Nutrient limitation of woody debris decomposition in a tropical forest:contrasting effects of N and P addition

1.Tropical forests represent a major terrestrial store of carbon (C), a large proportion of which is contained in the soil and decaying organic matter. Woody debris plays a key role in forest C dynamics because it contains a sizeable proportion of total forest C. Understanding the factors controlling the decomposition of organic matter in general, and woody debris in particular, is hence critical to assessing changes in tropical C storage. 2.We conducted a factorial fertilization experiment in a tropical forest in South China to investigate the influence of nitrogen (N) and phosphorus (P) availability onwoody debris decomposition using branch segments (5-cm diameter) of four species (Acacia auriculaeformis, Aphanamixis polystachya, Schefflera octophylla, Carallia brachiata) in plots fertilized with +N, +P, or +NP, and controls. 3.Fertilization with +P and +NP increased decomposition rates by 5-53% and the magnitude was species-specific. Contrary to expectations, we observed no negative effect of +N addition on decay rates or mass loss of woody debris in any of the four study species. Decomposition rates of woody debris were higher in species with lower C:P ratios regardless of treatment. 4.We observed significant accumulation of P in the woody debris of all species in plots fertilized with +P and +NP during the early stages of decomposition. N-release from woody debris of Acacia (N-fixing) was greater in the +P plots towards the end of the study, whereas fertilization with +N had no impact on the patterns of nutrient release during decomposition. 5.Synthesis: Our results indicate that decomposition of woody debris is primarily constrained by P availability in this tropical forest. However, contrary to expectations, +N addition did not exacerbate P-limitation. It is conceivable that decay rates of woody debris in tropical forests can be predicted by C:P or lignin:P ratios but additional work with more tree species is needed to determine whether the patterns we observed are more generally applicable

Foliar phosphorus fractions reveal how tropical plants maintain photosynthetic rates despite low soil phosphorus availability

Nitrogen (N) and phosphorus (P) are essential nutrients for plant metabolism, and their availability often limits primary productivity. Whereas the effects of N availability on photosynthetic capacity are well established, we still know relatively little about the effects of P availability at a foliar level, especially in P‐limited tropical forests. We examined photosynthetic capacity, leaf mass per area (LMA) and foliar P fractions in five woody plant species after 6 years of N and P fertilization in a lowland tropical forest. Foliar N:P ratios indicated P limitation of the unfertilized plants; accordingly, photosynthetic P‐use efficiency (PPUE) and LMA decreased with P addition, and foliar N and P concentrations increased, whereas N addition had little effect on measured foliar traits. However, P addition enhanced photosynthetic capacity only in one species and not in other four species. We then assessed plant acclimation to low P availability by quantifying four fractions of foliar P representing different functional pools: structural P, metabolic P (including inorganic P), nucleic acid P, and residual P. We found that P addition enhanced the concentrations of metabolic, structural, and nucleic acid P fractions in all species, but the magnitude of the effect was species‐specific. Our findings indicate that tropical species acclimate to low P availability by altering allocation of foliar P to meet the demand of P for photosynthesis. Importantly, species typical of lowland tropical forests in East Asia maintained their photosynthetic rate under low P availability. We conclude that P limitation of leaf photosynthetic capacity may not be as common as previously assumed due to plant acclimation mechanisms in low‐P tropical forests. Species‐specific strategies to allocate P to different foliar fractions represent a potentially important adaptive mechanism for plants in P‐limited systems

Reforestation in southern China: revisiting soil N mineralization and nitrification after 8 years restoration

Nitrogen availability and tree species selection play important roles in reforestation. However, long-term field studies on the effects and mechanisms of tree species composition on N transformation are very limited. Eight years after tree seedlings were planted in a field experiment, we revisited the site and tested how tree species composition affects the dynamics of N mineralization and nitrification. Both tree species composition and season significantly influenced the soil dissolved organic carbon (DOC) and nitrogen (DON). N-fixing Acacia crassicarpa monoculture had the highest DON, and 10-mixed species plantation had the highest DOC. The lowest DOC and DON concentrations were both observed in Eucalyptus urophylla monoculture. The tree species composition also significantly affected net N mineralization rates. The highest rate of net N mineralization was found in A. crassicarpa monoculture, which was over twice than that in Castanopsis hystrix monoculture. The annual net N mineralization rates of 10-mixed and 30-mixed plantations were similar as that of N-fixing monoculture. Since mixed plantations have good performance in increasing soil DOC, DON, N mineralization and plant biodiversity, we recommend that mixed species plantations should be used as a sustainable approach for the restoration of degraded land in southern China

