Belowground Biomass Production Research Articles

Cover Crop Systems Impact on Biomass Production, Carbon-to-Nitrogen Ratio, Forage Quality, and Soil Health in a Semi-arid Environment

Cover cropping is a soil restorative strategy that can save degraded soils and offer additional benefits relative to the traditional fallow-based practice in semi-arid cropping systems. This study aimed to (i) quantify the above (shoot)- and belowground (root) biomass production, nutritive value, and tissue carbon and nitrogen concentrations from different annual cool-season cover crop systems, and (ii) determine their effects on soil organic carbon, total nitrogen, soil respiration, and soil microbial population biomass in a semi-arid environment. Treatments used were monocultures of annual ryegrass (Lolium multiflorum Lam.), oat (Avena sativa L.), faba bean (Vicia faba L.), yellow sweetclover [Melilotus officinalis (L.) Lam], winter pea (Pisum sativum L.), two three-species mixtures (Mix 1: annual ryegrass + faba bean + yellow sweetclover and Mix 2: Oat + faba bean + winter pea), and a fallow laid out in a randomized complete block design with three replications. Averaged across years, Mix 2 produced greater shoot biomass (9714 kg DM ha-1; SE = 699) than all other cover crop systems except, the monoculture of oat (7970 kg DM ha-1; SE = 699). The plant tissue C/N ratio of the mixtures and monoculture legumes was mostly similar (range = 19.4 – 29.1). Overall, legumes produced superior relative feed value (RFV; 112 – 161) compared to grass monocultures and mixtures (RFV; 80 – 95). Soil gram-negative bacteria biomass was greatest under the yellow sweetclover monoculture. Based on the results of this study, the mixed cover crop systems (Mix 1 and Mix 2) offered a better chance of fulfilling the dual role of soil health improvement and feed quality for livestock in this semi-arid environment.

Surviving the desert's grasp: Decipherment phreatophyte Tamarix aphylla (L.) Karst. Adaptive strategies for arid resilience

Phreatophytes play an important role in maintaining the ecological services in arid and semi-arid areas. Characterizing the interaction between groundwater and phreatophytes is critical for the land and water management in such areas. Therefore, the identification of key traits related to mitigating desertification in differently adapted T. aphylla populations was the focus. Fifteen naturally adapted populations of the prominent phreatophyte T. aphylla from diverse ecological regions of Punjab, Pakistan were selected. Key structural and functional modifications involved in ecological success and adaptations against heterogeneous environments for water conservation include widened metaxylem vessels in roots, enlarged brachy sclereids in stems/leaves, tissues succulence, and elevated organic osmolytes and antioxidants activity for osmoregulation and defense mechanism. Populations from hot and dry deserts (Dratio: 43.17−34.88) exhibited longer roots and fine-scaled leaves, along with enlarged vascular bundles and parenchyma cells in stems. Populations inhabiting saline deserts (Dratio: 38.59−33.29) displayed enhanced belowground biomass production, larger root cellular area, broadest phloem region in stems, and numerous large stomata in leaves. Hyper-arid populations (Dratio: 33.54−23.07) excelled in shoot biomass production, stem cellular area, epidermal thickness, pith region in stems, and lamina thickness in leaves. In conclusion, this research highlights T. aphylla as a vital model for comprehending plant resilience to environmental stresses, with implications for carbon sequestration and ecosystem restoration.

Peat formation potential of temperate fens increases with hydrological stability

Peat formation is the key process responsible for carbon sequestration in peatlands. In rich fens, peat is formed by brown mosses and belowground biomass of vascular plants. However, the impact of ecohydrological settings on the contribution of mosses and belowground biomass to peat formation remains an open question. We established seven transects in well-preserved fens in NE Poland along an ecohydrological gradient from mesotrophic sedge-moss communities with stable water levels, to more eutrophic tall sedge communities with higher water level fluctuations. In each transect, we measured the production of brown mosses (using the plug method), aboveground vascular plant biomass (one year after cutting) and belowground biomass (using ingrowth cores). Decomposition rates of all biomass fractions were assessed using litter bags. The first-year surplus of potentially peat-forming fractions, i.e., mosses and belowground biomass, decreased with increasing water level fluctuations and along a vegetation gradient from sedge-moss to tall sedge communities. Moss production was highest in the sedge-moss fen with a stable water level at the ground surface. We did not detect any difference in belowground biomass production across the gradient but found it to be consistently higher in the upper 0–5 cm than in the deeper layers. The decomposition rate also showed no response to the gradient, but differed between biomass types, with aboveground biomass of vascular plants decomposing 2.5 times faster than belowground biomass and mosses. Pattern of peat formation potential along the ecohydrological gradient in rich fen was strongly driven by brown moss production. Sedge-moss fens with a stable water level at the ground surface have the highest peat formation capacity compared to other vegetation types. In the part of the gradient that is poorer in nutrients, vascular plants invest in belowground production, and mosses dominate the aboveground layer.

