Annual Effective Precipitation Research Articles

Environmental and biophysical effects of evapotranspiration in semiarid grassland and maize cropland ecosystems over the summer monsoon transition zone of China

Accurate quantification of semiarid energy partitioning and actual evapotranspiration (ETc) is necessary to understand the variability in regional energy and the water cycle, which is expected to intensify under climate change. The seasonal and interannual variability in surface energy and ET and its responses to environmental and biophysical factors of grassland and cropland with maize (Zea mays), and ecosystems over the East Asian summer monsoon transition zone of China, were investigated using multiyear (2003–2008) eddy covariance measurements. The study sites received 65–84% of the annual precipitation (Pr) during the East Asian summer monsoon (EASM; June–August), with the lowest values in the weak EASM years of 2004 and 2007. Seasonal and interannual variations in the portioning of net radiation to turbulent fluxes were mainly controlled by Pr via changes in soil water content (SWC) and vegetation growth. Drastic changes in the Bowen ratio, vegetation growth, and energy fluxes occurred after the onset of EASM. During the cool winter and dry spring and autumn, the sensible heat flux was the largest component of the energy balance, and the latent heat flux dominated during warm and wet periods of summer. Monthly ET was 24.8 and 25.6 mm for the grassland and cropland, respectively, and they peaked at 89.0 mm and 113.9 mm, respectively, in July. Monthly ET was positively correlated with monthly Pr, Ta, the soil water drought stress index, normalized difference vegetation index (NDVI), the surface conductance (Gs), and the Priestley–Taylor coefficient (ET/ETeq) during the growing seasons (April–September). Annual ET varied from 215 to 373 mm in grassland and from 227 to 390 mm in cropland, with the lowest value during the severe drought year of 2007. Interannual variations in ET were primarily controlled by annual effective precipitation frequency, and interannual variations in summer ET were modulated by the summer monsoon duration period through changes in summer Pr, SWC, and vegetation growth.

Biometeorological effects on carbon dioxide and water-use efficiency within a semiarid grassland in the Chinese Loess Plateau

Semiarid grassland ecosystems play a crucial role in global carbon and water cycles. Considerable attention has been devoted to the effect of biometeorological parameters on ecosystem carbon exchanges in semiarid regions. However, a gap remains regarding carbon and water flux in the Chinese Loess Plateau. In this study, we describe 6 years (2007–2012) of eddy-covariance carbon fluxes (CO2) and water-use efficiency (WUE) over a semiarid grassland site and their biometeorological controls. Interannual CO2 flux variations were analyzed based on a correlation analysis with measured biometeorological factors. The annual net ecosystem CO2 exchange (NEE) was negative (mean net carbon sink) across the entire period, varying from −236.3 (2012) to − 114.2 g C m−2 year−1 (2011), with a mean value of − 168.9 g C m−2 year −1. The normalized differential vegetation index is the most highly correlated with gross primary production (GPP) and evapotranspiration (ET) across several timescales. The effective precipitation frequency is an important factor influencing CO2 fluxes on an annual timescale, and soil water content was the second most important factor affecting CO2 fluxes on a monthly timescale. On an annual timescale, the semiarid grassland ecosystem WUE increased with the soil drought stress index, with ET decreasing more than GPP as soil drought increased. The monthly mean WUE varied from 0.44 to 2.51 g C kg−1 H2O, and the monthly WUE plateaued in October. Summer drought-induced leaf senescence caused GPP reduction in weaker summer monsoon years, leading to a notable reduction in WUE. We found obvious transitional characteristics in the response of WUE to soil water stress. We also found a strong positive relationship between the annual NEE and the annual effective precipitation frequency at the study site.

Dynamic response of land–atmosphere-coupling parameters to precipitation in the sparse-vegetated Asian summer monsoon transition zone

