Soil Surface Disturbance Research Articles

Organic matter composition in density fractions of Cerrado Ferralsols as revealed by CPMAS 13C NMR: Influence of pastureland, cropland and integrated crop-livestock

Integrated crop-livestock (ICL) is a promising land use system for the Brazilian Cerrado, but little is known about what this system might change in chemical composition of soil organic matter. In three long-term experiments (9–11 years old), located on Cerrado Ferralsols in Dourados, Maracaju and Campo Grande (Mato Grosso do Sul State, Brazil), we assessed the impact of continuous cropland (CC), ICL, and permanent pasture of Brachiaria decumbens (PP) on the C concentration and composition of the free light fraction (FLF), occluded light fraction (OLF) and heavy fraction (HF) of soil in the 0–5cm layer. CPMAS13C NMR spectroscopy was used to determine the percentage of alkyl, O-alkyl, aromatic and carboxyl C types. In Dourados and Maracaju, PP had the highest concentrations of organic C in whole soil and physical fractions, while ICL was intermediate and CC lowest. In Campo Grande, soil organic C concentration was similar among management systems. Distribution of organic C across physical fractions was not affected by management nor by experimental site, and on average the FLF, OLF and HF contained 7%, 26% and 67% of the total storage, respectively. Signal peaks of the four main C types appeared in all CPMAS 13C NMR spectra, but at different intensities. O-alkyl was the major C type (about 50%), carboxyl was the minor representative (generally less than 10%) and alkyl and aromatic C were intermediates. From FLF to OLF, the alkyl and aromatic C concentrations increased, possibly due to selective preservation of waxes, resins, cutin, suberin and lignin. The HF had greater O-alkyl and lower aromatic C concentrations than OLF, which might have been related to the accumulation of microbial carbohydrates on mineral surfaces of the HF. Along the sequence CC–ICL–PP, the most evident changes were greater of O-alkyl and lower alkyl C types, practically in all fractions and sites. In FLF and OLF, these changes were attributed to greater biomass input and less seed drill-induced disturbance of soil surface (lower decomposition of residues) in the PP and ICL. Additionally, in OLF, greater O-alkyl concentration in PP and ICL was attributed to physical protection of particulate organic matter derived from grass roots occluded inside soil aggregates. Our results suggest that PP and ICL systems increased or maintained soil organic C concentrations compared to CC, associated with a qualitative increase of the chemically labile O-alkyl C type which was possibly related to greater biomass addition and less soil disturbance.

Ongoing succession of biological soil crusts increases water repellency — a case study on Arenosols in Sekule, Slovakia

After soil surface disturbances biological soil crusts (BSC) cover rapidly the topmost soil millimeters. Depending on BSC age, development of soil water repellency, water infiltration and soil surface stability are influenced by this thin surface sealing. Within this study disturbed, early- mid- and late successional stages of BSC development were examined along a recovery transect. The results show an increase in water repellency and a decrease in water sorptivity and conductivity with ongoing BSC succession. Penetration resistance data shows very stable thin surface protection by cyanobacteria in early successional BSC that is non-repellent. Later successional stages show increased water repellency and lower water conductivity. We conclude that BSC development induces changes in surface structure and wettability. The soil surface wettability is strongly linked to the BSC community composition.

