Litter Biomass Research Articles

Meiofauna in stream habitats: temporal dynamics of abundance, biomass and secondary production in different substrate microhabitats in a first-order stream

Meiofaunal abundance, biomass and secondary production were investigated over 13 months in an unpolluted first-order stream. Four microhabitats were considered: sediment and the biofilms on dead wood, macrophytes and leaf litter. The relative contribution of the microhabitats to secondary production and the influence of environmental factors on meiofaunal density distribution were estimated. We expected (1) meiofaunal abundance and biomass to exhibit seasonal patterns, with more pronounced seasonal fluctuations on macrophytes and leaf litter than in the other microhabitats, (2) annual secondary production to be highest in sediment; however, the relative contribution of the microhabitats to monthly secondary production would change during the year, and (3) a bottom-up driven influence on meiofaunal density distribution in the microhabitats. Meiofaunal annual mean abundance, biomass and secondary production were 7–14 times higher in sediment and on dead wood than on macrophytes and leaf litter. Significant seasonal patterns described the meiofaunal abundance in sediment and on leaf litter as well as the biomass in sediment, on macrophytes and leaf litter. Organisms in sediment and on dead wood contributed 48 and 43%, respectively, to secondary production m−2, but in regard to the stream area covered by the microhabitats, sediment had the highest share (80%). Significant determinants of the density distribution were AFDM, protozoans, bacteria and Chl-a, which influenced all meiofaunal groups. Our study clearly indicates that meiofaunal organisms in sediment and on dead wood have a remarkable share on total secondary production of lotic systems which is especially relevant for forested low-order streams.

Tracking soil carbon processes in two temperate forests at different successional stages using stable and radioactive carbon isotopes

The profile characteristics of soil carbon reflect the combined effects of vegetation and erosion. However, the quantitative assessment of soil carbon in profile and its dynamics affected by vegetation restoration and erosion is still extremely inadequate. In this study, we synthesized soil and vegetation properties, stable carbon isotopic compositions, and radiocarbon ages to investigate the soil carbon processes in two temperate forests of different successional stages (Populus forest versus Quercus forest) on the Chinese Loess Plateau. The objectives of this study are to (1) examine the dynamics of soil organic carbon (SOC) and soil inorganic carbon (SIC) in the topsoil and subsoil, and (2) evaluate the effect of vegetation restoration and historical erosion on the changes of SOC and SIC in the temperate forests. We found that from Populus to Quercus forests, the SOC stock increased in the topsoil but declined in the subsoil, whereas the SIC stock exhibited a completely opposite variation trend. The significant increase in litter biomass enhanced the SOC in the topsoil, while a stronger historical erosion and priming effect would contribute to the decrease of SOC in the subsoil along succession. Changes in δ13C and Δ14C in the soil profile provided evidence that the turnover rate of SOC increase in the topsoil but decrease in the subsoil along succession. Over the past 10,000 years, due to soil erosion process, the estimated loss of the SOC and SIC was 26.2 and 64.1 Mg ha-1 in Populus forest and 20.2 and 42.6 Mg ha-1 in the Quercus forest. Our results indicated that the litter input and erosion processes make great effect on the carbon dynamics in the topsoil and subsoil of the study region.

Hojarasca de árboles de bosque tropical seco dispersos en pastizales

Introduction: Scattered trees from tropical dry forests (TDF) deposit significant amounts of leaf litter into pasture soils. Objective: To estimate the litterfall production during the dry season by scattered Lysiloma acapulcense (Kunth) Benth. and Vachellia pennatula (Schltdl. & Cham.) Seigler & Ebinger trees in pastures. Materials and methods: Ten scattered trees of each species were selected from a 10-ha pasture, and litter was collected during the dry season (November to May) and sorted into fractions. Leaf litter biomass, nitrogen (N) and lignin (L) content, and the lignin-nitrogen (L/N) ratio were assessed. Leaf litterfall was modelled over an annual cycle using a double logistic model. Means from all variables were compared between species using a t-test. Results and discussion: Litter, nitrogen and lignin content were similar between species. However, the L/N ratio was significantly higher (P Conclusion: The quantity and quality of leaf litter that scattered trees deposit in a pasture encourages the adoption of agroforestry systems, including tree species native to TDF

