Soil organic carbon storage and soil CO_2 flux in the alpine meadow ecosystem

High-resolution sampling,measurements of organic carbon contents and 14C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau,and application of 14C tracing technology were conducted in an attempt to investigate the turnover times of soil organic car-bon and the soil-CO2 flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12×104 kg C hm-2 to 30.75×104 kg C hm-2 in the alpine meadow eco-systems,with an average of 26.86×104 kg C hm-2. Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO2 flux ranges from 103.24 g C m-2 a-1 to 254.93 gC m-2 a-1,with an average of 191.23 g C m-2 a-1. The CO2 efflux produced from microbial decomposition of organic matter varies from 73.3 g C m-2 a-1 to 181 g C m-2 a-1. More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%―81.23% of total CO2 emitted from or-ganic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming,the storage,volume of flow and fate of the soil organic carbon in the alpine meadow ecosystem of the Tibetan Plateau will be changed,which needs further research.     

Soil organic carbon storage and soil CO<Subscript>2</Subscript> flux in the alpine meadow ecosystem

High-resolution sampling, measurements of organic carbon contents and ¹⁴C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau, and application of ¹⁴C tracing technology were conducted in an attempt to investigate the turnover times of soil organic carbon and the soil-CO₂ flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12×10⁴ kg C hm⁻² to 30.75×10⁴ kg C hm⁻² in the alpine meadow ecosystems, with an average of 26.86×10⁴ kg C hm⁻². Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO₂ flux ranges from 103.24 g C m⁻² a⁻¹ to 254.93 gC m⁻² a⁻¹, with an average of 191.23 g C m⁻² a⁻¹. The CO₂ efflux produced from microbial decomposition of organic matter varies from 73.3 g C m⁻² a⁻¹ to 181 g C m⁻² a⁻¹. More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%281.23% of total CO₂ emitted from organic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming, the storage, volume of flow and fate of the soil organic carbon in the alpine meadow ecosystem of the Tibetan Plateau will be changed, which needs further research. Supported by the National Natural Science Foundation of China (Grant Nos. 40231015, 40471120 and 40473002) and the Guangdong Provincial Natural Science Foundation of China (Grant No. 06300102)     

Vegetation and soil carbon storage in China

This study estimated the current vegetation and soil carbon storage in China using a biogeochemical model driven with climate, soil and vegetation data at 0.5° latitude-longitude grid spatial resolution. The results indicate that the total carbon storage in China's vegetation and soils was 13.33 Gt C and 82.65 Gt C respectively, about 3% and 4% of the global total. The nationally mean vegetation and soil carbon densities were 1.47 kg C/m2 and 9.17 kg C/m2, respectively, differing greatly in various regions affected by climate, vegetation, and soil types. They were generally higher in the warm and wet Southeast China and Southwest China than in the arid Northwest China; whereas vegetation carbon density was the highest in the warm Southeast China and Southwest China, soil carbon density was the highest in the cold Northeast China and southeastern fringe of the Qinghai-Tibetan Plateau. These spatial patterns are clearly correlated with variations in the climate that regulates plant growth and soil organi     

Geomorphic controls on floodplain sediment and soil organic carbon storage in a Scottish mountain river

River floodplains constitute an important element in the terrestrial sediment and organic carbon cycle and store variable amounts of carbon and sediment depending on a complex interplay of internal and external driving forces. Quantifying the storage in floodplains is crucial to understand their role in the sediment and carbon cascades. Unfortunately, quantitative data on floodplain storage are limited, especially at larger spatial scales. Rivers in the Scottish Highlands can provide a special case to study alluvial sediment and carbon dynamics because of the dominance of peatlands throughout the landscape, but the alluvial history of the region remains poorly understood. In this study, the floodplain sediment and soil organic carbon storage is quantified for the mountainous headwaters of the River Dee in eastern Scotland (663 km²), based on a coring dataset of 78 floodplain cross-sections. Whereas the mineral sediment storage is dominated by wandering gravel-bed river sections, most of the soil organic carbon storage can be found in anastomosing and meandering sections. The total storage for the Upper Dee catchment can be estimated at 5.2 Mt or 2306.5 Mg ha^-1 of mineral sediment and 0.7 Mt or 323.3 Mg C ha^-1 of soil organic carbon, which is in line with other studies on temperate river systems. Statistical analysis indicates that the storage is mostly related to the floodplain slope and the geomorphic floodplain type, which incorporates the characteristic stream power, channel morphology and the deposit type. Mapping of the geomorphic floodplain type using a simple classification scheme shows to be a powerful tool in studying the total storage and local variability of mineral sediment and soil organic carbon in floodplains. © 2019 John Wiley & Sons, Ltd.     

