Effects Of Changes In Rainfall Research Articles

Effects of Rainfall Variability and Land Cover Type on Soil Organic Carbon Loss in a Hilly Red Soil Region of Southern China

Rainfall intensity (RI) and land cover type are two important factors that affect soil erosion and thus the transfer and loss of soil organic carbon (SOC). However, the in situ quantitative monitoring of SOC loss under natural rainfall and various land cover types restored on eroded lands has not been thoroughly examined. In order to further study the effects of rainfall changes and vegetation types on SOC loss in the red soil region of Southern China, the Jiangxi Eco-Science Park of Soil and Water Conservation in De’an County, Jiangxi Province, was taken as the research object. Considering natural rainfall and based on the long-term field in situ monitoring of rainfall and runoff and sediment data, we studied the effects of three land cover types (bare land, orchards, and grass cover) on surface runoff, sediment production, and SOC loss in relation to 1 hour of RI during natural rainfall in the red soil region of Southern China during rainy seasons of 2020 and 2021 (March to August). Compared with bare land plots, the orchard and grass cover plots had surface runoff reductions of 67% and 98%, respectively, and sediment reductions of 79% and 99% over the two rainy seasons, respectively. With an increasing RI over 1 hour, total SOC loss increased for each of the three land cover types. More SOC loss was associated with sediments, and the enrichment ratio of SOC in the sediments (ERoc) decreased significantly. The ERoc values decreased in the following order: bare land (1.23) > orchard (1.08) > grass cover (0.81). Bare land exhibited the highest proportion of SOC associated with sediment in the total SOC loss (Ps), at 68.69%, followed by the orchard plots, at 55.02%, and then the grass cover plots at 49.24%. With the transfer of land cover type from bare land to orchard and to grass cover (decreased soil loss intensity, SLI), more SOC was lost associated with runoff in the form of dissolved organic carbon (DOC); the values of ERoc and organic carbon loss intensity (CLI) also decreased significantly. These findings are crucial to improving our understanding of the regulatory mechanisms of rainfall changes and land cover types on SOC loss during soil erosion.

Photosynthetic and Antioxidant Responses of Gymnocarpos przewalskii to Simulated Rainfall Changes

Gymnocarpos przewalskii is a rare Tertiary relict species, mainly distributed in desert areas of northwestern China. Changes in rainfall have a significant impact on the physiological characteristics of desert plants. In the present study, the effects of five simulated rainfall levels on the gas exchange parameters, chlorophyll fluorescence characteristics, and antioxidant system of G. przewalskii were studied. The results show that with increased rainfall the net photosynthetic rate (Pn) and transpiration rate increase significantly. The reduction in Pn is caused by stomatal and non-stomatal limitations under decreased rainfall. Decreased rainfall markedly improves the instantaneous water-use efficiency of leaves. With increased rainfall, the maximum photosynthetic rate, apparent quantum efficiency, and light utilization range significantly increase. Under reduced rainfall, the chlorophyll content, maximum photochemical efficiency of PSII, and steady-state optical quantum efficiency decrease and photoinhibition is caused in the PSII system. A rainfall reduction of 30% leads to massive production of superoxide anions and hydrogen peroxide, causing obvious peroxidation damage. Meanwhile, superoxide dismutase, peroxidase, and catalase in the leaves are significantly enhanced to remove excess reactive oxygen species and alleviate the injury to photosynthetic apparatus. Our study reveals the effect of rainfall changes on the photosynthetic characteristics and antioxidant system of G. przewalskii, and can improve understanding of the adaptive strategies of desert plants under future precipitation changes in northwestern China.

