Native Ground Cover Research Articles

Upland forest community composition and structure by ecoregion in 73 Florida state parks – Insights for ongoing management

Plot based forest/vegetation data is used to establish current conditions and inform natural resources management decisions. The Florida Department of Environmental Protection – Division of Recreation and Parks (DRP) manages 175 state parks. As part of its mission, DRP strives to restore landscapes and natural communities by reintroducing dynamic natural processes such as fire. DRP also uses other methods of active management to achieve desired future conditions (DFCs) in multiple communities including those characterized by longleaf pine (Pinus palustris Mill.) and native groundcover (GC) species. To meet the challenge of managing natural resources across the State, DRP initiated an objective and repeatable forest/vegetation inventory system. The primary objective of this paper was to analyze and summarize the resultant data and compare current community type (ComType) vegetation conditions. Current conditions were quantified using nested plots distributed within sample areas across 73 state parks and 15 ecoregions via the line-plot method. Over 37,000 plots were inventoried; 36% were in pine flatwoods. Ten actively managed and dominant ComTypes were central to this paper and when aggregated by ecoregion, 76 ComType by ecoregion (CTER) groups were examined. Descriptive statistics for various measurements, e.g., diameter at breast height, height, and density, were calculated for overstory, midstory and understory (vegetation layer) separately per CTER. Mean importance value index (IVI) was calculated by species or species-group per vegetation layer and CTER. Community classification was conducted via hierarchical clustering of CTERs per vegetation layer using mean IVI scores. Across CTERs, pine overstory and midstory abundance/stocking levels were generally low, non-pine overstory and midstory stocking levels were high, pine regeneration was sparse, and GC was dominated by leaf litter, pine straw, and non-pine woody seedlings. Results strongly suggest that some ComTypes were similar within certain ecoregions. Various pine species are considered dominant or one of the prominent overstory species for eight of the ten ComTypes. The ability to manage upland pine ComTypes using natural regeneration systems will become increasingly challenging in the near- to medium-term given relatively low overstory pine stocking for most CTERs, and the virtual lack of young pines within midstory and understory layers. Further investigations could help identify potential causal agents concerning low young pine stocking levels, e.g., timing and frequency of prescribed fires, frequency of logging, and/or increased competition from high densities of midstory non-pines and appropriate natural regeneration systems, e.g., seed tree, shelterwood, or group selection, or underplanting longleaf pine, that would accelerate understory pine recruitment.

THE STABILIZED DUNES: A PILOT STUDY ON THE EFFECT OF ACACIA TORTILIS ON GROUND VEGETATION, FROM THAR DESERT, INDIA

In modern days, sand dune stabilization works are very common in desert areas globally. The purpose is multifaceted; developmental needs, soil moisture conservation works, and prevention of desert spread being the main among them. In the Indian state of Rajasthan, the same works have been ongoing for a long in the Thar desert, primarily by the forest department. This study was aimed as a non replicated administrative study, which has reflected on the possible correlation between the stabilization work by afforestation and gradual loss of native shrub species of desert ecosystem as found from the pilot sites. The preliminary findings of this study were then verified against previous research and findings in other arid regions of the world. Simple counting of standing tree and shrub species was done from 1 sq. m. sample plots of both forest department plantation sites and non-forest land areas. It was found that area with matured grown Acacia tortilis has less ground coverage than other areas. Arid ecosystem has unique survival adaptations, the fast growth of an introduced foreign species impacting the native ground cover can be due to multiple ecological reasons. A much broader replicated study is necessary to ascertain this fact and thereby take necessary measures for preserving both the desert ecosystem and enhance the sand stabilization works

Efficacy of Blanket Vegetation Mats on Soil and Native Groundcover Plants under Treatment of High Concentration Deicing Salt

Efficacy of Blanket Vegetation Mats on Soil and Native Groundcover Plants under Treatment of High Concentration Deicing Salt

Re-Assembly of the Longleaf Pine Ecosystem: Effects of Groundcover Seeding on Understory Community, Fire Behavior and Soil Properties

