Direct Effects Of Precipitation Research Articles

Disentangling the multiple effects of precipitation on arthropod biomass: A commentary on Newell et al. (2022).

Relatively, little research has simultaneously examined the indirect (bottom‐up) and direct effects of precipitation on animals. Newell et al. (2022) examine this topic in cloud forests of Peru, unexpectedly finding little evidence of bottom‐up control of arthropod biomass, but instead evidence of direct effects of precipitation and vapor pressure deficit on arthropod biomass. This research suggests that direct effects of precipitation and desiccation on arthropod biomass should be more widely investigated, and this finding has important implications for understanding the effects of climate on terrestrial animals at multiple trophic levels.

Empirical analysis of the influences of meteorological factors on the interannual variations in carbon fluxes of a Quercus variabilis plantation

Influences of meteorological factors on the carbon fluxes of a forest ecosystem can vary with time scales. While many studies were made on daily to annual variations of measured carbon flux of forest ecosystems, few were conducted on the variations of observed carbon fluxes over longer (decadal or more) time scale. This study quantified the influences of meteorological variables on the measured carbon fluxes in a Quercus variabilis plantation from 2006 to 2021 using principal component analysis (PCA) and cluster analysis (CA). PCA was used to identify the most important meteorological variables. They are monthly mean daily maximum global radiation (Rg), monthly effective accumulated temperature (Tac), monthly mean daily maximum vapor pressure deficit (VPD), and monthly precipitation (PP). CA was used to group 192 observed months into four groups based on those four meteorological variables and their effects on the observed carbon fluxes. Structural equation modeling (SEM) was then used to quantify the relative importance and direct or indirect effects of those four meteorological factors on carbon fluxes at the interannual timescale in each of the four groups. The results showed that air temperature had dominant influence on net ecosystem productivity (NEP) and ecosystem respiration (Re) with its relative importance measured by standardized coefficients (SC) of 0.59 and 0.97, respectively. PP directly impacted gross primary production (GPP) with an SC of 0.40 and indirectly influenced NEP and Re. The importance of a given meteorological factor on carbon fluxes and the dominant meteorological factors varied among the four groups. Tac mainly influenced Re with a SC of 0.79 in Group 1 (the nongrowing season). The direct effects of PP on NEP and GPP and indirect effects on Re were most prominent in Group 2 (the transition stage between the nongrowing season and the growing season). Tac and PP had greater influences than other two variables in Group 3 (the transitional stage of early growth and vigorous growth and the transitional stage of steady growth and dormant period). NEP increased with Tac, while excessive rainy weather accompanied by a decrease in temperature and radiation reduced Re and GPP in Group 4 (the wet season). The short-term seasonal droughts with warm air temperatures but little precipitation (mainly in June) led to significant reductions in both GPP and NEP of the Quercus variabilis plantation ecosystem in the warm-temperate continental monsoon climate zone. Our results can be used to guide managing forest plantations in temperate region in China to maximize their carbon sequestration.

Effects of regulated dam discharge on plants and migratory waterfowl are mediated by salinity changes in estuaries

AbstractThe rapid increase in dam construction has resulted in a worldwide loss of natural river flows. Regulated dam discharge into estuaries can interrupt the spatiotemporal occurrence of brackish communities adapted to optimal salinity ranges, further threatening biodiversity and ecosystem function in the affected regions. We used annual survey records from the Nakdong River Estuary from 2009 to 2018 to identify the indirect effect of regulated dam discharge on plants and migratory waterfowl. Increased mean salinity during the spring season negatively influenced the area covered by plants and the number of days on which swans were present during winter. Moreover, the mean salinity during the early growing periods of plants providing food to waterfowl was regulated by the amount of freshwater discharge from the estuarine barrage rather than by the direct effect of precipitation. Conservation managers should consider the amount of dam discharge and the salinity conditions during spring to maintain sufficient food resources and supporting functions for migratory waterfowl in the estuary. Our study highlights the need for a comprehensive assessment of time‐lag effects to minimize the negative impacts resulting from regulated dam discharge.

