Perennial Vegetation Cover Research Articles

Establishing perennial strips in a cultivated floodplain for habitat restoration: monitoring over 4 years and success drivers

Floodplains, one of the most biologically diverse and productive ecosystems, are under threat from intensive crop production. Implementing perennial strips alongside agricultural ditches and streams could reduce negative impacts of intensive agriculture and restore wildlife habitats in cultivated floodplains. To successfully set up perennial strips, it is important to understand the parameters that drive their establishment. Here we assessed the establishment success of reed canarygrass (RCG; Phalaris arundinacea) strips in the lake Saint Pierre (LSP) floodplain, Québec, Canada by monitoring RCG biomass and vegetation height over 4 years and identify the factors driving its establishment. A total of 26 RCG strips across six municipalities of LSP were monitored. Biomass and vegetation height of RCG increased over time to reach an average of 5048 kg/ha in year 4 and 104 cm in year 3 in established strips. The RCG established successfully in 62% of surveyed plots and three environmental parameters explained 61% of this success. Establishment of RCG was most successful when a first rain came right after seeding (<3 days). High clay content and low elevation were associated with establishment failures. Overall, our results highlight the ability of RCG strips to restore dense perennial vegetation cover in cultivated floodplain, thereby providing suitable habitat for fish spawning during spring floods. This study provides significant insight into the drivers of establishment of perennial grass strips in highly constrained cultivated areas such as floodplains.

Soil Properties and Stoichiometry as Influenced by Land Use, Enclosures and Seasonality in a Semi-arid Dryland in Kenya

Agropastoralism and nomadic pastoralism constitute the main land use systems in semi-arid drylands in Kenya. However, limited studies have investigated how land use and management practices and seasonality affect soil properties that alter C, N, and P biogeochemical cycling in African drylands systems. Thus, this study was conducted to determine effects of: (1) sedentary agropastoral land-use system (SAL), (2) semi-nomadic pastoral land-use system (SNL)), (3) pasture enclosures and (4) seasonality on selected soil chemical properties and total C, N, and P stoichiometry in a semi-arid landscape in Kenya. Land use, enclosures, and seasonality affected chemical properties of soils and C, N, and P stoichiometry. Generally, Na, K, Ca, Mg and cation exchange capacity were higher in the dry than wet period. Soil C:N ratios were less than 5, while N:P and C:P ratios were 5–56 and 16–177, respectively. However, ratios of C:N, N:P and C:P were significantly higher in SNL than SAL. The C:P and N:P ratios in both land use systems were highly correlated (r2 > 0.70). During the wet season, C:N ratios of soils were higher inside enclosures in both land uses. Higher soil N:P and C:P ratios were observed during dry compared to wet seasons. The N:P and C:P ratios of soils were higher inside and outside enclosures in SAL and SNL, respectively. Land use, enclosures and seasonality exhibited different effects on chemical properties of soils and C:N:P stoichiometry ratios. Perennial vegetation cover in enclosures has a great potential to enhance soil health necessary to support pastoral land-use systems in semi-arid African drylands.

Establishment of reed canarygrass (Phalaris arundinacea) in the context of floodplain restoration: impact of companion plant and sowing rate

Habitat loss and degradation is a leading cause of the current biodiversity crisis. In the lake Saint-Pierre floodplain, agricultural intensification has led to the loss of substantial spawning and rearing areas for the yellow perch ( Perca flavescens Mitchill). Restoring perennial vegetation cover is key to ensure the persistence of the population, but the floodplain conditions limit our ability to do so. In this study, we tested the impact of companion plants ( Avena sativa L., Lolium multiflorum L.) and sowing rate on the establishment success of reed canarygrass ( Phalaris arundinacea L.; RCG) in year 2. RCG tolerates a wide range of environmental conditions and can provide the plant cover essential to the reproduction of yellow perch. We hypothesized that companion plants would reduce weed pressure and in turn improve RCG establishment, and that increasing the sowing rate would improve the establishment success. Contrary to our expectations, using companion plants generally reduced the cover and biomass of RCG. It also led to increased weed prevalence in most treatments. In addition, sowing at high rates did not impact RCG cover and biomass. Sowing RCG alone appears to be the most effective option to establish perennial vegetation supporting the recovery of the yellow perch population.

Improving ecosystem health in highly altered river basins: a generalized framework and its application to the Mississippi-Atchafalaya River Basin.

