and C:N of 69 common woody savanna and forest species at 16 sites vary with respect to differing disturbance regimes and soil fertility. We found that root [TNC] and the occurrence of storage organs were highest while root N was lowest for species growing at fire-driven sites, compared to herbivore-driven sites and competition-controlled forest species. Allocation to belowground biomass was higher at fire-dominated sites but root volume:stem basal area did not differ between disturbance regimes. None of the measured traits were found to differ between nutrient rich clayey soils and nutrient poor sandy soils. Our results suggest that disturbance related controls are important drivers of savanna belowground traits.

Repercussions of four herbicides on reproductive and vegetative development in potted grapevines

Background and Aims Spring drift of herbicides can have devastating consequences on grapevines. The impact of 2,4-dichlorophenoxyacetic acid (2,4-D), dichloro-2-methoxybenzoic acid (Dicamba), 2-methyl-4-chlorophenoxyacetic acid (MCPA) and glyphosate exposure on reproductive and vegetative development was investigated. Methods and Results Simulated herbicide drifts were applied to potted vines at the cessation of flowering. Leaf gas exchange and biomass, root structural biomass and carbohydrate reserves, fruit yield and compound bud necrosis were assessed, along with berry composition, including the primary metabolites, at fruit maturity. Fruit yield was reduced by 2,4-D without any detriment to most aspects of berry composition. While root structural development was curtailed by 2,4-D, Dicamba and MCPA, none of the herbicides altered the reserve level of root total non-structural carbohydrates. Primary bud necrosis was evident following 2,4-D and Dicamba exposure, especially in younger buds. Conclusions Exposure to 2,4-D may be particularly damaging to fruit yield during the current season because of an increased risk of bunch necrosis. Bud fruitfulness can be impaired by 2,4-D and Dicamba because of the increased potential for primary bud necrosis. Significance of the Study Auxin-type herbicides can limit fruit yield during the current and next season. Compared to cane pruning, spur pruning may minimise the detrimental effects of these herbicides on fruitfulness.

Effects of Elevated Ozone Levels on Photosynthesis, Biomass and Non-structural Carbohydrates of Phoebe bournei and Phoebe zhennan in Subtropical China.

To assess the impacts of ozone (O3) on carbon metabolism of subtropical broadleaved tree species, seedlings of Phoebe bournei and Phoebe zhennan were exposed to elevated O3 levels in open-top chambers (OTCs) from June to November 2014. Three treatments were conducted in nine total OTCs, including charcoal-filter air (CF) as a control treatment, low O3 treatment ‘O3-1’ (∼100 nl l-1), and high O3 treatment ‘O3-2’ (∼150 nl l-1). Our findings demonstrated that elevated O3 levels significantly decreased the net photosynthesis rates (Pn) and leaf, root, and total biomass of both species, while it did not significantly affect the root/shoot ratio in P. bournei and P. zhennan. O3-1 treatments significantly increased water soluble carbohydrates (WSC) in leaves of both tree species, while only increased the total non-structural carbohydrates (TNC) and starch in leaves of P. bournei; effects on P. zhennan were equivalent in comparison to the control treatment (CF). Likewise, there was no effect of treatment on the polysaccharide content of both tree species. The contents of polysaccharide, starch contents in fine roots of both species, and TNC in fine roots of P. bournei increased significantly in O3-1 compared to CF. O3-2 treatment significantly decreased starch and TNC in the fine roots of P. bournei, and significantly decreased polysaccharide, starch, WSC, and TNC in the fine roots of P. zhennan. Elevated O3 had no effects on leaf polysaccharide in both species, but O3-1 significantly increased polysaccharide in the fine roots of both species, and O3-1 significantly increased WSC in the leaves while decreased that in the fine roots of both species. These results suggested that elevated O3 levels have significant impacts on the carbon metabolism of both tree species in our study, with differential responses between tree species and among leaves and roots.