Planting native groundcover is often recommended to restore the understory of longleaf pine stands in the southeastern United States, but the effectiveness of such restoration activities remains poorly evaluated. We conducted a study in 25-year-old longleaf pine plantation stands in Georgia, USA, to examine the effects of seeding native groundcover on understory characteristics, fire behavior and soil properties. In 2015, four stands were seeded with five warm-season C4 grasses and a legume and four served as controls. In Fall 2020, we sampled the understory and analyzed soils collected from these stands, and in Spring 2021, fire behavior was evaluated. A total of 120 species were recorded in the understory across the stands, with the seeded species average foliar cover of 15%. There were no significant differences in species richness and Shannon diversity index of the seeded and control stands but understory species composition changed significantly. Soil properties and fire behavior during the prescribed fire also did not differ significantly between treatments, however, mean flame residence time was higher in seeded stands (108 s). Agricultural legacies of elevated soil P and old-field indicator species were prominent across stands. Overall, seeding had a minor effect on longleaf pine ecological characteristics in five years.

Effects of competition and habitat heterogeneity on native‐exotic plant richness relationships across spatial scales

AbstractAimThe biotic resistance hypothesis posits that greater native species richness limits invasions of exotic species. However, negative native‐exotic richness relationships (NERRs) may reverse with increasing spatial scale, seemingly refuting the hypothesis. Here, we explore the effects of species competitive interactions, environmental factors, habitat heterogeneity and vertical vegetation tiers on the NERRs across spatial scales in native forests.LocationNew Zealand.MethodsWe combined vegetation, land cover and climate data to predict exotic richness from native richness at different vertical tiers (ground to canopy), land cover, plant competition (tree basal area, native ground cover), mean annual temperature and total rainfall. We considered four spatial scales, from single 20 × 20 m plots on an 8‐km grid to groups of plots across grids up to 128 km. Habitat heterogeneity was measured using the variance of climatic conditions among plots within a group.ResultsA negative native tree‐exotic richness relationship (NTERR) was observed at plot level but reversed with increasing spatial scale. Species competitive interactions showed a negative relationship with exotic richness at small/intermediate scales (≤32 km). Rainfall and temperature heterogeneity contributed to the positive NTERR at the largest scale. Adjacent exotic grassland cover had a positive relationship with exotic richness across all scales but did not prevent the NTERR from reversing.Main conclusionsOur analysis shows the importance of considering vegetation structure and adjacent land covers, along with spatial heterogeneity and climatic factors, when testing the biotic resistance hypothesis in forest ecosystems. There is a clear indication that biotic resistance is primarily driven by native trees in the overstorey, probably by limiting resources available to ground tier plants. The results support the notion that the NERR is driven by competitive interspecific interactions at small spatial scales and by habitat heterogeneity at larger scales.

An innovative temporary escape ramp for deer and other wildlife

Concrete-lined water conveyance canals can be a significant source of mortality for ungulates and other wildlife, which can drown or become entrapped. Various types of wildlife escape structures have been deployed in canals with limited success. From 2011 to 2018, we used camera traps to monitor mule deer (Odocoileus hemionus) use of three different temporary wildlife escape structure designs with the goal of developing an effective escape structure for fawns. We monitored three to five locations at a hydroelectric water conveyance canal, operated by Pacific Gas and Electric Company in the foothills of Central California on the Sierra National Forest, in which trapped fawns had been detected previously during the maintenance period when the canal was dry. Mule deer activity and ramp use varied by year. During the monitoring period, deer were detected in the canal in all years except 2016 and 2017. Fawns and adults used the temporary escape structures to exit the canal in four of these years and 50% of mule deer detections showed ramp use overall. No deer were detected using the escape structures until jute netting and debris were added to the surface of the escape ramps in the third monitoring year. Prior to this modification, fawns were detected trapped in the canal investigating the ramps, but not using them to exit the canal. Deer may be more likely to utilize ramps covered with materials that mimic native ground cover. Seven other wildlife species were detected entering and exiting using the ramps with a general increase in use over years. Our temporary escape ramp design for small canals, when dry, appears to be novel and may be applicable in other areas. When compared to fencing or covering the canal, it is a relatively low-cost solution to reduce animal entrapment.