Nitrogen, phosphorus, and potassium co‐limitation in terrestrial ecosystems: A global meta‐analysis

Societal Impact StatementNitrogen, phosphorus, and potassium are essential elements for plant growth and are the primary nutrients in commercial fertilizers. However, the extent to which these nutrients individually limit plant growth is still unclear, as is the influence of their interactions. Using a meta‐analysis approach, plant growth was found to be co‐limited by nitrogen, phosphorus, and potassium. Furthermore, these findings demonstrate that multiple nutrient additions are primarily additive, with the exception of synergistic effects observed with NP additions on plant growth. These findings are important as they provide a timely and valuable reference for assessing the ecosystem‐scale consequences of increasing nutrient deposition caused by human activities.Summary Numerous field studies and a few meta‐analyses have confirmed that terrestrial primary production is individually or jointly limited by nitrogen (N) and phosphorus (P). Meanwhile, a recent synthesis emphasized that potassium (K) limitation in terrestrial ecosystems is more widespread than previously thought. However, it remains unclear whether N, P, and K co‐limit terrestrial production and how their interactions influence plant growth. Therefore, we conducted a globally comprehensive synthesis of a total 2877 observations to explore the individual and interactive effects of N, P, and K additions on plant growth. We found that N, P, K, NP, NK, PK, and NPK additions significantly increased aboveground biomass production (AGP) by 30.8%, 15.3%, 12.3%, 68.4%, 36.5%, 21.1%, and 78.7%, respectively. The combined addition of multiple nutrients resulted in a larger increase in AGP than a single addition of nutrients. These findings suggested that terrestrial production is widely co‐limited by N, P, and K. However, no significant responses of belowground biomass production (BGP) to nutrient additions were observed. Except for synergistic interactions between N and P additions, the responses of AGP to other pairs of nutrient additions were predominantly additive. This meta‐analysis highlights the importance of multiple‐nutrient limitation in regulating terrestrial primary production while pointing out that non‐additive effects (including synergistic and antagonistic) of multiple‐nutrient additions on terrestrial production are relatively rare.

Changes in Relationship between Forest Biomass Productivity and Biodiversity of Different Type Subtropical Forests in Southern China

Forest productivity is influenced by various factors, including biodiversity, environmental factors, functional traits, and forest types. However, the relative importance of these factors in determining the productivity of subtropical forests in southern China remains controversial. In this study, we analyzed a dataset of 24 forest plots from four subtropical forest types in the Nanling Mountains with the main goal of identifying and quantifying the relative contribution of the main driving factors of forest productivity in these forests. Generalized linear regression and structural equation modeling were used to examine the relationship between forest biomass productivity (aboveground, belowground and total), biodiversity (taxonomic diversity, phylogenetic diversity and functional diversity), and environmental variables (i.e., physiography and climate). The results indicated that both environmental factors and biodiversity played pivotal roles in explaining the biomass productivity of the Nanling subtropical forests. Environmental factors had the greatest influence on total productivity, while the impacts of different types of biodiversity on various productivity components (aboveground and belowground) varied notably. Taxonomic diversity showed the strongest positive effect on the aboveground and belowground biomass productivity. However, phylogenetic and functional diversity had negative effects on productivity. Furthermore, these relationships also exhibited variations when considering different altitude gradients, with low altitudes generally leading to negative biodiversity–productivity correlations. We contextualized our results regarding the three state-of-the-art theories about biodiversity–productivity relationships (selection probability, niche complementarity, and biomass ratio) and concluded that both selection probability and niche complementarity are the driving mechanisms of productivity in the subtropical forests of the Nanling Mountains. This study offers valuable insights into the functioning and biodiversity mechanisms of subtropical forest ecosystems in southern China.

