Measured Soil Variables Research Articles

The role of soil conditions in fine root ecomorphology in Norway spruce (Picea abies (L.) Karst.)

The present study is an attempt to investigate the pattern of morphological variability of the short roots of Norway spruce (Picea abies (L.) Karst.) growing in different soils. Five root parameters – diameter, length and dry weight of the root tip, root density (dry weight per water-saturated volume) and specific root area (absorbing area of dry weight unit) were studied with respect to 11 soil characteristics using CANOCO RDA analysis. The investigation was conducted in seven study areas in Estonia differing in site quality class and soil type. Ten root samples per study area were collected randomly from the forest floor and from the 20 cm soil surface layer. Eleven soil parameters were included in the study: humus content, specific soil surface area, field capacity, soil bulk density, pH (KCl and H2O dilution's), N and Ca concentrations, Ca/Al and C/N ratios, and the decomposition rate of fine roots (<2 mm dia.). Root morphological characteristics most strongly related to the measured soil characteristics in the different sites were specific root area, root density and diameter of the short roots, the means varying from 29 to 42 m2 kg−1, from 310 to 540 kg m−3 and from 0.26 to 0.32 mm, respectively; root density being most sensitive. The most favourable site and soil types resulting in fine roots with morphological characteristics for optimizing nutrient uptake (e.g. low short root density and high specific root area) were Umbric Luvisol (Oxalis), Dystric Gleysol (Oxalis) and Gleyic Luvisol (Hepatica). These soil types correspond to highly productive natural forest stands of Norway spruce in Estonia. All measured soil variables explained 28% of total variance of the root characteristics. The most important variables related to root morphology were the humus content, field capacity and specific soil surface area.

Methods for Comparing Spatial Variability Patterns of Millet Yield and Soil Data

AbstractThis paper investigates methods to compare spatial patterns of pearl millet [Pennisetum glaucum (L.) R. Br.] yield with spatial patterns of soil variables in a farmer's 1‐ha field on an undulating sand plain in Niger near ICRISAT‐SC. Spatial pattern comparisons are important for precision farming applications. Methods included the correlation coefficient, linear regression, a distance measure to compare separate maps and the cross‐correlation function. Millet grain yield varied from 0 to 2885 kg ha‐1 on 5 by 5 m sub‐plots. Pearl millet yield was correlated with measured soil variables at three different depths, elevation, and crust formation for two successive years. Only 30% of the total variation in millet dry yield was explained by regressing yield against soil variables. Detrended elevation showed a significant negative relation with yield (r = −0.421). The cation‐exchange capacity (CEC) at all the depths showed a significant negative relation with yield (r of −0.238 to −0.290) because crusting and erosion increase with CEC extending to distances up to 30 to 40 m. Pattern comparison using the cross‐correlogram related local hillocks in the area with high yields and local dips with low yields at a distance of 15 to 20 m. From this study, we concluded that the cross‐correlogram was beneficial to compare data at various distances. Yield patterns are best explained by soil variables related to erosion as the major determinign factor in the area.

Vegetation responses along edge-to-interior gradients in a high altitude tropical forest in peninsular India

A study was conducted in a high altitude tropical forest (shola forest) in peninsular India to examine the changes in floristic composition (mainly woody species regeneration) along an edge to interior gradient in relation to changes in edaphic and microenvironmental factors. Species inventory was taken in 25 m 2 plots, established at 10 m intervals along edge to interior transects. The measured soil variables included pH, organic carbon, total nitrogen, available phosphorus, and soil moisture. Microenvironmental factors including light transmittance, relative humidity, and air and soil temperatures also were monitored. Both edaphic and microenvironmental factors exhibited strong patterns along the edge to interior gradient. Forest edges were characterized by higher light transmittance, higher air and soil temperatures, and lower relative humidity. Soil variables including pH, organic carbon, total nitrogen, available phosphorus, and moisture increased toward the forest interior. Significant increases in organic carbon (53.9%), total nitrogen (47%), and soil moisture (55%) indicated a relatively fertile forest interior compared with the forest edge. A definite floristic compositional pattern also was observed along the edge to interior gradient which was correlated to the edaphic and microenvironmental variables as revealed by canonical correspondence analysis. It appears that edge effects in these high altitude forests penetrate to a distance of 15–30 m. Further, edaphic factors have an important influence on woody species regeneration, perhaps much more than microenvironmental factors. This indicates that any disturbance that significantly exposes theforest floor, thus lowering soil moisture and altering soil nutrient status, can adversely affect the regeneration of many of the shola species.

