Ecosystem productivity and carbon dynamics in Keibul Lamjao National Park, Manipur, India: a gray relational analysis perspective.

Spatial distribution of carbon balance in forest ecosystems across East Asia

This study investigated the optimization of computer numerical control (CNC) boring operation parameters for aluminum alloy 6061T6 using the grey relational analysis (GRA) method. Nine experimental runs based on an orthogonal array of Taguchi method were performed. The surface properties of roughness average and roughness maximum as well as the roundness were selected as the quality targets. An optimal parameter combination of the CNC boring operation was obtained via GRA. By analyzing the grey relational grade matrix, the degree of influenced for each controllable process factor onto individual quality targets can be found. The feed rate is identified to be the most influence on the roughness average and roughness maximum, and the cutting speed is the most influential factor to the roundness. Additionally, the analysis of variance (ANOVA) was also applied to identify the most significant factor; the feed rate is the most significant controlled factor for the CNC boring operations according to the weighted sum grade of the roughness average, roughness maximum and roundness.

Age effects on carbon fluxes in temperate pine forests

Elevated nitrogen (N) and phosphorus (P) depositions have greatly affected belowground carbon processes in forest ecosystems. However, open questions still remained on the effects of N and P depositions on belowground carbon processes, including soil respiration (RS), its source components—autotrophic respiration (RA) and heterotrophic respiration (RH), and total belowground carbon allocation (TBCA) in Moso bamboo forests—one of the most important forest types with wide distributions in subtropical China. To fill this knowledge gap, a two-year N, P, and NP experiment was conducted in Moso bamboo forests. Results showed that RS, RA, and RH had a strong seasonal variability and were exponentially correlated with soil temperature. N and P depositions did not change RS and RA. However, P deposition increased RH due to the stimulation of microbial activities, indicating a significant soil carbon loss under P deposition. N and P depositions did not affect TBCA. However, NP deposition significantly increased root carbon-use efficiency. Net ecosystem production (NEP) varied from 198 ± 104 to 529 ± 225 g C m−2 year−1, indicating that Moso bamboo is an important carbon sink. P deposition marginally decreased NEP, while N and NP depositions did not affect NEP, which indicates that N deposition alleviated the suppression of P deposition on NEP. These findings highlight the inconsistent responses of RA, RH, and NEP to N, P, and NP depositions, which should be differently considered to increase the accuracy of predicting belowground carbon dynamics.

Carbon dynamics of prescribed fire in pine- and oak-dominated forests on the mid-Atlantic coastal plain, USA

This paper deals with the optimisation of numerous criteria problems in the turning process of EN-8 steel by using Taguchi and Grey Relational Analysis. In order to investigate the machining parameters’ performance characteristics like nose radius, cutting speed, depth of cut and feed, considering multiple responses, i.e., tangential force and feed force, an orthogonal array L18, grey relational coefficients, grey relational grade and analysis of variance (ANOVA) are estimated. The study gives the lower magnitude of the feed force and tangential force and also optimal cutting parameters. The experiment achieved an average Grey Relational Grade of 0.70449, and the prediction of GRG for the optimal setting is 0.86235, which proves the improvement in GRG by 0.15787. The largest Grey Relational Grade is for experiment number 4, which gives the optimum parameter setting for the experiment as A1B2C1D1. The main effect plot (Fig. 3) shows the low values for tool nose radius, feed rate and depth of cut resulting in the minimum tangential force, which is 98.066° N and optimised value of the feed force, which is 107.873° N. The response table and response graphs are shown and ANOVA table reveals that significant factors are depth of cut, feed rate and nose radius in affecting the experimentation at 95 percent confidence level.KeywordsOptimizationTurning processEN 8 SteelGrey relational analysisTaguchiANOVA