Divergent responses of nematodes in plant litter versus in top soil layer to nitrogen addition in a semi-arid grassland

Nematodes are a crucial component of the soil food web, and play a key role in maintaining biodiversity and regulating soil nutrient cycling. Many studies have been done on the effects of N addition on the soil biota, but the effects of N addition on nematodes in plant litter versus in soil are not well understood, especially in semi-arid steppe ecosystems. Here we investigated the composition of nematode communities in plant litter versus in surface soil in two climatically contrasting years in a simulated N enrichment experiment with four N levels (0, 25, 50 and 100 kg N ha−1 yr−1) in a temperate semi-arid grassland. We found that nematodes in plant litter were more sensitive to N addition than that in surface soil, that is, the abundance and generic richness of nematodes in plant litter, but not in surface soil, manifest a significant difference among N addition rates at both community and guild levels. The abundance and generic richness of nematodes were significantly higher in 2015 (a year with relatively wet weather) than 2016 (a year with relatively dry weather) in soil, but the opposite was true on the abundance of nematodes in litter. The plant parasites and omnivores-predators were more abundant, whereas the bacterivores and fungivores were less abundant, in 2015 than 2016. Our results also indicate that litter C/N ratio and soil moisture have greater impact than litter biomass and plant species richness on the abundance of nematodes in litter layer, while soil moisture and resource availability have greater impact than soil N availability and pH on the abundance of nematodes in the top soil. These results provide new insights into the dynamics of nematode communities, and suggest that the litter layer is very important to maintain a stable nematode community in the steppe ecosystem under the fluctuating climate.

Soil Health Impacts of Rubber Farming: The Implication of Conversion of Degraded Natural Forests into Monoculture Plantations

High revenues from rubber latex exports have led to a rapid expansion of commercial rubber cultivation and, as a consequence, the conversion of different land use types (e.g., natural forests) into rubber plantations, which may lead to a decrease in soil health. In this study in Quang Tri Province, Vietnam, we determined: (1) the variation of soil health parameters along a chronosequence of rubber tree stands and natural forests and (2) the relationships and potential feedback between vegetation types, vegetation structures and soil health. Our results revealed that: (1) soil health was higher in natural forests than in rubber plantations with a higher values in higher biomass forests; (2) soil health was lower in younger rubber plantations; (3) soil health depends on vegetation structure (with significantly positive relationships found between soil health and canopy cover, litter biomass, dry litter cover and ground vegetation cover). This study highlights the need for more rigorous land management practices and land use conversion policies in order to ensure the long-term conservation of soil health in rubber plantations.

The Vertical Differences in the Change Rates and Controlling Factors of Soil Organic Carbon and Total Nitrogen along Vegetation Restoration in a Subtropical Area of China

The study was to investigate the change patterns of soil organic carbon (SOC), total nitrogen (TN), and soil C/N (C/N) in each soil sublayer along vegetation restoration in subtropical China. We collected soil samples in four typical plant communities along a restoration chronosequence. The soil physicochemical properties, fine root, and litter biomass were measured. Our results showed the proportion of SOC stocks (Cs) and TN stocks (Ns) in 20–30 and 30–40 cm soil layers increased, whereas that in 0–10 and 10–20 cm soil layers decreased. Different but well-constrained C/N was found among four restoration stages in each soil sublayer. The effect of soil factors was greater on the deep soil than the surface soil, while the effect of vegetation factors was just the opposite. Our study indicated that vegetation restoration promoted the uniform distribution of SOC and TN on the soil profile. The C/N was relatively stable along vegetation restoration in each soil layer. The accumulation of SOC and TN in the surface soil layer was controlled more by vegetation factors, while that in the lower layer was controlled by both vegetation factors and soil factors.

