Local Climatic Factors Research Articles

Could temperature and water availability drive elevational species richness patterns? A global case study for bats

ABSTRACTAim A global meta‐analysis was used to elucidate a mechanistic understanding of elevational species richness patterns of bats by examining both regional and local climatic factors, spatial constraints, sampling and interpolation. Based on these results, I propose the first climatic model for elevational gradients in species richness, and test it using preliminary bat data for two previously unexamined mountains.Location Global data set of bat species richness along elevational gradients from Old and New World mountains spanning 12.5° S to 38° N latitude.Methods Bat elevational studies were found through an extensive literature search. Use was made only of studies sampling 70% of the elevational gradient without significant sampling biases or strong anthropogenic disturbance. Undersampling and interpolation were explicitly examined with three levels of error analyses. The influence of spatial constraints was tested with a Monte Carlo simulation program, Mid‐Domain Null. Preliminary bat species richness data sets for two test mountains were compiled from specimen records from 12 US museum collections.Results Equal support was found for decreasing species richness with elevation and mid‐elevation peaks. Patterns were robust to substantial amounts of error, and did not appear to be a consequence of spatial constraints. Bat elevational richness patterns were related to local climatic gradients. Species richness was highest where both temperature and water availability were high, and declined as temperature and water availability decreased. Mid‐elevational peaks occurred on mountains with dry, arid bases, and decreasing species richness occurred on mountains with wet, warm bases. A preliminary analysis of bat richness patterns on elevational gradients in western Peru (dry base) and the Olympic Mountains, WA (wet base), supported the predictions of the climate model.Main conclusions The relationship between species richness and combined temperature and water availability may be due to both direct (thermoregulatory constraints) and indirect (food resources) factors. Abundance was positively correlated with species richness, suggesting that bat species richness may also be related to productivity. The climatic model may be applicable to other taxonomic groups with similar ecological constraints, for instance certain bird, insect and amphibian clades.

Nest Depredation, Brood Parasitism, and Reproductive Variation in Island Populations of Song Sparrows (Melospiza Melodia)

AbstractTheory suggests that the persistence of metapopulations will be influenced by the degree of synchrony in the dynamics of their component populations. Various studies have shown that climate can promote synchrony in the size of adjacent populations linked by dispersal, but fewer studies have examined the effects of climate on underlying demographic rates. We studied annual variation in the timing of breeding and reproductive rates in Song Sparrow (Melospiza melodia) on islands linked by dispersal to determine whether biotic factors acting at local scales or climatic factors acting at a regional scale were more influential of variation in demography. The onset of egg laying varied markedly among years but was roughly synchronous across islands within years. Despite this synchrony, island populations varied markedly in reproductive rate, mainly from spatial variation in nest depredation and brood parasitism. In general, populations farther from Vancouver Island and with fewer resident predators experienced less nest depredation and brood parasitism, and higher reproductive rates, than populations closer to Vancouver Island. Our results show that even when climate acts regionally to synchronize reproductive timing in adjacent populations, its effects on reproductive rate may be overridden by biotic factors that vary among populations.Depredación de Nidos, Parasitismo de Cría y Variación Reproductiva en Poblaciones Isleñas de Melospiza melodia

NEST DEPREDATION, BROOD PARASITISM, AND REPRODUCTIVE VARIATION IN ISLAND POPULATIONS OF SONG SPARROWS (MELOSPIZA MELODIA)

Theory suggests that the persistence of metapopulations will be influenced by the degree of synchrony in the dynamics of their component populations. Various studies have shown that climate can promote synchrony in the size of adjacent populations linked by dispersal, but fewer studies have examined the effects of climate on underlying demographic rates. We studied annual variation in the timing of breeding and reproductive rates in Song Sparrow (Melospiza melodia) on islands linked by dispersal to determine whether biotic factors acting at local scales or climatic factors acting at a regional scale were more influential of variation in demography. The onset of egg laying varied markedly among years but was roughly synchronous across islands within years. Despite this synchrony, island populations varied markedly in reproductive rate, mainly from spatial variation in nest depredation and brood parasitism. In general, populations farther from Vancouver Island and with fewer resident predators experienced less nest depredation and brood parasitism, and higher reproductive rates, than populations closer to Vancouver Island. Our results show that even when climate acts regionally to synchronize reproductive timing in adjacent populations, its effects on reproductive rate may be overridden by biotic factors that vary among populations. Depredación de Nidos, Parasitismo de Cría y Variación Reproductiva en Poblaciones Isleñas de Melospiza melodia

Why large-scale climate indices seem to predict ecological processes better than local weather.