Continued large-scale public investment in declining ecosystems depends on demonstrations of "success". While the public conception of "success" often focuses on restoration to a pre-disturbance condition, the scientific community is more likely to measure success in terms of improved ecosystem health. Using a combination of literature review, workshops and expert solicitation we propose a generalized framework to improve ecosystem health in highly altered river basins by reducing ecosystem stressors, enhancing ecosystem processes and increasing ecosystem resilience. We illustrate the use of this framework in the Mississippi-Atchafalaya River Basin (MARB) of the central United States (U.S.), by (i) identifying key stressors related to human activities, and (ii) creating a conceptual ecosystem model relating those stressors to effects on ecosystem structure and processes. As a result of our analysis, we identify a set of landscape-level indicators of ecosystem health, emphasizing leading indicators of stressor removal (e.g., reduced anthropogenic nutrient inputs), increased ecosystem function (e.g., increased water storage in the landscape) and increased resilience (e.g., changes in the percentage of perennial vegetative cover). We suggest that by including these indicators, along with lagging indicators such as direct measurements of water quality, stakeholders will be better able to assess the effectiveness of management actions. For example, if both leading and lagging indicators show improvement over time, then management actions are on track to attain desired ecosystem condition. If, however, leading indicators are not improving or even declining, then fundamental challenges to ecosystem health remain to be addressed and failure to address these will ultimately lead to declines in lagging indicators such as water quality. Although our model and indicators are specific to the MARB, we believe that the generalized framework and the process of model and indicator development will be valuable in an array of altered river basins.

Vegetation response to grazing and drought (13 yr) in a conservation area in the Succulent Karoo, South Africa

Rangelands of arid ecosystems are driven by internal and external environmental controls. Grazing pressure is an important anthropogenic driver, but stochastic environmental events such as rainfall variability and prolonged drought can have profound effects on arid vegetation. We investigated the effect of a prolonged drought and initial high grazing pressure on range condition, perennial vegetation cover, life form cover, vegetation composition and vegetation diversity at five monitoring sites in a conservation area in arid Succulent Karoo vegetation. The response of the rocky mountainous vegetation to drought and grazing differed notably from the response of the sandy plains vegetation. Range condition and perennial vegetation cover reduced drastically in all habitats, although the extent of deterioration was less in the mountainous habitats. Annual vegetation cover was associated with inter-annual rainfall variability. Species richness decreased at three of five sites, whereas species evenness increased at three of five sites. Shannon-Wiener index of diversity and Simpson's diversity index trends were inconsistent. Vegetation composition changed directionally from a quasi-stable state in all five monitoring sites as the drought persisted. The extent of the change was less in mountainous habitats indicating potentially higher resilience than in plains habitats, though grazing pressure was lower in the mountains than on the plains over the study period. The existence of quasi-stable states, together with the observed directional changes in vegetation composition in response to both drought and grazing, indicated that both equilibrium and non-equilibrium vegetation dynamics apply.

Satellite‐derived prefire vegetation predicts variation in field‐based invasive annual grass cover after fire

AbstractAimsInvasion by annual grasses (IAGs) and concomitant increases in wildfire are impacting many drylands globally, and an understanding of factors that contribute to or detract from community resistance to IAGs is needed to inform postfire restoration interventions. Prefire vegetation condition is often unknown in rangelands but it likely affects variation in postfire invasion resistance across large burned scars. Whether satellite‐derived products like the Rangeland Analysis Platform (RAP) can fulfill prefire information needs and be used to parametrize models of fire recovery to inform postfire management of IAGs is a key question.MethodsWe used random forests to ask how IAG abundances in 669 field plots measured in the 2‐3 years following megafires in sagebrush steppe rangelands of western USA responded to RAP estimates of annual:perennial prefire vegetation cover, the effects of elevation, heat load, postfire treatments, soil moisture–temperature regimes, and land‐agency ratings of ecosystem resistance to invasion and resilience to disturbance.ResultsPostfire IAG cover measured in the field was % and RAP‐estimated prefire annual herbaceous cover was %. The random forest model had an R2 of 0.36 and a root‐mean‐squared error (RMSE) of 4.41. Elevation, postfire herbicide treatment, and prefire estimates from RAP for the ratio of annual:perennial and shrub cover were the most important predictors of postfire IAG cover. Threshold‐like relationships between postfire IAG cover and the predictors indicate that maintaining annual:perennial cover below 0.4 and shrub cover below <10% prior to wildfire would decrease invasion, at low elevations below 1400 m above sea level.ConclusionDespite known differences between RAP and field‐based estimates of vegetation cover, RAP was still a useful predictor of variation in IAG abundances after fire. IAG management is oftentimes reactive, but our findings indicate impactful roles for more inclusively addressing the exotic annual community, and focusing on prefire maintenance of annual:perennial herbaceous and shrub cover at low elevations.