Classification of radicular biomass and monitoring of litter in Pantanal and Cerrado Mato-Grossense

The quantification of root biomass and the assessment of its dynamics in forest ecosystems has been intensified due to its important role in carbon sequestration and storage and the possible consequences under climate change conditions. In general, biomass stocks between and within forest ecosystems are highly variable. It is necessary to study all the different components of vegetation, however, the vast majority of the works found in the literature, address only the biomass of the aerial part of the plants, with few studies involving the quantification of these stocks by the roots, in the different ecosystems. The present study objective quantify and classify a root biomass with a depth of 0 to 10 cm, and to monitor accumulated litter in the soil (litter pool), in two different regions, in the Pantanal (Acurizal) and in the Cerrado (Sensu stricto) Mato-Grossense. The root biomass was obtained by means of unformed soil samples (0-10 cm) and the roots were classified by diameter, with the aid of digital calipers, between thick (> 10 mm), medium (5-10 mm), slightly thin (2-5 mm) and fine (<2 mm). The samples collected monthly between August 2018 and July 2019. Was observed that in both areas, about 90% of the roots collected, were fine (<2 mm). The root density in Acurizal was on average 124.92 g/m² and in Sensu stricto it was on average 57.5 g/m². The difference in root density in the soil, between the two study areas, significant (p<0.05). However, there no significant difference in root density between the dry and wet periods in each area. The monthly average of litter pool in the area of Acurizal and Sensu stricto was, respectively: 526.52 g/m² and 588.96 g/m². In both areas, the accumulated litter was significantly different between periods of drought and precipitation.

Effects of Defoliation, Litter, and Moss on Bromus arvensis in a Northern Mixed-Grass Prairie

Exotic winter annual grasses (Bromus spp.) are a problem in North American rangelands. Defoliation, litter, and mosses are thought to regulate invasive annual Bromus species. We conducted a field experiment that tested effects of mechanical mowing and fungicide applications on Bromus arvensis, other and total graminoids, forbs, litter, and moss. Treatments caused litter biomass and moss cover to vary, which enabled testing whether litter and mosses explain variation in B. arvensis biomass. Two yr after cessation of experimental treatments, mowing treatments caused persistent reductions in B. arvensis, total graminoid, and litter biomasses but had no effect on other graminoid and forb biomasses. We detected a positive relationship between litter and B. arvensis. Fungicide applications increased moss cover and other and total graminoid biomasses, thereby suggesting mosses and several graminoids were released from the suppressive effects of biota (e.g., lichen, pathogenic fungi) susceptible to the fungicide. We found no relationship, however, between moss cover and B. arvensis. In temperate and semiarid ecosystems, mowing during flowering and before seed drop coupled with removal of clippings is likely to help control invasive bromes and fungicide additions may increase grass production.

The Importance of Catchments to Mine-pit Lakes: Implications for Closure

Despite the large body of riparian literature for rivers and lakes, there are few studies on the catchments of mine pit lakes. Therefore, the broad objective of this research was to determine if catchment characteristics were related to pit lake nutrient concentrations. We hypothesised that: (1) catchment characteristics would vary among pit lakes, (2) pit lake catchments would differ from co-occurring naturally-forested catchments, and (3) connecting a pit lake (Kepwari) to a naturally-forested catchment via a river flow-through would increase C accumulation in the lake. The research was conducted in pit lakes of the Collie lake district in Western Australia and examined catchment characteristics (soil nutrients, litter biomass, vegetation, and biomass), carbon and sedimentation rates in pelagic and benthic materials, and establishment of a simple nutrient budget for Lake Kepwari. Broadly, results indicated that catchment vegetation differed significantly among pit lakes (although parts were similar to co-occurring natural forest), with differences largely driven by catchment age. None of the pit lake catchments had true riparian species surrounding the pit lakes. The hypothesis that connecting a pit lake to a watercourse would increase carbon concentrations and sedimentation was not supported. Most (87%) of the water that entered the lake was from the river, and river outflow was slightly greater than river inflow. However, the lake acted like a nutrient sink, with more N, P, and TOC calculated in the inflows than the outflow. We found that it took 10–15 years of growth for actively rehabilitated pit lake catchments to approximate natural forest and 60 years for unrehabilitated pit lake catchments. Active rehabilitation that includes riparian-specific planting would likely lead to better outcomes for pit lake catchment vegetation. Connecting a pit lake to a river substantially increased catchment size and large amounts of river-derived carbon were deposited in the lake. However, carbon concentrations were relatively low compared to the size of the lake. Our results suggest that active intervention is required if stakeholders are unwilling to wait decades for the biological development of pit lakes.