Phytoplankton and macroinvertebrate diversity and eco-exergy responses to rainfall diverge in semiarid reservoirs

Rainfall is a variable that drives community structure in aquatic ecosystems and is even more important in dry regions. Most studies have evaluated how the seasonal variation of rainfall influences aquatic communities. However, studies that evaluate the influence of spatial gradients of rainfall on aquatic organisms are scarce, especially regarding biological diversity and thermodynamic information. This study evaluated the response from diversity metrics and thermodynamic indices (eco-exergy and specific eco-exergy) in phytoplankton and benthic macroinvertebrate communities in 13 reservoirs distributed along a spatial gradient of rainfall in the Brazilian semiarid region. We hypothesized that the phytoplankton and benthic macroinvertebrate communities are congruent in response to the spatial gradient of rainfall in terms of diversity and thermodynamic indices in semiarid reservoirs. We expect to find higher values of biomass and the eco-exergy index under lower rainfall. To test our hypothesis, generalized linear models (GLMs) were used to relate the effects of rainfall changes on community structure. The eco-exergy and specific eco-exergy indices of the phytoplankton community were positively related to rainfall and reflected a greater investment in biomass production and genetic information (e.g., Chlorophyceae). As for the macroinvertebrate community, the reduction in rainfall promoted a greater investment in energy storage by generalist organisms (e.g., Melanoides tuberculata and some genera of Chironomidae). Thus, for a holistic evaluation of ecosystem health, the joint analysis of thermodynamic indices associated with an assessment of taxonomic composition, diversity and taxonomic richness is important, providing a more complete and multifaceted response. Additionally, thermodynamic indices better reflected the changes in both aquatic communities in response to rainfall, and were more sensitive than the diversity and richness indices. Consequently, the thermodynamic indices represent an efficient tool in the assessment of aquatic community responses to climate change, even when these communities respond in an opposite manner.

Effects of Grazing, Extreme Drought, Extreme Rainfall and Nitrogen Addition on Vegetation Characteristics and Productivity of Semiarid Grassland.

Grassland use patterns, water and nutrients are the main determinants of ecosystem structure and function in semiarid grasslands. However, few studies have reported how the interactive effects of rainfall changes and nitrogen deposition influence the recovery of semiarid grasslands degraded by grazing. In this study, a simulated grazing, increasing and decreasing rainfall, nitrogen deposition test platform was constructed, and the regulation mechanism of vegetation characteristics and productivity were studied. We found that grazing decreased plant community height (CWMheight) and litter and increased plant density. Increasing rainfall by 60% from May to August (+60%) increased CWMheight; decreasing rainfall by 60% from May to August (-60%) and by 100% from May to June (-60 d) decreased CWMheight and coverage; -60 d, +60% and increasing rainfall by 100% from May to June (+60 d) increased plant density; -60% increased the Simpson dominance index (D index) but decreased the Shannon-Wiener diversity index (H index); -60 d decreased the aboveground biomass (ABG), and -60% increased the underground biomass (BGB) in the 10-60 cm layer. Nitrogen addition decreased species richness and the D index and increased the H index and AGB. Rainfall and soil nitrogen directly affect AGB; grazing and rainfall can also indirectly affect AGB by inducing changes in CWMheight; grazing indirectly affects BGB by affecting plant density and soil nitrogen. The results of this study showed that in the semiarid grassland of Inner Mongolia, grazing in the nongrowing season and grazing prohibition in the growing season can promote grassland recovery, continuous drought in the early growing season will have dramatic impacts on productivity, nitrogen addition has a certain impact on the species composition of vegetation, and the impact on productivity will not appear in the short term.

Modeling the effect of rainfall changes to predict population dynamics of the Asian tiger mosquito Aedes albopictus under future climate conditions.