Vegetation structure and composition at different elevational intervals in the arid Tankwa Karoo National Park, South Africa

Study area: The study was conducted in the Tankwa Karoo National Park, one of the driest areas in South Africa. Historic overgrazing has resulted in the poor and often degraded state of vegetation in large parts of the Tanqua Karoo region.Aim: This study assessed the spatial variation of vegetation structure and composition in the three main vegetation types namely: Tanqua Karoo (TK), Tanqua Wash Riviere (TWR) and Tanqua Escarpment Shrubland (TES), along an elevational gradient.Method: Using the point intercept survey method, vegetation cover, plant height, species diversity, life forms, proportions of perennials and annuals were examined in 43 sites, widely distributed in these vegetation types.Results: There were 150 vascular plant species belonging to 83 genera and 29 families recorded across all sites. The most diverse vegetation type was TES with 96 species belonging to 61 genera and 26 families. The vegetation structure was comprised mainly of shrubs and dwarf shrubs with a high proportion of leaf and stem succulent species. The mean perennial vegetation cover throughout the study area was 28 and annuals covered 22%, but this cover varied significantly between the vegetation types. The most dominant life forms were chamaephytes, which comprised 64% of all species, with cryptophytes (18%), therophytes (16%) and nanophanerophytes (2%) less abundant. Surveyed sites in the TES showed a clear association with each other but there was an overlap in the species composition and environmental conditions between some TWR and TK sites. This study highlighted the important role of elevation and topography as drivers of vegetation characteristics.Conclusion: The findings from this study can be used as a vegetation baseline to identify and prioritise degraded areas for active restoration in order to limit further degradation. Considering climate change, elevational studies may provide additional insight into species dynamics across landscapes.Taxonomic reference: Plants of Southern Africa Checklist (South African National Biodiversity Institute 2016).Abbreviations: ANOVA = analysis of variance; GPS = Global Positioning System; LFA = Landscape Function Assessment; NDVI = Normalized difference vegetation index; PCA = principal component analysis; PCo-A = principal co-ordinate analysis; TES = Tanqua Escarpment Shrubland; TK = Tanqua Karoo; TKNP = Tankwa Karoo National Park; TWR = Tanqua Wash Riviere.

Soil‐test biological activity associates with soil aggregation characteristics under different land uses in North Carolina

AbstractSoil erosion is a major constraint to agricultural sustainability. Land management that protects soil from water erosion can be assessed from the fraction of aggregates stable upon water immersion. Conservation management with minimal soil disturbance is known to enhance water‐stable aggregation, but how annual vs. perennial vegetative cover affects soil biological activity and aggregation from soils varying in texture remains relatively unexplored. This study assessed the effects of long‐term conventional‐till and no‐till cropland, grassland, and woodland on dry‐stable and water‐stable mean‐weight diameter (MWD) from 25 research stations across North Carolina. Soil clay concentration varied from 36 to 279 g kg–1 and sand concentration varied from 392 to 904 g kg–1 (5–95% distribution). Across locations, water‐stable MWD followed the order: conventional‐till cropland (0.64 mm) < no‐till cropland (0.87 mm) < woodland (1.12 mm) = grassland (1.15 mm). Soil stability index (i.e., water‐stable MWD/dry‐stable MWD) followed a similar order: conventional‐till cropland (0.59 mm mm–1) < no‐till cropland (0.76 mm mm–1) < grassland (0.92 mm mm–1) = woodland (0.96 mm mm–1). Although water‐stable MWD was positively associated with clay concentration (r = .50, p < .001, n = 310), soil‐test biological activity had the strongest association with water‐stable MWD (r = .80). Soil‐test biological activity reflected biological manipulation of surface‐concentrated organic matter, as mediated by conservation land uses. This study revealed the large impact of surface organic C and N resources on water‐stable aggregation through soil biological manipulations interacting across a textural gradient.