Facultative mycorrhization in a fern (Struthiopteris spicant L. Weiss) is bound to light intensity

BackgroundThe establishment of mycorrhizal relationships between a fungus and a plant typically enhances nutrient and water uptake for the latter while securing a carbon source for the fungus. However, under a particular set of environmental conditions, such as low availability of light and abundant nutrients in the soil, the resources invested in the maintenance of the fungi surpass the benefits obtained by the host. In those cases, facultative mycorrhizal plants are capable of surviving without symbiosis. Facultative mycorrhization in ferns has been overlooked until now. The present study measured the response of Struthiopteris spicant L. Weiss, and its root-associated fungi to different levels of light and nutrient availability in terms of growth, mycorrhizal presence, and leaf nutrient content. This fern species exhibits a great tolerance to variable light, nutrient, and pH conditions, and it has been found with and without mycorrhizae. We conducted a greenhouse experiment with 80 specimens of S. spicant and three factors (Light, Phosphorus, and Nitrogen) resulting in eight treatments.ResultsWe found a significant influence of the factor light on fungal community composition, plant biomass, and nutrient accumulation. Departing from a lack of colonization at the initial stage, plants showed a remarkable increment of more than 80% in the arbuscular mycorrhizal fungi (AMF) richness and abundance in their roots when grown under high light conditions, compared with the ones in low light. We also observed an upward trend of C:P and C:N ratios and the above- and belowground biomass production when AMF abundance increased. Furthermore, the compositional analysis of the whole fungal communities associated with S. spicant roots revealed clear differences among low-light and high-light treatments.ConclusionsThis study is the first to investigate the importance of light and nutrient availability in determining fern-AMF relationships. We confirmed that Struthiopteris spicant is a facultative mycorrhizal plant. The composition and diversity of AMF found in the roots of this fern are strongly influenced by light and less by nutrient conditions. Our study shows that ferns respond very sensitively to changes in environmental factors, leading to shifts in the associated mycorrhizal communities.

Nutrient and Growth Response of Fagus sylvatica L. Saplings to Drought Is Modified by Fertilisation

The increased frequency of climate change-induced droughts poses a survival challenge for forest trees, particularly for the common beech (Fagus sylvatica L.). Drought conditions adversely affect water supply and nutrient uptake, yet there is limited understanding of the intricate interplay between nutrient availability and drought stress on the physiology, growth, and biomass accumulation in young trees. We aimed to address this knowledge gap by examining the effects of irrigation and fertilisation and their interaction with various parameters in common beech saplings, including foliar and root N, P, and K concentrations; height and diameter increments; and aboveground and belowground biomass production. Our findings revealed that a higher fertilisation dose increased nutrient availability, also partially mitigating immediate drought impacts on foliar N concentrations. Also, higher fertilisation supported the post-drought recovery of foliar phosphorus levels in saplings. Prolonged drought affected nitrogen and potassium foliar concentrations, illustrating the lasting physiological impact of drought on beech trees. While drought-stressed beech saplings exhibited reduced height increment and biomass production, increased nutrient availability positively impacted root collar diameters. These insights have potential implications for forest management practices, afforestation strategies, and our broader understanding of the ecological consequences of climate change on forests.

Comparative flooding tolerance of Typha latifolia and Phalaris arundinacea in wetland restoration: Insights from photosynthetic CO2 response curves, photobiology and biomass allocation

Tall helophytes such as Typha latifolia and Phalaris arundinacea often rapidly colonise after rewetting of former agricultural soil and are therefore often the first plants to contribute to the soil carbon pool. In this study we carried out a mesocosm experiment where these two species grew at three different water levels relative to the soil surface (−15 cm, 0 cm, +15 cm). After eight weeks' growth, measurements of photosynthetic CO2-response curves, stomatal conductance and chlorophyll fluorescence of photosystem II were carried out to detect flooding stress. After 10 weeks’ growth, the plants were harvested and biomass production, biomass allocation and specific leaf area were determined. T. latifolia had a higher and more stable photosynthetic performance across all water level treatments, which resulted in an overall higher aboveground and belowground production than P. arundinacea. In contrast, Vcmax and Jmax decreased by 41 % and 42 %, respectively from drained to flooded conditions with signs of flooding stress as impairment of the photosynthetic apparatus. Moreover, increasing water level resulted in maintenance of aboveground organs for P. arundinacea but a decrease in allocation to belowground organs. P. arundinacea did not invest in a higher specific leaf area to counter the decreased photosynthesis under flooding. From −15 cm to 0 cm water levels, P. arundinacea showed a 68 % reduction in belowground biomass, which has negative implication for carbon retention immediately after rewetting. In contrast, recolonization of T. latifolia is likely to be a suitable contributor to the soil carbon pool due to its stable physiology and high above- and belowground biomass production at all water depths, and also likely under natural water level fluctuations. We showed that even though both species are generally considered wetland plants, they are likely to support considerably different photosynthetic carbon assimilation and soil carbon sequestration rates.