The use of state‐and‐transition models in assessing management success

AbstractState‐and‐transition models (STM) are valuable tools that aid understanding and management of ecosystems. There also is potential for STMs to be used as a framework to assess whether management actions are achieving desired conservation objectives. However, few published examples exist where STMs have been used in this way. Using high‐quality empirical field data collected in endangered temperate woodlands across a 6‐year period, we explore whether a Box Gum Grassy Woodland STM employed in an Australian agri‐environment scheme can be used to assess whether management interventions are achieving an improvement in woodland Condition State. We found there was insufficient contextual information in the STM to facilitate its robust use as a framework for assessing whether management interventions were achieving conservation outcomes in Box Gum Grassy Woodlands. Weather was a key driver influencing management effectiveness, but its effects were absent from the STM, as were probabilities and time frames for transitions between Condition States. The deficiencies in the STM may preclude accurate conclusions about the effectiveness of the program. Given the influence of weather on the system, longer time frames are required to adequately assess the influence of management on key variables (e.g., native plant richness, native ground cover) underpinning the STM. This case study provides opportunities to understand the potential implications of using insufficiently contextualized STMs as frameworks for assessing whether management actions are achieving desired conservation objectives. It also provides opportunities to learn from what went wrong. To this end, based on our findings, we provide practical recommendations (applicable beyond our case study system) for improving the construction and implementation of STMs for the purposes of evaluating the success of management interventions in ecological restoration and conservation programs.

Comparison of the Particulate Matter Removal Capacity of 11 Herbaceous Landscape Plants

Background and objective Particulate matter (PM) has a fatal effect on health. There have been many studies on the use of plants such as trees and shrubs as eco-friendly and sustainable biofilter for the removal of PM. In forming more green space, ground cover plants play an important role in multi-layered planting. This study was conducted to investigate the ability of plants to reduce PM, targeting Korean native ground cover plants with high availability in urban green spaces. Methods For 4 species of Asteraceae, 4 species of Liliaceae, and 3 species of Rosaceae, one species of plants at a time were placed in an acrylic chamber (800 × 800 × 1000 mm, L × W × H) modeling an indoor space. After the injection of PM, the amount of PM remaining in the chamber over time was investigated. Results For all three types of PM (PM10, PM2.5, PM1), significant difference occurred in the amount of PM remaining between plant species after 1 hour in the Liliaceae chamber, 3 hours in the Asteraceae chamber, and 5 hours in the Rosaceae chamber. With Liliaceae, the leaf area and the amount of PM remaining in the chamber showed a negative (−) correlation. With the Asteraceae and Rosaceae, there was a weak negative correlation between the leaf area and the amount of PM remaining in the chamber. Conclusion When using ground cover plants as a biofilter to remove PM, it is considered effective to select a species with a large total leaf area, especially for Liliaceae.

Ground cover and native ant predation influence survival of metamorphic amphibians in a southeastern pine savanna undergoing restoration

Longleaf pine savannas historically supported abundant ground cover maintained by frequent fire but little other disturbance. Ground cover creates microclimates with lower temperatures, higher humidity, and increased soil moisture that may benefit wildlife, particularly small vertebrates such as amphibians. Today, most historical pine savannas have had extensive soil disturbance and altered fire regimes resulting in reduced ground cover and altered soil fauna communities including predatory invertebrates. We used a factorial terrestrial cage study to test the effects of native wiregrass (Aristida spp.) cover and the exclusion of a native predatory ant (Dorymyrmex smithi) on the survival of post‐metamorphic Ornate chorus frogs (Pseudacris ornata) and Gopher frogs (Rana capito). Although we were unable to achieve full ant exclusion, ant reduction in exclusion treatments and plant cover had an interactive effect on metamorph survival. Ant exclusion tended to increase Gopher frog survival and this effect was more pronounced when wiregrass was present. Within ant treatments, survival of Gopher frogs increased slightly with increasing wiregrass cover. Ornate chorus frogs had a high probability of survival (>95%) in all ant exclusion treatments regardless of wiregrass cover; however, in treatments without ant exclusion, survival increased with increasing wiregrass cover. Our results demonstrate that high abundances of a native ant species and low coverage of native wiregrass, which are legacies of historical soil disturbance and altered fire regimes, interact to elevate mortality of juvenile amphibians. Minimizing soil disturbance and restoring native ground cover are likely important for amphibian habitat management within historical southeastern pine savannas.