Machining is important in metal manufacturing process to achieve near-nett shape, good dimensional accuracy and aesthetic requirements. But the current scenario depicts that the manufacturing industries constant focus is on lowering cost solutions with reduced lead time, better surface quality, maintaining competitiveness and efficiency. The work material considered in this work is AISI4140 alloy steel. This work material is machined using carbide tool with cutting speed, feed and depth of cut taken as the process parameters. The responses considered against these process parameters are surface roughness and flank wear. Designs of experiments are used to conduct the experiments for minimization of surface roughness and flank wear. Orthogonal array design is implemented to conduct the several experiments. Surface Roughness is measured using Mitutoyo Surface roughness tester and flank wear are investigated using scanning electron microscope. The Taguchi grey or grey relation analysis correlates the experimental data and the desired data and calculates the grey relational coefficient. This grey relational coefficient is used to determine the overall grey relational grade corresponding to the selected responses. The grey relation coefficient and grade are presented in this paper and proves to be consistent. The response graph for average grey relational grade and ANOVA for grey relational grade are also presented.

In eastern North America, many deciduous forest ecosystems grow at the northernmost extent of their geographical ranges, where climate change could aid or impede their growth. This region experiences frequent extreme weather conditions, allowing us to study the response of these forests to environmental conditions, reflective of future climates. Here we determined the impact of seasonal and annual climate variations and extreme weather events on the carbon (C) uptake capacity of an oak‐dominated forest in southern Ontario, Canada, from 2012 to 2016. We found that changes in meteorology during late May to mid‐July were key in determining the C sink strength of the forest, impacting the seasonal and annual variability of net ecosystem productivity (NEP). Overall, higher temperatures and dry conditions reduced ecosystem respiration (RE) much more than gross ecosystem productivity (GEP), leading to higher NEP. Variability in NEP was primarily driven by changes in RE, rather than GEP. The mean annual GEP, RE, and NEP values at our site during the study were 1,343 ± 85, 1,171 ± 139, and 206 ± 92 g C m−2 yr−1, respectively. The forest was a C sink even in years that experienced heat and water stresses. Mean annual NEP at our site was within the range of NEP (69–459 g C m−2 yr−1) observed in similar North American forests from 2012 to 2016. The growth and C sequestration capabilities of our oak‐dominated forest were not adversely impacted by changes in environmental conditions and extreme weather events experienced over the study period.

Biometric and eddy-covariance based estimates of carbon fluxes in an age-sequence of temperate pine forests

Nature-based Solutions (NbS) can undoubtedly play a significant role in carbon neutrality strategy. Forests are a major part of the carbon budget in terrestrial ecosystems. The possible response of the carbon balance of southwestern forests to different climate change scenarios was investigated through a series of simulations using the forest ecosystem carbon budget model for China (FORCCHN), which clearly represents the influence of climate factors on forest carbon sequestration. Driven by downscaled global climate model (GCM) data, the FORCCHN evaluates the carbon sink potential of southwestern forest ecosystems under different shared socioeconomic pathways (SSPs). The results indicate that, first, gross primary productivity (GPP), ecosystem respiration (ER) and net primary productivity (NPP) of forest ecosystems are expected to increase from 2020 to 2060. Forest ecosystems will maintain a carbon sink, but net ecosystem productivity (NEP) will peak and begin to decline in the 2030s. Second, not only is the NEP in the SSP1-2.6 scenario higher than in the other climate change scenarios for 2025–2035 and 2043–2058, but the coefficient of variation of the NEP is also narrower than in the other scenarios. Third, in terms of spatial distribution, the carbon sequestration potential of northwest and central Yunnan is significantly higher than that of other regions, with a slight upward trend in NEP in the future. Finally, GPP and ER are significantly positively correlated with temperature and insignificantly correlated with precipitation, and the increasing temperature will have a negative and unstable impact on forest carbon sinks. This study provides a scientific reference for implementing forest management strategies and achieving sustainable development.