Land–atmosphere-coupling parameters usually relate to particular climatic conditions and seldom consider the influence of the inter-annual variability of precipitation. This results in large uncertainty in the estimation of land-surface physical variables. In the current study, observed data for five land–atmosphere-coupling parameters (surface albedo, soil thermal conductivity, aerodynamic roughness length, and the bulk transfer coefficients of momentum and sensible heat) were analysed and related to the inter-annual variability of precipitation on the Loess Plateau, China, from April 2006 to March 2013. This is an area with sparse vegetation. The results demonstrate that the land–atmosphere-coupling parameters are very sensitive to the inter-annual variability of precipitation. The surface albedo increased with increasing duration of snow cover. The other four parameters increased when annual effective precipitation (yearly sum of daily rainfall > 4 mm or daily snowfall > 0.1 mm) increased, and the sensitivity decreased when annual effective precipitation increased. Empirical relations between the five land–atmosphere-coupling parameters and the inter-annual variability of precipitation were derived via regression, with R2 values of 0.67, 0.85, 0.93, 0.99, and 0.95, respectively. The land-surface physical variables calculated with dynamic land–atmosphere-coupling parameters (considering the inter-annual variability of precipitation) were much closer to the observed data than those calculated with static land–atmosphere-coupling parameters. The relative error was reduced by > 80% in years with low precipitation. This indicates that the inter-annual variability of precipitation has a significant impact on the land-surface physical variables. The results demonstrate that land–atmosphere-coupling parameters, which take into account inter-annual variability of precipitation, provide a more realistic representation of the land surface.

Seasonal and inter-annual variability of the Bowen smith ratio over a semi-arid grassland in the Chinese Loess Plateau

Energy partitioning between grassland sensible (H) and latent (LE) heat fluxes is critical in determining boundary layer development, the hydrological cycle, weather and climate. In this report, we describe the seasonal and inter-annual variability of the Bowen ratio (β) over semi-arid grassland of the Loess Plateau in the north boundary belt of the summer monsoon of China. β was directly measured by an eddy covariance system over a 6-year period (2007–2012), during which the studied grassland experienced a large range in precipitation, extending from 555.5 mm (2007) to 262.8 mm (2011). The annual Bowen ratio (βa) based on annual energy budgets ranged from 0.90 (2007) to 1.93 (2011) with an annual mean value of 1.32, while the annual midday (10:00–16:00 GMT + 8) β ranged from 2.07 (2007) to 4.19 (2011) with an annual mean value of 3.02. The mean midday β during the dry years (3.66, 2009, 2010 and 2011) was higher than that observed during the wet years (2.39, 2007, 2008 and 2012). The 6-year annual mean values of the bulk surface resistance (Rs), aerodynamic resistance (Ra) and climatological resistance (Ri) varied from 272.27 to 410.10 s m−1, 31.62–34.89 s m−1 and from 64.5 to 87.13 s m−1, respectively, with annual mean values of 337.08, 32.83 and 73.05 s m−1, respectively. The normalized difference vegetable index (NDVI) had a direct influence on β as mediated by Rs, and there was a logarithmic function between ET/ETeq and Rs in the semi-arid grassland. A positive trend between β and the surface resistance (Rs*) normalized by the climatological and aerodynamic resistance was observed at this site. Moreover, the annual effective precipitation frequency was significantly related to the midday β during the growing and non-growing seasons, which indicated that the annual effective precipitation, not the annual precipitation, indirectly affected the annual β through its effect on the shallow soil water content (SWC). The results suggested that inter-annual variations in β was primarily controlled by an annual effective precipitation frequency and seasonal variations in β was directly affected by NDVI as mediated by Rs over the semi-arid grassland in the Chinese Loess Plateau.

Variation of carbon use efficiency over ten years in a subtropical coniferous plantation in southeast China

The forest carbon use efficiency (CUE=net ecosystem productivity/gross ecosystem photosynthesis) represents the carbon sequestration efficiency and is widely used to estimate carbon budgets. However, the annual trends in forest CUE need to be further studied. We explored the seasonal and interannual variation of CUE, and the affecting mechanisms based on eddy covariance measurements in a subtropical coniferous plantation during 2003–2012. The seasonal variation of CUE generally followed a bimodal curve, with lower values occurring during the summer drought period and winter. The seasonal variation of CUE was positively influenced by photosynthetic active radiation. The annual mean CUE was 0.23, with a range of 0.17–0.27.The annual effective precipitation frequency (EPF) indirectly and negatively influenced the annual CUE, through its positive effect on annual soil water content at 20cm depth (SWC20cm). During 2003–2012, there was a significant decreasing trend of annual CUE (p=0.049), and annual EPF and SWC20cm significantly increased (p<0.01). Annual CUE will likely decrease further if annual EPF and SWC20cm continue with their increasing trends in the future.