Apple fruit set is influenced by altered floral bud density but not by reduced carbohydrate reserves

The extent to which carbohydrate reserves contribute to apple (Malus × domestica Borkh.) fruit set is unclear. On ‘Royal Gala’/‘M9’ trees, we used postharvest early defoliation (12 days after harvest) to alter carbohydrate reserve accumulation compared with natural leaf fall. Superimposed over this, late winter bud thinning using artificial spur extinction (ASE, 6 buds cm(-1) branch cross sectional area) to manipulate the number of developing sinks in spring was compared with unmodified trees. Reducing bud density using ASE did not affect the concentration of total non-structural or soluble carbohydrates in root or spur tissues sampled at intervals from dormancy to final fruit set. However, ASE increased within-bud fruit set compared with unmodified trees. Early defoliation did not affect fruit set compared with natural defoliation, but reduced concentrations of total non-structural carbohydrates in roots in winter by 44% (264 to 147 mg g(-1) dry weight) and concentrations of starch in spurs in winter by 60% (19 to 7.7 mg g(-1)). Between dormancy and 1 week before bloom (WBB), total non-structural carbohydrate concentration declined in roots of naturally defoliated trees by 31%, and in spurs of naturally and early defoliated trees by 37 and 46% (respectively). In trees defoliated early, concentrations of total non-structural carbohydrates increased from their minimum at 1WBB in spurs and 2 weeks after bloom (WAB) in roots. In naturally defoliated trees total non-structural carbohydrates did not increase in roots during the measurement period, but increased in spurs between 5 and 9 WAB. Lack of differences in fruit set among defoliation treatments despite differences in non-structural carbohydrate concentration in spurs and roots implied that at concentrations observed here, stored carbohydrates in these tissues had little role in fruit set. This was supported by observations that total non-structural carbohydrate concentration declined before full bloom, not during fruit set, and total non-structural carbohydrate concentration increased during the period 2 to 4 WAB, when limitations in carbohydrate resources are thought most likely to affect fruit set.

The sweet side of global change-dynamic responses of non-structural carbohydrates to drought, elevated CO2 and nitrogen fertilization in tree species.

Non-structural carbohydrates (NSC) play a central role in plant functioning as energy carriers and building blocks for primary and secondary metabolism. Many studies have investigated how environmental and anthropogenic changes, like increasingly frequent and severe drought episodes, elevated CO2 and atmospheric nitrogen (N) deposition, influence NSC concentrations in individual trees. However, this wealth of data has not been analyzed yet to identify general trends using a common statistical framework. A thorough understanding of tree responses to global change is required for making realistic predictions of vegetation dynamics. Here we compiled data from 57 experimental studies on 71 tree species and conducted a meta-analysis to evaluate general responses of stored soluble sugars, starch and total NSC (soluble sugars + starch) concentrations in different tree organs (foliage, above-ground wood and roots) to drought, elevated CO2 and N deposition. We found that drought significantly decreased total NSC in roots (-17.3%), but not in foliage and above-ground woody tissues (bole, branch, stem and/or twig). Elevated CO2 significantly increased total NSC in foliage (+26.2%) and roots (+12.8%), but not in above-ground wood. By contrast, total NSC significantly decreased in roots (-17.9%), increased in above-ground wood (+6.1%), but was unaffected in foliage from N fertilization. In addition, the response of NSC to three global change drivers was strongly affected by tree taxonomic type, leaf habit, tree age and treatment intensity. Our results pave the way for a better understanding of general tree function responses to drought, elevated CO2 and N fertilization. The existing data also reveal that more long-term studies on mature trees that allow testing interactions between these factors are urgently needed to provide a basis for forecasting tree responses to environmental change at the global scale.

Evaluation of Bermuda grass (Cynodon dactylon (L.) Pers.) and Bahia grass (Paspalum notatum Flugge) for short-term drought tolerance targeting low-maintenance landscaping

Drought responses of turf-type Bermuda grass (Cynodon dactylon (L.) Pers.) and Bahia grass (Paspalum notatum Flugge) in relation to their growth, carbon allocation and accumulation of nonstructural carbohydrates were investigated. Seedlings were exposed to a 20 day terminal drought, followed by 20 day recovery with irrigation. Leaf dry matter was lower in water-stressed plants than control plants by the end of drought, but did not differ in roots. For both species, more carbon was allocated towards roots in response to drought. Total nonstructural carbohydrate (TNC) concentration in shoots was increased in drought-stressed plants of both species. However, root TNC concentrations in Bahia grass were decreased after drought. TNC pool sizes also showed a similar variation, hence correlated with TNC concentrations. Bahia grass maintained a better quality than Bermuda grass after the drought, having recorded a higher aesthetic score, higher relative water content and a lower electrolyte leakage. Results suggest that, both species are considerably tolerant to short-term drought though Bahia grass seems more promising.Int. J. Appl. Sci. Biotechnol. Vol 6(1): 12-16