Large-scale climatic indices such as the North Atlantic Oscillation are associated with population dynamics, variation in demographic rates and values of phenotypic traits in many species. Paradoxically, these large-scale indices can seem to be better predictors of ecological processes than local climate. Using detailed data from a population of Soay sheep, we show that high rainfall, high winds or low temperatures at any time during a 3-month period can cause mortality either immediately or lagged by a few days. Most measures of local climate used by ecologists fail to capture such complex associations between weather and ecological process, and this may help to explain why large-scale, seasonal indices of climate spanning several months can outperform local climatic factors. Furthermore, we show why an understanding of the mechanism by which climate influences population ecology is important. Through simulation we demonstrate that the timing of bad weather within a period of mortality can have an important modifying influence on intraspecific competition for food, revealing an interaction between climate and density dependence that the use of large-scale climatic indices or inappropriate local weather variables might obscure.

Diurnal foraging‐mode shifts and food availability in nectarivore assemblages during winter

Abstract Temporal fluctuations of food resources and foraging activities have been studied extensively, especially at longer timescales (monthly, seasonally, among years). However, short‐term variation (e.g. within days) is less well understood. Here we systematically quantified diurnal patterns of foraging by nectarivorous birds (meliphagid honeyeaters) that numerically dominated stands of a winter‐flowering eucalypt, the red ironbark, Eucalyptus tricarpa, in central Victoria, Australia. Diurnal variation in food resources also was measured. Data were collected in winter. Anecdotal observations that honeyeaters change from almost exclusive nectarivory early in the day to a higher fraction of insectivory – especially aerial hawking – later in the day were confirmed, although in areas of high flowering intensity, nectar‐feeding remained the dominant foraging activity throughout the day. Local climatic factors (ambient temperature, windiness and cloud cover) all varied systematically through the day. Together, results were consistent with a change in foraging emphasis to greater insectivory as a function of elevated activities of insects (especially aerial ones), which was probably fostered by higher ambient temperatures. Contrary to energetic expectations, the nectarivores were very active early in the morning when ambient temperatures averaged approximately 3°C, well below thermoneutral temperatures. We deduced that the potential benefits of gathering as much energy‐rich nectar as possible before it was depleted outweighed the high costs of activities at low temperatures.

Seasonal Cambial Anatomy and Development of Xylem in Dalbergia sissoo Growing Under the Influence of Combined Air Pollutants

Seasonal behavior of vascular cambium and development of xylem were compared between the trees of Dalbergia sissoo growing under the influence of combined air pollutants (affected) and in relatively unpolluted area (normal). The duration of radial growth lasted for seven months in normal trees and five months in affected ones. In the normal trees, cambial cells began to divide in April with the sprouting of new leaves and ceased in November after reaching peak in August. The cambial cell division in affected trees started in June with the arrival of rains, reached peak in August and then ceased in November. Cell divisions in the cambium and development of xylem were suspended from December to March and December to May in normal and affected trees, respectively. Comparison between the length of fusiform cambial cells in normal and affected trees also showed significant variation. Xylem is diffuse porous with indistinct growth rings but it can be delineated by the presence of fine band of terminal parenchyma cells in trees of both localities. However, considerable variations occurred in the frequency and dimensions of xylem elements. Relatively more number of vessels with less lumen diameter was the characteristic feature of the xylem of trees growing under pollution stress. Similarly annual average length of xylem fibers was relatively less in the trees of pollution stress. Annual increment of xylem for two successive years was also found less in affected trees. Periodicity of cambium and xylem development is discussed in relation to the local climatic factors and phenology of the trees.