An inferior competitor is a successful invader due to its stress tolerance and productivity

The invasion of ecosystems by non-native species is recognized as one of the most significant global challenges, particularly in semiarid regions where native biodiversity is already under stress from drought and land degradation. The implicit assumption is that invaders are strong competitors, but a greenhouse pairwise experiment conducted to examine intraspecific and interspecific competition effects of Opuntia ficus-indica, a widespread invader in semiarid ecosystems, with two species native to the highlands of Eritrea, Ricinus communis and Solanum marginatum, revealed that O. ficus-indica is a weak competitor. The unique ability of O. ficus-indica’s fallen cladodes to undergo vegetative growth becomes a fundamental trait contributing to its spread. This growth strategy allows O. ficus-indica to outgrow native species and establish a significant presence. In direct interaction, the competition in aboveground productivity measured by the logarithmic response ratio for O. ficus-indica was 3.4-fold and 5.9-fold higher than for R. communis and S. marginatum, respectively. Belowground, the native R. communis was facilitated (− 1.00 ± 0.69) by O. ficus-indica which itself suffered from high competition. This pattern became even more evident under water shortage, where aboveground competition for S. marginatum decreased 5.7-fold, and for O. ficus-indica, it increased 1.4-fold. Despite being a poor competitor, O. ficus-indica outperformed R. communis and S. marginatum in both aboveground (4.3 and 3.8 times more) and belowground (27 and 2.8 times more) biomass production, respectively. The findings of this study challenge the common interpretation that invasive species are strong competitors and highlight the importance of considering other factors, such as productivity and tolerance limits when assessing the potential impacts of invasive species on semiarid ecosystems.

Carbon stock potential of agroforestry systems in low hills of north-western Himalayas

The present experiment was conducted at Dr Y S Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh during 2019–21 to study the prevalent agroforestry systems and to assess their carbon stock potential. Sub-montane low hill zone of Chamba district of Himachal Pradesh was the study area with 15 farmers selected from each marginal, small and medium categories to carry out the study. Results of the investigation revealed that five agroforestry systems, viz. agrisilviculture, agrihorticulture, agrisilvihorticulture, silvopastoral and pastoralsilviculture were prevalent in the studied area. Maximum aboveground and belowground biomass production was recorded for the silvopastoral system among all the identified systems with least under pastoralsilviculture. Carbon stock potential among all the systems was recorded highest for the silvopastoral system (60.92 Mg/ha) and generally followed the order silvopastoral>agrisilvihorticulture>agrisilviculture>pastoralsilviculture>agrihorticulture. Farmer categories didn’t affect the carbon storage potential of the different agroforestry systems significantly. Soil carbon stock contributed more as compared to vegetation carbon stock with pastoralsilviculture having maximum soil:plant carbon ratio of 2.59. The study highlights the importance of the tree based land uses and offers the basis for selection of the potential system from the climate change mitigation point of view in the susceptible Himalayan region.

Impact of Puccinia punctiformis on Cirsium arvense performance in a simulated crop sequence