Soil carbon dynamics in different types of subtropical forests as determined by density fractionation and stable isotope analysis

Quantifying carbon (C) dynamics with forest land-use change is essential for predicting C sequestration and stabilization. Here, we combined density fractionation and stable isotope analysis to examine soil C dynamics after primary native broadleaf forests (BF) were converted to secondary forests (SF) and plantation forests (PF). The results showed that soil C stock at 0–30 cm depth decreased significantly from BF (70.8 Mg ha−1) to SF (60 Mg ha−1) and PF (53.9 Mg ha−1). Both soil C concentration and stock decreased, but soil δ13C of the light and heavy fractions increased, and these increases were more evident in the topsoil (0–10 cm) than in the subsoil (10–30 cm). The decrease of the heavy fraction C stocks accounted for 52.7% and 69.7% of the reduction of bulk soil C stocks with conversion of BF to SF and PF, respectively. Analysis of δ13C revealed that the input of new C into the light fraction of soil at 0–10 cm depth decreased by 13.1% with conversion of BF to SF, and by 34.0% with conversion of BF to PF. The decreases of soil C stocks in density fractions were primarily explained by soil properties (β = 0.70) but also by vegetation biomass C (β = 0.26), and were closely correlated with soil moisture content (0.69, the highest eigenvalue among soil properties) and floor litter biomass C (0.75, the highest eigenvalue among biomass C categories). Our findings help clarify the contrasting mechanisms explaining the dynamics of light and heavy fraction of soil C, and highlight the importance of both vegetation and soil in controlling changes in soil C dynamics in response to forest conversion. Accordingly, we recommend that management policies and actions should maximize biomass C inputs of degraded forests and minimize C losses. It follows that the preservation of primary forests might increase ecosystem C sequestration and thereby mitigate climate change.

Nitrogen effects on quantity, chemistry, and decomposability of Pinus densiflora and Quercus variabilis litters under elevated CO2 and warming

The effects of increased nitrogen (N) availability through atmospheric deposition on the quantity and quality of tree leaf litter have been widely reported. However, such N effects under co-elevated CO2 concentration ([CO2]) and air temperature (Tair) have not been investigated. In this study, changes in biomass and chemistry of litter of Pinus densiflora S. et Z. (pine) and Quercus variabilis Blume (oak) saplings with two levels of each N × [CO2] × Tair were investigated for two growing seasons. The levels of N, [CO2], and Tair were 2 and 6-fold of ambient N deposition, ambient and ambient + 285 ppmv, and ambient and ambient + 2.2 °C, respectively, on average across the two seasons. The concentrations of N, minerals, and carbon (C) compounds such as non-structural carbohydrate (NSC) and lignin as well as stoichiometry such as the ratio of C to N (C/N) and lignin to N (lignin/N) of litter were analyzed to determine litter chemistry. In addition, the legacy effect of changed chemistry on microbial decomposability of the litters were also assessed by measuring CO2 emission in a 60-day lab incubation experiment. The effect of high N addition on increasing litter production was consistent regardless of [CO2] and Tair for oak; however, for pine, N-induced increases in litter production were negated under elevated [CO2] and/or Tair, probably due to efficient uptake and use of N by pine under elevated [CO2] as well as lowered N demand via warming-induced stress under elevated Tair. High N-induced decreases in C/N and lignin/N was consistent across [CO2]-Tair combination for both species though other chemical components such as NSC and minerals including phosphorous, calcium, aluminum, and manganese varied inconsistently. The CO2 emission from the soils amended with litters of different chemistry was not correlated with litter chemistry, suggesting that changed litter chemistry under different N level × [CO2] × Tair may not affect litter decomposability in the soils. This study enlarges our understanding of the effect of increased N availability on litter quantity, chemical composition, and microbial decomposability under different [CO2] and Tair. However, a study with mature trees in a natural forest stand should further improve our understanding.