The population dynamics of mosquitoes in temperate regions are not as well understood as those in tropical and subtropical regions, despite concerns that vector-borne diseases may be prevalent in future climates. Aedes albopictus, a vector mosquito in temperate regions, undergoes egg diapause while overwintering. To assess the prevalence of mosquito-borne diseases in the future, this study aimed to simulate and predict mosquito population dynamics under estimated future climatic conditions. In this study, we tailored the physiology-based climate-driven mosquito population (PCMP) model for temperate mosquitoes to incorporate egg diapauses for overwintering. We also investigated how the incorporation of the effect of rainfall on larval carrying capacity (into a model) changes the population dynamics of this species under future climate conditions. The PCMP model was constructed to simulate mosquito population dynamics, and the parameters of egg diapause and rainfall effects were estimated for each model to fit the observed data in Tokyo. We applied the global climate model data to the PCMP model and observed an increase in the mosquito population under future climate conditions. By applying the PCMP models (with or without the rainfall effect on the carrying capacity of the A. albopictus), our projections indicated that mosquito population dynamics in the future could experience changes in the patterns of their active season and population abundance. According to our results, the peak population number simulated using the highest CO2 emission scenario, while incorporating the rainfall effect on the carrying capacity, was approximately 1.35 times larger than that predicted using the model that did not consider the rainfall effect. This implies that the inclusion of rainfall effects on mosquito population dynamics has a major impact on the risk assessments of mosquito-borne diseases in the future.

Effects of Rainfall on the Characteristics of Soil Greenhouse Gas Emissions in the Wetland of Qinghai Lake

Niaodao, a lakeside wetland, was used as the focus of this study to investigate the effect of rainfall changes on the greenhouse gas fluxes of wetland ecosystems. Wetland plots with different moisture characteristics (+25%, −25%, +75%, and −75% rainfall treatments and the control treatment (CK)) were constructed to observe in situ field greenhouse gas emissions at 11:00 and 15:00 (when the daily mean values were similar) in the growing season from May to August 2020 by static chamber–gas chromatography and to investigate the responses of wetland greenhouse gases to different rainfall treatments. The results showed the following: (1) The carbon dioxide (CO2) flux ranged from −49.409 to 374.548 mg·m−2·h−1. The mean CO2 emission flux was greater at 11:00 than at 15:00, and the +25% and +75% treatments exhibited substantially higher CO2 emissions. In addition, the CO2 flux showed a small peak at the beginning of the growing season when the temperature first started to rise. All treatments showed the effect of the CO2 source, and their effects were significantly different. (2) The methane (CH4) flux ranged from −213.839 to 330.976 µg·m−2·h−1 and exhibited an absorption state at 11:00 and an emission state at 15:00. The CH4 emission flux in August (the peak growing season) differed greatly between treatments and was significantly negatively correlated with the rainfall amount (p < 0.05). (3) The nitrous oxide (N2O) flux ranged from −10.457 to 16.878 µg·m−2·h−1 and exhibited a weak source effect throughout the growing season, but it was not significantly correlated with soil moisture; it was, however, negatively correlated with soil temperature. (4) The different treatments resulted in significant differences in soil physical and chemical properties (electrical conductivity, pH, total soil carbon, and total soil nitrogen). The rainfall enhancement treatments significantly improved soil physical and chemical properties.

The effect of rainfall changes on economic production

Macro-economic assessments of climate impacts lack an analysis of the distribution of daily rainfall, which can resolve both complex societal impact channels and anthropogenically forced changes1-6. Here, using a global panel of subnational economic output for 1,554 regions worldwide over the past 40 years, we show that economic growth rates are reduced by increases in the number of wet days and in extreme daily rainfall, in addition to responding nonlinearly to the total annual and to the standardized monthly deviations of rainfall.Furthermore, high-income nations and the services and manufacturing sectorsaremost strongly hindered by both measures of daily rainfall, complementing previous work that emphasized the beneficial effects of additional total annual rainfall in low-income, agriculturally dependent economies4,7. By assessing the distribution of rainfall at multiple timescales and the effects on different sectors, we uncover channels through which climatic conditions can affect the economy. These results suggest that anthropogenic intensification of daily rainfall extremes8-10 will have negative global economic consequences that require further assessment by those who wish to evaluate the costs of anthropogenic climate change.