Effectiveness and costs of invasive species control using different techniques to restore cerrado grasslands

Invasion by exotic grasses is a severe threat to neotropical grasslands conservation and a major challenge for their restoration. To restore fire‐prone cerrado grasslands in southeastern Brazil, which have been massively invaded by the African grass Urochloa decumbens, we tested prescribed fire, herbicides, and hoeing, by themselves or in different combinations. Techniques were compared using ecological indicators (decreasing invasive and increasing native vegetation cover and richness) and cost‐effectiveness. All treatments, except fire alone, were similarly effective in controlling the invasive grass, which was reduced to less than 5% cover after 2 years. However, only hoeing was effective in recovering both ground cover and richness of the native vegetation, which was the restoration goal. Despite not changing ground cover by native vegetation or alien grasses, fire was successful as a complementary technique, by depleting the seed bank of the invasive grass by 40%. Hoeing preceded by fire and followed by a grass‐selective herbicide was the most cost‐effective, requiring US$40 per hectare to increase native ground cover by one percentage point compared to US$93 per hectare if only hoeing. Despite the low cost and efficacy of glyphosate application for controlling the invasive grass, it must be followed by reintroducing the native ground cover through active restoration. If the restoration target is to recover both structure and richness of the native vegetation without planting, hoeing is the best solution to control alien grasses.

Lessons on direct seeding to restore Neotropical savanna

Tropical grassland-savanna mosaics are threatened globally, but they are challenging to restore because highly competitive pasture grasses inhibit recovery and are not shaded out by the patchy tree cover. We analyzed the outcomes of restoration projects and experiments established over four years in 55 ha of abandoned pastures dominated by invasive C4 grasses within the Neotropical savanna, Central Brazil. We tested the efficacy of direct seeding native grasses, forbs, shrubs and trees in reducing invasive grass cover and increasing native ground cover. We performed a series of experiments aimed at answering questions about the effect of seeding density, soil plowing to control invasive grasses, life form of ground cover species (grass, forb or shrub) and soil type on restoration outcomes. Relative native cover reached 34 ± 3% three rainy seasons after the first seeding experiment. Higher seeding densities and more soil plowing repetitions increased relative native cover. Soil type interacted with the life form of ground cover species to strongly influence relative native cover; two years after seeding, the highest relative native cover was achieved in rocky soils seeded with grasses (78 ± 6%) and the lowest was for seasonally waterlogged soils seeded with shrubs (15 ± 4%). Direct seeding can effectively establish many native Neotropical savanna species of different life forms with better restoration outcomes on rocky soils and with higher seeding densities. Further research is urgent to improve restoration methods, especially to control invasive grasses, to be able to achieve the large-scale restoration targets set internationally.

