Increase In Belowground Biomass Research Articles

Estimation on Individual-Level Carbon Sequestration Capacity of Understory Perennial Herbs

AbstractThe carbon sequestration capacity of plants has been used as a nature-based solution to reduce carbon emissions. Perennial herbs potentially contribute to carbon sequestration by allocating carbon to belowground parts as well as trees. As individual-level estimations have mainly been carried out for tree species, individual-level carbon sequestration for understory perennial herb species is poorly understood. To estimate the below- and aboveground carbon sequestration capacity, ten perennial herb species were planted for field experiment. Individual carbon sequestration by biomass was calculated by measuring the aboveground- and estimating belowground biomass gain at harvest. We further measured non-destructive aboveground parameters, such as photosynthesis and leaf area, to estimate the belowground biomass. Four species (Aconitum jaluense Kom., Aquilegea oxysepala Trautv. & C.A.Mey., Disporum smilacinum A.Gray, and Polygonatum odoratum var. pluriflorum (Miq.) Ohwi) showed the positive belowground carbon sequestration level during the experimental period. Correlation analyses indicated that the aboveground biomass and leaf area at senescence stage could be used as non-destructive estimates of belowground carbon sequestration. The perennial herb species habitat suitability for use as additional carbon sinks in urban forests and for forest restoration should be assessed based on the increase in belowground biomass.

Light grazing facilitates carbon accumulation in subsoil in Chinese grasslands: A meta-analysis.

Grazing by livestock greatly affects the soil carbon (C) cycle in grassland ecosystems. However, the effects of grazing at different intensities and durations on the dynamics of soil C in its subsoil layers are not clearly understood. Here, we compiled data from 78 sites (in total 122 published studies) to examine the effects of varying grazing intensities and durations on soil C content at different depths for grasslands in China. Our meta-analysis revealed that grazing led to an overall decrease in soil C content and productivity of above-ground vegetation (e.g., above-ground biomass and litter) but an increase in below-ground biomass. Specifically, the effects of grazing on soil C content became less negative or even positive with increasing soil depths. An increase of soil C content was consequently found under light grazing (LG), although soil C content still decreased under moderate and heavy grazing. The increase in soil C content under LG could be largely attributed to the increase of soil C content in subsoil layers (>20cm), despite that soil C content in surface soil layer (0-20cm) decreased. Moreover, the magnitude of increase in soil C content under LG in subsoil layers increased with grazing duration. A possible reason of the increase in soil C content in the subsoil layers was due to the increases in below-ground biomass. Our study highlights that LG may modify the allocation of C input and promote its accumulation in subsoil layers, thus offsetting the negative impact of grazing on surface soil C content, a finding that has significant implications for C sequestration in grasslands.

Caution Is Needed in Quantifying Terrestrial Biomass Responses to Elevated Temperature: Meta-Analyses of Field-Based Experimental Warming Across China

Certainty over warming-induced biomass accumulation is essential for addressing climate change. However, no previous meta-analysis has investigated this accumulation across the whole of China; also unclear are the differences between herbaceous and woody species and across plant phylogeny, which are critical for corresponding re-vegetation. We extracted data from 90 field-based experiments to reveal general patterns and driving factors of biomass responses all over China. Based on traditional meta-analyses, a warmer temperature significantly increased above- (10.8%) and below-ground (14.2%) biomass accumulation. With increasing warming duration (WarmD) and plant clade age, both above-ground and below-ground biomass showed significant increases. However, for herbaceous versus woody plants, and the whole community versus its dominant species, responses were not always constant; the combined synergies would affect accumulative response patterns. When considering WarmD as a weight, decreases in total above-ground biomass response magnitude were presented, and the increase in below-ground biomass was no longer significant; notably, significant positive responses remained in tree species. However, if phylogenetic information was included in the calculations, all warming-induced plant biomass increases were not significant. Thus, it is still premature to speculate whether warming induces biomass increases in China; further long-term experiments are needed regarding phylogeny-based responses and interspecies relations, especially regarding woody plants and forests.