Impacts of rainfall change on stormwater control and water saving performance of rainwater harvesting systems

Rainwater harvesting is widely implemented to deal with urban water scarcity and stormwater control issues. In the context of climate change, however, the impacts of rainfall change on rainwater harvesting systems (RHS) are still unknown in many regions. In this study, effects of rainfall change on both water saving and stormwater control performance of RHS across six cities in different climatic zones of Pakistan were investigated and location-specific and adaptive measures to mitigate the negative impacts of rainfall change on RHS were proposed. The commonly defined “dry gets drier, wet gets wetter” rainfall change pattern is not retained in the cities. Water saving performance of RHS is positively affected by increasing trend of rainfall at Khanpur and Peshawar, whereas negatively affected by rainfall decreases at Zhob and Murree. Conversely, increasing trend of rainfall is non-beneficial for stormwater control at Khanpur and Peshawar but rainfall decreases are beneficial at Zhob and Murree. Islamabad and Lahore do not have notable changes in performance of RHS due to the non-significant changing trends in rainfall. The impacts of rainfall change on performance of RHS are dependent on not only the trends and extents of local rainfall change, but also tank sizes and water demands. At Khanpur and Murree, the negative impacts of rainfall change on performance of RHS can be resolved by enlarging tank sizes. At Zhob and Peshawar, however, adjusting contributing areas or water demands should also be considered. Therefore, location-specific and adaptive measures should be adopted for RHS to accommodate rainfall change.

Effects of changes in rainfall and temperature on age- and sex-specific patterns of rural-urban migration in sub-Saharan Africa

We evaluate how changes in weather patterns affected rural-urban migration across 41 sub-Saharan African countries, by age and sex, over the 1980–2015 period. We combine recent age- and sex-specific estimates of net rural-urban migration with historical data on rainfall and temperature from the Climate Research Unit (CRU). We also compare standard unweighted estimates of rainfall and temperature to estimates weighted by the proportion of the country’s total rural population in the CRU grid. Results show that rural out-migration of young adults is the most sensitive to shifts in weather patterns, with lower rainfall, lower variability in rainfall, and higher temperatures increasing subsequent rural out-migration—though the last of these is not observed in weighted models. The strength of these effects has grown stronger over time for 20–24 year olds, though weaker above age 30. In contrast, increasing temperature variability is associated with a higher rural in-migration of children (0–9) and older adults (55–64). Gender differences in these effects are minimal and concentrated in areas which experienced heavy reductions in rainfall.

Changing rainfall frequency affects soil organic carbon concentrations by altering non-labile soil organic carbon concentrations in a tropical monsoon forest

Soil stores a substantial proportion of carbon (C), making it the greatest terrestrial C pool and pivotal to stabilizing the global climate system. Rainfall amounts and regimes have been changing in many places, but effects of precipitation changes on soil organic C (SOC) stabilization are not completely understood. Considerable attention has been focused on the consequences of changes in rainfall amounts, with rainfall regimes having been less studied. This study was conducted in a tropical climax forest to clarify the effects of rainfall changes on SOC fractions, with permanganate oxidation and density fractionations employed to divide the labile and non-labile SOC fractions. Two rainfall manipulation treatments, i.e., increased rainfall frequency with the total rainfall amount unchanged (IRF) and decreased rainfall amount by 50% with rainfall frequency unaltered (DRA), were conducted for two years, with ambient rainfall (AR) as the control. As a result, the IRF treatment increased the SOC concentration that mainly originated from increases in the non-labile SOC content. Relative to the AR control, the DRA treatment did not change the total SOC concentration although the labile SOC concentration increased. This typically is due to a small proportion of the labile fraction to the total SOC content. Our results suggest that this water-rich mature forest is resistant to rainfall amount changes to a great extent (e.g., decrease of 50% as in the present study) from the SOC stabilization perspective, while changes in rainfall frequency could exert more notable effects.

