Transition of carbon-nitrogen coupling under different anthropogenic disturbances in subtropical small mountainous rivers.

The commonly observed inverse relationship between dissolved organic carbon (DOC) and nitrate (NO3-) concentrations in aquatic systems can be explained by stoichiometric and thermodynamic principles regulating microbial assimilation and dissimilation processes. However, the interactive effects of human activities and dissolved oxygen (DO) on the DOC and DIN (dissolved inorganic nitrogen, mainly composed of NO3--N and NH4+-N) relations are not well identified, particularly in subtropical small mountainous rivers (SMRs). Here, we investigated the exports and relations of DOC-DIN in 42 Taiwan SMRs under different anthropogenic disturbances. Results showed that the island-wide mean concentrations of the three solutes in streams are generally low, yet the abundant rainfall and persistent supply contrarily lead to disproportional high DOC and DIN yields. The inverse DOC-NO3--N relation does not appear under well­oxygenated conditions, regardless of low or high human disturbance. However, a significant inverse relationship between DOC-NO3--N would emerge in highly-disturbed watersheds under low-oxygenated conditions (mean annual DO <6.5 mg L-1), where excess N accumulates as NH4+-N rather than NO3--N. The controlling mechanism of DOC-DIN relations would shift from energetic constraints to redox constraints in low-oxygenated conditions. Although riverine concentrations of DOC, NO3--N, and NH4+-N could be elevated by human activities, the transition of DOC-DIN relation pattern is directly linked to DO availability. Understanding the mechanism that drives CN coupling is critical for assessing the ecosystem function in the delivery and retention of DOC and DIN in aquatic ecosystems.

Soil and biomass carbon re-accumulation after landslide disturbances.

In high-standing islands of the Western Pacific, typhoon-triggered landslides occasionally strip parts of the landscape of its vegetative cover and soil layer and export large amounts of biomass and soil organic carbon (OC) from land to the ocean. After such disturbances, new vegetation colonizes the landslide scars and OC starts to reaccumulate. In the subtropical mountains of Taiwan and in other parts of the world, bamboo (Bambusoideae) species may invade at a certain point in the succession of recovering landslide scars. Bamboo has a high potential for carbon sequestration because of its fast growth and dense rooting system. However, it is still largely unknown how these properties translate into soil OC re-accumulation rates after landslide disturbance. In this study, a chronosequence was established on four former landslide scars in the Central Mountain Range of Taiwan, ranging in age from 6 to 41 years post disturbance as determined by landslide mapping from remote sensing. The younger landslide scars were colonized by Miscanthus floridulus, while after approx. 15 to 20 years of succession, bamboo species (Phyllostachys) were dominating. Biomass and soil OC stocks were measured on the recovering landslide scars and compared to an undisturbed Cryptomeria japonica forest stand in the area. After initially slow re-vegetation, biomass carbon accumulated in Miscanthus stands with mean annual accretion rates of 2 ± 0.5 Mg C ha-1 yr-1. Biomass carbon continued to increase after bamboo invasion and reached ~40% of that in the reference forest site after 41 years of landslide recovery. Soil OC accumulation rates were ~2.0 Mg C ha-1 yr-1, 6 to 41 years post disturbance reaching ~64% of the level in the reference forest. Our results from this in-situ study suggest that recovering landslide scars are strong carbon sinks once an initial lag period of vegetation re-establishment is overcome.

Dynamic responses of DOC and DIC transport to different flow regimes in a subtropical small mountainous river.