NATURAL REGENeRATION IN KEKILLA FERNLANDS IN THE PERIPHERY OF SINHARAJA WORLD HERITAGE SITE

In tropical moist climate Dicranopteris !inearis (Kekilla) fernland can develop as a resultof rain forest clearance followed by frequent burning. In Sri Lanka D. linearis fernlandsare capable of suppressing the natural regeneration of rain forest. Sinha raja WorldHeritage Site is one of the least disturbed and biologically unique lowland rain forest nowremaining in Sri Lanka. Some areas of the periphery of Sinharaja are covered with Dlenearis fern. Natural regeneration dynamics of soil seed banks need to be studied as apossible source of regeneration for forest restoration in these fern lands.This study was carried out to understand the natural regeneration of soil seed bank inKekilla fernland with reference to surface soil disturbance and trophographic levels in theperiphery of Sinharaja World Heritage Site.Three sites of Kekilla fernlands were selected for the study. Two surface soil disturbancetreatments were applied to each site. The first treatment (Root Removal) was applied at thebeginning of the study. The next treatment (Till) was applied to each site after six monthsfrom the first treatment. Seeds in the soil were allowed to germinate and seedlings werecounted once in two weeks during the first four months. After four months the seedlingswere recorded once a month. Transectswere laid out in each site to understand the floristiccomposition in surrounding vegetation of D. lenearis fernlands.Seedlings of 35 taxa were identified during the period of study. The study revealed thatboth soil disturbance treatments can facilitate the establishment of herbs, shrubs and treesin the fern land dominated by D. lenearis. Results showed that herbs, shrubs, grassesrepresented the greater proportions of seedling recruitment than pioneer trees. Seedlings ofprimary forest species were not existentSpecies composition of soil seed bank ill three-tophographic positions was not significantlydifferent. Numbers of species and seedling density were greatest in root removal treatment.Seedlings of primary forest species found in surrounding vegetation were not regeneratingin the plots studied. Only few pioneer tree seedlings were found in the plots, representingsurrounding vegetation of Kekilla fernland.

Effects of grazing, trenching and surface soil disturbance on ground cover in woody encroachment on the Cobar Pediplain, south-eastern Australia

This study investigated three possible reasons for low ground cover in an inter-patch in woody encroachment in semi-arid south-eastern Australia: (1) grazing by large herbivores, (2) competition with woody plants for resources, and (3) the smooth, crusted soil surface impeding litter lodgement and germination of seeds. Grazing exclusion, trenching (cutting roots of woody plants to 30 cm depth) and surface soil disturbance treatments were established in October 2008, and herbaceous ground cover and litter cover were measured after three, 16 and 30 months. Perennial grass cover in the ungrazed area was higher in trenched plots than in untrenched plots. Perennial grass cover in the grazed area was very low in trenched and untrenched plots. Herbaceous ground cover increased over time in ungrazed and trenched plots, much more than in grazed or untrenched plots. Soil disturbance did not affect herbaceous ground cover. Herbaceous ground cover was low in all treatments (<10%). Both grazing and cutting roots of woody plants affected herbaceous ground cover in this study. Herbaceous ground cover increased when roots of woody vegetation were severed (in the absence of grazing), indicating that herbaceous ground cover and woody vegetation compete for resources.

The short-term effects of surface soil disturbance on soil bacterial community structure at an experimental site near Scott Base, Antarctica

Humans are visiting Antarctica in increasing numbers, and the ecological effect of rapid soil habitat alteration due to human-induced physical disturbance is not well understood. An experimental soil disturbance trial was set up near Scott Base on Ross Island, to investigate the immediate and short-term changes to bacterial community structure, following surface soil disturbance. Three blocks, each comprising an undisturbed control, and an area disturbed by removing the top 2 cm of soil, were sampled over a time series (0, 7, 14, 21, and 35 days), to investigate changes to bacterial community structure using DNA profiling by terminal restriction fragment length polymorphism. The simulated disturbance did not cause any major shifts in the structure of the bacterial communities over the 35-day sampling period. Ordination showed that the bacterial community composition correlated strongly with soil EC (R 2 = 0.55) and soil pH (R 2 = 0.67), rather than the removal of the top 2 cm of surface material. Although the replicate blocks were visually indistinguishable from one another, high local spatial variability of soil chemical properties was found at the study site and different populations of bacterial communities occurred within 2 m of one another, within the same landscape unit. Given the current knowledge of the drivers of bacterial community structure, that is, soil EC, soil pH, and soil moisture content, a follow-up investigation incorporating DNA and RNA-based analyses over a time frame of 2–3 years would lead to a greater understanding of the effects of soil disturbance on bacterial communities.