Root herbivory controls the effects of water availability on the partitioning between above‐ and below‐ground grass biomass

Abstract The fraction of primary productivity allocated below‐ground accounts for a larger flow of carbon than above‐ground productivity in most grassland ecosystems. Here, we addressed the question of how root herbivory affects below‐ground allocation of a dominant shortgrass prairie grass in response to water availability. We predicted that high levels of root herbivory by nematodes, as seen under extreme drought in sub‐humid grasslands, would prevent the high allocation to root biomass normally expected in response to low water availability. We exposed blue grama Bouteloua gracilis, which accounts for most of the net primary productivity in the shortgrass steppe of the central and southern Great Plains, to three levels of water availability from extreme low to intermediate and extreme high crossed with a gradient of root­herbivore per cent abundance relative to the total nematode community in soil microcosms. As hypothesized, the effect of water availability on below‐ground biomass allocation was contingent on the proportion of root herbivores in the nematode community. The relationship between below‐ground biomass allocation and water availability was negative in the absence of root herbivory, but tended to reverse with increasing abundance of root feeders. Increasing abundance of root‐feeding nematodes prevented grasses from adjusting their allocation patterns towards root mass that would, in turn, increase water uptake under dry conditions. Therefore, below‐ground trophic interactions weakened plant responses and increased the negative effects of drought on plants. Our work suggests that plant responses to changes in precipitation result from complex interactions between the direct effect of precipitation and indirect effects through changes in the below‐ground trophic web. Such complex responses challenge current predictions of increasing plant biomass allocation below‐ground in water‐stressed grasslands, and deserve further investigation across ecosystems and in field conditions. A free Plain Language Summary can be found within the Supporting Information of this article.

Modeling the Direct Effect of Climate Change on the Cereal Production in Tunisia: A Micro-spatial Panel Cointegration Analysis

Unlike previous studies, this paper, by employing a cointegration technique on panel data, economically investigates the direct effect of climate change on the cereal production in the long-term via a new cereal disaggregated databases covering the period 1979-2012 for 24 governorates in Tunisia within a multivariate panel framework. The Pedroni panel cointegration test indicates that there is a long-run equilibrium relationship between the considered variables with elasticity’s estimated positive and statistically significant in the long-run. The results generally confirm that in the long term there is a strong positive correlation between the cereal production and the direct effect of precipitation and temperature for the whole panel. At the micro-spatial level, results of the long-run equilibrium relationship show that the cereal production is extremely dependent on rainfall in most governorates of cereals producers, especially the Northwest region of Tunisia. In fact, there are several initiatives and policies that must be undertaken by Government in an attempt to improve the long term production of cereals in the most affected governorates by the phenomenon of climate change such as the development of several important and regionally-based institutions and cooperation, providing subsidies to farmers.

Dynamics and responses of vegetation to climatic variations in Ziya-Daqing basins, China

Examining the direct and indirect effects of climatic factors on vegetation growth is critical to understand the complex linkage between climate change and vegetation dynamics. Based on the Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) data and meteorological data (temperature and precipitation) from 2001 to 2012, the trend of vegetation dynamics were examined in the Ziya-Daqing basins, China. The path analysis was used to obtain the information on the relationships among climatic factors and their effects on vegetation growth. It was found that the trends of growing season NDVI were insignificant in most plain dry land, while the upward trends were significant in forest, grass and dry land in Taihang Mountains. According to the path analysis, in 23% of the basins the inter-annual NDVI variation was dominated by the direct effect of precipitation, in 5% by the direct effects of precipitation and temperature, and in less than 1% by the direct effect of temperature or indirect effects of these two climatic factors. It indicated that precipitation significantly affected the vegetation growth in the whole basins, and this effect was not regulated by temperature. Precipitation increase (especially in July, August and September) was favorable to greenness enhancement. Summer temperature rising showed negative effect on plant productivity enhancement, but temperature rise in April was beneficial for the vegetation growth. When April temperature increases by 1°C, the onset date of greenness for natural vegetation will be 2 days in advance. There was a lag-time effect of precipitation or temperature on monthly NDVI for all land use types except grass.