Farmers’ perception of water contribution to household and farming system in the Offinso North District of Ghana: rainfall a critical climatic factor

Water resources are increasingly under pressure from population growth, economic activity, and climate change/variability. Using survey and community meetings, the paper analyzed water resources accessible to three farming communities in the Offinso North District and the effects of rainfall changes on their farming livelihood. The study revealed that the households depended on water from three sources, namely: groundwater through boreholes for drinking and domestic use; surface water through streams for drinking, domestic use and irrigating vegetable farms and atmospheric water (i.e. rainfall) for farming. For about 80% of the respondents, changes in rainfall pattern adversely affected their crops yield which has implication on their livelihoods. Access to irrigation facilities was virtually absent. Also, the non-application of water harvesting techniques for farming thus left these smallholder farmers to the ‘mercies of the weather’. Education on climate change and adaptation strategies coupled with technological know-how on water management is recommended for the communities in this forest-savanna transition zone where abrupt changes in rainfall pattern are new to their livelihoods. Keywords: Water Resources, Rainfall, Climate Change, Farming Households, Farm Productivity

Predicted rainfall changes disrupt trophic interactions in a tropical aquatic ecosystem.

Changes in the distribution of rainfall and the occurrence of extreme rain events will alter the size and persistence of aquatic ecosystems. Such alterations may affect the structure of local aquatic communities in terms of species composition, and by altering species interactions. In many aquatic ecosystems, leaf litter sustains detrital food webs and could regulate the responses of communities to changes in rainfall. Few empirical studies have focused on how rainfall changes will affect aquatic communities and none have evaluated if basal resource diversity can increase resistance to such rainfall effects. In this study, we used water-holding terrestrial bromeliads, a tropical aquatic ecosystem, to test how predicted rainfall changes and litter diversity may affect community composition and trophic interactions. We used structural equation modeling to investigate the combined effects of rainfall changes and litter diversity on trophic interactions. We demonstrated that changes in rainfall disrupted trophic relationships, even though there were only minor direct effects on species abundance, richness, and community composition. Litter diversity was not able to reduce the impact of changes in rainfall on trophic interactions. We suggest that changes in rainfall can alter the way in which species interact with each other, decreasing the linkages among trophic groups. Such reductions in biotic interactions under climate change will have critical consequences for the functioning of tropical aquatic ecosystems.

Implications of climate change on crop water requirements in arid region: An example of Al-Jouf, Saudi Arabia

This study investigated possible implications of climate change on crop water requirements (CWRs) from 2011 to 2050 in Al-Jouf, Saudi Arabia. CWR were predicted for four scenarios: (i) current temperature and rainfall (S1); (ii) temperature in 2050 and current state of rainfall (S2); (iii) rainfall in 2050 and current state of temperature (S3) and (iv) temperature and rainfall in 2050 (S4). Assuming no change in the regulations relating to agriculture and irrigation in future, CWR were predicted to be 873 and 931million cubic meters (MCM) per year for the S1 and S4 scenarios, respectively, indicating an increase of 58 MCM from 2011 to 2050. On an average, 1°C increase in temperature may increase the overall CWR by 2.9% in this region. Following linear pattern of increase, slope of CWR was determined as 1.5MCM/year from 2011, which is equivalent to the CWR of producing approximately 600tons of wheat/year. The increase of CWR was due to the increase in temperature mainly, while the effect of rainfall changes was minimal. Sensitivity analysis on crop growing seasons showed that the shift of wheat growing season might conserve significant amount of groundwater. This study might be useful in explaining the negative effects of climate change on CWR in Al-Jouf and better planning for water resources management.

Runoff responses to long-term rainfall variability in a shrub-dominated catchment

In this study we investigate how rainfall has changed between two nine year periods (1977–1985 and 2003–2011), and evaluate the effects of changes in rainfall on runoff from a shrub-dominated catchment in the southwestern USA. Analysis of rainfall characteristics shows that between these two periods there is an overall increase in annual rainfall, which corresponds with a long-term increase in rainfall in this region. Analysis of the frequency–magnitude distribution of rainfall events during these two periods indicates that there has not been a significant change in the return period of daily rainfall totals, whereas there has been a significant change in the return period of runoff-generating rainfall events. Between the two periods, there has been a large increase in the return period for a runoff event of a given magnitude. Although there has been an increase in rainfall between the two periods, results show that, contrary to what might be expected, an overall increase in rainfall has not resulted in an increase in runoff because of a change in the frequency–magnitude distribution of runoff-generating rainfall events. We anticipate that this reduction in runoff is due to a reduction in rainfall intensities between the two periods.