Relationships between resprouting ability, species traits and resource allocation patterns in woody species in a temperate forest

Summary Many woody plants resprout to restore above‐ground biomass after disturbances or to survive in stressful environments. Resprouting requires carbohydrate storage, but the general relationship between resource allocation patterns and resprouting ability remains unclear because it can be influenced by the disturbance regime to which species have adapted. We studied deciduous broadleaved trees that coexist in a Japanese cool‐temperate forest to investigate the relationships among the biomass and total non‐structural carbohydrate (TNC) allocation patterns of saplings, resprouting ability and functional traits. The study species comprised 16 single‐stemmed species that only resprout when above‐ground biomass loss occurs and eight multi‐stemmed species that resprout regardless of whether above‐ground damage occurs or not. Single‐stemmed species with better juvenile resprouting ability had larger roots, whereas multi‐stemmed species with better juvenile resprouting ability did not necessarily depend on below‐ground reserves. Species that retain their ability to resprout until a larger size had a higher root TNC content as saplings, suggesting that they can survive major disturbances such as fire and coppicing by resprouting supported by TNC stored in their roots. Species with shade‐tolerant traits (i.e. low foliar nitrogen indicating low photosynthetic capacity, high wood density indicating high defensive investment) had small below‐ground TNC reserves irrespective of resprouting types. On the other hand, multi‐stemmed species with high wood density and high LMA (indicating high photosynthetic capacity) had small above‐ground TNC reserves. Contrary to our hypothesis, a species’ maximum size did not relate to the size of its below‐ground reserves. By considering the differences in resprouting types, we suggest more complex control of resprouting than was formerly proposed. Variation in the resprouting ability of single‐stemmed species was based on a trade‐off between below‐ground reserves for resprouting and shade‐tolerant traits. However, multi‐stemmed species can vigorously resprout irrespective of the size of its below‐ground reserves. Their multi‐stemmed architecture, well‐defended wood, high photosynthetic capacity or large above‐ground carbohydrate reserves seem to respectively contribute to their persistence. Such variation in the resprouting strategy based on a trade‐off between shade tolerance and resource storage would promote species coexistence under a range of disturbance regimes and light environments.

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The response of ‘Ventana’, an early flowering cultivar, and ‘Camarosa’, an intermediate flowering cultivar, to nursery late-season nitrogen (N) applications and digging date were studied in strawberry (Fragaria x ananassa Duch). Two experiments were conducted. In the first experiment, runner plants dug on September 20 and October 11 from a high-latitude nursery in California, were established in growth chambers set at 25°/15oC day/night temperature, 12-h photoperiod, and grown for 90 days. Compared to the first experiment, in the second experiment plants received extra N (foliar-applied) in the nursery in late summer, and runner plants were not grown in GC but in open field (Irvine, California). In the second experiment, runner plants were dug on Sept 20 and Oct 2. In both experiments, plants dug in September were exposed to ~100 chilling units (CU: hours ≤7.2°C) and plants dug in October were exposed to ~300 CU. As a result, October-dug plants had greater crown and root dry weight, and greater concentration of starch and total nonstructural carbohydrates (TNC) in leaves, crowns and roots, compared to September-dug plants. In control plants, from September to October, root TNC concentration increased in ‘Camarosa’ from ~6% to ~11%, and in ‘Ventana’ from ~14% to ~21%, and leaf N concentration ranged from 1.47 to 1.81% in ‘Camarosa’, and from 1.60 to 1.96% in ‘Ventana’. Late-summer N applications increased plant N concentration and early-season yields. Late-summer nursery N applications reduced dead leaf biomass (DLB) and dead leaf area (DLA) in both cultivars, although ‘Ventana’ had lower DLB and DLA than ‘Camarosa’. ‘Ventana’ had a greater leaf number and flowered earlier, and had greater early fruit production than ‘Camarosa’. The genetic earliness of ‘Ventana’ would be correlated with the potential of the plant for accumulation of higher initial levels of leaf N and root TNC, and for having greater leaf longevity, compared to ‘Camarosa’. Key words: Fragaria x ananassa Duch., foliar urea, carbohydrates, chilling, plant maturity, early flowering cultivars.