Precipitation amount and frequency affect seedling emergence and growth of Reaumuria soongarica in northwestern China

Climate change is shifting the amount and frequency of precipitation in many regions, which is expected to affect seedling recruitment across ecosystems. However, the combined effects of precipitation amount and frequency on seedling recruitment remain largely unknown. An understanding of the effects of precipitation amount and frequency and their interaction on seedling emergence and growth of typical desert plants is vital for managing populations of desert plants. We conducted two experiments to study the effects of variation in precipitation on Reaumuria soongarica (Pall.) Maxim. First, greenhouse experiments were conducted to examine the effects of three precipitation amount treatments (ambient, +30%, and –30%) and two precipitation frequency treatments (ambient and –50%) on seedling emergence. Second, the morphological responses of R. soongarica to changes in precipitation amount and frequency were tested in a controlled field experiment. Stage-specific changes in growth were monitored by sampling in different growth seasons. Our results showed that precipitation amount significantly affected germination, seedling emergence, and growth of R. soongarica, and there was a larger effect with decreased precipitation frequency compared with ambient. Germination and seedling emergence increased as precipitation increased under the same frequency of precipitation. The highest emergence percentage was obtained with a 30% increase in precipitation amount and a 50% reduction in precipitation frequency. Compared with ambient precipitation, a 30% increase in precipitation amount increased above- and below-ground biomass accumulation of R. soongarica during the growth season. A decrease of 30% in precipitation amount also resulted in an increase in below-ground biomass and root/shoot ratio in the early stages of the growth season, however, above- and below-ground biomass showed the opposite results at the end of the growth season, with larger effects on above-ground than below-ground biomass under decreased precipitation frequency. When precipitation frequency decreased by 50%, values of all growth traits increased for a given amount of precipitation. We concluded that precipitation frequency may be as important as precipitation amount to seedling emergence and growth of R. soongarica, and that understanding the effects of precipitation variability on seedling recruitment requires the integration of both precipitation amount and frequency. In particular, the combination of a 30% increase in precipitation amount and 50% reduction in precipitation frequency increased the emergence and growth of seedlings, suggesting that alteration of amount and frequency of precipitation caused by climate change may have significant effects on seedling recruitment of R. soongarica.

Soil particulate organic matter increases under perennial bioenergy crop agriculture

Annual row crop agriculture contributes to carbon (C) losses from Midwest soils, while the establishment of perennial crops for food and fuel has the potential to increase soil C stocks. Perennial grasses eliminate the need for tillage and increase belowground biomass, both critical to the accumulation and conservation of soil organic matter and to soil C sequestration. The effect of C4 perennial grasses on particulate organic matter carbon (POM-C), consisting primarily of partially decomposed plant material, was evaluated in Illinois, where native switchgrass (Panicum virgatum L.) and a sterile hybrid of the Asian grass Miscanthus (Miscanthus x giganteus) were planted as bioenergy feedstocks at the University of Illinois Energy Farm in 2008. Six years after establishment of perennial crops, POM-C was compared with a maize-maize-soybean (Zea mays L., Glycine max L.) rotation typical of the area and a 28-species restored prairie. POM-C concentrations increased for all crops between 31 and 71% over 6 years, with the greatest increases in prairie and M. x giganteus soils. POM-C concentrations were highest at the 0–10 cm depth. Isotopic analyses showed 23–44% of POM-C was new C4 material under perennial bioenergy crops after 6 years. As soil organic matter is primarily plant-derived, increases in POM-C reflect increased organic matter inputs or decreases in the rate of decomposition from the cessation of tillage. Increases in POM-C under annual row crops may result from the incorporation of aboveground organic matter by tillage, while POM-C increases in untilled perennial crops mirror increases in belowground biomass. As soil aggregation protects POM-C from microbial degradation, untilled soils under long-term perennial crop production increase the residence time for soil C.