Transport of riverine dissolved carbon (including DOC and DIC) is a crucial process linking terrestrial and aquatic C reservoirs, but has rarely been examined in subtropical small mountainous rivers (SMRs). This study monitored DOC and DIC concentrations on a biweekly basis during non-event flow periods and at 3 h intervals during two typhoon events in three SMRs in southwestern Taiwan between January 2014 and August 2016. Two models, HBV (the Hydrologiska Byråns Vattenbalansavdelning model) and a three-endmember mixing model, were applied to determine the quantities of DOC and DIC transport from different flow paths. The results show that the annual DOC and DIC fluxes were 2.7-4.8 and 48.4-54.3 t C km-2 yr-1, respectively, which were approx. 2 and 20 times higher than the global mean of 1.4 and 2.6 t C km-2 yr-1, respectively. The DIC / DOC ratio was 14.08, which is much higher than the mean of large rivers worldwide (1.86), and indicates the high rates of chemical weathering in this region. The two typhoons contributed 12%-14% of the annual streamflow in only 3 days (about 1.0% of the annual time), whereas 15.0%-23.5% and 9.2%-12.6% of the annual DOC and DIC flux, respectively, suggested that typhoons play a more important role in DOC transport than DIC transport. The end-member mixing model suggested that DOC and DIC export was mainly from surface runoff and deep groundwater, respectively. The unique patterns seen in Taiwan SMRs characterized by high dissolved carbon flux, high DIC / DOC ratio, and large transport by intense storms should be taken into consideration when estimating global carbon budgets.

Unusual Roles of Discharge, Slope and SOC in DOC Transport in Small Mountainous Rivers, Taiwan.

Riverine dissolved organic carbon (DOC), responsible for riverine productivity, is rarely documented in subtropical small mountainous rivers (SMRs) where high rainfall and steep slopes are the main features. This study investigated the DOC export at eight sites in three Taiwan SMRs to characterize the dynamics and controlling factors of DOC transport. Results showed that the mean DOC concentration of ~0.78 mg L-1 is much lower than the global average of ~5.29 mg L-1. However, the mean DOC yield, ~22.51 kg-C ha-1 yr-1, is higher than the global average of 14.4-19.3 kg-C ha-1 yr-1. Comparing with worldwide rivers from literature, the annual discharge, slope, and SOC (soil organic carbon) are controlling factors as expected, though they influence in different ways. SOC stock likely regulated by elevation-dependent biomes dominate the DOC supply, while slope restrains the DOC generation due to shallow soil depth and fast runoff velocity. However, the abundant discharge flushing this persistent low supply leads to a large DOC export in the SMRs. Furthermore, the DOC dynamics during typhoon periods showed a clockwise hysteresis, suggesting that the DOC is mainly from the riparian zone or downslope area during the rising limb of the hydrograph. This study elucidates the DOC transport in SMRs and provides an atypical yet significant piece of understanding on DOC transport in a global context.

Effects of different N sources on riverine DIN export and retention in a subtropical high-standing island, Taiwan.

Increases in nitrogen (N) availability and mobility resulting from anthropogenic activities have substantially altered the N cycle, both locally and globally. Taiwan characterized by the subtropical montane landscape with abundant rainfall, downwind of the most rapidly industrializing eastern coast of China, can be a demonstration site for extremely high N input and riverine DIN (dissolved inorganic N) export. We used 49 watersheds with similar climatic and landscape settings but classified into low, moderate, and highly disturbed categories based on population density to illustrate their differences in nitrogen inputs (through atmospheric N deposition, synthetic fertilizers, and human emission) and DIN export ratios. Our results showed that the island-wide average riverine DIN export is ~ 3800 kg N km-2 yr-1, approximately 18 times the global average. The average riverine DIN export ratios are 0.30-0.51, which are much higher than the averages of 0.20-0.25 of large rivers around the world, indicating excessive N input relative to ecosystem demand or retention capacity. The low disturbed watersheds have a high N retention capacity and DIN export ratios of 0.06-0.18 in spite of the high N input (~ 4900 kg N km-2 yr-1). The high retention capacity is likely due to effective uptake by secondary forests in the watersheds. The moderately disturbed watersheds show a linear increase in DIN export with increases in total N inputs and mean DIN export ratios of 0.20 to 0.31. The main difference in land use between low and moderately disturbed watersheds is the greater proportion of agricultural land cover in the moderately disturbed watersheds. Thus, their greater DIN export could be attributed to N fertilizers used in the agricultural lands. The greater export ratios also imply that agricultural lands have a lower proportional N retention capacity and that reforestation could be an effective land management practice to reduce riverine DIN export. The export ratios of the highly disturbed watersheds are very high, 0.42-0.53, suggesting that much of the N input is transported downstream directly, and urges the need to increase the proportion of households connected to a sewage system and improve the effectiveness of wastewater treatment systems. The increases in the riverine DIN export ratio along the gradient of human disturbance also suggest a gradient in N saturation in subtropical Taiwan. Our results help to improve our understanding of factors controlling riverine DIN export and provide empirical evidence that calls for sound N emission/pollution control measures.