The region effect on mesoscale plant species richness between eastern Asia and eastern North America

The greater number of plant species in temperate eastern Asia compared to eastern North America has been ascribed to both local environment and regional characteristics, but the relative contributions of each have not been resolved. In this analysis, we related species richness of flowering plants in mesoscale floras (<104 km2) dominated by temperate forest vegetation to area, elevation, latitude, and several climate variables. When analyses were conducted separately within each region, area and, in eastern Asia, elevation, were the primary determinants of species richness. It appears that the number of species in mesic temperate floras within these regions is largely unrelated to the relatively narrow range of local climate factors associated with these floras. Analysis of covariance of the logarithm of species richness with the logarithm of area (b=0.148) and climate measurements as independent variables revealed a region effect, with species richness in eastern Asia exceeding that in eastern North America by 0.294 log10 units, or a factor of 2.0. Similar regional differences in species richness were apparent in floras compiled from larger areas. Understanding differences in plant species richness between regions requires consideration of regional influences, whose effects should be tested in comparative analyses based on floristic surveys of ecologically characterized small areas.

Autecology of the yellow-footed antechinus (Antechinus flavipes) in a fragmented landscape in southern Australia

Autecological data were collected on southern populations of the yellow-footed antechinus (Antechinus flavipes), during a wider study on the persistence of this species in a highly fragmented landscape of the southern Mt Lofty Ranges, South Australia. Data are presented to provide information on this species in the southern part of its range, to present a comparison with populations in other, more northern regions, and to provide an insight into the species' persistence in a fragmented system. Resulting recapture rates lend support to the presence of a male-biased dispersal strategy, which is the first published indication of such a strategy for the species. New information was also recorded for nest sites, with most sites occurring in tall Xanthorrhoea semiplana tateana, and only 33% found in tree cavities. Other results showed mostly comparable population densities and weights with other, more northern populations. However, differences were apparent with respect to juvenile dispersal behaviour and, to some extent, breeding times. Within-study populations also showed variation with regard to weights, density and breeding times. Forest animals were lighter, were largely of lower population densities, and were generally later breeders than animals that inhabited patches and strips of remnant vegetation. Such differences in weight and density may have been due to favourable 'edge effects' in patches and strips, while variations in breeding times may be due to local climatic or habitat factors. The life-history strategies and tolerance of habitat edges shown by A.�flavipes (presently and historically) provide some explanation for the species' persistence in this fragmented system.

Decadal‐scale variability in the Kuroshio marine ecosystem in winter

AbstractInterannual variation of winter copepod biomass during the last three decades of the twentieth century was examined in the Kuroshio, off central Japan in relation to climate regime shifts. The biomass levels of large copepods in the period before 1977 and in 1999 and 2000 were higher than those in the period between 1977 and 1998. The biomass of large copepods was positively related with the Southern Oscillation Index (SOI), in winter in the Northern Hemisphere, which also showed steplike shifts in 1976/77 and 1998/99. The biomass of large copepods was largely influenced by abundance of Calanus sinicus that has high rates of production compared with small copepods under food satiated conditions. Accordingly, the climatic regime shift accompanied by the climatic change in the tropical region seems to regulate interannual variation of winter biomass of large copepods in the Kuroshio through effects on food supply. There is less decadal variablity in the small copepod (SC) biomass than large copepod (LC) biomass, but more variablity in SC than in LC at periods 2–4 years. In contrast to the large copepods, the biomass of small copepods was not related to global climate indices but with the local climate factors such as SST in the Kuroshio and variability in the Kuroshio flow path. Causes for the differences in the biomass trends between large and small copepods are discussed.

