Relatively little is known about soil organic carbon (SOC) dynamics in montane ecosystems of the semi-arid western U.S. or the stability of current SOC pools under future climate change scenarios. We measured the distribution and quality of SOC in a mosaic of rangeland-forest vegetation types that occurs under similar climatic conditions on non-calcareous soils at Utah State University's T.W. Daniel Experimental Forest in northern Utah: the forest types were aspen [Populus tremuloides] and conifer (mixture of fir [Abies lasiocarpa] and spruce [Picea engelmannii]); the rangeland types were sagebrush steppe [Artemisia tridentata], grass-forb meadow, and a meadow-conifer ecotone. Total SOC was calculated from OC concentrations, estimates of bulk density by texture and rock-free soil volume in five pedons. The SOC quality was expressed in terms of leaching potential and decomposability. Amount and aromaticity of water-soluble organic carbon (DOC) was determined by water extraction and specific ultra violet absorbance at 254 nm (SUVA) of leached DOC. Decomposability of SOC and DOC was derived from laboratory incubation of soil samples and water extracts, respectively.
Although there was little difference in total SOC between soils sampled under different vegetation types, vertical distribution, and quality of SOC appeared to be influenced by vegetation. Forest soils had a distinct O horizon and higher SOC concentration in near-surface mineral horizons that declined sharply with depth. Rangeland soils lacked O horizons and SOC concentration declined more gradually. Quality of SOC under rangelands was more uniform with depth and SOC was less soluble and less decomposable (i.e., more stable) than under forests. However, DOC in grass-forb meadow soils was less aromatic and more bioavailable, likely promoting C retention through cycling. The SOC in forest soils was notably more leachable and decomposable, especially near the soil surface, with stability increasing with soil depth. Across the entire dataset, there was a weak inverse relationship between the decomposability and the aromaticity of DOC. Our data indicate that despite similar SOC pools, vegetation type may affect SOC retention capacity under future climate projections by influencing potential SOC losses via leaching and decomposition. 相似文献
Bermudagrass is an important warm‐season turfgrass species that is recalcitrant in regeneration in tissue culture. In a previous report, we observed that somatic embryogenesis of immature inflorescence culture was substantially improved when low levels of 2,4‐dichloro‐phenoxy acetic acid (1 mg/l) and 6‐benzylaminopurine (BAP, 0.01 mg/l) were included in the callus induction medium. The object of this study was to further improve the culture conditions to enhance somatic embryo formation and plantlet regeneration. It was shown that the abscisic acid supplement (2 or 5 mg/l) to the above callus induction medium further enhanced somatic embryogenesis in hybrid bermudagrass (Cynodon dactylon×Cynodon transvaalensis) cv. ‘Tifgreen’. The addition of gibberellic acid (0. 2 mg/l) to the BAP (1 mg/l)‐containing regeneration medium accelerated germination/regeneration of the somatic embryos. Secondary and repetitive somatic embryogenesis, which is rarely reported in monocots, was observed in common bermudagrass (Cynodon dactylon, cv. ‘Savannah’), and a full course of such a development was captured by a periodical microphotography. Scanning electron microscopy further confirmed the observation. 相似文献
Phaeozems of northeastern Germany and their position in holocene landscape development A typical soil association of NE-German young moraine area (Uckermark-region) including Phaeozems and colluvial deposits (Cumulic Anthrosols) was described macromorphologically using a trench profile and investigated by chemical standard analyses, humic compound analysis, pollen analysis and 14C-radiocarbon dating. Results are discussed in view of pedogenesis of Phaeozems. Conclusions were made concerning the holocene premedieval landscape development. A key position for reconstructing palaeoecological environmental conditions is held by “Black colluvium”. The “Black colluvium” is the relocated humous horizon of former Chernozems influenced by syn- and postsedimentary processes. The specific character of holocene landscape development and pedogenesis of the Uckermark-region is connected with the special natural conditions and history of land-use. 相似文献