Biological soil crusts greatly contribute to small-scale soil heterogeneity along a grazing gradient

Morphological and physiological characteristics of biological soil crusts (BSCs) enhance soil stability and fertility, and influence soil chemistry. However, the effect of BSCs on soil physico-chemical properties may vary depending on taxa (cyanobacteria, lichen, bryophytes) and species, and be susceptible to soil surface disturbance. We examined a wide variety of soil physico-chemical properties associated with five BSC components (cyanobacteria crust, one moss species, three lichen species) naturally occurring in the study area, and bare soil along a disturbance gradient in a semiarid grassland ecosystem in Central Mexico. We addressed the following questions: 1) Do different BSC components create distinct soil microsites characterized by a particular combination of physico-chemical properties? 2) Do distinct soil properties change beneath different BSC components? 3) Does grazing disturbance modify or override species-specific BSC effects? We found that BSC components and bare soil generated distinct soil microsites, however, this effect diminished with increasing grazing pressure. Also, most of the soil variables examined differed between BSC components and bare soil along the gradient. While soil properties associated with cyanobacteria were relatively similar compared to bare soil along the gradient, Diploschistes diacapsis and Lecidella sp. showed decreases in pH and marked differences in mineral nutrient concentration (i.e. variations in Na, Fe and Zn concentration respect to other BSC components and bare soil). Grazing intensity and frequency changed species-specific effects of D. diacapsis, specially modifying its effect on soil texture, diminishing its effect on pH, K and Na concentration, and increasing its effect on Ca and Zn concentration. We conclude that BSC components contribute to natural small-scale soil heterogeneity, and that soil disturbance substantially modifies the nature and magnitude of this effect with potentially important implications on ecosystem processes. Because of the potential influence of other factors (i.e. climate, vascular plants, microbial activity) on BSCs' relation to soil properties, this assertion should be tested including these factors and in multiple ecosystems.

Wind tunnel study of multiple factors affecting wind erosion from cropland in agro-pastoral area of Inner Mongolia, China

In this paper, the process of wind erosion on two kinds of soil from the agro-pastoral area of Inner Mongolia are studied using wind tunnel experiments, considering the wind speed, blown angle of wind and soil moisture content. The results showed that the modulus of soil wind erosion increases with an increase of wind speed. When the wind speed exceeds a critical value, the soil wind erosion suddenly increases. The critical speed for both kinds of soil is within the range of 7–8 m·s−1. For a constant wind speed, the rate of soil wind erosion changes from increasing to falling at a critical soil slope. The critical slope of loam soil and sandy loam soil is 20° and 10°, respectively. Soil moisture content has a significant effect on wind erosion. Soil wind erosion of both soils decreases with an increase of the soil water content in two treatments, however, for treatment two, the increasing trends of wind erosion for two soils with the falling of soil water content are no significant, especially for the loam soil, and in the same soil water content, the wind erosion of two soils in treatment one is significantly higher than treatment two, this indicates reducing the disturbance of soil surface can evidently control the soil wind erosion.

Soil carbon is only higher in the surface soil under minimum tillage in Vertosols and Chromosols of New South Wales North-West Slopes and Plains, Australia