Vegetation cover trends along the Botswana Kalahari transect

Vegetative response aspects of climate change studies include the determination of vegetation cover changes across climatic gradients. Vegetation characteristics and soil moisture measurements were obtained from four locations with decreasing rainfall along the Botswana Kalahari transect. These are referred to as Pandamatenga, (698 mm year −1), Maun (460 mm year −1), Okwa (407 mm year −1) and Tshane (365 mm year −1). Trends in major vegetative cover and soil components included species types and richness assessments which reflected certain changes southward but also showed interesting degrees of variability. This occurred despite the apparent homogeneity of the Kalahari sands and predominantly semi-arid savanna shrub–woodland vegetation cover. Despite linear decreases, both in rainfall and soil moisture content, results indicated high soil moisture variability at the Okwa location which relates to unique climatic and geological factors. Also many species are unique to specific locations for instance Pandametanga is characterized by Zambesian species while the Maun location is characterized by Colophosphermum mopane. This changes southwards as Acacias become more dominant and significantly co-occur with Grewia flava. While the average total numbers of plants decreased, total numbers of different species varied little from the wetter to the drier end of the moisture gradient. The association between rainfall and woody cover is negative implying that canopy cover extents (in terms of vegetation density) increase along the gradient due to increases in bush encroachment in drier areas. Therefore, while representing a continuum in terms of species numbers, in other respects (e.g. species types and ground cover components) vegetation zones in the Kalahari may be regarded as discontinuous units. Differences between mapped vegetation zones may be accounted for in terms of relatively unique ecosystem factors which function partly in response to geological conditions and partly in response to local (as opposed to regional) climatic factors. This appears to have led to ecosystem adaptive measures (in terms of species responses) rarely mirrored elsewhere along the gradient. Hence adaptability in terms of species migrations in response to relatively rapid climate changes may not readily take place over the Kalahari in Botswana.

Remote sensing: A technology for assessment of sugarcane crop acreage and yield

A study was conducted for identification and acreage estimation of sugarcane crop in KCP Sugar factory zones of Vuyyuru and Lakshmipuram using satellite remote sensing data during cane seasons of 1997 to 2000. The satellite data was analyzed using supervised classification techniques for acreage estimation and Normalized Difference Vegetation Index (NDVI) was employed for condition assessment and yield estimation. The acreage estimation was made possible after 100 days of planting of sugarcane and the cane crop is identifiable on satellite data after April month in the state of Andhra Pradesh. The relationship between yields of sugarcane with NDVI shown a positive correlation with correlation coefficient of 0.84. However, these relationships needs to be developed for each factory-wise in order to represent the local soil, climatic and biotic factors.

Biophysical controls of carbon flows in three successional Douglas-fir stands based on eddy-covariance measurements.

We measured net carbon flux (F(CO2)) and net H2O flux (F(H2O)) by the eddy-covariance method at three Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco)-western hemlock (Tsuga heterophylla (Raf.) Sarg.) sites located in the Wind River Valley of southern Washington State, USA. Stands were approximately 20, 40 and 450 years old and measurements were made between June 15 and October 15 of 1998 in the 40- and 450-year-old stands, and of 1999 in the 20- and 450-year-old stands. Our objectives were to determine if there were differences among the stands in: (1) patterns of daytime F(CO2) during summer and early autumn; (2) empirically modeled relationships between local climatic factors (e.g., light, vapor pressure deficit (VPD), soil water content, temperature and net radiation) and daytime F(CO2); and (3) water-use efficiency (WUE). We used the Landsberg equation, a logarithmic power function and linear regression to model relationships between F(CO2) and physical variables. Overall, given the same irradiance, F(CO2) was 1.0-3.9 mol m-2 s-1 higher (P < 0.0001 for both seasons) at the two young stands than at the old-growth stand. During summer and early autumn, F(CO2) averaged 4.2 and 6.1 mol m-2 s-1 at the 20- and 40-year-old stand, respectively. In contrast, the 450-year-old forest averaged 2.2 and 3.2 mol m-2 s-1 in 1998 and 1999, respectively. Increases in VPD were associated with reduced F(CO2) at all three stands, with the greatest apparent constraints occurring at the old-growth stand. Correlations between F(CO2) and all other environmental variables differed among ecosystems, with soil temperature showing a negative correlation and net radiation showing a positive correlation. In the old-growth stand, WUE was significantly greater (P < 0.0001) in the drier summer of 1998 (2.7 mg g-1) than in 1999 (1.0 mg g-1). Although we did not use replicates in our study, the results indicate that there are large differences in F(CO2) among Douglas-fir stands of different ages growing in the same general area, and that variations in age structure and site conditions need to be considered when scaling flux measurements from individual points to the landscape level.