Plant Communities Suitable for Green Roofs in Arid Regions

In extensive green roof settings, plant communities can be more robust than monocultures. In addition, native plants might be hardier and more ecologically sound choices than non-native plants in green roof systems. The objectives of this research were to (1) compare the performance of plant communities with that of monocultures and (2) compare the growth of natives to non-natives in a simulated green roof setting. We conducted a two-year experiment at an outdoor site in a desert environment using four plant morphological types (groundcover, forb, succulent and grass). Native plants selected were Chrysactinia mexicana, Melampodium leucanthum, Euphorbia antisyphilitica, and Nassella tenuissima, and non-natives were Delosperma nubigenum, Stachys byzantina, Sedum kamtschiaticum and Festuca glauca. Plants were assigned randomly to either monoculture or community and grown in 1 m × 1 m custom-built trays filled with 15 cm of a proprietary blend of 50/20/30 lightweight aggregate/sand/compost (by volume). Native forb, Melampodium, in community had greater coverage for four of the five measurements in the first year over native forb in monoculture and non-native forb regardless of setting. Native forb coverage was also greater than non-native forb for three of the four measurements in year 2, regardless of setting. Coverage of native grass was significantly greater than non-native grasses throughout the experiment. Coverage was also greater for eight of nine measurements for native succulent over non-natives succulent. However, non-native groundcover coverage was significantly greater than native groundcover for seven of nine measurements. On 1 November 2016, relative water content (RWC) for succulents (p = 0.0424) was greatest for native Euphorbia in monoculture at 88%. Native Euphorbia also had greater RWC than non-native Sedum on 4 April 2017 (78%) and 4 July 2017 (80%). However, non-native Sedum had greater root length (6548 cm), root dry weight (12.1 g), and root-to-shoot dry weight ratio (0.45) than native Euphorbia. At the end of year 2, the relative growth rate (RGR) of native Euphorbia of 0.15 g·g−1·d−1 was greater than that of Sedum. While the native succulent had a smaller root biomass, its greater RWC and RGR would indicate it had better plant water status and grew faster than the non-native. The lack of differences in plant performance regardless of assignment to monoculture or community would imply that communities and monocultures are equally suitable for arid region green roofs.

Competitive Responses and Effects of the Invasive Grass Microstegium vimineum during Oak Woodland Restoration

The relevance of diversity—invasibility studies to the conservation of biodiversity has been questioned on grounds that species-rich assemblages may not deter invasion by competitively superior invaders. Few studies have compared the competitive effects of invaders on native species individually vs. in mixture. Using field experiments, we measured competition between an invasive grass, Microstegium vimineum, and six species of large native groundcover plants. We first examined whether planting six native species was more effective than planting an equivalent number of a single species in competitively suppressing Microstegium. Using a split-plot design, naturally occurring patches of Microstegium were treated with one of the two planting treatments or a control. We monitored Microstegium emergence and percent cover through 2015 and into the spring of 2016. We then tested the competitive effect of Microstegium on plantings of native species within Microstegium patches using a removal experiment in 2016. Although initial transplant survival was high in spring 2015, subsequent mortality during the growing season was also high in both planting treatments and, thus, there was no evidence of competitive suppression of Microstegium. In contrast, removal of Microstegium benefited the growth (and flowering) of native transplants in 2016, and all native species were more or less equally affected. These results suggest that neither high native diversity nor the presence of certain native species is likely to be effective in constraining the abundance of invaders demonstrated to have strong competitive effects on most or all native species under conditions that favor both native diversity and the invader.

Northern Bobwhite Population Response to Intensive Mechanical Hardwood Clean-Up (Post Abstract)

Habitat degradation for northern bobwhite (Colinus virginianus) has occurred in many fire-maintained pine forests of the southeastern Coastal Plain due to encroachment of undesirable hardwoods over time. This is especially true for old-field lands where the highly combustible native groundcover has been eliminated. A management technique gaining in popularity recently is the removal of these hardwoods to improve habitat conditions for bobwhites. We used radio-telemetry and plantation hunting records to measure population parameters and hunting success on 1 such property before, during, and after an intensive mechanical hardwood ‘‘clean-up.’’ An 800-acre hunting course on Nilo Plantation near Albany, Georgia was the study area for this project and is a site where we have maintained a continuous year-round sample of radiomarked bobwhites since fall 1993, that now cumulatively totals > 500. These telemetry studies have revealed that bobwhite survival and reproductive output were declining and had reached low points the year prior to the initiation of hardwood clean-up. The clean-up operation consisted of mechanical felling of most mature hardwood in the pine uplands, followed by piling with root rakes, and then burning the piles. Kaplan-Meier survival estimates prior to the clean-up were Spring-Fall (15%), Fall-Spring (37%), and annual (6%). Cause specific mortality from avian depredation for the 2 Fall-Spring periods prior to clean-up averaged 35%. Broods produced per hen alive on 15 April was 0.42. During the 2 years since clean-up was completed, survival estimates have increased 2- to 5-fold now averaging: Spring-Fall (44%), Fall-Spring (73%), and annual (34%). Broods produced per hen alive on 15 April has almost doubled to 0.72. Cause-specific mortality from avian depredation during Fall-Spring has averaged only 6%. Plantation hunting success on this course had declined to a 20-year low of 3.2 coveys/hour but has since shown an almost 3-fold increase to a record high of 9.4 coveys/hour. This intensive hardwood clean-up has certainly improved the quality of the habitat on this site. We believe it also altered the predator context there by making the environment less suitable to the bobwhite’s natural enemies which contributed to the increased survival and reproductive output.