Oats hay supplementation to yak grazing alpine meadow improves carbon return to the soil of grassland ecosystem on the Qinghai-Tibet Plateau, China

Supplementation of livestock feed is a common strategy for improving animal production in pasture-based systems worldwide. On the Qinghai-Tibet Plateau of China, however, the grassland ecosystem is fragile and therefore sensitive to disruption by external forces. We therefore investigated the effects of supplementing yaks feed with oats hay on animal production, forage biomass, and carbon return in litter and dung as well as the effects on soil organic carbon stock. Two grazing systems—native grazing, or grazing with hay supplementation—were established in 2010. For the native grazing system, yaks were rotationally grazed in two paddocks (3.3 yaks/ha) with each 15 days during the warm season (July through October) and 20 days during the cold season (November through June). The hay supplementation system was the same as the native system except that each yak also received oats hay (1.5 kg/day, dry matter basis) during the cold season. For each system, yak growth, forage biomass of the pasture, carbon return from litter and dung to soil, and soil organic carbon stock were measured from 2010 to 2014. The yaks supplemented with oats hay had greater growth performance compared with non-supplemented animals, thereby providing economic benefits for herdsmen. With respect to carbon cycling, supplementation increased carbon return in litter and dung and consequently reduced the soil carbon stock loss. The results indicate that supplementation with oats hay positively impacted forage production and carbon cycling in alpine meadows and thus may help remediate degraded soils and improve grassland utilization on the Qinghai-Tibet Plateau.

Ecosystem carbon stocks in different aged tea agroforestry systems: implications for regional ecosystem management

Tea (Camellia sinensis) is often grown under a canopy of trees forming a distinctive agroforestry system covering an estimated area of 3.94 million ha of land globally. Although, tea is a major commercial crop in many countries in tropical and sub-tropical regions, including China, India and Sri Lanka, tea agroforestry systems (TAFS) have remained little studied for their role in carbon management and climate change adaptation/mitigation actions. We, therefore, undertook a detailed study on the storage of organic carbon in above- and below-ground vegetation and soil under age chronosequence of TAFS in North East India. The specific aim of this study was to quantify variations in soil physical and chemical properties, carbon storage in shade trees and tea bushes, and ecosystem carbon stocks under the chronosequence of TAFS. This study has established significant variations in soil properties and carbon storage in different aged TAFS. One of the salient findings is the decrease in soil bulk density and increase in water holding capacity with the age of TAFS in the 0–50 cm depth. The total vegetation C stock (shade trees + tea bushes + litter biomass) increased with increase in the age of TAFS, and the increase was as high as 25% in > 20 years compared to younger (< 10 years old) TAFS. The ecosystem C stock estimated at 162–187 Mg ha−1 was higher than many temperate and tropical agroforestry systems suggesting TAFS may effectively contribute to Clean Development Mechanisms CDM/REDD+ mechanisms of the United Nations Framework Convention on Climate Change (UNFCCC) once standard guidelines for market mechanisms are in place.