IMPACT OF THE NORTH ATLANTIC OSCILLATION ON MIDDLE EASTERN CLIMATE AND STREAMFLOW

Interannual to decadal variations in Middle Eastern temperature, precipitationand streamflow reflect the far-field influence of the North Atlantic Oscillation (NAO), a dominant mode of Atlantic sector climate variability. Using a new sea surface temperature (SST) based index of the NAO and availablestreamflow data from five Middle Eastern rivers, we show that the first principal component of December through March streamflow variability reflects changes in the NAO. However, Middle East rivers have two primary flooding periods.The first is rainfall-driven runoff from December through March, regulated on interannual to decadal timescales by the NAO as reflected in local precipitation and temperature.The second period, from April through June, reflects spring snowmelt and contributes in excess of 50% of annual runoff.This period, known locally as the khamsin, displays no significantNAO connections and a less direct relationship with local climatic factors, suggesting that streamflow variability during this period reflects land-cover change, possibly related to agriculture and hydropower generation, and snowmelt.

Statistical analysis of drainage density from digital terrain data

Drainage density ( D d), defined as the total length of channels per unit area, is a fundamental property of natural terrain that reflects local climate, relief, geology, and other factors. Accurate measurement of D d is important for numerous geomorphic and hydrologic applications, yet it is a surprisingly difficult quantity to measure, particularly over large areas. Here, we develop a consistent and efficient method for generating maps of D d using digital terrain data. The method relies on (i) measuring hillslope flow path distance at every unchanneled site within a basin, and (ii) analyzing this field as a random space function. As a consequence, we measure not only its mean (which is half the inverse of the traditional definition of drainage density) but also its variance, higher moments, and spatial correlation structure. This yields a theoretically sound tool for estimating spatial variability of drainage density. Averaging length-to-channel over an appropriate spatial scale also makes it possible to derive continuous maps of D d and its spatial variations. We show that the autocorrelation length scale provides a natural and objective choice for spatial averaging. This mapping technique is applied to a region of highly variable D d in the northern Apennines, Italy. We show that the method is capable of revealing large-scale patterns of variation in D d that are correlated with lithology and relief. The method provides a new and more general way to quantitatively define and measure D d, to test geomorphic models, and to incorporate D d variations into regional-scale hydrologic models.

Morphometric differentiation of the moor frog (Rana arvalis Nilss.) in Central Europe

Morphometric variation of 11 characters was studied in 14 samples of Rana arvalis from allopatric population groups in Central Europe, representing two subspecies formerly recognised: R. a. arvalis and R. a. wolterstorffi. All samples from Poland (nine) were collected from the area, which is believed to be populated by the nominal form. In addition, the isolated population of R. arvalis from the Eastern Carpathians of Romania was classified to that form. All the Hungarian samples fall into the range of R. a. wolterstorffi. No significant differences in body size between sexes and among the populations from the three geographic regions (Poland, Hungary and Romanian Eastern Carpathians) were found. Multivariate analysis of the differences in body shape among groups showed that the populations from Hungary differed from the nominal form mainly in the relative hindlimb length. However, substantial overlap in overall shape differences resulted in a relatively low percentage of correct classifications to the respective geographic groups in the Discriminant Analysis. Large intrapopulation variation in the values of the two ratios (SVL/TL and TL/IMT) formerly used for differentiate the two European subspecies of R. arvalis makes them unreliable characters for distinguishing the two forms. The pattern of morphometric variation does not match the overall genetic divergence of the R. arvalis populations, which suggests that the body shape differences in this species result from the phenotypic plasticity correlated with local climatic factors.