Effects of rainfall change on water erosion processes in terrestrial ecosystems: a review

Water erosion is the most destructive erosion type worldwide, causing serious land degradation and environmental deterioration. Against a background of climate change and accelerated human activities, changes in natural rainfall regimes have taken place and will be expected to become more pronounced in future decades. Long-term shifts may challenge the existing cultivation systems worldwide and eventually alter the spatiotemporal patterns of land use and topography. Meanwhile, specific features of soil crusting/sealing, plant litter and its decomposition, and antecedent soil moisture content (ASMC) will accompany rainfall variability. All these changes will increase pressures on soil erosion and hydrological processes, making accurate erosion prediction and control more difficult. An improved knowledge and understanding of this issue, therefore, is essential for dealing with the forthcoming challenges regarding soil and water conservation practices. In this paper, the characteristics of changes in natural rainfall, its role on terrestrial ecosystems, the challenges, and its effect on surface water erosion dynamics are elaborated and discussed. The major priorities for future research are also highlighted, and it is hoped that this will promote a better understanding of water erosion processes and related hydrological issues.

Twentieth century changes in montane vegetation in the eastern Free State, South Africa, derived from palynology of hyrax dung middens

The dating and pollen analysis of a hyrax dung deposit in a mountain rock shelter (Rooiberg Shelter II) are compared with that in a previous study from the same mountain range at the rural town Clarens, in South Africa. Calibration of radiocarbon measurements from the dung deposit provides different possibilities for the age of the sequence. Unlikely dates can be eliminated on the basis of pollen stratigraphy, comparisons with a previously studied accumu- lation from the last 30 yr, artificially increased radiocarbon levels in the upper samples as result of nuclear arms testing after 1954, the presence of historically introduced exotic elements, and the assumption of a relatively constant rate of dung accumulation. According to these consider- ations we suggest that the dung started accumulating at the beginning of the twentieth century. The pollen contents show marked changes in composition, indicating mainly open grass veg- etation with fynbos in the first half of this century and woody vegetation in the second half. A first marked increase of the woody component is estimated to have occurred around 1950, but it only became permanent in the 1960s. The fluctuating pollen sequence can best be interpreted in terms of the combined effects of rainfall changes, fire and stock grazing, the latter of which increased together with town expansion in the area during the course of this century. Considering historical events recorded in the area and the region in general, the results suggest that pollen in hyrax dung is a good recorder of vegetation change. Copyright © 1999 John Wiley & Sons, Ltd.

Rainfalls during great Forbush decreases

The changes of rainfall values during great Forbush decreases recorded by the low-latitudinal neutron monitor of Huancayo (47 events from 1956 through 1992) were examined. The data on precipitations were taken from the State of Sao Paulo and from the Amazonian region, Brazil. As a rule, the data from more than 50 meteorological stations were used for each events. The main result is the following: during strong decreases of cosmic-ray flux in the atmosphere (great Forbush decreases) the precipitation value is decreased. The effect of rainfall changes is seen more distinctly if wet seasons are considered.

Secular changes in wet season structure in central Sudan

Secular climatic change in central Sudan is analysed by examining changes in wet season structure over 80 years at 12 climatological stations. A wet season model is defined based on daily rainfalls, potential evapotranspiration and an assumed field capacity. Analysis centres on changes in the timing of the wet season (onset and termination) and the frequencies of wet season failures (null starts) and of breaks within the wet season. Significant contraction of the wet season is detected in the 200–300-mm zone, where null starts occurred for the first time this century during the 1970s. The frequencies of mid- and late-season breaks markedly increased in the recent drought period, emphasising the detrimental effects of rainfall changes on yields of rainfed crops.