An ecological land survey (ELS) of Fort Richardson land was conducted to map ecosystems at three spatial scales to aid in the management of natural resources. In an ELS, an attempt is made to view landscapes not just as aggregations of separate biological and earth resources, but as ecological systems with functionally related parts that can provide a consistent conceptual framework for ecological applications. Field surveys at 132 plots along 16 toposequences and at 99 other plots were used to identify relationships among physiography, geomorphology, soils, hydrology, and vegetation. The relationships revealed that the various ecosystem components were closely related to fire effects and geomorphic processes, such as floodplain development, landslide and slope instability, and coastal flooding. Associations among vegetation structures and geomorphic units were used to identify 51 ecotypes (local-scale ecosystems) that were effective at differentiating dominant species and plant associations. Ecosystem maps were developed at three spatial scales. Forty-six ecotypes (1:20,000 scale), How to get copies of ERDC technical publications:

Long-term tillage and crop residue management in the subarctic: fluxes of methane and nitrous oxide. Can. J. Soil Sci. 77: 565-570. Methane and nitrous oxide are important radiatively active gases that are influenced by agricultural practices. This study assesses long-term tillage, crop residue management, and N fertilization rates on the flux of these two gases at a high latitude site representing the northern fringe of large-scale agriculture. Cumulative methane uptake for the summer was higher from no-tillage plots than tilled plots. This was associated with lower soil water contents with tillage. Thus, the reduction in CH 4 uptake was attributed to water stress on methane oxidizers. At planting, soil water contents were near field capacity, and the no-till plots had the lowest uptake which was attributed to restricted diffusion of methane to active sites. A similar pattern of methane uptake to soil water content was found with the residue management treatments. Removing the straw lowered the soil water content and for most of the season methane uptake was also lower than where the straw had been left on the plots. Nitrogen fertilizer rate had little effect on methane uptake over the summer, but high N rates lowered consumption during the time of active nitrification early in the season. This corresponded to the time of maximum efflux of nitrous oxide. Nitrous oxide efflux was greatest at the high N rate where straw was retained on the plots. L'absorption cumulative de méthane durant l'été était plus abondante à partir des parcelles en régime de culture sans travail du sol que dans celles travaillées selon les méthodes classiques. Cette plus forte absorption était associée à l'abaissement de la teneur en eau du sol par les façons culturales répétées. Ainsi la moins forte absorption de CH 4 en régime de travail classique était attribuée au stress hydrique exercé sur les oxydants du méthane. Aux semailles, époque où la teneur en eau du sol est presque à la capacité au champ, ce sont les parcelles conduites en culture sans labour qui manifestaient la plus faible absorption, ce qui s'expliquait par une diffusion réduite du méthane vers les sites d'activité. Un rapport similaire de l'absorption du méthane avec la teneur en eau du sol était observé dans les traitements de gestion des restes de culture. L'enlèvement de la paille provoquait l'abaissement de la teneur en eau du sol, et pour la plus grande partie de la saison, l'absorption du méthane était elle aussi plus faible que là où la paille était laissée sur place. La dose de fumure N n'avait que peu d'effet sur l'absorption du méthane pour la totalité de l'été, mais la dose supérieure causait une réduction de la consommation de méthane dans la phase de nitrification active du début de la saison de végétation, qui coïncidait avec celle d'efflux maximum d'oxyde nitreux. L'efflux de N 2 O était particulièrement abondant à la dose supérieure de fumure N lorsque la paille était laissée sur place.

There are conflicting reports on the amount of N transferred from legumes to intercropped nonlegumes and on the need for N fertilizer to obtain high total dry matter yields on soil with low N availability. This study evaluates (i) the ability of fababean (Vicia faba L.) to meet its N requirements from biological N2 fixation: (ii) the amount of N transferred to intercropped oat (Avena sativa L.); and (iii) N fertilizer management to maximize dry matter production and N2 fixation in a cold soil. A randomized complete block experimental design with four replications was used with two rows of fababean alternating with two rows of oat. Urea was applied in bands between fababean or oat rows at 90 kg N ha−1 to get the following treatments: (i) oat with added N (+N), fababean +N, inoculated with Rhizobium leguminosarum bv. viceae (+I); (ii) oat +N, fababean without added N, inoculated (−N, +I); (iii) oat −N, fababean −N,+I; (iv) oat −N, fababean +N,−I; and (v) oat −N, fababean −N, + I. A second study compared uptake of 15N‐depleted fertilizer by oat and fababean, where the fertilizer was broadcast over the plot or band‐applied between rows of oat and fababean planted in alternate rows. Less than 1% of the uninoculated fababean plants nodulated in either experiment; thus, they were a good check for estimating N2 fixation using the difference method. Nitrogen fertilizer increased dry matter production of fababean in some years, but did not increase N uptake. There was little evidence of N transfer from fababean to oat. Oat depended on N fertilizer for maximum dry matter production 3 of the 4 yr. Maximum total dry matter production was achieved by fertilizing the oat and not the fababean in 3 of the 4 yr. The amount of N2 fixed by fababean averaged 50 kg N ha−1. Fababean plants obtained >50% of their N from broadcast urea, but <10% when urea was banded between oat and fababean rows. Configuring a commercial drill to band fertilizer between pairs of oat rows alternating with fababean is a practical way to maximize both N2 fixation and total dry matter production.

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Banding all fertilizer near the seed at planting saves time and often increases nutrient uptake and yields of small grains, but adds to the cost of the drill. Some growers have successfully banded all of the fertilizer with barley (Hordeum vulgare L.) in cold soils. This study compares banding 100, 66, 34, and 0% of the fertilizer with the seed and placing the remainder in a deep band between rows and broadcasting all fertilizer. Fertilizer rates were 90, 20, 37, and 18 kg ha−1 of N, P, K, and S, respectively; urea was the N source. Both tilled and no‐till treatments were included on a Volkmar silt loam (coarsesilty over sandy or sandy‐skeletal, mixed Aquic Cryochrept) at Delta Junction, AK. Banding 100% of the fertilizer with the seed in field studies reduced emergence 2 of 3 yr for both tillage treatments, but did not affect nutrient uptake or yields. Nitrogen uptake and grain yields were reduced by broadcasting the fertilizer in no‐till but was not affected in the tilled treatments. Seedling injury from urea applied with barley seed at soil temperatures of 5, 15, and 25 °C was evaluated in root‐zone temperature chambers using Tanana silt loam (loamy, mixed, nonacid Pergelic Cryaquept). These studies confirmed that percentage of emergence increased with reduced soil temperature when urea was placed with the seed, but that emergence rate was delayed at all temperatures. This indicates that the risk of injury from banding urea with the seed is less in cold soil than in warm soil, but there is still danger of injury to the crop.