Climate change effects on groundwater resources: a new assessment method through climate indices and effective precipitation in Beliş district, Western Carpathians

ABSTRACTClimate change is a topic of enormous interest due to its direct impact and long‐term consequences. The ongoing climate warming is triggering global impacts and it is likely to alter natural systems at the local scale, too. The observed climate variability in the Romanian Carpathians has been tackled by several researchers and the negative impact of climate change on groundwater vulnerability has also been assessed. A temporal analysis of four climate indices (De Martonne, UNEP Index, Johansson Continentality Index and Pinna Combinative Index) and crop evapotranspiration over the past 50 years was performed to understand the climate trends in the Beliş district, to estimate the effective precipitation in the area and to assess the effects of climate change on groundwater resources. Land cover data were extracted from satellite images and crop evapotranspiration data were evaluated based on field co‐efficients. An examination of the climate index trends and change points was carried out using the Rodionov test. In the study area, the climate indices indicated very humid and marine climate conditions. At the same time, it was noticed that the crop evapotranspiration values increased from 1961 to 2013 and the annual effective precipitation ranged between 200–300 mm. In order to understand the impacts of climate change on groundwater resources, an innovative method was proposed using an inference matrix that combines the climate indices and effective precipitation. Based on this method, the climate indices and effective precipitation for four decades indicated a low impact of climate change on groundwater resources in the Beliş district.

Changing hydrologic connectivity due to permafrost thaw in the lower Liard River valley, NWT, Canada

AbstractFlows from river basins in northwestern Canada have been rising in the last two decades as a result of climate warming. In the wetland‐dominated basins that characterise the southern margin of permafrost, permafrost thaw and disappearance, and resulting land‐cover change, is occurring at an unprecedented rate. The impact of this thaw on runoff generation in headwater basins is poorly understood. Permafrost thaw has the potential to fundamentally alter the cycling and storage of moisture inputs in this region by altering the type and relative proportions of the major land‐cover types, such as peat plateaus, channel fens and flat bogs. This paper examines streamflow changes in the four Water Survey of Canada gauged river basins (152–2050 km2) in the lower Liard River valley, Northwest Territories, Canada, a region where permafrost thaw has produced widespread loss of forest and concomitant expansion of permafrost‐free wetlands. Annual runoff in the lower Liard Valley increased by between 112 and 160 mm over the period of 1996–2012. The Mann‐Kendall non‐parametric statistical test and the Kendall‐Theil robust line were used to ascertain changes in streamflow. Historical aerial photographs from 1977 and high‐resolution satellite imagery (WorldView 2) from 2010 were used to measure the rate and pattern of permafrost thaw in a representative 6 km2 area of Scotty Creek. Permafrost thaw‐induced land‐cover change is both increasing the adjacency between runoff producing and transmitting land cover types and transforming certain land covers that store water into ones that produce runoff. This land‐cover change was found to be the single most important factor (37–61 mm) contributing to the observed increase in river discharge. Other contributing factors include increases in plateau runoff contributing areas (20–32 mm), increases in annual effective precipitation depth (18–30 mm), contribution of water from the melt of ice within permafrost (9 mm) and increases in baseflow (0.9–6.8 mm). Although runoff has significantly (p &lt; 0.05) increased in all four basins, the largest increases are in basins with a relatively high cover of flat bogs. Copyright © 2014 John Wiley &amp; Sons, Ltd.

English

&nbsp; The present research focuses on both past and future time scale in order to recognize the changes of effective precipitation trend in Ghazvin station. Therefore, in order to recognize the trend and behavior of past climate components, the components trend analysis have been done using Pierson and linear regression method. In order to study and analyze effective precipitation trend, the length of statistical data from 1959 to 2009 and data on climate temperature, precipitation, evapotranspiration, wind speed and radiation have been used. SCS method is used in calculating the effective precipitation. Also, the compound results of two models of CNRM-GISS-EH and CM3 have been used to evaluate the effect of regional climate change in the simulation of effective precipitation in 2050 and 2075 decades. The results of changes in effective precipitation trend for study period (1959 to 2009) indicates that the effective precipitation trend in spring is decreasing with the rate r=-0.10, however, the results in winter (r=0. 11), autumn (r=0. 24), and summer (r= 0. 16) indicates the increase of effective precipitation in recent decades. Also, it should be stated that the maximum increase of effective precipitation occurs in December with the rate 6 mm and the maximum decrease is in January with -1.91 in each decade. But, the average of the simulated results by the year 2075 indicates that the maximum decrease of effective precipitation is in July with 35.1% and the maximum increase will occur in August with 80.6%. Finally, however, the results indicate that the annual effective precipitation value in 2025 is increased with (1.7%) and in 2075 with (14.5%), but the great oscillation of these changes at summer, which is a dry period in Ghazvin, needs further management and planning for supplying the water requirement of different farming products, especially dry cultivation. &nbsp; Key words:&nbsp;Climate change, carbon dioxide increase, dry farming, effective precipitation, SCS, Ghazvin.

