Effects Of Precipitation Changes Research Articles

Effects of variation in precipitation on the distribution of soil bacterial diversity in the primitive Korean pine and broadleaved forests.

Patterns of precipitation have changed as a result of climate change and will potentially keep changing in the future. Therefore, it is critical to understand how ecosystem processes will respond to the variation of precipitation. However, compared to aboveground processes, the effects of precipitation change on soil microorganisms remain poorly understood. Changbai Mountain is an ideal area to study the responses of temperate forests to the variations in precipitation. In this study, we conducted a manipulation experiment to simulation variation of precipitation in the virgin, broad-leaved Korean pine mixed forest in Changbai Mountain. Plots were designed to increase precipitation by 30 % [increased (+)] or decrease precipitation by 30 % [decreased (-)]. We analyzed differences in the diversity of the bacterial community in surface bulk soils (0-5 and 5-10 cm) and rhizosphere soils between precipitation treatments, including control. Bacteria were identified using the high-throughput 454 sequencing method. We obtained a total 271,496 optimized sequences, with a mean value of 33,242 (±1,412.39) sequences for each soil sample. Being the same among the sample plots with different precipitation levels, the dominant bacterial communities were Proteobacteria, Acidobacteria, Actinobacteria, Planctomycetes, and Chloroflexi. Bacterial diversity and abundance declined with increasing soil depth. In the bulk soil of 0-5 cm, the bacterial diversity and abundance was the highest in the control plots and the lowest in plots with reduced precipitation. However, in the soil of 5-10 cm, the diversity and abundance of bacteria was the highest in the plots of increased precipitation and the lowest in the control plots. Bacterial diversity and abundance in rhizosphere soils decreased with increased precipitation. This result implies that variation in precipitation did not change the composition of the dominant bacterial communities but affected bacterial abundance and the response patterns of the dominant communities to variation in precipitation.

Climate variability as a dominant driver of post-disturbance savanna dynamics

How do climate variability and climate shifts influence vegetation patterns in dryland ecosystems? A landscape scale assessment of the effect of changes in precipitation on vegetation in three watersheds, spanning four southern African nations is undertaken and tests of statistical significance of vegetation changes developed. Concepts of resilience provide the framework for examining the influence of changes in both the mean and variance of annual precipitation on the ecological systems of southern Africa. They illustrate thresholds of change and their manifestation in the state of savanna ecosystems, which could previously only be postulated. Time series analyses indicate the fundamental role of precipitation mean and variability in modulating the states of savanna ecosystems. Here we show that the savanna dryland ecosystems have overall responded with increasing NDVI measures despite decreased precipitation since the mid to late 1970's. Areas which experienced diminished vegetative cover over time, are related to specific vegetation types, and declines in the variance of precipitation (even in the presence of overall increases in annual mean). The work highlights the importance of time-series analyses and explicit vegetation-precipitation linkages across this highly vulnerable region.

Impact of prolonged drought on rainfall use efficiency using MODIS data across China in the early 21st century

Frequency and severity of droughts are projected to increase in many regions, and their effects on temporal dynamics of the terrestrial carbon cycle remain uncertain. Ecosystem net primary productivity (NPP) is a key component of the carbon cycle, and rainfall use efficiency (RUE=NPP/precipitation) is an important measure of ecosystem stability and resilience. Here we investigated the temporal patterns of NPP and RUE and their key driving climate factors, during the early 21st century drought for four biomes in China: Needleleaf forest, Broadleaf forest, Woody savannas, and Grassland. Estimates of regional-scale NPP were based on the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) MOD17 NPP product. Our results confirmed recent findings that the impact of current-year precipitation on NPP was confounded by an array of biotic and abiotic factors. Whereas, the RUE responded strongly to variations in current- and previous-year drought for all the four biomes and the four biomes combined. We found that a dry year preceded by a wet year resulted in the highest RUE, and conversely, a wet year preceded by a dry year resulted in the lowest RUE. This was attributed to the legacy effect of precipitation changes in both wet and dry years, and to the resilience of the biomes in the dry years. Based on these results, we developed and validated a model of RUE based on the Palmer Drought Severity Index (PDSI) of both current and previous years which works well for these four biomes and all biomes combined. This model is particularly useful for understanding the impact of prolonged drought at the landscape scale because it is based on accessible satellite data and available meteorological data and the results have been tested across four major biomes.