Minimizing environmental impacts of solar farms: a review of current science on landscape hydrology and guidance on stormwater management

Abstract As solar energy becomes an increasingly cheap source of renewable energy, major utility-scale ground solar panel installations, often called ‘solar farms’, are rapidly growing. With these solar farms often covering hundreds of acres, there is the potential for impacts on natural hydrologic processes, including runoff generation and erosion. Here we review the current state of scientific research on the hydrology and water quality impacts of solar farms, as well as management recommendations for minimizing any impacts. The limited field measurements indicate the redistribution of soil moisture around solar farms, but the net impacts on runoff and erosion are less clear. Research focused on coupling solar farms with agriculture as ‘agrivoltaics’ demonstrates reduced evaporative water losses and associated crop stress, particularly in more arid regions. With regards to land and the stormwater management associated with solar farms, most US states currently do not have solar farm-specific recommendations and instead defer to standard stormwater management permits and guidance. In states with solar farm-specific guidance, typical recommendations include minimizing construction-related compaction, ensuring a high cover of perennial vegetation with minimal maintenance, and designing with pervious space between solar panel rows to promote infiltration of any runoff; in some cases, structural stormwater management like infiltration basins may be required. In general, solar farms can be designed to minimize the impact on landscape ecohydrological processes, but more research is needed to determine whether current recommendations are adequate. In particular, there is a need for more field research on less ideal sites such as those with higher slopes.

Urban runoff and stream channel incision interact to influence riparian soils and understory vegetation.

Riparian soil processes and vegetation are sensitive to water availability. Urbanization can alter riparian water availability by modifying stream flows and stream channel morphology. In cities, runoff from impervious surfaces tends to increase stormflow magnitudes, causing stream channels to incise, or downcut. This change in channel morphology has been linked to lowered water tables and drier conditions in temperate urban riparian zones, leading to shifts in riparian nitrogen (N) cycling and vegetation communities. In Mediterranean climates with distinct wet and dry periods, there is an additional dynamic to consider: runoff from urban water use can cause streams to flow when they would otherwise be dry. This dry-season stream flow could create increased, rather than decreased, water availability in urban riparian zones. However, channel incision may counteract this effect. We asked whether dry-season stream flow interacted with channel incision to influence riparian soil characteristics and understory vegetation along streams in Sacramento, California, which has a Mediterranean climate with an intense summer dry season. At 40 stream reaches that varied by severity of downcutting and presence of dry-season flow, we sampled soils and vegetation on top of stream banks and at the margin of the low-flow channel, an important location for nutrient cycling in dry climates. We measured soil moisture, organic matter, and ∂15 N, as well as total and perennial understory vegetation cover. We found that channel characteristics associated with incision limited the influence of dry-season stream flow on soil moisture, and this interaction appears to have lasting effects on soil organic matter and perennial vegetation on bank tops. At the stream margin, channel downcutting was associated with reduced soil organic matter and vegetation cover, while dry-season flow was associated with increased vegetation cover. Values of soil ∂15 N pointed to limited hydrologic linkage between stream flows and riparian bank soils along incised streams. Our findings suggest that channel incision could limit the ability of urban riparian ecosystems to mitigate low-flow water quality. However, where streams are not incised in Mediterranean climates, dry-season flows from urban runoff may actually increase riparian productivity and N cycling above historical levels.

Evaluating establishment of conservation practices in the Conservation Reserve Program across the central and western United States

The U.S. Department of Agriculture’s Conservation Reserve Program (CRP) is one of the largest private lands conservation programs in the United States, establishing perennial vegetation on environmentally sensitive lands formerly in agricultural production. Over its 35 year existence, the CRP has evolved to include diverse conservation practices (CPs) while concomitantly meeting its core goals of reducing soil erosion, improving water quality, and providing wildlife habitat. Ongoing threats to grasslands and decreased CRP acreage highlighted the need for a national evaluation of the effectiveness in providing the program’s intended benefits. To address this need, we conducted edge-of-field surveys of erosional features, vegetation, and soil cover on 1 786 fields across 10 CPs and 14 central and western states from 2016 to 2018. We grouped practices into three types (grassland, wetland, and wildlife) and states into six regions for analysis. Across practice types, ⩾99% of fields had no evidence of rills, gullies, or pedestaling from erosion, and 91% of fields had <20% bare soil cover, with region being the strongest predictor of bare soil cover. Seventy-nine percent of fields had ⩾50% grass cover, with cover differing by practice type and region. Native grass species were present on more fields in wildlife and wetland practices compared to grassland practices. Forb cover >50% and native forb presence occurred most frequently in wildlife practices, with region being the strongest driver of differences. Federally listed noxious grass and forb species occurred on 23% and 61% of fields, respectively, but tended to constitute a small portion of cover in the field. Estimates from edge-of-field surveys and in-field validation sampling were strongly correlated, demonstrating the utility of the edge-of-field surveys. Our results provide the first national-level assessment of CRP establishment in three decades, confirming that enrolled wildlife and wetland practices often have diverse perennial vegetation cover and very few erosional features.