Need-based nutritional intervention is effective in improving handgrip strength and Barthel Index scores of older people living in a nursing home: a randomized controlled trial.

BACKGROUND: Nutritional status is associated with physical functioning in older people. Protein-energy malnutrition can limit functional performance. OBJECTIVES: This study examined the effectiveness of a "need-based intervention" on improving the physical functioning of older adults living in nursing homes. DESIGN: A 24-week randomized, double-blind, controlled trial. SETTINGS: A privately managed geriatric nursing home in Taiwan. PARTICIPANTS: Ninety-two persons who were ≥65 years old, ≤25 kg/m(2), >1 month residence, non-bed-ridden, without acute infection, and able to self-feed or receive oral feeding. METHODS: Qualified participants were stratified by gender and then randomly assigned to either the control group (n=45) or the intervention group (n=47). Each participant in the intervention group would receive a 50 g/day soy-protein-based nutritional supplement when he/she was rated as undernourished, defined as Mini Nutritional Assessment score ≤24 and body mass index ≤24 kg/m(2). The supplement contained 9.5 g protein, 250 kcal energy, and all essential micronutrients. The supplementation would be suspended if either one of the two "at risk" conditions was not met at the next measurement (every 4 weeks). Handgrip strength and Barthel Index were measured at baseline, mid-point (week 12), and end-point (week 24) of the trial. Results were analyzed with Student's t-test and by the Generalized Estimating Equations controlled for nutritional status. RESULTS: The intervention significantly improved (a) handgrip strength of the older adults at weeks 12 and 24, and (b) the overall Barthel Index at week 24 (all p<0.05) according to the Generalized Estimating Equations. CONCLUSIONS: "Need-based intervention" can be an effective and useful strategy for improving the physical functioning of older adults living in nursing homes, without adverse effects. The results probably are the indirect results of the improved nutritional status. The study highlights the importance of routine screening and timely intervention in geriatric care. The applicability of this need-based strategy to community-living older adults is an important issue and should be evaluated. We can probably reap a greater benefit by eliminating the risk of malnutrition at the emerging stage.

Need-based intervention is an effective strategy for improving the nutritional status of older people living in a nursing home: a randomized controlled trial.

BACKGROUND: Nutrition is a key element in geriatric health. Protein-energy malnutrition is common in institutionalized persons. OBJECTIVE: This study examined the effectiveness of a need-based "routine screening and timely intervention" strategy in improving the nutritional status of persons living in nursing homes. DESIGN: A 24-week randomized, double-blind, controlled trial. SETTING: A privately managed geriatric nursing home in Taiwan. PARTICIPANTS: Ninety-two ≥65-year old persons who were ≤25kg/m(2), >1 month residence, able to self-feed or receive oral feeding, without acute infection and non-bed-ridden. METHODS: Prospective participants were stratified by gender and then randomly assigned to either the control group (n=45) or the intervention group (n=47). Each subject in the intervention group was given a 50g/day soy-protein-based nutritional supplement if he/she was rated as undernourished according to the Mini Nutritional Assessment (MNA, score ≤24) and BMI ≤24kg/m(2). The supplement contained 9.5g protein, 250kcal energy and all essential micro-nutrients. The supplementation would be suspended once either one of the "at risk" condition was corrected. Nutritional rating with the MNA took place at baseline and every 4 weeks during the trial. Biochemical indicators were measured at baseline, mid-point (week-12) and end-point (week-24). Results were analyzed with the two-sample t-test, and the generalized estimating equations (GEE) controlled for demographic and health-related variables. RESULTS: Of the 92 subjects, 82 completed the trial; 7 withdrew and 3 died during the trial. Results showed that the need-based intervention was an effective and appropriate strategy for improving the nutritional status of persons at risk of undernourishment. The intervention significantly improved body weight, BMI, mid-arm circumference, calf circumference, and serum albumin and cholesterol concentrations at all intervals (all p<0.05). However, the intervention did not significantly improve hematocrit, hemoglobin or lymphocyte count status. CONCLUSIONS: Results suggest that the need-based nutritional intervention can be a practical and useful strategy for improving the nutritional status of persons living in nursing homes and save on healthcare cost. The potential application of this strategy deserves the attention of health planners.

