Weekly water-loss from Spherical Water-loss lntegrators on a Clearing and below Secondary Growth 1 n Central Amazonia < * )

Spherical ceramic bulbs were set up as weeklj water-loss integrators on a clearing and below a 2 year-old Cecropia-commumty at Km 18 of the ManausItacoatiara Road. The mstruments worked well in distinguishing the particular responses of individual sites to the impact of atmospheric agents as s0\a1 radiation, air temperature, air humidity and wind. Water-loss was primarily dependent on the order ot magnitude of the weekly total of solar ediation und the presence or lack of a standL"'lg crop. Already a scarce secondary growth will reduce the weekly amount of water lost to the atmosphere considerably. Shelter-wood, however, considering the crop specific demands 1f introduced to tropical agriculture would provide favourable conditicns as far as the impact of atmospheric controls on the tropical environment are concernecL

Spherical ceramic bulbs were set up as weeklj water-loss integrators on a clearing an d below a 2 year-old Cecropia-commumty at Km 18 of the Manaus-Itacoatiara Road.The mstruments worked well in distinguishing the particular responses of individual sites to the impact of atmospheric agents as s0\a1 radiation, air temperature, air humidity and wind.Water-loss was primarily dependent on the order ot magnitude of the weekly total of solar ediation und the presence or lack of a standL"'lg crop.
Already a scarce secondary growth will reduce the weekly amount of water lost to the atmosphere considerably.Shelter-wood, however, considering the crop specific demands 1f introduced to tropical agriculture would provide favourable conditicns as far as the impact of atmospheric controls on the tropical environment are concernecL !NTRODUCTION : lhe water-loss from spherical porous ceramic is a useful means to estimate the efficiency of integrated environmental contrais as solar radiation , air temperature, air humidity.wind , etc. at a particular site.lhe data obtained, however, do not represent an accurate information on the evaporation and transpiration r ates of an individual surface o r tissue.But, these data indicate a characteristic response of a specific environment to the impact of its cuntrols.Especially in remo te areas away from routine weather stations.the spheri• cal water-loss i ntegrator renders a tentative ecological approach to anunknown environment.lhe spherical water-loss int egrators were set up in groups of two at a clearing and under cover of a 2 year-old secondary growth at Km 18 of the Manaus-ltacoatiara Road (fig.1).
The spherica l bulbs manufactured of pure white clay and burnt at about 800 oc. were set up on the slight slope of a 3 year old clearing about 40 em above the ground.While bulb 1 and bulb 2 were fully exposed to the atmospheric agents on the uncovered white sands.bulb 3 and bulb 4 were protected by a dense cover of Cecropia-commurities (Brinkmann and Góes Ribeiro, 1971).Bulb 2 and bulb 4 were exposed at mid-slope, while bulb 1 and bu lb 3 were set up at hill-top.The soils of the experimental site were poor white sands, typical for slash and burn agriculture experiments along the Road AM-10.The cleared plots are used tor the growing of maniok and pineapples but have to be abandoned after a couple of years as available plant nutrients are leached and crops suffer from serious nutrient deficiency.These particular soi ls were described by IPEAN (1969) .
The spherical water-loss i n te g r a to r s (volume about 1200 ml) were refilled with destilled water in weekly intervals.To avoid the development and spreading of colonies of fungi and bacteria in the pore-system of the bulbs, the water was blended with a strong fungicide.The surface of the bulbs, however.was brushed thoroughly every week before resetting of the instruments.
Although the ceramic bulbs did not have 6xactly the same size and volume, a laboratory test proved the fact, that water-loss over a prefixed period of hours was nearly the same for ali bulbs involved.Th e experiment was undertaken under controlled conditions for air temperature, ai r humidity and wind _ Under field conditions, however.water-loss was

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affected by the instantanuously available watet content and pressure in the bulbs exposed to the impact of solar radiation, i_ e. water-loss was not the same, when the bulbs were exposed to an equivalent impact of atmospheric contrais in the beginning or in the end of the weekly period of measurements.
Therefore, the identification of a varied environment was subject to water-loss measurements in volume %. week• 1 • As evaporation is widely controlled by solar radiation , the water-loss of the spherica l ceramic bulbs was related to the weekly total of solar radiation (cal.cm• 2 • week• 1 ) incident on the spherical surface of a Bellani radiation integrator (fig 2).