The impact of light quality and quantity on root-to-shoot ratio and root carbon reserves in aspen seedling stock

The available evidence suggests that for trembling aspen (Populus tremuloides) seedlings, a high root-to-shoot ratio (R:S) and high root total non-structural carbohydrate (NSC) concentration are the best predictors of future growth and outplanting success in harsh reclamation environments. To facilitate more consistent production of aspen seedlings with these characteristics requires the identification of the environmental conditions most responsible for directing resources to growth or to reserve storage. During nursery production, aspen seedlings are often sheltered from environmental stressors in greenhouses and exposed to variation in light quality and quantity, compared to outside conditions; the common result is that greenhouse grown seedlings exhibit greater allocation to shoot growth rather than to root structures and reserves. It is currently unclear whether this imbalance in R:S is the result of stronger environmental controls within a greenhouse on factors such as relative humidity, wind and temperature or rather on differences in the quantity and quality of light. In this study, we sought to determine what influence differences in both light quality and quantity, along with sheltering, has on the development of desired characteristics in aspen seedlings. To do so, we grew aspen seedlings in the field under one of six light treatments [unsheltered, full-sun (100 % full-sun); sheltered, full-sun (~90 %): sheltered, shaded (~40 %): sheltered, shaded blue (~40 %); sheltered, shaded red (~40 %); and sheltered, shaded low red/far-red ratio (~40 %)] to identify the combination of sheltering, light quality and quantity with the greatest influence on R:S and root NSC. The largest increase in desired characteristics was a peak in R:S and in root NSC for seedlings grown under unsheltered, full-sun conditions. These results suggest that growing seedlings outside, with pre-exposure to more stressful conditions prior to bud hardening, is the driver for the desired characteristics in species with indeterminate growth strategies such as aspen seedling stock.

Production and role of epicormic shoots in pruned hybrid poplar: effects of clone, pruning season and intensity

Pruning one third of crown length in summer produced the least number of epicormic branches after two growing seasons. Epicormic branches can be removed without compromising tree growth. The formation of epicormic shoots is often observed following pruning treatments, but their role in the overall tree growth is unknown. The objectives of this study were to examine how pruning intensity and season affect the production of epicormic branches and how their presence (or removal) affects tree growth and total non-structural carbohydrate reserves in the roots. Trees from four hybrid poplar clones were pruned in fall, spring, and summer at two intensities 1/3 and 2/3 of the crown length and an unpruned control. Produced epicormic branches were removed from half the trees. Pruning intensity and season were the most important factors affecting the number and biomass of epicormic shoots while clone was not. Pruning 1/3 crown length in summer reduced the emergence of epicormic shoots compared to 2/3 and spring or fall pruning. Two years after pruning, the removal of epicormic shoots did not affect height or diameter at breast height of trees, and their presence did not restore root total non-structural carbohydrates reserves to unpruned levels. We concluded that pruning should be done in summer at 1/3 of the crown length to reduce epicormic shoot formation and to avoid decreases in stem growth. If epicormic shoots appear, they can be removed without compromising tree growth.

Climate warming alters nitrogen dynamics and total non-structural carbohydrate accumulations of perennial herbs of distinctive functional groups during the plant senescence in autumn in an alpine meadow of the Tibetan Plateau, China

Although photoperiod is known to be the main factor driving plant senescence in perennial plants, temperature has also been shown to modulate this process, which suggests that climate warming will significantly impact the length of plant growing season and affect terrestrial productivity. To test this assumption, we measured the effects of simulated autumn warming on four perennial herbaceous species, i.e. Elymus nutans, Koeleria macrantha, Vicia unijuga and Allium atrosanguineum, representing two major plant functional groups (grasses and forbs), in a typical alpine meadow of the Tibetan Plateau. Warming was simulated using open-top chambers, and its effects on degradation of chlorophyll and nitrogen (N) concentration in leaves and stems were determined during the senescence processes in autumn. The potential effects of autumn warming on total non-structural carbohydrate (TNC) in roots, growth and flowering phenology were further investigated in the following year. We found that warming delayed chlorophyll degradation of perennial herbs in early phase but accelerated it in later phase, regardless of functional groups, which led to higher N concentrations in leaves and stems during the whole senescence period. Autumn warming also significantly increased TNC in roots as a result of the delayed process of chlorophyll degradation, although the magnitudes were dependent on functional groups, which may be explained by inherent differences in growth patterns and phenology between grasses and forbs. We demonstrate that warming can increase carbohydrate accumulation not only by enhancing activities of photosynthetic enzymes proved by many previous studies but by altering chlorophyll degradation and preferential allocation of resources to different compartments. Furthermore, these results suggest that the net effect of climate warming on terrestrial ecosystems will be determined by floristic composition, as contrasting immediate and lasting (one year) changes in nutrient use and carbon allocation in response to warming were observed among species.