The impact of precipitation change on nitrogen cycling in a semi‐arid ecosystem

SummaryClimatic change is altering ecosystem structure and function, especially in the southwesternUnitedStates where trees are near their physiological water stress threshold. In piñon‐juniper (Pinus edulis‐Juniperus monosperma;PJ) woodlands, increased drought is causing differential mortality of piñon resulting in an ecosystem that is becoming juniper dominated.Using a precipitation manipulation, we assessed how both increased and decreased precipitation altered ecosystem function beneath piñon and juniper. We predicted that changes in precipitation would alter nitrogen (N) availability and mineralization at the site. Further, we predicted that these responses would differ beneath piñon and juniper crowns due to plant‐level differences in transpiration andNuptake in response to drought.We found minimal interactions between tree species and the precipitation treatments onNcycling. However, across all years measured, soil nitrate decreased with increasing soil volumetric water content; a pattern that is likely due to reduced turnover in dry plots. In contrast, potential soil net‐nitrogen mineralization was reduced in water removal plots relative to water addition plots indicating that nitrogen cycling rates were slower under drought. Tree type also influenced nitrogen dynamics in this woodland. Across all 4 years, soilNavailability and potential soil net‐mineralization rates were higher in soils beneath piñon relative to juniper across all treatments. Interestingly, the observed shifts inNcycling were not reflected in the abundance ofNin microbial biomass or in ammonia‐oxidizing bacteria, which are responsible for nitrification. The observed patterns may be due to increasedNleaching from the soil during periods of increased rainfall or due to decreased microbial activity or plantNuptake when conditions are dry.The effect of precipitation change onNcycling may have long‐term consequences on the plant community in this semi‐arid ecosystem. Nitrogen concentrations are highest in the soil when water availability is low, thus whenNconcentrations are high, plants and microbes are relatively inactive and unable to use this resource.

Runoff variation affected by precipitation change and human activity in Hailiutu River basin, China

For recent years, runoff generation and hydrological processes in Hailiutu River basin have been greatly changed by climate change and human activity, especially water and soil conservation construction. In this study, the trends in precipitation, evapotranspiration (ET) and river runoff as well as the effects of precipitation change and human activity on runoff variation have been studied. The results showed that during 1960–2000, annual precipitation and river runoff, monthly precipitation and ET in September and October as well as monthly runoff in all months showed a significant decrease. In addition, peak flow and base flow had a large decrease. Under the joint influence of precipitation change and human activity, the mean annual runoff decreased by 35 million m3 from the baseline period (1960–1985) to the change period (1986–2000), which accounted for 60.9% and 39.1% of the total runoff decrease, respectively. Precipitation change played a primary role in the decrease of annual runoff whereas human ...

The impacts of climate change and land cover/use transition on the hydrology in the upper Yellow River Basin, China

summary Observed streamflow over the past decades in the upper Yellow River Basin (UYRB) was examined for changes in hydrological regime. The modified Variable Infiltration Capacity (VIC) model was employed to better understand climate change impact and long-term and recent land cover/use change impact as it relates to the ‘‘Grain for Green Project’’ and ‘‘Three Rivers Source Region Reserve’’ on water resources by examining mechanisms behind observed streamflow changes. UYRB hydrological regimes have undergone changes over the past decades as reflected by a decrease in wet and warm season streamflow, and annual streamflow. Progressively more streamflow has been generated in the early part of the year compared to the latter part, consequently leading to the earlier occurrence of the day representing the midpoint of yearly mass flow. VIC simulations suggest that these changes in observed streamflow were due to the combined effects of changes in precipitation, evapotranspiration, rainfall runoff, and baseflow and were caused primarily by climate change above Tang Nai Hai (TNH) hydrometric station. Below TNH where human activity is relative intense, land cover/ use change and reservoir release impacts became important. Changes in snowmelt runoff were negligible over the past decades. Owing to this, snowmelt runoff appeared to play only a modest role in the changing hydrology of the region. The conservation programs were shown to start to exhibit some positive impacts on water resources in the UYRB.