Climate extremes such as heat waves and droughts are projected to occur more frequently with increasing temperature and an intensified hydrological cycle. It is important to understand and quantify how forest carbon fluxes respond to heat and drought stress. In this study, we developed a series of daily indices of sensitivity to heat and drought stress as indicated by air temperature (Ta ) and evaporative fraction (EF). Using normalized daily carbon fluxes from the FLUXNET Network for 34 forest sites in North America, the seasonal pattern of sensitivities of net ecosystem productivity (NEP), gross ecosystem productivity (GEP) and ecosystem respiration (RE) in response to Ta and EF anomalies were compared for different forest types. The results showed that warm temperatures in spring had a positive effect on NEP in conifer forests but a negative impact in deciduous forests. GEP in conifer forests increased with higher temperature anomalies in spring but decreased in summer. The drought-induced decrease in NEP, which mostly occurred in the deciduous forests, was mostly driven by the reduction in GEP. In conifer forests, drought had a similar dampening effect on both GEP and RE, therefore leading to a neutral NEP response. The NEP sensitivity to Ta anomalies increased with increasing mean annual temperature. Drier sites were less sensitive to drought stress in summer. Natural forests with older stand age tended to be more resilient to the climate stresses compared to managed younger forests. The results of the Classification and Regression Tree analysis showed that seasons and ecosystem productivity were the most powerful variables in explaining the variation of forest sensitivity to heat and drought stress. Our results implied that the magnitude and direction of carbon flux changes in response to climate extremes are highly dependent on the seasonal dynamics of forests and the timing of the climate extremes.

Rainfall pulses can significantly influence carbon cycling in water‐limited ecosystems. The magnitude of carbon flux component responses to precipitation may vary depending on precipitation amount and antecedent soil moisture, associated with nonlinear responses of plants and soil microbes. The present study was carried out in a temperate grass ecosystem during 2013–2015 in the semiarid Loess Plateau of China, to examine the response of carbon fluxes to precipitation using the “threshold‐delay” model. The unique contribution of environmental variables such as precipitation amount and antecedent soil moisture before rainfall (SWC_antecedent) to carbon fluxes in response to rainfall was also investigated. The lower threshold of effective rainfall was 6.6 mm for gross ecosystem production (GEP), 8.5 mm for net ecosystem production (NEP), and 4.5 mm for ecosystem respiration (RE); and the upper threshold of effective rainfall was 21.4 mm for GEP and NEP, and 16.8 mm for RE. Rainfall amount was positively affected the relative rainfall responses of GEP, NEP, and RE. However, SWC_antecedent at 20 cm soil depth offset the response of GEP to rainfall pulses, and SWC_antecedent at 5 cm soil depth offset the response of NEP and RE to rainfall pulses, with corresponding partial slopes of linear regressions of −0.50, −0.40, and −0.52. These results indicated that NEP was more sensitive to rainfall pulses and RE was more sensitive to SWC_antecedent. These results demonstrate the importance of rainfall events of <10 mm and that the negative effect of SWC_antecedent should also be considered when estimating ecosystem carbon fluxes in this semiarid region.

Carbon, water and energy exchange dynamics of a young pine plantation forest during the initial fourteen years of growth