Pinus ponderosaalters nitrogen dynamics and diminishes the climate footprint in natural ecosystems ofPatagonia

SummaryUnderstanding climate effects on plant–soil interactions in terrestrial ecosystems remains challenging due to the fact that floristic composition covaries with climate, particularly along rainfall gradients. It is difficult to separate effects of precipitationper sefrom those mediated indirectly through changes in species composition. As such, afforestation (the intentional planting of woody species) in terrestrial ecosystems provides an ecological opportunity to assess the relative importance of climate and vegetation controls on ecosystem processes.We investigated the impacts of 35 years of afforestation on ecosystemNdynamics, in ecosystems ranging from arid shrub‐steppe to closed‐canopy forest inPatagonia,Argentina. Sites of natural vegetation and adjacent sites planted with a single exotic species,Pinus ponderosa,were identified in five precipitation regimes along a continuous gradient of 250–2200 mm mean annual precipitation (MAP). We evaluatedCandNparameters of vegetation and soil, as well as natural abundance of13Cand15Nin leaves, roots, ectomycorrhizae (EcM) and soils.In natural vegetation, most leaf traits (%N,C:Nratios, leaf mass per area, δ15Nvalues) demonstrated strong significant relationships withMAP, while these relationships were nearly absent in afforested sites. In addition, theEcMof native southern beech and pine trees were significantly enriched in15Nrelative to leaves at all sites where they were present. While soilCandNpools in both vegetation types increased withMAP, overall pool sizes were significantly reduced in afforested sites.Synthesis. Observed relationships between leaf traits and precipitation in natural vegetation may be driven largely by shifts in species composition and plant–soil interactions, rather than direct effects of precipitation. Our results suggest that a change in the species composition of the dominant vegetation is sufficient to alterCandNcycling independently of climate constraints: pine afforestation homogenizedNdynamics across sites spanning an order of magnitude ofMAP. These results highlight the important control of ectomycorrhizal associations in affectingCandNdynamics. Additionally, they serve to demonstrate that altering natural species composition alone is sufficient to cause large, detectable impacts onNturnover independently of direct climate effects.

Modelling the sensitivity of soil mercury storage to climate-induced changes in soil carbon pools

Abstract. Substantial amounts of mercury (Hg) in the terrestrial environment reside in soils and are associated with soil organic carbon (C) pools, where they accumulated due to increased atmospheric deposition resulting from anthropogenic activities. The purpose of this study was to examine potential sensitivity of surface soil Hg pools to global change variables, particularly affected by predicted changes in soil C pools, in the contiguous US. To investigate, we included a soil Hg component in the Community Land Model based on empirical statistical relationships between soil Hg / C ratios and precipitation, latitude, and clay; and subsequently explored the sensitivity of soil C and soil Hg densities (i.e., areal-mass) to climate scenarios in which we altered annual precipitation, carbon dioxide (CO2) concentrations and temperature. Our model simulations showed that current sequestration of Hg in the contiguous US accounted for 15 230 metric tons of Hg in the top 0–40 cm of soils, or for over 300 000 metric tons when extrapolated globally. In the simulations, US soil Hg pools were most sensitive to changes in precipitation because of strong effects on soil C pools, plus a direct effect of precipitation on soil Hg / C ratios. Soil Hg pools were predicted to increase beyond present-day values following an increase in precipitation amounts and decrease following a reduction in precipitation. We found pronounced regional differences in sensitivity of soil Hg to precipitation, which were particularly high along high-precipitation areas along the West and East Coasts. Modelled increases in CO2 concentrations to 700 ppm stimulated soil C and Hg accrual, while increased air temperatures had small negative effects on soil C and Hg densities. The combined effects of increased CO2, increased temperature and increased or decreased precipitation were strongly governed by precipitation and CO2 showing pronounced regional patterns. Based on these results, we conclude that the combination of precipitation and CO2 should be emphasised when assessing how climate-induced changes in soil C may affect sequestration of Hg in soils.

Impact of Satellite-Derived Forcings on Numerical Ocean Model Simulations and Study of Sea Surface Salinity Variations in the Indian Ocean