Net primary productivity and rain‐use efficiency as affected by warming, altered precipitation, and clipping in a mixed‐grass prairie

Grassland productivity in response to climate change and land use is a global concern. In order to explore the effects of climate change and land use on net primary productivity (NPP), NPP partitioning [fBNPP , defined as the fraction of belowground NPP (BNPP) to NPP], and rain-use efficiency (RUE) of NPP, we conducted a field experiment with warming (+3°C), altered precipitation (double and half), and annual clipping in a mixed-grass prairie in Oklahoma, USA since July, 2009. Across the years, warming significantly increased BNPP, fBNPP , and RUEBNPP by an average of 11.6%, 2.8%, and 6.6%, respectively. This indicates that BNPP was more sensitive to warming than aboveground NPP (ANPP) since warming did not change ANPP and RUEANPP much. Double precipitation stimulated ANPP, BNPP, and NPP but suppressed RUEANPP , RUEBNPP , and RUENPP while half precipitation decreased ANPP, BNPP, and NPP but increased RUEANPP , RUEBNPP , and RUENPP . Clipping interacted with altered precipitation in impacting RUEANPP , RUEBNPP , and RUENPP , suggesting land use could confound the effects of precipitation changes on ecosystem processes. Soil moisture was found to be a main factor in regulating variation in ANPP, BNPP, and NPP while soil temperature was the dominant factor influencing fBNPP . These findings suggest that BNPP is critical point to future research. Additionally, results from single-factor manipulative experiments should be treated with caution due to the non-additive interactive effects of warming with altered precipitation and land use (clipping).

不同降水及氮添加对浙江古田山4种树木幼苗光合生理生态特征与生物量的影响

Nitrogen deposition and uncertainty of precipitation are currently two of the most important ecological issues of global climate change in subtropical areas.To study the effects of nitrogen and precipitation on the eco-physiological traits and growth of subtropical trees,we set up a two-factorial experiment controlling the factors of precipitation and soil fertilization for the seedlings of Elaeocarpus glabripetalus,Liquidambar formosana,Schima superba and Cyclobalanopsis glauca for three years on Gutian Mountain in Zhejiang Province,China.Precipitation was set at three levels: natural precipitation(CK),increase of 30% natural precipitation and decrease of 30% natural precipitation.Soil fertilization was set at two levels: natural nitrogen and nitrogen addition of 10 g · m-2 · a-1NH4NO3.In general,the pH values in subtropical soil are low and the growth of most subtropical tree species may be limited by phosphorus deficiency in the soil not nitrogen availability,so we need to test if addition of nitrogen in soil will promote the eco-physiological traits and growth of the subtropical tree species.We also want to test how the interactive soil fertilization and precipitation changes affect the growth and photosynthetic traits in the four subtropical tree species.We periodically measured the seedlings' photosynthetic eco-physiological traits and their environmental growth factors for three years.The results showed that precipitation variation and nitrogen addition did have some effects on eco-physiological characteristics and total biomass across four tree species.We found that 10 g · m-2 · a-1 NH4NO3 nitrogen addition significantly improved the leaf chlorophyll synthesis(P0.05)and photosynthesis rate(P0.05)across the four subtropical tree seedlings.The addition of nitrogen also positively stimulated PSⅡ photochemical efficiency(Fv/Fm,PIABS)(P0.01)in the four subtropical tree seedlings.Addition of nitrogen significantly increased total biomass formation by more than 30%(P0.01).Hence,nitrogen addition would increase tree seedling photosynthesis ability and promote their growth in subtropical evergreen forest of Gutian Mountain.In contrast,we found that the effects of precipitation changes were less significant on the eco-physiological traits and total biomass for the four subtropical tree seedlings,Nevertheless,precipitation variations significantly influenced photosynthetic rate(P0.05),stomatal conduction and transpiration(P0.001) for some tree seedlings during the dry season of Gutian Mountain.Meanwhile,stomatal conduction was more sensitive to precipitation variations.The interactive effects of precipitation and nitrogen addition on the eco-physiological characteristics(excluding PIABS) and total biomass among the four tree species were not significant(P0.05).The differences in eco-physiological characteristics among the four tree species should attribute to their natural biological properties,while the difference in biomass among different tree species was due to the variations in precipitation change and nitrogen addition(P0.01)from this experiment.