Concrete sewer pipe corrosion induced by sulphuric acid environment

Corrosion of concrete sewer pipes induced by sulphuric acid attack is a recognised problem worldwide, which is not only an attribute of countries with hot climate conditions as thought before. The significance of this problem is by far only realised when the pipe collapses causing surface flooding and other severe consequences. To change the existing post-reactive attitude of managing companies, easy to use and robust models are required to be developed which currently lack reliable data to be correctly calibrated. This paper focuses on laboratory experiments of establishing concrete pipe corrosion rate by submerging samples in to 0.5 pH sulphuric acid solution for 56 days under 10ºC, 20ºC and 30ºC temperature regimes. The result showed that at very early stage of the corrosion process the samples gained overall mass, at 30ºC the corrosion progressed quicker than for other temperature regimes, however with time the corrosion level for 10ºC and 20ºC regimes tended towards those at 30ºC. Overall, at these conditions the corrosion rates of 10 mm/year, 13,5 mm/year and 17 mm/year were observed

Grey relational analysis of an integrated cascade utilization system of geothermal water

With the drastic decrease in fossil resources and rapid deterioration of the global environment, the utilization of geothermal resources has been strongly advocated. The combination of heat, power, and cold utility generation is commonly used to increase the utilization efficiency of geothermal resources. In this study, an integrated cascade utilization system of waste geothermal water (ICUWGW) from a flash geothermal power plant in China is established to increase the utilization efficiency of geothermal water. The waste geothermal water leaving the power plant is proposed for further use in cascade for two-stage LiBr/H2O absorption cooling, agricultural product drying, and residential bathing. Twelve candidate temperature schemes showing different inlet and outlet temperatures of every subsystem are proposed for the ICUWGW. Several criteria are selected for the evaluation and screening of the candidate schemes. Grey relational analysis incorporating analytic hierarchy process is conducted to screen the optimal temperature scheme for the ICUWGW to meet the comprehensive criteria of thermodynamics and economics. Results show that the optimal scheme features significant improvement in energy efficiency, exergy efficiency, and equivalent electricity generation efficiency compared with those of the current geothermal power plant. The investment payback time of the additional subsystems for cooling, drying, and bathing is 1.85 years. Exergy analysis is also conducted to determine the further optimization potential of the optimal ICUWGW. Sensitivity analysis of electricity price on the performance of the optimal ICUWGW is also performed

Exploring the influencing factors of unmet palliative care needs in Chinese patients with end-stage renal disease undergoing maintenance hemodialysis: a cross-sectional study

Abstract Background The role of palliative care for end-stage renal disease (ESRD) patients have been proven in some developed countries, but it is still unclear in the mainland of China. In fact, patients with ESRD experience many unmet palliative care needs, such as physical, psychological, social and spiritual needs, but the factors influencing these needs have not investigated. Methods A cross-sectional study was conducted at two hemodialysis centers in the mainland of China from January to September 2022. Convenience sampling was used to collect data on the participants' socio-demographics, clinical characteristics, the Palliative Care Outcome Scale (POS), the Dialysis Symptom Index (DSI), the Karnofsky Performance Status Scale (KPS), the Patient Health Questionnaire-9 item (PHQ-9), and the Social Support Rate Scale (SSRS). Data were analyzed using latent profile analysis, Kruskal–Wallis test, one-way analysis of variance (ANOVA), the chi-square test and multinomial logistic regression analysis. Results Three hundred five participants were included in this study, and divided palliative care needs into three categories: Class 1, mild palliative care needs (n = 154, 50.5%); Class 2, moderate palliative care needs (n = 89, 29.2%); Class 3, severe palliative care needs (n = 62, 20.3%). Based on the analysis of three profiles, the influencing factors of unmet needs were further analyzed. Compared with Class 3, senior high school education, the household per capita monthly income < 2,000, low KPS scores, high PHQ-9 scores, and low SSRS scores were less likely to be in Class 1 (OR = 0.03, P = 0.012; OR = 0.003, P < 0.001; OR = 1.15, P < 0.001; OR = 0.55, P < 0.001; OR = 1.35, P = 0.002; respectively) and Class 2 (OR = 0.03, P = 0.007; OR = 0.05, P = 0.011; OR = 1.10, P = 0.001; OR = 0.60, P = 0.001; OR = 1.32, P = 0.003; respectively), and high symptom severity were less likely to be in Class 1 (OR = 0.82, P = 0.001). Moreover, compared with Class 1, the household per capita monthly income < 2,000 (OR = 16.41, P < 0.001), high symptom severity scores (OR = 1.12, P = 0.002) and low KPS scores (OR = 0.95, P = 0.002) were more likely to be in Class 2. Conclusions This study showed that almost half of ESRD patients receiving MHD presented moderate to severe palliative care needs, and the unmet needs were mainly affected by education level, financial pressure, functional status, symptom burden and social support. In the future, it is important to identify the populations with the greatest need for palliative care and consider the influencing factors of unmet needs from a comprehensive perspective, so as to help them improve health-related quality of life