Responses of the land-surface process and its parameters over the natural vegetation underlying surface of the middle of Gansu in loess plateau to precipitation fluctuation

The Loess Plateau is well known as a specific region sensitive to global climate change, and thus its land-surface process is significantly influenced by climatic fluctuation. Up to now, the land-surface physical process over the Loess Plateau has been basically understood under a specific climatic condition, but the dynamic variation regularity of land-surface process in different climatic states is still lacking in its knowledge. Utilizing the continuous five-year data collected at the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) supported by the program 'the Loess Plateau Land-surface Process Experiment (LOPEX)', in this paper, we systematically analyze the regularity of responses of factors including land-surface water and energy budget as well as surface albedo and roughness to climatic fluctuation over the natural vegetation surface of Loess Plateau. The results show that the land-surface process and its relevant parameters are very sensitive to the fluctuations of annual precipitation. Besides, they respond markedly to annual rainfall amount and are also closely related to the nature of rainfall. Soil moisture fluctuales not fully with total amount of rainfall but rises with the increase of effective precipitation with which land-surface water and energy budget also vary. In addition, the vertical sensible heat advection goes up with rainfall increasing, while the trend of surface energy imbalance is opposite. The averaged albedo in summer half-year comes down with the increase of the ratio of effective precipitation to the climatic average, but yearly averaged albedo is evidently affected by the snow-accumulating winter time and rises with the increase of snow-accumulating hours. Soil thermal conductivity and surface roughness both increase with annual effective precipitation increasing to the climatic average, but they are more sensitive to the precipitation fluctuation under a low precipitation condition than under the normal precipitation condition. However, land-surface process parameters over the natural vegetable surface of Loess Plateau basically fluctuate between those of deserts and farmland, and have not yet broken the climatic restrictions. Fitting relationship is used to quantitatively reflect the regularity of response of the parameters to rainfall fluctuations so as to evidently eliminate possible bias brought to numerical models and microclimatic analysis by the previous fixed and un-dynamic changeable land-surface parameters.

The effect of forest harvesting and climatic variability on runoff in a large watershed: The case study in the Upper Minjiang River of Yangtze River basin

Summary Forest disturbance (or land cover change) and climatic variability are commonly recognized as two major drivers interactively influencing hydrology in forested watersheds. However, separating their relative contributions to hydrology is rarely examined, particularly in large watersheds (>1000 km 2 ). This study used a large watershed, the Upper Zagunao River watershed, situated in the upper reach of the Minjiang River, the Yangtze River basin, China as an example to demonstrate how the effects of forest harvesting and climatic variability on hydrology can be quantitatively separated. Long-term data on climate, hydrology and forest harvesting history are available from1953 to 1996. Time series cross-correlation analysis and non-parametric tests were performed first to identify possible responses of annual and seasonal runoff to forest harvesting, and to determine breakpoints of runoff change over its long-term time series. Then, modified double mass curve of accumulated annual effective precipitation (the residual of precipitation and evapotranspiration) and accumulated annual runoff was used to quantify the relative contributions of forest harvesting and climatic variability to annual runoff variation. Our analysis showed that the breakpoint of significant annual runoff change occurred in1969, about 10 yrs after the intensive harvesting period of 1955–1962, suggesting the delayed hydrological response in the studied large watershed. Over the period of 1970–1996, the average annual runoff increment attributed to forest harvesting was 38 mm/yr, while the annual runoff variation attributed to climatic variability was −38.3 mm/yr, clearly demonstrating that forest harvesting and climatic variability had offsetting effects on annual runoff. Our results also disclosed that the positive effect of forest harvesting on runoff decreased with forest recovery and eventually diminished about 20 yrs after intensive harvesting period.