Spatial patterns of top soil carbon sensitivity to climate variables in northern Chinese grasslands

Estimation of the sensitivity for soil organic carbon to climate change is critical for evaluating the potential response of the terrestrial biosphere to global change. In this study, we integrated CENTURY 4.5 model with GIS to assess the soil organic carbon sensitivity to climate variable shifting and atmospheric carbon dioxide enrichment in northern Chinese grasslands. The response of top soil (0–20 cm) organic carbon to climate change depended on the relative sensitivity of net primary productivity and soil respiration. A 4°C increase in soil temperature led to a loss of 4.7% of soil organic carbon in the Alpine Meadow region, but the same temperature increase led to a maximum loss of only 2.3% of soil organic carbon in the Temperate Steppe region. The effects of precipitation changes on soil organic carbon were varied depending on the moisture level of the local grassland system. The direct effect of carbon dioxide enrichment was to reduce carbon loss throughout northern Chinese grasslands, especially in droughty regions. Alpine Meadow was the most sensitive region under climate change, and it will become the biggest potential carbon source in Chinese grasslands as climate warming continues to occur. Increased atmospheric carbon dioxide concentrations led to net carbon sequestration in all grasslands and tended to diminish the carbon loss driven by precipitation and temperature changes.

Vegetation cover and rain timing co-regulate the responses of soil CO2 efflux to rain increase in an arid desert ecosystem

Climate models often predict that more extreme precipitation events will occur in arid and semiarid regions, where C cycling is particularly sensitive to the amount and seasonal distribution of precipitation. Although the effects of precipitation change on soil carbon processes in desert have been studied intensively, how vegetation cover and rain timing co-regulate the responses of soil CO2 efflux to precipitation change is still not well understood. In this study, a field manipulative experiment was conducted with five simulated rain addition treatments (natural rains plus 0%, 25%, 50%, 75%, 100% of local annual mean precipitation) in a desert ecosystem in Northwest China. The rain addition treatments were applied with 16 field rain enrichment systems on the 10th day of each month from May to September, 2009. Soil water content, soil temperature and soil CO2 efflux rates were measured in both bare and vegetated soils before and after the rain addition during a 3-week period for each rain treatment. The response magnitude and duration of soil CO2 efflux to rain addition depended not only on the rain amount but also on the type of vegetation covers and the timing of rain addition treatments. Soil water content responded quickly to the rain addition regardless of rain amount and timing, but soil CO2 efflux increased to rain addition only in May–July but not in late growing season (September). In addition, soil CO2 efflux from the bare and vegetated soils showed similar increase to rain additions in May–July, but they demonstrated distinct responses to rain addition in September. The differences in the responses of soil CO2 efflux to rain addition between the bare and vegetated soils could be explained by the root activities stimulated by added rain water, while the difference in soil CO2 efflux response to rain addition among treatment times could be attributed to soil water condition prior to rain addition and/or soil temperature drop following rain addition. Thus, both vegetation cover and rain timing can co-regulate responses of soil CO2 efflux to future precipitation change in arid desert ecosystems, which should be considered when predicting future carbon balance of desert ecosystems in arid and semiarid regions.