Effects of warming on chlorophyll degradation and carbohydrate accumulation of Alpine herbaceous species during plant senescence on the Tibetan Plateau.

Plant senescence is a critical life history process accompanied by chlorophyll degradation and has large implications for nutrient resorption and carbohydrate storage. Although photoperiod governs much of seasonal leaf senescence in many plant species, temperature has also been shown to modulate this process. Therefore, we hypothesized that climate warming would significantly impact the length of the plant growing season and ultimate productivity. To test this assumption, we measured the effects of simulated autumn climate warming paradigms on four native herbaceous species that represent distinct life forms of alpine meadow plants on the Tibetan Plateau. Conditions were simulated in open-top chambers (OTCs) and the effects on the degradation of chlorophyll, nitrogen (N) concentration in leaves and culms, total non-structural carbohydrate (TNC) in roots, growth and phenology were assessed during one year following treatment. The results showed that climate warming in autumn changed the senescence process only for perennials by slowing chlorophyll degradation at the beginning of senescence and accelerating it in the following phases. Warming also increased root TNC storage as a result of higher N concentrations retained in leaves; however, this effect was species dependent and did not alter the growing and flowering phenology in the following seasons. Our results indicated that autumn warming increases carbohydrate accumulation, not only by enhancing activities of photosynthetic enzymes (a mechanism proposed in previous studies), but also by affecting chlorophyll degradation and preferential allocation of resources to different plant compartments. The different responses to warming can be explained by inherently different growth and phenology patterns observed among the studied species. The results implied that warming leads to changes in the competitive balance among life forms, an effect that can subsequently shift vegetation distribution and species composition in communities.

Effects of mixing clones on hybrid poplar productivity, photosynthesis and root development in northeastern Canadian plantations

Mixing tree cultivars or species in forest plantations can be efficient to reduce the risk of pest damages and could have a positive effect on yields if complementarity or facilitation between trees occurs. Four hybrid poplar clones (747215, Populus trichocarpa Torrey & A.Gray×P. balsamifera L.; 915004 and 915005, P. balsamifera×P. maximowiczii Henry; and 915319 P. maximowiczii×P. balsamifera) were planted in monoclonal and polyclonal plantations in three sites located in Quebec, Canada, to assess effects of clonal diversity on (i) aboveground biomass productivity, (ii) net photosynthesis and nutrient status of trees, and (iii) root spatial distribution. Stem growth was measured over five growing seasons, while root development, foliar nutrient concentrations and photosynthesis were measured during the fifth growing season. Results showed frequent but not general overyielding of trees in the polyclonal plots compared to monoclonal plots, five years after plantation establishment. Overall, stem volumes were 21% higher in the polyclonal (7.4m3ha−1) vs. monoclonal (6.1m3ha−1) plots. Effects of clone mixing on growth were greater in sites where soil nutrients were more limiting. However, foliar macronutrient concentrations (N, P, K, Ca and Mg) in trees growing in polyclonal plots were similar to those in monoclonal plots. Root development differed between the two plot layouts, with mean root:shoot ratio being greater in monoclonal (0.41:1) vs. the polyclonal (0.35:1) plots. Mixing clones increased biomass allocation aboveground, which we attributed to reduced competition between individuals of different clones and could explain overyielding in the polyclonal plots. The root fraction most distant from the stem (⩾60cm) was greater in monoclonal (67% of total root biomass) compared to polyclonal (47% of total root biomass) plots, suggesting greater belowground competition in the former, which forced roots to extend further from the stems. Effects of plot layout on net assimilation rate (Pn) depended on site, with trees in polyclonal plots having greater Pn in two of the three sites. Root total non-structural carbohydrates were greater in the polyclonal (216mgg−1) compared to the monoclonal (159mgg−1) plots. Mixing hybrid poplar clones often resulted in greater aboveground growth, lower root:shoot ratios, and different spatial root distributions, when compared to clones planted in monocultures.

