Soil aggregate stability was an uncertain predictor of ecosystem functioning in a temperate and semiarid grassland

Abstract

Abstract. We estimate rangeland managers assessing ecosystem health have measured soil stability .800,000 times. Our aim was to use quantitative data from a site in the Northern Great Plains, USA and a semi-quantitative literature search to demonstrate the robustness of soil stability as an indicator of ecosystem functioning. Empirical data included measurements of plant and soil properties along a local livestock grazing gradient to determine whether soil stability (e.g., % water-stable aggregates) explained primary productivity and soil water transport for a mixed-grass prairie site in the Northern Great Plains. We measured: annual net primary productivity (ANPP), elevation, % soil moisture, measures of soil stability, and soil water transport (field-saturated infiltrability and sorptivity) across points spanning a local gradient in livestock grazing intensity (none vs. light to moderate stocking rates; mean distance separating points ¼ 39.9 m [range ¼ 5.2-71.3 m]). Across the sampled gradient, variation in ANPP was best explained by a model with field-saturated infiltrability and % soil moisture. Infiltrability explained slightly more of the variation. We then determined that moderate amounts of variation in infiltrability were explained by ANPP, % soil moisture, and % water-stable aggregates. We determined that most of this variation was explained by ANPP and then soil moisture. Our empirical findings indicate that plant production was correlated with infiltration though we could not determine whether variation in plant production was caused by variation in infiltration or vice versa. We generally failed to show that soil stability (e.g., % waterstable aggregates) was a useful predictor of primary productivity and soil water transport. Our semiquantitative literature review also indicated that soil stability was not a consistent predictor of either plant production or infiltration. The varying evidence reported here on whether soil stability is a predictor of ecosystem function illustrates the difficulty in identifying an indicator of ecosystem health that (1) is a predictor of ecosystem function across grassland types, (2) is sensitive to rangeland management, and (3) can be easily implemented by non-experts.

Base cations and micronutrients in soil aggregates as affected by enhanced nitrogen and water inputs in a semi-arid steppe grassland

“…The availability of base cations varies with edaphic properties, such 57 as soil pH (Katou, 2002), organic matter fractions (Oorts et al, 2003) and soil particle 58 sizes (Beldin et al, 2007). Prolonged N inputs generally causes soil acidification and 59 subsequent losses of soil cations (McLaughlin and Wimmer, 1999;Cheng et al, 2010), 60 and micronutrient availability may increase under soil acidification (Malhi et al, 1998) 61 causing toxicity to both plants and soil microorganisms in extreme cases (Bowman et Soil aggregate structure predominantly controls SOM dynamics (Six et al, 2004) 69 and microbial activities (Dorodnikov et al, 2009), and soil aggregate stability can 70 serve as an indicator for grassland ecosystem health (Reinhart et al, 2015). In 71 comparison with macroaggregates, microaggregates provide preferential sites for soil 72 C stabilization (Wang et al, 2015b) and the SOM herein is more microbial-processed 73 as evidenced by natural abundance stable 13 C values (Gunina and Kuzyakov, 2014; 74 Wang et al, 2015b).…”

Short-Term Effects of Changing Soil Management Practices on Soil Quality Indicators and Crop Yields in Greenhouses

“…Soil quality indicators provide information on the properties, characteristics and processes related to the soil functions and soil fertility [20][21][22][23]. Among them, biochemical indicators, because of their high sensitivity in short term, could be useful to assess the impact of any new management practice.…”

An approach to analysing plot scale infiltration and runoff responses to rainfall of fluctuating intensity

“…Overland flow resulting from rainfall is involved in many hydrological and geomorphic processes, including soil erosion (Holz et al ., ); agrochemical, nutrient, and pesticide leaching in croplands (Sigua et al ., , ; Ryan et al ., ; Srinivasan et al ., ; Bramorski et al ., ); and the translocation of seeds and organic matter (Bochet, ; Gourdin et al ., ). The infiltrability of soils is an especially important parameter for understanding infiltration excess (Hortonian) overland flow and may partially account for annual net primary productivity in some important ecosystems, including croplands (Stroosnijder, ; Shaver et al ., ; Reinhart et al ., ). Overland flow may arise through a number of mechanisms but in all cases is influenced by both rainfall and surface characteristics, the latter including soil infiltrability as modified by slope, ground cover, soil structure and horizonation, and microtopography (McCalla et al ., ; Rostagno, ; Hawke et al ., ).…”