Reduced carbon stock levels in Australian soil due to cropping provide a significant opportunity for carbon sequestration, and the recent initiative to consider soil carbon in domestic emissions trading requires a scientific assessment of soil carbon levels under a range of cropping soil management practices. Some of the previous research in southern and western New South Wales (NSW) showed that the rate of carbon decline in cropping soils is slowed under minimum tillage when the stubble is also retained. However, such comparison is rare in the NSW North-West Slopes and Plains region, particularly on the red soils (Chromosols) which are one of the major soil types in the region. We surveyed 50 dryland Chromosols, 72 dryland Vertosols, and 25 irrigated Vertosols on commercial farms across this region to examine the effects of conventional tillage, minimum tillage, and irrigation on total soil organic carbon. Samples of 0.1 m segments to 0.3 m depth were analysed for total organic carbon and other soil properties. Mid-infrared scans were used to predict the particulate, humus, and resistant soil organic carbon fractions. Bulk density was used to calculate total organic carbon stock for each segment, and equivalent soil mass (ESM) for 0–0.3 m. In Vertosols, for 0–0.3 m ESM, total organic carbon and particulate organic carbon were not different between management practices, whereas humic organic carbon and resistant organic carbon were consistently lower under conventional tillage. However, in 0–0.1 m, total organic carbon was greater under minimum tillage (15.2 Mg ha–1) than conventional tillage (11.9 Mg ha–1) or irrigation (12.0 Mg ha–1), reflecting less soil surface disturbance under minimum tillage. In Chromosols, only total organic carbon was higher under minimum tillage than conventional tillage in the 0–0.3 m ESM (39.8 v. 33.5 Mg ha–1) and in 0–0.1 m (19.7 v. 16.9 Mg ha–1). The strong influences of rainfall, temperature, bulk density, texture, and management history on soil carbon stocks suggested that these environmental and management factors require further consideration when gauging soil carbon sequestration potential under current and novel tillage practices in key regional locations.

Estoque de carbono em Latossolo Vermelho Distroférrico sob diferentes sistemas de manejo

The introduction of agriculture in areas with native vegetation generally results in a rapid loss of organic carbon in tropical environments, resulting in decreased soil quality. Thus, the objective of this study was to evaluate changes in carbon stocks and in some soil physical characteristics (bulk density - BD and total pore volume - PTV) under different management systems in the &lsquo;Cerrado' region of Goi&aacute;s State, Brazil. With this purpose, areas with four different management systems were selected in the Rio Verde municipality: no-tillage system with three years of implantation (NTS-3); conventional tillage system (CTS); and planted pasture with Brachiaria brizantha (PP). These areas were compared to an area of native &lsquo;cerrado' "; stricto sensu "; (NC). In each one of these areas soil samples were collected at 0-5, 5-10 and 10-20 cm depths. The design was completely randomized, with five replications. The areas of NC and CTS had at all analyzed depths lower values of BD, and greater PTV in relation to the areas of PP and NTS-3. The NC presented carbon contents and stocks similar to the NTS-3 areas and greater the PP and CTS. These results showed that the NTS-3, characterized by the maintenance of plant residues on the soil surface, crop rotation and minimal soil disturbance (tillage only in the line / tree planting), contributed to increase or to maintain soil carbon stocks.

Changes in vegetative communities and water table dynamics following timber harvesting in small headwater streams

In order to better understand the relationship between vegetation communities and water table in the uppermost portions (ephemeral–intermittent streams) of headwater systems, seasonal plot-based field characterizations of vegetation were used in conjunction with monthly water table measurements. Vegetation, soils, and water table data were examined to determine potential indicator species of near-surface water that could be used in rapid delineation of Streamside Management Zones (SMZs) by forest managers. Twelve watersheds were instrumented with three hundred screened wells, installed in grids of 25 per sub-watershed. Well locations were used to monitor water table and vegetation communities. Species were classified according to their wetland indicator status for Region 2; communities were evaluated using a prevalence index (PI). As part of a larger study, the uppermost reaches of the headwater systems were treated one of four treatments: (1) removal of all merchantable stems leaving understory intact with minimum surface soil disturbance (BMP1), (2) the same as treatment BMP1with the addition of logging debris in the drainage channel (BMP2), (3) total harvest with no BMPs applied (clearcut) and (4) no harvest (reference). Post-harvest increases in water table ranged from 1.6cm in BMP1 to 28.2cm in clearcut treatments during 2008, from 10.5cm in BMP1 to 54.2cm in BMP2 during 2009. PI differed significantly between channel and hillslope positions and represent distinctive vegetation communities. Forest clearcutting affected vegetation communities through combined direct and indirect disturbances. PI in the clearcut did not respond directly to changes in water table. In the two treatments where BMPs were employed, changes in vegetative communities corresponded to both changes in water table and changes in the microclimate as a result of harvesting intensity and changing stand heterogeneity. A vegetative indicator analysis, based on the presence of saturated soil conditions and water table elevation, was used to determine potential indicators of the true hydrologic boundaries of the headwater streams. Three potential indicator species (Viola blanda, Ludwigia glandulosa, and Arundinaria gigantean Ssp. Tecta) were more prevalent within “wet” channel positions but exhibited less total frequency of occurrence across the study areas than the fern species Polystichum acrostichoides, which is locally used for rapid estimation of intermittent stream extent). The combined use of the strong indicator species identified in this study and the “fern line” used by local industry foresters provides a means for rapid assessment of hydrologically functional SMZs in these headwater streams.