Assessing the influence of riparian invasion by the shrub Lonicera maackii on terrestrial subsidies to headwater streams

Invasion of Amur honeysuckle (Lonicera maackii) into riparian areas of headwater streams creates strong potential for alterations of terrestrial subsidies that may drive bottom-up effects on aquatic biota. In this study, we analyzed effects of L. maackii on terrestrial subsidies in stream sites that represented a gradient of invasion intensity in temperate deciduous forests of southwestern Ohio (USA). Leaf litter biomass, terrestrial and aquatic fine woody debris (0.5–9.9 cm diameter) volume and count, and terrestrial and aquatic coarse woody debris (>9.9 cm diameter) volume were analyzed. Based on previous research, we hypothesized that sites with a higher density of L. maackii would have decreased native species subsidies due to the dense overarching structure of the invasive shrub preventing materials from entering the stream. Over the course of the study, we found no evidence of differences in native leaf biomass across the invasion gradient. There were marginally significant effects of invasion level on fine woody debris, and regression analysis revealed a significant (R-squared 0.11; P = 0.043) negative relationship between L. maackii stem density and fine woody debris volume. Coarse woody debris volume was lower in sites with heavier invasion although no statistically discernible effects were detected. Regression analysis indicated a statistically significant negative relationship between L. maackii basal area and coarse woody debris volume (R-squared 0.14; P = 0.026). These results indicate linkage between invasion intensity and terrestrial subsidies mediated through the unique physiognomy of the invasive shrub. Riparian invasion of L. maackii may alter the fundamental biology of streams through alterations to deposition of terrestrial organic matter that serves as a structuring component of smaller waterways.

Floristic composition and carbon pools along altitudinal gradient: the case of gara–muktar forest, west hararghe zone, eastern Ethiopia

Forests play vital role in combating climate change through carbon sequestration in the atmosphere and serving as a carbon sink in the form of carbon pool systems of forest ecosystems. The species composition and carbon stock in the different carbon pools and analysis of the influence of the environmental gradients were studied by systematic sampling method collecting data in thirty-six quadrant plots of 20x20m each distributed along transect lines. Diameter at breast ≥5cm and total height measured for each tree in the main plot. Above and below ground biomass was estimated using allometric equation, while the litter carbon was estimated by taking 50% of dry biomass as carbon. Soil sample was collected using auguring method and analyzed following Walkley-Black method, while bulk density was performed using core sampling method. The data was analyzed was performed using one way ANOVA of R software. The carbon stocks in aboveground, belowground, litter biomass and soil organic carbon showed distinct variation along environmental gradients. The aboveground and below ground carbon stock was showed a decreasing trend along with increasing altitude, while soil organic carbon and liter carbon showed increasing trend along with increasing in altitude. The mean total above and below ground carbon stocks were 156.60t C ha-1 and 31.32t C ha-1 respectively whereas, litter carbon and soil organic carbon stocks were 2.72t C ha-1 and 125.86t C ha-1 (up to 30cm depth) respectively. The mean total carbon stock density in all carbon pool of Gara-Mukitar forest was found to be 316.6±67.15t C ha-1 from which 49.5% of carbon was contained in the above ground biomass, 9.9% in below ground biomass, 0.9% in litter carbon and 39.8% was stored in soil organic carbon (0-30cm depth). The analysis of carbon stock variation of different carbon pools along altitude of the forest showed a significant variation, whereas the above and belowground carbon stock variation with slope gradient was also significant except soil organic carbon and liter carbon. It result concluded that Gara-muktar Forest is a reservoir of high carbon, since it has a good capacity to sink carbon from the atmosphere having positive role in reduction of greenhouse gases and in contributing to climate change mitigation. Therefore, to enhance the carbon stock of forest in a sustainable way, it should be supported with proper community based forest management system.

Adsorption of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) from water using leaf biomass (Vitis vinifera) in a fixed-bed column study.