Data from: Nutrient limitation of woody debris decomposition in a tropical forest: contrasting effects of N and P addition

Tropical forests represent a major terrestrial store of carbon (C), a large proportion of which is contained in the soil and decaying organic matter. Woody debris plays a key role in forest C dynamics because it contains a sizeable proportion of total forest C. Understanding the factors controlling the decomposition of organic matter in general, and woody debris in particular, is hence critical to assessing changes in tropical C storage. We conducted a factorial fertilization experiment in a tropical forest in South China to investigate the influence of nitrogen (N) and phosphorus (P) availability on woody debris decomposition using branch segments (5 cm diameter) of four species (Acacia auriculaeformis, Aphanamixis polystachya, Schefflera octophylla, and Carallia brachiata) in plots fertilized with +N, +P, or +NP, and controls. Fertilization with +P and +NP increased decomposition rates by 5–53%, and the magnitude was species specific. Contrary to expectations, we observed no negative effect of +N addition on decay rates or mass loss of woody debris in any of the four study species. Decomposition rates of woody debris were higher in species with lower C : P ratios regardless of treatment. We observed significant accumulation of P in the woody debris of all species in plots fertilized with +P and +NP during the early stages of decomposition. N release from woody debris of Acacia (N-fixing) was greater in the +P plots towards the end of the study, whereas fertilization with +N had no impact on the patterns of nutrient release during decomposition. Synthesis: Our results indicate that decomposition of woody debris is primarily constrained by P availability in this tropical forest. However, contrary to expectations, +N addition did not exacerbate P limitation. It is conceivable that decay rates of woody debris in tropical forests can be predicted by C : P or lignin : P ratios, but additional work with more tree species is needed to determine whether the patterns we observed are more generally applicable

Data from: Tropical forest restoration: fast resilience of plant biomass contrasts with slow recovery of stable soil C stocks

1. Due to intensifying human disturbance, over half of the world’s tropical forests are reforested or afforested secondary forests or plantations. Understanding the resilience of carbon (C) stocks in these forests, and estimating the extent to which they can provide equivalent carbon (C) sequestration and stabilization to the old growth forest they replace, is critical for the global C balance. 2. In this study, we combined estimates of biomass C stocks with a detailed assessment of soil C pools in bare land, Eucalyptus plantation, secondary forest, and natural old-growth forest after over 50 years of forest restoration in a degraded tropical region of South China. We used isotope studies, density fractionation and physical fractionation to determine the age and stability of soil C pools at different soil depths. 3. After 52 years, the secondary forests had equivalent biomass C stocks to natural forest, whereas soil C stocks were still much higher in natural forest (97.42 t ha-1) than in secondary forest (58.75 t ha-1) or Eucalyptus plantation (38.99 t ha-1) and lowest in bare land (19.9 t ha-1). Analysis of δ13C values revealed that most of the C in the soil surface horizons in the secondary forest was new C, with a limited increase of more recalcitrant old C, and limited accumulation of C in deeper soil horizons. However, occlusion of C in microaggregates in the surface soil layer was similar across forested sites, which suggests that there is great potential for additional soil C sequestration and stabilization in the secondary forest and Eucalyptus plantation. 4. Collectively, our results demonstrate that reforestation on degraded tropical land can restore biomass C and surface soil C stocks within a few decades, but much longer recovery times are needed to restore recalcitrant C pools and C stocks at depth. Repeated harvesting and disturbance in rotation plantations had a substantial negative impact on the recovery of soil C stocks. We suggest that current calculations of soil C in secondary tropical forests (e.g. IPCC Guidelines for National Greenhouse Gas Inventories) could overestimate soil C sequestration and stabilization levels in secondary forests and plantations