Effects of Precipitation Change and Nitrogen Addition on Organic CarbonMineralization and Soil Microbial Carbon of the Forest Soils in Dinghushan,Southeastern China

Soil organic carbon(SOC) mineralization and soil microbial carbon(SMBC) play an important role in global C cycle.With method of incubation and chloroform fumigation extraction,the effects of precipitation change and nitrogen(N) addition on the SOC mineralization and SMBC were studied along a forest succession series including pine forest(PF),mixed pine and broadleaved forest(MF) and monsoon evergreen broadleaved forest(MEBF) at Dinghushan,Southestern China.The results showed that:(1) Increased precipitation could improve the mineralization of SOC in the late-successional forest plots,but the effect in the early-successional forest plots were not significant(P0.05).(2) Less precipitation(drought) resulted in lower content of SMBC in the monsoon forest soil(0～10 cm),while the doubled precipitation treatment had no significant effect on the SMBC content.(3) N deposition did not affect SMBC mineralization and SMBC in all of the three forests.It is important to take the quality of organic matter,C/N ratio,exogenous nitrogen and many other combined effects into consideration in the future studies on the responses of SOC mineralization and SMBC to climate change.Fig 4,Tab 2,Ref 37

Modelling probability of rainfall-induced shallow landslides in a changing climate, Otta, Central Norway

We analyse slope stability conditions for shallow landslides under an extreme precipitation regime with regard to present and future scenarios, in order to first study the effect of changes in precipitation on stability conditions, considering uncertainty in the model parameters, and second to evaluate which factors contribute the most to model output and uncertainty. We used a coupled hydrological-stability model to study the hydrological control on shallow landslides in different precipitation regimes, with reference to the case study of Otta, located in central east Norway. We included a wide range of climatic settings, taking intensity, duration of the extreme events and two different antecedent precipitation conditions into account. Eleven future scenarios were determined using results of down-scaled meteorological models. Considering the uncertainty in the soil parameters, we used the Monte Carlo approach and probability of failure resulting from 5,000 trials was calculated for each precipitation scenario. In unstable areas the probabilities of failure at present and future conditions were compared using a bootstrapping method. Sensitivity analysis was carried out to understand how variations in input parameters influence the output of the selected model. The results show changes in the modelled stability conditions only if the effect of antecedent precipitation is not taken into account. The uncertainties in the predicted extreme precipitation events, soil parameters, and antecedent precipitation conditions do not allow any accurate estimation of changes in stability conditions for shallow landslides.

Assessing the threat to montane biodiversity from discordant shifts in temperature and precipitation in a changing climate

Mountains are centres of global biodiversity, endemism and threatened species. Elevational gradients present opportunities for species currently living near their upper thermal limits to track cooler temperatures upslope in warming climates, but only if changes in precipitation are sufficiently in step with temperature. We model local population extirpation risk for a range of temperature and precipitation scenarios over the next 100 years for 16 848 vertebrate species populations distributed along 156 elevational gradients. Average population extirpation risks due to warming alone were < 5%, but increased 10-fold, on average, when changes in precipitation were also considered. Under the driest scenarios (minimum predicted precipitation), local extirpation risks increased sharply (50-60%) and were especially worrisome for hydrophilic amphibians and montane Latin America (c. 80%). Realistic assessment of risks urgently requires improved monitoring of precipitation, better regional precipitation models and more research on the effects of changes in precipitation on montane distributions.

Application of Archimedean copulas in the analysis of the precipitation extremes: effects of precipitation changes

Due to the influence of changing environment and intensifying human activities, hydrometeorological changes are becoming common. This study derives a bivariate joint distribution of total precipitation and precipitation days with daily precipitation exceeding the 75th percentile and falling below the 25th percentile. Chang points in the precipitation series are detected with more than one statistical method. Results indicate that (1) for P75 and D75, Kendal’s τ does not change significantly even when the existence of change points is taken into account. The selection of a copula is greatly impacted by the existence of a change point; (2) for P25 and D25, τ varies much, while the precipitation variations have no evident effects on the selection of a copula. Therefore, a copula should be selected after the detection of change points to avoid possible bias in results or conclusions. This study is of some merits in terms of risk evaluation based on copula-based probability analysis with available change points.