Effects of various tillage systems on soil CO2-C fluxes and on bacteria and fungi populations in Zea mays

The objective of this study is to determine the effects of strip tillage and full-width tillage treatments on soil carbon (IV) oxide-carbon (CO2-C) fluxes, bacterial and fungal populations in growing period of Zea mays. A row-crop rotary hoe with C type blades was used to create three strip widths by changing the connection of blades of the rotary hoe on the flanges. Strip widths were 22.5 (T30), 30 (T40) and 37.5 cm (T50). The full-width tillage practice (moldboard plow + disc harrow + leveler) gave 100% surface soil disturbance (T100) and was included in the experiment to make comparisons with the strip tillage system. During the growth of theZea mays, periodic measurements of CO2-C fluxes, bacterial and fungal populations were made. Statistically significant differences in CO2-C fluxes, microbial populations and soil bulk density were observed between the different tillage systems. Highest CO2-C fluxes and bacteria populations were observed with the full-width T100 treatment and the lowest values were observed in the T30 treatment during flowering and harvesting periods. Increasing tillage intensity increased soil CO2-C fluxes and bacteria population, but decreased fungi population and soil bulk density. Key words: Carbon IV oxide-carbon flux, strip tillage, strip width.

Inputs of nitrogen and organic matter govern the composition of fungal communities in soil disturbed by overwintering cattle

Abstract Overwintering cattle outdoors causes soil surface disturbance, substantial increases of soil Ntot, Corg, and P and a shift in pH to alkaline levels. Since fungi predominate in unfertilized soils with acidic pH and have filamentous hyphae, we hypothesized that changes caused by overwintering cattle outdoors (trampling, excreta returns, and changes in soil chemistry) will lead to suppressed species richness, lower biomass, and alter the structure of fungal communities. The research was conducted on an upland pasture used more than 10 years for cattle overwintering. Both culture-dependent and -independent methods were used for the determination of either fungal species composition (cultivation; DGGE) or biomass (numbers of CFU; concentration of fungal PLFA marker 18:2ω6,9). Soils under three different levels of cattle disturbance (S – severe, M – moderate, C – no disturbance/control) were investigated during three subsequent years. In addition, the DGGE analysis of soils was completed by comparison with analysis of fresh cattle excrements (Ex). The composition of fungal communities showed significantly higher richness and a substantial shift in species composition in cattle-disturbed soils (S, M) in comparison to the non-disturbed soil (C). The number of separated DGGE bands was significantly higher in S (30.67 ± 1.63; mean ± SD) and M (25.50 ± 1.64) soils than in the C soil (19.33 ± 1.75). Sequencing of typical bands revealed common fungal genera – Alternaria, Penicillium, Fusarium, Rhizopus, Isaria, and Metarhizium. Profiles of the S soil were enriched by bands of rumen-born anaerobic fungi (Neocallimastix, Cyllamyces) occurring mainly in profiles of excrements, where relatively low band richness (14.33 ± 1.15) was observed. The increasing level of cattle disturbance induced an increase in the biomass of complex fungal community over the three-year experimental period from 3.39 ± 2.11 (mean ± SD) nmol of fungal PLFA per gram of the C soil to 5.87 ± 3.16 in the M soil and 9.21 ± 4.69 in the S soil. Concentrations of soil Ntot and Corg were evaluated as the parameters significantly correlating with biomass as well as composition of the fungal community.