Soil organic carbon and nitrogen content of density fractions and effect of meadow degradation to soil carbon and nitrogen of fractions in alpine Kobresia meadow

This research was conducted on the non-disturbed native alpine Kobresia meadow(YF) and the severely degraded meadow(SDL) of Dari County of Qinghai Province.By a density fractionation approach,each soil sample was divided into two fractions:light fraction(LF) and heavy fraction(HF).The obtained fractions were analyzed for organic carbon(OC) and nitrogen(N) concentrations.The results showed:(1) the OC concentration in HF and LF was 3.84% and 28.63% respectively while the nitrogen concentration in HF and LF wa...     

Soil particle size distribution and induced soil carbon transport by ephemeral gully erosion in Mediterranean mountain arable land

In Mediterranean mountain agroecosystems, soil erosion associated with the development of ephemeral gullies is a common environmental problem that contributes to a loss of nutrient-rich topsoil. Little is known about the influence of ephemeral gully erosion on particle size distribution and its effect on soil organic (SOC) and inorganic (SIC) carbon among different sized soil particles in agricultural soils. In this study, laboratory tests were conducted using velocity settling tube experiments to examine the effects of erosion on sediment particle size distributions from an incised ephemeral gully, associated with an extreme event (235 mm). We also consider subsequent deposition on an alluvial fan in order to assess the distribution of SOC and SIC concentrations and dissolved carbon before and after the extreme event. Soil fractionation was carried out on topsoil samples (5 cm) collected along an ephemeral gully in a cultivated field, located in the lower part of a Mediterranean mountain catchment. The results of this study showed that the sediment transported downstream by runoff plays a key role in the particle size distribution and transportability of soil particles and associated carbon distribution in carbonate rich soils. The eroding sediment is enriched in clay and silt-sized particles at upslope positions with higher SOC contents and gradually becomes coarser and enriched in SIC at the end of the ephemeral gully because the finest particles are washed-out of the study field. The extreme event was associated with an accumulation of dissolved organic carbon at the distal part of the depositional fan. Assessment of soil particle distribution using settling velocity experiments provides basic information for a better understanding of soil carbon dynamics in carbonate rich soils. Processes of soil and carbon transport and relationships between soil properties, erodibility and aggregate stability can be helpful in the development of more accurate soil erosion models. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.     

The relationship between dissolved organic carbon in stream water and soil organic carbon pools at different spatial scales

The relationship between stream water DOC concentrations and soil organic C pools was investigated at a range of spatial scales in subcatchments of the River Dee system in north‐east Scotland. Catchment percentage peat cover and soil C pools, calculated using local, national and international soils databases, were related to mean DOC concentrations in streams draining small‐ (<5 km²), medium‐ (12–38 km²) and large‐scale (56–150 km²) catchments. The results show that, whilst soil C pool is a good predictor of stream water DOC concentration at all three scales, the strongest relationships were found in the small‐scale catchments. In addition, in both the small‐ and large‐scale catchments, percentage peat cover was as a good predictor of stream water DOC concentration as catchment soil C pool. The data also showed that, for a given soil C pool, streams draining lowland (<700 m) catchments had higher DOC concentrations than those draining upland (>700 m) catchments, suggesting that disturbance and land use may have a small effect on DOC concentration. Our results therefore suggest that the relationship between stream water DOC concentration and catchment soil C pools exists at a range of spatial scales and this relationship appears to be sufficiently robust to be used to predict the effects of changes in catchment soil C storage on stream water DOC concentration. Copyright © 1999 John Wiley & Sons, Ltd.     

Banking carbon: a review of organic carbon storage and physical factors influencing retention in floodplains and riparian ecosystems