Quantifying streamflow change caused by forest disturbance at a large spatial scale: A single watershed study

Climatic variability and forest disturbance are commonly recognized as two major drivers influencing streamflow change in large‐scale forested watersheds. The greatest challenge in evaluating quantitative hydrological effects of forest disturbance is the removal of climatic effect on hydrology. In this paper, a method was designed to quantify respective contributions of large‐scale forest disturbance and climatic variability on streamflow using the Willow River watershed (2860 km2) located in the central part of British Columbia, Canada. Long‐term (&gt;50 years) data on hydrology, climate, and timber harvesting history represented by equivalent clear‐cutting area (ECA) were available to discern climatic and forestry influences on streamflow by three steps. First, effective precipitation, an integrated climatic index, was generated by subtracting evapotranspiration from precipitation. Second, modified double mass curves were developed by plotting accumulated annual streamflow against annual effective precipitation, which presented a much clearer picture of the cumulative effects of forest disturbance on streamflow following removal of climatic influence. The average annual streamflow changes that were attributed to forest disturbances and climatic variability were then estimated to be +58.7 and −72.4 mm, respectively. The positive (increasing) and negative (decreasing) values in streamflow change indicated opposite change directions, which suggest an offsetting effect between forest disturbance and climatic variability in the study watershed. Finally, a multivariate Autoregressive Integrated Moving Average (ARIMA) model was generated to establish quantitative relationships between accumulated annual streamflow deviation attributed to forest disturbances and annual ECA. The model was then used to project streamflow change under various timber harvesting scenarios. The methodology can be effectively applied to any large‐scale single watershed where long‐term data (&gt;50 years) are available.

Modern vegetation–pollen–climate relationships for the Pampa grasslands of Argentina

AbstractAim To analyse the relationships between potential natural vegetation, pollen and climate in order to improve the interpretation of fossil pollen records and provide the background for future quantitative palaeoclimatic reconstructions.Location Pampa grasslands of Argentina, between 33–41° S and 56–67° W.Methods Modern pollen data were obtained from a pollen data base developed by the Grupo de Investigación de Paleoecología y Palinología, Universidad Nacional de Mar del Plata, Argentina (143 surface samples and 17 pollen types). Analysis of pollen and climate data involved multivariate statistics (cluster analysis and principal components analysis), scatter diagrams, Pearson’s correlation and isopoll mapping.Results Vegetation patterns at regional scales (grasslands and xerophytic woodlands) and local scales (edaphic communities) were identified by cluster analysis of pollen surface samples. The main climatic variables that appear to constrain the vegetation distribution and abundance of taxa are mean annual precipitation, annual effective precipitation and summer temperature. Individual pollen types such as Chenopodiaceae, Apiaceae, Cyperaceae, Prosopis, Schinus, Condalia microphylla and other xerophytic taxa are good indicators of moisture regime. Many pollen types are significantly correlated with summer temperature. The modern vegetation–pollen–climate relationships vary in a broadly predictable manner, supporting the contention that fossil pollen assemblages can be related to particular climatic characteristics.Main conclusions An expanded suite of modern analogues facilitated new insights into vegetation–pollen–climate relationships at the regional scale in Pampa grasslands. Relationships between individual pollen types and climate are appraised at a regional scale and new modern analogues are presented. The results provide the basis for improved vegetation and climate reconstruction from fossil records of the study area.

The relationship between NDVI and precipitation on the Tibetan Plateau

The temporal and spatial changes of NDVI on the Tibetan Plateau, as well as the relationship between NDVI and precipitation, were discussed in this paper, by using 8-km resolution multi-temporal NOAA AVHRR-NDVI data from 1982 to 1999. Monthly maximum NDVI and monthly rainfall were used to analyze the seasonal changes, and annual maximum NDVI, annual effective precipitation and growing season precipitation (from April to August) were used to discuss the interannual changes. The dynamic change of NDVI and the correlation coefficients between NDVI and rainfall were computed for each pixel. The results are as follows: (1) The NDVI reached the peak in growing season (from July to September) on the Tibetan Plateau. In the northern and western parts of the plateau, the growing season was very short (about two or three months); but in the southern, vegetation grew almost all the year round. The correlation of monthly maximum NDVI and monthly rainfall varied in different areas. It was weak in the western, northern and southern parts, but strong in the central and eastern parts. (2) The spatial distribution of NDVI interannual dynamic change was different too. The increase areas were mainly distributed in southern Tibet montane shrub-steppe zone, western part of western Sichuan-eastern Tibet montane coniferous forest zone, western part of northern slopes of Kunlun montane desert zone and southeastern part of southern slopes of Himalaya montane evergreen broad-leaved forest zone; the decrease areas were mainly distributed in the Qaidam montane desert zone, the western and northern parts of eastern Qinghai-Qilian montane steppe zone, southern Qinghai high cold meadow steppe zone and Ngari montane desert-steppe and desert zone. The spatial distribution of correlation coefficient between annual effective rainfall and annual maximum NDVI was similar to the growing season rainfall and annual maximum NDVI, and there was good relationship between NDVI and rainfall in the meadow and grassland with medium vegetation cover, and the effect of rainfall on vegetation was small in the forest and desert area.