AbstractThis study focuses on two major aspects: the impact of satellite forcings (winds and precipitation) on the simulations of a multilayer Indian Ocean (IO) model (IOM) and the analysis of the processes responsible for salinity variations in the Indian Ocean during dipole years (1994 and 1997). It is observed that the European Remote Sensing Satellite-2 (ERS-2) scatterometer wind-driven solutions describe the interannual variabilities of sea surface temperature (SST) more realistically than the National Centers for Environmental Prediction (NCEP) wind-driven solutions. The equatorial westward current jet [hereafter referred to as reverse Wyrtki jet (RWJ)] originating near the Sumatra coast in response to anomalous easterlies during fall of 1994 and 1997 is quite strong in the scatterometer-forced solutions. This RWJ is found to be weak in the NCEP solution. Two more experiments differing by their precipitation forcings [climatological and interannually varying Global Precipitation Climatology Project (GPCP) rainfall] are carried out. Model-simulated variables like SST, sea surface salinity (SSS), and mixed layer depth (MLD) have been compared with in situ observations to verify the performance of the model. The model suggests a dipolelike structure in surface salinity during late 1994 and 1997, with low salinity in the central equatorial Indian Ocean (EIO) and high salinity near the Sumatra coast. The low-salinity tongue is caused by the transport of fresh surface waters via RWJ, which is further strengthened by a southward branch (which is absent in normal years) coming from the Bay of Bengal. A major inference of the study is that the low-salinity tongue is caused mainly by advection, not by a direct effect of precipitation. On the contrary, the high salinity near the Sumatra coast is due to the strong upwelling caused by anomalous easterlies. Another inference made out of this study is that there is apparently a definite signature of the evolution of the dipole event in the MLD approximately 2 months prior to the peak occurring in SSS in the south EIO.

Effects of wet deposition on optical properties of the atmosphere over Bermuda and Barbados

Substantial spatial and temporal variabilities in chemical and physical properties of aerosols complicate attempts to model associated influences on global climate. Although wet deposition is the major mechanism by which most aerosols are removed from the atmosphere, direct effects of precipitation on radiative properties of the atmosphere are not well understood. To address this issue, attenuation coefficients for total insoluble constituents (ACt) and for nonvolatile (at 500°C) insoluble constituents (ACnv; primarily crustal dust) of precipitation at Bermuda and Barbados were measured at six wavelengths between 414 and 859 nm. Coefficients for volatile (at 500°C) insoluble constituents (ACv; primarily carbonaceous species) were calculated by difference. Between April and September, ACt at Bermuda was dominated by mineral constituents transported from North Africa, whereas carbonaceous species from North America were relatively low and exhibited no systematic seasonal variability. ACt and ACnv at Barbados were dominated by mineral dust, especially between April and September. Relative to ACv, ACnv decreased more rapidly with increasing wavelength. The wavelength dependencies of ACs for volatile and nonvolatile constituents at Bermuda were statistically indistinguishable from those at Barbados. The optical and chemical characteristics of precipitation were compared with scattering and absorption by ambient aerosols in associated air parcels to evaluate the influence of scavenging on the radiative properties of air. Although discernible relationships were evident, the small number of cases limited their applicability as reliable empirical predictors. However, these data do provide useful constraints for validating models of aerosol scavenging and wet removal on the optical properties of the troposphere.