Effects of strip and full-width tillage on soil carbon IV oxide-carbon (CO2-C) fluxes and on bacterial and fungal populations in sunflower

In strip tillage system, planting lines are cultivated while the inter-row spaces are left undisturbed. The objective of this study is to determine the effects of strip tillage and full-width tillage treatments on soil carbon IV oxide-carbon (CO 2 -C) fluxes, bacterial and fungal populations in growing period of sunflower ( Helianthus annus ). A row-crop rotary hoe with C type blades was used to create three strip widths by changing the connection of blades of the rotary hoe on the flanges. Strip widths were 22.5 (T30), 30.0 (T40) and 37.5 cm (T50). The full-width tillage practice (moldboard plow + disc harrow + leveler) gave 100% surface soil disturbance (T100) and was included in the experiment to make comparisons with the strip tillage system. A randomized complete block design with three replications was used. During the growth of the sunflower, periodic measurements of CO 2 -C fluxes and bacterial and fungal populations were made. Significant (p < 0.01) differences in CO 2 -C fluxes, microbial populations, soil bulk density and total porosity were observed between the different tillage systems. Highest CO 2 -C fluxes, bacteria populations and total porosity were observed in the full-width T100 application and the lowest values were observed in the T30 treatment during flowering and harvesting periods. Increasing tillage intensity increased soil CO 2 -C fluxes and bacteria population, but decreased fungi population and soil bulk density. Key words : Carbon IV oxide-carbon flux, soil bacteria and fungi, strip tillage, full-width tillage, sunflower.

Suspended solid yield from forest harvesting on upland blanket peat

AbstractForest harvesting activities, if not carefully carried out, can disturb the forest soils and can cause significant suspended solid concentration increases in receiving water. This study examined how harvesting, following forestry guidelines, influenced suspended solid concentrations and loads in the receiving water of a blanket peat salmonid catchment. The study site comprised of two forest coupes of 34‐year‐old conifers drained by a first‐order stream. The upper coupe was not felled and acted as a baseline ‘control’ catchment; the downstream coupe was completely harvested in summer 2005 and served as the ‘experimental’ catchment. Good management practices such as the proper use of brash mats and harvesting only in dry weather were implemented to minimize soil surface disturbance and streambank erosion. Stream flow and suspended solid measurements at an upstream station (US) and a downstream station (DS) in the study stream commenced over a year before felling took place. The suspended solid concentrations, yields and release patterns at US and DS were compared before and after harvesting. These showed that post‐guideline harvesting of upland blanket peat forest did not significantly increase the suspended solid concentrations in the receiving water and the aquatic zone need not be adversely affected by soil releases from sites without a buffer strip. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Experimental Analysis of Effects of Markers and Habitat Structure on Predation of Turtle Nests

Understanding how potential predator cues and habitat features affect predation of turtle nests is important because nest predators can influence the demographic structure of turtle populations. We constructed artificial turtle nests in an area used by nesting Painted Turtles (Chrysemys picta) to investigate the relative importance of visual and olfactory signals (both natural and anthropogenic) and edge effects on nest predation. Overall, 34% of the simulated nests displayed evidence of predation. Neither rocks or flags used to mark nests (visual and olfactory cues left by researchers) nor slough water (an olfactory signal inadvertently shed by nesting turtles) significantly influenced predation rates. Instead, predators (most likely raccoons) located artificial nests based solely on surface soil disturbance and proximity to habitat edges. These results suggest that predators use key natural cues (as opposed to anthropogenic markers) and habitat edges to locate Painted Turtle nests, as noted in prior observational studies at this site. These findings provide useful experimental insights into the impact of anthropogenic markers, surface soil disturbance, and habitat edges on nesting turtles and their predators.