Combined effects of earthworms and IAA-producing rhizobacteria on plant growth and development

Micrococcus luteus is considered a deleterious rhizo-bacteria (DRB) or a plant growth promoting rhizobacteria (PGPR) depending on the plant species. This bacteria is known to produce Indole Acetic Acid (IAA), a hormone that can affect plant growth. In this study, we tested the effect of M. luteus on the model plant Arabidopsis thaliana at three different concentrations (105, 106 and 107CFUml−1), to characterize its effect on plants according to its concentration, and eventually classify it as DRB or PGPR. These bioassays were conducted in the presence or absence of earthworms (Aporrectodea caliginosa), known to modify A. thaliana growth through the stimulation of IAA-producing bacteria. We wanted to test the ability of earthworms to synergistically enhance potential positive effects of the bacteria through dispersal or stimulation, or to control the negative effect of the bacteria through grazing or inhibition. This would help determine the potential of using earthworms as a vector or selective filter of bacteria inoculated or present in the field. M. luteus had a negative effect on plant growth proportional to the bacteria inoculum size. In the absence of bacteria, earthworms were responsible for an 85% increase in belowground biomass, but no effect on aboveground or total biomass was observed. When both organisms were present, the positive effect of earthworms progressively decreased with increasing densities of M. luteus. M. luteus affected floral organs and root system structure, whereas earthworms affected only root system structure. Therefore, M. luteus is a DRB for A. thaliana, and earthworms cannot be used as a biocontrol agent for this DRB in conditions such as those of our experiment.

The effects of elevated atmospheric humidity on soil respiration components in a young silver birch forest

The predicted increase in precipitation at northern latitudes is an important factor affecting the functioning of forest ecosystems, yet the influence of increased atmospheric humidity on the forest ecosystem carbon cycle is still largely unknown. Our objectives were to determine the effect of elevated atmospheric humidity on soil respiration in silver birch (Betula pendula Roth.) plantations in a Free Air Humidity Manipulation experimental facility (FAHM). Soil respiration was monitored monthly from May to October, in 2008 and 2009 in three control and in three misting plots; soil temperature and soil moisture were measured simultaneously. Fine-root and rhizome biomass of the understory was measured by sequential soil cores. Soil microbial biomass and basal respiration were measured using manometric respirometers. After the first two years of manipulation, humidification led to lower soil respiration. Soil temperature was the main factor influencing seasonal dynamics of soil respiration, describing up to 75% of the total variation of soil respiration. Soil moisture had a weak negative effect on soil respiration. Humidification caused a remarkable increase in below-ground biomass and the production of the understory, and a 28% increase in the basal respiration of microbes. However, above-ground biomass and root turnover rate of the understory were almost unchanged. Hence, elevated atmospheric humidity significantly affects carbon cycle of deciduous forest. However, further studies are necessary for a better understanding of soil respiration response to changes in atmospheric humidity, in order to predict carbon balance in changing climate conditions.

Seasonal Biomass and Starch Allocation of Common Reed (Phragmites australis) (Haplotype I) in Southern Alabama, USA

AbstractCommon reed (Phragmites australis) is a nonnative invasive perennial grass that is problematic in aquatic and riparian environments across the United States. Common reed often forms monotypic stands that displace native vegetation which provide food and cover for wildlife. To help maintain native habitats and manage populations of common reed in the United States, an understanding of its life history and starch allocation patterns are needed. Monthly biomass samples were harvested from sites throughout the Mobile River delta in southern Alabama, USA from January 2006 to December 2007 to quantify seasonal biomass and starch allocation patterns. Total biomass of common reed throughout the study was between 1375 and 3718 g m−2 depending on the season. Maximum aboveground biomass was 2200 ± 220 g m−2 in October of 2006 and 1302 ± 88 g m−2 in December of 2007. Maximum belowground biomass was seen in November of 2006 and 2007 with 1602 ± 233 and 1610 ± 517 g m−2 respectively. Biomass was related to ambient temperature, in that, as temperature decreased aboveground biomass (p = 0.05) decreased. Decreases in aboveground biomass were followed by an increase in belowground biomass (p < 0.01). Starch comprised 1 to 10% of aboveground biomass with peak temporary storage occurring in July and August 2006 and September to November of 2007. Belowground tissues stored the majority of starch for common reed regardless of the time of year. Overall, belowground tissues stored 5 to 20% of total starch for common reed with peak storage occurring in December 2006 and October 2007. Starch allocation to belowground tissues increased as temperatures decreased. Understanding seasonal life history patterns can provide information to guide management strategies by identifying the vulnerable points in biomass and starch reserves in common reed.