Biomass and Stored Carbohydrate Compensation after Above-Ground Biomass Removal in a Perennial Herb: Does Environmental Productivity Play a Role?

Many plant species are able to tolerate severe disturbance leading to removal of a substantial portion of the body by resprouting from intact or fragmented organs. Resprouting enables plants to compensate for biomass loss and complete their life cycles. The degree of disturbance tolerance, and hence the ecological advantage of damage tolerance (in contrast to alternative strategies), has been reported to be affected by environmental productivity. In our study, we examined the influence of soil nutrients (as an indicator of environmental productivity) on biomass and stored carbohydrate compensation after removal of aboveground parts in the perennial resprouter Plantago lanceolata. Specifically, we tested and compared the effects of nutrient availability on biomass and carbon storage in damaged and undamaged individuals. Damaged plants of P. lanceolata compensated neither in terms of biomass nor overall carbon storage. However, whereas in the nutrient-poor environment, root total non-structural carbohydrate concentrations (TNC) were similar for damaged and undamaged plants, in the nutrient-rich environment, damaged plants had remarkably higher TNC than undamaged plants. Based on TNC allocation patterns, we conclude that tolerance to disturbance is promoted in more productive environments, where higher photosynthetic efficiency allows for successful replenishment of carbohydrates. Although plants under nutrient-rich conditions did not compensate in terms of biomass or seed production, they entered winter with higher content of carbohydrates, which might result in better performance in the next growing season. This otherwise overlooked compensation mechanism might be responsible for inconsistent results reported from other studies.

Ontogenetic Changes in Carbohydrate Storage and Sprouting Ability in Pioneer Tree Species in Peninsular Malaysia

AbstractSprouting ability is highly variable among different tree species. In many cases, there are trade‐offs in carbon allocations between growth and storage in seedlings. However, this trade‐off is likely to change with growth stages from seedling to mature plant because carbon investments in reproductive activities and/or risk of disturbance also change by species and growth stage. To examine how sprouting ability and carbohydrate storage change with growth stage, we compared two tropical secondary‐forest trees, Macaranga bancana and M. gigantea, which have different ecological traits. Maximum tree size and growth rate are higher in M. gigantea. We monitored sprout growth and stored resources, including total non‐structural carbohydrate (TNC) and nitrogen in the root, among different tree sizes for 12 months following stem‐cutting treatment. Sprouting ability (total sprout mass) and TNC concentrations were significantly higher in small individuals than in larger specimens in both species. TNC concentration decreased in all size classes after stem cutting. Macaranga bancana had greater sprout survivorship than M. gigantea, which had higher sprouting ability in larger tree‐size classes. Thus, sprouting ability likely depends on root TNC concentration and tree‐size class in both Macaranga species. Higher TNC concentration and sprout survival rates in M. bancana may be related to greater carbon allocation in survival than in growth. This hypothesis is consistent with the ecological traits of M. bancana, such as its growth rate, which was lower than that of M. gigantea.

English

The pattern of total nonstructural carbohydrate (TNC) accumulation in strawberry ( Fragaria ananassa Duch.) nursery runner plants, cv. eCamarosaf, was determined for three growing seasons. Plant growth and fruit production patterns were also evaluated. The experiments were carried out on plants propagated in high latitude (41‹50' N) and high elevation (1292 m) nurseries in Siskiyou County, California. Plants were sampled beginning in late summer through early autumn and analyzed for dry mass (DM) and TNC. Plants from different digging dates were established in growth chambers (GC) at UC Davis or fruit evaluation plots in Irvine, California. In the nursery, TNC concentration in storage tissues increased steadily from the second week of September to the third week of October, and crown and root TNC concentration was positively correlated with the accumulation of chilling units (hours .7.2‹C). The root TNC concentration consistently increased from 6 to 10% DM from mid-September to the first week of October. Transplant growth and fruiting pattern were affected by digging date. Overall, the roots were more sensitive to chilling in terms of TNC accumulation, than the crowns. Therefore, roots would be the appropriate organ for assessing TNC status and potential digging dates of strawberry nursery runner plants early in the fall. Key words : Transplant, carbohydrate, chilling, growth analysis.

Morphological and physiological responses of beech and oak seedlings to canopy conditions: why does beech dominate the understory of unmanaged oak fuelwood stands?