Anjou wine growers perception and valorization of the terroir

&lt;p style="text-align: justify;"&gt;A “terroir” study, based on the “Basic Terroir Unit” concept (B.T.U.), has been realized in the french vineyard of Anjou (Loire Valley). In the characterization of B.T.U.’s natural factors, the geological component (geological stage and lithology) is the first key used to B.T.U. identification. The second affects the soil and its variability. A ground model has been elaborated as suitable to mapping small areas showing a sufficient homogeneous vine behavior. This pattern, based on the soil depth and the weathering intensity of the parent rock, allows to distinguish three main type of environments : “ rock, alteration, alterite”.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;Furthermore, a viticultural survey based on parcels has been carried out and coupled to the characterization and mapping of B.T.U. The data crossing, by an information geographic system (I.G.S.), of these two approaches allowed an analysis of the wine growers empirical perception and valorization of “terroir”.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;The survey has been realized among all wine-growers’ home, in the twelve main viticultural municipalities of the studied area. The different kinds of questions were about to : the socio-economical farm aspects, the vine and its ecophysiological behavior, the viticultural and oenological wine grower practices, the wine grower’s soil empirical knowledge, the climate and the parcel potentiality. Most questions presented three modalities of answers for each variable : “in the average, higher or lower than the average”. Results were treated with two methods : crossing selection and multiple factor analysis. These analysis were realized at two scales : the first one which was the ground model " rock, alteration, alterite " applied in the whole studied area, so called “general ground model” ; and the second one which was the B.T.U. for the both main geological systems : the metagrauwacke of the brioverian period and the green to grey sandstone schist of the ordovician-devonian period. At the first scale, the wine growers have well differentiated the both opposite rock and alterite environments, by climatic (air temperature, frost risk), pedoclimatic (temperature and soil moisture regime) and pedological (soil depth and stone content) criteria. The environment “ alteration ” is less well characterized from the survey but also from the characterization method of natural factors. The vine behavior (bud break earliness, canopy development in the both normal year and dry year) is also influenced, according to the survey, by the environment type. Wine growers have partly integrated these detected differences between parcels on their viticultural (grape variety, number of selection for grape harvesting) and oenological practices (kind of wine, vinification and marketing of wine per parcel, yeast using).&lt;/p&gt;&lt;p style="text-align: justify;"&gt;The analysis at the B.T.U. scale have confirmed the pertinence of the ground model “ rock, alteration, alterite ” on the perception of pedologic and pedoclimatic characteristics and a great influence of the geological system on the local climatic factors and on the vine behavior.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;The coherence of results between these two approaches (survey and integrated characterization) would allow the data acquisition, per survey, about several variables that are not directly collected during the B.T.U. mapping phasis.&lt;/p&gt;

The failure of a slope cut into the weathering profile developed over a porphyritic biotite granite

At about 1.00 a.m. on 24 September, 1981, at km 24.5 of the Kuala Lumpur–Karak highway, there occurred a failure of a 26 m high slope cut into the weathering profile developed over a porphyritic biotite granite. The failure, which is best classified a slump-flow, occurred some 5.7 years after the end of excavation and involved the downslope movement of about 2000 m 3 of weathered bedrock material (mainly gravelly silty sands) and a few coreboulders. Continued movement of failed material through minor slumping and gulleying led to eventual exposure of the failure surface which was mainly located along a relict fault plane striking parallel to, and dipping 48° towards, the highway. Failure occurred as a result of several converging factors; the triggering factor being ground vibrations set up at the time of passing of three large trucks. Conditions of instability, however, were already present in the slope materials through infiltration of rainwater that led to saturation and the loss of apparent or effective cohesion. Infiltration had been encouraged by clearing of vegetation at the top of the cut and the creation of a track along its western edge some 6 months prior to failure. Infiltration was also encouraged by rainfall patterns with the failure occurring after some 29 days with almost continuous daily rainfall; this wet period being preceded by an unusual 27 days of no rain. It is concluded that stability assessments of slope cuts in weathering profiles over granitic bedrock need to take into consideration not only shear strength parameters, but also local climatic and other environmental factors, including likely triggering factors.