Summer warming effects on biomass production and clonal growth of Leymus chinensis

Understanding how the biomass production and clone growth of perennial grasses respond to summer warming is crucial for understanding how grassland productivity responds to global warming. Here, we experimentally investigated the effects of summer warming on the biomass production and clonal growth of potted Leymus chinensis in a phytotron. Summer warming significantly decreased the biomass of both parent and daughter shoots, slightly increased the belowground biomass, and lead to a significant increase in root : shoot ratio. Warming significantly increased the total belowground bud number and decreased the daughter shoot number. Importantly, the proportions of each type of bud changed; vertical apical rhizome buds decreased, while horizontal rhizome buds increased in number. The change in proportions of each type of bud is closely related to the decrease in daughter shoot number, rhizome number and length, as well as the decrease in aboveground biomass and increase in belowground biomass. These results indicate that, as a rhizomatous, perennial grass, L. chinensis adopts a selective growth strategy that reduces the energy allocated to aboveground growth and emphasises the development of belowground organs. The implication is that continued summer warming, will further reduce the aboveground biomass production of temperate grasslands dominated by rhizomatous, perennial grasses. Inevitably, species that depend on these grasses for forage will suffer should global climate warming continue.

Effects of elevated CO2 concentration and nitrogen supply on biomass and active carbon of freshwater marsh after two growing seasons in Sanjiang Plain, Northeast China

An experiments were carried out with treatments differing in nitrogen supply (0, 5 and 15 g N/m2) and CO2 levels (350 and 700 micromol/mol) using OTC (open top chamber) equipment to investigate the biomass of Calamagrostis angustifolia and soil active carbon contents after two years. The results showed that elevated CO2 concentration increased the biomass of C. angustifolia and the magnitude of response varied with each growth period. Elevated CO2 concentration has increased aboveground biomass by 16.7% and 17.6% during the jointing and heading periods and only 3.5% and 9.4% during dough and maturity periods. The increases in belowground biomass due to CO2 elevation was 26.5%, 34.0% and 28.7% during the heading, dough and maturity periods, respectively. The responses of biomass to enhanced CO2 concentrations are differed in N levels. Both the increase of aboveground biomass and belowground biomass were greater under high level of N supply (15 g N/m2). Elevated CO2 concentration also increased the allocation of biomass and carbon in root. Under elevated CO2 concentration, the average values of active carbon tended to increase. The increases of soil active soil contents followed the sequence of microbial biomass carbon (10.6%) > dissolved organic carbon (7.5%) > labile oxidable carbon (6.6%) > carbohydrate carbon (4.1%). Stepwise regressions indicated there were significant correlations between the soil active carbon contents and plant biomass. Particularly, microbial biomass carbon, labile oxidable carbon and carbohydrate carbon were found to be correlated with belowground biomass, while dissolved organic carbon has correlation with aboveground biomass. Therefore, increased biomass was regarded as the main driving force for the increase in soil active organic carbon under elevated CO2 concentration.

Effects of drought stress and N supply on the growth, biomass partitioning and water-use efficiency of Sophora davidii seedlings

A greenhouse experiment was conducted in order to understand the adaptation responses to different water and N conditions, and further explore if additional N supply could improve the water-use efficiency (WUE) and adaptability of Sophora davidii seedlings under dry conditions. Two-month-old seedlings were subjected to a completely random design with three water (80, 40 and 20% water field capacity (FC)) and three N supply (N0: 0, Nl: 92 and Nh:184 mg N kg −1 soil) regimes. Drought stress dramatically decreased seedlings height, basal diameter, leaf number, leaf area, root length, and biomass production. An increase in below-ground biomass was observed indicating a higher root/shoot ratio (R/S) under drought stress conditions, and drought further decreased relative water content (RWC) and WUE. On the other hand, S. davidii seedlings exhibited strong responses to N supply, but the responses were inconsistent with the various N supply levels. Low N supply (Nl) increased seedlings height, basal diameter, leaf number, leaf area, and biomass production, but decreased root length. In contrast, high N supply (Nh) decreased or had little effect on these growth characteristics. N supply increased leaf percentages, but decreased fine root percentages. In addition, Nl rather than the other two N treatments increased leaf area ratio (LAR), leaf/fine root mass ratio (L/FR), R/S and RWC under severe drought stress (20% FC), even though these parameters could increase with the Nh treatment under well-watered condition (80% FC). Moreover, Nl also increased WUE under three water conditions, but Nh had little effect on WUE under drought stress conditions (40% FC and 20% FC). The results suggested that water and N co-limited the growth of S. davidii seedlings, and the seedlings exhibited great positive responses to Nl in this study. Appropriate or low N supply, therefore, would be recommended to stimulate growth, enhance WUE, alleviate drought stress, and consequently contribute to S. davidii seedling establishment under dry condition, but excess N supply should be avoided.