Rivers are dynamic components of the terrestrial carbon cycle and provide important functions in ecosystem processes. Although rivers act as conveyers of carbon to the oceans, rivers also retain carbon within riparian ecosystems along floodplains, with potential for long‐term (> 10² years) storage. Research in ecosystem processing emphasizes the importance of organic carbon (OC) in river systems, and estimates of OC fluxes in terrestrial freshwater systems indicate that a significant portion of terrestrial carbon is stored within river networks. Studies have examined soil OC on floodplains, but research that examines the potential mechanistic controls on OC storage in riparian ecosystems and floodplains is more limited. We emphasize three primary OC reservoirs within fluvial systems: (1) standing riparian biomass; (2) dead biomass as large wood (LW) in the stream and on the floodplain; (3) OC on and beneath the floodplain surface, including litter, humus, and soil organic carbon (SOC). This review focuses on studies that have framed research questions and results in the context of OC retention, accumulation and storage within the three primary pools along riparian ecosystems. In this paper, we (i) discuss the various reservoirs for OC storage in riparian ecosystems, (ii) discuss physical conditions that facilitate carbon retention and storage in riparian ecosystems, (iii) provide a synthesis of published OC storage in riparian ecosystems, (iv) present a conceptual model of the conditions that favor OC storage in riparian ecosystems, (v) briefly discuss human impacts on OC storage in riparian ecosystems, and (vi) highlight current knowledge gaps. Copyright © 2015 John Wiley & Sons, Ltd.     

Amount and reactivity of dissolved organic matter export are affected by land cover change from old-growth to second-growth forests in headwater ecosystems

Headwater forest ecosystems of the western USA generate a large portion of the dissolved organic matter (DOM) transported in streams across North America. Land cover changes that alter forest structure and species composition affect the quantity and composition of DOM transferred to aquatic ecosystems. Clear-cut harvesting affects ~1% of the forest area of North America annually, leaving most western forests in varying stages of regrowth and the total area of old-growth forest is decreasing. The consequences of this widespread management practice on watershed carbon cycling remain unknown. We investigated the role of land cover change, because of clear-cut harvesting, from mixed-species old-growth to lodgepole pine-dominated second-growth forest on the character and reactivity of hillslope DOM exports. We evaluated inputs of DOM from litter leachates and export of DOM collected at the base of trenched hillslopes during a 3-year period (2016–2018) at the Fraser Experimental Forest in north-central Colorado, USA. Dissolved organic carbon and total dissolved nitrogen were higher in lateral subsurface flow draining old- versus second-growth forest. Fluorescence spectroscopy showed that the DOM exported from the old-growth forest was more heterogeneous and aromatic and that proteinaceous, microbially processed DOM components were more prevalent in the second-growth forest. Biological oxygen demand assays revealed much lower microbial metabolism of DOM in litter leachate and subsurface exports from the old-growth forest relative to second growth. Old-growth and second-growth forests are co-mingled in managed ecosystems, and our findings demonstrate that land cover change from a mixture of conifer species to lodgepole pine dominance influences DOM inputs that can increase the reactivity of DOM transferred from terrestrial to aquatic ecosystems.     

Soil organic carbon and nitrogen content of density fractions and effect of meadow degradation to soil carbon and nitrogen of fractions in alpine <Emphasis Type="Italic">Kobresia</Emphasis> meadow

This research was conducted on the non-disturbed native alpine Kobresia meadow (YF) and the severely degraded meadow (SDL) of Dari County of Qinghai Province. By a density fractionation approach, each soil sample was divided into two fractions: light fraction (LF) and heavy fraction (HF). The obtained fractions were analyzed for organic carbon (OC) and nitrogen (N) concentrations. The results showed: (1) the OC concentration in HF and LF was 3.84% and 28.63% respectively while the nitrogen concentration in HF and LF was 0.362% and 1.192% respectively in 0–10 cm depth. C:N ratio was 10.6 in HF and 23.8 in LF respectively. (2) As far as the ratio of OC in given fraction to that in gross sample was concerned, dominance of OC in HF was obvious in the whole soil profile. OC in HF increased from 78.95% to 90.33%, while OC in LF decreased from 21.05% to 9.68% with depths. (3) Soil total OC amounted to 47.47 in YF while 17.63 g · kg⁻¹ in SDL, in which the OC content in HF decreased from 37.31 to 16.01 g · kg⁻¹ while OC content in LF decreased from 10.01 to 1.62 g · kg⁻¹. In other words, results of OC and N content show meadow degradation led to the loss of 57% OC in HF and 84% OC in LF from originally native ecosystem on alpine meadow. In addition, meadow degradation led to the loss of 43% N in HF and 79% N in LF from originally native ecosystem on alpine meadow. (4) The main reason for loss of C and N in LF during meadow degradation was not attributed to the decrease of OC and N concentration in LF and LF, but to the decrease in LF dry weight. Loss of N was far lower than loss of C in HF. This may suggest that there is difference in protection mode of C and N in HF. Supported by National Natural Science Foundation of China (Grant No. 30660120), Science Support Project in the Source Region of the Three Rivers (Grant No. 2005-SN-2)     