Ant community and habitat limit colony establishment by the fire ant, Solenopsis invicta

Summary Hypotheses of community assembly include limitation through habitat physical attributes, as well as competition among species. Such hypotheses must be resolved through experimental tests. Previous experiments have shown that: (i) fire ants of the monogyne social form occur mostly in highly disturbed habitat where they do not compete with mature colonies of co‐occurring ants; (ii) in native pine forests of northern Florida, habitat disturbance favours fire ants while simultaneously reducing native ants; (iii) fire ants thrive in these disturbances but do not persist as these become less disturbed over time; and finally, (iv) newly mated, dispersing/colony‐founding fire ant queens settle preferentially in such disturbed sites. We now show that by choosing disturbed sites, newly mated, monogyne fire ant queens greatly increase their chances of successful colony establishment. Experimental plots were created in the native ground cover of a north Florida pine forest with all combinations of tilling, shading or reduction of the native ant community. Newly mated fire ant queens, incipient colonies and small colonies were planted in these plots. Only five of 980 (0·5%) newly mated queen nests survived after 120 days, and only five of 400 incipient colonies (1·3%) survived after 30 days. All survivors were in plots with tilling and/or native ant reduction. Extrapolation indicated that 0·04% of newly mated queens and 0·1% of incipient colonies were likely to have survived at 1 year. In contrast, planting small colonies resulted in much higher rates of survival – in plots with native ant reduction, fire ants increased on baits throughout the year but decreased in unreduced control plots. Fifteen months after planting 108 colonies, 21 mounds (19%) were found in the ant‐reduced plots, but <2% of 108 colonies survived in the control plots. Taken together, these results show that by landing in disturbed habitat with its reduced native ant population, newly mated fire ants queens increase their chances of successful colony establishment. In contrast to much of the previous literature, our results suggest that ant community assembly proceeds primarily by queen habitat choice and secondarily by filtering and competition. A lay summary is available for this article.

Incorporating regional‐scale ecological knowledge to improve the effectiveness of large‐scale conservation programmes

AbstractLand‐stewardship programmes are a major focus of investment by governments for conserving biodiversity in agricultural landscapes. These programmes are generally large‐scale (e.g. >1000 km) spanning multiple biogeographic regions but developed using spatially limited (e.g. landscape‐scale; <100 km) ecological data interpolated across broad areas for one, or a few, well‐studied taxonomic groups. Information about how less‐studied taxa respond to regional differences in management and environmental effects has potential to further inform land‐stewardship conservation programmes, but suitable data sets are rarely available. In this study, we sought to enhance planning of large‐scale conservation programmes by quantifying relationships between reptile assemblages and key environmental attributes at regional scales within a large‐scale (>172 000 km2) Australian land‐stewardship programme. Using 234 remnant woodland monitoring sites spanning four distinct biogeographic regions, we asked: Do reptile assemblages show different environmental associations across biogeographically distinct regions? We found that environmental features important to reptile diversity differed over each region. Abundance and rare species richness of reptiles responded at regional‐scales to elevation, native groundcover and aspect. We identified four implications from our study: (1) large‐scale conservation schemes can achieve better outcomes for reptiles using regional‐scale knowledge of environmental associations; (2) regional‐scale knowledge is particularly valuable for conservation of rare reptile taxa; (3) consideration of abiotic environmental features which cannot be directly managed (e.g. aspect, elevation) is important; (4) programmes can be tailored to better support reptile groups at higher conservation risk. Our study shows that reptile‐environment associations differ among biogeographic regions, and this presents opportunity for tailoring stronger policy and management strategies for conserving large‐scale agricultural landscapes globally.