Adsorption of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) onto modified activated carbons (AC-H3PO4) produced from leaf biomass of Vitis vinifera leaf litter in a fixed bed column experiment was investigated in this study. The column bed was packed with the produced activated carbons in a uniform particle size of ˃ 64μm. Experimental parameters including the initial concentration of the solution, column bed height, the mass of adsorbent and flow rate were optimized to establish the best adsorption efficiency parameters for the system. Breakthrough and saturated time were estimated from the column fixed bed experimental data and analysed using the Adam-Bohart, Thomas model, and Yoon-Nelson models. Maximum sorption capacities of produced activated carbon ACH3PO4 based on Thomas model were 159.61 and 208.64mg/g for PFOA and PFOS, respectively. The results indicated the breakthrough and saturated time of the system increased concurrently with the increase in bed height and initial concentrations, while an increase in flow rate enhanced fractional bed utilization (FBU) efficiency of the column. Thomas and Yoon-Nelson model best describe the prediction of breakthrough data and sorption behaviour of PFOA and PFOS indicating suitability of AC-H3PO4 column design. Findings suggest that agro based adsorbent is a good alternative to non-ago based adsorbent. The surface characteristics of the phosphoric acid modified activated carbons AC-H3PO4 affirmed the removal of PFOA and PFOS from the contaminated water.

Carbon stock variation along altitudinal and slope gradients in gara–muktar forest, west hararghe zone, Eastern Ethiopia

Forests play vital role in combating climate change through carbon sequestration in the atmosphere and serving as a carbon sink. The species composition and carbon stock were studied along environmental gradients using systematic sampling method. Data were collected in the 36 quadrant plots of 20 x 20m each distributed along transect lines. Diameter at breast ≥5cm and total height measured for each tree in the main plot. Above and below ground biomass was estimated using allometric equation, while the litter carbon was estimated by taking 50% of dry biomass as carbon. Soil sample was collected using auguring method and carbon was analyzed following Walkley-Black method, while bulk density analyzed using oven dried method. The data was analyzed was performed using one way ANOVA of R software. The carbon stocks in aboveground, belowground, litter biomass and soil organic carbon showed distinct variation along environmental gradients. The aboveground and below ground carbon stock was showed a decreasing trend along with increasing altitude, while soil organic carbon and liter carbon showed increasing trend along with increasing in altitude. The mean above and below ground carbon stocks were 156.60 t C ha-1 and 31.32 t C ha-1 respectively whereas, litter carbon and soil organic carbon stocks were 2.72 t C ha-1 and 125.86 t C ha-1 respectively. The total carbon stock density of Gara- Mukitar forest was found to be 316.6±67.15 t C ha-1. Similarly 49.5% of carbon was contained in the above ground biomass, 9.9% in below ground biomass, 0.9% in litter carbon and 39.8% in soil organic carbon (0-30 cm depth), respectively. The analysis of carbon stock variation of different carbon pools along altitude of the forest showed a significant variation, whereas the above and belowground carbon stock variation with slope gradient was also significant except soil organic carbon and liter carbon. In conclusion Gara-muktar forest is a reservoir of high carbon, since it has a good capacity to sink carbon from the atmosphere having positive role in reduction of greenhouse gases. Therefore, proper community based forest management options should be implemented for its continuity.

Effect of elevated CO2 on litter functional traits, mass loss and nutrient release of two subtropical species in free air carbon enrichment facility

Assessing the impact of increasing carbon dioxide (CO2) on nutrient cycling requires understanding of the relationship between the concentration of CO2 and litter dynamics. It is, therefore necessary to understand leaf litter traits in response to increased atmospheric CO2. Variations in plant litter chemistry under elevated carbon dioxide (e−CO2) are the critical factors in ecosystem feedback. Litter fall, litter substrate quality, nutrient flux and decay rate in two tropical tree of Tectona grandis (Teak) and Butea monosperma (Butea) were examined. Saplings were exposed to elevated CO2 treatment (e−CO2 -550 ppm) and ambient CO2 (a−CO2; - 395 ppm) in the FACE (Free air CO2 enrichment) facility in CSIR- National Botanical Research Institute in Indo-Gangetic plain region. Litter was analysed for concentrations of carbon (C), nitrogen (N), soluble sugars (SS), lipids, lignin, cellulose, hemi-cellulose (HC) and C-based defensive compounds; soluble phenolics (SP). Nutrient concentration in naturally senesced litter for Butea and Teak was significantly different in elevated and ambient rings. Elevated CO2 significantly increased C/N (+8.27 % and +21.94 %), lowered mean litter N concentration (–3.27 % and -12.15 %), and affected the concentrations of soluble sugars, soluble phenolic and lipids in leaf litter of Butea and Teak plantations, respectively. Increase in litter biomass production (+19.75 % and 22.84 %) for both the plants under e−CO2, resulted in significant increase in the flux of N, SS, SP and lipid in to the soil. Elevated CO2 increased cellulose (+18.21 %; 12.30 %), hemicellulose (+8.48 %; +10.18 %) and lignin inputs to soils (+35.22; +43.36 %) in Butea and Teak plantation respectively. The study indicated that changes in litter biomass production and litter substrate quality during exposure to e−CO2 could significantly alter the input of nitrogen, soluble phenolic, soluble sugars, lipids, cellulose, and lignin to soils, and so also the biogeochemical cycle of the prevailing ecosystem.