Secondary forest succession after abandonment of traditional agricultural and silvicultural lands is occurring in many parts of the world. Quercus crispula Blume– Quercus serrata Murray fuelwood stands have so far been artificially maintained in natural Fagus crenata Blume forests, central Japan, by resprouting after cutting. It is known that unmanaged fuelwood stands return to F. crenata dominated stands. This study aimed to examine why the two Quercus species are replaced by F. crenata by investigating seedling morphological and physiological responses of the three species to canopy conditions (forest edge and understory). The two Quercus species allocated more carbon to roots and stored more total nonstructural carbohydrates in roots as compared with F. crenata. Therefore, the two Quercus species allocate more photosynthetic production to roots than aboveground growth to maintain sprouting ability. On the contrary, F. crenata increased the light-harvesting efficiency (i.e., low leaf mass per area and high chlorophyll concentration) in the understory and increased height growth at the forest edge by greater allocation to stem. These traits would be beneficial for an increase in survival in the understory and height growth at the forest edge. Therefore, it is suggested that Quercus species in unmanaged stands will be replaced by F. crenata, a competitively superior species.

Partitioning of carbon allocation to reserves or growth determines future performance of aspen seedlings

Increasingly, trembling aspen (Populus tremuloides Michx.) is being planted in stressful situations such as forest land reclamation, afforestation and forest restoration in North America. This is due to its fast potential for growth and high resiliency, but its indeterminate growth strategy provides a special challenge in creating suitable planting stock for these sites. Clues from naturally established aspen seedlings suggest that root total non-structural carbohydrate (TNC) reserves and root:shoot ratio could be strongly related to subsequent seedling establishment and growth. Carbon allocation in plants is generally partitioned between reserve accumulation and growth and development. Under conditions in controlled nurseries, the allocation of carbohydrates to reserves could be manipulated in order to produce seedlings designed for specific environmental conditions. To manipulate seedling characteristics we attempted to induce premature bud set during nursery culture while allowing continued photosynthesis. Treatments included applying different fertilizer regimes, light intensities, reducing photoperiod and use of a shoot growth inhibitor. The shoot growth inhibitor was the most reliable treatment and resulted in complete bud set, while blackout was successful only when seedlings were grown outside. Low nutrient treatments also resulted in early bud set; however, leaves were abscised much earlier. There was a distinct trade-off between growth and reserve accumulation with the late bud set. A longer period of height growth reduced root and total TNC reserves, while early bud set allowed for continued photosynthesis and produced the highest levels of root and total TNC reserves in seedlings. Increased TNC reserves of aspen planting stock was positively related to height growth after outplanting, with root TNC reserves as high as 33% of dry weight and root:shoot ratios greater than 2 associated with the best growth.

Ecophysiological responses of salt cedar (Tamarix spp. L.) to the northern tamarisk beetle (Diorhabda carinulata Desbrochers) in a controlled environment

The northern tamarisk beetle (Diorhabda carinulata Desbrochers) was released in several western states as a biocontrol agent to suppress Tamarix spp. L. which has invaded riparian ecosystems; however, effects of beetle herbivory on Tamarix physiology are largely undocumented and may have ecosystem ramifications. Herbivory by this insect produces discoloration of leaves and premature leaf drop in these ecosystems, yet the cause of premature leaf drop and the effects of this leaf drop are still unknown. Insect herbivory may change leaf photosynthesis and respiration and may affect a plant’s ability to regulate water loss and increase water stress. Premature leaf drop may affect plant tissue chemistry and belowground carbon allocation. We conducted a greenhouse experiment to understand how Tamarix responds physiologically to adult beetle and larvae herbivory and to determine the proximate cause of premature leaf drop. We hypothesized that plants experiencing beetle herbivory would have greater leaf and root respiration rates, greater photosynthesis, increased water stress, inefficient leaf nitrogen retranslocation, lower root biomass and lower total non-structural carbohydrates in roots. Insect herbivory reduced photosynthesis rates, minimally affected respiration rates, but significantly increased water loss during daytime and nighttime hours and this produced increased water stress. The proximate cause for premature leaf drop appears to be desiccation. Plants exposed to herbivory were inefficient in their retranslocation of nitrogen before premature leaf drop. Root biomass showed a decreasing trend in plants subjected to herbivory. Stress induced by herbivory may render these trees less competitive in future growing seasons.