Performance of Selected Native Ground Cover Species Under Induced Drought Conditions

Research related to water stress is becoming increasingly important as the changing climatic scenario is increasing aridity in many parts of the world. In this context, maintaining an acceptable landscape quality using less water has become a challenge. Ground covers are widely used in landscapes to fill spaces hence understanding how water stress affects ground covers is essential for selecting species that can sustain drought. Hence, the objective of this study was to determine the response of three native ground cover species Cynodon dactylon, Desmodium triflorum and Cyrtococcum trigonum for deficit irrigation and to identify the maximally acceptable irrigation deficit at which acceptable landscape quality could be maintained out of these species. A pot experiment was conducted to evaluate the growth performance and visual quality of the three ground cover species under three different water deficit levels (75%, 65% and 55% field capacity) and under 100% field capacity (control). Each treatment consisted of 25 replicates and pots were arranged in Completely Randomized Design. Growth parameters and lawn quality was determined and the quantitative data was analyzed with SAS statistical package and lawn quality was analyzed with non-parametric methods. Induced drought conditions had a significant inhibitory effect on growth parameters and the overall lawn quality of studied species. In all three species shoot and root, fresh and dry weights were significantly reduced with induced drought. However, in C. dactylon, compared to 75% and 65% field capacity levels, at 55% field capacity level fresh and dry weights of shoots and roots were not significantly reduced. Similar observations were recorded with D. triflorum except for shoot fresh weight. In C. dactylon and D. triflorum, overall appearance is reduced after 65 % field capacity level where as in C. trigonum, it was severely affected after 100 % field capacity level. Hence 65 % field capacity level can be considered as the acceptable irrigation deficit for C. dactylon and D. triflorum at which acceptable quality could be maintained. Compared to the other two species, deficit irrigation is not recommended for C. trigonum as it could reduce the visual quality. Journal of Environmental Professionals Sri Lanka: 2015 Vol. 4 No. 2: 25-35

유기농 사과과원에서 초생재배를 위한 자생지피식물의 선발

유기농 사과과원에서 초생재배를 위해 활용할 수 있는 자생지피식물 선정을 위하여 세 가지 자생식물이 잡초의 발생 및 과실의 특성과 토양의 화학성 변화에 미치는 영향에 대해서 조사하였다. 지피식물의 생육은 30 ㎝ (L) × 30 ㎝ (W) × 100 ㎝ (H) 밀도에서 측정되었으며, 조사 결과 긴병꽃풀의 초장과 건물중이 다른 식물체들에 비해서 큰 것으로 조사되었다. 토양 피복율이 낮았던 섬백리향과 좀씀바귀에서의 잡초 발생빈도와 발생량은 대조구와 거의 유사하였던 반면, 토양 피복율이 높았던 긴병꽃풀 처리구의 경우 대조구와 비교하여 잡초의 발생억제 효과가 큰 것으로 조사되었다. 또한 긴병꽃풀의 개화기는 ‘쓰가루’ 사과 품종의 개화시기 일치하여 방화곤충의 유인을 증가시켰으며, 이에 따라 착과율의 증대 효과도 있는 것으로 나타났다. 본 실험에서 지피식물의 피복에 따른 나무의 생육과 과일의 특성의 차이는 나타나지 않았으나, 토양의 화학성분은 대조구에 비해 지피식물 처리구에서 유기물 함량과 인산 함량이 다소 높게 나타나는 것으로 분석되었다. 시험결과 전반적으로 긴병꽃풀은 토양을 완전히 피복함으로써 잡초의 발생을 감소시켰고, 토양 화학성도 개선하여 사과 재배농가에 초생재배용 피복식물로서 활용 가능성이 큰 것으로 조사되었다. This study was conducted to select native ground cover plants for sod culture in an organic apple orchard by estimating the effect of three native ground cover plants, Glechoma hederacea, Thymus magnus, and Ixeris stolonifera, on the soil coverage, time-periodic weed occurrence, fruit characteristics, and soil chemical properties. The plant height of G. hederace, T. magnus and I. stolonifera were 15.0 ㎝, 13.4 ㎝ and 7.2 ㎝, respectively. The dry weight of G. hederace, T. magnus and I. stolonifera were 463 ㎏/10a, 247 ㎏/10a, and 255 ㎏/10a, respectively. The plant height and dry weight of G. hederacea were higher than in the other species. T. magnus and I. stolonifera having relatively lower soil cover rate during their life cycle produced a lot of weeds in the orchard as compared with the control. In contrast, G. hederacea showed 100 percentage of ground cover in the first year, and maintained high percentage of ground cover in the growing season of ‘Tsugaru’ apple for another 2 years. When the soil was covered with G. hederacea in the orchard for 3 years, the amount of weed was only 114 ㎏/10a and number of weeding was also reduced about 33% compared with control as well as the other species. There were no differences in the tree growth and fruit characteristics between the native ground cover plants and the control; however, positive effects of native ground cover plants on soil chemical properties were found. In G. hederacea, available P₂O₄content in soils remarkably increased and was a significant difference among native species. In addition, cation (Ca, Mg and K) content in soils increased by 39% in Ca, 6% in Mg, and 11% in K at G. hederacea compared with control. These results suggest that G. hederacea could be advantageous in terms of reducing the amount of herbicide applied and the labor required for weed control, and controlling soil chemical properties; therefore, it is a good candidate for sod culture in an organic apple orchard.