Cirsium arvense (Canada thistle) is a perennial weed that causes significant economic losses in agriculture. An extensive rhizomatous root system makes C. arvense difficult to manage, particularly in agricultural systems that use tillage as a primary management tool. There is a need for the development of integrated weed management toolsets that include C. arvense biological controls. Puccinia punctiformis (thistle rust) is an autoecious fungal pathogen that systemically infects C. arvense, with the potential to reduce host vigor over time. The goal of this study was to integrate the P. punctiformis biocontrol with a simulated annual cropping sequence in a greenhouse environment and evaluate C. arvense’s above-and belowground biomass production, and its competitive ability. Repeated P. punctiformis inoculations produced systemically infected C. arvense stems in greenhouse pots over time. Cirsium arvense that was inoculated with P. punctiformis had 1.6 grams/pot (p = 0.0019) less aboveground biomass and 5.6 grams/pot (p< 0.001) less belowground biomass, compared to the non-inoculated (control). Puccinia punctiformis and crop competition interacted additively to lower aboveground (p<0.001) and belowground (p<0.001) C. arvense biomass more than individual use of either the biocontrol or competition alone. The aboveground competition intensity of C. arvense in a mixed crop sequence, relative to non-inoculated C. arvense grown in a monoculture, was moderately impacted by the P. punctiformis biocontrol (p = 0.0987). These results indicate that systemic infection can reduce biomass production and the competitive ability of C. arvense. Overall, P. punctiformis can be integrated into competitive annual cropping sequences with the potential to reduce C. arvense vigor over time.

Afforestation of semi-arid regions of Mongolia: carbon sequestration in trees and increase of soil organic carbon

This work examines the variation of carbon sequestration (considered as the sum of above- and below-ground plant biomass production added to soil organic carbon) occurring in two sites (named respectively BN and ER) characterized by a semi-arid climate after planting three tree species (Populus sibirica, Ulmus pumila, and Hippophae rhamnoides). Soil organic carbon (SOC) was analyzed at four different depths (from 0–60 cm). In these two sites, the three tree species contributed differently to carbon sequestration. We found that above-ground plant biomass (leaf, branch, stem) was higher at the BN site whereas at the ER site prevailed below-ground biomass. That is probably due to the low tree density in BN site and the higher soil moisture content present in ER site. Among the three tree species considered, P. sibirica showed the highest biomass value. The SOC values were highest in the topsoil layer (0-40 cm) and decreased with depth. This works clearly shows that in semi-arid lands carbon sequestration depends on the environmental factors that characterize the site, the tree density, and the tree species selected.

Competition in a changing world: invasive aquatic plant is limited by saltwater encroachment

AbstractCompetitive interactions between native and nonindigenous species occur under conditions of ongoing environmental alterations related to urbanization and climate change, presenting a challenge to understanding invasiveness. Indigenous submerged aquatic vegetation species have been negatively impacted by nutrient enrichment and saltwater intrusion, while simultaneously experiencing a rapid spread in nonindigenous competitors. To better predict future shifts in freshwater macrophyte community dominance, investigations need to consider how these multiscale disturbances influence competitiveness of nonindigenous macrophytes. Using an outdoor greenhouse mesocosm setup for approximately 19 weeks over the course of subtropical winter, we experimentally examined how nutrient enrichment, salinity, and the interaction of both factors influence the competitive interactions between a native macrophyte with moderate salinity tolerance, wild celery (Vallisneria americana), and a highly invasive macrophyte with lower salinity tolerance, hydrilla (Hydrilla verticillata). We tested the factors of macrophyte composition (hydrilla monoculture, wild celery monoculture, or biculture), salinity (0, 4, or 8), and fertilization (ambient or fertilized) on biomass production, biomass allocation, and morphological metrics as responses to environmental condition and interspecific competition. Fertilizer enhanced wild celery leaf area (more than twofold) and shifted allocation toward aboveground biomass, but did not enhance hydrilla competitiveness. Salinity negatively affected wild celery leaf area (by 7.5%–67.8%) and biomass (by 4%–15%) and also reduced hydrilla belowground biomass production (by 6%–25%) but did not influence competition. An interaction effect of fertilizer and salinity negatively influenced hydrilla growth, however the combined factors did not influence competitive outcomes. The lack of evidence for a competitive advantage by hydrilla in this study demonstrates that salinity exposure sufficiently limits a highly invasive plant's competitive abilities and subsequent suppression of a native species.

Türkiye'nin Orta Karadeniz Bölgesi Ova Çayır Vejetasyonunda Hayvan Otlatılan Bir Alan ve Hayvan Otlatılmayan Korunmuş Bir Komşu Arazinin Yeraltı Biyokütlesi ve Verimliliği

The subject of this study is to determine the below-ground plant biomass and annual below-ground net primary production of lowland meadows in the Central Black Sea region. This study calculated the annual average amount of below-ground plant biomass, its seasonal distribution, annual primary production, and turnover values in the ungrazed and grazed meadow stands. Below-ground plant biomass, below-ground net primary production, and turnover of grazed stands were higher than in ungrazed stands. This turnover value shows that root biomass is renewed faster in grazed areas. Grazing, annual rainfall, and soil characteristics may have led to these different results.