In situ cultivation of aromatic plant species for the phytomanagement of an aged-trace element polluted soil: Plant biomass improvement options and techno-economic assessment of the essential oil production channel

Due to the presence of trace element (TE) in agricultural soils, wide areas are unproper for food production and the clean-up of soil is not a feasible option. Considering the potential remediation options, the use of aromatic plants producing a high quantity of biomass and developing high-added value sectors such as essential oil (EO) production could be valuable regarding one of the phytomanagement objectives, i.e. the restoration of an economic activity. The purpose of this study was hence to evaluate in situ the suitability of two aromatic crops, clary sage and coriander, for the phytomanagement of aged TE-polluted soils, taking into account plants' growth, development and biomass production, essential oil (EO) content and quality as well as a techno-economic feasibility analysis of the channel. In situ experiments have been carried out on two agricultural plots of 1.5 ha, a TE-polluted one (Pb: 394 ppm - Zn: 443 ppm - Cd: 7.2 ppm) and an unpolluted one (Pb: 22 ppm - Zn: 48 ppm - Cd: 0.4 ppm). Our findings have shown the ability of coriander and sage to grow similarly on both unpolluted and TE-polluted soil and to produce significant amounts of biomass. The pesticide residue and TE analyses have demonstrated that the EO only contained trace amounts of the contaminants, below or close to the limit of quantification of the method used and similar to marketed products. Mycorrhizal inoculation has also shown promising results by increasing the colonization rates of both aromatic plants, but did not result in higher biomass or EO amounts. Our study brings new evidence towards the potential of clary sage to be used for the phytomanagement of TE-polluted areas, given its perennial vegetation cover, tolerance to TE and obtained EO yields.

The Use of Very-High-Resolution Aerial Imagery to Estimate the Structure and Distribution of the Rhanterium epapposum Community for Long-Term Monitoring in Desert Ecosystems.

The rapid assessment and monitoring of native desert plants are essential in restoration and revegetation projects to track the changes in vegetation patterns in terms of vegetation coverage and structure. This work investigated advanced vegetation monitoring methods utilizing UAVs and remote sensing techniques at the Al Abdali protected site in Kuwait. The study examined the effectiveness of using UAV techniques to assess the structure of desert plants. We specifically examined the use of very-high-resolution aerial imagery to estimate the vegetation structure of Rhanterium epapposum (perennial desert shrub), assess the vegetation cover density changes in desert plants after rainfall events, and investigate the relationship between the distribution of perennial shrub structure and vegetation cover density of annual plants. The images were classified using supervised classification techniques (the SVM method) to assess the changes in desert plants after extreme rainfall events. A digital terrain model (DTM) and a digital surface model (DSM) were also generated to estimate the maximum shrub heights. The classified imagery results show that a significant increase in vegetation coverage occurred in the annual plants after rainfall events. The results also show a reasonable correlation between the shrub heights estimated using UAVs and the ground-truth measurements (R2 = 0.66, p < 0.01). The shrub heights were higher in the high-cover-density plots, with coverage >30% and an average height of 77 cm. However, in the medium-cover-density (MD) plots, the coverage was <30%, and the average height was 52 cm. Our study suggests that utilizing UAVs can provide several advantages to critically support future ecological studies and revegetation and restoration programs in desert ecosystems.