Climatic change and rainfall patterns: Effects on semi-arid plant communities of the Iberian Southeast

The structure and functioning of semi-arid ecosystems are strongly influenced by precipitation patterns. Water availability in such environments is highly pulsed, and discrete rainfall events interspersed with drought periods are important components of the annual water supply. Plant communities do not only respond to rainfall quantity, but also to variations in time, so that relatively small changes in rainfall frequency (i.e., pulsed inputs) may have strong effects on communities. Within the Mediterranean basin, climate change models forecast a decrease in mean annual precipitation and more extreme events (i.e., less rainy days and longer drought periods between events), along with seasonal changes. However, little is known on the consequences of these future precipitation changes on plant communities, especially in semi-arid environments. Here, we summarize the few experiments that have manipulated rainfall patterns in arid and semi-arid areas worldwide, and introduce the first results of a pioneer, long-term rainfall exclusion in the semi-arid southeast region of the Iberian Peninsula. The experiment is not only manipulating the amount of rainfall, but also its frequency and seasonal distribution in a grassland-shrubland in the Tabernas desert (Almería, Spain). This work monitored the effect of precipitation changes on different ecosystem processes for five years, at the species and community level, concluding that this plant community (as other communities studied in the same area) exhibited great resilience to changes in rainfall availability, likely caused by plant adaptation to large intra- and inter-annual precipitation variability.

Climate change effects on soil microarthropod abundance and community structure

Long-term ecosystem responses to climate change strongly depend on how the soil subsystem and its inhabitants respond to these perturbations. Using open-top chambers, we studied the response of soil microarthropods to single and combined effects of ambient and elevated atmospheric [CO2], ambient and elevated temperatures and changes in precipitation in constructed old-fields in Tennessee, USA. Microarthropods were assessed five years after treatments were initiated and samples were collected in both November and June. Across treatments, mites and collembola were the most dominant microarthropod groups collected.We did not detect any treatment effects on microarthropod abundance. In November, but not in June, microarthropod richness, however, was affected by the climate change treatments. In November, total microarthropod richness was lower in dry than in wet treatments, and in ambient temperature treatments, richness was higher under elevated [CO2] than under ambient [CO2]. Differential responses of individual taxa to the climate change treatments resulted in shifts in community composition. In general, the precipitation and warming treatments explained most of the variation in community composition. Across treatments, we found that collembola abundance and richness were positively related to soil moisture content, and that negative relationships between collembola abundance and richness and soil temperature could be explained by temperature-related shifts in soil moisture content.Our data demonstrate how simultaneously acting climate change factors can affect the structure of soil microarthropod communities in old-field ecosystems. Overall, changes in soil moisture content, either as direct effect of changes in precipitation or as indirect effect of warming or elevated [CO2], had a larger impact on microarthropod communities than did the direct effects of the warming and elevated [CO2] treatments. Moisture-induced shifts in soil microarthropod abundance and community composition may have important impacts on ecosystem functions, such as decomposition, under future climatic change.

Climate change impact on a groundwater‐influenced hillslope ecosystem

This study investigates the effect of climate change on a groundwater‐influenced ecosystem on a hill slope consisting of two vegetation types, one adapted to wet and one adapted to dry soil conditions. The individual effects of changes in precipitation, temperature, and atmospheric CO2 concentration are compared to the combined effect of these factors. Change in atmospheric conditions is based on the Netherlands. Projected climate change is obtained from an ensemble of nested global and regional climate models (GCMs and RCMs), representing the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios A2 scenario for 2100. For each GCM‐RCM combination, change factors were determined and transferred to a stochastic weather generator. All projections show higher temperatures and less annual precipitation. Simulations were performed using an ecohydrological model, consisting of a dynamic soil‐plant‐atmosphere‐continuum model that is fully coupled to a variably saturated hydrological model, using the stochastic weather data as input. Model results show that increasing atmospheric CO2 concentration results in higher biomasses because of higher water use efficiency and a decrease in evaporation downslope where vegetation growth is light limited. The change in precipitation regime (drier summers, wetter winters) causes a decreased biomass of especially the dry‐adapted species and increased upslope groundwater recharge, resulting in groundwater rise and an upward shift of wet‐adapted vegetation. Temperature rise results in decreased biomass because respiration increases stronger than carbon assimilation, while increased transpiration causes drier soils and a prolonged period of water‐limited growth. The combined effect is dominated by the increase in temperature and change in precipitation regime, causing decreased biomass throughout. Surprisingly, the effect on groundwater level depends on the degree by which precipitation distribution changes within the year, showing a drop at a small change and a rise when change is larger. This study thus shows that climate change effects on hydrology and vegetation are far from straightforward and call for fully coupled ecohydrological models and upslope‐downslope interaction.