Soil losses due to potato and sugar beet harvesting in NE China

The study of soil loss due to crop harvesting (SLCH) started only recently in soil erosion research. It describes the mass of adhering soil, soil clods and rock fragments that is lost from arable land during the harvesting of crops such as potato, sugar beet, sweet potato and cassava. Some research on mechanized agriculture in Europe revealed that soil loss rates due to crop harvesting can be comparable to water and tillage erosion rates. However, little is known about soil losses caused by manually harvested crops in other parts of the world. This study investigated SLCH for potato and sugar beet plots on farmer's fields spread over four regions in northeast China where harvesting is carried out by hand. Soil losses for sugar beet were on average 1·0 Mg/ha/harvest, ranging from 0·2 to 1·9 Mg/ha/harvest, and SLCH for potato ranged from 0·2 to 3·0 Mg/ha/harvest with an average of 1·2 Mg/ha/harvest. Soil moisture content, average root mass and plant density could explain 45 to 67 per cent of the variability of SLCH for sugar beet. The effect of soil texture was the opposite to findings of other studies, which could be attributed to the strong correlations among the variables and to the effect of the harvesting operator. SLCH variability for potatoes could best be explained by soil texture. SLCH for sugar beet was much lower than European SLCH values for this crop, which can be explained by differences in harvesting technique and agronomic practices. SLCH for potato was comparable to soil losses measured in Belgium, especially if clods are removed on the harvesting machine. However, clay contents of the soils were larger in this study and soil losses were lower than in Belgium for comparable clay contents. Although SLCH is not the dominant soil erosion process in NE China, it contributes to overall soil loss rates, which have already exceeded their critical tolerance limits in this region. Copyright © 2006 John Wiley & Sons, Ltd.     

秋季聚积蓝藻打捞对蓝藻生长及水质影响的原位实验

在巢湖西北半湖近岸设置3组小型围隔模拟秋季湖岸带蓝藻聚积,并用单片鳃式过滤器原位打捞蓝藻,研究秋季打捞对蓝藻生长的影响及其对营养盐、藻源性有机物的控制效应.初始围隔水体叶绿素a浓度为309.5±3.7μg/L,总氮和总磷浓度分别为3.32±0.14和0.30±0.04 mg/L.蓝藻衰亡分解释放的藻源性有机物为水体溶解性有机物的主要来源,荧光有机物以类蛋白物质为主.经过打捞,浮游植物生物量削减了41.7%,解除了蓝藻生长"密度制约",24 h细胞分裂频率及原位生长速率均增大,说明打捞在短期内增强蓝藻细胞生长活力,减缓藻源性有机物的释放.与秋季蓝藻衰亡趋势一致,实验周期内围隔中叶绿素a浓度逐渐降低,秋季打捞不会造成蓝藻水华再次暴发.打捞通过削减蓝藻生物量,使水体初级生产力、氮、磷、高锰酸盐指数得到显著控制;而且打捞还可以控制藻源性有机物的释放,使藻源性大分子有机物更易降解为小分子有机物.因此,在秋季对湖岸带聚积蓝藻进行物理打捞,不仅可以控制蓝藻生物量,还可以有效控制营养盐和有机物的释放,降低生态风险.     

Characterizing the dynamics of soil organic carbon in grasslands on the Qinghai-Tibetan Plateau

Carbon dynamics of grasslands on the Qinghai-Tibetan Plateau may play an important role in regional and global carbon cycles. The CENTURY model (Version 4.5) is used to examine temporal and spatial variations of soil organic carbon (SOC) in grasslands on the Plateau for the period from 1960 to 2002. The model successfully simulates the dynamics of aboveground carbon and soil surface SOC at the soil depth of 0-20 cm and the simulated results agree well to the measurements. Examination of SOC for eight typical grasslands shows different patterns of temporal variation in different ecosystems in 1960-2002. The extent of temporal variation increases with the increase of SOC of ecosystem. SOC increases first and decreases quickly then during the period from 1990 to 2000. Spatially, SOC density obtained for the equilibrium condition declines gradually from the southeast to the northwest on the plateau and showed a high heterogeneity in the eastern plateau. The results suggest that (i) SOC den-sity in the alpine grasslands shows remarkable response to climate change during the 42 years, and (ii) the net carbon exchange rate between the alpine grassland ecosystems and the atmosphere increases from 1990 to 2000 as compared with that before 1990.     