Effects of elevation and selective disturbance on soil climate and vegetation in big sagebrush communities

AbstractChanging climatic conditions prompt concerns about vegetation response to disturbance under future compared to past conditions. In this long‐term study, we examined soil climate and vegetation differences at lower, mid, and upper elevations in two separate locations in the Great Basin, USA. We hypothesized that soil climate and vegetation associations across the elevational gradient could help predict responses under future warming and drying. We measured soil water availability, soil temperatures, and vegetation cover in relation to fire and perennial herb removal at each elevation for 13–17 yr after treatment. Seasonal soil water availability increased, while soil temperature‐related variables decreased with increasing elevation. Soil water availability in spring was positively correlated with October through June precipitation (r2 = 0.53), while water availability in spring through fall was positively correlated with perennial plant cover (r2 = 0.65). Partition models separated low, mid, and high elevations by spring soil water availability and growing degree days when soil water was available (R2 = 0.93). Current soil climate and vegetation conditions at lower elevations could indicate future conditions at higher elevations under a warmer and drier climate. During the first years after removal of perennial grasses and forbs, there was an increase in soil water availability in spring at 13–30 cm soil depth that was associated with sagebrush establishment, particularly at upper elevations. In subsequent years, sagebrush continued to dominate even though little difference in soil water availability existed between disturbed and undisturbed plots. This indicates that quickly establishing sagebrush preempted resources and reduced perennial herb recovery. Resource preemption after disturbance will likely be a major driver of plant succession in the future as in the past. Species that establish best under future warmer and drier conditions are most likely to dominate after disturbance. A negative correlation (r2 = 0.34) between the standard deviation of annual spring soil water availability and perennial vegetation cover, which helps resist annual grass invasion, supports the hypothesis that greater resource fluctuation is associated with greater plant community invasibility. Current responses to fire and loss of native plant cover across elevational gradients can indicate future responses under a warmer and drier climate.

Effect of Buffer Zone Structure on Diversity of Aquatic Vegetation in Farmland Water Bodies

Farmland water bodies (FWBs) are marginal habitats in the agricultural landscape. However, regardless of their small size, they are refuges for natural vegetation and species-rich animal assemblages. They are especially important in areas where the intensification of agricultural activities reduces the ecological quality of the landscape. The study aimed to evaluate the effect of the habitat structure of the FWB buffer zone on macrophyte association diversity in the FWBs (n = 49). As many as 175 species of vascular plants, three stoneworts, and 40 (41–49 according to Chao2 estimator) plant associations were recognized, including 19 of high conservation priority. The occurrence of threatened associations (0–5 per FWB) was not correlated with the number of common (unthreatened) ones. The most important predictors of plant diversity (at the species level and the association level) were the connection of the FWB with a watercourse (positive effect), and the distance from the FWB to the nearest built-up areas (positive effect). The results suggest that even though the high percentage cover of perennial vegetation mitigates the effect of diffused pollutions of agricultural origin on FWB biota, its significance may become low when the distance from a built-up area to FWBs is small.

Using movement to inform conservation corridor design for Mojave desert tortoise

BackgroundPreserving corridors for movement and gene flow among populations can assist in the recovery of threatened and endangered species. As human activity continues to fragment habitats, characterizing natural corridors is important in establishing and maintaining connectivity corridors within the anthropogenic development matrix. The Mojave desert tortoise (Gopherus agassizii) is a threatened species occupying a variety of habitats in the Mojave and Colorado Deserts. Desert tortoises have been referred to as corridor-dwellers, and understanding how they move within suitable habitat can be crucial to defining corridors that will sustain sufficient gene flow to maintain connections among populations amidst the increases in human development.MethodsTo elucidate how tortoises traverse available habitat and interact with potentially inhospitable terrain and human infrastructure, we used GPS dataloggers to document fine-scale movement of individuals and estimate home ranges at ten study sites along the California/Nevada border. Our sites encompass a variety of habitats, including mountain passes that serve as important natural corridors connecting neighboring valleys, and are impacted by a variety of linear anthropogenic features. We used path selection functions to quantify tortoise movements and develop resistance surfaces based on landscape characteristics including natural features, anthropogenic alterations, and estimated home ranges with autocorrelated kernel density methods. Using the best supported path selection models and estimated home ranges, we determined characteristics of known natural corridors and compared them to mitigation corridors (remnant habitat patches) that have been integrated into land management decisions in the Ivanpah Valley.ResultsTortoises avoided areas of high slope and low perennial vegetation cover, avoided moving near low-density roads, and traveled along linear barriers (fences and flood control berms).ConclusionsWe found that mitigation corridors designated between solar facilities should be wide enough to retain home ranges and maintain function. Differences in home range size and movement resistance between our two natural mountain pass corridors align with differences in genetic connectivity, suggesting that not all natural corridors provide the same functionality. Furthermore, creation of mitigation corridors with fences may have unintended consequences and may function differently than natural corridors. Understanding characteristics of corridors with different functionality will help future managers ensure that connectivity is maintained among Mojave desert tortoise populations.