Biomass Leaching and Dynamics of Nutrients, Microbial Abundance and Activity During Decomposition of Seagrass Cymodocea rotundata Necromass

Examining how seagrass decomposition contributes to trophic pathways in marine ecosystems is crucial in understanding seagrass production. Decomposition rates of seagrasses may depend on many factors such as chemical composition and microbial colonization. In this study, microbial colonization and changes in chemical composition of decomposing material (necromass) of Smooth Ribbon Seagrass, Cymodocea rotundata of Bogtong Bay, Lahuy Island, Caramoan, Philippines were monitored. Seagrass litter were placed in litterbags and incubated in the seagrass meadow in situ for 56 d. Serial dilution, viable plate counts and microbial oxygen consumption analyses were done and gravimetry, Kjeldahl method and acid hydrolysis were used respectively to measure the change in carbohydrate, protein and nitrogen content of the decomposing necromass. Results showed that the decomposition processing rate was 0.27 to 2.51% biomass (g dw) loss per day with a half-life of 2.36 to 2.88 d. Growth of bacteria was greater than fungi throughout the course of experiment. Bacterial abundance (CFU mL-1) fluctuated throughout the experimental period while fungal abundance initially increased but gradually decreased and the initially observed marine fungi ceased to grow in decaying litter until the end of the experiment indicating that heterotrophic bacteria contribute more in the decomposition of seagrass litter. Oxygen consumption as well as protein, lipids and nitrogen content of litter decreased by as over the days of incubation. Therefore, as decomposition proceeds, litter biomass was leached resulting in carbohydrate content loss. But the remaining tissues of decaying C. rotundata were eventually colonized by bacteria and fungi. This further contributes to mineralization of the litter and gradual release of nutrients that could be considered as important trophic inputs to the ecosystem.

Dynamics of soil microbial metabolic activity during grassland succession after farmland abandonment

Secondary succession has a major influence on vegetation and soil biogeochemical processes, however, the dynamics of microbial metabolic activity and the driving factors during grassland succession after farmland abandonment remain unclear. Therefore, we examined variations in microbial biomass carbon (Cmic), soil basal respiration (BR), microbial quotient (Cmic:Corg), and metabolic quotient (qCO2) in sloping farmlands that had been abandoned for 0, 3, 8, 13, 18, 23 and 30 years on the Loess Plateau in China. Moreover, the plant, soil and microbial properties were determined to reveal the forces driving soil microbial metabolic activity. The results showed that compared to those of farmland, the Cmic significantly increased by 104.7% and 168.0%, while the qCO2 significantly decreased by 54.3% and 70.5%, respectively, in the late succession stages (23 and 30 years). Long-term succession (30 years) significantly enhanced the Cmic:Corg by 51.4%. In contrast, except for a decrease at 8 years, the BR changed little during grassland succession following farmland abandonment. These changes in microbial metabolic activity indicators were associated with shifts in litter biomass, soil organic carbon, available nitrogen, and soil fungi. Litter biomass and fungi were strongly affected the changes in microbial metabolic activity. This study provided new information regarding the dynamics of microbial metabolic activity during long-term secondary succession and enhanced our understanding of the linkages among plant, soil and microorganisms in semiarid ecosystems.