Effect of functional group richness and species richness in manipulated productivity–diversity studies: a glasshouse pot experiment

Species and functional group (grasses, legumes, creeping nonlegume forbs, rosette nonlegume forbs) richness of species assemblages composed of 16 species from four functional plant groups were manipulated to evaluate the productivity-diversity relationships in a greenhouse pot experiment. Pots were filled with sand, and supplied at two levels of nutrients. The plants were grown in monocultures, two, four, eight and 16 species mixtures. Individual two, four, and eight species mixtures differed in the richness of functional groups. Although the two characteristics of biodiversity, i.e. species and functional group richness, were necessarily correlated, it was shown that it is possible to separate their effect statistically, and also test for their common effect without pronounced loss of test power. There was a pronounced increase of average aboveground biomass and a mild increase in belowground biomass with biodiversity. The effect of functional group richness was more pronounced than the effect of the number of species. By using the method of Loreau and Hector (Nature 411 (2001) 72), selection and complementarity effects were statistically separated, and the overyielding index was calculated as a ratio of the productivity of a mixture to the productivity of its most productive component (to demonstrate transgressive overyielding). Positive values of complementarity and transgressive overyielding were both found, particularly in some rich communities and under high nutrient levels. Complementarity significantly increased only with functional group richness and mainly under high nutrients in the belowground biomass. Some species, when grown in monocultures, had decreased productivity under higher nutrients, and thus were more productive in mixtures than in monocultures. It seems that those species suffered from too high nutrient levels when grown in monocultures, but not in the presence of other species, which were able to use the nutrients in high concentrations and effectively decrease the nutrient levels. As a consequence, mixtures of high diversity were always more productive under high nutrients. The difference in species proportions between high and low nutrients, characterized by chord distance, increased with species richness. The relative change in productivity decreased with the number of functional groups. This suggests that species richness might lead to stabilization of aggregate characteristics (like total productivity) under changing environmental conditions by changing the proportions of individual species.

Effects of simultaneous changes in light, nutrients, and herbivory levels, on the structure and function of a subtropical turtlegrass meadow

The interactive effects of light, nutrients, and simulated herbivory on the structure and functioning of a subtropical turtlegrass bed were analyzed monthly from May to October 2001 in Perdido Bay, FL. For each of the three factors, two levels were evaluated in a factorial design with four replicates per treatment. The variables included: light, at ambient and 40% reduction; nutrients, at ambient and 2× ambient concentrations; and herbivory, with no herbivory and simulated effects of a density of 15 sea urchins/m 2. In practice, light levels turned out to be 40% of surface PAR for ambient conditions, and 16% for shaded plots. Biomass removed as herbivory represented, on average, slightly less than 20% of the above-ground biomass. Separate three-way ANOVAs found no significant three-way interactions for any of the response variables, and few two-way interactions. There were no significant nutrient effects on turtlegrass above-ground biomass, although nutrient additions produced significant decreases in epibiont biomass, and net above-ground primary production (NAPP); significant increases in below-ground biomass during the peak of the growing season. Shoot density and average number of leaves per shoot increased significantly, while the C/N ratio of the oldest leaf in the enriched plots decreased significantly. Light reduction significantly negatively affected all response variables, except below-ground biomass, shoot density and leaf length. Herbivory had isolated and inconsistent significant effects on below-ground biomass, shoot density, average number of leaves per shoot, and leaf length and width. Overall, our results indicate that nutrients are not limiting in Perdido Bay, and that nutrient additions had mostly detrimental effects. Light appeared to be the most important variable limiting seagrasses growth and abundance, and as with terrestrial plants, seagrasses seemed to respond more to light and nutrients than to herbivory. However, it is essential that additional tests of the single and interactive effects of the three key factors of light, nutrients and herbivory be done to evaluate the generality of our work, since our study is the first of its kind in seagrass meadows.