Climatic and hydrological instability in semi-arid equatorial East Africa during the late Glacial to Holocene transition: A multi-proxy reconstruction of aquatic ecosystem response in northern Tanzania

This paper reports new multi-proxy palaeoenvironmental data on the late Glacial-Holocene transition (c. 14.8–9.3 ka) in equatorial East Africa, in the form of microfossil assemblages (chironomids, diatoms and ostracods) recovered from the sediment record of Lake Emakat, Empakaai Crater, northern Tanzania. In the context of available palaeoclimatic and palaeoecological information from the region and previously published fossil pollen and carbon and nitrogen isotopic data for the same sediment sequence, we here reconstruct local lake-system response to regional climatic and hydrological instability during the period of post-glacial warming. The aquatic biological proxy indicators suggest that the water level and chemistry of Lake Emakat evolved, first from a shallow freshwater body at 14.8 ka to a deeper freshwater phase between c.14.4 and 10.3 ka and then to a markedly shallower, alkaline-saline environment after c.10.3 ka. The lake appears to have been deepest between 13.2 and 12.0 ka, at a time of climatic drying when moist montane forest vegetation within the lake's crater catchment was being replaced by open wood-and scrubland. Some palaeohydrological changes reconstructed for Lake Emakat are in phase with lake evolution elsewhere in the region and thus apparently track broad-scale climate changes, but some are not. Collectively these multi-proxy paleolimnological data indicate a complex adjustment of the local aquatic ecosystem to temporal variations both in total annual effective precipitation and its seasonal distribution. The lake's hydrological response was further conditioned by local factors, notably its geological and topographic setting.

Rainfall-runoff relationships expressed by distribution parameters

This study is concerned with the statistical parameters of precipitation and of runoff and the interrelations between corresponding parameters. Three processes are considered: the input process (mean annual effective precipitation), the transformation process (basin storage), and the output process (mean annual runoff). The input is assumed to be a pure-random series, with known statistical parameters. The transformation is characterized by an exponential recession curve with one parameter. With these assumptions, equations are developed expressing the statistical parameters of the output for any length of carryover. The validity of these equations is confirmed by means of computer-simulated series, which are analyzed for their moments. The type of distribution of the output is also established.

The Utility of Precipitation-Effectiveness Formulas for Plant Ecology

ANEW formula for precipitation effectiveness has recently been presented byJose Setzer.' fact that the effectiveness of precipitation depends on the evaporation, and this in turn on prevailing temperatures, necessitates a thorough study of the ways in which the several factors may interfere. Since Penck's first attempts, considerations of the interrelationship of the factors involved have been continually improved, and undoubtedly Setzer's suggestion regarding the greater effectiveness of temperature in the higher part of the scale is adequate to characterize the climatic situation of our country (Brazil). Generally, as in the present case, such data are immediately used as an explanation of vegetation types. However, we cannot rely solely on such formulas if we wish to understand the regional distribution, for example, of xerophytic and hygrophytic vegetation. There are other important factors that cannot be omitted, as a closer look at Setzer's exposition will bring out: The towns of Pirassununga, Sorocaba, Agudos, Aragatuba, and Itapeva possess the least humid climate in the state [of Sao Paulo]. Their annual effective precipitation is below the critical value of 64 on the Thornthwaite scale. natural vegetation is revealing. From Pirassununga to MogiMirim, from Sorocaba to Piramboia, around AraSatuba, and between Agudos and Campos Novos there are poor lands of savanna type. Shrubs are widely scattered and low (I2 to 212 or 3 meters when fully grown). There are many subxerophytic elements, and also some xerophytic ones (p. 254). At this point Setzer refers to a paper by the present writer and his colleagues.2 facts given by us, however, are different. vegetation found in the regions mentioned can be called neither xerophytic nor subxerophytic; such elements as Cactaceae and Bromeliaceae are almost completely lacking. plants that retain their foliage in the dry season are provided with broad and often delicate leaves, without heavy protection against excessive