Seedling establishment of five evergreen tree species in relation to topography, sika deer (Cervus nippon yakushimae) and soil surface environments

We investigated the seedling survival of five evergreen tree species over 3 years inside and outside deer-exclusion fences in a warm temperate evergreen broad-leaved forest on Yakushima Island, Japan. Seedling survival was examined in relation to topography, herbivory by sika deer, and the soil surface environment (i.e., soil surface wetness, light conditions, slope inclination, and soil disturbance). The study species included Myrsine seguinii Lév., Syzygium buxifolium Hook. et Arn. (Group A: species distributed on the upper slope of the study site), Litsea accuminata (Bl.) Kurata, Schefflera octophylla (Lour.) Harms (Group B: species distributed on the lower slope), and Cleyera japonica Thunb. p.p. emend. Sieb. et Zucc. (Group C: species distributed on both slopes). The soil surface environment on the upper slope was drier, lighter, and more easily disturbed than the lower slope. Generalized linear model analyses indicated that seedling survival in fenced and unfenced quadrats was greater on the upper slope than on the lower slope for Group A and B species but not for Group C species. A micro-spatial scale analysis revealed that seedling survival was correlated with soil wetness, ground light conditions, and soil disturbance but not slope inclination. These results indicate that seedling survival was correlated with topography, sika deer herbivory, and the micro-spatial scale environment. Topography-related differences in seedling survival appear to adequately reflect the observed adult plant distributions for Group A and C species but not for Group B species.

Effects of soil disturbance, seed rate, nitrogen fertilizer and subsequent cutting treatment on establishment of Bromus inermis seedlings on degraded steppe grassland in China

AbstractEstablishment of seedlings of Bromus inermis, a native grass species of China, into a degraded steppe grassland was studied in an experiment with a factorial combination of different soil disturbance (control and harrowing), cutting post‐sowing (control and cutting), nitrogen (N) fertilizer application (0 and 100 kg KNO3 hm−2) and seed rate (400, 800 and 1200 seeds m−2) treatments. Seedling emergence and survival rates, and plant performance, were followed over 2 years. Seedling emergence was increased by soil disturbance (harrowing). Cutting post‐sowing and N fertilizer application did not increase seedling emergence. Seedling survival rates at the end of first growing season were strongly influenced by harrowing and the use of higher seed rates. Seedling height was higher in the harrowing and the N fertilizer application treatments and at the higher seed rates. Seedling survival rates in the second growing season were low but much higher with harrowing than the other treatments. Soil disturbance by harrowing may have increased contact between seed and soil, and reduced competition from established plants. It is concluded that, for the restoration of degraded semi‐arid grassland in China by re‐seeding, soil surface disturbance is necessary for successful seedling establishment, and modest seeding rates should be used to control costs.

Visually assessing the level of development and soil surface stability of cyanobacterially dominated biological soil crusts

Biological soil crusts (BSCs) are an integral part of dryland ecosystems and often included in long-term ecological monitoring programs. Estimating moss and lichen cover is fairly easy and non-destructive, but documenting cyanobacterial level of development (LOD) is more difficult. It requires sample collection for laboratory analysis, which causes soil surface disturbance. Assessing soil surface stability also requires surface disturbance. Here we present a visual technique to assess cyanobacterial LOD and soil surface stability. We define six development levels of cyanobacterially dominated soils based on soil surface darkness. We sampled chlorophyll a concentrations (the most common way of assessing cyanobacterial biomass), exopolysaccharide concentrations, and soil surface aggregate stability from representative areas of each LOD class. We found that, in the laboratory and field, LOD classes were effective at predicting chlorophyll a soil concentrations ( R 2=68–81%), exopolysaccharide concentrations ( R 2=71%), and soil aggregate stability ( R 2=77%). We took representative photos of these classes to construct a field guide. We then tested the ability of field crews to distinguish these classes and found this technique was highly repeatable among observers. We also discuss how to adjust this index for the different types of BSCs found in various dryland regions.