Precipitation consistently promotes, but temperature inversely drives, biomass production in temperate vs. alpine grasslands

Comparisons of vegetation production between temperate and alpine grasslands are not well studied, and the understanding of the underlying mechanisms is still incomplete. To address this issue, we selected the Inner Mongolia and Tibet regions to conduct large-transect surveys for temperate grassland (TG) and alpine grassland (AG), respectively, in China, to reveal the universal and differential mechanisms of above- and belowground biomass production (GB, AGB and BGB) and precipitation use efficiencies (PUE) in the two grasslands. The relative importance of climatic factors on biomass and PUE is greater than that of soil and biological factors. Elevated mean annual precipitation (MAP) consistently increased GB in both TG and AG. Increased mean annual temperature (MAT) reduced GB by weakening the soil nutrient status in TG, whereas it increased GB by improving the soil nutrient status in AG. MAP promoted more AGB than BGB in TG, whereas MAT affected BGB more than AGB in AG. When the multicomponent heterogeneity of other factors in grasslands was eliminated, the effect of MAP on GB remained significant for both TG and AG. After removing the effect of multifactorial heterogeneity, however, the significant effect of MAP on PUE of the two grasslands was largely enhanced. From these results, we can conclude that climatic factors do not always exert identical effects on different grasslands. In particular, highlighting the divergent mechanisms of biomass production and precipitation use efficiency between temperate and alpine grasslands can improve the understanding of the carbon sink and hydraulic sensitivity of various grasslands.

Response Patterns of Fen Sedges to a Nutrient Gradient Indicate both Geographic Origin-Specific Genotypic Differences and Phenotypic Plasticity

In wet peatlands, plant growth conditions are largely determined by local soil conditions, leading to locally adapted vegetation. Despite that Carex species are often the prevailing vascular plant species in fen peatlands of the temperate zone, information about how these species adapt to local environmental conditions is scarce. This holds true especially for below-ground plant traits and for adaptations to fen-typical nutrient level variations. To address this research gap, we investigated how different geographic origins (Germany, Poland, The Netherlands) of C. acutiformis and C. rostrata relate to their response to varying nutrient availability. We performed a common garden experiment with a controlled gradient of nutrient levels, and analyzed above- and below-ground biomass production of both Carex species from the different geographic origins. We related these traits to environmental conditions of the origins as characterized by vegetation composition-derived indicator values for ecological habitat conditions. While we detected high above-ground phenotypic plasticity of Carex from different origins, our data point to below-ground genotypic differences, potentially indicating local adaptation: Rhizome traits of C. rostrata differed significantly between origins with different nutrient indicator values. These results point towards differences in C. rostrata clonal spread behavior depending on local peatland conditions. Therefore, local adaptations of plant species and below-ground biomass traits should be taken into account when studying peatland vegetation ecology, as key functional traits can differ between genotypes within a single species depending on local conditions.

Single and combined effects of fertilization, ectomycorrhizal inoculation, and drought on container-grown Japanese larch seedlings

Climate change can intensify drought in many regions of the world and lead to more frequent drought events or altered cycles of soil water status. Therefore, it is important to enhance the tolerance to drought and thus health, vigor, and success of transplantation seedlings used in the forestry by modifying fertilization and promoting mycorrhization. Here, we sowed seeds of Japanese larch (Larix kaempferi) in 0.2-L containers with 0.5 g (low fertilization; LF) or 2 g (high fertilization; HF) of slow-release fertilizer early in the growing season. One month later, we irrigated seedlings with non-sterilized ectomycorrhizal inoculum (ECM) or sterilized solution (non-ECM), and after about 2 months, plants were either kept well watered (WW; 500 mL water/plant/week) or subjected to drought (DR; 50 mL water per plant/week) until the end of the growing season. HF largely stimulated plant growth and above- and belowground biomass production, effects that are of practical significance, but caused a small decrease in stomatal conductance (Gs390) and transpiration rate (E390), which in practice is insignificant. ECM treatment resulted in moderate inhibition of seedling growth and biomass and largely canceled out the enhancement of biomass and foliar K content by HF. DR caused a large decrease in CO2 assimilation, and enhanced stomatal closure and induced senescence. DR also largely depleted foliar Mg and enriched foliar K. Although DR caused a large decrease in foliar P content in LF, it moderately increased P in HF. Likewise, DR increased foliar K in HF but not in LF, and decreased foliar P in ECM plants but not in non-ECM plants. Conversely, ECM plants exhibited a large enrichment in foliar P under WW and had a lower water potential under DR when grown in LF. These results indicate that the drought tolerance and health and vigor of Japanese larch seedlings can be modified by soil fertility and soil microorganisms. This study provides a basis for new multifactorial research programs aimed at producing seedlings of superior quality for forestation under climate change.