An Environmental Impact Assessment of Different Management Regimes in Eucalypt Plantations in Southern China Using Landscape Function Analysis

ABSTRACT There are global concerns regarding the detrimental environmental impacts of industrial forest plantations developed over the past 30 years. To address this concern, the Landscape Function Analysis methodology was used to rapidly assess indices of soil stability, water infiltration, and nutrient cycling within eucalypt plantations at different growth stages and under different management regimes in Guangxi Province, China. Results showed that these plantations under both regimes were approaching an ecologically functional state by the time of harvest. However, within the plantation management that included the burning of post-harvest biomass residues, indices of water infiltration, and nutrient cycling were significantly lower than within the plantation that retained post-harvest residues. Indicators of rain splash protection, perennial vegetation cover, and litter accumulation were all lower in the plantation that practiced residue burning and pre-planting cultivation. Retention of post-harvest residues improves landscape functionality at the time of re-planting. Our results indicate that burning and extensive cultivation prior to re-planting should be minimized.

Ventenata and Other Coexisting Exotic Annual Grass Control and Plant Community Response to Increasing Imazapic Application Rates

Ventenata (Ventenata dubia [Leers] Coss.) is an exotic annual grass that can invade intermountain rangeland plant communities, where it can form monotypic stands, degrade wildlife habitat, and reduce livestock forage. There is limited information on ventenata control in rangelands as it has only recently been identified as a substantial problem. Imazapic is a pre-emergent herbicide commonly used to control other exotic annual grasses and, therefore, is likely to control ventenata in rangelands. We evaluated five application rates of imazapic (0−175 g ae∙ha−1) on ventenata and other exotic annual grass control and plant community response at two rangeland sites in 2 yr (2014 and 2015). Imazapic reduced exotic annual grass (largely ventenata) cover and density, with greater control with increasing imazapic rates. Exotic annual grass density at the highest levels of control (82%−94%) was 184−299 plants∙m−2 the first yr after imazapic application. Exotic annual grasses fully recovered in the second or third yr after imazapic application. Bare ground generally increased with imazapic application. However, density of perennial vegetation (grasses and forbs) did not vary among treatments. Perennial vegetation cover generally did not increase with imazapic control of ventenata and other exotic annual grasses. Imazapic can control ventenata; however, even at the highest rates, control was not enough to shift the dominance from exotic annual species to perennial species. Integrating other treatments with imazapic application may be a strategy to improve ventenata control and increase perennial vegetation and will require further investigation. The difficulty and likely expense of achieving substantial and lasting control of ventenata suggest, similar to other exotic annual grasses, that preventing ventenata invasion and dominance should be a high management priority.

Sedimentary Marl mudstone as a substrate in a xeric environment revealed by microbiome analysis.

The sedimentary Marl mudstone soil is composed primarily of CaCO3, and is an important pedologic and geomorphologic element known as Marl, extensively dispersed in slopes and ridges in the northern Negev Desert, Israel. The wide Marl soil-layer areas are barren, with well-developed streamsides and no perennial vegetation cover. Soil systems in the Negev Desert have been widely studied, yet very little information was collected on Marl soils, and even less on the microbiome present in the Negev. Thus, an evaluation of the microbial-community inhabitants in a Marl soil layer was conducted in an attempt to distinguish between Marl with surface green mat and bare Marl soil layer. Our objective was to investigate the microbiome and abiotic components of the upper layer (0-5cm) of Marl and Marl-with-green-mat soil collected in the Negev Desert. Plate-counting enabled the estimation of fungal and bacterial population size, while nested polymerase chain reaction (nPCR) and Ion Torrent sequencing were used to analyze biological diversity. The results indicate significant differences in microbial biomass and microbial-community diversity between Marl and Marl-green mat, despite similar pH levels. Further study is needed to enhance understanding of the activity of the biotic components and their contribution to slope stabilization.