THE VERTICAL DISTRIBUTION OF SOIL ORGANIC CARBON AND ITS RELATION TO CLIMATE AND VEGETATION

As the largest pool of terrestrial organic carbon, soils interact strongly with atmospheric composition, climate, and land cover change. Our capacity to predict and ameliorate the consequences of global change depends in part on a better understanding of the distributions and controls of soil organic carbon (SOC) and how vegetation change may affect SOC distributions with depth. The goals of this paper are (1) to examine the association of SOC content with climate and soil texture at different soil depths; (2) to test the hypothesis that vegetation type, through patterns of allocation, is a dominant control on the vertical distribution of SOC; and (3) to estimate global SOC storage to 3 m, including an analysis of the potential effects of vegetation change on soil carbon storage. We based our analysis on .2700 soil profiles in three global databases supplemented with data for climate, vegetation, and land use. The analysis focused on mineral soil layers. Plant functional types significantly affected the vertical distribution of SOC. The per- centage of SOC in the top 20 cm (relative to the first meter) averaged 33%, 42%, and 50% for shrublands, grasslands, and forests, respectively. In shrublands, the amount of SOC in the second and third meters was 77% of that in the first meter; in forests and grasslands, the totals were 56% and 43%, respectively. Globally, the relative distribution of SOC with depth had a slightly stronger association with vegetation than with climate, but the opposite was true for the absolute amount of SOC. Total SOC content increased with precipitation and clay content and decreased with temperature. The importance of these controls switched with depth, climate dominating in shallow layers and clay content dominating in deeper layers, possibly due to increasing percentages of slowly cycling SOC fractions at depth. To control for the effects of climate on vegetation, we grouped soils within climatic ranges and compared distributions for vegetation types within each range. The percentage of SOC in the top 20 cm relative to the first meter varied from 29% in cold arid shrublands to 57% in cold humid forests and, for a given climate, was always deepest in shrublands, inter- mediate in grasslands, and shallowest in forests ( P , 0.05 in all cases). The effect of vegetation type was more important than the direct effect of precipitation in this analysis. These data suggest that shoot/root allocations combined with vertical root distributions, affect the distribution of SOC with depth. Global SOC storage in the to p3mo fsoil was 2344 Pg C, or 56% more than the 1502 Pg estimated for the first meter (which is similar to the total SOC estimates of 1500-1600 Pg made by other researchers). Global totals for the second and third meters were 491 and 351 Pg C, and the biomes with the most SOC at 1-3 m depth were tropical evergreen forests (158 Pg C) and tropical grasslands/savannas (146 Pg C). Our work suggests that plant functional types, through differences in allocation, help to control SOC distributions with depth in the soil. Our analysis also highlights the potential importance of vegetation change and SOC pools for carbon sequestration strategies.

Streams in the New Jersey Pinelands Directly Reflect Changes in Atmospheric Deposition Chemistry

AbstractThe major ion chemistry of precipitation and four undisturbed streams was measured in the New Jersey Pinelands (Pine Barrens) in 1970–1972 and 1984–1988. Over the interval, the sea salt corrected concentration of Ca and SO4 significantly declined in precipitation and all streams. Analytical problems prevented analysis of the change in precipitation H, but H significantly declined in all streams. The change in precipitation and stream water Mg and K was less consistent, but was generally toward lower concentrations in 1984–1988. After examining the potential contribution of analytical artifacts and changes in watershed characteristics and hydrology to these results, it was concluded that the changes in precipitation chemistry was real and resulted in direct changes in stream chemistry between 1970–1972 and 1984–1988. The direct effect of precipitation on stream water chemistry in the New Jersey Pinelands suggests that this region is an ideal locality to investigate future long‐term linkages between precipitation and surface water.

Multiple effects of precipitation on Salix lasiolepis and populations of the stem‐galling sawfly, Euura lasiolepis

AbstractRelatively low winter precipitation (e.g., 18–28 cm from October to May compared to 45 to 65 cm) caused reduced growth of the arroyo willow, Salix lasiolepis, with number of shoots per stem initiated and shoot length reduced. Resources were reduced for the stem‐galling sawfly, Euura lasiolepis, which declined in numbers after the relatively dry winter of 1980–81. Sawfly phenology was advanced relative to willow phenology in the 1981 generation, causing an additional reduction in resource availability. These direct effects of precipitation on the sawfly were increased by indirect effects on survivorship of the 1981 generation. Egg death in galls increased on water‐stressed willow plants, forming the major mortality in the generation. This resulted in very low survival in the generation and an even lower population in the 1982 generation, even though resources recovered after high precipitation during the 1981–82 winter (46.7 cm). An experiment using high, medium, and low water treatments on potted willow plants demonstrated that the effects on willows and sawflies could be reproduced using only water as a variable.

Doppler observations of associated ionospheric and magnetic fluctuations

Observations of ionospheric motions associated with magnetic micropulsations were conducted during a three-year period.Current theoretical models of the interaction indicate that observable Doppler shifts of high-frequency radio waves coherently reflected from the ionosphere should accompany all reasonably large geomagnetic disturbances, and vice versa, but this is not observed. Detailed studies of particular classes of events were therefore undertaken, involving spectral analyses, cross correlations, diurnal and seasonal occurrence statistics, and studies of associations with various types of ionospheric and magnetic records.Certain classes of magnetic pulsation events are found to be directly associated with F-region motions. Of the many possible mechanisms which may be responsible for these associations, two stand out as prime candidates: (i) hydromagnetic waves and (ii) neutral-gas waves modulating ionospheric electrojets. At mid-latitudes during quiet-sun years, the direct effects of precipitation of charged particles appear to be of much less importance.