Soil loss and displacement by heavy equipment in forest road subgrading projects

Forest soil is an important component of the natural environment, and is a primary medium for many biological activities. In this study, soil loss and displacement by excavator and bulldozer （heavy equipments） were measured on cut and fills slopes of forest roads located in Mazandaran province, lran. The volumes of soil losses were estimated by prismoidal analyses of cut and fill slopes deformation between two time treatments （under subgrading and two years later） in slope classes of 30-50% and 50-70%. Weights of soil losses were calculated by multiplying the volumes of soil losses （cm^3） to the general bulk density （1.3g/cm^3）. Soil displaced area by heavy equipment was evaluated according to earth working width. Results indicated that heavy equipment has significant effect on deformation of cut slope gradient and fill slope length （p〈0.0001）. During the two-year period, the cut （p〈0.0002） and fill （p〈0.0001） slope gradients were significantly deformed in different slope classes. The average soil loss by excavator and bulldozer were 160.35 t/ha·yr and 429.09 t/ha·yr, respectively. Moreover, the soil displaced area during the subgrading process by bulldozer was greater than excavator in both two slope classes （p〈0.05）. Soil loss and displacement in forest roads can be rednced by applying powerful excavators in subgrading project, especially in steep terrains.     

Soil organic carbon enrichment of dust emissions: magnitude,mechanisms and its implications for the carbon cycle

Soil erosion is an important component of the global carbon cycle. However, little attention has been given to the role of aeolian processes in influencing soil organic carbon (SOC) flux and the release of greenhouse gasses, such as carbon dioxide (CO₂), to the atmosphere. Understanding the magnitude and mechanisms of SOC enrichment in dust emissions is necessary to evaluate the impact of wind erosion on the carbon cycle. This research examines the SOC content and enrichment of dust emissions measured using Big Spring Number Eight (BSNE) wind‐vane samplers across five land types in the rangelands of western Queensland, Australia. Our results show that sandy soils and finer particulate quartz‐rich soils are more efficient at SOC emission and have larger SOC dust enrichment than clay‐rich aggregated soils. The SOC enrichment ratios of dusts originating from sites with sand‐rich soil ranged from 2·1–41·9, while the mean enrichment ratio for dusts originating from the clay soil was 2·1. We hypothesize that stronger inter‐particle bonds and the low grain density of the aggregated clay soil explain its reduced capacity to release SOC during saltation, relative to the particulate sandy soils. We also show that size‐selective sorting of SOC during transport may lead to further enrichment of SOC dust emissions. Two dust samples from regional transport events were found to contain 15–20% SOC. These preliminary results provide impetus for additional research into dust SOC enrichment processes to elucidate the impact of wind erosion on SOC flux and reduce uncertainty about the role of soil erosion in the global carbon cycle. Copyright © 2013 John Wiley & Sons, Ltd.     

Response of soil aggregate disintegration to the different content of organic carbon and its fractions during splash erosion

Aggregate disintegration is a critical process in soil splash erosion. However, the effect of soil organic carbon (SOC) and its fractions on soil aggregates disintegration is still not clear. In this study, five soils with similar clay contents and different contents of SOC have been used. The effects of slaking and mechanical striking on splash erosion were distinguished by using deionized water and 95% ethanol as raindrops. The simulated rainfall experiments were carried out in four heights (0.5, 1.0, 1.5 and 2.0 m). The result indicated that the soil aggregate stability increased with the increases of SOC and light fraction organic carbon (LFOC). The relative slaking and the mechanical striking index increased with the decreases of SOC and LFOC. The reduction of macroaggregates in eroded soil gradually decreased with the increase of SOC and LFOC, especially in alcohol test. The amount of macroaggregates (>0.25 mm) in deionized water tests were significantly less than that in alcohol tests under the same rainfall heights. The contribution of slaking to splash erosion increased with the decrease of heavy fractions organic carbon. The contribution of mechanical striking was dominant when the rainfall kinetic energy increased to a range of threshold between 9 J m⁻² mm⁻¹ and 12 m⁻² mm⁻¹. This study could provide the scientific basis for deeply understanding the mechanism of soil aggregates disintegration and splash erosion.     

