MauiNet and Environmental Diversity
Of Haleakala, Maui, Hawaii

H. Ikawa, G. Uehara, H. H. Sato, and C. E. Conrad
October, 2006

This webpage describes the MauiNet and some of the environmental diversity of Haleakala. Preliminary results of some of the activities of MauiNet are also presented here and publications associated with the different projects are included in the sections on Literature Cited and Literature Others. Succeeding webpages will fully describe the results of the activities of MauiNet.

Figure 1. Maui map with weather station sites of MauiNet.

Briefly, Haleakala is one of two mountain volcanoes on the island of Maui in the Hawaiian Islands. Rising 3,055 m (10,023 feet) above sea level, it is located on East Maui which is connected by a isthmus to West Maui, the second volcano (Figure 1).

MauiNet is a coined word representing an area of diverse agroenvironments on the northwest and west-facing slopes of Haleakala. It is an area where various studies were conducted by individuals of the College of Tropical Agriculture and Human Resources (CTAHR), University of Hawaii, and cooperators of Soil Conservation Service (now Natural Resouces and Conservation Service), USDA, and Forest Service, USDA. These studies occupied an area from Kihei near sea level eastward about 20 km (12 miles) to Puu Pahu on the slope of Haleakala at an elevation of 1650 m (5413 feet) and then from this elevation about 20 km (12 miles) northward to Haiku at the lower elevation.

Figures 2 and 3 are two images relating to Haleakala.

Figure 2. View of MauiNet from low elevation to west-facing mid-slope of Haleakala.


Figure 3. Cinder cones in Haleakala crater at summit.

Britten (1962) described Hawaii as a natural laboratory to study climate and plant response because of its diverse climatic zones. In his study of the growth and reproduction of white clover (Trifolium repens) on the west-facing slope of Haleakala, he measured temperatures at elevations of 1067 m (3500 ft.), 1524 m (5000 ft.), and 2134 m (7000 ft.). Air temperature decreased with elevation, with soil temperature having a similar pattern. The mean winter and summer air temperatures at the three elevations, as estimated from charts shown by Britten in his publication, are presented in Figure 4.

Figure 4. Estimated mean winter and summer air temperatures along western Haleakala.

The air and soil temperature relationships were as follows. At elevation of 670 m (2198 ft), the soil maxima were higher than the air maxima during the summer but lower in the winter. The soil minima, on the other hand, were consistently higher than air minima. At elevation of 1670 m (5479 ft), both air and soil temperatures were very similar, but the soil minima were again consistently higher than air minima. At elevation of 2340 m (7677 ft), soil temperatures were also higher than air temperatures, but the maxima-minima range was greater than at lower elevations. Emphasis was made on the importance of maxima-minima temperatures in diurnal and seasonal fluctuations for plant growth. Rainfall trends were also discussed by Britten (1962).

In 1982, five automatic-recording weather stations (CR-21), product of Campbell Scientific, Inc., of Logan, Utah, were installed in Kula and nearby areas on Maui by the Departments of Entomology, Horticulture, and Plant Pathology, College of Tropical and Human Resources (CTAHR), University of Hawaii. The purpose of this study, an integrated pest management project (HITAHR Project 939G), was to investigate the effect of weather on the occurrence and distribution of the various diseases and pests in the vegetable-producing areas of Maui. HITAHR is an acronym for Hawaii Institute of Tropical Agriculture and Human Resources.

Then, in 1983, and over a period of two years, in consultation with the University's Meteorology Department, 18 similar weather stations were installed by the Department of Agronomy and Soil Science . The instruments were programmed to collect data such as air and soil temperatures, solar radiation, relative humidity, soil moisture, and in some cases, wind speed and wind direction. Four of the total of 23 stations, however, were eventually discontinued because of malfunctions. A summary of the weather data, in particular, temperature and rainfall, will be presented in a later webpage. The location and brief description of the original 23 weather stations are listed in Table 1.

The soils of the station sites were also examined in cooperation with the Soil Conservation Service (now Natural Resources and Conservation Service), USDA. Representative soil profiles of 10 soil series were further described and collected by the USDA soil scientists for laboratory characterization at the National Soil Survey Laboratory, in Lincoln, Nebraska. The results of the soils studies are reported by the Soil Conservation Service, USDA, in cooperation with HITAHR, Univ. of Hawaii at Manoa (1984). Three other soil series were also described and these profile samples were characterized in the laboratory of Department of Agronomy and Soil Science, CTAHR, University of Hawaii.

The MauiNet studies included projects relating to soil-climate (HITAHR Project 197G), pineapple (HITAHR Project 103G), sugarcane (HITAHR Project 104G), and the NifTAL and IBSNAT projects (195 and 196S, respectively). NifTAL is an acronym for Nitrogen Fixing Tropical Agricultural Legume, while IBSNAT stands for International Benchmark Sites Network for Agrotechnology Transfer. The studies also included another project, which commenced in 1992, relating to the influence of climate and soil on the growth of three tree species (HITAHR Project 116).

The purpose of the soil-climate project was to test the soil-climate criteria of Soil Taxonomy and to determine the performance characteristics of the crop, pasture and forest lands on the northwest and west-facing slopes of Haleakala Mountain on Maui with different agroecological zones. Soil Taxonomy is the United States' system of soil classification and carries information on various soil properties including soil moisture and soil temperature in the various taxa.

The objective of the pineapple project was to study the effect of climate and location on the physiology and growth of pineapple at three different elevations, while that of the sugarcane project was to study the effect of not only climate but also irrigation water and nitrogen on the growth of sugarcane.

One of the objectives of the NifTAL Project was to study the behavior of Rhizobia in the different agroecological zones on Maui, while that of the IBSNAT Project was to collect the minimum soil and weather data to develop crop production models such as those for maize, soybeans, rice, and taro at three different sites.

The purpose of the climate-soil-tree species study was to examine the effect of climate and soil factors on the growth and survival of Hawaiian koa (Acacia koa), loblolly pine (Pinus taeda), and Caribbean pine (Pinus caribaea).

Figures and Images

The images showing the base maps of Maui as well as the various shapefiles of roads, rainfall isohyets, and solar radiation were downloaded from the Statewide Geographic Information System, Office of Planning, State of Hawaii. The image of the soil order map was obtained from the Natural Resources Conservation Service, USDA, Honolulu. ArcGIS 9 software of ESRI (Redlands, CA) was then used to combine the various layers to create the figures in this website.

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