Effectiveness of prescribed fire to re-establish sagebrush steppe vegetation and ecohydrologic function on woodland-encroached sagebrush rangelands, Great Basin, USA: Part I: Vegetation, hydrology, and erosion responses

Pinyon (Pinus spp.) and juniper (Juniperus spp.) woodland encroachment has imperiled a broad ecological domain of the sagebrush steppe (Artemisia spp.) ecosystem in the Great Basin Region, USA. As these conifers increase in dominance on sagebrush rangelands, understory vegetation declines and ecohydrologic function can shift from biotic (vegetation) controlled retention of soil resources to abiotic (runoff) driven loss of soil resources and long-term site degradation. Scientists, public land management agencies, and private land owners are challenged with selecting and predicting outcomes to treatment alternatives to improve ecological structure and function on these rangelands. This study is the first of a two-part study to evaluate effectiveness of prescribed fire to re-establish sagebrush steppe vegetation and improve ecohydrologic function on mid- to late-succession pinyon-and juniper-encroached sagebrush sites in the Great Basin. We used a suite of vegetation and soil measures, small-plot (0.5 m2) rainfall simulations, and overland flow experiments (9 m2) to quantify the effects of tree removal by prescribed fire on vegetation, soils, and rainsplash, sheetflow, and concentrated flow hydrologic and erosion processes at two woodlands 9-yr after burning. For untreated conditions, extensive bare interspace (87% bare ground) throughout the degraded intercanopy (69–88% bare ground) between trees at both sites promoted high runoff and sediment yield from combined rainsplash and sheetflow (~45 mm, 59–381 g m−2) and concentrated flow (371–501 L, 2343–3015 g) processes during high intensity rainfall simulation (102 mm h−1, 45 min) and overland flow experiments (15, 30, and 45 L min−1, 8 min each). Burning increased canopy cover of native perennial herbaceous vegetation by >5-fold, on average, across both sites over nine growing seasons. Burning reduced low pre-fire sagebrush canopy cover (<1% to 14% average) at both sites and sagebrush recovery is expected to take >30 yr. Enhanced herbaceous cover in interspaces post-fire reduced runoff and sediment yield from high intensity rainfall simulations by >2-fold at both sites. Fire-induced increases in herbaceous canopy cover (from 34% to 62%) and litter ground cover (from 15% to 36%) reduced total runoff (from 501 L to 180 L) and sediment yield (from 2343 g to 115 g) from concentrated flow experiments in the intercanopy at one site. Sparser herbaceous vegetation (49% cover) and litter cover (8%) in the intercanopy at the other, more degraded site post-fire resulted in no significant reduction of total runoff (371 L to 266 L) and sediment yield (3015 g to 1982 g) for concentrated flow experiments. Areas underneath unburned shrub and tree canopies were well covered by vegetation and ground cover and generated limited runoff and sediment. Fire impacts on vegetation, ground cover, and runoff and sediment delivery from tree and shrub plots were highly variable. Burning litter covered areas underneath trees reduced perennial herbaceous vegetation and increased invasibility to the fire-prone annual cheatgrass (Bromus tectorum L.). Cheatgrass cover increased from <1% pre-fire to 16–30%, on average, post-fire across the sites and was primarily restricted to areas around burned trees. High herbaceous cover (73%) under burned trees at the less degraded site resulted in similar low total runoff and sediment from concentrated flow experiments as pre-fire (136–228 L, 204–423 g). In contrast, fire-reduction of litter (from 79% to 49%) resulted in increased total runoff (from 103 L to 333 L) and sediment yield (from 619 g to 2170 g) from concentrated flow experiments in burned tree areas at the more degraded site. The experimental results demonstrate pinyon and juniper removal by prescribed fire can effectively re-establish a successional trajectory towards sagebrush steppe vegetation structure and thereby improve ecohydrologic function. Responses to burning at the more degraded site suggest results should be interpreted with caution however. Although burning substantially increased perennial grass cover and reduced fine-scale runoff and erosion at the more degraded site, poor sagebrush recovery, delayed litter recruitment, and persistent high concentrated flow erosion at that site suggest not all sites are good candidates for prescribed fire treatments. Furthermore, high levels of cheatgrass in burned tree areas (~30% of area) at both sites increases wildfire risk, but cheatgrass is expected to decline over time in absence of fire. Our results in context with the literature suggest fire-surrogate tree-removal treatments (e.g., tree cutting or shredding) may be more appropriate on degraded sites with limited pre-treatment sagebrush and perennial herbaceous vegetation and that seeding may be necessary to improve post-fire establishment of sagebrush steppe vegetation structure and associated ecohydrologic function under these conditions. Lastly, vegetation, runoff, and erosion responses in this study are not directly applicable outside of the Great Basin, but similar responses in woodland studies from the southwestern US suggest potential application of results to woodlands in that region. The concept of re-establishing vegetation structure to improve ecohydrologic function is broadly applicable to sparsely vegetated lands around the World.