Comparison of Botanical Composition, Soil Carbon Content, and Root Distribution of Subirrigated Meadows in The Nebraska Sandhills

Characterizing vegetation composition, carbon/nitrogen (C/N) content of soils, and root-mass distribution is critical to understanding carbon sequestration potential of subirrigated meadows in the Nebraska Sandhills. Five subirrigated meadows dominated by cool-season (C3) graminoids and five meadows dominated by warm-season (C4) grasses were selected throughout the Nebraska Sandhills. Vegetation, soil carbon and nitrogen, and root-mass density distribution were sampled in each meadow. Meadows dominated by C3 vegetation had 12% greater (P < 0.1) yields than meadows dominated by C4 vegetation. Total root-mass density was 30% greater (P < 0.1) in C4-dominated meadows than C3-dominated meadows. Total carbon and nitrogen content was 65% and 53% greater (P < 0.1), respectively, in the A horizon of C3-dominated meadows, but was 43% and 52% greater (P < 0.1), respectively, in the C horizon of C4-dominated meadows. Although meadows dominated by C3 vegetation had more carbon in the soil profile, much of the carbon in C3-dominated meadows appeared to be recalcitrant C4 carbon from historic vegetation.

Distribution of Dioecious Eastern Red Cedar (Juniperus virginiana) along an Environmental Gradient in Ogallala, NE.

Abstract The purpose of this research was to study the sex distribution and energy allocation of dioecious Eastern Red Cedars (Juniperus virginiana) along an environmental resource gradient. The trees surveyed were growing in a canyon located at the University of Nebraska’s Cedar Point Biological Research Station in Ogallala, Nebraska. Due to the geography of this canyon, environmental factors necessary for plant growth should vary depending on the tree’s location within the canyon. These factors include water availability, sun exposure, ground slope, and soil nitrogen content, all of which are necessary for carbon acquisition. Juniperus virginiana is a dioecious conifer. Dioecious plants maintain male and female reproductive structures on separate individuals. Therefore, proximal spatial location is essential for pollination and successful reproduction. Typically female reproductive structures are more costly and require a greater investment of carbon and nitrogen. For this reason, growth, survival and successful reproduction are more likely to be limited by environmental resources for females than for male individuals. If this is true for Juniperus virginiana, females should be located in more nutrient and water rich areas than males. This also assumes that females can not be reproductively successful in areas of poor environmental quality. Therefore, reproductive males should be more likely to inhabit environments with relatively lower resource availability than females. Whether the environment affects sexual determination or just limits survival of different sexes is still relatively unknown. In order to view distribution trends along the environmental gradient, the position of the tree in the canyon transect was compared to its sex. Any trend in sex should correspond with varying environmental factors in the canyon, ie: sunlight availability, aspect, and ground slope. The individuals’ allocation to growth and reproduction was quantified first by comparing trunk diameter at six inches above ground to sex and location of the tree. The feature of energy allocation was further substantiated by comparing carbon and nitrogen content in tree leaf tissue and soil to location and sex of each individual. Carbon and nitrogen in soil indicate essential nutrient availability to the individual, while C and N in leaf tissue indicate nutrient limitation experienced by the tree. At the conclusion of this experiment, there is modest support that survival and fecundity of females demands environments relatively richer in nutrients, than needed by males to survive and be reproductively active. Side of the canyon appeared to have an influence on diameter of trees, frequency of sex and carbon and nitrogen leaf content. While this information indicated possible trends in the relation of sex to nutrient availability, most of the environmental variables presumed responsible for the sex distribution bias differed minutely and may not have been biologically significant to tree growth.

EC31-133 The Management of Nebraska Soils (Revised March 1936)

The agricultural lands of this country are its greatest natural resource. History points out that nations with vast areas of good farm land are most likely to prosper and survive over long periods of time. Local communities, too, prosper and flourish in proportion to the productiveness of the surrounding land. Schools, social life, and business develop best in areas where the land is productive and properly managed and conserved. Nebraska, in common with other states, has suffered by the depletion of soil fertility. The reduction in acres in legumes and grasses, and the deplation of the organic matter in the surface soils, has likewise had its effect on the run-off of precipitation, soil blowing, and damage from drouth. In order to know what elements of fertility may become deficient and how soil fertility may be restored and maintained, we should understand the composition, character, and management of soils. In the following pages, some fundamentals of soil feritlity are given, followed later by a discussion of practical soil-management practices.