Herbaceous Layer and Soil Response to Experimental Acidification in a Central Appalachian Hardwood Forest

AbstractThe herbaceous layer (vascular plants ≤1 in in height) is an important component of forest ecosystems and a potentially sensitive vegetation stratum in response to acid deposition. This study tested several hypotheses concerning soil and herbaceous layer response to experimental acidification at the Fernow Experimental Forest in north‐central West Virginia. Fifteen circular sample plots (0.04 ha) were established in each of three watersheds: WS3 (an ≈ 20‐yr‐old watershed receiving acidification treatment with (NH4)2SO4), WS4 (&gt;80‐yr‐old control), and WS7 (≈ 20‐yr‐old control). The herb layer was sampled intensively in 10 1‐m2 subplots within each sample plot, including determination of species composition, cover, and random biomass harvests. Harvested plant material was separated by species and analyzed for macronutrients, micronutrients, and Al. Soft was sampled from harvest subplots and analyzed for texture, pH, organic matter, and macro‐ and micronutrients. Few differences among watersheds for virtually all measured soil variables indicated minimal response of soil fertility to the acidification treatment. The herbaceous layer was also quite similar among watersheds with respect to cover‐biomass and species diversity; WS7, however, had ≈ 70% higher herb layer cover that both Ws3 and WS4, a result of the predominance of a few high‐cover fern species and attributable to the north‐facing aspect of WS7 vs. south‐facing aspects of WS3/WS4. There was a high degree of species similarity among watersheds, suggesting no shift in species composition in response to acidification. There was also minimal response of element concentrations to acidification, although Fe and Al exhibited evidence of increased uptake in WS3. We conclude that, contrary to our expectations, there has been little substantive response of the soil and herb layer to acidification, but hypothesize that herbaceous layer species may experience toxicity problems with increased mobility of Al and micronutrients in the future.

Habitat factors influencing the distribution ofCymbopogon validusin Mkambati game reserve, Transkei

Abstract The factors influencing the distribution of Cymbopogon validus in Mkambati Game Reserve were investigated using multivariate techniques. C. validus was found to be present on nutrient‐rich, clay soils and absent from dystrophic, sandy soils. This could account for the patchy distribution of C. validus in the reserve and may limit its expansion into the surrounding grasslands. There was no correlation between measured soil variables and the density and size of C. validus plants within C. validus sites.

The effects of fire on the soil in a degraded semi-arid woodland .III. Nutrient pool sizes, biological activity and herbage response

The effect of experimental fire regimes on soil nutrient pool values, surface condition status and herbage growth was studied in a shrub-invaded woodland on massive red earths near Coolabah, New South Wales. Artificial fuel was burnt in spring on plots to achieve intervals of 1, 2, 3, 4, 5 and 10 years between fires. No differences between fire regimes were detected below 1 cm for any of the measured soil variables. Soil respiration declined linearly with increasing number of fires and increasing total fuel load. There were no differences or trend for available or total soil nitrogen, organic carbon or soil wettability in the 0-1 cm horizon, but relatively refractory elements such as P and K, derived from the ash from the artificial fuel, built up in the soil proportionately with increased fire number and total fuel load. The surface condition status of the soil as assessed by a monitoring method was strongly inversely related to the number of fires and total fuel load. Differences in herbage growth between fire treatments were not significant; however, where plots had been burnt five times, herbage growth was greater with increased variability (35.8 g me2, s.e. 19.0) compared with unburnt controls (10.7 g m-2, s.e. 1.7). Plots burnt seven times annually had similar means and variance to controls. Low herbage yields in control plots were attributed to the high biomass of mature shrubs, whilst increasing variability with number of fires was caused by the combination of patchy decreased shrub biomass and small-scale erosion-deposition cells which differentially distribute seeds across the soil surface. Plots burnt annually seven times had deposition beyond the plot area.

Effect of nitrogen and phosphorus fertilizers on the seed yield and oil concentration of oilseed rape (Brassica napus L.) and the prediction of responses by soil tests and past paddock use

The response of oilseed rape to applied nitrogen and phosphorus was investigated in 2 areas of the South East of South Australia. The nitrogen rates applied varied from 0 to 50 kg/ha, while phosphorus rates applied in the Mundulla area ranged from 0 to 20 kg/ha and 0 to 34 kg/ha in the Millicent area. At 9 sites in the Mundulla area, where soils were primarily sandy loam over clay, oilseed rape yields were increased significantly by applied nitrogen at 7 sites and by applied phosphorus at 2 sites. On heavy black clay and peat soils in the Millicent area, oilseed rape yields were increased significantly by applied nitrogen at 5 of the 12 sites and by applied phosphorus at 6 sites. Of the measured soil variables, anaerobic ammonium nitrogen measured in the top 10 cm best predicted responses in seed yield to applied nitrogen. The critical nutrient range was 45-65 mg/kg. The response of oilseed rape to applied nitrogen was highly correlated with past paddock use but varied between the 2 areas. From the prediction equations developed, it was concluded that, in the Mundulla area, a significant (P&lt; 0.05) nitrogen response was likely if the oilseed rape followed 2 or more crops, the last a non-legume, but was unlikely if the oilseed rape followed 1 or more years of pasture. At Millicent, a nitrogen response was likely if the oilseed rape was grown as the sixth crop in a continuous cropping program, and was unlikely if it was the first or second crop in the rotation, provided the preceding crop was a non-legume. The response of oilseed rape to applied phosphorus was highly correlated to extractable soil phosphorus measured in the top 10 cm (Colwell). The critical nutrient range was 20-25 mg/kg for the sandy loam soils at Mundulla and 40-50 mg/kg for the black clay and peat soils at Millicent. Nitrogen applications significantly increased seed oil content at 6 sites, significantly decreased it at 2 sites and had no effect at 13 sites. Phosphorus significantly increased seed oil content at only 1 site, significantly decreased it at 3 sites, and had no effect at the other 17 sites.