Evaluating the impact of soil redistribution on the in situ mineralization of soil organic carbon

Soil erosion, transport and deposition by water drastically affect the distribution of soil organic carbon (SOC) within a landscape. Moreover, soil redistribution may have a large impact on the exchange of carbon (C) between the pedosphere and the atmosphere. One of the large information gaps within this research domain, concerns the fate of SOC after erosion by water. According to different (mainly laboratory) studies, soil redistribution leads to aggregate breakdown, thereby exposing the contained SOC to mineralization. Our study aims to quantify the extent to which such increased mineralization occurs in a real field situation. Carbon dioxide (CO₂)‐efflux was measured in the field after an important erosion event for a continuous period of 112 days. The specific situation on the field ensured that almost none of eroded SOC was exported from the field. Measurements of CO₂‐efflux were done in areas with sediment deposition, as well as in comparable areas without sedimentation. Comparison of these measurements allowed the net effect of soil deposition on CO₂‐efflux to be assessed. Field data were complemented by measurements on incubated, undisturbed soil core samples, in order to disentangle the contribution of environmental factors (moisture, temperature) from any erosional effect on CO₂‐efflux. Results of these measurements on the field showed that CO₂‐efflux was regulated by a complex interplay of different factors (mostly soil porosity, soil moisture and soil temperature). In combination with the incubation measurements, it could be concluded that the processes of erosion and transport indeed led to an increased mineralization of SOC, as a result of aggregate breakdown and exposure of previously encapsulated SOC. This effect was, however, much smaller than observed in previous laboratory studies. Moreover, it was only important in the first weeks, immediately after the erosion event. The calculated net erosional effect on CO₂‐efflux represented a mere 1·6% of total SOC, originally present in the soil. Copyright © 2010 John Wiley & Sons, Ltd.     

Changes in ecosystem structure,function and hydrological connectivity control water,soil and carbon losses in semi‐arid grass to woody vegetation transitions

Connectivity has recently emerged as a key concept for understanding hydrological response to vegetation change in semi‐arid environments, providing an explanatory link between abiotic and biotic, structure and function. Reduced vegetation cover following woody encroachment, generally promotes longer, more connected overland flow pathways, which has the potential to result in an accentuated rainfall‐runoff response and fluxes of both soil erosion and carbon. This paper investigates changing hydrological connectivity as an emergent property of changing ecosystem structure over two contrasting semi‐arid grass to woody vegetation transitions in New Mexico, USA. Vegetation structure is quantified to evaluate if it can be used to explain observed variations in water, sediment and carbon fluxes. Hydrological connectivity is quantified using a flow length metric, combining topographic and vegetation cover data. Results demonstrate that the two woody‐dominated sites have significantly longer mean flowpath lengths (4 · 3 m), than the grass‐dominated sites (2 · 4 m). Mean flowpath lengths illustrate a significant positive relationship with the functional response. The woody‐dominated sites lost more water, soil and carbon than their grassland counterparts. Woody sites erode more, with mean event‐based sediment yields of 1203 g, compared to 295 g from grasslands. In addition, the woody sites lost more organic carbon, with mean event yields of 39 g compared to 5 g from grassland sites. Finally, hydrological connectivity (expressed as mean flowpath length) is discussed as a meaningful measure of the interaction between structure and function and how this manifests under the extreme rainfall that occurs in semi‐arid deserts. In combination with rainfall characteristics, connectivity emerges as a useful tool to explain the impact of vegetation change on water, soil and carbon losses across semi‐arid environments. Copyright © 2013 John Wiley & Sons, Ltd.     

Modelling water,nutrients, and organic carbon in forested catchments: a HYPE application

Both monitoring and model simulation are useful for understanding and detecting changes in the environment. To understand and simulate leaching in small forested catchments, it is important to have knowledge of soil processes. Here, we describe recent development of the Hydrological Predictions for the Environment (HYPE) model for forested catchments. HYPE includes an organic carbon (OC) variable in addition to previously published nitrogen (N), phosphorus (P), and water flow models. The aspects addressed in the current study included P concentrations under low‐flow conditions and high concentrations of inorganic N. HYPE was further developed based on nine small forested catchments (0.5–200 ha) in Sweden, which were calibrated separately using local data. The model (excluding the OC variable) was tested on a larger set of forest catchments from the operational HYPE model of Sweden (S‐HYPE). We observed the following: (1) dissolved organic P could make a significant contribution to the total P concentration in a stream during low‐flow periods, (2) the inorganic N concentration simulated in a stream improved when part of the atmospheric N was retained in the soil, (3) the soil flow path formulation was critical for simulating concentration dynamics, and (4) evaluating an additional variable (OC) further elucidated the soil runoff processes in the model. Copyright © 2016 Swedish Meteorological and Hydrological Institute. Hydrological Processes published by John Wiley & Sons, Ltd.