R.ESULTS AND DISCUSSION :
The spherical water-loss integrators recorded characteristic variations among each other as far as exposure to solar radiation was concerned.Away from the two significantly distinguished exposure types, i. e. the two groups  2).
The spherical ceramic bulbs set up on the clearing (bulb 1 and bulb 2) rendered the exspected departure in weekly water-loss at the top of the hill and at mid-slope, mainly 1n consequence of variat10ns in the duration of daity solar radiation.The incident solar radi• ation lasted at about 40 to 50 minutes a day longer at the hill-top, prevailing in the late afternoon.This had a considerable effect o the water-loss of the bulbs, because of longet the lasting maximum impact of integrateo atmospheric agents on bulb 1 ( tab. 1, fig .2) .
Obviously e similar relationship was observed for the couple of water-loss integrators set up below a 2 year-old Cecropia-community.fhe calculation of the ratios bulb 1 I bu lb 2 and bulb 3/ bulb 4 based on the average weekly water-loss (%) over the period o f measurements redered 1 .2 and 1 .3, respectively.i. e. the depanure of the water-loss according to exposure occured simultanuously and was not contl'{)lled by the vegetation cover present at the experimental site.
The water-loss of the spherical ceramic bulbs exposed to full impact of atmospheric agents (bulb 1 and bulb 2) was considerably higher than that of those bulbs (bulb 3 and bulb 4) partly protected by the cover of a 2 year-old secondary growth (tab.1, fig. 2) .
The spherical water-loss integrators set up below the secondary growth were exposed to only a fraction of the weekly total of incident solar radiation.Although the shade-etfect on the bulbs was heavy, the about 3 m high Cecropia-community allowed the penetration of solar radiation through the canopy for at least some hours a day dependent on t he angle of inci• dence and overcast.An important factor in controlling the water-loss of the ceramic bulbs was the vapor pressure defic1t in the near soil surface atmosphere.Relative a ir humidity at the experimental site was always at 100% at night, independent of exposure .But, during daytime the vapor pressure deficit was de• penoent mainly on direct solar radiation, i. e .with sun behind clouds, air humidity increased rapid1y below the secondary growth, likewis ~. but less pronou nced at the clearing.After rainfall, however, air humidity decreased rapidl ; at the clearing exposed to direct solar radiation, while it decreased only with a great time dalay below the Cecropia-community.Both events contribute considerably to the significantly great departure in water-loss of clearing exposed and secondary growth protected ceramic bulbs (fig.2) .
At the experimental site the distance between water-loss integrators set up on the clearing and those below the cover of the secondary growth was less than 30 meters.Collected data (tab.1, fig. 2) point out, that significant variations in water-loss occured at verk short distances, rendered by different solar radiation efficiency, obviously moderated by the standing crop.

CONCL USIONS :
The obtained water-loss data from the spherical ceramic bulbs exposed on the clearing and below a 2 year-old Cecropiacommunity at the experimental site are striking evidence of the usefulness of the set up instruments with regard to an evaluation ot the impact of atmospheric agents on the tropical environment.The sensitivity of the water-loss integrators was sufficiently high to distinguish already small differences in ex posure and vegetation cover over very short distances, when measured in weekly intervals .The spherical ceramic bulbs are a means that enables a tentative approach to sites where routine weather observations are lacking and the setting up of sophisticated microclimatic facilities is too expensive to be undertaken .The water-loss integrators, however, are not suitable for hourly or daily records because of their inefficiency to achieve short period responses to weather.The sphericai ceramic bulb method fails in the measurement of pl::tni: responses to the action of environmen~al contrais, but supplies favourable informations as far as the impact of atmospheric agents cn small ecological units is concerned.
The water-loss integrators open at least a route, to measure the response of the natural or man-made tropical environment to clim~tic quantíties in time and space.Obtained data also prove the tact, that a pre-determined shelter-wood system, evaluated for every particular crop, will provide tropical agricultura with a considerable benefit as f•ar as the impact ot environmental contrais as solar radiation, a ir humidity, a ir temperature and wind on crops is concerned.
ali 5 graphs were recorded coin~í• dently an obvious signal for a close correlation of the weekly total of solar radiation and t~.e accum ulative weekly water-loss."ihe presencu of vegetation or the exposure ot the bulbs on a clearing determined the amount of water lost to the atmosphere, but did not affect the seasonal distribution of the observed data (fig . ...... FIGURE I -Weekly totais of incident solar radialion (cal.cm-2.week•' ) and weekly water-los~ (volume%_ week-1) of 4 water-loss integrators (spherical ccramic bulbs) set up on a c learing and under cover of a Cccropia-community.

TABLE 1 -
Average water-loss (volume %) of spherical ccramic bulbs set up on a clearing and below sccondary growth at Km 18 of tbe Manaus-Itacoaliara Road (AM-10).