The older, the better: Ageing improves the efficiency of biochar-compost mixture to alleviate drought stress in plant and soil

Due to increased drought frequency following climate change, practices improving water use efficiency and reducing water-stress are needed. The efficiency of organic amendments to improve plant growth conditions under drought is poorly known. Our aim was to investigate if organic amendments can attenuate plant water-stress due to their effect on the plant-soil system and if this effect may increase upon ageing. To this end we determined plant and soil responses to water shortage and organic amendments added to soil. We compared fresh biochar/compost mixtures to similar amendments after ageing in soil.Results indicated that amendment application induced few plant physiological responses under water-stress. The reduction of leaf gas exchange under watershortage was alleviated when plants were grown with biochar and compost amendments: stomatal conductance was least reduced with aged mixture aged mixture (−79 % compared to −87 % in control), similarly to transpiration (−69 % in control and not affected with aged mixture). Belowground biomass production (0.25 times) and nodules formation (6.5 times) were enhanced under water-stress by amendment addition. This effect was improved when grown on soil containing the aged as compared to fresh amendments. Plants grown with aged mixtures also showed reduced leaf proline concentrations (two to five times) compared to fresh mixtures indicating stress reduction. Soil enzyme activities were less affected by water-stress in soil with aged amendments.We conclude that the application of biochar-compost mixtures may be a solution to reduce the effect of water-stress to plants. Our findings revealed that this beneficial effect is expected to increase with aged mixtures, leading to a better water-stress resistance over time. However, while being beneficial for plant growth under water-stress, the use of amendments may not be suited to increase water use efficiency.

Different harvest systems of Eucalyptus clone plantations affect above and belowground biomass production and nutritional sustainability

Different harvest systems of Eucalyptus clone plantations affect above and belowground biomass production and nutritional sustainability

Precipitation-mediated responses of plant biomass production and allocation to changing soil pH in semiarid grasslands

Biomass and its allocation are crucial to understand carbon cycling. Climate change and human disturbance potentially alter soil pH, but it remains unclear how biomass production and its partitioning respond to altered soil pH. Here, we investigated how changing soil pH (acidification and alkalization) affected above- and belowground biomass production and allocation (hereafter AB, BB and BB/AB, respectively) at nine sites representing desert, typical, and meadow grasslands with increasing precipitation across a 1500-km transect in Inner Mongolia, China. The results showed that soil acidification reduced AB in typical and meadow grasslands, whereas soil alkalization reduced AB in desert and typical grasslands. Changing soil pH did not affect BB in desert or typical grasslands, but reduced BB in meadow grasslands. Altered soil pH negatively impacted species richness, Shannon-Wiener diversity, and dominant species biomass across all grasslands. BB/AB was increased by soil acidification and alkalization along the study transect. Soil C, N and C:N ratio were not affected by changing soil pH in three types of grasslands. Response ratios of AB, BB/AB and dominant species biomass were positively correlated with precipitation under altered soil pH, whereas response ratios of BB were negatively correlated with precipitation under soil alkalization. Variance partitioning analysis showed that the response of biomass and its allocation to altered soil pH were mainly explained by community composition but not soil fertility. Structural equation model analysis demonstrated that precipitation mediated the responses of biomass distribution to soil pH changes in semi-arid grasslands mainly via altering the response of dominant species. Our results indicate that dry grasslands with low productivity and precipitation generally allocate more C to belowground than wet grasslands regardless of pH change. These findings can improve our predictions of carbon dynamics in grassland ecosystems under climate change.