Keibul Lamjao National Park (KLNP), Loktak lake Manipur, north-east India which is one of the 25 Ramsar sites of international importance and the biggest fresh water Lake in India. Macrophytes of the floating Phumdi mat environment of KLNP play an important role in the aquatic environment. An investigation was planned during the period of about three years from March, 2010 to December 2012, to study the diversity pattern of habitats of macrophytes available in six study sites of KLNP viz., 1.Kumbi, 2.Khordak, 3.Keibul, 4.Toya, 5. Nongmaikhong and 6. Sargam. All total 85 dominant plant species were recorded. Maximum plant species (49) was observed in Site-1 Kumbi (Altitude-780m) and minimum (27) in Site-3 Keibul (Altitude-772). The variation of plant species may be because of the slight variation of altitude. As the six study sites are distributed as floating aquatic environment in KLNP Loktak Lake, there is favourable place of the plants in higher altitude and altitude represents a complex gradient along which many environmental variables change concomitantly. In all the six study sites, common distribution of ten dominant plant macrophytes viz., Ageratum conizoides, Hedychium coronarium, Leersia hexandra, Oenanthe javanica, Phragmites karka, Polygonum sagittatum, Saccharum munja, Thelypteris interrupta and Zizania latifolia was noticed. Individual dominant plant was recorded in other sites also viz., Azola piñata in site-6; Xanthium atrumarium, Polygonum orientale, Dichrocephala latifolia and Cymbopogon citratus in site-2; Arundo plinii, Cuscuta reflexa, Gnaphalium luteo-album, Hydrilla verticillata, Marsilia minuta, Saccolepis interrupta, Selvenia cuculata and Utricularia spp. in site-1. Variation of IVI value of dominant plant species was observed in this study. Even though 85 dominant plants were selected for all the 6 sites, however, maximum plant richness expressed in IVI was recorded in case of Zizania latifolia (Site-5, IVI-87.5) and minimum IVI in case of Xanthium strumarium (Site-2, IVI-1.13). The diversity pattern and habitats of macrophytes in KLNP Phumdi environment might be due to water availability along the altitudinal gradient and other environmental factors suited in the study sites and expected to be an important factor affecting the survival and fecundity of plant population. We need to conserve the natural habitat of KLNP thereby maintaining the luxuriant growth of the seasonal and perennial, macrophytes, so as to maintain the natural flora and fauna of the park. These plants are the food of man and animal therefore, it needs a proper care and attention to protect them from over exploitation. Considering the diversity pattern of habitats of Macrophytes in KLNP, a floating mat Phumdi environment with high floral diversity and unique vegetation assemblage, it has been suggested that this track and adjoining sites should be declared as ecologically sensitive area not only the World Heritage Site.

Carbon budget estimation is crucial for scientifically assessing the ecosystem’s carbon sequestration capacity. Grasslands in the Qilian Mountains are widely recognized as vulnerable and sensitive to ongoing climate change. However, it is still unclear how the carbon budget of different grassland types responds to climate change in this area. Here, we evaluated the net primary productivity (NPP), soil heterotrophic respiration (RH), and net ecosystem productivity (NEP) of grassland ecosystems in the Qilian Mountains. Correlation analysis, linear regression, and standardized coefficient methodologies were employed to explore the response of NPP, RH, and NEP in various grassland types to changes in temperature, precipitation, and solar radiation over the past two decades. The results showed that the alpine meadow has the highest NPP and NEP while the temperate typical steppe has the highest RH. Grassland NPP, RH, and NEP increased significantly from 2001 to 2020, with a distinct spatial pattern of being low in the northwest and high in the southeast of the Qilian Mountains. NPP and NEP correlated with precipitation and solar radiation more closely than with temperature. Precipitation and solar radiation, respectively, explained 43.7% and 52.9% of grassland NEP alterations, and there was a threshold effect on the response of NEP and NPP to climate factors. Specifically, the NPP and NEP increased at first and then decreased as the precipitation, temperature, and solar radiation increased. The highest NEP and NPP occurred when precipitation ranged from 415 to 455 mm, along with temperatures between − 0.1–1.5 ℃ and solar radiation reaching 7685–7905MJ/m2. The warming and humidification of climate is conducive to the increase of NPP and NEP in alpine meadows and alpine steppes, but when the precipitation exceeds 415 mm and the temperature is greater than 1.5 ℃, the NPP and NEP begin to decrease. Solar radiation dominated changes in NPP and NEP of alpine meadows, alpine steppes, and temperate desert steppes. With the increase of solar radiation, NPP and NEP of these three grasslands first increased and then decreased. However, the changes in NPP and NEP of the temperate typical steppe were most affected by precipitation, and NPP and NEP first increase and then decrease with the increase of precipitation The higher the temperature, the higher the NPP, RH, and NEP of the temperate typical steppe. This study helps better understand how climate change impacts the carbon budget components of different grassland types in the Qilian Mountains and provides more theoretical thoughts on managing local grasslands sustainably.