OCCURRENCE OF INTERCELLULAR SPACES IN CAMBIAL RAYS KISHORE S. RAJPUT

Large intercellular spaces were found in uniseriate as well as multiseriate cambial rays of Tectona grandis L., Azadirachta indica A. Juss., and Tamarindus indica L. During the period when the cambium is inactive, some of the ray cambial cells became oval to circular, resulting in the development of intercellular spaces. However, the cells were polygonal and compactly arranged during active growth of the cambium. Similarly, such spaces were also noticed in the rays of phloem and xylem. The occurrence of intercellular spaces in cambial rays is correlated with the phenology of trees and local climatic factors, and their possible significance is discussed.

Earthworms as indicators of sustainable production in dryland cropping in southern Australia

Crop-monitoring by farmer groups has been established to identify agronomic and soil factors limiting crop yields and to promote the adoption of sustainable farming practices in South Australia. The use of earthworms as a potential indicator of sustainability has been investigated with a survey of 95 paddocks sown to wheat, barley or peas, within an area of about 3500 km 2. Mean annual rainfall ranged from less than 350 mm to more than 500 mm, and soils varied from coarse sands through lighter loams to heavy clays. The dryland cropping soils in South Australia have been colonized by four immigrant earthworm species, Aporrectodea rosea (Savigny), Aporrectodea trapezoides (Duges), Microscolex dubius (Fletcher) and Microscolex phosphoreus (Duges); populations are generally dominated by A. rosea. Population differences, such as the higher numbers of A. rosea recorded under barley than peas and more juveniles under peas than wheat, and the occasional abundance of other species in some paddocks may be used to indicate changes in soil conditions associated with management. Conservation tillage, retaining plant-residues and reducing cultivation, is being promoted as desirable in developing sustainable farming systems and the inverse relationship between earthworm abundance and intensity of tillage (r = −0.69 ∗∗∗) provides support for earthworms as a potential indicator of sustainability. Earthworm abundance showed a small but significant correlation between earthworm activity and grain yields (r = 0.44 ∗∗∗) and grain protein content (r = 0.52 ∗∗∗). A positive correlation between nitrogen fertilizer levels and earthworm numbers (r = 0.48 ∗∗∗) and biomass (r = 0.43 ∗∗∗) may be related to increased soil organic matter, derived from increased plant growth. The distribution and abundance of earthworms is dependent not only on management related to crop production, but also on local soil and climatic factors. Density and biomass were significantly higher in paddocks with higher annual rainfall and inversely correlated with levels of coarse sand. The soils, crops, climate, management and history of a region of the geographic scale surveyed here is probably too diverse to provide simple relationships between earthworms and plant productivity. It is important to distinguish the broad concept of sustainable productivity on a regional basis from the reality of productivity and sustainability on the spatial and temporal scales of activity of the organisms studied and the production and management processes involved. At an appropriate scale, ecological data on both the species composition and on functional groups within earthworm communities, may be useful indicators of crop production and its sustainability.

Water supply in monsoonal Asia: modelling and predicting small tank storage

Traditionally, small dams (tanks) have been both centres of village settlements and the source of irrigation in Asia. Being solely dependent on local rainfall characteristics and other climatic factors, the water storage behaviour closely follows the rainfall pattern. Carry-over of storage from year to year is rare because of natural evaporation and withdrawals for irrigation. The efficient allocation of storage, within any year, is analogous to the optimization of a time-varying exhaustible resource stock. This study attempts to model water storage of dams using weekly data with a view to intrayear optimization of storage. The behaviour of storage is approximated by a dynamic system driven by rainfall distribution and temperature, and characterized by a linear transfer function model following modification of rainfall to allow for losses. The order of the linear part of the model is identified and parameters estimated for three tanks in Sri Lanka using a recursive estimation procedure. This model can be used for the prediction of storage for a given rainfall scenario. This is demonstrated for past realistic rainfall experiences using stochastic simulation of storage.