Global climate change, rice productivity and methane emissions: comparison of simulated and experimental results

Irrigated rice production is a major food source for a large portion of the world’s population, and a major anthropogenic source of the greenhouse gas methane (CH 4). Potential impacts of global climate change [elevated carbon dioxide (CO 2) and/or elevated temperature] on rice can be predicted with simulation models, but experiments are necessary to determine how well these models mimic the responses of the field crop. This paper compares grain yield, biomass, and methane emissions from experiments at the International Rice Research Institute (IRRI) at Los Baños, the Philippines, with potential responses based on simulations using the ORYZA1 process model and the climate data from those experiments. Yield and biomass were compared for the 1995 and 1996 dry seasons (DS) and the 1994 wet season (WS). Emissions of CH 4 from rice fields were evaluated for the 1995 WS and 1996 DS. Simulated and experimental responses (adjusted for effects of the open-top chambers on plant growth) differed with climate change scenario, response parameter, and season. Under current climate conditions (ambient CO 2 and ambient temperature), simulated grain yield was 14% lower than the adjusted experimental grain yield in the 1996 DS, but was 17 and 37% higher than experimental grain yield in the 1995 DS and 1994 WS, respectively. With current climate, simulations underestimated experimental aboveground, belowground, and total biomass. The simulated CH 4 emissions were the same as the experimental emissions, assuming CH 4 emissions were 2.9% of the simulated total biomass carbon. With elevated CO 2 and ambient temperature, simulations predicted greater increases (compared with current climate) in grain yield, aboveground biomass, and total biomass, but generally smaller increases in belowground biomass and CH 4 emissions than the significant (at p < 0.05) increases that were found experimentally. With ambient CO 2 and elevated temperature, both simulations and experiments generally showed either no change or a decrease in grain yield and biomass, but none of the responses in the experiments were statistically significant. Simulated ambient CO 2 and elevated temperature resulted in a smaller decrease in CH 4 emissions than the significant decrease found in the experiments. For both elevated CO 2 and elevated temperature, simulated grain yield increased in all three seasons, whereas there were no significant effects on experimental grain yield. The simulations predicted smaller increases in belowground biomass and CH 4 emissions with elevated CO 2 and elevated temperature than the significant increases in the experiments. To better correspond to experimental results, this study suggested that current simulation models could be improved in terms of effects of temperature on grain yield and use of belowground biomass to estimate CH 4 emissions.

Recovery of15N-labelled fertilizer by Coastal bermudagrass in lignite minesoil

Minesoils developed from lignite surface mining in Texas are nutrient-poor and have a high N retention capacity. A major concern of landowners and soil conservationists is the response of Coastal bermudagrass to the application of low rates of ammonium-N fertilizer on these nutrient-poor minesoils. A glasshouse study, using15N-labelled ammonium sulfate fertilizer and lignite minesoil, was conducted to measure Coastal bermudagrass biomass production and fertilizer recovery during establishment in response to clipping at 2, 4, and 8 week intervals. At N rates of 0, 40, and 80 kg N ha−1,increases in N fertilization increased Coastal bermudagrass aboveground biomass 5-fold, but showed only small increases in belowground biomass. Recovery of ammonium-N fertilizer ranged from 54 to 63%. Roots contained approximately the same N content across all fertilizer rates suggesting that young, estabilishing, Coatal bermudagrass roots reserve N until their N requirement is met. As more N is obtained above that which was needed to maintain roots, then additional N taken up by the plant was transported to aboveground plant parts for growth. Frequent clipping intensified N transport to aboveground tissues. Reduced amounts of N were contained in roots after clipping due to reductions in root growth, biomass, and resource demand. Fertilization of Coastal bermudagrass at low N rates with different N fertilizer forms influenced the distribution of N in the plant and affected N recovery by different parts of the plant.