Land Response Units offer a means of grouping broad areas of land that have similar capabilities to produce biomass, and have similar sensitivities to man's uses. The capability of the land to produce flora and fauna is estimated by evaluating the soil ecofactors that sustain the environment, i.e., moisture, temperature, and nutrients. Moisture and temperature factors can be evaluated by classifying the soils using the Soil Taxonomy of the National Cooperative Soil Survey. Soil moisture regimes indicate plant available moisture, and soil temperature regimes indicate temperature conditions for plant growth. Nutrient regimes can be estimated by evaluating soil depth, color, texture, and pH. Sensitivity to man's uses is estimated by evaluating the erosion hazard, runoff potential, and slope gradient of the land. These three factors are used to estimate the ability of the land to accept man's activities without serious loss of productivity or stability. The Land Response Unit concept is adaptable for use on intensively managed agricultural lands as well as less intensively managed lands.

Ascospores of Neurospora tetrasperma germinated on topsoils of forest but not agricultural Hydrol Humic Latosols (Hydrendept). All the agricultural and some of the forest subsoils were inhibitory to spore germination. There was no correlation between pH or organic matter content and spore germination on soils. Results showed that all the major plant species in the forest accumulated a higher concentration of Al from soil than the sugar cane on the agricultural land. The biomass of the total forest plants also was much greater than that of the sugar cane. It is postulated, therefore, that effective accumulation of free Al ion from soil by forest plants results in decrease of fungitoxicity in forest soils.

At two sites on the front (oceanside), top, and back of the foredune, measurements were made of salt spray deposition and the quantity of cations (K, Na, Ca, and Mg) present on the surface and 20, 40, and 60 cm below the surface of the soil. Cationic inputs in salt spray were calculated by partitioning the cation content of bulk precipitation collected on the back of the fore dunes into salt spray and rainfall components. The biomass and cationic content of the dominant grasses and forbs were determined in all three zones from a combination of field measurements and estimates of the standing crop and from samples of each dominant species analyzed for their cationic content. On the average 55%, 34%, and 11% of the salt spray deposited on a foredune falls on the front, top, and back respectively. In all three zones Na (250—1,300 kg/ha°yr) was the most abundant cation input in the salt spray. It is followed by Mg (37—120 kg/ha°yr), Ca (19—120 kg/ha°yr), and Kg (13—77 kg/ha°yr). In rainfall, the annual input of cations was calculated to be 1.3, 26, 2.3 and 3.9 at Bodie Island and 1.0, 21, 3.4, and 3.0 kg/ha°yr at Ocracoke for K, Na, Ca, and Mg respectively. It appears that the total annual input of cations exceeds slightly their calculated annual outputs through leaching for all cations in all zones. Subsurface cation levels were very low: K (2—5 kg/ha), Na (17—88 kg/ha), Ca (5—17 kg/ha), and Mg (2—9 kg/ha). Estimates of the total standing crop of cations in the vegetation of a zone and inputs of cations in salt spray and rainfall indicate that the annual inputs of Na and Mg exceed their standing crops, while the annual input of K, and sometimes Ca, is smaller than its standing crop on the back.