Fifty-year rainfall change and its effect on droughts and floods in Wenzhou, China

Based on daily, monthly, seasonal and annual precipitation, monthly duration and flood-affected area data from 1954 to 2007, we examined the absolute and relative change trends of rainfall and their effects on hazard intensity in Wenzhou city, China. The long-term trend of precipitation was studied by linear regression, moving average, cumulative anomaly and Z index methods, respectively. Our results show that there was no significant downward trend of annual precipitation. In contrast, there was significant decrease in autumn, July, mid-January and early June and significant increase in early January and late May, especially in late June. During 1954 and 2007, although significant fluctuation existed in the absolute value of precipitation, the relative changes of wet and dry were not significant compared with the average. The 10-year decrease in precipitation was 23.37 mm in autumn, 14.85 mm in July, 0.33 mm in mid-January and 6.87 mm in early June; while the 10-year increase was 0.35 mm in early January, 3.05 mm in late May and 8.57 mm in late June, respectively. Moreover, we found that 1964, 1966, 1977 and 1995 were the transition periods when the rainfall Z index was at peaks, the flood intensity was high, and the drought intensity was relatively low. On the other hand, 1958, 1968, 1971, 1980, 1989 and 1992 were the periods when the rainfall Z index was at valleys, the flood intensity was low, and the drought intensity was relatively high. Taken together, we demonstrated the obvious effects of precipitation changes on flood and drought intensities.

Inter-comparison of methods for quantifying above-ground leaf litter decomposition rates

Above ground litter decomposition is the result of three interlinked processes: leaching, fragmentation and catabolism. Litter decomposition estimates are most commonly based on measurements of mass loss from litter residues, confined in mesh bags. This method provides a rough estimate of leaching and catabolism, while preventing fragmentation from occurring. Alternatively, litter decomposition is studied in the laboratory as microbial respiration of litter residue. In this case, generally only catabolism is measured. While those limits are often discussed, their careful assessment has never been attempted. We present here results from a study where the decomposition rate of Arbutus unedo leaf litter, at a throughfall manipulation experiment, was investigated using: 1) litterbags; 2) turnover based on litter input/standing litter pool; 3) 14C-bomb spike; 4) laboratory incubation; 5) DayCent modeling. Aims of this study were: 1) to quantitatively assess the hypothesis that the litterbags and the laboratory incubation methods, by preventing fragmentation, overestimate above ground litter mean residence time; 2) to evaluate the ability of the above methods to capture the effects of changes in precipitation on litter decay rates. Results confirmed our hypothesis and demonstrated that the litterbag and the laboratory incubation methods do capture the effects of the water manipulation treatment on litter decay rates.

Discharge simulations performed with a hydrological model using bias corrected regional climate model input

Abstract. Studies have demonstrated that precipitation on Northern Hemisphere mid-latitudes has increased in the last decades and that it is likely that this trend will continue. This will have an influence on discharge of the river Meuse. The use of bias correction methods is important when the effect of precipitation change on river discharge is studied. The objective of this paper is to investigate the effect of using two different bias correction methods on output from a Regional Climate Model (RCM) simulation. In this study a Regional Atmospheric Climate Model (RACMO2) run is used, forced by ECHAM5/MPIOM under the condition of the SRES-A1B emission scenario, with a 25 km horizontal resolution. The RACMO2 runs contain a systematic precipitation bias on which two bias correction methods are applied. The first method corrects for the wet day fraction and wet day average (WD bias correction) and the second method corrects for the mean and coefficient of variance (MV bias correction). The WD bias correction initially corrects well for the average, but it appears that too many successive precipitation days were removed with this correction. The second method performed less well on average bias correction, but the temporal precipitation pattern was better. Subsequently, the discharge was calculated by using RACMO2 output as forcing to the HBV-96 hydrological model. A large difference was found between the simulated discharge of the uncorrected RACMO2 run, the WD bias corrected run and the MV bias corrected run. These results show the importance of an appropriate bias correction.