A simple classification of soil types as habitats of biological soil crusts on the Colorado Plateau, USA

AbstractQuestion:Can a simple soil classification method, accessible to non‐experts, be used to infer properties of the biological soil crust (BSC) communities such as species richness, evenness, and structure?Location:Grand Staircase‐Escalante National Monument, an arid region of the Colorado Plateau, USA.Methods:Biological soil crusts are highly functional soil surface communities of mosses, lichens and cyanobacteria that are vulnerable to soil surface disturbances such as grazing. We sampled BSC communities at 114 relatively undisturbed sites. We developed an eight‐tier BSC habitat classification based upon soil properties including texture, carbonate and gypsum content, and presence of shrinking‐swelling clays. We used simple structural equation models to determine how well this classification system predicted the evenness, richness, and community structure of BSC relative to elevation and annual precipitation.Results:We found that our habitat classification system explained at least 3.5 × more variance in BSC richness (R2= 0.57), evenness (R2= 0.59), and community structure (R2= 0.34) than annual precipitation and elevation combined. Gypsiferous soils, non‐calcareous sandy soils, and limestone‐derived soils were all very high in both species richness and evenness. Additionally, we found that gypsiferous soils were the most biologically unique group, harboring eight strong to excellent indicator species.Conclusions:Community properties of BSCs are overwhelmingly influenced by edaphic factors. These factors can be summarized efficiently by land managers and laypeople using a simple soil habitat classification, which will facilitate incorporation of BSCs into assessment and monitoring protocols and help prioritize conservation or restoration efforts.

Variation of carbon storage by different reforestation types in the hilly red soil region of southern China

Reforestation is a mitigation option to reduce increased atmospheric carbon dioxide levels as well as its predicted climate change. As a result, several forestry-based carbon storage projects have been introduced in many countries. To quantify the dynamics of ecosystem carbon allocation as affected by different forest management practices, we measured the above- and belowground biomass accumulation over 14 years, as well as the tissue carbon concentrations of trees in four different types: three monospecific plantations of slash pine ( Pinus elliottii) (SPP), Chinese fir ( Cunninghamia lanceolata) (CFP), and tea-oil camellia ( Camellia oleifera) (TCP) and one natural secondary forest (NSF) ( Pinus massoniana and Cyclobalanopsis glauca). A regression equation was constructed using the diameter at breast height/basal diameter (DBH/BD) and elements of total tree biomass. The equation was subsequently utilized to estimate tree carbon storage. The carbon storage of understory, forest floor, and soil components was also estimated. Results indicated that NSF stored significantly more carbon (141.99 t/ha) than SPP (104.07 t/ha), CFP (102.95 t/ha), and TCP (113.09 t/ha). Most of the carbon was found in the soil pool (60.30% in SPP, 70.42% in CFP, 63.87% in TCP, and 59.36% in NSF). In addition, more than 60% of the soil carbon storage at 0–100 cm depth was stored in the upper 40 cm. With the exception of trees, each component of NSF, including the understudy, forest floor, and soil, possessed significantly higher carbon storage than that of the three plantations ( p < 0.05). Soil surface disturbance during forest management practices was one of the main factors reducing the soil and understory carbon storage of tree plantation stands. These results suggest that natural restoration is a superior approach for increasing the carbon storage potential in the hilly red soil region in reforestation projects compared to plantations. In addition, reducing soil surface disturbance during forest management practices might also play an important factor in improving carbon sequestration potential in above tree plantations.