Complementarity of the Mini-Nutritional Assessment and Activities of Daily Living for predicting follow-up mortality risk in elderly Taiwanese.

Physical functional ability and nutritional status are two major indicators for predicting the risk of mortality in older adults. The present study examined the complementarity of the Activities of Daily Living (ADL) and the Mini-Nutritional Assessment (MNA) for predicting follow-up 4-year all-cause mortality risk in elderly Taiwanese. We analysed data of the 'Survey of Health and Living Status of the Elderly in Taiwan', a population-based longitudinal cohort study which involved 2872 men and women of ≥ 65 years old at baseline (1999). We rated their functional dependency with the ADL scale and nutritional status with the MNA (both the long form, LF and the short form, SF) at baseline, and analysed the complementarity of the two scales in predicting follow-up 4-year all-cause mortality with Cox regression analysis and the net reclassification improvement (NRI) to quantify the improvement. The results showed that both ADL and MNA offered improvement in predicting follow-up mortality risk beyond that predicted by either one alone according to the Akaike information criterion and the NRI. The MNA-SF was nearly as effective as the MNA-LF in improving the predictive ability of the ADL. The present study suggests that the MNA (especially the SF because of its simplicity and time-saving feature) together with the ADL scale might be of value for predicting the mortality risk of frail elderly living in various settings.

Mini-Nutritional-Assessment (MNA) without body mass index (BMI) predicts functional disability in elderly Taiwanese.

Nutritional status and functional ability are mutually dependent especially in the elderly. This study examined the functional status-predictive ability of the MNA in a cross-sectional study. We analyzed the dataset of the "Survey of Health and Living Status of the Elderly in Taiwan" (SHLSET). Subjects were 2948≥65 year-old persons who were rated with the long-form (LF) and short-form (SF) MNA with or without BMI for the risk of malnutrition, and with the Activities of Daily Living (ADL) and the Instrument Activities of Daily Living (IADL) for functional status. The ADL and IADL scores were calculated according to rated nutritional status. Receiver Operating Characteristic (ROC) curves were generated for ADL and IADL status predicted by the MNA. Logistic regression was performed to evaluate the association of rated MNA scores with ADL or IADL status. Results showed that both SF and LF of MNA-T1 and T2 were able to predict ADL and IADL disabilities. Those who were rated malnourished or at risk of malnutrition had drastically higher risk of ADL or IADL dependency compared to those who were rated normal. The SF versions performed well in rating nutritional status and predicting ADL and IADL status. Overall, MNA-T2-SF performed at least equally well as MNA-T1-SF in rating functional decline. These results suggest the MNA is able to predict functional decline of the elderly. MNA-T2, especially the SF, a version without BMI should be particularly useful in clinical, long-term care and community settings.

Mini-Nutritional Assessment predicts functional decline of elderly Taiwanese: result of a population-representative sample.

Nutrition is a key element in geriatric health and is important for functional ability. The present study examined the functional status-predictive ability of the Mini-Nutritional Assessment (MNA). We analysed the dataset of the 'Survey of Health and Living Status of the Elderly in Taiwan', a population-based study conducted by the Bureau of Health Promotion of Taiwan. Study subjects (≥65 years old) who completed both the 1999 and 2003 surveys were rated with the long form and short form of the MNA at baseline and with the Activities of Daily Living (ADL) and the Instrument Activities of Daily Living (IADL) scales 4 years later (end-point). The ability of the MNA to predict ADL or IADL dependency was evaluated with logistic regression models. The results showed that the elderly who were rated malnourished or at risk of malnutrition at baseline generally had significantly higher ADL or IADL scores 4 years later. Lower baseline MNA scores also predicted a greater risk of ADL or IADL dependency. These associations exist even among the elderly who were free of ADL or IADL dependency at baseline. The results clearly indicate that the MNA is able to predict ADL and IADL dependency (in addition to rating current nutritional status) of the elderly. The MNA, especially the short form, should be a valuable tool for identifying elderly at risk of functional decline and/or malnutrition in clinical practice or community programmes.