Euonymus fortunei dominance over native species may be facilitated by plant–soil feedback

Positive plant–soil feedback (PSF) may be a mechanism of invader dominance, whereas PSF is often negative for native species. Previous work in Eastern deciduous forests of North America has shown that the invasive liana Euonymus fortunei participates in a net positive PSF with native groundcover Asarum canadense, indicating that PSF may contribute to invader dominance. However, to identify PSF as a general invasion driver for Euonymus, we must consider the average net pairwise feedback for multiple native–invasive species pairs, and compare this to the average net pairwise feedback amongst native–native pairs. Here, we test E. fortunei in net pairwise feedback against five native species, comparing native–invader feedback to feedback amongst natives over a gradient of light availability. PSF was on average neutral for invader–native pairs and on average negative for native–native pairs, indicating that Euonymus does not face the same constraints that limit the growth of native species. Because even neutral feedback can facilitate invasion, results indicate that PSF may facilitate invader dominance over a broad range of native functional groups and light conditions in Eastern deciduous forest.

Effects of Oak-hickory Woodland Restoration Treatments on Native Groundcover Vegetation and the Invasive Grass, Microstegium vimineum

An important goal of restoring fire to upland oak-dominated communities that have experienced fire exclusion is restoring groundcover plant species diversity and composition indicative of fire-maintained open habitats. Treatment-driven declines in rare forest specialists and increases in widespread ruderals and competitive non-native species, however, could negate the benefits of ecological restoration in these ecosystems. We tested the effects of treatment-related disturbances on native groundcover vegetation, density and proliferation of patches of an invasive grass, Japanese stiltgrass ( Microstegium vimineum ), and the net effects of treatment and the invasive grass on native groundcover vegetation. Results from multiple years of monitoring at two replicate sites in north Mississippi showed that thinning and burning significantly increased both groundcover species richness and the abundance of species indicative of fire-maintained open habitats. We found subtle increases in forest species in response to treatments, whereas most native ruderals did not increase significantly in response to the treatments over the long term. The density and competitive effect of the invasive Japanese stiltgrass increased dramatically at both sites in response to the restoration treatments. However, new patches of Japanese stiltgrass established in response to the treatments only at the site with the more recent history of agricultural disturbance. Results suggest that fire restoration treatments were effective in the absence of past agricultural disturbance and in areas lacking Japanese stiltgrass. At sites with a history of agriculture and large populations of Japanese stiltgrass, effective restoration may require eradication of Japanese stiltgrass and reintroduction or augmentation of competitive, native specialists of fire-maintained open habitats.